Patent Publication Number: US-6986686-B2

Title: Electrical plug for supplying electric power from a power supply to a medical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-048584, filed Feb. 23, 2001 the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a connector for medical instruments which feeds electrical power from a power supply to the medical instrument with the use of a socket and plug. 
   An ultrasound treating instrument for performing a surgical operation with the use of ultrasound has been known. The ultrasound treating instrument includes a handpiece having a transducer and transmits an ultrasonic vibration which is generated in the transducer to a probe coupled to the handpiece and performs a treating operation with a forward end of the probe set in contact with a living body. A socket of an electric power feeding cable is connected to a plug of the handpiece and, through the cable, the electric power from the power supply is fed to the transducer in the handpiece. 
   When the handpiece is used, an electric power feeding cable for transmitting a drive current is previously connected to a respective individual handpiece. The probes, if differing in types, etc., act differently upon the living tissue. The probes are different in types and kinds and selectively used in accordance with the use to which they are put. The exchange of the probes to be attached to the associated handpieces takes a lot of time and labor since they are of a detachable screw-threaded type. Such an operation is not convenient during a surgical operation. The exchange of probes has to be done quickly in accordance with the situation under which the surgical operation proceeds. It is, therefore, convenient to make exchanges for handpiece units each with an initially prepared probe attached thereto instead of effecting the exchange for probes each time. 
   In the case where the exchange of initially prepared handpiece units is done instead of the exchange of probes each time, the associated handpiece has to be replaced by another handpiece together with a cable connected thereto. 
   In this case, since such handpieces have to be initially prepared with their own special cable connected thereto, the same number of cables are needed and the situations around the instruments are messy such as the entangling of cables. Further, it is necessary to select the needed cable and re-connect it to a power supply. It is cumbersome to re-connect the selected cable to the power supply. 
   It may be considered that a common cable is used for associated handpieces. In this case, those electric contacts of a plug section of the handpiece and those electric contacts of a socket section of the cable side are exposed to the exterior. 
   Normally, the respective electric contact sections are exposed to the exterior and they are inadvertently touched by the user. If this is the case, then the contact surface of the electric contact section becomes soiled and there is a risk that the electric conduction performance will be lowered. 
   In order to prevent a lowing in the electric conduction performance of the electric contacts, one contact is formed of a male type pin and the other contact is formed of a female type narrow hole. By doing so, these contacts are fitted together to create an electric connection. The treating instrument of U.S. Pat. No. 5,395,240 is shown as a pin/hole fitting type. For this reason, the cleanability of the contact section is not good. 
   The ultrasound treating instrument used for surgery is oftened soiled with humor and blood deposited on its contact section. If this soiled state is left as it is, the electric conduction performance of the electric contact is lowered. For this reason, it is necessary to deeply clean the contact section. 
   In the pin/hole connection type, however, if the connection section surface is soiled with blood, etc., the cleanability of it is not good. In order to enhance such cleanability, it is possible to use a structure with the connection section area opened. In such an open structure, the opening section of the connector becomes greater and the electric connection section is liable to be touched by human fingers. If the contacts are inadvertently touched by a finger, etc., and a shorting occurs between the contacts, then a discharge sometimes occurs due to a charge built up in the transducer inside the handpiece under a temperature variation involved. Further, due to the greater opening section of the connector, there is also a risk that the contact section will be soiled again with a foreign substance deposited thereon. If, for example, the open structure of the U.S. Pat. No. 5,807,392 is applied to an ultrasonic handpiece, the area between the pin contacts is liable to be touched by a finger and a discharge unavoidably occurs due to the presence of a charge involved. 
   BRIEF SUMMARY OF THE INVENTION 
   A connector for a medical instrument according to the present invention comprises a medical instrument adapted to be rendered active upon receipt of electric power from a power supply to allow a treating operation to be performed on a subject; a socket connected to the medical instrument and having a first electrode to allow the electric power to be supplied to the medical instrument; and a plug provided on the medical instrument and adapted to engage the socket to allow the electric power from the power supply to the medical instrument, wherein the plug includes a second electrode having an exposed contact portion electrically connected to the first electrode to allow the medical instrument to be rendered active, at least the exposed contact portion of the second electrode being so located as an elongated portion as to extend along a moving direction in which the plug is connected to the socket, and an annular wall so provided as to surround at least the exposed contact portion of the second electrode. 
