PROTECTIVE ELEMENT FOR AN ELECTRIC POWER TOOL

Description

This nonprovisional application claims priority under 35 U.S.C. § 119(a) to European Patent Application No. 24154970.8, which was filed on Jan. 31, 2024, and which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a protective element as an additional shroud for the guard of a disk-shaped tool of an electric power tool, in particular an angle grinder, wherein the protective element is configured to be captively and reversibly connectable to the guard and to at least partially cover the tool. The invention also relates to a method for producing the protective element, and to an electric power tool equipped with this protective element.

Description of the Background Art

As a standard feature, most angle grinders have a guard that permits safe grinding with the disk-shaped tool. But when the tool is to be used for cutting by using the edge instead of the flat side, it is important to supplement the guard with an additional element in order to protect the user. The IEC 62841-2-3 standard for angle grinders specifies that they must provide sufficient protection both for grinding and for cutting. For this reason, it is common practice to provide an additional protective element for optional connection to the guard.

The guard often consists of a shield element in the shape of a circular segment, which is mounted on the head of the electric power tool by means of a connecting section. This shield element partially covers the disk-shaped tool in a rear axial direction, wherein the axial direction refers to the axis of rotation of the disk-shaped tool and the rear direction is the side of the guard facing the device. In addition to a flat protective surface, the shield element has a surrounding circumferential surface, which likewise serves to partially cover the tool in a radial direction. By means of an additional protective element, the electric power tool can be extended as needed such that the tool is also partially covered in a front axial direction. This extension makes it possible to also efficaciously protect the user from accelerated material particles, such as sparks, in the axial direction.

In order to make simple switching between the two functions of cutting and grinding possible for the user, it is common to mount an additional protective element on the shield element in a toolless manner, for example by clipping. The IEC 62841-2-3 standard specifies that the protective element must have a clear locking position for such a toolless attachment and that it should not experience any significant deterioration in condition.

Known from DE 10 2021 126 776 A1 is a cover element for a guard that can be attached in a toolless manner and that has a clamping part designed as a spring element whose tension in the installed position holds the cover element on the guard. The clamping part is connected to the cover element by means of a rivet, and the attachment points of the cover element that serve as supports are located on lateral cantilever arms of the cover element. Such an arrangement is mechanically delicate and relatively expensive to produce.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a protective element as an additional shroud for the guard of a disk-shaped tool of an electric power tool, in particular an angle grinder, wherein the protective element is configured to be captively and reversibly connectable to the guard in a simple, reliable, and robust manner.

The protective element according to the invention can be designed, in particular, as a cover element for the guard of a disk-shaped tool of an electric power tool, in particular an angle grinder, wherein the protective element is configured to be captively and reversibly connectable to the guard and to at least partially cover the tool. The protective element according to the invention is, for example, a cover for the guard. The protective element according to the invention includes a protective element body, having: a first end; a second end, wherein the second end is opposite the first end, in particular along a central axis M of the protective element; at least one attachment element that is mounted on the first end and is configured to be reversibly connectable to a guard edge of the guard during installation of the protective element on the guard; a receiving device for receiving a leaf spring, wherein the receiving device is arranged on the second end; wherein the leaf spring is arranged in the receiving device and is configured such that the leaf spring is tensioned in an installed position of the protective element on the guard and the guard is clamped between the leaf spring and the at least one attachment element.

The protective element according to the invention serves, for example, to partially cover a disk-shaped tool, in particular a grinding and cutting tool, of a power tool, in particular an angle grinder. The covering takes place from, for example, a front axial direction, wherein the protective element is designed, in particular, for retrofitting the power tool.

The protective element body can have a first wall (front) and a rear wall opposite this first wall, wherein the first wall and the rear wall preferably are connected by an outer wall of the protective element body that runs essentially parallel to a tool axis. The outer wall runs concentrically around the tool axis, in particular. The outer wall has the receiving device for the leaf spring, in particular.

