Caterpillar Tractor Co.

Caterpillar Inc.

Lawrence F Schexnayder

Wayne A Peterson

Leon E Hicks

Thomas J Hajek

Donald L Bianchetta

James Alvin Aardema

Andrew Henry Nippert

Srikrishnan T Tolappa

William J Spivey

Michael D Hudson

Michael Anthony A'Hearn

Donald J Larson

Jerome A Thies

A ride control system adapted for use in a fluid system of a machine to cushion the ride of the machine, the machine having a frame with an actuator arrangement disposed between the frame and a load to raise the load relative to the frame, the actuator arrangement having a raise port and being operative in a raise mode to raise the load to a desired height in response to pressurized fluid being directed to the raise port from a source of the pressurized fluid, the ride control system including an accumulator arrangement and a valve arrangement connected between the accumulator arrangement, the actuator arrangement, and the source of pressurized fluid, and operative to selectively connect the accumulator arrangement to the raise port of the actuator arrangement when in the raise mode while maintaining the load at the desired height.

Ride control

A force feedback popper valve has a valve element for controlling fluid flow from an inlet port to an outlet port. A meter-in orifice communicates pressurized fluid from the inlet port to a control chamber above the valve element. A pilot valve provides a meter-out orifice between the control chamber and the outlet port to selectively reduce the pressure level in the control chamber in response to a control force applied to the pilot valve. A feedback spring is disposed in the control chamber between the valve element and the pilot valve so that displacement of the valve element is proportional to the control force exerted against the pilot valve.

Poppet valve with force feedback control

Fluid regeneration circuits are useful for filling expanding sides of a hydraulic motor with fluid being exhausted from the other side. The components of the currently available regeneration circuits are disposed in or adjacent to the directional control valve such that the fluid used for regeneration must pass through relatively long motor conduits between the control valve and the hydraulic cylinder. The regeneration circuit of the present invention includes a load check valve which forces the fluid exhausted from the head end chamber of a hydraulic motor to pass through a poppet valve controllably opened by a control signal. A low pressure relief valve causes an increase in the fluid pressure of the exhausted fluid passing through the poppet valve such that when the pressure level exceeds the pressure level of the fluid in an expanding side rod end chamber of the hydraulic motor, the exhausted fluid passes through a regeneration check valve and fills the expanding rod end chamber. The components of the regeneration circuit can be mounted directly to the hydraulic motor or in close proximity thereto minimizing the length of conduits through which the fluid must traverse as well as bypassing the directional control valve.

Fluid regeneration circuit

Hydraulic control systems are useful for controlling actuation of hydraulic motors. Some such systems use spool type valves while other systems use poppet type valves, both of which have their advantages and disadvantages. The present hydraulic control system is a hybrid system utilizing a combination of both a spool type control valve and poppet type control valves in a single work circuit. Specifically, a spool type control valve has an inlet port connected to a variable displacement pump and a pair of flow amplifying poppet type valves are serially disposed between a pair of motor ports of the spool type valve and a pair of actuating chambers of a double acting hydraulic motor. The spool type control valve is operative to control pump-to-motor flow while one of the poppet type valves is operative to control motor-to-tank flow.

Hydraulic control system having poppet and spool type valves

Flow amplifying poppet valves are useful in hydraulic circuits requiring low leakage when the circuit is in a load holding condition. Pressure compensation of the known flow amplifying poppet valves has not been totally successful and thus, the output flow varies somewhat with changing pressure drops across the poppet valve. The subject pressure compensated flow amplifying poppet valve utilizes a pressure compensating valve and a compensating orifice disposed in a compensating flow path disposed in parallel with a valve device for controllably regulating fluid flow through a flow regulating passage. Fluid flow through the compensating flow path is restricted by the orifice to a flow rate substantially equal to the amount of fluid that can flow through a flow control slot in a valve element at a closed position of the valve element. The addition of the compensating flow path and the compensating valve greatly increases the pressure compensating capability of the pressure compensated flow amplifying poppet valve so that the fluid flow through the poppet valve remains substantially constant for a given position of the valve means regardless of changing load conditions.

Pressure compensated flow amplifying poppet valve

Hydraulic motors are conventionally employed in rotating the upper structure of excavators and the like. Protection from inertia induced hydraulic shock loads of some hydraulic control circuits involves the use of a separate bypass valve which continuously interconnects the motor conduits. The subject control circuit includes a pair of shunt valves each of which establishes restricted communication between the first and second motor conduits in a particular direction at their normal spring biased position. This allows limited free swing of the upper structure when the directional control valve is shifted from an operating position to the neutral position. However, shifting the directional control valve to an operating position causes the appropriate one of the shunt valves to shift to a blocking position so that no interconnection between the motor conduits exist. Thus, the disclosed control circuit causes all pressurized fluid directed into one of the motor conduits to be transmitted to the hydraulic motor for maximum efficiency.

