Abstract:
In order to further develop a surgical instrument with an energy-driven operating device, an energy storage device as well as a control device for driving the operating device as required and supplying it with energy from the energy storage device such that an optimum utilization of the capacity of the energy storage device is achieved without any risk for the surgeon or the patient, in particular in view of the different energy requirements of the individual operating processes, it is suggested that when a predetermined state of residual charge of the energy storage device is reached and/or it is fallen below for the first time the control device make its residual charge available for returning the tool into a rest position.

Description:
[0001]    This application claims the benefit of German Patent Application No. 10 2010 012 011.1 filed on Mar. 12, 2010. 
         [0002]    The present disclosure relates to the subject matter disclosed in German application number 10 2010 012 011.1 of Mar. 12, 2010, which is incorporated herein by reference in its entirety and for all purposes. 
       BACKGROUND OF THE INVENTION 
       [0003]    The invention relates to a surgical instrument with an energy-driven operating device, an energy storage device as well as a control device for operating the operating device as required and supplying it with energy from the energy storage device. 
         [0004]    Instruments of this type are known with an operating device which is driven electrically or pneumatically. Accumulators or batteries or rather gas cartridges serve as energy storage devices. 
         [0005]    The energy capacity is necessarily limited in the case of such instruments, with the risk that operating processes can no longer be finished when the charge capacity is exhausted. 
         [0006]    This is a problem, in particular, in the case of operations which relate to the central nervous system when the instruments are used to remove, for example, bones or tissue material from the patient with a considerable use of force, for example with so-called bone punches. 
         [0007]    In the case of bone punches, forces of approximately 700 to approximately 750 N occur when bone material is removed. If the supply of energy fails while a punch cutter is being transferred from an operating position into an end position, in which the operating process is brought to an end, it remains on the bone and can become locked in position. The problem for the surgeon is then that the bone punch cannot be released from the patient and replaced by another instrument ready for use. 
         [0008]    Other fields of use relate to clip appliers for, for example, vessel clips, anastomosis clips as well as aneurysm clips. Furthermore, the fields of use relate to so-called rongeurs or also other cutting instruments which must reliably remove body tissue or bone material in a manner similar to the punches specified above. 
         [0009]    It is important for all these fields of use that an operating cycle can be run through such that, afterwards, the instrument is again in a defined starting position or rest position. 
         [0010]    On the other hand, it is of significance in the case of the surgical instruments of the present invention that size and weight of the instrument are balanced with a view to ergonomic aspects. The space for accommodating the energy storage device is considerably restricted as a result. A generous dimensioning of the energy storage device from the point of view of safety cannot be realized for this reason alone. A permanent connection to an external energy source is also not desirable from an ergonomic point of view. 
         [0011]    In many cases, operations do, however, require a supply of energy which would necessitate too large a volume and weight for one single energy storage device. This situation, in which the energy storage device is exhausted during an operation once or several times, is, therefore, foreseeable in many cases. In such a case, care has to be taken for the reasons specified that the instrument does not remain in an undefined operating state when the energy storage device is exhausted since this would entail a risk for the patient being treated and, in addition, hinder the work of the surgeon. 
         [0012]    It has so far been suggested in the state of the art to dimension the energy storage device as far as possible such that all the operating processes can be completely finished with the charge capacity available. This can be brought about in the case of so-called clip appliers relatively simply in that the capacity of the clip magazine is reduced so that all the clips in the magazine can be applied before the energy storage device is exhausted. 
         [0013]    In the case of instruments, with which the energy requirements per operating step cannot be predetermined so easily and precisely, it has been suggested in EP 1 884 204 A2 to use a counter for monitoring the supply of energy and to stop use of the instrument when it is likely from the number of operating processes that the energy storage device is almost exhausted. 
         [0014]    Operation without any risk can be realized with this manner of proceeding only when the number of permissible operating processes is selected such that use of the instrument is stopped long before exhaustion of the energy storage device is reached. 
         [0015]    A similar measure is also suggested in U.S. Pat. No. 6,619,529 B1 for a surgical clip applier, with which a counter likewise records the operating processes and use of the instrument is stopped after a predetermined number of operating processes, i.e. clips applied. 
