Locking mechanism

A locking mechanism 10 comprises a pair of spaced profiled arcuate passages 26 between an outside of an inner coaxial member 12 and an inside of an outer coaxial member, e.g. drum 14. Each passage 26 has end sections 28 and a mid-section 30, the mid-section 30 being of reduced width. locking members, e.g. cylindrical discs 34, are movably located in each end section 28 and are urged by springs 32 so that they jam between the coaxial members 12, 14 at the mid-section 30. The jammed discs 34 prevent relative rotation between the members 12, 14, thereby engaging the locking mechanism. Engagement members 36 are provided in the mid-section 30 and are selectively movable along the mid-section 30 to urge the locking members 34 out of the mid-section 30 towards the respective end section 28, thereby disengaging the locking mechanism. Engagement members 36 are supported by a cover member 38 mounted on a shaft 44 connected to handles (58, fig 5) of a cattle crush. Refence is also made to an animal containment apparatus having the locking mechanism.