Note: Descriptions are shown in the official language in which they were submitted.
8290
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IMPROVED THERMAL_BARRIER EXTRUSION
Backqround of the Invention
The present invention relates to thermal barriers.
More particularly, the present invention relates to
thermal barrier extrusions utilized in providing in-
sulated frames for doors and windows.
At the present time, almost half of the aluminum
windows and doors sold in the United States utilize
thermal barrier extrusions. Thermal barrier extrusions
are typically aluminum extrusions used to make the
various parts of windows and doors such as the sash,
sill, threshold, and jamb. In addition they are used to
make the frames for mounting window, spandrel, and door
units. The thermal barrier extrusion generally provides
a longitudinal channel body which de~ines a longitudinal
U-shaped cavity into which is placed an insulating
material, ~uch as polyurethane or epoxy resin, to provide
a thermal barrier for thermal isolation of the mounting.
The most common method for preparing thermal
barriers involves pouring a fast setting polyurethane
liquid casting compound into the U-shaped cavity of the
extrusion. When the compound has hardened, the bottom of
the thermal barrier extrusion is cut away or otherwise
removed. Removal of the bottom of the thermal barrier
extrusion results in a thermal barrier having two
aluminum halves joined together by the polyurethane or
other thermally insulating material. No longer is there
a metallic, heat conducting bridge between the two
halves. Rather, the two halves are separated by the
polyurethane or other thermally insulating material. The
thermally insulating material serves as both a thermal
insulator and additlonally as a connective element.
In spite of their popularity and obvious energy-
saving characteristics thermal barriers suffer from two
major drawbacks or deficiencies. First, repeated temper-
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ature cycling of thermal barriers leads to longitudinal,
end-to-end shrinkage of the thermally insulating material
within the U-shaped cavity of the aluminum thermal
barrier extrusion. The shrinkage results in the formation
of gaps at the ends of the window or door frame extru-
sion. These gaps can cause water or air leakage into the
building with subsequent damage or energy loss. Shrinkage
of the thermally insulating material occurs due to a
complicated process which is not completely understood.
~owever, there is reason to believe that the problem is
caused mainly by the large difference in coefficients of
thermal expansion between aluminum and the thermally
insulating material, such as polyurethane. For example,
aluminum has a coefficient of thermal expansion of l.3 x
10 5 per degree Fahrenheit while that of polyurethane
ranges from 5 to 7 x 10 5 per degree Fahrenheit,
depending on composition. With changes in temperature
the polyurethane or other thermally insulating material
typic~lly expands or contracts more than the surrounding
aluminum. This differential expansion and contraction of
the thermally insulating material ultimately leads to
shrinkage of the thermally insulating material relative
to the extrusion. Since all thermal barriers are
composite structures, they are inherently susceptible to
this shrinkage problem. An effective solution to the
prcblem is highly desirable.
A second problem experienced with some thermal
barriers is insufficient impact strength. Aluminum and
other metallic extrusions are relatively ductile
materials which are relatively resistant to impact.
Polyurethane resin and other typical thermally insulating
materials are relatively brittle. As a result, the
thermal insulation portion of the thermal barrier often
splits and cracks when the thermal barrier is dropped,
cut, sawed or run through a punch press. In addition,
finished window and door assemblies may break d~ring
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installation if not handled carefully. The splitting or
cracking of the thermally insulating material is
extremely undesirable since the material is not only
functioning as insulation, but is additionally a con-
nective element which holds the two aluminum halves ofthe extrusion together.
It is presently desirable to provide thermal
barrier extrusions in which the thermally insulating
material is mechanically bound or otherwise secured
within the extrusion cavity to prevent or reduce
longitudinal shrinkage of the thermally insulating
material. Further, it would be desirable to provide
thermal barrier extrusions in which the tendency of the
thermally insulating material to split, crack or
otherwise fracture is reduced.
