FIXED CUTTER DRILL BITS WITH MECHANICALLY ATTACHED CUTTER ELEMENT ASSEMBLIES

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent application Ser. No. 63/642,702 filed May 4, 2024, and entitled “Fixed Cutter Drill Bits with Mechanically Attached Cutter Element Assemblies,” which is hereby incorporated herein by reference in its entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD

The present disclosure relates generally to earth-boring bits used to drill a borehole for the ultimate recovery of oil, gas or minerals. More particularly, the present disclosure relates to fixed cutter drill bits with mechanical attached cutter elements, as well as to methods of making the same and methods of using the same.

BACKGROUND

An earth-boring drill bit is typically mounted on the lower end of a drill string and is rotated by rotating the drill string at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied to the drill string, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone. The borehole thus created has a diameter generally equal to the diameter or “gage” of the drill bit.

Fixed cutter bits, also known as rotary drag bits, are one type of drill bit commonly used to drill boreholes. Fixed cutter bit designs include a plurality of blades angularly spaced about a bit face. The blades generally project radially outward along the bit face and form flow channels therebetween. Cutter elements are typically grouped and mounted on the blades. The configuration or layout of the cutter elements on the blades may vary widely, depending on a number of factors. One of these factors is the formation itself, as different cutter element layouts engage and cut the various strata with differing results and effectiveness.

The cutter elements disposed on the several blades of a fixed cutter bit are typically formed of extremely hard materials and include a layer of polycrystalline diamond (“PCD”) material. In the typical fixed cutter bit, each cutter element includes an elongate and generally cylindrical support member that is received and secured in a pocket formed in the surface of one of the several blades. In addition, each cutter element typically has a hard cutting layer of polycrystalline diamond or other superabrasive material such as cubic boron nitride, thermally stable diamond, polycrystalline cubic boron nitride, or ultrahard tungsten carbide (meaning a tungsten carbide material having a wear-resistance that is greater than the wear-resistance of the material forming the substrate), as well as mixtures or combinations of these materials. The cutting layer is mounted to one end of the corresponding support member, which is typically formed of tungsten carbide.

While the bit is rotated, drilling fluid is pumped through the drill string and directed out of the face of the drill bit. The fixed cutter bit typically includes nozzles or fixed ports spaced about the bit face that serve to inject drilling fluid into the passageways between the several blades. The drilling fluid exiting the face of the bit through nozzles or ports performs several functions. In particular, the fluid removes formation cuttings (for example, rock chips) from the cutting structure of the drill bit. Otherwise, accumulation of formation cuttings on the cutting structure may reduce or prevent the penetration of the drill bit into the formation. In addition, the fluid removes formation cuttings from the bottom of the hole. Failure to remove formation materials from the bottom of the hole may result in subsequent passes by cutting structure to essentially re-cut the same materials, thereby reducing the effective cutting rate and potentially increasing wear on the cutting surfaces of the cutter elements. The drilling fluid flushes the cuttings removed from the bit face and from the bottom of the hole radially outward and then up the annulus between the drill string and the borehole sidewall to the surface. Still further, the drilling fluid removes heat, caused by contact with the formation, from the cutter elements to prolong cutter element life.

BRIEF SUMMARY

Embodiments of fixed cutter drill bits for drilling earthen formations are disclosed herein. In one embodiment, a fixed cutter drill bit for drilling an earthen formation has a central axis and a cutting direction of rotation about the central axis. The drill bit comprises a bit body configured to rotate about the central axis in the cutting direction of rotation. The bit body includes a bit face and a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. The blade includes a socket extending from the leading side of the blade and penetrating the cutter-supporting surface of the blade. The socket has a central axis, an open end at the leading side of the blade, and a closed end distal the leading side of the blade. The socket has (i) a first width W1 in a front view of the blade measured parallel to a projection of the cutter-supporting surface across the socket in the front view at a first distance D1 measured perpendicular to the projection of the cutter-supporting surface in the front view, and (ii) a second width W2 in a front view of the blade measured parallel to the projection of the cutter-supporting surface across the socket in the front view at a second distance D2 measured perpendicular to the projection of the cutter-supporting surface in the front view. The second distance D2 is greater than the first distance D1 and the second width W2 at the second depth D2 is greater than the first width W1 at the first width W1. The drill bit also comprises a cutter element assembly mounted to the blade and extending from the cutter-supporting surface of the blade. The cutter element assembly comprises a cutter element carrier seated in the socket and fixably attached to the blade. The cutter element carrier includes a base having a central axis, a leading face proximal the leading side of the blade, and a trailing face distal the leading side of the blade. The base mates with the socket. In addition, the cutter element assembly comprises a cutter element fixably attached to the cutter element carrier.

In another embodiment, a fixed cutter drill bit for drilling an earthen formation has a central axis and a cutting direction of rotation about the central axis. The drill bit comprises a bit body configured to rotate about the central axis in the cutting direction of rotation. The bit body includes a bit face and a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. The blade includes a socket extending from the leading side of the blade and penetrating the cutter-supporting surface of the blade. Te socket has a central axis, an open end at the leading side of the blade, and a closed end distal the leading side of the blade. The socket is defined by a base surface of the blade extending axially relative to the central axis of the socket from the leading side of the blade, a first lateral side surface extending axially relative to the central axis of the socket from the leading side of the blade, and a second lateral side surface extending axially relative to the central axis of the socket from the leading side of the blade. The base surface of the blade is distal the cutter-supporting surface. The first lateral side surface and the second lateral side surface are disposed on opposite lateral sides of the central axis of the socket. Each lateral side surface extends from the cutter-supporting surface to the base surface of the blade. The first lateral side surface of the blade includes at least a portion that slopes or curves away from at least a portion of the second lateral side surface of the blade moving away from the cutter-supporting surface to toward the base surface of the blade in a front view of the blade. In addition, the drill bit comprises a cutter element assembly removably mounted to the blade and extending from the cutter- supporting surface of the blade. The cutter element assembly comprises a cutter element carrier seated in the socket and fixably attached to the blade. The cutter element carrier includes a base having a central axis, a leading end proximal the leading side of the blade, and a trailing end distal the leading side of the blade. The base of the cutter element carrier mates with the socket and has an outer surface comprising a cutter element facing surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base, a first lateral side surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base, and a second lateral side surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base. The blade facing surface of the base slidingly engages the base surface of the blade, the first lateral side surface of the base engages the first lateral side surface of the blade, and the second lateral side surface of the base engages the second lateral side surface of the blade. The cutter element assembly also comprises a cutter element fixably attached to the cutter element carrier.

Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic view of a drilling system including an embodiment of a drill bit in accordance with the principles described herein;

FIG. 2 is a perspective view of the drill bit of FIG. 1;

FIG. 3 is an end view of the drill bit of FIG. 2;

FIG. 4 is a partial cross-sectional schematic view of the bit shown in FIG. 2 with the blades and the cutting faces of the cutter elements rotated into a single composite profile;

FIG. 5 is a front perspective view of one of the blades and corresponding cutter element assemblies of the bit of FIG. 2;

FIG. 6 is a perspective end view of the blade of FIG. 5 with the cutter element assemblies removed;

FIG. 7 is a schematic front view of one of the sockets of the blade of FIG. 5;

FIG. 8 is a perspective front view of one of the cutter element assemblies of the bit of FIG. 2;

FIG. 9 is a side view of the cutter element assembly of FIG. 8;

FIG. 10 is a perspective view of the cutter element carrier of the cutter element assembly of FIG. 8;

FIG. 11 is a side view of the cutter element carrier of FIG. 10;

FIG. 12 is a perspective front view of an embodiment of a cutter element assembly in accordance with the principles described herein;

FIG. 13 is a side view of the cutter element assembly of FIG. 12;

FIG. 14 is a perspective front view of the cutter element carrier of the cutter element assembly of FIG. 12;

FIG. 15 is a side view of the cutter element carrier of FIG. 14;

FIG. 16 is a cross-sectional side view of an embodiment of a cutter element assembly in accordance with the principles described herein mounted to a blade of a fixed cutter drill bit;

FIG. 17 is a perspective view of the cutter element carrier of the cutter element assembly of FIG. 16;

FIG. 18 is a rear perspective view of the cutter element of the cutter element assembly of FIG. 16;

FIG. 19 is a perspective view of an embodiment of a cutter element assembly in accordance with the principles described herein;

FIG. 20 is an exploded view of the cutter element assembly of FIG. 19;

FIG. 21 is a cross-sectional side view of an embodiment of a cutter element assembly in accordance with the principles described herein mounted to a blade of a fixed cutter drill bit;

FIG. 22 is a perspective view of the cutter element assembly of FIG. 21;

FIG. 23 is a perspective view of the cutter element carrier of FIG. 21;

FIG. 24 is a perspective view of an embodiment of a cutter element assembly in accordance with the principles described herein;

FIG. 25 is a perspective view of the cutter element carrier of the cutter element assembly of FIG. 24;

FIG. 26 is a front perspective view of a blade of a fixed cutter drill bit and a plurality of the cutter element assemblies of FIG. 24 mounted thereto;

FIG. 27 is a perspective view of an embodiment of a cutter element assembly in accordance with the principles described herein;

FIG. 28 is an exploded view of the cutter element assembly of FIG. 27;

FIG. 29 is a front perspective view of an exemplary blade of a fixed cutter drill bit and an embodiment of a cutter element assembly in accordance with the principles described herein fixably attached thereto;

FIG. 30 is a front view of the exemplary blade and the cutter element assembly of FIG. 29;

FIG. 31 is a cross-sectional view of the exemplary blade and the cutter element assembly of FIG. 29 taken in section 31-31 of FIG. 29;

FIG. 32 is a front view of the exemplary blade of FIG. 29 with the cutter element assembly removed;

FIG. 33 is an exploded view of the cutter element assembly of FIG. 29; and

FIG. 34 is a cross-sectional view of the cutter element assembly of FIG. 33.

DETAILED DESCRIPTION

The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a particular axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Any reference to up or down in the description and the claims is made for purposes of clarity, with “up”, “upper”, “upwardly”, “uphole”, or “upstream” meaning toward the surface of the borehole and with “down”, “lower”, “downwardly”, “downhole”, or “downstream” meaning toward the terminal end of the borehole, regardless of the borehole orientation. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

Drill bits are typically made in a manufacturing plant or factory. From the plant or factory, the drill bits are transported to the field for use. When worn, bits are typically transported to a repair center or back to the originating factory for maintenance, repair, and/or replacement. During maintenance, the bits are heated, and the cutter elements are rotated and/or replaced. After maintenance, the drill bits are then transported back to field for further use. This “lifecycle” of drill bits includes wasteful, non-value-added activities, such as transport time from and back to the field, and the associated costs. During such non-value-added activities, bits are not being used in a way that generates revenue, but instead, are idle (e.g., while being transported).

During maintenance, matrix bit bodies are susceptible to cracking when heated due to the thermal mismatch of the interior steel core (for attaching the threaded pin) and the matrix bit body. Additionally, when bits are heated, the cutter elements may sustain thermal damage, which often results in loss of wear resistance, and in extreme cases, cracking. Furthermore, when the drill bits are heated and cutter elements are brazed, there is a risk of human error that the drill bit will be overheated or a cutter element will be placed directly into an acetylene flame, thereby potentially causing thermal damage. It should also be appreciated that a considerable amount of time is required to heat and braze cutter elements into a drill bit, and still further time is necessary after heating the drill bit to clean the bit (e.g., remove flux in a bath). Subsequent to such heating and cleaning, the drill bits are blasted (e.g., to remove excess braze) and then dye checked for potential cracks in the bit body and/or cutter elements.

