EXPLOSIVE BREACHING TOOL

Description

STATEMENT OF GOVERNMENT SUPPORT

The United States Government has rights in this invention pursuant to Contract No. DE-AC07-05ID14517 between the U.S. Department of Energy (DOE) and Battelle Energy Alliance, LLC.

FIELD OF THE INVENTION

Embodiments of the invention relate to an explosive breaching tool for a bar grating barricade. More specifically, embodiments of the invention relate to an explosive breaching tool having a flexible polymer casing that positions explosive charges between flats of the bar grating.

BACKGROUND

Bar grating, also known as turbine grating, is an extremely strong and durable load bearing product for use in industrial or architectural applications. Bar grating often appears on catwalks, platforms, factory floors, stair tread, and railing infill panels. Bar grating consists of a series of bearing bars, or flats, spaced apart and welded, press-locked, or swage-locked together with perpendicular cross bars. The flats are generally uniformly spaced with a distance typically between 3/4 inches to 2 inches apart. Bar grating can be manufactured from a variety of materials including stainless steel, steel, aluminum, fiberglass, and Iron. Bar grating is commonly used to support loads for pedestrian and vehicle traffic and the open design of the flats allows air, light, and debris to flow through.

Bar grating can also be used as a barrier or fence with the flats positioned horizontally and vertical cross bars or rods holding the flats together. In some applications, a particular advantage of using bar grating for fencing is the ability to see through the fence. The flats typically have a uniform width of from 1/8 inch to 2 inches, and a wider flat can increase the strength of the barrier. However, breaching the barrier can be difficult particularly with wide and thick flats made from strong materials. Breaching the barrier with explosives is often a necessity in military or law enforcement application where a hostile threat requires breaching the barrier quickly. The open design and the strength of the flats in the horizontal direction can reduce the impact of an explosive charge used in a breaching attempt.

There are generally no explosive products that have been successful at breaching typical steel bar grating at low net explosive weights. Typical explosive breach attempts result in the horizontal flats being pushed together or closing up in a manner comparable to a venetian blind. Linear shaped charge and explosive cutting tape may cut partially into the horizontal flats but fail to cut through the flats. Typical bulk charges result in the flats being crushed together but fail to breach the bar grating. Larger charges can knock down the barrier but present unacceptable blast overpressure exposure. Other breaching methods like torch cutting increase the amount of time operators are exposed to hostile threats. A large-scale industrial machine uses alternating steel cutters to mechanically (non-explosively) shear grating, but the machine is not easily field-deployable.

Therefore, it would be desirable to have an explosively-driven product tailored specifically to breaching bar grating. In addition, tailoring an explosive breaching tool to various sizes of bar grating could increase the effectiveness of the breaching attempt. Thus, there is a need for a customizable explosive tool that is rapidly deployable and keeps net explosive weights to a minimum to reduce user exposure to blast overpressure.

SUMMARY

In accordance with one aspect of the invention, an explosive breaching tool for steel bar grating includes a flexible polymer casing comprising a plurality of explosive charge mountings in a zipper configuration and a plurality of explosive charges positioned in the explosive charge mountings.

In accordance with another aspect of the invention, a casing for an explosive device includes a plate having a plurality of openings and a plurality of sleeves stacked in a first direction extending from the plurality of openings. Adjacent sleeves of the plurality of sleeves belong to a different one of a first line of sleeves and a second line of sleeves that are displaced from each other in a second direction perpendicular to the first direction.

In accordance with yet another aspect of the invention, a method of breaching steel bar grating includes forming an explosive breaching tool for steel bar grating via additive manufacturing, the explosive breaching tool comprising a flexible polymer casing comprising a plurality of explosive charge mountings in a zipper configuration. The method further includes positioning a plurality of explosive charges in the explosive charge mountings, affixing the explosive breaching tool on the steel bar grating by placing the explosive charges between flats of the steel bar grating with adjacent explosive charges on opposite sides of a respective flat, and initiating the explosive charges to create explosive shear across the flats.

