Multiple-glazed Breather Windows

Abstract

A multiple-glazed unit provided with breather apparatus comprising a capillary tube connected to an elongated column of desiccant material.

Parent Case Text

This application is a continuation of application Ser. No. 70,840, filed Sept. 9, 1970, now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to a novel multiple-glazed unit and, more specifically, to a multiple-glazed unit provided with a breather device. In particular, the invention relates to multiple glazed units provided with a breather device or apparatus comprising a length of capillary tubing connected to an elongated column of desiccant material. In accordance with the invention, a free end of the capillary tube is in open communication with the air surrounding the unit while the desiccant column, to which the capillary tube is connected at its opposite end, is in communication with the enclosed, insulating space of the multiple-glazed unit.

In the past, various types of breather devices have been used on multiple-glazed units. One such breather device is fully disclosed in U.S. Pat. No. 3,838,809, assigned to the assignee of the present invention. In accordance with the aforementioned patent, a multiple-glazed unit is constructed comprising a plurality of glass sheets separated at their marginal edges by a hollow spacer element containing a desiccant material, an elongated strip of mastic in sealing contact with the edges of the glass sheets and the spacer element and a pressure sensitive tape covering the strip of mastic. The unit is provided with an aperture or aligned opening through the tape, mastic and outer wall of the spacer element, to connect the atmosphere with the desiccant, and at least one other opening through the inner wall of the spacer element communicating with the insulating space of the unit. The openings or apertures permit the unit to "breathe" through the desiccant material due to changes of atmospheric conditions.

Although the aforementioned type of unit construction is useful, it has been found that it possesses a number of inherent deficiencies. For example, it has been found that the breather opening through the tape, mastic, and outer wall of the spacer element can be blocked, obstructed or pressed closed either by inadvertent or careless handling or by foreign material collecting therein. Moreover, the desiccant material may be caused to adsorb a considerable amount of moisture during breathing, such that the available quantity of desiccant to keep the unit dry is substantially diminished. Also, if the aperture through the tape, mastic, and outer wall of the spacer element is too large, liquid moisture from condensation, rain or leakage around the perimeter of the unit can enter this aperture causing a rapid reduction in the unit's dew point over what might be expected due solely to moisture vapor diffusion from changes in atmospheric conditions of temperature, barometric pressure, and humidity.

Accordingly, it is an object of this invention to provide an improved breather device for multiple glazed units such that the above-mentioned problems are eliminated or substantially reduced. In accordance with the invention, this object is accomplished by providing multiple glazed units with a breather device comprised of a capillary tube connected to a column of desiccant, so that a free end of the capillary tube is in open communication with the air surrounding the unit while the desiccant column, to which the capillary tube is connected at its opposite end, is in communication with the enclosed, insulating space of the unit.

The foregoing and other objects, features and advantages of the present invention will become more apparent from that which follows, when taken in conjunction with the drawings, in which:

FIG. 1 is a perspective view of a multiple-glazed unit constructed in accordance with this invention;

FIG. 2 is a cross-section along the line II--II of FIG. 1 showing details of a preferred edge construction incorporating the breather device of this invention;

FIG. 3 is a fragmentary perspective view, partly in section and partly broken away, of a side edge of the unit of FIG. 1 showing further details of a preferred embodiment of this invention; and

FIG. 4 is a cross-section similar to that of FIG. 2 showing details of another embodiment of this invention.

Illustrated in FIGS. 1 to 4 are acoustical multiple-glazed unit constructions that advantageously employ the breather device of this invention in their structures. Shown in FIGS. 1 to 3 are details of one preferred acoustical multiple-glazed unit 10 in which glass sheets 12 and 14 are of unequal thickness to achieve a mismatch of their resonent frequencies, hence better reduction of sound transmission through the unit. Also, glass sheets 12 and 14 are spaced apart to provide an insulating space therebetween of about 1 inch or greater, preferably from about 2 inches to about 4 inches, to enhance sound transmission loss through the unit. The marginal edge portions of the glass sheets are rigidly supported at the desired spaced apart distance by a perimeter spacer channel 16 adhered by a layer or bead of moisture-resistant, air-impermeable mastic 18 to the marginal edge portions of both glass sheets.

Spacer channel 16 is preferably composed of aluminum or galvanized steel and, in the embodiment shown, has an essentially U-shaped cross-section. As shown, the web 20 of spacer channel 16 is disposed adjacent the perimeter of the unit and the flanges or legs 22 of the U-channel extend inwardly of the unit therefrom. Flanges 22 are preferably L-shaped and their free ends are disposed in opposed, spaced relation to each other.

Inserted within spacer channel 16 and extending essentially coextensive in length with each side of the unit are four abutting lengths of dehydrator element 24. The composition of dehydrator element 24 is now fully disclosed in applicants' assignee's U.S. application Ser. No. 42,712, the disclosure of which is intended to be incorporated herein by reference. Broadly, dehydrator element 24 comprises a desiccant material dispersed in a matrix of moisture vapor transmittable material, such as a thermoplastic, block copolymer of styrene-butadiene rubber as is now disclosed in U.S. Pat. No. 3,265,765.

