PRESSURE RELEIF VALVE ACTUATED BY PILOT VALVE

摘要

A pilot valve (14) includes a body having a channel formed therein, an inlet chamber (112) formed along the channel, an inlet port (106) in communication with the inlet chamber, a control port (108) in communication with the channel, and a vent port (110) in communication with the channel. A piston (86) is movable within the channel in response to fluid pressure within the inlet chamber. A first spool is movable within the channel and is rigidly secured to the piston to move therewith. A pressure balanced second spool is movable within the channel and carries a vent-valve disc. The second spool has less mass than said first spool. The second spool also carries an inlet-valve disc (156), which cooperates with an inlet-valve seat (154) carried by the first spool to regulate fluid flow between the inlet chamber and the control port. A vent-valve seat (76) is rigidly secured to the body and cooperates with the vent-disc (174) carried by the second spool to regulate flow between the control port and the vent port. A first spring (130) urges the first spool in a direction opposite pressure in the inlet chamber. A second spring (184) is located between the piston and the second spool such that the piston resiliently bears on the second spool via the second spring to close the vent-valve when the inlet valve is open.