Supporting device

Abstract

The invention relates to a support device designed to bear against a workpiece with a contact surface (7) of a pressure piece (3) under compressive force, wherein the rigid assembly comprising the pressure piece (3) and a further rigid assembly of the support device comprising a base (1) bear against each other over a flat contact surface (10) during the intended use of the support device and can slide relative to each other. When the support device is unloaded, the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed against each other at stop surfaces and are thereby positively locked in a defined relative position to each other with respect to those directions that are parallel to the contact surface (10).

Description

[0001] The invention relates to a support device designed to bear against a workpiece with a contact surface under pressure. EP1535702B1 discloses a device according to the preamble of claim 1.

[0002] When a significant pressure is to be applied to a workpiece by a support device, it is common practice to guide the part of the support device that has the contact surface with the workpiece, hereinafter referred to as the "pressure piece," so that it can be moved relative to the base of the support device in such a way that the pressure piece can be displaced relatively easily about axes perpendicular to the applied pressure force, at least a small distance. This is intended to prevent damage to the workpiece surface if, for any reason, there is a slight lateral displacement between the workpiece and the base of the support device, or if the workpiece surface is not initially aligned exactly parallel to the contact surface of the pressure piece.

[0003] A well-known example of such a support device is the screw clamp assembly consisting of a screw and a pressure piece, in which the pressure piece and the end face of the screw are held together by a ball joint connection.

[0004] US 8025279 B2 discloses a screw clamp in which a pressure piece is connected to the end face of the screw only by a coil spring. While this can work well for holding a workpiece with a sensitive surface without damage, it is hardly suitable for the precise forming of a workpiece because, in operation, the pressure piece is not in a precisely defined position relative to the rest of the clamping device with respect to any degree of freedom.

[0005] Support devices with pressure pieces that are only pivotably attached to other parts of the support device are shown, for example, in documents DE 10064603 A1, DE 102016102011 B4, DE 102020131274 A1, DE 19751599 A1, DE 2747421 A1, EP 1967323 B1, EP 2185315 B1, EP 2442945 B1, EP 3310529 B1, EP 461994 B1 and US 2190585 A. Typically, an elasticity-based return mechanism is also provided, which holds the pressure piece in a neutral central position when unloaded.

[0006] Especially when using the support devices discussed above on straightening machines—that is, machines used to bring elongated or flat workpieces into a desired shape through plastic deformation—it has become apparent that even those support devices equipped with pivoting pressure pieces frequently leave damage on the workpiece surface. It has been determined that sliding relative movements at the contact surface between the pressure piece of the support device and the workpieces are causally related to this damage.

[0007] Patent applications US 5244195 A and US 2724298 A disclose support devices in which a pressure piece is displaceable relative to the base of the support device within a displacement range along a flat surface. Unfortunately, it has been found that even when these support devices are used in straightening machines, damage to workpieces due to sliding relative movement between the workpiece and the pressure piece occurs frequently. Within the scope of the present invention, it has been discovered that this damage is caused by the pressure piece being located at the edge of the displacement range relative to the base of the support device from the very beginning of its contact with the workpiece, and therefore cannot be displaced sufficiently far relative to the base of the support device, at least in one direction.

[0008] The object underlying the invention is to improve a support device for applying a pressure force to a workpiece, which has a base and a pressure piece movable relative to the base, in such a way that during operation there is less sliding relative movement at the contact surface between the pressure piece and the workpiece than in those known support devices according to the prior art in which the pressure piece is movable relative to the base along a flat contact surface.

[0009] To solve the problem, it is assumed that the rigid assembly comprising the pressure piece and the rigid assembly comprising the base of the support device, during the intended use of the support device, lie flat against each other on a flat contact surface and are movable relative to each other by sliding on this contact surface, wherein this contact surface is oriented normal to the pressure force to be transmitted by the support device.

