Abstract:
An endoscopic instrument for the connection to an operation robot. The endoscopic instrument includes an instrument housing, to which a shank with at least one instrument part arranged at the distal side of the shank connects distally. The instrument part and/or the shank are movable relative to the instrument housing and for this are each actively connected to control. The control can be coupled, via a translatorily movable coupling element coupled thereto and projecting out of the instrument housing, to a linear drive unit which can be connected to the instrument housing at the outer side.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2014 205 036.7 filed Mar. 18, 2014, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to an endoscopic instrument for the connection to an operation robot, with an instrument housing, with a shank which connects to the instrument housing, and with at least one instrument part arranged on a distal side of the shank, wherein the instrument part and/or the shank are movable relative to the instrument housing and for this are each actively connected to a control means (a control). 
       BACKGROUND OF THE INVENTION 
       [0003]    Operation robots are nowadays applied with an increasing number of surgical operations. Such an operation robot is known for example from US 2009/0234371 A1. This operation robot comprises several robot arms, at whose distal ends an endoscopic shank instrument is arranged each case, wherein this instrument is controlled by the operator from a console and serves for observing and/or manipulating on or in the body of a patient to be treated, depending on the type of instrument. 
         [0004]    The instruments which are provided for manipulation comprise an instrument head which a tool arranged thereon, at their respective distal shank end. Known instruments are provided with an instrument head which can be bent relative to the shank, wherein the tool or a tool carrier with the tool and provided on the instrument head can also be bent (angled) with respect to the instrument head. Instruments which additionally comprise an instrument shank which can be rotated about their longitudinal axis are also widespread. 
         [0005]    It is common to apply pull cables which are led through the shank into an instrument housing arranged at the proximal shank end, as control means, for the control of the rotation of the instrument shank and for the control of the bending of the instrument head as well as for the control of the tool or for actuating the instrument head and the tool. There, in the instrument housing, the pull cables are each non-positively coupled in movement to a rotatable actuation roller which is controlled by way of a rotatory drive motor. The actuation rollers are arranged next to one another in a common plane normal to their rotation axis. The drive motors which serve for actuating the pull cables are arranged in a drive unit which is releasably connectable to the instrument housing. 
         [0006]    Typically, the number of actuation rollers which are arranged in the instrument housing and which is determined by the number of degrees of freedom of movement of the instrument head, has a significant influence on the size of the instrument housing. Moreover, various cable deflections which are necessary in the instrument housing moreover also have an additional disadvantageous influence on the dimensions of the instrument housing and increase the assembly effort on manufacture of the instrument. Thus, the instrument housing is already relatively large with an instrument, in whose instrument housing only four actuation rollers are arranged. This size of the instrument housing has been shown to be disadvantageous if several of these shank instruments are to be applied together in a restricted space, as is the case with single-port operations for example, with which the shank instruments are simultaneously led to the region of operation via a common body opening. 
       SUMMARY OF THE INVENTION 
       [0007]    Against this background, it is an object of the invention to provide an endoscopic instrument of the type described above, which has a constructionally simplified movement coupling of the control means for the control of at least one instrument part arranged distally of the shank, and/or of the shank, to a drive unit, and which permits the creation of a compact instrument housing. 
         [0008]    The endoscopic instrument according to the invention is such an instrument which is used in combination with an operation robot. It comprises an instrument housing, onto which the shank connects at the distal side which is to say distally. At least one instrument part is arranged at the distal side of the shank usefully designed as a hollow shank. With regard to this instrument part, it can e.g. be the case of a tool or an instrument head serving as a tool carrier. The instrument part and/or the shank are movable relative to the instrument housing. In this context, one preferably envisages the instrument part being pivotable relative to the shank and to the instrument housing which is connected thereto, and the shank is rotatable about its longitudinal axis relative to the instrument housing. Several instrument parts can further preferably be arranged at the distal side of the shank and these are pivotable relative to one another and relative to the shank. Inasmuch as this is concerned, if hereinafter one speaks of the instrument part, this is also to be understood as several instrument parts. 
