Claims
- 1. In a hydraulic control system of the type including a plurality of hydraulic circuits, each circuit having pump means driven by a prime mover common to all circuits for pumping hydraulic fluid from a reservoir to a hydraulically operated implement individual to its circuit, the pump means in one of said circuits comprising a plurality of pumps and means for unloading one of said pumps including a pilot valve actuator having a plurality of pressure areas, means for applying pressures prevailing in said circuits against said pressure areas, said pilot valve actuator being shiftable to a position in which said one pump is unloaded when the sum of the pressures applied to said pressure areas reaches a preselected value.
- 2. A control system according to claim 1, wherein said pilot valve actuator is provided with a plurality of annular surfaces, each of which forms one of said pressure areas.
- 3. A control system according to claim 2 wherein said pilot valve actuator includes a poppet type valve having a conic face against which the pressure in said one circuit is applied, said valve having a shank provided with a plurality of steps each of which forms one of said annular pressure areas, and wherein pressure prevailing in at least one of the other of said circuits is applied against said annular pressure areas.
- 4. A control system according to claim 1 wherein said plurality of circuits comprises three circuits and wherein means are provided for applying the higher of the pressure values prevailing in the other two circuits to one of said pressure areas.
- 5. A control system according to claim 4 wherein said means for applying the higher of the pressure values comprises a branched passage leading from said last named pressure area to each of said circuits with check valve means in each branch.
- 6. A control system according to claim 1 wherein said plurality of circuits comprises two circuits each comprising a pair of pumps for supplying operating fluid to an implement individual to that circuit and a pilot valve actuator in each circuit having three pressure areas, means for applying to one of said pressure areas of the pilot valve actuator of each circuit the pressure prevailing in that circuit and the pressure prevailing in the other circuit downstream from both pumps of the other circuit to the second pressure area of each pilot valve actuator, and means for applying the discharge pressure of the unloadable pump in the other circuit to a third pressure area of each pilot valve actuator.
- 7. In a hydraulic control system comprising three hydraulic circuits, each circuit having pump means driven by a common prime mover for pumping hydraulic fluid from a reservoir to a hydraulically operated implement individual to that circuit, the pump means in one of said circuits comprising a plurality of pumps and means for unloading one of said plurality of pumps including a pilot valve actuator means responsive to the pressures prevailing in the circuits for unloading said one pump in response to a pressure value in excess of a preselected value.
- 8. A hydraulic control system according to claim 7 wherein said pilot valve actuator means includes means responsive to the sum of the pressures prevailing in said circuits for unloading said one pump when a preselected pressure value is reached.
- 9. A hydraulic control system according to claim 7 wherein said pilot valve actuator means includes means responsive to the sum of the pressure in the circuit having said unloadable pump and one of the pressures in the other two circuits for unloading said pump when the sum of said pressures reaches a predetermined value.
- 10. A hydraulic control system according to claim 9 wherein the pressure responsive means is responsive to the sum of the pressure in the circuit having said unloadable pump and the higher of the pressure values in the other two circuits.
- 11. In a hydraulic control system of the kind including a plurality of hydraulic circuits each having a pair of fluid supply pumps to be driven by a prime mover common to said circuits, each having an actuator to be operated by the pressurized hydraulic fluid in the circuit, and each circuit further including means for controlling the flow of fluid to the actuator of that circuit, the improvements which comprise: means in each circuit movable to unload one pump of that circuit; and means for effecting such movement of the movable means in response to fluid pressures increasing above a value determined by the available power of the common prime mover.
- 12. A system in accordance with claim 11, and further characterized in that said movable means comprises pressure-responsive valve means, and said last means comprises fluid flow conduit means cross-connecting the pressure-responsive valve means of each circuit with the other circuit.
- 13. A system in accordance with claim 12, and in which the valve means in each circuit includes, a part shiftable in response to a predetermined pressure difference thereacross to effect such unloading, and a pilot valve so disposed in circuit with said conduit means as to subject said part to such pressure difference when the pressure in the other circuits increases above said predetermined value.
- 14. A system in accordance with claim 13, and in which said pilot valve includes a poppet member subject to a force which biases it toward a closed position in which it does not subject said part to such difference, said poppet member being so connected in the system as to be subject to forces which oppose its bias, one such force being a function of a pressure prevailing at one side of said shiftable part, and the other such forces being a function of the pressures existing in the other circuits and communicated through said conduit means.
- 15. A system in accordance with claim 12, and in which said valve means comprises: a spool type control valve responsive to a predetermined imbalance of pressures thereacross to move to unloading position; and a poppet type pilot valve in communication with said spool valve and said conduit means and which, when unseated, subjects said spool valve to such imbalance of pressures, said poppet valve having a plurality of annular pressure areas against which the pressures in the other circuits are applied whereby the poppet is unseated when the pressure in said circuits increases above said predetermined value.
- 16. In a hydraulic control system of the type including at least three hydraulic circuits, and pump means individual to each circuit driven by a prime mover common to all circuits, the pump means of at least one circuit comprising two pumps: fluid flow control means in each circuit for directing fluid from the pump means to an implement indivdual to that circuit and means for unloading one pump of said one circuit, said latter means being responsive to the fluid pressure in any circuit increasing above a predetermined limit.
- 17. In a system in accordance with claim 16, the further characterization that said last recited means comprises pressure-responsive valve means in said one circuit movable to an unloading position, and conduit means for subjecting said valve means to the pressures prevailing in the three circuits.
- 18. In a system in accordance with claim 17, the further feature that one of said other circuits is also provided with pressure-responsive valve means movable to an unloading position, for unloading a portion of the fluid discharged by the pump means in that circuit, and in which system there is provided additional conduit means for subjecting the latter valve means to the pressure prevailing in the three circuits to shift said last named valve means to the unloading position in response to pressures above a predetermined value.
RELATED APPLICATIONS
This application is a continuation-in-part of our co-pending application Ser. No. 452,713 filed Mar. 20, 1974 now U.S. Pat. No. 3,868,821 granted Mar. 4, 1975.
US Referenced Citations (8)
Continuation in Parts (1)
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Number |
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452713 |
Mar 1974 |
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