| 摘要 |
A hydraulic cylinder having a piston position memory element is disclosed, and is particularly adapted for use with propulsion units for watercraft. A valve seat (76,242) is frictionally retained in a bore of a cylinder (24,200) and cooperates with a valve (72,266) in a piston (70,244) to stop the piston (70,244) in a preset position by blocking the flow of fluid through the valve (72,266). In a first embodiment, a poppet valve 60 is provided to allow a piston (70) to move to dissipate the energy of a collision of a watercraft propulsion unit with a stationary object, the piston (70) being provided with a valve (72) to allow the piston (70) to return to its original position. The valve seat (76) having remained in its original position and being provided with an unrestricted aperture (78) stops the piston (70) in its original position. In a second embodiment, a piston (244) includes concentrically mounted valves (260,266), a first valve (260) allowing a drive unit for a watercraft to deflect in response to a collision with a stationary object, and a second valve (266) allowing the drive unit to return to its original position, being stopped in original position by a valve seat (242) which has remained in original position, being provided with unrestricted apertures (254), and stops the flow of fluid through the second valve (266). A hydraulic system utilizing the first embodiment in a system including a pump assembly (20), a cylinder assembly (24) a base assembly (26) and a pressure amplifier assembly (28) is also disclosed.
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