These and other advantages and features of the present invention will be more readily understood from the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention together with the above and other objects and advantages will be best understood from the following detailed description of the preferred embodiment of the invention shown in the accompanying drawings, wherein:

FIG. 1 depicts an explosive breaching tool mounted in steel bar grating, according to embodiments of the invention.

FIG. 2 is an exploded view of the explosive breaching tool of FIG. 1, according to embodiments of the invention.

FIG. 3 is a perspective view of the explosive breaching tool of FIG. 1, according to embodiments of the invention.

FIG. 4 is a side view of a casing of the explosive breaching tool of FIG. 1, according to embodiments of the invention.

FIG. 5 depicts a pair of adjacent explosive charge mountings of a casing of the explosive breaching tool of FIG. 1 shown from sides of the explosive charge mountings that contact bar grating flats, according to embodiments of the invention.

FIG. 6 is a flow chart of a process for breaching bar grating using an explosive breaching tool, according to embodiments of the invention.

DETAILED DESCRIPTION

The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

One or more embodiments relates to an explosive breaching tool for breaching bar grating barriers. However, embodiments of the invention are equally applicable to breaching other barriers. While the invention is described with respect to a casing having explosive charge mountings that position explosive charges between flats of bar grating, embodiments of the invention contemplate explosive charge mountings positionable between portions of a barrier other than bar grating flats.

Referring now to FIG. 1, an explosive breaching tool 30 mounted in bar grating 32, also referred to as turbine grating, is shown, according to embodiments of the invention. The explosive breaching tool 30 comprises a flexible polymer casing 34 used to hold high explosives in a position to breach bar grating 32 (for example, steel bar grating). Bar grating 32 used as a barrier often includes a series of flats 38 positioned horizontally and held together with vertical reinforcement bars 40 extending through the flats 38. While a portion of the bar grating 32 is shown in FIG. 1, additional reinforcement bars 40 would connect the flats 38 in embodiments of the invention. The explosive breaching tool 30 includes a zipper-like configuration 42 that holds alternating small explosive charges between the flats 38. The explosive breaching tool 30 can be rapidly deployed on the bar grating 32, and upon detonation, the alternating charges create explosive shear points that breach the grating.

The explosive breaching tool 30 includes a flexible polymer casing 34 including a plate 44 having a plurality of openings 46 and a plurality of explosive charge mountings 36 (also referred to as sleeves) for the explosive charges on the plate 44 in a zipper-like configuration 42. The zipper configuration 42 positions the explosive charge mountings 36 between flats 38 of the steel bar grating 32 with adjacent explosive charge mountings 36 on opposite sides of a respective flat. The zipper configuration 42 positions adjacent explosive charge mountings 36 displaced from each other in a direction along the flat 38 to create an explosive shear across the flat.

Due to the zipper configuration 42, the explosive charges in the explosive charge mountings 36 attack the flats 38 from the top and bottom of the flat 38 using colliding shockwaves resulting from the alternating configuration of the small explosive charges along the flat. The colliding shockwaves effectively shear the flats 38 to breach the bar grating 32 barricade. The explosive breaching tool 30 can be used by law enforcement, military, or other response teams needing a rapidly deployable tool for breaching bar grating 32 used as a barrier while keeping net explosive weight to a minimum. The explosive breaching tool 30 could also be used by industry explosive demolition contractors to cut bar grating 32 used in construction.

Referring now to FIG. 2, an exploded view of the explosive breaching tool 30 is shown, according to embodiments of the invention. The explosive breaching tool 30 includes a flexible polymer casing 34 having a plate 44 with a plurality of openings 46 and a plurality of explosive charge mountings 36 extending from the openings 46. Explosive charges 39 are inserted in the explosive charge mountings 36 and the explosive charge mountings 36 are covered with sheet explosive 48. Heavy-duty tape 49 may be applied over the sheet explosive 48 to hold the sheet explosive 48 and the explosive charges 39 in the casing 34.