         [0009]    The instrument part and/or the shank are actively connected to control means which are actuatable in the instrument housing, for the movement control. Usefully, a pull means which is led from the instrument part through the shank into the instrument housing is provided as control means, at least for the instrument part which is arranged at the distal side of the shank. The actuation of the control means for the instrument part and/or for the shank is effected via drive motors which are actively connected thereto and are arranged in a drive unit of the instrument which is connectable to the instrument housing, and subject the control means to a pulling force for movement control of the instrument, if with regard to the control means, it is the case of a pull means. 
         [0010]    The basic idea of the invention lies in coupling the control means which are actively connected to the instrument part arranged distally of the shank and/or to the shank, in each case via a translatorily movable coupling element which is coupled in movement to these means, to a linear drive unit which can be connected onto the instrument housing at the outer side. The coupling element is preferably arranged in the instrument housing such that it projects out of the instrument housing. 
         [0011]    In combination with the pull means which are preferably used for the control of the instrument part arranged at the distal side of the shank, this means that a translation of the coupling element which is produced by the linear drive unit can be transmitted directly onto the pull means given a suitable design. Accordingly, the actuation rollers which until now are to be arranged in the instrument housing are no longer necessary, which leads to a considerable gain in space in the instrument housing, which is to say the creation of a comparatively small instrument housing, wherein the number of the individual components which were necessary until now for the movement transmission of the drive motor onto the control means can be significantly reduced. 
         [0012]    The instrument housing is advantageously designed in an essentially completely closed manner for the protection of the control means which are located therein, so that a part of the coupling element is to be led through an outer wall of the instrument housing. For this, usefully an opening corresponding to the movement path of the coupling element is formed on the outer wall of the instrument housing. The connection of the linear drive unit to the instrument housing and thus the coupling of the linear drive movement to the coupling element are usefully releasable in a repeated manner, in order to be able to separate the linear drive unit from the remaining instrument for cleaning or maintenance purposes for example. 
         [0013]    The coupling element is preferably arranged on a track-guided pull slide (carriage) in the instrument housing. A linear guide, in which the pull slide is displaceably guided, is accordingly preferably provided in the instrument housing. E.g. hollow profile rails or two guide strips which are aligned parallel to one another can serve as track guidance for the pull slides in a manner which is simple with regard to the design. The track guide is usefully aligned in the movement direction of the pull means. The pull slide which is led in the track guide is directly connected to the control means, in a particularly space-saving manner. 
         [0014]    The linear drive unit which can be coupled to the coupling element can be formed by a fluidically actuatable cylinder or by a linear motor which can be coupled to the coupling element in a direct manner via a coupling device which is connected thereto. A linear drive unit which comprises at least one rotatory drive motor, subsequent to which a gear designed for the conversion of the rotation movement of the motor shaft into a translation movement is arranged, is however preferably provided. An electric motor is preferably provided as a drive motor, but a fluidically actuated motor can also be used as the case may be. 
         [0015]    With regard to the gear which is arranged subsequently to the drive motor, it is preferably the case of a rack-and-pinion gear, whose rack is coupled in movement to a coupling device which is positively connectable to the coupling element on the instrument housing side. In this case, a pinion meshing with the rack is usefully arranged on the motor shaft of the drive motor, on the drive side. The linear drive unit advantageously comprises an essentially closed housing, in which at least the rack-and-pinion gear arranged subsequently to the drive motor, and the coupling device coupled in movement thereto are arranged. Hereby, usefully at least one opening is formed on an outer wall of the housing which lies in the connection direction of this housing to the instrument housing, through which opening the positive connection of the coupling element arranged on the instrument housing side to the coupling device on the linear drive side can be effected. 
         [0016]    The rack of the rack-and-pinion gear is preferably coupled in movement to a drive slide (drive carriage) which is track-guided in the linear drive unit and on which the coupling device is formed. The rack can preferably be connected to the drive slide in a direct manner or be formed directly on the drive slide. A guide track for the drive slide and which is arranged in the linear drive unit is usefully aligned corresponding to the movement path of the coupling element provided on the instrument housing side. Usefully, an opening is formed on an outer wall facing the instrument housing, on the preferably envisaged housing of the linear drive unit, through which opening the coupling device formed on the drive slide at least partly projects out of the housing, in order to permit a coupling of the coupling element to the coupling device. 
