Hydraulic or pneumatic power cylinder - has pressure operated device to indicate when piston is at end of stroke

摘要

A hydraulic or pneumatic power cylinder has a control valve for each direction of operation. Fluid entering the valve depresses the piston against a spring to allow the fluid to flow through a large orifices to an inlet. As the piston approaches the end wall a slide valve is closed and shuts off the small leak through a groove. Stopping the leakage equalises the pressure across the piston of the control valve. The piston moves upwards and aligns the two orifices so that pressure is transmitted to a device which indicates that the piston is at the end of its stroke.