Abstract:
Within a flexible angling joint tube which is connected to a rigid tip end section of an endoscopic insertion instrument and which is formed by connecting a predetermined number of angle rings successively and pivotally by the use of pivoting pins, a plural number of operating wires are passed in an axial direction via the respective pivoting pins. Fore ends of the operating wires are fixedly anchored at fixation points in boundary portions of the rigid tip end section and the flexible angling joint tube. An operating wire fixation point for at least one operating wire is shifted to an angular position in the circumferential direction from a normal position on an axial extension line from a row of pivoting pins. A wire guide pin is fixedly provided at least one of angle rings which are connected by the foremost pivoting pins to guide the one operating wire in such a way as to evade at least a top portion of the foremost pivoting pin as the one operating wire is pulled or pushed in the axial direction to bend the angling joint tube.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Art 
     This invention relates generally to endoscopic insertion instruments for medical use, and more particularly to a flexibly bendable, angling joint tube for use as an angle portion of endoscopic insertion instruments. 
     2. Prior Art 
     Firstly, illustrated in FIG. 8 is a general layout of a typical endoscopic insertion instrument in use in medical fields. The endoscopic insertion instrument is largely constituted by a manipulating head assembly  1 , a rod-like insert member  2  which is extended out on the front side of the manipulating head assembly  1  for insertion into a body cavity, and a universal cable  3  which is led out on the rear side of the manipulating head assembly  1  for connection to a light source. The insert member  2  comprises at least a rigid tip end section  2   a  which is internally provided with an observation means, an angle section  2   b  which is connected to the proximal end of the rigid tip end section  2   a , and a lengthy flexible body section  2   c  which extends from the manipulating head assembly  1  to the proximal end of the angle section. In the case of optical or directly viewing type endoscopes in general, an illumination window or windows  4  and an observation window  5  are provided in a distal end face of the rigid tip end section  2   a  as shown in FIG. 9 as an endoscopic observation means. The illumination windows  4  are provided for the purpose of projecting illumination light on intracavitary areas under observation, while the observation window  5  is provided for the purpose of observing intracavitary portions of interest therethrough. In addition, endoscopes of this sort are generally arranged to permit insertion of a surgical or therapeutic instrument such as forceps through the insertion instrument as soon as a disorder or a diseased portion is spotted in an intracavitary portion under observation through the observation window. For this purpose, an outlet  6  of a biopsy channel is opened in the distal end face of the rigid tip end section  2   a  side by side with the illumination and observation windows  4  and  5 . Further, a wash nozzle  7  is provided on the rigid tip end section to supply a wash liquid toward the observation window to wash away body fluids or other contaminant liquids therefrom, and then to supply compressed air to dissipate liquid droplets which may remain on the surfaces of the observation window after washing. 
     The angle section  2   b  is generally arranged as shown in FIG.  10 . Namely, the angle section  2   b  is in the form of a flexible tube  11  of a jointed ring structure consisting of a series of pivotally connected angle rings  10 . The flexible tube  11  is wrapped in metal wire mesh  12  which is in turn encased in an outer tube forming an outer skin layer  13 . The angle rings  10  of the flexible tube  11  includes end rings at the fore and proximal ends to be connected to the rigid tip end section  2   a  and the flexible body section  2   c , respectively, and angle rings which are connected in intermediate positions between the two end rings. FIG. 10 shows a fore end portion of the anglr section  2   b.    
