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 which is intended to bear against a workpiece with a contact surface under pressure.

[0002] When a support fixture is designed to apply a significant compressive force to a workpiece, it is common practice to guide the part of the support fixture that has the contact surface with the workpiece, which is also referred to as the "pressure piece," so that it can be moved relative to the base of the support fixture in such a way that the pressure piece can be moved relatively easily, at least a small distance, relative to the base around axes that are aligned perpendicular to the applied compressive force. This is intended to ensure that the contacted workpiece surface is not damaged if, for any reason, a slight lateral displacement occurs between the workpiece and the base of the support fixture, 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 and pressure piece assembly of a screw clamp, in which the pressure piece and the front side of the screw are held together by a ball joint connection.

[0004] US 8025279 B2 shows a screw clamp in which a pressure piece is connected to the face of the screw only via a coil spring. This may work well for damage-free holding of a workpiece with a sensitive surface, but is hardly applicable for the targeted, precise forming of a workpiece, since in actual use, the pressure piece is not in a precisely defined position relative to the rest of the pressure-applying device with respect to any degree of freedom. Support devices with pressure pieces which are held exclusively pivotably on other parts of the support device are shown, for example, in the 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.Usually, a return mechanism based on elasticity is also provided, by which the pressure piece is held in a neutral central position in the unloaded state.

[0005] Especially when using the support fixtures discussed above on straightening machines – i.e., machines used to shape elongated or flat workpieces into a desired shape through plastic forming – it has been shown that even those support fixtures equipped with pivoting pressure pads often leave annoying damage on the surface of the workpieces. It has been determined that sliding relative movements at the contact surface between the pressure pad of the support fixture and the workpieces are causally related to this damage.

[0006] The documents US 5244195 A and US 2724298 A show 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 is often disruptively caused by sliding relative movement between the workpiece and the pressure piece. Within the scope of the present invention, it was recognized that this damage is caused by the fact that the pressure piece is already located at the edge of the displacement range relative to the base of the support device at the beginning of the time in which it is in contact with the workpiece, and is therefore no longer sufficiently displaceable relative to the base of the support device, at least in one direction.

[0007] The object underlying the invention is to improve a support device for applying a compressive force to a workpiece, which support device has a base and a pressure piece that is 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.

[0008] 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 lie flat against one another on a flat contact surface during the intended use of the support device, and are movable relative to one another by sliding on this contact surface, wherein this contact surface is aligned normal to the compressive force to be transmitted by the support device as intended.

[0009] 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 one another at stop surfaces when the support device is unloaded, and are thereby held in a form-fitting manner in a defined relative position to one another with respect to those directions which are parallel to the flat contact surface along which the two assemblies can slide against one another when the support device is loaded.

[0010] This makes it easy to achieve both a secure holding of the two assemblies to each other and, when the load on the support device is removed, a reliable return movement of the assemblies to each other into a central starting position.

[0011] When the support device is 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, not, for example, by a balance of several spring forces. This position is completely independent of the exact magnitude of the return force, as long as it exceeds the minimum force required to press the two assemblies together at the stop surfaces.

[0012] 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 axis-parallel cutting 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 condition.

[0013] The exemplary support device shown comprises a base 1, a holding part 2, a pressure piece 3, a centering part 4, a screw 5 and a compression spring 6.

[0014] In its intended use, the support device is mounted on a larger device (not shown), such as a straightening machine, and during operation, the larger device presses its contact surface 7, which is the side of the pressure piece 3 facing away from the base 1, firmly against a workpiece (not shown). The direction of the compressive force coincides with the direction of the support device's longitudinal axis 9, shown in dash-dotted lines. All threads of the support device are coaxial with said longitudinal axis 9.

[0015] The support device according to the present example is to be mounted on the larger device (for example a straightening machine) by screwing the bolt thread 8 of the base 1, which is arranged away from the pressure piece 3, to a nut thread in the larger device.

[0016] The inherently rigid assembly of parts comprising the base 1 comprises, in addition to the base 1, also the holding part 2, which is connected to the base 1 by a further threaded connection and serves as a connecting piece to the further inherently rigid assembly which, among other things, comprises the pressure piece 3.

[0017] The rigid assembly comprising the pressure piece 3 contains, in addition to the pressure piece 3, the centering part 4 and the screw 5, which is guided through a bore in the centering part 4 and is in threaded engagement with a nut thread in the pressure piece 3.

[0018] The centering part 4 has an outer surface, which is a truncated cone surface arranged coaxially with the longitudinal axis 9, the diameter of which tapers as it approaches the contact surface 7 of the pressure piece 3. This truncated cone surface is surrounded by the surface of an opening in the holding part 2, which is coaxial with the longitudinal axis 9. The opening in the holding part 2 has a surface, which is also designed as a truncated cone surface, and is dimensioned and aligned such that it can lie flat against the surface of the centering part 4.

