Note: Descriptions are shown in the official language in which they were submitted.
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MAT FACED DOCT HOARD AND METHOD OF MANUFACTpRE THEREOF
This invention relates generally to air ducts manufactured
from resin-bonded fiber glass. More specifically, the present
invention relates to an improved air duct manufactured from
resin-bonded fiber glass that includes an improved interior
surface or air surface which provides less air resistance during
use and improved means for sanitizing the air duct.
BAC1CGROOND OF T8E INVENTION
Insulated air ducts are well known. Recent developments in
insulated air ducts include air ducts fabricated from fiber glass
board with a ~metallfc exterior facing. The insulated ducts have
.,the appearance of traditional ducts made from aluminum or
galvanized steel yet include the insulation benefits provided by
the fiber glass board.
However, problems have arisen with the use of fiber glass
board in the fabrication ofyinsulated air ducts. Specifically,
exposed fiber glass board will often accumulate dirt, dust and
microorganisms if not adequately cleaned and it is difficult as
well as expensive to clean the inside of an insulated duct.
Further, fiber glass board is relatively rough which can cause
' turbulent flow at the board surface thereby causing increased
friction loss and requiring additional energy to pump air through
the ducts.
. One previous attempt at solving the aforenoted problems is
the application of an acrylic coating on the interior surfaces of
the air, duct or on the surfaces of the fiber glass board exposed
to the flowing air. It has been found that a layer of acrylic
does provide a smoother surface than exposed resin-bonded fiber
glass board for improved duct efficiency. Further, it is
5. believed that the application of the acrylic will provide a
greater degree of laminar flow immediately adjacent to the board
at corners and other non-straight sections of duct than with
untreated fiber glass board. However, it is also believed that a
significant amount of turbulence still exists during normal
operating conditions even with the use of acrylic coatings. It
is also possible to include biocides in the liquid acrylic before
application to the exposed surface of the board. Biocides help
reduce the accumulation of microorganisms in the air ducts.
Despite the aforenoted advances, the application of acrylic
to fiber glass boards is not deemed to be entirely satisfactory.
First, a smoother interior surface providing a greater degree of
laminar flow adjacent to the anterior surface of the duct board
is desired. The acrylic does not provide as smooth an interior
surface as desired and therefore dirt, dust and microorganisms
still accumulate in the interior surfaces of the ducts. Further,
while the acrylic layer does provide the manufacturer with~an
opportunity to apply some biocides to the interior of the air
ducts, additional biocide treatment is desired. Because
manufacturers often instruct end users not to clean the interior
of the air ducts for fear of damage to the ducts, additional
biocida treatment is desired to reduce the likelihood of the
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accumulation and flourishment of microorganisms in the ducts
during use.
Therefore, there is a need in the insulation and
construction industries for an improved thermally insulated air
duct with an improved interior surface. The interior surface
should be smooth to reduce friction loss and to resist the
-accumulation of dirt and other debris. Further, the interior
surface must be treatable with biocides to reduce the likelihood
of accumulation of microorganisms inside the duct.
SUMMARY OF THE INVENTION
The present invention provides a significant contribution to
the art of manufacturing insulated air ducts by providing an
.;15 improved insulated air duct with a smooth interior surface mat
that may be treated with biocides and further that provides for
increased laminar flow adjacent to the duct board. The present
invention accomplishes this without adding substantially to the
cost of manufacture of insulated duct board or requiring changes
to the general methods of constructing and installing the
insulated dusts.
The improved insulated duct board for constructing insulated
afr ducts includes an outside facing means attached to the
outside surfaces of the fiber glass duct board. in the preferred
embodiment, the outside facing means consists essentially of a
foil-scrim-kraft which is adhered to the outer surface of the
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fiber glass board by a coating of adhesive. The fiber glass
board is preferably fabricated from inorganic glass fibers bonded
by a thermal setting resin to provide a tightly bonded fiber
glass mat. The inside or air surface of the fiber glass board is
again coated with adhesive and an air surface facing means is
applied to the adhesive. In the alternative, an air surfacing
means is coated with adhesive and applied to the fiber glass
board.
In the preferred embodiment, the air surface facing means is
a fabric made from a combination of glass fibers, polyester
fibers and styrene fibers. The preferred fabric for providing
the air surface spacing means is a lightweight, woven or
non-woven, fabric having a weight of about~l5 to about 35 pounds
15~ per 2880 square foot ream of fabric. The air surface facing
means mx~y be treated with biocide before or during fabrication
thereof or after it has been applied to the inner surface of the
fiber glass duct board.
In an alternative embodiment, a layer of acrylic is applied
to the inside surface of the duct board and the air surface
facing means is applied directly to the layer of acrylic or with
an adhesive. A biocide material may be mixed into the liquid
' acrylic material before it fs applied to the fiber glass duct
t5 board or the acrylic material may be coated with a biocide
material after it has been applied to the fiber glass duct board.