[0010] As an improvement according to the invention, it is proposed that the rigid assembly comprising the pressure piece and the rigid assembly comprising the base are pressed against each other at stop surfaces when the support device is unloaded, and are thereby held in a form-locking position relative to each other with respect to those directions which are parallel to that flat contact surface along which the two assemblies can slide against each other when the support device is loaded.

[0011] This makes it easy to achieve both a secure hold of the two assemblies to each other, and, when the support device is relieved of pressure, a reliable return movement of the assemblies to each other into a central starting position.

[0012] With the support device unloaded, the pressure piece is always returned to a precise starting position relative to the base assembly because this starting position is defined by stop surfaces, and not, for example, by a balance of several spring forces. The position is completely independent of the exact magnitude of any return force, as long as it exceeds the minimum force required to press the two assemblies together at said stop surfaces.

[0013] The invention is illustrated and explained in more detail with reference to drawings of an advantageous embodiment: Fig. 1: shows a sectional view with an axially parallel section plane of an exemplary advantageous support device according to the invention in the unloaded state. Fig. 2: shows the support device of Fig. 1 in the same view in the intended loaded state.

[0014] The illustrated exemplary support device has a base 1, a holding part 2, a pressure piece 3, a centering part 4, a screw 5 and a compression spring 6.

[0015] In its intended use, the support device is mounted on a larger device (not shown), for example, a straightening machine, and during operation, its contact surface 7, which is the side of the pressure piece 3 facing away from the base 1, is pressed firmly against a workpiece (not shown). The direction of the pressing force coincides with the direction of the longitudinal axis 9 of the support device, shown with a dashed line. All threads of the support device are coaxial with said longitudinal axis 9.

[0016] The support device is to be mounted on the larger device (for example, straightening machine) according to the present example by screwing the bolt thread 8 of the base 1, which is arranged away from the pressure piece 3, into a nut thread in the larger device.

[0017] That self-contained rigid assembly of parts which comprises the base 1 also includes, in addition to the base 1, the retaining part 2, which is connected to the base 1 by a further threaded connection, and serves as a connecting piece to that further self-contained rigid assembly which includes, among other things, the pressure piece 3.

[0018] The rigid assembly comprising the pressure piece 3 includes, in addition to the pressure piece 3, the centering part 4 and the screw 5, which is passed through a bore in the centering part 4 and engages with a nut thread in the pressure piece 3.

[0019] The centering element 4 has an outer surface which is a truncated conical surface arranged coaxially with the longitudinal axis 9, the diameter of which tapers towards the contact surface 7 of the pressure piece 3. This truncated conical surface is surrounded by the surface of an opening in the retaining element 2 which is also coaxial with the longitudinal axis 9. The opening in the retaining element 2 has a surface which is also designed as a truncated conical surface and is dimensioned and oriented such that it can bear in full contact with the surface of the centering element 4.

[0020] An elastic compression spring 6 rests on one side against a surface of the pressure piece 3 facing away from the contact surface 7, and on the other side against a surface of the holding part 2 facing the contact surface 7 of the pressure piece. The compression spring 6 therefore acts in such a way that, in the absence of other influences, it displaces the rigid assembly comprising the pressure piece 3 relative to the rigid assembly comprising the base 1, in the direction of the force to be transmitted onto a workpiece by the support device (i.e., upwards in the illustrations).

[0021] If the support device is not in contact with any workpiece, the rigid assembly encompassing the pressure piece 3 is displaced relative to the rigid assembly encompassing the base 1 such that the conical surface of the centering part 4 rests firmly against the previously described conical opening surface in the holding part 2, thereby positioning the centering part 4, and with it the entire assembly encompassing the pressure piece 3, coaxially with the longitudinal axis 9. The support device is then in the state described below. Fig. 1 . The stop surfaces mentioned above are, in this example, the conical surface of the centering part 4 and the conical opening surface in the holding part 2.

