Two stage gas pilot valve controlling gas flow to a reaction jet nozzle

Abstract

A multi-stage pilot valve is disclosed for selectively supplying a working fluid to and venting from a reaction jet main stage actuation chamber. In a preferred embodiment of the invention, the pilot valve comprises a solenoid actuated ball and socket flapper valve having a pressure inlet, an exhaust outlet and a service port. The first stage service port is in fluid communication with a second stage actuation chamber. A piston disposed in the second stage actuation chamber operatively engages a ball member of a ball-and-seat type valve comprising the second stage valve. The second stage valve also comprises a pressure inlet, an exhaust outlet and a service port. The piston and ball are sized relative to each other such that when the second stage actuation chamber is pressurized by the first stage, the force is sufficient to seat the ball against the second stage pressure inlet. This shuts off the flow of high pressure gases to the second stage service port and permits the second stage service port to vent through the exhaust port. When the second stage actuation chamber is vented by the first stage valve, the pressure acting on the ball is sufficient to seat the ball against the second stage exhaust outlet. This opens the second stage pressure inlet to permit high pressure gases to enter the second stage service port. The bi-directional movement of the ball member of the second stage valve is accomplished entirely by fluid pressure, thus enabling a fast responding, high flow rate regulation of the hot gases using low electrical power and eliminating the use of springs or other resilient members that would be of dubious reliability operating in a hot gas environment.