Abstract:
A medical instrument with a handle arranged at the proximal end, with a shankarranged on the handle, and with a tool arranged at the distal end of the shank. The medical instrument can provide several functionalities, for example the rotation about the longitudinal axis of the medical instrument, the pivoting of the tool relative to the longitudinal axis of the medical instrument and/or the actuation of the tool, for example the opening or closing of scissors. Some of these functionalities are activated with the aid of a single common actuation element. By moving the actuation element between several switch positions, different functionalities are selected, and these are activated, e.g. by rotation of the actuation element.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a medical instrument with a handle arranged at the proximal end, with a shank arranged on the handle, and with a tool arranged at the distal end of the shank. 
       BACKGROUND OF THE INVENTION 
       [0002]    In addition to the simple medical instruments with one functionality, e.g. the opening and closing of scissors as a tool, more recent developments have resulted in medical instruments that have several different functionalities. The German patent DE 197 80 579 B4, for example, discloses a pivotable endoscopic instrument which has a tool in the form of a forceps-like gripping element and which has a second functionality that allows the distal end with the tool to be swiveled relative to the rest of the endoscopic instrument. For actuation of the two functionalities, dedicated actuation devices are provided which are separate from each other and which are arranged at the proximal end of the endoscopic instrument. This arrangement of the actuation elements provided sufficiently good handling and operating efficiency. The increased number of functionalities meant that the range of use of the endoscope was extended and, in this way, the surgical effort during the endoscopic operation was lessened, in particular by a reduction of the insertion and removal from the body. 
         [0003]    This development was pursued and led to a medical instrument that has more than two functionalities. This is a tool that is opened and closed and that permits a rotation of the tool and also a pivoting of the distal end with the tool relative to the rest of the medical instrument. Each of these functionalities is operated by a dedicated actuation device at the proximal end. Such an instrument is known from the German laid-open specification DE 10 2012 007 649 A1. This instrument proves very versatile in terms of its possible uses during an endoscopic operation, but it requires thorough training of the operator in order to ensure reliable and safe handling especially under difficult operating conditions. 
         [0004]    Furthermore, the European patent EP 2 316 358 B1 discloses a medical instrument with two functionalities that can be controlled in alternation via a single common actuation element. The actuation element is movable to two switch positions, wherein the actuation element is movably coupled to the shank in a first switch position and is movably coupled to the tool in a second switch position, and, therefore, it can either rotate the shank or can open or close the tool. The actuation element has a selector shaft with two coupling parts and, depending on the switch position, the respective coupling part couples with a form fit to one of two mating coupling parts and thus creates the possibility, by actuating the actuation element via the selector shaft with the coupling part coupled with a form fit to the mating coupling part, of transmitting a movement to the tool for opening or closing thereof or to the shank for rotation thereof. This medical instrument has improved ergonomics but is open to improvement in terms of the safety of its handling. This medical instrument of the type in question was used to draw up the preamble. 
       SUMMARY OF THE INVENTION 
       [0005]    One object of the present invention is to make available a medical instrument that has improved ergonomics and operating safety along with more than one functionality. 
         [0006]    This object according to the invention is achieved by a medical instrument. Advantageous developments are also disclosed. 
         [0007]    The medical instrument according to the invention has a handle arranged at the proximal end, on which handle a shank is arranged, and a tool, in particular scissors, forceps or an HF coagulation tool, is arranged at the distal end of the shank. The handle has an actuation element with a selector shaft which, together with the actuation element, is movable at least to two switch positions. In a first switch position, which is provided for the activation of a first functionality, the selector shaft is movably coupled by form-fit engagement via a first coupling part to a first mating coupling part of a first output for the activation of the first functionality, whereas, in a second switch position for the activation of a second functionality, the selector shaft is movably coupled by form-fit engagement via a second coupling part to a second mating coupling part of a second output for the activation of the second functionality. In this way, depending on the switch position, a movement of the actuation element in the handle can be transmitted via the selector shaft to the first output or the second output and, in this way, the respective functionality of the instrument can be actuated. The medical instrument according to the invention is not limited to only two different switch positions for the activation of selective functionalities, and instead it is also possible for more than two different functionalities to be activated by different switch positions. 
