Abstract:
An electric bending endoscope comprises a bending portion arranged to an inserting portion, a bending driving unit and a buffering member. The bending driving unit bends the bending portion, and includes a motor, a first unit and a second unit. The motor generates driving force for bending the bending portion. The first unit holds the motor. The second unit includes a driving force transmitting member. The buffering member connects the first unit to an outer member of the inserting portion, a connecting code and a switch. The buffering member absorbs external force generated during the operation of the electric bending endoscope.

Description:
This application claims benefits of Japanese Application No. 2002-287851 filed in Japan on Sep. 30, 2002, the contents of which are incorporated by this reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electric bending endoscope which electrically bends a bending portion of an inserting portion. 
   2. Description of the Related Art 
   Recently, an endoscope is widely used. Various curing treatments are performed by inserting an elongated inserting portion in the celom so as to observe the organ in the celom or by using a treatment tool inserted in a therapeutic instrument channel as needed. In the industrial field, the endoscope observes and examines inner scratches and corrosion of a steam generator, a turbine, an engine and a chemical plant by inserting an elongated inserting portion. 
   The endoscope has a bending portion which is freely bent on a base end side of an edge portion in the elongated inserting portion. Further, the endoscope receives an instruction as the amount of bending, corresponding to a bending position or a bending speed of the bending portion, by means for inputting a bending operation such as a bending operation lever or a joystick arranged to an operating portion. In the endoscope, a bending operation wire is mechanically stretched or contracted based on the amount of bending inputted as the instruction so as to bend the bending portion. 
   The above-mentioned endoscope includes an electric bending endoscope in views of the operability. For example, Japanese Unexamined Patent Application Publication No. 2-159243 discloses one of the above-mentioned electric bending endoscopes, in which a built-in motor as bending driving means is controlled for rotation, the motor&#39;s driving force enables a bending operation wire to stretch or contract, and the bending portion is electrically bent. 
   In the electric bending endoscope disclosed in Japanese Unexamined Patent Application Publication No. 2-159243, a bending operation device unit is integrally formed by connecting, to a main frame as a main frame member and a subframe, the motor as the bending operation means, a sprocket as a rotator for the stretch operation which transmits the motor&#39;s driving force to the bending operation wire, and the entire bending and stretch mechanism forming portions such as a transmission gear train. Further, the bending operation device unit is enclosed in the operating portion. 
   Similarly to the electric bending endoscope disclosed in Japanese Unexamined Patent Application Publication No. 2-159243, Japanese Unexamined Patent Application Publication No. 4-256724 discloses an electric bending endoscope in which a bending operation device unit is integrally formed by connecting, to a main frame and the like, a bending and stretch mechanism forming portions and the bending operation device unit is enclosed in the operating portion. The electric bending endoscope disclosed in Japanese Unexamined Patent Application Publication No. 4-256724 accomplishes an object of the present invention to provide the electric bending endoscope which can accurately sets a locking state and a free state with the compact size, light weight, and simple structure. 
   SUMMARY OF THE INVENTION 
   Briefly, according to the present invention, an electric bending endoscope comprises a bending portion arranged to an inserting portion, a bending driving unit and a buffering member. The bending driving unit bends the bending portion, and includes a motor, a first unit and a second unit. The motor generates driving force for bending the bending portion. The first unit holds the motor. The second unit includes a driving force transmitting member. The buffering member connects the first unit to an outer member of the inserting portion, a connecting cord and a switch. The buffering member absorbs external force generated during the operation of the electric bending endoscope. 
   The objects and advantages of the present invention will become apparent from the following detailed explanation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view showing the schematic structure of an electric bending endoscope according to a first embodiment of the present invention; 
       FIG. 2  is a perspective view schematically showing the electric bending endoscope shown in  FIG. 1  after assembling, including a cut-off part; 
       FIG. 3  is a plan view showing the electric bending endoscope shown in  FIG. 2 ; 
       FIG. 4  is a diagram showing the entire structure of an electric bending endoscope apparatus having the electric bending endoscope according to the first embodiment; 
       FIG. 5  is a diagram schematically showing main portions of the electric bending endoscope shown in  FIG. 4  formed as units; 
       FIG. 6  is a cross-sectional view showing an attaching state of a gear box and a bending and stretch mechanism portion by using a tool, describing the operation, according to the first embodiment; 
       FIG. 7  is a plan view showing an attaching state of the bending and stretch mechanism portion including an inserting portion, describing the operation, according to the first embodiment; 
       FIG. 8  is a diagram showing the structure of a gear box having a pin used for the electric bending endoscope according to a second embodiment of the present invention; 
       FIG. 9  is a diagram showing the structure of the gear box having the pin according to a modification of the pin shown in  FIG. 8 ; and 
       FIG. 10  is a cross-sectional view showing the structure of an electric bending endoscope, further showing the layout of a bending and stretch mechanism and switches in an operating portion provided for the electric bending endoscope, including a cut-off part according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinbelow, a description is given of embodiments of the present invention with reference to the drawings. 
