DE19521060A1 - Retaining arm system esp. for surgical instruments - Google Patents

Abstract

The system has a clamp device for frictionless locking of a translationally or rotationally movable element of an arm segment of a holding arm system. At least one electrostrictive, esp. piezoelectric, actuator (1) acts frictionlessly upon a section of the element in reaction to a delivered electrical control signal. The actuator acts upon the section of the element directly in its longitudinal direction or indirectly via force transfer devices. The actuator can be a translator with a linear main longitudinal direction. It can be a multilayer or monolithic actuator.

Description

The invention relates to a clamping device for frictional Locking a translationally and / or rotationally movable Links, arm segments for a holding arm system, in particular for Holding surgical instruments, as well as such a holding arm system stem.

As part of ergonomic analyzes of the work system "Operating room for minimally invasive surgery" in particular those of the assisted surgeon are more stressful static holding work proven. This mainly results due to the lack or inadequate design more suitable Auxiliary devices for taking over static holding work. At for example, endoscope optics equipped with video cameras guided by the assistant on the instructions of the surgeon and over a quiet period of the operation for as long as possible hold. Signs of fatigue lead to an unintended "Wandering" and "trembling" of the endoscope image. The same applies for holding organ parts with the help of pliers or wound hook systems. Longer static holding work with holding Forces of more than 15% of the maximum force are tiring and thus reducing performance.  

Another aspect is the time and amount limit one of the support arm system or the end effector of the Sy force applied to a biological tissue or the the application area by the force exerted by pressure. Un Physiologically high pressure loads can lead to ischemia and eventually lead to irreversible tissue damage. The permissible forces depend on the respective fabric, the shape of the end effector and the duration of use.

Appropriate holding arm systems can help. In the state In terms of technology, there are basically three main groups of stops distinguish arm systems:

• - Special holding arm systems, the almost constant hold apply forces;
• - passive universal holding arm systems for variable holding forces;
• - Manipulator systems for active positioning and holding an end effector, e.g. B. in the manner of a robot arm.

Special holding arm systems are mostly weights moderately balanced systems. Dental are examples Holding arm systems for holding the driven drill, Opera tion microscope holding arm systems, systems for holding Opera tion lamps and for holding monitors. Little one Fluctuations in total weight or small from the outside acting forces are activated by passive locking (internal Friction that must also be overcome when positioning) or by active locking using electromagnetic Brakes caught.

For example, DE-C-41 42 634 describes an operation lam pent ceiling stand, which is a spring system for balancing the light Tenkörpers and an additional locking device that  works on the basis of an electroviscous liquid. By the Applying a voltage can change the viscosity of the clutch fluid of a coupling mounted in a rotor joint can be varied. Such devices are each for a spe end effector such as the dentist's drill sets. The weight forces to be held are only by Inertial forces when moving the corresponding masses borders.

Universal holding arm systems become different end effectors held. Here is a maximum of just a balance of Weight forces of the individual arm segments possible and sensible, because the end effectors and the respective reaction forces are prince are different. While the special holding arm systems on special holding bases, holding columns or attached to the ceiling the universal holding arm systems are practically without exception attached to the standard clamping rails of the operating table.

The following universal supports can be used in medical applications A distinction is made between arm systems:

• - With passive locking z. B. in the manner of a spiral arm (Gooseneck) or a ball chain arm with passive Preload;
• - With active locking without auxiliary energy with individually using screw terminals or with a central rotary arm retention;
• - with active locking with auxiliary energy (EP-A3- 0 293 760 A3, US-A-4 863 133 and US-A-4 807 618.)

Universal holding arm systems with passive locking are by an internal jamming of the joint elements locked. Which resulting holding forces are frictional forces that occur when moving the  Poor must be overcome. Leave by design in such universal holding arm systems with passive locking generate only small holding forces that are only sufficient for holding light instruments, for example monocular Endoscope optics. An advantage of such universal holding systems with passive locking is the good one-hand operability and the simple and filigree construction. The disadvantage is in particular the relatively low holding forces, so that they to hold heavier endoscopes or retractors are not suitable. Another disadvantage is the elastic spring back of the arms after letting go. This makes fine positioning one Endoscope optics not possible.

Universal holding arm systems with active locking without auxiliary sensors are robust and for many applications with low actuation gung rate well-suited devices, some of which are very high Can generate holding forces. For use on operations holding arm systems with a central rotating ratchet are a particular table tation advantageous because the entire system with one hand can be locked.

System-specific disadvantages of such holding arm systems are that the steps of positioning and locking an end Effectors can only be done with both hands, that by the same early release of up to seven degrees of freedom the need a fine positioning of an ambidextrous manipulation sword and that finally when locking a wing tighten the screw of the central joint block must become.

For this reason, end effectors that are used in the course of a Intervention often need to be repositioned, such as. B. Endo  scope optics, pliers or retractors, mostly still from assisted surgeons.

For orientation and three-dimensionally coordinated work ten of the surgeon or surgeons is of particular importance that the surgeon's attention to the operations field can remain focused. By looking away from the Surgeons from the surgical site can be customized by the surgeon selected, "virtual" lead structure must be lost and must the continuation of the operation. Also from for this reason, the demand has become more and more recent according to a universal holding system with active locking by means of Auxiliary energy provided.

The first commercially available universal holding system is in the US Patent 4,807,618. There is one in each arm segment pneumatic special actuator installed, which is an active Locking / unlocking one located in the arm segment Ball joint when applying pressure from a separate pressure air source or when the pressure is released. The disadvantages This system is seen in particular in that a separate compressed air source is necessary that when unlocking released compressed air can be returned from the surgical field must that the handling of the arm system within the Surgical field is very difficult because the arm segments are too long are that by the long arm segments the elastic Nachgie bigkeit of the holding arm is increased and that due to the Pneumatic delays when locking as well as when releasing each arm segment can arise, which is the operational flow change. Finally, there is an offset of the End effector clearly noticeable by several millimeters, so that one Fine positioning z. B. an endoscope optics is difficult.  

The linear pressure pistons of this system are in the EP-A-0 486 999 disclosed solution by annular pressure piston systems in the arm segments replaced. The appear Specialist the necessary pressures or areas and the seal problems and the sterilizability of the entire system questionable.

A universal holding system is known from EP-A-0 293 760, which with negative pressure to generate a frictional Locking of the joints works. The construction consists of two mutually perpendicular shoulder hinge joints, one Elbow hinge joint and a double ball joint. The En Tarretierung is by a push button switch in the distal Handle of the arm controlled. The description can be found men that the holding states of the arm segments only between a freely movable state and a state with increased Friction resistance in the joints can be switched. An advantage of the vacuum lock over the use of overpressure actuators is that by loosening the joints no possibly non-sterile air can get into the surgical field.

WO 91/15707 describes a hydraulically or pneumatically Lockable holding arm system. Furthermore, it will Concept of an actively movable fixed at the distal end Linear guide with an integrated rotation axis to the position nation of probes and other end effectors.

Such systems are also known from the known holding arm systems to mention that in the manner of a robot arm an end effector actively position and hold, i.e. parts of a manipulator form stems. A position is generally computer controlled recognized, actively started and with a defi in a computer  nated model of the real object, e.g. B. the surgical site, and with Planning data correlated. As an example, this is in DE-A-42 02 922 motor tripod described.

