US Patent 7770635 Wellbore tubular handling torque multiplier

A tubular handling torque multiplier includes a torque input end for connection to the quill of a top drive, a torque output end for connection at least indirectly to a well tubular joint to be driven to rotate, gears for adjusting the torque output from the torque output end from that torque input at the torque input end, an axial support between the torque input end and the torque output end to allow axial stress to be communicated from the torque output end to the torque input end and a fluid circulating path open between the torque input end and the torque output end.