   First Embodiment 
     FIGS. 1 to 7  show an electric bending endoscope according to a first embodiment of the present invention.  FIG. 1  is an exploded perspective view showing the schematic structure of an electric bending endoscope according to the first embodiment.  FIG. 2  is a perspective view schematically showing the electric bending endoscope shown in  FIG. 1  after assembling, including a cut-off part.  FIG. 3  is a plan view showing the electric bending endoscope shown in  FIG. 2 .  FIG. 4  is a diagram showing the entire structure of an electric bending endoscope apparatus having the electric bending endoscope according to the first embodiment.  FIG. 5  is a diagram schematically showing a main portion of the electric bending endoscope shown in  FIG. 4  as a unit.  FIGS. 6 and 7  are diagrams for explaining a method for attaching a gear box and a bending and stretch mechanism portion in the electric bending endoscope.  FIG. 6  is a cross-sectional view showing an attaching state of the gear box and the bending and stretch mechanism portion by using a tool, and describing the operation.  FIG. 7  is a plan view showing an attaching state of the bending and stretch mechanism portion including an inserting portion, and describing the operation. 
   First, a description is given of the system structure of an electric bending endoscope apparatus having the electric bending endoscope of the present invention with reference to  FIG. 4 . 
   Referring to  FIG. 4 , an electric bending endoscope apparatus  1  having an electric bending endoscope  2  comprises a bending driving portion  30  for electrically bending a bending portion  12  described later, arranged to the edge of an inserting portion  6 , a light source device (not shown) for supplying illumination light to the electric bending endoscope  2 , a video processor (not shown) for performing signal processing for image pick-up means incorporated in the electric bending endoscope  2 , and a bending control device  100  for controlling the driving operation of the bending driving portion in the electric bending endoscope  2 . Incidentally, the video processor is connected to a monitor (not shown), outputs a video signal to the monitor, and displays an endoscope image. 
   The electric bending endoscope  2  is continuously arranged to a base end of the inserting portion  6  and comprises an operating portion  7  which commonly functions as a grip portion  7   a  (refer to  FIG. 10 ). The electric bending endoscope  2  has a soft universal cord  80  extended from a side portion at the operating portion  7 . 
   A light guide or various signal cables (which are not shown) are inserted in the universal cord  80 . A connector portion (not shown) is arranged to an end portion of the universal cord  80 . Connecting cables from the light source device and the video processor (not shown) and a connecting cable from the bending control device  100  are connected detachably to the universal cord  80 . 
   Continuously arranged to the inserting portion  6  of the electric bending endoscope  2  is a hard edge portion  11  arranged to the edge thereof, a bending portion  12  which is arranged to a base end side of the edge portion  11  and is freely bent, and a flexible tube portion  13  which is long and flexible and is arranged to a base end side of the bending portion  12 . 
   The operating portion  7  of the electric bending endoscope  2  includes the grip portion  7   a  (refer to  FIG. 10 ) as a portion which is gripped by a user. In the operating portion  7 , a plurality of video switches (not shown) for remote control of the video processor are arranged at an upper portion of the grip portion  7   a . Arranged to a side surface of the operating portion  7  are an air and water supply button  66  for operating the air and water supply operation and a suction button  67  for a suction operation (refer to  FIG. 10 ). 
   Further, a therapeutic instrument inserting slit  73  (refer to  FIG. 10 ) for inserting a therapeutic instrument such as a biopsy clamp is arranged near a front end of the grip portion  7   a  of the operating portion  7 . The therapeutic instrument inserting slit  73  is connected to a channel for inserting the therapeutic instrument (not shown). A therapeutic instrument such as a clamp (not shown) is inserted in the therapeutic instrument inserting slit  73 , the edge of the therapeutic instrument is projected from the opening of the channel formed to the edge portion  11  via the channel for inserting the therapeutic instrument for biopsy, and the biopsy is performed. 
   The operating portion  7  comprises a bending operation input portion  20  for inputting the operation for bending the bending portion  12  such as a joystick and a track ball. 
   Further, a specific description is given of the electric bending endoscope  2 . A light guide  21  for transmitting the illumination light is inserted in the inserting portion  6  in the electric bending endoscope  2 . The light guide  21  reaches the connector portion of the universal cord  80  via the operating portion  7  from the base end side so as to transmit the illumination light from a light source lamp (not shown) arranged in the light source device. The illumination light transmitted from the light guide  21  illuminates a subject such as an affected part of the body from an edge surface of an illumination window (not shown) fixed to the edge portion  11  of the inserting portion via an illumination optical system  22 . 
   An illuminated subject image, namely, a subject image is captured from an observation window (not shown) arranged adjacently to the illumination window. The captured subject image is picked up by an image pick-up device  24  such as a CCD (Charge-Coupled Device) via an objective optical system  23  and is photoelectrically converted into an image pick-up signal. The image pick-up signal is transmitted via a signal cable  24   a  extending from the image pick-up device  24 , reaches the video connector of the universal cord  80  via the operating portion  7 , and is outputted to the video processor (not shown) via the connecting cable. The video processor processes the image pick-up signal from the image pick-up device  24  in the electric bending endoscope  2 , generates a standard video signal, and displays the endoscope image on a monitor. 
