Note: Descriptions are shown in the official language in which they were submitted.
20~9703
A LOW THERMAL CONDUCTING SPACER ASSEMBLY FOR
AN INSULATING GLAZING UNIT AND METHOD OF MAKING SAME
Back~round of the Invention
5 1. Field of the Invention
This invention relates to components for an insulating unit,
an insulating glazing unit and a method of making same and, in
particular, to an insulating glazing unit having an edge assembly to
provide the unit with a low thermal conducting edge, i.e. high
10 resistance to heat flow at the edge of the unit.
2. Discussion of Available Insulatin~ Units
It is well recognized that insulating glazing units reduce
heat transfer between the outside and inside of a home or other
structures. A measure of insulating value generally used is the
15 "U-value". The U-value is the measure of heat in British Thermal
Unit (BTU) passing through the unit per hour (Hr) - square foot
(Sq.Ft.) - degree Fahrenheit (F)
BTU
~Hr-Sq.Ft.F J.
As can be appreciated the lower the U-value the better the
thermal insulating value of the unit, i.e. higher resistance to heat
flow resulting in less heat conducted through the unit.
Another measure of insulating value is the "R-value" which is the
inverse of the U-value. Still another measure is the resistance
25 (RES) to heat flow which is stated in Hr-F per BTU per inch of
perimeter of the unit
~Hr-F ~
~BTU/inJ.
In the past the insulating property, e.g. U-value given for
30 an insulating unit was the U-value measured at the center of the
unit. Recently it has been recognized that the U-value of the edge
of the unit must be considered separately to determine the overall
thermal performance of the unit. For example, units that have a low
center U-value and high edge U-value during the winter season exhibit
35 no moisture condensation at the center of the unit, but may have
condensation or even a thin line of ice at the edge of the unit near
the frame. The condensation or ice at the edge of the unit indicates
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20~9703
that there is heat loss through the unit and/or frame i.e. the edge
has a high U-value. As can be appreciated, when the condensate or
water from the melting ice runs down the unit onto wooden frames, the
wood, if not properly cared for, will rot. Also, the larger
5 temperature differences between the warm center and the cold edge can
cause greater edge stress and glass breakage. The U-values of framed
and unframed units and methods of determining same are discussed in
more detail in the section entitled "Description of the Invention."
Through the years, the design of and construction materials
10 used to fabricate insulating glazing units, and the frames have
improved to provide framed units having low U-values. Several types
of units presently available, and center and edge U-values of
selected ones, are considered ln the following discussion.
Insulating glass edge units which are characterized by
15 (1) the edges of the glass sheets welded together, (2) a low
emissivity coating on one sheet and (3) argon in the space between
the sheets are taught, among other places, in U.S. Patent Application
Serial No. 07/468,039 assigned to PPG Industries, Inc. filed on
January 22, 1990, in the names of P. J. Kovacik et al. and entitled
20 "Method of and Apparatus for Joining Edges of Glass Sheets, One of
Which Has an Electroconductive Coating and the Article Made
Thereby." The units taught therein have a measured center U-value of
about 0.25 and a measured edge U-value of about 0.55. Although
insulating units of this type are acceptable, there are limitations.
25 For example, special equipment is required to heat and fuse the edges
of the glass sheets together, and tempered glass is not used in the
construction of the units.
In U.S. Patent No. 4,807,439 there is taught an insulting
unit marketed by PPG Industries, Inc. under the registered trademark
30 SUNSEAL. The unit has a pair of glass sheets spaced about 0.45 inch
(1.14 centimeters) apart about an organic edge assembly and air in
the compartment between the sheets. A unit so constructed is
expected to have a measured center U-value of about 0.35 and an edge
U-value of about 0.59. Although providing insulating gas e.g. argon
35 in the unit would lower the center and edge U-values, the argon in
time would diffuse through the organic edge assembly raising the
center and edge U-values to those values previously stated.
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The unit of U.S. Patent No. 4,831,799 has an organic edge
assembly and a 8as barrier coating, sheet or film at the peripheral
edge of the unit to retain argon in the unit. The thermal
performance of the unit is discussed in column 5 of the patent. U.S.
5 Patent Nos. 4,431,691 and 4,873,803 each teach a unit having a pair
of glass sheets separated by an edge assembly having an organic bead
having a thin rigid member embedded therein. Although the units of
these patents have acceptable U-values, they have drawbacks. More
particularly, the units have a short length, high resistance
10 diffusion path. The diffusion path is the distance that gas, e.g.
argon, air, or moisture has to travel to exit or enter the
compartment between the sheets. The resistance of the diffusion path
is determined by the permeability, thickness and length of the
material. The units taught in U.S. Patent Nos. 4,831,799; 4,431,691
15 and 4,873,803 have a high resistance, short diffusion path between
the metal strip or spacing means and the glass sheets; the remainder
of the edge assembly has a low resistance, long length diffusion path.
In U.S. Patent No. 3,919,023, there is taught an edge
assembly for an insulating unit that provides a high resistance, long
20 length diffusion path that may be used to minimize the loss of
argon. A limitation of the edge assembly of the patent is the use of
a metal strip around the outer marginal edges of the unit. This
metal strip conducts heat around the edge of the unit, and the unit
is expected to have a high edge U-value.
It was mentioned that the effect of the frame U-value on the
window edge U-value should be taken into account; however, a detailed
discussion of frames having low U-value is omitted because the
instant invention is directed to an insulating glazing unit that has
low center and edge U-values, is easy to construct, does not have the
30 limitations or drawbacks of the presently available insulating
glazing units, and may be used with any frame construction.
Summarv of the Invention
The invention covers an insulating unit having a pair of
glass sheets separated by an edge assembly to provide a sealed
35 compartment between the sheets having a gas therein. The edge
assembly includes a spacer that is structurally sound to maintain the
glass sheets in a fixed spaced relationship and yet accommodates a
2049703
certain degree of thermal expansion and contraction which typically
occurs in the several component parts of the insulating glazing
unit. A diffusion path having resistance to the gas in the
compartment e.g. a long thin diffusion path, is provided between the
5 spacer and the glass sheets, and the edge assembly has a high RES
value at the unit edge as determined using the ANSYS program.
The invention also covers a method of making an insulating
unit. The method includes the steps of providing an edge assembly
between a pair of glass sheets to provide a compartment
10 therebetween. The edge assembly is fabricated by providing a pair of
glass sheets; selecting a structurally resilient spacer, sealant
materials and moisture pervious desiccant containing material to
provide an edge assembly having a high RES as determined using the
ANSYS program and a long thin diffusion path. The glass sheets,
15 spacer, sealant material and desiccant containing materials are
assembled to provide an insulating unit having a high RES at the edge
as measured using the ANSYS program.
