Patent Application
20250114894
This claims priority to European Patent Application EP23201795.4, filed on Oct. 5, 2024, which is hereby incorporated in its entirety by reference herein.
The present invention relates to a clamping device for fastening a tool disc to a power tool, wherein the clamping device has a screw provided for being screwed into a drive spindle of the power tool in order to fasten the tool disc. In further aspects, the invention relates to a power tool having a drive spindle, to which a tool disc can be fastened by means of the proposed clamping device, and to a method for fastening a tool disc to such a power tool.
In the field of power tools, cut-off grinders and angle grinders are known which, as tools, have disc-shaped tools. Such disc-shaped tools, which are normally substantially circular, are referred to as tool discs, cut-off discs or grinding discs.
EP 4 227 040 A1 has disclosed a system for fastening a cranked grinding disc which can be connected, for example, to an angle grinder in order to grind off surfaces. A major advantage of the fastening system described in EP 4 227 040 A1 is that the tool disc can be fastened to the power tool or released from the power tool without the use of a further tool, that is to say in “keyless” fashion.
Cranked grinding discs, such as are used in the field of angle grinders, are generally pot-shaped, such that the knob of the fastening system that is disclosed in EP 4 227 040 A1 can be received by the recess of the cranked grinding disc. In this way, the knob of the fastening system is shielded from the grinding disc, and undesired contact between the substrate to be machined and the knob is prevented.
Depending on the direction of rotation of the grinding disc, such contact can cause the grinding disc to be tightened, such that it is virtually unreleasable, or to be released. Both situations are obviously undesirable. If the grinding disc is tightened such that it is virtually unreleasable, great effort is often necessary to release the grinding disc from the power tool. If, in the case of an opposite direction of rotation, the grinding disc is released, this can pose a risk of injury to the user of the power tool or nearby persons.
If the tool disc of a power tool has no recess and no cranked formation, there are as yet no known technical solutions in the prior art for fastening a tool disc to the power tool securely and in keyless fashion and at the same time reliably preventing undesired contact between a knob of the fastening system and the substrate.
An object of the present invention consists in providing a system for fastening a tool disc to a power tool, in the case of which the tool disc can also be of non-cranked, that is to say flat, design. The fastening system that is to be provided should firstly be secure and keyless, such that a user does not require any further tool, such as a screwdriver or the like, to stably fasten the tool disc to the power tool. Secondly, even for non-cranked, that is to say flat, tool discs, it should be ensured that the tool disc is neither tightened such that it is virtually unreleasable, nor released from the power tool, during operation.
According to the invention, a clamping device for fastening a tool disc to a power tool is provided, wherein the clamping device has a screw provided for being screwed into a drive spindle of the power tool in order to fasten the tool disc. The screw is mounted in a coupling module of the clamping device, wherein the coupling module has a first flange and an internal contour, wherein the clamping device gives rise to a form-fitting fastening of the tool disc to the power tool, and wherein the first flange prevents undesired loosening or tightening of the screw.
In the context of the invention, it is preferred that the first flange is designed such that undesired loosening or tightening of the screw of the clamping device is prevented. This can be achieved for example by virtue of the first flange having a substantially circular base surface, with the substantially circular base surface being surrounded at its circumference by a side wall. In this case, the design of the first flange achieves that the screw or its operating element is shielded with respect to the tool disc, such that contact between the operating element and the substrate to be machined is effectively prevented. At the same time, the proposed clamping device also makes it possible for the tool disc to be fastened to the power tool in keyless fashion, that is to say without the aid of a further tool. The clamping device may self-evidently have further optional features or components, which are known in part from EP 4 227 040 A1.
