Abstract: In percussion drilling such as earth drilling, a hammer piston driven by pressure medium is axially reciprocally movable in a drill body to transfer impact energy to a drill shank connectable to a drill bit. The axial position of the drill shank in the drill body is monitored, and the impact energy of the hammer piston is varied as a function of said position. For this purpose a sensor in the drill body produces a signal corresponding to the axial position of the drill shank in the drill body. By means of a control valve, the signal is used to control the pressure of the pressure medium actuating the hammer piston, thereby varying the impact energy.

Abstract: A method and a device for swivelling a spray nozzle, especially for spraying concrete, over a sector between two turning positions. The speed of the swivelling movement is kept constant, regardless of the nozzle attitude. By overriding an automatic swivel control unit, the turning positions can be replaced, and once the override ceases, automatic swivelling resumes between the new turning positions.

Abstract: A method for sealing cracks and cavities in different kinds of building constructions, such as building constructions in rock, concrete, brickwork and timber is disclosed, according to which holes communicating with the cracks or cavities are driven into the building construction. These holes are sealed outwardly and put in connection with a vacuum source so that the water present in the cracks or cavities is sucked by the negative pressure in the direction towards the holes. Crack sealing material e.g. cement, epoxy tar, setting plastic, silicate based sealant or the like, is then applied to the cracks or cavities and is, due to the negative pressure prevailing in them, drawn into its sealing positions in the building construction, where it is allowed to harden or set under the influence of the negative pressure.

Abstract: A drilling machine for drilling floors or walls having a frame in which a drilling rod is displaced by a screw member. A container on the frame is placed around the drilling rod to fasten the frame to the floor or wall, to cool the drill, and to collect the drilling debris.