Patent Publication Number: US-2019175257-A1

Title: Treatment instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2016/068287, filed Jun. 20, 2016, the entire contents of all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a treatment instrument that is configured to treat a treatment target with an end effector. 
     2. Description of the Related Art 
     U.S. Pat. No. 5,383,888 discloses a treatment instrument in which an end effector that treats a treatment target is provided at a distal end of a shaft. In this treatment instrument, a shaft is connected to a retainable housing, and by opening or closing a handle relative to a grip of the housing, a space between a pair of grasping pieces is opened or closed in the end effector. By the space between the grasping pieces being closed, a treatment target, such as a living tissue, is grasped between the grasping pieces. In addition, a rotating member (rotating knob) which is a part of the shaft is attached to the housing so as to be rotatable around a central axis of the shaft as a center. When an operating force that rotates the rotating member is applied, the shaft and the end effector rotate relative to the housing together with the rotating member with the central axis of the shaft as a predetermined rotation axis. As a result, an angular position of the end effector around the predetermined rotation axis changes. Furthermore, in this treatment instrument, the end effector bends with respect to the shaft (the central axis of the shaft) based on an operation with a bending operation portion (wing member) provided in the housing. 
     BRIEF SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a treatment instrument includes a rotating body and a housing. The rotating body includes a shaft which extends along a longitudinal axis; an end effector which is disposed on a distal side of the shaft; and a connecting portion including: a supported portion having a cylindrical outer peripheral surface, and an engaged portion which is adjacent to the supported surface. The housing includes a supporting portion which is configured to support the supported portion of the rotating body, the supporting portion being rotatable around a predetermined rotation axis; and an engaging portion that is configured to generate a frictional force larger than a frictional force between the supporting portion and the supported portion by coming into contact with the engaged portion. 
     Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a schematic diagram showing a treatment instrument according to a first embodiment. 
         FIG. 2  is a schematic perspective diagram showing a configuration of an end effector in the treatment instrument according to the first embodiment. 
         FIG. 3  is a schematic cross-sectional diagram showing an inner configuration of a housing in the treatment instrument according to the first embodiment. 
         FIG. 4  is a schematic cross-sectional diagram showing a state in which a central axis of a shaft coincides with a predetermined rotation axis of the housing in the treatment instrument according to the first embodiment. 
         FIG. 5  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft is shifted with respect to the predetermined rotation axis of the housing when a rotary element receives an external force from a direction deviated from the central axis (predetermined rotation axis), in the treatment instrument according to the first embodiment. 
         FIG. 6  is a schematic cross-sectional diagram showing a state in which a radius D 2  of a connecting portion of the rotating member is made larger than a radius D 1  shown in  FIG. 4 , in a treatment instrument according to a first modification of the first embodiment. 
         FIG. 7  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft is shifted with respect to the predetermined rotation axis of the housing when the rotary element shown in  FIG. 6  receives an external force from a direction deviated from the central axis, in the treatment instrument according to the first modification of the first embodiment. 
         FIG. 8  is a schematic cross-sectional diagram showing a state in which a projection for effectively generating a frictional force against the housing is arranged in the rotating member, in a treatment instrument according to a second modification of the first embodiment. 
         FIG. 9  is a schematic cross-sectional diagram showing a state in which a projection for effectively generating a frictional force against the rotating member is arranged in the housing, in a treatment instrument according to a third modification of the first embodiment. 
         FIG. 10  is a schematic cross-sectional diagram showing a state in which a friction plate for effectively generating a frictional force against the housing is arranged in the rotating member, in a treatment instrument according to a fourth modification of the first embodiment. 
         FIG. 11  is a schematic cross-sectional diagram showing a state in which a friction plate for effectively generating a frictional force against the rotating member is arranged in the housing, in a treatment instrument according to a fifth modification of the first embodiment. 
         FIG. 12  is a schematic perspective diagram showing a state in which a large number of jagged steps are formed on the rotating member for effectively generating a frictional force with respect to the housing, in a treatment instrument according to a sixth modification of the first embodiment. 
         FIG. 13A  is a schematic cross-sectional diagram showing a state in which a projection for effectively generating a frictional force with respect to the housing is arranged in the rotating member, and a recess fitted to a protrusion of the rotating member is arranged in the housing to effectively generate a frictional force with respect to the rotating member, in a treatment instrument according to a seventh modification of the first embodiment. 
         FIG. 13B  is a schematic cross-sectional diagram as seen from a direction along line  13 B- 13 B in  FIG. 13A . 
         FIG. 14A  is a schematic diagram showing a treatment instrument according to a second embodiment. 
         FIG. 14B  is a schematic diagram showing a rotary element and a rotating member as seen from a direction indicated by an arrow  14 B in  FIG. 14A . 
         FIG. 15  is a schematic diagram showing a treatment instrument according to a third embodiment with the end effector omitted from the drawing. 
         FIG. 16  is a schematic cross-sectional diagram showing a state in which a central axis of a shaft coincides with a predetermined rotation axis of a housing, in the treatment instrument according to the third embodiment. 
         FIG. 17  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing is indicated by a solid line, and a state in which the central axis of the shaft is shifted with respect to the predetermined rotation axis of the housing when a rotary element receives an external force from a direction deviated from the central axis, in the treatment instrument according to the third embodiment. 
         FIG. 18  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing by a solid line, and a state in which the central axis of the shaft is shifted with respect to the predetermined rotation axis of the housing when the rotary element receives an external force from a direction deviated from the central axis, and an outer peripheral surface of the shaft comes into contact with a friction ring at a distal end of the housing by a broken line, in a treatment instrument according to a first modification of the third embodiment. 
         FIG. 19  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing, in a treatment instrument according to a second modification of the third embodiment. 
         FIG. 20  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing by a solid line, and a state in which the central axis of the shaft is shifted with respect to the predetermined rotation axis of the housing when a rotary element receives an external force from a direction deviated from the central axis by a broken line, in the treatment instrument according to the second modification of the third embodiment. 
         FIG. 21  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing, in a treatment instrument according to a fourth embodiment. 
         FIG. 22  is a schematic cross-sectional diagram showing a state in which the central axis of the shaft coincides with the predetermined rotation axis of the housing by a solid line, and a state in which the central axis of the shaft is shifted with respect to the predetermined rotational axis of the housing when the rotary element receives an external force from a direction deviated from the central axis by a broken line, in the treatment instrument according to the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to  FIGS. 1 to 5 .  FIG. 1  is a diagram showing a treatment instrument (grasping treatment instrument)  1  of the present embodiment. The treatment instrument  1  shown in  FIG. 1  includes a predetermined rotation axis (longitudinal axis) R. Herein, one side in a direction along the predetermined rotation axis R is defined as a distal end side (an arrow C 1  side), and a side opposite to the distal end side is defined as a proximal end side (an arrow C 2  side). 
     The treatment instrument  1  includes a housing  2 , a shaft (sheath)  3  protruding with respect to the housing  2 , and an end effector  5 . The shaft  3  and the end effector  5  form a rotary element (rotating body)  6  with respect to the predetermined rotation axis R of the housing  2 . That is, the rotary element  6  includes the shaft  3  and the end effector  5 . 
     A central axis C is defined in the shaft  3 . The shaft  3  extends from the proximal end side to the distal end side along the central axis C. The end effector  5  is disposed at the distal end of the shaft  3 . The shaft  3  is rotatably supported with respect to the housing  2 . Thus, the shaft  3  supports the end effector  5  together with the shaft  3  so as to be rotatable around the central axis C. A side of the shaft  3  toward the housing  2  is the proximal end side, and a side toward the end effector  5  is the distal end side. The end effector  5  may be arranged on the central axis C, or may be arranged at a position shifted from the central axis C. As will be described later, in the present embodiment, the end effector  5  can move between a position arranged on the central axis C of the shaft  3  and a position arranged at a position shifted from the central axis C. Thus, in the present embodiment, the end effector  5  is bent with respect to the shaft  3 . 
     It is preferable that the shaft  3  is made of, for example, a metallic material such as a stainless steel material, and can be elastically deformed by a load of an external force F applied to the rotary element  6  from a direction deviated from the central axis C (the predetermined rotation axis R). For this reason, it is preferable that the shaft  3  has a bendability of bending appropriately by the load of the external force F applied to the rotary element  6  from a direction deviated from the central axis C (the predetermined rotation axis R). 
     The housing  2  is made of a resin material having electrical insulation properties. The housing  2  according to the present embodiment includes a housing main body  11  extending along a predetermined (immovable) rotation axis R, and a grip (fixed handle)  12  extending from the housing main body  11  along a direction (a direction indicated by arrows Y 1  and Y 2 ) intersecting the predetermined rotation axis R. The grip  12  is provided at a portion away from the predetermined rotation axis R. One end of a cable  13  is connected to the grip  12 . The other end of the cable  13  is connected to an energy control device (not shown). It should be noted here that a direction intersecting (substantially vertical to) the predetermined rotation axis R and intersecting (substantially vertical to) the extending direction of the grip  12  is defined as a width direction (a direction substantially vertical to a paper surface in  FIG. 1 ) of the housing  2 .  FIG. 1  is a diagram of the treatment instrument  1  as viewed from one side in the width direction of the housing  2 . 