   A connector for medical instruments according to the present invention comprises a medical instrument adapted to be rendered active upon receipt of an electric power to allow a treating operation to be performed on a subject; a socket having a first electrode for supplying an electric power from a power supply to the medical instrument; and a plug provided on the medical instrument and adapted to engage the socket to allow the electric power which is fed from the power supply to be supplied to the medical instrument, wherein the plug includes a projection provided at a central area; a second electrode provided on a peripheral surface of the projection and having at least a portion exposed on the peripheral surface of the projection and electrically connectable to the first electrode to allow the medical instrument to be rendered active; and an annular wall provided to surround the peripheral surface of the projection, the annular wall and projection being spaced apart a predetermined distance from each other to define a circular groove therebetween. 
   Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is an explanatory view showing an ultrasonic coagulation incising apparatus system according to a first embodiment of the present invention; 
       FIG. 2  is a perspective view showing a handpiece of the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 3A  is a view in longitudinal cross-section as taken along line A- 0 -A′ in  FIG. 2  showing a handpiece of the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 3B  is a view in transverse cross-section as taken along line B-B′ in  FIG. 3A ; 
       FIG. 3C  is a view in transverse cross-section as taken along line C-C′ in  FIG. 3A ; 
       FIG. 4  is a perspective view showing a handpiece plug section of a handpiece of an ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 5  is a view in longitudinal cross-section, as taken along line D-D′ in  FIG. 4 , showing a handpiece plug section of the handpiece; 
       FIG. 6  is a view in longitudinal cross-section showing the cleaning of the handpiece plug section of the handpiece in the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 7  is a side view of a handpiece plug section of the handpiece and a view in longitudinal cross-section of a handpiece socket of a detachable cable unit in the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 8  is a view in transverse cross-section as taken along line E-E′ in  FIG. 7  showing the handpiece socket in the detachable cable unit; 
       FIG. 9  is a view in transverse cross-section as taken along line F-F′ in  FIG. 7  showing the handpiece socket in the detachable cable unit; 
       FIG. 10  is a view in longitudinal horizontal cross-section showing the handpiece plug section of the handpiece and the handpiece socket of the detachable cable unit in the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 11  is a view in longitudinal cross-section showing a connected state of the handpiece plug section of the handpiece and handpiece socket of the detachable cable unit in the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 12  is a view in longitudinal horizontal cross-section showing a connected state of the handpiece plug section of the handpiece and handpiece socket of the detachable cable unit in the ultrasonic coagulation incising apparatus according to the first embodiment of the present invention; 
       FIG. 13  is a view in longitudinal cross-section showing a handpiece socket of a detachable cable unit relative to a handpiece plug section of a handpiece in an ultrasonic coagulation incising apparatus according to a second embodiment of the present invention; 
       FIG. 14  is a view in longitudinal cross-section showing a connected state of the handpiece plug section of the handpiece and handpiece socket of the detachable cable unit in the ultrasonic coagulation incising apparatus according to the second embodiment of the present invention; and 
       FIG. 15  is a perspective view showing a handpiece plug section of a handpiece in a ultrasonic coagulation incising apparatus according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   An ultrasonic coagulation incising apparatus according to a first embodiment of the present invention will be explained below by referring to  FIGS. 1  to  12 . 
     FIG. 1  shows a system of an ultrasound treating apparatus. This system comprises a plurality of, or a plurality of kinds of, treating instruments, here, handpieces  201 ,  201 ,  201   a , and a common detachable cable unit  203  having a socket  232  for allowing any of these to be removably attached thereto and a cable  202 . It is to be noted that an ultrasonic transducer for generating ultrasound vibration is inserted into the handpieces  201 ,  201  and  201   a.    
   Plug sections  231  of the handpieces  201 ,  201 ,  201   a  are of a commonly connectable type and can be detachably mounted in a socket  232  of the commonly detachable cable unit  203 . 
