| 摘要 |
For drill rods, an accessory unit which can be attached to the drill rod instead of a drill-rod section is provided. The accessory unit consists of a casing (11), having an outside diameter corresponding to the drill rod and provided with a threaded connection (12) on the drill-head side, and of a connecting rod (21) which runs in the casing (11) in such a way that it cannot rotate, can be telescoped out of the casing (11) towards the rotary-table side and is provided with a threaded connection (23) on the rotary-table side. When the accessory unit is used, only the part of the drill rod located between the accessory unit and the rotary table has to be lifted when the kelly is lifted for extending the drill rod. <IMAGE>
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