Patent ID: 7013792

Claim:
An actuator comprising: a hollow cylinder; a piston rod which is formed in a diameter smaller than an inner diameter of the cylinder and which is inserted into the cylinder in such a manner that relative movement is possible in an axial direction of the cylinder; and a locking mechanism which locks the relative movement of the piston rod with respect to the cylinder in a state in which one end of the piston rod protrudes from one end of the cylinder, wherein the locking mechanism comprises: a first surface provided on an inner surface of the cylinder and so inclined that the inside diameter of the cylinder gradually linearly increases toward one end the cylinder; a plurality of second surfaces arranged in an axial direction of the piston rod and parallel to one another, each second surface being so inclined that the diameter of the piston rod gradually linearly increases to said one end of the piston rod; and a locking member held between the first surface and any one of the second surfaces to lock the relative movement of the piston rod with respect to the cylinder.