| 摘要 |
<p>A drilling rod system for a borehole comprises an outer pipe (6), an intermediate pipe (19), and an inner pipe (28). A driving medium is fed to the drilling tool through the passage (34) within the inner pipe, and is returned after use through the passage (29) between the inner and intermediate pipes. A flushing medium is supplied to the tool through the passage (20) between the intermediate and outer pipes. The three pipes (6, 19, 28) are held fixedly spaced from one another by spacers along their length, e.g. studs (16) held in a cage (13) between outer pipe (6) and intermediate pipe (19), and protuberances (30) between intermediate pipe (19) and inner pipe (28). Spacer plates or balls may alternatively be used. <IMAGE></p> |
