Earth boring assembly with drag pipe

摘要

An earth boring assembly is provided with a hammer member at its leading end for impacting through an earth formation to form a boring therein. An expander cone is attached rearwardly of the hammer to expand the boring which has been formed by the hammer and drag pipes are connected to follow the hammer into the boring. Clamping means interposed between the expander cone and the drag pipe operate to automatically effect frictional locking engagement between the hammer and the drag pipe when the expander cone and the drag pipe are moved toward each other and to automatically release the frictional engagement when the members are moved away from each other. The clamping means may specifically comprise an annular slotted ring having wedge-shaped outer surfaces by means of which the ring is caused to become clamped and released about the hammer.