Importance

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Abstract

Disclosed herein is a drill stem having a core bit mounted thereon and an inner tube assembly having an inner tube mounting a corebreaker case that either has or in conjunction with the inner tube provides a corebreaker recess having an upwardly facing planar edge. Advantageously a stop ring and a non-axial split annular corebreaker are mounted in the recess with the stop ring being between the corebreaker and inner tube, even though the corebreaker may be axially slit and/or no stop ring used. The corebreaker has inner and outer peripheral surfaces that are of constant diameters, axial opposite transverse inner and outer planar edges while the recess is in part defined by planar edges. At least one of the parallel edges is inclined to the tube central axis when the core breaker is in its core taking position. The corebreaker is cockably movable between a datum position that its axis is inclined relative to the case axis for breaking a core and retaining the broken-off core in the inner tube as being retrieved, and the core taking position that the corebreaker axis is coextensive with or parallel to the central axes of the bit, inner tube and the corebreaker case to permit the core extending thereinto.

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First Claim