Multiple-glazed Unit For High Sound Transmission Loss

Abstract

A multiple-glazed window unit comprising a plurality of glass sheets which are substantially parallel to each other and separated from each other at marginal portions thereof by a metallic spacing element and a plurality of resilient spacing elements. The resilient spacing elements are of substantial thickness and separate the metallic spacing element from said sheets. In one embodiment of the present invention, the resilient spacing elements are attached to each other by a thin web.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U. S. Application Ser. No. 118,277, filed on Feb. 24, 1971, now abandoned, in the name of Pandit G. Patil.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a multiple-glazed window unit and, more particularly, to a spacing structure for separating a plurality of glass sheets at marginal portions of the unit to provide a sound transmission class (STC) of about, for example, 45 under ASTM Standard E90-70 for a 1-inch unit.

2. Description of the Prior Art

Multiple-glazed units comprise two or more sheets of glass spaced from one another to provide an insulating air space between the sheets. The sheets are spaced from each other by a marginal edge spacing structure and are usually adhered to the spacing structure by a mastic composition applied in a continuous film around the edges of the sheets, between each sheet and the spacing structure to provide a hermetic seal.

The most pertinent prior art of which I am aware comprises Ottenheimer, U. S. Pat. No. 2,525,717; Fish et al., U. S. Pat. No. 2,620,522; Mills, U. S. Pat. No. 2,710,994; and Stroud et al., U. S. Pat. No. 3,280,523.

The Ottenheimer patent discloses, for example, "three wall panels 10, which may be glass, wood, metal, or other material, are shown as retained in spaced parallel relationship by a preformed element 12 which encompasses the edges of the panels. The preformed element is externally embraced by a channel 14 formed of metal, preformed plastic, preformed polywood, or the like, which serves as a frame to support and protect it."

The Fish et al. patent discloses, for example, "Double glazed panels consist of two sheets of glass, spaced apart by a distance usually of the order of three eighths of an inch, and are used to give heat, and to some extent sound insulation."

The Mills patent discloses, for example, "a new and improved double glazed window unit for an oven door." The patent further states that the unit is "provided with sealing means adapted to effectively seal the space between the two panels of the unit and to provide a seal between the unit and the oven door in which it is used."

Stroud et al. relates to, for example, "a multiple glazing window unit and more particularly to an element for spacing two glass sheets of such a unit from each other about the periphery of the unit." The patent further states that, "The spacing element of the present invention is constructed to prevent the inward flow of mastic into the viewing area of the unit during the pressing operation and, to this end, includes a pair of flanges along the outside of a tubular spacing element that are adapted to be positioned between the two glass sheets of the unit inwardly of the marginal edges."

SUMMARY OF THE INVENTION

This invention relates to a multiple-glazed acoustical unit comprising a plurality of rigid, transparent sheets. The transparent sheets in any one unit can all be made of glass, or all be made of plastic, or some of glass and some of plastic. A malleable metallic spacing element is placed between each pair of transparent sheets. In one embodiment, the metallic spacing element has a web portion that extends substantially perpendicularly to the glass sheets and a plurality of leg portions, each of which is connected to the web portion. The leg portions extend substantially perpendicularly from the web portion in an outward direction. In another embodiment, the metallic spacing element is fabricated in the shape of a closed channel. In both embodiments, the metallic spacing element is free of any contact with the transparent sheets. A resilient spacing element of substantial thickness is placed between the metallic spacing element and each of the adjacent transparent sheets. A thin web may connect each of the resilient spacing elements. An adhesive sealing compound may extend between the metallic spacing element and each of the resilient spacing elements and also between each of the resilient spacing elements and its adjacent transparent sheet. A polyethylene backing member may extend continuously around the perimeter of said unit from the innermost transparent sheet to the outermost transparent sheet at the outer edge portions of the sheets. An inwardly facing, U-shaped channel extends around the polyethylene backing. This U-shaped channel has one leg in line contact with the innermost transparent sheet and another leg in line contact with the outermost transparent sheet. The spacing elements serve to separate the transparent sheets at the marginal portions thereof to provide a multiple-glazed unit with a high sound transmission loss. The thin web connecting each of the resilient spacing elements functions to facilitate assembly of the unit.

