Center discharge gas turbodrill

Abstract

A compact gas turbine motor and a speed reduction transmission capable of providing the speed and torque required for drilling with center discharge bits. The transmission includes two sun gears of different pitch diameters, keyed to the turbine shaft. Upper planet gears, whose carrier is fixed in place, drive an outer ring gear, which engages lower planet gears having a different pitch diameter. The lower planet gears engage the lower sun gear. Due to the different pitch diameters of the sun gears and planet gears, the gear carrier for the lower planet gears rotates in the same direction as the turbine shaft, but at a much slower rate. Exhaust gas from the turbine can be directed through one or more flow restriction elements to increase gas density in the turbine, further reducing turbine speed. The flow restriction element can comprise a venturi, to provide a vacuum assist to remove cuttings.

Dependencies are inferred from the claim text.