Drill rods or pipes come in sections that are joined by male threads, tapered convergently, and female sockets, threaded and tapered internally complementarily to the male threads. The drill strings are rotated in a direction that tends to tighten the joints. That, plus the fact that the joints are liable to get gritty material between the threads, makes breaking the joints difficult. Various power mechanisms have been proposed and used (e.g., U.S. Pat. Nos. 4,345,493, 5,727,432). Where non-rotating vises have been employed, they have held the rod while a pipe wrench or the like has been used to turn the section that is not gripped by the vise. The wrench has been turned either manually or by some power mechanism. The pipe wrench type joint breakers have the disadvantage that the gripping surface is limited, putting extreme pressure in a limited area, and may not provide sufficient gripping force. Another approach to turning the free section has been to provide jaws sliding in a cradle rotated on a radius concentric with the radius of a pipe or rod clamped between the jaws. However, this construction has heretofore been subject to wear, with metal-to-metal contact, and a tendency to distortion, which leads to misalignment between the sections of the string.
One of the objects of this invention is to provide an improved open top rotating vise, in which there is substantially no wear or distortion, and in which the rotation of the rotating vice is facilitated.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawings.