Air-hydraulic pump

摘要

An air-hydraulic pump wherein an air-motor drives the pump. The air-motor includes a reciprocal piston which is driven in one direction by fluid under pressure and is returned by a spring. A control valve is utilized to control the action of fluid under pressure on the piston with the control valve having an open position which is maintained by trapped fluid pressure within a piston chamber in which the control valve is positioned. The control valve is closed by physical contact thereof with an end wall of the cylinder movably mounting the piston at the end of the return stroke and a resilient member is positioned adjacent the cylinder end wall to maintain the control valve in closed position for a portion of the piston stroke as it moves away from the cylinder end wall in the pumping stroke to avoid a possible stall condition for the motor.