         [0016]    These concepts are unsatisfactory, in particular, for instruments which are more complex from an energy point of view since the supply of energy from the energy storage device can be used only very incompletely on account of the different energy requirements per operating process or, in another case, the risk is still present of the instrument no longer being supplied with the necessary energy while an operating process is being carried out, with the consequences described above. 
         [0017]    The object of the present invention is to further develop a surgical instrument of the type described at the outset such that an optimum utilization of the capacity of the energy storage device is achieved without any risk for the surgeon or the patient, in particular in view of the different energy requirements of the individual operating processes. 
       SUMMARY OF THE INVENTION 
       [0018]    This object is accomplished by an instrument in accordance with claim  1 . 
         [0019]    On account of the control device used in accordance with the invention, the capacity of the energy storage device can be used individually depending on the energy requirements of the individual operating processes and when a predetermined state of residual charge is reached and/or this is fallen below for the first time, the residual charge of the energy storage device is available for returning the tool into a rest position. 
         [0020]    In this way, a better exploitation of the energy stored in the energy storage device may be realized in the case of clip appliers, for example appliers for vessel clips, anastomosis clips, aneurysm clips etc. 
         [0021]    The control device of the instrument according to the invention preferably comprises a monitoring unit which detects the actual state of charge of the energy storage device and blocks any renewed activation of the tool when the predetermined state of residual charge is reached and/or it is fallen below for the first time. 
         [0022]    The predetermined state of residual charge is preferably selected such that the last operating process initiated can be safely finished. The operating cycle must not, therefore, be interrupted prematurely in order to be able to transfer the tool of the operating device into an end position and back again. 
         [0023]    If the mode of operation of the operating device necessitates a transfer of the tool from a rest position into an end position and back which requires a lot of energy, there is still an adequate supply of energy remaining for the transfer of the tool of the operating device back into the rest position. If the surgeon has possibly not completed all his work, the instrument can be exchanged or provided with a charged energy storage device. 
         [0024]    This is the case, in particular, for cutting and punching instruments, such as, for example, rongeurs, bone punches etc. In this case, as well, an improved exploitation of the supply of energy in the energy storage device is achieved in comparison with a rigidly predetermined number of operating processes. 
         [0025]    In this case, it may also be of advantage when the predetermined state of residual charge can be adjusted. The use of the supply of energy can thus be coordinated more exactly with the energy consumption of the respective operating steps to be carried out. 
         [0026]    The instrument according to the invention preferably has an indicator unit, in particular as part of the control device, which indicates the state of charge of the energy storage device. This can comprise an indicator function which shows that the predetermined state of residual charge has been reached and/or it is fallen below for the first time and so the surgeon not only recognizes the lack of functioning or the blocking of the operating device but information is indicated to him, in addition, concerning the reason for the blocking. 
         [0027]    The energy storage device will then be exchanged or fully charged again. Once the energy storage device has been exchanged or charged, the indicator unit will be reset again to the normal operating state. 
         [0028]    This indicator function can be configured in an optical and/or tactile manner. 
         [0029]    In the case of preferred instruments, the indicator unit can make the actual state of charge apparent and so during operating with the instrument the state of charge can be followed and, for example, the imminent blocking of the operating device recognized beforehand. Where applicable, the reaching and/or falling below for the first time of the predetermined state of residual charge will be indicated, in addition, with an additional indicator element. 
         [0030]    The instruments according to the invention often have a handle which can be advantageously used in many cases for accommodating the energy storage device. 
         [0031]    The energy storage device is preferably connected to the instrument so as to be exchangeable so that the used energy storage device can be exchanged for a fresh one when the predetermined state of residual charge is reached and/or it is fallen below. 
         [0032]    The energy storage device is preferably an energy storage device which can be charged and, where applicable, exchanged. 
         [0033]    It may also be provided for the instrument to be accommodated in a charging station as a whole, together with the energy storage device, for the purpose of charging the energy storage device. 
         [0034]    If gas cartridges are used as energy storage devices, it may be provided for the monitoring unit to comprise a pneumatically actuatable valve which allows activation of the operating device and, where applicable, transfer of the operating device from the rest position into the operating position or end position as long as the state of charge of the gas cartridge is above the predetermined state of residual charge. When the state of residual charge is reached and/or it is fallen below for the first time, the functioning for the transfer of the operating device from the operating position or end position into the rest position remains available, wherein the residual energy of the energy storage device will be used for this purpose. 