     Indicated at  10   a  is a front end ring  10   a  which is fitted in a rigid casing  9   a  of the rigid tip end section  2   a . An insulating cap  9   b  is fitted on a fore end face of the rigid casing  9   a . Accordingly, the fore end  10   a  constitutes part of a distal rigid section of the insert portion  2 . At a proximal end away from the rigid casing  9 , the front end ring  10   a  is provided with a pair of ear portions at the opposite right and left sides thereof, in overlapped relations with ear portions of a first angle ring  10   1 . The overlapped ear portions of the front end ring  10  and the first angle ring  10   1  are pivotally connected with each other by a pivoting pin  14 . These ear portions are formed in a flat plane. At the opposite end away from the front end ring  10   a , the first angle ring  10   1  is provided with axial extensions at the upper and lower sides thereof, in overlapping relations with axial extensions of a second angle ring  10   2 . These overlapped axial extensions are pivotally connected with each other by a pivoting pin  14 . In the same manner, the second angle ring  10   2 , third angle ring  10   3 , fourth angle ring  10   4  and so forth are pivotally connected one after another by means of pivoting pins  14  alternately by way of right and left ear portions and upper and lower axial extensions. Accordingly, two adjacent angle rings which are connected by way of the right and left ear portions are flexible toward and away from each other through a predetermined angle in vertical directions, while two adjacent angle rings which are connected by way of the upper and lower axial extensions are flexible toward and away from each other through a predetermined angle in lateral or rightward and leftward directions. Thus, the flexible tube  11 , which is formed by successively connecting a large number of angle rings  10  in the above-described manner, is flexible in upward and downward directions and in rightward and leftward directions as well. Since both of the metal wire mesh  12  and outer skin layer  13  which wrap in the flexible tube  11  are flexible, the angle section  2   b  can be turned arbitrarily in upward, downward, rightward and leftward directions. 
     For bending the angle section  2   b  into a desired direction, an angling knob  8  is provided on the manipulating head assembly  1 . For this purpose, a number of operating wires  15  are employed to transmit an operating force from the angling knobs  8  to the angle section  2   b . Since the angle section  2   b  are flexibly bent in four directions, namely, in upward, downward, rightward and leftward directions as mentioned hereinbefore, the operating wires  15  are constituted by four operating wires or two pairs of operating wires, including a first pair of upper and lower operating wires and a second pair of right and left operating wires. At the time of bending the angle section  2   b  in an upward or downward direction, an operator manipulates the angling knob  8  in such a way as to pull one of the upper and lower operating wires while pushing out the other wire. When bending the angle section  2   b  rightward or leftward, an operator manipulates the angling knob  8  in such a way as to pull one of the right and left operating wires while pushing out the other wire. By so doing, the angle section  2   b  is bent in a direction in which a tensile operating force prevails. Further, the upper and lower operating wires can be manipulated in combination with the right and left operating wires to turn the angle section  2   b  in a twisted form. 
     Accordingly, within the flexible tube  11 , the four operating wires are located strictly in predetermined four separate positions which are shifted from each other by 90 degrees in phase or in the circumferential direction and which are in the close proximity of inner surfaces of the flexible tube  11 . Besides, the operating wires  15  should be arranged to be movable smoothly in pushing and pulling directions or in axially in forward and backward directions but should be retained in the respective positions without deviations in radial and circumferential directions. For this purpose, the operating wires  15  are associated with guide means utilizing pivoting pins  14  as shown in FIG.  10 . 
     More specifically, the pivoting pins  14 , which function to pivotally connect preceding and succeeding angle rings  10 , are each provided with a bulged head portion which is projected radially inward within the flexible tube  11  to serve as a wire guide  16 . Each wire guide  16  is bulged in a dome-like shape and provided with a through hole or a wire passage  16   a  which is bored axially through its dome-like body. The operating wires  14  are slidably threaded respectively through the wire passages of the wire guides  16 . In this regard, it has also been known in the art to employ flat-head pivoting pins and to pass the operating wires  14  through lancing arches which are formed in the annular body portions of the angle rings  10 . Further, there may be employed guide pins, for example, as disclosed in Japanese Laid-Open Patent Application H3-68326, which are provided with a flange at one end, in addition to an aperture providing a guide passage for an operating wire. In this case, the guide pins are projected into the flexible tube from outside through apertures which are bored at predetermined positions of annular bodies of the angle rings. 