The first wall can have essentially the shape of an annular segment. It preferably is essentially planar or nearly perpendicular to the tool axis. The annular segment preferably is essentially one half of an annulus that runs essentially perpendicular to the tool axis.

The rear wall can have essentially the shape of an annular segment, and preferably is arranged nearly perpendicular to the tool axis after installation. An inclination of the first wall at an angle of up to 5° or 10° in relation to the rear wall, in particular in relation to a plane extending perpendicular to the tool axis, is especially preferred here. The annular segment preferably is essentially one half of an annulus that extends essentially perpendicular to the tool axis 50. In order to achieve a satisfactory covering function, the first wall preferably extends farther radially inward toward the tool axis than the rear wall does.

The leaf spring can be a metallic component, for example, made of stainless steel. In particular, it is an elongated component, in particular bar-shaped, in particular strip-shaped. The length of the leaf spring is several times greater than its height, in particular. A clamping between protective element and guard that is reliable over the long term is made possible by means of this simple shaping. Moreover, this shaping allows space-saving installation of the leaf spring.

The leaf spring preferably can be brought into a first position in which the leaf spring has little tension, in particular no tension, in which, in particular, the protective element is removed and is spaced apart from the guard. The leaf spring preferably can be brought into the installed position in which the protective element is captively and reversibly clamped to the guard by means of a clamping force of the leaf spring (40), in particular in the amount of 50 N.

The receiving device permits simple and reliable connection of the leaf spring to the protective element body. In particular, because of the receiving device, no separate connecting element that connects the leaf spring to the protective element body is required for this connection. The leaf spring engages with two receptacles of the protective element body, in particular. These receptacles are provided, in particular, in an outer wall of the protective element body. The receptacles are located opposite one another, in particular with respect to the central axis M of the protective element body. The central axis M runs perpendicular to the tool axis, in particular.

The receiving device preferably has two opposite regions, in particular with respect to a central axis (M) of the protective element body, wherein each region preferably has the following constituents: a clamping edge, wherein the leaf spring rests against the clamping edge in the receiving device; a contact section, wherein a distance A between the two contact sections is less than the length of the leaf spring; a transition edge, wherein the transition edge includes a transition from the receiving device, in particular the receptacle, to an inner circumference of the protective element body, in particular to an inner circumference of an outer wall of the protective element body.

Preferably, the protective element body can have a first wall and, perpendicularly opposite hereto, a rear wall, wherein a free space ‘F’ is defined below the first wall in the direction of the rear wall, wherein the free space is configured to permit the installation of the tool, in particular by means of a tilting.

Preferably, the protective element body can have an extension, wherein the extension is configured to surround the guard, in particular at a distance. The extension runs, in particular, radially inward toward the tool axis from an inner surface of the protective element body. The extension runs, in particular, concentrically around the tool axis and in the installed position is concentric to an outer wall of the guard.

Preferably, the first wall is arranged at an angle to the rear wall, preferably less than 5° or less than or equal to 3°.

Preferably, the at least one attachment element can be designed to permit an interlocking and/or frictional connection to the guard. Preferably, the at least one attachment element is hooklike. Preferably, a number N>0 of attachment elements are provided, in particular N=1 or preferably N=2. It is also preferred that N=3, 4, 5, or 6.

Preferably, the leaf spring can be metallic. Preferably, it contains an austenitic material, for example, nickel-chromium steel 1.4310, or is made of this austenitic material. High reliability is achieved as a result.

Preferably, the tension or the deflection of the leaf spring in the installed position can be accomplished in such a way that its center point is displaced radially outward toward an outer wall of the protective element body with respect to the tool axis.

Preferably, a material or the material of the protective element can be chosen from the group of thermoplastics, in particular polyamides, in particular glass-fiber reinforced thermoplastics.

Preferably, the protective element body can be designed with integral construction, which is also referred to here as “monolithic.” In particular, it is an injection-molded part or a component produced by an additive manufacturing process.

