Abstract: A mobile drilling rig has a rectangular tubular derrick or mast normally transported on the truck in a generally horizontal attitude. The mast is pivoted to vertical at the drilling site. A drill rotating power head is connected to a pull-down system located inside the mast tube and which includes a rectangular guide tube slidably mounted inside the mast tube, and two double-acting hydraulic cylinder assemblies situated in a telescoping arrangement with one cylinder assembly inside the other. A cylinder inside the inner hydraulic cylinder assembly has a closed upper end secured to the upper end of the guide tube and serves as a piston rod connected to the power head. The overall stroke of the pull-down system is greater than the typical conventional length of pipe in a drill string to facilitate adding and removing lengths of pipe. The power head is floating mounted to the guide tube.

Abstract: A mud pump assembly has a housing having a motor-mounting face directly connected to a standard hydraulic drive motor. The pump housing supports and partially encloses a bearing assembly which supports the pump impeller shaft. A face-type impeller shaft seal is located between the bearing assembly and the impeller. The motor case completes enclosure of the impeller shaft bearing assembly. A motor case drain line is coupled to the mud pump housing for continuous pressure lubrication of the bearing assembly. In one embodiment, case drain fluid is returned from the mud pump housing to the hydraulic fluid reservoir for the hydraulic motor.

Abstract: A mobile drilling rig includes a rectangular tube which is used for the derrick and is normally transported on the vehicle in a generally horizontal attitude. The derrick is pivoted to vertical position by a hydraulic cylinder. A pulldown system located inside the tube includes a double-acting hydraulic pulldown cylinder, drive pinions mounted to the piston rod, one gear rack fixed inside the tube and another gear rack slidable inside the tube. A drill-driving powerhead is slidably mounted on the outside of the tube and is connected to the slidable gear rack. The pinions connected to the pulldown cylinder piston rod engage both racks and, with a piston stroke less than half the length of the tube, drive the power head essentially the full length of the tube for the pull-down function.