Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Patent
1987-09-11
1989-04-18
Look, Edward K.
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
60445, 417218, F04B 4900
Patent
active
048215147
ABSTRACT:
A control circuit and specific embodiments thereof are provided using a four-port infinitely variable pilot operated pressure-compensator spool valve and a three-port infinitely variable pilot operated load sense spool valve in series to regulate the output pressure of a variable displacement radial piston pump. The valves are so constructed that both must be correctly positioned to put the pump into full stroke, while either valve can de-stroke the pump. The three-port valve is pilot controlled between the load sense pressure and the outlet pressure, while the four-port valve is controlled between the pump inlet and outlet pressures. A check valve and orifice are positioned between the two control valves and the crankcase control line of the pump to assist in stabilizing the pump output. A relief valve is provided on the crankcase line to minimize output spikes. In an alternative embodiment, a single three-port valve is controlled between the inlet and outlet pressures of the pump. A relief valve is provided to vent spikes in the crankcase pressure, allowing down-sizing of the crankcase orifice.
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Brandau Steven G.
Miller James A.
Schmidt Randy P.
Stephenson Dwight B.
Deere & Company
Look Edward K.
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