Importance

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Abstract

A boring apparatus comprises a drill pipe for being placed underground, an outer tube insertable into the drill pipe, and an inner tube axially movably inserted in the outer tube. The inner tube is locked against relative movement with respect to the drill pipe while being allowed to rotate therewith when locking members mounted on the inner tube partly project through locking member control windows in the outer tube into recesses defined in an inner surface of the drill pipe. An inner cutter and outer cutters mounted on a lower end of the inner tube can project beyond a lower end of the drill pipe, with the lowermost ends of the outer cutters being held in a projecting position radially outwardly of a circumferential surface of the drill pipe. When so positioned, the outer cutters are disposed more underground i.e., axially further away from the lower end of the drill pipe, than the inner cutter. The outer tube includes arcuate water stops and the inner tube includes engagement members which cooperate such that water can flow between the outer tube and the drill pipe when the inner and outer tubes are lifted upwardly with respect to the drill pipe.

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First Claim