Patent Publication Number: US-2023148840-A1

Title: Endoscope

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2020/024594 filed on Jun. 23, 2020, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscope having a channel tube for allowing insertion of a treatment instrument and performing air feeding, water feeding, or the like. 
     2. Description of the Related Art 
     Endoscopes are widely utilized in a medical field nowadays. The endoscopes enable organs in a body cavity as a subject to be observed by inserting an elongated insertion section into the body cavity. Further, an endoscope includes a channel tube inserted through the insertion section to enable various types of treatments to be performed using a treatment instrument inserted through the channel tube, and enable air feeding, water feeding, or the like through the channel tube to be performed. 
     A proximal end side of such a channel tube is connected to a tubular member such as a forceps pipe sleeve provided in an operation section. In this case, in order to ensure watertightness of a connection part between the channel tube and the forceps pipe sleeve or the like, the channel tube is commonly fixed to the forceps pipe sleeve or the like by bonding. 
     Japanese Patent Application Laid-Open Publication No. 2009-39465, for example, discloses a tube fixing member for fixing a piping tube (channel tube) to a piping pipe (tubular member) having a circumferential projection formed on an outer circumferential surface. The tube fixing member includes an inner tube overlaid on the piping tube so as to be slidable in an axis line direction and an outer tube overlaid on the inner tube so as to be slidable in the axis line direction, and a plurality of slits and a circumferential groove are formed in the inner tube. Then, the tube fixing member causes the circumferential groove to engage with a bulging part of the tube formed by the piping pipe, and slides the outer tube to press the bulging part, so that the piping tube can be connected to the piping pipe. 
     SUMMARY OF THE INVENTION 
     An endoscope according to an aspect of the present invention includes an insertion section inserted into a body of a subject, an operation section provided on a proximal end side of the insertion section, a channel tube provided in a direction of a longitudinal axis of the insertion section, a proximal end side of the channel tube being arranged in the operation section, and a pipe sleeve provided in the operation section and including a tube insertion hole on a distal end side, the proximal end side of the channel tube being inserted in the tube insertion hole, in which an inner diameter at a first position on a proximal end side of the pipe sleeve is larger than an inner diameter at a second position in a hole part that communicates with a proximal end of the tube insertion hole of the pipe sleeve, the inner diameter at the second position of the pipe sleeve is smaller than an inner diameter at a third position in the tube insertion hole, and the pipe sleeve includes an abutting surface at the proximal end of the tube insertion hole, the abutting surface abutting on the proximal end side of the channel tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a left side view showing an endoscope; 
         FIG.  2    is a cross-sectional view showing an essential part of an operation section; 
         FIG.  3    is an exploded perspective view showing the essential part of the operation section; 
         FIG.  4    is a cross-sectional view of a pipe sleeve; 
         FIG.  5    is an explanatory diagram of a contact stress acted on an O-shaped ring; 
         FIG.  6    is an exploded perspective view showing an essential part of an operation section according to a first modification; 
         FIG.  7    is an explanatory diagram of a contact stress acted on an O-shaped ring according to the first modification; 
         FIG.  8    is a cross-sectional view showing in an exploded manner the essential part of the operation section according to the first modification; and 
         FIG.  9    is a cross-sectional view showing in an exploded manner an essential part of an operation section according to a second modification. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are related to an embodiment of the present invention, and  FIG.  1    is a side view showing an endoscope. 
     An endoscope  1  shown in  FIG.  1    is an endoscope adapted to observation and treatment of kidney pelvis, a ureter, or the like, and is a disposable endoscope without the intention of reuse in the present embodiment. An essential part of the endoscope  1  is configured to include an elongated insertion section  2  inserted into a subject, an operation section  3  provided in a manner coupled to a proximal end side of a longitudinal axis (central axis) O 1  of the insertion section  2  with the interposition of a bend preventing portion  4 . 
     An essential part of the insertion section  2  is configured to include a distal end portion  10 , a bending portion  11 , and a flexible tube portion  12  sequentially from a distal end side in a direction along the longitudinal axis O 1 . 
     An image pickup unit connected to a signal line and illumination optics configured to irradiate the subject with illumination light transmitted by a light guide bundle (neither shown), for example, are provided inside the distal end portion  10 . 
