| 摘要 |
A blast hole drill comprising a mast including two parallel mast cords, a carriage, and a rotary head mounted on the carriage and adapted to engage a drill pipe. The rotary head includes a drive pinion on a rack on one of the mast cords, and the drive pinion is on one side of at least one of the mast cords. A backup wheel assembly is on the opposite side of the respective mast cord opposite the pinion and includes a wheel holding assembly support rotatably supporting a backup wheel, a yoke having an opening through the yoke, a plunger threadably received in the yoke opening, the wheel assembly support being slidably received on the plunger, and Belleville washers extending around the plunger and between the yoke and the wheel holding assembly support, the Belleville washers extending between an abutment on the plunger and the wheel holding assembly support.
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