Patent ID: 7997588

Claim:
A cylinder apparatus comprising: a cylinder containing a hydraulic liquid sealed therein; a piston slidably fitted within the cylinder so as to divide an interior of the cylinder into a first chamber and a second chamber; a piston rod, one end of which is connected to the piston and the other end of which is extended outside through the first chamber; an external cylinder provided at an outer periphery of the cylinder so as to form a reservoir between the cylinder and the external cylinder, the reservoir containing the hydraulic liquid and gas; a base valve dividing the second chamber from the reservoir; a first check valve provided with the piston so as to allow flow of the hydraulic liquid only from the second chamber side to the first chamber side; a second check valve provided with the base valve so as to allow flow of the hydraulic liquid only from the reservoir side to the second chamber side; a sole flow passage connecting the first chamber with the reservoir; and an electro-magnetic opening and closing valve which opens and closes the flow passage, wherein, when the electro-magnetic opening and closing valve is opened, the piston connected to the piston rod is slidably movable in the cylinder and, when the electro-magnetic opening and closing valve is closed, the piston connected to the piston rod is immovable in the cylinder.