CHUCK FOR AN EARTH BORING MACHINE

摘要

Rotary and axial forces are transmitted through a chuck to a rotary drill string. The chuck clampingly engages the drill string to transmit rotary and axial forces. A multiplicity of jaw elements in the chuck contact the drill string. The chuck includes a lower jaw retaining means and an upper jaw retaining means. Disengageable means are provided connecting the lower jaw retaining means and the upper jaw retaining means. Jaw actuating means are provided for moving the jaw elements to and from a rod gripping and rod release position.