US 2954838 A
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Description (OCR text may contain errors)
Oct. 4, 1960 2. E. M. NUORIVAARA 2,954,338
SOUND DEADENING OR ABSORBING WALL-BOARD Filed May 8, 1956 United States PatentO "ice SOUND DEADENING R ABSORBING WALLBOARD Zachris Enzio Mikael Nuorivaara, Overboelare-Grammont, Belgium, assignor to Svenska Tandsticks Aktiebolaget, Jonkoping, Sweden, a Swedish joint-stock company Filed May 8, 1956, Ser. No. 583,420
Claims priority, application Sweden May 18, 1955 1 Claim. (Cl. 181-33) The invention relates to a sound-reflection counteracting board. More particularly, the invention relates to a board for lining ceilings and walls in rooms in order to improve the acoustic conditions by the special structure of the board.
For facing walls and ceilings different kinds of wallboard are used, which may be either hard or more or less porous. The hard wallboard usually has a thickness of about 6 mm. and it is ordinarily made without any special covering layer. It is usual, however, to paint the board, especially as it does not absorb the paint. This board has a hard surface and reflects sound to a high degree. The more porous wallboard usually has a thickness of 6-13 mm. These boards need a surface layer, but as they absorb paint too much they are usually faced with paper and sometimes also painted. Without any surface layer these boards have a certain capacity of absorbing sound, but by applying the more dense paper the sound insulation is reduced, and particularly in large rooms the acoustics deteriorate and the sound reflection causes a disturbing effect.
A principal object of the present invention is to provide a board of the character stated, which considerably reduces the echo effect by splitting the sound waves in different directions.
An additional object of the invention is to provide a board, which reduces the reflected waves by increasing the absorption surface.
Another object of the invention is to provide a sound deadening board, which is simple in its construction and inexpensive in its manufacture.
A further object of the invention is to provide a sound deadening board, which maintains its form in spite of impressions therein.
A still further object of the invention is to provide a cheap sound deadening board, which has an ornamented surface.
With these and other objects in view, as will appear hereinafter, my invention consists in certain steps of the manufacture and arrangements of the porous board as will appear from the following description, claim and the accompanying drawing, in which Figure 1 is a plan view of a part of a sound absorbing board according to one embodiment of the invention, and
Figure 2 is a section along the line IIII in Figure 1 on an enlarged scale.
In the drawing, 1 indicates a fibre board or wallboard, 2 is a covering layer glued to the board, 3 a series of parallel ridges and 4 a series of other parallel ridges perpendicularly thereto so that pyramidal recesses are formed between the ridges.
Experiments have shown that the covering of the board in connection with the pressing operation in a wallboard press involves several difficulties, and the board is therefore made in the ordinary way and subjected in dry condition to the steps according to the invention.
Patented Oct. 4, 1960 The covering layer of lining may consist of sheets of any suitable material, such as fabric, plastic, metal foils, but it is preferred to use a porous paper which in the manufacture is weakly glued and therefore, in contact with the glue, can be stretched sufficiently without bursting when thedepressions are formed.
Before the paper is placed on the board a glue layer is applied either to the board or to the paper, whereafter the paper is rolled onto the board and the depressions are made. As the porous board is rather eleastic, the depressions would be partly levelled out, if they are not immediately made stiff and permanent in some way. For this reason a thermosetting resin of any known and suitable kind is used, which can be hardened or cured by heat and the press member for making the depression is heated so that the glue is hardened during the pressing operation and stiffens the walls of the depressions.
This operation may be performed in a press similar to an ordinary wallboard press but with only the one press plate heated and provided with an uneven surface corresponding to the desired pattern in the board. The same operation, however, may be carried out by feeding the board between two press rollers, one of which being heated electrically or by steam and having its surface patterned. In order to obtain the pattern shown in the drawing the one press roller may be provided on its surface with two series of grooves, one series perpendicular to the other, so that the surface is covered by adjacent, upstanding pyramids. The depressions in the board will thereby be pyramidal, but it is obvious that the board may also be provided with depressions of a conical or other suitable form.
When the sound waves reach a wall or a ceiling having a surface of such depressions, the waves are collected towards the bottom of the funnel-shaped depressions, and for absorbing the waves, holes 5 extending from the bottom and partly or entirely through the board are bored or punched so that the waves enter the holes and pass through the side walls thereof into the porous board. Another part of the waves are reflected and split up in several directions, and these feeble sound waves are only of an inconsiderable inconvenience. When they reach the next wall they are rapidly and efiiciently deadened.
The boards may be prepared in the following way. After the boards obtained from the wallboard press are cooled sufficiently to prevent too rapid setting of the glue a board is introduced between two feed rollers and forwarded on a table, on which the fore end first passes a glue station, where the glue is applied either by spraying or by a brush or roller. In the next station the web is supplied and pressed by a freely rotating roller against the glue layer so as to be at least partly impregnated with glue and capable of being somewhat stretched. In the third station the board thus coated is introduced between the pattern roller and a counterroller, of which the former is heated to such a high temperature, such as to 200 C., and rotates with such a low speed that the binding agent is cured between the rollers sufficiently to stiffen the walls of the depressions and prevent the compressed material from expanding.
What I claim is:
A sound-reflection counteracting wallboard, comprising essentially a stiff porous fibre board formed with shallow depressions covering substantially the entire surface of one side of the board and narrowing continuously from all sides to a point in the center of the depression, a layer of a cured thermo-setting binding agent covering the surface of the board provided with the depressions for reinforcing the surfaces of the de- J; pressions and maintaining their form, and a thin covering layer glued to the entire surface provided with the depressions and of a suflicient ductility to be depressed Without breaking, said board being provided with holes extending from the lowest portion of said depressions at 5 least partly through the board.
References Cited in the file of this patent UNITED STATES PATENTS 1,781,797 Williams Nov. 18, 1930 10 Cunnington Apr. 5, 1938 Wagner Jan. 16, 1940 Davies Apr. 24, 1951 Gerard Sept. 22, 1953 FOREIGN PATENTS Great Britain Sept. 13, 1950 Germany Oct. 11, 1951