Rotational force transmission mechanism, force-attenuating apparatus, medical device, and medical instrument-operation mechanism

A medical device comprising:

• a flexible sheath;
• an arm section protruding from a tip of the sheath and capable of conducting a first bending operation and allowing a procedure instrument to be inserted therethrough;
• and
• a bending operating part operated when the arm section is bent, wherein the bending operating part comprises a rotational force transmission mechanism comprising:
• a rotation-inputting member freely rotative and driven by a predetermined operating member in a predetermined first direction around a rotation axis and a second direction opposite to the first direction around the rotation axis;
• a first rotation-transmitting member having a first rotational driving force receiving portion which is capable of contacting the rotation-inputting member, the first rotation-transmitting member is configured to be pushed and rotated in the first direction around the rotation axis by making the first rotational driving force receiving portion contacting with the rotation-inputting member when the rotation-inputting member rotates in the first direction;
• a second rotation-transmitting member coaxially disposed with the first rotation-transmitting member stacking to the first rotation-transmitting member in a direction of axis of the rotation axis so as to overlap each other, the second rotation-transmitting member having a second rotational driving force receiving portion which is capable of contacting the rotation-inputting member, and configured to be pushed and rotated in the second direction by making the second rotational driving force receiving portion contacting with the rotation-inputting member when the rotation-inputting member rotates in the second direction;
• a connection member configured of an elastic member and disposed so that a rotational force acts in a direction in which a relative rotational positional relationship between the first rotation-transmitting member and the second rotation-transmitting member is maintained, the connection member being configured to pull the second rotation-transmitting member in the first direction by a rotation of the first rotation-transmitting member in the first direction and rotates the second rotation-transmitting member in the first direction, and configured to pull the first rotation-transmitting member in the second direction by a rotation of the second rotation-transmitting member in the second direction and rotates the first rotation-transmitting member in the second direction;
• and
• a rotation-outputting member rotated and driven in the second direction by being contacted and pushed by the first rotation-transmitting member being pulled by the connection member and rotating in the second direction, and rotated and driven in the first direction by being contacted and pushed by the second rotation-transmitting member being pulled by the connection member and rotating in the second direction,
• wherein when an external force is applied onto the rotation-outputting member and a torque having a predetermined value or greater is applied onto the rotation-inputting member, the connection member as a force-attenuating apparatus elastically deforms to absorb and attenuate the torque, thereby the rotation-outputting member is prevented from the torque having the predetermined value or greater to be transferred thereto.