   A bending piece  25   a  at the front end of rotatably connected bending pieces  25  forming the bending portion  12  is connected to a base end portion of the edge portion  11  of the inserting portion in the electric bending endoscope  2 . A bending piece  25   b  at the final end of the bending pieces  25  is connected to an edge side of the flexible portion  13 . 
   A bending operation wire  26  is inserted in the inserting portion  6  to bend the bending portion  12  in the vertical and horizontal directions of an observation field of view. The edge of the bending operation wire  26  is fixed and held to the bending piece  25   a  at the front end by wax at positions corresponding to the vertical and horizontal directions of the bending portion  12 . Referring to  FIG. 5 , the bending portion  12  is bent in a desired direction and the edge portion  11  is positioned in a desired direction by stretching or contracting the bending operation wire  26  in accordance with the directions. 
   The bending operation wire  26  is connected to a chain  26 A via a connecting portion  27  in a bending and stretch mechanism portion  4 , and is stretched or contracted by the bending driving portion  30  in the operation portion  7 , thereby electrically bending the bending portion  12  (refer to  FIG. 5 ). The two bending operation wires  26  or the two chains  26 A are shown in the vertical or horizontal direction in  FIGS. 4 and 5 . 
   The bending driving portion  30  comprises the gear box  3  as a unit indicating the feature of the first embodiment and the bending and stretch mechanism portion  4  connected and fixed to the gear box  3  as a unit. 
   Referring to  FIG. 5 , the bending and stretch mechanism portion  4  comprises a sprocket  31  which winds the base end portion of the chain  26 A for fixing and holding and which stretches or contracts the chain  26 A, and a final gear  39  which is coaxially supported to the sprocket  31  and which transmits the driving force from a motor  32 . The gear box  3  comprises the motor  32  for rotating the sprocket  31 , and a decelerating gear train (also referred to as a gear train)  28  which transmits the driving force of the motor  32  to the final gear  39  and which decelerates the rotating speed of the motor  32  to generate large torque. 
   In (the bending driving portion  30  of) the gear box  3 , a clutch  33  for disconnecting the driving force of the motor  32  is arranged between the sprocket  31  and the motor  32 . Thus, (the bending driving portion  30  of) the gear box  3  disconnects the transmission of the driving force of the motor  32  by using the operation of the clutch  33  and enables a free operation of the angle. The clutch  33  is operated under the control of a control portion  35  arranged to the bending control device  100 . The clutch  33  may manually be operated. 
   A signal line  32   a  is extended from the motor  32  in the gear box  3 . The motor  32  in the gear box  3  receives a motor driving signal from a motor amplifier  34  arranged to the bending control device  100  via the signal line  32   a  in the universal cord  80 . The motor amplifier  34  is connected to the control portion  35  and is controlled by the control portion  35 . 
   The motor  32  comprises an encoder  36  which detects a rotating position as means for detecting the rotating position. A signal line  36   a  extending from the encoder  36  in the universal cord  80  is connected to the control portion  35 . The encoder  36  outputs to the control portion  35 , a rotating position signal indicating the detected rotating position of the motor  32 . 
   The sprocket  31  in the bending and stretch mechanism portion  4  converts the rotation of the motor  32  into advancing and returning motion of the chain  26 A. A potentiometer  37  for detecting the rotating position as the means for detecting the rotating position is connected to the sprocket  31 . A signal line  37   a  extending from the potentiometer  37  in the universal cord  80  is connected to the control portion  35 . Thus, the potentiometer  37  outputs to the control portion  35 , a rotating position signal indicating the detected rotating position of the sprocket  31 . 
   Reference numeral  38  denotes a switch for detecting a clutch operation and detects whether the clutch  33  is ON or OFF. A signal line  38   a  extending from the switch  38  for detecting the clutch operation in the universal cord  80  is connected to the control portion  35 . Consequently, the switch  38  for detecting the clutch operation outputs to the control portion  35 , a clutch operation signal indicating the detected operation of the clutch  33 . 
   As mentioned above, the bending operation input portion  20  such as the joystick or the track ball is arranged to the grip portion  7   a  of the operating portion  7  in the electric bending endoscope  2 . The signal line  20   a  extending from the bending operation input portion  20  in the universal cord  80  is connected to the control portion  35 . As a result, the bending operation input portion  20  outputs to the control portion  35 , a bending operation signal indicating the inputted bending operation. 
   The control portion  35  controls the motor amplifier  34  and drives the motor  32  in accordance with the bending operation signal from the bending operation input portion  20  based on the signals from the encoder  36  and the potentiometer  37  as the means for detecting the rotating position, thereby bending the bending portion  12 . 
   To accomplish the above objects, the electric bending endoscope  2  used for the electric bending endoscope apparatus  1  with the above-mentioned structure is devised. The devised electric bending endoscope  2  will be described according to the first embodiment with reference to  FIGS. 1 to 3 . 
   According to the first embodiment, referring to  FIG. 1 , the electric bending endoscope  2  comprises the gear box  3  and the bending and stretch mechanism portion  4  forming the bending driving portion  30  for bending the bending portion  12  which are formed as units, respectively. 
