Clamping device

Abstract

A clamping device (10) for securing workpieces has a body (11) on which a contact surface (16) for a section of a workpiece is arranged, a centering mandrel (17) projecting outwards from the body (11) beyond the contact surface (16, 116), a pair of clamping elements (20) each having a pressure end (19), a tension element (24) coupled to the clamping elements (20) and an actuator (22) for applying a tension force to the tension element (24).The clamping elements (20) are movably arranged in the body (11) and coupled to the tensioning element (24) such that, in a released position of the tensioning element (24), their contact ends (19) are inserted into slots (18) formed on opposite sides of the centering mandrel (17) and into the centering mandrel (17). In a clamped position of the tensioning element (24), obtained from the released position by applying a tensile force to the tensioning element (24), their contact ends (19) extend radially out of the slots (18) towards the contact surface (16), with their end faces (21) of the contact ends (19) pointing towards the contact surface (16). The tensioning element (24) has an integrated tensile force limiting mechanism.

Description

[0001] The present invention relates to a clamping device for securing workpieces with the features of the preamble of claim 1.

[0002] In industrial, especially machine-based, manufacturing processes, but also for repairs, it is generally necessary to fix and clamp workpieces in a predetermined orientation. Such precise positioning and orientation of workpieces is also required for accurate measurement of these workpieces, for example, using tactile or photogrammetric methods, as employed in prototype development and quality control.

[0003] Clamping devices are required for such workpiece clamping. Depending on the type and shape of the workpieces, very different clamping devices are used. For example, clamping clamps can be used to hold and clamp sheet metal workpieces. A special type of clamping device is designed to secure workpieces that have openings or cutouts. These clamping devices extend through the openings and clamp the workpiece at the edge of the opening by applying a pressure piece. The present invention relates to such a clamping device.

[0004] 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.

[0005] Descriptions of such clamping devices, also known as hook clamps, can be found in the prior art, for example in DE 103 39 322 A1 or DE 10 2020 114 986 A1. As shown in the latter document, these clamping devices exist in a manually operated version, in which a toggle lever is typically tensioned to extend the clamping elements with their contact ends and pull them against the surface of the workpiece to be clamped. However, such clamping elements also exist in an automatically operated version, for example hydraulically or pneumatically, as described, for example, in US 2018 / 0015580 A1 or DE 10 2016 015 041 A1.

[0006] This type of 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 securely fixed using these clamping devices, also known as hook clamps. Consequently, such clamping devices are widely used by automotive manufacturers.

[0007] 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. On the other hand, 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 support surface and the opposing end faces of the clamping elements in a given clamping position, in order to adapt the clamping element to the material thickness of the workpiece being clamped. In practice, however, it sometimes happens that—either because the adjustment for adapting to the thickness of the workpiece is not sufficiently precise, or because the material thickness of different workpieces clamped successively varies—even within a possible tolerance—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.If this happens, 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.

[0008] The present invention aims to address this problem.

[0009] This problem is solved by a clamping device with the features of claim 1. Advantageous further developments of a clamping device according to the invention are specified in dependent claims 2 to 17.

[0010] 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, as is also the case with known clamping devices of this type, 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. Furthermore, the arrangement and mounting of the clamping elements are 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 the case with the state of the art, you can grasp a workpiece placed on the support surface on the opposite side and thus clamp the workpiece between the contact surface and the end faces of the clamping elements.

[0011] 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, i.e.,This is not a predetermined breaking point or anything similar, but rather a mechanism that engages when a maximum tensile force is exceeded, without impairing the overall functionality of the clamping device. In particular, 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 a fixation is still applied, thus maintaining the clamping force. The mechanism merely prevents this force from becoming too high and thus potentially damaging the clamping device or the workpiece.