     In any case, fore ends of the operating wires  15  are fixed either to the front end ring  10   a  or to the rigid casing  9  of the rigid tip end section. For fixing the fore ends of the operating wires  15 , it is the general practice to provide inward lancing arches  17  on the front end ring  10   a , passing fore end portions of the operating wires  15  through the lancing arches  17 , folding back the passed fore end portions to one side of the lancing arch  17 , and fixing the folded fore end portions by soldering  18 . Alternatively, after passing a fore end portion of an operating wire through a lancing arch which is provided on the front end ring, a ball-like bulging is formed at the fore end of the operating wire to stop same from coming out of the lancing arch. Further, in some cases, grooves are provided on the outer periphery of the rigid casing, and fore ends of operating wires are fixedly anchored in the grooves by soldering or other means. 
     Fitted internally of and through the insert member  2  are various components including a light guide which is extended as far as the illumination windows  4 , a signal cable from a solid-state image sensor which is located at the focus of an optical objective lens system in the observation window  5  (or an image guide in the case of an optical endoscope), a biopsy channel which is connected to the instrument projecting outlet  6 , and a fluid conduit tube which is connected to the washing nozzle  7 . All of these components are flexible at least in bending directions, and accordingly are fitted, so to say, in an unfixed state within limited internal spaces of the angle section  2   b  and the flexible body section  2   c  without being fixed in particular positions. As seen in FIG. 10, the observation window  5  on the rigid tip end section  2   a  is constituted by an axial bore  5   a , and an optical objective lens system  20  having its lens tube  21  fitted in the axial bore  5   a . The optical axis of the objective lens system  20  is bent through 90 degrees by a prism  22  which is located at the rear end of the lens tube  21 . As an image pickup means, a solid-state image sensor device  23  is mounted on a substrate circuit board  24  and connected with the prism  22  through a cemented joint. Indicated at  25  is a signal cable which is connected to the substrate wiring board  24  of the solid-state image sensor device  23 . Further, the instrument projecting outlet  6  is provided on the rigid tip end section  2   a  at a position substantially beneath the observation window  5 . This instrument projecting outlet  6  is constituted by a passage which is bored axially through the rigid tip end section  2   a , and a connector pipe  26  which is fitted in the instrument projecting outlet  6  and projected out of the rigid tip end section  2   a  by a predetermined length on the side of the angle section  2   b . Connected to the projected proximal end of the connector pipe  26  is a fore end of a flexible tube which serves as the biopsy instrument channel  27 . 
     The internal space of the front end ring  10   a , which is connected to the rigid casing  9   a , forms part of a rigid fore end portion of the insert rod portion  2  and accommodates therein various components, including part of the lens tube  21  and the prism  22  of the endoscopic observation means which is mounted in the rigid tip end section  2   a , along with the solid-state image sensor device  23  and its substrate circuit board  24  and the connector pipe  26  of the biopsy instrument channel  27 . These components are restricted by the positions of the through bore  5 a and the instrument projecting outlet  26  which are provided on the rigid tip end section  2   a  either to mount the endoscopic observation means or to fit in the connector pipe  26 . Further, although not shown in the drawings, the above-mentioned light guide as well as the fluid conduit tube is connected to an aperture hole which is provided on the rigid tip end section  2   a  through a rigid pipe having a proximal end thereof projected into the internal space of the front end ring  10   a.    
