Enhanced Lateral Chipping in Deep Hole Drilling

摘要

Percussive drilling hammer assembly (20) arranged for temporary reduction of hydrostatic pressure locally at the points of material removal by periodically interrupting a flow of liquid towards the drill bit through at least one liquid channel (26). The drilling hammer assembly is provided with a liquid flow interrupting device which is arranged to abruptly and periodically interrupt the flow of liquid in a manner synchronized with the percussion frequency of the drill hammer impact piston (23), to thereby induce negative pressure waves from the point of interruption only in a direction towards the drill bit (21).