Importance

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Abstract

An improved open throat power tong assembly is provided of the type useful for making up and breaking apart threaded pipe joints. The power tong assembly includes a cage plate assembly with a plurality of pipe gripping heads and a partial ring having a plurality of internal cam surfaces. The heads are forced into gripping engagement with the pipe by relative rotational movement between the cam surfaces and the heads mounted in the cage plate assembly. The cage plate assembly may be both supported by and rotationally guided by a plurality of ball bearing assemblies mounted to the cage plate assembly. The bearing balls are biased into engagement with an arc-shaped groove provided in the upper and lower surfaces of the partial ring. During operation of the tong, the ball bearing assemblies ride in the deepest depression track of the groove, but may purposefully ride up the groove sidewall during the final make-up and initial break-out operation.

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First Claim