| 摘要 |
Apparatus for making and breaking joints in drill pipe strings has three jaws each of which is adjustable to an infinite number of settings. The jaw-adjustment means are symmetrical about a central plane, and incorporate a spherical section. Different portions of the spherical section operate relative to closing and self-energizing of each jaw, the particular operative portion depending upon the exact set or adjusted position of the jaw. Each jaw is constructed for stable clamping of a drill type portion, with only one side of each jaw having a die element that is rotatably mounted. The jaw-adjustment mechanism effects both opening and closing of the jaw, there being no necessity to manually pull on a jaw portion at any time.
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