Dehydrator element 24, as shown, preferably has a modified U-shaped cross-section, such that when inserted in spacer channel 16 an elongated space 26 is defined between dehydrator element 24 and the web 20 of spacer channel 16. Residing in this space 26 is an elongated column of desiccant 28, forming a part of the breather apparatus 29 of this invention. Connected to one end of the column of desiccant 28 is a capillary tube 30. Capillary tube 30 extends through an eyelet or grommet 34 supported in aligned apertures 36 in desiccant tube 32 and the web 20 of spacer channel 16. Eyelet or grommet 34 clinches tube 32 to web 20.

As best shown in FIG. 3, desiccant tube 32 is an elongated tube filled with a desiccant 28, such as silica gel. The tube 32 is shown closed at its upper end with a small piece of moisture-resistant, air-impermeable mastic 38 and at its lower end with a piece of air-permeable felt 40 or the like. Capillary tube 30 is fixed in place with an end portion 42 connected to or in communication with desiccant column 28 by means of a layer or bead of moisture-resistant, air-impermeable mastic 44 adhered or bonded to tube end portion 42, the web 20 of spacer channel 16, the peripheral edges of the glass sheets 12 and 14 and marginal edge portions of the outer faces of the glass sheets. The free end 46 of capillary tube 30 extends downwardly, outside the layer of mastic 44, for a length of about 3 to 12 inches to help minimize moisture vapor diffusion during breathing. A capillary tube 30 having an inside diameter of about 0.025 inch has been found to be satisfactory.

Channeling 48 of essentially U-shaped cross-section extends completely around the perimeter of the unit to protect its edges and to protect capillary tube 30. Channeling 48 is comprised of several channel sections that are joined or butted together at their ends. As shown, the free end 46 of capillary tube 30 resides in a space 50 defined between mastic layer 44 and the web 52 of channeling 48. Since, in the embodiment shown, channeling 48 is comprised of butted channel sections, air may ingress of egress through these butt joints and pass through capillary tube 30 and desiccant column 28 to permit the insulating space between glass sheets 12 and 14 to breathe.

FIG. 4 depicts a cross-section of another embodiment of this invention. In this embodiment, in lieu of dehydrator element 24, bags of desiccant 54 (one of which is shown) are placed in spacer channel 16, the channel 16 is filled with an air permeable material 56, such as fiber glass or polyurethane foam and the channel is closed with a perforated or foraminous metal strip 58. In all other respects and, in particular, with regard to the breather device 29 of this invention, the construction of the embodiment of FIG. 4 is identical to that of FIGS. 1 to 3.

EXAMPLE

The following deals with a means of determining the length of the desiccant column required for a multiple-glazed breather window of this invention.

Statistically, it has been determined that for a maximum number of design conditions the minimum amount of desiccant required is that needed to adsorb the moisture entering the unit at 85.degree. F and 50 percent relative humidity for one air space volume change created by a barometric change of 1.0 inch of mercury and a 10.degree. F change in air temperature. Accordingly, consider a unit 74 inches .times. 90 inches with a 4 inch air space. Using the perfect gas equation:

V.sub.2 = (V.sub.1 .times. T.sub.2 .times. P.sub.1)/(T.sub.1 .times. P.sub.2)

where

V.sub.1 = original air space volume = 74 inches .times. 90 inches .times. 4 inches/1728 = 15.42 ft.sup.3

T.sub.1 = original sealing temperature = 75.degree. F

P.sub.1 = original sealing pressure = 30.5 inches of mercury

V.sub.2 = design volume

T.sub.2 = design temperature = 85.degree. F

P.sub.2 = design pressure = 29.5 inches of mercury

V.sub.2 = 16.24. Therefore, .DELTA.V = V.sub.2 - V.sub.1 = 0.82 ft.sup.3

Air density = 0.07285 pounds of dry air/ft.sup.3

Pounds of dry air/.DELTA.V = 0.82 .times. 0.07285 = 0.05974 pounds

Humidity ratio = 0.013 pounds of water/pound of dry air

Pounds of water/.DELTA.V = 0.0594 .times. 0.013 = 0.000776 pounds

Silica gel adsorbs four percent of its weight at 0.degree. F dew point. The minimum amount of silica gel required for one air space volume change is:

Silicia gel = (0.000776 .times. 454)/0.04 = 8.808 grams

A 1/4 inch .times. 1/4 inch tube contains 1.22 grams of silica gel per inch.