In an alternative embodiment of the invention, the first flange may have a base surface that extends beyond the side walls of the first flange. The side walls of the first flange preferably form a collar that shields the operating element of the screw from the tool disc, such that contact or physical contact between the operating element and the substrate to be machined is effectively prevented. The protruding regions of the base surface serve to enlarge the area of contact between the second flange and the tool disc, such that the forces resulting from the tightening of the screw of the clamping device can be better distributed. The flange may have an inner region, which may be set back in relation to an outer circumferential region. Space can thus be provided for a securing ring. Furthermore, owing to the set-back inner region of the flange, a defined bearing region can be realized at the outer diameter of the tool disc.
It has been found that, by providing the first flange, it is possible to avoid a situation in which—depending on the direction of rotation of the tool disc—the screw tightens, such that it is virtually unreleasable, or loosens. This advantage is made possible in particular for non-cranked tool discs that are not already protected against such undesired contact owing to their design. Non-cranked tool discs are in particular of flat design, such that they have no recess in which an operating element of the screw of the clamping device can be received. In the context of the proposed clamping device, this function is performed by the first flange, which may have side walls for shielding the operating element from the tool disc. In the context of the invention, the first flange may preferably also be referred to as “outer flange”, because the first flange, in the fastened state, that is to say for example during the operation of the power tool, is arranged on that side of the tool disc which faces away from the power tool. It is preferably possible for the first flange or its base surface to have different sizes or diameters. It is thus advantageously possible for tool discs of different size to be fastened to the power tool by means of the clamping device.
Particularly stable form-fitting fastening of the tool disc to the power tool can advantageously be achieved by means of the internal contour of the clamping device. The internal contour may preferably be designed as a dihedron or have a dihedron. Owing to the internal contour of the clamping device, the tool disc can be fastened to the power tool in particular in keyless, that is to say tool-free, fashion. The internal contour preferably has an internal profile that can interact with a drive spindle of the power tool in order to generate a particularly stable form-fitting shaft-hub connection. The shaft-hub connection thus generated is formed in particular between the drive spindle of the power tool and the screw of the proposed clamping device, wherein the screw of the clamping device is screwed into the drive spindle of the power tool. Here, the screw is led through the internal contour and the first flange of the clamping device and through the tool disc. The drive spindle of the power tool may preferably be flattened on two sides. In the context of the power tool, the spindle preferably constitutes an output shaft by which the tool disc of the power tool can be driven. In the context of the invention, it is preferred that the shaft-hub connection allows a rotational driving action, such that the rotational movement of the drive spindle of the power tool can be transmitted to the power tool.
With the invention, it is advantageously possible to provide a means for tool-free fastening of cut-off discs for cut-off devices or cut-off grinders such as petrol-powered saws, angle grinders and/or battery-powered cut-off devices, without limitation to these. A further advantage of the invention consists in that, through the use of different first flanges, the clamping device can be particularly easily adapted to different sizes or diameters of tool discs. In particular, with the invention, undesired contact between the operating element of the clamping device or of the screw and the substrate can be avoided, whereby unintended loosening or tightening of the screw during the operation of the power tool is advantageously prevented.
By contrast to the fastening system described in EP 4 227 040 A1, the proposed clamping device has an outer flange that can be arranged indirectly or directly between the screw and the tool disc. The outer flange, which in the context of the present invention is referred to as “first flange”, is preferably designed so as to ensure that no undesired contact occurs between the operating element and the substrate. It is thus advantageously possible to prevent the screw of the clamping device from loosening, or from tightening such that it is virtually unreleasable, during the operation of the power tool. The first flange may be provided as a separately installed component of the clamping device, such that it can be offered in various sizes for the purposes of fastening or clamping tool discs of different size to the power tool. The clamping device may preferably comprise a tool-free nut, which in the context of the invention preferably constitutes a clamping element. The preferably tool-free nut, which in the context of the invention is preferably also referred to as “internal contour”, preferably has an M8 thread, and may be designed as a dihedron.
