| 摘要 |
A top drive is used to connect successive lengths of casing. The casing is gripped by a mechanism (100) which comprises a support (5) which is attached to the top drive by a drive plate (4). A circular plat e (9) is rotatably mounted in the support (5) and is associated with four jaw assemblies (50). In use the mechanism (100) is lowered onto a lengt h of casing until the circular plate (9) engages the top of the casing. When the top drive is rotated in one sense the support (5) rotates relative to the circular plate (9). This causes toothed cylinders (14) to rotate which, in turn, rotates eccentric members (12 and 13) which advance the jaws (15) into gripping engagement with the casing. Further rotation of the top drive rotates the casing and screws it into the casing below.
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