| 摘要 |
Bore hole underreamer in a terrestrial formation, intended in particular for oil drilling and especially to be fixed in the vicinity of a drill head, the underreamer having a hollow body (1), with a longitudinal axis (3), which has an external wall (5), at least two cylindrical bores (7) provided through the external wall (5) and whose axes (9) are transverse to the longitudinal axis (3), the bores being distributed over the circumference of the hollow body, and in each of the bores, a cylindrical widening arm (11) which has a cutting end (13), disposed on the outside of the body and provided with blades (15) for widening the hole, which is arranged in the bore like a hydraulic piston, so as to be able to slide therein between an active position in which this cutting end (13) is distant from the body, and an inactive position, and whose other end, inside the body, is intended to receive from a fluid a pressure capable of pushing the said arm into its active position, the underreamer having a locking member (21) common for the said arms, which can occupy a locking position in which this member locks the arms in their inactive position, which is immobilized in the body, in a releasable fashion, in the locking position, and which, when it is released, can leave the said locking position under a thrust from at least one of the arms subjected to the pressure capable of pushing the said arm into its active position.
|