Preferably, the leaf spring can have a length between 40 and 100 mm, preferably between 50 and 90 mm, preferably between 60 and 80 mm. In particular, the leaf spring has a height preferably between 5 and 30 mm, preferably between 8 and 20 mm, preferably between 10 and 15 mm. In a preferred exemplary embodiment, the leaf spring has dimensions of L×H×T=70×12.7×1 mm, which is to say a thickness T=1 mm. The thickness can be between 0.3 mm and 3 mm, in particular.

In the installed state of the protective element, the leaf spring inserted in the receiving device preferably has a deflection of between 2 mm and 6 mm, in particular approximately 4.1 mm in a preferred exemplary embodiment. In this case the leaf spring rests against the clamping edge. The deflection is determined, in particular, as the maximum excursion of the leaf spring in the direction along the central axis of the protective element body, in particular through the center of the leaf spring.

Preferably, the leaf spring inserted in the receiving device has no deflection when the protective element is not installed on the guard. In the uninstalled state of the protective element, the leaf spring is arranged to be free in the receiving device, with no tension and with play.

The distance from the clamping edge to the transition edge of the protective element, measured in a direction parallel to the central axis M, is: approximately 4.7 mm in the case of a guard for a tool disk with diameter=115 mm; or approximately 3.4 mm in the case of a guard for a tool disk with diameter=125 mm; or approximately 2 mm in the case of a guard for a tool disk with diameter=150 mm.

The distance from the clamping edge to the transition edge measured in a direction parallel to the central axis M can be determined such that the deflection of the leaf spring is constant when the protective element is installed, independent of the diameter of the tool disk and of the protective element. In this case, the deflection of the leaf spring is determined such that the required pull-off force per standard is met. The distance is dependent on the diameter of the tool disk, the abrasive, and the spring properties of the leaf spring used. Starting from the use of a leaf spring with the same parameters (length, width, thickness, spring properties) for protective elements with different diameters, the larger the diameter of the tool disk, the smaller this distance is. In other words, when the same leaf spring is used, this distance increases as the diameter of the tool disk and of the protective element decreases. Tool disks or abrasives are known with diameters of 100 mm, 115 mm, 125 mm, 150 mm, 180 mm, and 230 mm. In accordance with the invention, the described distance can be determined as a function of the diameter such that the deflection of the leaf spring, and consequently the clamping force generated, is constant. This distance can be determined independently of the abovementioned diameters for any desired diameter of a tool disk.

The invention also relates to an angle grinder that has a guard and has a protective element according to the invention that can be connected to this guard.

The invention also relates to a method for producing the protective element, having the steps: creating the protective element body by means of a method, for example by means of injection molding or additive manufacturing; and inserting the leaf spring into the receiving device of the protective element body.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

FIG. 1a shows the perspective view of a protective element according to the invention in accordance with an exemplary embodiment.

FIG. 1b shows a detail of the protective element from FIG. 1a.

FIG. 2 shows a section of a cross-sectional view of the protective element from FIG. 1a viewed perpendicularly to a tool axis.

FIG. 3 shows a detail of the view from FIG. 2.

FIG. 4 shows a cross-sectional view of the protective element from FIG. 1a viewed perpendicularly to a tool axis.

FIG. 4a shows a detail from FIG. 4.

FIGS. 5 and 6 each show a cross-sectional view of a protective element according to the invention viewed perpendicularly to a tool axis, according to two additional different exemplary embodiments.

FIG. 5a shows a detail from FIG. 5.

FIG. 6a shows a detail from FIG. 6.

FIG. 7 shows a perspective, side view of the protective element from FIG. 1a to be attached to a guard, in a representation sectioned parallel to the tool axis.

FIG. 8 shows a perspective, side view of the protective element from FIG. 1a attached to a guard, in a representation sectioned parallel to the tool axis, as well as a grinding wheel during the process of its installation on a spindle of an angle grinder.

FIG. 9 shows a cross-sectional view of the protective element from FIG. 8.

FIG. 10 shows the protective element from FIG. 1 in a front view.

