System for allocating fluid from multiple pumps to a plurality of hydraulic functions on a priority basis

1. A control valve assembly for a hydraulic system having a variable displacement first pump and a second pump which supply fluid from a tank for powering a plurality of hydraulic actuators, the control valve assembly comprising:

a supply conduit connected to the first pump for conveying fluid to the plurality of hydraulic actuators;

a return conduit for conveying fluid to the tank;

a plurality of control valves, each having a first inlet coupled to receive fluid from the supply conduit and a variable metering orifice for controlling flow of fluid from the first inlet to one of the plurality of hydraulic actuators, each control valve also including a variable bypass orifice, wherein the variable bypass orifices of the plurality of control valves are connected in series between a bypass node and the return conduit thereby forming a bypass passage, and wherein the bypass node is operatively connected to receive fluid from the second pump;

a plurality of first flow direction limiting devices, each providing a path through which fluid is able to flow only from the supply conduit to the first inlet of one of the plurality of control valves; and

a plurality of second flow direction limiting devices, each providing another path through which fluid is able to flow only from the bypass passage to the first inlet of one of the plurality of control valves.

2. The control valve assembly as recited in claim 1 wherein in each of the plurality of control valves, the variable bypass orifice decreases in size as the variable metering orifice increases in size.

3. The control valve assembly as recited in claim 1 further comprising a displacement control circuit operatively coupled to control displacement of the first pump in response to demand for fluid by the plurality of hydraulic functions.

4. The control valve assembly as recited in claim 3 further comprising a circuit branch which conveys fluid from the displacement control circuit to the bypass node.

5. The control valve assembly as recited in claim 3 wherein the displacement control circuit comprises:

a flow summation node coupled to a displacement control port for the first pump; and

each of the plurality of control valves having a variable source orifice through which fluid flows from the supply conduit to the flow summation node, wherein the variable source orifice increases in size as the variable metering orifice in the same control valve increases in size.

6. The control valve assembly as recited in claim 5 :

further comprising an additional control valve having a second inlet coupled to receive fluid from the supply conduit and having a variable metering orifice for controlling flow of fluid from the second inlet to another hydraulic actuator; and

wherein the displacement control circuit further comprises a secondary supply conduit in which the flow summation node is defined and an orifice separating the secondary supply conduit into first section and a second section, wherein the variable source orifice of the additional control valve is connected to the first section and the variable source orifices of the plurality of control valves are connected to the second section.

7. The control valve assembly as recited in claim 6 further comprising an orifice in the supply conduit between where the additional control valve is connected to the supply conduit and where the plurality of control valves are connected to the supply conduit.

8. The control valve assembly as recited in claim 5 wherein at least one of the plurality of control valves including a flow limit valve for restricting fluid flow through the variable source orifice in response to pressure at the flow summation node.

9. The control valve assembly as recited in claim 1 wherein each first flow direction limiting device and each second flow direction limiting device comprises a check valve.

10. The control valve assembly as recited in claim 1 further comprising a flow control device through which fluid flows from the bypass passage into the supply conduit.

11. The control valve assembly as recited in claim 10 wherein the flow control device opens and closes in response to pressure in the bypass passage.

12. The control valve assembly as recited in claim 10 wherein the flow control device is connected to the bypass passage between two of the plurality of control valves.

13. The control valve assembly as recited in claim 1 further comprising a series connection of a check valve and an orifice through which fluid flows from the bypass passage into the supply conduit.

14. The control valve assembly as recited in claim 1 wherein each of the plurality of second flow direction limiting devices connects one of the first inlets to the bypass passage between a different pair of the plurality of control valves.

15. The control valve assembly as recited in claim 1 wherein the first inlets for two of the plurality of control valves are connected by second flow direction limiting devices to the bypass passage between the same pair of the plurality of control valves.

16. The control valve assembly as recited in claim 1 wherein the second pump is a variable displacement pump.

17. The control valve assembly as recited in claim 1 wherein the second pump is a fixed displacement pump.

18. The control valve assembly as recited in claim 1 wherein connection of the variable bypass orifices in series defines a first order in which the plurality of control valves are connected between the bypass node and the return conduit, and wherein the plurality of control valves are connected in a different second order to the supply conduit.

19. The control valve assembly as recited in claim 18 wherein the different second order is opposite to the first order.

20. The control valve assembly as recited in claim 1 further comprising at least one additional control valve, each having a second inlet coupled to receive fluid from the supply conduit without receiving fluid from the bypass passage and a variable metering orifice for controlling flow of fluid from the second inlet to another hydraulic actuator.

