Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING, OR HOLDING
  • B25B5/00—Clamps
  • B25B5/06—Arrangements for positively actuating jaws
  • B25B5/08—Arrangements for positively actuating jaws using cams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING, OR HOLDING
  • B25B5/00—Clamps
  • B25B5/06—Arrangements for positively actuating jaws

Definitions

• the present invention relates to a clamping device for securing workpieces with the features of the preamble of claim 1.
• clamping devices are required for this type of workpiece clamping. Depending on the type and shape of the workpieces, very different clamping devices are used. For example, clamping jaws can be used to hold and clamp sheet metal workpieces.
• a special type of clamping device is designed to secure workpieces with openings or cutouts. These devices extend through the openings and clamp the workpiece at the edge of the opening by applying a pressure piece. to clamp and fix in place.
• the present invention relates to such a clamping device.
• Such clamping devices also known in this field as hook clamps, have a body with a contact surface and a centering mandrel that projects outwards beyond the contact surface. In use, this centering mandrel is inserted through the opening in the workpiece and retracted. Extendable clamping elements with, in particular, hook-shaped pressure ends are mounted in the centering mandrel. When the centering mandrel is inserted through the opening in the workpiece, these pressure ends are extended and lowered by actuating an actuator, typically into opposing positions, onto a surface surrounding the edge of the opening in the workpiece. There, they exert pressure on the workpiece and against the contact surface on which the opposite side of the workpiece rests.
• an actuator typically into opposing positions
• clamping devices also known as hook clamps
• hook clamps can be found in the prior art, for example in the DE 103 39 322 A1 or also in the DE 10 2020 114 986 A1
• clamping devices exist, as shown in the aforementioned publication, in a manually operated version, where typically a toggle lever is cocked to extend the clamping elements with their pressure points and pull them against the surface of the workpiece to be clamped.
• clamping elements also exist in an automatically operated version, for example hydraulically or pneumatically, as described, for instance, in the US 2018/0015580 A1 or also in the DE 10 2016 015 041 A1 .
• clamping device has proven its worth and is used, although not exclusively, particularly in the automotive industry, where sheet metal body parts often have numerous openings and cutouts that are ideally suited as reference points for clamping the workpiece and can be precisely secured using such clamping devices, known as hook clamps. Thus, Such clamping devices are widely used, especially by automotive manufacturing companies.
• clamping elements When using such clamping elements, it is essential that they apply a sufficient clamping force to securely fix the component or workpiece, preventing it from shifting out of the clamping position. Conversely, the applied clamping force must not be so great as to risk damaging the workpiece, for example, by deforming a sheet metal part surrounding the opening. Particular attention must be paid to the material thickness of the workpiece being clamped, such as the sheet metal thickness of a component in the area surrounding the opening through which the clamping device's centering mandrel passes. Accordingly, known clamping devices offer the possibility of adjusting the distance between the contact surface and the opposing end faces of the clamping elements in a given clamping position, thus adapting the clamping element to the material thickness of the workpiece.
• the clamping device clamps the workpiece with excessive clamping force. Besides the risk of damaging the workpiece, excessive clamping force can also lead to damage to the clamping device itself.
• a common type of damage is damage, breakage, or deformation of the clamping elements. When this occurs, the clamping device is no longer suitable for further use; either parts of the clamping device, usually the clamping elements, must be replaced, or the entire clamping device must be replaced.
• the present invention aims to address this problem.
• a clamping device according to the invention for securing workpieces has, as is also common in the prior art, a body on which a contact surface for a section of a workpiece is arranged. It further has a centering mandrel projecting outwards from the body beyond the contact surfaces. Furthermore, the clamping device according to the invention provides a pair of clamping elements, each having a pressure end, in particular a hook-shaped one. A tension element is also provided, which is coupled to the clamping elements. Finally, the clamping device according to the invention has, also as is already known from the prior art, an actuator with which a tensile force can be applied to the tension element.
• the clamping elements are movably arranged within the body and coupled to the tensioning element in such a way that, in a released position of the tensioning element, their contact ends are retracted into slots formed on opposite sides of the centering mandrel, thus not protruding beyond the outer contour of the centering mandrel.
