Clamping device and coordinate measuring machine

Abstract

Clamping device (10) for fixing a workpiece (18), comprising: - a basic body (12); - a tool holder (16) connected to or formed in the base body (12), which has a through hole (20) for receiving the workpiece (18); - a first fixed clamping jaw (24a) that at least partially surrounds the through hole (20); - a second fixed clamping jaw (24b) that at least partially surrounds the through hole (20); - a third fixed clamping jaw (24c) at least partially surrounding the through hole (20); - a first movable clamping jaw (26a) which at least partially surrounds the through hole (20) and is arranged between the first fixed clamping jaw (24a) and the second fixed clamping jaw (24b); - a second movable clamping jaw (26b) which at least partially surrounds the through hole (20) and is arranged between the second fixed clamping jaw (24b) and the third fixed clamping jaw (24c); - a third movable clamping jaw (26c) that at least partially surrounds the through hole (20) and is arranged between the third fixed clamping jaw (24c) and the first fixed clamping jaw (24a); and - a clamping nut (36) which surrounds the three fixed clamping jaws (24a, 24b, 24c) and the three movable clamping jaws (26a, 26b, 26c) and is designed to exert a force on the three movable clamping jaws (26a, 26b, 26c) when the clamping nut (36) is rotated, wherein the three fixed clamping jaws (24a, 24b, 24c) and the three movable clamping jaws (26a, 26b, 26c) are integrally connected to the base body (12) and are separated from each other by slots (28).

Description

[0001] The present invention relates to a clamping device for fixing a workpiece. Such clamping devices are also commonly referred to as clamping elements. In manufacturing technology, they serve to fix (clamp or clamp) a workpiece or tool during a machining process.

[0002] The clamping device according to the invention is particularly suitable for use in dimensional metrology. The present invention also relates to a coordinate measuring machine with such a clamping device and a measuring sensor for measuring the workpiece fixed in the clamping device.

[0003] Clamping devices, which can be designed as collets, for example, are already well-known in the prior art. They primarily serve to clamp or secure workpieces with cylindrical outer contours. Conically shaped workpieces or workpieces with freeform geometries are very difficult to clamp using conventional collets. Due to purely geometric reasons, clamping such a complexly shaped workpiece with a conventional collet would be relatively unstable, since collets are usually cylindrical and therefore only partially fit the outer contour of such workpieces.

[0004] In principle, it is of course possible to adapt the geometry of the clamping device to the outer contour of the workpiece to be clamped. Such a complexly shaped clamping device is known, for example, from DE 10 2007 049 862 A1. DE 10 2015 114 582 A1 also shows such a clamping device whose clamping geometry is adapted to the outer contour of the workpiece to be clamped. However, such devices are very complex to manufacture and therefore relatively expensive. Conventional machining processes are generally poorly suited for the production of such clamping devices. Other exemplary clamping devices are known from CN 1109399A, US 4,930,955 A, DE 103 40 052 A1, DE 100 51 556 B4, WO 2009 / 132426 A1, US 2014 / 0001714 A1 and DE 103 13 015 A1.

[0005] Another problem with clamping conically shaped workpieces or workpieces with freeform geometry is that conventional clamping devices for such workpieces usually do not allow exact axial positioning of the workpiece.

[0006] Such inaccuracies are unacceptable, especially in dimensional metrology. Dimensional metrology places very high demands on measurement accuracy, which depends directly on the accuracy of the clamping of the workpiece. The workpiece must therefore be held stably and with repeatable accuracy in a specific position. Furthermore, it is important that the workpiece remains easily accessible despite being clamped.

[0007] Coordinate measuring machines (CMMs) are used, for example, to inspect workpieces as part of quality assurance or to determine the complete geometry of a workpiece through reverse engineering. Numerous other applications are also conceivable. During measurement with a CMM, the workpiece is scanned at various points on its surface or across its entire surface using a tactile probe and / or an optical sensor. During this scanning process, the coordinates of each probe point are recorded. These coordinates can then be combined into a model of the workpiece, which can be used, for example, to verify whether the workpiece was manufactured correctly.

[0008] The workpiece being measured usually remains stationary during the measurement process. However, it is easy to understand that the way the workpiece is clamped has a significant impact on the accuracy of the measurement. It is equally important that the workpiece is clamped in the fixture with repeatable accuracy to allow for repeated measurements without inaccurate results. Another crucial factor in achieving such repeatability is the inclusion of an axial stop. However, as already mentioned, this has so far only been feasible with considerable effort when clamping workpieces with conical or complex external contours.

