Abstract: A drilling apparatus of the type including a platform, a pair of spaced, parallel, substantially vertical guide rails, and a power swivel which is guided along the guide rails is provided with a pair of space support surfaces positioned on the underside of the swivel. In addition, a pair of collapsible pedestals are mounted on the platform, each pedestal positioned under a respective support surface such that the swivel rests on the pedestals when lowered toward the platform. These pedestals are provided with a collapse strength chosen such that the pedestals collapse in a controlled, progressive manner, substantially without damage to the guide rails, in the event the swivel falls from at least a predetermined height. In this way both the platform and any drill string attached to the swivel are protected from excessive loads associated with abrupt deceleration of the swivel, and the incidence of string breakage due to such abrupt deceleration is at least substantially reduced.

Abstract: An automatically self-centering clamp for down-hole tubulars includes a frame which defines guides for two opposed clamping jaws. Each clamping jaw is pivotably attached to a rocker arm, and the two rocker arms are in turn pivotably attached to a tension member which extends therebetween. The tension member is mounted to the frame so as to be free to move in the direction of the clamping axis of the clamp as necessary to follow the movement of the jaws. A hydraulic cylinder is provided to pivot the rocker arms about the tension member, thereby positioning the jaws in the guides formed by the frame. A rotatable pivot plate is mounted to rotate within the frame, and link members are provided to link each of the rocker arms with a respective point on the pivot plate. The link members and the pivot plate act to maintain the rocker arms in symmetrical positions such that the jaws remain centered about a predetermined clamping axis for a wide range travel of the jaws.

Abstract: In a dual conduit drill pipe section having concentric inner and outer tubes, a plurality of centering lugs are provided which are disposed between the inner and outer tubes and include bearing surfaces which are adapted to reduce the friction and wear associated with the movement of the inner tube with respect to the outer tube. The inner tube is secured to the outer tube at one point along each pipe section by a heat meltable adhesive which bonds an anchor ring which is secured to the inner tube to a shoulder defined in the inner surface of the outer tube.

Abstract: A stabilizer for use with a string of single tube or dual concentric drill pipe above a bit having analogous tubular members adapted for fluid tight interconnection with the pipes of said string to provide a conduit for drilling fluid. A stabilizer means encircles the stabilizer body and is adapted to contact the hole wall. The stabilizer means includes a sleeve bearing mounted to rotate with respect to the stabilizer body and a stabilizer sleeve mounted stationary on the sleeve bearing. A port means in the stabilizer body provides fluid communication between the drilling fluid conduit and the stabilizer sleeve and/or thrust bearing. An exit port means in the lower end of the stabilizer means provides fluid communication between the stabilizer sleeve bearing and the outside of the stabilizer.