Fail safe hydraulic piloted pressure reducing and regulating valve

摘要

A hydraulic piloted pressure reducing and regulating valve which is fail safe for holding the valve at the last selected operating pressure in the event of the loss of control signals. A pressure regulating valve having a body and a control piston therein is provided with a pilot piston in the body which is adapted to be connected to a hydraulic pilot pressure. A spring is provided between the pilot piston and the control piston whereby the control piston can move in response to flow demands in the valve. A rod is connected to the pilot piston with a locking sleeve engaging the rod and releasably locking the rod and pilot piston against movement. A hydraulic pressure port is in communication with the space between the rod and the sleeve for releasing the rod upon application of pressure to the port. The port and the pilot piston are separately connected to a hydraulic fluid supply and a control system whereby upon failure the valve will maintain the last selected operating pressure.