       FIG. 2  is a diagram showing a configuration of the end effector  5 . As shown in  FIGS. 1 and 2 , the end effector  5  is rotatable relative to the housing  2  around the rotation axis R (central axis C) together with the shaft  3 , and is bendable relative to the shaft  3  (central axis C). It is preferable that the end effector  5  is rotatable relative to the housing  2  around the rotation axis R (central axis C) together with the shaft  3 , and is capable of bending relative to the shaft  3  (central axis C) (see  FIG. 14B ). As the shaft  3  rotates around the central axis C, an angular position around the rotation axis R of the end effector  5  changes. Furthermore, a bending direction (directions indicated by arrows B 1  and B 2 ) of the end effector  5  intersects (substantially vertical to) the predetermined rotation axis R. The end effector  5  includes a relay member  15 , a first grasping piece  16 , and a second grasping piece  17 . The relay member  15  is attached to the distal end of the shaft  3  so as to be bendable relative to the shaft  3 . That is, a bending joint  18  is formed between the shaft  3  and the relay member  15 . In addition, in the end effector  5 , the space between a pair of grasping pieces  16  and  17  can be opened and closed. Opening and closing directions (directions indicated by arrows X 1  and X 2 ) of the grasping pieces  16  and  17  intersect the central axis C, and intersect the inflecting direction of the end effector  5 . 
     As shown in  FIG. 2 , the first grasping piece  16  is pivotably attached to the relay member  15  via a supporting pin (supporting portion)  19 . That is, the relay member  15  is provided with the supporting pin  19  that supports the first grasping piece  16 . The first grasping piece  16  is pivotable about the supporting pin  19  as a center. In the present embodiment, a pivot axis T 1  of the first grasping piece  16  with respect to the relay member  15  passes through the supporting pin  19 , and is substantially coaxial with a central axis of the supporting pin  19 . Then, the pivot axis T 1  extends substantially in parallel with the bending direction of the end effector  5 . That is, an extension direction of the pivot axis T 1  intersects the central axis C of the shaft  3 , and intersects the opening and closing directions of the grasping pieces  16  and  17 . As the first grasping piece  16  rotates about the supporting pin (supporting portion)  19  as a center, the first grasping piece  16  opens or closes relative to the second grasping piece  17 . In addition, the supporting pin (supporting portion)  19 , together with the shaft  3  and the end effector  5 , is rotatable around the predetermined rotation axis R relative to the housing  2 . 
     Herein, in one embodiment, the second grasping piece  17  is formed integrally with or fixed to the relay member  15 . In another embodiment, the second grasping piece  17  is also pivotally attached to the relay member  15 . Furthermore, in another embodiment, a rod member (not shown) extends from an internal portion of the relay member  15  toward the distal end side, and the second grasping piece  17  is formed by a protruding portion of the rod member from the relay member  15  to the distal end side. 
     As shown in  FIG. 1 , a handle (movable handle)  21  is turnably attached to the housing  2 . As the handle  21 , which is an opening/closing operation input portion, turns relative to the housing  2 , the handle  21  opens or closes relative to the grip  12 . That is, the handle  21  can be opened and closed relative to the grip  12 . In the present embodiment, since it is the pistol type treatment instrument  1 , the handle  21  is positioned on a side where the grip  12  is positioned with respect to the rotation axis R and on the distal end side with respect to the grip  12 . A movement direction of the handle  21  in the opening operation and the closing operation relative to the grip  12  is substantially parallel to the rotation axis R. In some embodiments, the handle  21  may be provided on the proximal end side with respect to the grip  12 . In another embodiment, the handle  21  and the grip  12  are provided on opposite sides to each other with the rotation axis R as a center, and a moving direction of the handle  21  in the opening operation and the closing operation relative to the grip  12  may be substantially vertical to the rotation axis R. 
     In addition, in the present embodiment, a rotating dial (operation element)  23  is attached to the housing  2  as a bending operation input unit (operation input unit). For example, by turning the rotating dial  23 , an operation of bending the end effector  5  relative to the shaft  3  is inputted. As shown in  FIG. 2 , bending drive members  28 A and  28 B, such as wires or leaf springs, extend along the rotation axis R in an internal portion of the shaft  3 . Distal ends (one ends) of the bending drive members  28 A and  28 B are connected to the relay member  15  of the end effector  5 . In addition, proximal ends of the bending drive members  28 A and  28 B are mechanically connected to the rotating dial  23  via a pulley (not shown), etc. provided in an internal portion of the housing  2 . Operation input is performed by the rotating dial (bending operation input unit)  23 , whereby an operating force is transmitted to the bending drive members  28 A and  28 B, and the bending drive members  28 A and  28 B move along the predetermined rotation axis R (central axis C) relative to the shaft  3  and the housing  2 . Thereby, the end effector  5  is bent relative to the shaft  3  (central axis C) in the bending direction (the directions indicated by the arrows B 1  and B 2 ). 
     Herein, the bending drive members  28 A and  28 B are rotatable relative to the housing  2  around the predetermined rotation axis R (central axis C) together with the shaft  3  and the end effector  5 . In addition, the rotating dial  23  may be rotatable around the predetermined rotation axis R (central axis C) relative to the housing  2  together with the shaft  3  and the end effector  5 , and may not rotate together with the shaft  3  and the end effector  5  around the predetermined rotation axis R (central axis C). Furthermore, in the present embodiment, the rotating dial  23  is attached to a proximal end surface of the housing main body  11 , but a position of the rotating dial  23  is not limited thereto. For example, a bending operation input unit, such as the rotating dial  23 , may be attached to an outer surface of the housing main body  11  facing a side opposite to a side on which the grip  12  is positioned with respect to the predetermined rotation axis R. 
     A rotating member  25 , which is a part of the shaft  3 , is supported on the distal end side of the housing main body  11 . It is preferable that the rotating member  25  is formed of a resin material having electrical insulation properties. The rotating member  25  includes a rotating knob  26 A to be operated and a connecting portion  26 B to be connected to the housing  2 . The rotating knob  26 A and the connecting portion  26 B are formed in an appropriate cylindrical shape. In order to generate a large rotational moment with a small force, the maximum radius (distance from the central axis C) D 0  of the rotating knob  26 A is appropriately large. It is preferable that the maximum radius (distance from the central axis C) D 0  of the rotating knob  26 A is formed larger than the maximum radius (distance from the central axis C) D 1  of the connecting portion  26 B. 
     The shaft  3  is supported by the housing  2  in a state of being inserted into an internal portion of the housing main body  11  from the distal end side. The rotating member  25  is fixed to the shaft  3 , and rotates together with the shaft  3  and the end effector  5  around the rotation axis R relative to the housing  2 . 
     In the present embodiment, an operating force for rotating the shaft  3  and the end effector  5 , that is, the rotary element  6  around the predetermined rotation axis R (central axis C) is applied to the rotating member  25  as the rotating operation input unit. 
     Operation buttons  27 A and  27 B are attached to the housing  2 . Each of the operation buttons  27 A and  27 B is pressed to perform operation input. When an operation input is made by each of the operation buttons  27 A and  27 B, the treatment instrument  1  is operated in a predetermined operation mode. At this time, for example, similarly to known treatment instruments, either high-frequency current, ultrasonic vibration, or heater heat is applied as a treatment energy to the treatment target grasped between the grasping pieces  16  and  17 . In one embodiment, when the treatment instrument  1  is operated in a predetermined operation mode on the basis of an operation input of any one of the operation buttons  27 A and  27 B, an electric motor is driven so that a staple may be pierced into the treatment target grasped between the grasping pieces  16  and  17 . 
       FIG. 3  is a diagram showing a configuration of the internal portion of the housing  2 .  FIG. 3  shows a cross section that is substantially vertical to (intersecting) the width direction of the housing  2 . In addition, in  FIG. 3 , the bending drive members  28 A and  28 B, and a configuration for transmitting the operating force from the rotating dial  23  to the inflection drive members  28 A and  28 B, etc. are omitted. As shown in  FIG. 3 , in the internal portion of the housing (housing main body  11 ), a tubular movable member  31  is attached to the rotating member  25  from the proximal end side (arrow C 2  side). The movable member  31  extends along the predetermined rotation axis R (central axis C) and is movable along the predetermined rotation axis R relative to the housing  2  and the shaft  3 . However, a rotation of the movable member  31  around the rotation axis R relative to the shaft  3  is restricted, and the movable member  31 , together with the shaft  3  and the end effector  5 , is rotatable around the predetermined rotation axis R relative to the housing  2 . 
