Pressure recovery system

1. A system for supplying hydraulic flow to a load, the system comprising:

a pump;

a flow amplifier for, when actuated, supplying fluid to the pump; and

a flow control valve for controlling the flow of fluid to the load, fluid not directed to the load being directed to the flow amplifier to actuate the flow amplifier;

wherein the flow control valve has an inlet connected to an outlet of the pump, an outlet for supplying fluid to the load to which hydraulic flow is to be supplied, and a bypass flow outlet connected to the flow amplifier for driving the flow amplifier for supplying fluid to an inlet of the pump.

2. A system as set forth in claim 1 , wherein the flow amplifier when actuated receives fluid from a sump, combines the fluid from the sump with fluid used to actuate the flow amplifier, and provides the fluid to the pump.

3. A system as set forth in claim 2 , wherein the pump is connected to the sump through a check valve.

4. A system as set forth in claim 1 , wherein the flow amplifier is one of a gerotor pump, a vane pump, an axial piston pump and a spur gear pump.

5. A system as set forth in claim 1 , wherein the flow amplifier is a dual port gerotor pump, fluid directed to the flow amplifier from the control valve driving the gerotor, the gerotor when driven drawing fluid from a sump and providing fluid to the pump.

6. A system as set forth in claim 4 , wherein the flow amplifier when actuated receives fluid from a sump, combines the fluid from the sump with fluid used to actuate the flow amplifier, and provides the fluid to the pump.

7. A system as set forth in claim 1 , wherein an inlet of the pump is connected to the sump through a check valve.

8. A system as set forth in claim 1 , wherein the flow amplifier is a positive displacement device.

9. A system as set forth in claim 1 , wherein the flow amplifier is a dual port gerotor pump configured to be driven by fluid directed to the flow amplifier from the control valve, and when driven drawing fluid from a sump and providing fluid to the pump.

10. A system as set forth in claim 1 , wherein the flow amplifier is a vane pump with a split inlet port configured to be driven by fluid directed to the flow amplifier from the control valve, and when driven drawing fluid from a sump and providing fluid to the pump.

11. A system as set forth in claim 2 , operable in low, mid and high speed ranges, wherein

at low speed, when pump flow is less than the load's maximum flow rate, the flow control valve normally will not be activated and all flow from the pump is directed to the load, whereby there is no bypass flow and the flow amplifier is not activated such that the pump pulls all of its flow directly from the sump, through a check valve;

at mid speed, when pump flow is greater than the load's maximum flow rate but the pump has not reached its cavitation speed yet, the flow control valve is activated so that only the required flow is directed to the load, with the remainder of the flow being bypass flow that is directed to the flow amplifier that then provides some make-up flow to the pump inlet, while the pressure in a makeup circuit will be minimal since it will match the pressure of the flow from the sump through the check valve; and

at high speed, when the flow amplifier is creating more flow than the pump, and the flow amplifier starts to pressurize the pump inlet, the check valve on the primary pump line is closed and the pressure on the pump inlet will rise above atmospheric pressure, increasing the speed at which the pump can be operated without cavitating.

12. A method of operating a system for supplying hydraulic flow to a load, the system including a pump, a flow actuator for, when actuated, supplying fluid to the pump, and a control valve for controlling the flow of fluid to the load, fluid not directed to the load being directed to the flow amplifier to actuate the flow amplifier, wherein the flow control valve has an inlet connected to an outlet of the pump, an outlet for supplying fluid to the load to which hydraulic flow is to be supplied, and a bypass flow outlet connected to the flow amplifier for driving the flow amplifier for supplying fluid to an inlet of the pump; the method comprising operating the system in low, mid and high speed ranges, wherein

at low speed, when pump flow is less than the load's maximum flow rate, the flow control valve normally will not be activated and all flow from the pump is directed to the load, whereby there is no bypass flow and the flow amplifier is not activated such that the pump pulls all of its flow directly from the sump, through a check valve;

at mid speed, when pump flow is greater than the load's maximum flow rate but the pump has not reached its cavitation speed yet, the flow control valve is activated so that only the required flow is directed to the load, with the remainder of the flow being bypass flow that is directed to the flow amplifier that then provides some make-up flow to the pump inlet, while the pressure in a makeup circuit will be minimal since it will match the pressure of the flow from the sump through the check valve; and

at high speed, when the flow amplifier is creating more flow than the pump, and the flow amplifier starts to pressurize the pump inlet, the check valve on the primary pump line is closed and the pressure on the pump inlet will rise above atmospheric pressure, increasing the speed at which the pump can be operated without cavitating.