Self actuating underreamer

Details Self actuating underreamer Self actuating underreamer

2006-10-10

2010-06-08

Bagnell, David J (Department: 3676)

Boring or penetrating the earth

Cutter element laterally shiftable below ground

Pivoted about substantially longitudinal axis

C175S290000, C175S057000

Reexamination Certificate

active

07730974

ABSTRACT:
An underreamer for well drilling comprises pivotally extendible roller cutters that extend slightly beyond the diameter of the pilot drill bit but are retained in their retracted position by the casing. Upon encountering an obstruction, the underreamer is pushed out of the casing, allowing the outer edges of the cutters to contact the obstruction. Continued downward pressure of the drill stem causes the roller arms to pivot outward to a fully extended position in which the cutters enlarge the hole to a diameter larger than the casing by rotation of the drilling stem. The advance of the casing relative to the underreamer forces the cutters to retract into the casing.

REFERENCES:
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patent: 6920944 (2005-07-01), Eppink et al.
patent: 6929076 (2005-08-01), Fanuel et al.
patent: 7048078 (2006-05-01), Dewey et al.

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