Abstract: A fluid flow control device has an inlet, an outlet and an exhaust port all for an operating fluid. A pilot inlet receives a pilot pressure signal which operates a valve stem actuator via a piston. The valve stem is operable to open a supply valve between the inlet and outlet and, to open an exhaust valve disposed between the outlet and the exhaust. In a further position both the valves are closed. A first fluid leak path is provided between the valve stem and the supply valve for allowing fluid to leak through the supply valve chamber when the supply valve is open and a second fluid leak path is defined by the exhaust valve for allowing fluid to leak through the exhaust valve chamber. The leak paths provide for a force balancing arrangement. A quick exhaust feature allows exhaust flow through the device.

Abstract: A fluid flow control device has an inlet, an outlet and an exhaust port all for an operating fluid. A pilot inlet receives a pilot pressure signal which operates a valve stem actuator via a piston. The valve stem is operable to open a supply valve between the inlet and outlet and, to open an exhaust valve disposed between the outlet and the exhaust. In a further position both the valves are closed. A first fluid leak path is provided between the valve stem and the supply valve for allowing fluid to leak through the supply valve chamber when the supply valve is open and a second fluid leak path is defined by the exhaust valve for allowing fluid to leak through the exhaust valve chamber. The leak paths provide for a force balancing arrangement. A quick exhaust feature allows exhaust flow through the device.

Abstract: A fluid flow control device has an inlet, an outlet and an exhaust port all for an operating fluid. A pilot inlet receives a pilot pressure signal which operates a valve stem actuator via a piston. The valve stem is operable to open a supply valve between the inlet and outlet and, to open an exhaust valve disposed between the outlet and the exhaust. In a further position both the valves are closed. A first fluid leak path is provided between the valve stem and the supply valve for allowing fluid to leak through the supply valve chamber when the supply valve is open and a second fluid leak path is defined by the exhaust valve for allowing fluid to leak through the exhaust valve chamber. The leak paths provide for a force balancing arrangement. A quick exhaust feature allows exhaust flow through the device.

Abstract: A fluid flow control device such as a volume booster has an inlet, an outlet and an exhaust port all for an operating fluid. A pilot inlet receives a pilot pressure signal which operates a valve stem actuator via a piston. The valve stem is operable to open a supply valve between the inlet and outlet and, separately and independently, to open an exhaust valve disposed between the outlet and the exhaust. In a further position both the valves are closed. Movement of the stem in a reciprocal manner by the piston causes a respective annular shoulder to engage a respective valve and lift it off a valve seat against the force of a biasing spring. A first fluid leak path is provided between the valve stem and the supply valve for allowing fluid to leak through the supply valve chamber when the supply valve is open and a second fluid leak path is defined by the exhaust valve for allowing fluid to leak through the exhaust valve chamber.