In the context of the invention, it is very particularly preferred that the first flange is connected non-detachably or substantially non-detachably to the clamping device or to the internal contour of the clamping device. Owing to the connection of internal contour and first flange, a coupling module is formed by which the tool disc can be fastened to the power tool. The provision of the coupling module that comprises the internal contour and the first flange advantageously allows both the attachment of the tool disc to the power tool and the attachment of the flange that is required for this purpose. The constituent parts of the proposed clamping device can be provided in different embodiments and sizes in order to allow different sizes of tool discs and flanges and/or different types of tool discs to be installed. In the context of the invention, it is preferred that the internal contour forms, with the screw, a preassembled unit that can be led through an opening in the first flange. In other words, the opening in the first flange and the outer diameter of the internal contour of the clamping device are designed such that the preassembled unit consisting of internal contour and screw can be passed through the opening in the first flange. The screw can subsequently be led through a central opening in the tool disc and screwed into the drive spindle of the power tool. For this purpose, the drive spindle may have an internal thread at an end, into which internal thread the screw or the preassembled unit consisting of internal contour and screw can be screwed. The screw of the clamping device is mounted in a coupling module, wherein the coupling module has the first flange and the internal contour.
In the context of the invention, it is preferred that the first flange has an opening and a base surface. The first flange preferably has a substantially circular base surface, wherein the opening in the first flange is preferably arranged centrally, that is to say in the middle, in the first flange. The base surface may in particular be of flat design. If the base surface of the first flange is of flat or substantially flat design, it is preferred in the context of the invention that the first flange has a side wall which runs at a circumference of the first flange and which preferably has the effect that the first flange has or assumes a pot-like shape. The first flange preferably has a substantially circular base surface, with the substantially circular base surface being surrounded at its circumference by a side wall. The base surface and the side wall of the first flange shield the operating element of the screw or of the clamping device from the tool disc and thus prevent contact between the operating element and the substrate to be machined. In other words, the base surface and the side wall of the first flange are configured to shield the operating element of the screw or of the clamping device from the tool disc in order to prevent contact between the operating element and the substrate. A situation in which the screw is undesirably tightened or loosened can thus advantageously be avoided.
In the context of the invention, it is preferred that the screw has an operating element, a thread, a screw head, and a bearing surface for making contact with the first flange. The operating element may preferably be in the form of a knob or a grip. To fasten the tool disc to the power tool or to its drive spindle, the user can grip the screw by its operating element and tighten it. The tool disc is thus advantageously axially clamped to the drive spindle of the power tool, wherein this fastening is advantageously possible without the aid of a further tool such as a screwdriver or the like. With the invention, it is consequently possible to achieve tool-free, that is to say keyless, fastening of a tool disc to a power tool, wherein, at the same time, it can be ensured even for flat tool discs that no contact occurs between the operating element of the screw and the underlying surface to be machined. Thus, with the proposed clamping device, the tool disc can firstly be fastened in tool-free fashion to the power tool, and it is secondly ensured that the screw of the clamping device does not tighten, such that it is virtually unreleasable, or undesirably loosen during the operation of the power tool. A power tool that is safe to operate and easy to handle can thus be provided, in particular even if flat tool discs are used.
Aside from the operating element, the screw may have a screw head. The screw head may for example be contained or recessed in the operating element (see the figures). For example, the head of the screw may have a hexagonal shape. Aside from the operating element and the screw head, the screw may have a bearing surface for making contact with the first flange. The bearing surface of the screw can enlarge the area of contact between the screw and the first flange, wherein the bearing surface of the screw is preferably in contact with the base surface of the first flange. In this way, the forces that arise as a result of the tightening of the screw in the internal thread of the drive spindle of the power tool can be distributed over a larger area, whereby a particularly stable and smoothly running fastening of the tool disc to the power tool can be provided. The screw may furthermore have a thread by which the screw can be screwed into the internal thread of the drive spindle. The thread of the screw is preferably an external thread.
