Patent ID: 6662559
Filing Date: 2003-12-16
Classification: B63H,F15B

Abstract:
A hydraulic actuator comprising:a motor configured to operate in a selected one of a first and a second direction; a pump assembly coupled to the motor, wherein the pump assembly is configured to pressurize hydraulic fluid; a cylinder bore, wherein the cylinder bore has an upper chamber and a lower chamber separated by a movable piston member; a first plurality of pressure actuated valves that regulate the flow of high pressure hydraulic fluid to the upper chamber and low pressure fluid from the lower chamber, wherein the first plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operated in the first direction; a second plurality of pressure actuated valves that regulate the flow of high pressure hydraulic fluid to the lower chamber and low pressure fluid from the upper chamber, wherein the second plurality of pressure actuated valves are actuated in response to pressure generated by the pump assembly when the motor is operated in the second direction; a reservoir configured to hold hydraulic fluid; a pump vent; and a pump passageway, wherein the pump passageway is configured to transfer hydraulic fluid from the pump vent to the reservoir.