DE69122273T3 - Double glazing unit - Google Patents

Abstract

An insulating unit (150) has a pair of glass sheets (12,14) about an edge assembly (152) to provide a compartment (18) between the sheets. The edge assembly has a U-shaped spacer (158) made of metal, metal coated plastic, gas and moisture impervious polymer, or gas and moisture impervious film coated polymer. The outer legs (156) of the spacer (158) and the glass (12,14) provide a long diffusion path to limit the diffusion of argon gas out of the compartment (18). The edge assembly (152) has materials selected and sized to provide edge assembly having an RES-value of at least 75. A spacer (158) for use in insulating units includes a plastic core having a gas impervious film e.g. a metal film or a halogenated polymer film. Also taught herein are techniques for making the unit (150) and spacer (158). The unit (150) has a long diffusion path to increase the time period in which insulating glass e.g. Argon gas may be retained in the compartment (18). The increased RES-value provides a unit (150) that has a low thermal conducting edge (152). In this manner heat loss through the marginal edge (152) of the unit (150) is reduced. <IMAGE>

Description

The present invention is applicable to an insulating glazing unit, specifically to an insulating glazing unit with edge assembly, and serves to provide the unit with edges of low thermal conductivity, or, in other words, edges with a high heat flow resistance.

Discussion of the insulation units available on the market

It is generally accepted that insulated glazing units reduce the transfer of heat between the exterior and interior of a dwelling unit or building structure. A unit of measurement commonly used to determine insulation value is called the "U-value". This U-value is the amount of heat in British Thermal Units (BTU) that passes through the unit per hour (h) - square foot (Sq.Ft.) - degrees Fahrenheit (ºF);

From this it can be seen that the lower the U-value, the better the thermal insulation value of a unit, i.e. the greater the resistance to heat flow, which ultimately means that less heat is passed through the unit.

Another unit of measurement for measuring the insulation value is the "R-value", which is inversely related to the U-value. An additional measurement option is the determination of the resistance (RES) to the heat flow, which is determined in h-ºF per BTU and inch of the unit circumference.

Previously, the insulating capacity specified for an insulating unit, e.g. U-value, was that measured at the centre of the corresponding unit. Recently, however, it has been recognised that the U-value of the Unit edges must be considered separately to determine the overall thermal performance of a unit. For example: units with a low U-value in the centre and a high U-value at the edges will not show moisture condensation in the centre during the winter, but may show condensation or even a thin line of ice on the edge of the unit near the frame. Condensation or ice formation on the edge of the unit indicates that there is heat loss through the unit and/or frame, ie that the edges have a high U-value. It also follows that if the condensate or water from melting ice runs down the unit and hits wooden frames, these will slowly start to rot if not specifically treated. In addition, the larger temperature differences between the warm centre and the cold edge can cause greater stress at the edges and glass breakage. The U-value of framed and unframed units and the methods for determining it are discussed in more detail in the chapter "Description of the invention".

Over the years the design, materials used to construct the double glazing units and also the frames have improved significantly, making low U-value framed units available. The following discussion looks at several models of units currently on the market, as well as the centre and edge U-values of a selected few.

There are edge-assembled insulating glazing units in which (1) the edges of the glass panes are welded together, (2) one of the glass panes has a coating to reduce emissivity, and (3) the space between the panes is filled with argon.

The units shown here have a measured centre U-value of approximately 0.25 and a measured edge U-value of approximately 0.55. Although insulating glazing units of this type are acceptable, they do have their limitations. For example, special equipment is required to seal the edges of the to heat and weld glass panes together, nor is toughened glass used in the manufacture of the units.

US-A-4,807,439 describes an insulating unit marketed by PPG Industries Inc. under the registered trademark SUNSEAL. This unit has two panes of glass spaced approximately 0.45 inches apart, an organic edge assembly, and air in the space between the panes. For a unit constructed in this way, the expected center U-value is approximately 0.35 and the edge U-value is approximately 0.59. Although supplying the unit with insulating gas, such as argon, will lower the center and edge U-values, over time the argon would evaporate through the organic edge assembly, causing the center and edge U-values to rebound to the previously stated levels.

The device of US-A 4,831,799 has an organic edge assembly and a gas barrier coating, layer or film on the edge edges of the device to retain argon. The thermal behavior of the device is discussed in column 5 of the patent.

US-A-4,431,691 and 4,873,803 both present a unit in which the two glass panes are separated by an edge assembly that has an organic sealing reinforcement with an embedded thin, rigid rod. Although the units of these patents offer an acceptable U-value, they have their downsides. More specifically, these units have a short, highly resistant diffusion path. The diffusion path is the path that gas, e.g. argon, air, or moisture, must travel to leave or enter the space between the panes. The resistance of the diffusion path is determined by the permeability, thickness and length of the material. The units of US-A-4,831,799; 4,431,691; 4,431,691 and 4,873,803 have a short, high-resistance diffusion path between the metal strip or spacer and the glass panels; the rest of the edge assembly has a low-resistance, long diffusion path.

Patent US-A-3,919,023 describes an edge assembly for an insulating glazing unit which has a provides a highly resistant, long diffusion path and could be used to minimize argon loss. A limitation of this edge assembly is the use of a metal strip around the outer edge edges of the unit. This metal strip conducts heat around the edge of the unit, so its edge U-value is expected to be high.

It has already been mentioned that the effect of the frame U-value on the window edge U-value should also be considered, but a detailed debate on low U-value frames will be omitted here as the present invention relates to an insulating glazing unit with low centre and edge U-values which is easy to manufacture, has none of the limitations or disadvantages of the insulating glazing units currently available on the market and can also be used with any frame construction.

Summary of the invention

The invention relates to an insulating glazing unit having two glass panes separated by an edge assembly, creating a sealed space between the panes in which a gas is filled. The edge assembly includes a structurally flexible spacer that holds the glass panes at a fixed distance from each other, but at the same time tolerates a certain amount of thermal volume expansion and contraction that typically occur in the individual components of an insulating glazing unit. A diffusion path resistant to the gas filled in the space, e.g. a long, narrow diffusion path, is provided between the spacer and the glass panes, and the edge assembly provides a high RES value at the edges of the unit, as determined using the ANSYS program.