         [0017]    The coupling element, in a constructionally simple manner, is a projection projecting out of the instrument housing, wherein a recess for the positive receiving of the projection is formed on the coupling device. The projection which is provided on the part of the instrument housing and the recess which is formed on the coupling device on the liner drive side are hereby usefully arranged in a manner such that the projection engages into the recess formed on the coupling device, on connection of the linear drive unit to the instrument housing, wherein a reference travel of the drive slide can be necessary for this as the case may be. 
         [0018]    The coupling element is advantageously resiliently mounted on the slide in the connection direction of the instrument housing and the linear drive unit, in order to permit the engagement of the projection into the recess of the coupling device after a reference travel of the drive slide. This design permits the evasion of the projection when the projection arranged on the instrument housing side, and the recess formed on the coupling device arranged on the linear drive side are not arranged in a congruent manner on connection of the linear drive unit to the instrument housing, wherein the projection after a reference travel of the drive slide locks into the recess in a manner impinged by spring force. A further measure which is advantageous in this respect lies in the fact that the regions adjacent the recess forming guide ramps for the coupling element, on the drive slides, so that the reference travel of the drive slide is not inhibited by the projection. 
         [0019]    In particular, if with regard to the instrument part arranged at the distal side, it is the case of an instrument part pivotable relative to the shank, preferably at least one pull cable is provided for this instrument part as a control means. Thus, two pull cables acting antagonistically upon the instrument part can be fastened on the instrument part in a direct or indirect manner, and these pull cables are led through the shank into the instrument housing, where they are coupled in movement in each case to a coupling element able to be coupled to a drive motor of the linear drive unit. 
         [0020]    However, a design with which only one pull cable, whose two ends are connected to the instrument part in an antagonistically acting manner, is provided as a control means for the instrument part arranged at the distal side of the shank is preferred. In this case, only one coupling element coupled in movement to the pull cable and, on the part of the linear drive unit, only one drive motor are required for the movement control of the instrument part arranged at the distal side of the shank in this case. The pull cable is hereby advantageously guided in the instrument housing in a deflection roller guide, wherein the movement coupling of the pull cable to the coupling element is envisaged in a region between the shank and a deflection roller which is distanced furthest in the pull direction from the instrument part which is to be controlled. 
         [0021]    The coupling of movement of the pull cable to the coupling element is advantageously effected via a pull slide. Thus, the pull cable is preferably connected to a pull slide on which the coupling element is formed and which can be displaced in the pull direction of this pull cable. The pull slide is usefully guided in a guide track which is arranged in a manner corresponding to the pull direction of the pull cable, in the instrument housing. 
         [0022]    A section of the pull cable is preferably formed by a pull rod. In this context, one envisages both ends of the pull cable being fastened at both ends of the pull rod. The pull cable is preferably fastened on the pull slide on the section formed by the pull rod, wherein the connection of the pull cable to the pull slide is favorably not designed in a rigid manner. Instead, the pull rod is advantageously resiliently mounted on the pull slide on two projections which are distanced to one another in the pull direction of the pull cable, in order to protect the pull cable from an overload. 
         [0023]    The shank for the control of its rotation movement is preferably coupled in movement to a pinion which in the instrument housing meshes with a rack coupled in movement to a coupling element, despite the fact that a pull cable which is coupled in movement to a coupling element in the described manner could be used as a control means for the control of the rotation movement of the shank. 
         [0024]    The coupling element is advantageously designed on a pull slide which is connected to the rack. Hereby, the coupling element, with which it is preferably the case of a projection, is arranged at a side of the rack which is away from the toothing and projects out of the instrument housing in the already described manner. 
         [0025]    As has been already noted, the instrument according to the invention can comprise several movable instrument parts on the distal side of its shank. In a preferred design, the instrument according to the invention as movable instrument parts comprises an instrument head pivotably arranged at the distal end of the shank, and a tool carrier pivotably arranged on the instrument head relative to the instrument head. Further preferably, with regard to the tool arranged on the tool carrier it is the case of a jaw tool, so that two jaw parts which are pivotable relative to one another are arranged on the tool carrier. Advantageously, the instrument head, the tool carrier and the two jaw parts of the tool are each coupled in movement to a pull cable as control means, wherein the individual pull cables in the already described manner can be coupled via a coupling element which is coupled in movement thereto and is led out of the instrument housing, in each case to a drive motor of a linear drive unit connectable to the instrument housing. 