According to embodiments of the invention, the outer portion of both the casing 34 and the explosive charges 39 are angled. That is, the outer side 52 of the explosive charge mountings 36 extend from the plate 44 at an angle toward an inner portion of the casing 34, with the explosive charges 39 having a geometry matching the explosive charge mountings 36. The angled sides 53 of the explosive charges 39 align explosive force in a direction to ensure maximum shearing force across the flats 38 (FIG. 1) and promotes the formation and focusing of explosive Mach Stems. The angled sides 53 also reduce the net explosive weight without impairing the shearing effect of the explosive. The opposing sides 55 of the explosive charge mountings 36 and the opposing sides 54 of the explosive charges 39 extend perpendicular from the plate 44, according to embodiments of the invention.

According to embodiments of the invention, the casing 34 can be formed using additive manufacturing. For example, the casing 34 may be 3D printed using a flexible polymer 56 that is non-reactive with standard military and commercial plastic explosives (e.g. C4 explosives). The casing 34 could be molded in silicone or other suitable flexible materials rather than being 3D printed. For example, the casing 34 could be a flexible thermoplastic polyurethane or silicon molded casing 34. However, if a mission-specific casing 34 is desired (e.g. cutting bar grating 32 (FIG. 1) of a particular size and thickness), additive manufacturing offers the flexibility to tailor the product to the mission. The use of additive manufacturing to create unique and more effective configurations for the breaching charges provides significant advantages for the tactical breaching community. For example, the tactical breaching community desires a reduction in blast overpressure exposure to reduce injuries and prevent traumatic brain injury. Blast overpressure exposure can be reduced using breaching tools 30 that are designed to be more effective with less explosive.

Using additive manufacturing to form the casing 34 allows for optimizing the explosive weight, type, and deployment configuration for a desired application. The explosive charges 39 may comprise RDX-based explosives 60 (e.g. C-4 or C-3 detasheet). According to embodiments of the invention, the explosive charges 39 may include hand-packed RDX plastic explosive. Alternatively, an HMX-based explosive 64 (FIG. 5) including PBXN-9 could reduce the size requirements of the breaching tool 30 as well as the net explosive weight while maintaining or improving the effectiveness of the breaching tool 30. The sheet explosive 48 may include 3 mm RDX sheet explosive to detonate each of the individual explosive charges 39. The sheet explosive 48 is coupled to a remotely operated detonator cord 65.

Referring no to FIG. 3, a perspective view of the explosive breaching tool 30 is shown, according to embodiments of the invention. The sleeves 36 are spaced apart from each other to sandwich a steel bar grating flat 38 (FIG. 1) between the sleeves 36. The sleeves 36 may have a 0.1, 0.2, 0.3, 0.4, or 0.5 inch space therebetween for a steel bar grating flat 38 (FIG. 1). However, the sleeves 36 may be spaced apart from each other according to the desired application and the spacing may be larger for other types of barriers (e.g. 0.75, 1, 1.25, 1.5 inches, etc.). The sleeves 36 are formed from a thin wall of flexible material 56 which may include flexible thermoplastic polyurethane formed using additive manufacturing or they could be molded from silicone. The sleeves 36 may have a thickness of 0.05, 0.01, 0.15, 0.2, or 0.25 inches, or any suitable thickness. Each sleeve 36 may be 3D printed with the plate 44.

