Coupler for coupling an accessory to a dipper arm and a control system for such a coupler

1. A quick hitch coupler for coupling an accessory to a dipper arm of a back actor, the quick hitch coupler comprising a body member adapted for coupling to the dipper arm, a fixed engaging means mounted on the body member for engaging a first one of a pair of coupling pins mounted on the accessory, a moveable engaging means mounted on the body member for engaging a second one of the pair of coupling pins of the accessory, the moveable engaging means being moveable between an engaged state with the moveable engaging means engaging the second coupling pin while the fixed engaging means engages the first coupling pin for coupling the accessory to the coupler, and a disengaged state for disengaging the second coupling pin, a latch co-operable with the fixed engaging means for retaining the first coupling pin of the accessory engaged in the fixed engaging means the latch being alternately operable in a latched state co-operating with the fixed engaging means for retaining the first coupling pin in the fixed engaging means, and an unlatched state for releasing the first coupling pin from the fixed engaging means, an urging means for urging the latch into the latched state, and a drive means acting between the moveable engaging means and the latch for urging the moveable engaging means between the engaged state and the disengaged state, and for urging the latch from the latched state to the unlatched state against the urging action of the urging means when the moveable engaging means is in the disengaged state.

2. A quick hitch coupler according to claim 1 wherein the drive means and the urging means co-operate with each other so that the drive means only operates the latch between the latched and the unlatched state when the moveable engaging means has been moved from the engaged to the disengaged state.

3. A quick hitch coupler according to claim 1 further comprising a limit means provided on the body member for co-operating with the moveable engaging means for defining a disengaged position of the moveable engaging means when the moveable engaging means is in the disengaged state.

4. A quick hitch coupler according to claim 1 wherein the latch is pivotally mounted on the body member, and is pivotal between the latched and the unlatched states.

5. A quick hitch coupler according to claim 1 wherein the drive means is a two part drive means, the respective parts of the drive means being moveable relative to each other for driving the moveable engaging means and the latch, one of the moveable parts of the drive means being connected to the latch, and the other of the moveable parts of the drive means being connected to the moveable engaging means so that on movement of the respective parts relative to each other the moveable engaging means is operated between the engaged and the disengaged states, and the latch is operated between the latched and the unlatched state.

6. A quick hitch coupler according to claim 5 wherein both parts of the drive means are moveable relative to the body member.

7. A quick hitch coupler according to claim 5 wherein the drive means comprises a ram, and one of the parts is formed by a housing of the ram, while the other part is formed by a piston rod of the ram.

8. A quick hitch coupler according to claim 1 wherein the moveable engaging means is slideable between the engaged and the disengaged state, and advantageously, is slideable in the body member with rectilinear motion between the engaged and the disengaged states.

9. A quick hitch coupler according to claim 1 wherein the urging means acts between the latch and the body member.

10. A quick hitch coupler according to claim 1 wherein the urging means is provided by a spring.

11. A quick hitch coupler according to claim 10 wherein the urging means comprises a tension spring.

12. A quick hitch coupler according to claim 10 wherein the urging means comprises a compression spring.

13. A quick hitch coupler according to claim 1 wherein the fixed engaging means comprises a pair of fixed jaws formed by the body member and defining an open mouth for receiving the first coupling pin between the fixed jaws.

14. A quick hitch coupler according to claim 13 wherein the latch co-operates with the fixed jaws for retaining the first coupling pin within the open mouth and between the fixed jaws.

15. A quick hitch coupler according to claim 13 wherein a pair of latches are provided at respective opposite sides of the fixed jaws.

16. A quick hitch coupler according to claim 1 wherein the moveable engaging means defines an open mouth for receiving the second coupling pin therein.

17. A quick hitch coupler according to claim 16 wherein the moveable engaging means defines the open mouth with the body member.

18. A quick hitch coupler according to claim 17 wherein the fixed engaging means comprises a pair of fixed jaws formed by the body member and defining an open mouth for receiving the first coupling pin between the fixed jaws, and the open mouths defined by the respective moveable and fixed engaging means face in respective opposite directions outwardly away from each other.

19. A dipper arm having a quick hitch coupler according to claim 1 .

20. An accessory mounted to a dipper arm by the quick hitch coupler according to claim 1 .

21. An earth working apparatus comprising a dipper arm having a quick hitch coupler according to claim 1 mounted thereon.