     As a mechanism that the first grasping piece  16  relatively performs an opening operation relative to the second grasping piece  17  by opening the handle  21  relative to the grip  12 , and the first grasping piece  16  relatively performs a closing operation relative to the second grasping piece  17  by closing the handle  21  relative to the grip  12 , various mechanisms can be adopted. 
     In the internal portion of the housing  2  according to the present embodiment, a slider member  32  is arranged on an outer peripheral surface of the movable member  31 . The handle  21  is connected to the movable member  31  via the slider member  32 . The movable member  31  is rotatable around the predetermined rotation axis R relative to the handle  21 . In addition, in the internal portion of the housing  2 , a driving rod  33 , which is an opening/closing driving member, is fixed to the movable member  31  via a connecting pin  35 . The driving rod  33  extends along the rotation axis R from the internal portion of the movable member  31  through the internal portion of the shaft  3 . Since the driving rod  33  is fixed to the movable member  31 , when the operating force of the rotating member  25  is applied, the driving rod  33  rotates together with the shaft  3 , the end effector  5 , and the movable member  31  around the predetermined rotation axis R (central axis C) relative to the housing  2 . 
     An urging member  37 , such as a spring, is provided in the internal portion of the housing  2 . One end of the urging member  37  is connected to the housing  2 , and the other end is connected to the handle  21 . The urging member  37  urges the handle  21  to be in a state of opening relative to the grip  12 . 
     By applying an operating force to the handle  21  and opening or closing the handle  21  relative to the grip  12 , the movable member  31  and the driving rod  33  move along the predetermined rotation axis R (central axis C) relative to the shaft  3  and the housing  2 . As shown in  FIG. 2 , one end (distal end) of the driving rod (driving member)  33  extending through the internal portion of the shaft  3  is connected to the first grasping piece  16  of the end effector  5 . In the present embodiment, the driving rod  33  is connected to the first grasping piece  16  via a connection pin  36 . As the movable member  31  and the driving rod (driving member)  33  move along the predetermined rotation axis R, at least the first grasping piece  16  turns about a support pin  19  with respect to the relay member  15 . As a result, the space between the grasping pieces  16  and  17  is opened or closed. At this time, the support pin  19  serves as a fulcrum for pivotal movement of the first grasping piece  16 , and the connection pin  36  serves as a force point for exerting a driving force from the driving rod  33  to the first grasping piece  16 . In an embodiment in which the second grasping piece  17  is also rotatable relative to the relay member  15 , a distal end of the driving rod (opening and closing driving member)  33  is connected to the second grasping piece  17  in addition to the first grasping piece  16 . In this case, as the driving rod  33  moves along the rotation axis R, both of the grasping pieces  16  and  17  turn relative to the relay member  15 , and the space between the grasping pieces  16  and  17  is opened or closed. 
     In the present embodiment, by the urging member  37 , the first grasping piece  16  is urged to a state of being opened with respect to the second grasping piece  17 , and the end effector  5  is urged to a state in which the space between the grasping pieces  16  and  17  is opened. 
     As shown in  FIGS. 3 and 4 , the housing main body  11  of the housing  2  is provided with an engagement projection (supporting portion)  41  protruding toward the predetermined rotation axis R. Thus, in the present embodiment, the engagement projection  41  is arranged on an inner peripheral surface of the housing  2 . As an example, the engagement projection (inner flange)  41  is provided over the entire circumference around the predetermined rotation axis R. Although not shown, the engagement projection  41  may be formed, for example, at appropriate intervals in a circumferential direction around the predetermined rotation axis R. Thus, one engagement projection  41  may be provided, or a plurality of engagement projections  41  may be provided. 
     An engagement recess (supported portion)  42  that is recessed toward the inner peripheral side is provided in the connecting portion  26 B of the rotating member  25  which is a part of the shaft  3 . The engagement recess  42  is provided over the entire circumference around the rotation axis R. By engaging the engagement projection  41  with the engagement recess  42 , the shaft  3  is supported by the housing  2  so as to be rotatable around the predetermined rotation axis R. 
     Thus, the engagement recess  42  can move around the rotation axis R relative to the engagement projection  41 . The rotating member  25  of the shaft  3  is rotatable around the predetermined rotation axis R relative to the housing  2 . Accordingly, the engagement projection  41  and the engagement recess  42  form a joint assembly (connecting portion)  40  that connects the shaft  3  so as to be rotatable around the predetermined rotation axis R of the housing  2 . 
       FIGS. 4 and 5  are diagrams showing a configuration of the joint assembly  40  (the engagement projection  41  and the engagement recess  42 ) between the shaft  3  and the housing  2 .  FIG. 4  shows a state in which the central axis C of the shaft  3  coincides with the predetermined rotation axis R of the housing  2 .  FIG. 5  shows a state in which the central axis C of the shaft  3  is shifted with respect to the predetermined rotation axis R of the housing  2  by an external force F to the rotary element  6 , that is, the end effector  5  and/or the shaft  3 . 
     As shown in  FIGS. 4 and 5 , the engagement projection  41  of the housing  2  includes a supporting portion (rotation supporting surface)  51  and an engaging portion (sliding resistance generating portion)  52 . The supporting portion  51  defines a cylindrical inner peripheral surface with respect to the predetermined rotation axis R. The supporting portion  51  supports the rotary element  6  so as to be rotatable around the predetermined rotation axis R. The engaging portion  52  is adjacent to the supporting portion  51  along the central axis C. The engaging portion  52  includes a projection facing surface (first receiving surface)  53  facing the distal end side and a projection facing surface (second receiving surface)  54  facing the proximal end side. 
     The engagement recess  42  of the rotating member  25  of a part of the shaft  3  includes a supported portion (rotation supporting surface)  61  and an engaged portion (sliding resistance generating portion)  62 . That is, the rotary element  6  includes the supported portion  61  provided on the shaft  3  and supported by the supporting portion  51  of the housing  2 . The supported portion  61  defines a cylindrical outer peripheral surface with respect to the central axis C. The engaged portion  62  is adjacent to the supported surface  61  along the central axis C. The engaged portion  62  includes a recessed facing surface (first contact surface)  63  facing the proximal end side and a recessed facing surface (second contact surface)  64  facing the distal end side. 
     It is preferable that the supporting portion  51  and the supported portion  61  are formed of a material that suppresses generation of a frictional force when in contact, or are subjected to surface processing that suppresses generation of a frictional force. It is preferable that the supporting portion  51  and the supported portion  61  are formed of a material having a small friction coefficient, e.g. polyoxymethylene:POM, etc., and having good slidability (lubricity). Thus, the supported portion  61  can rotate smoothly relative to the supporting portion  51 . In this way, in the present embodiment, the supporting portion  51  of the housing  2  and the supported portion  61  of the shaft  3  cooperate to form a rotation supporting mechanism  70 . 
     The recessed facing surface (first contact surface)  63  facing the proximal end side of the engagement recess  42  faces the projection facing surface (first receiving surface)  53  facing the distal end side of the engagement projection  41 . The recessed facing surface (second contact surface)  64  facing the distal end side of the engagement recess  42  faces the projection facing surface (second receiving surface)  54  facing the proximal end side of the engagement projection  41 . The projection facing surface  53  of the engagement projection  41  and the recessed facing surface  63  of the engagement recess  42 , and the projection facing surface  54  of the engagement projection  41  and the recessed facing surface  64  of the engagement recess  42 , each, are formed so as to generate a large frictional force when in contact, as compared with the frictional force (sliding resistance) between the supporting portion  51  and the supported portion  61 . For example, the projection facing surface  53  of the engagement projection  41  and the recessed facing surface  63  of the engagement recess  42  are preferably formed of a material that generates a large frictional force when in contact, or are subjected to surface processing so as to easily generate a frictional force. Similarly, the projection facing surface  54  of the engagement projection  41  and the recessed facing surface  64  of the engagement recess  42  are preferably formed of a material that generates a large frictional force when in contact, or are subjected to surface processing so as to easily generate a frictional force. 
     In the present embodiment, the engaging portion  52  of the housing  2  and the engaged portion  62  of the shaft  3  cooperate to form a lock mechanism  80 . In the present embodiment, the lock mechanism  80  is disposed in the supporting portion  51  of the housing  2  and the supported portion  61  of the shaft  3 . Then, the lock mechanism  80  suppresses the rotation of the rotary element  6  around the predetermined rotation axis R, as one of positions of the rotary element  6  closer to the end effector  5  than a support position supported by the supporting portion  51  deviates from the predetermined rotation axis R. Herein, the rotation of the rotary element  6  around the predetermined rotation axis R is suppressed at a (different) position (the projection facing surface  53  of the engaging portion  52 ) adjacent to the supporting portion  51 . Specifically, the engaging portion (frictional resistance portion)  52  cooperates with the engaged portion  62 , and generates a sliding resistance in a direction around the axis of the predetermined rotation axis R at a position more apart from the predetermined rotation axis R than the supporting portion  51 . 