Moreover, cutter elements mounted to the blades of fixed cutter drill bits typically extend from the formation facing surfaces of the blades to an extension height measured perpendicularly from the formation facing surface. In general, a greater extension height allows for increased depth-of-cut into the formation during drilling and increased rate-of-penetration (ROP) of the drill bit during drilling. Most conventional cutter elements, which are directly brazed into mating pockets formed in the blades, are typically limited to extension heights equal to about 50% of the diameter of the cutting faces of the cutter elements. Such limitation is due, at least in part, to the strength of the connections (e.g., the brazed bond) between the cutter elements and the blades, as well as the fact that the cutter elements are directly attached to the blades.

For at least the foregoing reasons, there exists a need for drill bits than can be maintained and repaired more efficiently, cutter elements that can be mounted to blades with reduced risk of thermal damage, and cutter elements that can be mounted to the blades with sufficient attachment strengths to enable increased extension heights. Accordingly, embodiments described herein are directed to drill bits including cutter elements that are mechanically coupled to the blades extending from the bit bodies, cutter elements that can be mounted to blades with reduced risk of thermal damage, and cutter elements that can be mounted at greater extension heights. In some embodiments, the blades are configured for relatively quick removal and attachment of cutter elements. As a result, rather than require transport to a factory or repair center, a field office can be positioned in the field for rapid drill bit build customization, repair, and maintenance. In other words, the drill bits and cutter elements thereon can be repaired, maintained, and replaced (as desired) on site, without transport over long distances (after initial delivery to the field). In some embodiments disclosed herein, the cutter elements can be replaced at the field location without requiring heating of the bit, which requires time for both heating and cooling of the bit, as well as presents the risk of thermal damage to the cutter elements. Further, the cutter elements can be brazed in a controlled, lab environment separate from the bit, thereby avoiding the time required need to heat and cool the entire drill bit, increasing the speed of the brazing process, reducing the propensity for thermal damage to the cutter elements, and reducing the amount of time the cutter elements are exposed to a deleterious oxygen containing atmosphere at elevated temperatures.

Referring now to FIG. 1, a schematic view of an embodiment of a drilling system 10 in accordance with the principles described herein is shown. Drilling system 10 includes a derrick 11 having a floor 12 supporting a rotary table 14 and a drilling assembly 90 for drilling a borehole 26 from derrick 11. Rotary table 14 is rotated by a prime mover such as an electric motor (not shown) at a desired rotational speed and controlled by a motor controller (not shown). In other embodiments, the rotary table (for example, rotary table 14) may be augmented or replaced by a top drive suspended in the derrick (for example, derrick 11) and connected to the drillstring (for example, drillstring 20).

Drilling assembly 90 includes a drillstring 20 and a drill bit 100 coupled to the lower end of drillstring 20. Drillstring 20 is made of a plurality of pipe joints 22 connected end- to-end, and extends downward from the rotary table 14 through a pressure control device 15, such as a blowout preventer (BOP), into the borehole 26. The pressure control device 15 is commonly hydraulically powered and may contain sensors for detecting certain operating parameters and controlling the actuation of the pressure control device 15. Drill bit 100 is rotated with weight-on-bit (WOB) applied to drill the borehole 26 through the earthen formation. Drillstring 20 is coupled to a drawworks 30 via a kelly joint 21, swivel 28, and line 29 through a pulley. During drilling operations, drawworks 30 is operated to control the WOB, which impacts the rate-of-penetration of drill bit 100 through the formation. In this embodiment, drill bit 100 can be rotated from the surface by drillstring 20 via rotary table 14 or a top drive, rotated by downhole mud motor 55 disposed along drillstring 20 proximal bit 100, or combinations thereof (for example, rotated by both rotary table 14 via drillstring 20 and mud motor 55, rotated by a top drive and the mud motor 55, etc.). For example, rotation via downhole motor 55 may be employed to supplement the rotational power of rotary table 14, if required, or to effect changes in the drilling process. In either case, the rate-of-penetration (ROP) of the drill bit 100 into the borehole 26 for a given formation and a drilling assembly largely depends upon the WOB and the rotational speed of bit 100.

During drilling operations, a suitable drilling fluid 31 is pumped under pressure from a mud tank 32 through the drillstring 20 by a mud pump 34. Drilling fluid 31 passes from the mud pump 34 into the drillstring 20 via a desurger 36, fluid line 38, and the kelly joint 21. The drilling fluid 31 pumped down drillstring 20 flows through mud motor 55 and is discharged at the borehole bottom through nozzles in face of drill bit 100, circulates to the surface through an annular space 27 radially positioned between drillstring 20 and the sidewall of borehole 26, and then returns to mud tank 32 via a solids control system 36 and a return line 35. Solids control system 36 may include any suitable solids control equipment known in the art including, without limitation, shale shakers, centrifuges, and automated chemical additive systems. Control system 36 may include sensors and automated controls for monitoring and controlling, respectively, various operating parameters such as centrifuge rpm. It should be appreciated that much of the surface equipment for handling the drilling fluid is application specific and may vary on a case-by-case basis.

Referring now to FIGS. 2 and 3, drill bit 100 is a fixed cutter bit, sometimes referred to as a drag bit, and is designed for drilling through formations of rock to form a borehole. Bit 100 has a central or longitudinal axis 105, a first or uphole end 100a, and a second or downhole end 100b. Bit 100 rotates about axis 105 in the cutting direction represented by arrow 106. In addition, bit 100 includes a bit body 110 extending axially from downhole end 100b, a threaded connection or pin 120 extending axially from uphole end 100a, and a shank 130 extending axially between pin 120 and body 110. Pin 120 couples bit 100 to a drill string (not shown), which is employed to rotate the bit 100 in order to drill the borehole. Bit body 110, shank 130, and pin 120 are coaxially aligned with axis 105, and thus, each has a central axis coincident with axis 105.

The portion of bit body 110 that faces the formation at downhole end 100b includes a bit face 111 provided with a cutting structure 140. Cutting structure 140 includes a plurality of blades that extend from bit face 111. As best shown in FIG. 4, in this embodiment, cutting structure 140 includes three angularly spaced-apart primary blades 141 and three angularly spaced apart secondary blades 142. Further, in this embodiment, the plurality of blades (for example, primary blades 141, and secondary blades 142) are uniformly angularly spaced on bit face 111 about bit axis 105. In particular, the three primary blades 141 are uniformly angularly spaced about 120° apart, the three secondary blades 142 are uniformly angularly spaced about 120° apart, and each primary blade 141 is angularly spaced about 60° from each circumferentially adjacent secondary blade 142. In other embodiments, one or more of the blades may be spaced non-uniformly about bit face 111. Still further, in this embodiment, the primary blades 141 and secondary blades 142 are circumferentially arranged in an alternating fashion. In other words, one secondary blade 142 is disposed between each pair of circumferentially-adjacent primary blades 141. Although bit 100 is shown as having three primary blades 141 and three secondary blades 142, in general, bit 100 may comprise any suitable number of primary and secondary blades. As one example only, bit 100 may comprise two primary blades and four secondary blades.

Referring still to FIGS. 2 and 3, in this embodiment, primary blades 141 and secondary blades 142 are integrally formed as part of, and extend from, bit body 110 and bit face 111. Primary blades 141 and secondary blades 142 extend generally radially along bit face 111 and then axially along a portion of the periphery of bit 100. In particular, primary blades 141 extend radially from proximal central axis 105 toward the periphery of bit body 110. Primary blades 141 and secondary blades 142 are separated by drilling fluid flow courses 143. Each blade 141, 142 has a leading edge or side 141a, 142a, respectively, and a trailing edge or side 141b, 142b, respectively, relative to the direction of rotation 106 of bit 100.

Each blade 141, 142 includes a cutter-supporting surface 144 that generally faces the formation during drilling and extends circumferentially from the leading side 141a to the trailing side 142 of the corresponding blade 141, 142. During drilling operations, cutter-supporting surface 144 generally faces the surrounding formation, and thus, may also be referred to herein as formation-facing surface 144. In this embodiment, a plurality of cutter element assemblies 200 are fixably attached to each blade 141, 142 and extend from cutter-supporting surface 144 of each blade 141, 142. Cutter element assemblies 200 are generally arranged adjacent one another in a radially extending row proximal the leading side 141a of each primary blade 141 and each secondary blade 142. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies 200) may be arranged differently.

As will be described in more detail below, each cutter element assembly 200 includes a cutter element carrier 210 fixably mounted to the corresponding blade 141, 142 and a cutter element 230 fixably secured to and carried by the carrier 210. Although cutter element assemblies 200 are fixably mounted to blades 141, 142, and thus, do not move rotationally or translationally during drilling operations, cutter element assemblies 200 are mechanically attached to blades 141, 142 such that any one or more cutter element assemblies 200 can be independently removed for repair, maintenance, or replacement. Accordingly, drill bit 100, as well as other embodiments of drill bits described herein, may be referred to as “modular;” and further, cutter element assemblies 200, as well as other embodiments of cutter element assemblies described herein, may be referred to as removably attached or secured to the blades.

As will be described in more detail below, each cutter element 230 includes an generally cylindrical support base or substrate 231 and a cylindrical disk or tablet-shaped, hard cutting layer 232 bonded to the exposed end of substrate 231. Substrate 231 is typically made of a carbide material such as tungsten carbide, whereas cutting layer 232 is typically made of polycrystalline diamond or other superabrasive material. Substrate 231 has a central axis 235, and as will be described in more detail below, is received and secured in a pocket formed in the corresponding carrier 210, which in turn is fixably received by and secured to the corresponding blade 141, 142 to which it is mounted. The cylindrical disc, hard cutting layer 232 defines a cutting face 233 of the corresponding cutter element 230. In this embodiment, each cutting face 233 is the same and is planar. However, in other embodiments, one or more cutting faces (e.g., cutting faces 233) may not be completely planar, but rather, be non-planar. As used herein, the phrase “non-planar” may be used to refer to a cutting face that includes one or more curved surfaces (for example, concave surface(s), convex surface(s), or combinations thereof), a plurality of distinct planar surfaces that intersect at distinct edges along the cutting face, or both. In this embodiment, some cutter elements 230, which are also labeled with reference numeral 230′, may be directly attached to the cutter-supporting surface 144 of the corresponding blade 141, 142 without a corresponding carrier 210.

In the embodiments described herein, each cutter element assembly 200 is mounted such that the central axis 235 of the corresponding cutter element 230 is oriented substantially parallel to or at an acute angle relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100). Such orientation results in the corresponding cutting face 233 being generally forward-facing relative to the cutting direction of the bit (for example, cutting direction 106 of bit 100). The point or portion of cutting face 233 of each cutter element 230 positioned furthest from the cutter-supporting surface 144 of the corresponding blade 141, 142 as measured perpendicular to the corresponding cutter-supporting surface 144 defines a cutting tip 234 of cutting face 233.

Referring still to FIGS. 2 and 3, bit body 110 further includes gage pads 147 of substantially equal axial length measured generally parallel to bit axis 105. Gage pads 147 are circumferentially-spaced about the radially outer surface of bit body 110. Specifically, one gage pad 147 intersects and extends from each blade 141, 142. In this embodiment, gage pads 147 are integrally formed as part of the bit body 110. In general, gage pads 147 can help maintain the size of the borehole by a rubbing action when cutter element assemblies 200 wear slightly under gage. Gage pads 147 also help stabilize bit 100 against vibration.

