Abstract: In a scavenger is supplied through a scavenging pipe (26) to the internal pipe string (11), the scavenging pipe (25) extending through a bore (27) of the hammer piston (17) of the hammer drill. Due to a rotary drive (14), the drilling strings (10,11) are rotated which are connected to the shank (13) extending into the rotary drive (14). The scavenger is conducted through the scavenging pipe (26) into the shank (23) and from there into the internal pipe string (11). The external diameter of the scavenging pipe (26) is inferior to the inner diameter of the bore (27) of the hammer piston (17), and of the scavenging bore (23). Sealing between the scavenging pipe (26) and the scavenging bore (23) is effected by a thick head piece (33) at the end of the scavenging pipe. Said head piece (33) contains a seal rubbing along the cylindrical scavenging bore wall if the hammer piston (17) strikes on the shank (13).

Abstract: To rotate a pipe (17) to be urged into the ground, a rotary disk (20) clamped at said pipe (17) is pivotable on a table (19) which carries two groups of driving cylinders (40, 41). While the first group is operative to carry out the working stroke in order to turn the rotary disk (20) the return stroke is performed by the second group thus ensuring a continuous rotation of the rotary disk (20) or a standstill in one sense of rotation.