[0009] It is therefore an object of the present invention to provide an improved clamping device which is particularly suitable for clamping conical or complex shaped workpieces and which meets the immense requirements for the accuracy of the clamping, as are particularly required in the field of dimensional metrology.

[0010] This problem is solved according to a first aspect of the invention by a clamping device according to claim 1, which comprises the following components: - a basic body; - a tool holder connected to or formed in the base body, which has a through hole for receiving the workpiece; - a first fixed clamping jaw that at least partially surrounds the through-hole; - a second fixed clamping jaw that at least partially surrounds the through hole; - a third fixed clamping jaw that at least partially surrounds the through hole; - a first movable clamping jaw that at least partially surrounds the through hole and is arranged between the first fixed clamping jaw and the second fixed clamping jaw; - a second movable clamping jaw that at least partially surrounds the through-hole and is arranged between the second fixed clamping jaw and the third fixed clamping jaw; - a third movable clamping jaw, at least partially surrounding the through-hole, which is arranged between the third fixed clamping jaw and the first fixed clamping jaw; and - a clamping nut which surrounds the three fixed clamping jaws and the three movable clamping jaws and is designed to exert a force on the three movable clamping jaws when the clamping nut is turned wherein the three fixed clamping jaws and the three movable clamping jaws are integrally connected to the base body and separated from each other by slots.

[0011] According to a second aspect of the invention, the problem is solved by a clamping device according to claim 2, which comprises the following components: - a basic body; - a tool holder connected to or formed in the base body, which has a through hole for receiving the workpiece, wherein the through hole of the tool holder extends along a longitudinal axis along which the workpiece can be inserted into the tool holder; - a first fixed clamping jaw that at least partially surrounds the through-hole; - a second fixed clamping jaw that at least partially surrounds the through-hole; and - a first movable clamping jaw that at least partially surrounds or projects into the through hole; wherein the first fixed clamping jaw, the first movable clamping jaw and the second fixed clamping jaw are arranged offset from each other along the longitudinal axis such that the first movable clamping jaw is arranged longitudinally between the first fixed clamping jaw and the second fixed clamping jaw.

[0012] The clamping device according to the invention thus comprises (at least) two fixed, immovable clamping jaws and (at least) one movable clamping jaw, which is arranged locally between the two fixed clamping jaws. "Immovable" and "fixed" respectively mean that the two fixed clamping jaws cannot be moved relative to the base body, whereas the movable clamping jaw can be moved relative to the base body. The prefixes "first" and "second" (and below also "third") in the terms "fixed clamping jaw" and "movable clamping jaw" serve only for terminological distinction and do not specify a total number or a particular order of the respective clamping jaws.

[0013] The (at least) two fixed clamping jaws of the clamping device according to the invention serve to position the workpiece. The (at least) one movable clamping jaw, on the other hand, serves to fix the workpiece. In other words, the two fixed clamping jaws preferably serve as axial stops for the workpiece, so that at least the axial position of the workpiece within the clamping device is unambiguously defined by means of the two fixed clamping jaws. Preferably, the two fixed clamping jaws serve not only to determine the axial position, but also to unambiguously determine the entire spatial position of the workpiece in all three spatial directions. The movable clamping jaw, on the other hand, serves to clamp or fix the workpiece. This increases the stability of the workpiece clamping and prevents it from unintentionally coming loose from the clamping device.

[0014] With such a clamping device, even complexly shaped components can be clamped precisely, stably, and with repeatable accuracy. The component to be clamped (workpiece) is inserted into the through-hole of the tool holder of the clamping device according to the invention. The through-hole of the tool holder preferably extends along a longitudinal axis, along which the workpiece can be inserted into the tool holder in such a way that, when fixed in the clamping device, it protrudes through the clamping device.

[0015] The clamping jaws preferably all border directly on this through-hole or at least partially surround it. This means that the clamping jaws form at least part of the circumference of the through-hole.

[0016] According to a preferred embodiment, the cross-sectional area of ​​the through-hole decreases along the longitudinal axis. Preferably, the cross-sectional area of ​​the through-hole decreases continuously along the longitudinal axis.

