| 摘要 |
An apparatus ( 10 ) for use in boring is described, the apparatus including a rotatable drive shaft ( 12 ), a cam member ( 20 ) and followers ( 16 ) for converting rotational motion into reciprocal motion, and a shroud ( 24 ) having a cutting edge ( 26 ) driven by the cam member and followers. The shroud may be selectively engageable with the cam member and followers, allowing the drive shaft to be removed through the shroud. A fluid circulation arrangement ( 31 ), ( 13 ) allows air to be injected into loose drilling substrate, so assisting removal of drill cuttings from the boring apparatus. Also described is a drill string incorporating a similar arrangement, allowing the drill string to be reciprocated within a bore. The drill string may further include casing sections, which may have intumescent coatings to allow the sections to be fixed in a wellbore.
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