Abstract: A hydraulic system comprising a fixed displacement pump driven by a prime mover operable at variable speeds and a flow control valve operable to return a portion of the hydralic fluid from the outlet of the pump to the inlet of the pump and draw fluid from a reservoir to replenish the fluid at the inlet when the pump is operated at higher speeds. An auxiliary passage extends from the reservoir and communicates with the inlet of the pump upstream from the system flow drawn from the reservoir by the opening of the flow control valve and normally isolated during low speed operation from the bypass flow by the flow control valve thereby providing auxiliary flow to the inlet at lower speeds.

Abstract: An electrically controllable valve assembly for hydraulic adjustment of a piston includes a pilot valve controllable by an electronic controller. The pilot valve has a spool and a restrictor array comprising first and second variable restrictor means and a fixed restrictor means, through which flows an auxiliary bleedflow of hydraulic fluid. The variable restrictor means are adjusted in opposite directions in order to produce from the bleed flow a control pressure which is responsible for positioning of the piston of the valve assembly. A pressure drop is taken off at the fixed restrictor means, and acts on the spool to produce a negative feedback action, thereby always to produce a given displacement control flow, irrespective of the system pressure, while avoiding control oscillations.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, a pilot operated meter-in valve to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, and pilot operated meter-out valves associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve is sensed and caused to produce a force opposing the movement of the meter-out valve controlling flow from the actuator.

Abstract: A variable pressure drop proportional motor controlled directional valve comprising a valve body, a bore in the body, and a cylindrical spool slideable in the bore. A force motor is operatively connected to the spool for moving the spool. The body has a pressure inlet port extending to the bore and spaced outlet ports extending to the bore on opposite sides of said pressure port. The spool has an axial passage and generally radial passages such that when the spool is moved, the radial passages will provide communication between the pressure inlet port and one of the outlet ports. A member is adjustably positioned in the spool for varying the orifice area to at least one of the radial passages so that the pressure drop between the axial passage and the radial passage can be adjustably varied.

Abstract: A hydraulic system for controlling hydraulic motors for driving a tracked vehicle which circuit utilizes a single manual control lever to control valve control units to direct pilot pressure to actuate bi-directional valves that control the direction of movement of the hydraulic motors.

Abstract: A variable displacement pump control system comprising a variable displacement pump having a movable element for controlling pump displacement, a hydraulic motor for moving the movable element, and a transducer for producing an electric signal corresponding to the actual position of the movable element. A comparator compares the electrical signal from the transducer and an electrical signal corresponding to the desired displacement of the pump and produces an error signal. A control operates in response to the error signal to meter fluid flow from the pump output to the hydraulic motor. The control comprises a relief valve, a compensator valve and a servo valve. The servo valve is preferably a single-stage valve that includes damping orifices to provide stability.

Abstract: An electro-hydraulic servo valve system comprising a two-stage spool type servo valve including a first stage comprising an electrical force motor and a second stage including a spool for controlling flow to an actuator. The force motor is operable upon receipt of a command electrical signal to move the spool. A first feedback is operable to cause the force motor to stop the movement of the spool. A second feedback is also operable to stop the movement of the spool at a predetermined position. The second feedback has a greater gain than said first feedback so that it normally dominates in the system. The second feedback comprises a pair of identical electrical sensors connected in parallel, and operable by movement of the spool.

Abstract: A rotary valve for changing the connections of the fluid inlet passages and the fluid outlet passages of a Gerotor type fluid rotary machine in which the fluid is contracted and expanded by a plurality of cavities defined by the teeth formed on a stator and a rotor in response to the orbital rotation of the rotor formed with one less external tooth than the number of the internal teeth on the stator. The rotary valve selectively communicates the fluid passages with the Gerotor cavities by means of its rotary commutator which orbits with a phase difference of 90.degree. with respect to the Gerotor rotor, and the commutator is rotatably accommodated in a spacer disposed between an end cover and a port member having a plurality of fluid passages. The clearance at each side of the commutator is permanently determined by means of the width of the spacer.The commutator comprises spaced members that move in unison with a sealing ring interposed between the two members.

Abstract: A fluid pressure energy translating device of the sliding vane type comprising a cam ring including an internal contour, a rotor having a plurality of vanes rotatable therewith and slidable relative thereto in slots in the rotor with one end of each vane engaging the internal contour. The rotor and internal contour cooperate to define one or more pumping chambers between the periphery of the rotor and the cam contour through which the vanes pass carrying fluid from an inlet port to an outlet port. At least one cheek plate is associated with the body and rotor. Two pressure chambers are formed for each vane and each vane has two surfaces, one in each chamber, both being effective under pressure in the respective chambers to urge the vanes into engagement with the cam. A generally annular internal feed passage is formed entirely within the rotor and communicates with one set of the pressure chambers.

Abstract: A variable gain servo solenoid controlled directional valve comprising a valve body having an elongated bore, a sleeve in the bore, a spool reciprocable in the sleeve and a force motor for reciprocating the spool and/or sleeve. The valve body has an inlet pressure port and outlet pressure ports to the interior of the sleeve. The spool controls the flow through the sleeve and is movable from a null position to selective positions permitting flow to the outlets of the body. The sleeve includes a bypass channel formed on the periphery thereof. Upon shifting of the spool fluid flow is under the control of the spool to one of the outlets in the body. Upon continued movement of the spool the sleeve is moved axially so additional fluid will flow from the inlet port in the body through the bypass channel to the selected output port of the body without passing through the interior of the sleeve.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to the actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator, and a pilot operated check valve operable for controlling flow from the meter-in valve means to one end of the actuator and for preventing flow out the end of said actuator, the pilot operated check valve being operable at a lower pilot pressure than the meter-out valve means and including time delay means such that the valve functions to prevent flow out of the actuator after a predetermined time delay from the time when pilot pressure to said meter-out valve means is interrupted, insuring relief valve protection.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, pilot operated meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve means is sensed and caused to produce a force opposing the movement of the meter-in valve means by the pilot pressure resulting in a smooth and accurate control of the movement of the actuator.

Abstract: A variable displacement vane pump is provided in which a pair of rings having oval-shaped inner contours are rotatably mounted in side-by-side relationship. The rings are adapted for relative rotation to each other from a first position wherein the inner contours are in register with each other and a moved position wherein the inner contours are out-of-register, and means are provided for effecting the relative rotation, which include a gear system operatively connected to the rings. A rotor member is mounted for rotation within the rings and is formed with a plurality of circumferentially spaced recesses which extend the entire axial length of the rotor. Each of the recesses carries a pair of vanes in abutting relationship. The vanes are mounted for radial movement in the recesses and are adapted for slidable contact with the inner contours of the rings. The vanes form two side-by-side rows of vanes with each row in tracking relationship with the inner contours of the rings.

Abstract: A hydraulic system comprising a full flow supercharged variable displacement pump and a fixed displacement charge pump adapted to be driven by the same prime mover as the variable displacement pump for supplying fluid to the variable displacement pump. An orifice is provided in the supply line to the variable displacement pump, a circuit is provided from a point downstream of the orifice to tank pressure, and a feedback valve is provided in series with the circuit. The feedback valve comprises a pair of mutually and oppositely adjustable flow restrictions in series with said circuit. The restrictions are connected to the displacement varying means to vary them equally and oppositely in proportion to the movements of the displacement varying means.