[0017] This design has the advantage that it allows workpieces, especially those that taper conically or otherwise along one of their axes, to be unambiguously positioned with respect to their axial position in the clamping device. As already mentioned, this axial positioning is preferably achieved using the (at least) two fixed or immobile clamping jaws.

[0018] According to a further embodiment, the first fixed clamping jaw has a first contact surface for contact with the workpiece, the distance of which from the longitudinal axis decreases along the longitudinal axis. This first contact surface of the first fixed clamping jaw is therefore preferably inclined with respect to the longitudinal axis. It can be a conical surface, a semi-conical surface, or a freeform surface. Preferably, the distance of the first contact surface from the longitudinal axis decreases continuously along the longitudinal axis.

[0019] This is particularly preferred not only for the first fixed clamping jaw, but also for the second fixed clamping jaw. Accordingly, the second fixed clamping jaw preferably has a second contact surface for contact with the workpiece, the distance of which from the longitudinal axis decreases (preferably continuously) along the longitudinal axis.

[0020] This is a simple way to reduce or taper the cross-sectional area of ​​the through-hole along its longitudinal axis. This allows for very precise axial positioning of the workpiece within the clamping device in a relatively simple and cost-effective manner, and is particularly advantageous when the workpiece to be clamped has a conical or otherwise tapered shape along one of its axes.

[0021] According to a further embodiment, the first contact surface arranged on the first fixed clamping jaw is designed as a freeform surface, preferably adapted to the outer contour of the workpiece. Likewise, the second contact surface provided on the second fixed clamping jaw is preferably designed as a freeform surface, adapted to the outer contour of the workpiece.

[0022] By adapting the contour of the fixed clamping jaws to the outer contour of the workpiece to be clamped in this way, the positioning accuracy can be improved even further.

[0023] To also improve the stability of the workpiece clamping, the contour of the clamping surface of the (at least) one movable clamping jaw can of course also be adapted to the outer contour of the workpiece.

[0024] According to a further embodiment, the clamping device has a second movable clamping jaw that at least partially surrounds the through hole, a third movable clamping jaw that at least partially surrounds the through hole, and a third fixed clamping jaw that at least partially surrounds the through hole.

[0025] In total, the clamping device according to this embodiment has six clamping jaws, namely three fixed and three movable clamping jaws. Of course, it would also be possible for the clamping device according to the invention to have more than three fixed and more than three movable clamping jaws. However, the embodiment with three fixed clamping jaws and three movable clamping jaws has the advantage that both the positioning of the workpiece via the three fixed clamping jaws using a three-point or three-surface clamping system and the fixing of the workpiece via the three movable clamping jaws using a three-point or three-surface clamping system are achieved.

[0026] In the aforementioned embodiment with a total of six clamping jaws, it is preferred that the second movable clamping jaw is arranged between the second fixed clamping jaw and the third fixed clamping jaw, and that the third movable clamping jaw is arranged between the third fixed clamping jaw and the first fixed clamping jaw. Particularly preferred in this case are the six clamping jaws arranged side by side in a circumferential direction around the longitudinal axis, such that a fixed clamping jaw is always arranged between two movable clamping jaws and a movable clamping jaw is always arranged between two fixed clamping jaws. The six clamping jaws are then preferably all integrally connected to one and the same base body of the clamping device, similar to a collet chuck, and separated from each other by slots.

[0027] The latter collet-like design can also be provided for the aforementioned case of three clamping jaws (two fixed clamping jaws and one movable clamping jaw), wherein the first fixed clamping jaw, the first movable clamping jaw and the second fixed clamping jaw are arranged next to each other in a circumferential direction around the longitudinal axis.

[0028] According to an alternative embodiment, the first fixed clamping jaw, the first movable clamping jaw, and the second fixed clamping jaw are arranged offset from one another along the longitudinal axis. The individual clamping jaws are then preferably arranged one above and one below the other along the longitudinal axis. However, even in this embodiment, the first movable clamping jaw is still preferably arranged between the first fixed clamping jaw and the second fixed clamping jaw.

[0029] In the latter embodiment, it is particularly preferred that the first fixed clamping jaw and the second fixed clamping jaw are each designed in a ring shape and completely surround the through hole.

[0030] In this context, "ring-shaped" does not necessarily refer to a slit-shaped cross-section. "Ring-shaped" can refer to any type of closed contour, the cross-section of which may deviate from a round shape, for example, an oval cross-section or any contour, which may even be partially angular.