     Within the internal space of the front end ring  10   a , a lancing arches  17  and a soldered connection  18  are provided at four different positions for fixing fore ends of the operating wires  15 , taking up a relatively large portion of the internal space of the front end ring  10   a . On the other hand, positional relations within the front end ring  10   a  of the respective component parts which are fitted in the insert member  2  are restricted by positions of the illumination and observation windows  4  and  5 , instrument projecting outlet  6  and washing nozzle  7 , which are located in such positions as would be necessary or at least desirable from the standpoint of operating the endoscope. For instance, it is desirable for the observation window  5  to be located in a position which is as close as possible to a line connecting the upper and lower operating wires  15 . On the other hand, it is desirable to locate the illumination windows  15  on the opposite lateral sides of the observation window  5  for the purpose of uniformly illuminating an observation view field. Further, for washing the observation window  5 , the position of the washing nozzle  7  is naturally determined and restricted by that function. The instrument projecting outlet  6  should desirably be located in a position which is as close as possible to the observation window  5  and immediately beneath the observation window  5  or as close as possible to a center line of upward and downward bending movements, which connects the upper and lower operating wires  15 . However, if the respective components are located in most desirable positions form the standpoint of endoscopic operation, interferences are very likely to occur between these component parts and the lancing arches  17  or the soldered connections  18 . Therefore, when laying out the instrument projecting outlet  6  and illumination windows  4  on the basis of a position of the observation window  5 , difficulties are usually encountered in locating these parts in most suitable positions. 
     Regarding the operating wires  15 , the distance between the lacing arches  17  and foremost wire guides, through which the operating wires are threaded, remains unchanged, so that this part does not contribute to bending of the angle section  2   b  to any substantial degree. Accordingly, the positions of the lancing arches  17  can be shifted in the circumferential direction in case they interfere with positions of the instrument projecting outlet  6  and illumination windows  4 . However, if the positions of the lancing arches  17  are shifted, the operating wires  15  are bent angularly between the foremost wire guides  16  and the lancing arches  17  and therefore are subjected to larger friction forces within the wire guides  16  each time when the wires  15  in a slackened state are pulled into a tensioned state for an angling operation, making it difficult to move the operating wires  15  smoothly in addition to increased possibilities of damages to the wires  15 . In this connection, the angular bending of the operating wires  15  can be moderated by increasing the distance between the foremost wire guides  16  and the lancing arches  17 . However, an increase of that distance is inevitably reflected by an increase in length of the rigid portion at the distal end of the insert rod portion  2 , which makes it difficult to introduce the endoscope smoothly into a body cavity smoothly and without arousing much pains on the part of a patient. 
     SUMMARY OF THE INVENTION 
     With foregoing situations in view, it is an object of the present invention to provide an angling joint tube to be connected to a proximal end of a rigid tip end section of an endoscopic insertion instrument as an angle section, having an operating wire fixation point, which fixedly anchors a fore end of one of operating wires of the angling joint tube, shifted by a predetermined angle from a normal position in the circumferential direction, in combination with a wire guide member which is arranged to minimize a slant angle of the operating wire running toward the angularly shifted wire fixation point. 
     It is another object of the present invention to provide an angling joint tube of the sort as mentioned above, which permits a greater freedom in laying out various component parts to be fitted into the endoscopic insertion instrument, without necessitating to increase the diameter of the insertion instrument. 
     It is a further object of the present invention to provide an angling joint tube of the sort as mentioned above, which can prevent interference between a fore fixation point of an operating wire of the angling section and a biopsy channel even in a case an observation window and an instrument projecting outlet of the biopsy channel on a rigid tip end section of the endoscopic insertion instrument are both located in the proximity of a center line of upward and downward bending movements of the rigid tip end section. 
     According to the present invention, in an endoscopic insertion instrument having a flexibly bendable angle section connected contiguously to a proximal end of a rigid tip end section and adapted to be manipulated through a plural number of operating wires, the angle section including a flexible tube formed by pivotally and successively connecting a plural number of angle rings through pivoting pins, the operating wires being extended axially through the flexible tube via the pivoting pins and having fore ends thereof fixedly anchored at operating wire fixation points in boundary portions between the flexible tube and the rigid tip end section to bend the angling section in an arbitrary direction by pulling or pushing the operating wires, there is provided an angling joint tube for use as an angle section of an endoscopic insertion instrument, which is characterized by the provision of: at least an operating wire fixation point shifted by a predetermined angle in circumferential direction of the flexible tube from a normal position on an axial extension line from a row of pivoting pins to fix at least one operating wire in an angularly shifted position; a wire guide fixedly mounted on a wire guide pin fixedly planted at least on one of angle rings, which are connected by a foremost one in the row of pivoting pins, and arranged to guide the one operating wire in such a way as to evade at least a top portion of the foremost pivoting pin as the operating wire is manipulating in a pulling or pushing direction. 