A method for manufacturing an insulating unit is also presented. The method also includes the steps required to assemble the edge assembly between the glass panes, i.e. to form the tight gap. To manufacture the edge assembly, two glass panes are required; a structurally elastic spacer, appropriate sealing material and moisture permeable desiccant material to ensure the edge assembly has a high RES value (as measured using the ANSYS program) and a long, narrow diffusion path. Glass panes, spacers, sealing material and desiccant material are used together to obtain an insulating unit with a high RES value at the edges, as also measured using the ANSYS program.

The preferred insulation unit in the invention has an environmentally resistant coating, e.g. a low E coating, on at least one pane surface. Adhesive sealant on each of the outer surfaces of the U-shaped cross-section spacer secures the panes to the spacer. A strip of moisture permeable adhesive tape with desiccant is applied to the inner surface of the spacer.

The spacer contains a structurally elastic core, e.g. a plastic core, coated with a moisture- and/or gas-impermeable film; this may be a metallic film or a halogen-containing polymer film made of polyvinylidene chloride or fluoride or polyvinyl chloride or polytrifluorochloroethylene.

Apart from that, the spacer can also consist entirely of a polymeric material, which must have both structurally elastic and moisture or gas impermeable characteristics, such as halogen-containing polymer materials, including polyvinyl chlorides or fluorides, or polyvinyl chlorides or polytrifluorochloroethylene.

A method for manufacturing U-shaped spacer bars used to manufacture the spacer frames for the insulating glazing units also includes the steps to be applied to the corresponding metal workpiece; this metal workpiece with sealing reinforcement of moisture and/or gas permeable adhesive seal is positioned on a surface between pairs of profile rollers arranged at a certain distance from each other and is then passed through; the profile rollers are shaped in such a way that they Form the metal substrate around the sealing reinforcement step by step into a spacer rod, whereby the cross-section is determined beforehand, here for example U-shaped cross-section.

The spacer frame has a notch to identify the opposing outer sides and at least one continuous corner. A method also includes the steps necessary to produce a spacer bar cross-section sufficient to produce a frame of a predetermined size. The opposing surfaces of the spacer bar are beveled inwardly as they are bent around their indentation to form a continuous corner. The step to form a continuous corner is repeated until the opposing ends are brought together and sealed, e.g. by welding.

Short description of the drawings

Figures 1 to 4 show cross-sectional views of edge assemblies found in insulation units built according to the known state of the art.

Figure 5 is a floor plan of an insulation unit with generic edge assembly.

Figure 6 is a view taken along lines 6-6 of Figure 5.

Figure 7 is the left half of the view of Figure 6 and shows the heat flow lines through the unit.

Fig. 8 shows a similar view to Fig. 7, but without heat flow lines.

Figure 9 provides a table showing the edge temperature distribution for units with different types of edge assemblies.

Figure 10 is a partial view of an edge assembly incorporating elements of the invention.

Fig. 11 is a cross-sectional view of another embodiment of the spacer of the present invention.

Fig. 12 shows a view of an edge strip incorporating elements of the present invention with a sealing reinforcement made of moisture and/or gas permeable adhesive tape mixed with desiccant.

Figure 13 is a side elevational view of a roll forming station used to form the edge strip of Figure 12 into a spacer bar incorporating elements of the present invention.

Figures 14 to 16 provide views taken along lines 14 to 16 of Figure 13.

Figure 17 is a view of a continuous corner of the spacer frame of the present invention, having the profile shown in Figure 18.

Fig. 18 is a partial side view of a spacer bar profile notched and folded before being bent to form the continuous corner of the spacer frame shown in Fig. 17, according to the postulates of the invention and incorporating its elements.

Figure 19 is a view similar to Figure 18, and illustrates another type of continuous corner of a spacer frame incorporating elements of the present invention.

Fig. 20 is a view similar to Fig. 10 and shows another possible embodiment of the invention.

Description of the invention

In the following discussion, certain numbers refer to certain elements, and the units described have two panes of glass; however, those who are more knowledgeable will note that units with more than two panes of glass, as shown in Fig. 20, are also considered.

Turning to Figures 1 to 4, there are shown four general types of prior art edge assemblies used to make insulating glazing units. Unit 10 in Figure 1 comprises two glass panes 12 and 14 separated from each other by an edge assembly 16 to provide a gap 18 between the panes. The edge assembly 16 includes a hollow metal spacer 20 having a desiccant 22 therein which serves to absorb any moisture in the gap and holes 23 (only one of which appears in Figure 1) which provide communication between the desiccant and the space. The edge assembly 16 further includes an adhesive sealant 24, such as silicone, in the lower portion of the spacer 20 (see Figure 1) to secure the spacer 20 and the glass sheets to one another, and a sealant 25, such as butyl sealant, in the upper portion of the spacer 20 to prevent the leakage of insulating gas into the space 18. The edge assembly 16 of the unit 10 is similar to the types marketed by Cardinal Glass, as well as to the insulating units of patents US-A-2,768,475; 3,919,023; 3,974,823; 4,520,611 and 4,780,164.

Unit 30 in Fig. 2 comprises glass panes 12 and 14 with their edges welded together at 32 to create space 18. One of the glass panes, for example pane 12, has a coating 34 thereon to reduce emissivity. Unit 30 shown in Fig. 2 is similar to the insulating units marketed by PPG Industries, Inc. under the trademark OptimEdge, and to the units of US-A-4,132,539 and 4,350,515.

As for Figure 3, it depicts unit 50, which is referred to in US-A-4,831,799.

In unit 50, the glass panes 12 and 14 are separated by an edge assembly 52 to create the gap 18. The edge assembly 52 includes a moisture permeable foam material 54 mixed with desiccant 56 to absorb moisture in the gap 18, a moisture impermeable sealant 58 to prevent moisture from entering the gap 18, and a gas barrier coating, layer or film 60 disposed between the foam material 54 and the sealant 58 to prevent the escape of insulating gas from the gap 18. Units similar to unit 50 are covered in US-A-4,807,419.

Figure 4 shows Unit 70, which was used in US-A- 4,431,691 and 4,873,803.

In unit 70, the glass panes 12 and 14 are separated by an edge assembly 72 to create the gap 18. The edge assembly 72 includes a moisture permeable adhesive tape 74 with desiccant 76 and a metal rod 78 therein.