Referring now to FIG. 4, an exemplary profile of blades 141, 142 is shown as it would appear with blades 141, 142 and cutting faces 233 rotated into a single rotated profile. In rotated profile view, blades 141, 142 form a combined or composite blade profile 148 generally defined by cutter-supporting surfaces 144 of blades 141, 142. In this embodiment, the profiles of surfaces 144 of blades 141, 142 are generally coincident with each other, thereby forming a single composite blade profile 148.

Composite blade profile 148 and bit face 111 may generally be divided into three regions conventionally labeled cone region 149a, shoulder region 149b, and gage region 149c. Cone region 149a is the radially innermost region of bit body 110 and composite blade profile 148 that extends from bit axis 105 to shoulder region 149b. In this embodiment, cone region 149a is generally concave. Adjacent cone region 149a is generally convex shoulder region 149b. The transition between cone region 149a and shoulder region 149b, referred herein to as the nose 149d, occurs at the axially outermost portion of composite blade profile 148 (relative to bit axis 105) where a tangent line to the blade profile 148 has a slope of zero. Moving radially outward, adjacent shoulder region 149b is the gage region 149c, which extends substantially parallel to bit axis 105 at the outer radial periphery of composite blade profile 148. As shown in composite blade profile 148, gage pads 147 define the gage region 149c and the outer radius R110 of bit body 110. Outer radius R110 extends to and therefore defines the full gage diameter of bit 100.

Referring briefly to FIG. 3, moving radially outward from bit axis 105, bit 100 and bit face 111 include cone region 149a, shoulder region 149b, and gage region 149c as previously described. Primary blades 141 extend radially along bit face 111 from within cone region 149a proximal bit axis 105 toward gage region 149c and outer radius R110. Secondary blades 142 extend radially along bit face 111 from proximal nose 149d toward gage region 149c and outer radius R110. Thus, in this embodiment, each primary blade 141 and each secondary blade 142 extends substantially to gage region 149c and outer radius R110. In this embodiment, secondary blades 142 do not extend into cone region 149a, and thus, secondary blades 142 occupy no space on bit face 111 within cone region 149a. Although a specific embodiment of bit body 110 has been shown in described, one skilled in the art will appreciate that numerous variations in the size, orientation, and locations of the blades (for example, primary blades 141, secondary blades, 142, etc.), and cutter elements (for example, cutter element assemblies 200) are possible.

Bit 100 includes an internal plenum extending axially from uphole end 100a through pin 120 and shank 130 into bit body 110. The plenum allows drilling fluid to flow from the drill string into bit 100. Body 110 is also provided with a plurality of flow passages extending from the plenum to downhole end 100b. As best shown in FIGS. 2 and 3, a nozzle 108 is seated in the lower end of each flow passage. Together, the plenum, passages, and nozzles 108 serve to distribute drilling fluid around cutting structure 140 to flush away formation cuttings and to remove heat from cutting structure 140, and more particularly cutter element assemblies 200, during drilling.

Referring again to FIGS. 2 and 3, on each blade 141, 142, cutter element assemblies 200 are arranged side-by-side in a row along the corresponding cutter-supporting surface 144 proximal leading side 141a, 142a. Thus, in this embodiment, cutter element assemblies 200 are positioned radially adjacent one another on a given blade 141, 142. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies 200) may be arranged in rows with one or more cutter element having a different geometries on the same blade (for example, blade 141, 142).

Referring now to FIGS. 5 and 6, enlarged views of one exemplary blade 141 are shown. In FIG. 5, cutter element assemblies 200 are shown mounted to blade 141, however, in FIG. 6, cutter element assemblies 200 are removed. Although one exemplary primary blade 141 is shown in FIGS. 5 and 6 and will be described, it is to be understood that the other primary blades 141 and secondary blades 142 are generally the same.

Blade 141 includes a plurality of radially adjacent recesses or sockets 150 for receiving cutter element assemblies 200, and in particular, receiving mating cutter element carriers 210 of cutter element assemblies 200. Each socket 150 extends into the blade 141 generally perpendicularly from leading side 141a and cutter-supporting surface 144. Thus, each socket 150 intersects and extends through leading side 141a, cutter-supporting surface 144, and the convex edge between the corresponding cutter-supporting surface 144 and leading side 141a.

Referring now to FIGS. 6 and 7, one socket 150 will be described it being understood the other sockets 150 are the same. Socket 150 has a central or longitudinal axis 155, a first or open end 150a at leading side 141a, and a second or closed end 150b opposite end 150a and distal the leading side 141a. Central axis 155 is oriented parallel to central axis 235 of substrate 231 of the corresponding cutter element 230 and parallel to cutting direction 106 of bit 100 at the radial position of the corresponding cutter element 230. Open end 150a is positioned forward of and leads closed end 150b relative to relative to cutting direction 106 of bit 100. Accordingly, open end 150a may also be referred to as leading end 150a and closed end 150b may also be referred to as trailing end 150b.

Referring still to FIGS. 6 and 7, socket 150 is defined by generally trapezoidal profile projected into blade 141 from leading side 141a and open end 150a to trailing end 150b in a direction parallel to central axis 155. Thus, each cross-section of socket 150 taken in a plane oriented perpendicular to axis 155 generally has the same size, shape, and trapezoidal geometry. As best shown in FIG. 7, in this embodiment, socket 150 is generally symmetric about a reference plane R (illustrated with a dashed line in FIG. 7) oriented perpendicular to a projection P₁₄₄ of cutter-supporting surface 144 across socket 150 (illustrated with the dotted line in FIG. 7) and containing central axis 155 in front view of the blade 141 along axis 155. However, in other embodiments, the socket (e.g., socket 150) is not symmetric about a plane (e.g., reference plane R).

Socket 150 is defined by a plurality of surfaces formed by the surrounding blade 141 including a base surface 151 extending axially (relative to axis 155) from open end 150a to closed end 150b, a pair of lateral side surfaces 152 extending axially (relative to axis 155) from open end 150a to closed end 150b, and a rear support surface 153 defining closed end 150b. In this embodiment, a cutter element assembly support 145 integral with blade 141 extends from cutter-supporting surface 144 at trailing end 150b of socket 150 and defines a portion of rear support surface 153 extending axially (relative to bit axis 105) from cutter-supporting surface 144. As will be described in more detail below, cutter element assemblies 200 are received into mating sockets 150 with cutter element carriers 210 slidingly engaging surfaces 151, 152, 153.

In this embodiment, base surface 151 is a planar surface oriented parallel to central axis 155, parallel to cutter-supporting surface 144, and perpendicular to leading side 141a. Base surface 151 extends laterally between side surfaces 152. In addition, base surface 151 is distal cutter-supporting surface 144 and spaced therefrom. As best shown in FIG. 6, a counterbore 156 extends perpendicularly from base surface 151 into blade 141.

Referring again to FIGS. 6 and 7, lateral side surfaces 152 are laterally spaced apart (on opposite sides of central axis 155), and in this embodiment, are planar surfaces oriented parallel to central axis 155 and extend perpendicularly from leading side 141a. Lateral side surfaces 152 are disposed along opposite lateral sides of base surface 151 and generally extend from base surface 151 to cutter-supporting surface 144. In this embodiment, a concave (bowed inwardly) rounded transition surface is provided between base surface 151 and each lateral side surface 152, and a convex (bowed outwardly) rounded transition surface is provided between each lateral side surface 152 and cutter-supporting surface 144 of blade 141.

Lateral side surfaces 152 generally slope or taper away from each other moving from cutter-supporting surface 144 to base surface 151. Stated differently, lateral side surfaces 152 generally slope or taper toward from each other moving base surface 151 to cutter-supporting surface 144. In particular, as shown in FIG. 7, each lateral side surface 152 is oriented at an angle a relative to the reference plane R. In embodiments described herein, each angle α ranges from 0° to 90°, and preferably ranges from 25° to 75°. As lateral side surfaces 152 generally taper away from each other moving perpendicularly from the projection P₁₄₄ of cutter-supporting surface 144, surfaces 152 may be described as negative draft surfaces, and further, each angle α may be described as being a negative draft angle. In this embodiment, each lateral side surface 152 is oriented at the same angle α, and in particular, the angle α of each lateral side surface 152 is 55°.

Referring still to FIG. 7, socket 150 has a width W₁₅₀ in front view of the corresponding blade 141, 142 (as viewed perpendicular to leading side 141a, 142a along central axis 155 as shown in FIG. 7) measured (i) parallel to the projection P₁₄₄ of cutter-supporting surface 144, and (ii) perpendicular to the reference plane R. As lateral side surfaces 152 generally taper away from each other moving perpendicularly to the projection P₁₄₄ of cutter-supporting surface 144, the width W₁₅₀ generally increases moving from the projection P₁₄₄ of cutter-supporting surface 144 toward base surface 151. Stated differently, socket 150 may be described as having a first width W_150-1 at a first depth or distance D_150-1 measured perpendicularly from the projection P₁₄₄ of cutter-supporting surface 144, a second width W_150-2 at a second depth or distance D_150-2 measured perpendicularly from the projection P₁₄₄ of cutter-supporting surface 144 that is greater than the first depth D_150-1, where second width W_150-2 (at the greater depth D_150-2) is greater than the first width W_150-1 (at the lesser depth D_150-1). Accordingly, socket 150 may be described as having a “dovetail” shape or geometry in a front view of the blade 141. It should be appreciated that such geometry generally resists and/or prevents mating cutter element carrier 210 (and hence cutter element assembly 200) from being pulled or removed from socket 150 in a direction perpendicular to the projection P₁₄₄ of cutter-supporting surface 144 (i.e., upwardly as shown in FIG. 7).

Although lateral side surfaces 152 are planar surfaces that continuously slope away from each other moving perpendicularly from cutter-supporting surface 144 in this embodiment, in other embodiments, the lateral side surfaces (e.g., side surfaces 152) may not be planar and/or may not continuously slope away from each other. However, in embodiments described herein, each socket (e.g., each socket 150) preferably has a first width measured at a first depth (e.g., a first depth W₁₅₀) measured perpendicularly from the cutter-supporting surface (e.g., cutter-supporting surface 144), a second width (e.g., a first depth W₁₅₀) at a second depth measured perpendicularly from the cutter-supporting surface that is greater than the first depth, where the second width (at the greater depth) is greater than the first width (at the lesser depth) such that the geometry of the socket and mating cutter element carrier (e.g., carrier 210) generally resist and/or prevent the cutter element carrier and associated cutter element assembly (e.g., cutter element assembly 200) from being pulled or removed from the socket in a direction perpendicular to cutter-supporting surface.

Referring again to FIGS. 6 and 7, rear support surface 153 is disposed at closed end 150b and extends axially (relative to bit axis 105) from base surface 151 along blade 141 and support 145. In addition, rear support surface 153 extends laterally (relative to central axis 155) between lateral side surfaces 152. In this embodiment, a concave (bowed inwardly) rounded transition surface is provided between base surface 151 and rear support surface 153, and a concave (bowed inwardly) rounded transition surface is provided between rear support surface 153 and each lateral side surface 152. In this embodiment, rear support surface 153 is a planar surface oriented perpendicular to base surface 151, cutter-supporting surface 144, central axis 155, and cutting direction 106 of bit 100.