In view of the above prior art, the invention lies Task based on a clamping device for friction Locking a translationally and / or rotationally movable Links, an arm segment for a holding arm system, in particular for holding surgical instruments, and finally a hold arm system using such an arm segment admit which one-handed usability when loosening, Posi tion and locking, free movement of the distal End effector attached end bracket in the released Condition in all six spatial directions within the work range and easy positioning of arm segments and enable end effectors. Attention should be paid of the surgeon are used as little as possible and the usability in the sterile area, the usability of the sterile area, equipped with different standards standard instruments, an intraoperative assembly, one if possible minor impairment of the operator's field of vision and one Attachment of the holding arm to a standard rail of the Opera tion table be possible.

The above object is achieved by a clamp direction for the frictional engagement of a translatory and / or rotato risch movable member, which is characterized in that one toward a section of the limb in response to one guided electrical control signal frictionally acting, elec Trostrictive, in particular piezoelectric actuator is provided in this way hen is that it is directly in its direction of expansion or indirectly on the direction of force deflection on the mentioned section  acts. Advantageous further developments of this clamping device are given in claims 2 to 14.

For example, the clamping device according to the invention enables a maximum holding force in any position depending on the application and at least between 5 and 50 N, the spatial offset caused by the locking is smaller than 2 mm, and the lock is in a maximum of 100 ms and a release possible in 100 to 500 ms.

An arm segment for a holding arm system, especially for the neck ten surgical instruments that such a clamping device is used as a ball according to a preferred embodiment articulated (claims 15 to 17). Furthermore, such Arm segment in a further version than a Kombina tion of a ball joint with a swivel joint (Claims 18 to 23).

For the passage or supply of the signal lines through the Arm segment can be embodiments according to the claims 24 to 17 may be provided. A special embodiment of a Ball joint according to claim 28 has the advantage that it is a contains simple anti-twist device. An inexpensive and a Multiple execution of an actively lockable / detachable ball gel kes is characterized by the features of claims 29 to 33 net. Finally, one or more of these are in accordance with the invention Support arm system using large arm segments, in particular for holding surgical instruments at the operating table, in the an pronounced 34.  

Further features and advantages of the invention result from the following description shown in the drawing Embodiments. Show it

Fig. 1 shows schematically an embodiment of a multiple arm segments according to the invention containing Haltearmsystems;

FIG. 2a to g embodiments of piezoelectric actuators;

FIGS. 3a and 3b biasing devices for piezoelectric Aktua factors;

FIG. 4a and b each a variant of a first embodiment according to the invention of an arm segment, which has a ball joint with a piezoelectric clamping apparatus;

Figs. 5a and b, respectively in longitudinal section and in elevation of a second embodiment according to the invention of the arm segment, which has a ball joint with piezoelectric Klemmvor direction;

Fig. 6 schematically and partially sectioned an Invention embodiment of an arm segment in the form of a ball joint, which is equipped with a preloaded pie zoelectric clamping device;

Fig. 7a and b show an embodiment of the present invention a pre direction for frictionally arresting a Rotie leaders shaft in longitudinal section and cross section;

Fig. 8a and b schematically an embodiment of a clamping device according to the invention for a linearly moving Stan ge each in longitudinal and in cross section;

Fig. 9 to 17 respectively different further embodiments of clamping devices of a ball joint for frictional locking;

FIG. 18 is a holding arm according to the invention, the arm segments are covered with a sterile enclosure;

Fig. 19 to 22 respectively different embodiments of a fastening device for fastening a holding arm system on an operating table rail; and

Fig. 23 is an application of the invention at a Neurochir urgischen armrest.

In Fig. 1 is an overall view of a flat rate Haltearmsystems designated A is schematically and in perspective according to the invention is shown. The holding arm system A is fastened as a whole by means of an operating table attachment a to a table rail of an operating table. The operating table attachment a is described in more detail below.

One with the operating table attachment a directly on the table rail of the Stand b attached to the operating table points to its proximal End of a connection socket for receiving a commercially available Plug e with quick coupling function. About this connector e are all electrical lines for supply voltages and sensing and command signals connected to the system. The Stand b only has one in the illustrated embodiment distal end.

This end has an interface for coupling a first one Arm segments c1 with a clamping device according to the invention, the Z. B. can be designed as a ball joint. The first As shown, arm segment c1 can be further arm segments Connect c2, c3, with arm segments c2, c3 shown in the Example also with clamping devices according to the invention are provided and have the shape of a ball joint. The seg ment c4 forms a handle that controls the selection of the Switching state of the piezoelectric actuators of the clamps can have elements. At the distal end of the handle a quick coupling can be provided for coupling one end effector d or an end effector guide. The end effector can e.g. B. a medical instrument, an endoscope, a retractor, a limb support, support, or probe.

Fig. 1 also shows a foot switch f and a control unit g, which can have a voltage monitoring, operating status display elements, a so-called ischemia warning and an interface for connecting the foot switch.

Piezoelectricity is a special case of electrostriction. With the so-called inverse piezo effect, an applied Voltage a deformation of the piezo element. The maximum possible expansion of the element depends on the kera Miksorte, the original length and rigidity of the piezo electrical converter, the applied electrical field strength and the acting force.

In the unloaded case, the relative linear expansion is one Piezoceramic with maximum field strengths of 1-2 kV / mm depending on Material and manufacturing process at 0.1 to 0.17%. The for the Application in the arm segments of interesting piezoelectric Actuators are translational actuators and have relative ones Travel ranges that fall in the above range from 0.1 to 0.17%. Depending on the for a maximum force or expansion The necessary control voltage is differentiated between high voltage actuators, low voltage actuators and Multi-layer actuators. The latter require the least amount of control voltage from 5 to 150 V. Furthermore, between stack actuators, which are made up of thin ceramic layers with intermediate electrodes are built, and monolithic actuators to distinguish. The Low-voltage and in particular multi-layer actuators are out thinner ceramic layers. You have the same Height and cross-sectional area in comparison to the high chip growth actuator with decreasing layer thickness send capacity. Monolithic actuators in the required Dimensions are currently under development and testing.

The maximum permissible static load for a translator designed piezoelectric stack actuator is 90% of Maximum stroke, with a stack of 35 mm diameter at approx.  30 to 35 kN. While the permissible load is approximately proportions tional to the cross-section is the maximum stroke at the maximum Field strength approximately proportional to the length.

For use in an arm segment of a holding arm system the piezoelectric actuator expands against a path-dependent load. The maximum achievable adjustment paths and forces are very strong in optimizing stiffness and the constructive design of the joint and actuator position tion or clamping dependent.

FIGS. 2a to g show continuous and in principle with the present invention, the suitable embodiments of high-voltage and low-voltage actuators. The designs are variable in their lengths and cross sections. All piezoelectric actuators used in the invention are consistently identified by the number 1 be. In the case of stack actuators 1 , the electrodes of the individual piezoceramic disks are contacted laterally via soldering webs 3 , to which the cable connections 2 of the bipolar voltage supply are then also soldered. To increase the creepage distances, additional, non-active, ceramic insulation end plates 9 can be glued to both end faces of the actuators. In the equivalent diagram of Fig. 2e, and in all applications of the piezoelek trical actuators is further characterized by a double arrow, the main ausdehungsrichtung of the piezoelectric actuator shown.

A disadvantage of the piezoceramic stack is the relatively high sensitivity to tensile and shear stresses. For this reason, the mechanical pressure preload, which is typically favorable, of typically 10 to 20% of the maximum pressure load capacity also has the physical effect of increasing the maximum elongation by up to 20% due to the increase in the piezo module. To avoid torsional and bending loads, end pieces 4 shown in FIG. 2f can be connected, for example, directly to the piezoelectric actuator 1 or indirectly via a bending element 5 formed as a solid body joint ( FIG. 2).