[0019] An elastic compression spring 6 rests on the one hand on a surface of the pressure piece 3 facing away from the contact surface 7, and on the other hand on 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 to a workpiece by the support device (in the illustrations therefore upwards).

[0020] If the support device is not in contact with any workpiece, the rigid assembly comprising the pressure piece 3 is displaced relative to the rigid assembly comprising the base 1 in such a way that the conical surface of the centering part 4 lies flush against the previously described conical opening surface in the holding part 2, whereby the centering part 4 and with it the entire assembly comprising the pressure piece 3 is positioned coaxially to the longitudinal axis 9. The support device is then in the state according to Fig. 1 . In this example, the stop surfaces mentioned above are the conical surface of the centering part 4 and the conical opening surface in the holding part 2.

[0021] Fig. 2shows the state of the support device when its contact surface 7 is pressed against a workpiece with a force that is greater than the force exerted by the compression spring 6. The assembly comprising the pressure piece 3 is displaced relative to the assembly comprising the base 1, counter to the action of the compression spring 6, in the direction of the base 1. The two previously discussed truncated cone surfaces are axially displaced relative to one another such that they no longer touch one another. The inherently rigid assembly comprising the pressure piece 3 and the inherently rigid assembly comprising the base 1 rest against one another on a common flat contact surface 10, which is aligned normal to the compressive force intended to be transmitted to a workpiece by the support device - i.e. normal to the longitudinal axis 9.Since in this position the two previously discussed truncated cone surfaces no longer touch each other, the rigid assembly comprising the pressure piece 3 can be displaced perpendicular to the longitudinal axis 9 relative to the rigid assembly comprising the base 1, whereby only the frictional force at the contact surface 10 has to be overcome.

[0022] By appropriately selecting the materials and surfaces of those parts of the support device that contact at the contact surface 10, it is easily possible to ensure that, during use, 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 that is contacted by the contact surface 7. This prevents damage to both the workpiece and the contact surface 7 of the pressure piece 3 in accordance with the invention.

[0023] The desired sliding properties at the contact surface 10 can be achieved, for example, by the parts in contact there being made of surface-hardened tool steel and, ideally, also being slightly oiled.

[0024] Since the rigid assembly comprising the base 1 is formed from at least two individual parts to be joined together, and since the rigid assembly comprising the pressure piece 3 is also formed from at least two individual parts to be joined together, the entire support device is easy to assemble, even though it comprises interlocking assemblies.

[0025] Within the scope of the inventive concept, numerous modifications to the illustrated design of a support device are possible. Without claiming to be exhaustive, several of them will be briefly mentioned: Instead of using rotationally symmetrical stop surfaces, the two aforementioned assemblies can also be brought into contact with several pairs of flat wedge surfaces that serve as stop surfaces, in order to center the assemblies relative to one another.

[0026] Instead of a single elastic compression spring that presses in the axial direction, several elastic compression springs can be used that press radially from opposite sides.

[0027] Instead of elastic compression springs, elastic tension springs can also be used.

[0028] Permanent magnets can also be used instead of elastic springs.

[0029] Instead of pairs of truncated cone surfaces or several pairs of wedge surfaces, hook connections or connections of two interlinked ring-like parts can also be used to prevent a complete loosening of the two assemblies and to achieve a precisely defined positioning of the two assemblies relative to each other in the unloaded operating state.

Claims

1. A support device which is intended 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, which comprises a base (1), bear flatly against one another on a contact surface (10) during the intended use of the support device and are movable relative to one another by sliding on this contact surface (10), wherein the contact surface (10) is flat and aligned perpendicular to the compressive force to be transmitted by the support device, characterized in thatthat the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed against one another at stop surfaces when the support device is unloaded, and are thereby held in a form-fitting manner in a defined relative position to one another with respect to those directions which are parallel to the contact surface (10).

2. Support device according to claim 1, characterized in that both the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) each consist of at least two individual parts which can be connected to one another.

3. Support device according to claim 1 or 2, characterized in thatthe rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed against one another at stop surfaces by one or more elastic springs which are part of the support device and / or by one or more magnets which are part of the support device when the support device is unloaded.

4. Support device according to one of claims 1 to 3, characterized in that the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed against one another on two coaxially arranged truncated cone surfaces when the support device is unloaded.

5. Support device according to one of claims 1 to 3, characterized in that the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed together on several pairs of wedge surfaces when the support device is unloaded.

6. Support device according to one of claims 1 to 3, characterized in that the rigid assembly comprising the pressure piece (3) and the rigid assembly comprising the base (1) are pressed against one another on a pair of two hooks or on a pair of two rings and / or on a pair of one hook and one ring when the support device is unloaded.

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