DETAILED DESCRIPTION

FIG. 1a illustrates the perspective view of a protective element 100 according to the invention, also referred to as a cover. The protective element has a protective element body 18. The latter has, on its front, a wall 14—facing upward in FIG. 1a—and a further rear wall 16—facing downward in FIG. 1a—opposite thereto, wherein the wall 14 and the rear wall 16 are connected by an outer wall 17 that runs essentially parallel to the tool axis 50.

The protective element 100 is designed as a cover element in that it has the wall 14 serving as cover wall, with which a disk-shaped tool can be partially covered. The protective element 100 was developed in order to be safely and reversibly connected to a guard 30 and in so doing to cover at least a part of the disk-shaped tool and thus to protect a user or to avoid an undesirable action of the tool on a workpiece. The protective element body 18, which is part of the protective element 100, possesses a further specific structure: it has a section with a first end 10 and a section with a second end 20 opposite the first end. The first end 10 is therefore the open end shown in FIG. 1a and the second end 20 is the closed end of the protective element body 18 opposite thereto, wherein the ends are opposite one another along a radial direction M that runs perpendicular to the tool axis 50.

In addition, the present exemplary embodiment of the protective element 100 shows a first functional group with two attachment elements 11 that are mounted on the first end 10 of the protective element 100. These attachment elements 11 were designed to enter into a reversible connection with a guard edge 32 of the guard 30. A reliable attachment and covering of the tool by the protective element 100 and the guard 30 is ensured by this design of the protective element 100 in combination with a second functional group.

FIG. 1b illustrates the securing of the protective element 100 in accordance with the invention on a guard 30. Shown enlarged is the first functional group, which is positioned on the first end 10 of the protective element 100, accordingly on the guard edge 32, and which has multiple attachment elements 11, of which one is shown in FIG. 1b. In the exemplary embodiment shown, these attachment elements 11 are connected structurally seamlessly, in particular monolithically, to the protective element body 18, and are designed here as projections of an edge 13 of the protective element body 18 that faces in the direction of the first end 10. The arrangement and the shape of the attachment element 11 has the effect that an inner surface of the rear wall 16 of the protective element body 18 can rest against an outer surface of the guard 30 in contiguous contact.

The attachment element 11 serves as an end support. It is, in particular, a hook element, which here has an opening 12 facing in the direction of the protective element body 18. A protective element 100 preferably has two attachment elements 11. Alternatively, however, exactly one attachment element 11 or more than two attachment elements 11 can also preferably be provided.

In the exemplary embodiment shown, the attachment elements 11 are designed with a U-shaped or V-shaped opening 12. In the installed state, each attachment element 11 surrounds the guard 30 at its guard edge 32 and is tensioned in the direction of the guard 30 with the aid of a second function group. An interlocking and/or frictional connection between the guard 30 and the protective element 100 is produced with the aid of the first and second functional groups as a result.

The depicted opening 12 serves the purpose of facilitating effortless and safe installation of the protective element 100 by making possible simple mounting on the guard 30 or its guard edge 32. Each individual attachment element 11 has a specific length of approximately 15 millimeters—measured along the guard edge 32—in the exemplary embodiment shown, by which means an optimal securing of the protective element 100 is ensured. In addition, the attachment elements 11 were intentionally placed distant from the tool axis 50, shown in FIG. 2, in order to ensure stable and reliable attachment. This means in particular that an attachment element is positioned closer to an outer circumference of the protective element 100 than to a center of the protective element 100 through which the tool axis 50 passes in the installed position. This positioning contributes to increasing the structural strength of the protective element 100 in the installed position by making possible a sturdy connection to the guard 30.

In FIG. 2, the second functional group for attaching the protective element 100 to the guard 30 can be seen; this group is positioned at the second end 20 of the protective element 100, the end opposite the first end 10. This second functional group includes a receiving device 21 that is configured to receive a leaf spring 40 and that is specifically designed for the installation and the functionality of the leaf spring 40. The receiving device 21 in this case includes two clamping edges 22—that are opposite with respect to a central axis M of the protective element 100—and contact sections 23, which serve the purpose of correct installation and reliable insertion of the installed cover.

