Patent ID: 7958947

Claim:
Damping device for inserting into a housing of an impulse producing drilling machine, for damping shockwave reflexes from a drill string connected to the drilling machine and including a first damping piston ( 7 ) for direct or indirect action against the drill string and for applying a pressure in the direction of the drill string, said damping device further including: a second damping piston ( 9 ) for applying pressure in the direction against the drill string against a fixed stop ( 11 ) arranged in the housing, wherein the first and second damping pistons are movable independent of each other in their respective working areas and arranged such that movement of one said damping piston in said working area thereof does not cause movement of said other damping piston in said working area thereof, and wherein the first damping piston ( 7 ) is movable between advance positions, as seen in a direction of the drill string, in which only said first damping piston exerts a force against the drill string, and retracted positions, in which said first damping piston cooperates with the second damping piston ( 9 ) to jointly exert force against the drill string, and wherein the first damping piston and the second damping piston are each adapted to act against the drill string directly, or to act against the drill string indirectly over a drill bushing ( 5 ), a shank adapter ( 4 ) or both.