the medical bipolar coagulation instrument , as shown especially in fig1 and 2 , consists essentially of a hollow shaft 1 configured as a suction / flushing channel , a handle 2 mounted on the proximal end of the shaft 1 , and two electrode tips 3 and 4 that extend beyond the hollow shaft 1 on the distal end . as can be seen in particular from fig2 , the hollow shaft 1 is configured in several layers consisting of an inner tube 5 , an electrically insulating layer 6 that coaxially surrounds the inner tube 5 , an outer tube 7 that coaxially surrounds the inner tube 5 as well as the insulating layer 6 , and an electrically insulating layer 8 that coaxially surrounds the outer tube 7 . in the illustrated embodiment the insulating layers 6 and 8 , which on the one hand electrically insulate the tubes 5 and 7 with respect to one another and on the other hand electrically insulate the shaft 1 from the outside , are configured as shrink hoses that surround the tubes 5 and 7 in form - locked manner . it is also possible of course to obtain the electrical insulation of the tubes 5 and 7 with respect to one another and from the environment also by means of other electrically insulating layers , such as by coating the tubes 5 and 7 with electrically insulating layers made of plastic or ceramic material . the tubes 5 and 7 , in turn , are at least partly electrically conductive in configuration , so that the tubes 5 and 7 simultaneously constitute the electrodes of the bipolar coagulation instrument . to configure the actual electrode tips 3 and 4 , on the distal ends of the inner tube 5 and of the outer tube 7 , tubular sections are configured , protruding in finger - like manner , which extend beyond the distal end of the shaft 1 , as shown in fig1 and 3 . these finger - like protruding electrode tips 3 and 4 are positioned opposite one another on the distal end of the shaft 1 . the multi - layered structure of the hollow shaft 1 can be seen both from the explosion drawing in fig2 and in particular from fig3 and 4 , which show the distal end of the shaft 1 that includes the electrode tips 3 and 4 . the external insulating layer 8 has been omitted from fig3 to allow a clearer view of the configuration of the electrode tips 3 and 4 as a distal extension of the tubes 5 and 7 . it can also be seen from fig3 and 4 how the tubes 5 and 7 are geometrically configured in the area of the transition to the electrode tips 3 and 4 . to ensure a form - locked positioning and gapless insulation of the insulating layers 6 and 8 on the tubes 5 and 7 in the area of the distal free ends of the tubes 5 and 7 , beveled surfaces 5 a and 7 a , inclined diagonally inward , are configured on the free ends of the tubes 5 and 7 . the configuration of the tubes 5 and 7 , which constitute the hollow shaft 1 , as electrodes of the bipolar coagulation instrument has the advantage that the entire free cross - section of the hollow shaft 1 is available as a suction and / or flushing channel and no cabling is required inside the shaft 1 . to configure the hollow shaft 1 as a suction and / or flushing channel , the handle 2 comprises on its proximal end a suction and / or flushing connection 9 for coupling to an external suction and / or flushing line . the handle 2 in addition comprises a current connection 10 by which the tubes 5 and 7 configured as electrodes can be charged with current . to make it possible for the operator to be able easily and quickly to regulate the suction capacity via the hollow shaft 1 configured as a suction and / or flushing channel , the hollow shaft 1 in the area of the handle 2 comprises a throttle opening 11 that connects the interior of the suction and / or flushing channel with the ambient air . in the illustrated embodiment the throttle opening 11 is configured as a borehole running essentially radially . different - shaped throttle openings 11 , such as oval , rectilinear , or similarly configured openings , are also possible of course . as can be seen in particular from fig5 and 6 , the throttle opening 11 is configured and placed on the handle in such a way that the operator can open and close the throttle 11 again with one finger , for instance with a finger of the hand that is also being used for holding the handle 2 to guide the instrument . the throttle opening 11 here is advantageously of such dimensions that with the throttle opening 11 completely opened , the suction capacity essentially comes to a stop , because so much ambient air is drawn in by the opened throttle opening 11 that the suction capacity does not extend as far as the distal end of the shaft 1 . the farther the operator closes the throttle opening 11 with a finger , the stronger becomes the suction capacity inside the hollow shaft and thereby the suction capacity from the operating area by way of the distal end of the shaft 1 . to prevent the eventuality in the area of the throttle opening 11 of a short - circuit between the tubes 5 and 7 , which are constructed as electrodes , as a result of liquid or of shunting by the operator &# 39 ; s finger , in the area of the throttle opening 11 , in the outer tube 7 , a recess 12 is configured surrounding the throttle opening 11 at a distance on all sides , for instance in the form of a clearance milling , as can be seen from fig6 , in which the outer insulating layer 8 has been omitted to allow better visibility . as can be seen from fig2 , the outer insulating layer 8 in the area of the throttle opening 11 also comprises a recess 13 that surrounds the throttle opening 11 at a distance on all sides , in order to ensure complete closing of the throttle opening 11 by means of one of the operator &# 39 ; s fingers . a bipolar coagulation instrument as described above is differentiated in particular in that , on the one hand , it is composed in simple manner using only a few components and thus is configured so that it can be installed at reasonable price and , on the other hand , because of the configuration of the tubes 5 and 7 , which constitute the hollow shaft 1 , as electrodes of the bipolar coagulation instrument , the entire free cross - section of the hollow shaft 1 is available as a suction and / or flushing channel . in addition , the configuration of the throttle opening 11 allows for easy , rapid , and effective regulation of the suction capacity in the interior of the hollow shaft 1 , which is configured as a suction and / or flushing channel .
the invention relates to a bipolar coagulation instrument having a hollow shaft configured as a suction and / or flushing tube and having two electrodes that are electrically insulated with respect to one another and extend beyond the distal end of the shaft . to provide a bipolar coagulation instrument that is both of simple structure and ensures an effective suction / flushing capacity , it is proposed with the invention that the hollow shaft should consist of two electrically conductive tubes coaxially mounted on one another that are electrically insulated with respect to one another and from the outside , so that the tubes constitute the electrodes .