   Here, as the handpieces, three handpieces are prepared: the handpiece  201  with a hook probe unit  205  attached thereto, the handpiece  201  with a scissors probe unit  206  attached thereto, and the handpiece  201   a  of a different kind with a trocar unit attached thereto. 
   The hook probe unit  205  and scissors probe unit  206  are detachable/exchangeable relative to the same handpiece  201  and commonly usable relative to one handpiece  201 . The handpieces  201  and  201   a  have different ultrasonic resonant frequencies. 
   The hook probe unit  205  has a hook probe  208 . As shown in  FIG. 2 , the hook probe  208  is formed with a threaded section  208   b  on its base end portion  208   a . The threaded section  208   b  of the probe  208  is threaded into, and connected to, a threaded section  212   a  of a probe attaching section  212  formed in the forward end portion of a later-described horn  211  of the handpiece  201 . A sheath  214  is fitted over the hook probe  208 . A high frequency feeding terminal  213  is provided on a base end  215  of the sheath  214 . As shown in  FIG. 3A , with a base end portion  215  of the sheath  214  fitted on the forward end portion of the handpiece  201 , the base end portion  215  is removably attached to a sheath connection section  216  provided on the forward end of the handpiece  201 . 
   The scissors probe unit  206  has a scissors probe  221 . A threaded section is formed on the base portion of the scissors probe  221 . By threading this threaded section into the threaded section  212   a  of the probe attaching section  212  formed on the forward end of the horn  211  of the handpiece  201 , the scissors probe  221  is fastened to the horn  211 . A sheath  223  including a handle  222  is fitted over the scissors probe  221 . The base end portion  224  of the sheath  223  is removably attached to a sheath connection section  216  in such a state as to be fitted over the forward end portion of the handpiece  201 . 
   The trocar unit  207  is different from the hook probe unit  205  and scissors probe unit  206  in terms of its ultrasonic resonant frequency. For this reason, the trocar probe  225  is attached to the handpiece  201   a  for exclusive use. The trocar probe  225 , although not shown, is fastened to the threaded section formed in a horn of the handpiece  201   a  as in the case of the above-mentioned handpiece. An outer sheath tube  226  is fitted over the trocar probe  225 . A base end portion  227  of the outer sheath tube  226  is removably attached to the handpiece  201   a.    
   As shown in  FIG. 1 , the handpieces  201  and  201   a  each have a handpiece plug section  231  at their proximal side end. The respective handpiece plug sections  231  are of the same type and have the same configuration. For this reason, it is possible to removably fit a common socket over the plug section  231 . 
   The handpiece plug section  231  is so constructed that the handpiece socket  232  provided on one side end of the cable  202  of the detachable cable unit  203  can be removably attached to the handpiece plug section  231 . A generator plug  233  detachably connected to a power supply generator  234  is provided on the other end of the cable  202  of the cable unit  203 . Electric power is supplied as a drive power from the power supply generator  234  through the generator plug  233  and cable  202  to a contact provided in the handpiece socket  232 . 
   As shown in  FIG. 2 , the sheath connection section  216  for connection to the sheaths  214  and  223  is provided at the forward end of the handpiece  201 . An outer covering member of the handpiece  201  is comprised of an outer case  235  formed with an annular wall. An indicator mark  236  is attached to a site on the upper surface of an outer periphery of the outer case  235  so as to provide a location mark upon the attachment of the handpiece socket  232  to the handpiece plug  231 . The handpiece plug section  231  has a position aligning groove  237  serving as a guide when the socket is attached to the plug, a connector shell  238  formed with an annular wall and having a later-described contact in its inside, and a lock guide  239  formed on the outer periphery of the connector shell  238  to allow the insertion of a lever when the lever is used to fix the handpiece socket  232  in place. 
     FIG. 3A  is a view in longitudinal cross-section of a portion as taken along line A-O-A′ in FIG.  2 . The internal structure of the handpiece  201  will be explained below by referring to FIG.  3 A. 