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The improved fiber glass duct board is fabricated as
follows. First, a plurality of fiber veils is created using
known means (i.e. flame attenuation technology, rotary spinner
technology, etc.). The fiber veils are deposited on a moving
collection chain to form a fiber blanket. Binder has been
applied to the fiber veils and fumes resulting trom the
application of binder to hot glass fibers are at. least partially
controlled by suction fans disposed underneath the collection .
chain.
l0
The fiber blanket is at least partially compressed
underneath at least one seal roller to form a fiber glass board
before a layer of adhesive is deposited on top of the board via
an over spray applicator. The~air surface facing means is
applied to the upper surface of the board on top of the layer of
adhesive and the board with the air surface facing means adhered
to it is cured in an oven. After the board exits the oven, the
bottom facing, preferably in the form of a foil-scrim-kraft with
adhesive previously applied to it, is adhered to the undersurface
of the now-cured board. The duct board is now ready to be sized
and cut and packaged.
It is therefore an object of the present invention is to
' provide an improved fiber glass duct board with a smooth interior
surface to minimize the collection of dust and dirt inside the
fabricated air ducts.
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Another object of the present invention is to provide an
improved fiber glass duct that provides reduced friction between
the interior surfaces of the duct and the flowing air.,
Yet another object of the present invention is to provide an
improved method of manufacturing fiber glass duct board.
HRIEB DESCRIPTION OF T8E DR7lWINGB
The invention is illustrated more or less diagrammatically
in the accompanying drawings, wherein:
Figure 1 is a partial perspective view of a piece of fiber
glass duct board made in accordance with the present invention:
Figure 2 is a partial side sectional view of a fiber glass
duct board during fabrication, particularly illustrating the
compressed fiber glass blanket or board and air surface facing
means in a flighted oven:
Figure 3 is a partial side sectional view of a completed
fiber glass duct board made in accordance with the present
invention: and
' Figure 4 is a schematic illustration of a method of
manufacturing fiber glass duct board in accordance with the
present invention.
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It should be understood that the drawings are not
necessarily to scale and that the embodiments are sometimes
illustrated as diagrammatic representations and fragmentary
views. Details which are not necessary for an understanding of
the present invention or which render other details difficult to
perceive may have been omitted. It should be understood, of
course, that the invention is not necessarily limited to the
particular embodiments illustrated herein.
DET11ILED DEBCRIPTIOld OF THE INVENTION
Like reference numerals will be used to refer to like or
similar parts from Figure to Figure in the following description
of the drawing.
The dramatic improvement contributed by the present
invention is best understood after consideration of the
conventional materials used in fabricating insulated air ducts.
Specifically, it will be noted that even high quality resin-
bonded fiber glass has a relatively rough surface: The rough
surface causes at least two problems. First, the relatively
rough surface of resin-bonded fiber glass will accumulate dirt,
dust and provide a habitat for microorganisms. Second, the air
flow directly adjacent to the surface at straight sections and
especially at corners is less likely to be laminar and more
5 likely to be turbulent thereby causing friction loss and
increasing the amount of energy needed to pump the air through
the system.' An application of acrylic materials to resin-bonded
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212 ~ ~1'~ ~.
fiber glass duct boards is an improvement over the exposed resin-
bonded fiber glass but still does not provide as smooth a surtace
as desired.
As seen in Figure 1, the duct board l0 includes a
resin-bonded fiber glass board 11 with an upper surface 12 that
carries an interior air surface facing means or air surface mat
13. The exposed surface 13a of the mat 13 is smoother than the
exposed surface 12 of the board 11. The undersurface of the
board li carries a foil-scrim-kraft 14 which is preferably
fire-resistant as well as a vapor retarder.
The mat 13 is preferably attached to the board 11 with a
coating of adhesive (not shown in Figure 1) which is applied to
~15 the board 11 during fabrication as will be discussed with respect
to Figure 4 below. The fire-resistant foil-scrim-kraft (FSK) 14
is attached to the undersurface of the board il by applying a -
coating of adhesive (not shown in Figure l: see Figure 4) to the
FSK l4 prior to adhering the FSK l4 to the undersurface of the
board li: Of course, as will be discussed below, adhesive may be
applied to the undersurface of the board ll for attaching the FSK
14 as opposed to applying the adhesive to the FSK or other
alternative outside facing means id.
ZS Figure 2 is an illustration of one step of the preferred
method of manufacturing the duct board 10 more completely
illustrated in Figure 4. Specifically, the board 11 has been
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compressed and an air surface facing means or air mat 13 has been
applied to the upper surface thereof. The board 11 and facing 13
axe then transported into a flighted oven 15 (see Figure 4). A
top flight'ls is provided with a shoe 17 and a bottom flight 18
is provided with a shoe 19 to create the shiplap ends shown
generally at 21, 22. The shiplap-type edges 21, 22 are useful
for providing duct boards 11 that may be readily fabricated
together with a minimum of cutting. Further, alternative Plights
to those shown at 16, 18 and alternative shoes to those shown at
17, 19 may be provided to fabricate boards with v-grooves, angled
ends (not shown in the Figures).
