Automatic over-center system

1. In combination with an apparatus having an articulated work arm that is movable to a transport position and a hydraulic operating system therefore, a control circuit comprising:

a switching device operably connected with the work arm hydraulic operating system having a first position configured for directing flow in a first direction and a second position configured for directing flow in a second direction that is reversed from the first direction;

an electrically activated switch electrically connected with the switching device;

an electrical source for operating the electrically activated switch; and

a switching mechanism electrically connected in series between the electrical source and the electrically activated switch to control the operation of the electrically activated switch, the switching mechanism including a manually-actuated operator switch and a position-actuated switch located remotely from the operator switch in an operative position associated with the work arm and responsive to the position of the work arm so as to connect the electrical source to the electrically activated switch when the operator switch is closed and the work arm is at a preselected position in order to reverse fluid flow from the hydraulic operating system applied to the work arm.

2. The control circuit of claim 1 wherein the switching device is positioned between an operator control and at least one main valve of the hydraulic operating system, whereby the switching device is moved from the first position to the second position to reverse the signal sent by the operator control to the at least one main valve when the operator switch is closed and the work arm is at the preselected position connecting the electrical source to the electrically activated switch.

3. In combination with an apparatus having an articulated work arm that is movable to a transport position and a hydraulic operating system therefore a control circuit comprising:

a switching device operably connected with the work arm hydraulic operating system having a first position configured for directing flow in a first direction and a second position configured for directing flow in a second direction that is reversed from the first direction;

an electrically activated switch electrically connected with the switching device;

an electrical source for operating the electrically activated switch;

a switching mechanism electrically connected in series between the electrical source and the electrically activated switch to control the operation of the electrically activated switch, the switching mechanism including a manually-actuated operator switch and a position-actuated switch located remotely from the operator switch in an operative position associated with the work arm and responsive to the position of the work arm so as to connect the electrical source to the electrically activated switch when the operator switch is closed and the work arm is at a preselected position in order to reverse fluid flow from the hydraulic operating system applied to the work arm; and

wherein the switching device is located in a valve manifold mounted on a lift cylinder of the hydraulic operating system.

4. The control circuit of claim 3 wherein the valve manifold has a resolver operably connected to main valves of the hydraulic operating system, the resolver detecting the flow of hydraulic fluid through the main valves and sending a resolved pilot signal to the switching device based on relative pressures in the main valves.

5. The control circuit of claim 4 wherein the manifold has two pair of hydraulic control valves which are in fluid communication with the main valves of the hydraulic operating system, a primary valve pair in fluid communication with a primary flow path and a secondary valve pair in fluid communication with a secondary reverse flow path whereby, during normal operation, the switching device directs the resolved pilot signal to the secondary valve pair, closing the secondary valve pair and the secondary reverse flow path.

6. The control circuit of claim 4 wherein the manifold includes two pair of hydraulic control valves which are in fluid communication with the main valves of the hydraulic operating system, a first valve pair in fluid communication with a first flow path and a second valve pair in fluid communication with a second reverse flow path whereby, during a stowing operation of the articulated work arm, the switching device directs the resolved pilot signal to the first valve pair, closing the first valve pair and the first flow path and opening the second reverse flow path.

7. The control circuit of claim 5 wherein each of the valves of the first valve pair and the second valve pair are poppet valves.

8. The control circuit of claim 5 wherein the valves of the first valve pair are larger than the valves of the second valve pair, whereby a larger volume of hydraulic fluid flows through the first valves than through the second valves.

9. An apparatus having an articulated work arm that is movable to a transport position and a hydraulic operating system therefore, the apparatus comprising:

an operator control configured to transmit work arm commands to the work arm hydraulic operating system:

a switching device operably connected with the work arm hydraulic operating system;

a control circuit having a electrically activated switch electrically connected with the switching device, an electrical source for operating the electrically activated switch and a switching mechanism electrically connected in series between the electrical source and the electrically activated switch to control the operation of the electrically activated switch;

the switching mechanism including a manually-actuated operator switch and a position-actuated switch located remotely from the operator switch in an operative position associated with the work arm and responsive to the position of the work arm so as to connect the electrical source to the electrically activated switch when the operator switch is closed and the work arm is at a preselected position;

whereby the switching device is moved from a first position to a second position to reverse the signal sent by the operator control to the work arm hydraulic operating system when the operator switch is closed and the work arm is at the preselected position connecting the electrical source to the electrically activated switch.