The preferred insulating unit of the invention has an
environmental coating, e.g. a low-E coating on at least one sheet
20 surface. Adhesive sealant on each of the outer surfaces of the
spacer having a "U-shaped" cross section secures the sheets to the
spacer. A strip of moisture pervious adhesive having a desiccant is
provided on the inner surface of the spacer.
Further, the invention covers a spacer that may be used in
25 the insulating unit. The spacer includes a structurally resilient
core e.g. a plastic core having a moisture/gas impervious film e.g. a
metal film or a halogenated polymeric film such as polyvinylidene
chloride or flouride or polyvinyl chloride or polytrichlorofluoro
ethylene.
Additionally, the spacer may be made entirely from a
polymeric material having both structural resiliency and moisture/gas
impervious characteristics such as a halogenated polymeric material
including polyvinylidene chloride or flouride or polyvinyl chloride
or polytrichlorofluoro ethylene.
The invention also covers a strip for shaping into spacer
stock for use in the fabrication of insulating units. The strip
includes a metal substrate having a bead of moisture and/or gas
20~9703
pervious adhesive secured to a surface of the substrate. The metal
substrate after forming into the spacer stock e.g. U-shaped spacer
stock can withstand higher compressive forces than the bead.
Further, the invention also covers a method of making
5 U-shaped spacer stock for use in fabricating a spacer frame for
insulating units. The method includes the steps of passing a metal
substrate having a bead of moisture and/or gas pervious adhesive
positioned on a surface between spaced pairs of roll forming wheels
shaped to gradually bend the metal substrate about the bead into
10 spacer stock having a predetermined cross sectional shape, e.g.
U-shaped cross section.
Still further, the invention covers a spacer frame for an
insulating unit, the spacer frame having a groove to define opposed
outer sides and having at least one continuous corner, and methods of
15 making same. A method includes the steps of providing a section of
spacer stock sufficient to make a frame of a predetermined size.
Opposed surfaces of the spacer stock are biased inwardly while the
spacer stock is bent about the depressions of the spacer stock to
form a continuous corner. The step to form a continuous corner is
20 repeated until the opposite ends are brought together and sealed e.g.
by welding.
Brief Descri~tion of the Drawings
Figs. 1 thru 4 are cross sectional views of edge assemblies
of prior art insulating units.
Fig. 5 is a plan view of an insulating unit having a generic
spacer assembly.
Fig. 6 is a view taken along lines 6-6 of Fig. 5.
Fig. 7 is the left half of the view of Fig. 6 showing heat
flow lines through the unit.
Fig. 8 is a view similar to the view of Fig. 7 having the
heat flow lines removed.
Fig. 9 is a graph showing edge temperature distribution for
units having various type of edge assemblies.
Fig. 10 is a sectional view of an edge assembly
35 incorporating features of the invention.
Fig. 11 is a cross section of another embodiment of a spacer
of the instant invention.
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Fig. 12 is a view of an edge strip incorporating features of
the invention having a bead of a moisture and/or gas pervious
adhesive having a desiccant.
Fig. 13 is a side elevated view of a roll forming station to
5 form the edge strip of Fig. 12 into spacer stock incorporating
features of the instant invention.
Figs. 14 thru 16 are views taken along lines 14 thru 16
respectively of Fig. 13.
Fig. 17 is a view of a continuous corner of a spacer frame
10 of the instant invention made using the spacer section shown in Fig.
18.
Fig. 18 is a partial side view of a section of spacer stock
notched and creased prior to bending to form the continuous corner of
the spacer frame shown in Fig. 17 in accordance to the teachings and
15 incorporating features of the inventions.
Fig. 19 is a view similar to the view of Fig. 18
illustrating another continuous corner of a spacer frame
incorporating features of the invention.
Fig. 20 is a view similar to the view of Fig. 10 showing
20 another embodiment of the invention.
Description of the Invention
In the following discussion like numerals refer to like
elements, and the units are described having two glass sheets;
however, as is appreciated by those skilled in the art, units with
25 more than two sheets as shown in Fig. 20 are also contemplated.
With reference to Figs. 1-4 there are shown four general
types of prior art edge assemblies used in the construction of
insulated glazing units. Unit 10 of Fig. 1 includes a pair of glass
sheets 12 and 14 spaced from one another by an edge assembly 16 to
30 provide a compartment 18 between the sheets. The edge assembly 16
includes a hollow metal spacer 20 having a desiccant 22 therein to
absorb any moisture in the compartment and holes 23 (only one shown
in Fig. 1) providing communication between the desiccant and the
compartment. The edge assembly 16 further includes an adhesive type
35 sealant 24 e.g. silicon at the lower section of the spacer 20 as
viewed in Fig. 1 to secure the spacer 20 and the glass sheets
together and a sealant 25 e.g. a butyl sealant at the upper section
-- 7 --
2Q19703
of the spaç;er 20 to prevent the egress of insulating gas i~ the
compartment 18. The edge assembly 16 of the unit 10 i8 similar to
the type of units sold by Cardinal Glass and also similar to *he
insulating units taug~t in U.S. Patent ~08. 2,768,475; 3,919,023;
5 3,974,823; 4,520,611 and 4,780,164~ -
Uhit 30 in Fig. 2 includes the glass s~eets 12 and 14 haring
their etges welded together at 32 to pro~ide the cqmpartment 18. One
of the glass sheets e.g. skQet 12 has a low emissirity coating 34.
- The unit 30 shown in Fig. 2 is similar to the irsulating u~its sold
1~ by P~G In~ustries, I~c. under lts trademark OptimEdge and~is also
similar to the u~its. taught in ~.S. Pate~t ~08. 4,132,539 a~d
~,350,515,.
~ ith refere~ce to Eig. 3 there is show~ u~it 50 taught i~
U.-S. Patent No. 4,831,799,
..jS. The unit 50 has-the gla8s sheets 12 and 14 separated by
an edge assembly 52 to proride the compartment 18. The edge assem~ly
52 includes a moisture pervious foa~ material 54 haring a desiccant
56 therein to absorb moisture i~ t~e compartment 18, a moisture
.imperrious seala~t 58 to prere~t moisture in the.air from moring into
20 t~e compartment 18 an~ a gas barrier coating, sheet or film 60
between t~e foam material 54 and s;ealant 58 to prerent egress of the
: insulatlng gas in the compartme~t 18. Units similar to t~e u~it 5
are taught i~ ~.S. Patent Nos. 4,807,419.
