US 2668123 A
Description (OCR text may contain errors)
Feb. 2, 1954 R P, copi-:LAND 2,668,123.
METHOD OF PRDUCING ACOUSTICAL TILE Filed sept. 25. 194s Patented Feb. 2, 1954 UNITED STATES i ATENT OFFICE METHOD 0F PRODUCING ACOUSTICAL TILE Application September Z5, 1948, Serial No. 51,273
My invention relates to acoustical tiles or panels formed of Fiberglas or other mineral fibers, or other suitable material such as gypsum plaster or the like, in which there is continuous intercommunication' for the passage of sound in all directions from any part of the structure to the adjacent parts, in contrast with a tile made of organic bers such as Wood or bagasse in which there are no such inter-communication passage- Ways for the sound in all directions for facilitating the dissipation of sound into the body of the tile.
A Fiberglas tile of the thickness of 3A inch and weighing about 300 grams per square foot, with its face plain, unperforated, and'unpainted, is highly eiiective with respect to the absorption of sound. When the face of such a tile has been given two or three or four layers or coats of paint sprayed on evenly, the coefficient of sound absorption is very slightly increased with each additional coat of paint added. With the application of additional coats of paint sprayed on after the fourth coat, the coemcient of absorption may be decreased slightly with each additional coat added, but a total of at least nine or ten such coats can be applied before the coenicient is lowered to a point correspondingto the coefcient of the unpainted tile.
Ordinarily a tile is given two coats of paint sprayed on in the course of the manufacture of the tile for the market. In connection with such a tile, it has been found that a single coat of paint brushed on after the second spray coat causes a radical decrease in the coefficient oi sound absorption of the tile, unless the tile has rst had its face perforated so as to provide a great number of openings at spaced intervals in the face of the tile. When a suitable number of such openings are provided by the removal of the body material by a drilling operation or by the use of a hollow punch which takes out a core of the material upon the withdrawal of the punch, such perforating or punching ordinarily is accompanied by a substantial decrease in the coeilicient of sound absorption, In the ease of a 3A" thick Fiberglas tile weighing about 5%; of a pound per square foot, this decrease amounts to almost 8%, signied by a drop of the eoelncient from about 65 to 60. ln spite of this loss in the sound absorption coei'licient of the panel by reason of the formation of the openings by the removal oi body material, the art has used such expedient very extensively, since it is found that as a result of such perforating operation a coat of paint, or aV series of coats of paint in succession, can be brushed on the face of the tile after such per- 4 Claims. (Cl. 117-11) forating operation without any further decrease in the coeicient of sound absorption, so long as the openings or perforations are kept effectively open.
It is the object of my invention to provide a new and improved form and arrangement of tile and the openings therein whereby the best possible results may be obtained both with respect to the original effectiveness and with respect to the possibility of maintaining a high degree of sound absorptiveness.
I have found that small and shallow perforations or openings, that is perforations or openings having a diameter in the range from e to Tse of an inch and a depth of from 1A; to d; of an inch, in the face of a tile having a homogeneous structure throughout its thickness, such as a Fiberglas tile or a gypsum Iplaster tile of light weight, are much more effective for producing sound absorption than are larger and deeper perforations, Wherefore it is highly desirable that such openings be kept to a minimum size and depth effective for sound absorption purposes, while at the same time being of such size as to make it possible readily to keep the perforations open.
I have found that for the practice of my invention superior results are obtained by the use of a solid punch for forming shallow openings so as to compress the material of the tile somewhat at the bottom faces of the openings without the removal of any core or plug of the material. By providing the perforations by means of a punching operation without removing any of the body material, the mass of the material is kept to a maximum for obtaining the highest degree of sound absorption possible, and at the same time the face portion of the material at the bottom face of the opening is compressed so as to provide increased density for further enhancing the sound absorption eect.
I have found also that highly satisfactory re suits are obtained by the provision of openings by such compression method in rows and cross rows at about half inch intervals over the face of the tile, with such openings of a diameter of substantially .165 of an inch and substantially a quarter of an inch (.25) in depth. I have found that in the use of a tile o1" such arrangement the original effectiveness for sound absorption is very high, and that the tile can be cleaned and redecorated from time to time by the application of coats ci paint brushed on without seriously interfering with the effectiveness of the tile for sound absorption.