         [0008]    According to the invention, at least one part of the coupling parts has at least one resilient locking element which is designed to be able to couple with a form fit to a corresponding recess on the associated mating coupling part. Preferably, several resilient locking elements are provided which can engage in several corresponding recesses. Alternatively to this, it is also possible, according to the invention, that at least one of the mating coupling parts has one or more resilient locking elements which, in a corresponding way, are able to couple with a form fit to corresponding recesses on the corresponding coupling part of the selector shaft. By virtue of this inventive resilient design of the locking elements, the handling and therefore also the ergonomics of the medical instrument can be improved, since the introduction of the resilient locking elements into the corresponding recess to establish the form-fit engagement in the relevant switch position can be done more easily and, in particular, more comfortably in the force profile. In addition, the resilient design of the locking elements permits a particularly reliable form fit, which has a very positive effect on the safety of the medical instrument during handling, in particular under difficult operating conditions. It has thus been possible to keep to a minimum the number of actuation elements needed for the actuation of several functionalities and thus to maintain the ergonomics and maneuverability of the medical instrument at a high level. 
         [0009]    It has proven particularly expedient for the resilient locking elements to be arranged in a seat in a coupling part or mating coupling part so as to be movable with a spring action, such that the resilient locking elements in the seat can be moved in the direction of or away from the center axis of the shank, i.e. in a radial direction, and can thus be moved into form-fit engagement in a corresponding recess or moved out of the latter. By means of the preferred guiding of the movement of the resilient locking elements by the seat, it is possible for several pairs of resilient locking elements and associated seats to be arranged in a very compact circle about the center axis of the shank in a coupling part or mating coupling part, which leads to a very compact and safe coupling by means of form-fit engagement, which thus transmits the movement of the actuation element very safely and reliably to the output for the actuation of the corresponding functionality. By virtue of the resilient design of the locking elements, which allows the locking elements to be pressed flexibly by a spring into the corresponding seats, it is possible, according to the invention, on the one hand in the coupled state, to insert the locking element as deep as possible into the seat, in particular as far as the bottom thereof, and thereby to achieve a very safe form-fit coupling, and, on the other hand, when necessary, to move the locking element back into the recess counter to the spring force and thus create flexibility and safety during the switching procedure, which is not found in the prior art with rigid locking elements and recesses. 
         [0010]    By providing an abutment to limit the in particular radial mobility of the resilient locking elements, it is possible to ensure the safety of the medical instrument while at the same time maintaining the advantageous ergonomics, since a sliding out and therefore separation of the movable locking element from the seat and thus the risk of loss is prevented. The abutment is embodied in particular by formation of a narrowing in the seat, which narrowing effects a limitation of the movable locking elements. By the provision of spring elements to embody the resilient locking elements, an arrangement is created which, in particular by spring force, moves the resilient locking elements in the direction of the abutment by spring force. In the state of maximum excursion of the locking elements, secure engagement in the associated corresponding seat is permitted. 
         [0011]    In addition to the possibility of forming the abutment by an additional structural part in the coupling part or mating coupling part, it has proven particularly expedient to form the abutment and the coupling part or mating coupling part in one piece, which increases the stability of the whole part and thus improves the safety of the medical instrument according to the invention. It has proven advantageous to provide not just one abutment for limiting the movement of the resilient locking element, but two such abutments between which the locking element can move freely under the action of a spring. The abutment on the spring side is chosen such that the spring is preferably only partially compressed, such that damage to the spring can be prevented. In addition to the provision of a compression spring, it is also alternatively possible to provide a tension spring with suitably adapted abutments or also an elastomer spring element. 
         [0012]    By virtue of the preferred design of the selector shaft with recesses and/or resilient locking elements arranged rotationally symmetrically about the circumference of the selector shaft, it is possible to keep the material load of the selector shaft low and thereby ensure the reliability and stability of the function of the instrument according to the invention to a particular degree. It has proven particularly advantageous to provide three or four resilient locking elements or recesses in each coupling part of the selector shaft, which is arranged rotationally symmetrically, i.e. uniformly about the circumference of the selector shaft or the coupling part thereof. This particularly advantageous number of coupling elements for form-fit engagement on a coupling part or correspondingly on the mating coupling part permits a very efficient, optimized force distribution along with reduced manufacturing outlay. This arrangement proves surprisingly safe and its handling is very ergonomic. 
