Abstract: A surface, e.g., a concrete surface, is worked by guiding a lance (23) which comprises a water jet mouthpiece (27) coupled to the high-pressure water over the surface in a working path and at the same oscillating the lance transversely to the working path. The oscillation is driven by an eccentric mechanism (30, 31) and has a stable eccentric position when the mechanism is rotated in the one direction and a stable eccentric position when it is rotated in the other direction. The two positions have a different eccentricity and impart different widths to the working. The working depth and the working width can be changed by changing the direction of rotation.

Abstract: A surface, e.g., a concrete surface, is worked by guiding a lance (23) which comprises a water jet mouthpiece (27) coupled to the high-pressure water over the surface in a working path and at the same oscillating the lance transversely to the working path. The oscillation is driven by an eccentric mechanism (30, 31) and has a stable eccentric position when the mechanism is rotated in the one direction and a stable eccentric position when it is rotated in the other direction. The two positions have a different eccentricity and impart different widths to the working. The working depth and the working width can be changed by changing the direction of rotation.

Abstract: A machine for working a surface with a high-pressure water jet, comprising a mobile chassis (11) with a boom (14) that carries a lance (22) with a nozzle (23) for spraying water, and a drive unit (35) that comprises a motor and control units for the chassis and the boom. The chassis (11) comprises an underframe (33) and a carrier unit (34) shiftably mounted on the underframe, which carrier unit carries the boom (14) and the drive unit (35) so that the machine's center of gravity can be shifted by shifting the carrier on the underframe.

Abstract: A machine for working a surface with a high-pressure water jet, comprising a mobile chassis (11) with a boom (14) that carries a lance (22) with a nozzle (23) for spraying water, and a drive unit (35) that comprises a motor and control units for the chassis and the boom. The chassis (11) comprises an underframe (33) and a carrier unit (34) shiftably mounted on the underframe, which carrier unit carries the boom (14) and the drive unit (35) so that the machine's centre of gravity can be shifted by shifting the carrier on the underframe.

Abstract: A method for working a concrete surface uses a water jet ejected from a nozzle of a nozzle holder. The nozzle holder reciprocates in cutting sweeps and moves together with a working apparatus in steps between the cutting sweeps. The water jet is directed in directions of the sweeps, and at the end of each sweep, the nozzle holder is swung into a new angle of attack for a subsequent cutting sweep. At the end of a cutting sweep, the nozzle holder begins to swing backwards simultaneously as its linear velocity increases to permit the target area to remain substantially unchanged at the start of the stepping of the working apparatus so that the water jet makes a cut forwardly in the stepping direction. The stepping and change of angle of attack are completed simultaneously immediately prior to the commencement of a subsequent cutting sweep.

Abstract: A device for working at hard material. The device comprises a container (4) with a sieve (6) where abrasive is sieved under a liquid surface (7). Liquid is supplied to the suction conduit (13) of a low pressure pump (8) for creation of a slurry which is pumped to a pressure vessel (10). This pressure vessel is then pressurized for the feeding of abrasive to a high pressure conduit (2) where the abrasive is mixed with high pressure liquid which is supplied to a nozzle (3) for the creation of a jet stream.