DESCRIPTION OF THE DRAWINGS

A complete understanding of the invention may be obtained from the foregoing and following description thereof, taken together with he appended drawings, which are not drawn to scale, and in which:

FIG. 1 is a fragmentary sectional view of a double-glazed unit in accordance with the present invention;

FIG. 2 is a fragmentary sectional view of a double-glazed unit in accordance with a further embodiment of the present invention; and

FIG. 3 is a fragmentary sectional view of a double-glazed unit in accordance with a still further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a double-glazed unit 10 is shown comprising two sheets of glass 12 and 14 arranged in a substantially parallel relationship. The glass may be tempered, colored, laminated or have other special strength or optical properties. The invention is not limited to glass sheets, and other transparent sheets such as the various polycarbonates or other plastics may be substituted for glass. The sheets are separated at their marginal edges by a continuous spacing structure 16. Structure 16 comprises a spacing element 18 of malleable metal, resilient spacing elements 20, polyethylene backing 22, and a U-shaped channel 24. In the embodiment shown in FIG. 1, the glass sheets 12 and 14 are illustrated as 3/8 inch and 1/4 inch in thickness, respectively. Bear in mind that these thicknesses are set forth for example only, and the only importance associated with the glass thickness is that one sheet is preferably thicker than the other. The differing thicknesses insure that there is a coincidence frequency mismatch, which means that the coincidence dip of one sheet will occur at a frequency where the other sheet has no such coincidence dip. Therefore, most sound transmitted through one sheet will be at a frequency that does not coincide with the coincidence dip of the other sheet and will not pass through the other sheet. By making the ratio of thicknesses at least 11/2:1, I insure that this mismatch of coincidence frequencies will increase the sound transmission loss of the unit. It is also preferred that the unit be installed with the thicker sheet adjacent the outside of the building since this is where the unit is most likely to be subjected to an impact, such as by a person throwing a stone at the unit.

The metallic spacing element 18 comprises two leg portions 26 and 28 which extend in a direction that is substantially parallel to the sheets of glass, and a web portion 30 that is substantially perpendicular to leg portions 26 and 28. Web portion 30 extends beyond resilient spacing elements 20 at 29 and 31 to provide additional support for these elements. It is important that metallic spacing element 18 does not contact either sheet of glass or "decoupling" (defined hereinbelow) will be destroyed. While most rigid materials are satisfactory, metallic spacing element 18 is normally constructed of aluminum due to the inexpensiveness of that materiaL.

A resilient spacing element 20 is placed between each leg portion 26 and 28 of metallic spacing element 18 and its adjacent glass sheet. In fabricating the resilient spacing elements, a concept referred to as "decoupling" must be kept in mind. In the past, it has been customary to allow a metallic spacer to either engage the glass sheets or to be spaced therefrom by a thin resilient mass. It has now been discovered that this is not satisfactory to prevent sound transmission through the unit. As used in this disclosure, the term "decoupling" refers to a concept of separating one side of the window unit from the other side of the unit by materials having different moduli of elasticity to prevent a substantial amount of sound and vibration from passing through the unit. It is therefore important that the modulus of elasticity of resilient spacing elements 20 be different from the modulus of elasticity of spacing element 18. In fact, it has been discovered that the ratio of the elastic modulus of spacing element 18 to the elastic modulus of the resilient spacing elements 20 should not be less than 600 to insure "decoupling". Furthermore, the height of the elements 18 and 20 should not be less than 3/8 of an inch or spacing structure 16 will be weak and therefore unstable, and the sound transmission loss of the unit will decrease.

The thickness of the resilient spacing elements 20 bears directly on the sound transmission characteristics of the window unit. If the spacing elements 20 are too thin, there will be no decoupling effect and the window unit will transmit a greater amount of sound. The maximum thickness of each resilient spacing element 20 is a function of the width of the air space 32 between the two glass sheets 12 and 14. The function can be expressed as follows:

Air space 1/2 inch 1 inch 2 inches 4 inches Thickness 1/16 inch 1/8 inch 1/4 inch 1/2 inch

These figures appear to indicate that the width of resilient spacing elements 20 should be at least about one-eighth the width of the air space 32.

