Patent ID: 6510908
Filing Date: 2003-01-28
Classification: E21B

Abstract:
A blast hole drill comprising:a frame supported for movement over the ground, a mast supported by the frame for movement relative to the frame between a vertical position and a plurality of non-vertical positions, said mast being formed of a plurality of mast cords, at least two of which are fixed in parallel relationship to each other, a carriage, a rack on at least one of said parallel mast cords, a rotary head mounted on said carriage and adapted to engage a drill pipe, said rotary head including a drive pinion on said rack for moving said rotary head carriage along said mast, and means for mounting said carriage on said parallel mast cords, said mounting means having said drive pinion on one side of at least one of the mast cords, and a backup wheel assembly on the opposite side of the respective mast cord opposite said pinion and including a wheel holding assembly support rotatably supporting a backup wheel, a yoke attached to said carriage and having an opening through the yoke, a plunger received in the yoke opening, said wheel assembly support being slidably received on said plunger, resilient means extending around said plunger and between the yoke and the wheel holding assembly support for biasing said wheel holding assembly support away from said yoke, and means for fixing the resilient means against the wheel assembly support so that said wheel is pressed against said mast cord by said resilient means.