         [0013]    Alternatively or additionally, it has also proven particularly expedient for the selector shaft to be designed with mirror symmetry, such that its two ends with the coupling parts are designed in mutual mirror symmetry to each other. The manufacturing quality and therefore the safety of the medical instrument can be additionally increased in this way, since the number of different structural parts is reduced and, therefore, the manufacture is simplified and thus the risk of incorrect function is reduced and thus the safety of the medical instrument is increased. 
         [0014]    By the advantageous provision of a tapering in the end area of the selector shaft, it is possible in a particularly advantageous way, when transferring the actuation element with the selector shaft from one switch position to the other, to achieve a secure positioning of the coupling parts in the mating coupling parts, since the tip formed by the tapering permits an advantageous orientation, particularly in conjunction with a correspondingly tapering recess in the area of the mating coupling. It is thus possible to avoid the selector shaft being damaged by jamming in the area of the switch positions. Such a tapering is preferably provided at each end of the selector shaft. 
         [0015]    By the provision of a rotary wheel or a cam as part of the actuation element, the possibility is afforded of moving and actuating the actuation element very easily and reliably by hand and therefore ergonomically safely. The actuation element can be actuated in different ways, for example by rotation but also by axial movement, such that, on the one hand, it is possible to use one of the actuation types to choose the switch position and thus the desired functionality of the medical instrument according to the invention, and to use the other actuation mode to activate and thus actuate the functionality of the medical instrument in the desired manner. 
         [0016]    The provision of a rotary wheel permits, for example, practically blind actuation by rotation to any desired positions, without the user having to cast a glance at the actuation element. This permits very simple handling. The provision of a single cam permits targeted gripping of the cam and very simple and differentiated actuation in the different actuation modes, which proves very functional and ergonomic after the cam is found. The provision of an alternative single cam additionally permits the preferred coupling of the actuation element to a motorized drive, since the drive is connected with a form fit to the cam and the movement of the motorized drive is in this way reliably transmitted to the actuation element. In addition to the possibility of a form-fit connection with the aid of the single cam, there are also further possibilities with several recesses and elevations. This form-fit connection between the motorized drive and the actuation element is preferably releasable. 
         [0017]    The actuation element for transmitting movement to the outputs is preferably in each case rotatable about an in particular common rotation axis. In other words, depending on the switch position in which the actuation element is located, an individual defined output is always rotatable by a rotation of the actuation element, and therefore a defined functionality assigned to this output can be activated. More preferably, the actuation element is axially movable to its switch positions parallel to its rotation axis, as a result of which a very simple and reliable and therefore ergonomic operation is ensured. 
         [0018]    In addition to the switch positions in which it is movably coupled to the outputs via the selector shaft, the actuation element can preferably also be movable to at least one further switch position, in which the actuation element is movably coupled to none of the outputs for a functionality. This creates a neutralization of the actuation element, which is of particular importance especially for checking the functionalities or for maintenance or for the disassembly or assembly of the medical instrument according to the invention. It is thereby possible to improve the permanent safety of the instrument according to the invention. 
         [0019]    It has proven particularly advantageous to provide one or more recesses, in particular all the recesses, with a run-on surface which, as the distance from the switch position decreases, effects an increasing restoring force of the spring element engaging in the recess. This ensures a very good and reliable handling of the medical instrument according to the invention during the switching procedure. This design has the effect that, at the start of the transfer to a switch position, the resistance force, which arises from the fact that the locking element is shortened counter to the spring force upon contact with the selector shaft in the area of the corresponding recess, is low and thus a positioning can be very easily and reliably ensured, whereas, as the switch position is increasingly approached, the resistance is slowly increased by the design of the run-on surface and, in this way, a form-fit pressing of the locking elements into the recess and thus a very reliable form fit is ensured. 
         [0020]    In addition, as a supplement or alternative to the run-on surface in the recess, it has proven particularly expedient to design the recess in such a way that, in the area of a switch position, a run-off surface is provided which, as the distance from the relevant switch position decreases, provides a decreasing restoring force of the locking element. In this way, it is possible to form a depression in the recess, which effects a locking action when the locking element resiliently engages in the depression-like recess. It is thus possible to achieve a haptic feedback of the safe attainment of the switch position, which improves the handling and ergonomics of the medical instrument according to the invention. The dimensions of the depression are adapted to the spatial conditions, in particular the size of the locking elements and the desired extent of haptic feedback. A deep depression, which permits a substantial insertion of the locking element into the depression and is associated with a strong deep gradient, leads to a distinct haptic feedback, whereas a shallow depression leads only to a low haptic feedback. In addition, the run-off surface leads to a dedicated positioning of the locking element relative to the selector shaft with the depression-shaped recesses, since the locking elements are pressed into the depression by the spring action and, in this way, a lateral thrust by the run-off surface is generated, which moves the selector shaft to the switch position. This supports the improved handling. 
