A LOCKING DEVICE
A linear to rotary convertor automatically assumes a locked position when controlling drive forces are terminated, the convertor employs a double acting hydraulic cylinder assembly with hydraulic fluid applied at (16 and 17) on opposite sides of a main piston in the form of a scroll cylinder shaft (18). Once the tapered locking elements are in position, hydraulic fluid to (16 and 17) is irrelevant to the continued operation of the assembly which is essentially and effectively a rigid coupling between the standard quick hitch ears (20) and pin ears (21). A locking spring disk (42) normally overcomes the unlocking spring disks (43 and 44) so that the cones (36, 37, 38 and 39) are in locking register. On application of the first drive means hydraulic fluid is delivered into the annular space illustrated at (19) to assist the springs (43 and 44) to overcome the bias of the locking spring (42) by moving unlocking piston (45) to the right thereby enabling the unlocking springs (43 and 44) to apply separating bias to release the engagement of the cone surfaces (36, 37, 38 and 39) so that application of hydraulic fluid under pressure at (16 or 17) will cause the scroll cylinder shaft (18) to rotate and thereby rotate the ears (20) to a desired position. Upon release of hydraulic pressure to the first drive means, the device will automatically revert to the locked position. A second embodiment uses a first hydraulic pressure to unlock the cones and then a second higher pressures applied to both maintain the unlocking pressure but also as a differential across the main piston to rotate the output. This provides a single joystick control where an operator selects the required angle and the unlocking and rotation actions are initiated under the single manual control.