     The distal end portion  10  is further provided with a channel opening part  10   a  to be connected to a distal end of a channel tube  15  (see  FIGS.  2  and  3   ) which will be described later. 
     The bending portion  11  is configured so as to be bendable in four directions of up, down, left and right directions, for example, in accordance with an operation of a bending operation lever  25  which will be described later provided in the operation section  3 . 
     The flexible tube portion  12  is configured by a tubular member having flexibility. 
     The operation section  3  has an enclosure  20  having a substantially rectangular parallelepiped shape which is long in a direction of the longitudinal axis O 1  of the insertion section  2 , for example, and a region from an intermediate place of the operation section  3  to the proximal end side is set as a grasping section  21  for a user or the like to grasp the operation section  3 . 
     The bending operation lever  25  is provided at the proximal end of the operation section  3 . In the present embodiment, the bending operation lever  25  is a joystick-type operation lever, for example, and is configured so as to be movable in a tilted manner in all the directions including the front, back, left and right directions as viewed from the user grasping the grasping section  21  such that the distal end side (the insertion section  2  side) is directed to the lower side. Then, the user or the like is able to operate the bending operation lever  25  to move in a tilted manner with the thumb of a hand grasping the grasping section  21 , for example. Note that although four bending operation wires (not shown) caused to extend in a protruding manner from the insertion section  2  into the operation section  3 , for example, are connected to the bending operation lever  25  so as to operate the bending portion  11  in a bending manner in conjunction with the tilted movement of the bending operation lever  25 , these components are well known and explanation is thus omitted. 
     A front-side projecting portion  22  having a substantially triangular side view shape is provided on a front side of the operation section  3  closer to the distal end side than the grasping section  21 . A universal cable  26  through which the signal line, the light guide bundle, and the like from the insertion section  2  are inserted is caused to extend in a protruding manner from a lower surface of the front-side projecting portion  22 . More specifically, a bend preventing portion  27  is held on a screen side of the front-side projecting portion  22 , and the universal cable  26  penetrates the bend preventing portion  27  and is caused to extend in a protruding manner obliquely downward. 
     A rear-side projecting portion  23  having a substantially triangular side view shape is further provided on a rear surface side of the operation section  3  on the distal end side with respect to the grasping section  21 . A forceps pipe sleeve  28  as a tubular member is caused to protrude from an upper surface of the rear-side projecting portion  23 . In other words, the forceps pipe sleeve  28  of the present embodiment is caused to protrude obliquely upward from the upper surface of the rear-side projecting portion  23  so as to ensure excellent insertion performance when the user or the like inserts a treatment instrument with a hand opposite to the hand grasping the grasping section  21 . Consequently, the forceps pipe sleeve  28  of the present embodiment is set such that a central axis O 2  passing through a treatment instrument insertion opening  28   a  as an opening part is different from the axial direction of the central axis O 1  of the insertion section  2  (that is, such that the central axis O 2  intersects with the central axis O 1  inside the operation section  3 ). 
     Inside the operation section  3 , the channel tube  15  extending in a protruding manner from the insertion section  2  is connected to the forceps pipe sleeve  28 . Herein, the channel tube  15  is made of a material having excellent sliding performance, such as polytetrafluoroethylene, so as to improve insertion performance of the treatment instrument and the like. 
     Next, a configuration on the distal end side of the operation section  3  will be described with reference to  FIGS.  2  and  3   . 
     As shown in  FIG.  3   , the enclosure  20  that configures the operation section  3  of the present embodiment is formed separately to the left and right by a first enclosure member  30  that mainly configures a right portion and a second enclosure member  31  that mainly configures a left portion. 
     Recessed parts  35  each having a semicircular shape with a diameter substantially identical to the diameter of a proximal end side of the bend preventing portion  4  are respectively provided in wall parts that form distal end surfaces of the first enclosure member  30  and the second enclosure member  31 . Further, keys  36  each having a semicircular shape protruding in a radially inner direction are respectively provided in the respective recessed parts  35 . 
     The respective recessed parts  35  and the respective keys  36  are intended for forming a stepped through-hole having a circular shape as a whole when the first enclosure member  30  and the second enclosure member  31  are joined, and holding a proximal end side of the insertion section  2  in the operation section  3  with the interposition of the bend preventing portion  4 . 