Before discussing the construction of the insulating unit and, in particular, the construction of the edge assembly of the present invention, it seems appropriate to say a few words about heat transfer through an insulating glazing unit in order to appreciate the value of the present invention. In the discussion that follows, the U-value will be used to compare and classify the heat transfer taking place, or in other words, the resistance to the heat flow passing through the glazing unit, in order to reduce heat loss. Those in the know know that the lower the U-value, the lower the heat transfer - and vice versa. The U-value of an insulating unit can be determined using the following equation.

(1) Ut = (Ac/At)Uc + (Ae/At)Ue + (Af/At)Uf

where U is the unit of heat transfer in British heat unit/hour - square foot - ºF (BTU/h- Sq.Ft.-ºF.)

A means the area to be assessed in square feet

c denotes the center of the unit

e denotes the edge of the unit

f denotes the frame

t is the total value for the unit, taking into account all the parameters under discussion. In Figures 5 and 6, a generic insulation unit 90 is shown in which the glass panes 12 and 14 are separated by an edge assembly 92 to create the gap 18. The edge assembly 92 is referred to as a generic edge assembly for the purposes of the discussion here, but is not limited to this design. Now, specifically with regard to Figure 5, it can be observed that unit 90 - for discussion purposes - has an edge region 94 which, from the extending approximately 3 inches (7.62 centimeters) inward from the edge margins 95 of the unit and having a central region 96. The interface between the edge region 94 and the central region 96 of unit 90 is indicated in Figure 5 by dashed line 98.

The left half of the unit 90 shown in Figure 6 is illustrated in Figure 7, with the figures relating to heat transfer through the unit omitted to maximize clarity during the subsequent debate. With reference to Figures 5, 6 and 7, it is necessary to say that during winter, heat moves from the interior of an enclosed space, such as a dwelling, through the peripheral region 94 and central region 96 of unit 90 to the outside world. Turning specifically to Figure 7, it is noted that in the central region 96 of the unit, the heat flow pattern is generally perpendicular to the isotherm formed by the large areas of the glass panes 12 and 14; in Figure 7, the heat flow pattern is illustrated by the arrow-like lines 100. The direction of the heat flow pattern changes as one approaches the edge 95 of the unit, as illustrated by arrow lines 102, until at the edge 95 of the unit the heat flow pattern again becomes perpendicular to the large area of the glass panes (see arrow lines 104). As those familiar with the subject will appreciate, a frame mounted around the edge of the unit will have certain effects on the flow patterns, particularly on flow patterns 102 and 104. However, for the purpose of simplifying the discussion here, the effect of the frame on flow patterns 102 and 104 will not be discussed further here, but what has been discussed so far is considered to be sufficient background information for a proper appreciation of the present invention.

The heat flow through the central region 96 of unit 90 can be varied by making changes in the thermal behavior of the glass panes 12 and 14, the distance between the glass panes and the gas in the space 18. Now consider the distance between the glass panes, i.e. the gap.

Gaps with dimensions of (0.250-0.500 inches) 0.63-1.27 centimeters are considered sufficient to allow an insulating gas layer, the dimension to be used also depending on the insulating gas to be filled. In the lower range, krypton is preferable, in the upper range, air and argon. In general, it can be found that a gap of less than (0.250 inches) 0.63 centimeters is not large enough for gases such as air or argon to form a significant gas insulating layer, and that in the gaps above (0.500 inches) 1.27 centimeters, gas flows (for example when using krypton) have sufficient mobility to cause convection therein, moving heat between the glass surfaces, for example from the glass pane facing the interior of the dwelling to the glass pane facing the outside.

As mentioned previously, the heat flow in the unit can also be affected by changing the gas that is filled into the space. For example, if you use a gas that has a high thermal insulation value, this will also increase the performance of the unit; in other words, the U-value in the middle and edges of the unit will go down. To give an example, which is not a claim of this invention, argon has a higher thermal insulation value than air. If argon is filled instead of air in an otherwise identically constructed unit, this will lower the U-value.

Another technique for influencing the thermal insulation value of the central region is to use panes with high thermal insulation values and/or panes with an emissivity reducing coating. Types of emissivity reducing coatings that can be used in the practice of the invention are described in US-A-4,610,771, 4,806,220, and 4,853,256.

Increasing the number of glass panes increases the number of gaps between them, thereby increasing the insulating effect in the center and peripheral areas of the unit.

Now the discussion is moving towards heat loss in the edge region of the unit. In Fig. 8 there is shown an edge section of the unit 90 shown in Figs. 5 and 6. The letters A and E indicate the points where the heat flow is generally perpendicular to the glass surface. As the edge of the unit is approached, the glass begins to appear as an extended surface with respect to the edge, causing the heat flow paths 100 at the edge of the unit to begin to bend or curve as illustrated in Fig. 7 by the numeral 102. This bending occurs in the edge region 94 shown in Figs. 6 and 7. Between the letters B and D, the heat flow is resisted primarily by the edge assembly 92, rather than by the glass at the edge of the unit. With regard to Fig. 9, curves 120, 130 and 140 show the heat loss in the edge region for various edge assemblies. However, Figure 9 should not be considered an absolute list, but rather a general guide to better understand heat flow through edge assemblies. Curve 120 illustrates the heat loss curve for an edge assembly with high thermal conductivity, such as that which would be obtained using an aluminum spacer; aluminum spacers are generally used to manufacture the types of edge assemblies shown in Figure 1. Curve 130 illustrates the heat loss curve for an edge assembly which has a lower thermal conductivity than the aluminum spacer edge assembly; this could be, for example, an edge assembly with a plastic spacer similar to that shown in Figure 3. Line 140 illustrates the edge heat loss curve for a unit having glass edges such as those shown in Figure 2. Although not a claim of the invention, it is expected that an edge assembly incorporating the elements of the present invention will provide a heat loss profile similar to that described in curve 140, or heat loss profiles that range in the hatched areas between curves 130 and 140.

As can be seen in Figure 9, the profile for an aluminum spacer, illustrated by curve 120, shows that the aluminum spacer offers little resistance to heat flow at the edge of the unit (between points A and C), thus registering a colder edge on the surface of the unit facing the interior of the dwelling. The profile for an organic spacer, for example made of polymeric material, illustrated by curve 130, shows that the organic spacer offers high resistance to heat flow, resulting in a warmer glass surface inside the dwelling and, ultimately, low heat loss at the edge of the unit. This is particularly illustrated by the profile of curve 130 between points A and C. The edges of welded glass panels (see example in Figure 2) offer higher resistance than a metal spacer assembly, but lower than plastic edge assemblies. The temperature distribution of units with welded edges between points A and C is illustrated by the part of line 140 that is located between curves 120 and 130 between points A and C (see graph Fig. 9).

