US2450911A

US2450911A - Acoustical structure

Info

Publication number: US2450911A
Authority: US
Inventors: Arthur D Park; Norman A Johnson
Original assignee: Armstrong Cork Co
Current assignee: Armstrong World Industries Inc
Priority date: 1943-07-20
Filing date: 1943-07-20
Publication date: 1948-10-12
Anticipated expiration: 1965-10-12

Description

Oct. 12, 1948. A. D. PARK ETAL ACOUSTICAL STRUCTURE Filed July 20, 1943 FIG.

FIG

FIG. 4

FIG,

Patented Oct. 12,1948

ACOUSTICAL STRUCTURE Arthur D. Park and Norman A. Johnson, Lancaster, Pa., assignors to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Application July 20, 1943, Serial No. 495,426

6 Claims.

This invention relates to acoustical structures and, more particularly, to a decorative monolithic building structure which is incombustible and possesses a high coefficient of sound absorption;

Variou acoustical structures have been proposed heretofore. For example, one type included studding secured to abase, and burlap or felt sheets disposed thereover and secured to the studding. A second type consisted of artificially perforated metal pans holding sound-absorbing material, the pans being mechanically secured by suitable means to a ceiling. These structures are satisfactory from the standpoint of acoustics; they are not satisfactory'in an esthetic sense for they are not particularly decorative or ornamental but present a crude, unfinished, incomplete appearance. Such structures have been used to some extent for their utilitarian functions but they cannot be used in any place Where it is essential that they constitute an attractive decoration.

When the first structure is in use, the burlap, being susceptible to atmospheric conditions, swells or bellies so that it sags away from the studding thus presenting an unattractive appearance and necessitating that the burlap fabric be removed and tightened, or replaced. In

addition, it is not fireproof which materially decreases the number of places in which such structure might be used. The pan type structure, while fireproof, possesses no decorative value and, in fact, detracts from the appearance of any room in which it is used. This metal pan structure, moreover, is expensive, difllcult to erect, and extremely difiicult to keep clean during use. The disadvantages pointed out above contribute towardthe lack of success of such structures even though they possess a satisfactory coefficient of sound absorption.

The chiefobject of our invention is to eliminate the disadvantages inherent in prior acoustical structures.

I An object of our invention is to provide an incombustible acoustical structure attractive appearance. Other objects of our invention will be readily perceived from thefollowing description.

' This invention relates to an acoustical structure which comprises, in combination, a base, a highly porous, inorganic. sound absorbing backing layer disposed over the base, and a decorative facing disposed over said layer, said facing being composed of inorganic material and possessing substantially no acoustical value per so while containing sufficient natural openings to permit the passage of sound waves therethrough to the sound-absorbing layer.

The attached drawing illustrates a preferred embodiment of our invention, in which Figure 1 is a plan View of the acoustical structure of our invention, the facing being partially removed to'disclose the backing layer;

Figure 2 is a sectional view of the acoustical structure shown in Figure 1;

Figure 3 is a plan view, greatly magnified, of a section of facing material;

Figure 4 is a plan view, greatly magnified, of a section of backing material; and

Figure 5 is a sectional view of a modified form of our invention.

Referring to the drawing, there is illustrated an acoustical structure including a backing layer 2 of sound-absorbing material and a decorative facing 3 0f sound-pervious material having substantially no acoustical value per se and possessing sufficient naturally formed openings to permit the passage of sound waves therethrough. A layer of any suitable adhesive 4 secures the backing 2 to a base 5 which may be the ceiling of a home, office or auditorium. The decorative facing 3 is secured to the backing 2 by means of a layer 6 of adhesive.

The backing layer 2 is composed of a plurality of blocks of rigid or semi-rigid mats of inorganic material and possesses a high coefiicient ofsound absorption. Such blocks or mat are composed of felted inorganic fibers such as felted mats are rough, irregular and uneven in contour conveyor which carries the pack through a series of automatic operations, notably, the application of a binding agent, for example a phenol-aldehyde resin, compression to desired density while heating to set the binder, cooling, if desired, while still under compression, and cutting to desired size.

