Reversible ploughs

A reversible plough has a double acting hydraulic ram connected between the headstock and the reversing spindle to reverse the plough frame from a left handed to a right handed ploughing position, and vice versa. Hydraulically operating mechanism is provided in the headstock both to switch the flow of hydraulic fluid from one to the other end of the double acting ram and to apply additional reversing torque to the spindle at the midway position. The mechanism comprises two hydraulic cylinders acting upon a fork pivotally mounted in the headstock and engaging with a roller spaced radially of the spindle. As the midway position is approached, the roller displaces the fork from a rest position whereupon the fork is rotated by the cylinders to drive the reversing spindle through the midway position. Internal fluid pathways in the two cylinders effect the change of fluid flow to the double acting ram.

I claim:

1. A reversible plough comprising a headstock for connection to a tractor and having a reversing spindle rotatably mounted therein; a plough frame secured to the reversing spindle for rotational reversing movement relative to the headstock between left and right handed ploughing positions, the frame being adapted for the mounting of left and right handed plough bodies, and a double acting hydraulic ram supported in the headstock and connected with the reversing spindle, the ram being adapted when supplied with hydraulic fluid at one end thereof to rotate the frame from one ploughing position to a midway position and when subsequently supplied with hydraulic fluid at the other end thereof to rotate the frame from the midway position to the other ploughing position, characterised in that there is provided a hydraulically operating mechanism (9, 10, 14, 15, 13, 12, 26) connected between a source of hydraulic fluid (17, 18) and the double acting ram (16) and cooperating mechanically with the reversing spindle (4), the mechanism serving at the midway position of the plough frame both to switch the flow of hydraulic fluid from one to the other end of the double acting ram and to apply additional reversing torque to the spindle.

2. A reversible plough according to claim 1, characterised in that the mechanism includes hydraulic piston and cylinder means (9, 10, 14 15) serving through extending or retracting movement thereof to apply additional reversing torque to the spindle (4), the piston and cylinder means having ports connected through hydraulic conduit respectively with opposite ends of the double acting ram (6) and with the source of hydraulic fluid (17, 18) and having internal fluid pathways communicating between said ports to connect the source with one end of the double acting ram in an extended position of the piston and cylinder means and with the other end of the double acting ram in a retracted position of the piston and cylinder means.

3. A reversible plough according to claim 2, characterised in that the hydraulically operating mechanism further comprises a first coupling element (12, 13) mounted in the headstock so as to be movable relative thereto under the action of the piston and cylinder means between two rest positions, the first coupling element being normally held in a rest position, and a second coupling element (26) carried on the reversing spindle and so cooperating with the first coupling element as to displace it from a rest position as the reversing spindle approaches the midway position, mutual engagement of the two coupling elements thereafter serving to drive the reversing spindle through the midway position as the first coupling element is moved to its other rest position under the action of the piston and cylinder means.

4. A reversible plough according to claim 3, characterised in that the hydraulic piston and cylinder means comprises a pair of hydraulic cylinders (9, 10) with associated pistons (14, 15), each cylinder and associated piston being connected between the headstock and the first coupling element (12, 13) so that extension of the respective piston moves said element in respective opposite senses.

5. A reversible plough according to claim 3 or claim 4, characterised in that the first coupling element comprises a fork (12) pivotally mounted in the headstock and the second coupling element comprises a roller (26) which is parallel to and spaced radially from the reversing spindle.

6. A reversible pough according to claim 5, characterised in that the second coupling element comprises a pair of spaced cam plates (52, 52') extending radially of the reversing spindle and having the roller rotatably mounted therebetween with said fork being provided with two guide pins (57, 57') extending in opposite directions and cooperating with the peripheries (53, 54, 56, 53', 54', 56') of the respective cam plates, wherein the two cam plates are so shaped that engagement of one guide pin with the associated cam plate holds the fork (12)) in an extreme angular position in each ploughing position of the frame, the shape of the cam plates permitting rocking movement of the fork immediately before the midway position is reached.

7. A reversible plough according to claim 5, characterized in that the second coupling element comprises cam means (50) cooperating with the first coupling element otherwise than at the midway position to hold the first coupling element in a rest position.

8. A reversible plough according to claim 5, characterized in that the piston and cylinder means is adapted to hold the first coupling element in a rest position, said displacement of the first coupling element from a rest position by the second coupling element serving to drive the piston and cylinder means over-centre.

9. A reversible plough according to claim 3 or claim 4, characterised in that the second coupling element comprises cam means (50) cooperating with the first coupling element otherwise than at the midway position to hold the first coupling element in a rest position.

10. A reversible plough according to claim 3 or claim 4, characterised in that the piston and cylinder means is adapted to hold the first coupling element in a rest position, said displacement of the first coupling element from a rest position by the second coupling element serving to drive the piston and cylinder means over-centre.

11. A reversible plough according to claim 1, characterised in that the hydraulically operating mechanism has rest positions associated respectively with the ploughing positions of the frame and is adapted if displaced from one rest position to move with a hydraulic power stroke to the other rest position, the reversing spindle being arranged as the midway position is approached to displace the mechanism from a rest position, consequential movement of the mechanism to its other rest position then driving the reversing spindle through the midway position.

12. A reversible plough according to claim 11, wherein the mechanical coupling of said mechanism with the reversing spindle is so arranged that the torque applied to the reversing spindle during said power stroke of the mechanism increases to a maximum at the exact midway position.