| 摘要 |
<p>A hydraulic piston and cylinder assembly (10) has a casing structure (12) defining a reservoir port (24w), a cylindrical bore (24d, 24h), and an internal annular groove (24h) opening in the bore and communicating with the reservoir port. A piston (14) is slidably mounted in the bore for movement between a rearward retracted position in which the forward end (24a) of the piston is positioned proximate but forwardly of the internal groove (24h) and a forward extended position in which the forward end of the piston is positioned remotely (24q) forwardly of the internal groove. An annular seal (32) is positioned in the internal groove and includes an inner annular flexible lip (32c) which sealingly and resiliently engages the outer periphery of the piston (14) as the piston moves between its retracted and extended positions. The piston includes an annular external groove (14f) proximate a forward end of the piston which, with the piston in its retracted position, is positioned in axial alignment with the seal and receives the inner annular lip (32c) of the seal with an annular space (42) therebetween. The inner lip (32c) of the seal and the groove (14f) thus coact with the piston in its retracted position to define a fluid flow path .(42) interconnecting the reservoir port (24w) and the bore (24d) to equalize the pressure between the reservoir port and the bore.</p> |
