Self-modulating control valve for high-pressure fluid flow

A stabilized modulating valve for fluid flow comprising:

• a valve body having inlet and outlet ports;
• a main valve disc and associated seat between the ports to control the fluid flow therebetween;
• said main disc comprising at least two axially spaced piston portions of different diameters in which the portion of smaller diameter is proximate the seat engaging portion;
• first and second cylinder portions furnished in the valve body receiving respectively the smaller and larger piston portions of the main disc in sealing relationship;
• a first pressure chamber defined by the larger piston portion and the valve body acting on the larger piston portion to urge the main disc against its seat;
• a second pressure chamber defined by the smaller piston portion and the larger piston portion to urge the main disc away from its seat,
• a third pressure chamber adjacent the seat engaging portion of the main disc to urge the disc away from its seat, said third chamber being formed in the disc between its seat engaging portion and the smaller piston portion and adapted to be connected to the outlet port when the main disc leaves its seat;
• port means formed in the body forming said first cylinder portion substantially closed by the smaller piston when the main disc is seated, whereby axially motion of the main disc away from its seat displaces the smaller piston to connect the inlet port to both the third pressure chamber and the outlet port through said port means;
• second conduit means coupling the inlet port to the second pressure chamber;
• and
• adjustable pressure control means to vary the fluid pressure in the first chamber to change the pressure selectively to seat and unseat the main disc.