FIGS. 3a and b show spring elements 7 for realizing a mechanical bias which exert a compressive force on the body of the piezoelectric actuator 1. The actuator is biased between two with the spring element 7 form or materially connected end plates 6 , 6 'with about 10-20% of its nominal force. It is important here that the Federsteifig speed is adjusted so that the spring force does not increase significantly with an additional deflection by the amount of the maximum stroke of the actuator. An adjusting screw 8 can be used to adjust the biasing force of the spring element 7 . The spring element 7 can additionally for sealing and mechanical damping of the actuator z. B. filled with silicone rubber or other flexible, insulating sealant. The examples shown in Fig. 3 for such Vorpannvorrich lines can be used depending on the design of the Klemmvor directions or the arm segments. They are not necessary where mechanical pre-tensioning is guaranteed in another way.

As will be explained in more detail below in connection with the actuation of the actuators, the piezoceramic can be acted on with up to 20% of its negative nominal voltage (e.g. -20 V at + 100 V nominal voltage U _n ) without the losing piezoelectric properties. This shortens the actuator in its main direction of expansion shown by the double arrow ( Fig. 2e). However, it must not be exposed to mechanical tensile stresses. This effect can be used to a limited extent to improve the degree of effectiveness.

In the following, a distinction is made between the following states depending on the control voltage U _s supplied:

For the clamping devices or Arm segments apply in principle that the devices in size, shape and proportions from those shown in the drawing guides may differ. It only becomes the basic one Principle of operation explained. Some details are exaggerated shown.

FIGS. 4a and b show a first exporting invention approximate shape of an arm segment having a clamping element for frictionally locking catch of a ball joint. Two elements of a holding arm system are connected via connecting pieces 12 , 12 'to the ball joint. The ball 11 of the ball joint is between a sleeve-shaped union nut 13 with a conical seat and a pressure plate 14 , which can speak to the plate 4 according to FIG. 2f. Preferably, the pressure plate together with the ball 11 has a flat, ie no longer punctiform, radial frictional connection.

The pressure plate 14 is secured by a locking pin 17 against the pot-shaped or sleeve-shaped actuator container 16 (container sleeve) against rotation. The actuator 1 is taken up in the con tainer sleeve 16 with a substantially closed bottom. If an electrical voltage of suitable polarity is applied to the cable connections 2 , the actuator 1 expands and presses the ball 11 via the pressure plate 14 against the conical ball seat which is formed on the union nut 13 . It depends on the electrical field strength, the rigidity of the structure in the frictional connection, the mechanical bias of the actuator 1 and the ball seat, the total length of the piezoelectric actuator 1 and the overall free to be bridged to an increase in the pressure plate between 14 , the ball 11 and its ball seat effective frictional forces and thus the wearable friction torque from the ball joint.

While in Fig. 4a game and preload by means of the ball seat nut 13 , which is provided with tool receiving holes 10 , can be variably adjusted and secured by a lock nut 15 , the game and the preload must be in the embodiment shown in Fig. 4b can be set exactly by the position of the union nut 13 relative to the container sleeve 16 and are not variable bel. In both cases, the tightening torque should be a multiple of the permissible holding torque of the ball joint. Additional security measures, such as gluing and welding the union nut 13 to the actuator container 16 , are possible. The actuator can also be electrically insulated and mechanically damped by introducing plastic insulation mass 18 , such as silicone rubber.

FIGS. 5a and b show a device in the form of a ball joint in combination with a swivel arm segment formed with an inventive clamping in longitudinal section and in elevation. Two elements of a holding arm system are connected via connecting pieces 12 , 12 'to the ball swivel. The ball 11 of the ball joint is between a sleeve-shaped union nut 13 with a conical seat and a pressure plate 14 in the same way as the ball joint according to FIG. 4a, ie with a flat, no longer punctiform radial force transmission. The pressure plate 14 is secured by a locking pin 17 ge against the container sleeve 16 , which contains the piezoelectric actuator 1 , against rotation.

In addition to the embodiment shown in FIG. 4 a, the device has a swivel joint and generally two side notches 21 offset in the union nut 13 by 180 °. The side notches 21 are designed such that the upper connecting piece 12 can easily be brought into the position shown in dashed lines in Fig. 5b in a side notch 21 . This then has the ball joint with the inserted in the side notch 21 th upper connector 12 a freedom of movement of up to, for example, 130 ° from the central axis indicating the longitudinal direction of the Klemmvorrich device.

When the upper connector is inserted into one of the side notches 21 12, by the additional axis of rotation of Drehge Lenk the upper connector 12 with the ball 11, together with the containing the ball seat nut 13, the lock nut 15 and a threaded sleeve 20 with respect to the actuator 1 Containing container sleeve 16 are rotated. This results in an almost spherical movement space between the upper connector 12 and the lower connector 12 'of the joint, which, if one of the connectors 12 , 12 ' to z. B. is angled 45 ° (not shown in Fig. 5), can actually reach almost 360 ° in all directions. If cables have to be routed over the joint, a limitation of the rotation about the axis of rotation can expediently take place. For this purpose, a radially inwardly projecting anti-rotation pin 19 a and one with the sem cooperating pin 19 b in the container sleeve 16 are seen in the cap nut 13 , which z. B. can limit to 355 °.

When an electrical voltage of suitable polarity is applied to the cable connections 2 , the piezo 1 in the container sleeve 16 expands and presses over the pressure plate 14 against the ball 11 of the ball joint and this against the seat in the union nut 13 . The nut 13 presses the upper edge of the threaded sleeve 20 against a ausgebil Deten on the container sleeve 16, outer collar. Depending on the voltage or field strength supplied, the rigidity of the structure in the power flow and the mechanical preload of the actuator, the ball seat, the axis of rotation, the total length of the actuator and the overall free play to be bridged, there is an increase in the between ball and Ball seat on the one hand and between rule's threaded sleeve 20 and container sleeve 16 on the other hand effective frictional forces and thus of the moment transmitted by the ball and swivel joint.

Game and preload are variably adjustable by the union nut 13 , and by the lock nut 15 , the threaded sleeve 20 can be secured against the union nut 13 . Are Selbstver course, also from that in Fig. 5a and b shown from different solutions guide form an anti-rotation, z. B. possible by welding or gluing the parts 13 and 20 . The piezoelectric actuator 1 located inside the container sleeve 16 can be additionally electrically insulated and mechanically damped by introducing plastic insulation compound 18 .

This general possibility of electrical insulation and damping of the actuator 1 and of the mounting aids 10 is no longer discussed in detail below.

Fig. 6 shows a further embodiment of an arm segment according to the invention, designed as a ball joint, with a piezoelectric actuator for frictionally locking the ball joint. Here, the use of a spring element 7 ( Fig. 3b) for mechanically biasing the actuator 1 is shown as an example. In contrast to FIG. 4, the latter does not sit in a separate container sleeve, since it is mechanically stiffened by the spring element 7 itself. The spring element 7 is secured by a locking pin 17 against rotation relative to the inner space for the actuator 1 with the spring element 7 and the ball 11 of the ball joint union nut 13 .