Minimum length of desiccant column = 8.808/1.22 = 7.2 inches

It is recommended that a safety factor of 10 be used and, therefore, a column of desiccant of 7.2 .times. 10 = 72 inches is required. Accordingly, the recommended amount of desiccant required in a breather column is that amount which will adsorb 10 times the quantity of moisture entering the unit from one air space volume change based on the specified design conditions.

Although the foregoing disclosure has been made in connection with acoustical window units, it should be apparent that the breather device of this invention may be used with other multiple-glazed units as well. Acoustical multiple-glazed units were selected for this disclosure because, due to their larger enclosed volume than standard units, e.g., up to 1 inch thick, they are more susceptible to breakage if they are not provided with a breather device. Also, it should be understood that the glass sheets or glass panels of a typical, transparent, multiple-glazed unit of the invention may be clear, tinted (colored), coated or coated and tinted. In connection with transparent tinted, coated or coated and tinted glass, an advantage of the use of the breather device of this invention is that it keeps the glass sheets or panels flat regardless of changes in atmospheric conditions. Bowed glass, resulting from a pressure difference between the inside and the outside of a multiple-glazed unit, causes light to reflect unevenly, thus distorting the uniformity of appearance and color of a unit. By maintaining the glass flat with the use of the breather device of this invention, the uniformity of appearance and color of a multiple-glazed unit, particularly a unit having an outer glass sheet coated with a transparent reflective film, is greatly enhanced.

Although the present invention has been described with particular reference to the specific details of certain embodiments thereof, it is not intended that such details shall be regarded as limitations on the scope of the invention except insofar as included in the accompanying claims.

Claims

We claim:

1. In a glazing unit comprised of a pair of rigid sheets supported in opposed, spaced relation to each other by perimeter, marginal edge spacer means defining with said sheets an enclosed space therebetween, said perimeter spacer means having a dehydrator carried thereby in communication with said enclosed space, the improvement which comprises a breather device comprising:

an elongated tube filled with a column of desiccant supported by said perimeter spacer means, said elongated tube having a first opening in the wall of said tube adjacent one end thereof and located in the enclosed space of said unit adjacent said dehydrator, and a second opening in the wall of said tube spaced from said first opening and adjacent the other end of said elongated tube, and

an elongated, open-ended capillary tube having one end thereof connected to said elongated tube at said second-named opening therein and the other end thereof exposed and open to the atmosphere surrounding said glazed unit to provide an open passage for air between the enclosed space of said glazed unit and the atmosphere surrounding said unit,

whereby the atmosphere surrounding said glazed unit is free to pass through said elongated, open-ended capillary tube and through substantially the entire column of desiccant within said elongated tube into the enclosed space of said glazed unit.

2. The glazing unit of claim 1 in which the dehydrator comprises a desiccant material dispersed in a matrix of moisture vapor transmittable material.

3. The glazing unit of claim 1 in which the dehydrator comprises bags of desiccant material.

4. The glazing unit of claim 2 which further includes sections of channeling disposed about the perimeter of the unit and wherein said capillary tube has a free end residing in a space defined between said channeling and adjacent edge portions of said unit.

5. The glazing unit of claim 3 which further includes sections of channeling disposed about the permimeter of the unit and wherein said capillary tube has a free end residing in a space defined between said channeling and adjacent edge portions of said unit.

6. The glazing unit of claim 3 wherein said spacer means comprises a channel member containing an air permeable material and said channel member is closed on a side facing said enclosed space with a foraminous strip.

7. The glazing unit of claim 1 wherein at least one of said rigid sheets is comprised of tinted glass.

8. The glazing unit of claim 1 wherein at least one of said rigid sheets is comprised of glass coated with a transparent, reflective film.

9. In a glazing unit comprised of a pair of rigid sheets supported in opposed, spaced relation to each other by perimeter, marginal edge spacer means defining with said sheets an enclosed space therebetween, said perimeter spacer means having a dehydrator carried thereby in communication with said enclosed space, the improvement which comprises a breather device comprising:

an elongated tube filled with a column of desiccant, said elongated tube being separate from and located adjacent said perimeter spacer means and having a first opening adjacent one end thereof located in communication with the enclosed space of said unit adjacent said spacer means, and a second opening spaced from said first opening and located adjacent the other end of said elongated tube in communication with and open to the atmosphere surrounding said unit to provide an open passage for air between the enclosed space of said unit and the atmosphere surrounding said unit,

whereby air from within the enclosed space of said unit and from the atmosphere surrounding said unit is free to pass through substantially the entire column of desiccant within said elongated tube.

10. The glazing unit of claim 9 which further includes an elongated open-ended capillary tube having one end thereof connected to said elongated tube at said second-named opening therein and the other end thereof exposed and open to the atmosphere surrounding said unit to further provide said open passage for air between the enclosed space of said unit and the atmosphere surrounding said unit,

whereby air from within the enclosed space of said unit and from the atmosphere surrounding said unit is free to pass through said elongated open-ended capillary tube and through substantially the entire column of desiccant within said elongated tube.