• the arrangement and mounting of the clamping elements are further such that, in a clamped position of the tensioning element obtained from the released position by applying tensile force to the tensioning element, their contact ends extend radially out of the slots towards the contact surface, with their end faces pointing towards the contact surface. In this position, as is also the case in the prior art, a workpiece placed on the contact surface can be gripped on the opposite side and thus clamped securely between the contact surface and the end faces of the contact ends of the clamping elements.
• the special feature of the clamping device according to the invention is that the tensioning element has an integrated tensile force limiting mechanism.
• This tensile force limiting mechanism ensures that the tensile force applied to the clamping elements, which in turn limits the clamping force or the contact force with which the clamping elements are pressed against the workpiece with the end faces of their contact surfaces, thus pressing the workpiece against the contact surfaces, is limited. This prevents excessive clamping force from being applied to the workpiece and avoids the aforementioned problems and potential damage.
• the tensile force limiting mechanism is, in particular, reversible according to the invention; that is, it is not a predetermined breaking point or the like, but rather a mechanism that engages when a maximum tensile force value is exceeded, without impairing the overall functionality of the clamping device.
• the engagement of the tensile force limiting mechanism when clamping a workpiece does not prevent the clamping device from securely fixing the workpiece. A tensile force sufficient for such fixation is still applied, and thus the clamping force is maintained. It merely prevents this force from becoming too high and thus potentially causing damage to the clamping device or damage to the workpiece.
• the tensile element is divided in the axial direction in which the tensile force is applied, comprising at least a first tensile element section and at least a second tensile element section.
• the actuator engages the first tensile element section to apply or transmit the tensile force to the tensile element.
• the clamping elements are coupled to the second tensile element section; thus, the tensile force is transmitted to the clamping elements via this second tensile element section, thereby translating the tensile force into both the contact force and the clamping force of the clamping elements.
• a spring element is arranged in the tension element section, which simultaneously couples these two tension element sections and transmits a tensile force below a maximum force determined by the spring force from the first tension element section to the second tension element section.
• the tensile force exceeds the maximum force, it deforms elastically.
• a tensile force exceeding the maximum force is no longer translated into an increase in the clamping force exerted on the workpiece by the clamping elements, but instead leads to a deformation of the spring element, where it is absorbed and compensated.
• the clamping device can still securely clamp the workpiece at the maximum determined clamping force.
• the excess tensile force is absorbed by the spring element, causing it to deform and thus being converted into clamping energy within the spring element, thereby diverting it from the actual clamping process.
• first tension element section comprises a pull rod section
• second tension element section comprises a sleeve section.
• the pull rod section then extends with one free end into the interior of the sleeve section, and a first bearing structure is formed on the pull rod section, while a second bearing structure is formed on the sleeve section.
• the two bearing structures, first and second are separated from each other in the axial direction of the tension element, and the spring element is arranged between the first and second bearing structures, engaging with each bearing structure.
• the applied tensile force is thus transmitted from the pull rod section via the first bearing structure to the spring element, from the spring element via the second bearing structure to the sleeve section, and from there in turn to the clamping elements. If the tensile force exceeds the specified maximum force, the sleeve section deforms. The spring element is deactivated without any further transmission of the tensile force to the sleeve section. The contact or clamping force remains at the predetermined maximum force value.
• the spring element can, in particular, be a helical spring acting as a compression spring, arranged within the sleeve section and around the tie rod section. This allows for a compact design and also enables a precise calculation of the spring force, which determines the maximum force, by appropriately selecting the helical spring in terms of its material thickness, length, and the spacing between adjacent spring coils.
• the first bearing structure can be formed by a disc-like, circumferential projection or collar at the free end of the drawbar section
• the second bearing structure can be formed by a shoulder section projecting into the interior of the sleeve section at an open end of the sleeve.
• the spring element in particular the coil spring, can then be arranged between the disc-like projection and the shoulder section, bearing against the aforementioned structures at their respective ends and thereby transmitting the applied tensile force until it deforms upon reaching a maximum force and no longer transmits any further force to the sleeve section.
• connection between the first and second tension element sections may also include a hinge connection that is tiltable transversely to the axial direction.
