Abstract: An improved drilling rig having a drillhead assembly positioned onto a mast for vertical movement therewith. The drillhead assembly is hung by cables threaded from a hoist assembly positioned at the top end of the mast. One or more cable return assemblies are positioned at the bottom end of the mast. The cables are counter-wound on the hoist assembly such that the cables roll off of the hoist assembly in the direction towards the drillhead assembly at the same rate the cables are pulled onto the hoist assembly from the direction towards the cable return assemblies. The drillhead assembly has a drive motor assembly rotatably mounted within a frame. A break-out tool assembly is mounted at the lower end of the mast. The break-out tool assembly has means for grasping rotating a length of string so as to separate the lengths of string.

Abstract: Plasma arc welding apparatus including a plasma torch having a body defining a flow passage for plasma gas an orifice through which plasma gas exits the torch as a high-temperature jet stream utilizes an actuatable slope control valve operatively connected in relatively close flow proximity with the torch orifice. By controlling the adjustment of the actuatable valve, the flow of plasma gas through the torch orifice is accurately controlled.

Abstract: Plasma arc welding apparatus including a plasma torch having a body defining a flow passage for plasma gas an orifice through which plasma gas exits the torch as a high-temperature jet stream utilizes an actuatable slope control valve operatively connected in relatively close flow proximity with the torch orifice. By controlling the adjustment of the actuatable valve, the flow of plasma gas through the torch orifice is accurately controlled.

Abstract: For clampingly holding a drill rod or the like, clamp apparatus that includes a mounting frame having spaced side members, a jaws holder having upwardly diverging end walls and bounding an opening for clamp jaws, longitudinally spaced jaw actuators that include piston cylinder combination having cylinders pivotally mounted on the jaw holder, and piston rods for moving jaw brackets upwardly and outwardly of one another, each bracket having an inclined leg extending into the jaw opening in slidable relationship with the adjacent end wall and into slots in the holder side walls, and side walls that have interleaving portions that maintain the brackets at substantially the same elevation relative one another while permitting the brackets moving longitudinally toward and away from one another, and a pin for releasably mounting each jaw to the respective bracket in abutting relationship to the adjacent bracket leg to move therewith, the jaws having semi-circular rod receiving recesses, the holder having oppositely

Abstract: High-low speed rotary drive mechanism for rotatably driving driven elements of a tool, for example a hydraulic chuck, while permitting axial movement of the driven elements relative thereto, said mechanism including a housing, a tubular spindle rotatably mounted by the housing top and bottom walls, drive lugs joined to the spindle inner peripheral wall for driving the driven elements, an axially lower main drive gear fixed to the spindle to drive the spindle, a reversible hydraulic motor mounted on the housing for driving the main drive gear at high speed, low torque, an upper gear mounted on the spindle between the lower gear and the top wall for rotation relative the spindle, an elongated rack having teeth intermeshing with the upper gear for driving the upper gear at high torque, low speed, and a poppet type ratchet assembly mounted by the upper gear to rotate therewith.