Positioning arm

Abstract

A positioning arm for positioning instruments, devices or tools, is disclosed. The positioning arm includes at least two arm elements pivotably connected to one another about a pivot axis via a central joint. At least one of the arm elements includes a further joint at an end opposite the central joint. The positioning arm includes a blocking device for blocking and releasing the central joint and the at least one further joint. The blocking device is arranged on the central joint and effects the blocking and release of the further joints via at least one transmission device formed on the arm elements. The transmission device is formed by a pair of gripper arms which also form the arm elements.

Claims

1. A positioning arm for positioning instruments, devices or tools, the positioning arm comprising: at least two arm elements arranged pivotably connected to one another about a pivot axis by means of a central joint, wherein at least one of the at least two arm elements comprises at least one further joint arranged at an end opposite to the central joint, a blocking device configured to block and release the central joint and the at least one further joint, wherein the blocking device is arranged at the central joint and is configured to effect the blocking and unblocking of the further joints via at least one transmission device formed at the arm elements, and wherein the transmission device comprises a pair of pincer arms arranged to simultaneously also form the arm elements.

2. The positioning arm according to claim 1, wherein: each of the at least two arm elements comprise one of the at least one further joint and wherein the blocking device comprises a transmission device associated with one of the at least one further joint.

3. The positioning arm according to claim 1, wherein the at least one further joint comprises a rotatable clamping body.

4. The positioning arm according to claim 3, the rotatable clamping body comprises at least one of a ball and a rotating sleeve.

5. The positioning arm according to claim 1, wherein: each of the pair of pincer arms comprises a lever arm and a gripping arm, the lever arm is configured to be connected with its rear ends aligned in a region of the central joint by means of the blocking device, and wherein the gripping arm is arranged to form a part of the at least one further joints.

6. The positioning arm according to claim 1, wherein the blocking device comprises an actuating element configured to displace in an axial direction of the central joint and connect to an actuating device.

7. The positioning arm according to claim 6, wherein the actuating device is comprises a rotary handle comprising a clamping handle connected to an eccentric or a motor.

8. The positioning arm according to claim 1, wherein one of the further joints comprises a fastening device configured to attach to an operating table, and another of the further joints is configured to connect to an adapter configured to attach to different instruments, devices or tools.

9. The positioning arm according to claim 1, wherein the pincer arms comprise identical parts.

10. The positioning arm according to claim 1, wherein the pincer arms comprise a light metal, a light metal alloy or a plastic material.

11. The positioning arm according to claim 1, wherein the blocking device comprises latching elements arranged or formed on the transmission device.

12. The positioning arm according to claim 8, wherein the adapter comprises at least one shaped body configured to cooperate with a complementarily shaped receptacle of a holder of the tool, device or instrument.

13. The positioning arm according to claim 12, wherein the shaped body is configured to be fixed in the receptacle by means of a slider arranged on the holder.

14. The positioning arm according to claim 1, wherein the blocking device is configured and arranged to time-delay lock the central joint and the further joints.

15. The positioning arm according to claim 1, wherein at least one spring element configured and arranged to counteract a closing force of the blocking device is arranged in a region of the central joint.

16. The positioning arm according to claim 1, wherein at least one spring element configured and arranged to preload at least one of the arm elements into a predetermined basic position is arranged in a region of the central joint.

17. The positioning arm according to claim 3, wherein the clamping body is arranged connected by means of a tie rod to a connecting joint connecting two pincer arms.

18. A positioning arm for positioning instruments or tools, the positioning arm comprising: at least two arm elements arranged pivotably connected to one another about a pivot axis by means of a central joint, wherein at least one of the arm elements comprises a further joint arranged at an end opposite to the central joint, a blocking device configured to block and release the central joint and the at least one further joint, wherein the blocking device is arranged at the central joint and is configured to effect blocking and unblocking of the further joints via at least one transmission device formed at the arm elements, and wherein one of the at least one further joints is configured to connect to a universal adapter suitable for fastening different tools.

19. The positioning arm according to claim 18, wherein the universal adapter comprises at least one shaped body configured to cooperate with a complementary shaped receptacle of a holder for a tool or instrument.

20. The positioning arm according to claim 19, wherein the at least one shaped body comprises a three-sided prism with rounded corners and edges, and wherein the shaped body and the receptable are configured to clamp non-destructively to a sterile foil at least partially surrounding the positioning arm or the tool.

