US2326763A - Acoustic material - Google Patents

Description

Aug. 17, l943.` D. D. QRANDELL l 2,325,763

ACOUSTIC MATERIAL Filed June 28, 1939 SOUND ABSORB/NG BCOY /L /MPER V/OUS COA TNG u o o o o o o o a u u o u o o o o n u o a D n n n o o o u o a o e e v o o o a a u u u u o DEcoRAT/VE n o a u n u n o COA TNG o o n o n n n o n o u a n o o c n o o o Q c o o o INV'ENTOR ATTORNEYS Patented Aug. 17, 1943 ACOUSTIC MATERIAL Dean D. Crandell, Buffalo, N. Y., assignor to National Gypsum Company, Buialo, N. Y.

Application June 2-8, 1939, Serial No. 281,663

1 Claim. (Cl. 15de-44) This invention relates to an acoustical material.

Various materials and compositions of materials have heretofore been proposed for the production of sound proof or sound absorbent walls for building construction and the like. While various objections have arisen to hitherto known constructions, a prime difiiculty has been the problem of decoration since it has either been impossible to paint or otherwise decorate or redecorate the surface of the material after erection of the building, or such painting or decoration could be accomplished only to the impairment or utter destruction of the sound absorbing or sound proofing qualities ofthe structure.

The present invention produces and provides an acoustic material, generally in the form of a slab-like wall element, the exposed surface of which may be painted, either by brushing or spraying, not only immediately after completion of the wall construction, but subsequently, as often as desired, without in any way destroying or reducing the original acoustical qualities of the wall.

This result is lachieved by providing as a base or body for the acoustical element a block or slab of a highly sound absorbent material. In the form of the invention which is disclosed herein as being illustrative of the principles thereof I employ a self-sustaining slab of relatively low density fiber board, the same being conventionally formed from wood pulp or other cellulosic fibrous material.

To this base I apply, either by spraying or brushing or in any convenient manner, a coating prepared by mixing an adhesive, usually` an organic glutinous or starchy material with whiting or other pulverant chalky substance with sufcient liquid to form a slurry. After application the coating is permitted to harden and dry thoroughly whereuponthe coating is perforated by the formation of relatively shallow holes in the coated surface of the element, usually by simultaneously piercing the'coating at a number of points. Such piercing of the coating is found to permit sound waves to have access to the exposed sound deadening or absorbing material to a sufficient extent to absorb approximately the same per cent of sound as the same sound absorbing material absorbs when not provided with the finish taught by my present invention.

In the accompanying drawing:

Fig. 1 is a front or face view of an element adapted to be used as an exposed wall element and constructed in accordance with. the principles of my invention, tne several areas of the element being shown to indicate diagrammatically the several steps or operations which comprise my new method of producing an acoustic wall element;

Fig. 2 is a similar vie'w showing the finished element fragmentarily and on an enlarged scale with respect to Fig. 1; and,

Fig. 3 is a fragmentary cross sectional view, on a still further enlarged scale, showing the relatively impervious ,coating and the perforations therethrough.

In Fig. 1 of the drawing the four zones displayed indicate, reading fromtop to bottom, four conditions of the building element occurring serially during the production of the element. The top zone represents the initial untreated block or slab of fibrous material having a high degree of sound and liquid absorption. The next zone represents the block after it has been coated with the relatively impervious coating referred to heretofore. The third zone shows the block after perforations have been formed through the 'coating and in fact shows the completed building element, ready to be incorporated in a building Wall and subsequently decorated in any conventional manner Without having its eiciency as a sound absorbing elementl affected in any way. The fourth zone shows the block as it appears after it has been incorporated in a wall construction and decorated as indicated.

The body of sound absorbing material is designated at l0 in the drawing and in its preferred form comprises what is known in the building art as low density fiber board. This board is conventionally formed by subjecting wet wood pulp or other cellulose fiber pulp to pressure, usually at elevated temperatures. The slabs so .formed are of low density but are sufficiently compact to be self-sustaining and sufiiciently strong and rigid as to be conveniently handled without liability of breakage or disintegration.

Another property of low density ber board is its very high sound absorption. 'I'his quality makes its use as an acoustic material highly advantageous but in the past a marked objection to its use has resided in the fact that it is next to impossible to coat the material because of its very strong tendency to absorb liquids. Again, even if suiiicient paint or the like were applied to form a coating, or if a sufficiently thick material were applied with like result, the board would then lose its sound absorbing quality.

In pursuing my invention I so treat the body of sound insulating material as to not destroy 4its sound absorbing-'ability while making it possible lto apply conventional wall finishes such as paint andthe like to its surface. In proceeding to accomplish thisaim I prepare a slurry or dispersion which in the preferred form comprises an. adhesive orA bindingmaterial which may be starch, casein, soybean flour,v glue, or other material having the indicated properties together with an inorganic ller such as Whiting, precipitated chalk, marl, light-weight; gypsum, .or the like.

\ As specific examples, I may employ an aqueous dispersion which in the dry state comprises soya bean protein' and 90% ller or a dispersion of 50% starch and 50% whiting. i A coating of the dispersion so formed may readily be sprayed or brushed upon a surface of the sound absorbing body and is found to form a layer which is sufficiently impermeable to the vehicles used in conventional paints, of both -the oil and water variety, as to' satisfactorily meet the requirements of the present invention. In the drawing the coating is designated l I.

After the coating has thoroughly dried, I form perforations therethrough. Such perforations are desired to be wholly through the coating but l extend as little as is practically possible into the body of the sound absorbing material itself. As to size, a prime requisite is that the opening so formed be of sufcient diameter or distance across as not to be closed or bridged over by a subsequent painting operation when such paint is applied either by spraying or brushing. It is found that openings approximately alf in diameter give results quite satisfactory from this standpoint.

In the illustrated example, the openings designated at i2 in the drawing are uniformly distributed over the coated surface of the board and in such example I have shown the openings so spaced that they occur approximately seven to the square inch.

The lower zone of Fig. 1 represents the block or board I0 after it has been incorporated in a wall structure andprovided with one or more surface coatings of paint as at I3.

the art of sound deadening and sound insulation particularly. Y

While specific examples ofthe general principle involved in this invention have been referrea to herein, it is tobe understood that a full range of equivalents is in contemplation and that such modifications as appear to those skilled in the art jmay be made without departing from the spirit and scope of my invention as dened in the appended claim I claim:

An acoustic construction comprising a body of low density, compacted, cellulosic fibrous material having a surface thereof coated with a material relatively impervious topaint vehicles and comprising a dispersion of protein and an inorganic ller, said coating being friable by nature and provided with a plurality of perforations whereby the underlying brousmaterial *is par- -without closing or filling said openings and being of a total depth only slightly greater than the thickness of said coating.

=DEAN D. CRANDELL.

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