In the context of the invention, it is preferred that the screw does not make direct contact with the first flange. A ball bearing and/or a bearing ring may preferably be provided between the screw or its bearing surface and the first flange. The contact between the bearing surface of the screw and the first flange may preferably be indirect or direct. In the context of the invention, the wording “direct contact” preferably means that there is contact in the sense of physical contact between the bearing surface of the screw and the first flange. By contrast, in the context of the invention, the wording “indirect contact” preferably means that additional objects such as the bearing ring or a ball bearing are arranged between the screw and the first flange and thus prevent direct physical contact between the screw and the first flange.
In the context of the invention, it is preferred that the clamping device has a second flange which, in a fastened state, is arranged between the drive spindle and the tool disc. In the context of the invention, the second flange may preferably also be referred to as “inner flange”, because the second flange, in the fastened state, that is to say for example during the operation of the power tool, is arranged on that side of the tool disc which faces towards the power tool. The clamping device is in particular designed to axially clamp the tool disc to the power tool or its drive spindle. Here, the tool disc can be fastened to a second flange that is assigned to the drive spindle of the power tool, wherein the clamping device has a screw that can be screwed into a drive spindle of the power tool in order to firmly clamp the tool disc. The second flange preferably has a bearing surface and a centring means. In the fastened state, that is to say for example during the operation of the power tool, the bearing surface of the second flange is arranged against the inner side of the tool disc, wherein the inner side of the tool disc is preferably that side of the tool disc which faces towards the power tool. The centring means of the second flange is preferably a central opening that is preferably designed such that it can receive the internal contour of the clamping device. In the context of the invention, it is preferred that the bearing surface of the second flange enlarges the area of contact between the second flange and the tool disc, wherein the bearing surface is in particular in contact with the inner side of the tool disc. In this way, the forces that arise as a result of the tightening of the screw in the internal thread of the drive spindle of the power tool can be distributed over a larger area, whereby a particularly stable and smoothly running fastening of the tool disc to the power tool can be provided. The second flange and the drive spindle preferably form the tool fitting of the power tool for receiving the tool disc.
In the context of the invention, it is preferred that the first flange, in a fastened state, is arranged indirectly or directly between the tool disc and the screw. If the first flange is arranged directly between the tool disc and the screw, there are preferably no further optional components arranged between the first flange and the tool disc and the first flange and the screw or its bearing surface. If the first flange is arranged indirectly between the tool disc and the screw, it is for example possible for a circlip to be arranged, as an additional optional component of the clamping device, between the tool disc and the screw or its bearing surface. In other words, the clamping device may have a circlip that is arranged between the tool disc and the second flange. The circlip may be configured to connect the clamping device to the outer flange. It is thus advantageously possible to prevent the outer flange from being lost when it is not being used by the user. For example, the first flange may be pressed on directly, or compression rings, nuts, grub screws and/or cross pins may be used for fastening purposes, without limitation to these. The first flange may also be caulked, without the use of rivets.
In a second aspect, the invention relates to a power tool, preferably in the form of a cut-off grinder, wherein the power tool has a drive spindle and a proposed clamping device. The clamping device is designed for fastening a tool disc to the drive spindle of the power tool. The terms, definitions and technical advantages introduced for the clamping device preferably apply analogously to the operating method for the power tool. The drive spindle has, at an end, an internal thread that is connectable to the screw of the clamping device in order to fasten the tool disc to the drive spindle of the power tool. The internal thread of the drive spindle is in particular configured to receive the screw of the clamping device. This means that the screw of the clamping device can be screwed into the internal thread of the drive spindle in order to fasten the tool disc to the power tool or in order to axially clamp the tool disc to the power tool. It is preferred in the context of the invention that the drive spindle is flattened on two sides. Preferably, the drive spindle may have an external contour that can be connected circumferentially form-fittingly to the internal contour of the coupling module for conjoint rotation. It has proven to be advantageous if the power tool comprises a second flange which, by means of an anti-rotation safeguard, is connected or connectable circumferentially form-fittingly to the drive spindle for conjoint rotation.