     In this instance, it is desirable for a wire guide pin to be provided on each one of the two angle rings which are connected by the foremost pivoting pin which is evaded by the operating wire, and in the same angular positions on the two angle rings in the circumferential direction thereof. In this connection, for ensuring smooth movements of the operating wire and at the same time for protection of the operating wire, the two wire guide pins through which the one operating wire is threaded are preferably welded to the respective angle rings in a tilted state in a direction of moderating a slant angle of the operating wire which is bent toward the angularly shifted wire fixation point. 
     In routing the operating wires through the angling joint tube, each one of the operating wires can be threaded successively through guide holes of wire guide portions which are provided on the pivoting pins which are arranged in rows in the axial direction to successively connect the angle rings of the flexible tube. In this case, the pivoting pin to be evaded by one operating wire is preferably constituted by a flat-head pivoting pin. 
     The above and other objects, features and advantages of the present invention will become apparent from the following particular description of the invention, taken in conjunction with the accompanying drawings which show by way of example one preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a fragmentary longitudinal section through a fore end portion of an endoscopic insertion instrument, including an angle section employing an angling joint tube according to the present invention; 
     FIG. 2 is a schematic cross section, taken on line II—II in FIG. 1; 
     FIG. 3 is a schematic longitudinal section of a flexible tube, taken  18  on line III—III of FIG. 1; 
     FIG. 4 is a schematic front view of a wire guide pin; 
     FIG. 5 is a schematic sectional view, taken on line V—V of FIG. 4; 
     FIG. 6 is a schematic sectional view, taken on line VI—VI of FIG. 4; 
     FIG. 7 is a schematic view of a wire guide pin fixedly anchored in an angle ring; 
     FIG. 8 is a schematic view of an endoscope, showing general layout of the endoscope; 
     FIG. 9 is an outer view of a fore distal end portion of an insertion instrument of the endoscope shown in FIG. 8; 
     FIG. 10 is a longitudinal section of a prior art endoscopic insertion instrument; and 
     FIG. 11 is a cross-sectional view of one of lancing arches shown in FIG.  10 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereafter, the present invention is described more particularly by way of its preferred embodiment shown in the accompanying drawings. In the following description of a preferred embodiment which has no differences in particular from the above-described prior art in basic layout of component parts except layout of a path or paths of an operating wire or wires in the angle portion of the endoscope, those component parts which are equivalent or identical with the counterparts in the above-described prior art are designated by similar reference numerals or characters to avoid repetitions of same explanations. 
     As shown in FIGS. 1 and 2, from the standpoint of maneuverability of the endoscope and of biopsy or surgical instruments, a center line of a view field through the observation window  5  on the rigid tip end section  2   a  should desirably be located on or close to a center line of vertical or upward and downward bending movements, while the instrument projecting outlet  6  should desirably be located immediately beneath the observation window  5  and as close as possible to the center line of the upward and downward bending movements. Provided at a position above the lens tube  21  and prism  22 , which are fitted in the observation window, is a lancing arch  17  for fixing an upper operating wire  15  which is pulled at the time of turning the rigid tip end section in an upward direction. Located beneath the lens tube  21  and prism  22  are a connector pipe  26  which is extended rearward from the instrument projecting outlet  6  and a biopsy channel  27  which is in turn fitted on a proximal end of the connector pipe  26 , on an axial extension line from a wire guide  16  of a pivoting pin  14  on the front end ring, through which a lower operating wire is threaded as indicated by a reference numeral  115 . This lower operating wire  115  is pulled at the time of a downward turning or bending operation. 