         [0026]    The invention is hereinafter explained in more detail by way of embodiment examples which are represented in the drawing. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    In the drawings, shown in a schematically simplified manner, and in different scales in each case: 
           [0028]      FIG. 1  is a perspective plan view showing an endoscopic instrument for the connection to an operation robot, without a linear drive unit; 
           [0029]      FIG. 2  is a perspective bottom view showing the endoscopic instrument according to  FIG. 1  without a linear drive unit; 
           [0030]      FIG. 3  is a perspective bottom view showing a proximal end region of the instrument according to  FIG. 1 , without a linear drive unit; 
           [0031]      FIG. 4  is a perspective bottom view showing a proximal end region according to  FIG. 3 , omitting a part of the instrument housing; 
           [0032]      FIG. 5  is a view according to  FIG. 4 , with a linear drive unit connected on the instrument housing; 
           [0033]      FIG. 6  is a perspective plan view showing the linear drive unit according to  FIG. 5 ; 
           [0034]      FIG. 7  is a perspective representation showing a coupling element which is provided on the instrument side, in the condition coupled to a drive motor of the linear drive unit; 
           [0035]      FIG. 8  is a perspective individual representation showing the coupling element according to  FIG. 7 ; 
           [0036]      FIG. 9  is a perspective representation showing a further embodiment of the coupling element; 
           [0037]      FIG. 10  is a perspective representation, in a first view, showing the coupling element which is shown in  FIG. 8 , with an arrangement on a pull slide; 
           [0038]      FIG. 11  is a perspective representation, in a second view, showing the coupling element represented in  FIG. 8 , with the arrangement on a pull slide; 
           [0039]      FIG. 12  is a perspective representation, in a third view, showing the coupling element which is shown in  FIG. 8 , with an arrangement on a pull slide; 
           [0040]      FIG. 13  is a perspective representation showing a drive train of the linear drive unit according to  FIG. 6 ; 
           [0041]      FIG. 14  is a lateral view showing the endoscopic instrument according to one of the preceding figures; 
           [0042]      FIG. 15  is a perspective bottom view showing the instrument according to  FIG. 14 ; and 
           [0043]      FIG. 16  is a detail view from  FIG. 4 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    With regard to the endoscopic instrument represented in the drawing, it is the case of a shank instrument with a shank  2  which is designed as a hollow shank and on which an instrument head  4  is arranged at the distal side. An instrument housing  6 , into which a proximal end region of the shank  2  engages and there in a mounting device  8  ( FIGS. 4 and 5 ) is rotatably mounted relative to the instrument housing  6 , is provided at the proximal side of the shank  2 . 
         [0045]    It is evident from  FIGS. 5 ,  14  and  15  that the instrument head  6  is pivotably articulated on the shank  2  via a joint pin  10  and is pivotable in a plane transverse to the longitudinal extension of the shank  2 . A tool carrier  12  is articulated on the instrument head  4  at the distal side via a joint pin  14 , in a manner such that the tool carrier  12  can pivot in a plane normal to the pivot plane of the instrument head  4 . The tool carrier  12  carries a jaw tool with two jaw parts  16  and  18  which are pivotable relative to one another. 
         [0046]    The movement control of the instrument head  4 , of the tool carrier  12  which is articulated thereon, and of the jaw parts  16  and  18  is effected via three pull cables  20 ,  22  and  24 , wherein the instrument head  4 , the tool carrier  12  and the two jaw parts  16  and  18  are each coupled in movement to one of the pull cables  20 ,  22  and  24  in an antagonistically acting manner, which is not evident from the drawing. 
         [0047]    The pull cables  20 ,  22  and  24  are led through the shank  2  into the instrument housing  6  and there are each tensioned by way of a deflection roller arrangement. Hereby, the pull cable  24  merely wraps one deflection roller  26  which is arranged in the proximal end region of the instrument housing  6 . The pull cable  22  on a deflection roller pair  28  which is arranged in the instrument housing  6  proximally of the proximal shank end, and on a deflection roller pair  30  arranged laterally distanced thereto, leads to a deflection roller  32  which is arranged next to the deflection roller  26  and around which it wraps. In a similar manner, the pull cable  24  is guided on a deflection roller pair  34  arranged in the instrument housing  6  proximally of the proximal shank end, and on a deflection roller pair  36  arranged laterally distanced thereto, to a deflection roller  38  which is arranged next to the deflection roller  26  and around which it wraps. 
         [0048]    The deflection roller pairs  28 ,  30 ,  34  and  36  are mounted together on a mounting body  40  which is arranged on a base plate  42  of the instrument housing  6 . The base plate  42  forms a part of the outer wall of the instrument housing  6 . A mounting body  44  which is likewise arranged on the base plate  42  and at its side which is away from the base plate  42  is provided with three recesses  46 ,  48  and  50 , in which the defection rollers  26 ,  32  and  38  are rotatably mounted on a common mounting pivot  52  ( FIG. 16 ) serves for mounting the deflection rollers  26 ,  32  and  38 . 