   The sheath connection section  216  is so constructed as to allow the sheath ( 214 ,  223 ) to be attached/detached in a simpler way. That is, the sheath connection section  216  comprises a C ring  216   a  having a C-shaped configuration for securing a proper attaching/detaching amount of force, a C-ring frame  216   b  incorporated to prevent the C-ring  216   a  being dropped, a coupling screw member  216   d  fixed to an inner case  241  constituting a structure of the handpiece  201 , and a screw member  216   c  which, together with the screw member  216   d , makes an axial length adjustment. 
   A bolted Langevin type transducer  242  is held in the inner case  241  and converts a received drive current to an ultrasonic vibration by energy conversion. The Langevin type transducer  242  is fixed in place by abutting a flange  211   a  which is formed on the proximal side end of the horn  211  against a rib  243  formed on the inner surface of the inner case  241 . A packing  245  is located in front of the flange  211   a . By threading the fixing nut  246 , that is, a threaded section  246   a  of the fixing nut  246 , into a threaded section  247  formed in the inner case  241 , the bolted Langevin type transducer  242  is fixed to, and is located in, the inner case  241 . In a boundary area between the fixing nut  246  and the horn  211 , an O-ring  248  is provided to ensure a water-tight seal between the horn  211  and the fixing nut and also prevent an axial displacement of the bolted Langevin type transducer  242 . At a contact surface between the inner case  241  and the fixing nut  246 , an O-ring  249  is provided to prevent the intrusion of vapor and liquid from the exterior. 
   The bolted Langevin type transducer  242  is of such a type that a stacked array of piezoelectric elements  251  for converting a drive electric current to an ultrasonic vibration is pressure-fixed to the rear end surface of the flange  211   a . A terminal  252  for feeding electric power is held between corresponding piezoelectric elements  251 . 
   Now an explanation will be made below about the inner structure of the handpiece plug section  231 . The connector shell  238  is provided in the handpiece plug section  231 . A case  255  for electroconductive members is provided inside of, and in contact with, the connector shell  238 . A fixing nut  256  for fixing the case  255  is fixed in place by threading a threaded section  238   a  which is formed on the connector shell  238  into a threaded section  256   a  formed in the fixing nut  256 . 
   The connector shell  238 , case  255  and fixing nut  256  are assembled as one unit and inserted into the proximal end portion of the inner case  241  in an arrayed position. These are fixed in place in the inner case  241  by means of an adhesive and pin  257 . The outer sheath  235  is fixed by an adhesive to the outer side of the inner case  241 . In order to ensure positional alignment, a projection  235   a  is fitted in an associated slit of the connector shell  238 . A packing  261  sandwiched between the connector shell  238  and fixing nut  256 , as well as an O-ring  262  located at a contact area between the inner case  241  and the outer case  235 , prevents the unsightly emergence of the adhesive to the exterior, upon being cured. 
   In the unit of the connector shell  238 , case  255  and fixing nut  256 , 4 contacts  265  for supplying the drive current from the handpiece socket  232  are provided, substantially concentrically on the peripheral surface of a connector projection  266  located at a central position of the connector shell  238 . The contact  265  has a polarity and its forward end portion extends as a plate-like portion to provide a corresponding electrode terminal. A drive current feeding terminal  267  and drive current feeding terminal  268 , as will be explained below, are press-fitted into the electroconductive members  269  and these are connected to the electroconductive members  269 . The respective electroconductive members  269  are arranged in a hole in the case  255  and, as shown in  FIG. 3B , a terminal  271  is inserted into the end portion of each electroconductive member  269  from the opposite side and is fixed to the corresponding electroconductive member  269  by means of a fixing screw  272 . The terminal  271  is formed with a U-shaped end portion and, to this, a lead wire  273  connected to the bolted Langevin type transducer  242  is soldered and connected. 
   The polarities of those contacts  265  are set to those of the drive current feeding terminals  267  and  268  for conducting the drive current shown in FIG.  3 C and those of handpiece detection terminals  275  and  276  for conducting an electric current for detecting the type of handpiece  201 . 