Hydraulic swing motor control circuit

A hydrostatic transmission (10) includes a variable displacement pump (12) for driving a fluid motor (14) in first and second directions. First and second high pressure conduits (20,22) connects the pump (12) and motor (14) in a continuous fluid circuit. A control pump (40) supplies make-up fluid to the first and second high pressure conduits (20,22) and simultaneously provides pressurized control fluid to a system control (50) for controlling the operation of the hydrostatic transmission (10). First and second low pressure conduits (24,26) are respectively disposed about the first and second high pressure conduits (20,22) and defines first and second spaces (28,30) therebetween. A pressure control arrangement (32) is connected to the first and second spaces (28,30) to control the maximum pressure level in the spaces (28,30) upon the failure of one of the high pressure conduits (20,22). By controlling the pressure level in the spaces (28,30), pressurized control fluid is maintained for the system control (50).

Maintaining hydrostatic system control pressure

Hydrostatic transmission having an overspeed control

A hydraulic control system having a pump and circuits connecting the pump to a pair of hydraulic motors through first and second circuits is provided with a priority valve system operative to provide a priority of fluid pressure to the first motor up to a predetermined minimum pressure and thereafter to maintain the pressure in the first circuit and simultaneously supply fluid to the second motor of the second circuit. The priority valve system is also responsive to a load on a second motor to split the flow of fluid between the two motors above the predetermined minimum pressure up to a second pressure after which the second predetermined pressure is maintained in the first circuit while fluid is being supplied to the second conduit.

Hydraulic rock breaker circuit for an excavator

A method and plural embodiments of apparatus for delivering a pressure-compensated supply of fluid to a hydraulic steering circuit, wherein first and second pumps are respectively operated by a vehicle engine and by a ground wheel when the vehicle is in motion, output fluid from the two pumps being simultaneously directed to the steering circuit by a control valve with inlet relief valve means modulating output pressure of the sources in response to operation of the control valve. One embodiment contemplates dual inlet relief valves for separately modulating output from the two pumps while another embodiment contemplates one of the pumps having a variable output.

Dual source hydraulic steering system

A sealing structure for use in an oil-cooled disc brake apparatus or the like, having a buffer seal for providing extended life and improved functioning of the face seals thereof. The buffer seal provides a pressure-regulating function in controlling the delivery of lubricating coolant fluid to the brake and face seals.

Sealing arrangement for brake housing

A load check and bypass valve includes a check valve providing fluid flow from an inlet-outlet port to a motor port while blocking reverse flow therethrough and a bypass valve resiliently biased to a closed position for blocking fluid flow through a bypass connecting the motor port with the inlet-outlet port. The bypass valve has an opened position permitting fluid flow therethrough and is movable to its opened position by a selectively controllable actuating device. A first force exerting device is provided for exerting a force on the bypass valve urging it towards its opened position and is connected to the motor port by a first passage. A second force exerting device is provided for exerting a force on the bypass valve urging it towards its closed position and is connected to the motor port through a second passage. A check valve is disposed in the second passage providing fluid flow therethrough from the motor port to the second force exerting device while blocking reverse fluid flow therethrough. An orifice communicates with the second passage between the check valve and the second force exerting device.

Load check and bypass valve

A fluid system has first and second hydraulic jacks each having a load supporting end connected to a source of fluid through a control valve. First and second pilot operated valve assemblies are positioned between the control valve and the load supporting ends with each valve assembly having a first check valve positioned in a chamber and being movable between a first position at which communication between the associated load supporting end and the control valve is blocked and a second position at which the associated load supporting end is in fluid communication with the control valve. A second check valve is associated with the first check valve and is movable between a first position at which communication between the chamber and the control valve is blocked and a second position at which the chamber is in fluid communication with the control valve. A first piston is provided for urging the second check valve toward the first position and a second piston is provided for initially moving the second check valve to the second position and for subsequently moving the first check valve to the second position. A signal device senses the load pressure in the load supporting ends and delivers first and second control signals to the first piston of the respective first and second valve assemblies.

Fluid system having load pressure equalizing valve assemblies

A brake cooling circuit which includes a pump for circulating cooling fluid to the brakes in a scraper portion of a tractor scraper combination is driven by a motor powered by hydraulic fluid communicated through conduits leading to one of the implements of the scraper. Selective actuation of the brake cooling circuit may be accomplished manually by the operator. Automatic actuation of the brake cooling circuit is also provided upon a signal of a high temperature condition in the brakes. The vehicle hydraulic circuit is designed to override the cooling circuit upon actuation of the implement by the operator. Upon completion of the work cycle of the implement, the cooling circuit is reactuated. The cooling circuit is comprised of the motor driving the pump and the fan, a radiator, conduits for communicating cooling fluid through the radiator and to the brakes, a control assembly, and a separate source of cooling fluid. In the control assembly, vehicle air pressure is used to operate a series of valves to divert a limited flow of pressurized hydraulic fluid from the implement circuit to run the motor.

Brake cooling circuit

A control system has override for fluid operated work elements served by at least two variable displacement pumps each serving a separate circuit. At least two work elements are served by the first circuit and at least one work element is served by the second circuit. The discharge rate of the first pump is controlled by a signal delivered from a summing valve in response to the pressures of the first and second circuits during operation of a preselected one of the work elements of the first circuit and controlled by a modified pilot pressure signal in response to operation of only the other work element of the first circuit.

Growing community of inventors

Joliet, IL, United States of America

Lawrence F Schexnayder