Referring now to FIGS. 8 and 9, one cutter element assembly 200 will be described it being understood that each cutter element assembly 200 is the same. As previously described, cutter element assembly 200 includes cutter element carrier 210 and cutter element 230 fixably mounted and secured thereto. As also previously described, each cutter element 230 includes cylindrical substrate 231 and cylindrical hard cutting layer 232 bonded to substrate 231. Each substrate 231 has a central axis 235, and each cutting layer 232 defines a cutting face 233. More specifically, each cutter element 230 has a leading end 230a relative to cutting direction 106 of bit 100, a trailing end 230b axially opposite end 230a (relative to axis 235), and a radially outer surface 234 extending axially from leading end 230a to trailing end 230b. Cutting face 233 is disposed at leading end 230a. Trailing end 230b comprises a planar surface 236. In this embodiment, cutting face 233 and planar surface 236 are disposed in planes oriented perpendicular to axis 235. Outer surface 237 includes a cylindrical surface 237a extending axially from leading end 230a to trailing end 230b along both cutting layer 232 and substrate 231. In this embodiment, outer surface 237 also includes a pair of circumferentially-spaced flats 237b extending along cylindrical surface 237a from leading end 230a to trailing end 230b. Cutting tip 234 is circumferentially positioned between flats 237b at the intersection of cutting face 233 and cylindrical surface 237a. Cutter element 230 also includes a sloped indexing flat 237c (illustrated with hidden lines in FIG. 9) extending radially inward and axially rearward (relative to axis 235) from outer surface 237 to planar surface 236. Sloped indexing flat 237c is angularly spaced 180° from cutting tip 234 adjacent trailing end 230b.

Referring now to FIGS. 8-11, cutter element carrier 210 has a first end 210a and a second end 210b opposite end 210a. When cutter element assembly 200 is seated in a mating socket 150, first end 210a is positioned forward of and leads second end 210b relative to the cutting direction 106 of bit 100. Accordingly, first end 210a may also be referred to as leading end 210a, and second end 210b may also be referred to as trailing end 210b.

Cutter element carrier 210 is generally L-shaped, monolithic member in side view. In particular, cutter element carrier 210 includes a base 211 extending from leading end 210a to trailing end 210b and a cutter element support block 220 extending from base 211 at trailing end 210b. As a result, base 211 and support block 220 define a receptacle or pocket 218 extending axially from leading end 210a of cutter element carrier 210 to support block 220. Pocket 218 is sized to receive and mate with cutter element 230.

As best shown in FIGS. 10 and 11, base 211 has a central or longitudinal axis 215, a leading face 211a at end 210a, and a trailing face 211b at end 210b. In addition, base 211 has an outer surface including a blade facing surface 212 extending axially (relative to axis 215) from leading end 210a to trailing end 210b, a pair of lateral side surfaces 213 extending axially (relative to axis 215) from leading face 211a to trailing face 211b, and a cutter element facing surface 214 extending axially (relative to axis 215) from leading face 211a to support block 220. Blade facing surface 212 and cutter element facing surface 214 are radially spaced apart (relative to axis 215), and each extends laterally (relative to axis 215) between lateral side surfaces 213. Thus, lateral side surfaces 213 are disposed along opposite lateral sides of blade facing surface 212 and extend from blade facing surface 212 to cutter element facing surface 214 along pocket 218, and extend from blade facing surface 212 to support block 220 rearward of pocket 218.

In this embodiment, leading face 211a and trailing face 211b are defined by planar surfaces oriented perpendicular to central axis 215, blade facing surface 212 is a planar surface oriented parallel to central axis 215, and lateral side surfaces 213 are laterally spaced planar surfaces (on opposite sides of axis 215) oriented parallel to central axis 215. Blade facing surface 212 of carrier 210 slidingly engages and is flush with mating base surface 151 of socket 150, and lateral side surfaces 213 of carrier 210 slidingly engage and are flush with mating lateral side surfaces 152 of socket 150. Thus, as best shown in FIG. 5, the outer surface of base 211 is sized and shaped to mate with a corresponding socket 150 and slidingly engage surfaces 151, 152 defining socket 150 as shown in FIG. 5. In other words, base 211 has a geometry that is the same as socket 150. Namely, base 211 has a generally trapezoidal profile extending from leading face 211a to trailing face 211b in a direction parallel to central axis 215. Thus, each cross-section of base 211 taken in a plane oriented perpendicular to axis 155 generally has the same size, shape, and trapezoidal geometry. As previously described, in this embodiment, socket 150 is symmetric about the reference plane R in front view of the blade 141 (FIG. 7), and thus, in this embodiment, mating base 211 is also symmetric about the reference plane R when base 211 is seated in socket 150. However, in other embodiments, the base of the cutter element carrier (e.g., base 211 of carrier 210) may not be symmetric about a reference plane (e.g., reference plane R).

Referring again to FIGS. 10 and 11, in this embodiment, cutter element facing surface 214 includes a concave cylindrical surface 214a extending axially from leading face 211a and a cutter element indexing surface 214b extending axially from cylindrical surface 214a to support block 220. Surfaces 214a, 214b extend laterally between side surfaces 213. As will be described in more detail below, indexing surface 214b engages mating indexing surface 237c of cutter element 230 to aid in rotationally indexing and positioning of cutter element 230 when it is seated in pocket 218. In this embodiment, indexing surface 214b is a planar surface that slopes radially upward (relative to axis 215) moving axially (relative to axis 215) from cylindrical surface 214a to support block 220. More specifically, indexing surface 214b is oriented at an acute angle relative to a reference plane oriented parallel to blade facing surface 212. The radially outer cylindrical surface 237a of cutter element 230 mates and slidingly engages cylindrical surface 214a, and thus, cylindrical surface 214a has a radius of curvature that is the same or substantially the same as the outer radius of cylindrical surface 237a of cutter element 230, and further, cylindrical surface 214a may also be referred to as a seat for cutter element 230. In this embodiment, a convex (bowed outwardly) rounded transition surface is provided between blade facing surface 212 and each lateral side surface 213, and a convex (bowed outwardly) rounded transition surface is provided between each lateral side surface 213 and cutter element facing surface 214. In addition, in this embodiment, a convex (bowed outwardly) rounded transition surface is provided between leading face 211a and each surface 212, 213, 214a, and a chamfer or bevel is provided between trailing face 211b and each surface 212, 213.

Referring still to FIGS. 10 and 11, support block 220 has a central axis 225 oriented parallel to axis 215 and coaxially aligned with axis 235 (FIG. 8) and an outer surface including a leading face 220a facing pocket 218, a trailing face 220b at end 210b, and a convex cylindrical radially outer surface 221 extending axially (relative to axis 225) from leading face 220a to trailing face 220b. In this embodiment, leading face 220a and trailing face 220b are defined by planar surfaces oriented perpendicular to central axis 225. Leading face 220a intersects indexing surface 214b and trailing face 220b is contiguous with trailing face 211b of base 211. In this embodiment, a chamfer or bevel is provided between trailing face 220b and cylindrical outer surface 221, and a concave (bowed inwardly) round transition surface is provided between each lateral side surface 213 of base 211 and cylindrical outer surface 221 of support block 220.

As best shown in FIG. 11, in this embodiment, a throughbore 219 extends from cylindrical outer surface 221 into support block 220 radially opposite blade facing surface 212 (relative to axis 225), and through support block 220 and base 211 to blade facing surface 212. The central axis of throughbore 219 is oriented perpendicular to blade facing surface 212. In this embodiment, throughbore 219 is internally threaded.

As previously described, blade facing surface 212 of carrier 210 slidingly engages and is flush with mating base surface 151 of socket 150, and lateral side surfaces 213 of carrier 210 slidingly engage and are flush with mating lateral side surfaces 152 of socket 150. Accordingly, as shown in FIG. 10, base 211 may be described as having a width W₂₁₁ measured perpendicularly to a reference plane containing axes 215, 225 that generally increases moving from cutter element facing surface 214 toward blade-facing surface 212. Stated differently, and similar to socket 150, base 211 may be described as having a first width W₂₁₁ at a first distance from cutter element facing surface 214 (measured in the reference plane containing axes 215, 225) that is less than a second width W₂₁₁ of base 211 at a second distance from cutter element facing surface 214 (also measured in the reference plane containing axes 215, 225), wherein the second width W₂₁₁ (at the greater second distance) is greater than the first width W₂₁₁ (at the lesser first distance). Thus, base 211 may also be described as having a dovetail geometry or shape in a front view of the cutter element carrier 210.

Cutter element carrier 210 can be made of a material suitable for a particular application and/or to enhance durability of cutter element assembly 200. For example, carrier 210 (or portion thereof) can be made of a high strength material, a high abrasion resistant material, a corrosion resistant material, or combinations thereof. Examples of suitable materials for carrier 210 include, without limitation, steel, super alloy, cemented carbide, matrix or similar high-performance or hard material, Stellite, Inconel, Monel, metal alloys with niobium or nickel, or combinations thereof (e.g., steel, carbide, steel, hardfacing, superalloy, and carbide).

Referring again to FIGS. 8 and 9, cutter element 230 is positioned in mating pocket 218 of cutter element carrier 210 and fixably secured thereto to form cutter element assembly 200. In particular, to secure cutter element 230 to carrier 210 within mating pocket 218, cutter element 230 is disposed within pocket 218 with axes 225, 235 generally coaxially aligned, outer cylindrical surface 237a of cutter element 230 adjacent mating cylindrical surface 214a of base 211, planar surface 236 at trailing end 230b of cutter element 230 adjacent leading face 220a of support block 220, and indexing flat 237c of cutter element 230 adjacent mating indexing surface 214b of carrier 210. Next, melted or “wet” brazing filler material is applied between the foregoing adjacent, mating surfaces and flows therebetween via capillary action. Cutter element 230 may be rotated relative to carrier 210 during the process to allow maximal dispersion of the wet brazing filler material between (i) mating cylindrical surfaces 214a, 237a; (ii) mating planar surface 236 and leading face 220a; and (iii) mating indexing surfaces 237c, 214b. Surface area coverage of the wet brazing material can be visually confirmed as cutter element 230 is rotated by viewing outer cylindrical surface 237a and planar surface 236 of cutter element 230. It should be appreciated that indexing flat of cutter element 230 adjacent mating indexing surface 214b of carrier 210, as well as planar surface 236 at trailing end 230b of cutter element 230 adjacent leading face 220a of support block 220, may move in and out of flush contact as cutter element 230 is rotated. However, as the brazing process is being finished, planar surface 236 is urged into flush contact with leading face 220a, and indexing flat of cutter element 230 is urged into flush contact with mating indexing surface 214b of carrier 210 to firmly secure cutter element 230 to carrier 210 with cutting tip 234 in the desired location (e.g., radially opposed base 211 of carrier 210). As the brazing filler material cools and solidifies, cutter element 230 is fixably secured to carrier 210 with mating surfaces 214a, 237a attached flush together, planar surface 236 and leading face 220a attached flush together, and indexing flat of cutter element 230 and indexing surface 214b of carrier 210 attached flush together. In general, each cutter element assembly 200 is assembled in the foregoing manner.