   As shown in  FIG. 3C , a cross-like groove  277  is formed in a surface contacting with the case  255  on the connector shell  238  side and further, in that contacting surface, a groove  279  is also formed to set a resistor  278  for detecting the type of handpiece  201 . After the resistor  278  has been set in the groove  279 , a silicone rubber  282  is filled in that gap and, by doing so, the terminals  278   a  of the resistor  278  are fixed onto a slit in the handpiece detection terminals  275  and  276 . In the cross-like groove  277 , a corresponding cross-like projection  281  on the surface of the case  255  contacting with the connector shell  238  is set and a silicone rubber  282  is filled in that gap. An O-ring  283  is provided at a contacting surface between the inner case  241  and the fixing nut  256 , an O-ring  284  is provided at a contacting area between the case  255  and the fixing nut  256 , and, further, an O-ring  285  is provided at a contacting area between the electroconductive member  269  and the case  255 . By doing so it is possible to prevent the intrusion of a vapor or liquid from these areas into an inside. 
   The electroconductive member  269  conducts a drive current fed from the drive current feeding terminals  267  and  268 . The terminals of a capacitor  286  are soldered to the U-shaped groove of the two terminals  271 . Further, these are covered with a heat shrinkable tube  287 . The capacitor  286  is fixed by silicone rubber  289  to the case  255 . 
   As shown in  FIG. 3A , a partition wall  291  is formed inside the inner case  241  and a through hole  292  is formed in the partition hole  291 . The lead wire  273  set out above extends through the through hole  292 . By doing so, the arranging position of the lead wires  273  is restricted, thereby preventing any entangling contact between the transducer  242  and the part of the lead wires  273 . For this reason, the heat shrinkable tube  287  covered around the lead wire  273  prevents the generation of frictional heat by the ultrasonic vibration as well as prevents the occurrence of short-circuiting. 
   Next, an explanation will be made below about the handpiece plug  231  of the handpiece  201 . As shown in  FIG. 4 , the connector shell  238  is formed with an annular wall surrounding the connector projection (projecting section)  266 . The connector projection  266  is situated at a central area in the connector shell  238  and located in a concentrical fashion. Fitting slits  295  for guiding, as well as contacts  265 , are provided at the outer peripheral surface of the connector projection  266 . The contact  265  is formed of a narrow strip-like plate and its longitudinal direction is located along a longitudinal axis direction of the connector projection  266 . That is, the electrode element formed of an electrode forming plate extends in an insertion direction in which the socket  232  is inserted over the plug  231 . 
   Between the connector projection  266  including the contacts  265  and the connector shell  238 , a fitting space  296  is concentrically defined as a bottomed circular groove as shown in FIG.  5  and the connector projection  266  is so defined as to leave a predetermined distance (width) relative to the connector shell  238 . In this case it is desirable that the width of the fitting space  296  be less than that of a finger. As shown, the height of the connector shell or the annular wall of the connector shell from the bottom of the groove is higher than that of the projection from the bottom of the groove. 
   The electrode elements of the contact  265  are partly exposed at the peripheral surface of the connector projection  266 . The exposed portion of the electrode element is located a predetermined distance, for example, more than a width of the contact  265 , away from a bottom surface  297  of a connector fitting groove constituting a circumferential groove. The exposed contact portion of the electrode element is also located deep into the circumferential groove from the forward end surface of the connector projection  266 . For example, the exposed portion of the electrode element is formed down to a deep position of the circumferential groove which is spaced by more than the width of the contact  265 . 
   The fitting space  296  is so dimensioned as not to allow a finger to be normally inserted therein.  FIG. 6  shows the state in which a brush section  299  of a cleaning brush  298  is inserted into, and withdrawn out of the fitting space  296 . 
     FIG. 7  shows the handpiece plug sections  231  of the handpieces  201 ,  201   a  and handpiece socket  232  of the detachable cable unit  203 . 
   The handpiece socket  232  has a cup-like socket case  301  therein and a first annular wall is formed by the socket case  301 . A socket end component part  302  is fixed to the forward end of the socket case  301  by means of an adhesive. A substantially pipe-like inner socket  303  is formed inside the socket case  301 . The inner socket  303  forms a second annular wall. The socket case  301  and inner socket  303  are arranged in a concentrical relation with a circumferential groove space defined therebetween. The second annular wall is lower than the first annular wall and located deep in the first annular wall. 