• a hinge connection allows tilting or misalignment in the orientation between the second and first tension element sections by at least a certain degree. This allows, for example, a slight tilting of the centering mandrel or the arrangement of the clamping elements in the case of an uneven workpiece surface or an uneven thickness of the edge around the opening into which the centering mandrel of the clamping device is inserted.
• the actuator of the clamping device according to the invention can in particular have a toggle lever, preferably manually operated.
• This toggle lever can in particular engage a lever actuating mechanism arranged inside the body and can then advantageously be detachably connected to it and, in particular, be removable from it.
• This can be advantageous, for example, if, after clamping the workpiece, the area in which the clamping device is located is to be accessed, for example, with a measuring device or with a machining tool, and a protruding clamping lever would be in the way.
• the clamping device advantageously has return springs arranged between the tensioning element and the body, which apply a return force to the tensioning element acting in the direction of the release position. Such return springs then cause the tensioning element to return to the release position when the actuator is moved to release the clamping, and ensure that the clamping elements return securely to their position recessed in the centering mandrel, so that the workpiece can then be lifted from the centering mandrel, or the centering mandrel can be removed from the workpiece.
• the body of the clamping device according to the invention can be essentially cylindrical.
• the contact surface can then be arranged on a cylindrical end face of the body, and the centering mandrel can project outwards from the cylindrical end face of the body.
• the contact surface can be arranged in an annular shape around the centering mandrel.
• the contact surface is formed on a ring element that is rotatably mounted on the body around the centering mandrel, in particular by at least 360°.
• the contact surface needs to have recesses to accommodate, for instance, webs or ribs located in the area around the opening through which the centering mandrel is to be inserted when the workpiece is clamped. These recesses can then be aligned as appropriate.
• the ring element can be interchangeable, so that ring elements of different types and sizes, with differently dimensioned contact surfaces or with different contours of the contact surfaces, can be arranged on the body of the clamping device according to the invention, adapted to a workpiece to be clamped.
• the tensioning element can be arranged, in particular, inside the cylindrical body and run along the longitudinal axis of the cylinder. In this way, the tensioning force is applied along the longitudinal axis of the cylinder.
• the centering mandrel can have a conically tapered shape. This serves, on the one hand, to center and thus align the workpiece to be clamped, and can also be useful when workpieces with openings of different diameters are to be clamped on the clamping device according to the invention.
• the centering mandrel is displaceable along the body in a longitudinal direction and is pre-tensioned in a flared position by a compression spring.
• the centering mandrel can essentially plunge into the component of the body and yield if the workpiece has an opening with a diameter that is smaller than the maximum width or maximum diameter of the centering mandrel at one end. The centering mandrel then yields against the compression spring force until the workpiece rests on the contact surface.
• the centering mandrel together with the arrangement of the clamping elements, is rotatably mounted on the body about a longitudinal axis of the centering mandrel, in particular rotatably by at least 360°.
• Such rotatability can be fixed by appropriate fixing mechanisms. so that the clamping device is first aligned in a fixed position, for example arranged on a clamping frame or rack, by adjusting and rotating the centering mandrel in a position that is most favorable for clamping and handling, and then secured by fixing this rotational position.
• Figures 1 to 7 The first design variant is shown.
• the second design variant is then described, which is shown in Figures 8 to 14 is shown, whereby in the description In this second design variant, reference will be made to the description of the first design variant, at least where identical or similar constructive and functional features are present.
• Figures 1 to 7 The first design variant is shown.
• the second design variant is then described, which is shown in Figures 8 to 14 is shown, whereby in the description In this second design variant, reference will be made to the description of the first design variant, at least where identical or similar constructive and functional features are present.
• FIG. 1 shows a possible embodiment of a clamping device 10 according to the invention.
• the clamping device 10 comprises a body 11, which is cylindrical in shape and mounted on a base plate 12.
• the base plate 12 has bores 13 which can be used to secure the clamping device 10 according to the invention to a clamping frame, a clamping rack, or a similar device component.
• a contact ring 15 is arranged, which has a contact surface 16 on its upper side, which in this example is planar.
