Patent ID: 6199641
Filing Date: 2001-03-13
Classification: E21B

Abstract:
A gripping device for releasably engaging an elongate member, the gripping device comprising:a housing including a central opening for accepting an elongate member therethrough; a first plurality of slip carrier blocks spaced circumferentially about the opening, each slip carrier block having a rear surface and a sloping front face, the sloping front faces together forming a slip bowl bore with a diameter and the slip carrier blocks each being radially moveable between a fully retracted position and an advanced position to adjust the diameter of the bore; a slip mounted on each sloping front face to move over the front face, the slips being selected to engage the elongate member and to be slidable along the slope of the front face into a loaded position; and a motor to drive the movement of the slip carrier blocks, the motor being selected to exert a driving force on the slip carrier blocks which is insufficient to permit the carrier blocks to move radially outwardly when the slips are in the loaded position wherein the slip carrier blocks each include a plurality of curved gear teeth formed on one of their upper surface or their lower surface and the gripping device further comprises a spiral gear plate including an annular surface and a central opening through the upper annular surface, the upper annular surface having formed thereon elongate gear teeth spiraling inwardly toward the central opening and selected to mesh with the curve gear teeth of the slip carrier blocks, the spiral gear plate positioned in the device such that its central opening corresponds with the central opening to drive the slip carrier blocks radially by the elongate gear teeth acting against the curved gear teeth.