Abstract:
The invention relates to an endoscope having a shaft in which at least one working channel is positioned and having on the distal end of the shaft an endoscope head, such that the part of the working channel contained in the endoscope head can be rotated with respect to the related working channel by a Bowden cable that is mounted on a control handle on the proximal end by a collet. To configure an endoscope in such a manner that it ensures simple construction as well as a constantly even tension of the Bowden cable, it is proposed with the invention that the depth of insertion of a cable cord of the Bowden cable into the collet can be limited by a pressure element acting on the cable cord and collet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority of German patent application No. 10 2005 041 454.0 filed on Aug. 31, 2005, the content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to an endoscope having a shaft in which at least one working channel is positioned and having on the distal end of the shaft an endoscope head, such that the part of the working channel contained in the endoscope head can be rotated with respect to the related working channel by a Bowden cable that is mounted on a control handle on the proximal end by a collet. 
     BACKGROUND OF THE INVENTION 
     In order to allow a medical instrument brought into the surgical area by way of the working channel to be directed accurately to the area of application, a known method is to configure the part of the working channel situated in the endoscope head so that it can be rotated with respect to the related working channel by means of a Bowden cable. In the endoscope introduced in EP 1 112 019 B1, the Bowden cable serving to rotate the working channel is mounted on the proximal end by means of a collet mounted on a control handle. By means of the collet, the cable cord of the Bowden cable is grasped by clamping and is held clamped in the collet according to the depth of insertion. 
     This known construction for clamping the Bowden cable has the disadvantage that the cable cord can be inserted so deep in the collet that the cable cord becomes too taut and it becomes scarcely possible to rotate the working channel. To minimize this danger, the working channel and thus the cable cord of the Bowden cable must first be moved into a predetermined starting position so that thereafter a sufficient but not too taut tightening of the cable cord by the collet is possible. This known clamping method is, on the one hand, complicated and, on the other hand, does not prevent faulty tightening of the cable cord. 
     On this basis, it is the object of the invention to produce an endoscope of the aforementioned type in such a way that a constantly even tension of the Bowden cable is ensured, along with simple construction. 
     SUMMARY OF THE INVENTION 
     The fulfillment of this object according to the invention is characterized in that the depth of insertion of a cable cord of the Bowden cable into the collet can be limited by a pressure element applied to the cable cord and collet. 
     Because the invention limits the depth of insertion of the cable cord of the Bowden into the collet, it becomes possible for the first time to maintain constant uniform depth of insertion and thus also a uniform tension of the cable cord. The risk of faulty tightening of the cable cord in assembling the Bowden cable is avoided thanks to this structural design. 
     According to a practical embodiment of the invention it is proposed that a cone is configured on the proximal end of the collet so that it engages with a counter-cone that is configured in a nut that can be screwed onto the collet. The engagement of cone and counter-cone ensures a secure and straight mounting of the collet in the nut, so that in the cone of the collet at least one clamping slit is configured running in the longitudinal direction of the collet whereby the cable cord is fixed in the collet by clamping when the collet cone runs up against the counter-cone. 
     To ensure that the counter-cone is always form-fitting contiguous to the cone of the collet, the pressure element according to the invention acts on the counter-cone by means of at least one spring element. 
     In addition, according to a preferred embodiment of the invention it is proposed that the pressure element is configured as a cap-shaped component, so that the axial length of the pressure element corresponds to the preferred and maximal insertion depth of the cable cord into the collet. Because the cap-shaped pressure element is spring-loaded and contiguous with the counter-cone, which defines the final position of the collet in the nut, there results an always uniform and predetermined tightening of the cable cord, because upon screwing the nut onto the collet positioned coaxially on the cable cord, the cable cord on the proximal end, corresponding only to the axial length of the pressure element, can extend above the collet. Thus, in installing the Bowden cable on the control handle, the insertion depth of the cable cord is restricted by the pressure element. 
     It is further proposed with the invention that the spring element is supported on the distal end on a surrounding collar of the cap-shaped pressure element and on the proximal end on a rear wall of the nut that is configured as a cap nut. 
     To ensure that the cable cord of the Bowden cable is always perfectly centered in the pressure element, it is proposed with the invention that a closed rear wall of the cap-shaped pressure element is configured tapering toward the outside. 
     It is finally proposed with the invention that the counter-cone is configured on a sleeve that can be inserted into the nut, so that the sleeve can be fixed secure against rotation in the nut, for instance by cementing, in order to prevent turning the sleeve that is equipped with the counter-cone while screwing on the nut. 
     To allow simple, level screwing of the nut onto the collet, on the distal end of the sleeve a non-threaded recess is configured. This recess, which extends the inner diameter of the sleeve, allows the collect to be centered in the nut. 