[0012] One way to implement such a tensile force limiting mechanism is specified in more detail in dependent claim 2. In such an embodiment, 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.According to the invention, a spring element is arranged between the first and second tension element sections. This spring element couples the two sections and transmits a tensile force, below a maximum force determined by the spring force, from the first to the second section. However, it deforms elastically when the tensile force exceeds this maximum force. Thus, in this design, 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. Instead, it deforms the spring element, where it is absorbed and compensated.As mentioned above, even with excessive force applied when the actuator is actuated, for example due to an excessively thick workpiece, the clamping device can ensure a secure clamping of the workpiece with the maximum determined clamping force; the excess force component of the tensile force is absorbed by the spring element, leading to its deformation and thus being converted into clamping energy in the spring element and thus withdrawn from the actual clamping process.

[0013] An embodiment as described above can be implemented, in particular, such that the first tension element section comprises a pull rod section and the 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 and engages with each of them.Here, the applied tensile force is transferred 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 spring element deforms without any further transfer of the tensile force to the sleeve section. The contact or clamping force remains at the specified maximum force value.

[0014] 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.

[0015] The first bearing structure can be formed by a disc-like, circumferential projection or collar at the free end of the drawbar section, and 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.

[0016] Furthermore, in the clamping device according to the invention, in a more detailed embodiment of the tensile force limiting mechanism as described above, the connection between the first and second tension element sections may also include a hinge connection that is tiltable transversely to the axial direction. Such 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.

[0017] 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.

[0018] The clamping device according to the invention advantageously has return springs arranged between the tensioning element and the body, which apply a restoring force to the tensioning element 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.

[0019] In a preferred embodiment, 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. In particular, the contact surface can be arranged in a ring shape around the centering mandrel. To achieve greater flexibility in adjusting and adapting the clamping device to a workpiece, it is advantageous to provide that the contact surface is formed on a ring element which is rotatably mounted on the body around the centering mandrel, in particular by at least 360°.This can be advantageous, for example, if the mounting surface needs to have recesses to accommodate, for instance, webs or ribs located around the opening through which the centering mandrel is inserted when the workpiece is clamped. These recesses can then be aligned accordingly. Furthermore, the ring element can be interchangeable, allowing ring elements of different types and sizes, with differently sized bearing surfaces or with different contours, to be arranged on the body of the clamping device according to the invention, adapted to the workpiece being clamped.

[0020] In one of the embodiments described above, where the clamping device has a cylindrical body, 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 tensile force is applied along the longitudinal axis of the cylinder.

[0021] In the clamping device according to the invention, 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. In particular, it can be provided that the centering mandrel is displaceable along the body in a longitudinal direction and is pre-tensioned in a flared position by a compression spring. In such an arrangement, the centering mandrel can essentially plunge into the component of the body and move out of the way if the workpiece has an opening with an opening diameter that is smaller than the maximum width or maximum diameter of the centering mandrel at one foot.The centering mandrel then deflects against the compression spring force until the workpiece lies on the contact surface.

[0022] Further flexibility is achieved with the clamping device according to the invention if the centering mandrel, together with the arrangement of the clamping elements, is rotatably mounted on the body relative to 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 initially aligned in a fixed position, for example, on a clamping frame or rack, by adjusting and rotating the centering mandrel to a position that is most favorable for clamping and handling, and then secured by fixing this rotational position.

