A two-stage proportional control valve assembly comprising:</claim-text> 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 d 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. view more

A method of controlling flow rates of a first fluid utilizing fluid pressure supplied by a second fluid comprising the steps of:</claim-text> converting an electrical signal into a force imparted to a directional valve that controls a flow of the d fluid to a double-acting actuator; moving the directional valve in response to the force converted from the electrical signal between a first position that directs a flow of the second fluid to a first surface of the double-acting actuator and a second position that directs a flow of the second fluid to a second surface of the double-acting actuator; providing feedback between the double-acting actuator and the directional valve that overcomes the force imparted to the directional valve and restores the directional valve to a neutral position at which differential flows of the second fluid to the first and second surfaces are blocked; moving the double-acting actuator through a range of positions corresponding to different amounts of the feedback between the double-acting actuator and the directional valve at the neutral position of the directional valve; and linking movement of the double-acting actuator to movement of a flow-regulating valve that controls flow rates of the first fluid for changing flow rates of the first fluid through the flow-regulating valve in response to changes in the electrical signal. view more