The heat loss is greater for an edge assembly with a metal spacer, particularly an aluminum spacer, than for glass because the aluminum spacer has a higher thermal conductivity (aluminum is a better conductor of heat than glass or organic material). The effect of the higher thermal conductivity of the aluminum spacer is also seen at point D, where the curve 120 for the aluminum spacer shows a higher temperature at the outside surface of the unit than curve 140 or curve 130. The heat that maintains the higher temperature at D for the aluminum spacer is dissipated from the interior of the home, resulting in a greater heat loss at the edge of the unit than for units with glass or organic spacers; also greater than that resulting from the edge assembly of the invention, as will be discussed in more detail below.

The heat loss in an edge assembly with organic spacer is less than that of edge assemblies with metal spacers or welded glass because the organic spacer has a lower thermal conductivity. The effect of the lower thermal conductivity of the organic spacer is illustrated by line 130 at point D, which indicates a lower temperature than for glass and metal spacers, clearly showing that the conductive heat loss through an organic spacer is less than that for glass and metal spacers.

A phenomenon that occurs in units with high edge heat loss on very cold days is the formation of a thin layer of condensation or ice on the inside of the unit, near the frame. This ice or condensation can occur even if the center of the unit is free of moisture.

As discussed previously, units with argon-filled gaps and polymer edge assemblies may well have a low U-value initially, but this will increase over time since polymer spacers generally do not hold argon. To hold argon, an additional film coating is necessary, a film such as that described in US-A-4,831,799. The disadvantage of the unit described in US-A-4,831,799 is that the film has a short diffusion path, a topic discussed above. However, the opportunity exists to improve argon retention through material selection, for example by choosing hot melt sealants such as HB Fuller 1191 and HB Fuller 1081A, as well as Butyl Sealant 4442 from PPG Industries, Inc., which hold argon better than most polyurethane adhesives.

Referring to Figure 10, the insulation unit 150 is shown with the edge assembly 152 in which elements of the present invention have been used to space the glass panes 12 and 14 and to create the gap 18. The edge assembly 152 includes a moisture and/or gas impermeable adhesive sealant layer 154 to bond the glass panes 12 and 14 to the legs 156 of the metal spacer 158. The sealing layers 154 act both as a barrier against moisture entering the unit and as a gas blockage to prevent the escape of insulating gas, such as argon, from the gap 18. With regard to the loss of gas filled into the unit, it should be noted that in practice the length of the diffusion path and the thickness of the sealing tape are selected in accordance with the gas permeability of the sealing material so that the loss rate of the filling gas is compatible with the desired service life of the unit. The suitability of the unit to be filled with gas is checked using a European standard, DIN 52293. Preferably the loss rate of filling gas should be less than 5% per year and even more optimal would be a loss rate of less than 1% per year.

Regarding moisture penetration into the unit, the shape of the sealing tape is chosen so that the amount of moisture actually penetrating through the edge elements (i.e. sealing reinforcement and spacers) can be absorbed by an appropriate amount of desiccant, calculated to cover the desired life of the unit. It is preferable to use an adhesive sealant for the spacers of Figures 10 and 11 with a moisture permeability of less than 20 gm mm/M² per day (using ASTM F 372-73). Even more optimal would be a permeability of less than 5 gm mm/M² per day.

The ratio between the amount of desiccant in the unit and the permeability of the sealant and its shape can be varied depending on the desired service life of the insulation unit.

An additional adhesive sealant layer or structural adhesive layer 155, which need not only consist of silicone and/or hot melt adhesive, can be applied in the edge groove of the unit formed by the center leg 157 of the spacer and the corner edges of the glass panes. As will now be seen, the sealant is not part of the invention but can be any of those already registered, for example that disclosed in US-A-4,109,431 mentioned.

A thin layer 160 of moisture permeable adhesive tape, containing desiccant 162, is applied to the inner surface of the center leg 157 of spacer 158 to absorb moisture from gap 18, as shown in Fig. 10. In addition, desiccant may also be applied along the inner surface of legs 156. The permeability of adhesive layer 160 is not a requirement of the present invention; however, it should be large enough to the moisture in gap 18 to allow it to be absorbed by the desiccant. Adhesive materials having a permeability of over 2 gm mm/M² per day may be used in the practice of the invention, as mentioned above in connection with ASTM F 372-73. Edge assembly 152 provides unit 150 with low thermal conductivity at the edge, i.e. there is in fact a high resistance to heat loss, a long diffusion path and structural integrity with sufficient elasticity to accommodate a certain degree of thermal expansion and contraction that typically occur in the various components of the insulating glazing unit.

In order to properly appreciate the high resistance to heat loss offered by the edge assembly of the present invention, the mechanisms of heat conduction through the edges of an insulation unit are presented below.

The heat loss through the edge of the unit is a result of the thermal conductivity of the materials used and their physical arrangement, the thermal conductivity of the frame and the surface film coefficient. The surface film coefficient is the transfer of heat from the air to the glass on the warm side of the unit, and the transfer of heat from the glass to the air on the cold side of the unit. This coefficient depends on weather and environmental factors. Since weather and environment are controlled by nature and not by the design of the unit, no further discussion is considered necessary on this point. The effect of the frame will be discussed later. The debate here will be limited to the thermal conductivity of the materials at the edge of the unit and their physical arrangement.

The resistance of the edges to heat loss in an insulating glazing unit with glass panes separated by an edge assembly is calculated by the following equation (2).

(2) RHL = G&sub1; + G&sub2; + ... Gn + S&sub1; + S&sub2; + ... + Sn

where REL is the resistance to heat loss at the edges of the unit per hour - ºF/BTU/in. of unit circumference (h-ºF/BTU/in.).

G is the heat loss resistance of a pane in h- ºF/BTU/in.

S is the heat loss resistance of the edge assembly in h-ºF/BTU/in.