The union nut 13 with the ball seat is screwed to an end screw 22 which forms the bottom of the interior. This end screw 22 can be integrally formed with the lower connector 12 '. The screw connection of the union nut 13 with the end screw 22 is secured with a weld seam 23 . When a voltage is applied to the connecting lines 2 , the actuator 1 expands against the prestressing force of the spring element 7 . As a result, the ball 11 is pressed into the ball seat and the actuator 1 with the spring element 7 against the bottom of the end screw 22 ge. Thus, in turn, there is an increase in the frictional force between the ball 11 and the pressure plate 6 of the spring element 7 on the one hand and between the ball 11 and the seat on the other hand, which is formed in the union nut 13 . The other parts and functions of the arm segment according to FIG. 6 correspond to the embodiment according to FIG. 4, have the same reference numerals and are not further explained.

In FIGS. 7a and b in the longitudinal and cross-section a detail of a clamping device for frictionally Arretie tion of a rotating shaft 24 is shown. This embodiment can be formed on an arm segment either separately or together, for example with a ball joint. The shaft 24 is enclosed by a container sleeve 16 containing the actuator 1 . It is important that a tight fit or a sliding fit is set between the bearing bush of the hub 25 for the shaft 24 and the container sleeve 16 . This can ensure that the piezoelectric actuator is not tilted and that no noticeable play occurs in the locked state. The principle is primarily suitable for slowly rotating shafts.

The locking device consists of the container sleeve 16 , the actuator 1 , the pressure plate 14 and the end screw connection 22 and is floating. In an expansion of the Aktua tors 1 by applying a voltage to the connecting lines 2 , the shaft 24 via the pressure plate 14 against the final screw connection 22 and in the training on the container sleeve 16 th seat, and thereby the frictional force between the shaft 24 and the container sleeve 16 and the other between the shaft 24 and the pressure plate 14 increased. By supporting the container sleeve relative to the bearing bush 25 , the rotation of the shaft 24 is inhibited relative to the bearing bush 25 . The mechanical bias or the game can be set to the end screw 22, not shown in detail.

The clamping device according to FIGS. 8a and b serves for frictionally locking a linearly guided rod or a slide by means of piezoelectric actuators 1 and 1 '. The two actuators are arranged opposite the rod 26 which can move back and forth in the transverse direction. This arrangement offers additional security in the event of failure of one of the actuators 1 or 1 '. The clamping device consists of the actuators 1 , 1 ', the pressure plates 14 , the container sleeve 16 and the end screw connection 22 and is floating in a recess of a sliding bearing 27 with a tight fit or sliding seat, ie without noticeable play. When the Aktua gates 1 , 1 ', the pressure plates 14 are pressed against the rod 16 . The increase in the frictional forces between the Anpreßplat th 14 and the rod 26 leads due to the play-free mounting of the pressure plates 14 and the container sleeve 16 relative to the sliding bearing 27 to an inhibition or locking of the push rod 26 relative to the sliding bearing 27th

FIGS. 9a and b show a partial longitudinal section and a cross-sectional view of a detail of a clamping device according to the invention provided with a ball bearing, which has a central cable passage for a harness 36 and a rotation. A ball 28 , which has a central bore with a conical outlet (can be seen in longitudinal section according to FIG. 10) or is designed as a hollow ball, is with a fit into the bore or integrally connected to the ball 28 ver connecting tube 30 (analogous to the connector 12 , here, however, designed as a tube for the cable passage) and has a plane defined by the axis of ball 28 and connecting tube 30 (ball joint main axis) around the running groove 29 . The ball 28 of the ball joint is rotatably and axially non-displaceably mounted in a ball seat which is formed by two split bearing shell halves 31 . The bearing shells 31 are mounted on a carrier 35 . Around the equator and coaxially to the axis of the ball seat, a locking ring 32 is arranged and guided axially in a groove in the ball seat 31 . The radial bearing, however, does not take place in the ball seat 31 , but on the circumference of the ball 28 .

The anti-rotation ring 32 has two radial, 180 ° ver set driving pins 37 , the common axis of which extends through the center of the ball 28 mounted in the ball seat 31 . Here by the rotation of the anti-rotation ring 32 about the coaxial axis of the ball seat is coupled to the corresponding rotation of the ball about this axis or about the ball joint main axis. The rotation of the ball joint about the two axes perpendicular to the main axis of the ball joint is limited by design, inter alia, by the bearing shells 31 . The rotation about the ball joint main axis, however, is provided by a locking pin 33 provided in the anti-rotation ring 32 in combination with an arranged in the bearing shell 31 stop pin 34 z. B. limited to 355 °. With the same anti-rotation principle, in particular the design of the bearing shells 31 and the support 35 can vary, as shown in the following FIGS . 10 and 11, and also the continuation of the cable space 36 through the arm segment or the ball joint can vary.

Fig. 10 shows in partial longitudinal section a clamping device for frictionally locking a ball joint forming an arm segment with a central cable guide. Two elements e.g. B. a support arm system are connected via connecting tubes 30 to the ball joint. The ball 28 of the ball joint is between a sleeve-shaped union nut 13 with a conical ball seat formed on its inside and a pressure cup 38 with a conical seat. The Andruckbe cher 38 is secured against rotation by a locking pin 17 relative to the container sleeve 16 , which contains the actuator 1 .

The operating principle of the locking is based on the non-taxial application of the pressure force of the pressure plate 14 or 4 of the device shown in FIGS. 4a and b. Instead of the pressure plate 14 occurs here, however, the pressure cup 38 , which enables the cable harness 36 to be guided through the ball joint center and provides storage space 40 for the excess of the cable harness 36 , which is required for the rotation of the joint about the longitudinal axis. The anti-rotation 28 of the ball is done with a retaining ring 32 in the manner described with reference to FIGS. 9a and b. Deviating from this, however, the axial guidance of the locking ring 32 takes place in a groove formed between the union nut 13 and an adjusting screw 39 (radial guidance on the circumference of the ball). The stop pin 34 of the anti-rotation device is seated in a radial bore in the union nut 13 . The groove for the axial mounting of the locking ring 32 is defined by the axial gap between the union nut 13 and the adjusting screw 39 , is set with play and then z. B. secured by adhesive.

The bias and the play of the ball bearing are, as already described above, set by the position of the union nut 13 relative to the container sleeve 16 and secured by means of the Ge nut 15 Ge. Damping and isolation of the piezoelectric actuator 1 in the container sleeve 16 can, as already mentioned, be carried out with flexible plastic 18 .

The embodiment of a designed as a combined ball / swivel arm segment with a device according to the invention Vorrich for friction locking and integrated cable management is shown in Fig. 11. The principle of action of the articulated mechanism and the locking largely correspond to the device described in FIGS. 5a and b. Two links or elements of a holding arm system are connected to the overall joint via connecting pipes 30 . The ball 28 of the ball joint is mounted between a cup-shaped, laterally slotted union nut 13 with a flat, almost punctiform seat and a pressure plate 31 designed with a conical seat. It is important that the contact points of the ball 28 with the three ball axes each have sufficiently large resulting lever arms.

The pressure plate 41 of the actuator 1 is secured by a locking pin 33 against the container sleeve 16 against twisting. Likewise, the pressure plate 31 provided with the conical seat is secured against rotation by a locking pin 33 seated in the union nut 13 . The cable outlet is on one side of the piezo. The axial mounting of the locking ring 32 limiting the rotation of the ball happens in a groove milled into the union nut and on the other hand in the conical ball seat of the pressure plate 31 provided for the groove. Again, it is particularly important that the securing ring 32 does not touch the bottom of the groove even when the joint is locked. This is done by the radial guidance of the anti-rotation ring 32 on the circumference of the ball.

