US Patent 7506704 Downhole swivel joint

A downhole releasable swivel joint comprises a mandrel and a housing. A resilently deformable retaining device maintains the components in the illustrated first relative axial position until downward movement of the housing is stopped and a sufficient load is applied to the mandrel to overcome the retaining force of the retaining device whereupon the mandrel is able to move downwardly relative to the housing to adopt a second relative axial position. Apertures are provided in the wall of the mandrel and apertures are provided in the wall of the housing. When the mandrel is in the illustrated first relative axial position the apertures and are isolated from each other by a seal. When the mandrel is in the second relative axial position the apertures communicate with each other to permit flow from the interior of the mandrel to the exterior of the housing.