Abstract: The invention concerns a drilling apparatus for enlarging a bore in the ground, comprising a drilling head (6) having a drilling bit (12); a percussion piston (14) which is driven by a drive medium (9) and which impacts against the drilling bit (12), and a hollow drill string (8) to which the drilling head (6) is fixed and through the cavity of which the drive medium (9) is passed to the percussion piston (14). The drill string (8) is surrounded by a hollow outer string (3) enclosing an annular space which surrounds the drill string (8) and through which the drive medium (9) is passed out of the borehole. The invention further concerns a method of enlarging an existing borehole, using a drilling head of that kind.

Abstract: The invention concerns a drilling system having a drilling head (2, 2′) fixed to a drill string (3) which comprises an outer pipe (12, 12′) and a percussion string (13, 13′) inserted therein, wherein the percussion string (13, 13′) comprises a plurality of rods (14, 14′) which bear against each other with their end faces (19, 20; 19′, 20′). One object of the present invention is to provide a drilling system with an inner percussion string, which permits a greater variation in the drilling direction and which can be used as a directional drilling system. To attain that object the outer pipe (12) is adapted to be deformable along its longitudinal axis and the end faces (19, 20) which bear against each other of two rods (14) are so designed that they bear against each other substantially in surface contact upon inclined positioning of the axes of the two rods (14) relative to each other.

Abstract: The invention concerns a drilling apparatus for enlarging a bore in the ground, comprising a drilling head (6) having a drilling bit (12); a percussion piston (14) which is driven by a drive medium (9) and which impacts against the drilling bit (12), and a hollow drill string (8) to which the drilling head (6) is fixed and through the cavity of which the drive medium (9) is passed to the percussion piston (14). One object of the invention is to ensure improved removal of the drive medium out of the borehole. That object is attained in that the drill string (8) is surrounded by a hollow outer string (3) enclosing an annular space which surrounds the drill string (8) and through which the drive medium (9) is passed out of the borehole. The invention further concerns a method of enlarging an existing borehole, using a drilling head of that kind.

Abstract: Disclosed is a device for directional drilling including a drill head mounted on a drill column. A driving device applies an axial driving force to the drill column. A delivery device supplies a wash medium to the drill head through a channel in the drill column. The device provides for increased removal of material and drilling through hard materials by by providing a housing on the drill head having a receptacle for an axially movable piston and a piston drive for producing strikes of the piston acting on the drill head. A connecting link permits an axial movement between the drill head and the drill column. A channel for the wash medium may be sealed at least with respect to the end faces of the piston.

Abstract: The invention concerns a drilling system having a drilling head (2, 2′) fixed to a drill string (3) which comprises an outer pipe (12, 12′) and a percussion string (13, 13′) inserted therein, wherein the percussion string (13, 13′) comprises a plurality of rods (14, 14′) which bear against each other with their end faces (19, 20; 19′, 20′). Known systems were suitable exclusively for producing straight boreholes. One object of the present invention is to provide a drilling system with an inner percussion string, which permits a greater variation in the drilling direction and which can be used as a directional drilling system. To attain that object the outer pipe (12) is adapted to be deformable along its longitudinal axis and the end faces (19, 20) which bear against each other of two rods (14) are so designed that they bear against each other substantially in surface contact upon inclined positioning of the axes of the two rods (14) relative to each other.

Abstract: The invention pertains to a hydraulic rotary drive for the rotating rod assembly of a drilling machine which contains at least two hydraulic motors (1-3) with the motor shafts (34-36) that are connected to a common output shaft (11) by means of a gear, with a clutch (4-6) being arranged between the motor shaft (34-36) of each hydraulic motor (1-3) and the gear such that the rotational movement of each hydraulic motor (1-3) can be disengaged from the rotational movement of the output shaft (11). The invention aims to develop a highly variable rotary drive for ground and rock drilling machines.