   As mentioned above, the operating portion  7  (refer to  FIG. 4 ) accommodates the gear box  3  and the bending and stretch mechanism portion  4 . 
   Referring to  FIGS. 2 and 3 , the gear box  3  mainly comprises an outer gear frame  9  forming the external view of the gear box  3  and an inner gear frame  10  accommodated in the outer gear frame  9 . 
   The inner gear frame  10  is made of a hard material, e.g., aluminum diecast, coaxially supports the motor  32 , and builds in the encoder  36  and the potentiometer  37 . Further, although not shown, the bending input portion  20  such as the joystick is fixed to the inner gear frame  10  via a connecting member on the top surface. 
   The decelerating gear train  28  (not shown in  FIGS. 1 and 2 ) is arranged to the side surfaces on both sides of the inner gear frame  10 . The driving force of the motor  32  is transmitted to the final gear  39  (refer to  FIG. 5 ) in the bending and stretch mechanism portion  4  via the decelerating gear train  28 . 
   As shown in  FIGS. 2 and 3 , the bending portion  12  comprises two motors  32 , two encoders  36 , and two potentiometers  37  sodas to be bent in the vertical direction or in the horizontal direction. Corresponding thereto, two decelerating gear trains  28 , two final gears  39 , and two sprockets  31  are provided. Further, according to the first embodiment, the bending portion  12  may be bent in the vertical direction or in the horizontal direction by providing one motor  32 , one encoder  36 , and one potentiometer  37  and, corresponding thereto, by one decelerating gear train  28 , one final gear  39 , and one sprocket  31 . 
   The inner gear frame  10  has, on the top surface, a connecting and fixing member  8  for fixing the main frame  4 A as a main part of the bending and stretch mechanism portion  4 , which will be described later. 
   The outer gear frame  9  for accommodating the inner gear frame  10  has, on the bottom side of the inserting portion  6 , a pair of an attaching hole  3 B and a guide portion  3   b  as fixing means for connecting and fixing the bending and stretch mechanism portion  4  or the rotating shaft  4 B as a unit. Further, the outer gear frame  9  has, on the side surface of the side of the bending and stretch mechanism portion  4  therein, an opening  3 A for fitting to the bending and stretch mechanism portion  4 . The attaching hole  3 B guides and accommodates the rotating shaft  4 B in the bending and stretch mechanism portion  4  via the guide portion  3   b  formed by being notched from the bottom surface side of the outer gear frame  9 , and coaxially supports the rotating shaft  4 B by the fitting of a positioning and fixing portion  5 . 
   Referring to  FIG. 1 , the positioning and fixing portion  5  comprises: an attaching hole  5   b  for being fit into the rotating shaft  4 B; a positioning piece  5   a  which is arranged to be projected to the inner surface side and which is R-shaped matching the inner peripheral surface of the attaching hole  3 B; and at least three positioning pins  5   c  which are arranged in the outer-peripheral direction and which are fit into three positioning holes  3   a  formed near the attaching hole  3 B of the outer gear frame  9 . 
   When the rotating shaft  4 B is connected and fixed to the gear box  3 , the bending and stretch mechanism portion  4  is fit into the opening  3 A, and the rotating shaft  4 B is accommodated in the attaching hole  3 B. Simultaneously, a base end portion of the rotating shaft  4 B is fit into the attaching hole  5   b  of the fixing portion  5  from both sides thereof, and the positioning piece  5   a  is fit into the inner-peripheral portion of the attaching holes  3 B so as to position the rotating shaft  4 B to the gear box  3 . Further, the positioning pin  5   a  is fit into the positioning hole  3   a  for the connection and fixing. Thus, the positioning operation is accurately performed and, thus, the final gear  39  coaxially arranged to the rotating shaft  4 B is accurately engaged and connected to a low-speed gear train  28  (not shown in  FIG. 1 ). 
   Referring to  FIGS. 1 and 3 , the bending stretch mechanism portion  4  has the rotating shaft  4 B on a base end side thereof. A subframe  4 C and the main frame  4 A as the main frame member are attached near the center of the rotating shaft  4 B. A pair of sprockets  31  and a pair of final gears  39  are arranged to both sides of the bending and stretch mechanism portion  4  to coaxially be supported. Therefore, the sprocket  31  and the final gear  39  are rotated integrally with the rotating shaft  4 B. The rotating shaft  4 B and the main frame  4 A may not directly be fixed. That is, the rotating shaft  4 B and the bending and stretch mechanism portion  4  are formed independently, and are formed as a part of the components of the gear box  3  which is detachably attached thereto. In this case, the main frame  4 A is connected and fixed to the gear box  3  by using only the connecting and fixing member  8 . 
   As shown in  FIGS. 1 and 3 , when the subframe  4 C has two bending and stretch paths, the subframe  4 C is arranged to partition the chain  26 A for engagement with the sprocket  31 . Upon bending the bending portion  12 , the stretch operation of the chain  26 A is accurately performed without the contact state of the chain  26 A with each other. 
