Caterpillar Inc.

Gregory W Heinz

Donald L Bianchetta

The use of a pair of small variable displacement hydraulic pumps in a hydraulic system offers some advantages. The output of the two pumps of the known systems is normally not combined, but is selectively combined under a majority of the operating conditions. The subject load sensing hydraulic control system has first and second hydraulic circuits with each circuit having a plurality of pilot operated control valves operatively connected to a variable displacement pump. The output flow of both pumps is normally made available to both hydraulic circuits through a combiner valve so that the output capability of both pumps can be used to satisfy the demand for fluid by a single control valve or by one or more of the control valves from each circuit. A valve arrangement connects the highest load pressure of the control system to both pumps when the output flow thereof is being combined. Under certain operating conditions of some of the control valves, the combiner valve and the valve arrangement are selectively moved to a position to isolate the first and second hydraulic circuits from each other and to direct the highest load pressure of each circuit only to the displacement controller of the pump connected to that circuit.

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Minooka, IL, United States of America

Gregory W Heinz