Patent ID: 7143845

Claim:
A drilling apparatus comprising: a carriage; a mast disposed on the carriage and carrying an up-down feed system; and a rotation mechanism adapted for rotating a drill string, the rotation mechanism mounted to the feed system for up-and-down movement, and comprising: a housing forming an interior chamber, a hydraulically driven motor with a motor casing, and a rotation transmission mechanism disposed in the chamber and including a gear system having a high-speed power input section operably connected to the motor, and a low-speed power output section adapted for connection to a drill pipe section, wherein the rotation transmission mechanism further includes an anti-vibrational inertial body forming part of the high speed power input section for storing rotational energy to even-out rotary speed variations and resist the generation of vibrations during drilling operations, wherein the anti-vibrational inertial body and a high-speed gear of the power input section are both formed by the same piece of material, and wherein the inertial body at least partially encloses a portion of the motor casing.