Process and apparatus for locking and releasing of a drilling shaft with essentially vertical axis

摘要

Apparatus and method for the locking and releasing of a train of drilling shafts having an essentially vertical axis employ wedges adapted to penetrate an opening in a rotation table of a wellhole in order to lock upon a shaft projecting from the opening while another shaft is screwed to or unscrewed from the upper end of the first-mentioned shaft. The wedges have a tapered external shape complementary to the shape of the opening and an internal shape complementary to the external shape of the shafts. Each wedge is individually attached to an associated arm connected to a vertically movable plate by means of an articulation and a jack that applies the wedge to a shaft. The attachment of the wedges to the arms has sufficient freedom to permit the wedges to engage a shaft and center the shaft between the wedges automatically before the wedges are lowered into the opening of the rotation table to lock the engaged shaft therebetween.