It should be appreciated that cutter element 230 can be removed from pocket 218 of carrier 210 for maintenance, repair, or replacement by heating carrier 210 and/or cutter element 230 to melt the brazing therebetween, and then rotating and pulling cutter element 230 from pocket 218. In embodiments without mating indexing features (e.g., without indexing flat of cutter element 230 and mating indexing surface 214b of carrier 210), the cutter element (e.g., cutter element 230) can be rotated relative to the cutter element carrier (e.g., carrier 210) to position a fresh or unworn portion of the cutting edge of the cutting layer (e.g., cutting layer 232) for engaging the formation during subsequent drilling operations by heating the cutter element carrier and/or the cutter element to melt the brazing therebetween and then rotating the cutter element relative to the carrier, and then re-brazing the cutter element to the cutter element carrier as previously described. These processes for attaching cutter element 230 to carrier 210, removing cutter element 230 from carrier 210, and rotating cutter element 230 relative to carrier 210 are preferably performed without carrier 210 attached to bit 100, which offers the potential to speed the process by eliminating the need to heat and cool the entire bit 100, as well as enable the brazing to be done in a controlled lab environment separate from the bit 100. To minimize exposure of cutter element 230 to excess heat, carrier 210 can be heated and/or a heat sink applied to cutter element 230.

Referring now to FIGS. 5-8, once formed as described above, cutter element assembly 200 is fixably and mechanically secured to drill bit 100 within a corresponding socket 150. In particular, cutter element assembly 200 is aligned with a corresponding socket 150 of blade 141 such that central axis 235 of substrate 231 is generally coaxially aligned with central axis 155 of socket 150 and trailing end 210b of carrier 210 proximal open end 150a of socket 150. Next, cutter element assembly 200 is axially advanced (relative to axes 155, 235) into socket 150 with base 211 slidingly disposed in mating socket 150. More specifically, cutter element assembly 200 is axially advanced (relative to axes 155, 235) into socket 150 with blade facing surface 212 of carrier 210 slidingly engaging mating base surface 151 of socket 150 and lateral side surfaces 213 of carrier 210 slidingly engaging mating lateral side surfaces 152 of socket 150 until trailing faces 211b, 220b axially abut, engage, and are flush with rear support surface 153 of socket 150. With cutter element assembly 200 fully seated in socket 150, a bolt or set screw 217 (FIG. 9) is threadably advanced through throughbore 219 until its tip is seated in counterbore 156 in blade 141. As best shown in FIG. 5, when cutter element assembly 200 is attached to blade 141, cylindrical outer surfaces 221, 237a are generally contiguous with the outer surface of cutter element assembly support 145.

In the manner described, cutter element assembly 200 is fixably and mechanically secured to the corresponding blade 141. It should be appreciated that set screw 217 (disposed in counterbore 156 of blade 141) prevents cutter element assembly 200 from sliding axially (relative to axes 155, 235) out of mating socket 150 via open end 150a, while mating engagement of base 211 and the surfaces defining socket 150 prevent base 211 (and hence, cutter element assembly 200) from sliding out of socket 150 perpendicularly to cutter-supporting surface 144, as well as prevents cutter element assembly 200 from rotating relative to blade 141. Thus, cutter element assembly 200 is fixably attached to blade 141 such that it cannot move rotationally or translationally relative to blade 141. However, cutter element assembly 200 can be removed from blade 141 for repair, maintenance, or replacement by performing the foregoing steps in reverse order. Thus, cutter element assembly 200 may be described as being mechanically attached to blade 141 and removably attached to blade 141. Although attachment of one cutter element assembly 200 to one blade 141 has been described, it should be appreciated that each cutter element assembly 200 is mounted to the corresponding blade 141, 142 and can be removed from the corresponding blade 141, 142 in the foregoing manners.

In the embodiment of cutter element assembly 200 previously described and shown in FIGS. 8 and 9, cutter element 230 is fixably attached to cutter element carrier 210 via brazing. In particular, the wet brazing filler material is applied between outer cylindrical surface 237a of cutter element 230 adjacent mating cylindrical surface 214a of base 211, planar surface 236 at trailing end 230b of cutter element 230 adjacent leading face 220a of support block 220, and indexing flat of cutter element 230 adjacent mating indexing surface 214b of carrier 210. Without being limited by this or any particular theory, the greater the contact surface area of surfaces of carrier 210 and cutter element 230 that are brazed together, the stronger the bond therebetween. Cylindrical surface 214a of base 211 extends circumferentially and contacts outer cylindrical surface 237a of cutter element 230 through an angle of about 45°. To further enhance the bond between cutter element 230 and carrier 210, in some embodiments, the surface area of contact for brazing between cylindrical surface 214a of base 211 and outer cylindrical surface 237a of cutter element 230 can be increased. For example, referring now to FIGS. 12 and 13, an embodiment of a cutter element assembly 300 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Cutter element assembly 300 includes a cutter element carrier 310 and a cutter element 230 fixably mounted and secured to carrier 310. Cutter element 230 is as previously described. Cutter element carrier 310 is substantially the same as cutter element carrier 210 previously described with the exception that the contact surface area between cutter element carrier 310 and cylindrical outer surface 237a of cutter element 230 is enhanced, and further, indexing surface 214b is not provided.

Referring now to FIGS. 14 and 15, cutter element carrier 310 includes base 211 as previously described and support block 220 as previously described. However, in this embodiment, cutter element carrier 310 includes a pair of lateral sidewalls 313 integral with support block 220 and base 211. In particular, lateral sidewalls 313 extend axially (relative to axes 215, 225) from leading end 210a to trailing end 210b, and extend circumferentially (about axes 225, 235) from base 211 along (i) the intersections of lateral side surfaces 213 and (ii) the radially outer surface 221 of support block 220. Each sidewall 313 has a first or leading end 313a at end 210a, a second or trailing end 313b at end 210b, a first side 314a extending axially from leading end 313a to trailing end 313b, and a second side 314b extending axially from leading end 313a to trailing end 313b. First side 314a is integral with base 211 and second side 314b is distal base 211. In addition, each sidewall 313 has a radially inner surface 315 facing pocket 218 and cutter element 230. Inner surface 315 is a concave cylindrical surface that is contiguous with cylindrical surface 214a of base 211, and mates and engages the radially outer cylindrical surface 237a of cutter element 230. Thus, radially inner surface 315 has a radius of curvature that is the same or substantially the same as the outer radius of cylindrical surface 237a of cutter element 230.

Referring against to FIGS. 12 and 13, cutter element 230 is attached to cutter element carrier 310 in the same manner as previously described with respect to cutter element 230 and carrier 210 to form cutter element assembly 300 with the exception that the wet brazing filler material is also provided between outer cylindrical surface 237a of cutter element 230 and mating cylindrical inner surfaces 315 of sidewalls 313. Collectively, cylindrical surface 214a of base 211 and cylindrical inner surfaces 315 of sidewalls 313 extend circumferentially and contact outer cylindrical surface 237a of cutter element 230 through an angle of about 180°, thereby increasing the contact surface area between carrier 310 and outer cylindrical surface 237a of cutter element 230, and offering the potential to increase the strength of the brazed bond therebetween. Cutter element assembly 300 is attached to a corresponding blade 141, 142 in the same manner as previously described with respect to cutter element assembly 200.

In the embodiments of cutter element assemblies 200, 300 previously described, cutter element 230 is brazed to cutter element carrier 210, 310 along mating cylindrical surfaces 214a, 237 (and cylindrical inner surfaces 315 for cutter element assembly 300); (ii) mating planar surface 236 and leading face 220a; and (iii) the mating indexing flat of cutter element 230 and indexing surface 214b of carrier 210. Although brazing between the foregoing surfaces restricts and/or prevents relative radial movement of cutter element 230 relative to carrier 210, 310 (relative to axes 225, 235), for some applications, it may be desirable to further enhance the strength of resistance to relative radial movement of the cutter element (e.g., cutter element 230) relative to the cutter element carrier (e.g., cutter element carrier 210, 310). For example, referring now to FIG. 16, an embodiment of a cutter element assembly 400 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Cutter element assembly 400 includes a cutter element carrier 410 and a cutter element 430 fixably mounted and secured to carrier 410. Cutter element 430 and carrier 410 are substantially the same as cutter element 230 and carrier 210 previously described, respectively, with the exception that cutter element 430 and carrier 410 include mating features or structures that enhance the strength of resistance to relative radial movement of cutter element 430 relative to cutter element carrier 410.

Referring now to FIGS. 16-18, cutter element carrier 410 includes base 211 as previously described and support block 220 as previously described. However, in this embodiment, support block 220 includes a projection 411 integral with support block 220 and extending axially (relative to axis 225) from leading face 220a into pocket 218. In this embodiment, projection 411 is a cylindrical member with a central axis coaxially aligned with axis 225.

Cutter element 430 includes substrate 231 as previously described and cutting layer 232 as previously described. However, in this embodiment and best shown in FIG. 18, substrate 231 includes a recess 432 extending axially (relative to axis 235) from planar surface 236. In this embodiment, recess 432 is cylindrical and has a central axis coaxially aligned with axis 235. Recess 432 is sized, shaped, and positioned to slidingly receive and mate with projection 411.

Referring now to FIG. 16, cutter element 430 is attached to cutter element carrier 410 in the same manner as previously described with respect to cutter element 230 and carrier 210 to form cutter element assembly 300 with the exception that projection 411 is disposed in mating recess 432 and the wet brazing filler material may also be provided between projection 411 and substrate 231. Positioning of projection 411 in recess 432 and brazing of projection 411 to substrate 231 increases the contact surface area between carrier 410 and cutter element 430, increases the strength of the brazed bond therebetween, and increases the strength of the resistance to relative radial movement of cutter element 430 relative to cutter element carrier 410. Cutter element assembly 400 is attached to a corresponding blade 141, 142 in the same manner as previously described with respect to cutter element assembly 200.

In the embodiment of cutter element assembly 400 previously described and shown in FIG. 16, cutter element carrier 410 includes projection 411 and cutter element 430 includes mating recess 432 to enhance the strength of resistance to relative radial movement of cutter element 430 relative to cutter element carrier 210, 310. However, in other embodiments, the positions of the projection (e.g., projection 411) and the mating recess (e.g., recess 432) can be flipped. Namely, the projection can be provided on the cutter element and the mating recess can be provided in the cutter element carrier (e.g., cutter element carrier 410). For example, referring now to FIGS. 19 and 20, an embodiment of a cutter element assembly 500 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Cutter element assembly 500 includes a cutter element carrier 510 and a cutter element 530 fixably mounted and secured to carrier 510. Cutter element 530 is substantially the same as cutter element 230 previously described with the exception that cutter element 530 includes a projection 533 and does not include flats 237b in this embodiment. Cutter element carrier 510 is the same as cutter element carrier 210 previously described with the exception that cutter element carrier 510 includes a throughbore 512 and does not include throughbore 219 as cutter element carrier 510 relies on an alternative mechanism to secure cutter element carrier 510 within socket 150 and prevent cutter element carrier 510 from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144. Engagement of mating projection 533 and throughbore 512 enhances the strength of resistance to relative radial movement of cutter element 530 relative to cutter element carrier 510.

Cutter element carrier 510 includes a base 511 and a support block 520. Base 511 and support block 520 are the same as base 211 and support block 220, respectively, as previously described, with the exception that throughbore 219 is eliminated and support block 520 includes throughbore 512 extending axially (relative to axis 235) from leading face 220a to trailing face 220b. In this embodiment, throughbore 512 is cylindrical and has a central axis coaxially aligned with axis 225.

Cutter element 530 includes a substrate 531 and a cutting layer 532 fixably attached and bonded to substrate 531. Substrate 531 and cutting layer 532 are the same as substrate 231 and cutting layer 232, respectively, as previously described with the exception that projection 533 extends from trailing end 230b and flats 237b along outer surface 237 are eliminated. Projection 533 extends axially (relative to axis 235) from planar surface 236. In this embodiment, projection 533 is a cylindrical member with a central axis coaxially aligned with central axis 235. Projection 533 is sized, shaped, and positioned to be slidingly received by and mate with throughbore 512. Projection 533 and substrate 531 may be a monolithic (single piece) or may be separate components that are fixably attached.

