Lightweight unit

June 16, 1936.

2,043,988

G. B. BROWN

LIGHTWEIGHT UNIT

Filed Feb. 28, 1933

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Patented June 16, 1936

2,043,988

Claims.

„eT?^iS?ⁿ,^{VentiOn reIates} to a lightweight unit, particularly a preformed acoustical unit, ^{15 a}? ^{object of the} invention to provide an £t^{Ut effective}> lightweight sound-absorbing or thermal insulating unit comprising f£^Pt£^{al and edge} Portions coacting to increase ^{and rlgidity while} Preserving the X®.^{aU 10W denslty}’ adaptability, and other desirabie properties _Of the unit, including the appearance thereof, other objects and advantages will appear as the description of the invention progresses.

Briefly stated, the preferred embodiment of the invention, comprises an acoustical unit including a central or body portion of spaced sheets, that are per se relatively ineffective in sound-absorption ami that define between them a labyrinth ^communicating spaces, and ^d/^{dg0 Sealing and} reenforcing elements adhered to the central portion, the said edge and central portions being constructed preferably of the same materials, whereby they are adapted to react identically under changing conditions of environment. The invention comprises, also a 25 unit of the type described in which the edge sealing elements and also an element applied to the back thereof are sound-impermeable and adapt&lt; , ““imize the passage of sound and the circulation of air through the edges and back «ο of the unit. Further, the invention comprises an acoustical element including sound-absorbing spaces and parallel, closely spaced, narrow slits eonnectm^g the said spaces with each other and with an exterior surface of the element.

which·^{lnventlon 18 ffl}ustrated in the drawing in

Fig. 1 shows a plan view of a preferred type oi acoustical unit, which is in part broken down to show the inner structure of the unit⁴⁰ , ' ^{2shows an ed}ge view of the unit illustrated

2n Fig. 1;

Fig. 3 shows a cross sectional view on line 3__3

Of Fig. 1;

Fig. 4 shows a plan view, in part broken away of a modified form of central portion or soundabsorbing. element; and

Fig. 5 is a cross sectional view on line S__5 of

Fig. 4.

In the various figures like reference characters denote like parts.

^{S prefomed} lightweight ; unit, particularly adapted for the absorption of sound comprising a sound-absorbing element · constituting tne central portion j, and edge sealing and reenforcing strips or elements 2, i_n10

UNITED STATES PATENT OFFICE

2,043,988 lightweight unit a corporation of New York Application February 28, 1933, Serial No. 658,937 (Cl. 154—44) , tegrally united, as by sodium silicate adhesive to the said central portion. The unit is provided with a sound-permeable outer sheet 3, which is really a part of the sound-absorbing structure, ^L^may referred to, for convenience, 5 as the facing element. Also, the unit is provided, at its back, with an outer backing sheet 4 that is preferably sound-impermeable

The central or body portion I comprises, suitabiy composited sheets that are in themselves 10 relatively ineffective in sound-absorption but define sound-absorbing spaces or passages 5. The composite includes sheets 6 of irregular surface alternated with sheets 7 of plane surface. The sheets of irregular surface may be corrugated 15 and arranged in the assembly with the corrugations in one sheet extending at an angle say crosswise, to the corrugations in adjacent sheets. The composited alternating sheets of plane and ^{ar sur}„^{face are} provided with perforations 20 r openings 8, spaced sufficiently closely to admit, incident sound and providing lateral communication between the spaces defined between the sheets., The perforations in adjacent sheets of the same type of surface may be non-register- 05 ™^s Predion, together with the crossing 01 the corrugations in adjacent corrugated sheets, provides for maximum discontinuity of communication between the spaces, and causes sound within the unit to undergo numerous de- 30 flections m paths that may be of great length as compared to the wave length of the sound itself.

In the modification shown in Figs. 4 and 5 the openings adapted to admit incident sound* are 35 long slits, say saw kerfs 9. In the individual layers, consisting each of a sheet of plane surface and a corrugated sheet adhered thereto, the saw kerfs extend through the sheet of plane surface, to divide it into a plurality of narrow 40 parallel bands, and extend also through the tops of the corrugations on one side of the several corrugated sheets, to cause the numerous spaces deflned by the troughs in the corrugated sheet and the plane sheet to communicate with each 45 other.

