| 摘要 |
A tong for rotating tubulars, the tong having, in certain embodiments, a ton g outer case, a rotary movably mounted in the case for rotating a tubular, apparatus for rotating the rotary to rotate the tubular, at least one grippe r or jaw (50) movably mounted in the case and movable by the rotary for grippi ng the tubular, the at least one gripper or jaw having at least one cam followi ng member or roller (51, 52), and at least one non-circular cam surface (20, 30 ) on the rotary, the at least one cam following member or roller contacting an d movable on the at least one non-circular cam surface for maintaining a desir ed position of the at least one gripper or jaw with respect to the tubular. In certain embodiments a specific cam angle, within certain tolerances, is maintained substantially the entire length along a cam surface.
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