FLOATING FLUID-OPERATED ACTUATOR

摘要

The piston of a reciprocating hydraulic actuator carries a pump which is driven by an electric motor and which supplies oil from the low pressure chamber of a cylinder to the high pressure chamber thereof in order to advance the piston. An exhaust valve in the piston is normally held in a closed position by magnetic force created by energizing a coil and, when closed, enables pressurization of the high pressure chamber of the cylin- der. When a second coil is energized, the magnetic field of the first coil is negated and the valve is opened by a spring to permit oil to exhaust from the high pressure chamber to the low pressure chamber and permit a second spring to retract the piston. If both the pump motor and the second coil are de-energized, the first coil keeps the valve closed and causes the piston to remain in a commanded position. The actuator may be controlled by a floating single pole, double throw switch and its piston is automatically shifted to its fully retracted position by the second spring if electrical power to the actuator is lost.