21. The control valve assembly as recited in claim 1 further comprising at least one additional control valve, each having a second inlet coupled to receive fluid from only the bypass passage and a variable metering orifice for controlling flow of fluid from the second inlet to another hydraulic actuator.

22. A control valve assembly for a hydraulic system having a variable displacement first pump and a second pump which supply fluid from a tank for powering a plurality of hydraulic actuators, the control valve assembly comprising:

a supply conduit connected to convey fluid from the first pump for conveying fluid to the plurality of hydraulic actuators;

a return conduit for conveying fluid to the tank;

a flow summation node coupled to a displacement control port for the first pump;

a plurality of control valves, each having a variable metering orifice for controlling flow of fluid from a first inlet to a hydraulic actuator, and having a variable source orifice through which fluid flows from the supply conduit to the flow summation node, wherein the variable source orifice increases in size as the variable metering orifice in the same control valve increases in size, and each control valve including a variable bypass orifice that decreases in size as the variable metering orifice in the same control valve increases in size, wherein the variable bypass orifices of the plurality of control valves are connected in series between a bypass node and the return conduit thereby forming a bypass passage, wherein the bypass node is operatively connected to receive fluid from the second pump and is coupled to the flow summation node;

a plurality of first flow direction limiting devices, each providing a path through which fluid is able to flow only from the supply conduit to the first inlet of one of the plurality of control valves; and

a plurality of second flow direction limiting devices, each providing another path through which fluid is able to flow only from the bypass passage to the first inlet of one of the plurality of control valves.

23. The control valve assembly as recited in claim 22 wherein each first flow direction limiting device comprises a source check valve; and each second flow direction limiting device comprises a bypass supply check valve.

24. The control valve assembly as recited in claim 23 further comprising a flow control device through which fluid flows from the bypass passage into the supply conduit.

25. The control valve assembly as recited in claim 24 wherein the flow control device opens and closes in response to pressure in the bypass passage.

26. The control valve assembly as recited in claim 24 wherein the flow control device is connected to the bypass passage between two of the plurality of control valves.

27. The control valve assembly as recited in claim 22 further comprising a series connection of a check valve and an orifice through which fluid flows from the bypass passage into the supply conduit.

28. The control valve assembly as recited in claim 22 further comprising an orifice and a check valve operatively connected in series for conveying fluid from the flow summation node to the bypass node.

29. The control valve assembly as recited in claim 22 further comprising:

an additional control valve having a variable metering orifice for controlling flow of fluid from a second inlet to another hydraulic actuator, and having a variable source orifice through which fluid flows from the supply conduit to the flow summation node, wherein the variable source orifice increases in size as the variable metering orifice in the same control valve increases in size, and the additional control valve including a variable bypass orifice connected in series with the variable bypass orifices of plurality of control valves; and

a secondary supply conduit in which the flow summation node is defined and having an orifice separating the secondary supply conduit into first section and a second section, wherein the variable source orifice of the additional control valve is connected to the first section and the variable source orifices of the plurality of control valves are connected to the second section.

30. The control valve assembly as recited in claim 29 further comprising an orifice in the supply conduit between where the additional control valve is connected to the supply conduit and where the plurality of control valves are connected to the supply conduit.

31. The control valve assembly as recited in claim 22 wherein the second pump is a variable displacement pump.

32. The control valve assembly as recited in claim 22 wherein the second pump is a fixed displacement pump.

33. The control valve assembly as recited in claim 22 further comprising an additional control valve having a second inlet coupled to receive fluid from the flow summation node without receiving fluid from the bypass passage, and having a variable metering orifice for controlling flow of fluid from the second inlet to another hydraulic actuator, and further having a variable source orifice through which fluid flows from the supply conduit to the flow summation node, wherein the variable source orifice increases in size as the variable metering orifice in the additional control valve increases in size, and the additional control valve including a variable bypass orifice connected in series with the variable bypass orifices of plurality of control valves.

34. The control valve assembly as recited in claim 22 further comprising at least one additional control valve, each having a second inlet coupled to receive fluid from only the bypass passage and having a variable metering orifice for controlling flow of fluid from the second inlet to another hydraulic actuator.

35. The control valve assembly as recited in claim 22 wherein connection of the variable bypass orifices in series defines a first order in which the plurality of control valves are connected between the bypass node and the return conduit, and wherein the plurality of control valves are connected in a different second order to the supply conduit.

36. The control valve assembly as recited in claim 35 wherein the different second order is opposite to the first order.