21. (canceled)

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0028] Further features, advantages and embodiments of the invention will be apparent from the following description based on the figures, wherein:

[0029] FIG. 1 depicts a perspective view of a positioning arm according to the invention with two arm elements connected in a central joint, each formed by a pair of pincer arms, and each comprising a further externally located joint, the clamping bodies of the externally located joints being formed by rotating sleeves and balls received therein,

[0030] FIG. 2 depicts a variant of FIG. 1, in which the clamping bodies of the outer joints are formed by balls and an instrument in the form of a hook is arranged on one of the outer joints on a universal adapter,

[0031] FIG. 3 depicts the variant shown in FIG. 2 with a central catch mechanism in the area of the central joint,

[0032] FIG. 4 depicts the variant shown in FIG. 2 with two decentralized catch mechanisms in the area of the central joint,

[0033] FIG. 5 depicts a variant of FIGS. 1 to 4 in which the blocking device of the central joint can be actuated by a clamping handle connected to an eccentric instead of a rotary handle,

[0034] FIG. 6 depicts the variant shown in FIG. 5 with the clamping handle open,

[0035] FIG. 7a depicts longitudinal section through the central joint with a rotary handle and two spring elements designed as disk springs,

[0036] FIG. 8a depicts variant of FIG. 7 with a clamping handle and a centrally arranged spring element in the form of a coil spring,

[0037] FIG. 9 the depicts four pincer arms forming the two arm elements side by side in a perspective view from the side of the central joint,

[0038] FIG. 10 depicts the pincer arms shown in FIG. 9 side by side in a perspective view from the side of the other joints,

[0039] FIG. 11a depicts variant of the pincer arms shown in FIGS. 9 and 10, with separately formed latching elements that can be positively connected to the pincer arms,

[0040] FIG. 12 depicts the variant shown in FIG. 2 in a perspective view from below with the holder for the hook-shaped tool removed from the universal adapter,

[0041] FIG. 13 depicts Enlarged view of the connection between the universal adapter and the holder shown in FIG. 12,

[0042] FIG. 14 depicts an enlarged view of a rotating sleeve as shown in FIG. 1,

[0043] FIG. 15-17 depicts different holders for different instruments or tools can be coupled with a universal adapter engaged in FIG. 15,

[0044] FIG. 18 depicts a variant of FIG. 1 with a spring element arranged in the region of the central joint and resiliently preloading the arm elements, the spring element being designed as an exemplary torsion bar spring, one of the pincer arms in the region of the central joint having been removed to illustrate this,

[0045] FIG. 19 depicts the variant according to FIG. 18 with completely shown pincer arms and a sterile sleeve or foil indicated in the area of the universal adapter,

[0046] FIG. 20 depicts a variant of FIG. 4 with motor actuation of the locking device in the area of the central joint,

[0047] FIG. 21 depicts a variant with a tie rod mounted in a clamping body and attached to a connecting joint of the pincer arms, with one pincer arm omitted,

[0048] FIG. 22 depicts the variant according to FIG. 21 with both pincer arms,

[0049] FIG. 23 depicts the variant according to FIG. 21 in exploded view in a first perspective,

[0050] FIG. 24 depicts the variant according to FIG. 22 in exploded view in a second perspective,

[0051] FIG. 25 depicts a positioning arm with a magnetic attachment located at the outer end of the first arm element,

[0052] FIG. 26 depicts a positioning arm with a flange plate arranged at the outer end of the first arm element, and FIG. 27 depicts a variant with shortened pincer arms.

DETAILED DESCRIPTION OF THE INVENTION

[0053] As used throughout the present disclosure, unless specifically stated otherwise, the term or encompasses all possible combinations, except where infeasible. For example, the expression A or B shall mean A alone, B alone, or A and B together. If it is stated that a component includes A, B, or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as at least one of do not necessarily modify an entirety of the following list and do not necessarily modify each member of the list, such that at least one of A, B, and C should be understood as including not only one of A, only one of B, only one of C, or any combination of A, B, and C.

[0054] Similar elements are generally indicated in the figures with the same or similar reference numerals.

[0055] A positioning arm 100 shown in FIG. 1 comprises a first arm element 110 and a second arm element 120, which are connected to each other by a central joint 130. At an end remote from the central joint 130, the first arm element 110 comprises a further joint 140 through which the positioning arm 100 is connectable to a fastening device 160.