   A fitting projection  304  is formed in a direction toward the inside of the first annular wall and contacts  305  are located inside the fitting projection  304 . As shown in  FIG. 7 , a position aligning projection  306  is formed on the upper inner surface portion of the socket case  301 . 
   The contacts  305  are incorporated by an insert-molding method into a contact support  307 . The contact support  307  is inserted from a cable side into the socket case  301  and, relative to its surface contacting with the socket case  301 , an O-ring  308  is provided. The cable side end of the contact  305  projects from the contact support  307  and this projecting end is press-fitted into, and connected to, a compression-bonded terminal  309 . A heat shrinking tube  311  is covered on the outside of this connection section. 
   As shown in  FIG. 8 , a cross-like partition wall  312  is formed on the cable-side end surface of the contact support  307  to secure a greater creeping distance between the elements. These portions are covered with a filling case  313 , made of a transparent resin, in an axial direction. And silicone rubber  314  is filled into that inside gap. As shown in  FIG. 7 , a main support  317  is fixed to the socket case  301  in such a manner as to retain the filling case  313  and contact support  307  thereby and is so done by connecting a threaded section  321  on the main support  317  to a threaded section  322  in the socket case. Between the contacting surfaces of the socket case  301  and main support  317 , a packing  323  is provided to prevent the intrusion of liquid from the exterior. 
   The lead wire  273  press-fitted in the compression-bonded terminal  309  leaves wire portions with an outer sheath member stripped off the cable  202 . A shield  327  provided between the lead wire  273  and the outer sheath member is folded back on the outer surface of the cable  202  and its outside is compression bonded and fixed by a compression bond body  328 . As shown in  FIG. 9 , three fixing screws  330  are threaded from three side directions into a fixing ring  329  with their forward ends abutted against the compression bond body  328 . By doing so, the compression bond body  328  is fixedly supported, thereby preventing displacement of the cable in an axial direction and in a rotation direction. In order to hold down the fixing ring  329  in which the main support  317  is fitted, a fold prevention rubber support  334  is fixed to the main support  317  through the threading of the threaded sections  335  and  336 . 
   A packing  337  is provided between the main support  317  and the fold prevention rubber support  334  and a close-contacting rubber  338  is provided between the cable  202  and the fold preventing rubber support  334 , thereby preventing the intrusion of liquid through these portions. The fold prevention rubber  343  is mounted by latching an inner circular surface projection  342  to a flange  341  formed on the outer side surface of the main support  317 . A socket cover  345  externally covers these and is fixed to the socket case  301  through the threading of the threaded sections  346  and  347 . 
   Although, in  FIG. 7 , only two contacts are shown, four terminals are provided relative to the contacts  305  and the contacts  305  are so provided as to correspond to four poles. Into the respective terminals, the compression-bonded terminals  309  are press-fitted. These terminals are provided as a handpiece detection terminal  351  and handpiece detection terminal  352  and a drive current terminal  353  and drive current terminal  354 . A handpiece detection current and drive current are supplied to the corresponding terminals. 
     FIG. 10  is a view in longitudinal cross-section as taken in a horizontal plane of the handpiece socket  232 . As shown in  FIG. 10 , an angular hole  361  is formed at the left/right side wall portions of the socket case  301  and a lever  362  extending from a socket end component part  302  is disposed in the hole  361 . An inner layer  363  of an inwardly curved configuration is formed as an engaging section inside the lever  362 . A lock edge  364  and inclining surface  365  are provided at the end portion of the inner lever  363 . 
   An angular elongated slit  366  is formed at the left and right side wall portions of the inner socket  303 . In the slit  366 , a corresponding contact  305  extending from a contact support  307  is so arranged as to be elastically urged against an abutting surface  367  formed in the slit  366 . The slit  366  and contact  305  are arranged at four places in a symmetrical fashion. The slit  366  is provided parallel to the longitudinal axis of the socket. One end of the contact  305  is fixedly supported on the contact support  307  and the other end portion of the contact  305  can be elastically deformed on its partway. 
   As shown in  FIG. 10  where the handpiece  201  is cut along a horizontal longitudinal cross-section, a lock hole  368  is formed as a lock section in an inner case  241  at a position of the handpiece plug section  231 . An inclining surface  369  is formed near an opening of a lock guide  239 . 