10. The apparatus of claim 9 wherein the operator switch is located in an operator compartment of the apparatus.

11. The apparatus of claim 9 wherein the position-actuated switch is located at the base of a lift cylinder and is indexed to detect a vertical position of the articulated work arm.

12. The apparatus of claim 9 wherein the switching device is positioned between the operator control and a main valve of the hydraulic operating system.

13. The apparatus of claim 9 wherein the switching device is located in a valve manifold mounted on a lift cylinder of the hydraulic operating system.

14. An apparatus having articulated work arm that is movable to a transport position and a hydraulic operating system therefore, the apparatus comprising:

a switching device operably connected with the work arm hydraulic operating system;

a control circuit having a electrically activated switch electrically connected with the switching device, an electrical source for operating the electrically activated switch and a switching mechanism electrically connected in series between the electrical source and the electrically activated switch to control the operation of the electrically activated switch;

the switching mechanism including a manually-actuated operator switch and a position-actuated switch located remotely from the operator switch in an operative position associated with the work arm and responsive to the position of the work arm so as to connect the electrical source to the electrically activated switch when the operator switch is closed and the work arm is at a preselected position;

whereby the switching device is moved from a first position to a second position to reverse the signal sent by an operator control when the operator switch is closed and the work arm is at the preselected position connecting the electrical source to the electrically activated switch; and

wherein the valve manifold has a resolver operably connected to main valves of the hydraulic operating system, the resolver detecting the flow of hydraulic fluid through main valves and sending a resolved pilot signal to the switching device based on relative pressures in the main valves.

15. The apparatus of claim 14 wherein the manifold has two pair of hydraulic control valves which are in fluid communication with the main valves of the hydraulic operating system, a first valve pair in fluid communication with a first flow path and a second valve pair in fluid communication with a second reverse flow path whereby, during normal operation, the switching device directs the resolved pilot signal to the second valve pair, closing the second valve pair and the second reverse flow path.

16. The apparatus of claim 15 wherein the valves of the primary valve pair are larger than the valves of the secondary valve pair, whereby a larger volume of hydraulic fluid flows through the primary valves than through the secondary valves.

17. A method of storing a work arm activated by a hydraulic cylinder in an over-center position with respect to a base of the apparatus, the method comprising the steps of:

activating a manually-actuated operator switch;

retracting the hydraulic cylinder to bring the work arm toward the base of the work vehicle in response to an operator-generated signal;

activating a position-actuated switch when the work arm has reached the over-center position;

energizing a switching device which reverses the operator-generated signal; and

extending the hydraulic cylinder to bring the work arm toward the base of the work vehicle when the boom has reached the over-center position in response to the same operator-generated signal which retracted the hydraulic cylinder; and

wherein the switching device is located in a valve manifold mounted on the hydraulic cylinder, the valve manifold having a resolver operably connected to main valves which supply the hydraulic cylinder with hydraulic fluid, the resolver detecting the flow of hydraulic fluid through the main valves and sending a resolved pilot signal to the switching device based on relative pressures in the main valves.

18. The method as recited in claim 17 wherein the manifold has two pair of hydraulic control valves which are in line with the main valves, a first valve pair in line with a first flow path and a second valve pair in line with a second reverse flow path whereby, during normal operation, the switching device directs the resolved pilot signal to the second valve pair, closing the second valve pair and the second reverse flow path.

19. The method as recited in claim 17 wherein the manifold has two pair of hydraulic control valves which are in fluid communication with the main valves, a first valve pair in line with a first flow path and a second valve pair in fluid communication with a second reverse flow path whereby, during a stowing operation of the work arm, the switching device directs the resolved pilot signal to the first valve pair, closing the first valve pair and the first flow path and opening the second reverse flow path.