         [0035]    In an alternative, preferred embodiment of the invention it is provided for the energy storage device of the instrument to comprise a first and a second storage element, wherein the monitoring device makes the second storage element available for the transfer of the operating device from the operating or end position back into the rest position when the predetermined state of residual charge of the first storage element is reached and/or it is fallen below for the first time. 
         [0036]    A small, second storage element is adequate for this purpose since energy need be kept only for the last partial step of an operating process. The main storage device in the form of the first storage element then supplies the energy for all the preceding operating processes. A spring compressed during the operating process can also serve as a small, second storage element. 
         [0037]    In the case of the bone punch, the monitoring of the state of charge of the first storage element is then sufficient since it can safely be assumed that an adequate amount of energy will still be available in the other storage element for returning the operating device into the rest position following the last possible operating process. 
         [0038]    Alternatively, a second storage element of the same size or larger can be provided in one preferred instrument and so the first storage element serves to transfer the operating device from the rest position into the operating and end position and the second storage element serves to transfer the operating device back into the rest position. This lends itself, in particular, for the supply of energy to bone punches since the energy requirements for the transfer of the operating device into the operating and end position necessitate more energy than the return movement from the end position into the rest position. 
         [0039]    The second storage element preferably has an energy content which is greater than approximately 105%, in particular approximately 110%, of the energy which is required at the most for the required number of return movements. Typically, a pneumatic cylinder which is of larger dimensions will be provided for the advancing of the tool into the operating and/or end position than for the return of the tool into the rest position. 
         [0040]    In a further, preferred embodiment, both storage elements are connected to form a unit so that both storage elements must, of necessity, always be replaced together. At the same time, the exchange can be carried out with one single procedure. 
         [0041]    The invention relates, in addition, to a method for operating an energy-driven surgical instrument according to claim  12 . 
         [0042]    Advantageous developments of this method are the subject matter of claims  13  to  16 . 
         [0043]    These and other advantages of the invention will be explained in greater detail in the following on the basis of the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  shows an instrument according to the invention in the form of a pneumatically driven clip applier; 
           [0045]      FIG. 2  shows a schematic circuit diagram of a first control of an instrument according to the invention in accordance with  FIG. 1 ; 
           [0046]      FIG. 3  shows an instrument according to the invention in the form of a pneumatic bone punch; 
           [0047]      FIG. 4  shows a schematic circuit diagram of a control for the instrument according to the invention in accordance with  FIG. 3 ; 
           [0048]      FIG. 5  shows a schematic circuit diagram of an alternative control for the instrument according to the invention in accordance with  FIG. 3 ; and 
           [0049]      FIGS. 6A and 6B  show two variations of an indicator unit for an instrument according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]      FIG. 1  shows an instrument according to the invention in the form of a pneumatically driven clip applier  10  with an operating device  12  (shown only partially) designed as an applier, a handle  14  as well as an energy storage device in the form of a gas cartridge  16 . 
         [0051]    The clip applier  10  comprises a compressed gas drive (not shown) which is arranged in its handle  14  and actuates the applier mechanism. The clip applier  10  is controlled via a push-button switch  18  which projects out of the handle  14  which is preferably in the shape of a pistol. 
         [0052]    A connection flange  20  which can be releasably connected to the gas cartridge  16  protrudes at the lower end of the handle  14 . For the connection to the handle  14 , the gas cartridge  16  has a short connection piece  22 , with which the gas cartridge  16  can be connected to the connection flange  20  of the handle in a gas-tight manner. 
         [0053]    With respect to the details of the gas-tight connection between handle  14  and gas cartridge  16 , attention may be drawn to DE 203 18 275 U1, to the content of which reference is made in full in this connection. 
         [0054]    The clip applier  10  according to the invention is characterized by a control device  24 , as is apparent by way of example from the circuit diagram of  FIG. 2 . 
         [0055]    The control device  24  is connected to the gas cartridge  16 , which has, for example, a tank filled with CO 2  at a pressure of approximately 60 bar, via an adapter interface  26  (connection flange  20  and short connection piece  22 ). 
         [0056]    A supply line  28  leading from the adapter interface  26  to the control device  24  is connected via a branch  29  to a monitoring unit  30  which provides a connection to the operating pressure line  34  of the applier  10  by means of a switching element  32  when the gas pressure in the supply line  28  is sufficient for the actuation of the clip applier  10 . 