         [0021]    A particularly preferred embodiment of the medical instrument according to the invention has recesses and/or corresponding resilient locking elements, of which one, some or all are designed conically such that they taper laterally or widen laterally as the distance from the switch position decreases. With this conical, wedge-shaped design, it is possible to ensure that a slight lateral offset during the switching procedure, i.e. during the transfer to the switch position and thus an approximation to the switch position, on account of the positioning action of the conical design of the recesses or of the locking elements leads to a lateral movement, particularly in the form of a rotational repositioning. In this way, an undesired blocking or impeding of the switching procedure can be substantially ruled out, which particularly improves the safety and the maneuverability and ergonomics of the present medical instrument according to the invention. 
         [0022]    It has proven particularly advantageous to design not just some of the locking elements with a conical shape, but to provide all the locking elements of a coupling part or mating coupling part, and additionally the corresponding recesses, with the corresponding conical shape, such that a particularly effective form-fit engagement is obtained, which permits high transmission of force. It is not necessary that all the locking elements or all the recesses are conical, and instead this can also be only partially the case, but also a combination of conically shaped and non-conically shaped corresponding elements is possible and is chosen according to requirements and manufacturing possibilities. 
         [0023]    A particularly safe and easily maneuverable medical instrument according to the invention has a selector shaft which exclusively has recesses in its coupling parts, which recesses are arranged in particular rotationally symmetrically about the circumference of the selector shaft, and resilient locking elements corresponding to the recesses and/or on the mating couplings which are connected to the respective output for the actuation of the functionality of the medical instrument. With this design, it is possible for the selector shaft to be made compact and light, which makes the actuation by means of the actuation element simpler and safer. In addition, this selector shaft according to the invention proves not to be structurally complex. The inventive arrangement of the corresponding resilient locking elements in the mating coupling, which is not moved for the switching procedure, leads to a very robust and reliable arrangement that is less susceptible to defects and is easy to produce. In particular, it permits the modular production of the individual components, mating coupling with resilient locking elements and output and the production of the selector shaft with actuation element. Overall, this preferred design of the invention leads to a very compact, reliable and safe medical instrument, which is distinguished by special ergonomics. 
         [0024]    It has also proven advantageous to design the medical instrument with the resilient switching gear in such a way that it is possible to choose preferably in pairs of alternatives either, on the one hand, the functionality rotation of the shank or of the tool and, on the other hand, actuation of the tool or, on the one hand, the functionalities rotation of the shank or of the tool and, on the other hand, the pivoting of the tool relative to the longitudinal axis of the medical instrument or the shank of the medical instrument. These combinations permit a particularly advantageous and efficient and ergonomic handling of the medical instrument. In addition, it has also proven expedient for the pivoting relative to the longitudinal axis of the medical instrument or of the shank to be combined with the alternative functionality of the tool actuation. The tool actuation has proven in particular to be the opening and closing of the tool, e.g. in the form of forceps or scissors, but also for example the handling of an HF tool, in particular by increasing the size of the HF loop electrode or reducing the size of the latter, or an additional excursion of the tool. 
         [0025]    In other words, the medical instrument according to the invention with several functionalities is distinguished by the fact that it is possible to switch between these functionalities by means of an actuation element, in particular by movement of an actuation element, and that, in the different switch positions, different coupling parts and mating coupling parts engage in one another with a form-fit, since it is not rigid components that engage in one another with a form-fit, but at least partially movable components which are spring-mounted and at least partially ensure the form-fit engagement. By virtue of the flexible position-changing, form-fitting parts, the adoption of the switch position is made easier, without the form-fit action being impaired to any relevant extent. Thus, the medical instrument according to the invention proves to be of a particularly advantageous design in ergonomic terms. In addition, it also proves particularly safe to handle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The invention is described below with reference to an example in the figures. The invention is not limited to this example. 