[0056] At an end remote from the central joint 130, the second arm element 120 comprises a further joint 150 through which the positioning arm 100 is connectable to a universal adapter 170.

[0057] The first arm element 110 is formed by an outer pincer arm 111 and an inner pincer arm 112, which are connected to each other at a connecting joint 113 formed, for example, by a bolt 1131. The outer pincer arm 111 comprises a lever arm 1111 starting from the central joint 130 and a gripping arm 1112 between the connecting joint 113 and the further joint 140. The inner pincer arm 112 comprises a lever arm 1121 starting from the central joint 130 and a gripping arm 1122 behind the connecting joint 113 in the direction of the further joint 140.

[0058] At least one gripper 1113 is formed on the gripping arm 1112 and at least one gripper 1123 is formed on the gripping arm 1122. The inside of the gripping arm 1112 comprises a concave recess 1114 and the inside of the gripping arm 1122 comprises a concave recess 1124. The grippers 1113 of the gripping arm 1112 and the grippers 1123 of the gripping arm 1122 enclose a clamping body 141 of the further joint 140, which in FIG. 1 is in the form of a rotating sleeve 143. The rotating sleeve 143 is shown enlarged in FIG. 14. The rotating sleeve 143 comprises a ring groove 1431 at a distance from its rear end. The rotating sleeve is divided into four segments 1432 by four slits 1433 evenly distributed in the outer shell parallel to the axis. The slits 1433 extend beyond the ring groove 1431. The diameter of the front circular opening of the rotating sleeve 143 is such that a ball 142 is insertable into the interior of the rotating sleeve 143 by slightly expanding the segments 1432. The interior of the rotating sleeve 143 preferably comprises a bulbous shape adapted to the ball 142.

[0059] The ball 142 is connected to a cylindrical connecting piece 144, which preferably has an external thread formed thereon that is not shown and which can be screwed into a matching internal thread of the fastening device 160, which is also not shown.

[0060] The second arm element 120 is formed by an outer pincer arm 121 and an inner pincer arm 122, which are pivotably connected to one another in a connecting joint 123 formed, for example, by a bolt 1231. The outer pincer arm 121 comprises a lever arm 1211 starting from the central joint 130 and a gripping arm 1212 between the connecting joint 123 and the further joint 150. The inner pincer arm 122 comprises a lever arm 1222 starting from the central joint 130 and a gripping arm 1222 behind the connecting joint 123 in the direction of the further joint 150.

[0061] At least one gripper 1213 is formed on the gripping arm 1212 and at least one gripper 1223 is formed on the gripping arm 1222. The inside of the gripping arm 1212 comprises a concave recess 1214 and the inside of the gripping arm 1222 comprises a concave recess 1224. The grippers 1213 of the gripping arm 1212 and the grippers 1223 of the gripping arm 1222 enclose a clamping body 151 of the further joint 150, which in FIG. 1 is configured in the form of a rotating sleeve 153. The rotating sleeve 153 is shown enlarged in FIG. 14. The rotating sleeve 153 comprises a ring groove 1531 at a distance from its rear end. The rotating sleeve 153 is divided into four segments 1532 by four slits 1533 evenly distributed in the outer wall parallel to the axis. The slits 1533 extend beyond the ring groove 1531. The diameter of the front circular opening of the rotating sleeve 153 is such that a ball 152 is insertable into the interior of the rotating sleeve 153 by slightly expanding the segments 1532. The interior of the rotating sleeve 153 preferably comprises a bulbous shape adapted to the ball 152.

[0062] The ball 152 is connected to a cylindrical connecting piece 154, which preferably comprises a male thread (not shown) that can be screwed into a matching female thread of a carrier 171 of the universal adapter 170, which is also not shown.

[0063] FIGS. 9 to 11 show the four pincer arms 111, 112, 121 and 122 as individual parts. It can be seen from the illustrations that the four pincer arms 111, 112, 121 and 122 can be manufactured as identical parts to the greatest possible extent, which greatly simplifies manufacture and stock-keeping. Furthermore, it can be seen from these figures that the pincer arm 111 comprises a bore 1119 formed as a through bore at its end facing the central joint 130. Similarly, the pincer arm 112 comprises a bore 1129, the pincer arm 121 comprises a bore 1219, and the pincer arm 122 comprises a bore 1229.

