Abstract:
An apparatus for retaining an optical viewing device, for example a microscope ( 8 ), on a stand having a parallelogram carrier arm ( 5   a   , 5   b   , 5   c   , 5   d ), comprises an adjustable-length strut ( 6 ) acting through a pivot point of the carrier arm and an opposite link of the carrier arm. The strut ( 6 ) provides, in different variants, inclination adjustment, and/or vibration damping of the carriers arm.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of the German patent application 101 63 354.8 filed Dec. 21, 2001 which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention concerns an apparatus for retaining an optical viewing device, for example a microscope, having movable retaining carriers, arranged in parallelogram fashion, with a diagonal support element. The term “support element” is to be understood, for example, as diagonal struts or the like that can transfer forces in a mechanical/geometric arrangement and thus can serve to support or retain, and/or to change the position of, the viewing device. They operate in accordance with lever and/or moment laws, and optionally contain adjustment apparatuses in order thereby to take into account or bring about changed conditions so as to guarantee retention of and/or a change in the position of the viewing device. 
     BACKGROUND OF THE INVENTION 
     The apparatus is intended to be usable on a stand foot or on a stand column such as a stand arm, but also on other stands such as ceiling or wall mounts. 
     Retention of an optical viewing device by means of a stand having a stand arm is necessary in a wide variety of applications, especially in the field of medical technology. These stand arms are often embodied as one-armed carriers which are held in position by means of spring mechanisms and/or lockable brakes, and/or are motor-driven. 
     WO 99/01693-A presents a stand that is marketed by the Applicant as MS  1 . Like previous models as well, it has a carrier arm, constructed as a parallelogram, whose geometrical extension is defined by an obliquely arranged support spring, the support spring serving as weight compensation for the load of the viewing device. In this known assemblage, the spring force is adjustable so that different weights of different or differently equipped viewing devices can be supported or compensated for. 
     EP 866 260 A discloses a toothed-belt-supported support element that transfers the forces for weight compensation (balance) by means of its geometrical arrangement. 
     In conventional assemblages, diagonal struts are thus used essentially in order to support specifically arranged carrier arms or carrier arm parts in a desired position, and to direct the stress on those assemblages obliquely into the stand columns. In some circumstances, this task could also be achieved, in the context of these assemblages for performing support functions, if no parallelogram at all were present, but rather the entire assemblage were boom-shaped. 
     Conventional diagonal struts often also have:
     An integrated spring force of a gas spring, as already mentioned above, to compensate for (the weight of) the load.   One or more damping elements, for example gas springs or special rubber bumpers having defined spring and damping characteristics (vibration damping).   Liquid dampers.   

     The inventor has recognized that the known systems are disadvantageous in the following ways:
     a) Insufficient stability in the vertical direction of the microscope (parallel to the optical axis), and thus low positioning accuracy. As a result of poorly controllable vibration stability, unsharp or unstable images can occur with a slow-reacting autofocus system.   b) Heavy construction, in order to achieve improve stability and low-vibration characteristics.   c) Large retention forces are necessary. The elements are thus of solid construction, thereby also (because of the increased weight) resulting in sluggishness and insufficient mobility.   

     SUMMARY OF THE INVENTION 
     It is thus the object of the invention to create an apparatus which makes possible stable, vibration-free, and reproducible retention of an optical viewing device and/or which eliminates the disadvantages indicated above. In particular, improved vibration behavior in the vertical direction is to be achieved. The mechanical properties of the assemblage are also intended to result in higher strength for the overall assemblage. The weight of the overall assemblage is intended to be minimized. 
     This object is achieved by means of an apparatus for retaining an optical viewing device, for example a microscope, on a stand, having at least one support element that braces the stand parts with respect to one another, the support element being arranged or equipped so that in the operating state, a coordination of load-bearing stand parts, in particular the links of a parallelogram-like carrier arm, results. According to the present invention, the bracing support element acts upon the geometrical or physical properties of a parallelogram carrier arm in such a way that the carrier arm becomes distorted or mechanically overrigid. 
     This inventive idea is not intended to exclude embodiments that can be adjusted in remote-controlled fashion in such a way that the geometry-related force effects, or supporting or damping effects, of the support element are modified as necessary. Similarly, “distortion” and “overrigidity” mean in the context of the invention that the support element could also, within specific but narrow limits, yield in damping fashion or act resiliently. 
     A controlled and arbitrarily effected distortion of stand parts with respect to one another is critical to achieving the effect according to the present invention. 
     The term “support element” in the context of the invention also encompasses multiple support elements, e.g. arranged next to one another, that act together. 
