Caterpillar Tractor Co.

Kenneth R Lohbauer

Donald L Bianchetta

Sammy J Rhodes

Donald L Hopkins

John W Bridwell

Neil W Kroth

Paul C Moots

James E Scheidt

A fluid control system (10) for controlling the torque of a fluid motor (22) and varying the flow to the fluid motor (22) has a mechanism (56) to control the torque and flow in proportion to the operator's input to a pilot operated control valve (16) that controls the fluid motor (22). The mechanism (56) controls the torque and flow of the fluid motor (22) during both acceleration and deceleration of the fluid motor (22). The fluid control system eliminates the need for special, complicated control valves.

Fluid system with flow compensated torque control

A fluid system has at least first and second circuits, each connected to a pressurized fluid source. Each circuit has at least one preselected work element connected to the fluid source through a respective preselected controlling valve. A blocker valve is connected to one of the circuits and has an actuating assembly and is of a construction sufficient for controllably passing fluid from a preselected location on one of the circuits to a preselected location on the other circuit.

Crossover plural circuit fluid system

A fluid system has a plurality of pumps, left and right track motors and a plurality of work elements. First elements are provided for controllably delivering fluid from a first plurality of pumps to the left track motor and for controllably bypassing the left track motor and delivering fluid from at least one of the first plurality of pumps to a separate respective work element. Second elements are provided for controllably delivering fluid from a different plurality of said pumps to the right track motor and for controllably bypassing the right track motor and delivering fluid from at least one of the second plurality of pumps to a separate respective work element.

Fluid control system with priority flow

A hydraulic circuit is provided for powering and controlling an excavator or the like, with a plurality of pumps supplying pressurized fluid for the circuit. The circuit is arranged so that fluid is provided in a manner to permit positive independent control of the various implement motors of the machine, with means provided so that fluid may also be combined to operate selected implement motors for faster operation and maximum efficiency of the machine.

Hydraulic circuitry for an excavator

A load supporting hydraulic system having a pilot operated main control valve is provided with pilot controlled load check valve operative to permit free flow of fluid from said control valve toward the load supporting means of the system in response to pilot pressure and to block fluid flow from the load supporting means toward the control valve. The system includes vent valve means operative with the main control valve to permit the load check valve to be opened by fluid pressure in the load supporting means to allow fluid flow therefrom to the reservoir.

Hydraulic control system for load supporting hydraulic motors

A fluid control circuit for regulating fluid flow between a pressurized fluid source and a hydraulic motor, including a control valve having a movable spool for communicating fluid entering an inlet chamber from the source with service chambers in communication with the motor, a dump valve limiting communication of the inlet chamber with a drain in response to spring means and fluid communicated to the dump valve through a passage open to either of the service chambers when it is placed in communication with the inlet chamber by the control valve spool, the passage otherwise communicating the dump valve with a drain so that fluid communication between the inlet chamber and drain is limited only by the spring means. The force of the spring means may also be varied in certain embodiments of the invention. During operation of a second hydraulic motor by an additional control valve in communication with the inlet chamber, the dump valve is conditioned to provide pressure modulation in the inlet chamber by means of a bypass valve responsive to the additional control valve.

Low-effort proportional control valve

A load supporting hydraulic system having a pilot operated main control valve is provided with pilot controlled load check valve operative to permit free flow of fluid from said control valve toward the load supporting means of the system in response to pilot pressure and to block fluid flow from the load supporting means toward the control valve. The system includes valve means operative independent of the main control valve to permit the load check valve to be opened by fluid pressure in the load supporting means to allow fluid flow therefrom to the reservoir. The system further includes safety valve means for blocking fluid flow to pilot control means.

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Joliet, IL, United States of America

Kenneth R Lohbauer