In contrast to the embodiment shown in FIG. 10, the device additionally has a swivel joint, which is formed by the threaded sleeve 20 which can be rotated on the outside of the container sleeve 16 , and an axially closed, but open to one side union nut 13 . This lateral opening is designed in such a way that the connecting tube 30 can be moved easily in this opening when the joint is not locked. This results in an almost spherical movement space between the two connecting tubes 30 of the joint, which can actually reach 360 ° in all directions by angling the connecting pieces, for example by 45 °. Since the wire harness 36 is to be guided through the joint, the rotation around the axis of rotation is limited in the form shown. For this purpose, a radially inward locking pin 19 a and a pin 19 b seated in the axial end face of the container sleeve are provided in the union nut 13 as a stop for the pin 19 a. This allows the rotation to z. B. 355 ° can be limited.

When an electrical voltage of suitable polarity is applied to the cable connections of the actuator 1 , the ball 28 is pressed against the bottom of the union nut 13 via the pressure plates 41 and 31 . The union nut 13 presses the upper edge of the threaded sleeve 20 against the collar of the container sleeve 16 . Depending on the electrical field strength, the rigidity of the structure in the power flow and the mechanical preload of the actuator, the ball seat, the axis of rotation, the total length of the piezo and the total free play to be bridged, there is an increase in the amount between the ball and the ball seat on the one hand, and threaded sleeve 20 and container sleeve 16, on the other hand, effective frictional forces and thus of the torque that can be transmitted from the ball and swivel joint. Backlash and tension can be variably adjusted by the union nut 13 . The union nut is secured against rotation relative to the threaded sleeve 20 by the lock nut 15 . The actuator 1 and also part of the cable storage space 40 for the cable harness 36 can be isolated and damped by introducing plastic insulation compound 18 .

Another embodiment according to the invention of a ball joint forming an arm segment with a solid-state clamping device designed as a piezoelectric actuator for frictionally locking the ball joint is shown in FIGS . 12a and b. In a similar way, Festkörperklemmvor devices for locking translational degrees of freedom or axes and shafts can be realized. Two elements e.g. B. a holding arm systems are connected by connecting tubes 30 to the ball joint. The ball 28 of the ball joint is mounted between the clamping jaws of a clamping body 42 with a solid body joint in the central part and freely rotatable in the unclamped state. The support points (below a point; above four point-like surfaces offset by approximately 30 to 45 ° spatially) should be arranged so that the largest possible lever arm of the attacking friction forces to the three spatial axes ( Fig. 12b).

The necessary for jamming and fixing the solid body joint, two side bodies, which are offset by 180 ° at the start of the clamping body 42 , can optionally be made so wide on the side of the ball 28 that the connecting piece or connecting tube 30 in this side notch can be moved. The cross section of the clamping body 42 can differ from the circular cross section in order to provide sufficiently large end faces for the actuator 1 .

In FIG. 12, the actuator is installed in transverse position using a bending element end piece 5 according to FIG. 2. The indicated prestressing screws 50 tension the joint between the bending element end piece 5 and the clamping body 42 of the solid body joint and fix the actuator 1, optionally glued to the bending element end piece 5, in its position. A joint 21 ', which extends from the central connecting web of the clamping body 42 first in the axial direction and then downwards, ensures the margin that is necessary for the bending of the solid body joint and thus for the clamping action of the clamping body 42 .

By applying an electrical voltage of suitable polarity to the cable connections 2 , the actuator 1 expands and presses the arms of the clamping body 42 apart on the side of the actuator 1 . As a result, the spherical jaws of the clamping body 42 are compressed. The ball is thus pinched from both sides.

Depending on the electric field strength and the other parameters already mentioned, there is an increase in the frictional forces acting between the ball and the ball seat and thus the torque that can be transmitted by the ball joint. Bias and play of the devices of the ball seat and the actuator) can be adjusted by a corresponding ball or actuator-side undersize or oversize and by an adjusting screw 44 and secured with known means. This embodiment of an actively lockable ball joint with solid-body mechanism allows a path translation b: a according to the lever arm lengths a, b and, under certain conditions, an improvement in the efficiency of the actuator 1 compared to the variants of a clamping device described so far. As a result, shorter and cheaper actuators with a high permissible nominal load can be used. It is important here that the bending stiffness of the middle bending web of the clamping body 42 is as small as possible, but its tensile stiffness in the transverse direction and the bending stiffness of the clamping jaws of the clamping body and the branches on the side of the actuator are as great as possible.

If the Fig. 13a and b illustrate another embodiment of a process executed as a ball joint Haltearmsegments passive clamping effect and an active release mechanism according to the invention. The passive locking of the ball joint by spring pressure and the active release of the locking by means of a piezoelectric actuator. A spring assembly 43 clamps the ball 28 of the ball joint in the same way as in FIG. 12 via a solid body joint of the clamping body 42 . The clamping force is adjustable via a screw 45 , which acts on the spring assembly 43 . The ball 28 is secured against rotation according to the principle already described by means of an anti-rotation ring 32 . This is necessary if a wire harness 36 is led through the interior of the ball joint or arm segment.

FIG. 13a and the detailed view of Fig. 13b show possible variants for axial mounting of the rings Verdrehsiche approximately 32 via a split ball thrust bearing cup 48. This bearing shell 48 can be clamped and fixed in the ball seat by a tension fitting screw 47 . Another possibility would be a cohesive connection 23 of the bearing shell 47 and the clamping body 42 . Please note that the lateral mobility of the ball joint is restricted when using an anti-rotation device. The connector 30 must not be moved into the side notch 21 , otherwise the locking ring 32 may be damaged Ver.

The piezoelectric actuator 1 is preferably installed transversely, as shown in Fig. 13a. To avoid bending stresses in the actuator 1 , a rocker wedge end piece 46, possibly glued onto the actuator 1 , can be provided with a joint pretensioning screw 50 . The actuator 1 is adjusted by an adjusting screw 44 so that it mechanically exerts virtually no force on the clamp body regardless of any mechanical preload that may be provided in the articulated state "locked" corresponding to the switching state "-1". By applying an electrical voltage of suitable polarity for the "joint state released" corresponding to the switching state 1 or 2 (see above), the actuator 1 expands. Here, he presses the ball-side jaws of the clamping body 42 apart against the restoring force of the spring assembly 43 and the solid-state joint, thereby relieving the ball seat. Thus, depending on the electrical field strength generated by the applied voltage, the stiffness speed, the structure in the power flow and the mechanical preload of the piezo, the overall length of the same and the overall free play to be bridged, a reduction in the effective between the ball and ball seat Frictional force and thus to reduce the torque that can be transmitted by the ball joint, that is, to release the clamping device. The spring assembly should have a slight increase in the restoring force when expanding the piezoelectric actuator.

The embodiment of a ball joint shown in FIG. 14 is based in principle on the same principle of action with passive locking. The clamping force is set using an adjusting screw 49 . To release the ball joint, the actuator 1 must expand against the elastic restoring force of the clamping body 42 in the inclusive adjusting screw 49 . Instead of a plate spring 43 ( FIG. 13), the actuator 1 is preloaded in FIG. 14 with a spiral spring according to FIG. 3. The detailed design of the ball seat is not shown in detail in this FIG. 14 and can be carried out in any of the ways previously described with reference to FIGS. 12 and 13.

