Two stage solenoid actuated valve, system, and method of actuation

Claim 1

A valve assembly comprising a first pilot stage adapted to have its inlet coupled to a fluid source and its outlet connected to a fluid outlet, said first pilot stage having an inlet flow restricting orifice and an outlet flow restricting orifice with each flow restricting orifice having precalculated and nonvariable dimensions and being nonmodulated, solenoid valve means coupled between said orifices, a second stage divided into first and second sections, a second stage orifice between said first and second sections within which a single movable second stage valve plug reciprocates without mechanical bias, said second stage valve plug having an outer smooth imperforate continuous surface with a substantially parabolic contour to provide a predetermined flow area between said second stage orifice and said parabolic contour as said second stage valve plug moves through said second stage orifice between an open state and a closed state, a main fluid inlet communicating with said first section and a main fluid outlet communicating with said second section without any balancing device coupled to said second stage valve plug in said main fluid outlet, said first pilot stage being coupled to said second stage valve plug and said first section not by mechanical connection except for fluid communication for controlling the time of movement of said second stage valve plug from one of the states to the other, and the predetermined dimensions of (1) said parabolic contour of said second stage valve plug (2) said second stage orifice and (3) said inlet and outlet flow restricting orifices being chosen in a predetermined relation for providing substantially linear flow rate change when said second stage valve plug moves thereby to provide substantially zero flow jerk.