In Figure 4 we have attempted to reproduce a small section, greatly magnified, of a glass wool fiber mat so produced. It will be noted the mat is composed of many enlaced and entangled small or fine fibers and that it is highly porous. These enlaced and entangled fibers are aided in their retention in mat form by the phenol-aldehyde binder discussed above. Such glass fiber are incombustible, a property of great importance in this particular application. The fiber mat so produced provides a maximum of dead air spaces which renders it of particular value in the absorption of sound. In addition, such material withstands heat, rot, dampness and decay thus assuring a. long life in service.

The facing 3 comprises an inorganic material likewise capable of resisting heat, rot, dampness and decay, and is composed of thin sheets of felted glass fibers such as the glass fiber material commonly used as a retainer mat in electrical storage batteries. We are not certain as to the manner in which this particular material is made but we believe it may be generally similarly to the glass wool mats described above. The binder used is believed to be starch; the fibers are generally of greater length than the glass wool fibers used in the manufacture of the mats and are slightly coarser than such fibers. Such fibers are commonly called bonded mat fiber and are purchased in finished sheets having a highly decorative appearance and so thin as to possess substantially no acoustical value per se.

In Figure 3 we have attempted to reproduce a small section, greatly magnified, of a bonded wool mat sheet as a ready means of comparison with the backing layer. Thus, it will be observed that the fibers forming the facing are considerably greater in length than the fibers forming the backing and are slightly greater in diameter. The sheet so formed is highly porous and presents many natural openings therethrough to permit the passage of sound waves to the sound absorbing backing. In addition, the sheet is so thin as to possess substantially no acoustical value per se while being sound pervious. The terms naturally formed openings" or natural openings are used herein to denote openings naturally occurring during the formation of the sheet facing in contradistinction to openings artificially formed in the sheet facing after manufacture thereof.

A sheet composed of bonded wool mat glass fibers is characterized by its tendency to return to its initial position or unfold when bent; this characteristic is of particular importance when the sheet is employed as a facing in the manufacture of acoustical structures. As pointed out above, the facing is generally adhesively secured to the backing. Frequently, at the corners or edges of the room in which the structure is erected, it is necessary that the facing extend for a slight distance without support; since the backing is formed of a plurality of mats of irregular and rough contour so that the joints between adjacent mats are open and uneven, in many cases, it is necessary that the facing extend thereover without support. Since this particular facing material is capable of maintaining its planar posimat fiber is applied thereover.

tion without support, it will be appreciated that a more finished and ornamental structure may be obtained.

The adhesive used to secure the sound-absorbing backing layer 2 to the base 5 may comprise a mixture of drying oil, resin and filler carried in a suitable solvent. In securing the facing 3 to the backing 2, we have found a satisfactory bond may be obtained by dissolving a polymerized isobutylene of high molecular weight in a suitable solvent such as methyl chloride, toluol, benzol, etc. It will be understood our invention is not limited to the employment of the adhesives described above for any suitable adhesives may be used to secure the backing layer to the base and the facing to the backing layer.

In the erection of the acoustical structure of our invention the mats of glass wool fiber possessing sound-absorbing characteristics are adhesively secured to the base 5. As pointed out above, these mats are rough, irregular, and uneven; consequently the joints therebetween are irregular and apparent to the casual observer. In addition, the exterior surface of the mats, when such mats are disposed in the structure, is somewhat irregular. Thus a structure so formed would be unsatisfactory in itself for, while its coeflicient of sound-absorption would be satisfactory, its appearance would be so unsatisfactory in an estheti-c sense as to prevent its use. Accordingly, it is essential that a suitable facin as described above be disposed thereover. A thin layer of adhesive is spread over the backing layer 2 and while it is still tacky the sheet 3 of bonded This sheet may be applied conveniently in the same manner, for example, as wallpaper is applied to a plastered surface. The sheet as previously described is characterized by its inherent tendency to return to original position when bent; consequently, it serves in effect to bridge over the irregularities of the backing layer and to present a substantially planar surface. It is essential in our invention that the sheet of bonded mat fiber cover more than one of the mats composing the backing, since this eliminates :a plurality of joints in the facing. Similar sheets are disposed over the backing layer and seams are formed between the sheets by overlapping adjacent sheets slightly, and cutting both sheets through at the same time. This sheet material cuts with a perfectly clean or sharp edge since cutting the glass fibers amounts to, in effect, breaking each glass fiber at the desired point. Such practice ensures a perfect fit so that the seams formed between sheets are substantially invisible to the casual observer, whereby the structure possesses a decorative appearance and forms a highly satisfactory acoustical ceiling.

