Medical treatment endoscope

1. A medical treatment endoscope comprising:

a sheath having a flexibility;

arm members configured to be capable of advancing from and retracting into the sheath, and having a bending part that projects out from a front end of the sheath and performs bending actions;

a wire member configured to bend the bending part;

an open/close mechanism which directs the arm members from a direction along a central axis of the sheath to a rotational direction deviated from the central axis of the sheath around a base axis of the arm members, and from the rotational direction deviated from the central axis of the sheath around the base axis of the arm members to a direction along the central axis of the sheath;

a viewing device and an illuminating member that are disposed to a front end side of the sheath;

the open/close mechanism includes:

an open/close operating member, configured to open the arm members by moving in a proximal end direction of the sheath, the open/close operating member at least partially protrudes from an opening of a distal end of the sheath and inserted in a freely advancing and retracting manner into the sheath;

linking parts, connected to the open/close operating member at a first end thereof and connected to a proximal position of the arm members at a second end thereof, and configured to be capable of turning according to the open/close operating member which advances and retracts for converting an advance/retract action of the arm members into an open/close action around the base axis of the arm members of the open/close mechanism; and

supporting members connected to the linking parts at a first end of the supporting members to be rotatable and connected to the sheath to freely advance and retract so as to support the arm members;

wherein the arm members comprise two arm members that are arranged in a radial direction of the sheath, and at least one part of the open/close operating member is disposed at a position in an area between central axes of the two arm members in a cross-section along the central axis of the sheath.

2. The medical treatment endoscope according to claim 1 , wherein front ends of the two arm members are capable of relative displacement with respect to the viewing device and the illuminating member by means of at least one of a bending action of the bending part and a directional transition of the two arm members by the open/close mechanism.

3. The medical treatment endoscope according to claim 2 , further comprising;

a frame; and

a bending operating part to which a procedure operating part for a procedure device for performing a procedure in an organ is attachable, for bending the bending part.

4. The medical treatment endoscope according to claim 1 , wherein in the cross-section along the central axis of the sheath, the open/close operating member is disposed closer to the central axis of the sheath than a position at which the two arm members are disposed.

5. The medical treatment endoscope according to claim 1 , wherein a connecting part for the linking part and the two arm members are provided so as to be positioned between a connecting part for the open/close operating member and the linking part, and the front end of the sheath, while in a state that the linking part is caused the two arm members to approach the central axis of the sheath, as a result of movement of the front end of the open/close operating member in the first direction to approach the central axis of the sheath.

6. The medical treatment endoscope according to claim 5 , wherein the open/close operating member is disposed to an area opposite the viewing device, between the two arm members.

7. The medical treatment endoscope according to claim 1 , wherein the viewing device is disposed to the distal end of the sheath, and the open/close mechanism opens and closes the two arm members at a more distal position than a position at which the viewing device is disposed.

8. The medical treatment endoscope according to claim 1 , wherein a distal end of the open/close operating member which is connected to a front end of the linking parts is disposed at a more distal position of the arm members than that of the second end of the linking parts which is connected to the supporting members such that a pantograph framework is formed by the linking parts and the supporting members.