It is another object of my invention to improve tiles and processes of this type in sundry details hereinafter pointed out. The preferred form of my improved tile is illustrated in the accompanying drawing in which:
Fig. 1 is a face View of a fragmentary portion of a tile embodying a preferred forni of my improvements.
Fig. 2 is a vertical sectional View taken substantially at the line 2 2 of Fig. l.
Fig. 3 is an enlarged detail view of a fragmentary portion of a tile showing one of the openings in the face of the tile.
Fig. 4 is a view similar to Fig. 3 but showing in position in the opening the punch by which such opening was formed; and
Fig. 5 is a face View of a fragmentary portion of a completed tile ready for application to a Wall.
Referring now to the several figures of the drawing, in which corresponding parts are in dicated by the saine reference characters, in dicates a Fiberglas tile in the forni of a square block. or panel approximately one square foot in areaapproximately threehuarters of an inch thick, and weighing about three-duarters ci pound, being formed o'f glass libere suitably scoured together by means of a resin adhesive or otherwise with sufficient tenacity for enabling the block to hold its shape while being handled for installation and for holding its position peiI` manently in a Wall. A series of such blocks are designed to be secured on the face or" a ceiling or other -vali as is usual with sound absorption panels, being secured'in position preferably by the use of a suitable cement.
In the operation of producing my blocks or panels, the panel is iirst formed the desired shape and size with the glass fibers their normal color condition as produced. Forforations or openings i i are produced in the of the panel by pressing a punch 52. or a set oi such punches if desired, into the face or" the panel so as to compress the material of the panel ahead oi the punch and thus provide an opening or perforation the transverse face of which at the bottom of the opening is substantially more compact and dense than the portions of the block surrounding the opening'. This is indicated di agrarninatically in the drawing by horizontal score lines below the openings.A The pressure of the punch into the face of the material serves to break the cross positioned fibers, leaving the side face portions of the openings of substantially the saine density as before the punching.
The openings Ii are preferably produced in roi/vs and cross rows at about half inch intervals, and preferably extend into the material of the panel substantially a quarter of an inch. None of the material oi the panel is removed by the formation of the openings by the punch or punches I2. The openings as illustrated are oi a diameter of about .165 of an inch and of a depth of substantially a quarter of an inch as above specified, and the tile with such periorations or openings at half inch intervals has proven highly eiective and highly desirable from every standpoint.
The punch l2 is preferably solid at its operative face but it may be of any form suitable for insurl ing that the fibers shall be pushed ahead for substantially compressing the bers at the bottom face ofthe opening, and insuring that the .punch may be removed without the removal of a plug or core of such bers from the opening.
The openings Il may be formed in the face of the panel without the application oi any coat of paint to the panel before the punching operation, as shown in Fig. l. In the preparation of my improved panel by the preferred method, however, I first apply a coat of paint sprayed or otherwise suitably applied in the forni of a thin even lm on the face to be punched. The openings or perforations l! are then produced, after which the panel preferably is given a second coat of paint sprayed on the punched face of the panel. A coat of paint may then be brushed on, either before or after the panel has been applied to a wall. Such a panel is shown in 5, having a brushed on coat of paint i3 covering the face of the panel. With the panel provided initially with a thin even coat of paint before the perforating operation, the punch is able to provide a cleanout round opening i i with very little or no roughness of the contour of the opening.
I have found that when openings of. substantially 1/5 of an inch diameter substantially' 1/21 of an inch in depth are produc l at hal.. incl intervals in the face of a Fiberglas panel by my improved method as above described i hout the removal of a core, such punching operation is effected without any decrease the coefficient of sound absorption, in contrast with the decrease in the coeiicient when the cores are removed `iroin the openings. I have .found also that when such panel has been ,hunched as specified and is then given a coat of paint brushed on, either' with or Without an intermediate coat of paint sprayed on after the punching operation, such coat oi paint brushed on actually increases the coefficient of sound absorption, rather than substantially decreasing it as would be expected in thc light of Well-established data with respect to the application of paint brushed on Without the preliminary punching. I have found, moreover, that the application of additional costs of paint brushed on the iacc of such panel after the application of the initial brushed on coat does not decrease the coefficient of sound absorption to any substantial extent, it being possible to apply at least eight or ten coats of paint brushed on under these conditions Without any substantial decrease in the coefficient oi sound absorption, and possible to apply ad ',onal coats of paint brushed on after such ii st eight or ten coats Without any marked or ab .upt decrease in the coelicient of sound absorption, so long as the openings remain open Without being closed by the paint.
