Patent ID: 8839919

Claim:
A shock absorber used for decreasing an impact force at a time of stopping a reciprocating unit main body having a reciprocating rod incorporated therein, the reciprocating unit main body also having a cylinder chamber formed therein, wherein the cylinder chamber is partitioned into two pressure chambers by a piston fixed to one end of the reciprocating rod, the shock absorber comprising: an outer cylindrical body attached to the reciprocating unit main body, both end portions of the outer cylindrical body being formed with respective openings; a hollow rod having a through hole opened toward each opening of the outer cylindrical body, the hollow rod being mounted inside and coaxially with the outer cylindrical body so as to be axially movable relatively to the outer cylindrical body, and moving axially with the reciprocating rod within the outer cylindrical body at a time of decreasing the impact force, wherein the reciprocating rod is inserted in the through hole so as to protrude from each end of the through hole, and so as to protrude from each opening of the outer cylindrical body; an annular piston provided outside the hollow rod, partitioning a liquid accommodating space into a first liquid chamber and a second liquid chamber formed between the hollow rod and the outer cylindrical body, and applying a resistance force to a flow of the 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 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 on the outer cylindrical body, wherein the hollow rod is coaxial with the reciprocating rod and with the cylindrical chamber of the reciprocating unit main body.