- In Fig. 4 there is shown unit 70 taught in U.S. Patent Nos. 4,431,691 and
25 4,873,803. The unit 70 has the glass sheets 12 and 14 separated by an edge assembly 72 to
~ provide the compar~nent 18. The edge assembly 72 includes a moisture pervious a&esive
74 having a desiccant 76 and a metal member 78 therein.
Before teaching the construction of the insulating unit, more particularly the edge
30 assembly of the instant invention, a discussion of the heat transfer ~rough an insulated unit
is deemed appropriate to fully appreciate the instant invention. In the
.
. ' ; :
- 8 -
2049703
following discussion the U-value will be used to compare or rate heat
transfer i.e. resistance to heat flow through a glazing unit to
reduce heat loss. As is appreciated by those skilled in the art the
lower the U-value the less heat transfer and vice versa. The U-value
5 for an insulating unit can be determined from the following equation.
(1) Ut = (Ac/At)Uc + (Ae/At)Ue + (Af/At)Uf
where U is the measure of heat transfer in British Thermal
Unit/hour-square foot-F (BTU/Hr-Sq.Ft.-F.)
A is area under consideration in square feet
c designates the center of the unit
e designates the edge of the unit
f designates the frame
t is total unit value of the parameter under discussion
Shown in Figs. 5 and 6 is a generic insulating unit 90 having the
15 glass sheets 12 and 14 separated by an edge assembly 92 to provide
the compartment 18. The edge assembly 92 is considered for the
purposes of this discussion a generic edge assembly and is not
limited by design. With specific reference to Fig. 5, the unit 90
for purposes of the discussion has an edge area 94 which is the area
20 between the peripheral edge 95 of the unit and a position about 3.0
inches (7.62 centimeters) in from the peripheral edge, and a central
area 96. The interface between the edge area 94 and center area 96
of the unit 90 is shown in Fig. 5 by dotted lines 98.
The left half of unit 90 shown in Fig. 6 is shown in Fig. 7
25 having the numerals removed for purposes of clarity during the
following discussion relating to heat transfer through the unit.
With reference to Figs. 5, 6 and 7 as required, during the winter
season, heat from inside an enclosure e.g. a house moves through the
edge area 94 and center area 96 of the unit 90 to the outside.
30 Referring now to Fig. 7, at the center area 96 of the unit, the heat
flow pattern is generally perpendicular to the isotherm which is the
major surfaces of the glass sheets 12 and 14 and is illustrated in
Fig. 7 by arrowed lines 100. The direction of the heat flow pattern
changes as the peripheral edge 95 of the unit is approached as
35 illustrated by arrowed lines 102, until at the peripheral edge 95 of
the unit the heat flow pattern is again perpendicular to the major
surface of the glass sheets as illustrated by arrowed lines 104. As
` - - 9 -
2049703
,
can be appreciated by those skilled in the art, a frame mounted about
the periphery of the unit has an effect on the flow patterns, in
particular, flow patterns 102 and 104. For purposes of this
discussion the effect of the frame on flow patterns 102 and 104 is
5 omitted, and the above discussion is considered sufficient to provide
a background to appreciate the instant invention.
The heat flow through the center area 96 of the unit 90 may
be modified by changes in the thermal properties of sheets 12 and 14,
the distance between the sheets and gas in the compartment 18.
lO Consider now the distance between the sheets i.e. the compartment
spacing. Compartments having 8 spacing between about 0 250-0 500
inch (0.63-1.27 centimeters) are considered acceptable to provide an
insulating gas layer with the preferred spacing depending on the
insulating gases used. Krypton gas is preferred at the low range,
15 air and argon are preferred at the upper range. In general, below
0.250 inch (0.63 centimeter) the spacing is not wide enough e.g. for
air or argon gas to provide a significant insulating gas layer and
above O.S00 inch tl.27 centimeters), gas currents e.g. using krypton
gas in the compartment have sufficient mobility to al~ow convection
20 thereby moving heat between the glass surfaces, e.g. between the
glass surface facing the house interior to the glass surface facing
the house exterior.
As previously mentioned, heat flow through the unit may also
be modified by the type of gas used in the compartment. For example,
25 using a ga~ that has a high thermal insulating value increases the
performance of the unit, in other words it decreases the U-value at
the center and edge areas of the unit. By way of example, but not
limiting to the invention, argon has a higher thermal insulating
value than air. Everything else relating to the construction of the
30 unit being equal, using argon would lower the U-value of the unit.
Another technique to modify the thermal insulating value of
the center area is to use sheets having high thermal insulating
values and/or sheets having low emissivity coatings. Types of low
emissivity coatings that may be used in the practice of the invention
35 are taught in U.S. Patent Nos. 4,610,771; 4,806,i20; and 4,853,256. Also
increasing the number of glass sheets increases the number of
-- 10 --
-
2049703
compartments thereby increasing the insulating effect at the center
and edge areas of the unit.
The discussion will now be directed to the thermal loss at
the edge area of the unit. With reference to Fig. 8 there is shown
5 an edge portion of the unit 90 shown in Figs. 5 and 6. The letters A
and E are the points where heat flow is generally perpendicular to
the glass surfaces. As the edge of the unit is approached the glass
begins to act as an extended surface relative to the edge and causes
the heat flow paths 100 to curve or bend at the edge of the unit as
10 illustrated in Fig. 7 by numerals 102. This curvature occurs in the
edge area 94 shown in Figs. 6 and 7. Between the letters B and D the
flow of heat is primarily resisted by the edge assembly 92 rather
than the glass at the unit edge. With reference to Fig. 9 curves
120, 130 and 140 show the edge heat loss for different types of edge
15 assemblies. Fig. 9 should not be interpreted as an absolute
relationship but as a general guide to better understand the heat
flow through the edge assembly. Curve 120 illustrates the heat loss
pattern for an edge assembly that is highly heat conductive e.g. an
aluminum spacer generally used in the construction of edge assemblies
20 of the types shown in Fig. 1. Curve 130 illustrates the heat loss
pattern for an edge assembly that is less heat conductive than an
edge assembly having an aluminum spacer e.g. an edge assembly having
a plastic spacer similar to the construction of the edge assembly
shown in Fig. 3. Line 140 illustrates the edge heat loss pattern for
25 a glass edge unit of the type shown in Fig. 2. Although not limiting
to the invention, the edge assembly incorporating features of the
invention is expected to provide a heat loss pattern similar to curve
140 and heat loss patterns within the shaded areas between curves 130
and 140.
