Commercial Intertech Limited

Gregory T Coolidge

A pressure-responsive hydraulic control system (10) has a load-sensing flow-compensated pump (S) connected to a plurality of work sections; with a direction control valve (26, 26') and a pressure compensator valve in each work section; and with a flow-regulated logic check system (45); a flow-metered logic check system (40); an isolation circuit (60, 160, 260); and an induced load check system (70). Each pressure compensator valve is supplied flow-metered fluid from the respective direction control valve and supplies flow-regulated fluid to a hydraulic motor. The flow-regulated logic check system (45) provides a flow-regulated maximum output signal, and the flow-metered logic check system (40) provides a flow-metered maximum output signal. The isolation circuit (60, 160, 260) has an isolation valve (61, 161, 261) and a relief valve (67, 167, 267), receives the flow-regulated maximum output signal and flow-metered maximum output signal, supplies a load signal to the pump and supplies an isolation outlet signal to the induced load check system (70). The induced load check system compares the isolation outlet signal to the flow-regulated fluid signal for the respective work section and supplies the higher to the pressure compensator valve for that work section, whereby the pressure compensating valves and the relief valve are isolated from induced loads introduced in the flow-regulated maximum output signal by loads on the hydraulic motors. In lieu of an isolation circuit, a relief circuit (360) may be provided for certain applications.

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Fort Wayne, IN, United States of America

Gregory T Coolidge