Referring still to FIGS. 19 and 20, cutter element 530 is attached to cutter element carrier 510 in the same manner as previously described with respect to cutter element 230 and carrier 210 to form cutter element assembly 200 with the exception that projection 533 is seated in mating throughbore 512 and the wet brazing filler material may be provided within recess 522 between projection 533 and support bock 520. Positioning of projection 533 in throughbore 512 and brazing of projection 533 to support bock 520 increases the contact surface area between carrier 510 and cutter element 530, increases the strength of the brazed bond therebetween, and increases the strength of the resistance to relative radial movement of cutter element 530 relative to cutter element carrier 510.

As previously described, in this embodiment, throughbore 219 is not provided, and thus, set screw 217 is not employed to secure cutter element assembly 500 within mating socket 150 of a corresponding blade 141, 142. Rather, in this embodiment, carrier 510 is slidingly disposed within the mating socket 150 as previously described with respect to cutter element assembly 200, and then carrier 510 is brazed to the corresponding blade 141, 142 to secure cutter element assembly 500 to blade 141, 142. In particular, wet brazing filler material is provided within socket 150 between the corresponding blade 141, 142 and cutter element carrier 510, and then allowed to cool and solidify to fixably secure carrier 510, and hence cutter element assembly 500, to the corresponding blade 141, 142. Thus, in this embodiment, the brazing between carrier 510 and the corresponding blade 141, 142 prevents cutter element assembly 500 from exiting socket 150 in blade 141, 142 in a direction generally perpendicular to cutter-supporting surface 144.

In the embodiments of cutter element assemblies 200, 300, 400 previously described, cutter element carrier 210, 310, 410, and more specifically base 211, is slidingly seated in mating socket 150, and then, set screw 217 is threaded through throughbore 219 in support block 220 into counterbore 156 to mechanically and removably secure cutter element assembly 200, 300, 400 to the corresponding blade 141, 142. Thus, engagement of set screw 217 and mating counterbore 256 generally prevent cutter element assembly 200, 300, 400 from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144. However, in other embodiments, alternative mechanisms may be used to prevent the cutter element assembly (e.g., 200, 300, 400) from exiting the corresponding socket (e.g., socket 150) in the blade (e.g., blade 141, 142) in a direction generally perpendicular to the cutter-supporting surface (e.g., cutter-supporting surface 144). For example, referring now to FIGS. 21 and 22, an embodiment of a cutter element assembly 600 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Cutter element assembly 600 includes a cutter element carrier 610 and a cutter element 230 as previously described fixably mounted and secured to carrier 610. Cutter element carrier 610 is the same as cutter element carrier 210 previously described with the exception that cutter element carrier 610 does not include throughbore 219 as cutter element carrier 610 relies on an alternative mechanism to secure cutter element carrier 610 within socket 150 and prevent cutter element carrier 610 from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144.

Referring now to FIGS. 21-23, cutter element carrier 610 includes base 611 and support block 620. Base 611 and support block 620 are the same as base 211 and support block 220, respectively, as previously described, with the exception that throughbore 219 is eliminated (i.e., not included) and a recess 619 (FIG. 21) is provided in blade facing surface 212.

Cutter element 230 is attached to cutter element carrier 510 in the same manner as previously described with respect to cutter element 230 and carrier 210 to form cutter element assembly 600. In this embodiment, cutter element assembly 600 is attached to a corresponding blade 141, 142 in substantially the same manner as previously described with respect to cutter element assembly 200 with the exception that a pin 660 is relied on (instead of set screw 217) to prevent cutter element assembly 600 from exiting socket 150 in blade 141, 142 in a direction generally perpendicular to cutter-supporting surface 144. In particular, and as best shown in FIG. 21, a biasing member 661 is seated in counterbore 156, and then pin 660 is sliding disposed in counterbore and seated on biasing member 661. Biasing member 661 biases or urges pin 660 out of counterbore (i.e., upwardly in FIG. 21). In this embodiment, biasing member 661 is a spring. Cutter element assembly 600 is slidingly advanced into socket 150 in the same manner as previously described with respect to cutter element assembly 200 while pin 660 is urged (against the biasing force of biasing member 661) into counterbore 156. Recess 619 moves into alignment with counterbore 156 and pin 660 as trailing faces 211b, 220b of carrier 620 axially abut, engage, and are flush with rear support surface 153 of socket 150, thereby allowing the biasing force of biasing member 661 to urge the end of pin 660 distal biasing member 661 into mating recess 619 as shown in FIG. 21. As best shown in FIG. 21, pin 661 is partially disposed in both recess 619 and counterbore 156, thereby preventing cutter element assembly 600 from exiting socket 150 in blade 141, 142 in a direction generally perpendicular to cutter-supporting surface 144.

Referring now to FIG. 24, an embodiment of a cutter element assembly 700 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Similar to cutter element assembly 600 previously described, cutter element assembly 700 employs a mechanism other than engagement of set screw 217 and mating counterbore 256 to prevent cutter element assembly 700 from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144. In this embodiment, cutter element assembly 700 includes a cutter element carrier 710 and a cutter element 730 fixably mounted and secured to carrier 710. Cutter element carrier 710 is the same as cutter element carrier 210 previously described with the exception that cutter element carrier 710 does not include throughbore 219 as cutter element carrier 710 relies on an alternative mechanism to secure cutter element carrier 710 within socket 150 and prevent cutter element carrier 710 from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144. More specifically, and as shown in FIGS. 24 and 25, cutter element carrier 710 includes base 711 and support block 720. Base 711 and support block 720 are the same as base 211 and support block 220, respectively, as previously described, with the exception that throughbore 219 is eliminated (i.e., not included). Cutter element 730 is the same as cutter element 230 previously described with the exception that cutter element 730 does not include flats 237b on outer surface 237. Cutter element 730 is attached to cutter element carrier 710 in the same manner as previously described with respect to cutter element 230 and carrier 210 to form cutter element assembly 700.

Referring now to FIGS. 24 and 26, in this embodiment, cutter element assembly 700 is attached to a corresponding blade 141, 142 in substantially the same manner as previously described with respect to cutter element assembly 200 with the exception that set screw 217 is not employed to secure cutter element assembly 700 within mating socket 150 of a corresponding blade 141, 142. Rather, in this embodiment and similar to cutter element assembly 500 previously described, carrier 710 is slidingly disposed within the mating socket 150 as previously described with respect to cutter element assembly 200, and then carrier 710 is brazed to the corresponding blade 141, 142 to secure cutter element assembly 700 to blade 141, 142. In particular, wet brazing filler material is provided within socket 150 between the corresponding blade 141, 142 and cutter element carrier 710, and then allowed to cool and solidify to fixably secure carrier 710, and hence cutter element assembly 700, to the corresponding blade 141, 142. Thus, in this embodiment, the brazing between carrier 710 and the corresponding blade 141, 142 prevents cutter element assembly 700 from exiting socket 150 in blade 141, 142 in a direction generally perpendicular to cutter-supporting surface 144.

Referring now to FIG. 26, the brazing between carrier 710 and the corresponding blade 141, 142 strengthens the bond therebetween to offer the potential for enhanced exposure of cutting face 233. Without being limited by this or any particular theory, the greater the exposure of a cutting face (e.g., cutting face 233), the greater the potential depth-of-cut (DOC) of the corresponding cutter element and rate-of-penetration (ROP) of the corresponding drill bit. In particular, cutting face 233 of each cutter element 730 has a diameter D₂₃₃ and extends to an extension height H₂₃₃ measured perpendicularly from cutter-supporting surface 144 of the corresponding blade 141 to cutting tip 234. As previously described, cutting tip 234 defines the portion or point of cutting face 233 positioned furthest from the cutter-supporting surface 144 of the corresponding blade 141, 142. Due to the strength of the connection between cutter element assembly 700 and the corresponding blade 141 (resulting from both brazing between carrier 710 and the corresponding blade 141, as well as mating geometries of base 711 and socket 150 as previously described), the ratio of the extension height H₂₃₃ of each cutting face 233 to the diameter D₂₃₃ of each cutting face 233 can range from 0.50 to 1.00, alternatively range from 0.60 to 1.00, and alternatively range from 0.80 to 1.00. As comparison, for most conventional cylindrical cutter elements that are directly brazed to a pocket in a blade of a drill bit, the ratio of the extension height of the corresponding cutting face to the diameter of the corresponding cutting face is typically less than 0.50. Thus, embodiments described herein that include both brazing between the carrier (e.g., carrier 710) and the corresponding blade (e.g., blade 141, 142) as well as mating geometries between the base of the carrier (e.g., base 711) and the corresponding socket in the blade (e.g., socket 150) as described herein, offer the potential for increased extension height (e.g., extension height H₂₃₃), increased ratio of extension height to cutting face diameter, increased DOC, and increased ROP.

In the embodiment of cutter element assembly 500 previously described and shown in FIGS. 19 and 20, cutter element 530 includes a substrate 531 and a cutting layer 532 fixably attached and bonded to substrate 531. As with other cutter elements disclosed herein (e.g., cutter element 230 including substrate 231 and cutting layer 232), substrate 531 is typically made of a carbide material such as tungsten carbide and cutting layer 532 is typically made of polycrystalline diamond or other superabrasive material. However, in other embodiments, the substrate made of the carbide material (e.g., substrate 231, 531) may be eliminated such that the entire cutter element is made of the polycrystalline diamond or other superabrasive material. For example, referring now to FIGS. 27 and 28, an embodiment of a cutter element assembly 800 that can be used on drill bit 100 in place of one or more cutter element assemblies 200 is shown. Cutter element assembly 800 includes a cutter element carrier 810 and a cutter element 830 fixably mounted and secured to carrier 810. Cutter element 830 has the same geometry as cutter element 530 previously described with the exception that cutter element 830 does not include a substrate (e.g., substrate 531 is eliminated) such that cutter element 830 is entirely made of polycrystalline diamond or other superabrasive material. In particular, cutter element 830 includes cutting layer 832 and a projection 833 extending therefrom. In this embodiment, projection 833 is a cylindrical member with a central axis coaxially aligned with the central axis of cutting layer 832, which is coaxially aligned with central axis 225 when cutter element assembly 800 is formed (FIG. 27). Cutting layer 832 is the same as cutting layer 532, 232 previously described. Projection 833 is similar to projection 533 previously described but is made of the same material as cutting layer 832 and is integral or monolithically formed with cutting layer 832.

Cutter element carrier 810 is the same as cutter element carrier 510 previously described with the exception that cutter element carrier 810 is a split carrier including a through slit or cut 813. In particular, cutter element carrier 810 includes a base 811 and a support block 820. Base 811 and support block 820 are the same as base 511 and support block 520, respectively, as previously described, with the exception that slit 813 extends axially (relative to axes 225, 215) through base 811 and support block 820 and extends radially (relative to axis 225) from throughbore 512 to blade facing surface 212. In this embodiment, slit 813 is generally disposed in a plane containing axes 215, 225. Slit 813 allow for some resilient flexion between the portions of carrier 810 disposed on opposite lateral sides of slit 813. For example, the portions of carrier 810 on opposite lateral sides of slit 813 can be pushed or urged apart to slightly increase the lateral width of slit 813, and the portions of carrier 810 on opposite lateral sides of slit 813 can be pushed or urged together to slightly decrease the lateral width of slit 813. It should be appreciated that similar to a split ring or C-ring, increasing the lateral width of slit 813 increases the diameter or lateral width of throughbore 512, and decreasing the lateral width of slit 813 decreases the diameter or lateral width of throughbore 512.

