Pilot operated control valve

Claim 1

A hydraulic circuit comprising a source of fluid under pressure, a double-acting fluid motor, a control valve for selectively communicating the source with opposite sides of the motor, the control valve including a valve body defining a pair of bores each having a slidable spool including means forming a restrictive orifice for continuously communicating opposIte ends of the bores, one end of each valve bore being in communication with one side of the motor, the other end of each bore forming an actuating chamber, each bore including axially spaced apart passage means in communication respectively with the source and a fluid drain, each spool having axially spaced apart port means for selectively communicating the one end of the respective bore with one of the source and drain with spring means tending to center each spool in a position where the axially spaced apart passage means in each bore are blocked from communication with its one end, a pilot system including a pilot valve means for seletively directing pilot fluid under pressure to the actuating chamber in one bore, the actuating chamber in the other bore being placed in communication with a fluid drain, the passage of pilot fluid from the actuating chamber of the one bore through the restrictive orifice of the associated one spool shifting the one spool to communicate the source with the one bore and the associated side of the motor to thereby combine source fluid and pilot fluid to actuate the motor, the other spool being shifted by the flow of displaced fluid from the motor across its respective orifice to communicate its bore and the associated side of the motor with the fluid drain, the other spool being responsive to displaced fluid flow from the motor in excess of a predetermined amount to progressively restrict communication of the motor with the fluid drain.