         [0049]    The pull cable  20  in the region between the defection roller pair  30  and the defection roller  32  is guided in the instrument housing  6  parallel to the longitudinal extension of the shank  2 . The pull cable  24  is likewise led parallel to the longitudinal extension of the shank  2 , in the region between the deflection roller pair  36  and the defection roller  38 . This also applies to the pull cable  22  which is guided in the instrument housing between the pull cables  20  and  24 . The pull cables  20 ,  22  and  24  are each subjected to a pull force in this region, for the control of the instrument head  4 , the tool carrier  12  as well as the jaw parts  16  and  18 , and this will be dealt with in more detail hereinafter. 
         [0050]    A section of the pull cable  20  is formed by a pull rod  52 , in the region between the deflection roller pair  30  and the deflection roller  32 . In a similar manner, a section of the pull cable  22  is also formed by a pull rod  56 , and a section of the pull cable  24  in the region between the deflection roller pair  36  and the deflection roller  38  is formed by a pull rod  58 . 
         [0051]    The pull cable  20  in the region of the pull rod  54  is fastened on a pull slide  60 , which in the instrument housing  6  is guided in a guide track  62  aligned parallel to the guiding of the pull cable  20  and formed by two guide strips  64  and  66  which are arranged on the base plate  42  of the instrument housing  6 . The guide strips  64  and  66  as well as the pull slide  60  are designed for forming a swallowtail guide. 
         [0052]    A guide strip  68  is arranged on the base plate  42  of the instrument housing  6 , on the side of the guide strip  66  which is away from the guide strip  64 , in a manner distanced to the guide strip  66 . The guide strip  68  together with the guide strip  66  forms a guide track  70  which is designed as a swallowtail guide, in which a pull slide  72 , on which the pull cable  22  is fastened via the pull rod  56  is linearly guided. 
         [0053]    A further guide strip  74  is arranged on the base plate  42  at the side of the guide strip  68  which is away from the guide strip  66 , in a manner distanced to this guide strip  68 . The guide strip  74  together with the guide strip  68  forms a guide track  76  in the form of a swallowtail guide for a pull slide  78 . The pull cable  24  is fastened on the pull slide  78  via the pull rod  58 . 
         [0054]    The construction of the pull slides  60 ,  72  and  78  is evident from the  FIGS. 7 ,  10 - 12  as well as  16 , in which the pull slide  60  is represented by way of example. The pull slides  72  and  78  are constructionally identical to the pull slide  60 . 
         [0055]    The pull slides  60 ,  72  and  78  each comprise a hollow-rail-like base body  80  with an essentially U-shaped cross section. The pull slides  60 ,  72  and  78  each lie on the base plate  42  of the instrument housing  6 , via a flat base  82  formed on the base body  80 . Walls  84  and  86  extend normally to the flat sides of the base  82 , on the two longitudinal sides of the base  82 . The outer sides of the walls  84  and  86  which are away from one another are each provided with bevellings for forming the swallowtail guide. The wall  86  extends beyond a flat side of the base  82  which faces the base plate  42  of the instrument housing  6 . An elongate rail  88  is formed there on the wall  86 , and this rail extends beyond the wall  86  in the longitudinal direction of this wall  86  at its two ends. 
         [0056]    As is particularly evident from  FIGS. 2 and 3 , the rail  88  of the pull slide  60  engages into an elongate opening  90  which is formed on the base pate  42  of the instrument housing  6  and which is formed on this base plate  42  in the region of the guide track  62 . In a manner corresponding to this, the rails  88  of the pull slide  72  engage into an opening  92  formed in the region of the guide track  70 , and the rail  88  of the pull slide  78  engages into an opening  94  formed in the region of the guide track  76 . The openings  90 ,  92  and  94  are in each case designed longer than the rails  88  of the pull slides  60 ,  72  and  78 , in order to permit a linear displacement of the pull slides  60 ,  72  and  78 . 
         [0057]    In each case a fastening block  96  for fastening the pull rods  54 ,  56  and  58  of the pull cables  20 ,  22  and  24  is arranged on the flat side of the bases  82  of the pull slides  60 ,  72  and  88 , said flat side being away from the base plate  42  of the instrument housing  6  (see in particular  FIG. 16 ). The fastening blocks  96  each comprise two projections  98  and  100  which are distanced to one another in the longitudinal direction of the pull sides  60 ,  72  and  78  respectively and which project normally to the flat sides of the base  82 . The two projections  98  and  100  are each provided with a bore which extends through the projections  98  and  100  in the longitudinal direction of the fastening block  96 . The pull rods  54 ,  56  and  58  on the respective pull slides  60 ,  72  and  78  are led through the bores of the projections  98  and  100 , wherein the pull rods  54 ,  56  and  58  in the intermediate space between the projections  98  and  100  are surrounded by two helical springs  102  and  104  which are arranged next to one another, as well as a fixation sleeve  106  arranged between the helical springs  102  and  104 . The pull rods  54 ,  56  and  58  are fastened on the fastening block  96  of the respective slide  60 ,  72  and  78  via this arrangement of the helical springs  102  and  104  as well as of the fixation sleeve  106 , wherein the helical springs  102  and  104  form an overload protection for the pull cables  20 ,  22  and  24 . 
