Power tong

摘要

An open mouth power tong is described having a novel arrangement for preventing relative rotation between the tong cage plates and rotary gear in situations where the pipe is not gripped at the completion of the camming action and in situations where the tong parts must be aligned for placing the tong on a pipe or removing it from a pipe. The assembly includes a pair of arcuate grooves formed in the upper surface of the rotary gear--one for use in make up operations and the other for use in break out operations. A rigid pin member is provided for extending through one of a pair of apertures formed in the upper cage plate. When the camming action is complete, i.e., when the cam followers have reached the extremities of the cam surfaces, the rigid pin member engages the remote boundary of the respective arcuate groove so as to join the cage plates and rotary gear and cause them to rotate together. When it is desired to align the tong parts for pipe access, the pin engages the near boundary of the groove.