Patent ID: 8727968

Claim:
A medical treatment endoscope comprising: an endoscope main body which includes an elongated insertion portion having an arm-inserted lumen and an image capturing mechanism disposed in a distal end of the insertion portion; an arm bending part which is provided so as to protrude or retract freely from the arm-inserted lumen, has a treatment tool lumen for allowing an endoscope treatment tool to be inserted therethrough and is capable of bending freely; and a positioning mechanism which positions the arm bending part in the state of protruding from the arm-inserted lumen with respect to the endoscope main body; and an operating portion which operates so as to bend the arm bending part, wherein the positioning mechanism includes an engaging member which is provided at a proximal end of the arm bending part, and an engaged member which is provided at an inner wall of a distal end of the arm-inserted lumen and engages with the engaging member at a position where the arm bending part protrudes from an opening of the arm-inserted lumen in at least one of a circumference direction and an axial direction, wherein the member includes: a first stopper which freely protrudes from an retracts into an outer peripheral surface of an arm and is connected to the arm, and a second stopper which freely protrudes or retracts from the outer peripheral surface of the arm and is connected to the arm at a position that faces the first stopper in a radial direction of the arm, wherein the engaged member includes: a first wall formed on an inner wall of the arm-inserted lumen outward in the radial direction; a second wall formed on the inner wall of the arm-inserted lumen outward in the radial direction at a position away from the first wall in the circumferential direction; a contact wall portion formed in the inner wall of the arm-inserted lumen outward in the radial direction and extending in the circumferential direction at a position between the first wall and the second wall; and a concave portion formed at a position that faces the second wall, wherein the second stopper engages with an inside of the concave portion when the second stopper is protruded from the outer peripheral surface of the arm in the state where the first stopper that protrudes from the outer peripheral surface of the arm contacts with the contact wall portion and the second wall.