     As shown in  FIG. 4 , the engaging portion  52  of the housing  2  is located adjacent to the distal end side and the proximal end side of the supporting portion  51  along the predetermined rotation axis R. Thus, the position of the supporting portion  51  of the housing  2  and the position of the engaging portion  52  are different from each other. Similarly, the engaged portion  62  of the shaft  3  is located adjacent to the distal end side and the proximal end side of the supported portion  61  along the central axis C. Thus, the position of the supported portion  61  of the shaft  3  and the position of the engaged portion  62  are different from each other. 
     In the rotation supporting mechanism  70 , the supporting portion  51  of the engagement projection  41  of the housing  2  and the supported portion  61  of the engagement recess  42  of the shaft  3  cooperate with each other, to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . Herein, an inner diameter of the supporting portion  51  with respect to the rotation axis R is larger than an outer diameter of the supported portion  61  with respect to the central axis C. At this time, the supporting portion  51  of the engagement projection  41  of the housing  2  is rattled, that is, plays with respect to the supported portion  61  of the engagement recess  42  of the shaft  3 . In this state, when an operator rotates the rotating knob  26 A of the rotating member  25 , the central axis C of the shaft  3  rotates in a state coincident with or parallel to the predetermined rotation axis R of the housing  2 . 
     In the position shown in  FIG. 4 , an outer peripheral surface of the supported portion  61  of the rotating member  25  and an inner peripheral surface of the supporting portion  51  of the housing  2  can partially contact each other. At this time, depending on a relationship between the outer diameter of the supported portion  61  of the rotating member  25  and the inner diameter of the supporting portion  51  of the housing  2 , the supported portion  61  of the rotating member  25  moves (escapes) to an opposite side across the predetermined rotation axis R relative to the position (a state in which the central axis C is parallel to the predetermined rotation axis R) of the supporting portion  51  of the housing  2  which is currently in contact, and can make the central axis C of the shaft  3  coincide with or close to the predetermined rotation axis R of the housing  2 . Thus, when the rotating member  25  is rotated about the axis of the predetermined rotation axis R (central axis C) relative to the housing  2 , the rotating member  25  can be rotated in a state in which the sliding resistance is reduced (minimized). Therefore, in a state in which the predetermined rotation axis R of the housing  2  and the central axis C of the shaft  3  are made to coincide with each other, the joint assembly  40  minimizes the sliding resistance around the predetermined rotation axis R between the housing  2  and the shaft  3 . 
     As shown in  FIG. 5 , at a position closer to the distal end of the end effector  5  than the rotating member  25  of the rotary element  6 , that is, the end effector  5  and/or the shaft  3 , a load (external force) F from a direction deviated from the rotation axis R of the housing  2  can be applied. 
     Particularly, in the present embodiment, the urging member  37  disposed in the internal portion of the housing  2  urges to a state where the first grasping piece  16  is opened relative to the second grasping piece  17 . Thus, for example, even when the end effector  5  is on the axis of the central axis C of the shaft  3 , when the external force F is applied from a side of the grasping piece  16  in a state where the first grasping piece  16  is opened with respect to the second grasping piece  17 , a force to turn the end effector  5  about the central axis C is applied. 
     When the end effector  5  is at a position deviated from the central axis C of the shaft  3  and the external force F is applied to the end effector  5 , a force to turn the end effector  5  about the central axis C is applied. This state can be maintained regardless of whether the first grasping piece  16  of the end effector  5  is opened or closed with respect to the second grasping piece  17 . 
     It is to be noted that an unintended external force F around the central axis C may also be applied to the shaft  3  itself. 
     For this reason, a rotational moment around the central axis C may be generated on the end effector  5  and/or the shaft  3  by the external force F from a position deviated from the central axis C. The rotating member  25  which is a part of the shaft  3  tries to rotate around the central axis C. Herein, as described above, the supporting portion  51  of the engagement projection  41  of the housing  2  is rattled, that is, plays with respect to the supported portion  61  of the engagement recess  42  of the shaft  3 . Thus, due to the load of the external force F on the end effector  5  and/or the shaft  3 , the rotating member  25  is also inclined relative to the housing  2  due to rattling (play) with respect to the housing  2 . That is, for example, as shown in  FIG. 5 , when an external force from a position deviated from the central axis C of the shaft  3  is applied to the rotary element  6 , the central axis C of the shaft  3  is shifted from the predetermined rotational axis R of the housing  2 , from a position shown in  FIG. 4  to a position shown in  FIG. 5 . Thus, the central axis C of the shaft  3  is shifted with respect to the predetermined rotation axis R of the housing  2 . At this time, the central axis C of the shaft  3  intersects or is arranged to be a skew positional relation with respect to the predetermined rotation axis R of the housing  2 . 
     An example shown in  FIG. 5  is intended to explain the present embodiment in an easily understandable manner. A maximum inclination angle (inclination amount) of the central axis C of the rotating member  25  (shaft  3 ) with respect to the predetermined rotation axis R of the housing  2  can be set as appropriate. 
     In the position shown in  FIG. 5 , the recessed facing surface  63  of the engaged portion  62  of the rotating member  25  is in contact with the projection facing surface  53  of the engaging portion  52  of the housing  2 . At this time, a contact position (friction occurring position) between the projection facing surface  53  of the engaging portion  52  and the recessed facing surface  63  of the engaged portion  62  is at a position of a distance d 1  (≥D 1 ) in a radial direction with respect to the predetermined rotation axis R. 
     While the external force F is applied to the rotary element  6 , the recessed facing surface  63  of the engaged portion  62  of the rotating member  25  continues to contact the projection facing surface  53  of the engaging portion  52  of the housing  2 . Thus, a sliding resistance around the predetermined rotation axis R continues to be generated between the housing  2  and the rotating member  25 . Accordingly, even if the external force F is applied to the rotary element  6  as shown in  FIG. 5 , and a force for rotating the end effector  5  and/or the shaft  3  around the central axis C is applied, a braking action due to a sliding resistance which suppresses the rotation around the predetermined rotation axis R relative to the housing  2  continues to be generated in the rotating member  25 . As the external force F increases, an inclination amount with which the central axis C of the shaft  3  is inclined with respect to the predetermined rotation axis R of the housing  2  increases. As the inclination amount increases, the recessed facing surface  63  of the engaged portion  62  of the rotating member  25  gradually and strongly comes into contact with the projection facing surface  53  of the engaging portion  52  of the housing  2 . Thus, as the external force F increases, the braking action due to the sliding resistance which suppresses the rotation of the shaft  3  (the rotating member  25 ) around the predetermined rotation axis R relative to the housing  2  also increases. Therefore, an unintentional rotation of the rotating member  25  relative to the housing  2  is suppressed. In this way, as the unintentional rotation of the rotating member  25  relative to the housing  2  is suppressed, the rotation around the central axis C of the shaft  3  is suppressed, and furthermore, the rotation of the end effector  5  around the central axis C is suppressed. 
     It is possible to rotate the rotating member  25  around the central axis C by an intention of the operator in a state where the external force F is applied to the end effector  5  and/or the shaft  3 . In this case, the rotating member  25  may be rotated around the predetermined rotation axis R against the sliding resistance (frictional force) generated by the external force F between the rotating member  25  and the housing  2 . As shown in  FIG. 3 , in the rotating member  25 , there is an outer peripheral surface of the rotating knob  26 A that places the operator&#39;s finger at a position (radius D 0 &gt;D 1 ), in particular, radially apart from the central axis C (predetermined rotation axis R). Thus, when the operator rotates the rotating member  25  around the central axis C, for reasons of moments based on a difference in size of radii D 0  and D 1 , the rotating member  25  can be rotated against the sliding resistance (frictional force) generated between the rotating member  25  and the housing  2  with a smaller force. Therefore, for example, by turning the end effector  5  at a position shifted from the axis of the central axis C around the central axis C, the operator can push aside a biological tissue, for example, by the end effector  5 . When the operator rotates the rotating member  25  against the frictional force (sliding resistance) , the central axis C of the shaft  3  tries to move so as to coincide with the predetermined rotation axis R of the housing  2  so as to avoid friction between the engaging portion  52  and the engaged portion  62 . 
     As described above, according to the treatment instrument  1  of the present embodiment, the following can be said. 
     In the treatment instrument  1  according to this embodiment, for example, by an external force F from a direction deviated from the predetermined rotation axis R, any one of the positions of the rotary element  6  which are closer to the end effector  5  than the support position supported by the supporting portion  51 , can be shifted from the predetermined rotation axis R. Then, the engaging portion (sliding resistance generating portion)  52  and the engaged portion (sliding resistance generating portion)  62  of the lock mechanism  80  of the joint assembly  40  generates a sliding resistance around the predetermined rotation axis R between the housing  2  and the rotary element  6 , when the central axis C is shifted relative to the predetermined rotation axis R. 