• a centering mandrel 17 projects axially from the cylindrical body 11 and is aligned with its center. Slots 18 are provided or formed laterally in this centering mandrel 17, through which a pressure end 19 of each clamping element 20 (see Figure 5) projects laterally from the centering mandrel 17.
• the pressure ends 19 are hook-shaped and have an end face 21 that, in the position shown in the figures, points downwards and towards the support surface 16.
• an actuating lever 22 can be seen, which is connected to a toggle lever mechanism 23 formed inside the body 11.
• the clamping device 10 or rather the clamping elements 20, are shown in a clamped position.
• the clamping device 10 can also assume a released position in which the clamping elements 20 with their pressure ends 19 are arranged in the slots 18 inside the centering mandrel 17.
• a clamping mechanism is designed by which, by actuating the actuating lever 22, the clamping elements 20 can be moved back and forth between the clamped position shown in the figures and a release position not shown in detail here, and by which a clamping or pressing force is exerted on the clamping elements 20 in the clamped position.
• the toggle lever mechanism 23 engages a tension element 24, which in turn is coupled to the clamping elements 20.
• the pulling element 24 is pulled downwards in one direction away from the tip of the centering mandrel 17, thereby also pulling the clamping elements 20 downwards and simultaneously pivoting them outwards through the slots 18 of the centering mandrel 17 with their pressure ends 19, guided by guide pins 26 and 27 fixed to the body 11 and running in a guide slot 25 of the clamping elements 20.
• the clamping elements 20 are pivotably mounted on a hinge pin 28 on the pulling element 24.
• the special feature of the clamping element 10 is that it has a tensile force limiting mechanism that restricts the clamping force applied to the clamping elements 20 by actuating the operating lever 22. If too great a force is applied by the operating lever 22, it is no longer transmitted to the clamping elements 20.
• the pulling element 24 first comprises a rod section 29, which runs within a lower part of the body 11 and along a longitudinal central axis 30 of this body 11.
• the toggle lever mechanism 23 engages this rod section and, when the actuating lever 22 is pressed, transmits a tensile force to it.
• the rod section 29 has a free end at an upper section located within the body 11, at which A collar 31 is formed around the rod section 29, which is located inside a sleeve section 32, which is part of a second section of the tension element 24.
• This sleeve section 32 has a circumferential shoulder 33 at one lower end, projecting inwards into the sleeve opening.
• a compression spring 34 designed as a helical spring, is arranged inside the sleeve section 32 between the shoulder 33 and the collar 31 and around the rod section 29. This compression spring 34 thus forms a coupling and connection between the two sections of the tension element 24, the rod section 29 and the sleeve section 32.
• a contact block 37 is coupled to the sleeve section 32, more precisely to bearing legs 35 that extend from it and are integrally connected to it, via connecting pins 36.
• This mounting block 37 has a spherical cap-shaped surface 38 on one underside, which abuts a correspondingly shaped recess 39 formed in the free end of the rod section 29. This creates a hinge, allowing the mounting block 37 to pivot about the axis formed by the connecting pins 36 relative to the sleeve section 32.
• the clamping elements 20 are connected to the mounting block 37 by the hinge pins 28.
• the compression spring 34 transmits this clamping force undiminished from the rod section 29 to the sleeve section 32 and thus to the contact block 37, and from there to the clamping elements 20, which are pulled downwards and, due to the interaction with the guide pins 26, 27, simultaneously extend their contact ends 19 outwards from the slots 18 in the centering mandrel 17 and are thereby drawn with their end faces 21 towards the contact surfaces 16.
• a workpiece which has an opening through which the centering mandrel 17 is passed can be clamped in an area surrounding this opening between the contact surfaces 16 and the end faces 21 of the clamping elements 20. If, for example, due to If the workpiece has a different material thickness in the sections where the two clamping elements 20 rest with their end faces 21, causing an offset, this can be automatically compensated for by a corresponding transverse force applied to the clamping block 37. This causes the clamping block 37 to rotate about the connecting pins 36, and the spherical cap-shaped surface 38 to move articulated within the corresponding recess 39.
• the compression spring 34 is compressed by further downward pulling of the rod section 28. This force component is then no longer transmitted to the sleeve section 32 and thus not to the clamping elements 20.
