Importance

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Abstract

A large diameter rock drill includes a tubular body and a central shaft longitudinally axially disposed with respect to the body. The shaft extends longitudinally axially above the top edge of the body and is attached to a drive means. A plurality of angularly spaced apart vertical plates are attached to the inside wall of the body and the shaft. Each of the plates has a lower edge which tapers downwardly and inwardly from the inside wall of the body toward the longitudinal axis of the drill near its lower end. The plates' lower edges taper downwardly and inwardly and have an array of closely packed pockets mounted thereon, each pocket receiving a drill tooth. The radially outermost pockets are affixed to vertically extending, outwardly projecting ribs on the body. The teeth face downwardly and outwardly, and are angled in a clockwise or counterclockwise direction. The teeth in adjacent arrays are offset from one another by an amount which results in substantially each tooth cutting around a unique circular path as the rock drill is rotated. A plurality of teeth are mounted on the lower circumferential outer periphery of the body, pointing downwardly and outwardly and angled in either a clockwise or counterclockwise direction. A pilot drill is mounted on the lower end of the drill. An expander attachment, having arrays of teeth which complement those on the basic unit and circumferentially disposed body teeth, may be secured around the basic rock drill unit in order to enlarge the effective drilling diameter of the drill.

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First Claim