[0031] In the latter embodiment, the two fixed clamping jaws are preferably designed as through holes that together form the through hole of the tool holder. The central longitudinal axes of the fixed clamping jaws, which in this case are designed as annular through holes, preferably align with each other, so that the workpiece can be inserted into the clamping device through both fixed clamping jaws. The contour of the annular through holes is preferably adapted to the outer contour of the workpiece to be clamped. In this embodiment, the two fixed clamping jaws are particularly important for the axial positioning of the workpiece.

[0032] According to a further embodiment, the clamping device has a clamping element designed to move the first movable clamping jaw relative to the base body in order to fix the workpiece in the tool holder. In the case of an embodiment with more than one movable clamping jaw, the clamping element is preferably designed to move all movable clamping jaws simultaneously relative to the base body in order to fix the workpiece in the tool holder.

[0033] The clamping element can comprise a clamping nut, a screw, or a pneumatic actuator. In principle, it would also be conceivable for the clamping element to have a hydraulic or electric actuator. Preferably, the clamping element acts directly on the movable clamping jaw(s).

[0034] According to a further preferred embodiment, the clamping element has a clamping nut which surrounds the first fixed clamping jaw, the first movable clamping jaw, and the second fixed clamping jaw and is designed to exert a force only on the first movable clamping jaw when rotated, and not on the first fixed clamping jaw and the second fixed clamping jaw. It is understood that in the case of an embodiment with more than three clamping jaws, the clamping nut surrounds all clamping jaws accordingly and is designed to exert a force only on the movable clamping jaws when the clamping nut is rotated, and not on the fixed clamping jaws.This is preferably achieved by offsetting the outside of the fixed clamping jaws radially inwards compared to the at least one movable clamping jaw, so that a conical clamping surface arranged on the clamping nut only comes into contact with corresponding conical counter surfaces arranged on the outside of the movable clamping jaws when the clamping nut is rotated, but not with the outside of the fixed clamping jaws.

[0035] According to a further preferred embodiment, the clamping device according to the invention is manufactured by an additive manufacturing process. Preferably, the clamping device according to the invention is manufactured by means of 3D printing.

[0036] This allows for a very cost-effective and simple method of manufacturing the clamping device. Furthermore, this has the advantage that relatively complex contact or clamping surfaces can be produced on the clamping jaws, which can be precisely adapted to the outer contour of the workpiece to be fixed.

[0037] Manufacturing processes of this type are known, for example, from DE 10 2013 217 422 A1 and DE 10 2012 219 137 A1.

[0038] The clamping device according to the invention can also be provided together with the workpiece to be fixed therein, wherein an inner contour of the through-hole of the tool holder has at least one freeform surface, the shape of which corresponds to a freeform surface belonging to the outer contour of the workpiece.

[0039] As mentioned at the outset, the invention relates not only to the clamping device according to the invention, but also to a coordinate measuring machine with such a clamping device and a measuring sensor for measuring the workpiece.

[0040] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0041] In this regard, it should be explicitly mentioned again that the above embodiments do not only refer to an embodiment of the clamping device according to the invention with a total of three clamping jaws (two fixed clamping jaws and one movable clamping jaw), but can also refer in an equivalent form to embodiments of the clamping device according to the invention in which more than two fixed clamping jaws and more than one movable clamping jaw are used.

[0042] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description. They show: Fig. 1 a perspective view of a first embodiment of the clamping device according to the invention; Fig. 2 a sectional view of the in Fig. 1 clamping device shown; Fig. 3 a perspective view of the in Fig. 1 clamping device shown with workpiece inserted therein; Fig. 4 a top view of the in Fig. 1 clamping device shown; Fig. 5 a perspective view of a second embodiment of the clamping device according to the invention; Fig. 6 a sectional view of the in Fig. 5 clamping device shown; Fig. 7 a perspective view of a third embodiment of the clamping device according to the invention; Fig. 8 a sectional view of the in Fig. 7 clamping device shown; Fig. 9 a perspective view of a fourth embodiment of the clamping device according to the invention; Fig. 10 a sectional view of the in Fig. 9 clamping device shown; and Fig. 11 a coordinate measuring machine according to an embodiment of the present invention.

[0043] The Fig. Figures 1-4 show a first embodiment of the clamping device according to the invention in various views. The clamping device is characterized in its entirety by the reference numeral 10 in each figure. According to the first embodiment, the clamping device 10 is designed in the form of a collet chuck.