As can be seen in Fig. 9, the profile for an aluminum spacer
represented by the curve 120 shows that the aluminum spacer at the
edge of the unit (between points A and C) offers little resistance to
heat flow thus allowing a cooler edge at the surface of the unit
inside the house. The profile for an organic e.g. polymeric spacer
35 represented by the curve 130 shows the organic spacer to have a high
resistance to heat flow allowing for a warmer glass surface inside
the house resulting in reduced heat loss at the edge of the unit.
20~9703
This is particulsrly illustrated by the curve 130 between points A
and C. Edges of welded glass sheets e.g. as shown in Fig. 2 offer
more resistance than the metal type spacer assembly but less than the
plastic type edge assembly. The temperature distribution of edge
5 welded units between points A and C is represented by the line 140
which is between lines 120 and 130 between points A and C on the
graph of Fig. 9.
The heat loss for an edge assembly using a metal spacer, in
particular an aluminum spacer is greater than for glass because the
10 aluminum spacer has a higher thermal conductivity (aluminum is a
better conductor of heat than glass or organic materials). The
effect of the higher thermal conductivity of the aluminum spacer is
also evident at point D which shows the curve 120 for the aluminum
spacer to have a higher temperature than the curve 140 or the curve
15 130 at the outside surface of the unit. The heat to maintain the
higher temperature at D for the aluminum spacer is conducted from
inside the house thereby resulting in a heat loss at the edge of the
unit greater than the edge heat loss for units having glass or
organic spacers, and greater than the edge assembly of the invention
20 as will be discussed in detail below.
The heat loss for an edge assembly having an organic spacer
is less than the heat loss for edge assemblies having metal spacers
or welded glass because the organic spacer has a lower thermal
conductivity. The effect of the lower thermal conductivity of the
25 organic spacer is shown by line 130 at point D which has a lower
temperature than the glass and metal spacers illustrating that
conductive heat loss through the organic spacer is less than for
glass and metal spacers.
A phenomenon of units having high edge heat loss is that on
30 very cold days, a thin layer of condensation or ice forms at the
inside of the unit at the frame. This ice or condensate may be
present even though the center of the unit is free of moisture.
As was discussed, units that have argon in the compartment
and polymeric edge assemblies may have an initial low U-value, but as
35 time passes, the U-value increases because polymeric spacers as a
general rule do not retain argon. To retain argon an additional film
such as that taught in U.S. Patent No. 4,831,799 is required. The
- 12 - 2049~0~
drawback of the unit of this U.S. Patent No. 4,831,799 is that the
film has a short diffusion path as was discussed supra. As can be
appreciated argon retention can be improved by selection of materials
e.g. hot melt adhesive sealants such as HB Fuller 1191, HB Fuller
5 1081A and PPG Industries, Inc. 4442 butyl sealant retaln argon better
than most polyurethane adhesives.
With reference to Fig. 10 there is shown insulating unit 150
having edge assembly 152 incorporating features of the invention to
space the glass sheets 12 and 14 to provide the compartment 18. The
10 edge assembly 152 includes a moisture and/or gas impervious adhesive
type sealant layer 154 to adhere the glass sheets 12 and 14 to legs
156 of metal spacer 158. The sealant layers 154 act as a barrier to
moisture entering the unit and/or a barrier to gas e.g. insulating
gas such as argon from exiting the compartment 22. With respect to
15 the loss of the fill gas from the unit, in practice the length of the
diffusion path and thickness of the sealant bead are chosen in
combination with the gas permeability of sealant material so that the
rate of loss of the fill gas matches the desired unit performance
lifetime. The ability of the unit to contain the fill gas is
20 measured using a European procedure identified as DIN 52293.
Preferably, the rate of loss of the fill gas should be less than 5%
per year and more preferably it should be less than 1% per year.
With respect to the ingress of moisture into the unit, the
geometry of the sealant bead is chosen so that the amount of moisture
25 permeating through the perimeter parts (i.e. sealant bead and spacer)
is a quantity able to be absorbed into the quantity of desiccant
within the unit over the desired unit lifetime. The preferred
adhesive sealant to be used with the spacer of Figs. 10 and 11 should
have a moisture permeability of less than 20 gm mm/M2 day using ASTM
30 F 372-73. More preferably, the permeability should be less than 5 gm
mm/M2 day.
The relationship between the amount of desiccant in the unit
and the permeability of the sealant (and its geometry) may be varied
depending on the overall desired unit lifetime.
An additional adhesive sealant type layer or structural
adhesive layer 155 e.g. but not limited to silicone adhesive and/or
hot melts may be provided in the perimeter groove of the unit formed
- 13 -
t ! 2 0 ~ 9 7 0 3
by midtle lèg 157 of the spacer and marginal edges of the glass
sheets. As can now be appreciated the sealant is not limiting to the
invention and may be any of the ty~es known in the art e.g. the type
taught in U.S. Patent No. 4,109,43L A thin layer 160 of a moisture pervious
adhesive'having'a desiccant 162 therein to absorb moisture in the
compartment 18 is provided on the inner surface of the middle leg 157
of the spacer 158 as viewed in Fig. 10. The desiccant may also be
placet along the inner surface of the legs 156 as well as the middle
leg 157. The ~ermeability of'the-adhesive layer 160 is not limiting
1Q to the invention but should be sufficiently permeable to moisture
within com~artment 18 80 that the desiccant therein can absorb
moisture within the compartment. Adhesive materials having a
permeability of greater than 2 gm mm/M2 day as determined by the
-above referred to AST,M F 372-73 may be used in the ~ractice of the
~5 invention. The edge assembly 152 provides the unit 150 with a low
thermal conductive path through the edge i.e. a high resistance to
heat 1088, a,long diffusion path and structural integrity with
sufficient structural resilience to accommodate a certain degree of
, thermal expansion and ,contraction which typically occurs in the
20 several component parts of the insulating glazing unit.
To fully a~preciate the high resistance to heat 1088 of the
edge assembly of the instant invention) the following discussion of
the mechanism of thermal conductivity through the edge of an
insulated unit is presented.
The heat 1088 through an edge of a unit is a function of the
thermal conductivity of the materials used, their physical
arrangement, the thermal conductivity of the frame and surface film
coefficient. Surface film coefficient is transfer of heat from air
to glass at the warm side of the unit and heat transfer from glass to
30 air on the cold side of the unit. The surface film coefficient
depends on the weather and the environment. Since the weather and
environment are controlled by nature and not by unit design, no
further ,discussion is deemed necessary. The frame effect will be
discussed later leaving the present discussion to the thermal
35 conductivity of the materials at the unit edge and their physical
arrangement.