         [0057]    The switching element  32  is shown in  FIG. 2  in a first operating position, in which the gas pressure which acts via the branch  29  is sufficient to neutralize the adjustable pressure force of a spring  36 . If the gas pressure in the supply line  28  drops to or for the first time below a predetermined threshold pressure which corresponds to a state of residual charge of the gas cartridge  16 , the switching element  32  will be displaced by the spring  36  from its position shown in  FIG. 2  into a second position, in which the connection of the operating pressure line  34  to the supply line  28  is interrupted. At the same time, the supply line  28  will be connected to a venting opening  35  of the switching element  32  and the cartridge  16  made pressure-less. As a result, the activation of the instrument is blocked. 
         [0058]    The threshold value of the state of residual charge is set, for example, by means of the pretensionable spring  36  such that a reliable functioning of the clip applier  10  is provided until this pressure is reached and also when it is fallen below for the first time, i.e. an adequate closing pressure can still be applied for the clip last applied. 
         [0059]    The return movement of the applier  10  can be brought about, for example, by a spring of the operating device  12  which is pretensioned during the application process since, for this purpose, no particularly high forces are required. This spring then undertakes the function of a second energy storage element. 
         [0060]    The state of reaching or falling below the predetermined state of residual charge will preferably be made apparent to the user by means of an indicator unit  40  which can be of very different designs. 
         [0061]    In the embodiment of  FIG. 2 , the monitoring unit  30  is equipped with an additional switching function which forms part of the indicator unit  40 . The indicator unit  40  is connected to the supply line  28  of the energy storage device  16  via a control line  42 . 
         [0062]    The indicator unit  40  has an indicator element  44  with a pneumatically extendable warning indication plunger  46 . If the pressure in the supply line  28  drops to that of the state of residual charge of the gas cartridge  16 , the plunger  46  will be moved out of its rest position  48  into an indication position  50  (position illustrated by dash dot lines), in which it projects beyond the surface  52  of the handle  14 , as will be explained in the following. As a result, a signal which can be discerned sensorially (haptically) in the best possible manner will be given to the user of the instrument. 
         [0063]    First of all, however, a separate pressure storage device  54 , which is connected to the control line  42  via a changeover valve  56 , will be filled with the initial pressure of the energy storage device  16  present in the control line  42 . If the pressure in the control line  42  drops and the spring  36  presses the monitoring device  30  into its second switching position, the supply line  28  and also the control line  42  will be vented. As a result, the energy storage device  16  will be vented at the same time, as described above. A line  47  previously vented via the monitoring device  30  will now be closed by the monitoring device  30 . In the pressure-less state on the input side  58 , the changeover valve  56  will switch the separate pressure storage device  54  to a line  45  which connects the changeover valve to the line  47  and the indicator element  44 . Since the line  47  is blocked, the pressure of the separate pressure storage device  54  will become effective in the indicator unit  44  and convey the indicator plunger  46  out of the rest position  48  into the extended indication position  50 . 
         [0064]    The indication that the threshold value for the energy storage device  16  has been reached or it is fallen below will occur suddenly and in a very perceptible manner. 
         [0065]    Alternatively (not shown), the pressure of the energy storage device is allowed to act on a spring which presses the warning plunger into the indication position. If the operating pressure is sufficient, the warning plunger remains in the retracted, hidden position; if the pressure drops below the threshold value, the pressure chamber of the warning plunger will be vented and the spring presses the warning plunger momentarily into the indication position. 
         [0066]    In accordance with a further alternative (not shown), the warning plunger travels out of the rest position into the indication position proportionally to the decreasing operating pressure. 
         [0067]    In accordance with a further alternative (not shown), the warning plunger is pressed successively out of the indication position into the rest position when the pressure of the energy storage device decreases. 
         [0068]      FIG. 3  shows an instrument which is designated with the reference numeral  70  and is in the form of a bone punch with an operating device  72  and a handle  74 . The handle  74  has a short connection piece  76 , by means of which an energy storage device, in particular a gas pressure cartridge, can be releasably connected to the bone punch  70 . 
