Abstract: A double shoulder drill stem connection for high torque applications includes a thread taper within a range between about 1.0 and 1.2 inch per foot. The thread form is characterized by a stab angle between about 35 and 42 and a load angle between about 25 and 34 degrees and by a short thread height with elliptical roots and with crests having an angle which slopes in an opposite direction with respect to the joint centerline from the thread taper. A drill string includes a tool joint having different inner diameters for a substantial axial length to provide enhanced strength in the threaded portion of the joint.

Abstract: A filter assembly is disclosed which includes a downwardly sloping skirt portion, a gasket, filter media, and a supply suction tube. The gasket is integral with a top section of the skirt portion. The filter media, which may be pleated for increased filtering capabilities, is positioned at the bottom of the skirt portion such that unfiltered fluid will be gravity biased to pass through the filter media. The suction tube is integral with the skirt and has a first end and a second end. The first end is adapted to be connected to a pump, while the second end extends through the skirt such that the filtered fluid can be drawn through the suction tube when the pump is activated.

Abstract: A polyphase cylindrical electrical machine including a non-salient stator, a rotor and an air-gap therebetween, together with a winding energisable to apply alternating current to exert two magnetic fields to rotate about the machine axis to produce a non-rotating force in a selected direction radially of the machine axis, the fields rotating in the same direction and having pole numbers differing by two, the fields being exerted by said current at one frequency to act on the machine rotor with said non-rotating force.

Abstract: A drilling mud saver valve connected to the lower end of a kelly allows down flow of mud or other drilling fluid when pumps are actuated to circulate drilling fluid, but closes when the pumps are off, thereby retaining drilling fluid thereabove in the kelly to prevent loss of fluid when the kelly and valve are disconnected from the drill pipe.The valve includes a tubular body and a top sub screwed therein. A replaceable seat is carried by the lower end of the top sub. A poppet type valve closure is urged upwardly against the seat by a helical spring strong enough to close the valve against the weight of drilling mud in the kelly.The poppet valve closure has a central flow passage therethrough, communicating with the stem and controlled by an upwardly opening check valve, to communicate drill pipe pressure to the kelly when the pumps are off. The check valve closure is frangible for easy break out if wire line tools need to be run through the valve.