[0044] The clamping device 10 has a substantially cylindrical base body 12, which in this case can be attached to a mounting plate 14. A tool holder 16 is provided in the base body 12, which in this case is formed by the base body 12 itself. The tool holder 16 serves to hold a workpiece 18. Fig. Figure 3 shows an example workpiece 18 as it can be mounted or fixed in the clamping device 10.

[0045] The tool holder 16 has a through hole 20 that penetrates the base body 12 and extends along a longitudinal axis 22. The through hole 20 is formed by several clamping jaws 24, 26. These clamping jaws 24, 26 together surround the through hole 20 and are located in the Fig. The first embodiment shown in 1-4 is arranged side by side in the circumferential direction around the longitudinal axis 22.

[0046] In total, the clamping device 10 according to the first embodiment has six clamping jaws 24, 26. Three of the six clamping jaws 24, 26 are designed as fixed clamping jaws. These are clamping jaws 24a, 24b and 24c. These fixed clamping jaws 24a-24c are immovable relative to the base body 12 of the clamping device 10. The remaining three clamping jaws 26a, 26b and 26c are movable clamping jaws that can move relative to the base body 12. According to the Fig. In the first embodiment of the clamping device 10 shown in 1-4, all six clamping jaws 24, 26 are integrally connected to the base body 12 and separated from each other by slots 28.

[0047] The fixed clamping jaws 24 and the movable clamping jaws 26 are arranged alternately side by side, such that a fixed clamping jaw 24 is always positioned between two movable clamping jaws 26, and a movable clamping jaw 26 is always positioned between two fixed clamping jaws 24. For easier differentiation, the clamping jaws 24 and 26 are numbered according to their position. The fixed clamping jaw 24a is referred to as the first fixed clamping jaw 24a, the fixed clamping jaw 24b as the second fixed clamping jaw 24b, and the fixed clamping jaw 24c as the third fixed clamping jaw 24c. Similarly, the movable clamping jaw 26a is referred to as the first movable clamping jaw 26a, the movable clamping jaw 26b as the second movable clamping jaw 26b, and the movable clamping jaw 26c as the third movable clamping jaw 26c.

[0048] As especially from Fig. As can be seen in Figure 4, the first movable clamping jaw 26a is arranged between the first fixed clamping jaw 24a and the second fixed clamping jaw 24b. The second movable clamping jaw 26b is arranged between the second fixed clamping jaw 24b and the third fixed clamping jaw 24c. The third movable clamping jaw 26c is arranged between the third fixed clamping jaw 24c and the first fixed clamping jaw 24a.

[0049] The three fixed clamping jaws 24a-24c serve to axially position the workpiece 18, i.e., to position it along the longitudinal axis 22. The movable clamping jaws 26a-26c serve to fix or clamp the workpiece 18. To clamp the workpiece 18, these are moved radially towards the workpiece 18, i.e., perpendicular to the longitudinal axis 22.

[0050] To ensure axial positioning along the longitudinal axis 22, the tool holder 16 is preferably designed such that the through-hole 20 tapers downwards along the longitudinal axis 22. The cross-sectional area of ​​the through-hole 20 thus decreases along the longitudinal axis 22. Preferably, the cross-sectional area of ​​the through-hole 20 decreases continuously along the longitudinal axis 22. This is achieved by designing the fixed clamping jaws 24a-24c to be inclined with respect to the longitudinal axis 22. This automatically results in a kind of conical taper of the through-hole 20, which is at least approximately Fig. 2 is recognizable.

[0051] The contact surfaces 30a-30c of the fixed clamping jaws 24a-24c, as well as the contact surfaces 32a-32c of the movable clamping jaws 26a-26c, are preferably adapted to the outer contour of the workpiece 18. If the workpiece 18 is conical, these surfaces are also conically shaped. If the workpiece 18 is, as in the figure shown in Fig. In the exemplary case shown in Figure 3, concerning a workpiece whose outer contour is formed by freeform surfaces, the contact surfaces 30a-30c and 32a-32c are also designed as freeform surfaces to enable the most precisely defined and stable contact with the workpiece 18 possible. This type of shape adaptation not only ensures that the workpiece 18 is uniquely positioned along the longitudinal axis 22, but also that it can only be inserted into the clamping device 10 in a single position. As can be seen in particular from Fig. As can be seen in Figure 3, the workpiece 18 protrudes through the clamping device 10 when it is inserted into the through hole 20.

