| 摘要 |
Borehole opener, particularly for enlarging this hole underneath a casing in the field of oil prospecting, comprising a body (2) of longitudinal axis (3), a duct (4) for drilling fluid, formed longitudinally in the body (2), and at least two hole-opening arms (5) which have an active part (7) equipped with cutting means (8), which are distributed symmetrically in the body (2) about the longitudinal axis (3), and which are arranged therein in such a way that they can be moved between a position of rest (9) in the body (2) and an active position (10) partially out of the body (2); in this hole opener in order to move it from the position of rest (9) to the active position (10), each arm (5) has a face (12), internal to the body (2), designed to be subjected directly, in the same way as an active face of a piston, to the pressure of the drilling fluid flowing through the body (2).
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