Patent Publication Number: US-2020297370-A1

Title: Shaft for an endoscopic instrument, endoscopic instrument and endoscopic system

Description:
The present invention relates to a shaft for an endoscopic instrument, in particular for an endoscopic medical instrument. The present invention also relates to an endoscopic instrument with such a shaft and to an endoscopic system. 
     Endoscopic surgical techniques have prevailed for a variety of surgical procedures. In this case, an endoscopic instrument set, which in particular can comprise an endoscope and one or more endoscopic instruments, is routed through a natural or an artificial body opening created with the aid of an incision to an operation area located inside the body. For this purpose, endoscopic instruments have a long extended shaft, at the distal end of which, i.e., the end away from the user, a tool is arranged to perform surgical manipulations, which tool can be actuated by a handlebar arranged at the proximal end, i.e., the end close to the user, of the shaft via an elongated transmission element arranged in the shaft. The shaft can be rigid or flexible. During an endoscopic procedure, the handlebar remains outside the body opening, while the shaft with the tool is inserted through the body opening. 
     According to a widespread type, endoscopic instruments have a working insert which carries the tool at its distal end and which may also comprise the transmission element. Here, the working insert is detachably connected to the shaft of the instrument. In particular, after having performed an endoscopic procedure, the instrument can be disassembled for cleaning and/or sterilization, the working insert being detached from the shaft and removed from a shaft tube of the shaft; the handlebar can also be separated from the shaft. Furthermore, different tools may be required depending on the type and progress of an endoscopic procedure. Therefore, a working insert required in each case is usually selected and inserted into the shaft and connected to it. Likewise, a working insert with a first type of tool, such as a cutting tool, can be replaced by another working insert with a different type of tool, such as a gripping tool. For the detachable connection of the working insert to the distal end region of the shaft, a connection which is designed in the manner of a bayonet connection is particularly advantageous. 
     DE 100 38 576 C1 discloses a medical instrument with a shaft and a tool removably fastened to a distal end of the shaft, the shaft having an inner shaft and a tubular shaft surrounding the inner shaft and being longitudinally displaceable relative thereto. The tool is locked to the shaft in a locking position of the tubular shaft advanced relative to the inner shaft and can be removed from the shaft in a release position of the tubular shaft retracted relative to the inner shaft. A distal end of the inner shaft has a bayonet-like recess with a section which initially runs axially and then circumferentially, a holder being formed at the proximal end of the tool, which holder can be inserted into the bayonet-like recess with a transversely running section. 
     According to DE 10 2012 007 648 A1, a medical instrument comprises an outer shaft, a handling device at the proximal end of the outer shaft, a tool at the distal end of the outer shaft, with a first effecting device for a first function and a second effecting device for a second function, and a first and a second transmission device in the outer shaft for transmitting a force or a torque for controlling the first or second effecting devices. The tool and the outer shaft have coupling devices for a detachable mechanical connection of the tool to the distal end of the outer shaft. The coupling devices can comprise bayonet coupling devices. 
     Generic shafts for medical endoscopic instruments are sold by KARL STORZ SE &amp; Co. KG, for example under the name “ClickLine® Metall-AuBenschaft” with the article number 33300 and under the name “RoBi® Metall-AuBenshaft” with the article number 38600. 
     The detachable connection between the shaft and the working insert can in principle result in an undesirable play, in particular due to the tolerance fields provided at the connection point between the shaft and the working insert. This can impair the actuation of the working insert, for example a so-called “lost motion” can lead to inaccurate actuation of the tool. When implementing narrower tolerance fields, on the other hand, there are restrictions with regard to compatibility with existing instruments, for example the use of a working insert corresponding to a wider tolerance field with a shaft that is designed for narrower tolerances may be excluded. 
     It is an object of the present invention to provide a shaft for an endoscopic instrument, an endoscopic instrument and an endoscopic system, the disadvantages mentioned above being avoided as far as possible. In particular, it is an object of the invention to provide a shaft for an endoscopic instrument as well as an endoscopic instrument and an endoscopic system, wherein a higher actuation accuracy can be achieved and at the same time a high degree of insert flexibility and compatibility is guaranteed. 
     This object is achieved by a shaft according to claim  1 , by an endoscopic instrument according to claim  14  as well as by an endoscopic system according to claim  15 . 
     Advantageous developments of the invention result from the dependent claims. 
     A shaft according to the invention is designed for an endoscopic instrument, in particular for a medical endoscopic instrument, and can therefore be used for minimally invasive surgical procedures. Such a shaft can be designed as part or assembly of an endoscopic instrument, in particular a medical endoscopic instrument, or can be assembled together with other components to form an endoscopic instrument. The shaft is in particular rigid or essentially rigid and can be part or assembly of a rigid endoscopic instrument. On the other hand, the shaft can also be designed to be flexible. 
     A shaft according to the invention has a connecting section which is arranged in a distal end region of the shaft. The connecting section can be formed, for example, by a distal end section of the shaft or a shaft tube which is encompassed by or represents the shaft. A connecting device is formed at the connecting section for a detachable connection between the shaft and a working insert, whereby the working insert is replaceably connected with the shaft, that is, one working insert can be replaced by another. Such a working insert can in particular have a surgical tool, which can comprise, for example, one or more pivotably mounted jaws, which can be actuated by a longitudinal displacement of a transmission element connected to the jaws and routed inside the shaft with a handlebar arranged at the proximal end of the shaft. For this purpose, the working insert can be inserted into the shaft at least in sections and connected to the connecting section of the shaft. In this way, the connecting section can, for example, enclose or surround a section of the working insert, so that a particularly reliable connection between the shaft and a working insert can be implemented, the shaft serving to support the working insert. 