     In order to achieve such holding, a key groove  4   a  to be fitted over the respective keys  36  is provided on a proximal end side of the bend preventing portion  4 . 
     Then, when the first enclosure member  30  and the second enclosure member  31  are joined, a proximal end portion of the bend preventing portion  4  is held between the respective recessed parts  35 , and the respective keys  36  are fitted in the key groove  4   a . This causes the bend preventing portion  4  holding a proximal end side of the insertion section  2  to be fixed in a state positioned on the enclosure  20  in a predetermined manner. Then, such fixing of the bend preventing portion  4  causes the proximal end side of the insertion section  2  to be provided in a manner coupled to the operation section  3 . 
     In the first enclosure member  30  and the second enclosure member  31 , recessed parts  37  each having a semicircular shape with a diameter substantially identical to the diameter of a proximal end side of the bend preventing portion  27  are respectively provided in a wall part that forms the lower surface of the front-side projecting portion  22 . Further, keys  38  each having a semicircular shape protruding in the radially inner direction are respectively provided in the respective recessed parts  37 . 
     The respective recessed parts  37  and the respective keys  38  are intended for forming a stepped through-hole having a circular shape as a whole when the first enclosure member  30  and the second enclosure member  31  are joined, and holding a proximal end side of the universal cable  26  with the interposition of the bend preventing portion  27 . 
     In order to achieve such holding, a key groove  27   a  to be fitted over the respective keys  38  is provided on the proximal end side of the bend preventing portion  27 . 
     Then, when the first enclosure member  30  and the second enclosure member  31  are joined, a proximal end portion of the bend preventing portion  27  is held between the respective recessed parts  37 , and the respective keys  38  are fitted in the key groove  27   a . This causes the bend preventing portion  27  holding the proximal end side of the universal cable  26  to be fixed in a state positioned on the enclosure  20  in a predetermined manner. In other words, such fixing of the bend preventing portion  27  causes the proximal end side of the universal cable  26  to be provided in a manner coupled to the operation section  3 . 
     In the first enclosure member  30  and the second enclosure member  31 , recessed parts  39  each having a semicircular shape with a diameter larger than an outer diameter of the forceps pipe sleeve  28  are respectively provided in a wall part that forms the upper surface of the rear-side projecting portion  23 . Further, keys  40  each having a semicircular shape protruding in the radially inner direction are respectively provided in the respective recessed parts  39 . 
     The respective recessed parts  39  and the respective keys  40  are intended for forming a stepped through-hole having a circular shape as a whole when the first enclosure member  30  and the second enclosure member  31  are joined, and holding an intermediate place of the forceps pipe sleeve  28  in the operation section  3 . 
     In order to achieve such holding, a pair of outward flanges  28   b  each having a diameter substantially identical to the diameter of the recessed parts  39  are provided in the intermediate place of the forceps pipe sleeve  28  at an interval substantially identical to the width of the keys  40 . 
     Then, when the first enclosure member  30  and the second enclosure member  31  are joined, the respective outward flanges  28   b  are held between the respective recessed parts  39  with the interposition of the respective keys  40 . This causes the forceps pipe sleeve  28  to be fixed in a state positioned on the operation section  3  in a predetermined manner such that a proximal end side protrudes to the outside of the enclosure  20  and a distal end side is arranged inside the enclosure  20 . 
     Herein, as shown in  FIGS.  2  and  4   , a first tapering hole  28   c  that decreases in diameter from the treatment instrument insertion opening  28   a  as a proximal end toward a distal end side is provided inside the forceps pipe sleeve  28  on the proximal end side. The first tapering hole  28   c  is a hole for connecting a syringe or the like not shown, and has an inner diameter, a taper angle, and the like strictly managed. 
     On the other hand, a tube insertion hole  28   d  having a diameter substantially identical to the diameter of the channel tube  15  is provided inside the forceps pipe sleeve  28  on the distal end side. The tube insertion hole  28   d  is caused to extend with a length L more than or equal to a predetermined length in the direction of the central axis O 2  of the forceps pipe sleeve  28 , and allows insertion of a proximal end side of the channel tube  15 . Herein, “having a diameter substantially identical” means that the outer diameter of the channel tube  15  and the inner diameter of the tube insertion hole  28   d  substantially match within a range that allows manufacturing tolerances. More specifically, “having a diameter substantially identical” indicates that the outer diameter of the channel tube  15  and the inner diameter of the tube insertion hole  28   d  substantially match to such a degree that the channel tube  15  can be inserted in the tube insertion hole  28   d  even in a case where there are manufacturing tolerances. The length of the tube insertion hole  28   d  in this case is set to be sufficiently longer than the length (a design value) of the channel tube  15  on the proximal end side designed to be inserted in the tube insertion hole  28   d.    