   The main frame  4 A is the main frame member of the bending and stretch mechanism portion  4 , and is plate-shaped with proper intensity. The main frame  4 A is arranged to the subframe  4 C at a predetermined interval. Referring to  FIGS. 2 and 3 , a bending portion  4   a  is formed near a portion for connecting the main frame  4 A to the gear box  3  therein. The connecting and fixing member  8  is fixed to the bending portion  4   a  by screwing a screw  8   b , thereby making the stronger connecting and fixing state of the main frame  4 A and the gear box  3 . 
   In this case, the other end portion of the connecting and fixing portion  8  is arranged to the top surface of the inner gear frame  10  as a hard member, and is fixed to the inner gear frame  10  by the screw operation of the screw  8   a.    
   The connecting and fixing member  8  is made of a hard member such as a stainless member for the purpose of obtaining the intensity. Further, the intensity of the connecting and fixing member  8  may be improved by property changing the thickness or width. 
   According to the first embodiment, referring to  FIGS. 1 and 2 , the outer gear frame  9  covers the inner gear frame  10  which is built in. However, the outer gear frame  9  is not limited to this and may have neither top surface nor bottom surface of the outer gear frame  9  so as to expose the inner gear frame  10  to which the connecting and fixing member  8  is fixed so as to improve the maintenance and the assembility (refer to  FIG. 8 ). 
   Next, a detailed description is given of the operations of the electric bending endoscope  2  with reference to  FIGS. 1 to 3  and  6  and  7 . 
   It is assumed that in the electric bending endoscope  2  shown in  FIG. 2 , the maintenance of the bending and stretch mechanism portion  4  is necessary and the bending and stretch mechanism portion  4  is replaced with a new one. 
   In this case, referring to  FIG. 1 , in the electric bending endoscope  2  according to the first embodiment, the gear box  3  and the bending and stretch mechanism portion  4  are structured as the units, respectively. Thus, referring to  FIG. 2 , the connecting and fixing member  8  for connecting and fixing the gear box  3  and the bending and stretch mechanism portion  4  is detached. That is, screws  8   a  and  8   b  for fixing the connecting and fixing member  8  to the inner gear frame  10  and the main frame  4 A are rotated and detached, thereby detaching the connecting and fixing member  8 . 
   Next, the bending and stretch mechanism portion  4  is detached from the gear box  3 . Namely, the positioning and fixing portions  5  for fixing and holding the rotating shaft  4 B of the bending and stretch portion  4  to the outer gear frame  9  is detached from the attaching holes  3 B, thereby resetting the fixing and holding state of the rotating shaft  4 B. Further, the rotating shaft  4 B is moved to the opening side of the guide portion  3   b , thereby resetting the engaging state between the low-speed gear train  28  in the gear box  3  and the final gear  39  in the bending and stretch mechanism portion  4 . The bending and stretch mechanism portion  4  is completely detached from the gear box  3 . 
   When the rotating shaft  4 B is independently formed of the bending and stretch mechanism portion  4  and is formed as a part of the components of the gear box  3 , the rotating shaft  4 B is attached to the gear box  3  and only the connecting and fixing member  8  for connecting the gear box  3  to the main frame  4 A of the bending and stretch mechanism portion  4  is detached, and the chain  26 A is detached from the operation bending wire  26 , thereby detaching the bending and stretch mechanism portion  4  from the gear box  3 . That is, the bending and stretch mechanism portion  4  can be exchanged without the detachment of the rotating shaft  4 B from the gear box  3 . 
   The detached bending and stretch mechanism portion  4  is replaced with the new bending and stretch mechanism portion  4 . Unlike the conventional technology by which the entire bending operation devices in the operating portion are resolved and the expensive gear box  3  is replaced though it has relatively long life, only the inexpensive bending and stretch mechanism portion  4  which has relatively a short life is easily detached and replaced. 
   Next, it is assumed that the exchanged new bending mechanism portion  4  is connected and fixed to the gear box  3 . In this case, reversed operation of the detachment of the bending and stretch mechanism portion  4  may be executed. 
   That is, the rotating shaft  4 B of the bending and stretch mechanism portion  4  is enclosed in the attaching hole  3 B of the gear box  3 , the base end portions on both sides of the rotating shaft  4 B are fit into the attaching hole  5   b  of the positioning and fixing portion  5 , and the positioning side  5   a  is fit into the inner-peripheral surface thereof, thereby positioning the rotating shaft  4 B to the gear box  3 . Further, the positioning pin  5  is fit into the positioning hole  3   a , thereby executing the connection and fixing. Thus, the low-speed gear train  28  in the gear box  3  is engaged with and is connected to the final gear  39  in the bending and stretch mechanism portion  4 . 
   When the rotating shaft  4 B is formed independently of the bending and stretch mechanism portion  4  and is formed as a part of the components of the gear box  3 , the rotating shaft  4 B is attached to the gear box  3  and the chain  26 A in the bending and stretch mechanism portion  4  is engaged with the sprocket  31  in the rotating shaft  4 B and the chain  26 A comes into contact with the operation bending wire  26 . After that, the main frame  4 A in the bending and stretch mechanism portion  3  is positioned to the gear box  3  and the bending and stretch mechanism portion  4  is connected and fixed to the gear box  3  by using the connecting and fixing member  8 . 
