Abstract:
A connection mechanism is provided with a plate member formed with a polygonal hole, the plate member including a first plate and a second plate overlaid with each other, each of the first plate and the second plate being formed with the polygonal hole, a shaft member formed with a polygonal column section fitted in the polygonal hole formed on the plate member, and a fixing mechanism that fixes the first plate and the second plate with each other to retain a status where the first plate and the second plate are urged oppositely in a rotational direction about a central axis of the shaft member.

Description:
BACKGROUND OF THE INVENTION 
     The following descriptions relate to a connection mechanism for connecting a plate member and a shaft member employed, for example, in an endoscope. 
     Generally, at an operation section of an endoscope, connection mechanisms such as a mechanism for operating a bending portion of an insertion section of the endoscope, a mechanism for changing an rising angle of a treatment tool and the like are provided. Such a mechanism employs a connection mechanism which connects the plate member with the shaft member such that the plate member does not rotate relative to the shaft member. 
     Typically, in such a connection mechanism, a portion of the shaft member is formed to have a shape of a polygonal column, and a polygonal opening to be engaged with the polygonal column portion is formed on the plate member. By fitting the polygonal column portion into the polygonal opening, the plate member and the shaft member do not rotate with respect to each other. An example of such a configuration is disclosed in Japanese Patent Provisional Publication No. HEI 9-98942. 
     When the above structure is employed, due to manufacturing errors, there may be some play between the plate member and the shaft member in the rotational direction. If an endoscope having such a problem is shipped as a product, an operator of the endoscope may not operate the endoscope (e.g., the operator may not control the degree of bend of the bendable section as intended). 
       FIG. 9  shows a conventional connection mechanism to deal with the above problem, and  FIG. 10  is a cross section taken along line X-X in  FIG. 9 . In  FIGS. 9 and 10 ,  92  denotes the plate member, and  91  denotes the shaft member. According to this example, screw holes  93  which extend substantially in a radial direction with respect to a central axis  91   ax  of the shaft member  91  are formed on the plate member  92 . The shaft member has a polygonal column section  91   x  which is inserted in a polygonal opening  92   x . Then, by inserting screws  94  through the screw holes  93  and fastening the same, tip ends of the screws  94  press-contact the polygonal column section  91   x  in the radial directions, respectively, thereby play between the plate member  92  and shaft member  91  can be prevented. 
     In order to prevent the play between the plate member  92  and the shaft member  91  effectively, however, as shown in  FIG. 10 , at least three screws  94  should be used to push the polygonal column section  91   x  in different directions. That is, if only a single screw  94  is used, the plate member may incline with respect to a plane perpendicular to the central axis  91   ax  of the shaft member  91 . Since the three screws  94  should be employed, assembling work of the structure shown  FIGS. 9 and 10  is inefficient. Further, in the structure shown in  FIGS. 9 and 10 , the screws  94  may be loosened relatively easily, and after elapse of a relatively short period, play may occur between the plate member  92  and shaft member  91 . 
     SUMMARY OF THE INVENTION 
     The present invention is advantageous in that an improved connection mechanism for connecting the shaft member formed with the polygonal section and the plate member formed with a corresponding polygonal opening without play therebetween with a relatively simple structure. 
     According to an aspect of the invention, there is provided a connection mechanism, which is provided with a plate member formed with a polygonal hole, the plate member including a first plate and a second plate overlaid with each other, each of the first plate and the second plate being formed with the polygonal hole, a shaft member formed with a polygonal column section fitted in the polygonal hole formed on the plate member, and a fixing mechanism that fixes the first plate and the second plate with each other to retain a status where the first plate and the second plate are urged oppositely in a rotational direction about a central axis of the shaft member. 
     Since the first plate and the second plate are urged oppositely in the rotational direction, the polygonal section of the shaft is kept tightly fitted in the polygonal hole. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is an exploded perspective view of a connection mechanism according to a first embodiment. 
         FIG. 2  is a side view of an endoscope employing the connection mechanism shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional side view of the connection mechanism according to the first embodiment. 
         FIG. 4  is a cross-sectional plan view of the connection mechanism taken along line IV-IV in  FIG. 3 . 
         FIG. 5  is a cross-sectional side view of a connection mechanism according to a second embodiment. 
         FIG. 6  is a cross-sectional side view of a connection mechanism according to a third embodiment. 
         FIG. 7  is a plan view of the connection mechanism according to the third embodiment. 
         FIG. 8  is a plan view of a connection mechanism according to a fourth embodiment. 
         FIG. 9  is a cross-sectional side view of a conventional connection mechanism. 
         FIG. 10  is a cross-sectional plan view of the conventional connection mechanism taken along line X-X in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, referring to the accompanying drawings, connection mechanisms according to embodiments of the invention will be described. 
       FIG. 2  shows a side view of an endoscope  100  to which a connection mechanism according to the invention is applicable. The endoscope  100  has a flexible insertion section  1  and a distal end portion thereof is formed to be a bendable section  2 . The bendable section  2  is driven by operation of an operation unit  3  connected to the proximal end of the insertion section  1 . 