   Now, the operation of the ultrasonic coagulation incising apparatus will be explained below. In use, the generator plug  233  of the detachable cable unit  203  is connected to the power supply generator  234 . The hook probe unit  205  and scissors probe unit  206  are previously attached to the handpiece  201  and, further, the trocar unit  207  is attached to the handpiece  201   a.    
   First, when the trocar unit  207  is used, the handpiece socket  232  of the detachable cable unit  203  is fitted over the handpiece plug section  231  of the handpiece  201   a  to which the trocar unit  207  has been attached. At this time, an assembly operation is performed while the position aligning projection  306  is guided along the position aligning groove  237 . When the handpiece socket  232  of the detachable cable unit  203  is attached to the handpiece plug section  231 , the inclining surface  365  of the inner lever  363  of the lever  362  is guided along the lock guide  239  and clear of the inclining surface  369 , so that the lock edge  364  is fitted into the lock hole  368 . Since the contact  305  is urged toward an inward direction, the contact  305  is set in positive contact with the contact  265  as shown in  FIGS. 11 and 12 , thus securing their electrical connection. 
   On the other hand, a handpiece detection current from the generator is immediately supplied through the generator plug  233 , cable  202 , lead wire  273  and compression-bonded terminal  309  to the handpiece detection terminal  351  and handpiece detection terminal  352  and through the contact  265  contacting the contact  305  to the handpiece detection terminal  275  and handpiece detection terminal  276 . Since the resistor  278  is connected to the forward ends of the handpiece detection terminal  275  and handpiece detection terminal  276 , the resistance values are detected and setting is made on the generator  234  side to allow a resonant frequency and electric current suitable for the handpiece  201  to be supplied as a drive current. 
   In the structure thus arranged, the handpiece socket  232  is externally fitted over the handpiece plug section  231  and a strength increased when an external force was exerted on the handpiece  201  and handpiece socket  232 . Since the fitting projection  304  is fitted in the fitting slit  295  for guiding, an optimal positional relation is ensured for electrical connection. The electrical connection capability is therefore never lowered, even if a torque moment is exerted on it. 
   Then, when a forward end of the trocar unit  207  attached to the handpiece  201   a  is set in contact with the abdominal wall of the patient and a foot switch, not shown, is depressed, a drive current from the generator  234  is conducted through the generator plug  233  and cable  202  and then through the lead wire  273  to the compression-bonded terminal  309  and then through the contact  305  constituting an inner contact surface of the inner socket  305  constituting an inner contact surface of the inner socket  303  and the contact  265  to the handpiece  201   a . The drive current is supplied from the drive current feeding terminals  267 ,  268  through the electroconductive member  269 , terminal  271  to the lead wire  273  and it is converted to an ultrasonic vibration by means of the bolted Langevin type transducer  242 . At that time, the ultrasonic vibration acts on the abdominal wall at the forward end of the trocar unit  207  to allow the abdominal wall to be pierced. 
   After this, the outer sheath tube  226  is retained and it is used to allow a treating tool to be inserted for a surgical operation under an endoscope. In a similar manner, another new outer sheath tube  226  is also set in the pierced abdominal wall. By doing so, a requisite number of outer sheath tubes are set in the pierced abdominal wall and retained there. 
   When the handpiece socket  232  is to be removed from the handpiece  201   a , the lever  362  is depressed and, by doing so, the handpiece socket  232  is pulled out of the handpiece plug section  231 . Then the lock edge  364  is unlocked from the lock hole  368  and the handpiece socket  232  can be readily removed out of the handpiece  201   a.    
   This removed handpiece socket  232  is attached to the handpiece  201  to which the hook probe unit  205  or scissors probe unit  206  has been attached. Then, the resistance of the resistor in the handpiece  201  is detected and the generator supplies a drive current so as to set a resonant frequency and current value suitable for the handpiece  201 . 
   If the foot switch is depressed in a proper timing, the drive current from the generator  234  is supplied to the handpiece  201  and it is converted to an ultrasonic vibration, so that a treating operation can be performed at the forward end of the respective probe. 