JThe central portions are relatively compressible and non-rigid and have inadequate strength for many purposes. Furthermore, the edges thereof, if the central portion were used alone 50 as an acoustical unit, would present a more or less uneven 01· ragged appearance and would provide no firm, strong area for nailing or similarly securing to a supporting substructure These disadvantages are overcome by the edge 55

2,043,988 are then passed over a pin roll, while being pressed thereagainst, and thus provided with perforations closely spaced and adapted to admit incident sound. For example, the sheets may be pressed against a roller carrying closely spaced 5 piercing pins, say % inch apart. Preferably the sheet of plane surface is nearest to the roller during the perforating operation, so that the pins pierce holes completely through the plane sheet and partly through the adjacent corrugated 10 sheet, particularly through the elevated portions of the corrugated sheet adjacent to the plane

If the central unit is to be of the type illustrated in Figs. 4 and 5, one-ply sheets of the type de- 15 scribed, but not perforated, are passed -under a gang of closely spaced rotating saws, as, for example, saws adapted to cut kerfs 3½ inch wide and % inch apart. The composite is passed through with the sheet of plane surface turned 20 towards the saws, and the spacing on the sheets with respect to the saws is such that the saw kerfs extend through the plane sheet and divide it into a series of narrow parallel bands but extend only sufficiently far into the corrugated 2j sheet to saw through the tops of the corrugations adjacent to the plane sheet.

One-ply composite sheets, provided with the sound-permeable openings as described above, are then assembled and adhered together, into a cen- 30 tral or body portion of desired thickness, say 1 inch. The adhering is effected by means of adhesive, of type described, applied over the high spots of the corrugations in the several composites of one-ply thickness. ^3j

A central or body portion so made is then united to the edge elements 2. These elements are provided in proper length and with tongues or grooves at their ends. The edges of the central portion are first heavily coated with an aque- 40 ous solution of sodium silicate or the like. The edge elements 2 are then oriented properly and forced against the silicated edges of the central portion, to give a firm bond therewith and also to cause the ends of the said edge elements to 4o be joined with each other, as illustrated in the figures. This may be done by hand or by a device commonly known as a “bulldozer”. During this, uniting of the edges to the central portion, distortion of the relatively weak central portion is 50 avoided by rigid plates disposed both above and below the central portion and maintained in position, to prevent bulging of the central portion during the pressing of the strips against the edges thereof. ,

The central portion with the adhered edges is then provided with the backing and facing sheets. As stated, the backing sheet is suitably imperforate asbestos paper of plane surface and the facing element is a sheet having the appearance of a modified basket weave, with slits in the areas intermediate the elevated and depressed portions. The facing element may be yieldable and is made in any convenient manner, as by providing a sheet of asbestos paper with discontinuous, staggered, ^Jparallel slits and then elevating areas between certain of the slits and depressing the adjacent areas. This may be done by passage of the sheet between coacting rollers, having on their surfaces meshing elevations and depressions and means &lt;0 for cutting slits in the areas intermediate the said elevations and depressions.

When the facing and backing sheets have been provided, they may be applied by hand to the appropriate surfaces of the partially formed unit ³ portions 2. These portions are rigid, preferably impermeable to sound, and integrally united to the central portion on the edges thereof. The edge portions establish the thickness of the unit, 6 strengthen it, prevent the passage of sound and the circulation of air through the edges of the unit, and provide desirable nailing strips, by means of which the unit may be attached to a suitable support.

The preferred material of construction is porous felted fibers of the type of asbestos. Thus, the central portion may be composed largely of asbestos paper. Such paper contains usually a small proportion of a binder, such as starch, and 15 of cellulosic fibers such as newsprint, say in the proportion of 20 parts by weight of the newsprint to 80 parts of asbestos. The asbestos paper may be thin, weighing, for example, 5 pounds per hundred square feet of the paper. The paper 20 may be provided with irregularities of surface, such as corrugations or indentations, in conventional manner.

The sheets comprising the backing and also the facing element may be constructed of the 25 same material as the paper described. These outer sheets, however, are conveniently made somewhat thicker than the sheets within the central portion, say twice as thick, in order to assist in maintaining the dimensions of the finished 30 unit. The facing element of type described is sufficiently stiff and strong to be shape-retaining, yet is substantially non-vibratile under the influence of incident sound.

