William R. Hamilton - Houston TX
Harry D. Hebard - Burnet TX
Hughes Tool Company - Houston TX
A drill pipe spinner having a body with an open throat for receiving a drill pipe. A pair of cylindrical driven rollers are mounted on the body for rotation about a vertical axis. A pair of pressure arms are pivotally mounted on the body for rotation about a primary pivot pin. A pair of secondary pressure arms are mounted on the primary pressure arms, for rotation relative to the primary pressure arm about a secondary pivot pin. A pair of cylindrical pressure rollers are mounted on the secondary pressure arms, for holding the drill pipe against the driven roller. A pair of piston and cylinder assemblies exert force on the secondary pressure arms, to cause the secondary pressure arms to rotate. The moment arms between the piston and cylinder assemblies and the primary pivot pins are shorter than the moment arms between the piston and cylinder assemblies and the secondary pivot pins. Springs, mounted between the primary and secondary pressure arms, cause the primary pressure arms to rotate with the secondary pressure arms, about the primary pivot pins, until the pressure rollers have contacted the drill pipe.