[0023] Further features and advantages of the invention will become apparent from the following description of possible embodiments and the accompanying figures. These show: Fig. 1 a perspective view of a clamping device designed according to the invention in a first possible embodiment; Fig. 2 the clamping device according to Fig. 1 in a side view and with clamping elements in a clamping position; Fig. 3 the clamping device according to Fig. 1 in a view opposite the side view Fig. 2 Side view rotated by 90°; Fig. 4 a top view of the clamping device according to Fig. 1 from above; Fig. 5 the clamping device according to Fig. 1 in a line of intersection G - G in Fig. 3 longitudinal section view taken; Fig. 6 the clamping device according to Fig. 1 in a line of intersection H - H in Fig. 4 longitudinal section view taken; Fig. 7 the clamping device according to Fig. 1in a line of intersection I - I in Fig. 4 Longitudinal section view taken; Fig. 8 a perspective view of a clamping device designed according to the invention in a second possible embodiment; Fig. 9 the clamping device according to Fig. 8 in a side view and with clamping elements in a clamping position; Fig. 10 the clamping device according to Fig. 8 in a view opposite the side view Fig. 9 Side view rotated by 90°; Fig. 11 a top view of the clamping device according to Fig. 8 from above; Fig. 12 the clamping device according to Fig. 8 in a line of intersection G - G in Fig. 10 longitudinal section view taken; Fig. 13 the clamping device according to Fig. 8 in a line of intersection H - H in Fig. 11 longitudinal section view taken; and Fig. 14 the clamping device according to Fig. 8 in a line of intersection I - I in Fig. 11 longitudinal section view taken;

[0024] The figures show, in seven different views each, two possible embodiments of a clamping device according to the invention, a first embodiment variant in the Figures 1 to 7 , a second form of design in the Figures 8 to 14These embodiments are explained in more detail below as exemplary implementations of the invention described above in general terms. Further advantages and features of the invention will also become apparent from this explanation in general terms and independently of the specific embodiments. These embodiments are not limiting; rather, there are numerous other embodiments of the invention described above in general terms and claimed herein. It should also be noted that the figures and drawings are not to be understood as complete and comprehensive construction drawings, nor are they necessarily to scale. Rather, the figures are to be understood as technical sketches in which essential features and aspects of the invention and the respective specific embodiment are depicted and illustrated.

[0025] The first embodiment of a clamping device designed according to the invention, as described in the following, will first be explained in more detail below. 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 of this second embodiment variant, reference will be made to the description of the first embodiment variant at least where identical or at least similar constructive and functional features are present. Figures 1 to 7 .

[0026] In the Figures 1 to 4 is initially presented in four different views, a three-dimensional view ( Figure 1 ), a first side view ( Figure 2 ), a second side view rotated 90° relative to the first side view ( Figure 3 ) and supervision from above ( Figure 4Figure 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.

[0027] At an upper end 14 of the body 11, a contact ring 15 is arranged, which has a contact surface 16 on its upper side, which in this example is planar. Centrally located to the contact ring 15, 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. In this example, 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.

[0028] Furthermore, an actuating lever 22 can be seen, which is connected to a toggle lever mechanism 23 formed inside the body 11. In the Figures 1 to 4In the figures shown, and also in the subsequent figures, 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 retracted in the slots 18 inside the centering mandrel 17.

[0029] Inside corpus 11, as shown in the sectional views of the Figures 5 to 7As can be seen, 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. By actuating the actuating lever 22 and thus the toggle lever mechanism 23, the pulling element 24 is pulled downwards in one direction away from the tip of the centering mandrel 17, which also pulls down the clamping elements 20 and simultaneously, guided by guide pins 26 and 27 fixed to the body 11 running in a guide slot 25 of the clamping elements 20, pivots outwards through the slots 18 of the centering mandrel 17 with their pressure ends 19.For this purpose, the clamping elements 20 are pivotably mounted on a hinge pin 28 on the tension element 24.

[0030] 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.

[0031] In this embodiment, this is achieved by dividing the pulling element 24 into two parts. The pulling element 24 first comprises a rod section 29, which runs within a lower part of the body 11 and is oriented 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 plate-like circumferential collar 31 is formed. The rod section 29 lies inside a sleeve section 32, which is part of a second section of the pulling element 24. This sleeve section 32 has a circumferential shoulder 33 at its lower end, projecting inwards into the sleeve opening.Between the shoulder 33 and the collar 31, and around the rod section 29, a compression spring 34, designed as a helical spring, is arranged inside the sleeve section 32. 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 contact 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 contact 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 means of the hinge pins 28.

