Abstract: A machine applies screwing and unscrewing torque between successive drill pipes with an essentially vertical axis extending through a tapered opening in a turntable for a well bore. The machine includes a mechanism for applying a high initial unthreading torque and a high final threading torque between successive drill pipes and a mechanism for rapid screwing and unscrewing of successive drill pipes. The machine also includes a clamping mechanism having a bolster and a plurality of shims. The shims have outer portions tapered to fit into the opening of the turntable and have inner portions with a shape corresponding to the shape of the drill pipes. Each shim is supported individually on the bolster by a device that moves the shim into engagement with a drill pipe to grip the same and with sufficient freedom to permit the shims to center the pipe between them automatically. The bolster is lowered to cause the shims to enter the opening in the turntable.

Abstract: 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.

Abstract: A machine to apply screwing and unscrewing torque to successive drilling shafts employs upper and lower claws, one of which is fixed and the other of which rotates through a limited angular range. Each claw comprises a pair of right-angle branches extending oppositely from a base and terminating in spaced relation to provide a permanent opening at one side of the claw opposite to the base. Each claw has a jaw comprising three gripping elements positioned essentially at the vertices of an equilateral triangle, one gripping element being fixed to the base and the other gripping elements being movably mounted on the branches at opposite sides of the opening. One claw comprises a pair of parts relatively movable vertically to form a viewing opening when the machine is not applying torque.