     The connection is configured in particular in the manner of a bayonet connection. Accordingly, in particular a connection in the manner of a bayonet lock can be produced between the connecting device and a working insert. Such a bayonet connection can be produced in a simple manner, in particular with little handling effort, and at the same time ensures a high degree of connection reliability. To create a connection in the manner of a bayonet lock, it can be provided that the two connection partners can be inserted into one another along their longitudinal axes and can be secured or fixed by turning them in opposite directions. In particular, a working insert can be inserted into the shaft and then rotated relative to the shaft, that is to say rotated about a longitudinal axis of the shaft. This can be carried out with only a few simple steps. 
     The connecting device has a plurality of engagement structures for the connection engagement of working inserts of different structural shapes, which are referred to here as different types of working inserts. For this purpose, the connecting device comprises at least one first engagement structure for a connection engagement of an engagement element of a working insert of a first type, i.e., of a first type of working insert. The engagement structure associated with the connecting device can be referred to in particular as a bayonet engagement structure and the engagement element associated with the working insert can in particular be referred to as a bayonet engagement element or bayonet blade. Through a bayonet-like engagement of the engagement element of the working insert of the first type in the first engagement structure of the connecting device, in particular a bayonet connection can be produced, by means of which a base of the working insert is fixedly connected in the longitudinal direction of the shaft to its distal end section, wherein the connection can also be released again by an opposite rotation about a longitudinal axis of the shaft. 
     According to the invention, the connecting device further comprises at least one second engagement structure for a connection engagement of an engagement element of a working insert of a second type, i.e., of a second type of working insert. By engaging the engagement element of the second type of working insert in the second engagement structure of the connecting device, a connection, in particular a bayonet connection, can be created in a corresponding manner, by means of which a base of the working insert of the second type is fixedly connected in the longitudinal direction of the shaft to its distal end section, wherein the connection can also be released by an opposite rotation about the longitudinal axis of the shaft. 
     According to the invention, the first and the second engagement structures are arranged and/or designed differently. This means that the first and the second engagement structures are arranged, for example, in different positions, in particular separately from one another, on the connecting section and/or are dimensioned differently and/or have different shapes. 
     By the fact that the connecting device has a plurality of different engagement structures, wherein one type of working insert can be brought into connection engagement with one of the engagement structures and whereby a connection engagement with another engagement structure can be produced by replacing the type of working insert with another type of working insert, it is possible to connect working inserts of different types in an optimal way to the connecting section and thus to the shaft. In particular, the different engagement structures can be designed for different connection tasks or connection properties. 
     The configuration according to the invention provides the possibility, for example, of designing at least one of the engagement structures for already existing types of working inserts and a further engagement structure for a new type of working insert. The different engagement structures can also be designed with regard to different tolerance fields of the different types of working inserts. The shaft can also be used together with already existing types of working insert due to the plurality of engagement structures. This ensures a high degree of replaceability and versatility in the use of the shaft. 
     According to an advantageous embodiment of the invention, the first and second engagement structures are arranged and/or designed differently in such a way that the first engagement structure permits the connection engagement with the engagement element of the working insert of the first type and blocks a connection engagement with the engagement element of the working insert of the second type, and that the second engagement structure permits the connection engagement only with the engagement element of the working insert of the second type and blocks a connection engagement with the engagement element of the working insert of the first type. This allows, in particular, a connection engagement only between the first type of working insert and the first engagement structure and, by replacing the type of working insert, a connection engagement only between the second type of working insert and the second engagement structure, while connection engagements between the engagement element of the first type of working insert with the second engagement structure and vice versa are impossible. Such a configuration of the connecting device can also be viewed as a mechanical coding. Such a mechanical coding can advantageously be designed by differently shaped, dimensioned and/or arranged engagement structures. To produce a mechanical coding, accordingly, the engagement structures can have different shapes, in particular each have their own or individual shape. Likewise, the engagement structures can each be dimensioned differently, so that a coding is formed due to the different sizes of the engagement structure. Finally, it is also possible to form a coding by means of a specific arrangement of the engagement structures, in particular by arranging the different engagement structures at different sections or positions of the shaft. 
     Such coding can further improve operational reliability as well as user-friendliness. Such a coding can in particular facilitate the establishment of a correct connection between the shaft and a working insert and reduce the risk of incorrect or inadequate connections between the shaft and working insert. The coding can be designed, for example, to allow only matched connection pairs and/or to block undesired connection pairs. 
     The first and the second engagement structures can advantageously be arranged differently in that the second engagement structure is arranged at a different distance from a distal end of the shaft in comparison with the first engagement structure. According to this embodiment, the connecting device thus has a second engagement structure for a connection engagement of an engagement element of a working insert of the second type, the second engagement structure being arranged at a distance from a distal end of the shaft, which differs from a corresponding distance of the first engagement structure, that is to say is smaller or larger, in particular by more than the manufacturing tolerances that may exist in the respective types of working inserts. In this way, a connection engagement between an engagement element of a working insert, which is arranged at a corresponding distance, for example, from a stop attachable to the distal end, with an engagement structure associated with the respective type of working insert, can be ensured in a simple and reliable manner, and at the same time an engagement with another type of the working insert, wherein the engagement element is disposed at a different distance therefrom, can be prevented. 
