Abstract: A shaft cylinder having an opening at a front end thereof, a tip holder movable in an axial direction of the shaft cylinder, a tip projectable and retractable in conjunction with a movement of the tip holder, an annular member loosely fitted onto an inner periphery of the opening of the shaft cylinder to be movable in an axial direction of the shaft cylinder with respect to the shaft cylinder, and an elastic member capable of connecting the tip holder and the annular member such that the tip holder and the annular member are movable relatively to each other. A contact surface tapered toward the front end is formed on at least a part of an outer periphery of the annular member. A cutout is formed on the annular member such that an inner diameter of the annular member is reduced when a load is received by the contact surface.

Abstract: The present invention includes: a shaft cylinder having an opening at a front end thereof, a tip holder movable in an axial direction of the shaft cylinder, a tip projectable and retractable in conjunction with a movement of the tip holder, an annular member loosely fitted onto an inner periphery of the opening of the shaft cylinder to be movable in an axial direction of the shaft cylinder with respect to the shaft cylinder, and an elastic member capable of connecting the tip holder and the annular member such that the tip holder and the annular member are movable relatively to each other. A contact surface tapered toward the front end is formed on at least a part of an outer periphery of the annular member. A cutout is formed at a part of the annular member such that an inner diameter of the annular member is reduced when a load is received by the contact surface. A guide surface tapered toward the front end is formed on the part of the inside surface of the shaft cylinder.