Caterpillar Tractor Co.

Paul C Moots

Howard A Marsden

Willard J Haak

Kenneth R Lohbauer

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 hydraulic system including a hydraulic motor having a port adapted to be connected to a reservoir and a hydraulic fluid pump. A normally closed check valve connects the port to the reservoir and includes two, hydraulically opposed, differential surfaces, one being smaller than the other and being disposed to be responsive to pressure at the port. Included is a normally closed, pilot-operated, first metering valve having an inlet and an outlet and a second metering valve also having an inlet and an outlet along with a shiftable metering element interposed therebetween. A spring biases the element towards a position minimizing flow between the inlet and the outlet and a pressure responsive surface is disposed on the element in bucking relation to the spring. The first valve inlet is connected to the second valve outlet and to a larger surface of the check valve and the port is connected to the second valve inlet as well as connected to direct pressure to the second valve pressure responsive surface. The first valve outlet is connected to the reservoir. The first valve controls the degree to which the check valve may open while the second valve provides load compensation in the circuit.

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East Peoria, IL, United States of America

Paul C Moots