Caterpillar Tractor Co.

Howard L Johnson

Walter Z Ruseff

John A Junck

Control for load sharing pumps

A spool valve including a valve body having a bore intercepted by at least two axially spaced ports and a spool reciprocally received within the bore and having two axially spaced lands separated by a groove, one side wall of the groove being adjacent one of the lands and defining a shoulder. At least one shallow metering slot is disposed in the other of the lands and opens to the groove through another side wall thereof opposite from the first mentioned side wall. The slot has an increasing depth in the direction toward the groove and a cross sectional area taken transversely to the axis of the spool at any point along the slot less than the area of the top of the slot from the point to the end of the slot remote from the groove. An additional slot is disposed in the shoulder and opens to the groove, has a ramp-like bottom, and a width different from that of the metering slot.

Flow force balanced spool valve

A hydraulic system including a hydraulic pump, a hydraulic motor having at least one port and a hydraulic reservoir. A main spool valve is interposed between the motor and the pump and reservoir and has a spool shiftable between positions connecting the pump to the port, connecting the reservoir to the port, and blocking fluid flow to or from the port. A single combination check and flow control valve is interposed between the main spool valve and the port. A fluid responsive surface opens the combination valve to permit relatively free flow of fluid therethrough when the spool is in the first mentioned position thereof. A pressure responsive surface and a control valve provides for partial opening of the combination valve to meter fluid flow therethrough when the spool is in the second position thereof. A spring is operative to close the combination valve to prevent fluid flow therethrough when the spool is in the last mentioned position thereof.

Combination check and flow control valve for hydraulic systems

A supply or demand margin valve for use in hydraulic systems having at least one load provided with hydraulic fluid under pressure by a main pump, a pilot pump and at least one control valve for the load. The margin valve includes a valve body having a bore with a spool reciprocally received within the bore. A first port in the body extends to the bore and is adapted to be connected to the pilot pump. A second port in the body extends to the bore and spaced in relation to the first port and is adapted to be connected to a component of a hydraulic system other than a pilot pump. A spring is disposed in the valve body for applying a biasing force to the spool to urge the spool in one direction and a third port is in fluid communication with the pressure responsive surface and is adapted to be connected to a main pump so as to apply a force to the spool to urge the spool in the same direction as the spring. A fourth port connects with a pressure responsive surface for applying a force to the spool in bucking relation to the spring and a feedback passage in connection with an additional pressure responsive surface is in fluid communication with the second port for applying an additional force to the spool in bucking relation to the spring.

Margin valve

A hydraulic system including a bidirectional hydraulic motor having first and second fluid ports, a pump, a control valve for selectively connecting the pump to (a) the first port and venting the second port and (b) the second port and venting the first port, a modulating valve interposed between the pump and the control valve for varying flow from the pump to the control valve, a pilot for the modulating valve, and a resolver for selecting the lowest pressure at the motor ports and for directing a fluid signal proportional thereto to the pilot to control the modulating valve.

Low pressure signal driven flow control system

A hydraulic system including a pressure and flow compensated pump, a source of pilot fluid under pressure, a plurality of hydraulic circuits each including a work performing device, a plurality of controls, one for each circuit, each including a pilot operated flow valve for connecting the associated work performing device to the pump and an operator positioned valve connected to the pilot source for selectively directing pilot fluid to the corresponding flow valve, the work performing devices and the flow valves being connected in parallel. The system further includes a supply margin valve having pressure responsive surfaces respectively connected to the pump and to the work performing devices for providing a control signal to the pump to cause the same to supply fluid at a pressure equal to the pressure required by the work performing devices plus a predetermined margin and a first demand margin valve having pressure responsive surfaces respectively connected to the pump and to the work performing devices for decreasing the pressure of pilot fluid directed to some, but not all, of the operator positioned valves when the predetermined margin is not met. There is further included a second demand margin valve having pressure responsive surfaces respectively connected to the pump and to the work performing devices for decreasing the pressure of the pilot fluid directed to at least one of the others of the operator positioned valves when the predetermined margin is not met by more than a predetermined amount so that the first demand margin valve will decrease pilot pressure to certain of the valves before the second demand margin valve decreases pilot pressure to the other of the valves.

Hydraulic system with priority control

A check valve comprises a housing defining a valve seat thereon and a valve member reciprocally mounted in the housing to normally engage the seat for blocking fluid flow therepast. Two pairs of split retaining members are mounted in axially spaced relationship on a stem of the valve member and are expanded axially thereon by a compression coil spring for biasing the valve member to its closed position. A stop member is secured on an end of the stem of the valve member to prevent movement of one pair of the retaining members therepast. A slot is formed axially through the stop member and extends partially in the stem of the valve member to expose an end of the spring. In assembling the valve, a tool is inserted into the slot to compress the spring whereby the one pair of retaining members may be mounted on the valve member, between the spring and the stop member. The housing, having the precalibrated check valve mounted therein, may be attached as a unitary cartridge onto a main housing having other valves suitably integrated therein.

