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US 4,362,217 AGranted
Downhole shearers
OwnerFrederick Fletcherinventor
Life of this patent
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OwnerFrederick Fletcherinventor
Estimating the term…
The present specification describes and claims a downhole casing shearer for use in drilling bore holes. The casing shearer comprises an elongate, generally cylindrical sub-member which is connected between a drilling bit and a drill rod string and which engages within a hollow cylindrical shearer, the trailing end of the shearer being connected to a conventional bore hole liner, so that the shearer may rotate about its longitudinal axis with the liner stationary. The sub-member and shearer are interlocked by a releasable locking mechanism which prevents relative rotation therebetween but which allows both for the axial drilling pressure to be applied to the shearer and the shearer to be lifted, and for the drilling bit, sub-member and rod string to be lifted through the liner leaving the shearer and liner in the bore hole, when the locking mechanism is released.
A downhole casing shearer for use in drilling bore holes, comprising a sub-member and a hollow cylindrical shearer, the sub-member being adapted to be connected between a drilling bit and a drilling rod string and being insertable at least partially within the shearer, releasable locking means being provided for locking the sub-member and shearer together to prevent relative rotational movement therebetween, one end region of the shearer being provided with rearwardly directed teeth, said shearer further being adapted to be rotationally connected to a casing liner for lining the bore in which the shearer is used enabling the shearer to rotate while the liner moves axially in the bore.
Dependencies are inferred from the claim text.