Patent ID: 7156189

Claim:
An apparatus comprising a drill bit, a hammer mechanism for hammering the drill bit in a first axial direction and in a second axial direction, opposite to the first axial direction, the hammer mechanism comprising at least a first mass and first impact surface to hammer the drill bit in the first axial direction and at least a second mass and second impact surface to hammer the drill bit in the second axial direction and a selection mechanism for controlling whether, at a given point in time, the drill bit is hammered in the first or second axial direction; wherein the drill bit is elongated and the first and second axial directions are opposite each other along the length of the drill bit; and the hammer mechanism comprises the first mass and the first impact surface and the second mass and the second impact surface with the first and second masses moveable relative to and along a center line of the drill bit and wherein impact of the first mass on the first impact surface results in a force exerted on the drill bit in the first direction and impact of the second mass on the second impact surface results in a force exerted on the drill bit in the second direction; and wherein the first and second masses are positioned on opposite sides of a vibrating element, which, when vibrating, causes the first mass to oscillate between the vibrating element and the first impact surface or causes the second mass to oscillate between the vibrating element and the second impact surface.