A ROCK DRILLING ARRANGEMENT

摘要

A rock drilling arrangement comprises a drill tube (11) with a downhole drilling machine (12) that has a pressure liquid driven impact motor arranged to deliver impacts to a drill bit. The drill tube forms a supply conduit for the drive fluid and channels in the drill bit form exit passages for the spent drive fluid. A spring loaded one-way valve is arranged in the supply conduit in connection with the downhole drilling machine and it comprises a valving element (23) slideable against a guide (26) so that a liquid filled chamber (27) is formed that has a leakage connection with the liquid downstream of the valving element. The valve will be sufficiently slow not to react to the pressure fluctuations during an impact cycle but it will close rapidly when the supply of pressure fluid is interrupted.