Referring still to FIGS. 27 and 28, cutter element 830 is attached to cutter element carrier 810 in a similar manner as previously described with respect to cutter element 530 and carrier 510 to form cutter element assembly 500 with the exception that projection 833 is seated in mating throughbore 512 but is not brazed therein. Rather, in this embodiment, projection 833 is sized, shaped, and positioned to be slidingly received by and mate with throughbore 512. Inclusion of slit 813 and the flexion of carrier 810 enable projection 833 to be fixably secured within throughbore 512 via interference fit when carrier 810 is seated in mating socket 150, which urges the portions of carrier 810 on opposite lateral sides of slit 813 together, thereby decreasing the lateral width of slit 813 and radially compressing support block 820 around and against projection 833. Thus, projection 833 of cutter element 830 is seated in throughbore 512 of carrier 810, and then carrier 810 is slidingly urged into the mating socket 150 as previously described with respect to cutter element assembly 200, which compresses the portions of carrier 810 on opposite lateral sides of slit 813 together, thereby generally closing slit 813 and radially compressing support block 820 around and against projection 833 to secure projection 833 within throughbore 512 via interference fit. Then, carrier 810 is brazed to the corresponding blade 141, 142 to secure cutter element assembly 800 to blade 141, 142. In particular, wet brazing filler material is provided within socket 150 between the corresponding blade 141, 142 and cutter element carrier 810, and then allowed to cool and solidify to fixably secure carrier 810, and hence cutter element assembly 800, to the corresponding blade 141, 142.

In the embodiment of drill bit 100 previously described, cutter element assembly 200 is mechanically coupled to a corresponding blade 141 via engagement of the outer surface of base 211 of cutter element carrier 210 with the mating surfaces of blade 141 defining socket 150 generally prevent cutter element carrier 210 (and hence cutter element assembly 200) from exiting socket 150 in a direction generally perpendicular to cutter-supporting surface 144, and positioning of set screw 217 within throughbore 219 of carrier 210 with its tip positioned in counterbore 156 in blade 141 prevents cutter element assembly 200 from sliding axially (relative to axes 155, 235) out of mating socket 150 via open end 150a at leading side 141a of blade 141. In other embodiments, the cutter element assembly may be mechanically coupled to the corresponding blade via an alternative mechanical mechanism to prevent the cutter element assembly from exiting the mating socket via the open end of the socket along the leading side of the corresponding blade. For example, in other embodiments, a bolt or set screw (e.g., set screw 217) may be positioned in another location while still mechanically coupling the cutter element assembly to the blade while preventing the cutter element assembly from exiting the mating socket via the open end of the socket along the leading side of the corresponding blade.

Referring now to FIGS. 29 to 31, an enlarged view of an exemplary blade 141 of a fixed cutter drill bit and an embodiment of a cutter element assembly 900 mechanically coupled thereto is shown. Although one exemplary primary blade 141 and one cutter element assembly 900 is shown in FIGS. 29 to 31 and will be described, it is to be understood that a plurality of cutter element assemblies 900 may be mounted to the same primary blade 141, one or more other primary blades 141, one or more secondary blades 142, or combinations thereof.

As will be described in more detail below, cutter element assembly 900 includes a cutter element carrier 910 and a cutter element 930 fixably mounted to carrier 910. Cutter element 930 includes a substrate 931 and a cutting layer 932 fixably attached and bonded to substrate 931. Substrate 931 and cutting layer 932 are the same as substrate 231 and cutting layer 232, respectively, as previously described with the exception that flats 237b along outer surface 237 are eliminated.

Primary blade 141 is as previously described, and thus, includes a leading side 141a, a trailing side 141b, and a cutter-supporting surface 144 extending from leading side 141a to trailing side 141b, each as previously described. In addition, blade 141 includes a recess or socket 150′ for receiving cutter element assembly 900, and in particular, receiving mating cutter element carrier 910 of cutter element assembly 900. Similar to socket 150 previously described, socket 150′ extends into the blade 141 from leading side 141a and cutter-supporting surface 144. Thus, each socket 150′ intersects and extends through leading side 141a, cutter-supporting surface 144, and the convex edge between cutter-supporting surface 144 and leading side 141a.

Referring now to FIGS. 29 to 32, socket 150′ has a central axis 155′, a first or open end 150a′ at leading side 141a, and a second or closed end 150b′ opposite end 150a′ and distal the leading side 141a of blade 141. In this embodiment, central axis 155′ is oriented generally parallel to or at an acute angle relative to the cutting direction of the corresponding drill bit (e.g., cutting direction 106 of bit 100) at the radial position of cutter element 930. Open end 150a′ is positioned forward of and leads closed end 150b′ relative to relative to the cutting direction of the bit. Accordingly, open end 150a′ may also be referred to as leading end 150a′ and closed end 150b′ may also be referred to as trailing end 150b′. In this embodiment, closed end 150b′ is defined by a planar surface oriented perpendicular to axis 155′. As shown in FIGS. 31 and 32, an internally threaded counterbore 156′ extends perpendicularly from closed end 150b′ into blade 141.

Referring now to FIG. 32, in this embodiment, socket 150′ is defined by curved, generally teardrop profile projected into blade 141 from leading side 141a and open end 150a′ to trailing end 150b′ in a direction parallel to central axis 155′. Thus, each cross-section of socket 150′ taken in a plane oriented perpendicular to axis 155′ generally has the same size, shape, and tear drop geometry. In this embodiment, socket 150′ is generally symmetric about a reference plane R (illustrated with a dashed line in FIG. 32) oriented perpendicular to a projection P₁₄₄ of cutter-supporting surface 144 across socket 150 and containing central axis 155′ in front view of the blade 141 along axis 155′. However, in other embodiments, the socket (e.g., socket 150′) is not symmetric about a plane (e.g., reference plane R).

Socket 150′ is defined by a continuously curved, smooth surface formed by the surrounding blade 141, generally extending about central axis 155′, oriented parallel to axis 155′, and having laterally spaced ends at cutter-supporting surface 144. The continuously curved surface defining socket 150′ may be described as including a generally concave base surface 151′ distal cutter-supporting surface 144 and extending axially (relative to axis 155′) from open end 150a′ to closed end 150b, and a pair of curved lateral side surfaces 152′ extending from base surface 151′ to cutter-supporting surface 144 and extending axially (relative to axis 155′) from open end 150a to closed end 150b′. Surfaces 151′, 152′ are oriented parallel to central axis 155′, with lateral side surfaces 152′ being disposed on opposite lateral sides of central axis 155′. In this embodiment, each lateral side surface 152′ includes a concave section 152a′ extending from concave base surface 151′ and a convex section 152b′ extending from the concave section 152a′ to cutter supporting surface 144. As will be described in more detail below, cutter element assembly 900 is received into mating socket 150′ with cutter element carrier 910 slidingly engaging surfaces 151′, 152′ defining socket 150′.

Due to the teardrop prismatic geometry of socket 150′ (and in particular the curved geometry of lateral side surfaces 152′ including both convex sections 152b′ extending from cutter-supporting surface 144 and concave sections 152a′ distal cutter-supporting surface 144 and extending from convex sections 152b′), laterally opposed portions 152c′ of lateral side surfaces 152′ generally slope or curve away from each other moving in a direction generally away from cutter-supporting surface 144 toward base surface 151′, and thus, may be referred to as negative draft surfaces. As shown in FIG. 32, such laterally opposed portions 152c′ of side surfaces 152′ are generally located at the transitions between convex sections 152b′ and concave sections 152a′.

Referring still to FIG. 32, socket 150′ has a width W_150′ in front view of the corresponding blade 141 (as viewed perpendicular to leading side 141a generally along central axis 155′ as shown in FIG. 32) measured (i) parallel to the projection P₁₄₄ of cutter-supporting surface 144, and (ii) perpendicular to the reference plane R. As portions 152c′ of lateral side surfaces 152′ generally taper away from each other moving away from cutter-supporting surface 144, the width W_150′ generally increases moving along portions 152c′ away from cutter-supporting surface 144. Stated differently, socket 150′ may be described as having a first width W_150-1′ at a first depth or distance D_150-1′ measured perpendicularly from the projection P₁₄₄ of cutter-supporting surface 144, a second width W_150-2′ at a second depth or distance D_150-2′ measured perpendicularly from the projection P₁₄₄ of cutter-supporting surface 144 that is greater than the first depth D_150-1′, where second width W_150-2′ (at the greater depth D_150-2′) is greater than the first width W_150-1′ (at the lesser depth D_150-1′). Accordingly, similar to socket 150 previously described, socket 150′ may also be described as having a dovetail geometry or shape in a front view of the blade 141. It should be appreciated that such geometry generally resists and/or prevents mating cutter element carrier 910 (and hence cutter element assembly 900) from being pulled or removed from socket 150′ in a direction generally perpendicular to the projection P₁₄₄ of cutter-supporting surface 144 (i.e., upwardly as shown in FIG. 32).

Referring now to FIGS. 33 and 34, as previously described, cutter element assembly 900 includes cutter element carrier 910 and cutter element 930 fixably mounted and secured thereto. Cutter element 930 includes cylindrical substrate 931 and cylindrical hard cutting layer 932 bonded to substrate 931 as previously described.

Cutter element carrier 910 has a first end 910a and a second end 910b opposite end 910a. When cutter element assembly 900 is seated in a mating socket 150′, first end 910a is positioned forward of and leads second end 910b relative to the cutting direction of the corresponding bit. Accordingly, first end 910a may also be referred to as leading end 910a, and second end 910b may also be referred to as trailing end 910b.

Cutter element carrier 910 has a monolithic body including a base 911 extending from leading end 910a to trailing end 910b and a cutter element support block 920 extending from base 911 at trailing end 910b. As a result, base 911 and support block 920 define a receptacle or pocket 918 extending axially from leading end 910a of cutter element carrier 910 to support block 920. Pocket 918 is sized to receive and mate with cutter element 930.

Referring still to FIGS. 33 and 34, base 911 has a central or longitudinal axis 915, a leading face 911a at end 910a, and a trailing face 911b at end 910b. As best shown in FIG. 34, in this embodiment, a cylindrical counterbore 919a extends axially relative to axis 915 from leading face 911a and a cylindrical throughbore 919b extends axially relative to axis 915 from counterbore 919a to trailing face 911b. Counterbore 919a and throughbore 919b are coaxially aligned with counterbore 919a having a diameter greater than the diameter of throughbore 919b. As a result, an annular shoulder 919c extends radially inward relative to axis 915 from counterbore 919a to throughbore 919b.

As best shown in FIG. 30, the outer surface of base 911 is sized and shaped to mate with a corresponding socket 150′ and slidingly engage surfaces 151′, 152′ defining socket 150′. In other words, base 911 has a geometry that is the same as socket 150′. Namely, base 911 has a generally teardrop profile extending from leading face 911a to trailing face 911b in a direction parallel to central axis 915. Thus, each cross-section of base 911 taken in a plane oriented perpendicular to axis 915 generally has the same size, shape, and teardrop geometry. As previously described, in this embodiment, socket 150′ is symmetric about the reference plane R in front view of the blade 141 (FIG. 32), and thus, in this embodiment, mating base 911 is also symmetric about the reference plane R when base 911 is seated in socket 150′. However, in other embodiments, the base of the cutter element carrier (e.g., base 911 of carrier 910) may not be symmetric about a reference plane (e.g., reference plane R).