In a further aspect, the invention relates to a method for fastening a tool disc to a power tool. The terms, definitions and technical advantages introduced for the clamping device and the power tool preferably apply analogously to the fastening method. The method for fastening the tool disc to the power tool is characterized by the following method steps:
The clamping device according to the invention has the advantage that the screw of the clamping device can neither tighten nor loosen during the operation of the power tool, because the coupling module, as part of the clamping device, is paired form-fittingly with the drive spindle for conjoint rotation. It has proven to be advantageous if the internal contour of the coupling module is designed as a dihedron with an M8 thread. The drive spindle of the power tool preferably has a corresponding external contour that is configured to receive the internal contour and/or the screw of the clamping device. Alternative form-fitting, rotationally conjoint pairings, for example in the form of form-fitting shaft-hub connections, may likewise be used. In the context of the invention, it is preferred that the internal contour or the dihedron can be milled by means of a standard M14 angle grinder fitting.
The internal thread of the drive spindle is preferably an internal thread at the end. The internal thread can be set back in the axial direction relative to a head surface of the drive spindle. The screw preferably projects in the axial direction beyond the coupling module, in particular relative to a cylindrical subsection of the coupling module. The coupling module is preferably of cylindrical design. The coupling module preferably has a cylindrical subsection which can project through a central opening in the tool disc. The cylindrical subsection of the coupling module can project into a central opening in the first flange.
In a preferred embodiment, the clamping device has a knob, which is designed to exhibit a circumferential form fit with the screw for conjoint rotation. The knob can form an operating element, and in the context of the invention is preferably also referred to as the “operating element of the screw” or the “operating element of the clamping device”. Particularly simple handling of the clamping device is thereby possible. It is possible to dispense with an additional installation tool, such as an installation wrench. The clamping device thus in particular allows tool-free, that is to say keyless, fastening of the tool disc to the power tool.
Further advantages emerge from the following description of the figures. The figures, the description and the claims contain numerous features in combination. A person skilled in the art will expediently also consider the features individually and combine them to form sensible further combinations.
In the figures, identical and similar components are denoted by the same reference signs.
In the figures:
The figures show preferred embodiments of the proposed fastening system. The fastening system illustrated in
The first flange 17 has a central opening 4 for the leadthrough of the screw 2 and has a base or bottom surface 5. The base surface 5 is preferably substantially circular, such that the outer edge of the first flange 17 forms a substantially circular circumference. A side wall 6 may extend at the circumference of the first flange 17, which side wall forms a collar of the first flange 17 and has the effect that the first flange 17 is of pot-shaped design.
This embodiment of the invention is illustrated in
By means of these measures or design embodiments of the first flange 17, it can be achieved that the operating element 3 of the clamping device 10 is shielded with respect to the tool disc 300. In this way, contact between an underlying surface and the operating element 3 of the clamping device 10 can be prevented, and it can be ensured that the screw 2 of the clamping device 10 does not unintentionally loosen during the operation of the power tool 100, or that—in the case of an opposite direction of rotation of the tool disc 300—the screw 2 does not tighten such that it is virtually unreleasable.
The internal contour 16 of the coupling module 1 or of the clamping device 10 may be designed as a tool-free nut and comprise an M8 thread. The internal contour 16 may in particular be designed as a dihedron, wherein the screw 2 can be mounted in an interior 15 of the internal contour 16. The screw 2 may be somewhat longer than the outer walls of the internal contour 16, such that the screw 2 protrudes out of the interior 15 of the internal contour 16. The screw 2 can then advantageously also be used as a centring aid. A pin 18 may also be provided, as a further centering aid, on the end of the screw 2. This embodiment of the invention is illustrated in
A second flange 8 may be provided between the drive spindle 20 and the power tool 100. The second flange 8 has a central opening which, in the context of the invention, can preferably be referred to as a centering means 13. Furthermore, the second flange 8 may have a bearing surface 11 that is in contact with the tool disc 300 when the tool disc 300 is fastened to the power tool 100. The second flange 8 may also have a rotational driving means designed for example as a dihedron or as a hexagon.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23201795.4 | Oct 2023 | EP | regional |
