Power tongs

Abstract

A power tong system for engaging or disengaging threaded pipe sections has an annular rotary member that is supported against lateral thrust and include a hinged portion that is pivotable to permit side access to a pipe. The rotary member is rotated about its central axis by a peripheral drive chain engaging the rotary member through a relatively small wrap angle. The free end of the hinged portion and the opposing end of the principal body of the rotary interlock and become more secure in self-centering fashion under the spreading forces that are exerted during operation. An interlock and latching system insure against erroneous sequencing and operation without full closure of the hinged mechanisms. Structurally rigid head plates on opposite sides of the rotary member are slidable relative to the housing, and incorporate spaced apart radial bearing slots that guide oppositely disposed heads that engage the pipe with hardened die elements. Twisting moments on the heads are absorbed in the head plates, such that the heads are subjected only to uniform and symmetrical forces. Balanced radial and rotational forces are applied to the pipe in both the engage and disengage directions without a need for frictional restraint or braking force on any member. The system operates smoothly and quietly, can generate extremely high torques and has very long die life.