| 摘要 |
A power tong includes a frame having arcuate front portions defining a throat, a cage plate assembly mounted on the frame for rotation about a central axis and a ring gear also mounted on the frame for rotation about the axis. The throat receives the pipe to be rotated, and the cage plate and ring gear include die means for gripping the pipe. The ring gear and cage plate cooperate to rotate the pipe within the frame, which remains stationary. The design of the power tong is such that the arcuate front portions of the frame are more flexible than the cage plate assembly and ring gear combination, and strain is primarily taken up by the ring gear and cage plate. In addition, the cage plate and ring gear are sufficiently rigid such that they may not flex to a degree that teeth on the ring gear flex more than the backlash in the gear train that drives the ring gear. Finally, the ring gear includes offset cam surfaces, which help to ensure that the pipe is centrally located within the ring gear, the cam surfaces having identical elliptical sections.
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