Summary of the Invention
According to an aspect of the invention, a
composite structure which is adapted for use as a
thermal barrier comprises:
a metallic channel body having a C shaped left
side, a C-shaped right side facing said left side, an
open bottom extending between the two sides and an open
top def ining a longitudinal thermal barrier cavity,
whèrein said C-shaped sides each includes horizontal top
and bottom portions and a vertical side portion
extending therebetween;
a solid, void free thermally insulating material
located in sàid thermal barrier cavity in an amount
sufficient to substantially fill said thermal barrier
cavity and wherein said thermally insulating material
contracts over a period of time more than said channel
body thereby resulting in longitudinal shrinkage of said
thermally insulating material relative to said channel
body and wherein said insulating material is susceptible
to impact fracture to allow separation of said channel
body left side and right side;
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a plurality of projections attached to said channel
body and extending vertically into said thermally
insulating material from each of said horizontal top and
bottom portions of said C-shaped sides, said projections
having a cross-sectional configuration whose width
increases away from the point of attachment to thereby
provide bidirectional locking of the thermally
insulating material within the channel body to reduce
longitudinal shrinkage of said thermally insulating
material relative to said channel body and increase the
resistance of said channel body to sep ration of said
right and left sides by fracture of said thermally
insulating material.
In accordance with the present invention, the
improved thermal barrier is provided in which shrinkage
of the thermally insulating material relative to the
metal extrusion is substantially reduced and in which
the resistance of the thermally insulating material to
fracturing is also increased.
The present invention is based upon a thermal
barrier which comprises a longitudinal channel body or
extrusion having a left side, a right side, a bottom
extending between the two sides and an open top. The
channel body defines a longitudi,nal thermal barrier
cavity into which thermally insulating material is
introduced. As a feature of the present invention, a
plurality of projections are provided which extend from
the channel body into the thermal barrier cavity. The
projections have cross-sectional configurations whose
width increases beyond the point of attachment of the
projection to t~e cavity wall. In all the prior art the
width of the projections is constant or diminishing
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beyond the point of attachment to the cavity wall.
Examples of the prior art include projections whose
cross-sectional configuration or shape is semi-circular,
square, rectangular, or triangular where the base and not
the apex is the point of at*achment to the cavity wall.
In ways well known to those skilled in the art, the
projections typified by the prior art secure the separate
portions of the aluminum extrusion to the thermally
insulating material to prevent transverse and rotational
movement. However, the prior art projection configura-
tions are essentially uniaxial, acting along the X or
horizontal axis. No provisions are made to prevent
movement of the thermally insulating material along the Y
or vertical axis. We have found if contraction along the
Y axis as a result of low temperature is not prevented,
then longitudinal end-to-end shrinkage of the thermally
insulating material within the channel body cavity
occurs.
Quite unexpectedly it was found that projections of
a certain characteristic cross section or shape drama-
tically reduce or prevent longitudinal end-to-end
shrinkage of the thermally insulating material within the
cavity caused by temperature cycling. Projections whose
cross section or shape includes an increase in width away
from the point of attachment to the cavity ~all prevent
not only transverse and rotational movement of the
aluminum sections as in the prior art, but prevent or
substantially reduce the previously described shrinkage.
As a particular feature of the present invention,
the projections may inc~ude a neck portion attached at
one end to the channel body and a head portion attached
to the other end of the neck. By providing projections
in which the width of the neck portion is less than the
width of the head portion, the tendency of the thermally
insulating material to contract at low temperatures more
than the surrounding aluminum is prevented. In other
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words, because the projections act bidirectionally to
resist movement of the thermally insulating material
along both the X (horizontal) and Y (vertical) axis of
the extrusion, movement along the Z (longitudinal) axis
is also resisted to a remarkable and unexpected degree.
As will be discussed in detail below the projec-
tions in accordance with the present invention provide
another amazing and surprising benefit, namely,
tremendous increases in the impact resistance of the
finished thermal barriers. With the present invention
the resistance to fracturing the thermally insulating
material during manufacture and installation is greatly
reduced.
