Redundant pressurizing valve

摘要

A pressurizing valve having a housing with a bore therein for retaining concentric first and second pistons within a sleeve having an end wall with an entrance port connected to a first conduit. A spring within the bore urges a first face on the first piston toward a first seat which surrounds the entrance port and a second face on the second piston toward a second seat surrounding an annular opening in the first piston. The fluid pressure in the first conduit acts on the first face to overcome the spring and move the first piston away from the entrance port to allow fluid to flow to an exit port in the housing. This type flow continues until such time that the first piston fails to move when the fluid pressure thereafter acts on the second face to move the second piston and allow the fluid to flow to the exit by way of the annular opening and a plurality of axial opening in the first piston to maintain the fluid pressure in the first conduit substantially constant.