[0064] At least two of the pincer arms 111, 112, 121 and 122 comprise latching elements 1115, 1125, 1215 and 1225. In FIGS. 9 and 10, latching elements 1115, 1125, 1215 and 1225 are formed directly on pincer arms 111, 112, 121 and 122. The latching elements 1115, 1125, 1215 and 1225 comprise toothing 1116, 1126, 1216 and 1226, respectively.

[0065] In an alternative embodiment shown in FIG. 11, the latching elements 1115, 1125, 1215 and 1225, which are provided with toothing 1116, 1126, 1216 and 1226, are designed as independent disc-shaped components and each comprise two bolts 115 on the side opposite the toothing, which are configured to be positively engaged with corresponding locating holes 114 on the pincer arms 111, 112, 121 and 122.

[0066] The pincer arms 111, 112, 121 and 122 comprise an offset shape, with a transversely extending bore being provided approximately in the center of the offset for forming the connecting joints 113 and 123, respectively, by means of a through bolt. In these areas of the transversely extending bores, rectangular cutouts 1117, 1127, 1217 and 1227 are formed on the four pincer arms 111, 112, 121 and 122, which cutouts extend approximately to the center of the respective pincer arms and, in the assembled state, allow a respective pair of pincer arms 111 to engage with 112 and 121 with 122.

[0067] The pincer arms 111, 112, 121 and 122 can be manufactured inexpensively as identical parts in a robust design as an aluminum die casting or as a plastic injection molding.

[0068] The central joint 130 forms a pivot axis 131 for the first arm element 110 and the second arm element 120. The central or middle joint 130 connectsas best shown in FIG. 7by means of a threaded rod 1322 through the bores 1119, 1129, 1219 and 1229 the rear ends of the first arm element 110 formed pincer-like by the outer pincer arm 111 and the inner pincer arm 112 and the rear ends of the second arm element 120 formed pincer-like by the outer pincer arm 121 and the inner pincer arm 122.

[0069] In each case, the outer pincer arm 121 of the second arm element 120, the inner pincer arm 112 of the first arm element 110, the inner pincer arm 122 of the second arm element 120 and the outer pincer arm 111 of the first arm element 110 lie alternately one above the other from bottom to top. The threaded rod 1322 is connected at its upper end to an operating element formed as a rotary handle 1321 or, as shown in FIGS. 5, 6 and 8, as a clamping handle 1324 provided with an eccentric 1325.

[0070] The lower end of the threaded rod 1322 is screwed eitheras shown in FIG. 7into a nut 1323 oras shown in FIG. 8directly into an internal thread of the outer pincer arm 121 formed in the area of the bore 1219.

[0071] The threaded rod 1322, in conjunction with the operating elements, namely the rotary handle 1321, the clamping handle 1324 or a motor 1326 indicated in FIG. 20, and the anchorage in the nut 1323 or the internal thread of the pincer arm 121, forms a blocking device 132.

[0072] The motor 1326 is preferably driven by an accumulator arranged in the housing, which is preferably integrally formed on the pincer arm 111, wherein the operating elements 1327 are arranged in an ergonomically favorable manner and the housing, as shown in FIG. 20, can also be used in an ergonomically favorable manner as a handle when guiding the positioning arm 100 into the desired position.

[0073] Tightening the operating elements 1321, 1324 or 1326 presses the ends of the pincer arms 111, 112, 121 and 122 against each other. In an only slightly tightened state, a swiveling movement about the pivot axis 131 is still possible. If, on the other hand, the operating elements 1321, 1324 or 1326 are tightened strongly, the swiveling movement of the arm elements 110 and 120 relative to each other is blocked in the central joint 130.

[0074] This locking can be reinforced by the interlocking toothing 1116, 1126, 1216 and 1226 of the latching elements 1115, 1125, 1215 and 1225. Two variants are possible here. As shown in FIG. 3, in a first variant a central engagement of the two latching elements 1126 and 1226 is possible. This embodiment is preferred when it is desirable to block the other joints 140 and 150 before blocking the center joint 130.

[0075] On the other hand, as shown in FIGS. 4, 5, 6 and 7, a second variant also allows decentralized engagement at two pairs of latching elements 1115 with 1225 and 1215 with 1125. In this case, an intermediate position of a spacer sleeve 133 is advantageous. This second variant is preferably used if locking of the central joint 130 is desired before locking of the other joints 140 and 150.