- 14 - 20497~3
The resistance of the edge of the unit to heat loss for an
insulating unit having sheet material separated by an edge assembly
is given by equation (2).
(2) RHL = Gl + G2 + ... + Gn + Sl + S2 + -- ~ Sn
where RHL is the resistance to edge heat loss at the edge of the
unit in hour - F/BTU/inch of unit perimeter
(Hr-F/BTU/in.)
G is the resistance to heat loss of a sheet in Hr-F/BTU/in.
S is the resistance to heat loss of the edge assembly in
Hr-F/BTU/in.
For an insulating unit having two sheets separated by a single edge
assembly equation (2) may be rewritten as equation (3).
(3) RHL = Gl + G2 + Sl
The thermal resistance of a material is given by equation
(4)-
(4) R = L/KA
where R is the thermal resistance in Hr-F/BTU/in.
K is thermal conductivity of the material in
BTU/hour-inch-F.
L is the thickness of the material as measured in inches
along an axis parallel to the heat flow.
A is the area of the material as measured in square inches
along an axis transverse to the heat flow/in. of
perimeter.
The thermal resistance for components of an edge assembly
that lie in a line substantially perpendicular or normal to the major
surface of the unit is determined by equation (5).
(5) S = Rl + R2 + -- + Rn
where S and R are as previously defined.
In those instances where the components of an edge assembly
lie along an axis parallel to the ma~or surface of the unit, the
thermal resistance (S) is defined by the following equation (6).
(6) S = 1 + 1 + ... + 1
Rl R2 Rn
where R is as previously defined.
20~9~7i[)3
- 15 -
Combining equations (3), (5) and (6) the resistance of the
edge of the unit 150 shown in Fig. 10 to heat flow may be determined
by following equation (7).
5(7) RHL = R12 + R14 + 2R154 + 2R156 + 1 + 1 +
Rl57 R160 Rl55
where RHL is as previously defined,
R12 and R14 are the thermal resistance of the glass sheets,
Rls4 is the thermal resistance of the adhesive layer 154,
Rlss is the thermal resistance of the adhesive layer 155,
Rls6 is the thermal resistance of the outer legs 156 of the
spacer 158,
Rls7 is the thermal resistance of the middle leg 157 of the
spacer 158, and
R160 is the thermal resistance of the adhesive layer 160.
Although equation (7) shows the relation of the components
to determine edge resistance to heat loss, Equation 7 is an
approximate method used in standard engineering calculations.
Computer programs are available which solve the exact relations
20 governing heat flow or resistance to heat flow through the edge of
the unit.
One computer program that is available is the thermal
analysis package of the ANSYS program available from Swanson Analysis
Systems Inc. of Houston, PA. The ANSYS program was used to determine
25 the resistance to edge heat loss or U-value for units similar to
those shown in Figs. 1-4.
The edge U-value, defined previously, while being a measure
of the overall effect demonstrating the utility of the invention is
highly dependent on certain phenomena that are not limiting to the
30 invention such as film coefficients, glass thickness and frame
construction. The discussion of the edge resistance of the edge
assembly (excluding the glass sheets) will now be considered. The
edge resistance of the edge assembly is defined by the inverse of the
flow of heat that occurs from the interface of the glass and sealant
35 layer 154 at the inside side of the unit to the interface of glass
and sealant layer 154 at the outside side of the unit per unit
increment of temperature, per unit length of edge assembly
_ 16 - 20497~ `
perimeter. The glass sealant interfaces are assumed to be isothermal
to simplify the discussion. Support for the above position may be
found, among other places, in the paper entitled Thermal Resistance
Measurements of Glazing System Edge-Seals and Seal Materials Using a
5 Guarded Heater Plate Apparatus written by J. L. Wright and H. F.
Sullivan ASHRAE TRANSACTIONS 1989, V.95, Pt.2.
In the following discussion and in the claims, a parameter
of interest is the resistance to heat flow of the edge assembly per
unit length of perimeter ("RES").
As mentioned above, the ANSYS finite element code was used
to determine the RES. The result of the ANSYS calculation is
dependent on the assumed geometry of the cross section of the edge
assembly and the assumed thermal conductivity of the constituents
thereof. The geometry of any such cross section can easily be
15 measured by studying the unit edge assembly. The thermal
conductivity of the constituents or the edge assembly RES value can
be measured as shown in ASHRAE TRANSACTIONS identified above. The
following thermal conductivity values for edge assembly materials are
given in the article. Additional values may be found in Principles
20 of Heat Transfer 3rd ed. by Frank Kreith.
MaterialThermal Conductivitv
Butyl .24 W/mC (.011 BTU/hr-in-F)
Silicone.36 W/mC (.017 BTU/hr-in-F)
Polyurethene.31 W/mC (.014 BTU/hr-in-F)
304 stainless steel13.8 W/mC (.667 BTU/hr-in-F)
Aluminum202. W/mC (9.75 BTU/hr-in-F)
Let us now consider the RES calculated for edge assemblies
of the units of Figs. 1-4. The construction of the edge assembly 16
of the unit 10 of Fig. 1 included a hollow aluminum spacer 20 between
30 the glass sheets; the spacer had a wall thickness of about 0.025 inch
(0.06 centimeter), a side length perpendicular to the major surface
of the glass sheets 12 and 14 of about 0.415 inch (1.05 centimeters),
and a side length generally parallel to the ma~or surface of the
glass sheets 12 and 14 of about 0.3 inch (0.76 centimeter); adhesive
35 layers 24 of butyl having a thickness of about 0.003 inch (0.008
centimeter); and a silicone structural seal 16 filling the cavity
formed by the spacer 20 and glass sheets 12 and 14. The edge
~ - 17 - 20~9~7~
assembly RES-value of the unit (10) constructed as above discussed
using the ANSYS program was calculated to be 4.65 hr-F/BTU per inch
of perimeter.
The construction of the edge assembly 32 of the unit 30 of
5 Fig. 2 included a pair of glass sheets spaced about 0.423 inch (1.07
centimeters) apart; an edge wall designated by number 32 having a
thickness of about 0.090 inch (0.229 centimeter). The ed8e assembly
RES-value of the unit 30 constructed as described above using the
ANSYS program was calculated to be 104 hr-F/BTU per inch of
10 perimeter.