           [0027]      FIG. 1  shows an example of a medical instrument according to the invention in a side view, 
           [0028]      FIG. 2  shows a schematic longitudinal section through a part of the handle of a medical instrument according to the invention, 
           [0029]      FIG. 3  shows a schematic cross section through a portion of the handle, along the section line A-A according to  FIG. 2 , and 
           [0030]      FIG. 4  shows another cross section through a part of the handle, along the section line B-B according to  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The endoscopic medical instrument  1  shown by way of example in  FIG. 1  has a handle  2 , which is arranged at the proximal end of the medical instrument  1 . The distal end of the handle  2  is adjoined by the shank  3 , at the distal end of which the tool  4  is arranged in turn. The tool  4  is in the form of medical scissors or forceps with two jaw parts that can be moved toward and away from each other. This movement  42  of the tool  4  is represented by the indicated arrow  42 . As a further functionality of the medical instrument  1 , the distal end of the shank  3  with the tool  4  can be pivoted, this pivoting movement  41  being represented by the corresponding arrow  41 . The pivoting takes place relative to the shank  3 , which forms the main axis of the medical instrument  1 . As a further functionality, the medical instrument  1  affords the possibility of moving the shank  3  in a rotation movement  40  in which the tool  4  with the shank  3  is moved in rotation about the longitudinal axis of the shank. This rotation movement  40  is represented by the rotation arrow  40 . 
         [0032]    The different functionalities can be controlled with the aid of the handle  2  at the proximal end of the medical instrument  1 . The tool  4  is opened and closed with the aid of the grip  5 . The functionality of the rotation movement  40  and of the pivoting movement  41  is controlled with the aid of the actuation element  10 . The two movements  40  and  41  are controlled in alternation, wherein this takes place depending on the positioning of the actuation element  10 , and the extent of the rotation movement  40  or of the pivoting movement  41  is defined by the rotation of the actuation element  10 . The reduction in the means for actuating the medical instrument  1  satisfies an important condition for an efficient and ergonomic design of a medical instrument  1  with a plurality of functionalities  40 ,  41 ,  42 . 
         [0033]      FIG. 2  shows a longitudinal section through a portion of a handle  2  in an embodiment of the invention. 
         [0034]    The actuation element  10  has a radially protruding cam  11  which is provided for operating and actuating, on the one hand, an axial movement and, on the other hand, a rotation movement about the rotation axis of the actuation element  10 . Moreover, the actuation element  10  has a selector shaft  15  which, together with the cam  11 , forms the actuation element  10 . The selector shaft  15  extends to both sides of the cam  11 , which represents the center of the selector shaft  15 . The selector shaft  15  has a symmetrical structure with respect to the cam  11 , i.e. the first end  16  of the selector shaft  15  has the same structure as the second end  17  of the selector shaft  15 , which ends extend to both sides of the cam  11 . This results in a structurally simple configuration of the selector shaft  15 , which increases the manufacturing reliability and thus the quality of the medical instrument  1 . 
         [0035]    The actuation element  10  can be moved axially between two switch positions. In the first switch position as shown in  FIG. 2 , the first end  16  of the selector shaft  15 , with the first coupling part  22  arranged thereon, extends into a first mating coupling part  23 , which is coupled to a first output  21  for transmitting the movement of the first coupling part  22  to the first output  21 . 
         [0036]    The first coupling part  22  of the selector shaft  15  has recesses  24  in which resilient locking elements  34 , which are part of the first mating coupling part  23 , engage with a form fit. This allows the rotation movement of the cam  11  to be transmitted, via the selector shaft  15  with the first coupling part  22  with its recesses  24 , to the resilient locking elements  34  of the first mating coupling part  23  and thus to the first output  21 . Thus, in the first switch position shown, the rotation movement  40  of the shank  3  and thus of the tool  4  can be activated with the aid of the cam  11 . 
         [0037]    In the first mating coupling part  23 , which annularly encloses the first end  16  of the selector shaft  15  in the first switch position, the resilient locking elements  34  are arranged in seats  35 . The seats  35  are formed as radially extending recesses in the first mating coupling  23 , which allow the inserted resilient locking elements  34  to be guided in a radial movement. Also arranged in the seats  35  is a spring element  36 , which applies a radial spring force to the resilient locking element  34 . Both at the inner end of the seat  35  and also at the outer radial end of the seat  35 , a respective abutment  37  is provided which limits the radial mobility of the resilient locking element  34 . This ensures that the locking element  34  remains in the seat  35  and therefore in the first mating coupling  23 , and the functionality of the resilient locking elements  34  is thereby ensured. 