The embodiment of a ball joint shown in FIG. 15 is also based in principle on the same principle of action with passive locking and active relief or unlocking by a piezoelectric actuator 1 . The clamping force is not set using an adjusting screw, but rather via a defined undersize of the ball seat relative to the ball 28 . The undersize required for passive clamping of the ball can be produced in various ways, whereby the mountability of ball 28 and actuator 1 and, if the cable is routed centrally, an anti-rotation device may also have to be taken into account. The undersize can be caused by

• a) appropriate processing of the ball seat in Sprags,
• b) by appropriate machining of the surfaces in the division plane with optimal division of the clamping body 42 ,
• c) by a defined, plastic deformation of the clamp body,
• d) by designing the lower, preferably approximately spherical, ball seat corresponding to or similar to FIG. 17 (self-locking adjusting wedge 57 ) or
• e) can be achieved by designing the upper, front ball seat in accordance with or similar to FIG. 13 (split bearing shells with tension fitting screws 47 ).

Provided that the ball 28 can be used with elastic deformation of the clamping body 42 , the undivided embodiment of the clamping body shown in Fig. 15 is preferred. The ball seat not shown in detail in FIG. 15 can then be designed in accordance with the embodiment shown in FIG. 12.

If the insertion of the ball under purely elastic deformation of the clamping body 42 is not possible, a parting plane (dashed lines) can be provided. The clamping body 42 is then by means of fitting 52 , such as. B. dowel pins or dowel screws, adjusted and joined together by screws 51 in a form-fitting or otherwise cohesive manner after inserting the ball 28 .

If the ball seat is designed in accordance with the embodiments according to FIG. 13 or 17, a division of the clamping body 42 for inserting the ball is also not necessary. If the ball 28 is clamped in with the corresponding nominal clamping force, the actuator 1 is inserted with the rocker end piece 46 and, with the length of the piezoelectric actuator provided a minimum length, when it is in the switching state "-1", by means of the adjusting screw 44 to the stop, ie free of force or 0 -5% of its nominal load set. The clamping force acting on the ball 28 should not drop below the nominal clamping force.

To release the ball joint, the piezoelectric actuator 1 must expand against the elastic restoring force of the clamping body 42 (switching state "1" corresponds to "joint released").

Fig. 16 also shows an embodiment for passive clamping of a ball joint. The nominal clamping force for frictionally locking the ball 28 is in turn achieved by the restoring forces of the elastically deformed clamping body due to a corresponding undersize of the ball seat (generation of the undersize see above). Particularly in the case of desired circular and small cross sections, the transverse installation of the piezoelectric actuator shown in FIGS . 12 to 15 is no longer possible under certain conditions. Fig. 16 shows a prior ferred embodiment for a longitudinal installation of an actively dissolving the piezoelectric actuator 1.

By applying an electrical voltage of suitable polarity to the cable connections of the actuator 1, the actuator expands and presses the jaws of the clamping body 42 apart via a spreading member 53 . Here, depending on the electric field strength, the rigidity of the structures in the force flow, the mechanical preload of the piezo, the ball seat, the total length of the piezoelectric actuator and the overall free play to be bridged, the effective between ball and ball seat is reduced Frictional forces and thus to reduce the torque that can be transmitted by the ball joint. Biasing and play of the device can be adjusted via an appropriate undersize or oversize on the ball or actuator side, as well as through an adjusting screw 44 , which can be secured by known means.

The expansion body 53 is designed symmetrically and has above a solid base plate corresponding to the cross section of the actuator 1 defined solid joints with reduced flexural strength. In order to reduce the losses caused by play and setting the parting lines, the expansion body 53 can be screwed 50 by means of a pre-tensioning joint, or it can be fixed with a material bond. The ball seat and optionally the cable passage as well as insulation and damping material are not shown in detail in Fig. 16, but can be found in the previously described embodiments.

Figures 17a and b show, as already mentioned, an exporting approximate shape for the design of the lower ball seat with adjustment Barem fit measurement (reduced or excess, for embodiments with lateral active or passive clamping of the ball 11).. While the upper ball seat with two to four small support points z. May be implemented as shown in FIG. 12, the lower ball seat of a self-locking secured with a screw 56 Justierkeiles 57 can be carried out with a point of support in the form. After inserting the ball 11 , this adjusting wedge 57 is pressed in according to the clamping forces provided in the ball seat and secured cohesively by the screw 56 or alterna tively.

Referring to Figs. 1 to 17, an entire Haltearmsy stem, physical, and structural principles piezoelek tric actuators and various types of embodiments constructed as joints arm segments with such piezoelectric actuators rule for frictional locking / release Rotato-driven and translational degrees of freedom have been described.

Fig. 18 shows a complete universal holding arm system equivalent to that shown in Fig. 1, but partially cut. In contrast to FIG. 1, a tubular sterile cover or sheath h is drawn over the arm segments c1, c2, c3 designed according to the invention as ball joints, and over part of the distal handle c4 and part of the stand b. On the distal side, the sheath h ends at a sterile protective shield i and on the proximal side at a sterile protective shield j behind a collar of the stand b. When rolled up, the sterile sheath h comes to rest on the proximal part of the handle c4.

In Fig. 19a is a device for fixing the Haltearmsystems or fiction, modern whose tripod b of an operating table shown at a position designated with 71 table rail. By a hand nut 133 , both the table fastening device 73 on the table rail 71 of the operating table and the tripod b relative to the table fastening device 73 are locked. When tightening the hand cap nut 133 , a spring 135 is first compressed, which resiliently supports a lower bolt 137 until a conical clamping sleeve 134 is placed on a pressure sleeve 136 . In this position, the cone clamping sleeve 134 is radially compressed in the cone clamping area, the friction forces acting on the stand b being increased. Fer ner presses the cone clamping sleeve 134 over the pressure sleeve 136 against the lower latch 137 , which is deflected via a device in the table mounting device dowel pin 138 and pressed from below against the table rail 71 of the operating table, thereby increasing the frictional forces between the table fastening device 73 and the table rail 71 become. The handover nut 133 has bores 139 into which an extension sleeve 140 shown in FIG. 19d can be inserted. Although the hand cap nut 133 is designed with regard to its outer diameter, its grip and its thread pitch so that it can be tightened by hand, the holes 139 in the hand cap nut 133 can also serve as assembly aids for attaching an additional tool.

In Fig. 19d, a variant of the Tischbefestigungsvorrich device is shown, which has one or more on the circumference of the union nut 133 distributed and retractable tightening lever 142 to increase the torque. Further, the embodiment of the extension sleeve 140 shown, with the holes 139 of the coupling nut 133 to be inserted with the name pivot 141 is shown. The extension sleeve 140 , the length of which can be selected depending on the tripod length as required, also has, in one variant, an annular groove 143 , into which a surgical drape 144 can be inserted and secured against slipping. In general, the fully sterilizable table mounting device 73 can be clamped over the sterile surgical drape 144 to the table rail 41 of the operating table. With the extension sleeve 140, however , the surgical drape 144 can optionally be pulled over the table fastening device 73 and the proximal end of the stand b with the union nut 133 and fixed in the groove 143 of the sterile extension sleeve 140 .

The loosening and locking of tripod b and OR table attachment device 73 by means of the union nut 133 are then still possible from the sterile area by attacking the extension sleeve 140 . For this purpose, the extension sleeve 140 can also have holes 139 or tightening lever 142 such as the union nut 133 . Of course, the conical clamping sleeve shown in the preferred embodiment can be replaced by other clamping means.