The sheet material is somewhat transparent or translucent so that the backing may appear vaguely therethrough. To eliminate this disadvantage, preferably, the facing 3 is painted with any suitable fiat type interior paint. The paint coating may be applied before or after the sheet material is placed in position. It is essential of course that the paint coating be so applied to the fibers as to adhere to the fibers without bridging over the openings therebetween and we have found that an atomized sprayed coating is desirable.

The structure so formed may be characterized as monolithic. It is incombustible and hence may be used in many places where materials of equivalent coefiicient of sound absorption may not be used. In addition, it provides a ready and easily erected ornamentation for an auditorium, office, or room, as well as providing the usual advantages of a sound-absorbing structure.

In Figure 5, we have disclosed a modified form of our invention in which a mechanical erection ,system is used to secure the sound-absorbing backing layer to the base. In this structure T bars 1 may be provided which are secured by means of wire 8 to the base 5. The sound-absorbing mats 2 of glass wool fiber are provided with openings or recesses in their edges adapted to receive an arm of bar 1. To erect the structure, the mats are supported by the'bars I, the openings in each mat receiving arms of bars I so that each mat is supported between adjacent bars 1 and rests on the arms thereof. The facing 3 composed of thin sheets of bonded mat fiber is formed over the backing layer 2 in the manner described above.

It will be observed our invention possesses numerous advantages. The materials composing the structure are incombustible so that the structure may be erected even in restricted zones. It is attractive in appearance and considerably improves the decorative value of the ceiling on which it is erected. Many attempts have been made with little or no success by manufacturers of acoustical structures to eliminate the undesirable appearance of the joints; our invention provides a structure in which the joints are practically invisible to the casual observer. The structure is quickly and easily formed and unskilled labor may be used in its manufacture. Our invention fulfills a pressing demand by architects and decorators for a, simple, plain, easily erected, incombustible, highly sound-absorbing structure Which may be used in restricted zones.

While we have described and illustrated a preferred embodiment of our invention, it will be understood our invention is not limited thereto, since it may be otherwise embodied within the scope of the following claims.

We claim:

1. In a sound absorbing structure for walls and other surfaces, a base, a plurality of mats of highly porous, sound absorbing, inorganic fibrous material disposed over the base and presenting a rough and irregular outer surface, and a decorative facing in sheet form disposed over a plurality of said mats and adhesively joined to said mats and presenting a substantially planar exposed surface bridging over the irregular surface contour and joints between said mats, said facing comprising a thin, open, preformed, self- 6 sustaining web of felted glass fibers characterized by an inherent tendency to return to its original position when bent and released, which characteristic results in the facing web lying fiat and planar regardless of the irregularities in the sound absorbing mats to which the web is attached.

2. The combination of claim 1 in which the mats are formed of felted glass fibers.

3. The combination of claim 1 in which the mats are formed of felted glass fibers and the facing web is formed of glass fibers of a length greater than the length of the fibers in the mats.

4. The combination of claim 1 in which the mats are secured to the base by an adhesive.

5. The combination of claim 1 in which the mats are formed of felted glass fibers and in which the mats are secured to the base by means of an adhesive.

6. The combination of claim 1 in which T bars are suspended from the base and in which the mats are supported by said T bars.

ARTHUR D. PARK.

NORMAN A. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 612,733 Kelly Oct. 18, 1898 880,784 Ferres Mar. 3, 1908 1,442,328 De Long Jan. 16, 1923 1,832,571 Nash Nov. 17, 1931 1,869,367 Dean Aug. 2, 1932 1,880,153 Rosenzweig Sept. 27, 1932 1,910,810 Nash May 23, 1933 2,030,157 Schlenker Feb. 11, 1936 2,077,713 Ross et a1 Aug. 2, 1932 2,160,001 Saborsky May 30, 1939 2,160,638 Bedell et a1 May 30, 1939 2,175,226 Slayter Oct. 10, 1939 2,234,560 Keyes Mar. 11, 1941 2,355,608 Stieger Aug. 15, 1944 FOREIGN PATENTS Number Country Date 4,914 Great Britain Feb. 27, 1911 128,132 Austria "May 10, 1932 442,251 Great Britain Feb. 5, 1936 482,809 Great Britain Apr. 5, 1938 OTHER REFERENCES The Architectural Forum, page 116, Nov. 1942.