   Preferably, the bending and stretch mechanism portion  4  is positioned and fixed to the gear box  3  at the position at which the loss is minimum when the driving force of the motor  32  is transmitted to the advance and return of the chain  26 A and the bending operation wire  26 . 
   According to the first embodiment, in order to satisfy the above requirements, referring to  FIGS. 6 and 7 , the bending and stretch mechanism portion  4  is positioned to the gear box  3  with much higher accuracy by using the positioning tool  14  for the connecting and fixing. 
   Referring to  FIGS. 6 and 7 , the positioning tool  14  is made of a cubic-shaped hard member having four planes of different heights, and comprises grooves  14 A for regulating the gear box forming the first and second lower planes and grooves  14 B for regulating the bending and stretch mechanism portion forming the third and fourth places higher than the first and second ones. 
   The groove  14 A for regulating the gear box regulates three directions (x-, y-, and z-directions) of the gear box  3 , and comprises: a first regulating surface  14   a  for slidably moving the gear box  3  and for regulating the vertical direction (z-direction) of the gear box  3 ; a second regulating surface  14   b  which is vertically to the first regulating surface  14   a  and which regulates the longitudinal direction (y-direction) of the gear box  3 ; and a third regulating surface  14   e  which is vertically arranged to the second regulating surface  14   b  and which regulates the horizontal direction (x-direction) of the gear box  3 . 
   The groove  14 B for regulating the bending and stretch mechanism portion comprises: a fourth regulating surface  14   c  which has the main frame  4 A of the bending and stretch mechanism portion  4  thereon and which regulates and supports the gear box  3  in the vertical direction (z-direction); a fifth regulating surface  14   d  which is vertically to the fourth regulating surface  14   c  and which regulates the horizontal direction (x-direction) of the main frame  4 A; and a sixth regulating surface  14   f  which regulates the longitudinal direction (y-direction) of the main frame  4 A of the bending and stretch mechanism portion  4  to the gear box  3 . 
   A regulating portion  4   a  for regulating the position of the main frame  4 A to the gear box  3  is formed by making a part of the side surface of the edge of the main frame  4  contact with the sixth regulating surface  14   f.    
   The height dimension of the fourth regulating surface  14   c  (difference in height from the first regulating surface  14   a ) is previously set at the best fixing position to the gear box  3 . 
   It is assumed that the bending and stretch mechanism portion  4  is positioned to the gear box  3  by using the positioning tool  14  for the connecting and fixing. In this case, referring to  FIG. 6 , the gear box  3  is placed onto the groove  14 A for regulating the gear box in the positioning tool  14 , and the bending and stretch mechanism portion  4  fixed to the gear box  3  is placed onto the groove  14 B for the bending and stretch mechanism of the positioning tool  14  by using the positioning and fixing portion  5 . 
   In this state, the gear box  3  is slid onto the first regulating surface  14   a  and comes into contact with the second and third regulating surfaces  14   d  and  14   e . Further, the main frame  4 A of the bending and stretch mechanism portion  4  is slid onto the fourth regulating surface  14   c  and comes into contact with the fifth regulating surface  14   d . Furthermore, the regulating portion  4   a  of the main frame  4 A comes into contact with the sixth regulating surface  14   f . Consequently, the main frame  4 A of the bending and stretch mechanism portion  4  is positioned to the gear box  3  in the x-, y-, and z-directions thereof with ease and continuous high-accuracy, irrespective of the manual operation of the operator. 
   After that, the main frame  4 A of the bending and stretch mechanism portion  4  is fixed to the gear box  3  by using the connecting and fixing member  8  so that the positioning state is maintained and the bending and stretch mechanism portion  4  is strongly connected to the gear box  3 . Namely, one end portion of the connecting and fixing member  8  is fixed onto the inner gear frame  10  as the hard member by the screwing operation of the screw  8   a , and the other end portion of the connecting and fixing member  8  is fixed onto the bending portion  4   a  of the main frame  4 A by the screwing operation of the screw  8   b.    
   The bending and stretch mechanism portion  4  is positioned to the gear box  3  at the position at which the loss becomes minimum upon transmitting the driving force of the motor  32  to the advance and return of the chain  26 A and the bending operation wire  26 , and the main frame  4 A is strongly connected and fixed to the gear box  3 . 
   Thus, since the bending and stretch mechanism portion  4  is connected and fixed to the gear box  3  at the best position, the transmission loss of the driving force is minimum and the motor  32  can be reduced in size as much as possible. As a result, the entire operating portions including the gear box  3  is reduced in size. Further, the gear rate of the low-speed train  28  in the gear box  3  is small and therefore the response performance of the bending operation is improved. 
   After completing the attachment of the bending and stretch mechanism portion  4 , a connecting tube  17  is attached via a substrate  15  and a connecting member  16  which are arranged to the edge portion of the bending and stretch mechanism portion  4 . Then, a cap  18  of the inserting portion  6  is fit into the other end side of the connecting tube  17  and the inserting portion  6  is attached by screwing a screw  19  via a screw hole  18   a  of the cap  18  and via a screw hole  17   a  of the connecting tube  17 . 
