| 摘要 |
<p>A by-pass tool (10) which is insertable into a drill string comprising: a transverse by-pass port in the wall of the casing (14); a control sleeve (15) mounted in the casing for axial movement between first and second end positions; a ball-receiving seat provided in the tool to receive a first deformable activating ball (18) to be launched down the drill string when it is required to adjust the tool from its first operating mode to its second operating mode; and, a releasable locking arrangement (23, 24) which can be actuated to a locking mode by the movement of the sleeve to the second end position in order to hold the sleeve in the second end position, said locking arrangement being disabled by movement of the first activating ball (18) lengthwise of the tool during adjustment of the tool from the second mode to the first mode.</p> |
