| 摘要 |
An adjustment device consisting of at least one drill string element (40) rigidly secured in rotation to the drill string in the region of the drilling tool. The element (40) comprises portions (41, 43, 46) of which the outer bearing surfaces are arranged along a cylindrical surface which is substantially coaxial with the drill string (48) and has a diameter substantially equal to the nominal diameter of the hole (4). Said portions are arranged around the axis so as to generate, during part of the drill string rotation, and by reaction on the element (40) of the wall of the hole (4), tipping forces urging the drilling tool out of the drilling plane. The bearing portions (45,46) may partially consist of variable-diameter movable blades.
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