The contact section 23, which here is L-shaped in design, with the L shape being shown mirror-inverted in the upper region in the depicted exemplary embodiment, is placed in alignment with the tool axis 50 in each case. The distance A between the outermost edges 26 of the contact sections 23, which are perpendicularly opposite one another in the direction of the central axis M of the cover, is less than the length of the leaf spring 40 that is inserted into the receiving device 21. The distance X between the inner edges 27 of the contact sections 23, which are perpendicularly opposite one another in the direction of the central axis M of the cover, is greater than the length of the leaf spring 40 that is inserted into the receiving device 21. This configuration ensures that the leaf spring 40 can be inserted safely and without loss in the receiving device 21 by allowing reliable locking and secure seating.

The leaf spring 40 is strip-shaped, with a maximum dimension along its longitudinal extent. The dimensions of the leaf spring 40 are 70×12.7>1 mm in the exemplary embodiment shown. The dimensions of the distances A and X and the length of the leaf spring 40 are determined such that the leaf spring 40 can be inserted into the receiving device 21 with play, which is to say loosely. When the leaf spring 40 is inserted, it is bent to a sufficient degree that its length is slightly shorter than the distance A, so that the leaf spring 40 can be inserted into the receiving device 21. In the installed state, when the protective element 100 is attached to the guard 30, the clamping edges 22 form contact points for the leaf spring 40.

FIG. 3 illustrates a transition edge 24 of the receiving device 21 to the inner circumference of the protective element 100. This depiction illustrates the region in which the receiving device 21 transitions into the inner circumference D of the protective element 100. This transition region formed by the transition edge 24 marks the section in which the structural elements of the receiving device 21 transition into the inner region of the protective element 100 in order to ensure a continuous and smooth connection that holds the leaf spring 40 as part of the second functional group.

FIG. 4 shows the exemplary structural component dimensions to accomplish a pull-off force, which here is realized by a specific deflection of 4.1 mm for the employed leaf spring 40 made of the material 1.4310. The material 1.4310 of the metallic leaf spring 40 here is a nickel-chromium steel with an austenitic structure, which is known as classic stainless spring steel on account of its good ductility and hardness.

The intended deflection of the leaf spring 40 is accomplished in the installed position in such a way that its center point is displaced radially outward toward the outer wall (17) of the protective element body (18) with respect to the tool axis (50). In particular, the deflection is accomplished such that, on the side facing the tool axis 50, the leaf spring 40 is bent away from the circumferential surface of the guard 30 toward the clamping edges 22. The positioning of the second functional group was determined accordingly in order to ensure a specific deflection of the leaf spring 40 of 4.1 mm. This deflection is provided in order to achieve the desired pull-off force in accordance with the specified requirements.

The market-determinant abrasive diameters are 115, 125, and 150 mm. In addition, other diameters of abrasives are also known, for example 100 mm, 180 mm, and 230 mm. Since the inner diameter of a protective element 100 corresponds essentially to the outer diameter of a corresponding guard 30, and this diameter or radius influences the deflection of the leaf spring 40, the second functional group is arranged as a function of the corresponding diameter.

As FIGS. 4 and 4a show, the distance s from the clamping edge 22 to the transition edge 24 in the case of a guard 30 for a tool disk with a diameter of 115 mm is approximately s=4.7 mm. This dimension describes the specific distance between the clamping edge 22 and the transition region 24, measured in a direction parallel to the central axis M, on the guard 30 with a specified length of 115 mm.

With respect to the protective element 200 from FIGS. 5 and 5a, the distance s between the clamping edge 22 and the transition edge 24 in the case of a guard 30′ is approximately s=3.4 mm for a tool disk with a diameter of 125 mm. This statement describes the distance between the clamping edge 22 and the transition region 24, measured in a direction parallel to the central axis M, on a guard 30′ with a specified length of 125 mm.