For an insulating glazing unit with two glass panes separated by a simple edge assembly, equation (2) can be reformulated as equation (3).

(3) RHL = G&sub1; + G&sub2; + S&sub1;

The thermal resistance of a material is given by equation (4).

(4) R = L/CA

where R is the thermal resistance in h-ºF/BTU/in.

K is the thermal conductivity of the material in BTU/hour-inch-ºF.

L is the material thickness, measured in inches along an axis parallel to the heat flow.

A is the area of the material measured in square inches along an axis transverse to the heat flux/inch of circumference.

The thermal resistance for the components of an edge assembly that lie in a substantially perpendicular or vertical line to the largest surface of the unit is determined using equation (5).

(5) S = R&sub1; + R&sub2; + ... + Rn

where S and R are the previously defined values.

In those special cases where the components of a edge assembly along an axis parallel to the largest surface of the unit, the thermal resistance (S) is defined by the following equation (6).

where R is the previously defined value.

By combining equations (3), (5) and (6), the heat flow resistance at the edge of the unit 150 shown in Fig. 10 can be determined by the following equation (7).

where RHL is the previously defined value,

R₁₂ and R₁₄ are the thermal resistance of the glass panes,

R₁₅₄ is the thermal resistance of the adhesive layer 154,

R₁₅₅ is the thermal resistance of the adhesive layer 155,

R₁₅₆ is the thermal resistance of the outer legs 156 of the spacer 158,

R₁₅₇ is the thermal resistance of the central leg 157 of the spacer 158, and

R₁₆₋₀ is the thermal resistance of the adhesive layer 160.

Although equation (7) shows the relationship between the components, it is only an approximate method of determining the resistance to heat loss at the edge, which is used for standard engineering calculations. There are computer programs that calculate the exact relationships, determine the heat flow across the edges or the heat flow resistance of the same.

A computer program that is available on the market for this purpose is the thermal analysis package within the ANSYS program, from Swanson Analysis Systems Inc., Houston, PA. The ANSYS program was developed to determine the heat loss resistance at edges or to determine the U-value of units that had similar properties to those shown in Figures 1 to 4.

Although the edge U-value (previously defined) is a unit of measure that determines the overall performance, the demonstration of the usefulness of the present invention also depends to a large extent on certain phenomena that are not part of it, namely, for example, the film coefficient, the thickness of the glass and the frame construction. We now turn to the discussion of the edge resistance of the edge assembly (excluding glass panes). The edge resistance of the edge assembly is defined by the reversal of the heat flow that takes place from the glass-sealant interface 154 on the inside of the assembly to the glass-sealant interface 154 on the outside of the assembly per unit temperature rise, per unit length of the edge assembly circumference. To simplify the discussion, it is assumed that the glass-sealant interfaces are isothermal. Support for the above claim can be found, among others, in the paper entitled "Thermal Resistance Measurements of Glazing System Edge-Seals and Seal Materials Using a Guarded Heater Plate Apparatus" written by J. L. Wright and H. F. Sullivan ASHRAE TRANSACTIONS 1989, V. 95, P. 2.

In the following discussion and in the claims, one of the parameters of interest is the heat flow resistance of the edge assembly per unit length of circumference ("RES").

As previously mentioned, the ANSYS finite element code was used to determine the RES. The result of the ANSYS calculation depends on the assumed geometry of the edge assembly cross section as well as the assumed thermal conductivity of the components. The geometry of one of these cross sections can be easily measured by analyzing the edge assembly unit in question. The thermal conductivity of the components, or the RES value of the edge assembly, can be measured as shown in ASHRAE TRANSACTIONS (see above). The following thermal conductivity values for edge assembly materials are given in the article. Additional values can also be found in "Principles of Heat Transfer, 3rd. ed.", by Frank Kreith.

Material thermal conductivity

Butyl 0.24 W/wC (0.011 BTU/h-in-ºF)

Silicone 0.36 W/mC (0.017 BTU/h-in-ºF)

Polyurethane 0.31 W/mC (0.014 BTU/h-in-ºF)

Stainless steel 304 13.8 W/mC (0.667 BTU/h-in-ºF)

Aluminum 202 W/mC (9.75 BTU/h-in-ºF)

Now to the RES value calculated for the edge assemblies of the units of Figures 1 through 4. The construction of the edge assembly 16 of unit 10 of Figure 1 includes a hollow aluminum spacer 20 between the glass panes; the spacer has a wall thickness of about (0.025 inches) 0.06 centimeters, a vertical side length, perpendicular to the major face of the glass panes 12 and 14, of about (0.415 inches) 1.05 centimeters, and a horizontal side length, generally parallel to the major face of the glass panes 12 and 14, of about (0.3 inches) 0.76 centimeters; and butyl adhesive layers 24, having a thickness of about (0.003 inches) 0.008 centimeters; and a structural silicone gasket 16 filling the cavity formed by spacer 20 and glass panels 12 and 14. The edge assembly RES value of unit (10) - constructed as just described - was calculated using the ANSYS program and was found to be 4.65 h-ºF/BTU per inch of circumference.

The construction of the edge assembly 32 of unit 30 in Figure 2 consists, among other things, of a pair of glass panes separated by a distance of about (0.423 inches) 1.07 centimeters; an edge wall, identified by the number 32, having a thickness of about (0.090 inches) 0.229 centimeters. The edge assembly RES value of unit 30 - constructed as just described - was calculated using the ANSYS program and was 104 h-ºF/BTU per inch of circumference.

The structure of the edge assembly 52 of unit 50 in Fig. 3 comprises a pair of glass panes 12 and 14 separated by a gap of about (0.50 inches) 1.27 centimeters; a desiccant-filled structural foam element about (0.25 inches) 0.64 centimeters thick bonded to the glass surfaces; an aluminum-coated plastic diffusion membrane and a butyl edge seal about (0.25 inches) 0.64 centimeters thick. The aluminum coating between the foam element and the seal was too thin for accurate measurement. The edge assembly RES value of unit 50, constructed as just described, was calculated using the ANSYS program and was found to be 104.0 hr-ºF/BTU per inch of circumference.

