Electrohydraulic servovalve

A two-stage electrohydraulic miniature servovalve comprising an electromagnetic positioner, a jet pipe pilot stage, and a four-way hydraulic valve incorporating position follower type spool control, including an outer body having a bore therethrough, a sleeve secured within the bore, a metering spool positioned within the sleeve, said sleeve and spool having interacting lands and grooves therein for metering fluid through the valve in accordance with the relative axial position of the spool and sleeve including two metering grooves on the internal diameter of the sleeve and five lands separated by four grooves on the spool valve including a central land of smaller diameter than the other lands, two metering lands adapted to coincide with the metering grooves in the sleeve with the spool centrally aligned in the sleeve and two end lands for sealing between the ends of the spool and the internal diameter of the sleeve.

A two-stage electrohydraulic miniature servovalve comprising an electromagnetic positioner, a jet pipe pilot stage, and a four way hydraulic valve incorporating position follower type spool control, including an outer body having a bore therethrough, a sleeve secured within the bore, a metering spool positioned within the sleeve, said sleeve and spool having interacting lands and grooves therein for metering fluid through the valve in accordance with the relative axial position of the spool and sleeve, said metering spool including a longitudinal axis, said electromagnetic positioner including a drive arm having an axis, said pilot stage including a jet pipe member secured to the end of the drive arm including a jet pipe nozzle extending on the axis of the drive arm and perpendicularly to the metering spool and a jet pipe feeder passage within the drive arm which extends substantially perpendicularly to the jet pipe nozzle and metering spool and which feeder passage is in hydraulic communication with the jet pipe nozzle, a source of hydraulic fluid under pressure and a second nozzle having a larger capacity than the jet pipe nozzle positioned adjacent the jet pipe feeder passage for passing the fluid under pressure into the jet pipe feeder passage.

A two-stage electrohydraulic miniature servovalve comprising an electromagnetic positioner including a mounting plate, a drive arm, flexture tube means resiliently mounting the drive arm on the mounting plate, an armature secured to the drive arm, pole pieces mounted on the mounting plate positioned on each side of the drive arm in close relation to the ends of the armature, electric coils positioned on the pole pieces for producing an electromagnetic force on the armature in proportion to electric current passed through the coils, and permanent magnets secured to the mounting plate positioned between the mounting plate and the armature for producing a permanent magnetic force on the armature whereby control of the movement of the drive arm is effected in accordance with the interaction between the magnetic forces produced by the electric current and the magnets operating on the armature, a jet pipe pilot stage, and a four-way hydraulic valve incorporating position follower type spool control, including an outer body having a bore therethrough, a sleeve secured within the bore, a metering spool positioned within the sleeve, said sleeve and spool having interacting lands and grooves therein for metering fluid through the valve in accordance with the relative axial position of the spool and sleeve.

A two-stage electrohydraulic servovalve comprising an electromagnetic positioner, a jet pipe pilot stage and a four-way hydraulic valve incorporating position follower type spool control wherein the electrohydraulic servovalve includes a metering spool therein having a longitudinal axis and a drive arm and wherein the pilot stage includes a jet pipe nozzle extending on the axis of the drive arm and perpendicularly to the metering spool and a jet type feeder passage within the drive arm which extends perpendicularly to the jet pipe nozzle and metering spool whereby the jet pipe feeder passage, jet pipe nozzle and metering spool are on three mutually perpendicular axes, which feeder passage is in hydraulic communication with the jet pipe nozzle, a source of hydraulic fluid under pressure and means positioned adjacent the jet pipe feeder passage for passing the fluid under pressure into the jet pipe feeder passage comprising a second nozzle having a larger capacity than the jet pipe nozzle.