For the protective element 300 from FIGS. 6 and 6a, the distance s between the clamping edge 22 and the transition edge 24 along a guard 30″ for a tool disk with a diameter of 150 mm is approximately s=2 mm. This statement describes the distance between the clamping edge 22 and the transition region 24, measured in a direction parallel to the central axis M, on a guard 30″ that is designed for an abrasive with a diameter of 150 mm.

As is evident, the clamping edge 22 is positioned closer to the tool axis 50 with increasing diameter of the guard. These different arrangements are intended to achieve the requisite deflection of the leaf spring 40 of 4.1 mm with varying diameters of the guard 30. In this way, the necessary clamping force is generated in order to ensure the required pull-off force of 50 N according to the standard (DIN EN IEC 62841-2-3 (VDE 0740-2-3):2022-07, in particular Annex AA), and to do so independently of the diameter of the guard 30 or the grinding wheel.

The specification regarding the replacement of a grinding wheel while the protective element 100 is installed requires a height of the protective element 100 that is greater than that of the guard 30.

FIG. 7 displays a section through a protective element 100 that is mounted over an installed guard 30. It is evident that the protective element 100 has a free space F, which is located above the guard 30 in the exemplary embodiment shown.

It is made clear in FIG. 8 that the free space labeled ‘F’ of an installed protective element 100 can be used in order to install a grinding wheel 30 or a comparable tool. A grinding wheel can be inserted at an angle into the guard 30 on the shaft of a power tool and fastened, using the free space F. On account of the free space F, this is possible with the protective element 100 installed.

To further facilitate installation of the protective element 100, the wall 14 of the protective element 100 that serves as cover wall 14 and that covers the grinding wheel in the outward axial direction is arranged at an angle of approximately 3 degrees together with the free space ‘F’ in the exemplary embodiment shown.

In the exemplary embodiment shown in FIG. 9, an extension 15 is present on the protective element 100 that serves to keep the protective element 100 stable during operation by means of an interlocking contact. This extension 15 is placed at the height of the center line of the protective element 100 and is located at a distance from the rear wall 16 of the protective element 100. The extension 15 is dimensioned such that the protective element 100 is arranged immovably in operation of the power tool. In addition, the extension 15 is likewise arranged at an angle of approximately 3 degrees to the rear wall 16 in order to ensure that installation of the protective element 100 and a grinding wheel 31 is not adversely affected by the extension 15. The first wall 14, the cover wall, is opposite the rear wall 16. Both walls 14 and 16 have a slight inclination relative to a plane exactly perpendicular to the tool axis 50, wherein the wall 14 has a greater inclination than the rear wall 16. Both walls 14 and 16 therefore run only essentially perpendicular to the tool axis 50.

The rear wall 16 and the second wall 14 are monolithically connected by the outer wall 17. The extension 15, which runs in the circumferential direction around the tool axis 50, is provided in the transition region between the wall 14 and the outer wall 17. The outer wall 17 runs parallel to the tool axis 50. The protective element body 18 is an injection-molded part, in particular. The first wall 16 is shaped such that it rests flat against an outer wall of the guard 30 in the installed position of the protective element 100, wherein this outer wall extends nearly perpendicular to the tool axis.

FIG. 10 shows the rear wall 16 and the wall 14 of the protective element 100, which are connected by the outer wall 17, in a rear view. The outer wall 17, which runs concentrically around the tool axis 50 in the circumferential direction, has the receiving device 21 for the leaf spring 40. The rear wall 16 has essentially the shape of an annular segment, and here is essentially planar or nearly perpendicular to the tool axis 50. The annular segment is essentially one half of an annulus here. The wall 14, the front, also has essentially the shape of an annular segment, and is nearly perpendicular to the tool axis 50 here. The annular segment is essentially one half of an annulus here. In order to achieve a satisfactory covering function, the wall 14 extends farther radially inward toward the tool axis 50 than the rear wall 16 does. The maximum possible protection of the tool disk can be achieved in this way.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.