     Herein, at a position closer to the end effector  5  than a support position where the shaft  3  of the rotary element  6  is supported by the supporting portion  51  of the housing  2 , the joint assembly  40  generates a sliding resistance around the predetermined rotation axis R in the rotary element  6  (shaft  3 ). In addition, herein, the joint assembly  40  is adjacent to a support position (supported portion  61 ) supporting the shaft  3  of the rotary element  6  by the supporting portion  51  of the housing  2 , and generates a sliding resistance in a direction around the predetermined rotation axis R with respect to the engaging portion  52  by the engaged portion  62  which is apart from the predetermined rotation axis R than the support position. That is, the sliding resistance around the predetermined rotation axis R is generated in the rotary element  6  (shaft  3 ). In this manner, the lock mechanism  80  can suppress the rotation of the rotary element  6  around the predetermined rotation axis R. Therefore, for example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, rotation of the end effector  5  and the shaft  3  around the axis of the predetermined rotation axis R unintended by the operator can be effectively prevented by the lock mechanism  80 . 
     On the other hand, when the operator intends to rotate the end effector  5  and the shaft  3  around the predetermined rotation axis R intentionally, the rotating knob  26 A having the radius DO larger than the radius D 1  of a portion generating the sliding resistance maybe rotated. Thus, the operator can easily rotate the rotating knob  26 A around the predetermined rotation axis R against the sliding resistance by the rotational moment. 
     In  FIG. 5 , an example has been described in which the recessed facing surface  63  facing the proximal end side of the engaged portion  62  of the rotating member  25  is in contact with the projection facing surface  53  facing the distal end side of the engaging portion  52  of the housing  2 , when the central axis C of the shaft  3  is inclined with respect to the predetermined rotation axis R of the housing  2 . Other than that, it is also preferable that the recessed facing surface  64  facing the distal end side of the engaged portion  62  of the rotating member  25  comes into contact with the projection facing surface  54  facing the proximal end side of the engaging portion  52  of the housing  2 . In addition, it is also preferable that the recessed facing surface  63  facing the proximal end side of the engaged portion  62  of the rotating member  25  comes into contact with the projection facing surface  53  facing the distal end side of the engaging portion  52  of the housing  2 , at the same time, the recessed facing surface  64  facing the distal end side of the engaged portion  62  of the rotating member  25  comes into contact with the projection facing surface  54  facing the proximal end side of the engaging portion  52  of the housing  2 . 
     Herein, an example has been described in which the engagement projection  41  is formed in the housing  2 , and the engagement recess  42  is formed in the rotating member  25  of the shaft  3 . Although not shown, these may be opposite. Namely, it of course is preferable that the engagement recess  42  is formed in the housing  2 , and the engagement projection  41  is formed in the connecting portion  26 B of the rotating member  25 . 
     First Modification 
     A maximum radius D 2  of the connecting portion  26 B shown in  FIG. 6  is formed larger than the maximum radius D 1  (see  FIG. 4 ) of the connecting portion  26 B described in the first embodiment. As shown in  FIG. 7 , when the external force F is applied to the rotary element  6 , the central axis C of the shaft  3  of the rotary element  6  is inclined with respect to the predetermined rotation axis R of the housing  2 . A contact position (friction occurring position) between the recessed facing surface  63  of the engaged portion  62  and the projection facing surface  53  of the engaging portion  52  is at a position of a distance d 2  (≥D 2 ) with respect to the predetermined rotation axis R. The distance d 2  is larger than the distance d 1  (see  FIG. 5 ) described in the first embodiment. Thus, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , it is possible to generate a larger rotational torque (sliding resistance) than the example described in the first embodiment. Therefore, an effect of suppressing the rotation around the predetermined rotation axis R in a state where the external force F is applied to the rotary element  6  can be higher in this modification than in the example described in the first embodiment. 
     Second Modification 
     This modification can be combined with the first embodiment and the first modification as appropriate. 
     As shown in  FIG. 8 , a protrusion  65  is formed on the recessed facing surface  63  of the engaged portion  62 . The protrusion  65  protrudes toward the proximal end side from the recessed facing surface  63  of the engaged portion  62 . It is preferable that the protrusion  65  is annularly formed around the central axis C. When the protrusion  65  is brought into contact with the projection facing surface  53  of the engaging portion  52 , the contact is stronger for the protrusion than that of the recessed facing surface  63  of the engaged portion  62  described in the first embodiment. Therefore, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , as compared with the example (see  FIG. 5 ) described in the first embodiment, it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R. 
     Third Modification 
     As shown in  FIG. 9 , a protrusion  55  is formed on the projection facing surface  53  of the engaging portion  52  of the engagement recess  42 . The protrusion  55  protrudes toward the recessed facing surface  63  of the engaged portion  62 . It is preferable that the protrusion  55  is formed in an annular shape. Thus, when the protrusion  55  is brought into contact with the recessed facing surface  63  of the engaged portion  62  by the external force F to the rotary element  6 , the contact is stronger for the protrusion than that of the projection facing surface  53  of the engaging portion  52  described in the first embodiment. Therefore, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , as compared with the example (see  FIG. 5 ) described in the first embodiment, it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R. 
     Note that this modification can be appropriately combined with, for example, the first embodiment, the first modification, and the second modification. 
     Fourth Modification 
     As shown in  FIG. 10 , a friction plate  66  is fixed to the recessed facing surface  63  of the engaged portion  62 . It is preferable that the friction plate  66  is formed in an annular shape. It is preferable that the friction plate  66  is made of a material having a large friction coefficient, such as a rubber material. The friction plate  66  protrudes toward the proximal end side from the recessed facing surface  63  of the engaged portion  62 , and increases the frictional force when the projection facing surface  53  of the engaging portion  52  contacts. Thus, when the friction plate  66  is brought into contact with the projection facing surface  53  of the engaging portion  52 , a larger frictional force is exhibited than the contact of the recessed facing surface  63  of the engaged portion  62  described in the first embodiment. Therefore, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , as compared with the example (see  FIG. 5 ) described in the first embodiment, it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R. 
     This modification can be appropriately combined with, for example, the third modification. 
     Fifth Modification 
     As shown in  FIG. 11 , a friction plate  56  is fixed to the projection facing surface  53  of the engaging portion  52 . It is preferable that the friction plate  56  is formed in an annular shape. The friction plate  56  increases the frictional force when the recessed facing surface  63  of the engaged portion  62  contacts. Thus, when the friction plate  56  is brought into contact with the recessed facing surface  63  of the engaged portion  62 , a larger frictional force is exhibited than the contact of the projection facing surface  53  of the engaging portion  52  described in the first embodiment. Therefore, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , as compared with the example (see  FIG. 5 ) described in the first embodiment, it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R. 
     This modification can be appropriately combined with, for example, the second modification. 
     Sixth Modification 
     As shown in  FIG. 12 , multiple steps  67  are formed along a circumferential direction of the central axis C on the recessed facing surface  63  of the engaged portion  62 . That is, the recessed facing surface  63  of the engaged portion  62  is formed in a jagged shape. Thus, when the recessed facing surface  63  of the engaged portion  62  is brought into contact with the projection facing surface  53  of the engaging portion  52 , the projection facing surface  53  of the engaging portion  52  is hooked at a position protruding toward the proximal end side along the central axis C of the recessed facing surface  63  of the engaged portion  62 . Therefore, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R, as compared with the example (see  FIG. 5 ) described in the first embodiment. 
     In  FIG. 12 , an example has been described in which the step  67  is formed on the recessed facing surface  63  of the engaged portion  62 . Besides, the step  67  may be formed on the recessed facing surface  64  of the engaged portion  62 . In addition, the step  67  may be formed on the projection facing surface  53  of the engaging portion (sliding resistance generating portion)  52 , or may be formed on the projection facing surface  54  of the engaging portion  52 . 
     Seventh Modification 
     As shown in  FIGS. 13A and 13B , on the recessed facing surface  63  of the engaged portion  62 , one or more protrusions  68  are formed. Herein, five protrusions  68  are arranged at vertexes of a regular pentagon with respect to the central axis C. The protrusions  68  protrude from the recessed facing surface  63  of the engaged portion  62  toward the proximal end side along the central axis C. 
     As shown in  FIG. 13A , a recess  58  is formed on the projection facing surface  53  of the engaging portion  52 . The number of the recesses  58  may be the same as that of the protrusions  68 , a larger number, or a smaller number. 
     The protrusion  68  can be fitted to the recess  58  at one or more positions. Thus, in this modification, when the same external force F is applied to the same position of the end effector  5  and/or the shaft  3 , it is possible to generate a large sliding resistance (frictional force) around the predetermined rotation axis R, as compared with the example (see  FIG. 5 ) described in the first embodiment. 
