Importance

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Abstract

A device for joining an element to a string of elements already mounted, including threaded rods and tubular casing elements covering the walls of a borehole, for use in drilling equipment including a rotary head driving said string with a combined movement of rotation about a substantially vertical axis and translation along said axis. The device includes a clamping device for clamping and guiding a single element, coupled to a friction screwing device (18). The clamping and guiding device is adapted for holding the single element in an axially aligned position relative to the elements already mounted. The clamping and guiding device is idly mounted to, and suspended from the rotary head. The friction screwing device has a rotating portion and a non-rotating portion. The rotating portion is provided with a lower friction device sliding along and rotating about an output rotary shaft of the rotary head. The non-rotating portion is fast for rotation with the rotary head and has actuators acting on said friction device. When extended, the actuators urge the friction device to engage and rotate the single rod or casing element such that the lower end thereof is screwed to the uppermost element of the string.

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First Claim