Patent ID: 7331570
Filing Date: 2008-02-19
Classification: F16F

Abstract:
1. A gas spring, comprising: a casing having a circumferentially continuous inner surface defining in part a main gas chamber and a secondary gas chamber; a piston rod assembly at least partially received in the casing for reciprocation between extended and retracted positions; a retainer received at least in part in the casing and having a through bore sized to receive at least part of the piston rod assembly as it reciprocates between its retracted position and extended position, an outer surface having a portion disposed generally immediately adjacent to the inner surface of the casing and a reduced diameter portion having an intermediate and circumferentially continuous wall surface between and radially spaced from both the casing inner surface and the bore and generally opposed to and directly facing the casing inner surface, the intermediate wall surface and the casing inner surface being radially spaced apart and directly facing each other throughout their circumferences to each define at least in part the secondary gas chamber; and the secondary gas chamber opens generally axially onto the main gas chamber when the piston rod assembly is in its retracted position and in cooperation with the piston rod assembly when received in part between the intermediate wall surface and the casing inner surface to separate the secondary gas chamber from the main gas chamber to compress a gas in the secondary gas chamber to act on the piston rod assembly during at least a portion of the movement of the piston rod assembly toward its extended position.