Fig. 20 shows an apparatus for separate locking of the tripod b, and the table attachment means. Thereby it the nut 139 again as shown in FIG. 19, the conical clamping sleeve tightened 134, but it presses here not against a spring, but directly against the table fixture 73 whereby the tripod b opposite the Tischbefestigungsvor direction 73 locked is. The locking of the table fastening device 73 relative to the table rail 71 is carried out by a clamping screw 147 , which is actuated by means of a handwheel 147 via a driving pin 146 . When tightening the clamping screw 145 , the lower latch 137 , which is deflected via the dowel pin 138 , is pressed against the table rail 71 , whereby the frictional forces between the table fastening device and the table rail 71 are increased.

In Fig. 21, a table fastening device 73 is Darge, in which again, as in Fig. 19, the stand b and the table fastening device are locked together. The table fixing device comprises a clamping screw 151 which via an eccentric lever 148, the rear jaw of the table fixing device 73 b on the tripod and a clamping plate 150 against a lower Exzenterspannbacke suppressed, which is deflected over the stored in the table fixture 73 dowel pin 138 and against the table rail 71 of the operating table is pressed. This leads to an increase in the effective frictional forces between the stand b and the table fastening device 73 and between the latter and the table rail 71 and to the positive holding of the table rail 71 between the upper jaw of the table fastening device 73 and the lower eccentric jaw 149 . Springs 152 hold the clamping plate 150 in its recess when the stand b is removed and resiliently support the lower eccentric clamping jaw 149 . As a result, the lower eccentric clamping jaw 149 acts when the table fastening device 73 is placed on the table rail 71 of the operating table when the clamping device is released as a snap lever protection which effects a first securing of the fastening.

FIGS. 22a-c finally show another execution form of a table fixture for separate Arretie tion of tripod b and the fixing device itself, as has been already indicated in FIG. 1. When tightening a clamping screw 151 via an eccentric clamping lever 154 , the stand b is tightened in the table fastening device 73 and locked in a frictionally locking manner. The attachment of the Tischbefestigungsvor direction 73 on the table rail 71 , however, takes place with a lower eccentric clamping lever 153 . For the lower eccentric clamping lever 153 an embodiment with reverse clamping direction is shown. This embodiment of the lower eccentric tensioning lever 153 has the advantage over the variant shown in the overall illustration of FIG. 1 that the eccentric pulls the entire device when tightening on the table rail 71 and can thus be used more reliably.

A further application of a device according to the invention for frictionally locking a translationally moving rod and a ball joint results from FIG. 23. This device forms a neurosurgical armrest which is to be seen as a special embodiment of a holding arm system. In principle, such an armrest can also be coupled as an end effector d (cf. FIG. 1) with a corresponding interface to a universal holding arm shown in FIG. 1. However, the embodiment shown in FIG. 23 takes into account the special requirements and, in principle, corresponds in its kinematics largely to conventional, purely mechanical support systems.

On a base plate 163 , a clamping body 61 is mounted with a ball joint 62 that can be released or locked by means of piezoelectric actuator 1 according to one of the embodiments shown in FIGS . 2 to 6 and 9 to 17. A lower stand tube 162 is fastened to the ball, into which a threaded pin 160 is inserted. A middle stand tube 161 , in which the actuator 1 is mounted, is screwed onto this threaded pin 160 . The arms of a spreader 159 mounted on the actuator 1 protrude through two side slots offset by 180 ° - there can be a maximum of four offset by 90 ° - of the middle stand tube 161 . On the slotted end of the middle stand tube 161 , a Ge brace 158 is also welded, which has defined wedge-shaped contact surfaces (inclined plane) for the spreader 159 . The upper stand tube 157 is pushed over the counter holder 158 , the spreader 159 and the middle stand tube 161 , which is closed at the top by an arm support rail 155 . The upper sta tivrohr 157 including armrest 155 is supported by a central spring 156 against the counter bracket 158 . When the spring 156 is relaxed, the upper and middle stand tubes 157 and 161 still protrude into one another. In addition, two stop rings, not shown, can prevent the two tripod tubes from sliding apart.

By applying an electrical voltage to the connecting lines of the actuator, the actuator 1 expands and presses the arms of the spreader 159 over the inclined planes of the counter holder 158 laterally against the wall of the upper stand tube 157 . As shown, the wall of the upper stand tube z. B. be reinforced in this area by an outer reinforcing tube 164 . This results in a function of the electric field strength ke, and the other parameters already mentioned several times, to reduce the effective friction forces between the spreader 159 and the upper stand tube 157 and to loosen the Klemmvor direction.

The preload and the play of the device can be adjusted by means of the screw connection of the middle stand tube 161 with the thread 160 and secured by a lock nut 15 . The spreader 159 is designed symmetrically and has above its solid base plate corresponding to the cross section of the piezoelectric actuator 1 defined solid body joints of reduced bending stiffness. Otherwise, instead of the base plate 163 , a table fastening device can also be provided, as described above.

Claims (38)

1. Clamping device for frictionally locking a translationally and / or rotatably movable member of an arm segment of a holding arm system, characterized in that at least one electrostrictive, in particular piezoelectric, actuator ( 1 ) acting in a frictional manner on a section of the member in response to a supplied electrical actuating signal. is provided so that it acts directly in its direction of expansion or indirectly by means of force deflecting means on said section. 2. Clamping device according to claim 1, characterized in that the actuator ( 1 ) is designed as a translator with a linear main expansion direction. 3. Clamping device according to claim 1 or 2, characterized records that the actuator is a multi-layer actuator. 4. Clamping device according to claim 1 or 2, characterized in that the actuator ( 1 ) is a monolithic actuator. 5. Clamping device according to one of the preceding claims, characterized in that a spring element ( 7 ) which prestresses the actuator ( 1 ) in its main direction of expansion is seen. 6. Clamping device according to claim 5, characterized in that the actuator ( 1 ) between two with the spring element ( 7 ) connected to the end plates ( 6 , 6 ') is biased. 7. Clamping device according to one or more of the claims 1 to 6, characterized in that the movable member is the ball ( 11 ) of a ball joint and the actuator ( 1 ) is provided outside the ball ( 11 ) so that it with a be movable end plate ( 6 ) acts directly or indirectly on the outer surface of the ball ( 11 ). 8. Clamping device according to claim 7, characterized in that the direction of expansion of the actuator ( 1 ) intersects the center of the ball ( 11 ). 9. Clamping device according to one or more of claims 6 to 8, characterized in that said movable end plate ( 6 ) of the piezoelectric actuator ( 1 ) acts with its surface facing the ball via a pressure plate ( 14 ) on the outer surface of the ball. 10. Clamping device according to one or more of claims 1 to 6, characterized in that the movable member is a rotating shaft ( 24 ) and the actuator ( 1 ) in response to the electrical control signal with its movable end plate ( 6 ) directly or via a pressure plate ( 14 ) acts on the peripheral surface of the shaft. 11. Clamping device according to one of claims 1 to 6, characterized in that the movable member is a linearly movable rod ( 26 ) and at least one piezoelectric actuator ( 1 ) is provided, with its movable end plate ( 6 ) via a pressure plate ( 14 ) acts on an outer surface of the rod. 12. Clamping device according to claim 11, characterized in that two opposing piezoelectric actuators ( 1 , 1 ') are provided so that they have a pressure plate ( 14 ) with their movable end plates ( 6 ) on opposite sections of the Attack the pole. 13. Clamping device according to claim 12, characterized in that the directions of expansion of the two actuators ( 1 , 1 ') are opposite and colinear. 14. Clamping device according to one or more of the preceding claims, characterized in that the piezoelectric actuator can assume the following states depending on a supplied control voltage U _s : where U _n indicates the nominal voltage of the actuator at which it assumes its maximum expanded state. 15. Arm segment for a holding arm system, in particular for Hold surgical instruments characterized by a Clamping device according to one or more of the preceding Expectations.   16. Arm segment according to claim 15, which forms a lockable ball joint and has:

