US Patent 7410013 Boring and drilling apparatus

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.