US 3206346 A
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Sept. 14, 1965 E. NUORIVAARA METHOD OF TREATMENT OF POROUS WALLBOARD Filed March 21, 1961 United States Patent O 3,206,346 METHOD OF TREATMENT OF POROUS WALL-BOARD Ensio Nuorivaara, Kuopio, Finland Filed Mar. 21, 1961, Ser. No. "97,290 Claims priority, application Finland, Nov. 19, 1960,
1,913/ 60 p v Claims. '(Cl. 156209) This invention refers to a method of reducing the dimensional changes taking place in the plane of porous wallboard due to moisture variation and the stresses resulting therefrom.
It is known, that an undesirable property of porous wallboard is the dimensional variation thereof caused by variations of moisture. The moisture in the board is somewhat greater during storage than when the board is fixed to the base surface underneath. If the board is glued to a rigid base, such "as a concrete wall, a .plastered surface or the like and the moisture in the same varies slightly there will be formed in the board stresses that are so great that the base surface, the glue or the board itself will give way, with the result that the board comes loose from its support.
In order to prevent the board from loosening from a rigid, solid foundation, the fastening of the board is often carried by nailing the same to a wooden frame assembly which is secured to the base. The boards fixed in this manner are able to move sufliciently where the nail holes are situated to compensate for dimensional variation. This manner of fastening, however has several disadvantages. In the first place the method becomes rather expensive due to the necessary construction of a wooden frame, secondly it reduces the area of the room and thirdly there is left a large space between the board and the foundation underneath, which from the danger of fire makes the house unsafe.
In order to overcome the above drawbacks there has been suggested the use of an intermediate flexible element which will permit the dimensional changes in the board. Such intermediate flexible element may be a flexible plastic glue which secures the board to the base. Such methods of fastening are expensive however and between the board and the base there is also left an air space.
There has been additionally suggested the use of a panelling slab which by means of grooves can be made to yield in such a degree that the slab is allowed freely to breathe during the different stages of moisture, in which case there would not be any stresses in the slab. This method seems to be the best of the known methods, but even this has the disadvantage that it requires a great deal of glue and the forming of the grooves is rather difficult.
The present invention has as its principal object to provide wallboard of the above stated kind which is free from all the above stated disadvantages. A characteristic feature of the invention is that the board is suitably compressed momentarily to a thickness less than half of its original thickness, such that its internal strucure is altered.
A board treated according to this invention can without further treatment be fastened to a base surface by means of gluing. Hereafter the board has insufficient strength to tear itself free from its base, because the internal structure of the board has been changed such that the fibers are no longer interconnected as effectively as before and will give way to a certain extent.
According to one very advantageous embodiment of the invention the board is pressed for an instant to a thickness equal to less than half of the original thickness.
3,206,346 Patented Sept. 14, 1965 ice After being treated in the above manner the changes in the dimension of the board owing to moisture variation will be only /3 of that of the original board and the internal strength will be only of the strength of the original board.
The invention is further illustrated by thespeci'fication and the drawing showing an embodiment which 'is most adaptable in the practice, in which drawing FIG. 1 shows .a pressing :operation in the treatment of a board,
FIG. 2 shows the surface ofa treated board, and
FIG. 3 shows a section taken .along line JII"IIII in FIG. 2.
In the drawing the numeral 1 designates an ordinary porous wallboard whichis fed along by the top roller 2 and the bottom roller 3 in a direction shown by the arrow 4. Simultaneously these rollers press the board just for an "instant so that the thickness of the :board becomes less than half of the original thickness. The pressing period is short so that the change in the form of the board 1 is not permanent and the board will attain its original thickness.
The surface of the top roller 2 is provided with elevations or teeth 5, between which there is formed excavations 6. These teeth and excavations constitute an effective means whereby the inner structure of the board 1 can be changed while simultaneously the surface of the board is made decorative in order to meet the demands for internal panelling of a room. FIGURES 2 and 3 illustrate an embodiment in the arrangement of the elevations and excavations formed on the surface of the board 1.
In the event the porous wallboard is intended to be used for inside panelling, it is appropriate to cover one or both of its sides with a layer of material such as paper, cloth, metal or the like. The fastening of such layer to the board can most suitably be performed simultaneously with the pressing operation. For this purpose the surface of the board is covered with a layer or film of glue, and on top of this adhesive layer the said covering layer is placed before the board is fed between between the rollers 2 and 3. In order to expedite the binding properties in the glue it is advisable to heat one or both of the rollers. The heating of the rollers will also harden the elevations and excavations.
The layer on the surface of the board also provides additional stiffness to the board and improves its external appearance. Furthermore the layer prevents moisture from entering into the board. Especially when a metal outer layer is used, such as aluminum, is the moisture totally prevented from penetrating into the board.
The above is intended only to illustrate the inventive idea of the invention. The different embodiments adaptable in practical use may thus vary while remaining within the limits of the following claims. This refers especially to how thin the board has to be pressed during the treatment, and this again depends on how great the moisture changes are that the board has to withstand at the place where it is to be used.
Also the number of rollers may vary. In certain cases it is preferable to perform the pressing of the board between several successive pairs of rollers, between which the board is pressed gradually with increased pressure.
What is claimed is:
1. A method of treating a porous compressible fibre board of determinable thickness to provide dimensional stability thereof under moisture variation, said method comprising deforming the internal structure of the board by momentarily and temporarily compressing the board to a thickness which is less than half the original thickness of the board and allowing the board to resiliently 3 assume its original thickness immediately after the cornpressing of the board;
2. A method of treating a porous fibre board of determinable thickness, said method comprising deforming the internal structure of the board by advancing said board between a pair of rollers which are spaced apart a distance which is less than one half the thickness of the board whereby said board is momentarily and temporarily compressed to a thickness less than one half the original thickness of the board as the board passes between the rollers, and allowing said board to assume substantially its original thickness after it passes through said rollers, the deforming of the internal structure of the board under the compression of the rollers and the subsequent assumption of its original thickness conferring on said fibre board dimensional stability when exposed to varying humidity conditions.
3. A method as claimed in claim 2 wherein one of said rollers is provided with teeth to locally intensify the compression of said board.
4. A method as claimed in claim 2 comprising adherently fixing a covering layer on at least one of the surfaces of said board prior to the advancement through said rollers so that the layer is simultaneously compressed with the board.
5. A method as claimed in claim 4 comprising heating said rollers to provide an elevated temperature thereof.
References Cited by the Examiner UNITED STATES PATENTS 2,136,730 11/38 Sweetland 156-580 2,477,300 7/49 Karfiol et al.
2,537,126 1/51 Francis 15447 2,600,843 6/52 Bush.
2,694,026 11/54 Johnson 161-165 2,711,380 6/55 Pintell.
2,859,489 11/58 Morrison 161156 2,954,838 10/60 Nuorivaara 11711 FOREIGN PATENTS 821,537 10/59 Great Britain.
EARL M. BERGERT, Primary Examiner.
CARL F. KRAFFT, Examiner.