The edge sealing and reenforcing elements also 35 are made preferably of the same materials as the central portion, in order that the central portion and the edge sealing members may show the same behavior under changing conditions, such as uniform expansion and contraction with changes in 40 atmospheric humidity. The edge sealing strips may consist of asbestos fibers in the form of millboard. For a unit that is 16 inches square by 1 inch thick, the edge sealing strips may be 1 inch wide from front to back and y₂ inch thick. They 45 are suitably joined, at their ends, as in the tongue and groove joint illustrated at 10.

The facing element 3 may consist of sheet material of irregular surface, including imperforate, that is, sound-impermeable elevated portions I i 50 and portions 12 that are depressed with respect to the elevated portions and that contain openins adapted to admit incident sound. In the form illustrated, the facing element has the appearance of a modified basket weave structure, 55 with the cross strips omitted, and is provided with slits 13, in the areas intermediate the tops of the elevated portions and the bottoms of the depressed portions.

In making an acoustical unit of the type de60 scribed, there are first provided the component materials such as sheets of plane-surfaced asbestos paper and corrugated asbestos paper, asbestos millboard, and the adhesive that it is desired to use in compositing the various parts. 65 These parts may be put together in convenient manner, as, for example, by hand or by machine.

The sheets of paper that are to constitute the central portion are cut to desired size, say 15¼ x 15¼ inches. The tops of the corrugations 70 in the corrugated paper are provided with a coating of sodium silicate solution as the adhesive, and there are then formed a number of composites consisting of sheets of plane surface and corrugated surface, of one-ply thickness of each 75 kind of paper. These composited one-ply sheets

2,043,088 and adhered thereto by means of sodium silicate or other suitable adhesive material. Or, the facing and backing sheets may be applied by means of rollers. In this method the facing and 5 backing sheets are first formed in long lengths and are drawn between spaced rollers, so that the facing sheet rides.on one roller and the backing sheet on the other and there is left between the sheets space for feeding therein the incom10 Plete unit comprising the central portion and adhered edge strips. Adhesive is applied to the inner side of the backing sheet and to the backs of the depressed portions of the facing sheet before the sheets are passed over the said rollers.

Between the rollers the sheets are pressed against the proper surfaces of the unit and are adhered thereto.

After passage of the assembly from the rollers it is trimmed roughly, as by cutting the facing and 20 backing sheets approximately at the edges of the unit.

The unit with adhered facing and backing sheets is then subjected to an operation to establish approximately uniform thickness there25 of, and to set the unit in final shape and size. Thus, the unit may be compressed between steamheated plates maintained at selected distances apart in a hydraulic press and held therein until the moisture present in the unit, including water 30 added with the adhesive, is removed by evaporation.

During this operation the edge strips, which are relatively incompressible as compared to the easily crushed central portion, in connection with 35 the spacing of the plates in the press, establish the thickness of the final unit.

When it is desired to have a facing element more stiff and rigid than is asbestos paper, the facing element of the dried unit may be sprayed 40 or painted over its surface with a solution of shellac, a phenol-aldehyde product (bakelite) or other suitable stiffening agent.

The thus finished surface is then again dried. Finally, the unit is sized and/or provided with 45 beveled edges as illustrated. FOr this there may be used cutting wheels of carborundum or the like.

Since the equipment used in the various steps of the manufacture is not a part of the Invention, 50 it is considered unnecessary to illustrate it.

Units made as described, in 1-inch thickness, have been found to absorb 50 to 65% of incident sound of a frequency of 512 cycles per second.

When it is desired to construct such a unit 55 for use as thermal insulation, the procedure outlined may be followed with the exception that the perforations, slits or other sound-permeable openings are omitted from the structure.

Likewise, the backing or facing elements may co be omitted if their functions are not desired. The facing element, along with other functions, adds to the desirable appearance of the unit and provides a surface that may be painted, as by spraying or brushing, without closing the slits or open65 ings disposed rearwardly with respect to the tops of the elevated portions.

The details that have been given are for the purpose of illustration and not restriction. Variations within the scope of the appended claims 70 may be made without departing from the spirit and scope of the invention.