     Specifically, the operation unit  3  is provided with a bendable section operating knob  4  (hereinafter, simply referred to as a knob), which is rotatable with respect to the operation unit  3 . By rotating the knob  4 , one of a plurality of operating wires connected to the bendable section  2  is pulled, and the bendable section  2  is bent by an amount (i.e., angle) corresponding to the rotated amount of the knob  4 . In  FIG. 2 ,  6  denotes a bent state retaining knob to be used for retaining the bent state of the bendable section  2 . 
       FIG. 3  is a cross-sectional side view of the connection mechanism according to the first embodiment. In  FIG. 3 ,  60  denotes a braking mechanism for applying frictional force for preventing the rotational movement of the knob  4  in accordance with the operation of the bent state retaining knob  6 . The braking mechanism  60  is secured to a shaft member  7  which is fixedly secured onto the flame of the operation unit  3 . A plate member  10  unrotatably connected to the shaft member  7  serves as a fixed member for braking operation. 
     It should be noted that the various braking mechanisms have been known, and since the present invention relates to a connection mechanism, which is a part of the braking mechanism and may be applied to other connecting mechanism, the operation of the braking mechanism  60  will not be described for brevity. An example of such a braking mechanism is disclosed in Japanese Patent Provisional Publication No. 2007-313292. 
     The shaft member  7  is provided with a polygonal column portion  7   x . According to the first embodiment, a regular hexagonal column is employed. However, any other polygonal column may be used. The shaft member  7  has a cylindrical shape at portions other than the polygonal column portion  7   x . At a boundary between the cylindrical portion and the polygonal portion  7   x , as shown in  FIG. 3 , a step  7   a  is formed. 
     The plate member  10  includes first plate  11  and second plate  12 , which are overlaid in the direction of the central axis  7   ax  of the shaft member  7  with each other, as shown in  FIG. 4  showing a cross-sectional plan view of the connection mechanism taken along line IV-IV in  FIG. 3 , and  FIG. 1  showing an exploded perspective view. 
     As clearly shown in  FIG. 1 , the second plate  12  has a disk-like member. On the first plate  11 , a circular recess  13  is formed such that the second plate  12  is loosely fitted in the recess  13 . 
     On the first plate  11  and second plate  12 , polygonal (i.e., in the first embodiment, hexagonal) openings  11   x  and  12   x  to which the polygonal section  7   x  of the shaft member  7  tightly fitted in are formed, respectively. 
     As shown in  FIG. 3 , the first plate  11  is fitted on the polygonal section  7   x  such that the lower surface of the first plate  11  contacts the step  7   a , and the second plate  12  is fitted on the polygonal section  7   x  and loosely fitted in the recess  13 . With this structure, the plate member  10  does not rotate relative to the shaft member  7 . 
     However, due to manufacturing errors, the size of the polygonal openings  11   x  and  12   x  may be not tightly fitted on the polygonal column section  7   x , and play may remain in the rotational direction with respect to the central axis  7   ax  of the shaft  7 . 
     As shown in  FIG. 1  and  FIG. 4 , a screw hole  8  is formed on the first plate  11  such that a central axis  8   ax  of the screw hole  8  extends from an outer circumferential surface to the recess  13 . As shown in  FIG. 4 , the direction where the screw hole  8  extends (i.e., the direction of the central axis  8   ax  of the screw hole  8 ) is inclined with respect to a tangential line  7   t  at which the central axis  8   ax  of the screw hole  8  intersects a circumferential surface of the second plate  12  (i.e., the screw hole  8  extends in a non-radial direction). Further, a screw  9  having a coned tip end is screwed in the screw hole  8  from the outer periphery of the first plate  11  toward the second plate  12 . 
     By fastening the screw  9  tightly, the first plate  11  and the second plate  12  are urged to rotate in opposite directions as indicated by arrows in  FIG. 4 . Therefore, the polygonal opening  11   x  and polygonal opening  12   x  fasten the polygonal column section  7   x  in opposite directions. As a result, the plate member  10  is fixedly secured onto the polygonal column section  7   x  without any play at all in the rotational direction. 
     It should be noted that the present invention need not be limited to the above-described exemplary embodiment, and various modifications may be made without departing from the scope of the invention. 
       FIG. 5  is a cross-sectional side view of a connection mechanism according to a second embodiment. According to the second embodiment, a groove  12   a  having a V-shaped cross section may be formed on the circumferential surface of the second plate  12  so that part of the pressing force of the screw  9  is converted to urge the second plate  12  toward the first plate  11 . 
       FIG. 6  is a cross-sectional side view of a connection mechanism according to a third embodiment, and  FIG. 7  is a plan view of the connection mechanism according to the third embodiment. According to the third embodiment, a screw hole  8 A is formed on the first plate  11  in the direction parallel to the central axis of the shaft  7 , and a loose hole  80  allowing a screw  9 A with play is formed on the second plate  12 . According to the third embodiment, the user manually applies force to rotate the first plate  11  and the second plate  12  in opposite directions as indicated by arrows in  FIG. 6 , and with applying the urging force, the screw  9 A is fastened tightly. 
       FIG. 8  is a plan view of a connection mechanism according to a fourth embodiment. The fourth embodiment has a structure similar to the third embodiment except that a plurality of screws  9 A (thus, a plurality of holes  8 A) are used. 
     The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2007-163337, filed on Jun. 21, 2007, which is expressly incorporated herein by reference in its entirety.