DRILL STEM GUIDE ASSEMBLY FOR ROTARY BLAST HOLE DRILLS

摘要

ABSTRACTA rotary blast hole drilling apparatus haying a tilt-able mast supported by adjustable mast braces and having a drillstem guide is described. The drill stem guide assembly is pro-vided for substantially frictionlessly gripping the drill stem,especially during angled drilling. The entire drill stem guideassembly can pivot substantially 90 degrees to permit passage ofa rotary gear box drive assembly for the drill stem as it movestowards the lower end of the mast. The assembly includes clampjaws which are opened and closed about the drill stem through alink which has a toggle effect when the jaws are closed so thatthe weight of the drill stem cannot open the jaws.