Patent ID: 6601821
Filing Date: 2003-08-05
Classification: F02M,F15B,F16K

Abstract:
A two-stage proportional control valve assembly comprising:a flow-regulating valve that regulates a flow of a first fluid; a double-acting actuator powered by a second fluid for moving the flow-regulating valve in different open and closed directions for correspondingly opening and closing the flow-regulating valve; a directional valve that controls a flow of the second fluid to the double-acting actuator; an electrical actuator that converts a control signal into a force acting on the directional valve for adjusting a position of the double-acting actuator in accordance with the control signal; the double-acting actuator having (a) a first surface arranged for exposure to fluid pressure of the second fluid for moving the flow-regulating valve in the open direction and (b) a second surface arranged for exposure to fluid pressure of the second fluid for moving the flow-regulating valve in the closed direction; and the directional valve being movable under influence of the electrical actuator between (a) a first position that directs a flow of the second fluid to the first surface of the double-acting actuator and (b) a second position that directs a flow of the second fluid to the second surface of the double-acting actuator.