In choosing a material for a resilient spacing element 20, it is desirable to choose a material having a hardness (durometer) of from 20 on a Shore A scale to 60 on a Shore D scale; a specific gravity of from 0.85 to 2.45, and preferably about 1.1; and a percentage elongation from about 100 to about 950.

A backing 22 extends from an outside edge of sheet 12 to an outside edge of sheet 14. Backing 22 can be made of any soft material and polyethylene is an example of a suitable material. This backing 22 increases the sound transmission loss of the window unit by preventing substantial contact between the glass sheets and a U-shaped channel 24. If there was any substantial contact, sound could pass from one sheet of glass to the other through channel 24 and decoupling would be destroyed.

U-shaped channel 24 is constructed of a spring steel such as a stainless steel and is used to provide even pressure on the glass sheets to maintain stability of the unit. It extends around the perimeter of the unit and helps to protect the air space 32 from moisture and dirt of the atmosphere.

Any contact between channel 24 and glass sheets 12 and 14 is detrimental and should be minimized since it decreases sound transmission loss. It is therefore important that there is only line contact between the channel 24 and the sheets 12 and 14. A double-glazed unit 357/8 inches by 827/8 inches consisting of a 3/8-inch pane and a 1/4-inch pane and separated by a 2-inch air space has an STC of 46 without channel 24 and an STC of 45 with channel 24. It is still used, however, since it damages the acoustical properties of the unit only slightly (as long as contact between the channel and the glass sheets is minimized) and it adds stability to the unit.

It is important that the spacing structure 16 be maintained as an integral unit. For this purpose, an adhesive sealing compound is used to bond glass sheets 12 and 14 to resilient elements 20 at 38 and elements 20 are bonded to metallic element 18 at 40. Many commercially available sealing comounds are satisfactory and the polybutene sealing compound described in U. S. Pat. No. 2,974,377 to G. E. Kunkle is an example of a satisfactory adhesive. In addition, polyethylene backing 22 is laminated on its top and bottom surface with an adhesive sealant such as the one described in U. S. Patent Application Ser. No. 49,779, filed June 25, 1970, in the name of G. H. Bowser.

The air space 32 between the glass sheets must be free from any moisture. In accordance with the present invention, the spacing structure 16 provides a hermetically sealed panel. As is customary in the prior art, a breather device is provided so that expansion of air within air space 32 does not shatter the glass sheets. U. S. Patent Application Ser. No. 70,840, filed on Sept. 9, 1970, by Stewart et al., is an example of a suitable breather device and has been indicated diagrammatically at 42 in FIG. 1. In addition, desiccant is provided in the resilient elements 20.

Double-glazed acoustical units measuring 357/8 inches by 827/8 inches and constructed according to the present invention with one pane being 3/8-inch glass and the other pane being 1/4-inch glass were tested for sound transmission class (STC) under ASTM Standard E90-70 and the following results were obtained:

Air Space 1/2 inch 1 inch 2 inches 4 inches STC 38 39 45 48

referring to FIG. 2, there is shown another embodiment of the present invention. The unit in FIG. 2 is similar to that illustrated in FIG. 1, and like elements have received like numerals. The dimensions and characteristics set forth hereinabove in connection with the unit illustrated in FIG. 1 also apply to the embodiment ilustrated in FIG. 2. A thin web 21 connects resilient spacing elements 20' to one another. Web 21 may be fabricated as an integral part of resilient spacing elements 20' or it may be a separate piece attached to elements 20'. In either case, web 21 functions to facilitate assembly of the unit 10', since elements 20' may be snapped over metallic spacing element 18. Without web 21, it takes additional effort to assemble a unit.

It is extremely important that web 21 be maintained as thin as possible. It is understood that if web 21 is too thin it will be weak and therefore add little structural integrity to spacing structure 16'. But, if the web 21 is too thick, the sound transmission class of the unit will decrease. For example, if web 21 does not exceed approximately 1/8 inch in thickness, the change in sound transmission class is inconsequential. But, if web 21 is 1/4 inch, the STC rating of a unit will decrease by approximately 8 percent.