     Herein, an example has been described in which the protrusion  68  is formed on the recessed facing surface  63  of the engaged portion  62  and the recess  58  is formed on the projection facing surface  53  of the engaging portion  52 , but these may of course be opposite. 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIGS. 14A and 14B . This embodiment is a modification of the first embodiment including each modification, and the same members or members having the same function as those described in the first embodiment are denoted by the same reference numerals as much as possible, and a detailed description thereof will be omitted. 
     In the first embodiment including the first to seventh modifications, an example in which the end effector  5  can actively move at the distal end of the shaft  3  has been described. In addition, an example in which a pair of the grasping pieces  16  and  17  (see  FIGS. 1 and 2 ) of the end effector  5  can be relatively opened and closed has been described. Herein, an example will be described in which the end effector  5  is formed integrally with the distal end of the shaft  3 , and the end effector  5  is bent with respect to the shaft  3 . That is, in the present embodiment, the end effector  5  is curved with respect to the shaft  3 , and is located at a position shifted from the central axis C. 
     In the present embodiment, operation buttons  27 A,  27 B, and  27 C are attached to the main body  11  of the housing  2 . Each of the operation buttons  27 A,  27 B, and  27 C is pressed to perform an operation input. When an operation input is performed with each of the operation buttons  27 A,  27 B, and  27 C, the treatment instrument  1  is operated in a predetermined operation mode. At this time, for example, similarly to known treatment instruments, either one or more of high-frequency current, ultrasonic vibration, and heater heat is applied as a treatment energy to the treatment target with which the end effector  5  is in contact. 
     Even in this case, for example, in the same manner as shown in  FIGS. 4 and 5  (or  FIGS. 6 and 7 ), when the external force F is applied to the rotary element  6 , the central axis C of the shaft  3  can be inclined with respect to the predetermined rotation axis R of the housing  2  to stop the rotation of the rotary element  6  relative to the housing  2 . Thus, for example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator can be effectively prevented by the lock mechanism  80 . 
     On the other hand, when the operator operates the rotating knob  26 A of the rotating member  25 , for reasons of the rotational moment with respect to the predetermined rotation axis R against the frictional force between the housing  2  and the rotating member  25 , for example, the rotating knob  26 A can be rotated so as to push aside the living tissue by the end effector  5 . 
     When the rotating member  25  is arranged in the internal portion of the housing main body  11 , a structure (structure in which the shaft  3  is supported at a plurality of portions with respect to the housing  2 ) described in a third embodiment or a fourth embodiment can also be adopted. 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIGS. 15 to 17 . This embodiment is a modification of the first embodiment including the first to seventh modifications and the second embodiment, and the same members or members having the same function as those described in the first and second embodiments are denoted by the same reference numerals as much as possible, and a detailed description thereof will be omitted. 
     In the first embodiment, an example in which the rotating member  25  is arranged at the distal end portion of the housing main body  11  has been described. Herein, as shown in  FIG. 15 , an example in which a part of the rotating knob  26 A of the rotating member  25  protrudes from a side of the housing main body  11  will be described. 
     In the first embodiment, as shown in  FIGS. 4 and 5 , an example in which the rotating member  25  is supported at one position with respect to the housing main body  11  has been described. That is, in the first embodiment, an example in which the treatment instrument  1  includes one joint assembly  40  has been described. Herein, as shown in  FIG. 16 , an example in which the rotating member  25  is supported at two positions (a plurality of positions) with respect to the housing main body  11  will be described. That is, in the present embodiment, an example in which the treatment instrument  1  includes a first joint (joint assembly)  140  and a second joint (joint assembly)  240  will be described. 
     In the present embodiment, the rotating member  25  includes a rotating knob  26 A, the first connecting portion (proximal end side connecting portion)  26 B and a second connecting portion (distal end side connecting portion)  26 C. 
     As shown in  FIG. 16 , the housing main body  11  is formed with openings  11 A and  11 B through which the rotating knob  26 A protrudes. It is preferable that the openings  11 A and  11 B are formed on a side surface of the housing main body  11  shown in  FIG. 15 . In the housing  2 , a first engagement projection  141  is formed on the proximal end side along the predetermined rotation axis R with respect to the openings  11 A and  11 B. In the housing  2 , a second engagement projection  241  is formed on the distal end side along the predetermined rotation axis R with respect to the openings  11 A and  11 B. 
     A first engagement recess  142  engaging with the first engagement projection  141  of the housing  2  is formed on the outer peripheral surface of the first connecting portion  26 B of the rotating member  25 . The first engagement projection  141  and the first engagement recess  142  constitute the first joint (joint assembly)  140 . A second engagement recess  242  engaging with the second engagement projection  241  of the housing  2  is formed on an outer peripheral surface of the second connecting portion  26 C of the rotating member  25 . The second engagement projection  241  and the second engagement recess  242  constitute the second joint (joint assembly)  240 . 
     Herein, for simplicity of explanation, it is assumed that the maximum radius of the first connecting portion  26 B is the same as that of the second connecting portion  26 C, which is D 1 . The maximum radius D 1  of the first connecting portion  26 B and the second connecting portion  26 C is smaller than the maximum radius D 0  of the rotating knob  26 A. 
     An opening  2 A through which the shaft  3  passes is formed at the distal end of the housing main body  11 . The opening  2 A has an inner diameter larger than the outer diameter of the shaft  3  so as to allow the shaft  3  to bend appropriately. Thus, the shaft  3 , i.e., the rotary element  6  can bend relative to the central axis C by the external force F from a direction deviated from the predetermined rotation axis R. 
     The engagement projection  141  of the housing  2  includes a supporting portion (rotation supporting surface)  151  and an engaging portion  152 . The supporting portion  151  defines a cylindrical inner peripheral surface with respect to the predetermined rotation axis R. The engaging portion  152  is adjacent to the supporting portion  151  along the predetermined rotation axis R. The engaging portion  152  includes a projection facing surface (first receiving surface)  153  facing the distal end side and a projection facing surface (second receiving surface)  154  facing the proximal end side. 
     The engagement recess  142  of the rotary member  25  of a part of the shaft  3  includes a supported portion (rotation supporting surface)  161  and an engaged portion  162 . The supported portion  161  defines a cylindrical outer peripheral surface with respect to the central axis C. The engaged portion  162  is adjacent to the supported surface  161  along the central axis C. The engaged portion  162  includes a recessed facing surface (first contact surface)  163  facing the proximal end side and a recessed facing surface (second contact surface)  164  facing the distal end side. 
     In the present embodiment, the supporting portion  151  of the housing  2  and the supported portion  161  of the shaft  3  cooperate to form a rotation supporting mechanism  170 . The engaging portion  152  of the housing  2  and the engaged portion  162  of the shaft  3  cooperate to form a lock mechanism  180 . 
     Between the projection facing surface  153  of the engaging portion  152  and the recessed facing surface  163  of the engaged portion  162 , and/or between the projection facing surface  154  of the engaging portion  152  and the recessed facing surface  164  of the engaged portion  162 , a sliding resistance (friction) can be generated by an inclination of the central axis C of the shaft  3  of the rotary element  6  with respect to the predetermined rotation axis R. 
     As shown in  FIG. 17 , the engagement projection  241  of the housing  2  includes a supporting portion (rotation supporting surface)  251  and an engaging portion  252 . The supporting portion  251  defines a cylindrical inner peripheral surface with respect to the predetermined rotation axis R. The engaging portion  252  is adjacent to the supporting portion  251  along the central axis C. The engaging portion  252  includes a projection facing surface (first receiving surface)  253  facing the distal end side and a projection facing surface (second receiving surface)  254  facing the proximal end side. 
     The engagement recess  242  of the rotating member  25  of a part of the shaft  3  includes a supported portion (rotation supporting surface)  261  and an engaged portion  262 . The supported portion  261  defines a cylindrical outer peripheral surface with respect to the central axis C. The engaged portion  262  is adjacent to the supported surface  261  along the central axis C. The engaged portion  262  includes a recessed facing surface (first contact surface)  263  facing the proximal end side and a recessed facing surface (second contact surface)  264  facing the distal end side. 
     Between the projection facing surface  253  of the engaging portion  252  and the recessed facing surface  263  of the engaged portion  262 , and/or between the projection facing surface  254  of the engaging portion  252  and the recessed facing surface  264  of the engaged portion  262 , a sliding resistance (friction) can be generated by the inclination of the central axis C of the shaft  3  of the rotary element  6  with respect to the predetermined rotation axis R. 
     In the present embodiment, the supporting portion  251  of the housing  2  and the supported portion  261  of the shaft  3  cooperate to form a rotation supporting mechanism  270 . The engaging portion  252  of the housing  2  and the engaged portion  262  of the shaft  3  cooperate to form a lock mechanism  280 . 
