| 摘要 |
An apparatus connected with a derrick, comprising two or more hydraulic piston/cylinder arrangements (10, 11) for raising and lowering a yoke (8) which travels on guide rails (7) in the derrick (1) itself. The yoke (8) comprises at least two sheaves (12) each running its own wire line (13). The sheaves (12) are rotatably attached to a rigid connection (20, 21, 24) between the sheaves (12), and the rigid connection (20, 21, 24) is rotatably connected to the upper end of each piston/cylinder arrangement (10, 11).
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