Referring to FIG. 3, there is shown an additional embodiment of the present invention. The unit 10" of FIG. 3 is similar to the one illustrated in FIG. 2, and like elements have received like numerals. In this instance, spacing element 18" is box-shaped in cross section with a desiccant material such as a silicon gel being located in the space 19 within spacing element 18". Further details of element 18" may be obtained from U. S. Pat. No. 2,684,266 to Oscar D. Englehart.

While the present invention has been described thus far as having two transparent sheets, it should be understood that the invention is not limited to such, and any suitable number of transparent sheets may be used in accordance with the present invention. It is necessary, however, that at least two of the transparent sheets be separated by materials having varying moduli of elasticity as hereinabove described.

Claims

Having now fully disclosed the invention, what I claim is as follows:

1. A multiple-glazed acoustical unit comprising:

a. a pair of transparent sheets of different thickness having opposed, facing surfaces spaced at least about 1/2 inch apart;

b. a primary spacing element between said transparent sheets and free of any contact with said sheets;

c. a first resilient spacing element of at least about 1/16 inch thickness between said primary spacing element and one of said transparent sheets, said first resilient spacing element having a Shore A hardness of at least about 20 and being free of any contact with the other of said transparent sheets;

d. a second resilient spacing element of at least about 1/16 inch thickness between said primary spacing element and said other of said transparent sheets, said second resilient spacing element having a Shore A hardness of at least about 20 and being free of any contact with said one of said transparent sheets; and

e. said primary spacing element, said first resilient spacing element and said second resilient spacing element separating said transparent sheets at marginal portions thereof to provide a multiple-glazed unit, said multiple-glazed unit having a sound transmission class of at least about 38 as determined by ASTM Standard E90-70.

2. A multiple-glazed unit as recited in claim 1 which further includes a thin resilient web connecting said first resilient spacing element and said second resilient spacing element.

3. A multiple-glazed unit as recited in claim 1 wherein said transparent sheets are spaced at least about 1 inch apart, said first and second resilient spacing elements are of at least about 1/8 inch thickness and said unit has a sound transmission class of at least about 39.

4. A multiple-glazed unit as recited in claim 1 wherein said transparent sheets are spaced at least about 2 inches apart, said first and second resilient spacing elements are of at least about 1/4 inch thickness and said unit has a sound transmission class of at least about 45.

5. A multiple-glazed unit as recited in claim 1 wherein said transparent sheets are spaced at least about 4 inches apart, said first and second resilient spacing elements are of at least about 1/2 inch thickness and said unit has a sound transmission class of at least about 48.

6. A multiple-glazed acoustical unit as recited in claim 1, wherein said primary spacing element is comprised of a rigid material.

7. A multiple-glazed acoustical unit as recited in claim 1, wherein said primary spacing element is comprised of aluminum.

8. A multiple-glazed acoustical unit as recited in claim 1, wherein at least one of said transparent sheets is comprised of glass.

9. A multiple-glazed acoustical unit as recited in claim 1, wherein at least one of said transparent sheets is comprised of plastic.

10. A multiple-glazed acoustical unit as recited in claim 6, wherein said primary spacing element has a web portion that extends substantially perpendicularly to said transparent sheets and a plurality of leg portions, each of which is connected to said web portion, said leg portions extending substantially perpendicularly from said web portion in an outward direction.

11. A multiple-glazed acoustical unit as recited in claim 6, wherein said primary spacing element is box shaped.

12. A multiple-glazed acoustical unit as recited in claim 11, wherein desiccant material is provided in said primary spacing element.

13. A multiple-glazed acoustical unit as recited in claim 1, wherein an adhesive sealing compound extends between said primary spacing element and each of said resilient spacing elements and between each of said resilient spacing elements and the adjacent transparent sheet.

14. A multiple-glazed acoustical unit as recited in claim 1, wherein an adhesive sealing compound and a polyethylene backing member extends continuously around the perimeter of said unit from one of said transparent sheets to another of said transparent sheets at the outer edge portions thereof.

15. A multiple-glazed acoustical unit as recited in claim 14, wherein an inwardly facing U-shaped channel extends around said polyethylene backing member, said U-shaped channel having one leg in line contact with said one of said transparent sheets and another leg in line contact with said another of said transparent sheets.

16. A multiple-glazed acoustical unit as recited in claim 15, wherein said U-shaped channel is comprised of stainless steel.