         [0058]    It is evident from  FIG. 12  that an opening  108  extending transversely to the longitudinal extension of the wall  86  through this wall is formed on the wall  86  of the pull slides  60 ,  72  and  78 . A coupling element  110  which can be coupled to a drive motor of a linear drive unit  146  connectable to the instrument housing  6  is led through the opening  108 , wherein this is yet explained in more detail hereinafter. 
         [0059]    The coupling element  110  is represented in  FIG. 8  and a further coupling element  112  is represented  FIG. 9 . Both coupling elements  110  and  112  have a positive-fit body in the form of a projection  114 , on which a spring element  116  connects with regard to the coupling element  110 , and a spring element  118  connects with regard to the coupling element  112 . The spring element  116  of the coupling element  110  has a spring body which is shaped in a meandering manner, whereas the spring element  118  of the coupling element  112  has an annular spring body. 
         [0060]    The arrangement of the coupling elements  110  on the pull slides  60 ,  72  and  78  is such that the positive fit body  114  of the coupling element  110  is led through the opening  108  formed on the wall  86  and projects at the outer side of the base plate  42  of the instrument housing  6  which is away from the pull slides  60 ,  72  and  78  respectively, whereas the spring element  116  of the coupling element  110  is supported in a frame  120  formed on the wall  86 . 
         [0061]    The shank  2  at its proximal end which projects into the instrument housing  6  proximally of the mounting device  8  is surrounded by a toothed ring  112  ( FIGS. 4 and 5 ). The toothed ring  122  is connected to the shank  2  in a rotationally fixed manner. A pull slide  124  is displaceably arranged transversely to the longitudinal extension of the shank  2 , between the toothed ring  122  and the base plate  42  of the instrument housing  6 . Hereby, the pull slide  124  is guided in a guide track  126  which is formed by guide strips  128  and  130 . The pull slide  124  comprises a base  132 , via which it lies on the base plate  42  of the instrument housing  6 . Walls  134  and  136  extend normally to the flat sides of the base  132 , on the two longitudinal sides of the base  132 . The outer sides of the walls  134  and  136  which are away from one another are each provided with bevellings for forming a swallowtail guide. The inner sides of the guide strips  128  and  130  which face one another comprise corresponding bevellings, in a manner corresponding to this. A rack  138  which is meshed by a toothed ring  122  is formed on an upper side of the wall  134  which away from the base  132 . 
         [0062]    The wall  136  of the pull slide  124  extends beyond a flat side of the base  132  which faces the base plate  42  of the instrument housing  6 . An elongate rail  140  which extends beyond the wall  136  in the longitudinal direction of the wall  136  at its two ends is formed on the wall  136  there. 
         [0063]    The rail  140  of the pull slide  124  engages into an elongate opening  142  which is formed on the base plate  42  of the instrument housing  6  and which is formed on the base plate  42  in the region of the guide track  126  ( FIGS. 2 and 3 ). The opening  142  is aligned normally to the openings  90 ,  92  and  94 . The opening  142  is designed longer than the rail  140  of the pull slide  124 , in order to permit a linear displacement of the pull slide  124 . 
         [0064]    An opening extending transversely to the longitudinal extension of the wall  136  and through this is formed on the wall  136  of the pull slide  124 , as with the pull slides  60 ,  72  and  78 , but is not evident from the drawing. The coupling element  112  which is represented in  FIG. 9  and which can likewise be coupled to a drive motor of a linear drive unit connectable to the instrument housing  6  is led through this opening. 
         [0065]    The arrangement of the coupling element  112  on the pull slide  124  is such that the positive-fit body  114  of the coupling element  112  is led through the opening formed on the wall  136 , and projects at the outer side of the base plate  42  of the instrument housing  6 , said outer side being away from the pull slide  124 , whereas the spring element  118  of the coupling element  112  is supported in a frame  144  formed on the wall  136 . 
         [0066]    As has already been noted, a linear drive unit  146  can be connected onto the instrument housing  6 . The connection of this linear drive unit  146  onto the instrument housing  6  is effected via a housing part  148  of the linear drive unit  146  which can be connected to the instrument housing  6  by way of a clip connection. The housing part  148  is designed in an open manner at its side which faces the instrument housing  6 . 
         [0067]    The housing part  148  at the side which is away from the instrument housing  6  is closed by a base plate  150 , whose dimensions correspond to the dimensions of the base plate  42  of the instrument housing  6 . Two fastening clips  152  which positively and peripherally engage the housing part  148  connected to the instrument housing  6  are arranged on the instrument housing  6  on two side walls which are away from one another, for the releasably connection of the housing part  148  to the instrument housing  6 . Two projections  154  which engage into holes  156  formed on the base plate  42  of the instrument housing  6  and which project in the direction of the instrument housing  6  are formed on the base plate  150  of the housing part  148 , for simplifying the assembly of the instrument housing  6  and the housing part  148 . 