For a unit similarly designed to unit 50 in Figure 3, and having two panes of glass 12 and 14, spaced 0.45 inches apart; a silicone adhesive layer 54, approximately 0.475 inches thick, including desiccant; a moisture-impermeable butyl sealant 58, approximately 0.187 inches thick, the expected edge assembly RES value - using the ANSYS program - is approximately 84.7 h-ºF/BTU per inch of circumference. A comparison of the edge assembly RES value is provided for the different constructions possible for units of the type shown in Figure 3 to further illustrate the effects of material and dimensional changes on the edge assembly RES value.

The edge assembly construction of Unit 70 in Figure 4 includes two glass panes spaced approximately (0.45 in.) 1.143 cm apart; an adhesive butyl edge seal approximately (0.312 in.) 0.767 cm wide, with desiccant and embedded aluminum spacer approximately (0.010 in.) 0.025 cm thick. The edge assembly RES value of Unit 70, constructed as just described, was calculated using the ANSYS program and was 4.50 h-ºF/BTU per inch of circumference.

The construction of the edge assembly 150 of the present invention (shown in Figure 10) includes two glass panes, separated by a distance of about (0.47 inches) 1.20 centimeters; a moisture and argon impermeable polyisobutylene layer 154, about (0.10 inches) 0.254 centimeters thick and about (0.250 inches) 0.64 centimeters high (see Figure 10); a U-shaped section bar 156 made of 304 stainless steel, having a thickness of about (0.007 inches) 0.018 centimeters, the center leg having a width of about (0.430 inches) 1.09 centimeters (see Figure 10) and the outer legs each having a height of about (0.250 inches) 0.64 centimeters (also see Figure 10); a desiccant-impregnated polyurethane layer 160 having a height of approximately (0.125 inches) 0.32 centimeters and a width (as shown in Figure 10) of approximately (0.416 inches) 1.05 centimeters; a secondary polyurethane gasket 155 having a width of approximately (0.450 inches) 1.143 centimeters and a height of approximately (0.125 inches) 0.32 centimeters (as shown in Figure 10). The edge assembly RES value of unit 50, constructed as just described, was calculated using the ANSYS program and was found to be 79.1 hr-ºF/BTU per inch of circumference.

In Fig. 11, a cross-section of another embodiment made with the spacer of the present invention is shown. The spacer 163 has a structurally resilient core 164. In the practical application of the invention, it should be non-metallic, preferably using a polymer core, for example a glass fiber reinforced U-shaped plastic rod 164 coated with a thin insulating gas impermeable film 165. For example, if air, argon or krypton are used in the space, then the thin film 165 can be metal. Both the structure of the spacer and the gas barrier film are chosen so that the gas remains inside throughout the desired life of the unit. For a spacer as in Fig. 11, where argon is used as the filling gas and polyvinylidene chloride as the barrier film, the polyvinylidene chloride should preferably have a thickness of at least 5 thousandths, optimally a thickness of over 10 thousandths would be.

If a material other than polyvinylidene chloride is used as If a barrier film is used, its thickness must be selected to ensure filling gas retention throughout the desired life of the unit, depending on the gas used.

The retention properties exhibited by the unit of the present invention are measured via the above-mentioned DIN 52293.

In the case of argon, the film 165 should be a (0.0001 inch) 0.000254 centimeter thick aluminum film or a 0.005 inch thick polyvinylidene chloride film. As used herein, the argon impermeable material has an argon permeability of less than 5%/year. The invention contemplates using a core 164 and a thin film layer 165 or multiple layers 164 and 165 to constitute a lamellar structure. If spacer 163 is used and aluminum film is substituted for spacer 155 of unit 150 of Figure 10, the expected edge assembly RES value for unit 150 of Figure 10 is about 120. This is about a 50% increase in RES value due to the spacer being replaced by a thin metal-clad plastic spacer. If spacer 163 is used in conjunction with a 0.0005 inch thick polyvinylidene chloride film, the expected edge assembly RES value of unit 150 of Figure 10 is also about 120.

The present invention also provides a spacer 163 as shown in Figure 11, the body of which is made entirely of a polymeric material having moisture and gas impermeable characteristics. Such a spacer body may be reinforced (for example with glass fiber), but would will have a high edge assembly RES value, expected to be comparable to that of the spacer of Figure 11.

The spacer of the present invention not only acts as a barrier to the insulating gas in space 18, but is also structurally sound. This term, as used here and in the claims, means that the spacer holds the glass panes at a certain distance apart, while locally allowing the bending vibrations of the glass that may result from changes in air pressure, temperature and wind loads. The fact that the panes are held at a certain fixed distance also means that the spacer prevents the glass panes from moving toward each other when the edges of the unit are secured in the glazing frame. It is obvious that less force is exerted on the edges of residential glazing units mounted in wood frames than on the edges of industrial and commercial glazing units mounted in metal facade cladding via pressure glazing. Allowing local bending vibrations means that the spacer allows the corner edge parts of the glass to rotate around its edge during loading of the types described, but restricts any other movement than rotation, i.e. parallel displacements. The degree of structural elasticity depends on the type of material and its thickness. For example, if it is metal, the material can be thin, while plastic - to achieve the same structural elasticity - must be used much thicker or reinforced, e.g. with glass fiber.

Embodiments of the present invention can be used to improve the performance of units constructed in accordance with the prior art. For example, if the spacer of unit 10 in Figure 1 is replaced with a stainless steel spacer, the edge assembly RES value is expected to increase from 4.65 to 18.2 h- ºF/BTU per unit circumference. If the thickness of the metal from (0.025 in.) 0.06 centimeters to (0.005 in.) 0.0127 centimeters, the edge assembly RES value of unit 10 on Figure 1, using the ANSYS program, increases from 4.65 to 96.1 h-ºF/HTU per inch of circumference. If the aluminum strip of the unit of Figure 4 is replaced with a strip of stainless steel, the edge assembly RES value increases from 4.5 to 44.4 h-ºF/BTU per unit of circumference.