[0076] By blocking the middle joint 130 by means of the blocking device 132, the other joints 140 or 150 are also blocked simultaneously or with a slight time delay. When the pincer ends are pressed together at the lever arms 1111, 1121, 1211 and 1221 of the pincer arms 111, 112, 121 and 122, the gripping arms 1112 and 1122 of the first arm element 110 and the gripping arms 1212 and 1222 of the second arm element 120 are simultaneously pressed together. They thereby enclose the clamping bodies 141 and 151, respectively, which are formed either by balls 142 and 152, respectively, or by rotating sleeves 143 and 153, respectively, the rotating sleeves 143 and 153, respectively, in turn also being suitable for receiving balls 142 and 152, respectively, according to a particularly advantageous variant.

[0077] By means of different diameters of the balls 142 or 152 and/or by means of different thicknesses of spacer sleeves 133, it is possible to set very precisely which of the joints 130, 140 and or 150 locks first and which locks last when the blocking device 132 is actuated. According to an advantageous variant, for example, the joint 140 can block first after the positioning arm 100 has been roughly pivoted into the required position of use. When the blocking device 132 is further tightened, the central joint 130 can then block next, for example, and the further joint 150 last, after an instrument 190 arranged there on the universal adapter 170 has been rotated or pivoted into the target position. The sequence just described is only to be seen as an example. Any other sequence is also possible with a corresponding adjustment of the diameters or the diameters of the balls 142 or 152 and/or the rotating sleeves 143 or 153 and/or the thickness of the spacer washers 133. It is also possible to influence the timing of the locking of the respective joint 130, 140 or 150 by changing the length ratios of the lever arms to the gripping arms on the respective pair of pincer arms.

[0078] Instead of the latching elements 1115, 1125, 1215 and 1225, an outer cone 1118 on the pincer arm 111 engaging in an inner cone 1228 on the pincer arm 122 and an outer cone 1218 on the pincer arm 121 engaging in an inner cone 1128 on the pincer arm 112 can also assist the blocking device 132 in blocking the central joint 130, as shown in FIG. 8.

[0079] To ensure that the blocking device 132 of the central joint 130 opens easily when the rotary handle 1321, the clamping handle 1324 or the motor 1326 is opened, it is advantageous if at least one spring element 134 counteracts the closing force. In FIG. 8, a spiral compression spring surrounding the threaded rod 1322 is arranged in the central area of the threaded rod 1322 as an axial spring element 134 for this purpose. In FIG. 7, two spring elements 134 in the form of disk springs are arranged at an axial distance from one another between the pincer arms 111 and 122 and between the pincer arms 112 and 121, respectively, surrounding the threaded rod 1322.

[0080] Handling of the positioning arm 100 according to the invention is advantageously additionally facilitated by the fact that, as shown in FIGS. 18 and 19, a further spring element 135 is provided by means of which the first arm element 110 and the second arm element 120 are resiliently preloaded in a defined position relative to one another. Expediently, this is an extended position in which the first arm element 110 and the second arm element 120 enclose an angle of 180. In the embodiment shown, the further spring element 135 is formed as a torsion leg spring which surrounds the threaded rod 1322 and whose ends are fixed to a stop 1351 on the pincer arm 112 or to a stop 1352 on the pincer arm 122.

[0081] As can be seen in FIG. 19, the fastening devices 160 are configured to be screwed into a holder, not shown, by means of a screw 163 connected to a rotary handle 162, which can be fastened, for example, to the side rails of an operating table. Locking toothing 164 is configured to also assist in securely fixing the positioning arm 100 in place.

[0082] At the other end on the patient side, a universal adapter 170 is particularly preferably provided adjacent to the second joint 150, which can be connected to the connecting piece 154, for example, by screwing it into a carrier 171. The universal adapter 170 comprises a shaped body 173, which is particularly preferably designed in the manner of a three-sided prism. The shaped body 173 is configured to be positively connected to a receptacle 181 on a holder 180, the shaped body 173 thereby being pressed in a wedge shape against the two inclined front flanks of the receptacle 181 when a slider 184, which is displaceably mounted on the holder 180, is pressed against it from behind by means of a rotary handle 182. The universal adapter 170 may additionally comprise a rotation axis 172 formed by a screw 175 with a rotary handle 174 arranged thereon (FIG. 19). Locking disks 176 on the carrier 171 and locking disks 177 on the shaped body 173 enable the shaped body 173 to be finely rotated and locked relative to the carrier 171, so that the holder 180 seated on the shaped body 173 can be correspondingly finely rotated and locked with the tools 190.