         [0068]    It is particularly evident from  FIG. 15  that four guide rails  158 ,  160 ,  162  and  164  which are aligned parallel to the longitudinal extension of the shaft  2  and parallel to one another are arranged on the flat side of the base plate  150  of the housing part  148  of the linear drive unit  146 , said flat side being away from the instrument housing  6 . The guide rails  158  and  160  form a guide track  166 , in which a drive slide  168  is linearly displaceably guided. The guide rails  160  and  162  form a guide track  170 , in which a drive slide  172  is linearly displaceably guided. A guide track  174  for a drive slide  176  is formed by the guide rails  162  and  164 . 
         [0069]    The drive slides  168 ,  172  and  176  are designed in a constructionally identical manner. Their design is evident from  FIGS. 7 and 13 , in which the drive slide  168  is shown in an exemplary manner. The drive slides  168 ,  172  and  176  are designed in an essentially cuboid manner, wherein at their longitudinal sides which are away from one another they comprise a wedge-like recess  178  extending over the entire length of the drive slide  168 ,  172  or  176 . The recesses  178  in combination with a corresponding profiling on the inner sides of the guide rails  158 ,  160 ,  162  and  164  which face one another, serve for forming a swallowtail guide. An elongate hole  180  aligned in the longitudinal direction of the drive slide  168 ,  172  and  176  is moreover formed on the drive slides  168 ,  172  and  176  respectively. A longitudinal side of the elongate hole  180  is provided with a toothing and forms a rack  182 . 
         [0070]    A bearing block  184  which carries three electrically operated, rotatory drive motors  186 ,  188  as well as  190  is supported on the sides of the guide rails  158 ,  160 ,  162  and  164  which are away from the base plate  150  of the housing part  148 . The arrangement of the drive motors  186 ,  188  and  190  on the bearing block  184  is such that a motor shaft  192  of the drive motor  186  engages into the elongate hole  180  formed on the drive slides  168 , a motor shaft  192  of the drive motor  188  engages into the elongate hole  180  formed on the drive slide  172  and a motor shaft  192  of the drive motor  190  engages into the elongate hole  180  formed on the drive slide  176 . A pinion  194  which meshes with the rack  182  in the elongate hole  180  of the related drive slide  168 ,  172  and  176  is arranged in each case on the ends of the motor shafts  192  of the drive motors  186 ,  188  and  190 . 
         [0071]    A coupling device  196  is arranged next to the elongate hole  180 , on the flat side of the drive slides  168 ,  172  and  176  which is away from the drive motors  186 ,  188  and  190 . The coupling device  196  is formed by an elongate rail  198  which extends at both longitudinal ends of the drive slides  168 ,  172  and  176  beyond this. A prominence  200  with two side surfaces tapering to one another at a shallow angle is formed in the region of the middle of the rail  198  at the side which is away from the drive slides  168 ,  172  and  176 . A recess  202  extending in the direction of the drive slides  168 ,  172  and  176  is formed in the region of the middle of the prominence  200 . 
         [0072]    The coupling devices  196  of the drive slides  168 ,  172  and  176  engage into three elongate openings  204 ,  206  and  208  which are formed on the base plate  150  of the housing part  148 . Hereby, the prominences  200  with the recess formed therein in the housing part  148  project in a freely accessible manner in the direction of the instrument housing  6 . 
         [0073]    Apart from the four guide rails  158 ,  160   162  a well as  164 , two further guide rails  210  and  212  aligned normally to the guide rails  158 ,  160 ,  162  and  164  and parallel to one another are arranged on the flat side of the base plate  150  of the housing part  148  of the linear drive unit  146 , said flat side facing away from the instrument housing  6 . The guide rails  210  and  212  form a guide track  214 , in which a drive slide  216  is linearly displaceably guided. 
         [0074]    The drive slide  216  is designed in a constructionally identical manner to the drive slides  168 ,  172 . A bearing block  218  carrying an electrically operated rotatory drive motor  220  is supported on the sides of the guide rails  210  and  212  which are away from the base pate  150  of the housing part  148 . The bearing block  218  together with the bearing block  184  forms a common construction unit. 
         [0075]    The arrangement of the drive motor  220  on the bearing block  218  is such that a motor shaft of the drive motor  220  engages into the elongate hole  180  formed on the drive slide  216 , which is not evident from the drawing, wherein a pinion arranged at the end of the drive shaft meshes with the rack  182  in the elongate hole  180 . 
         [0076]    Next to the elongate hole  180 , a coupling device  196  with an elongate rail  198  and with prominence  200  having a recess  202  and arranged on said rail is arranged on the flat side of the drive slide  216  which faces away from the drive motor  220 . This coupling device  196  of the drive slide  216  engages into an elongate opening  222  which is formed on the base plate  150  of the housing part  148  and which is aligned normally to the openings  204 ,  206  and  208 , wherein the prominence  200  with the recess  202  formed thereon projects in the housing part  148  in the direction of the instrument housing  6  in a freely accessible manner. 
         [0077]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
       APPENDIX 
       [0078]      
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 2 
                 shank 
               