The zipper configuration 42 includes a plurality of sleeves 36 stacked in a first direction 64 extending from the openings 46 in the plate 44. Adjacent sleeves 36 belong to a different one of a first line of sleeves 66 and a second line of sleeves 68 that are displaced from each other in a second direction 70 perpendicular to the first direction 64. The first and second lines of sleeves 66, 68 are displaced from each other in the second direction 70 such that explosive charges positioned in adjacent sleeves 36 create explosive shear across the respective steel bar grating flat 38 (FIG. 1). For example, the displaced distance 71 might be any suitable distance in tenth of an inch increments from 0.1 inches to 2 inches or more. Each of the sleeves 36 has an inner side 55 positioned on a side thereof toward an inward direction of the casing 34. The zipper configuration 42 positions adjacent sleeves 36 along the flats 38 (FIG. 1) such that the respective inner sides 55 face opposing directions. According to embodiments of the invention, the inner sides 55 of each of the sleeves 36 are planar or substantially planar to maximize explosive shear. In some embodiments of the invention, offsetting the explosive charges with a gap therebetween may reduce the maximum shearing pressure and potentially result in bent flats rather than breaching the flats. In some embodiments of the invention, the sleeves 36 position the explosive charges such that they do not overlap in the second direction 70 to prevent the explosive force above and below the flats from balancing each other and reducing the shearing force.

According to embodiments of the invention, each sleeve 36 includes first and second opposing surfaces 72, 74 extending perpendicular from the plate 44 and third and fourth opposing surfaces 52, 55 each connecting the first and second opposing surfaces 72, 74. Each sleeve 36 has a rounded end 80 opposite the plate 44 extending tangentially from the first surface 72 and the second surface 74. The rounded end allows the explosive charge to easily slide in between two flats 38 (FIG. 1) of the steel bar grating 32 (FIG. 1).

The third surface 52 is positioned on a side of the sleeve 36 facing an outward direction of the casing 34 providing an outer side of the sleeve while the fourth surface 55 is positioned on a side of the sleeve 36 facing an inward direction of the casing 34 providing the inner side of the sleeve. The third surface 52 extends from the plate 44 at an inclined angle. The fourth surface 55 extends perpendicular to the plate 44 but could extend from the plate 44 at an incline angle. According to embodiments of the invention, the first and second surfaces 72, 74 are symmetrical with one end mounted flush with the third surface 52 and the opposing end overhanging the fourth surface 55. A portion of the first surface 72 and the second surface 74 may extend past the fourth surface 55 creating an edge 82, 84 inclined to the back plate 44. The inclined edges 82, 84 improves the structural integrity of the sleeve 36.

Referring now to FIG. 4 a side view of the casing 34 is shown, according to an embodiment of the invention. FIG. 4 shows six explosive charge mountings/sleeves 36 stacked in a zipper configuration 42. However, the casing 34 could include any suitable number of sleeves 36 (for example, any suitable integer number of 2 to 36 sleeves or more). Each sleeve 36 is shown with the first and second surfaces 72, 74 extending perpendicular from the plate 44 and coupled together with a rounded surface 80 forming D-shaped cross section 86. The rounded surface 80 can easily slide in between two steel bar grating flats 38 (FIG. 1).

For example, the bar grating 32 (FIG. 1) may consist of horizontal steel flats 38 (FIG. 1) spaced approximately 1 inch apart and the rounded surface 80 may slide between the flats. According to an embodiment of the invention, the sleeves 36 have a length 73 approximately 1.75 inches extending from an open end at the plate 44 to a closed end 80 having approximately a 0.5 inch radius. The first and second surfaces 72, 74 may have a one-inch width at the end adjacent the curved surface 80 and a larger width (e.g. 1.25, 1.5, 1.75, or 2 inches, etc.) at the end adjacent the plate 44. In an alternative embodiment, the sleeves 36 have approximately a one-inch square opening adjacent the plate 44 for receiving an explosive charge extending through a corresponding opening in the plate 44.