     Inside the forceps pipe sleeve  28 , a first cylindrical hole  28   e  is provided in a manner coupled to a distal end of the first tapering hole  28   c.    
     Inside the forceps pipe sleeve  28 , a second tapering hole  28   f  that decreases in diameter from the proximal end side toward the distal end side communicates with a distal end of the first cylindrical hole  28   e.    
     Inside the forceps pipe sleeve  28 , a second cylindrical hole  28   g  as a hole part communicates with a distal end of the second tapering hole  28   f.    
     The first cylindrical hole  28   e , the second tapering hole  28   f , and the second cylindrical hole  28   g  are intended for relaying the first tapering hole  28   c  and the tube insertion hole  28   d.    
     Inside the forceps pipe sleeve  28 , a seal holding hole  28   h  as an elastic member storage part communicates with a distal end of the tube insertion hole  28   d . The seal holding hole  28   h  is formed by a recessed part provided in a recessed manner from a distal end surface of the forceps pipe sleeve  28  in a direction of the longitudinal axis O 2 . 
     Then, a continuous through-hole that penetrates the forceps pipe sleeve  28  from the proximal end side to the distal end side is formed by the first tapering hole  28   c , the first cylindrical hole  28   e , the second tapering hole  28   f , the second cylindrical hole  28   g , the tube insertion hole  28   d , and the seal holding hole  28   h.    
     Herein, an inner diameter r 1  at a proximal end (a first position) of the first tapering hole  28   c  is set to be larger than an inner diameter r 2  in the second cylindrical hole  28   g  (a second position) that communicates with the tube insertion hole  28   d . The inner diameter r 2  in the second cylindrical hole  28   g  (the second position) is set to be smaller than an inner diameter r 3  in the tube insertion hole  28   d  (a third position). The inner diameter r 2  in the second cylindrical hole  28   g  (the second position) is set to be smaller than or equal to an inner diameter of the channel tube  15 . An inner diameter r 4  in the seal holding hole  28   h  (a fourth position) is set to be larger than the inner diameter r 3  in the tube insertion hole  28   d  (the third position). 
     The inner diameter r 2  in the second cylindrical hole  28   g  (the second position) and the inner diameter r 3  in the tube insertion hole  28   d  (the third position) change discontinuously. Accordingly, an abutting surface  28   i  on which a proximal end of the channel tube  15  can abut is formed at a proximal end of the tube insertion hole  28   d.    
     Inside the operation section  3  (the enclosure  20 ), the channel tube  15  caused to extend in a protruding manner from a proximal end of the insertion section  2  is connected to the tube insertion hole  28   d  of the forceps pipe sleeve  28  by insertion. In order to ensure airtightness and liquid tightness between the forceps pipe sleeve  28  and the channel tube  15 , an O-shaped ring  45  as an elastic member is held in the seal holding hole  28   h  in a state penetrated by the channel tube  15 . 
     Describing specifically, the proximal end side of the channel tube  15  inserted through the insertion section  2  is caused to directly extend in a protruding manner inside the operation section  3  without being connected to a relay channel tube or the like. 
     The channel tube  15  is arranged inside the operation section  3  in a state bent from the axial direction of the central axis O 1  of the insertion section  2  toward the axial direction of the central axis O 2  of the forceps pipe sleeve  28 . Then, the proximal end side of the channel tube  15  is inserted in the tube insertion hole  28   d  in an unbonded state after penetrating the O-shaped ring  45 . 
     Note that since the material such as polytetrafluoroethylene is commonly a material having a low affinity with an adhesive, pretreatment such as etching treatment (tetra-etch treatment) needs to be performed when bonding the channel tube  15  made of polytetrafluoroethylene or the like. However, since the channel tube  15  of the present embodiment is inserted in the tube insertion hole  28   d  in the unbonded state, etching treatment or the like is not performed. 
