Abstract: A method of processing perforated gypsum boards is disclosed. When the gypsum boards have been perforated the following steps are performed while the boards are being moved individually along a path. The moving boards are sprayed with pressurized water which is directed towards the opposite surfaces of the boards so as to enter apertures or slots formed by the perforation of the boards, and then water is removed from the moving boards by blowing pressurized air against the boards and sucking water therefrom, wherein dust on the boards is entrained into the water and removed from the boards together with the water.

Abstract: A method of processing perforated gypsum boards is disclosed. When the gypsum boards have been perforated the following steps are performed while the boards are being moved individually along a path. The moving boards are sprayed with pressurized water which is directed towards the opposite surfaces of the boards so as to enter apertures or slots formed by the perforation of the boards, and then water is removed from the moving boards by blowing pressurized air against the boards and sucking water therefrom, wherein dust on the boards is entrained into the water and removed from the boards together with the water.

Abstract: In order to be able to mount a suspended ceiling in places where the space between the ceiling and the overlying structure exceeds 40 mm there is according to the invention used a generally known metal suspension element (2, 3) with a T-iron (4,5).On these T-irons (4,5) there are mounted plaster boards (6) in that on the back of the boards there are glued two metal strips (7,8), i.e. one with a backwardly bent edge (8) overlapping one of the flanges (5) and a metal strip (7) abutting on the flange (5) in the mounted position of the board. It is thereby possible to place the boards loosely and to take them down according to requirements without any need of tools. The structure will allow the mounting of an additional insulation layer on top of the boards (6). At the same time the structure will appear as plane ceiling surface i.e. with concealed support profiles (4,5). This simplifies maintenance.

Abstract: In order that holes may be produced in a simple and safe manner in a plaster plate (1) to be used as sound adjuster in a room, holes (15) are punched out of the plate, e.g. in the shape of slits, by means of a cutting tool. Hereby the considerable dust and noise inconveniences caused by the hitherto known machining are avoided. By slits (15) that must lie close to each other, it is possible to punch in two stages, i.e. first with double distance and then in the space between. This prevents fracture of the plaster and tearing of any paper that may be on the surface. The cutting tool is provided with punches (7, 8), in a shape corresponding to the holes. Each punch is provided with an inclined blade (10) which forms an angle of the horizontal of 13.degree.. The cross sectional shape of the blade is V-shaped, with two blades (11) running along the sides of the punch.