Downhole unit for use in boreholes in a subsurface formation

Details Downhole unit for use in boreholes in a subsurface formation Downhole unit for use in boreholes in a subsurface formation

1997-11-06

1999-10-26

Schoeppel, Roger

Boring or penetrating the earth

Cutter element laterally shiftable below ground

Plural selectively shiftable cutter elements

175267, 175292, E21B 402

Patent

active

059710853

ABSTRACT:
A downhole unit for use in subsurface boreholes, for example a bias unit for imparting a lateral bias to the drill bit to control the direction of drilling, includes a main body and a number of pads pivotally mounted on the main body for engagement with the walls of the borehole. A thrust member is disposed inwardly of each pivotal pad and is movable along a guide passage in the main body to transmit movement to the pad. Each thrust member is movable by hydraulic pressure and a fluid-tight sliding seal is provided between the thrust member and its guide passage. The outer surface of each thrust member or the inner surface of the guide passage, or both, is in the form of a portion of a toroid centred on the pivot axis of the respective pad so as to minimise lateral movement of the seal as the thrust member moves along the passage. This also allows relative displacement between the thrust member and pad to be avoided, so that the thrust member can be integral with the pad or rigidly connected to it.

REFERENCES:
patent: 3881776 (1975-05-01), Fashbaugh et al.
patent: 4776397 (1988-10-01), Akkerman
patent: 5725061 (1998-03-01), Van Steenwyk et al.

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