Abstract: Pressure-air driven percussion device for a down-the-hole drill with a hammer-piston which is axially reciprocally movable in a hammer-piston chamber through a driving device. The hammer-piston in operation acting with a hammer-end against an upper end of a drill bit which is positioned inside a chuck. An air-cushion for reducing percussive power is arranged to be formed at the hammer-end of the hammer-piston in positions where the drill bit has been moved past a predetermined distance in the percussion direction. The drill bit is sealingly slidingly supported in a drill bit bushing, and the hammer-end of the hammer-piston is formed so that it sealingly cooperates with the drill bit bushing in the positions in order to form the air-cushion.

Abstract: Pressure-air driven percussion device for a down-the-hole drill (1) with a hammer-piston (86) which is axially reciprocally movable in a hammer-piston chamber (18) through a driving device (9), said hammer-piston (6) in operation acting with a hammer-end (16) against an upper end (17) of a drill bit (2) which is positioned inside a chuck (3), wherein an air-cushion for reducing percussive power is arranged to be formed at the hammer-end of the hammer-piston in positions where the drill bit (2) has been moved passed a predetermined distance in the percussion direction. The drill bit (2) is sealingly slidingly supported in a drill bit bushing (5), and the hammer-end (16) of the hammer-piston (6) is formed so that it sealingly cooperates with the drill bit bushing (5) in said positions in order to form said air-cushion (19). The invention also concerns a down-the-hole drill (1).

Abstract: Down-the-hole drilling machine comprising a housing (1) with a hammer piston (5) movable to-and-fro and intended to exert a drill bit (3) to impacts. The hammer piston is formed with two piston heads (6,7) and a waist (9) between them. An intermediate wall (10) is arranged around the waist (9) so that two chambers (11,12) are formed on either side of the intermediate wall. The chamber (11) between the intermediate wall and the forward piston head (6) is continuously pressurized via a first channel (13) in the intermediate wall. The chamber (12) is via a second channel (15) in the intermediate wall connected to a space (16) in front of the hammer piston (5). Through this double drive areas are obtained during the working stroke of the hammer piston.

Abstract: A water driven hammer device has a machine housing and a hammer piston movable to-and-fro in the machine housing. The hammer piston is guided in the machine housing in two guides separated from each other. The guides are formed from two parts each having different inner diameters, and the parts with the largest inner diameters on the guide are turned towards each other. A room between the guides is pressurized and chambers on the other side of the guides are kept at a lower pressure, resulting in fluid flow through the guides for centering the hammer piston in the machine housing to avoid seizure of the hammer piston.

Abstract: Fluid driven down-the-hole drilling machine. The hammer piston (2) of the down-the-hole drilling machine is adjacent to its front end provided with a cylindrical part (6). The drill bit (3) is provided with a first impact surface (41) which receives impacts during drilling, a second impact surface (42) and an annular section (7) which surrounds the cylindrical part (6) between the impact surfaces. The second impact surface (42) receives the impact energy of the hammer piston at reversed feeding of the housing (1) of the down-the-hole drilling machine for freeing the drill bit when it has become stuck.

Abstract: Drill string component for use at drilling with a liquid driven down-the-hole drilling machine (1) comprising three coaxial tubes (2,4,6) for forming channels for supply of driving medium to the down-the-hole drilling machine, return of the driving medium after it has done its work and supply of flushing medium to the bore hole. The outer tube (2) of the drill string component is provided with a first end piece (7) which is axially displaceable relative to the outer tube and axially lockable relative to the outer tube in an outer position so that the inner tubes (4,6) are protected against damage when the drill string component is not connected with another drill string component, the hammer device (1) or a rotary device (9) for rotation of the drill string.

Abstract: Down-the-hole drill comprising a housing (1), a hammer piston (6) movable to-and-fro in the housing and intended for impacting a drill bit (5). A back piece (3) provided with an extension (12) with a valve part (17) cooperates with a part (8) of a central channel in the hammer piston. This part of the central channel comprises a zone (16) with larger diameter than adjacent parts at an intermediate part of this part. This results in that pressure medium can pass the valve part when it is situated at the zone and that the valve part and the hammer piston sealingly cooperate when the valve part is on either side of the zone.

Abstract: Down-the-hole drilling machine comprising a housing in form of a tube (1), a hammer piston (6) being movable to-and-fro in the tube and intended for impacting a drill bit (5). The hammer piston is at its ends provided with end sections in form of polygons with rounded corners (51, 52). These end sections are turned relative to each other an angle which is half as large as the angle between two adjacent corners.

Abstract: Damping device for a percussion rock drilling machine. A damper piston (22) and a compressed air cushion in a damping chamber (23) transfer feeding force from the drill machine housing (11) to the drill string (15). A venting valve (51) is arranged for venting the damping chamber (23) after which the damping chamber can be pressurized with a selectable pressure.