Hydraulic vehicle stabilizer system with two-stage bi-rotational hydraulic pump system

1. A hydraulic system for operating a double-acting hydraulic actuator including a cylinder and a piston to which a piston rod is connected, the piston separating an extend chamber of the cylinder from a retract chamber of the cylinder, the hydraulic system comprising:

a first bi-directional pump and a second bi-directional pump that together can be coupled to and operatively driven bi-directionally by a prime mover, each pump having extend and retract ports that function as pressure and suction pumps depending on the direction of operation of the pumps;

a first extend circuit portion for fluidly connecting the extend port of the first pump to the extend chamber of the hydraulic actuator;

a first retract circuit portion for fluidly connecting the retract port of the first pump to the retract chamber of the hydraulic actuator;

a second extend circuit portion for fluidly connecting the extend port of the second pump to the first extend circuit portion;

a second retract circuit portion for fluidly connecting the retract port of the second pump to the first retract circuit portion;

a non-return check valve connecting the second extend circuit portion to the first extend circuit portion for blocking reverse flow from the first extend circuit portion to the second extend circuit portion while permitting flow from the second extend circuit portion to the first extend circuit portion;

an unloader valve connected to the second extend circuit portion between the non-return check valve and the extend port of the second pump, the unloader valve being responsive to fluid pressure in the first extend circuit portion such that unloader valve will open to a drain path when the fluid pressure in the first extend circuit portion increases above a predetermined value;

a pressure responsive return check valve connecting the second retract circuit portion to the first retract circuit portion for normally blocking flow reverse flow from the first retract circuit portion to the second retract circuit portion while permitting flow from the second retract circuit portion to the first retract circuit portion, the return check valve being responsive to pressure in the second extend circuit portion to allow reverse flow when the pumps are being operated to extend the actuator; and

an excess fluid dump valve connected to the first extend circuit portion for diverting to a drain path excess fluid exiting from the extend side of the actuator during actuator retraction, the excess fluid dump valve being normally closed during actuator extension and open in response to pressure in the first retract circuit portion during actuator retraction.

2. A hydraulic system as set forth in claim 1 , further comprising an extend relief valve connected to the first extend circuit portion and operationally responsive to fluid pressure in the first extend circuit portion for allowing flow from the first extend circuit portion to a drain path when the fluid pressure in the first extend circuit portion increases above a prescribed amount.

3. A hydraulic system as set forth in claim 2 , further comprising a retract relief valve connected to the first retract circuit portion and operationally responsive to fluid pressure in the first retract circuit portion for allowing flow from the first retract circuit portion to a drain path when the fluid pressure in the first retract circuit portion increases above a prescribed amount.

4. A system as set forth in claim 1 , further comprising the prime mover coupled to both pumps.

5. A system as set forth in claim 1 , wherein the first pump is a high pressure, low volume pump, and the second pump is a low pressure, high volume pump.

6. A system as set forth in claim 1 , further comprising the actuator.

7. A stabilizer system comprising:

a hydraulic cylinder assembly having a piston and rod supported therein;

a low pressure bi-rotational pump element connected via flow passages to a piston side and a rod side of the hydraulic cylinder assembly;

a high pressure bi-rotational pump element connected via flow passages to the piston side and the rod side of the hydraulic cylinder assembly;

wherein when the pump elements are rotated in a first direction fluid is supplied to the piston side of the cylinder for extending the rod by the high pressure bi-rotational pump element at least when a system pressure on the piston side exceeds a prescribed level, and by the low pressure bi-rotational pump element at least when the system pressure on the piston side is below the prescribed level;

wherein when the pump elements are rotated in a second direction fluid is supplied to the rod side of the cylinder for retracting the rod by the high pressure bi-rotational pump element at least when the system pressure on the rod side exceeds the prescribed level, an not by the low pressure bi-rotational pump; and

wherein the piston side of the hydraulic cylinder has a larger area than the rod side of the hydraulic cylinder such that during retraction of the hydraulic cylinder a greater amount of fluid exits the piston side of the hydraulic cylinder than enters the rod side of the hydraulic cylinder.

