US Patent 7341236 Pilot operated valve with a pressure balanced poppet

A pilot operated valve has a main poppet that selectively controls flow of fluid between first and second ports in response to pressure in a control chamber on one side of the main poppet. The main poppet has an aperture extending between the control chamber and the first port. A pilot piston slides within the aperture and has the pilot passage with a pilot orifice and a first disk spring biases the pilot piston with respect to the main poppet. A pilot valve element selectively engages the pilot orifice to open and close the pilot passage and thereby controls motion of the main poppet. Forces from the first disk spring and a pressure differential between control and pilot chambers alter a position of the pilot valve seat with respect to the main poppet. The change in position compensates for effects on valve operation due to variation of the pressure at the two ports.