     According to a preferred embodiment of the invention, the connecting device has at least one recess running in the longitudinal direction, in particular at least one longitudinal slot or at least one longitudinal groove, the longitudinal slot or the longitudinal groove being designed for the longitudinal routing of an engagement element of a working insert according to the first and/or the second type. The longitudinal slot or the longitudinal groove can run in the longitudinal direction of the shaft, in particular approximately parallel to a longitudinal axis of the connecting section, and is preferably open in the distal direction in order to facilitate insertion of the engagement element when connecting the working insert to the shaft. A radial projection, which forms an engagement element of a working insert, can be routed through the longitudinal slot or the longitudinal groove, for example. In a particularly preferred manner, the longitudinal slot or the longitudinal groove is suitable for the longitudinal routing of the engagement element of both the first and the second type of working insert. The longitudinal slot or the longitudinal groove can be formed, for example, in a distal end section of a shaft tube, which distal end section represents the connecting section of the shaft, wherein the longitudinal groove is preferably formed inside the shaft tube. 
     The first and the second engagement structures are preferably formed in each case by a recess running in the transverse direction, in particular by a transverse slot running transverse to the longitudinal axis of the shaft or of the connecting section, or by a transverse groove running transverse to the longitudinal axis. Here, the transverse slot or the transverse groove of the first engagement structure is designed for longitudinal fixing of the engaging element of the working insert according to the first type and the transverse slot and the transverse groove of the second engagement structure for longitudinal fixing of the engaging element of the working insert of the second type. The transverse slots or transverse grooves are formed, for example, in a distal end section of a shaft tube which forms the connecting section of the shaft, the transverse groove preferably being formed inside the shaft tube. 
     The engagement structures designed as transverse slots or transverse grooves are further preferably formed separately from one another. In a particularly preferred manner, the engagement structures or the transverse slots or transverse grooves can each run transversely to the longitudinal slot or to the longitudinal groove and open into the longitudinal slot or the longitudinal groove. Such an arrangement, in particular of longitudinal slots and transverse slots, can be easily implemented in terms of production technology. In addition, this can in particular ensure the possibility of establishing a connection in the manner of a bayonet lock with a working insert, as well as by a corresponding arrangement of the longitudinal groove and transverse grooves or also of the longitudinal slot and transverse grooves as well as of the longitudinal groove and transverse slots. In this case, a projection or a correspondingly shaped form element of a working insert can be introduced in the longitudinal direction of the shaft through a longitudinal slot or a longitudinal groove and, starting from the longitudinal slot or the longitudinal groove, can be transferred into one of the transverse slots or transverse grooves. The transverse slots or transverse grooves serve for the longitudinal fixation of a projection or of an engagement element of a working insert designed corresponding to the respective transverse slot or the respective transverse groove. In this case, such a projection or such a form element of a working insert can project in radial direction relative to adjacent sections of the working insert. 
     It can furthermore be advantageous if the engagement structures, in particular the engagement structures designed as transverse slots or transverse grooves, are formed independently of one another and/or spaced apart from one another in a longitudinal direction of the connecting section. In a particularly preferred manner, the transverse slots, in particular the at least two transverse slots associated with a longitudinal slot or the at least two transverse grooves associated with a longitudinal groove, can be at different distances from the distal end of the shaft. In this way, a connection, in particular a bayonet-shaped connection and at the same time a mechanical coding can be made possible in a particularly simple and reliable manner. For example, a transverse slot or a transverse groove, which is arranged further away from the distal end of the shaft, can be designed for establishing a connection with a new type of working insert, wherein the greater distance from the distal end can ensure that this transverse slot or this transverse groove from previous types of the working insert, in which the corresponding engagement element is arranged at a shorter distance from the distal end, is not reached for a connection engagement. A suitable association of transverse slots or transverse grooves with certain types of working inserts can thus be established. 
     The first and second engagement structures are preferably designed differently in that the second engagement structure is dimensioned differently from the first. According to this embodiment, the connecting device thus has a second engagement structure for a connection engagement of an engagement element of a working insert of a second type, the second engagement structure having a dimensioning that differs from a corresponding dimensioning of the first engagement structure. For example, the second engagement structure corresponding to an engagement element of the second type of working insert can be designed to be larger or wider or deeper in the axial and/or radial direction than the first engagement structure associated with the first type of working insert, in particular by more than any existing manufacturing tolerances of the respective type of working insert. This allows in a simple and reliable way to ensure a connection engagement between a suitably configured engagement element of a working insert with an engagement structure dimensioned for the particular type of working insert and at the same time, prevents an engagement with a type of working insert the engaging element of which is dimensioned differently. 
     The first and second engagement structures are preferably dimensioned differently from one another in that they have different widths, the width in particular being a dimensioning in the longitudinal direction of the connecting section. In particular, the first and second engagement structures can be designed as transverse slots or transverse grooves, the transverse slot or the transverse groove of the first engagement structure having a width different from a width of the transverse slot or the transverse groove of the second engagement structure. For example, two transverse slots which are associated with a longitudinal slot or originate from the same longitudinal slot can have a different width. The same applies to two transverse grooves. The different widths of the transverse slots or transverse grooves can be formed corresponding to engagement elements designed as projections or form elements on different types of working insert. A transverse slot or a transverse groove with a relatively small width can thus block the connection engagement of an excessively wide projection or form element of another type of working insert. For example, it can be provided that a projection or form element of a first type of working insert is routed through the longitudinal slot to different transverse slots or transverse grooves, but can only be moved into a specific transverse slot or a specific transverse groove. In this way, it can be achieved in a particularly simple and reliable manner that a connection engagement between a correspondingly configured engagement element of a working insert of the first type is only possible with the first engagement structure and between a correspondingly configured engagement element of the second type of working insert is only possible with the second engagement structure. 