         [0038]    In the first switch position shown, the resilient locking element  34  engages with a form fit in the corresponding recess  24  of the first coupling part  22 . The locking element  34  is pressed against the bottom of the recess  24  by the spring force of the spring element  36 . The excursion of the resilient locking element  34 , within the context of the mobility defined by the abutments  37 , is dependent on an object arranged in the inner area of the first mating coupling part  23 , which object is formed in the first switch position by the selector shaft  15  with the first coupling part  22 . 
         [0039]    At its first end  16 , the first coupling part  22  has a conically tapering tip. When the selector shaft  15  is moved axially into the first switch position, the conically tapering first end  16  of the selector shaft  15  is thus inserted into the area between the locking elements  34  fully deflected by the spring elements  36 . The locking elements  34  meet the cone of the tip and, as the distance of the selector shaft  15  from the first switch position decreases, are deflected less and less counter to the spring force until they slide into the recesses  24  and have then assumed the final excursion in the radial direction in the first switch position. 
         [0040]    The flexible, situation-dependent positioning of the resilient locking elements  34  ensures very safe and comfortable handling of the medical instrument  1  upon adoption of the switch position. The conical profile of the first end  16  of the first coupling part  22  of the selector shaft  15  provides a slow increase in the resistance force against the adoption of the first switch position, which provides the safe and comfortable handling. This is also achieved by the fact that the bottom of the recess  24  has an area with a run-on surface which in accordance with the conically extending first end  16  of the selector shaft  15  increases the radius of the selector shaft  15  and thus forces the bearing locking element  34  back counter to the spring force of the spring element  36 . 
         [0041]    By the provision of a run-off surface  26  in the recess  24 , the resilient locking element  34  can be locked in the recess  24  as soon as it reaches the first switch position. This is achieved by the fact that the radius of the selector shaft  15  decreases as the distance from the first end  16  of the selector shaft  15  increases, and therefore, when brought to the first switch position, with decreasing distance from this switch position, a decreasing restoring force of the resilient locking element  34  is provided since the latter can be more strongly deflected on account of the decreasing radius. This locking action gives the user haptic feedback that the first switch position is reached. Moreover, this run-off surface  26  has the effect that the adoption of this first switch position is supported by the spring force and, therefore, the adoption of this first switch position is made easier and, at the same time, the unwanted sliding out from this first switch position can be prevented on account of the increasing spring force during the movement out. This permits a very safe and comfortable ergonomically advantageous handling of the instrument  1  according to the invention with the switching between different switch positions. 
         [0042]    The second end  17  with the second coupling part  32  of the selector shaft  15  has a structure corresponding to the first end  16  with the first coupling part  22 . The same applies to the structure of the second mating coupling part  33 , which corresponds to the first mating coupling part  23  and is movably coupled to the second output  31 . It has the same arrangement of resilient locking elements  34  which are designed to be spring-loaded and radially movable in seats  35  by spring elements  36 . Their radial mobility is likewise limited by abutments  37 . In  FIG. 2 , the second mating coupling part  33  and the second coupling part  32  are shown in an uncoupled state. This state represents the first switch position. By axial movement of the actuation element  10  with the selector shaft  15 , the selector shaft  15  leaves the first switch position shown, the form fit between the first coupling part  22  and the first mating coupling part  23  with their resilient locking elements  34  and the corresponding recesses  24  is canceled, the actuation element  10  is located in an intermediate position in which the selector shaft  15  is not movably coupled with a form fit either to the first mating coupling part  23  or to the second mating coupling part  33 , and, consequently, cannot transmit any movement force to the two outputs  21 ,  31 . If the actuation element  10  is moved further axially in the direction of the second mating coupling part  33 , then, as has been described before accordingly for the first mating coupling part  23 , it comes into form-fit engagement with the second mating coupling part  33  and thereby permits a movement transmission from the actuation element  10  to the second output  31  for the activation of the associated functionality. 