The construction of the edge assembly 52 of the unit 50 of
Fig. 3 included a pair of 81ass sheets 12 and 14 spaced about 0.50
inch (1.27 centimeters) apart; a desiccant filled foam structural
member about 0.25 inch (0.64 centimeter) thick adhered to the glass
15 surfaces; an aluminum coated plastic diffusion barrier and a butyl
edge seal about 0.25 inch (0.64 centimeter) thick. The aluminum
coating between the foam member and seal was too thin for accurate
measurement. The edge assembly RES-value of the unit 50 constructed
as above described using the ANSYS program was calculated to be 104.0
20 hr-F/BTU per inch of perimeter.
A unit similar to the unit 50 of Fig. 3 having a pair of
glass sheets 12 and 14 spaced 0.45 inch (1.143 centimeters) apart; an
adhesive layer 54 of silicone having a thickness of about 0.187 inch
(0.475 centimeter) with desiccant therein; a moisture impervious
25 sealant 58 of butyl having a thickness of about 0.187 inch (0.475
centimeter) is expected using the ANSYS program to have an edge
assembly RES-value using the ANSYS program of about 84.7 hr-F/BTU
per inch of perimeter. A comparison of the edge assembly RES-value
for the different constructions of units of the type shown in Fig. 3
30 are given to show the effect material changes and dimensions have on
the edge assembly RES-value.
The construction of the edge assembly of the unit 70 of Fig.
4 included a pair of glass sheets spaced about 0.45 inch (1.143
centimeters) apart; an adhesive butyl edge seal about 0.312 inch
35 (0.767 centimeter) wide with a desiccant and an aluminum spacer about
0.010 inch (0.025 centimeter) thick imbedded therein. The edge
assembly RES-value of the unit 70 constructed as above described
using the ANSYS program was calculated to be 4.50 hr-F/BTU per inch
of perimeter.
- 18 - 20~9703
The construction of the edge assembly 150 of the instant
invention shown in Fig. 10 included a pair of glass sheets spaced
about 0.47 inch (1.20 centimeters) apart; a polyisobutylene layer 154
which is moisture and argon impervious had a thickness of about 0.010
5 inch (0.254 centimeter) and a height as viewed in Fig. 10 of about
0.250 inch (0.64 centimeter); a 304 stainless steel U-shaped channel
156 had a thickness of about 0.007 inch (0.018 centimeter), the
middle or center leg had a width as viewed in Fig. 10 of about 0.430
inch (1.09 centi~eters) and outer legs each had a height as viewed in
10 Fig. 10 of sbout 0.250 inch (0.64 centimeter); a desiccant
impregnated polyurethane layer 160 had a height of about 0.125 inch
(0.32 centimeter) and a width as viewed in Fig. 10 of about 0.416
inch (1.05 centimeters); a polyurethane secondary seal 155 had a
width of about 0.450 inch (1.143 centimeters) and a height of about
15 0.125 inch (0.32 centimeter) as viewed in Fig. 10. The edge assembly
RES-value of the unit 150 constructed as above described using the
ANSYS program was calculated to be 79.1 hr-F/BTU per inch of
perimeter.
Shown in Fig. 11 is the cross sectional view of another
20 embodiment of a spacer of the instant invention. Spacer 163 has a
structurally resilient core 164. The core in the practice of the
invention may be non-metal and is preferably a polymeric core e.g.
fiberglass reinforced plastic U-shaped member 164 having a thin film
165 of insulating gas impervious material. For example when air,
25 argon or krypton is used in the compartment, the thin film 165 may be
metal. The structure of the spacer as well as the gas barrier film
are chosen so that the unit will contain the fill gas for the desired
unit lifetime. A spacer according to Fig. 11 using argon as a fill
gas and employing polyvinylidene chloride as the barrier film, the
30 preferred thickness of the polyvinylidene chloride will be at least 5
mils and more preferably it will be greater than 10 mils.
If a material other than polyvinylidene chloride is used as
the barrier film, the proper thickness to retain the fill gas for the
desired unit lifetime may be ad~usted depending on the material's gas
35 containment characteristics.
The fill gas retention characteristics of the unit according
to the instant invention is measured by the above referred DIN 52293.
_ 19 -
2049703
For argon, the film 165 may be a 0.0001 lnch (0.000254
centimeter) thick aluminum film or a 0.005 inch thick film of
polyvinylidene chloride. As used herein the argon impervious
material has a permeability to argon of less than 5%/yr. The
5 invention contemplates having a core 164 and a thin layer of film 165
or several layers 164 and 165 to build up a laminated structure.
Using the spacer 163 having the aluminum film in place of the spacer
155 of the unit 150 in Fig. 10 the edge assembly RES-value for the
unit 150 of Fig. 10 is expected to be about 120. This is about a 50%
10 increase in the RES-value by changing the spacer to a thinly metal
cladded plastic spacer. Using the spacer 163 having a polyvinylidene
chloride film of a thickness of 0.005 inch, the edge assembly
RES-value of the unit 150 of Fig. 10 is also expected to be about 120.
The instant invention also contemplates having a spacer 163
15 of Fig. 11 whose body is made entirely from a polymeric material
having moisture/gas impervious characteristics. Such a spacer body
may be reinforced (e.g. fiberglass reinforced) but would not include
any film barrier (i.e. the spacer 163 would not include a thin film
165). Such a polymeric material would preferably be a halogenated
20 polymeric material including polyvinylidene chloride, polyvinylidene
flouride, polyvinyl chloride or polytrichlorofluoro ethylene. The
edge assembly of such a spacer 163 made entirely of a polymeric
material would have a high edge assembly RES-value expected to be
comparable to the spacer of Fig. 11.
The spacer of the instant invention, in addition to acting
as a barrier to the insulating gas in the compartment 18, is
structurally sound. As used herein and in the claims "structurally
sound" means the spacer maintains the glass sheets in a spaced
relationship while permitting local flexure of the glass due to
30 changes in barometric pressure, temperature and wind load. The
feature of maintaining the glass sheets in a fixed spacer
relationship means that the spacer prevents the glass sheets from
significantly moving toward one another when the edges of the unit
are secured in the glazing frame. As can be appreciated less force
35 is applied to the edges of residential units mounted in a wooden
frame than to edges of commercial units mounted by pressure glazing
in metal curtainwall systems. Permitting local flexure means the
- 20 -
2049703
spacer allows rotation of the marginal edge portions of the glass
about its edge during loading of the types described while
restricting movement other than rotation i.e. translation. The
degree of structural soundness is related to type of material and
5 thickness. For example metal may be thin where plastic to have the
same structural soundness must be thicker or reinforced e.g. by fiber
glass.