[0052] As mentioned, the fixed clamping jaws 24a-24c serve to position the workpiece 18, and the movable clamping jaws 26a-26c serve to fix the workpiece 18. The movement of the movable clamping jaws 26a-26c is effected by means of a clamping element 34, which is located in the Fig. The first embodiment shown in Figures 1-4 has a clamping nut 36. This clamping nut 36 has knurling on its outer edge to facilitate manual gripping. The clamping nut 36 is connected to the base body 12 of the clamping device 10 via an external thread 38 that engages with a corresponding internal thread 40. The external thread 40 is located on an inner surface of the base body 12 facing the clamping nut 36.

[0053] The movable clamping jaws 26a-26c are moved by rotating the clamping nut 36 about the longitudinal axis 22. During this rotation, the clamping nut 36 moves simultaneously along the longitudinal axis 22 relative to the base body 12 due to the threaded connection 38, 40. On its inner side, the clamping nut has a conical clamping surface 42 in the region of its lower end, which slides on a similarly conical outer surface of the movable clamping jaws 26a-26c during the movement of the clamping nut 36 (see Fig. 2) This causes the movable clamping jaws 26a-26c to move radially, transversely to the longitudinal axis 22.

[0054] However, the fixed clamping jaws 24a-24c do not move relative to the base body 12 during the movement of the clamping nut 36. This is due, among other things, to the fact that the clamping surface 42 of the clamping nut 36 does not come into contact with the outer surface of the fixed clamping jaws 24a-24c. The outer surface of the fixed clamping jaws 24a-24c is set back slightly at this point from the movable clamping jaws 26a-26c, creating a small gap 44 between the clamping nut 36 and the respective fixed clamping jaw 24a-24c (see Fig. 2).

[0055] In this way, a very easy-to-use and cost-effective clamping device 10 can be realized, which is particularly suitable for clamping and fixing complexly shaped workpieces 18. In the case of the Fig. The workpiece 18 shown as an example in point 3 could, for instance, be an artificial hip bone.

[0056] Fig. Figures 5-6 show a second embodiment of the clamping device 10 according to the invention in a perspective view and a sectional view. Here, too, the tool holder 16 of the clamping device 10 has a through-hole 20 that penetrates the base body 12 and serves to hold the workpiece to be clamped. In contrast to the one in Fig. In the first embodiment shown in 1-4, the clamping device 10 has the clamping device shown in accordance with the Fig. The second embodiment shown in Figures 5-6 has only two fixed clamping jaws 24a', 24b' and one movable clamping jaw 26a'.

[0057] As before, the first movable clamping jaw 26a' is arranged between the first fixed clamping jaw 24a' and the second fixed clamping jaw 24b'. However, the three clamping jaws 24a', 26a', 24b' are no longer arranged side by side around the longitudinal axis 22, but are offset from one another along the longitudinal axis 22. The fixed clamping jaws 24a', 24b' are each ring-shaped and completely surround the through-hole 20. They still serve to axially position the workpiece 18 along the longitudinal axis 22. As before, it is also preferred according to the second embodiment that the contact surfaces 30a', 30b' of the fixed clamping jaws 24a', 24b' are conical or designed as free-form surfaces that are attached to the outer contour of the workpiece 18 to be clamped. The installation areas 30a', 30b' are therefore not exactly ring-shaped in the sense of being circular.The term "ring-shaped" is understood here in a broad sense, as any kind of closed contour.

[0058] The cross-sectional area of ​​the through-hole 20 also decreases along the longitudinal axis 22 according to the second embodiment of the clamping device 10 according to the invention. It is particularly preferred that the cross-sectional area of ​​the through-hole 20 decreases along the longitudinal axis 22 in the area of ​​the first fixed clamping jaw 24a' and in the area of ​​the second fixed clamping jaw 24b' in order to ensure the axial fixation of the workpiece 18, as mentioned above.

[0059] The only movable clamping jaw 26a' is located in the Fig. In the second embodiment shown in Figures 5-6, the first movable clamping jaw 26a' is designed as before as a component or element that is integrally connected to the base body 12. The movement of the first movable clamping jaw 26a' is effected by means of a clamping nut 36, which, as in the first embodiment, is connected to the base body 12 via a corresponding threaded connection 38, 40. The previously described principle of movement via the conical clamping surface 42 arranged at the lower end of the clamping nut 36 is also, according to the second embodiment shown in Figures 5-6, designed as a component or element that is integrally connected to the base body 12. Fig. realized in the second embodiment shown in 5-6.

