Patent ID: 7040421

Claim:
Liquid driven downhole drilling machine comprising a housing ( 11 , 12 ), a drill bit ( 13 ) mounted in a guiding bushing ( 31 ) to be angularly fixed but axially limitedly movable thereto, a piston hammer ( 30 ) arranged to impact a shank ( 14 ) of the drill bit, and a valve ( 40 ) for controlling reciprocation of the piston hammer, the valve alternately pressurising and depressurising a pressure chamber ( 47 ) in which there is a piston area ( 46 ) that drives the piston hammer forwards when the chamber is pressurised, wherein the guiding bushing ( 31 ) is rotatably guided in the housing ( 11 , 12 ) and, via a one-way coupling ( 29 ), coupled to a turnable sleeve ( 22 ) that has axial ridges ( 24 ) that bound a number of chambers ( 25 , 26 , 27 ) and form turning pistons for turning the turnable sleeve in a first and second direction, a number of these chambers being coupled in parallel with said pressure chamber ( 47 ) so as to be pressurised and depressurised simultaneously therewith.