Abstract: A thread coupling for a drill string for percussive drilling has a male thread (5) and a cooperating female thread (4). The male thread is arranged on a first drill string element (3) having a first impact surface (6). The female thread is arranged on a second drill string element (2) having a second impact surface (7). The male and female threads are conical, and the crests (8) of the male thread (5) have a radius of curvature more than thirty degrees of the pitch of the thread.

Abstract: Drill tube provided with a check valve and comprising a tube (1) and two end pieces (2,3). One of the end pieces comprises a first contact surface (4) for limiting the movement of a valve body (5) when the check valve is open and a second contact surface (6) against which a valve seat (7) rests. The valve seat is held in place by a lock ring (8) which preferably has circular cross section. The cooperating surfaces (12,11) on the valve body and valve seat are plane.

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 thread coupling for percussive drilling has a first drill string element (2) with an internal thread (3) and a second drill string element (6) with a spigot (7) which is provided with an external thread (8) for cooperation with the internal thread (3). A contact surface (10) on the second drill string element (6) is lined with a wear resistant additional material which covers 50-100%, preferably, 50-90%, of the contact surface. The wear resistant material is preferably a stellite which has been applied by means of plasma welding, or is a ring which has been soldered to the contact surface.

Abstract: This invention relates to a vibration dampening grinding cup for handheld grinding machines for the grinding of hard metal buttons on button bits, comprising a grinding head and a shaft made with a common axial channel for cooling medium, which distinguishes in that the shaft is formed with a driver part at its free end and an annular groove between this part and the grinding head, and that a bushing of rubber is arranged on the shaft adjacent to the grinding head, and a holder for such a grinding cup, which distinguishes in that it comprises a substantially cylindrical socket with an axial through channel, whose one end is connected with the rotor of the handheld grinding machine and through the other end of which shaft of the grinding cup is intended to be entered for installing the driver part of the shaft in a correspondingly formed driving part of the channel of the socket and to be fastened through introduction of balls situated in holes in the wall of the socket at the other end of the socket into the

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: Rock drilling device comprising a drilling tool with a set of tubes (7) and a set of rods (9) arranged therein. The drilling tool comprises a number of sections which each comprises a tube (7), a rod (9) and an end piece (11). The rod is provided with projections (10) at least near one of its ends for cooperation with parts (13,14) with reduced diameter in the tube and end piece respectively. The part (13) in the tube limits the movement of the rod in a direction away from the end piece. The part (14) in the end piece limits the movement of the rod in a direction towards the end piece. All thread connections (12) between different sections of the drilling tool and between tube and end piece within each section are made in the same way and thus equally easy to break.

Abstract: Device in hammer machines. The device comprises a machine housing (1) and a hammer piston (2) movable to-and-fro in the machine housing. A drilling tool connected to the machine housing comprises a drill bit (5), a set of tubes (4) for rotating the drill bit and a set of rods (3) for transferring impact energy to the drill bit. A rod (11) situated adjacent to the drill bit is provided with an axial channel (7) and a radial channel (8) for supplying flushing medium to the flushing channel (6) of the drill bit. The distance (S) from the front end (9) of the drill bit to channel (8) is larger than the length (L) of the hammer piston (2).