Patent ID: 8511392

Claim:
A swivel sub for connection in a work string between a workstring and a downhole apparatus, the sub comprising a first substantially cylindrical body, including a sleeve portion having one or more first teeth arranged thereon; a second substantially cylindrical body being partially located within the sleeve portion and the bodies being arranged to rotate relative to each other; a sliding sleeve, including one or more second teeth arranged thereon, to mutually engage with the first teeth; the sliding sleeve being axially moveable between a first position wherein the first and second teeth are disengaged and there is an overlap between the sleeve portion and the sliding sleeve, and a second position wherein the first and second teeth are engaged; wherein the first and second bodies include central bores therethrough, such that the sub has a central bore running axially therethrough, and the sliding sleeve is directly exposed to a first fluid pressure from the central bore of the sub and directly exposed to a second fluid pressure outside the sub; and wherein the sliding sleeve is moved by virtue of a pressure differential between the first and second pressures.