| 摘要 |
<p>A top drive (2) is employed to connect two stands of casing (15, 16). In the preferred embodiment, the top drive (2) is connected to a telescopic drive shaft (6) which has a head (12) which can be clamped onto the casing (16). The torque applied to the connection can be controlled by controlling the current or hydraulic pressure applied to the top drive (2). The main elevator (11) is supported by a pair of bails (10) which are suspended from a support block (9) fast on the upper section (7) of the telescopic drive shaft (6).</p> |