     If the engagement structures are designed as transverse grooves, the transverse grooves of the first and second engagement structures can alternatively or in addition to the different width have a different depth. Furthermore, alternatively or additionally, the transverse slots or transverse grooves can have different cross-sectional shapes. Also in this case, a corresponding coding can be implemented in a simple and reliable way. 
     According to a particularly preferred embodiment of the invention, the transverse slots or transverse grooves are arranged and designed differently in such a way that a transverse slot or a transverse groove at a greater distance from a distal end of the connecting section has a greater width than a transverse slot or a transverse groove at a smaller distance from the distal end. The connecting section can be designed, for example, as a distal end section of a shaft tube, which at the same time forms the distal end section of the shaft, so that in this case the transverse slot or the transverse groove with the greater width is at a greater distance from the distal end of the shaft than the transverse slot or the transverse groove with a smaller width. In this way, a second type of working insert with a larger dimensioned projection or form element can be routed through the longitudinal slot or the longitudinal groove, wherein, due to the larger dimensioning, an insertion into the transverse slot or the transverse groove of the first engagement structure, which has a smaller width, is blocked. Only a transverse slot or a corresponding transverse groove arranged further away from the distal end of the connecting section or of the shaft has a width suitable for the connection engagement with the projection or form element of the second type of working insert. In contrast, the transverse slot or the transverse groove of smaller width can be provided for a first type of working insert the corresponding projection or corresponding form element of which can be routed along the longitudinal slot or the longitudinal groove only up to the transverse slot and the transverse slot of smaller width, for example, due to a corresponding arrangement of the projection or form element, in particular due to corresponding length dimensions of the working insert of the first type. Such an arrangement and dimensioning of transverse slots can suitably achieve an association of transverse slots or transverse grooves with different types of working inserts. In this manner, with a single shaft, different connecting tasks can be implemented in a particularly advantageous manner. 
     Alternatively or in addition to an arrangement of the engagement structures, these being arranged one behind the other in the longitudinal direction of the shaft or at different distances from the distal end of the shaft, the different engagement structures can also be arranged at different radial distances relative to a longitudinal axis of the shaft. In this case, the shaft, in particular in the region of the connecting section, can be formed from two shaft sections arranged one inside the other. For example, a first longitudinal slot with a first transverse slot extending therefrom can be provided at a first radial distance from the longitudinal axis of the shaft, and a second longitudinal slot with a second transverse slot extending therefrom can be provided at a second radial distance from the longitudinal axis of the shaft, which is, for example, greater than the first radial distance; alternatively, longitudinal grooves and related transverse grooves can be provided at different radial distances from the longitudinal axis in a corresponding manner. In this way too, mechanical coding can be implemented in a simple and reliable manner. 
     According to a preferred configuration, the different engagement structures, in particular the engagement structures designed as transverse slots or transverse grooves, can be designed to generate different tolerance fields in connection engagement with different types of working insert. For example, a transverse slot or a transverse groove at a smaller distance from the distal end of the shaft can be designed for connection engagement with an already existing type of working insert and can accordingly be designed for a relatively wide tolerance field. In contrast, a transverse slot or a transverse groove at a greater distance from the distal end of the shaft can be designed for connection engagement with a new type of working insert, in which a narrower tolerance field can be implemented. To this end, in the new type of working insert, a narrower tolerance of pairs of parts can be used, based on the distance between the distal end of the connecting section and a distal side of a transverse slot, compared with a corresponding distance between a distal side of a projection which engages in the transverse slot when the connector is engaged, and a corresponding stop of the work insert. At least one of the engagement structures can thus be designed with respect to a relatively narrow tolerance field, in order to reduce the play between the shaft and the working insert when a corresponding connection is made with a suitable type of working insert. The accuracy of the actuation can thus be improved, since in this way a possible lost motion can be reduced or completely avoided. For example, when using new types of working insert, less play between the working insert and the shaft can be achieved. In addition, it can be avoided by such a configuration that the respective types of working insert come into connection engagement with an unsuitable engagement structure. 
     The connecting device preferably has multiple first engagement structures and multiple second engagement structures, the multiple first engagement structures being arranged offset with respect to one another in the circumferential direction of the connecting section and the multiple second engagement structures likewise being arranged offset with respect to one another in the circumferential direction. In particular, the connecting device can have two first engagement structures and two second engagement structures, which are arranged opposite each other in the circumferential direction of the connecting section. For example, the connecting device can have two or more longitudinal slots or longitudinal grooves, as a result of which a further improved routing when inserting a working insert to be connected is ensured and an improved connection can be made possible. Two longitudinal slots are preferably arranged opposite one another in the circumferential direction of the connecting section, i.e., the longitudinal slots are offset from one another by 180° with respect to the longitudinal axis of the connecting section and are therefore arranged symmetrically. When connected to a working insert, uniform force transmission can be ensured in this way. It is further preferred that at least two transverse slots can be provided for each longitudinal slot. Preferably, all transverse slots starting from the respective longitudinal slot can run in the same orientation in the circumferential direction, such as clockwise from the respective longitudinal slot, as viewed from the distal end of the shaft. In a particularly preferred manner, the combination of a longitudinal slot and at least two transverse slots can be provided several times in an identical manner. Two or more such combinations can be arranged or formed symmetrically relative to a longitudinal axis of the shaft. Furthermore, the above statements apply in the same way to any combination of a longitudinal slot and at least two transverse slots, it also being possible for grooves to be provided instead of slots. 