According to embodiments of the invention, adjacent sleeves 36 are spaced approximately 0.2 inches apart. However, they could be spaced any suitable distance, for example, 0.1, 0.15, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 inches apart. According to embodiments of the invention, a design that holds the explosives closely to the flats can prove 100% effective in shearing the bar grating. Thus, a steel bar grating 32 (FIG. 1) can be measured so that a flexible thermoplastic polyurethane casing 34 can be printed with dimensions that facilitate effective and rapid deployment on a barrier made of the steel bar grating 32 (FIG. 1). FIG. 4 shows six sleeves 36 positioned along a casing having a length 75 of 7 inches, according to embodiments of the invention. However, casings having a length of up to 36 inches are contemplated in other embodiments.

Referring now to FIG. 5, a side view of a pair of adjacent explosive charge mountings/sleeves 36 of the casing 34 (FIG. 4) is shown, according to embodiments of the invention. As referred to above, the first surface 72 is generally parallel to the second surface 74 and coupled via a curved surface 80. The curved surfaces 80 can be easily inserted between two flats 38 of steel bar grating 32 of FIG. 1. As the explosive charge mounting 36 is pushed between two flats 38, the first and the second surfaces 72, 74 of FIG. 5 maintain a close fit with the flats to increase blast pressure against the flat. The first and second surfaces 72, 74 have a wider end 88 that couples to the plate 44 and tapers to a shorter end 90 at the curved surface 80, according to embodiments of the invention. The third and fourth surface 52, 55 connect the first and second surfaces 72, 74 forming portions of the sleeve 36. The third surface 52 couples to the edge of the first and second surfaces 72, 74 and extends from the plate 44 at an acute angle 92, according to embodiments of the invention. The fourth surface 55 extends perpendicular from the plate 44 and the first and second surface 72, 74 cantilever over the fourth surface 55, according to embodiments of the invention. An explosive charge 39 (FIG. 2) having a geometry corresponding to the explosive charge mounting 36 is inserted into each of the explosive charge mountings 36.

Referring now to FIG. 6, with continued reference back to FIGS. 1-3, a process 100 for breaching steel bar grating 32 using the explosive breaching tool 30 is shown, according to an embodiment of the invention. The process begins at STEP 102 by forming an explosive breaching tool 30 for steel bar grating 32 via additive manufacturing, the explosive breaching tool 30 comprises a flexible polymer casing 34 comprising a plurality of explosive charge mountings 36 in a zipper configuration 42. Forming the explosive breaching tool 30 for steel bar grating 32 via additive manufacturing comprises forming a thermoplastic plate 44 having a plurality of openings 46 spaced apart according to the thickness of the flats 38, and forming the plurality of explosive charge mountings 36 as a plurality of thermoplastic sleeves 36 stacked in a first direction 64 and extending from the plurality of openings 46. Adjacent thermoplastic sleeves 36 of the plurality of thermoplastic sleeves 36 belonging to a different one of a first line of sleeves 66 and a second line of sleeves 68 that are displaced in a second direction 70 perpendicular to the first direction 64.

The process continues at STEP 104 by positioning a plurality of explosive charges 39 in the explosive charge mountings 36. Positioning the plurality of explosive charges 39 in the explosive charge mountings 36 includes placing a C4, C3, or PBX explosive charge in each of the explosive charge mountings 36, covering the explosive charges 39 with a sheet explosive 48, and operatively connecting the sheet explosive 48 to a remotely operated detonator 65.

The process continues at STEP 106 by affixing the explosive breaching tool 30 on the steel bar grating 32 by placing the explosive charges 39 between flats 38 of the steel bar grating 32. Adjacent explosive charges 39 are positioned on opposite sides of a respective flat 38. The explosive breaching tool 30 may be manually pushed into the steel bar grating 32 with each flat 38 holding the explosive charge mountings 36. The process concludes at STEP 108 by initiating the explosive charges 39 to create explosive shear across the flats 38. The explosive charges 39 may be coupled to a detonator cord 65 that can be initiated remotely from the steel bar grating 32 for safety of the operator. The explosive shears rupture the flats 38 to breach the steel bar grating 32.