Base 911 has an outer surface including a blade facing surface 912 extending axially (relative to axis 915) from leading end 910a to trailing end 910b, a pair of lateral side surfaces 913 extending axially (relative to axis 915) from leading face 911a to trailing face 911b, and a cutter element facing surface 914 extending axially (relative to axis 915) from leading face 911a to support block 920. Blade facing surface 912 and cutter element facing surface 914 are radially spaced apart (relative to axis 915), and each extends laterally (relative to axis 915) between lateral side surfaces 913. Thus, lateral side surfaces 913 are disposed along opposite lateral sides of blade facing surface 912 and extend from blade facing surface 912 to cutter element facing surface 914 along pocket 918, and extend from blade facing surface 912 to support block 920 rearward of pocket 918.

In this embodiment, leading face 911a is defined by a planar surface and trailing face 911b is defined by planar surface oriented perpendicular to central axis 915, blade facing surface 912 is a generally cylindrical convex surface oriented parallel to central axis 915, and lateral side surfaces 913 are laterally spaced curved surfaces (on opposite sides of axis 915) oriented parallel to central axis 915. As best shown in FIGS. 29 and 30, the outer surface of base 911 is sized and shaped to mate with a corresponding socket 150′ and slidingly engage surfaces 151′, 152′ defining socket 150′. Thus, based 911 has a geometry that is generally the same as socket 150′. More specifically, blade facing surface 912 of carrier 910 slidingly engages and is flush with mating base surface 151′ of socket 150′, and lateral side surfaces 913 of carrier 910 slidingly engage and are flush with mating lateral side surfaces 152′ of socket 150′.

Referring again to FIGS. 33 and 34, in this embodiment, cutter element facing surface 914 is a concave cylindrical surface extending axially from leading face 911a to support block 920. Surface 914 extends laterally between side surfaces 913. The radially outer cylindrical surface 237a of cutter element 930 mates and slidingly engages cylindrical surface 914, and thus, cylindrical surface 914 has a radius of curvature that is the same or substantially the same as the outer radius of cylindrical surface 237a of cutter element 930, and further, cylindrical surface 914 may also be referred to as a seat for cutter element 930. In this embodiment, blade facing surface 912 and each lateral side surface 913 are smoothly and continuously curved.

Referring still to FIGS. 33 and 34, support block 920 has a central axis 925 oriented at an acute angle relative to axis 915 in side view as shown in FIG. 34, and is coaxially aligned with axis 235 of substrate 931. In addition, support block 920 has an outer surface including a leading face 920a facing pocket 918, a trailing face 920b at end 910b, and a convex cylindrical radially outer surface 921 extending axially (relative to axis 925) from leading face 920a to trailing face 920b. In this embodiment, leading face 920a is defined by planar surfaces oriented perpendicular to central axis 925 and trailing face 920b is defined by a planar surface oriented at an acute angle relative to central axis 925.

As previously described, blade facing surface 912 of carrier 910 slidingly engages and is flush with mating base surface 151′ of socket 150′, and lateral side surfaces 913 of carrier 910 slidingly engage and are flush with mating lateral side surfaces 152′ of socket 150′. Accordingly, as shown in FIG. 30, base 911 may be described as having a width W₉₁₁ measured perpendicularly to a reference plane containing axes 915, 925 that generally increases moving away from cutter element facing surface 914 toward blade-facing surface 912. Stated differently, and similar to socket 150′, base 911 may be described as having a first width W₉₁₁ at a first distance from cutter element facing surface 914 (measured in the reference plane containing axes 915, 925) that is less than a second width W₉₁₁ of base 911 at a second distance from cutter element facing surface 914 (also measured in the reference plane containing axes 915, 925), wherein the second width W₉₁₁ (at the greater second distance) is greater than the first width W₉₁₁ (at the lesser first distance). Thus, similar to base 211 previously described, base 911 may also be described as having a dovetail geometry or shape in a front view of the cutter element carrier 910.

Cutter element carrier 910 can be made of a material suitable for a particular application and/or to enhance durability of cutter element assembly 900. For example, carrier 910 (or portion thereof) can be made of a high strength material, a high abrasion resistant material, a corrosion resistant material, or combinations thereof. Examples of suitable materials for carrier 910 include, without limitation, steel, super alloy, cemented carbide, matrix or similar high-performance or hard material, Stellite, Inconel, Monel, metal alloys with niobium or nickel, or combinations thereof (e.g., steel, carbide, steel, hardfacing, superalloy, and carbide).

Referring again to FIGS. 33 and 34, cutter element 930 is positioned in mating pocket 918 of cutter element carrier 910 and fixably secured thereto to form cutter element assembly 900. In particular, to secure cutter element 930 to carrier 910 within mating pocket 918, cutter element 930 is disposed within pocket 918 with axes 925, 235 generally coaxially aligned, outer cylindrical surface 237a of cutter element 930 adjacent mating cylindrical surface 914 of base 911, and planar surface 236 at trailing end 230b of cutter element 930 adjacent leading face 920a of support block 920. Next, melted or “wet” brazing filler material is applied between the foregoing adjacent, mating surfaces and flows therebetween via capillary action. Cutter element 930 may be rotated relative to carrier 910 during the process to allow maximal dispersion of the wet brazing filler material between (i) mating cylindrical surfaces 914, 237a; and (ii) mating planar surface 236 and leading face 920a. Surface area coverage of the wet brazing material can be visually confirmed as cutter element 930 is rotated by viewing outer cylindrical surface 237a and planar surface 236 of cutter element 930. It should be appreciated that planar surface 236 at trailing end 230b of cutter element 930 adjacent leading face 920a of support block 920 may move in and out of flush contact as cutter element 930 is rotated. However, as the brazing process is being finished, planar surface 236 is urged into flush contact with leading face 920a. As the brazing filler material cools and solidifies, cutter element 930 is fixably secured to carrier 910 with mating surfaces 914, 237a attached flush together, and planar surface 236 and leading face 920a attached flush together.

It should be appreciated that cutter element 930 can be removed from pocket 918 of carrier 910 for maintenance, repair, or replacement by heating carrier 910 and/or cutter element 930 to melt the brazing therebetween, and then rotating and pulling cutter element 930 from pocket 918. These processes for attaching cutter element 930 to carrier 910, removing cutter element 930 from carrier 910, and rotating cutter element 930 relative to carrier 910 are preferably performed without carrier 910 attached to blade 141, which offers the potential to speed the process by eliminating the need to heat and cool the entire bit, as well as enable the brazing to be done in a controlled lab environment separate from the bit. To minimize exposure of cutter element 930 to excess heat, carrier 910 can be heated and/or a heat sink applied to cutter element 930.

Referring now to FIGS. 29 to 31, once formed as described above, cutter element assembly 900 is fixably and mechanically secured to blade 141 within a corresponding socket 150′. In particular, cutter element assembly 900 is aligned with a corresponding socket 150′ of blade 141 such that central axis 915 of base 911 is generally parallel to central axis 155′ of socket 150′ with trailing end 910b of carrier 910 proximal open end 150a′ of socket 150′. Next, cutter element assembly 900 is axially advanced (relative to axes 155′, 915) into socket 150′ with base 911 slidingly disposed in mating socket 150′. More specifically, cutter element assembly 900 is axially advanced (relative to axes 155′, 915) into socket 150′ with blade facing surface 912 of carrier 910 slidingly engaging mating base surface 151′ of socket 150 and lateral side surfaces 913 of carrier 910 slidingly engaging mating lateral side surfaces 152′ of socket 150′ until trailing faces 911b, 920b axially abut, engage, and are flush with trailing end 150b′ of socket 150′. With cutter element assembly 900 fully seated in socket 150′, a bolt 917 (FIG. 31) is coaxially advanced through counterbore 919a and throughbore 919b, and then threaded into mating throughbore 156′ in blade 141 until the head of bolt 917 is seated against annular shoulder 919c as shown in FIG. 31.

In the manner described, cutter element assembly 900 is fixably and mechanically secured to the corresponding blade 141. It should be appreciated that bolt 917 prevents cutter element assembly 900 from sliding axially (relative to axes 155′, 915) out of mating socket 150′ via open end 150a′, while mating engagement of base 911 and the surfaces defining socket 150′ prevent base 911 (and hence, cutter element assembly 900) from sliding out of socket 150′ perpendicularly to cutter-supporting surface 144, as well as prevents cutter element assembly 900 from rotating relative to blade 141. Thus, cutter element assembly 900 is fixably attached to blade 141 such that it cannot move rotationally or translationally relative to blade 141. However, cutter element assembly 900 can be removed from blade 141 for repair, maintenance, or replacement by performing the foregoing steps in reverse order. Thus, cutter element assembly 900 may be described as being mechanically attached to blade 141 and removably attached to blade 141.

In the manner described, embodiments of cutter element assemblies (e.g., cutter element assemblies 200, 400, 500, 600, 700, 800, 900) and associated cutter element carriers (e.g., carriers 210, 310, 410, 510, 610, 710, 810, 910) can be fixably and removably secured to blades of a drill bit (e.g., blades 141, 142). In some embodiments, the cutter element assemblies and associated carriers are mechanically and removably mounted in mating sockets (e.g., sockets 150) in the blade and then maintained therein (within the socket) via a removable attachment mechanism such as a set, biased pin, bolt, or the like. The cutter element assemblies and associated carriers can be removed by performing the mounting steps in reverse. If a particular cutter element assembly, cutter element, or carrier is excessively worn, the cutter element assembly can be removed from the drill bit for repair, maintenance, or replacement of the entire cutter element assembly or component thereof (e.g., carrier and/or cutter element), and a new, repaired, or maintained cutter element assembly (or component thereof) can be mounted to the blade.

In some embodiments disclosed herein, the cutter element assemblies and associated carriers are also brazed to the corresponding blade within the mating socket. In general, such brazing can be employed in connection with any of the embodiments disclosed herein to strengthen the connection between the cutter element carrier and the corresponding blade. Moreover, although brazing is disclosed as one option for enhancing the strength of the connection between the cutter element carrier and the corresponding blade, adhesion means other than brazing such as Locktite®, epoxy, or the like can be employed bond the cutter element carrier to the corresponding blade.

In some embodiments, the cutter element (e.g., cutter element 230, 430, 530, 730, 930) is disposed in a mating pocket of the carrier (e.g., pocket 218, 918) and brazed to the carrier. The individual cutter elements can be brazed to corresponding carriers (prior to attachment to the bit) in a controlled lab environment. In some embodiments, an automated system can be used to quick heat the cutter element to a precise temperature and then drop the temperature back down quickly. These options avoid the pitfalls associated with heating the entire bit or individual cutter elements for extended periods of time. In such embodiments, the cutter element can be rotated relative to the carrier and/or removed from the carrier during repair, maintenance, or replacement operations by heating the cutter element and/or the carrier to melt the brazing. Such may be done while the carrier is mounted to the blade or when the carrier is not mounted to the blade.

While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. In addition, it should be appreciated that features disclosed in connection with any one or more embodiment may be used in connection with any one or more other embodiments. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

Each and every claim is incorporated into the specification as an aspect of the present disclosure. Thus, the claims are a further description and are an addition to the aspects of the present disclosure. The discussion of a reference herein is not an admission that it is prior art to the presently disclosed subject matter, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural or other details supplementary to those set forth herein. In the event of conflict, the present specification, including definitions, is intended to control.