     It can furthermore be advantageous if the connecting section is designed as part of an outer shaft, in particular as a distal end section of a shaft tube which forms the outer shaft. The shaft tube, at least the connecting section, is preferably rigid. Such an outer shaft can preferably be provided with a sheath, for example, by which a protective function or electrical insulation is provided. For example, the shaft tube can be made of a metallic material, such as stainless steel, and the sheath can be made of a plastic material, which can rest on the outside of the shaft tube in the form of a shrinking tube. The outer shaft can also be designed to route a transmission element inside, for example a drawbar or an inner shaft. A tool of a working insert connected to the shaft can be actuated in an advantageous manner by means of such a transmission element. The outer shaft can surround the transmission element in a suitable manner and route it movably. The shaft according to the invention may in particular be totally designed as an outer shaft or have an outer shaft, wherein the connecting section is advantageously formed at a distal end of the outer shaft. 
     Another aspect of the present invention relates to an endoscopic instrument, in particular a medical endoscopic instrument, with a shaft which is formed as previously described, and with at least one working insert which is detachably connected to the connecting section of the shaft via the connecting device of the shaft. If the connection between the working insert and the shaft is now detached, another working insert, for example a different type of working insert, can be connected to the shaft instead of the removed working insert. Depending on the type of working insert, a connection engagement with different engagement structures of the shaft can be established. The engagement structures can therefore be designed or structured for different connection tasks. 
     The working insert has, in particular, a surgical tool which can be formed by one or more pivotably mounted jaw parts which are connected to an elongate transmission element and can be actuated by a longitudinal displacement of the transmission element from the proximal end of the shaft. Preferably, the working insert comprises a base which is, as described above, designed for connecting to the connecting section particularly in the manner of a bayonet connection, and which carries at least one engagement element for this purpose. The base is designed in particular approximately cylindrical in sections and dimensioned for insertion into the connecting section of the shaft, the insertion depth being limited by a stop. The at least one engagement element is arranged at such a distance from the stop that it can be brought into connection engagement in an engagement structure of the connecting section. At a distal end of the base, for example, a fork device is arranged for the pivotable mounting of at least one jaw part of the surgical tool, which can be designed, for example, for cutting or grasping tissue. The fork device can have two opposite pivot bearings. Furthermore, the base can have a feed-through for the transmission element connected to the pivotable jaw parts and can accordingly be tubular. The transmission element can thus be passed through the shaft and extend as far as the fork device. At the proximal end of the shaft, a handle, for example a handlebar, can be detachably attached, which can be connected to the transmission element in order to transmit an actuation by a user to the transmission element and further to the tool of the working insert. 
     Another aspect of the present invention relates to an endoscopic system, in particular a medical endoscopic system, with a shaft designed as described above and with at least one working insert of the first type and at least one working insert of the second type. Here, as described above, the working insert of the first type is designed for connection engagement with the first engagement structure of the connecting section of the shaft and the working insert of the second type is designed for connection engagement with the second engagement structure of the connecting section. The working insert of the first and that of the second type are preferably designed differently in such a way that the working insert of the first type only enables connection engagement with the first engagement structure and that of the second type only enables connection engagement with the second engagement structure. In particular, the working insert of the second type has at least one engagement element which is arranged and/or dimensioned and/or shaped differently in comparison to at least one engagement element of the work element of the first type and thereby only permits the connecting section with the respectively associated engagement structure. The endoscopic system thus comprises the shaft and a plurality of different types of working insert, which can be connected individually and interchangeably to the connecting section of the shaft by the connecting device. The endoscopic system is therefore formed by combining the shaft with at least one working element of the first type of working insert and at least one working element of the second type of working insert, wherein, as described above in relation to the shaft, a connection engagement with the different engagement structures of the shaft is established depending on the type of working insert. 
     Because a first type of working insert can be brought into connection engagement with the first engagement structure and a connection engagement with the second engagement structure can be established by replacement with a second type of working insert, the engagement structures can be designed for different connection tasks and accordingly, the working inserts can be configured differently. On the one hand, this increases operational reliability and at the same time guarantees a wide range of possible uses. 
     According to a particularly preferred configuration of the endoscopic system, a tolerance field between the first type of working insert and the corresponding first engagement structure can differ from a tolerance field between the second type of working insert and the corresponding second engagement structure. In particular, the respective tolerances of pairs of parts can differ. For example, conventional tolerance fields can be implemented for existing types of working inserts, so that backward compatibility with such types of working insert is maintained, and at the same time, a narrower tolerance field can be selected and implemented for new types of working insert, so that a lower degree of play is achieved when using such types of working insert, or any lost motion can be reduced or avoided altogether. 
     According to a method according to the invention for configuring an endoscopic instrument, an endoscopic instrument is provided that comprises a shaft, which is designed as described above, and a working insert according to the first type, which is connected to the shaft. The at least one engagement element of the working insert is thus in connection engagement with the at least one first engagement structure of the connecting section of the shaft. By rotating about the longitudinal axis of the shaft or the connecting section and removing it in the distal direction, the working insert is detached from the connecting device and separated from the shaft, in particular in the manner of a bayonet connection. A working insert according to the second type is also provided. By inserting it into the shaft from the axial direction and finally rotating it about the longitudinal axis, said working insert according to the second type is connected to the shaft. The working insert of the second type is configured differently from the first one such that the at least one engagement element of the second type of working insert comes into connection engagement with the second engagement structure of the connecting section of the shaft. 