     Herein, a partition wall  46  as a restriction member is provided inside the enclosure  20  at a position proximate and opposed to a distal end of the forceps pipe sleeve  28  held in the enclosure  20  (see  FIGS.  2  and  3   ). 
     The partition wall  46  is intended for preventing the O-shaped ring  45  from coming off the seal holding hole  28   h . Thus, the partition wall  46  is arranged at a position where the interval from the distal end of the forceps pipe sleeve  28  is less than the thickness of the O-shaped ring  45  (more preferably, less than ½ of the thickness of the O-shaped ring  45 ), and is formed integrally with the first enclosure member  30 , for example. The partition wall  46  is provided with a slit  46   a  having a substantially U-shape, and the channel tube  15  is inserted in the tube insertion hole  28   d  in a state having passed through the slit  46   a.    
     Watertightness can be ensured without bonding insofar as the O-shaped ring  45  has an outer diameter having a size larger than or equal to an opening of the seal holding hole  28   h  provided on the distal end side of the forceps pipe sleeve  28  and an inner diameter smaller than or equal to the outer diameter of the channel tube  15 . A force of the O-shaped ring  45  to return to an original state under compression restricts coming off of the channel tube  15 . 
     In other words, when the O-shaped ring  45  in a state through which the channel tube  15  is inserted is inserted in the seal holding hole  28   h  as shown in  FIG.  5   , the O-shaped ring  45  is sandwiched between the inner wall surface (an inner circumferential surface) of the seal holding hole  28   h  and an outer circumferential surface of the channel tube  15  to become elastically deformed. In the present embodiment, more specifically, the O-shaped ring  45  is sandwiched among the inner wall surface of the seal holding hole  28   h  (the inner circumferential surface of the forceps pipe sleeve  28 ), the outer circumferential surface of the channel tube  15 , and a wall surface of the partition wall  46 , and is pushed against the respective surfaces (see solid arrows in  FIG.  5   ) to become elastically deformed. 
     This brings the O-shaped ring  45  into elastic contact with the inner wall surface of the seal holding hole  28   h , the outer circumferential surface of the channel tube  15 , and the wall surface of the partition wall  46 . In other words, by virtue of the restoring force, the O-shaped ring  45  comes into elastic contact at least with the inner wall surface of the seal holding hole  28   h  and the outer circumferential surface of the channel tube  15 . Then, a contact stress (see open arrows in  FIG.  5   ) of the O-shaped ring  45  brought into elastic contact produces frictional forces between the O-shaped ring  45  and the seal holding hole  28   h  and between the O-shaped ring  45  and the channel tube  15 . Accordingly, the proximal end side of the channel tube  15  is held inside the tube insertion hole  28   d.    
     A guide wall  47  as an auxiliary member is further provided inside the operation section  3  at a position corresponding to at least a part of a bending region A of the channel tube  15  and at a position that conforms to an outer side of bending of the channel tube  15 . 
     The guide wall  47  is intended for, when a treatment instrument or the like inserted from the treatment instrument insertion opening  28   a  of the forceps pipe sleeve  28  passes through the bending region A in the channel tube  15 , restricting the treatment instrument or the like pressing an inner wall of the channel tube  15  to move in a direction to the outer side of the bending. Thus, the guide wall  47  has a wall surface having a shape bending from the axial direction of the central axis O 1  of the insertion section  2  in the axial direction of the central axis O 2  of the forceps pipe sleeve  28  (that is, a shape bending along the bending shape of the channel tube  15 ). The treatment instrument or the like is thus prevented from moving in the direction to the outer side of the bending, and is guided to the insertion section side of the endoscope along bending of the wall surface of the guide wall  47 . Herein, the direction to the outer side of the bending indicates a direction directed to the guide wall  47  as seen from the bending region A in the channel tube  15  (that is, a direction directed from the bending region A in the channel tube  15  toward the outer side of the bending of the channel tube  15 ). 
     Rigidity of the guide wall  47  is ensured by being made of a material more rigid than the material of the channel tube  15 , and is formed integrally with the first enclosure member  30 , for example. 
     Note that although the guide wall  47  is preferably made of a material more rigid than the material of the channel tube  15  as described above, rigidity may be ensured by changing the thickness (thickening) even if the same material is used, for example. 
