Modulating action non-flowing pilot operated relief valve

摘要

A pilot valve includes a body having a channel formed therein, an inlet chamber formed along the channel, an inlet port in communication with the inlet chamber, a control port in communication with the channel, and a vent port in communication with the channel. A piston 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 second spool is movable within the channel and carries a vent-valve disc. The second spool also carries an inlet-valve seat which cooperates with an inlet-valve disc carried by the first spool to regulate fluid flow between the inlet chamber and the control port. A vent-valve seat is rigidly secured to the body and cooperates with the vent-disc carried by the second spool to regulate flow between the control port and the vent port. A first spring urges the first spool in a direction opposite pressure in the inlet chamber. A second spring 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.