| 摘要 |
A drill rod which is adapted to be mounted in end to end relationship with corresponding lengths of drill rod to define a drill string between a drill rig and a down-the-hole drilling tool, said drill rod comprising an inner tube (11) adapted to be threadably coupled in an end to end relationship with the inner tube (11) of corresponding length of drill rod, said inner tube (11) supporting an outer sleeve (30) the ends of which are to be brought into end to end sealing engagement with the outer sleeves (30) of adjacent drill rods when the inner tubes (11) are threadably interengaged, an annular space formed between the sleeve (30) and inner tube (11), said annular space being in open communication with the annular spaces of adjacent lengths of drill rods when connected in an end to end engagement, said sleeve (30) being supported from the inner tube at each end by a plurality of angularly spaced elements (18 and 22) which extend across the annular space from one element to the other to engage the opposed face of the other element, wherein the inner tube (11) accommodates the torsional forces induced on the drill string in use.
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