Patent ID: 8342301

Claim:
A shock absorber used for decreasing an impact force at a time of stopping a reciprocating rod connected with a reciprocating unit main body, the shock absorber comprising: an outer cylindrical body provided with open ends and with an attaching portion to be detachably attached to the reciprocating unit main body; a hollow rod having a through hole opened toward each end of the outer cylindrical body, into which the reciprocating rod is inserted and in which the reciprocating rod moves axially through the outer cylindrical body in decreasing the impact force, the hollow rod being axially mounted inside and coaxially with the outer cylindrical body so as to be movable axially along the outer cylindrical body; the outer cylindrical body and the hollow rod defining a liquid accommodating space formed between an outer circumferential surface of the hollow rod and an inner circumferential surface of the outer cylindrical body, and the reciprocating rod extending through the outer cylindrical body without exposure to the liquid accommodating space; an annular piston provided outside the hollow rod so as to be slidable axially along the hollow rod within the liquid accommodating space, said annular piston partitioning the liquid accommodating space into a first liquid chamber and a second liquid chamber, and defining between an outer circumferential face of the annular piston and an inner circumferential face of the outer cylindrical body an outside gap for applying a resistance force to a flow of liquid from the first liquid chamber to the second liquid chamber at a time of an impact-force absorption movement of the hollow rod, and defining between an inner circumferential face of said annular piston and an outer circumferential face of the hollow rod an inside gap for guiding the liquid from the second liquid chamber to the first liquid chamber during a restoring motion of the hollow rod; and a spring provided in the first liquid chamber, for restoring the hollow rod, after an impact-force absorption, to an original position, the spring extending between a first spring receiver provided on the hollow rod and a second spring receiver provided in the outer cylindrical body.