   According to the first embodiment, the inserting portion  6 , which is frequently used and to which external force is applied, is connected to the inner gear frame  10  as the hard member of the gear box  3  via the high-intensity members such as the cap  18 , the connecting tube  17 , the connecting member  16 , the main frame  4 A of the bending and stretch mechanism portion  4 , and the connecting and fixing member  8 . Thus, any external force (surplus force) is sufficiently absorbed during operating the electric bending endoscope  2 . Then, the tolerance is excessively improved and the transmission loss can be minimum. 
   According to the first embodiment, the gear box  3  and the bending and stretch mechanism portion  4  are detachably formed as units, respectively. Thus, the simple structure improves the assembility and the maintenance performance and the maintenance costs are reduced in the electric bending endoscope. 
   The bending and stretch mechanism portion  4  is positioned and fixed to the gear box  3 , by using the positioning tool  14 , at the best position at which the transmission loss of the driving force becomes minimum. The motor  32  can be reduced in size and this contributes to the small size of the entire operating portions including the gear box  3 . Further, the gear rate of the low-speed train  28  in the gear box  3  is small and therefore the response performance of the bending operation is improved. 
   Further, the main frame  4 A of the bending and stretch mechanism portion  4  is connected and fixed to the inner gear frame  10  as the hard member via the connecting and fixing member  8 . Therefore, any external force (surplus force) is sufficiently absorbed during the operation and the tolerance is excessively improved. 
   Second Embodiment 
     FIGS. 8 and 9  show an electric bending endoscope according to a second embodiment of the present invention.  FIG. 8  is a diagram showing the structure of a gear box having a pin used for the electric bending endoscope according to the second embodiment.  FIG. 9  is a diagram showing the structure of the gear box having a pin according to a modification of the pin shown in  FIG. 8 . Incidentally, the same components as those of the electric bending apparatus according to the first embodiment are designated by the same reference numerals in  FIGS. 8 and 9 , a description thereof is omitted, and only different portions are described. 
   According to the second embodiment, unlike the first embodiment, holding means for holding the universal cord  80  arranged in the operating portion  7  is fixed to the inner gear frame  19  of the gear box  3 . 
   Specifically, referring to  FIG. 8 , the outer gear frame  9  of the gear box  3  is formed without the top surface and the bottom surface so that the inner gear frame  9  accommodated therein is exposed. Further, a stop tool  40  as holding means for holding the universal cord  80  is fixed to the inner gear frame  9  as the hard member, by using the screw  41 . 
   In addition, referring to  FIG. 8 , the stop tool  40  comprises a ring-shaped holding portion  40 A to which the universal cord  80  is fit by screwing a screw  42  and a fixing portion  40 B which fixes the holding portion  40 A to the inner gear frame  10  of the gear box  3  by at least three plate members or stick members. 
   The holding portion  40 A has screw holes  40   a  and  40   b  at predetermined positions on the peripheral surface thereof. A connector  80 A arranged to the edge portion of the universal cord  80  is fit and is held to the gear box  3  by screwing a screw  42  via a screw hole arranged to the connector  80 A and the screw holes  40   a  and  40   b.    
   Other structure is the same as that according to the first embodiment. 
   Therefore, according to the second embodiment, the external force (surplus force) is forcedly applied to the universal cord  80  during the operation. The universal cord  80  is fixed and held to the inner gear frame  10  as the hard member of the gear box  3  by using the stop tool  40 , thereby absorbing the external force (surplus force) via the universal cord  80 . Thus, the tolerance is remarkably improved and the engagement state (connecting state) is best held between the low-speed gear train  28  in the gear box  3  and the final gear  28  of the bending and stretch mechanism portion  4 . Thus, the transmission loss of the driving force is reduced and the bending operation performance is preferably obtained. Other advantages are the same as those according to the first embodiment. 
   According to a modification of the second embodiment, the stop tool  40  as the holding means comprises the holding portion  40 A into which the universal cord  80  is fit, a fixing portion  40 B which is made of at least two plate members or stick members extended from the holding portion  40 A, and a connecting member  44  which connects the fixing portion  40 B by screwing a screw (not shown) and which fixes the fixing portion  40  to the inner gear frame  10  in the gear box  3 . Thus, the stop tool  40  as the holding means may fix and hold the universal cord  80 . In this case, the same advantages according to the first embodiment are obtained. 
   Third Embodiment 
     FIG. 10  shows an electric bending endoscope according to a third embodiment of the present invention, and is a cross-sectional view showing the structure of the electric bending endoscope, further showing the layout of a bending and stretch mechanism and switches in an operating portion provided for the electric bending endoscope, including a cut-off part according to the third embodiment of the present invention. Incidentally, the same components as those of the electric bending apparatus  2  shown in  FIG. 10  according to the third embodiment are designated by the same reference numerals and are not described, and only different portions are described. 
