| 摘要 |
A core sampling device comprising a drill bit assembly, a drive shoe arranged to house the drill bit, a core sampling tube and a retraction tube. The drill bit assembly includes a bit housing, which is drivingly engaged by the drive shoe, and a series of drill segments which are pivotally attached to the housing to be capable of pivoting between a drilling position and a retracted position. The segments are maintained in the drilling position by the core sampling tube when this is in a forward position, but are allowed to adopt the retracted position when the sampling tube is withdrawn. The core sampling tube engages the drill bit assembly via the retraction tube whereby continued withdrawal of the core sampling tube causes withdrawal of the drill bit assembly from within the drive shoe.
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