Figure 3 is a partial view of a finished duct board 10 made
in accordance with the present invention. The upper or inside
surface 12 accommodates the face mat 13 and the lower or outer
surface 23 carries the foil-scrim-kraft 14. The fiber glass
insulation 11 is resin-bonded Piber glass with low thermal
conductivity properties and improved sound absorption
coefficients.
The,prePerred method of manufacturing the duct board 10 is
illustrated in Figure 4. A plurality of fiber glass veils,
indicated generally at 31 are created via rotary spinner means,
or other suitable means for manufacturing glass fibers. The
'S veils 31 are deposited on the collection chain 32 to create a
fiber blanket 33. In the preferred method, negative pressure is
applied underneath the collection chain 32 with suction fans (not
g
CA 02128974 1999-03-15
shown) to control the amount of fumes created by the application
of binder onto the hot glass fibers 31. The fiber blanket 33 is
compressed by a seal roll 34 before adhesive 35 is applied to the
upper surface 12 (see also Figure 1) thereof by an over spray 36.
After the adhesive 35 is applied to the upper surface 12 of the
compressed blanket 33a, the air surface facing means or surface
mat 13 is laid down on top of the adhesive thereby adhering the
mat 13 to the upper surface 12 of the compressed blanket 33a. -
The surface mat 13 is preferably provided in roll form, indicated
generally at 37. The compressed fiber blanket 33a and mat 13 are
then transported into a flighted oven 15 for heating and further
compressing by the top flight 16 and bottom flight 18 (see also
Figure 2). The compressed and now-cured blanket 11 is
transported underneath edge cut saws 38. The bottom facing or
foil-scrim-kraft 14 is provided in roll form indicated generally
at 40. Adhesive is applied to one side of the facing 14 by the
adhesive applicator 41 and the adhesive-bearing surface 14a is
then applied to the undersurface 23 of 'the cured and compressed
blanket 11. Top pressure is supplied b;y the roller 39. The cut
off knife 43 completes the fabrication and the finished boards 10
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are ready t~ bP hffYPlj 4l1 t'h Ctar!lti nr~f orn~ i r~w~nnt /r~~,f-
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CA 02128974 1999-03-15
According to a preferred embodiment, a layer of acrylic
material is deposited on top of the upper surface of the fiber
blanket after the compression of the fiber blanket and before
the application of the coating of adhesive. The layer of
acrylic material being disposed between the air surface means
and the fiber glass board. Furthermore, a biocide is applied
to the layer of acrylic material.
As noted above, the preferred i:abric for the mat 13 is a
blend of glass fibers, polyester fibers and styrene based
polymers. Use of air surface facing means 13 made in
accordance with the present invention reduces the friction loss
correction factors attributable to the friction between the
flowing air and
20
30
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212~~1'~~
the inner or upper surface 12 of the duct board. The preferred
adhesive is a polyvinyl acetate or other resin-based adhesive.
Polyvinyl acetate emulsion can be mixed with a water soluble
biocide and water soluble fire retardants. Polyvinyl acetate and
other adhesives can be used to coat the interior surfaces of the
ducts as well as providing excellent adhesive properties between
the surface mat 13 and the interior surface 12 0! the Tiber glass
board 11. It is deemed preferable, but not an absolute
requirement, to use a water based adhesive. The fire-resistant
foil-scrim-kraft (FSK) or outer facing means 14 also acts as a
vapor retarder and further increases the thermal performance of
the duct.
Returning briefly to Figure 4, the thickness of the fiber
blanket or pelt 33 as it leaves the forming chamber 44 can range
from about six inches to about twenty inches. The temperature of
the (lighted curing oven 15 ranges from about 350'F to about
500'F. The time the duct boards il remain in the oven 15 ranges
from about 1 to about 3 minutes. As shown in Figure 4, the
flights 16, 18 are moving and the speeds range from about 50 to
about 170 feet per minute.
Thus, an improved resin-bonded fiber glass duct board 10 is
provided with a smooth interior surface mat 13 which provides a
smoother surface for less dust and dirt accumulation as well as
less accumulation of microorganisms. Further, the air surface
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mat 13 may also be easily treated with biocides to reduce the
likelihood of accumulation of microorganisms.
. Although only one preferred embodiment of the present
invention has been illustrated and described, it will at once be
apparent to those skilled in the art that variations may be made
within the spirit and scope of the invention. Accordingly, it is
intended that the scope of the invention be limited solely by the
scope of the hereafter appended claims and not by any specific
wording fn the foregoing description.
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