8. A stabilizer system as set forth in claim 7 , further comprising a flow control device between the rod side of the hydraulic cylinder and the low pressure pump that when open and closed respectively permits and blocks flow of fluid between to the rod side of the hydraulic cylinder assembly and the low pressure pump, whereby during the extending of the rod the pressure at an outlet of the low pressure pump maintains the check valve in an open state such that fluid can flow to an inlet of the low pressure pump from the rod side of the hydraulic cylinder assembly.

9. A stabilizer system as set forth in claim 8 , wherein the check valve is a pilot operated check valve whereby during the extending of the rod the pressure at an outlet of the low pressure pump maintains the check valve in an open state such that fluid can flow to an inlet of the low pressure pump from the rod side of the hydraulic cylinder assembly.

10. A stabilizer system as set forth in claim 7 , further comprising a pilot operated check valve between the piston side of the hydraulic cylinder and a reservoir, the pilot operated check valve configured to remain closed during extension of the rod and to open during retraction of the rod in response to pressure at the rod side of the hydraulic cylinder such that excess fluid from the piston side of the hydraulic cylinder can flow to the reservoir.

11. A stabilizer as set forth in claim 7 , further comprising a stabilizer leg coupled to the rod, the stabilizer leg extendable and retractable in response to movement of the rod and configured to engage the ground for supporting a vehicle when secured thereto.

12. A vehicle having a frame, at least one wheel for supporting the vehicle for movement over a surface, and the stabilizer system as set forth in claim 7 , wherein the stabilizer system is mounted to the vehicle and further includes a stabilizer leg extendable and retractable in response to movement of the rod and configured to engage the ground for supporting the vehicle.

13. A stabilizer system as set forth in claim 7 , wherein the high pressure pump and low pressure pump are part of a dual-stage bi-rotational pump unit.

14. A stabilizer system as set forth in claim 7 , wherein the high pressure pump and low pressure pump are driven by an electric motor.

15. A stabilizer system as set forth in claim 14 , wherein the electric motor is a DC motor.

16. A hydraulic circuit connectable to a hydraulic cylinder for extending and retracting a rod of the hydraulic cylinder comprising:

a first flow passage connectable to a piston side of the hydraulic cylinder and second flow passage connectable to a rod side of the hydraulic cylinder;

a low pressure bi-rotational pump element connected to the flow passages for supplying fluid thereto; and

a high pressure bi-rotational pump element connected to the flow passages for supplying fluid thereto;

wherein when the pump elements are rotated in a first direction fluid is supplied to the first flow passage by the high pressure bi-rotational pump element being at least when a system pressure in the first passage exceeds a prescribed level, and the low pressure bi-rotational pump element at least when the system pressure in the first passage is below the prescribed level;

wherein when the pump elements are rotated in a second direction fluid is supplied to the second passage by the high pressure bi-rotational pump element at least when the system pressure in the second passage exceeds the prescribed level, and outflow from the low pressure bi-rotational pump is bypassed around the second passage.

17. A hydraulic circuit as set forth in claim 16 , further comprising a check valve between the second flow passage and the low pressure pump that when open and closed respectively permits and blocks flow of fluid between the second flow passage and the low pressure pump.

18. A hydraulic circuit as set forth in claim 17 , wherein the check valve is a pilot operated check valve whereby during rotation of the pumps in the first direction the pressure at an outlet of the low pressure pump maintains the check valve in an open state such that fluid can flow to an inlet of the low pressure pump from the second flow passage.

19. A hydraulic circuit as set forth in claim 16 , further comprising a pilot operated check valve connecting the first flow passage to a reservoir, the pilot operated check valve is configured to remain closed when fluid is supplied to the first flow passage by at least one of the pump elements, and to open when fluid is supplied to the second flow passage by at least one of the pump elements, wherein the pilot operated check valve operates in response to pressure in the second flow passage.

20. A stabilizer system comprising hydraulic circuit as set forth in claim 16 and a hydraulic cylinder having a piston side coupled to the first flow passage and a rod side couple to the second flow passage.