         [0069]    The bone punch may be actuated via a push-button switch  78 . An operating process initiated via the push-button switch  78  comprises the advancing movement of a punching tool out of a rest position in the direction towards a counter bearing (details not shown), between which the tissue or bone material to be removed is arranged. Once the tool has reached its end position and has severed the tissue or bone material, a further operating process will be triggered, in which the tool is returned from the end position into its rest position. 
         [0070]    This process requires a lot of energy, in part, since the tool can become stuck in the tissue or bone material. As a result, it is important for the reliable functioning of the bone punch that sufficient energy is available for this operating process since, otherwise, there is the risk of it remaining bonded to tissue or bone material in a force locking manner. 
         [0071]      FIG. 4  shows a first embodiment of a circuit diagram for the instrument  70  according to the invention and shown in  FIG. 3 . A tank  82 , for example a CO 2  cartridge with a filling pressure of 60 bar, serves as energy storage device. The tank  82  is connected releasably to the connection  76  of the handle  74  via an adapter interface  84 . 
         [0072]    The schematically illustrated operating device  72  with a punching tool has a first cylinder  86 , with which the punching tool can be transferred from the rest position into an operating position. A second cylinder  88  makes the continuation of the movement of the punching tool possible from the operating position into an end position, if necessary with increased force. A return of the punching tool of the operating device  72  into the rest position is brought about by means of a third cylinder  89 . Since greater forces are generally required for the return movement, the operative surface of the third cylinder  89  is selected to be larger than that of the first cylinder  86 . 
         [0073]    A first control valve  90  is actuated via the push-button switch  78  and this has three switching positions. 
         [0074]    In a first switching position a (as shown in  FIG. 4 ), the control valve  90  connects the energy source (tank  82 ), which is optionally connected via a regulator  92 , to a supply line  94  which is connected, on the other hand, to the third cylinder  89 . In this state, the compressed gas keeps the punching tool in its rest position. 
         [0075]    A supply line  96  to the first cylinder  86  of the operating device  72  is connected to a venting opening  98  in this state. A supply line  100  to the second cylinder  88  is likewise connected to the venting opening  98  and so the return movement of the cylinder during the transfer of the punching tool into the rest position can take place without any appreciable counterpressure. 
         [0076]    If the push-button switch  78  is actuated, the first control valve  90  reaches, first of all, a second switching position b, in which the compressed gas drawn from the regulator  92  passes into the first cylinder  86  via the supply line  96  and moves the punching tool in the direction of the operating position. At the same time, the supply line  100  is connected to the venting opening  98  and vents the chamber of the second cylinder  88 . The supply line  94  is likewise connected to the venting opening  98  and so the advancing movement in the direction of the operating position can take place essentially without any counterpressure. 
         [0077]    If the push-button switch  78  is pushed right in, the first control valve  90  moves into its third switching position c, in which the supply line  100  and, therefore, the second cylinder  88  are also supplied with compressed gas from the tank  82  so that the punching process can be reliably brought to a conclusion. In this respect, the punching tool passes from the operating position into the end position. Tissue or bone material is thereby severed. 
         [0078]    Afterwards, the surgeon will release the push-button switch  78  and the first control valve  90  returns to the first switching position a on account of the spring force of the spring  102 . The third cylinder  89  will be acted upon with compressed gas via the supply line  94  whereas the supply lines  96 ,  100  are connected to the venting opening  98 . The return movement of the punching tool of the operating device  72  is, therefore, brought about practically without any counterpressure. 
         [0079]    The supply lines  96  and  100  are, in accordance with the invention, not supplied directly with the compressed gas drawn from the regulator  92  but rather they can be interrupted via a second control valve  104  which engages in the supply lines.  FIG. 4  shows the second control valve  104  in its first switching position a, in which it releases the supply lines  96 ,  100 . The second control valve  104  is held in its first switching position a contrary to the spring force of a spring  106  by the pressure force of the gas supply in the tank  82  which acts via a line  108 . 
         [0080]    If the pressure in the tank  82  drops below a predetermined threshold value (state of residual charge), the spring  106  presses the second control valve  104  into its second switching position b, in which the supply lines  96 ,  100  coming from the first control valve  90  are interrupted and end blindly in the second control valve  104  while their sections on the side of the punching tool are short-circuited with one another and vented. A supply of the punching tool with compressed gas is no longer possible in this switching position b, i.e., a renewed activation of the tool of the operating device is blocked. 