Method for assembling a cartridge-type valve

A pilot-operated spool valve including a valve body, a bore in the body, ports in the body and extending to the bore, a spool in the bore and axially shiftable therein, at least one pilot associated with an end of the spool for applying a shifting force to the spool, at least one spring in the body for applying a biasing force to the spool, and an adjustment for the biasing spring including a rotatable and axially movable member received in the body and engaging the spring, a cam surface in the form of interengaging threads on the member and the body for axially moving the member in response to rotation thereof, a rotatable actuator for rotating the member, a mount for the actuator so that the actuator can rotate only and is restrained against axial movement, and an axially extendable connection between the actuator and the member.

External centering spring adjustment for a spool valve

A construction vehicle has a work implement, such as a bucket-carrying boom, pivotally mounted thereon to be raised and lowered by one or more double-acting hydraulic cylinders. A directional control valve is conditioned to selectively communicate pressurized fluid to the rod end of each cylinder, for example, through a check valve. When the fluid pressure in the rod end of the cylinder exceeds a predetermined level, a pilot signal will be communicated to a modulating valve which will open to closely control and modulate the flow of the fluid exhausted from the head end of the cylinder. A pilot relief valve is interconnected between the head end of the cylinder and the modulating valve to cooperate therewith to relieve excessive fluid pressures. The above system is duplicated for selectively pressurizing the head end of the cylinder and for exhausting the rod end thereof.

Anti-cavitation and pressure modulating relief valve for controlling

Pressurized fluid is supplied to fluid-driven mechanisms by a variable displacement supply pump through a check valve and a flow control valve. A compensator receiving a pressure feedback signal from the control valve side of the check valve increases pump displacement in response to a pressure signal drop and decreases pump displacement in response to a rise in the signal pressure to compensate for variations in demand. Part of the supply pump output is used to drive a small fluid motor which turns a small pressure signal-amplifying pump connected in parallel with the check valve. The check valve opens to transmit the variable displacement pump output to the driven mechanisms when the control valve is opened. When the flow control valve is closed the check valve also closes enabling the fluid motor and pressure signal-amplifying pump to maintain the feedback signal to the compensator at a high pressure while the actual output pressure of the supply pump drops owing to the reduced displacement caused by the high feedback signal. The resulting internal pressure reduction in the supply pump during standby periods greatly reduces leakage which translates into power and fuel or energy savings.

Power conservation means for variable displacement pump fluid supply

A check valve comprises a housing defining a valve seat thereon and a valve member reciprocally mounted in the housing to normally engage the seat for blocking fluid flow therepast. Two pairs of split retaining members are mounted in axially spaced relationship on a stem of the valve member and are expanded axially thereon by a compression coil spring for biasing the valve member to its closed position. A stop member is secured on an end of the stem of the valve member to prevent movement of one pair of the retaining members therepast. A slot is formed axially through the stop member and extends partially in the stem of the valve member to expose an end of the spring.

Cartridge type check valve

A piston pump having a housing and an angularly adjustable swash plate for controlling piston displacement and the flow of fluid discharged from the pump has improved control means for controllably positioning the swash plate in response to a modified load pressure signal.

Piston pump assembly having load responsive controls

A closed center control valve for double acting motors having an inlet passage and a pair of control passages is provided with pre-sized restrictions in the control passages to control the flow rate to the motor so that a pre-selected velocity of movement of the motor is achieved.

All hydraulic motor grader circuitry

A hydraulic system including a source of pressurized fluid, a plurality of hydraulic motors with a plurality of control valves for directing fluid from the source to the motors, a dual-stage relief valve for the system for normally establishing a first pressure for part of the system for some of the motors and a second pressure for part of the system for the remainder of the motors and responsive to at least a pair of the control valves of the system for establishing the higher pressure includes a balanced resolver valve disposed between the pair of directional control valves and the relief valve and operative to prevent simultaneous communication of the pair of valves with the relief valve.

Spring centered balanced resolver valve

A fluid system of work elements of a work vehicle has first, second, and third fluid circuits each having a pump connected to a work element through a control valve assembly that is operated by a pilot pump. A fluid control means is provided for controllably combining fluid from each of the circuits with another one of the circuits.

Growing community of inventors

Joliet, IL, United States of America

Howard L Johnson