Unit 150 of the present invention, with a spacer structure 152 as shown in Figure 10, has an expected edge heat loss similar to that shown by line 140. Unit 150 of the present invention, with a spacer structure 163 as shown in Figure 11, has an expected edge heat loss that is between curves 130 and 140, but close to 130. Although the edge assembly of the present invention has an RES value that is lower than that of edge assemblies with organic spacers (see corresponding type in Figure 3), it offers clear advantages. More specifically, the spacer is made of metal, gas and moisture impermeable plastic, with a metal-coated plastic core, a reinforced metal-coated plastic core, a plastic core coated with gas and moisture impermeable film, a plastic core coated with gas and moisture film and reinforced, which makes it much more structurally resilient. The diffusion path is longer, or in other words, the length and thickness of the gas and moisture impermeable adhesive sealing material is greater in the unit of the present invention, which means that for the same type of material (filling the diffusion path), the longer, narrower diffusion path of the present invention reduces the fill gas loss over other units. The argon gas path is longer because it is confined to the adhesive layers 154 (see Figure 10), whereas in organic spacers the diffusion path runs across the entire width of the spacer surface. The unit shown in Fig. 3 has a metal barrier built in to reduce argon loss. The metal film covering the plastic or the PVDC coated plastic have a thickness of about (0.001-0.003 inches) 0.00254 to 0.00762 centimeters, which is a short diffusion path. The present invention has a so-called long diffusion path, that is, it is longer than about (0.003 inches) 0.00762 centimeters, and also a narrow diffusion path, that is, it is narrower than about 0.125 inches) 0.32 centimeters. The unit detailed in Fig. 10 has a diffusion path length of about (0.250 inches) 0.64 centimeters and a diffusion path width of about (0.010 inches) 0.254 centimeters. The path length can be increased by increasing the height of the spacer legs and the path width can be narrowed by reducing the distance between the spacer legs and the adjacent glass pane.

In actual testing, a unit with the edge assembly of the present invention and a unit with an edge assembly as shown in Figure 3 have shown essentially identical RES values. It is believed that the sealing reinforcement inside the spacer has insulated it from convective cooling by the gases contained in the space.

As previously discussed, the information of the present invention can be used to increase the edge assembly RES value of a unit by using the spacer of Figure 11. Forming a glass fiber reinforced plastic core 164 and then sputtering a fine aluminum film 165 or bonding a gas/moisture impermeable film, such as a PVDC film, using any suitable technique will prevent argon from escaping and essentially limit its path to the sealant or adhesive between the spacer and the glass, as previously discussed for unit 150 of Figure 10.

As can now be seen, the unit of the present invention provides an edge assembly having a metal spacer, a metal-coated plastic spacer, or a plastic spacer or has a multi-layer plastic spacer that can hold insulating gas other than air, such as argon, and also has a relatively high edge assembly RES value or low U-value and structural elasticity.

Now the discussion turns to the U-value of the frame of the unit. The frame also conducts heat and sometimes, for example in the case of metal frames, these conduct significantly more heat than the edge assembly of the unit, so the edge heat loss through the frame overshadows any increase in thermal resistance at the edge of the unit. Wooden frames, metal frames with thermal barriers or plastic frames have a high resistance to heat loss, so the thermal behavior at the edges of the unit, i.e. the heat loss taking place there, would carry more weight.

The invention is not only limited to units with two panes of glass, but can also be used in units with more panes, see, as an example, unit 250 in Fig. 20.

Let us now turn to a discussion of a method of making the glazing unit of the present invention. As will soon be apparent, this unit can be made in any manner.

In Figure 12, an edge strip 169 is shown having substrate 170, sealing reinforcement 160 with moisture permeable adhesive and desiccant 162 mixed therein. In practicing the present invention, the substrate should preferably be a moisture and gas impermeable material (e.g., metal or a plastic composition as previously described) to contain the insulating gas in the interspace and prevent moisture from entering the interspace, and should have structural integrity and resilience to maintain the glass panes at the proper spacing from one another, but also to allow them to undergo a certain degree of thermal volume expansion and contraction typically occurring in the various components of the insulating glazing unit. In practice, in this invention, the substrate was made of 304 stainless steel, having a thickness of about (0.007 inches) 0.0178 centimeters, a width of about (0.625 inches) 1.588 centimeters, and a length sufficient to form a spacer frame positionable between panes of glass of, for example, (24 inches) 0.6 square meters. The sealing reinforcement 160 is made of polyurethane with a desiccant mixed therein. It is applied to a height of about (1/8 inch) 0.32 centimeters and a width of about (3/8 inch) 0.96 centimeters in the center of the substrate 170 using any suitable method.

As previously mentioned, the desiccant reinforcement can be any type of adhesive or polymer material that is moisture permeable and allows for intermixing with desiccant. This allows the desiccant to be housed in the adhesive or polymer material and fixed to the substrate while maintaining communication with the space. The materials recommended in this context, although not part of the patent claim, are polyurethanes and silicones. Furthermore, the sealing reinforcement can also be the spacer dehydrator element described in U.S. Patent No. 3,919,023 (- the information of which is also incorporated herein by reference).

Furthermore, it is possible to provide one or both sides of one or more glass panes with an environmentally resistant coating, such as that mentioned in US-A-4,610,771; 4,806,220; 4,853,256; 4,170,460; 4,239,816 and 4,719,127.

In the implementation of the invention, both the metal substrate after it has been formed into the spacer rod and the sealing reinforcement have sufficient structural strength and elasticity to keep the glass panes separated from each other, but at the same time allow them to undergo a certain amount of thermal volume expansion and contraction that typically occurs in the various components of the glazing unit. In one of the embodiments of the In accordance with the invention, the spacer is structurally more stable than the sealing reinforcement, that is, the spacer is structurally resilient enough to keep the panes separated while the sealing reinforcement is not. In another embodiment of the invention, both the spacer and the sealing reinforcement may be. The sealing reinforcement may, for example, be a desiccant in a special spacer, such as described in Bowser's U.S. Patent No. 3,919,023. As those skilled in the art will know, a metal spacer can be manufactured over a series of curves and shaped to withstand various types of compressive force. The invention relating to the sealing reinforcement 160 applied to the substrate 170 is defined as follows: the substrate 170 (workpiece) is formed into a single-wall U-shaped spacer bar, the resulting U-shaped spacer bar being capable of withstanding the compressive force values necessary to keep the glass panes spaced apart from one another, regardless of the structural stability of the sealing reinforcement. Those skilled in the art will know that the magnitude and value of the compressive forces, as well as the structural stability, vary depending on the type of use of the unit. For example, if the unit is secured in position by clamping the edges of the unit (e.g. in a facade), the spacer must have sufficient strength to hold the glass pane spaced apart while it is under the compressive forces of the clamping operations. When a spacer is used in the stop bar of a wooden frame, and a seam seal is used to seal the unit in situ, the spacer needs just as much structural stability to space the glass panes as one mounted in a clamp-in unit.

