Pneumatic preloaded actuator

Abstract

A two position straight line motion actuator utilizes a double ended pneumatic spring to provide most of the energy required to transit back and forth between the two positions. The actuator is held in its initial position against the force of the pneumatic spring by hydraulic pressure applied to a latching piston. Transition from the initial or first position to the second position is initiated by opening a flow path around the latching piston to cancel the effects of the high pressure latch, thus allowing the air spring to power the actuator to its second position. As the actuator moves toward the second position, the second air spring dampens actuator motion converting the kinetic energy of the actuator moving portion into potential energy in the form of highly compressed air, thus cocking the second air spring. Return of the actuator is blocked by the fluid latch. Upon command, a valve opens the flow path around the latch, allowing the latch to release the actuator to return to its initial position. Supplemental hydraulic pressure is valved into the latching chamber during the latter part of travel of the moving portion of the actuator to overcome system friction and to assure that the actuator moves fully to its initial position. Both the speed and the distance traveled by the moving actuator portion may be controlled by pre-pressurization of the air chambers.