     Accordingly, the at least one engagement element of the second type of working insert is arranged and/or configured differently than that of the first type of working insert. The working inserts can be replaced, for example, during an endoscopic procedure, or after an endoscopic procedure the working insert of the first type can be detached from the shaft, at least the shaft can be cleaned and/or sterilized, and the working insert of the second type can be connected to the shaft before another endoscopic procedure. The method according to the invention can comprise further steps, for example the removal and/or attachment of a handlebar. 
     The above statements regarding the shaft also apply in the same way to the endoscopic instrument and to the endoscopic system and to the method for configuring the endoscopic instrument. 
     It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention. 
    
    
     
       Further aspects of the invention result from the following description of a preferred exemplary embodiment and the attached drawing. The Figures each show schematically: 
         FIG. 1  shows a shaft according to an embodiment of the present invention with a working insert inserted in a side view; 
         FIG. 2  shows a perspective view of the distal end section of the shaft of  FIG. 1 ; 
         FIG. 3  shows a perspective view of the shaft of  FIG. 2  with a partially inserted working insert of a first type; 
         FIG. 4  shows a perspective view of the shaft of  FIG. 2  with the fully inserted and connected working insert of the first type; 
         FIG. 5  shows a perspective view of the shaft of  FIG. 2  with the partially inserted working insert of a second type; 
         FIG. 6  is a perspective view of the shaft of  FIG. 5  with the fully inserted and connected working insert of the second type. 
     
    
    
     As illustrated in  FIG. 1 , a shaft  10  for a medical endoscopic instrument  1  according to an exemplary embodiment of the present invention comprises a proximal section  2 , an elongated central section  11  and a distal end section  12 . Shaft  10  is dimensioned for insertion into a cavity inside the body, for example, for insertion into a working channel of an endoscope, which is inserted into the cavity inside the body during an endoscopic procedure. Proximal section  2  of shaft  10  can have a connection  3 , for example a rinsing connection, and a connecting mechanism  4 , which is only illustrated by way of example in  FIG. 1 , for connection to a handlebar, not shown. Connecting mechanism  4  can be designed such that the handlebar can be rotatably attached, so that shaft  10  can be rotated relative to the handlebar about the longitudinal axis of shaft  10 . 
     A tool  5  is connected to distal end section  12  of shaft  10  and, in the exemplary embodiment shown, is designed as a pair of scissors with two scissor blades  6 ,  6 ′ that can be pivoted relative to distal end section  12  of shaft  10 . Tool  5  is part of a working insert  30  which is inserted into shaft  10  on the distal side. Working insert  30  further comprises a base  7 , which is designed on the distal side as a fork  29 , in which scissor blades  6 ,  6 ′ are pivotally mounted. Working insert  30  abuts on distal end  14  of shaft  10  with a stop of base  7 . As will be explained in more detail below with reference to  FIGS. 2 to 6 , an insertion section  32  of base  7  is inserted and connected to in distal end section  12  of shaft  10 , which distal end section  12  is designed as a connecting section  16  for this purpose (see  FIGS. 2 to 6 ). 
     Inside shaft  10  is a drawbar  8  that is slidably disposed in the longitudinal direction of shaft  10 . The proximal end of drawbar  8  is formed by a connecting element, for example a ball  9 , which can be connected to a movable part of the handlebar in order to move drawbar  8  in the longitudinal direction by actuating the movable part. Drawbar  8  can transfer both tensile and shear forces in the longitudinal direction of shaft  10 . Drawbar  8  is connected to scissor blades  6 ,  6 ′ by an articulated joint and also forms part of working insert  30 . By displacing drawbar  8  in the distal direction, scissor blades  6 ,  6 ′ can be opened and closed by shifting in the proximal direction; a reverse mode of action of drawbar  8  is also conceivable, scissor blades  6 ,  6 ′ being closed by displacing drawbar  8  in the distal direction and being opened by displacing it in the proximal direction. Shaft  10  is designed as a metallic shaft tube, which can be surrounded by an electrically insulating sheath  38 . Electrical connections for RF voltage can be arranged on the handlebar, for example. 
       FIG. 2  shows a perspective view of distal end section  12  of shaft  10 , which is formed by a metallic shaft tube  13 . Distal end  14  of shaft  20  is formed on distal end section  12 . Distal end section  12  of shaft  10  forms a connecting section  16 . Connecting section  16  has a connecting device  18  for connecting a replaceable working insert, which is not shown in  FIG. 2 , to connecting section  16 . For this purpose, connecting device  18  has a plurality of engagement structures  20 ,  22  for the connection engagement of different types of working inserts. To this end, a type of working insert, such as a working insert of a first type, can be brought into connection engagement with a first engagement structure  20 , and by replacing the working insert with another type of working insert, such as a working insert of a second type, a connection engagement with a second engagement structure  22  can be produced, which is explained in more detail below with reference to  FIGS. 3 to 6 . 
