Patent ID: 8721657

Claim:
A medical instrument for performing a medical procedure within a body cavity, the medical instrument comprising: an insertion part comprising a bending part capable of bending in a predetermined range; a manipulating part which manipulates the bending part; and a wire which is arranged to be capable of moving in a longitudinal direction with respect to the insertion part and which connects the bending part with the manipulating part, wherein, the manipulating part comprises: a handle capable of being rotated and controlled in a predetermined direction to bend the bending part; a drive shaft which is connected to the handle at a first end thereof, which is connected to a proximal end of the wire at a second end thereof, and which is capable of rotating by rotation of the handle and by advancing and retreating of the wire; a bearing which is substantially-coaxially arranged with respect to the drive shaft to be rotatable and which is fixed to a proximal end of the insertion part; and a spring which is engaged to the drive shaft at a first end thereof, which is connected to the handle at a second end thereof, which is formed to be twisted attachably and detachably around both a first outer peripheral surface of the drive shaft and a second outer peripheral surface of the bearing at a predetermined winding diameter thereof, the winding diameter thereof being configured to vary by rotation of the drive shaft, wherein: the bending part is bent by the wire being pulled by the drive shaft rotating in the predetermined direction in accordance with the rotation of the handle in the predetermined direction, a tensile force acting on the wire is generated when the bending part is bent, the winding diameter of the spring is decreased by the drive shaft rotating in an opposite direction of the predetermined direction by the tensile force without the handle rotating, an inner peripheral surface of the spring comes in contact with both the first outer peripheral surface of the drive shaft and the second outer peripheral surface of the bearing, and both the drive shaft and the bearing are fastened with the spring by the winding diameter of the spring decreasing so that the rotation of the drive shaft is stopped and the drive shaft is connected to the bearing with the drive shaft being incapable of rotating, and the bending part is kept bent by the spring preventing the drive shaft from rotating.