Brief Descri~tion of the Dr~
Fig. 1 is a cross-sectional view of a prior art
thermal barrier extrusion having square projections and a
flat bottom.
Fig. 2 is a cross-sectional view of a prior art
thermal barrier extrusion having rounded projections and
a recessed bottom.
Fig. 3 is a cross-sectional view of a prior art
thermal barrier extrusion having rounded projections and
a flat bottom.
Fig. 4 is a cross-sectional view of a prior art
thermal barrier extrusion having square projections and a
recessed bottom.
Fig. 5 is a cross-sectional view of an exemplary
longitudinal channel body in accordance with the present
3~ invention in which the thermal barrier cavity is empty.
Fig. 6 is a detailed sectional view of the channel
body shown in Fig. 5 wherein the thermal barrier cavity
is filled with thermally insulating material.
Fig. 7 is a cross-sectional view of a second
exemplary thermal barrier extrusion in accordance with
the present invention.
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Fig. 8 is a perspective view of a third exemplary
longitudinal channel body and associated frame members
prior to filling of the thermal barrier cavity with
thermally insulating material.
Fig. 9 is a detailed sectional view of Fig. 8
showing the channel body.
Fig. 10 is the same as Fig. 9 except that the
thermal barrier cavity has been filled with thermally
insulating material.
Fig. 11 shows the final thermal barrier in which
the middle bottom portion of the channel body has been
removed and a window pane has been mounted in place.
Fig. 12 is a cross-sectional view of a fourth
exemplary thermal barrier extrusion in accordance with
the present invention.
Fig. 13 is a cross-sectional view of a fifth
exemplary thermal barrier in accordance with the present
invention.
Detailed Description of _he Inventio
A partial sectional view of a prior art thermal
barrier is shown generally at 10 in Fig. 1. The thermal
barrier 10 includes a longitudinal channel body 12 having
a left side 14, a right side 16, a bottom 18, and an open
top 20. The channel body 12 defines a longitudinal
thermal barrier cavity 22 which is filled with thermally
insulating material 24. The channel body 12 includes
four longitudinal projections 26 which extend from the
channel body into the thermal barrier cavity. The ends
of ridges 26 have a square cross sectional shape. The
bottom 18 of channel body 12 includes a central portion
28 (shown between the vertical phantom lines) which is
removed from the channel body 12 to provide the finished
thermal barrier in which the right and left halves of the
channel body are connected together only by the thermally
insulating material 24.
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A second prior art thermal barrier is shown gen-
erally at 30 in Fig~ 2. The thermal barrier 30 includes
a channel body 32 having a left side 34, a right side 36,
a bottom 38 and an open top 40. The body 32 defines a
thermal barrier cavity 42 which is filled with thermally
insulating material 44. The channel body 32 includes four
proiections 46 which extend into the cavity 42. The
projections 46 are basically the same as the projections
26 shown in Fig. 1 except that the ends of the ridges 46
are rounded. The channel body 32 includes a recessed
bottom portion 48 (bounded on each end by horizontal
phantom lines) which is removed to provide the finished
thermal barrier in which the two channel body sides are
connected together by the thermally insulating material
44.
A third exemplary prior art thermal barrier is
shown generally at 50 in Fig. 3. The thermal barrier 50
includes a channel body 52 having a left side 54, a right
side 56, a bottom 58 and an open top 60. The channel
body 52 defines a thermal barrier cavity 62 which is
filled with thermally ins~lating material 64. The
channel body ~2 includes projections 66 which extend
inward into the cavity 62. The projections 66 are the
same as the projections 46 shown in Fig. 2. The channel
body 52 also includes a flat central portion 68 (shown
between vertical phantom lines) which is removed to
provide the finished thermal barrier in which the two
channe~ body sides are connected together by the
thermally insulating material 64.