Users of the explosive breaching tool 30 may include military or law enforcement explosive breachers. Mission outcomes are typically vital to national and homeland security and breaching teams often use specialized tools. While breaching tools are purchased monthly to annually for training and application, the ability to manufacture the explosive breaching tool 30 as needed via 3D printing offers convenience, adaptability, and ensures supply availability. Other users include educational, scientific, and industrial explosives organizations (e.g. national laboratories and explosives demolition contractors).

Beneficially, embodiments of the invention provide an explosive breaching tool 30 for breaching steel and other bar grating 32. The explosive breaching tool 30 can be quickly and manually deployed on a steel bar grating 32 barrier, is customizable and limits the amount of required explosives reducing user exposure to blast overpressure. The explosive breaching tool 30 may be customized to fit on flats 38 of the bar grating 32 that are 3/16 inch thick and 1¼ inch wide. The explosive breaching tool 30 can be 3D printed out of flexible polymer 56 for ease of installation on the steel bar grating 32. An operator can initiate the explosive charges 39 from a remote location and breach the barrier with explosive shear across each flat 38 of the bar grating 32. Two or more explosive breaching tools 30 can be spaced apart on a section of bar grating to explosively cut the section from a bar grating barrier.

Therefore, according to one embodiment of the invention, an explosive breaching tool for steel bar grating includes a flexible polymer casing comprising a plurality of explosive charge mountings in a zipper configuration and a plurality of explosive charges positioned in the explosive charge mountings.

According to another embodiment of the invention, a casing for an explosive device includes a plate having a plurality of openings and a plurality of sleeves stacked in a first direction extending from the plurality of openings. Adjacent sleeves of the plurality of sleeves belong to a different one of a first line of sleeves and a second line of sleeves that are displaced from each other in a second direction perpendicular to the first direction.

According to yet another embodiment of the invention, a method of breaching steel bar grating includes forming an explosive breaching tool for steel bar grating via additive manufacturing, the explosive breaching tool comprising a flexible polymer casing comprising a plurality of explosive charge mountings in a zipper configuration. The method further includes positioning a plurality of explosive charges in the explosive charge mountings, affixing the explosive breaching tool on the steel bar grating by placing the explosive charges between flats of the steel bar grating with adjacent explosive charges on opposite sides of a respective flat, and initiating the explosive charges to create explosive shear across the flats.

Having described the basic concept of the embodiments, it will be apparent to those skilled in the art that the foregoing detailed disclosure is intended to be presented by way of example. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations and various improvements of the subject matter described and claimed are considered to be within the scope of the spirited embodiments as recited in the appended claims. Additionally, the recited order of the elements or sequences, or the use of numbers, letters or other designations therefor, is not intended to limit the claimed processes to any order except as may be specified. All ranges disclosed herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof. Any listed range is easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as up to, at least, greater than, less than, and the like refer to ranges which are subsequently broken down into sub-ranges as discussed above. As utilized herein, the terms “about,” “substantially,” and other similar terms are intended to have a broad meaning in conjunction with the common and accepted usage by those having ordinary skill in the art to which the subject matter of this disclosure pertains. As utilized herein, the term “approximately equal to” shall carry the meaning of being within 15, 10, 5, 4, 3, 2, or 1 percent of the subject measurement, item, unit, or concentration, with preference given to the percent variance. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the exact numerical ranges provided. Accordingly, the embodiments are limited only by the following claims and equivalents thereto. All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication or patent document were so individually denoted.

All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

One skilled in the art will also readily recognize that where members are grouped together in a common manner, such as in a Markush group, the present invention encompasses not only the entire group listed as a whole, but each member of the group individually and all possible subgroups of the main group. Accordingly, for all purposes, the present invention encompasses not only the main group, but also the main group absent one or more of the group members. The present invention also envisages the explicit exclusion of one or more of any of the group members in the claimed invention.