Embodiments of the instant invention may be used to improve
the performance of the prior art units. For example replacing the
10 spacer of the unit 10 of Fig. 1 with a stainless steel spacer is
expected to increase the edge assembly RES-value from 4.65 to 18.2
hr-F/BTU per unit of perimeter. If the metal thickness is changed
from 0.025 inch (0.06 centimeter) to 0.005 inch (0.0127 centimeter)
the edge assembly R-value of the unit 10 of Fig. 1 using the ANSYS
15 program goes from 4.65 to 96.1 hr-F/BTU per inch of perimeter.
Replacing the aluminum strip of the unit in Fig. 4 with a stainless
steel strip increases the edge assembly RES from 4 5 to 44.4
hr-F/BTU per unit of perimeter.
The unit 150 of the instant invention having the spacer
20 assembly 152 shown in Fig. 10 is expected to have an edge heat loss
similar to that of line 140. The unit 150 of the instant invention
having the spacer assembly 163 shown in Fig. 11 is expected to have
an edge heat loss between line 130 and 140 but close to line 130.
Although the edge assembly of the instant invention has an edge
25 assembly RES-value less than the RES-value for edge assemblies having
organic spacers of the type shown in Fig. 3, the edge assembly of the
instant invention has distinct advantages. More particularly, the
spacer is metal, gas and moisture impervious plastic, metal cladded
plastic core, metal cladded reinforced plastic core, gas moisture
30 impervious film cladded plastic core, gas moisture film cladded
reinforced plastic core and is therefore more structurally sound.
The diffusion path i.e. the length and thickness of the gas and
moisture impervious adhesive sealant material is longer in the unit
of the instant invention and therefore for the same type of material
35 filling the diffusion path, the longer, thinner diffusion path of the
instant invention reduces the rate of fill gas loss. The argon gas
path is longer because it is limited to the adhesive layers 154 (see
~- - 21 -
2049703
Fig. 10) whereas in organic spacers the diffusion path is through the
entire width of the spacer surface. In the unit of Fig. 3 a metal
barrier is provided to reduce argon loss. The metal film coated on
the plastic or PVDC coated plastic has a thickness in the range of
5 about 0.001-0.003 inch (0.00254-0.00762 centimeter) which is a short
diffusion path. The instant invention has a long diffusion path e.g.
greater than about 0.003 inch (0.00762 centimeter) and a thin
diffusion path e.g. less than about 0.0125 inch (0.32 centimeter).
The unit shown in Fig. 10 has a diffusion path length of about 0.250
10 inch (0.64 centimeter) and a diffusion path thickness of about 0.010
inch (0.254 centimeter). The path length can be increased by
increasing the height of the legs of the spacer and the path
thickness decreased by decreasing the spacing between the legs of the
spacer and ad~acent glass sheet.
In actual tests a unit having an edge assembly of the
instant invention and a unit having the edge assembly shown in Fig. 3
had essentially identical RES values. It is believed that the bead
on the interior of the spacer may have insulated the spacer from
convection cooling by the gases in the compartment.
As was discussed the teachings of the invention may be used
to increase edge assembly RES-value of a unit by using the spacer
shown in Fig. 11. Shaping a fiberglass reinforced plastic core 164
and then sputtering a thin film 165 of aluminum or adhering in any
convenient manner a gas/moisture impervious film such as a PVDC film
25 prevents the egress of argon limiting the path essentially to the
sealant or adhesive between the spacer and glass as was discussed for
the unit 150 of Fig. 10.
As can now be appreciated the unit of the instant invention
provides an edge assembly having a metal spacer, a metal coated
30 plastic spacer or a plastic spacer or a multi-layered plastic spacer
that retain insulating gas other than air, e.g. argon, has a
relatively high edge assembly RES-value or low U-value and has
structural soundness.
The discussion will now be directed to the U-value of the
35 frame of the unit. The frame also conducts heat and in certain
instances e.g. metal frames conduct sufficiently more heat than the
edge assembly of the unit such that the edge heat loss through the
- 22 -
20~9~03
, !
frame overshadows any increase in thermal resistance to heat 108B
pro~ided at the edge of the unit, Wooden frames, metal frames with
thermal breaks or plastic frames have high resistance to heat 1089
and the performance of the edge heat 1088 of the unit would be more
5 dominant.
The invention is not limited to units having two sheets but
may be practiced to make units having two or more sheets e.g unit
250 shown in Fig. 20
The discussion will now be directed to a method of
10 fabricating the glazing unit of the instant invention. As will be
appreciated the unit of the instant invention may be fabricated in
any manner; however, the construction of the unit is discussed using
selected ones of the edge assembly components taught in U.S. Patent
5,177,916 based on one of the present prior.;ty applications and entitled
15 S~ACE~ AND SPAC~R FRAM3 FOR AN INSULATING G~AZING UNIT AND METHOD OF
MAKING SAMB.
With reference to Fig. 12~ there is shown an edge strip 169
having a substrate 170 having the bead 160 of moisture pervious
adhesive having the desiccant 162 mixed therein. In the preferred
20 practice of the invention the substrate is made of a material, e.g.
metal or composite o~ plastic as previously described, that is
moisture and gas impervious to maintain the insulating gas in the
compartment and prevent the ingress of moisture into the compartment,
and has structural integrity and resiliency to maintain the glass
25 sheets in spaced relation to one another and yet accommodates a
- certain degree of thermal expansion and contraction which typically
occurs in the se~eral component parts of the insulating glazing
unit. In the practice of the in~ention, the substrate was made of
` 304 stainless steel ha~ing a thickness of about 0.007 inch (0.0178
30 centimeter) thick, a width of about 0.625 inch ~1.588 centimeters)
and a length sufficient to make s~acer frame to be positioned between
glass sheets e.g, a 24-inch ~0.6 meter) sguare shaped unit The bead
160 is a polyurethane having a desiccant mixed therein. A bead about
1/8 inch ~0.32 centimeter) high and about 3/8 inch ~0.96 centimeter)
35 wide is applied to the center of the substrate 170 in any con~enient
manner.
- 23 -
204970~
As can be appreciated the desiccant bead may be any type of
adhesive or polymeric material that is moisture pervious and can be
mixed with a desiccant. In this manner the desiccant can be
contained in the adhesi~e or polymer material and secured to the
5 substrate while having communication to the compartment. Types of
materials that are recommended, but the invention is not :imited
thereto, are polyurethanes and silicones. Further the bead may be
the spacer dehydrator element taught in U.S. Patent No. 3,919,023.