[0022] Fig. 2The state of the support device is shown when its contact surface 7 is pressed against a workpiece with a force greater than the force exerted by the compression spring 6. In this state, the assembly comprising the pressure piece 3 is displaced relative to the assembly comprising the base 1, contrary to the action of the compression spring 6, in the direction of the base 1. The two previously discussed truncated conical surfaces are axially displaced relative to each other so that they no longer touch. The rigid assembly comprising the pressure piece 3 and the rigid assembly comprising the base 1 abut each other at a common, flat contact surface 10, which is oriented perpendicular to the pressure force that the support device is intended to transmit to a workpiece – i.e., perpendicular to the longitudinal axis 9.Since in this position the two previously discussed truncated cone surfaces no longer touch each other, the rigid assembly encompassing the pressure piece 3 is displaceable normal to the longitudinal axis 9 relative to the rigid assembly encompassing the base 1, whereby only the frictional force at the contact surface 10 has to be overcome.

[0023] By appropriately selecting the materials and surfaces of those parts of the support device that contact each other at the contact surface 10, it is easily achieved that, in operation, the assembly comprising the pressure piece 3 can slide perpendicular to the applied pressure force relative to the assembly comprising the base 1, instead of sliding between the contact surface 7 of the pressure piece 3 and the surface of the workpiece being machined, which is contacted by the contact surface 7. Thus, according to the invention, damage to both the workpiece and the contact surface 7 of the pressure piece 3 is avoided.

[0024] The desired sliding properties at the contact surface 10 can be achieved, for example, by making the parts in contact there from surface-treated tool steel, and ideally also by applying some oil.

[0025] Since the rigid assembly comprising the base 1 is formed from at least two parts to be joined together, and since the rigid assembly comprising the pressure piece 3 is also formed from at least two parts to be joined together, the entire support device is easy to assemble, even though it comprises interlocking assemblies.

[0026] Within the scope of the invention, numerous variations of the depicted design of a support device are possible. Several of these are briefly mentioned below, without claiming to be exhaustive: Instead of rotationally symmetrical stop surfaces, the two aforementioned assemblies can also be brought into contact with several pairs of flat wedge surfaces serving as stop surfaces in order to center the assemblies relative to each other.

[0027] Instead of a single elastic compression spring that pushes in the axial direction, several elastic compression springs can also be used, which push radially from opposite sides.

[0028] Elastic tension springs can also be used instead of elastic compression springs.

[0029] Permanent magnets can also be used instead of elastic springs.

[0030] Instead of pairs of truncated cone shell surfaces or several pairs of wedge surfaces, hook connections or connections of two linked ring-like parts can also be used to prevent the two assemblies from completely separating and to achieve a precisely defined positioning of the two assemblies relative to each other in the unloaded operating state.

Claims

1. Support device, which is designed to bear against a workpiece with a contact surface (7) of a pressure piece (3) under a pressing force, wherein the rigid assembly which includes the pressure piece (3) and another rigid assembly of the support device, which includes a base (1), lie flat against each other at a contact surface (10) during the intended usage of the support device and are movable relative to each other by sliding along this contact surface (10), wherein the contact surface (10) is planar and oriented normally to the pressing force to be transmitted by the support device, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are pressed together at stop surfaces when the support device is unloaded and are thereby held in a defined relative position to one another in an interlocking manner with respect to those directions which lie parallel to the contact surface (10).

2. Support device according to claim 1, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are each comprised of at least two individual components which can be connected with each other.

3. Support device according to claim 1 or 2, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are, when the support device is unloaded, pressed together at stop surfaces by one or more flexible springs, which form part of the assembly, and / or by one or more magnets, which form part of the assembly.

4. Support device according to one of claims 1 to 3, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are, when the support device is unloaded, pressed together at two conical frustum surfaces arranged coaxially with respect to one another.

5. Support device according to one of claims 1 to 3, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are, when the support device is unloaded, pressed together at multiple pairs of wedge surfaces.

6. Support device according to one of claims 1 to 3, characterised in that the rigid assembly which includes the pressure piece (3) and the rigid assembly which includes the base (1) are, when the support device is unloaded, pressed together at a pair of hooks or a pair of two rings and / or a pair of a hook and a ring.

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