               
                   
                 4 
                 instrument head 
               
               
                   
                 6 
                 instrument housing 
               
               
                   
                 8 
                 bearing device 
               
               
                   
                 10 
                 joint pin 
               
               
                   
                 12 
                 tool carrier 
               
               
                   
                 14 
                 joint pin 
               
               
                   
                 16 
                 jaw part 
               
               
                   
                 18 
                 jaw part 
               
               
                   
                 20 
                 pull cable 
               
               
                   
                 22 
                 pull cable 
               
               
                   
                 24 
                 pull cable 
               
               
                   
                 26 
                 deflection roller 
               
               
                   
                 28 
                 deflection roller pair 
               
               
                   
                 30 
                 deflection roller pair 
               
               
                   
                 32 
                 deflection roller 
               
               
                   
                 34 
                 deflection roller pair 
               
               
                   
                 36 
                 deflection roller pair 
               
               
                   
                 38 
                 deflection roller 
               
               
                   
                 40 
                 mounting body 
               
               
                   
                 42 
                 base plate 
               
               
                   
                 44 
                 mounting body 
               
               
                   
                 46 
                 recess 
               
               
                   
                 48 
                 recess 
               
               
                   
                 50 
                 recess 
               
               
                   
                 52 
                 bearing pivot 
               
               
                   
                 54 
                 pull rod 
               
               
                   
                 56 
                 pull rod 
               
               
                   
                 58 
                 pull rod 
               
               
                   
                 60 
                 pull slide 
               
               
                   
                 62  
                 guide track 
               
               
                   
                 64  
                 guide strip 
               
               
                   
                 66  
                 guide strip 
               
               
                   
                 68 
                 guide strip 
               
               
                   
                 70  
                 guide track 
               
               
                   
                 72  
                 pull slide 
               
               
                   
                 74  
                 guide strip 
               
               
                   
                 76  
                 guide track 
               
               
                   
                 78  
                 pull slide 
               
               
                   
                 80  
                 base body 
               
               
                   
                 82 
                 base 
               
               
                   
                 84 
                 wall 
               
               
                   
                 86 
                 wall 
               
               
                   
                 88  
                 rail 
               
               
                   
                 90 
                 opening 
               
               
                   
                 92 
                 opening 
               
               
                   
                 94  
                 opening 
               
               
                   
                 96 
                 fastening block 
               
               
                   
                 98  
                 projection 
               
               
                   
                 100 
                 projection 
               
               
                   
                 102 
                 helical spring 
               
               
                   
                 104 
                 helical spring 
               
               
                   
                 106 
                 fixation screw 
               
               
                   
                 108 
                 opening 
               
               
                   
                 120 
                 coupling element 
               
               
                   
                 112 
                 coupling element  
               
               
                   
                 114 
                 projection 
               
               
                   
                 116 
                 spring element 
               
               
                   
                 118 
                 spring element 
               
               
                   
                 120 
                 frame 
               
               
                   
                 122 
                 toothed ring 
               
               
                   
                 124 
                 pull slide 
               
               
                   
                 126 
                 guide track 
               
               
                   
                 128 
                 guide strip 
               
               
                   
                 130 
                 guide strip 
               
               
                   
                 132 
                 base 
               
               
                   
                 134 
                 wall 
               
               
                   
                 136 
                 wall 
               
               
                   
                 138 
                 rack 
               
               
                   
                 140 
                 rail 
               
               
                   
                 142 
                 opening 
               
               
                   
                 144 
                 frame 
               
               
                   
                 146 
                 linear drive unit 
               
               
                   
                 148 
                 housing part 
               
               
                   
                 150 
                 base plate 
               
               
                   
                 152 
                 fastening clips 
               
               
                   
                 154 
                 projection 
               
               
                   
                 156 
                 hole 
               
               
                   
                 158 
                 guide rail 
               
               
                   
                 160 
                 guide rail 
               
               
                   
                 162 
                 guide rail 
               
               
                   
                 164 
                 guide rail 
               
               
                   
                 166 
                 guide track 
               
               
                   
                 168 
                 drive slide 
               
               
                   
                 170 
                 guide track 
               
               
                   
                 172 
                 drive slide 
               
               
                   
                 174 
                 guide track 
               
               
                   
                 176 
                 drive slide 
               
               
                   
                 178 
                 recess 
               
               
                   
                 180 
                 elongate hole 
               
               
                   
                 182 
                 rack 
               
               
                   
                 184 
                 bearing block 
               
               
                   
                 186 
                 drive motor 
               
               
                   
                 188 
                 drive motor 
               
               
                   
                 190 
                 drive motor 
               
               
                   
                 192 
                 motor shaft 
               
               
                   
                 194 
                 pinion 
               
               
                   
                 196 
                 coupling device 
               
               
                   
                 198 
                 rail 
               
               
                   
                 200 
                 prominence 
               
               
                   
                 202 
                 recess 
               
               
                   
                 204 
                 opening 
               
               
                   
                 206 
                 opening 
               
               
                   
                 208 
                 opening 
               
               
                   
                 210 
                 guide rail 
               
               
                   
                 212 
                 guide rail 
               
               
                   
                 214 
                 guide track 
               
               
                   
                 216 
                 drive slide 
               
               
                   
                 218 
                 bearing block 
               
               
                   
                 220 
                 drive motor 
               
               
                   
                 222 
                 opening