         [0043]    The inventive resilient design of the locking elements  34  for the form-fit engagement in the associated, corresponding recesses  35  of the coupling parts  22 ,  32  or of the mating coupling parts  23 ,  33  ensures, on the one hand, a very safe and good transmission of force for the activation of the corresponding functionality of the medical instrument  1 , since the spring force ensures a particularly good form fit, which is marked by the locking elements  34  bearing in the recesses  24 . On the other hand, a very comfortable and ergonomically advantageous transfer of the actuation element  10  to the different switch positions is also achieved by the spring action, particularly in conjunction with the different designs of the selector shaft  15  with the different run-on surfaces  25  and run-off surfaces  26  and the conical design of the ends  16 ,  17  of the selector shaft  15 . This leads overall to a very safe and ergonomically advantageous design of the medical instrument  1  according to the invention with a reduced number of actuation devices  10  on the handle  2  and a greater number of functionalities than the number of the actuation devices. 
         [0044]      FIG. 3  shows a cross section through the first coupling part  22  and the first mating coupling part  23  in a first switch position along the section line A-A according to  FIG. 2 . 
         [0045]    The first coupling part  22 , which is arranged at the first end  16  of the selector shaft  15 , has four recesses  24  which are arranged radially symmetrically and therefore uniformly about the circumference of the selector shaft  15  and which all have the same shape. Four resilient locking elements  34 , which are part of the first mating coupling part  23 , engage with a form fit in these four recesses  24 . The resilient locking elements  34  are arranged in a ring-shaped housing of the first mating coupling part  23 , in which for each locking element  34  there is a seat  35  that extends in the radial direction and has, at its respective radial end, an abutment  37  that limits the radial mobility of the resilient locking element  34 . This prevents the locking element  34  from sliding out of or being lost from the first mating coupling part  23 . A spring element  36 , which is in the form of a compression spring, is provided in each of the seats  35 . With the aid of its spring force, the spring element  36  presses the locking element  34  radially inward in the direction of the axis of rotational symmetry of the first mating coupling part  23 . As is shown in  FIG. 3 , the radial mobility is limited by the bottom of the recesses  24  of the first coupling part  22 . There, the resilient locking element  34  comes into abutment and thereby effects a very safe and reliable, form-fit coupling, which ensures a good transmission of force and transmission of movement from the actuation element  10  to the first output  21 . 
         [0046]    The first mating coupling part  23  has a structure composed of two rings which, inserted one into the other, form a common ring. The seats  35  are introduced as recesses with the inner abutment  37  into the inner ring. In the context of the production of the mating coupling part  23 , a locking element  34  is first of all introduced into each of the seats  35  of the inner ring, followed by the associated spring element  36 . Thereafter, this unit is introduced into the outer second ring, which has a closed configuration, such that a single common ring-shaped mating coupling part  23  is obtained. The outer ring thus forms the second radially outer abutment  37  for the spring element  36  or for the locking element  34 . This design of the mating coupling part permits very safe and simple production for a medical instrument  1  according to the invention. 
         [0047]      FIG. 4  shows a cross section through a second mating coupling part  33  during the first switch position from  FIG. 2  along the section line B-B. It shows a structure corresponding to the first mating coupling part  23  of  FIG. 2  and  FIG. 3 . 
         [0048]    In contrast to  FIG. 3 , the resilient locking elements  34  are deflected further, since they are not limited in their radial excursion by the selector shaft  15 . In this situation shown, no force transmission or movement transmission to the second output  31  can take place on account of the lack of form-fit engagement between actuation element  10  with the selector shaft  15  and the second mating coupling part  33 . It is therefore clear that this first switch position, as is shown in  FIG. 2 , permits efficient, safe and ergonomically advantageous movement coupling to the first output  21  and thus for the activation of the associated functionality, namely the rotation of the shank  3 , whereas at the same time, as is shown in  FIG. 4 , a movement coupling and to the second output  31  and thus an activation of the associated functionality, namely the pivoting of the tool  4  relative to the main axis of the medical instrument  1 , is excluded. Axial movement of the actuation element  10  brings about, in the above-described advantageous and ergonomically comfortable and safe way, the connecting of the second coupling part  32  into the second mating coupling part  33  and therefore the attainment of the second switch position, which is associated with the uncoupling of the first coupling part  22  from the first mating coupling part  23 . A transmission of movement is thus permitted by form-fit engagement of the resilient locking elements  34  in the associated, corresponding recesses  24  of the second coupling part  32 , and thus a transmission of the rotating movement of the actuation element  10  to the second output  31  and thus an activation of the second functionality and thus an excursion of the tool  4  relative to the longitudinal axis of the medical instrument  1  or of the shank  3 .