   When the hook probe unit  205  and scissors probe unit  206  are used in an exchangeable way, a handpiece  201  with one of these probe units is removed from the handpiece socket  232  by depressing the lever  362  and another handpiece  201  with the other probe unit is attached to the handpiece socket  232  and this new handpiece is used. 
     FIG. 6  shows the state in which the fitting space  296  at the handpiece plug section  231  of the handpiece ( 201 ,  201   a ) is washed. Washing is made by moving a brush section  299  of a cleaning brush  298  into and out of the fitting space  296  of the handpiece plug section  231 . The brush section  299  can reach the inner corners of the fitting space  296 . Further, the fitting space  296  has a gap of about 2 to 4 mm and the operator&#39;s finger, etc., cannot be inserted into the gap. However, the brush section  299  of the cleaning brush  298  can be inserted into the space  296 , so that it is possible to clean the fitting space  296 . 
   According to this structure, the connector can be fitted into the fitting space and, since the cleaning brush can be inserted into this narrow space, the cleanability of electric contacts in the connector is improved. As a result, it is possible to prevent a lowering in electrical conduction capability. Needless to say, the inside of the cable-side socket is wider than the fitting space of the handpiece and there arises no problem from the standpoint of its washing. In case a liquid such as water enters the connector, the contacts are located a given distance away from the inner bottom of the connector and, even if a little amount of liquid is accumulated there, there arises no shortening between the contacts. If a somewhat greater amount of liquid is pooled inside the connector, the handpiece ( 201 ,  201   a ) is tilted toward a lateral side direction and, by doing so, the liquid is flowed out of the connector. Therefore, there arises no “shorting” problem. In the handpiece socket  232  on the detachable cable unit  203  side, even if a liquid enters the inside of the contact, the slit  366  is provided on the rear side of the contact and serves as a liquid drain, so that it is quickly drained. Therefore, no shorting occurs between the contacts. 
   According to the present embodiment, needless to say, the desired probes can be quickly exchanged without the need of connecting and disconnecting the probes through their threaded sections. 
   According to the present invention, as set out above, there is provided a connector for medical instruments capable of detachably connecting the plug for the medical instrument to the socket for power supply, the connector ensuring an electrical conduction capability by preventing electric contacts in the connector from being soiled and preventing an operator&#39;s finger from unduly touching the electric contacts. 
   An ultrasonic coagulation incising apparatus according to a second embodiment of the present invention will be described below by referring to  FIGS. 13 and 14 . The second embodiment constitutes a variant of the first embodiment and an explanation will be made below mainly about its different aspect. 
   A packing  401  is provided at that surface of a socket case  301  on the detachable cable unit  203  side against which a connector shell  238  is abutted. As shown in  FIG. 14 , when a handpiece socket  232  is attached to a handpiece plug section  231 , the end face of the connector shell  238  is abutted against the packing  401 . In this attached state, even if the associated parts are exposed to a liquid, the liquid cannot enter the inside of the connector, so that it is possible to prevent a shorting between contacts. According to the second embodiment of the present invention it is possible to obtain the same advantages as those of the first embodiment. 
   An ultrasonic coagulation incising apparatus according to a third embodiment of the present invention will be described below by referring to FIG.  15 . The third embodiment constitutes a variant of the first embodiment of the present invention and an explanation will be made below mainly about its different aspect. 
   In this ultrasonic treating instrument, a handpiece is comprised of one kind of system and it is not necessary to provide a detection resistor. As shown in  FIG. 15 , therefore, it is only necessary that a contact  265  be arranged in two places. 
   The advantages of this variant are the same as those of the first embodiment of the present invention except that it is not possible to use a different handpiece. 
   Although the above-mentioned first to third embodiments have been explained as being preferred embodiments of the present invention, the present invention is not restricted to the first to third embodiments. That is, the present invention relates to a connector for medical instruments including a medical instrument unit having a plug and a medical instrument unit having a socket engaging the plug. The present connector can be applied to all those medical instrument units which, when the plug and socket engage each other, are rendered active based on an electric power fed from a power supply. For example, the present invention can be used for a plug/socket system involving an electric surgical knife and heating surgical knife. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.