a housing having a piston bore extending axially including an open end with a notch connected radially to the piston bore, an upper stop surface and a lower stop surface;

a piston slidably supported in the piston bore comprising a plurality of rack teeth on the outer circumferential surface thereof;

a piston spring provided in the piston bore biasing the piston in a protruding direction from the housing; and

a circlip member comprising:

an expandable ring-shaped body engaged with the rack teeth of the piston having at least one wavy portion that elastically deforms in an axial direction, and

an operatable handle portion for expanding the ring-shaped body extending outside of the housing through the notch connected radially to the piston bore;

wherein the rack teeth of the piston are formed such that when the ring-shaped body of the circlip member engages with the upper stop surface of the piston bore, the piston is permitted to move in the protruding direction and when the ring-shaped body of the circlip member engages with the lower stop surface of the piston bore, the piston is restricted to moving in the retracting direction and the wavy portions of the ring-shaped body of the circlip member deform in the axial direction.