   According to the third embodiment, in addition to the components according to the second embodiments, bending operation means  70  having a joystick  70   a , various switches such as the air and water supply button  66 , the suction button  67 , and a scope switch (not shown) are connected to the inner gear frame  10  of the gear box  3  arranged in the operating portion  7 , via mediating members  71  and  72 . 
   Referring to  FIG. 10 , the outer gear frame  9  of the gear box  3  is formed without the top surface and the bottom surface such that the inner gear frame  9  accommodated therein is exposed. Further, fixed to the inner gear frame  10  as the hard member by screwing screws (not shown) are the mediating member  71  for fixing the joystick  70   a  and the mediating member  72  for fixing various switches such as the air and water supply button  66 , the suction button  67 , and a scope switch (not shown). 
   Other structures are the same as those according to the first and second embodiments. 
   According to the third embodiment, fixed and held to the inner gear frame  10  as the hard member of the gear box  3  are the joystick  70   a  to which the external force is forcedly applied during the operation of the endoscope including the bending operation and various switches such as the air and water supply button  66 , the suction button  67 , and the scope switch (not shown), via the mediating members  71  and  72 , thereby absorbing the external force (surplus force) via the operating members. Similarly to the second embodiment, the tolerance is excessively improved. Further, the engagement state (connecting state) is best held between the low-speed gear train  28  in the gear box  3  and the final gear  28  of the bending and stretch mechanism portion  4 . Thus, the transmission loss of the driving force is reduced and the preferable bending operation performance is obtained, that is, the equipment performance is improved. 
   Other advantages are the same as those according to the first and second embodiments. 
   In the electric bending endoscope  2  according to the third embodiment, the bending operability is improved. Technologies for improvement of the bending operability are disclosed here. 
   Referring to  FIG. 10 , in the electric bending endoscope  2  of the present invention, the center axis of the sprocket  31  of the bending and stretch mechanism portion  4  contact with the gear box  3  (not shown) is arranged to the front side of the operating portion  7  to which the various switches (the air and water supply button  66  and the suction button  67 ) are arranged, with respect to the center axis of the inserting portion  6 . On the grip portion  7   a  in the operating portion  7 , arranged to the chain  26 A engaged with the sprocket  31  in the contact state, opposed thereto, are a pair of cylindrical members  65  having the slidability for bending the chain  26 A along the center axis of the inserting portion  6 . Thus, the center axis of the sprocket  31  is arranged to the front side of the operating portion  7 , with respect to the center axis of the inserting portion  6 . Therefore, a contact portion of a thumb base of the grip portion  7   a  in the operating portion  7  becomes a sloped surface as shown in  FIG. 10 , and the grip portion  7   a  is easily gripped. 
   Further, in the electric bending endoscope  2  shown in  FIG. 10 , an angle θ 1  is formed between the center axis of the inserting portion  6  and the center axis of the joystick  70   a  as the bending operation input means  70  at the neutral position thereof, and is (135°±150°). An inclined angle θ 2  of the joystick  70   a  is ±30° from the center of the joystick  70   a . The inclined center position of the joystick  70   a  is arranged in front of the operating portion  7  with respect to the center axis of the inserting portion  6 . Thus, upon gripping the grip portion  7   a  substantially in the vertical state by the four fingers except for the thumb of the operator, the thumb operated by the joystick  70   a  is naturally placed to the position contact to the joystick  70   a . Since the inclined angle θ 2  is ±30° from the center of the joystick  70   a , it is possible to prevent the deviation of the top position of the joystick  70   a  out of a thumb-operable range. 
   Further, in the electric bending endoscope  2  shown in  FIG. 10 , an angle θ 3  is formed between the center axis of the joystick  70   a  at the neutral position thereof and the operation direction of the operation switches including at least the air and water supply button  66  and the suction button  67 . The angle θ 3  is 30° or more. 
   When the angle θ 3  is not more than 30° where the angle θ 3  is formed between the center axis of the joystick  70   a  operated by the thumb at the neutral position thereof and the operation direction of the operation switches by the index finger or middle finger, the force is applied to the index finger and the middle finger upon operating the joystick  70   a  by the thumb. The opposed operation switches (the air and water supply button  66  and the suction button  67 ) are pressed irrespectively of the operator&#39;s desire. Alternatively, upon operating the operation switches by the middle finger or the index finger, the joystick  70   a  might be pressed by the thumb though he does not desire it. However, in the example, as mentioned above, the angle θ 3  of 30° or more is formed between the center axis of the joystick  70   a  at the neutral position thereof and the operation direction of the operation switch including at least the air and water supply button  66  and the suction button  67 . Thus, both upon operating the joystick  70   a  by the thumb and upon operating the operation switches by the middle finger or the index finger, the above operation results in reducing the danger for operating the operation switches (the air and water supply button  66  and the suction button  67 ) arranged to the opposed surface of the operating portion or the joystick  70   a  though he does not desire this. 
   The above technologies improve the operability of the electric bending endoscope  2 . 
   Having described the preferred embodiments of the invention referring to the accompanying drawings, it should be understood that the present invention is not limited to those precise embodiments and various changes and modifications thereof could be made by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.