A fourth exemplary prior art thermal barrier is
shown generally at 70 in Fig. 4. The thermal barrier 70
includes a channel body 72 having a left side 74, a right
side 76, a bottom 78, and an open top 80. The channel
body 72 defines a thermal barrier cavity 82 which is
filled with thermally insulating material 84. The
channel body 72 includes projections 86 which extend into
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the cavity 82. The projections 86 are the same as the
pro]ections 26 shown in Fig. 1. The channel body 72 also
includes a recessed bottom portion 88 which is similar in
design to the bottom portion 48 shown in Fig. 2. The
bottom portion 88 is also designed to be removed to
provide the finished thermal barrier in which the right
and left sides of the channel body are connected together
by the thermally insulating material 84.
A first exemplary thermal barrier in accordance
with the present invention is shown generally at 90 in
Figs. 5 and 6. The thermal barrier 90 includes a
longitudinal channel body 92 which includes horizontal
frame members 94 as shown in Fig. 5. The frame members
94 do not form any part of the invention and are included
as showing exemplary structures which are included as
part of the overall door or winaow frame. The channel
body 92 includes a left side 95, right side 96, bottom 98
and an open top 100. The channel body 92 defines a
thermal barrier cavity 102 which is filled with thermally
insulating material 104 (see Fig. 6).
The channel body 92 includes four projec~ions 1~6.
The projections 106 each includes a head portion 110
which is connected directly to the horizontal portions
10~ of the channel body. As can be seen from Fig. 6, the
width as indicated in phantom at 112 of the projection
106 increases beyond the point of attachment of the
projection 106 to the channel body 92.
As previously mentioned it was discovered in
accordance with the present invention that projections
whose width increases beyond the point of attachment
create bidirectional locking of the thermally insulating
material within the channel body. This bidirectional
locking prevents movement during temperature cycling not
only in the X (horizontal) axis, but in the Y (vertical)
axis as well. When movement in the Y and X axes is
restrained or prevented, movement in the Z (longitudinal)
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axis is also prevented to a surprising degree. In
general, projections whose width increases beyond the
point of attachment to the channel body can be further
described as having a neck attached to the channel body
and a head which is wider than and is attached to the
neck.
The channel body 92 includes a central bottom
portion 114 which is similar to the bottom portions 48
and 88 shown in Figs. 2 and 4. Bottom portion 114 is
also designed to be removed to provide a finished thermal
barrier having two U-shaped channel body sides 95 and 96
connected together by the thermal insulating material
104.
A second exemplary embodiment is shown generally at
116 in Fig. 7. The second embodiment includes a longi-
tudinal channel body 118 which includes a left side 120,
right side 122, bottom 124, and open top 126. The
channel body 118 defines a thermal barrier cavity 128
which is filled with thermally insulating material 130.
The channel body 118 includes projections 132. The
projections 132 each include a head portion 136 and a
neck portion 138 located between the horizontal side
portion 134 of the channel body 118 and head portion 136.
The embodiment shown in Fig. 7 is basically the same as
the embodiment shown in Fig. 6 except that the interior
side 140 of the horizontal portion 134 is sloped inward
to produce a clearly defined neck portion 138. The head
portion 136 may be characterized as having an oval shaped
cross section including a middle portion and rounded
edges located on each side of the middle portion. The
oval shaped head 136 is connected to the neck 138 at the
middle portion of the head.
The extrusion bottom 124 also includes a central
bottom portion 125 which is removed to provide the final
thermal barrier having two channel body sides connected
together by the thermally insulating material 130.
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Thermal cycling tests were conducted to determine
the percent of shrinkage of various thermally insulating
materials when placed within the various channel bodies
shown in Figs. 1-7. The thermally insulating materials
tested were polyurethane resins available commercially
and referred to as Product A, Product B, Product C,
Product D and Product E. Product A and Product B are
medium strength, fast curing polyurethane materials.
Product C is a high strength, heat resistant polyurethane
material. Product D is a low strength, low heat
resistant polyurethane material and Product E is a high
strength, high heat resistant polyurethane material.
