| 摘要 |
<p>Overrunning load control including a hydraulic motor (10) having a part adapted to be connected to a reservoir (48) and a hydraulic fluid pump (20). A normally closed check valve (46) connects the port to the reservoir and includes two, hydraulically opposed, differential surfaces (52, 54) 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 (80) having an inlet (88) and an outlet (90) and a second metering valve (58) also having an inlet (68) and an outlet (66) along with a shiftable metering element (60) interposed therebetween. A spring (62) biases the element towards a position minimizing flow between the inlet and the outlet and a pressure responsive surface (70) is disposed on the element in bucking relation to the spring. The first valve inlet (88) is connected to the second valve outlet (66) and to a larger surface (54) of the check valve, and the port is connected to the second valve inlet (68) as well as connected to direct pressure to the second valve pressure responsive surface (70). The first valve outlet (90) is connected to the reservoir (48). The first valve controls the degree to which the check valve may open while the second valve provides load compensation in the circuit.</p> |
