Abstract: A power tong (1) or back-up tong has a sliding jaw assembly (6) that may be advanced into the throat (4) of the tong for engagement with a pipe. A camming surface (11) on the inside circumference of the ring gear (10) advances the sliding jaw assembly into full engagement with the well pipe when the ring gear (10) is rotated with respect to the jaw assembly.

Abstract: A power tong or back-up tong has a jaw assembly that is advanced into engagement with a pipe through a cam follower that contacts the camming surface on the inside circumference of a ring gear, the cam follower being in the form of a series of roller elements arranged as a circulating bearing. In a preferred form, the roller elements are cylindrical roller bearings and the jaw assembly is mounted for sliding advancement towards the pipe to be engaged. In an alternate variant the cam follower includes an indexing guide that maintains the cylindrical roller bearings in proper alignment.

Abstract: A tong assembly having a powered tong mounted over a backup tong is supported at its rear by a post with torque measuring means. The powered tong is supported at its front, near its throat, by one or more struts that extend downwardly to the backup tong. Such strut(s) provide support for the powered tong when the assembly is placed on a support surface for storage. The struts each have a joint with a retracted condition in which the joint is rigid when the tong is placed on a support surface, and an extended condition in which the joint allows a degree of lateral displacement when the tong assembly is applying torque to a pipe string. This maximizes the amount of torque passing through the rearward post, and therefore ensures a more accurate sensing of applied torque by the torque-measuring device.