     Additional characteristics and advantages of the invention can be seen by referring to the appended sketches, in which an embodiment of the endoscope according to the invention is depicted in exemplary manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective side view of the distal end of an endoscope according to the invention. 
         FIG. 2  shows a view as in  FIG. 1  but with the endoscope head covering removed. 
         FIG. 3  shows a perspective side view of the endoscope head separated from the endoscope shaft. 
         FIG. 4  shows a detailed partial side view of a control handle for an endoscope according to the invention. 
         FIG. 5  shows an enlarged cut-out view of detail V from  FIG. 4 , but in the assembled state. 
         FIG. 6  shows a front view of the drawing in  FIG. 2 . 
         FIG. 7  shows a front view of the endoscope with the endoscope head removed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1  is seen the distal end of an endoscope  1  having an endoscope head  3  that constitutes the distal end of an endoscope shaft  2  and forms an extension of the endoscope shaft  2 . 
     Inside the shaft  2 , as can be seen in  FIG. 7 , several channels are configured, running in the longitudinal direction, in particular a working channel  4 , an irrigation channel  5   a , an air channel  5   b , and two illumination channels  6 . In addition, the lens system  7  of the endoscope  1  extends in the longitudinal direction of the entire shaft  2 . 
     To ensure that the operator working with the endoscope always has a clear view of the surgical area, the rinse water exiting from the irrigation channel  5   a  is diverted by a duct  8  made of baffle plate onto the lens system  7  and the light systems positioned in the illumination channels  6 , so that in the illustrated embodiment the rinse liquid is conducted to the lens system  7  and to the illumination channels  6  by correspondingly positioned conducting channels  9 , as seen in particular in  FIG. 7 . After completion of the lens system rinsing, the irrigation liquid drops are blown away by the air stream emerging from the air channel  5   b.    
     In addition to this drying of the lens system  7 , the air stream conducted by the air channel  5   b  serves to inflate the organs to make it possible thus to insert the endoscope  1  into the examination area with as little friction as possible. 
     The endoscope head  3  is connected with the endoscope shaft  2  of the endoscope  1  in the illustrated embodiment by a sleeve  11  that can be screwed onto an outer thread  10  of the endoscope head  2  and that at the same time constitutes the outer housing of the endoscope head  3 . 
     Finally,  FIG. 2  shows a side view corresponding to  FIG. 1 , but with the sleeve  1  removed so that the inner structure of the endoscope head  3  is now recognizable. As can be seen from this image as well as from  FIG. 3 , the endoscope head  3  is constructed as a housing divided in two in the axial direction of the shaft  1  in such a way that the working channel  4  is positioned in the one housing section and the lens system  7 , the illumination channels  6  for the lighting systems, and the irrigation channels  5  are positioned in the other housing section. 
     The extension of the working channel  4  in the endoscope head  3  has the peculiarity that this part  4   a  is configured in the shaft  1  so that it can rotate with respect to the related working channel  4  in the plane of the impact plate  12 . Because of this ability of the distal part  4   a  of the working channel  4  to rotate, it is possible to direct a medical instrument, which has been inserted from the proximal end of the endoscope  1  into the working channel  4 , accurately to the surgical area. The distal part  4   a  of the working channel  4  rotates around a pivot axis  13  by means of a Bowden cable  14  that is mounted in the shaft  1  and can be actuated by a control handle  15  on the proximal end of the endoscope  1 , as is shown in  FIG. 4 . 
     As can further be seen from  FIGS. 2 and 3 , the rotatable part  4   a  of the working channel  4  is pre-tensioned by a spring element  16  in a starting position in order to have a defined starting position of the working channel  4  from which the movable part  4   a  can rotate. Because of this starting position it is possible to define a zero point, so that the optical axis constitutes a thoroughly appropriate starting position/zero point position. In order to maintain this starting position also during motion, it is advantageous to provide a stopping device by which the rotatable part  4   a  of the working channel  4  can be fixed in this starting position. 
     The Bowden cable is assembled and disassembled on the rotatable part  4   a  of the working channel  4  and on the control handle  15  as follows: 
     At the beginning of the installation, a cable cord  17  of the Bowden cable  14  is inserted into a Bowden cable casing  18  and then the Bowden cable casing  18  including the cable cord  17  is introduced from the distal end of the endoscope head  3  into a Bowden cable channel  19  configured in the shaft  1 . 
     Then the endoscope head  3  is secured by the screw-in sleeve  11  on the endoscope shaft  2 . The cable cord  7  is pushed into the Bowden cable casing  18  until the cable cord  17  on the proximal end emerges again from the Bowden cable channel  19  in the area of the control handle  15 . The cable cord  17  is secured on the proximal end on the control handle  15  by a collet  20  that can be mounted onto the cable cord  17  and is clamped shut by screwing on a nut  21  with the cable cord  17 . The rotatable part  4   a  of the working channel  4  can now be displaced by the control handle  15 . 