Aluminum extrusions having the six different cavity
designs set forth in Figs. 1-7 were filled with each of
the above five polyurethane materials and cured according
to conventional procedures. Three specimens of each
filled thermal barrier extrusion were then subjected to
twenty temperature cycles. The temperature cycles were
as follows: 4 hours at -40F followed by 1 hour at 75F
followed by 4 hours at 180F followed by 15 hours at 75F
to thereby provide a total timè of 24 hours for each
cycle.
The results of the shrinkage testing are summar-
ized in Table l. As the results show, the extrusion
designs in accordance with the present invention (Figs.
5-7) provide reduced polyurethane shrinkage for those
materials which exhibited shrinkage in the prior art
cavity designs shown in Figs. 1-4.
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The cavity design shown in Figs. 6 and 7 was
further tested under contaminated surface conditions
which promote thermal insulation shrinkage. In these
tests, three different thermally insulating materials
(Product ~, Product C, Product E) were used. Prior to
filling the extrusion with insulating material, the
extrusion was dipped in a 1~ by weight solution of
Cerechlor~ S-45 chlorinated paraffin (available from
Diamond Shamrock Co.) in methyl ethyl ketone and the
solvent allowed to flash off. In one instance a ten % by
weight solution of Cerechlor S-45 in methyl ethyl ketone
was used. The oily residue on the surface o~ the
extrusion prior to filling was quite perceptible for the
1% solutions. The 10% ~olution dip left the extrusion
sticky to the touch. The chlorinated paraffin was
deliberately chosen for contaminating the extrusion to
promote insulating material shrinkage since it is a
common ingredient in extrusion die lubricants. Three
sample~ for each insulation material/contaminated
extrusion combination were tested by subjecting them to
twenty thermal cycles as described above. ~o shrinkage
of any of the materials was detected including the
extrusion which was contaminated with the 10% Cerechlor
S-45 solution.
Impact testing of four of the above listed insu-
lation material~ (Product B, Product C, Product D and
Product E) was conducted on the extrusion cavity designs
shown in Figs. 1-7. The impact testing was designed to
measure resistance to breakage of the thermally
insulating material along the longitudinal axis of the
finished extrusion where the bottom portions (28, 48, 68,
88, 114 and 125) have been removed. Three inch lengths
of the fini~hed extrusions were fixed along one side and
an impact point was located two inches away from the
fixed side of the extrusiGn which was on the other side
of the insulating material. This provided a two inch
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moment arm for the impact tests.
The results of the impact tests are shown in Table
II. The values are given in foot-po~nds per three inch
extrusion length at 77F and are an average of ten
determinations.
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AS can be seen from the test results shown in Table
II, the extrusion designs (Figs. 5-7) in accordance with
the present invention provide consistent increases in the
resistance of the thermally insulating materials to
breakage along the longitudinal axis extending between
the two aluminum extrusion halves.
A third exemplary embodiment in accordance with the
present invention is shown generally at 150 in Figs.
8-11. This embodiment includes a longitudinal channel
body 152. As shown in Fig. 8, the channel body 152 is
attached to and supported by auxillary fin structures 154
and 156. These fin structures are typically aluminum
extrusions which are extruded along with the 'ongitu-
dinal channel body 152 to provide additional frame
structure for mounting into the door or window opening.
The auxillary fin structures 154 and 156 do not form a
part of the invention and are included for illustrative
purposes only.
Referring to Fig. 9, the channel body 152 includes
a left side 158, a right side 160, a bottom 162, and an
open top 164. The sides 158 and 160 extend upward as at
166 and 168, respectively, to provide a channel or window
mounting flange mean~ into which a window pane or other
structure is seated. The channel body 152 defines a
thermal barrier cavity 170 into which thermally insula-
ting material is introduced. The channel body 152
further includes upper projections 172. The upper
projections 172 each includes a neck portion 176 which is
attached to horizontal portion 174 of the channel body
and head portion 178. The projections 172 are basically
the same as the projections 132 shown in Fig, 7 except
that the projections 172 each includes an outwardly
extending surface 180 along the necX portion 176. The
outwardly extending surface 180 increases the width of
the neck portion 176 and also modifies the oval shape of
the head 178 to provide the cross-sectional design shown
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in Fig. 9.