Further, as can now be appreciated one or both sides of one
or more sheets may have an environmental coating such as the one
taught in U.S. Patent Nos. 4,610~771; 4,806,220; 4,853,256;
4,170,460; 4,239,816 and 4,719,127. - -
~
In the practice of the invention the metal subs~rate afterforming into spacer stock and the bead has sufficient structural
strength and resiliency to keep the sheets spaced apart and yet
accommodates a certain degree of thermal expansion and contraction
which typically occurs in the several component parts of the
insulating glazing unit. In one embodiment of the in~ention the
spacer is more structurally stable than the bead i.e. the spacer i9
sufficiently structurally stable or dimensionally stable to maintain
the sheets spaced from one another whereas the bead cannot. In
another embodiment of the invention both the spacer and the bead
can. For example, the bead may be a desiccant in a preferred spacer
taught in U.S. Patent No. 3,919,023 to Bowser. As can be appreciated
by those skilled in the art, a metal spacer can be fabricated through
a series of bends and shaped to withstant various compressive
forces. The in~ention relating to the bead 160 carried on the
substrate 170 is defined by shaping the substrate 170 into a single
walled U-shaped spacer stock wlth the resultant U-shaped spacer stock
being capable of withstanding ~alues of compressi~e force to maintain
the sheets apart regardless of the structural stability of the bead.
As can be appreciated by those skilled in the art the measure and
value of compressive forces and structural stability varies depending
on the use of the unit. For example if the unit is secured in
position by clamping the edges of the unit such as in curtainwall
- 24 -
ZC)497~).3
systems, the spacer has to have sufficient strength to maintain the
glass sheet apart while under compressive forces of the clamping
action. When the use is mounted in a rabbit of a wooden frame and
caulking applied to seal the unit in place, the spacer does need as
5 much structural stability to maintain the glass sheets apart as does
a spacer of a unit that is clamped in position.
The edges of the strip 150 are bent in any convenient manner
to form outer legs 156 of a spacer 158 shown in Fig. 10. For example
the strip 170 may be pressed between bottom and top rollers as
10 illustrated in Figs. 13-16.
With reference to Fig. 13 the strip is advanced from left to
right between roll forming stations 180 thru 185. As will be
appreciated by those skilled in the art, the invention is not limited
to the number of roll forming stations or the number of roll forming
15 wheels at the stations. In Fig. 14 the roll forming station 180
includes a bottom wheel 190 having a peripheral groove 192 and an
upper wheel 194 having a peripheral groove 196 sufficient to
accommodate the layer 160. The groove 192 is sized to start the
bending of the strip 170 to a U-shaped spacer and is less pronounced
20 than groove 198 of the bottom wheel 200 of the pressing station 181
shown in Fig. 15 and the remaining bottom wheels of the downstream
pressing station 182 thru 185.
With reference to Fig. 16, the lower wheel 202 of the roll
forming station 185 has a peripheral groove 202 that is substantially
25 U-shaped. The spacer stock exiting the roll forming station 185 is
the U-shaped spacer 158 shown in Fig. 10.
As can now be appreciated the grooves of the upper roll
forming wheels may be shaped to shape the bead of material on the
substrate.
In the practice of the invention the bead 160 was applied
after the spacer stock was formed e.g. the substrate formed into a
U-shaped spacer stock. This was accomplished by pulling the
substrate through a die of the type known in the art to form a flat
strip into a U-shaped strip.
As can be appreciated, everything else being egual, loose
desiccant is a better thermal insulation than desiccant in a moisture
pervious material. However, handling and containing loose desiccant
- 25 - 20497~
in a spacer in certain instances is more of a limitation than
handling desiccant in a moisture pervious matrix. Further having the
desiccant in a moisture pervious matrix increases the shelf life
because the desiccant takes a longer period of time to become
5 saturated when in a moisture and/or gas pervious material as compared
to being directly exposed to moisture. The length of time depends on
the porosity of the material. However, the invention contemplates
both the use of loose desiccant and desiccant in a moisture pervious
matrix.
The spacer stock 158 may be formed into a spacer frame for
positioning between the sheets. As can be appreciated, the layers
154 and 155, shown in Fig. 10 may be applied to the spacer stock or
the spacer frame. The invention is not limited to the materials used
for the layers 154 and 155; however, it is recommended that the
15 layers 154 provide high resistance to the flow of insulating gas in
the compartment 18 between the spacer 152 and the sheets 12 and 14.
The layer 155 may be of the same material as layers 154 or a
structural type adhesive e.g. silicone. Before or after the layers
154 and/or 155 are applied to the spacer stock, a piece of the spacer
20 stock i8 cut and bent to form the spacer frame. Three corners may be
formed i.e. continuous corners and the fourth corner welded or sealed
using a moisture and/or gas impervious sealant. Continuous corners
of spacer frame incorporating features of the invention are shown in
Figs. 17 and 19. However, as can be appreciated, spacer frames may
25 be formed by joining sections of the spacer stock and sealing the
edges with a moisture and/or gas impervious sealant or welding the
corners together.
With reference to Fig. 18 a length of the spacer stock
having the bead is cut and a notch 207 and creases 208 are provided
30 in the spacer stock in any convenient manner at the expected bend
lines. The area between the creases is depressed e.g. portion 212 of
the outer legs 156 at the notch are bent inwardly while the portions
on each side of the crease are biased toward each other to provide a
continuous overlying corner 224 as shown in Fig. 17. The
35 non-continuous corner e.g. the fourth corner of a rectangular frame
may be sealed with a moisture and/or gas impervious material or
~ - 26 - 2~
welded. As can be appreciated the bead at the corner may be removed
before forming the continuous corners.
With reference to Fig. 19, in the practice of the invention
spacer frame 240 was formed from a U-shaped spacer stock. A
5 continuous corner 242 was formed by depressing the outer legs of the
spacer stock toward one another while bending portions of the spacer
stock about the depression to form a corner e.g. 90 angle. As the
portions of the spacer stock are bent the depressed portions 244 of
the outer legs move inwardly toward one another. After spacer frame
10 was formed, layers of the sealant were provided on the outer surface
of the legs 18 of the spacer frame and the bead 26 on the inner
surface of the middle leg of the spacer frame. The unit 10 was
assembled by positioning and adhering the glass sheets to the spacer
frame by the sealant layers 154 in any convenient manner.
A layer lSS of an adhesive if not previously provided on the
frame is provided in the peripheral channel of the unit (see Fig. 10)
or on the periphery of the unit. Argon gas is moved into the
compartment 18 in any convenient manner to provide an insulating unit
having a low thermal conducting edge.
As can be appreciated by those skilled in the art, the
invention is not limited by the above discussion which was presented
for illustrative purposes only.