     In the rotation supporting mechanism  170 , the supporting portion  151  of the engagement projection  141  of the housing  2  cooperates with the supported portion  161  of the engagement recess  142  of the shaft  3  to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . In the rotation supporting mechanism  270 , the supporting portion  251  of the engagement projection  241  of the housing  2  cooperates with the supported portion  261  of the engagement recess  242  of the shaft  3  to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . Herein, it is preferable that the first joint  140  is formed with less rattling than the second joint  240 . 
     As shown in  FIG. 17 , when the external force F is received from a position deviated from the central axis C with respect to the rotary element  6 , the shaft  3  is elastically deformed and bent as indicated by a broken line in  FIG. 17 , and the rotating member  25  is elastically deformed relative to the main body  11  of the housing  2 . At this time, an amount of deformation of the rotating member  25  is larger at the second connecting portion  26 C having a short distance to a point of application of the external force F than at the first connecting portion  26 B having a long distance to the point of application of the external force F. Thus, a deviation of the central axis C of the shaft  3  with respect to the predetermined rotation axis R of the housing  2  is greater at the second connecting portion  26 C than at the first connecting portion  26 B. 
     The treatment instrument  1  of the present embodiment supports the shaft  3  with respect to the housing  2  at two positions (joints  140 ,  240 ) along the predetermined rotation axis R. Thus, as compared with the example (see  FIG. 5 ) in which the shaft  3  is supported at one position (joint assembly  40 ) with respect to the housing  2  described in the first embodiment, it is possible to make it difficult to incline the shaft  3 . On the other hand, the shaft  3  has a bendability which can shift the rotary element  6  with respect to the predetermined rotation axis R of the housing  2  due to the elastic deformation by a load of the external force F applied to the rotary element  6  from a direction deviated from the predetermined rotation axis R. For this reason, the central axis C of the shaft  3  is shifted with respect to the predetermined rotation axis R by the bending of the shaft  3  with respect to the housing  2 . 
     Due to the elastic deformation of the second connecting portion  26 C of the rotating member  25 , the recessed facing surface  263  of the engaged portion (sliding resistance generating portion)  262  of the engagement recess (supported portion)  242  of the rotating member  25  contacts the projection facing surface  253  of the engaging portion  252  of the engagement projection  241  of the housing  2 . For this reason, sliding resistance between the housing  2  and the rotating member  25  is generated in the same manner as described in the first embodiment. Accordingly, even if the external force F is applied to the rotary element  6  as indicated by broken lines in  FIG. 17  and a force to rotate the end effector  5  and/or the shaft  3  around the central axis C is applied, a braking action for suppressing rotation relative to the housing  2  continues to be generated in the rotating member  25 . As the external force F increases, the recessed facing surface  263  of the engaged portion  262  of the rotating member  25  strongly contacts the projection facing surface  253  of the engaging portion  252  of the housing  2 . Thus, as the external force F increases, the braking action (sliding resistance) around the rotation axis R of the housing  2  against the rotation member  25  also increases. 
     Therefore, rotation of the shaft  3  around the central axis C of the shaft  3  is suppressed along with the unintentional rotation of the rotating member  25  relative to the housing  2  being suppressed, and furthermore, the rotation of the end effector  5  around the central axis C is suppressed. When the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, for example, rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator can be effectively prevented by the lock mechanism  280 . 
     On the other hand, when the operator intends to rotate the end effector  5  and the shaft  3  around the predetermined rotation axis R intentionally, the rotating knob  26 A having the radius D 0  larger than the radius D 1  of a portion generating the sliding resistance maybe rotated. Thus, the operator can easily rotate the rotating knob  26 A around the predetermined rotation axis R against the sliding resistance by the rotational moment. Therefore, for example, the operator can push aside the living tissue by turning the end effector  5 , which is at a position deviated from the central axis C, around the central axis C. When the operator rotates the rotating member  25  against the frictional force (sliding resistance), the central axis C of the shaft  3  tries to move to coincide with the predetermined rotation axis R of the housing  2  so as to avoid generation of friction between the engaging portion  252  and the engaged portion  262 . 
     For example, it is a matter of course that when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, depending on the magnitude of the external force F, the lock mechanism  180  can also cooperate with the lock mechanism  280  to exert the function of preventing rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator. 
     First Modification 
     As shown in  FIG. 18 , a friction ring  2 B is formed on an inner peripheral surface of the opening  2 A at the distal end of the main body  11  of the housing  2 . 
     Thus, when the outer peripheral surface of the shaft  3  is brought into contact with the friction ring  2 B, it is possible to suppress unintentional rotation of the shaft  3  around the predetermined rotation axis R due to the external force F in cooperation with the lock mechanism  280  (and the lock mechanism  180 ). 
     Second Modification 
     In this modification, an example in which the shaft  3  is supported by the housing  2  at a position apart from the rotating member  25  to exert the braking action on the shaft  3  will be described. 
     As shown in  FIGS. 19 and 20 , in the present modification, a joint (joint assembly)  340  prepared by deforming the structure of the second joint (joint assembly)  240  is formed. 
     On the inner peripheral surface of the main body  11  of the housing  2 , an engagement projection  341  facing an outer peripheral surface of a flange  3 A is formed. An engaging portion  352  generating a frictional force is formed on an inner peripheral surface of the engagement projection  341  with respect to the predetermined rotation axis R. 
     On the outer peripheral surface of the shaft  3 , the flange  3 A protruding outward in the radial direction with respect to the central axis C is formed. An outer diameter of the flange  3 A is smaller than an inner diameter of the engaging portion  352  of the engagement projection  341  of the housing  2 . The outer peripheral surface of the flange  3 A is processed or coated so as to generate an appropriate friction between with the engaging portion  352  to be described later. In the present embodiment, the engaging portion  352  of the housing  2  and an engaged portion  362  on the outer peripheral surface of the flange  3 A of the shaft  3  cooperate to form a lock mechanism  380 . 
     As shown in  FIG. 20 , when receiving the external force F from a position deviated from the central axis C with respect to the rotary element  6 , the shaft  3  elastically deforms as indicated by broken lines in  FIG. 20 . The engaged portion (sliding resistance generating portion)  362  of the shaft  3  comes into contact with the engaging portion  352  of the housing  2 . Thus, a sliding resistance is generated between the housing  2  and the flange  3 A of the shaft  3  in the same manner as described above. 
     Therefore, for example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R can be effectively prevented by the lock mechanism  380 . 
     For example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, depending on the magnitude of the external force F, the lock mechanism  180  can also cooperate with the lock mechanism  380  to exert the function of preventing the rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator. 
     Fourth Embodiment 
     Next, a fourth embodiment will be described with reference to  FIGS. 21 and 22 . This embodiment is a modification of the first to third embodiments including each modification, and the same members or members having the same function as those described in the first to third embodiments are denoted by the same reference numerals as much as possible, and a detailed description thereof will be omitted. 
     In the treatment instrument  1  described in the first embodiment, as shown in  FIG. 4 , an example in which the engagement projection  41  is formed in the housing  2 , and the engagement recess  42  is formed in the rotating member  25  has been described. In the present embodiment, as shown in  FIG. 21 , an example will be described in which engagement recesses  442  and  542  are formed in the housing  2 , and engagement projections  441  and  541  are formed in the rotating member  25 . The rotating member  25  includes a rotating knob  26 A, a first connecting portion (proximal end side connecting portion)  26 D, and a second connecting portion (distal end side connecting portion)  26 E. 
     As shown in  FIG. 21 , the treatment instrument  1  includes a first joint (joint assembly)  440  and a second joint (joint assembly)  540 . 
     The first joint  440  includes the engagement projection (supporting portion)  441  and the engagement recess (supported portion)  442 . 
     The engagement projection (supporting portion)  441  protruding toward the inner peripheral side is provided in the first connecting portion  26 D of the rotating member  25 . As an example, the engagement projection (inner flange)  441  is provided over an entire circumference around the central axis C of the shaft  3 . Although not shown, the engagement projection  441  may be formed, for example, at appropriate intervals in a circumferential direction around the central axis C of the shaft  3 . Thus, one engagement projection  441  maybe provided, or a plurality of engagement projections  441  may be provided. 
     On the outer peripheral surface of the main body  11  of the housing  2 , an engagement recess (supported portion)  442  that is recessed toward the inner peripheral side is provided. The engagement recess  442  is provided over the entire circumference around the rotation axis R. By the engagement projection  441  being engaged with the engagement recess  442 , the shaft  3  is supported by the housing  2  so as to be rotatable around the predetermined rotation axis R. 
     Thus, the engagement projection  441  can move around the predetermined rotation axis R relative to the engagement recess  442 . The rotating member  25  of the shaft  3  is rotatable around the predetermined rotation axis R relative to the housing  2 . Therefore, the engagement projection  441  and the engagement recess  442  form a joint assembly (connecting portion)  440  that connects the shaft  3  so as to be rotatable around the predetermined rotation axis R of the housing  2 . 