• a) one-sided to the ball ( 11 ) of the ball joint for pressure effect open container sleeve ( 16 ) containing the piezoelectric actuator's ( 1 );
• b) at the open end of the container sleeve ( 16 ) axially movable pressure plate ( 14 ) which is movable from the movable end plate ( 6 ) of the actuator ( 1 ) in the direction of its expansion;
• c) a rigid ball joint sleeve ( 13 ) which is fixedly connected to the container sleeve ( 16 ) and has a ball seat on its inner wall section;
• d) a ball ( 11 ) of the ball joint lying between the pressure plate ( 14 ) and the ball seat;
• e) two connecting pieces ( 12 , 12 '), each of which is connected to the ball ( 11 ) and the container sleeve ( 16 ), the ball ( 11 ) with its connecting piece ( 12 ) being rotatable in the non-locked state and in one by the Ku gelsitz, the ball joint sleeve ( 23 ) and the shape and size of the connector on the ball seat ( 12 ) definable solid angle pivotable and by means of the piezoelectric actuator ( 1 ) and via the pressure plate ( 14 ) transmitted friction in their rotational and pivoting movement can be locked.

17. Arm segment according to claim 16, characterized in that the container sleeve ( 16 ) is connected to the ball joint sleeve ( 13 ) by means of a non-rotatable screw connection. 18. Arm segment according to claim 15, which forms a ball joint in combination with a swivel, which is characterized by:

• - the features a), b), d) and e) of claim 16 and additionally by:
• - A ball joint sleeve ( 13 ), which has two 180 ° against each other offset side notches ( 21 ), is rotatably mounted on the swivel joint on the container sleeve ( 16 ) and has a ball seat formed on its inner wall section, wherein
• - The side notches are designed in such a way that the connecting piece ( 12 ) seated on the ball ( 11 ) can be brought easily into each of the side notches ( 21 ) when the actuator is not activated and
• - The swivel joint is formed on the cylindrical outer wall of the container sleeve ( 16 ) rotatably mounted sleeve ( 18 ) and an on the spherical face of this sleeve ablie outer collar of the container sleeve ( 16 ), so that on the ball joint and on the swivel in In response to activation of the actuator, a friction torque is transmitted, which locks the movement of both joints.

19. Arm segment according to claim 18, characterized in that rotation limiting means ( 19 a, 19 b) are provided for limiting the angle of rotation between the container sleeve ( 16 ) and ball joint sleeve ( 13 ). 20. Arm segment according to claim 16, 18 or 19, characterized in that the connecting pieces ( 12 , 12 ') each form integral parts with the ball ( 11 ) and the bottom of the container sleeve ( 16 ). 21. Arm segment according to claim 19, characterized in that the connecting pieces ( 12 , 12 ') are linear rods. 22. Arm segment according to claim 20, characterized in that at least one of the connecting pieces ( 12 , 12 ') is angled. 23. arm segment according to claim 22, characterized in that the angle of the bend is 45 °. 24. Arm segment according to one or more of claims 16 to 23, characterized in that in the region of the bottom of the container sleeve ( 16 ) at least one cable bushing for supply lines to the actuator is provided. 25. Arm segment according to one or more of claims 15 to 24, characterized in that the ball ( 11 ) is hollow or has a central through hole, so that coaxial openings are formed in the direction of the associated connecting piece ( 12 ) and in the opposite direction and that both connec tion pieces ( 12 , 12 ') are hollow rods. 26. Arm segment according to one of claims 15 to 25, characterized in that the ball ( 11 ) has a coaxial through bore which widens conically at the end opposite the associated connecting piece ( 12 ). 27. Arm segment according to one of claims 15 to 26, characterized in that means ( 33 , 34 ) are provided for limiting the rotation of the ball ( 11 ) about a through the ball axis and the main axis defined by the axis of the associated connector. 28. Arm segment according to one or more of claims 15 to 27, characterized in that the ball ( 11 ) in a plane defined by its axis and the axis of the connecting piece (ball joint main axis) has a circumferential outer groove ( 29 ) that the ball seat by a bearing shell ( 11 ) is formed, which is fixed to the inner wall of the ball sleeve ( 35 ) and the ball ( 11 ) is rotatably mounted in the bearing shell ( 31 ) that coaxially to the axis of the ball seat, an anti-rotation ring guided in a groove in the ball seat ( 32 ) is arranged, which is mounted radially on the circumference of the ball ( 11 ), and that the United anti-rotation ring ( 32 ) has two radial, 180 ° offset driving pins ( 37 ), the common axis through the center of the ball ( 11th ) goes, whereby the rotation of the anti-rotation ring ( 32 ) about the axis of the ball seat is coupled to the corresponding rotation of the ball ( 11 ) about this axis and the rotation about the ball main joint axis is limited by an anti-rotation pin ( 33 ) provided in the anti-rotation ring in combination with a stop pin ( 34 ) in the bearing shell ( 31 ). 29. Arm segment according to claim 15, which is an actively lockable and releasable ball joint forms, characterized by a with a solid body clamp with clamp bake to lock / release a ball stored in it of the ball joint, with the actuator on the solid body joint of the sprag acts so that when the control signal is applied Ball clamped between the jaws or the Clamping effect of the clamping body is canceled. 30. arm segment according to claim 29, characterized in that in the case of the actively lockable ball joint, the actuator on the side of the solid-state joint opposite the ball attacks.   31. Arm segment according to claim 29, characterized in that the actuator in the case of the actively releasable ball joint attacks on the ball side of the solid-state joint. 32. arm segment according to one of claims 29 to 31, characterized characterized in that the main direction of expansion of the actuator perpendicular to one through the longitudinal axis of the sprag and the ball center going axis stands. 33. arm segment according to claim 31, characterized in that on the opposite side of the solid from the actuator Joint spring means are provided which have a passive clamping force produce. 34. Holding arm system especially for holding surgical Instruments at the operating table, characterized by the ver using one or more arm segments according to at least any one of claims 15 to 33. 35. Device for attaching a holding arm system according to claim 34 or a tripod for holding the holding arm system on a table rail of an operating table characterized in that a hand nut ( 133 ) for simultaneous attachment of a table fastening device ( 73 ) and the tripod (b) relative to Table fastening device ( 73 ) is provided. 36. Apparatus according to claim 35, characterized in that a lower bolt ( 137 ) for pressing the Tischbefestigungsvor direction ( 73 ) against a table rail ( 71 ) of the operating table is provided. 37. Device according to one of claims 35 and 36, characterized in that the hand cap nut ( 133 ) has bores ( 139 ) for receiving an extension sleeve ( 140 ). 38. Apparatus according to claim 37, characterized in that the extension sleeve ( 140 ) has an annular groove ( 143 ) for receiving a sterile surgical drape ( 144 ).