     In an apparatus that is to be used frequently according to the present invention, the support element is inserted approximately diagonally in a carrier arm (parallelogram) comprising four carriers, in which three of the carriers are pivotable relative to the fourth and/or relative to one another. 
     According to a development of the invention, the support element is modifiable in length in motorized fashion, at least one remotely controllable drive system preferably being provided for the change in length. 
     The drive system can be arranged outside the support element or also inside it, and can encompass both electrical and pneumatic motors. Spindle drives, telescoping elements, or the like, and their equivalents, are especially encompassed. 
     A further variant is obtained if the support element is modifiable in length, for example by the user, and is lockable in each length setting, preferably by way of an (in particular, remotely controllable) brake. This can be embodied in such a way that the support element is arranged like an extendable telescoping tube as an approximately diagonal strut in a parallelogram, and in the idle position is locked by a brake that locks the telescoping elements with respect to one another. 
     For stereotactic operations or presentations in particular, it is advantageous if a motion- and position-sensing unit and a position-memorizing unit, which make possible repeatable positioning at predefined or selected positions, are provided. 
     A high degree of automation can be achieved if the motion- and position-sensing unit and/or the position memorizing unit comprise at least one processor-based control system and preferably at least one motion- and position-sensing unit for automatic control of the displacement or positioning. 
     Control systems of this kind can also be utilized in user-specific fashion by the fact that the process control system optionally senses the respective position, inclination, etc. of the carrier and then controls the drive systems so that a specific position is assumed for a specific surgeon. To improve damping behavior, the support element can be equipped with a damping element that is arranged in series or in parallel with the actual support element (e.g. a diagonal strut). According to a development, the invention can also encompass motion, position, angle, or vibration sensors which permit the stand to be used in combination with a control system, or to be integrated into an image-guided surgery (IGS) system and used in computer-controlled fashion. 
     Particular precision in the use of the invention can be achieved if the support element is retained in zero-clearance fashion in its articulation points and relative to its drive systems. 
     All the variants mentioned can be combined in any fashion in order to achieve optimum goal-oriented results. 
     In addition, the following improvements are achieved by using an apparatus according to the present invention as described above:
     Good stability with lightweight design.   Little vibration, despite the lightweight design.   In variants having a drive system (with or without brake): definable and controllable inclination angles or vertical positions of the optical viewing device.   In variants having an electronic control system: capability for combination with an autofocus system of the microscope.   Simply designed solution, retrofittable and effective.   

     Although reference is made in the above text to a surgical microscope, the invention is nevertheless not, limited thereto, but rather is also available to other users of optical devices with retention by means of a stand arm (e.g. projectors, video and photographic cameras, theodolite systems, etc.). 
     The Parts List and the drawings, together with the subject matter described in the Claims, are an integral constituent of the disclosure of this Application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be presented on the basis of a number of exemplary embodiments with reference to the schematic drawings, in which: 
         FIG. 1  schematically shows a portion of a conventional stand having a parallelogram carrier with an adjustable-length diagonal strut according to the present invention; 
         FIG. 2  schematically shows the overall configuration of a stand having a stand arm configured in the manner of a parallelogram with a braked diagonal strut, a counterweight, and a column; 
         FIG. 3  shows the configuration of  FIG. 1  with an adjustable-length diagonal strut and a motion- and position-sensing unit, as well as an electronic activation system for the diagonal strut drive system; 
         FIG. 4  shows the configuration of  FIG. 3  with a motor-driven diagonal strut and a second diagonal strut, acting independently thereof, having a brake for motorized stiffening and a joystick control system for a wide variety of control variants; 
         FIG. 5  shows a variant of the configuration according to  FIG. 4  with an electronic control system and a motion- and position-sensing unit; and 
         FIG. 6  shows a variant having a spindle inside the parallelogram. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically shows a portion of a conventional stand having a parallelogram carrier  5   a – 5   d  and an adjustable-length diagonal strut  6  according to the present invention. Diagonal strut  6  stiffens parallelogram carrier  5   a – 5   d  by the fact that it presses by force (preloaded by a motor  11 ) from carrier  5   a  into the bearing between carriers  5   b  and  5   c . In the lower region it has a spindle  17  that is rotationally mounted in a thread  12  of a pivoting bearing  10  on retaining carrier  5   a . A double arrow  21  indicates the axial force or displacement of diagonal strut  6 . 
     The weight of a microscope  8  is thus supported by parallelogram  5   a – 5   d  that is stiffened by means of diagonal strut  6 . A control system  15 , into which an input  16  can be entered by the user, controls motor  11  via a control line  20 . 