[0083] The prism of the shaped body 173 has no sharp corners and edges. If a sterile covering foil 200 (see FIG. 19) is placed between them, the foil 200 will not be damaged. This ensures that the sterile barrier formed by the covering foil 200 is not violated. At the same time, the prism of the shaped body 173 always allows a good and, above all, secure form fit (with and without the covering foil 200 in between), which ensures that the position of the instrument 190 attached to the universal adapter 170 is not changed.

[0084] As can be seen from FIGS. 15 to 17, the universal adapter 170 is configured to be used to connect a wide variety of tools and instruments 190 easily and quickly. In FIG. 15, the tool 190 is formed by a hook 191. In FIG. 16, a tool holder 186 is arranged on the holder 180, on which a needle guide 192 for guiding a needle 194 is mounted in the shown example. In FIG. 17, the holder 180 is equipped, by way of example, with a pair of tweezers 195 which can be fixed to the holder 180 by clamping. The holder 180 is preferably provided with a further rotation axis 185, so that the tool 190 can be rotated relative to the tool holder 186 and locked by means of a rotary handle 187.

[0085] The universal adapter 170 represents an independently inventive feature in its own right, as it is connectable by its shaped body 173 to any holders 180 for any tools 190, 191, 192, 193, 194 and 195. As a result, any tools 190, 191, 192, 193, 194 and 195 can be arbitrarily placed and quickly changed on a plurality of such positioning arms 100 as required during an operation. The positioning arm 100 according to the invention is also suitable for attaching preferably remotely operable robotic systems or patient positioning systems to the universal adapter 170. The locking of the joints 130, 140, 150 is so stable in the locked state that the entire operating table can be raised on the universal adapter 170 without the set position of the joints 130, 140, 150 changing in the slightest.

[0086] As can be seen from FIGS. 9 to 11, the positioning arm 100 according to the invention comprises very few pincer arms 111, 112, 121 and 122 which can be easily disassembled and assembled, so that disassembly for sterilization is possible in a simple manner.

[0087] Sterility can also be achieved in a simple manner by drawing a sterile covering foil 200 over the entire positioning arm 100. This is only indicated in FIG. 19 in the area of the further joint 150. The universal adapter 170 allows this cover 200 to be clamped non-destructively between the shaped body 173 and the receptacle 181 on the holder 180.

[0088] FIGS. 21 to 24 show another variant of a pincer arm. In this, the clamping body is formed by a partially hollow ball 1420, In a bore of the ball 1420, one end of which is provided with a thread 1421 and the other end of which is provided with slits 1422 arranged crosswise to each other, one end of a tie rod 1423 with a ball head 1424 is mounted. A shaft 1426 of the tie rod 1423 penetrates the slots 1422, and the tie rod 1423 is supported on the connecting joint 113 or a bolt 1131 forming the connecting joint by a bearing eye 1425 located at the other end of the tie rod 1423 and opposite the ball head 1424.

[0089] After the tie rod 1423 is inserted into the bore of the ball 1420, a connecting piece 1440 with its thread 1441 attached to one end is screwed into the thread 1421 of the ball 1420.

[0090] The ball 1420 is pulled by means of the tie rod 1423 when the pincer arms 111 and 112 are pressed together against a recess 1114, which is flatter in this case, of a gripper 1113 at the end of the pincer arms 111 and 112, thereby arresting a movement of the ball 1420. The teeth of the gripper 1113 are designed to be shorter in this variant than in the variants described first, in which the teeth of the grippers 1113, 1123, 1213, 1223 engage around the clamping bodies 141, 151 or the balls 142, 152 to more than half their diameter.

[0091] FIG. 25 shows a further fastening option of a positioning arm according to the invention, in which a connecting piece 144 of a joint 140 is connected to a magnetic holder 210, which can be set to an active position or out of operation by means of a magnetic switch 212. By means of the magnetic holder 210, this positioning arm can be very easily fixed to metallic surfaces and released again.

[0092] In FIG. 26, a connecting piece 144 of a joint 140 is connected to a flange plate 220 which comprises a plurality of bores 222 for attachment, for example by screws, to a carrier or to a wall.

[0093] FIG. 27 shows a particularly small embodiment of a positioning arm in which the pincer arms 111, 112; 121 and 122 are very short and compact.

[0094] The scope of protection of the present invention is given by the claims and is not limited by the features illustrated in the description or shown in the figures.