     The structure of the nut  21 , configured as a cap nut, and of the collet  20 , as well as the manner of tightening the cable cord  17  can be seen from the enlarged detail view in  FIG. 5 . 
     As can be seen from the sectional view in  FIG. 5 , the proximal end of the collet  20 , onto which the nut  21  is mounted, is configured as a cone  20   a . For insertion of the collet  20 , the nut  21  has a pocket hole boring  22 , which is inserted essentially flush with the bore hole  22  shutting off a sleeve  23 , whose proximal end constitutes a counter-cone  23   a  to the cone  20   a  of the collet  20 . The depth of insertion of the collet  20  into the sleeve  23  and thus also into the nut  21  is thus limited by the fact that the cone  20   a  of the collet  20  comes into essentially form-fitting contact on the counter-cone  23   a  of the sleeve  23 . To prevent rotation of the sleeve  23  inside the nut  21  upon screwing the nut  21  onto the collet  20 , the sleeve  23  is fixed against rotation in the pocket hole  22  of the nut  21 , for instance by cementing. 
     The nut  21  is secured on the collet  20  by an outer thread  20   b  that is configured on the collet  20  and engages with an inner thread  23   b  configured in the sleeve  23 . As can be seen from  FIG. 5 , a non-threaded recess  23   c  is configured in order to facilitate level screwing of the nut  2  onto the collet  20 . 
     To enable the cable cord  7  to be fixed in the collet  20  by screwing the nut  21  onto the collet  20  and by pressing the counter-cone  23   a  of the sleeve  23  onto the cone  20   a  of the collet  20 , at least one clamping slit  24  is configured in the collet running in the longitudinal direction of the collet  20 , as is shown in  FIG. 4 . This clamping slit  24  allows a reduction of the diameter of the collet  20  and thus a clamping of the cable cord  17  positioned in the collet  20  when a radially acting force component is exerted on the collet  20 . 
     Perfect actuation of the rotatable part  4   a  of the working channel  4  by the Bowden cable  14  depends on the correct tightness of the cable cord  17  of the Bowden cable  14 . For this purpose it is necessary to ensure that the cable cord  17  is inserted neither too far nor too little into the collet  20  and thus into the nut as well. If the cable cord  17  is inserted too deeply into the collet  20  and thus also into the nut  21 , this causes too taut a tightening of the cable cord  17 , so that it is barely possible to displace the rotatable part  4   a . A similar situation occurs with too weak a tightening of the cable cord  17  because of too short an insertion of the cable cord  17  into the collet  20 . 
     For assembly and disassembly of the collet  20  on the cable cord  17  and/or in the nut  21 , the collet  20  can be moved forward and backward in the longitudinal direction by means of a control lever  26  positioned on the control handle  15 . 
     In the embodiment illustrated in  FIG. 5 , the depth of insertion of the cable cord  17  into the collet  20  is limited by a cap-shaped pressure element  25 , which is pre-tensioned by a spring element  27  so that it is contiguous with the sleeve  23  on the proximal end. The spring element  27  here is positioned in the pocket hole  22  of the nut  21  on the proximal end in such a way that the spring element  27  is supported on the distal end on a surrounding collar  25   a  of the cap-shaped pressure element  25  and on the proximal end on a rear wall of the nut  21 , which is configured as a cap nut. 
     The advantage of this structure is that the cable cord  17  is always held tight in a firmly defined position. This is ensured by the fact that, upon insertion of the collet  20  into the nut  21 , the cable cord  17  presses against the pressure element  25 , which in turn constantly presses against the cable cord  17  by means of the spring element  27 . As can be seen from  FIG. 5 , a closed rear wall  25   b  of the cap-shaped pressure element  25  is configured as tapering toward the outside, so that the proximal end of the cable cord  17  inside the pressure element  25  is always positioned exactly centered in the pressure element  25  and the pressure always acts centrally on the cable cord  17 . The cable cord  17  is of such dimensions that it is long enough in the starting condition to press against the pressure element  25 . As a result of this configuration of the pressure element  25 , the possibility of user-caused errors is definitely minimized. 
     To ensure that the cable cord  17  can be tightened several times with sufficient stability, the cable cord  17  is soldered tightly at the distal end, which is positioned on the rotatable part  4   a  of the working channel  4 . 
     The endoscope head  3  is disassembled in reverse sequence and begins with the loosening of the nut  2  to release the cable cord  17 . Then the sleeve  11  is unscrewed and the endoscope head  3  is withdrawn from the endoscope shaft  2 . 
     An endoscope of this configuration is characterized in that a correct tension of the cable cord  17  of the Bowden cable  17  is always ensured.