     According to the embodiment having such a configuration, by bringing the O-shaped ring  45  into elastic contact at least with the channel tube  15  and the forceps pipe sleeve  28  in an elastically deformed state, and holding the proximal end side of the channel tube  15  inside the tube insertion hole  28   d  by means of the frictional forces caused by the contact stress of the O-shaped ring  45  brought into elastic contact, the proximal end side of the channel tube  15  can be connected to the forceps pipe sleeve  28  with a simple configuration and easy operability. 
     In other words, by providing the seal holding hole  28   h  for storing the O-shaped ring  45  in the distal end side of the forceps pipe sleeve  28  in a recessed manner, sandwiching the O-shaped ring  45  between the inner wall surface of the seal holding hole  28   h  and the outer circumferential surface of the channel tube  15  to become elastically deformed, and bringing the O-shaped ring  45  into elastic contact at least with the inner wall surface of the seal holding hole  28   h  and the outer circumferential surface of the channel tube  15 , the proximal end side of the channel tube  15  can be connected to the forceps pipe sleeve  28  with a simple configuration and easy operability. 
     Since the endoscope  1  includes the operation section  3  provided on the proximal end side of the insertion section  2 , the forceps pipe sleeve  28  having the treatment instrument insertion opening  28   a  for insertion of a treatment instrument and provided in the operation section  3  such that the axial direction of the central axis O 2  passing through the treatment instrument insertion opening  28   a  is different from the axial direction of the insertion section  2 , the flexible channel tube  15  caused to extend in a protruding manner inside the operation section  3  in a state bending from the proximal end of the insertion section  2  toward the forceps pipe sleeve  28  and connected to the forceps pipe sleeve  28  by insertion, and the guide wall  47  that is provided inside the operation section  3  and can come into contact with the outer side of the bending of the channel tube  15  by abutting on the channel tube  15 , the proximal end side of the channel tube  15  can be appropriately connected to the forceps pipe sleeve  28  with a simple configuration and easy operation. 
     In other words, by adopting the configuration in which the channel tube  15  is connected to the forceps pipe sleeve  28  by insertion in the unbonded state, the channel tube  15  can be connected to the forceps pipe sleeve  28  without performing etching treatment or the like even in a case where the channel tube  15  is made of a material such as polytetrafluoroethylene having a low affinity with an adhesive. In this case, by providing the guide wall  47  inside the first enclosure member  30  to be able to come into contact with the outer side of the bending of the channel tube  15 , it is possible to prevent the channel tube  15  from coming off the forceps pipe sleeve  28  more appropriately than in a case where there is the O-shaped ring alone even in a case where a force that presses the channel tube  15  in the direction to the outer side of the bending occurs in the bending region A of the channel tube  15  when inserting a treatment instrument or the like in the channel tube  15 . 
     Further, by setting the angle formed by the central axis O 2  of the opening (the treatment instrument insertion opening  28   a ) of the forceps pipe sleeve  28  and a tangent line to the guide wall  47  at a position where the guide wall  47  and the central axis O 2  of the opening of the forceps pipe sleeve  28  intersect at less than or equal to 45 degrees as shown in  FIG.  2   , a force in a direction parallel to the guide wall  47  (that is, a force F 2  of traveling in the channel tube  15 ) is larger than a force in a direction vertical to the guide wall  47  (that is, a force F 1  in a direction of pressing the guide wall  47 ) in a force F of inserting the treatment instrument or the like. This minimizes pushing of the channel tube  15 , and thus, prevention of coming off of the channel tube  15  can further be expected. 
     Since connection between the forceps pipe sleeve  28  and the channel tube  15  is a configuration obtained by mere insertion without bonding, it is not necessary to manage the length of the channel tube  15  from the proximal end of the insertion section  2  to the forceps pipe sleeve  28  very strictly as compared with a configuration in which the channel tube  15  is connected to the distal end side of the forceps pipe sleeve  28  by bonding or the like. In other words, insofar as a sufficient length for maintaining an insertion state of the channel tube  15  is ensured in the tube insertion hole  28   d  even in a case where an insertion depth of the channel tube  15  in the tube insertion hole  28   d  is slightly shallow, for example, a manufacturing error or the like can be absorbed by the tube insertion hole  28   d  even if the length of the channel tube  15  extending in a protruding manner from the proximal end of the insertion section  2  is made slightly shorter by the manufacturing error or the like. Consequently, it is easier to manage the length of the channel tube  15 , and operability can be improved more. 