         [0081]    In order to make the surgeon aware of the operating state of the instrument and in order to indicate the fact that the energy storage device needs to be changed, the instrument is preferably equipped with an indicator unit  110  for the state of charge of the energy storage device. For this purpose, the second control valve  104  preferably has a second function, the two switching states a′ and b′ of which are shown in the right-hand half of the second control valve  104 . 
         [0082]    In the first switching position of the second control valve  104  a and a′, respectively, during which the instrument can be actuated as usual, a small pressure storage device  108  for an indicator device  111  is filled with compressed gas of the tank  82  by means of a supply line  112 . The pressure storage device  108  is connected to the supply line  112  by a changeover valve  114 . An adjusting cylinder  116  for an indicator element  118  (e.g., in the form of a pin) of the indicator device  111  is connected via a line  120  to an additional connection of the changeover valve  114 . During the regular operation of the instrument, i.e. as long as the pressure in the tank  82  is sufficient to keep the second control valve  104  in its switching position a and a′, respectively, this line  120  is connected to a venting opening via a line  122 , which likewise leads to the second control valve  104 , and it is, therefore, without pressure. 
         [0083]    If the pressure of the compressed gas prevailing in the tank  82  drops below a threshold value, the second control valve  104  will be transferred into its second switching position b and b′, respectively, by means of the spring force of the spring  106 . In this switching position b′, the supply line  112  is interrupted from the side of the regulator  92 . At the same time, the part of the supply line  112  which leads to the pressure storage device  108  will be vented on the side of the second control valve  104 . The line  122  is blocked at the control valve  104 . In this situation, the changeover valve  114  switches over so that the pressure of the pressure storage device  108  now acts on the adjusting cylinder  116  of the indicator device  111  and the indicator element  118  travels out of its rest position into its indication position (in  FIG. 4  the position shown by dashed lines). The information concerning the blocked drive of the punching tool is thus transmitted to the surgeon working with the instrument sensorially and so he can replace the energy storage device (tank  82 ). 
         [0084]    The punching tool of the operating device  72  can still be brought reliably into its starting position in this state, as described above, and so the instrument can be removed from the field of operation without any problem. 
         [0085]    Another configuration of the instrument according to the invention in  FIG. 3  is shown in  FIG. 5 . Instead of the single tank  82 , a double tank  130  is used in this case, the one chamber  132  of which is used for the advancing movement of the punching tool of the operating device  72  and the other chamber  134  of which is used for the return movement of the punching tool into the rest position. 
         [0086]    The control functions are, in part, similar to those of the embodiment of  FIG. 4  and so the same reference numerals have been used for the same parts. 
         [0087]    This control of  FIG. 5  differs with respect to its functioning from that described previously, in principle, in that a renewed activation of the tool of the operating device  72  will not be blocked when the state of residual charge of the energy storage device drops to or below a predetermined threshold value but rather two separate energy storage modules are used: one module for the operating phase (tool is moved out of the rest position into the operating position and subsequently into the end position), the other module during the return movement of the tool into the rest position. The two energy storage modules can, by all means, advantageously form one constructional unit. 
         [0088]    Since the operating phase typically requires a somewhat greater energy consumption than the return movement of the tool, for example approximately 10%, it is ensured with the same dimensioning of the storage capacity of the modules that the tool can be returned to the rest position after every operating phase. Even if the supply of energy during an operating phase should start to run low, it is guaranteed that the tool can be returned to the rest position again. Only the last operating step would need to be repeated once the energy storage device has been changed. 
         [0089]    In detail, the one energy storage module in the form of the pressure chamber  132  is releasably connected to the handle  74  of the instrument via an adapter interface  136 . This also applies for the other module, the pressure chamber  134 . 
         [0090]    Supply lines  138  and  139 , respectively, lead from the pressure chambers  132 ,  134  to a control valve  140 , from there a supply line  142  leads to the pressure regulator  92  which is connected to the control valve  140  with a supply line  146  and, finally, can be optionally connected to the three cylinders  86 ,  88 ,  89  by means of the supply lines  94 ,  96 ,  100 . 
         [0091]    In the non-actuated state of the push-button switch  78 , the control valve  140  is held in the switching position a shown in  FIG. 5  by means of the spring force of the spring  144 . 