[0032] If a clamping force is applied to the rod section 29 of the tension element 24 via the actuating lever 22, and this clamping force is less than the force required to deform the compression spring 34, 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. In this way, 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, a misalignment occurs in the sections where the two clamping elements 20 rest with their end faces 21 due to differing material thicknesses of the workpiece, this misalignment can be automatically compensated for by a corresponding transverse force acting on 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. If the force applied to the tension element 24 by the actuating lever 22 exceeds a maximum force required for clamping the workpiece—a maximum force represented by the spring force of the compression spring 34—the compression spring 34 is compressed by further downward pulling of the rod section 28, and this force component is 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, such as breakage or deformation of the clamping elements 20.

[0033] 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.

[0034] The toggle lever mechanism 23 is designed such that, when the actuating lever 22 is moved into the clamping position, it is moved beyond a dead center, thus locking the clamping position. In this position, the actuating lever 22, which is detachably attached to the toggle lever mechanism 23, can be released 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.

[0035] As already mentioned above, 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 described in the Figures 8 to 14 shown is numbered 110 as a clamping device. Furthermore, for example, the centering mandrel is not shown there, as in Figures 1 to 7with 17, but here designated as 117. With regard to the construction and interaction of the components thus designated, 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.

[0036] The difference of the second in the Figures 8 to 14 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 7The difference lies in the fact that 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.

[0037] 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. In such a case, 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.If the workpiece is then released again by moving the actuating lever 122 into the release position, 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. Reference symbol list

[0038] 10, 110 Clamping device 11, 111 Body 12, 112 Base plate 13, 113 Bore 14, 114 End face 15, 115 Mounting ring 16, 116 Mounting surface 17, 117 Centering mandrel 18, 118 Slot 19, 119 Pressure end 20, 120 Clamping element 21, 121 End face 22, 122 Actuating lever 23, 123 Toggle lever mechanism 24, 124 Pull element 25, 125 Guide slot 26, 126 Guide pin 27, 127 Guide pin 28, 128 Joint pin 29, 129 Rod section 30, 130 Longitudinal center axis 31, 131 Collar 32, 132 Sleeve section 33, 133 Shoulder 34, 134 Compression spring 35, 135 Bearing leg 36, 136 Connecting pin 37, 137 Mounting block 38, 138 Spherical cap surface 39, 139 Recess 40, 140 Return spring 41, 142 Shoulder 42, 142 Shoulder 143 Pin 144 Sleeve 145 Slot 146 Spring 147 Needle bearing 148 Head piece

Claims

1. Clamping device (10, 110) for securing workpieces, comprising: • a body (11, 111) on which a contact surface (16, 116) for a section of a workpiece is arranged; • a centering mandrel (17, 117) projecting outwards from the body (11, 111) beyond the contact surface (16, 116); • a pair of clamping elements (20, 120), each having a pressure end (19, 119), in particular a hook-shaped one; • a tension element (24, 124) coupled to the clamping elements (20, 120); and • an actuator (22, 122) for applying a tensile force to the tension element (24, 124), wherein the clamping elements (20, 120) are arranged to be movably oriented in the body (11, 111) and are connected to the tension element. (24, 124) are coupled in such a way that, in a released position of the pulling element (24, 124), their contact ends (19, 119) engage in slots (18, 118) formed on opposite sides in the centering mandrel (17, 117) and in the centering mandrel (17,117) are retracted and that, starting from the release position, they are in a clamping position of the tension element (24, 124) obtained by applying the tensile force to the tension element (24, 124), with their pressure ends (19, 119) extending radially out of the slots (18, 118) in the direction of the contact surface (16, 116) and with end faces (21, 121) of the pressure ends (19, 119) pointing in the direction of the contact surface (16, 116), , characterized by the fact that the tensile element (24, 124) has an integrated tensile force limiting mechanism.