     In the positional relations as described above, a lancing arch  17  which fixedly anchors the fore end of the lower operating wire  115  is provided in a position which is shifted by a predetermined angle in the circumferential direction from a normal position to avoid interference with the instrument projecting outlet  27 , that is to say, to make a space for the instrument projecting outlet  27 . Accordingly, it becomes possible to set the instrument projecting outlet  27  in a most desirable position on the rigid tip end section  2   a . If desired, the top position of the front end ring  10   a  and/or the position of a lancing arch of a right or left operating wire may be similarly shifted by a certain angle in the circumferential direction, for the purpose of increasing the freedom of layout of the respective internal component parts of the rigid tip end section  2   a.    
     Illustrated in FIG. 3 is an exemplary embodiment in which, of the four operating wires of the endoscope, the position for fixing the fore end of the lower operating wire  115  is shifted from a normal position in the circumferential direction. As seen in that figure, the first angle ring  10   1 , next to the front end ring  10   a  is pivotally connected to the latter on the opposite right and left sides by means of pivoting pins. At the same time, the first angle ring  10   1  is pivotally connected to a next or second angle ring  10   2  on the upper and lower sides thereof. Similarly, the second angle ring  10   2  is pivotally connected to a next or third angle ring  10   3  on the right and left sides, the third angle ring  10   3  is pivotally connected to a next or fourth angle ring  10   4  on the upper and lower sides, and the fourth angle ring  10   4  is pivotally connected to a next or fifth angle ring  105  on the right and left sides thereof. 
     At the proximal end of the angle section  2   b  which is connected to the flexible body section  2   c , more particularly, at the point of pivotal connection between the third and fourth angle rings  10   3  and  10   4  which are pivotally connected with each other by a pivoting pin  14  with a wire guide  16 , the lower operating wire  115  is threaded through a wire passage hole  16   a  of the wire guide  16 . However, as indicated at  114 , the first and second angle rings  10   1  and  10   2  are connected by a flat pivoting pin without a wire guide. Therefore, the operating wire  115  is bypassed by the flat pivoting pin  114  and threaded through a lancing arch  117  which is provided on the front end ring  10   a  at a radially shifted position relative to an axial extension line from the pivoting pin  14 . This arrangement permits to increase the length of that part of the operating wire  115  which is angularly bent in the circumferential direction, that is to say, to moderate the bending angle of the operating wire  115 . Namely, an angular shift in the circumferential direction of the position of the lancing arch  117  can be absorbed to some extent between the lancing arch  117  and the pivoting pin  14  which pivotally connects the fourth and fifth angle rings  10   4  and  10   5 . 
     Further, the flat pivoting pin  114 , which is provided with no wire guide and therefore bypassed by the operating wire  115 , is projected from the inner peripheral surface of the flexible tube  11 . Accordingly, it is necessary to prevent the operating wire  115  from entangling around the pivoting pin  114  or colliding against and riding over the large diameter portion  114   a  of the pivoting pin  114  at the time when the operating wire  115  is deflected in a lateral direction, namely, at the time when the operating wire  114  in a slackened state in a meandering shape is tensioned by a pull or at the time of a compound bending operation using the upper and lower operating wires in combination with the right and left operating wires. 
     To this end, the operating wire  115  is guided in such a way as to dodge the flat pivoting pin  114 . More specifically, a wire guide pin  131  is planted in an aperture which is bored in the annular body portion of each one of the first and second angle rings  10   1  and  10   2  which are connected by the flat pivoting pin  114 , at a position approximately intermediate between the pivoting pin  114  and the lancing arch  117 . As shown in FIGS. 4 to  6 , these guide pins  131  are each constituted by a main body  133  with a guide hole  132  which is diverged toward the opposite ends thereof, and a stopper flange  134  which is provided at outer end of the main body  133 . The aperture which is provided in the angle pin for mounting the wire guide pin  131  is formed in an diameter which is larger than the outside diameter of the main body  133  of the wire guide pin  131  but smaller than the flange  134 . Thus, the wire guide pins  131  can be inserted into the flexible tube from outside the angle rings  10   a  and  102  such that the respective wire passage holes  132  lie in the axial direction of the angle section  2   b , and fixed in position from outside by spot welding. 