The corners of strip 150 are formed in any manner to form the outer legs 156 of spacer 158 of Fig. 10. Strip 170, for example, should be pressed by means of lower cylinders and upper rollers as illustrated in Figs. 13-16.

As far as Fig. 13 is concerned, the strip is passed from left to right between the profile rolling stations 180 to 185. Those familiar with the subject will recognize that the number of profile rolling stations or the number of profile rollers at the individual stations do not represent a requirement of the invention. In Fig. 14, the profile rolling station 180 comprises a lower cylinder 190 with a recess 192 and an upper roller 194 with a recess 196, which are sufficient to accommodate the layer 160. The recess 192 is sized to initiate the bending of the strip 170 into a U-shaped spacer and is less pronounced than the recess 198 of the lower cylinder 200 of the profile rolling station 181 of Fig. 15, as well as those of the other lower cylinders of the downstream rolling stations 182 to 185.

Referring to Figure 16, it is noted that the lower cylinder 202 of the roll forming station 185 has a recess 204 which is entirely U-shaped. The spacer rod extending from the roll forming station 185 is the U-shaped spacer 158 of Figure 10.

It is now also clear that the recesses of the upper profile rollers can be designed accordingly in order to form the material reinforcement on the workpiece.

In the practice of the invention, the sealing reinforcement 160 was applied only after the spacer bar had been formed, i.e., the workpiece had been converted into a U-shaped spacer bar. This was accomplished by pulling the substrate through one of those dies known to convert flat strips into U-shaped ones.

It has been proven that, when comparing under completely equal conditions, a loose desiccant provides better thermal insulation than a desiccant contained in a moisture-permeable material. However, in certain cases, handling a loose desiccant or a spacer with a loose desiccant is also a difficulty or limitation; a desiccant on a moisture-permeable matrix is easier to handle.

In addition, if the desiccant is in a moisture-permeable matrix, the shelf life is longer because the desiccant takes longer to saturate than if it is directly exposed to moisture. The time it takes to saturate depends on the porosity of the material. However, the invention provides for the use of both loose desiccant and desiccant in a moisture-permeable matrix.

The spacer rod 158 can be formed into a spacer frame that is positioned between the panes. As can be seen, the layers 154 and 155 of Figure 10 can be applied to both the spacer rod and the spacer frame. The invention makes no claim on the materials used for the layers 154 and 155; however, it is recommended that the layer 154 provide a high resistance to the flow of the insulating gas in the gap 18 (between the spacer 152 and the panes 12 and 14). The layer 155 can be made of the same material as the layer 154 or of a structural adhesive such as silicone. Before or after the layers 154 and/or 155 are applied to the spacer bar, a piece of the spacer bar is cut and bent to form the spacer frame. Three of the corners may be bent, i.e., continuous corners, the fourth must be welded or sealed using a moisture and/or gas impermeable sealant. Continuous corners of a spacer frame incorporating elements of the present invention are shown in Figures 17 and 19. As can be seen, the spacer frames may also be formed by joining pieces of the spacer bar together and sealing or welding the edges with a moisture and/or gas impermeable sealant.

As for Fig. 18, a section of the spacer rod with sealing reinforcement was cut off and provided with a notch 207 at the expected bending line and The area between the beads is depressed, causing the portion 212 of the outer legs 156 to bend inward at the notch, while the areas on either side of the beads are beveled against each other to form the continuous, superimposed corner 224 shown in Figure 17. The non-continuous corner, ie the fourth corner of a rectangular frame, may be sealed or welded with moisture and/or gas impermeable material. As a result, the sealing reinforcement at the corners may be better removed before the continuous corners are formed.

Referring to Fig. 19, it should be noted that in the practice of the invention, the spacer frame 240 was formed from a U-shaped spacer bar. The continuous corner 242 was formed by lowering the outer legs of the spacer bar against each other while bending portions of the spacer bar around the depression to form a corner, i.e., a 90º angle. As the portions of the spacer bar are bent, the lowered portions 244 of the outer legs move into each other. After the spacer frame was formed, layers of sealant were applied to the outer surface of the legs 156 of the spacer frame and the sealing reinforcement 26 was attached to the inner surface of the center leg of the spacer frame. The unit 10 was assembled by positioning the glass panels in the spacer frame and bonding them with the sealant layers 154 using any suitable method.

If a layer of adhesive 155 has not already been applied to the frame, it is now applied to the edge groove of the unit (see Figure 10) or to the edge itself. Argon is then filled into the gap 18 using any suitable method to thereby obtain an insulating unit having a low thermal conductivity at its edge.

Claims (5)

1. Insulating glazing unit (150) with a pair of glass panes (12, 14) which are fixedly spaced apart from one another and separated by an edge assembly (152) for forming a gas-containing sealed space (18), in which the edge assembly (152) comprises a structurally elastic spacer (158) made of metal with a U-shaped cross-section with two opposite outer legs (156) which are connected to one another by a central leg (157), wherein a moisture- and/or gas-impermeable sealant (154) is arranged on the outer legs (156), which sealant fastens the glass panes (12, 14) to the opposite legs (156) of the spacer (158) and on the surface of the central leg (157) of the spacer facing away from the space (18). spacer (158) a moisture-impermeable seal (155) is present, and provides a gas diffusion path having a thickness of less than 0.32 cm (0.125 inches) and a length of at least 0.32 cm (0.125 inches) so that the gas loss in the space (18) is less than 5% per year, measured according to DIN 52293, and results in an RES value of the edge assembly (152) of at least 10, determined using the ANSYS program. 2. Unit according to claim 1, wherein the space (18) contains an insulating gas. 3. Unit according to claim 1, wherein at least one glass pane has an environmentally resistant coating. 4. The unit of claim 1, wherein the edge assembly (152) further comprises a layer (160) of a moisture-permeable material containing a desiccant (162) on at least a portion of the inside of the spacer (158). 5. The unit of claim 1, wherein the unit further comprises three or more glass panes each separated from each other by an edge assembly (152), the edge assembly (152) and adjacent pairs of glass panes being connected together to form a long, narrow diffusion path, and each edge assembly (152) having a high edge assembly RES value determined using the ANSYS program.