• the clamping elements 20 continue to clamp only with the specified maximum force. In particular, the clamping effect can be maintained safely and with a force that does not exceed the maximum force, thus preventing any damage to the clamped workpiece or damage to the clamping device 10, for example, breaking or deformation of the clamping elements 20.
• the tensioning element 24 When the actuating lever 22 is moved upwards from the lowered position shown in the figures, in which it pulls the tensioning element 24 downwards and thus triggers the movement of the clamping elements 20 into the clamping position, the tensioning element 24 also moves upwards and the clamping elements 20 are moved out of the extended clamping position in a reverse movement and their pressure ends 19 are retracted into the slots 18 of the centering mandrel 17 and recessed there.
• a return spring 40 assists this movement; it is arranged between a shoulder 41 inside the body 11 and a shoulder 42 provided on the outside of the sleeve section 32.
• the toggle lever mechanism 23 is designed such that, when the actuating lever 22 has been moved into the clamping position, it is moved beyond a dead center and thus locks the clamping position. In this position The actuating lever 22, which is detachably attached to the toggle lever mechanism 23, can be detached and removed so that it does not obstruct subsequent work on the clamped workpiece.
• the support ring 15 is rotatable relative to the body 11, allowing it to be rotated about the longitudinal center axis 30, in particular by at least 360°. This can be especially important if the contact surface 16 is not uniformly flat and even, but, for example, has recesses to accommodate webs or other projections of a workpiece that is to be clamped with the clamping device 10.
• the second embodiment of a clamping device according to the invention shown here is as described in the Figures 8 to 14 It has been shown that the essential constructive features and functions are identical in structure and design to those shown in the Figures 1 to 7 The illustrated embodiment is shown. Accordingly, in the Figures 8 to 14 the assignment of reference symbols corresponding to the reference symbols in the Figures 1 to 7 This is done by simply prefixing the respective reference numerals of identical elements with a "1", so that the clamping device according to the second embodiment, which is in the Figures 8 to 14 shown is numbered as clamping device 110. Furthermore, for example, the centering mandrel is not there, as in Figures 1 to 7 with 17, but here designated as 117.
• the clamping device 110 corresponds to the clamping device 10 from the first embodiment described above, so that the preceding description can be referred to in this respect.
• the preceding description reads accordingly to the illustration of the Figures 8 to 14 and analogously to the embodiment shown here, wherein the reference numeral "1" is to be placed before each of the reference numerals used above, i.e., for example, reference numeral 20 is to be read as 120, etc.
• the illustrated embodiment of the clamping device 110 is related to the preceding embodiment of the clamping device 10 according to the Figures 1 to 7
• the fact is that the The centering mandrel 117 is not fixed to the body 111, but is mounted on it so as to be longitudinally displaceable.
• the centering mandrel 117 has a head piece 148 which is mounted longitudinally displaceable within the body 111 and is connected by pins 143 to a sleeve 144, which is also longitudinally displaceable in a section of the body 111 located further towards the base plate 112.
• the pins 143 are guided in slots 145 formed in the side wall of the body 111.
• the end face of the sleeve 144 facing the base plate 112 rests on a spring 146, which in turn is supported by the body 111. This allows the centering mandrel 117 to plunge into the body 111 in the direction of the base plate 112, whereby the spring 146 is compressed and thus exerts a restoring force.
• This design allows the clamping device 110 to clamp workpieces that have an opening through which the centering mandrel 117 must pass, but whose opening width or diameter is smaller than the diameter of the centering mandrel 117.
• the edge of the opening abuts a section of the centering mandrel 117 and, by compressing the spring 147, pushes the centering mandrel 117 downwards until the workpiece rests on the support surface 116.
• the mechanism of the tensioning element 124 and its associated components also moves away from the centering mandrel 117, so that in this position the clamping elements 120 can be clamped by actuating the actuating lever 122 as described above.
• the workpiece can be lifted off and the centering mandrel 117 with the further mechanism arranged on it emerges again from the body 111, pushed upwards by the force of the spring 146.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Clamps And Clips (AREA)

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Publications (1)

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Citations (5)

• 2024
  • 2024-04-25 EP EP24172585.2A patent/EP4640374A1/fr active Pending

Patent Citations (5)

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