[0060] Fig. 7 and Fig. Figure 8 shows a third embodiment of the clamping device 10 according to the invention. This resembles the one in Figure 8. Fig. The second embodiment shown in 5-6. The clamping device 10 also differs from the one shown in Fig. 7 and Fig. In the third embodiment shown in Figure 8, there are only two fixed clamping jaws 24a'', 24b'' and one movable clamping jaw 26a''. The two fixed clamping jaws 24a'', 24b'' are again essentially ring-shaped, with the through-hole 20 no longer being a continuous bore, but rather formed by the two ring-shaped fixed clamping jaws 24a'', 24b'', which themselves are designed as through-holes with a cavity or free space between them. The two fixed clamping jaws 24a'', 24b'' are aligned with each other such that their central axes each lie on the common longitudinal axis 22. The movable clamping jaw 26a'' is again arranged between the two fixed clamping jaws 24a'', 24b''. The three clamping jaws 24a'', 26a'', 24b'' are arranged offset from each other along the longitudinal axis 22, similar to the second embodiment.

[0061] To guarantee the positioning of the workpiece 18 along the longitudinal axis 22, the contact surfaces 30a'', 30b'' of the fixed clamping jaws 24a'*', 24b'' taper along the longitudinal axis 22 and are designed conically and / or as freeform surfaces depending on the outer contour of the workpiece 18 to be fixed.

[0062] A key difference of the in Fig. third embodiment shown in 7-8 to the one in Fig. The second embodiment shown in Figures 5-6 differs in the manner of movement of the first movable clamping jaw 26a''. A pneumatic actuator 46 is provided as the clamping element 34, which acts on the movable clamping jaw 26a''. The pneumatic actuator 46 is configured to move the first movable clamping jaw 26a'' translationally.

[0063] The in Fig. The fourth embodiment of the clamping device 10 shown in Figures 9-10 is very similar to the one shown in Fig. The third embodiment shown in Figures 7-8. The two fixed clamping jaws 24a''', 24b''' are again designed as annular through-holes, which are arranged offset from each other along the longitudinal axis 22. The first movable clamping jaw 26a''', located between them, is moved here not by a pneumatic actuator, but by means of a clamping screw 48, which functions as a clamping device 34.

[0064] Fig. Figure 11 shows an exemplary coordinate measuring machine 100 in which the clamping device 10 according to the invention can be used. The in Fig. The coordinate measuring machine 100 shown in Figure 11 is designed in a so-called portal design. However, coordinate measuring machines in other designs (cantilever, bridge, or pedestal designs) are also possible.

[0065] At the in Fig. The coordinate measuring machine 100 shown in Figure 11 is a tactile coordinate measuring machine with a tactile measuring sensor 50, which has a tactile measuring probe 52. During a measurement, this tactile measuring probe 52 can be moved in all three spatial directions X, Y, and Z in order to scan a workpiece clamped in the clamping device 10 at various points and thus ultimately measure its shape or at least individual shape features. However, instead of a tactile measuring machine 100, the coordinate measuring machine could also be an optical coordinate measuring machine, which optically scans the workpiece to be measured using an optical measuring sensor. It is also conceivable that the coordinate measuring machine 100 is a so-called multi-sensor coordinate measuring machine, in which both optical and tactile measuring sensors are used.The clamping device 10 according to the invention is particularly suitable for use in such a coordinate measuring machine 100, since it enables a very stable, precise and repeatable method of clamping the workpiece, which is of considerable importance for its dimensional measurement. In addition, the clamping device according to the invention enables a type of clamping in which the workpiece 18 to be measured remains easily accessible.

[0066] Finally, it should be noted that in particular the Fig. The first embodiment of the clamping device 10 according to the invention, as shown in Figures 1-4, can also be designed with only three clamping jaws 24, 26, namely with two fixed clamping jaws 24a, 24b and a movable clamping jaw 26a arranged between them. It is also conceivable that the clamping device 10 according to this embodiment uses more than a total of six clamping jaws 24, 26.