     By setting the inner diameter r 2  in the second cylindrical hole  28   g  to be smaller than the inner diameter r 3  in the tube insertion hole  28   d  and the inner diameter r 2  in the second cylindrical hole  28   g  to be smaller than or equal to the inner diameter of the channel tube  15 , a surface of the channel tube  15  on the proximal end side (a proximal end surface formed by the thickness of the channel tube  15 ) can fall within a projection plane of the abutting surface  28   i . Consequently, also in a case of inserting a treatment instrument from the treatment instrument insertion opening  28   a  side along the first and second tapering holes  28 ,  28   f  and the like, it is possible to prevent a distal end of the treatment instrument from being caught (stuck) by the surface of the channel tube  16  on the proximal end side, and insertion performance of the treatment instrument can be improved. 
     Since the endoscope  1  of the present embodiment is a disposable endoscope and does not require cleaning at high temperature and high pressure, sealing of the connection part between the forceps pipe sleeve  28  and the channel tube  15  is not particularly required insofar as the treatment instrument is inserted in the channel tube  15 . On the other hand, if the seal holding hole  28   h  that configures the inner circumference of the forceps pipe sleeve  28  and the outer circumference of the channel tube  15  are sealed with the O-shaped ring  45  which is a seal member, airtightness and liquid tightness of the connection part between the forceps pipe sleeve  28  and the channel tube  15  can be ensured. Employment of such a seal structure enables the channel tube  15  to be utilized not only for the application of allowing insertion of a treatment instrument or the like but also as an air feeding or water feeding channel. In this case, by providing the partition wall  46  to be opposed to the distal end of the forceps pipe sleeve  28  inside the first enclosure member  30 , it is possible to appropriately prevent the O-shaped ring  45  from coming off the forceps pipe sleeve  28  with a simple configuration, and sealing performance can be maintained. 
     Since the partition wall  46  and the guide wall  47  are formed integrally with the first enclosure member  30 , it is possible to appropriately prevent the number of components from increasing and achieve structural simplification. 
     Herein, also in the forceps pipe sleeve  28  not having the seal holding hole  28   h , the O-shaped ring  45  can also be sandwiched between the distal end surface of the forceps pipe sleeve  28  and the partition wall  46  opposed to the distal end surface of the forceps pipe sleeve  28  to become elastically deformed as shown in  FIG.  6    to  FIG.  8   , for example. Then, by setting the interval between the distal end surface of the forceps pipe sleeve  28  and the partition wall  46  such that the O-shaped ring  45  as elastically deformed comes into elastic contact with the outer circumferential surface of the channel tube  15 , effects similar to the effects of the above-described embodiment can be exerted. 
     In this case, in order to prevent the O-shaped ring  45  from being damaged by an edge of the partition wall  46  or the like when assembling the forceps pipe sleeve  28  to the first enclosure member  30  and the second enclosure member  31 , it is desirable to form a tapering surface  46   b  in a distal end portion of the partition wall  46  as shown in  FIG.  8   , for example. In other words, by forming the tapering surface  46   b  tilted from the proximal end side to the distal end side in a direction away from the distal end surface of the forceps pipe sleeve  28  in the distal end portion of the partition wall  46 , the O-shaped ring  45  can be arranged between the distal end surface of the forceps pipe sleeve  28  and the partition wall  46  without the O-shaped ring  45  being damaged by the partition wall  46  when assembling the forceps pipe sleeve  28  to the first enclosure member  30  and the second enclosure member  31 . 
     In a case where the partition wall  46  is formed separately of a picture wall part  60  on the first enclosure member  30  side and a picture wall part  61  on the second enclosure member  31  side as shown in  FIG.  9   , for example, tapering surfaces  60   a ,  61   a  can also be provided respectively in distal end portions of the respective picture wall parts  60 ,  61 . 
     Note that the present invention is not limited to each embodiment described above, but various modifications and alterations can be made, and they also fall within the technical scope of the present invention. It goes without saying that components of the embodiment described above and components of each modification can be combined as appropriate.