Flow control valve

Claim 1

A force balance controlled fluid flow pressure valve for control of fluid flow comprising: a valve body having a body chamber, a supply port and a return port and a supply valve means and a return valve located between said supply and return ports; pressure-force sensing means for sensing fluid forces in said valve body chamber; a first closure means coupled to said pressure-force sensing means and responsive to movement of said sensing means to selectively open and close said supply valve means for increasing pressure in said valve body chamber; a second closure means coupled to said pressure-force sensing means and responsive to movement of said sensing means to selectively open and close said valve seat means for decreasing pressure in said valve body chamber; shaft means journaled for rotation and adapted to be rotatably driven by a motor means; spring means about said shaft means for exerting a force on said pressure-force sensing means to act in opposition to fluid pressure forces exerted on an opposite side of said sensing means; a pair of longitudinal slots on said valve body, each of said slots being parallel with said shaft means; follower means formed of a low friction material and threadedly engaged with said shaft means and engaged with each of said slots for axial movement of said follower means with respect to said shaft means responsive to rotation of said shaft means, said follower means thereby compressing said spring means toward and away from said pressure-force sensing means; a pair of adjustable stop means, each being axially adjustably positionable in one of said slots to limit movement of said follower means between two adjustably predetermined locations in said slot; and a dashpot means for attenuating fluid flow-induced oscillations, said dashpot means including a dashpot plate and a platen plate assembly dividing said valve body chamber into an inlet chamber and a dampened flow chamber, said piston plate assembly providing a seat for said spring means for the transmission of the pressure generated by said spring means to said pressure force sensing means, and an annular space of at least several thousands of an inch width about said piston plate assembly for permitting the flow of fluid between said inlet chamber and said dampened flow chamber and for the attenuation of fluid flow-induced oscillations, while allowing freedom of movement of said piston plate assembly through said dashpot plate.