Claims

[1] Clamping device (10) for fixing a workpiece (18), comprising: - a basic body (12); - a tool holder (16) connected to or formed in the base body (12), which has a through hole (20) for receiving the workpiece (18); - a first fixed clamping jaw (24a) that at least partially surrounds the through hole (20); - a second fixed clamping jaw (24b) that at least partially surrounds the through hole (20); - a third fixed clamping jaw (24c) at least partially surrounding the through hole (20); - a first movable clamping jaw (26a) which at least partially surrounds the through hole (20) and is arranged between the first fixed clamping jaw (24a) and the second fixed clamping jaw (24b); - a second movable clamping jaw (26b) which at least partially surrounds the through hole (20) and is arranged between the second fixed clamping jaw (24b) and the third fixed clamping jaw (24c); - a third movable clamping jaw (26c) that at least partially surrounds the through hole (20) and is arranged between the third fixed clamping jaw (24c) and the first fixed clamping jaw (24a); and - a clamping nut (36) which surrounds the three fixed clamping jaws (24a, 24b, 24c) and the three movable clamping jaws (26a, 26b, 26c) and is designed to exert a force on the three movable clamping jaws (26a, 26b, 26c) when the clamping nut (36) is rotated, wherein the three fixed clamping jaws (24a, 24b, 24c) and the three movable clamping jaws (26a, 26b, 26c) are integrally connected to the base body (12) and are separated from each other by slots (28). [2] Clamping device (10) for fixing a workpiece (18), comprising: - a basic body (12); - a tool holder (16) connected to or formed in the base body (12), which has a through hole (20) for receiving the workpiece (18), wherein the through hole (20) of the tool holder (16) extends along a longitudinal axis (22) along which the workpiece (18) can be inserted into the tool holder (16); - a first fixed clamping jaw (24a) that at least partially surrounds the through hole (20); - a second fixed clamping jaw (24b) at least partially surrounding the through hole (20); and - a first movable clamping jaw (26a) that at least partially surrounds or projects into the through hole (20); wherein the first fixed clamping jaw (24a), the first movable clamping jaw (26a) and the second fixed clamping jaw (24b) are arranged offset from each other along the longitudinal axis (22) such that the first movable clamping jaw (26a) is arranged longitudinally between the first fixed clamping jaw (24a) and the second fixed clamping jaw (24b). [3] Clamping device according to claim 1 or 2, wherein the first fixed clamping jaw (24a) and the second fixed clamping jaw (24b) are immovable relative to the base body (12), and wherein the first movable clamping jaw (26a) is movable relative to the base body (12). [4] Clamping device according to claim 1, wherein the through hole (20) of the tool holder (16) extends along a longitudinal axis (22) along which the workpiece (18) can be inserted into the tool holder (16) in such a way that it protrudes through the clamping device (10) when fixed in the clamping device (10). [5] Clamping device according to claim 2 or 4, wherein the cross-sectional area of ​​the through hole (20) decreases along the longitudinal axis (22). [6] Clamping device according to claim 5, wherein the first fixed clamping jaw (24a) has a first contact surface (30a) for contact with the workpiece (18), the distance of which from the longitudinal axis (22) decreases along the longitudinal axis (22). [7] Clamping device according to one of claims 1-6, wherein the first fixed clamping jaw (24a) has a first contact surface (30a) for contact with the workpiece (18), which is designed as a freeform surface which is preferably adapted to the outer contour of the workpiece (18). [8] Clamping device according to claim 4, wherein the three fixed clamping jaws (24a, 24b, 24c) and the three movable clamping jaws (26a, 26b, 26c) are arranged side by side in a circumferential direction around the longitudinal axis (22). [9] Clamping device according to claim 2, wherein the first fixed clamping jaw (24a) and the second fixed clamping jaw (24b) are each designed in an annular shape and each completely surround the through hole (20). [10] Clamping device according to claim 2 or 9, wherein the clamping device (10) has a clamping element (34) which is designed to move the first movable clamping jaw (26a) relative to the base body (12) in order to fix the workpiece (18) in the tool holder (16). [11] Clamping device according to one of claims 1-10, wherein the clamping device (10) is manufactured by an additive manufacturing process. [12] Clamping device according to one of claims 1-11, with the workpiece (18), wherein an inner contour of the through hole (20) of the tool holder (16) has at least one freeform surface, the shape of which corresponds to a shape of a freeform surface belonging to the outer contour of the workpiece (18). [13] Coordinate measuring machine (100), comprising: - a clamping device (10) according to any one of claims 1-12; and - a measuring sensor (50) for measuring the workpiece (18).

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