By the use of my improved me hod of producing sound absorption tiles or panels, by which the openings in the face of the tile are formed by a solid punch without the removal of any cere or plug of the material oi the tile, I provided tiles which are radically inproved over the prior art tiles in that they are highly effective in use and are capable of being redecorated inany times by the redecoration methods ordinarily in vogue Without deterioration in the action oi the tiles for sound absorption purposes. 'lhis is in marked contrast with the results attainable by the use of the prior art products, and my invention is to be judged as or great importance accordingly. l consider it also of substantial importance that l ain able to eiiect the perforation operation Without any decrease in the coeflicient of soun-:l absorption in contrast with the usual decrease as expected :in connection with other methods.
It is also important in connection with niy invention that the initial coat of paint be ap'- plied on the face of the panel before the punching operation, since in that way comparatively high reflectivity is obtained in spite of the provision of the openings. This high reflectivity is in many cases of substantial importance, from the standpoint of room lighting.
The following table is presented for showing sound absorption coeicients and noise reduction coeicients for Fiberglas panels of similar form but differing from each other as to the DIO- vision of perforations and as to the paint treatment of the panels, with data in each instance for tests in connection with sounds of different frequencies.
Sound Absorption Coeflicients for different Noise frequencies Reduction Coefs 250 500 1,000 2,000
Panels without perforations:
Paintedlspray coat .102 .409 .776 .857 .552 Three brush coats added... .229 .283 .274 .200 .269 Panels with perforations half inch centers, ye deep and .195 diam., with plugs removed:
Painted 1 spray coat .147 .320 .664 .868 .500 Three brush coats addedl .147 .36S .925 .842 .570 Panelswithperforationshalfmch centers, Ae deep and .195' diam., with no plugs removed:
Paintedlspray coat 159 .399 .785 .856 .550 Three brush coats added.-. .171 .479 .883 .836
This table shows the results of tests on Fiberglas panels of an inch thick, weighing about of a pound per square foot.
While I prefer to employ the form of tile as above described and produced by the novel methods specified, my invention is not to be limited to such form and such method except so far as the same may be specifically claimed, it being understood that changes might well be made in the form or the method without departing from my invention.
1. The method of treating lightweight sound absorptive panels formed of mineral fibers which comprises spraying a coat of paint on one face of such a panel, then providing openings at spaced intervals in the face of the panel of a diameter of from 5 of an inch to 1% of an inch and of a depth of from 1A; to 1%; of an inch by pressing punch means into the face of the panel and thus pushing the material of the panel ahead of the punch means so as to compress the Inaterial of the panel at the bottom face portions of the openings being formed, and then applying a second coat of paint on the face of the panel about the openings.
2. The method of treating lightweight soundabsorptive panels formed of mineral bers as set forth in claim 1 in which the openings in the face of the panel have a diameter of substantially .165 of an inch and a depth of substantially .25 of an inch.
3. The method of treating lightweight soundabsorptive panels formed of mineral fibers which comprises spraying a coat of paint on one face of such a panel, then providing openings at spaced intervals in the face of the panel of a diameter of from 1% of an inch to 1% of an inch and of a depth of from 1A; to 1%; of an inch by pressing punch means into the face of the panel and thus pushing the material of the panel ahead of the punch means so as to compress the material of the panel at the bottom face portions of the openings being formed, and then brushing a second coat of paint on the face of the panel about the openings.
4. The method of treating lightweight soundabsorptive panels formed of mineral bers as set -592 forth in claim 3 in which the openings in the face of the panel have a diameter of substantially .165 of an inch and a depth of substantially .25 of an inch.
RANDOLPH P. COPELAND.