The channel body 152 includes lower projections
182. The lower projections 182 are ~he same as the
projections 132 shown in Fig. 7. If desired, the upper
and lower channel projections 172 and 182 may be
reversed. Also, a structure in which all of the
projections have the cross-sectional configuration of
projections 172 is possible in accordance with the
present invention.
Fig. 10 shows the channel body 152 after it has
been filled with thermally insulating material 184.
After the thermally insulating material 184 has cured,
the central bottom portion 186 is removed to provide the
finished thermal barrier shown in Fig. 11. In the
finished thermal barrier, the thermally insulating
material 184 provides thermal insulation between the
remaining left side 158 and right side 160 of the channel
body 152. As further shown in Fig. 11, a window 187 is
mounted within the channel body 152 utilizing a suitable
sealant material 188 which is well ~nown in the art.
A fourth exemplary thermal barrier extrusion is
shown generally at 190 in Fig. 12. The fourth exemplary
thermal barrier 190 includes a channel body 192 having a
left side 194, a right side 196, a bottom 198 and an open
top 200. The central bottom middle portion 202 which is
bounded by horizontal phantom lines is designed to be
removed after the thermally insulating material 204 has
been poured into the thermal barrier cavity 206 and
cured. As with the other embodiments, removal of the
middle bottom portion 202 provides the finished thermal
barrier wherein the left side 194 and right side 196 of
the channel body 192 are separated by the thermally
insulating material 204. The channel body 192 includes
lower projections 208. The lower projections 208 are
basically the same as the projections 106 shown in Fig.
6. The channel body 192 further includes upper
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projections 210. The upper projections 210 are similar
to the lower projections 208, except that outer surface
212 is provided to produce a modified head portion where
the oval shape of the head portion is modified as shown
in Fig. 12.
A fifth exemplary thermal barrier extrusion is
shown generally at 214 in Fig. 13. The barrier 214
includes a channel body 216 having a left side 218, right
side 220, bottom 222 and open top 224. The channel body
10216 defines a thermal barrier cavity 226 into which
thermally insulating material 228 is introduced. The
channel body 216 is basically the same as the channel
body 192 shown in Fig. 12 except that different
projections 230 are provided.
15The projections 230 each includes a neck portion
234 which is connected to horizontal portion 232 of the
channel body and head portion 236. The head portion 236
has a circular cross section and includes a notched
portion 238 adjacent to the neck portion 234 and located
on the side of the head 236 closest to the channel body
side. The projection 230 configuration shown in Fig. 1~
is particularly preferred because the notch 238 provides
an added gripping channel for mechanically locking the
thermally insulating material 228 within the thermal
barrier cavity 226.
In addition to the polyurethane materials pre-
viously listed, any of the other known polyurethane
resins or foams may be utilized so long as they provide
the desired thermal insulation. In addition, other
thermally insulating materials such as epoxy resins may
be utilized. The channel body is preferably made from a
metal or metal alloy. Aluminum and aluminum alloys are
the preferred channel body or extrusion material. Any of
the metals known and commonly used to prepare thermal
barrier extrusions are suitable for use in accordance
with the present invention.
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Having thus described exemplary embodiments of the
present invention, it should be noted by those skilled in
the art that the within disclosures are exemplary only
and that various other alternatives, adaptations and
modifications may be made within the scope of the present
invention. Thus, by way of example and not of limita-
tion, if desired, a channel body can be made in which
more than four channel projections are utilized and in
which each of the projections has a different cross-
sectional configuration. Accordingly, the present
invention is not limited to the specific embodiments as
illustrated herein, but is only limited by the following
claims.
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