     Engagement structures  20 ,  22  are designed as transverse slots  24 ,  26 . Transverse slots  24 ,  26  run from a longitudinal slot  28  in a circumferential direction of shaft  10 . As seen from distal end  14 , transverse slots  24 ,  26  run clockwise from the longitudinal slot  28 . Longitudinal slot  28  opens at distal end  14  of shaft  10 . Longitudinal slot  24  runs along a longitudinal direction of shaft  10  or parallel to a longitudinal axis of connecting section  16 . Such a connecting device  18  consisting of a longitudinal slot  28  and transverse slots  24 ,  26  is suitable for establishing a connection in the manner of a bayonet lock. 
       FIG. 2  also shows that an arrangement of a longitudinal slot  28 ′ and two transverse slots  24 ′,  26 ′ is also provided in a position offset by 180° in the circumferential direction. Accordingly, connecting device  18  can advantageously have two longitudinal slots  28 ,  28 ′ arranged opposite one another with respect to the longitudinal axis of connecting section  16 , from which two transverse slots  24 ,  26  or  24 ′,  26 ′ start out. 
     Transverse slots  24 ,  26  are arranged at a different distance from distal end  14  and have different widths. Due to the different widths and the different distances from distal end  14 , transverse slots  24 ,  26  form a mechanical coding. Such a mechanical coding can block the connection engagement between a type of working insert, which corresponds to the second type of working insert, and first transverse slot  24  and allow the connection engagement between this type of working insert and second transverse slot  26 . In case of another type of working insert, which corresponds to the first type, a connection engagement can be established with first transverse slot  24 , whereas a connection engagement can be blocked between such a type of working insert and second transverse slot  26 , which will be also explained in more detail with reference to  FIGS. 3 to 6 . The same applies to transverse slots  24 ′,  26 ′ arranged opposite one another. 
       FIG. 3  shows a perspective view of shaft  10  with a partially inserted working insert  30  according to the first type, and in  FIG. 4  working insert  30  is fully inserted into shaft  10  and connected to it. 
     Working insert  30  has a base  7  which comprises a fork  29  and an approximately cylindrical insertion section  32 . Fork  29  is designed for the pivotable mounting of jaw parts, not shown here, of tool  5 , for example scissor blades  6 ,  6 ′(see  FIG. 1 ), and has two pivot bearings  37 ,  37 ′ for this purpose. Insertion section  32  of working insert  30  can be inserted into connecting section  16  of shaft  10 . A projection  34  or a plurality of projections  34  is formed at insertion section  32 . Projection  34  is routed along longitudinal slot  28  when the insertion section  32  is inserted into connecting section  16  of shaft  10 . In the example illustrated, two mutually oppositely arranged projections are provided, of which only one projection  34  is visible in  FIG. 3 . Projection  34  is routed in longitudinal slot  28 , and the second projection in longitudinal slot  28 ′(see  FIG. 2 ). 
     After insertion of insertion section  32  into connecting section  16  of shaft  10  and suitable routing of projection  34  in longitudinal slot  28 , projection  34  can reach first transverse slot  24 . In this position, working insert  30  can be rotated about the longitudinal axis of shaft  10 , so that projection  34  comes into connection engagement with first transverse slot  24 . At the same time, the second projection, which is routed through opposite longitudinal slot  28 ′, comes into connection engagement with opposite transverse slot  24 ′. As a result, working insert  30  can be fixed in the longitudinal direction relative to shaft  10 , as shown in  FIG. 4 , the axial and the subsequent circumferential movement of projection  34  being represented by arrows in  FIG. 4 . The connection engagement between projection  34  and transverse slot  24  can be maintained with a securing device, not shown here, or can only be released by overcoming a predetermined force, for example drawbar  8 , which passes through base  7  and is connected to the jaw parts of tool  5  (see  FIG. 1 ), can form a rotation lock. 
     Due to the limited length of insertion section  32  and the formation of a collar-shaped stop  36  at which insertion section  32  ends, projection  34  of working insert  30  can only be brought into engagement with transverse slot  24 . Any further insertion of insertion section  32  is blocked by contacting distal end  14  by stop  36 , so that projection  34  of working insert  30  of the first type of working insert cannot be brought in connection engagement with second transverse slot  26  which is further spaced apart from distal end  14 . 
     Transverse slot  24  with the smaller width can be provided for the connection engagement with an already existing type of working insert or several types of existing working inserts, which, for example, differ with regard to the type of jaw parts, but in which insertion section  32  is designed as described above. Accordingly, first transverse slot  24  can be designed for the connection with relatively large tolerance fields  24 . In connection engagement with projection  34  of working insert  30 , therefore, there can be a relatively large play. However, this ensures the backward compatibility of shaft  10  with existing working inserts. 
       FIG. 5  shows a perspective view of shaft  10  with a partially inserted working insert  31  of a second type, and in  FIG. 6  working insert  31  is fully inserted into shaft  10  and connected to it. 
     Working insert  31  is a working insert of a second type, which is designed differently from previously described working insert  30 . Working insert  31  also has a base  7 , which comprises a fork  29  and an approximately cylindrical insertion section  33 . Fork  29  is also designed for the pivotable mounting of jaw parts, not shown here, of tool  5 , for example scissor blades  6 ,  6 ′ or also of another type of tool such as a gripping forceps. Insertion section  33  of working insert  30  can be inserted into connecting section  16  of shaft  10 . A projection  35  is formed on insertion section  33  and is routed along longitudinal slot  28  when insertion section  33  is inserted into connecting section  16  of shaft  10 . In the example shown, there are also two projections arranged opposite one another, of which only one projection  35  can be seen in  FIG. 5 . 