         [0092]    In this switching position a, the supply line  138  is blocked by the control valve  140  while the supply line  139  coming from the pressure chamber  134  is switched through to the supply line  142 . Since the pressure chamber  134  serves the purpose of returning the tool into the rest position, the line  146  is connected to the supply line  94  in the switching position a and acts on the third cylinder  89  with compressed gas. 
         [0093]    The supply lines  96  and  100  of the first and second cylinders  86 ,  88  are connected to the venting device  98  via the control valve  140  and so the return movement of the tool into the rest position can essentially take place without any counterpressure. 
         [0094]    If the push-button switch  78  is actuated and the control valve transferred into the switching position b, the supply line  139  is blocked while the supply line of the pressure chamber  132  is connected via the regulator  92  to the supply line  96  and, therefore, to the first cylinder  86 . The compressed gas of the pressure chamber  132  which is fed into the first cylinder  96  moves the tool of the operating device  72  out of the rest position into an operating position while the third cylinder  89  is vented and the second cylinder  88  is ventilated. 
         [0095]    The switching position c of the control valve  140  will not become active until the push-button switch  78  is pressed in entirely. In this case, the third cylinder  89  remains vented while the second cylinder  88  is acted upon, in addition, with compressed gas and so the tool of the operating device  72  is moved into the end position with the pressure prevailing in the first and second cylinders  86 ,  88  and the operating step can be finished. When the push-button switch  78  is released, the control valve  140  is moved back into the switching position a with the force of a spring and the supply of compressed gas described at the outset will start to return the tool into the rest position. 
         [0096]    In order to inform the surgeon about the state of charge of the energy storage device or keep him informed, it may be provided for the state of charge of the pressure chamber  132  to be made visible and, in particular, also tangible via an indicator unit. The supply line  122  shown in  FIG. 5 , which branches off the supply line  138  of the pressure chamber  132 , can serve this purpose. 
         [0097]    One example for this has already been explained in conjunction with the embodiment of the invention according to  FIG. 4 . Further examples for an indicator unit for instruments according to the invention will be described in conjunction with  FIGS. 6A and 6B . 
         [0098]      FIG. 6A  shows an indicator unit  150  which is connected to the supply line  122  coming from the pressure chamber  132 . The pressure of the pressure chamber acts on a cylinder  152 , in which a piston  154  is mounted for longitudinal displacement. 
         [0099]    The gas pressure prevailing in the supply line  122  or rather in the cylinder  152  moves the piston  154  contrary to the force of a spring  156  to the right in  FIG. 6A  so that an indicator element  160 , which is mounted on the piston  154  and is, for example, in the shape of a pin, travels out of the housing of the handle  74  with its free end proportionally to the gas pressure. If the gas pressure decreases, the spring  156  presses the indicator element  160  successively back into the retracted initial position, in which the free end of the pin is accommodated in the handle  74 . The state of charge of the pressure chamber  132  may, therefore, be read from the position of the extended pin. The pin may also be provided with markings (not shown) for better judging the state of charge. 
         [0100]      FIG. 6B  shows an alternative embodiment of an indicator unit  170  which is likewise connected to the supply line  122 . The indicator unit comprises a cylinder  172 , in which a piston  176  loaded with a spring  174  is arranged. A pin-like indicator element  178  is mounted on the piston  176  and its free end can travel out beyond the surface of the handle  74 . 
         [0101]    If the gas pressure in the pressure chamber is high, the force of the pressure is sufficient to press the piston to the left in  FIG. 6B  contrary to the action of the spring  174  so that the free end of the indicator element  178  is essentially flush with the surface of the handle. The spring  174  presses the indicator element out of its first position proportionally to the decreasing gas pressure and the free end of the pin projects ever more beyond the surface of the handle  74 , the lower the pressure in the pressure chamber  132 . 
         [0102]    In this case, as well, markings (not shown) on the pin of the indicator element are recommended so that it is apparent when the pressure in the pressure chamber is insufficient for any further operation with the instrument. 
         [0103]    In general, it is to be noted that the embodiments described in the above can, of course, be converted by the person skilled in the art such that electrical energy storage devices replace the gas pressure storage devices. The person skilled in the art will then replace the pneumatic circuits described by corresponding electrical ones with the same function.