     By fixing the wire guide pins  131  to the angle rings  10   1  and  10   2  by spot welding as described above, it becomes possible to omit a post-fixation treatment such as a washing treatment which would become necessary in case the wire guide pins are fixed by soldering or the like. Besides, if desired, dummy operating wires may be threaded through the wire passage holes  132  of the wire guide pins  131  before spot welding the latter to the angle rings. In such a case, by connecting the operating wires  115  to the dummy wires and then pulling out the dummy wires, the operating wires  115  can be smoothly threaded through the wire passage holes  132  of the wire guide pins  131  despite the positions of the wire guide pins  131  are shifted in the circumferential direction as compared with the wire guides  16  on the pivoting pins  14 . 
     In the manner as described above, after being threaded through a wire passage hole  16 a of a wire guide  16  on a pivoting pin  14  which connects the third and fourth angle rings  10   3  and  10   4 , the operating wire  115  is passed successively through the wire guide pins  131  which are provided on the angle rings  10   2  and  10   1 , and then the fore end of the operating wire  115  is threaded through the lancing arch  117  and folded back and fixed by soldering. Thus, the operating wire  115  is routed completely clear of the flat pivoting pin  114 , being guided angularly relative to the longitudinal axis of the angling section  2 b between the pivoting pin  14  and the wire guide pin  131  on the second angle ring  10   2  and parallel with the longitudinal axis between the two wire guide pins  131 . From the wire guide pin  131  on the first angle ring  10   1  to the lancing arch  117 , the operating wire  115  is guided angularly again relative to the longitudinal axis of the angling section  2   b.    
     At the interval between the second angle ring  10   2  and the third angle ring  10   3 , the operating wire  115  is guided in a rectilinear form so that a pulling force on the operating wire  115  acts to reduce the breadth of the interval, permitting to apply a bending force to the second and third angle rings  10   2  and  10   3  in a reliable manner and with a smaller load. Accordingly, the operating wire  115  can be manipulated smoothly at the time of bending the angling section  2   b  downward. Besides, since the operating wire  115  is guided to evade the flat pivoting pin  114  in an assured manner as described above, it can be retained out of contact with the flat pivoting pin  114  at the time of pushing and pulling operations. 
     In this instance, as a result of location of the lancing arch  117  in an angularly shifted position, the operating wire  115  is slanted from the longitudinal axis of the angling section  2   b , starting from the pivoting pin  14  between the third and fourth angle rings  10   3  and  10   4 . In this regard, actually the distance of this slant section can be made large enough for minimizing the slant angle of the operating wire  115 . In order to further reduce the slant angle of the operating wire  115  for ensuring its smooth movements, the wire guide pins  131  can be fixed to the angle rings  10   1  and  10   2  in an inclined state as shown in FIG.  7 . This can be done by spot-welding a circumferential portion of the stopper flange  134  as indicated at S. By so doing, the flange  134  as a whole can be fixed to the outer peripheral surface of the angle ring in an inclined state. 
     As shown in FIG. 3, the main body  133  of the wire guide pin  131  on the angle ring  10   1  is tilted in the direction of arrow D thereby to moderate the slant angle of the operating wire  115  between the wire guide pin  131  to the lancing arch  117 . On the other hand, the wire guide pin  131  on the angle ring  10   2  is tilted inversely in the direction of arrow U to moderate the slant angle of the operating wire  115  between the wire guide pin  131  and the wire guide  16  on the pivoting pin  14 . These arrangements contribute to make the movements of the operating wire  115  smooth at the time of bending the angling section  2   b  in a downward direction, and to lessen the load of operation. 
     As a guide member for threading an operating wire at a predetermined radial position within the flexible tube of the angling section, a lancing arch may be formed in the annular body portion of the angle ring in place of the above-described pivoting pin with a wire guide portion if desired.