     Insertion section  33  of working insert  31  has a greater length than insertion section  32  of previously described working insert  30  of the first type. Projection  35  is thus arranged at a greater axial distance from stop  36  than in the first type of working insert described above. Working insert  31  of the second type of working insert differs from working insert  30  of the first type shown in  FIGS. 2 and 3  also with regard to the dimensioning of projection  35  or the projections  35  in the longitudinal direction, wherein projection  35  or projections  35  is or are dimensioned to be larger in the axial direction than projection  34  or projections  34  of the first type of working insert. Projection  35  also will be routed along respective longitudinal slot  28  upon insertion of insertion section  33  in connecting section  16  of shaft  10 . In particular, one projection  35  can be routed in a longitudinal slot  28 ,  28 ′ (see  FIG. 2 ). 
     After insertion of insertion section  33  into connecting section  16  of shaft  10  and suitable routing of projection  35  in longitudinal slot  28 , projection  35  can reach transverse slot  24 . However, due to the larger dimension of projection  35  in the longitudinal direction, it cannot be moved into transverse slot  24 , which is too narrow for this purpose. The establishment of a connection engagement between projection  35  and transverse slot  24  is thus blocked. The movement of projection  35  in the axial direction and the blocked movement in the circumferential direction are indicated in  FIG. 5  by the long arrow and the crossed-out arrow. 
     Upon further insertion of insertion section  33  into connecting section  16  of shaft  10  and a suitable routing of projection  35  in longitudinal slot  28 , projection  35  can reach transverse slot  26 . In this position, working insert  31  can be rotated about the longitudinal axis of shaft  10 , so that projection  35  comes into connection engagement with transverse slot  26 . The movement of projection  35  in the axial direction and then in the circumferential direction is indicated by the arrows in  FIG. 6 . As a result, working insert  31  can be fixed in the longitudinal direction relative to shaft  10 . At the same time, the second projection, which is routed through opposite longitudinal slot  28 ′, comes into connection engagement with opposite transverse slot  26 ′. The connection engagement between projection  34  and transverse slot  26  can be maintained with a securing device, not shown here, or can only be released by overcoming a predetermined force, for example drawbar  8 , which accordingly passes through base  7  and is connected to the jaw parts of tool  5  (see  FIG. 1 ), can form a rotation lock. 
     Transverse slot  26  with the greater width and at a greater distance from distal end  14  can be provided for connection engagement with new types of working insert or also with a working insert  31  which has a tool designed differently from the first type of working insert. Accordingly, transverse slot  26  can be designed for the connection with relatively narrow tolerance fields. In connection engagement with projection  35  of working insert  31 , a relatively small play can therefore be implemented, so that any lost motion can be reduced or completely avoided. As mentioned above, however, transverse slot  24  arranged closer to distal end  14  ensures the backward compatibility of shaft  10  with existing types of working insert. 
     Simultaneously with the engagement of projection  34  or  35 , stop  36  of working insert  30 ,  31  can abut on distal end  14  of shaft  10  or the connecting section. In this way, the handling when connecting respective working insert  30 ,  31  to shaft  10  can be facilitated by means of the bayonet connection. Furthermore, to simplify handling, chamfers  39 ,  39 ′ can be provided on both sides of the distal mouth of longitudinal slots  28 ,  28 ′ and a bevel  40 ,  41  can be provided on the proximal side of projections  34 ,  35  (see  FIGS. 2 to 6 ). The bayonet connection is released in each case by rotating base  7  in the opposite direction about the longitudinal axis and leading insertion section  32 ,  33  out of connecting section  16  in the distal axial direction. 
     Shaft  10  can, including connecting section  16 , be formed by a rigid shaft tube, for example, made of stainless steel. In the exemplary embodiment shown, shaft  10  is also equipped with a sheath  38 , which consists, for example, of a plastic material and can serve for electrical insulation. In  FIGS. 2 to 6 , sheath  38  is shown to be transparent. In the exemplary embodiment shown, sheath  38  is slightly widened in distal end section  12  of shaft  10  to facilitate the insertion of working insert  30 ,  31  and the creation of the bayonet connection. 
     The overall result is a shaft  10  which ensures greater operational reliability or operating accuracy and, at the same time, versatility. 
     As has been explained above with reference to  FIG. 1 , shaft  10  together with working insert  30 ,  31  connected therein, including drawbar  8  and optionally with a handlebar attached at the proximal section  2  of shaft  10  can form a medical endoscopic instrument  1 . Furthermore, shaft  10  together with multiple working inserts  30  and  31  of different types can form an endoscopic system, in particular a medical endoscopic system, or can be part of such an endoscopic system. 
     For the sake of clarity, not all reference numerals are shown in all figures. Reference numerals not explained for a figure have the same meaning as in the other figures. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  instrument 
           2  proximal section 
           3  connection 
           4  connecting mechanism 
           5  tool 
           6 ,  6 ′ scissor blade 
           7  base 
           8  drawbar 
           9  ball 
           10  shaft 
           11  middle section 
           12  distal end section 
           13  shaft tube 
           14  distal end 
           16  connecting section 
           18  connecting device 
           20  engagement structure 
           22  engagement structure 
           24 ,  24 ′ transverse slot 
           26 ,  26 ′ transverse slot 
           28 ,  28 ′ longitudinal slot 
           29  fork 
           30  working insert 
           31  working insert 
           32  insertion section 
           33  insertion section 
           34  projection 
           35  projection 
           36  stop 
           37 ,  37 ′ pivot bearing 
           38  sheath 
           39 ,  39 ′ chamfer 
           40  bevel 
           41  bevel