2. Clamping device (10, 110) according to claim 1, characterized by the fact thatThe tension element (24, 124) is formed in an axial direction in which the tensile force is applied, comprising at least a first tension element section (29, 129) to which the actuator (22, 122) acts, and a second tension element section (32, 132) to which the clamping elements (20, 120) are coupled, wherein a spring element (34, 134) is arranged between the first tension element section (29, 129) and the second tension element section (32, 132), which transmits a tensile force below a maximum force determined by the spring force from the first tension element section (29, 129) to the second tension element section (32, 132), and deforms elastically when the tensile force exceeds the maximum force.

3. Clamping device (10, 110) according to claim 2, characterized by the fact thatthe first tension element section (29, 129) has a pull rod section, and the second tension element section (32, 132) has a sleeve section, wherein the pull rod section extends into the interior of the sleeve section with a free end, and wherein a first bearing structure (31, 131) is formed on the pull rod section, and wherein a second bearing structure (33, 133) is formed on the sleeve section, wherein the first (31, 131) and the second (33, 133) bearing structure are spaced apart from each other in the axial direction of the tension element (24, 124), and wherein the spring element (34, 134) is arranged between the first (31, 131) and the second (33, 133) bearing structure and engages the bearing structures (31, 33, 131, 133) respectively.

4. Clamping device (10, 110) according to claim 3, characterized by the fact that the spring element (34, 134) is a coil spring which is arranged inside the sleeve section and around the drawbar section.

5. Clamping device (10, 110) according to one of claims 3 or 4, characterized by the fact that the first bearing structure (31, 131) is formed by a plate-like, circumferential projection at the free end of the drawbar section and the second bearing structure (33, 133) is formed by a shoulder section projecting into the interior of the sleeve section at an open end of the sleeve.

6. Clamping device (10, 110) according to one of claims 2 to 5, characterized by the fact that the connection between the first (29, 129) and the second (32, 132) tension element section includes a hinge connection (38, 39, 138, 139) that can be tilted transversely to the axial direction.

7. Clamping device (10, 110) according to one of the preceding claims, characterized by the fact that the actuator (22, 122) has a toggle lever, in particular a hand-operated one.

8. Clamping device (10, 110) according to claim 7, characterized by the fact thatthe knee lever (22, 122) engages a lever positioning mechanism (23, 123) arranged inside the body (11, 111) and is detachably connected to it, in particular is removable from it.

9. Clamping device (10, 110) according to one of the preceding claims, characterized by Return spring means (40, 140) arranged between the pull element (24, 124) and the body (11, 111) for applying a return force to the pull element (24, 124) acting in the direction of the release position.

10. Clamping device (10, 110) according to one of the preceding claims, characterized by the fact that the body (11, 111) is essentially cylindrical and the contact surface (16, 116) is arranged on a cylindrical end face (14, 114) of the body (11, 111) and the centering mandrel (17, 117) projects outwards from the cylindrical end face (14, 114) of the body (11, 111).

11. Clamping device (10, 110) according to claim 10, characterized by the fact thatthe mounting surface (16, 116) is arranged in a ring shape around the centering mandrel (17, 117).

12. Clamping device (10, 110) according to claim 11, characterized by the fact that the contact surface (16, 116) is formed on a ring element (15, 115) which is attached to the body (11, 111) in such a way as to be rotatable around the centering mandrel (17, 117), in particular by at least 360°.

13. Clamping device (10, 110) according to one of claims 10 to 12, characterized by the fact that the pulling element (24, 124) is arranged inside the cylindrical body (11, 111) and lying along the longitudinal axis of the cylinder (30, 130).

14. Clamping device (10, 110) according to one of the preceding claims, characterized by the fact that the centering mandrel (17, 117) has a longitudinal axis (30, 130) and is arranged on the body (11, 111) together with the arrangement of the clamping elements (19, 119) so as to be rotatable about the longitudinal axis (30, 130), in particular by at least 360°, relative to the body (11, 111).

15. Clamping device (110) according to one of the preceding claims, characterized by the fact that the centering mandrel (117) is displaceable on the body (111) in a longitudinal direction of the centering mandrel (117) and is pre-tensioned in a flared position by means of a compression spring (146).

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