     As shown in  FIG. 21 , the engagement projection  441  of the rotating member  25  includes a supporting portion (rotation supporting surface)  451  and an engaging portion (sliding resistance generating portion)  452 . The supporting portion  451  defines a cylindrical inner peripheral surface with respect to the central axis C of the shaft  3 . The engaging portion  452  is adjacent to the supporting portion  451  along the central axis C. The engaging portion  452  includes a projection facing surface (first receiving surface)  453  facing the distal end side and a projection facing surface (second receiving surface)  454  facing the proximal end side. 
     The engagement recess  442  on the outer peripheral surface of the housing  2  includes a supported portion (rotation supporting surface)  461  and an engaged portion (sliding resistance generating portion)  462 . The supported portion  461  defines a cylindrical outer peripheral surface with respect to the predetermined rotation axis R. The engaged portion  462  is adjacent to the supported surface  461  along the rotation axis R. The engaged portion  462  includes a recessed facing surface (first contact surface)  463  facing the proximal end side and a recessed facing surface (second contact surface)  464  facing the distal end side. 
     The recessed facing surface (first contact surface)  463  facing the proximal end side of the engagement recess  442  faces the projection facing surface (first receiving surface)  453  facing the distal end side of the engagement projection  441 . The recessed facing surface (second contact surface)  464  facing the distal end side of the engagement recess  442  faces the projection facing surface (second receiving surface)  454  facing the proximal end side of the engagement projection  441 . 
     The projection facing surface  453  of the engagement projection  441  and the recessed facing surface  463  of the engagement recess  442 , and the projection facing surface  454  of the engagement projection  441  and the recessed facing surface  464  of the engagement recess  442 , each, are formed so as to generate a large frictional force when in contact, as compared with the frictional force (sliding resistance) between the supporting portion  451  and the supported portion  461 . 
     In the present embodiment, the supporting portion  451  of the housing  2  and the supported portion  461  of the shaft  3  cooperate to form a rotation supporting mechanism  470 . The engaging portion  452  of the housing  2  and the engaged portion  462  of the shaft  3  cooperate to form a lock mechanism  480 . 
     The second joint  540  includes the engagement projection (supporting portion)  541  and the engagement recess (supported portion)  542 . 
     As shown in  FIG. 22 , the engagement projection (supporting portion)  541  protruding toward the inner peripheral side is provided in the second connecting portion  26 E of the rotating member  25 . As an example, the engagement projection (inner flange)  541  is provided over the entire circumference around the central axis C of the shaft  3 . Although not shown, the engagement projection  541  may be formed, for example, at appropriate intervals in the circumferential direction around the central axis C of the shaft  3 . Thus, one engagement projection  541  may be provided, or a plurality of engagement projections  541  may be provided. 
     On the outer peripheral surface of the main body  11  of the housing  2 , the engagement recess (supported portion)  542  that is recessed toward the inner peripheral side is provided. The engagement recess  542  is provided over the entire circumference around the rotation axis R. By the engagement projection  541  being engaged with the engagement recess  542 , the shaft  3  is supported by the housing  2  so as to be rotatable around the predetermined rotation axis R. 
     Thus, the engagement projection  541  can move around the predetermined rotation axis R relative to the engagement recess  542 . The rotating member  25  of the shaft  3  is rotatable around the predetermined rotation axis R relative to the housing  2 . Accordingly, the engagement projection  541  and the engagement recess  542  form the joint (connecting portion)  540  that connects the shaft  3  so as to be rotatable around the predetermined rotation axis R of the housing  2 . 
     The engagement projection  541  of the rotating member  25  includes a supporting portion (rotation supporting surface)  551  and an engaging portion (sliding resistance generating portion)  552 . The supporting portion  551  defines a cylindrical inner peripheral surface with respect to the central axis C of the shaft  3 . The engaging portion  552  is adjacent to the supporting portion  551  along the central axis C. The engaging portion  552  includes a projection facing surface (first receiving surface)  553  facing the distal end side and a projection facing surface (second receiving surface)  554  facing the proximal end side. 
     The engagement recess  542  on the outer peripheral surface of the housing  2  includes a supported portion (rotation supporting surface)  561  and an engaged portion (sliding resistance generating portion)  562 . The supported portion  561  defines a cylindrical outer peripheral surface with respect to the predetermined rotation axis R. The engaged portion  562  is adjacent to the supported surface  561  along the rotation axis R. The engaged portion  562  includes a recessed facing surface (first contact surface)  563  facing the proximal end side and a recessed facing surface (second contact surface)  564  facing the distal end side. 
     The recessed facing surface (first contact surface)  563  facing the proximal end side of the engagement recess  542  faces the projection facing surface (first receiving surface)  553  facing the distal end side of the engagement projection  541 . The recessed facing surface (second contact surface)  564  facing the distal end side of the engagement recess  542  faces the projection facing surface (second receiving surface)  554  facing the proximal end side of the engagement projection  552 . 
     The projection facing surface  553  of the engagement projection  541  and the recessed facing surface  563  of the engagement recess  542 , and the projection facing surface  554  of the engagement projection  541  and the recessed facing surface  564  of the engagement recess  542 , each, are formed so as to generate a large frictional force when in contact, as compared with the frictional force (sliding resistance) between the supporting portion  551  and the supported portion  561 . 
     The engaging portion  552  is at a position adjacent to the distal end side and the proximal end side of the supporting portion  551 . Thus, a position of the supporting portion  551  and that of the engaging portion  552  are different from each other. Similarly, the engaged portion  562  is at a position adjacent to the distal end side and the proximal end side of the supported portion  561 . Thus, a position of the supported portion  561  and that of the engaged portion  562  are different from each other. 
     The supporting portion  551  of the housing  2  and the supported portion  561  of the shaft  3  cooperate to form a rotation supporting mechanism  570 . The engaging portion  552  of the housing  2  and the engaged portion  562  of the shaft  3  cooperate to form a lock mechanism  580 . 
     In the rotation supporting mechanism  470 , the supporting portion  451  of the engagement projection  441  of the housing  2  cooperates with the supported portion  461  of the engagement recess  442  of the shaft  3  to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . In addition, in the rotation supporting mechanism  570 , the supporting portion  551  of the engagement projection  541  of the housing  2  cooperates with the supported portion  561  of the engagement recess  542  of the shaft  3  to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . 
     The supporting portion  551  of the engagement projection  541  of the rotating member  25  cooperates with the supported portion  561  of the engagement recess  542  of the housing  2  to make the central axis C of the shaft  3  coincide with the predetermined rotation axis R of the housing main body  11  of the housing  2 . Herein, an inner diameter of the supporting portion  551  with respect to the central axis C is formed to be larger than an outer diameter of the supported portion  561  with respect to the predetermined rotation axis R. Thus, the supporting portion  551  of the engagement projection  541  of the rotating member  25  is rattled, that is, plays with respect to the supported portion  561  of the engagement recess  542  of the housing  2 . For this reason, for example, when an external force from a position deviated from the central axis C of the shaft  3  is applied to the rotary element  6 , the central axis C of the shaft  3  is displaced from the predetermined rotation axis R of the housing  2 , from a position indicated by a solid line to a position indicated by a broken line in  FIG. 22 . 
     Herein, the treatment instrument  1  of the present embodiment supports the shaft  3  with respect to the housing  2  at two positions (joints  440 ,  540 ) along the predetermined rotation axis R. Thus, as compared with the example (see  FIG. 5 ) in which the shaft  3  is supported at one position (joint assembly  40 ) with respect to the housing  2  described in the first embodiment, it is possible to make it difficult to incline the shaft  3 . On the other hand, the shaft  3  has a bendability which can displace the rotary element  6  with respect to the predetermined rotation axis R of the housing  2  due to the elastic deformation by a load of the external force F applied to the rotary element  6  from a direction deviated from the predetermined rotation axis R. For this reason, the central axis C of the shaft  3  is displaced with respect to the predetermined rotation axis R by the bending of the shaft  3  relative to the housing  2 . 
     At this time, the rotation of the rotary element  6  around the predetermined rotation axis R can be suppressed by the lock mechanism  580 . More specifically, the lock mechanism  580  can suppress the rotation of the rotary element  6  around the predetermined rotation axis R at a position different from that of the supporting portion  551 . Accordingly, for example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator can be effectively prevented by the lock mechanism  580 . 
     When the operator intends to rotate the end effector  5  and the shaft  3  around the predetermined rotation axis R intentionally, the rotating knob  26 A having the radius DO larger than the maximum radius D 3  with respect to the predetermined rotation axis R in the main body  11  of the housing  2  may be rotated. Thus, the operator can easily rotate the rotating knob  26 A around the predetermined rotation axis R against the sliding resistance by the rotational moment. 
     For example, when the external force F is applied to the end effector  5  arranged at a position deviated from the central axis C, depending on the magnitude of the external force, the lock mechanism  480  can also cooperate with the lock mechanism  580  to effectively prevent rotation of the end effector  5  and the shaft  3  around the predetermined rotation axis R unintended by the operator. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.