Power plants – Pressure fluid source and motor – Having condition responsive control in a system of...
Patent
1994-03-01
1996-07-30
Nguyen, Hoang
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of...
60452, F16D 3102
Patent
active
055400507
ABSTRACT:
Hydraulically actuated grapple tongs mounted to a log skidder are useful, for example, in gripping a bunch of logs that are being dragged from one site to another. Maintaining a grip on the logs during the dragging operation with known hydraulic systems generates heat within the hydraulic systems. The subject hydraulic system includes first and second variable displacement load sensing pumps commonly connected to a control valve which controls fluid flow to an actuator. A load pressure signal is directed through a first signal line to a displacement controller of the first pump and to a pressure responsive valve normally resiliently biased to a position at which the first signal line is communicated to a displacement controller of the second pump. When the load pressure signal in the first signal line exceeds a predetermined value, the valve is moved to a position blocking communication of the load signal to the displacement controller of the second pump. This causes the displacement of the second pump to be reduced to a low standby condition so that only the fluid from the first pump is used to maintain a constant pressure in the actuator. The maximum displacement of the first pump is considerably less than the maximum displacement of the second pump so that the amount of heat generated in the hydraulic system when a constant pressure is maintained in the actuator is minimized.
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Caterpillar Inc.
Grant John W.
Nguyen Hoang
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