     As is evident from  FIG. 4 , a control system  15   a  of this kind can be combined e.g. with a joystick  22  or the like in order to permit easily operable handling. 
       FIG. 2  schematically shows the configuration of a stand for a surgical microscope  8  having a column  1 , a rotary joint  2  for a stand arm  3 , a rotary joint  4  for the four movable retaining carriers  5   a – 5   d  arranged in the manner of a parallelogram, and a diagonal strut  6  according to the present invention having a brake  7  that, in the released state, allows a vertical motion of retaining carrier  5   c.    
     Vertical retaining carrier  5   a  is not movable in the vertical direction. It is optionally rotatable in bearing  4 . In the braked state, raising or lowering of carriers  5   b ,  5   c , and  5   d  is prevented. 
     Brake  7  is depicted in only symbolically simplified fashion. In most applications, it will have electrically activated brake pads that brake portions of diagonal strut  6  with respect to one another. A certain frictional effect prior to final braking can intentionally exist so as thereby to achieve frictional damping. This damping process of course is effective only as long as the brake is not applied in the stiffened state of parallelogram  5 . Normally, no motion should occur in the stiffened state. In the context of a particular embodiment of the invention, however, in extraordinary load situations a damping effect or an at least slight yielding of diagonal strut  6  could be effective as an overload safety feature. 
     A counterweight  9  balances, via a bearing  13 , the weight of microscope  8  and retaining carriers  5   b–d . Brake  7  thus does not have an explicit retaining function but rather only a stiffening function, and optionally a vibration-damping function for the parallelogram. 
       FIG. 3  schematically shows a stand arm according to  FIG. 1 , but with a motion- and position-sensing unit  14  that is joined to carrier  5   b  but can also be arranged on the other carriers  5   c ,  5   d , or  6 . Motion- and position-sensing unit  14  is depicted only as a symbol, which could also depict multiple motion- and position-sensing units or the like. 
     Equipped with a suitable program, electronic control unit  15 —which is supplied not only with the user&#39;s input  16  but also, via a measurement line  19 , with information from motion- and position-sensing unit  14 —is used to activate motor  11  via control line  20 . 
     Double arrows  21  indicate the ability of diagonal strut  6  to become longer inside parallelogram  5 . 
     The term “motor-driven” is understood to mean assemblages having any desired motorized drive systems, such as electrical, electric-motor, hydraulic, pneumatic, or the like. 
     Depicted in the configuration shown in  FIG. 4  is a “double diagonal strut,” symbolically made up of a first diagonal strut  6   a  and a second diagonal strut  6   b , which performs the support function together with first diagonal strut  6   a . The two diagonal struts  6   a  and  6   b  have different purposes. While the one ( 6   a ) has the purpose already described in  FIGS. 1 and 3 , the other ( 6   b ) has approximately the purpose of brake  7  as shown in  FIG. 3 , so that the two complement one another in terms of effect. 
     A symbolically depicted joystick  22  allows brake  7  and motor  11  to be controlled via control lines  20   a  and  20   b.    
     The assemblage shown in  FIG. 5  further differs in that a motion- and position-sensing unit  14 , which corresponds approximately to motion- and position-sensing unit  14  indicated above and permits automatic positioning of carriers  5   b ,  5   c , and  5   d  if the program in the control system is equipped accordingly, is additionally provided. Control lines  20   a  and  20   b  serve to transmit control information from control system  15  to motor  11  and to brake  7 . 
     The assemblage according to  FIG. 6  shows, as a possible variation, a motor  11  which rotates a spindle  17  that is mounted in a nut  18  on the diagonal strut and thus allows a change in the length of diagonal strut  6 . 
     PARTS LIST 
     
         
           1  Column or stand foot 
           2  Stand foot rotary joint 
           3  Stand arm 
           4  Stand arm rotary joint  5   a, b, c, d  Movable retaining carriers or carriers or struts, arranged in parallelogram fashion 
           6  Strut  6   a ,  6   b  (support element) 
           7  Brake 
           8  Microscope 
           9  Counterweight 
           10  Pivoting bearing 
           11  Motor 
           12  Thread 
           13  Bearing 
           14  Motion- and position-sensing unit for motion and/or vibration and/or position or the like 
         Control system;  15   a  Control system with joystick 
           16  Input signals 
           17  Spindle 
           18  Nut 
           19  Measurement line 
           20   a, b  Control line 
           21  Double arrow 
           22  Joystick