Note: Descriptions are shown in the official language in which they were submitted.
CA 02676111 2011-04-28
AIR DIFFUSER AND METHOD FOR CREATING AN AIR DIFFUSER
Field of the Disclosure
[0001] The patent disclosure generally pertains to discharge air diffusers and
more
specifically to a fabric diffuser with programmed airflow.
Background of Related Art
[0002] There are a wide variety of air diffusers for directing and dispersing
filtered air into
a room. A diffuser's ability to properly direct and thoroughly disperse the
air is particularly
important when the diffuser serves a room that contains a fume hood. A fume
hood is an
exhaust air register typically used for drawing toxic air from a controlled
workstation so that
the toxic air does not escape into the rest of the room. Air diffusers
replenish the volume of
air that the fume hood draws from the room; however, if the diffuser produces
adverse air
currents, the currents of air might blow or draw the toxic air out from under
the fume hood,
thereby allowing the toxic air to escape and circulate throughout the room.
[0003] To address this problem, air diffusers often include louvers or guide
vanes to direct
the airflow in certain directions. In addition to guide vanes, porous
materials have been used
to evenly disperse the air. Although the combination of guide vanes and porous
materials can
provide an effective air diffuser, such a combination of elements can add
unnecessary cost to
the diffuser. Moreover, exposed guide vanes installed downstream of the porous
material can
be unsightly. Alternatively, guide vanes can be internally installed and
hidden by the porous
material, but then the guide vanes can be generally inaccessible, which can
make it difficult
to aim the airflow in a desired direction.
[0004] Consequently, a need exists for a simple yet effective air diffuser
that is particularly
suited for critical applications.
Summary
[0005] In some examples, an air diffuser includes a porous fabric panel with
areas of
different porosities.
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[0006] In some examples, the fabric panel has some regions with a flow
coefficient of
between 80 and 320 cubic feet per minute through an area of one square foot at
a pressure
drop of 0.5 inches of water, and the panel has other regions that have a flow
coefficient of
between 130 and 500.
[0007] In some examples, the regions of different flow coefficients are
adjacent each other
to promote intermixing of air therebetween.
[0008] In some examples, a ratio of the first region's average flow
coefficient to the second
region's average flow coefficient is between 0.3 and 0.9.
[0009] In some examples, a ratio of the first region's area to the second
region's area is
between one and ten.
[0010] In some examples, the fabric panel covers an area of 3 to 20 square
feet such as, for
example, about 8 square feet.
[0011] In some examples, the second region includes a plurality of slits each
of which has
a length and a width, wherein the length is at least three times greater than
the width.
[0012] In some examples, the slits are laser cut into the fabric material by
feeding the
material underneath a pulsating laser.
[0013] In some examples, the slits are substantially parallel to each other.
[0014] In some examples, the diffuser includes a screen that helps break the
velocity
pressure within the diffuser.
[0015] In some examples, areas of relatively high flow coefficient are biased
toward the
ceiling to encourage airflow in that area.
Brief Description of the Drawings
[0016] Figure 1 is a bottom view of one example of an air diffuser.
[0017] Figure 2 is a side view of the air diffuser of Figure 1.
[0018] Figure 3 is cross-sectional end view taken along line 3-3 of Figure 1.
[0019] Figure 4 is an exploded view of Figure 3.
[0020] Figure 5 is a perspective view of a screen used in the diffuser of
Figure 1.
[0021] Figure 6 is a perspective view illustrating a method of creating an air
diffuser.
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Detailed Description
[0022] Figures 1 - 3 show an air diffuser 10 that gently ventilates a room
12 by discharging
air 14 in a strategic flow pattern. The flow pattern promotes thorough
intermixing of the air
yet avoids creating deleterious air currents within the room. Air diffuser 10
includes a fabric
panel 16 with programmed porosity and other integral features that enable
panel 16 to both
disperse and direct the air without having to rely on mechanical louvers or
guide vanes to do
so.
[0023] Basically, fabric panel 16 is attached to and suspended from a back
pan 18 to create
a plenum 20 between the two. A blower, or some other equivalent air mover,
forces air 14
into plenum 20 via an air inlet 22 of back pan 18. The air pressure within
plenum 20 may be,
for example, between 0.1 and 0.25 inches of water higher than that within room
12 so that the
air in plenum 20 forces panel 16 to bulge outward to define a substantially
continuous arced
surface as shown in Figure 3. To control the shape of the diffuser 10 under
pressure (e.g., in a
substantially arced shape), diffuser 10 may include two appropriately shaped
end panels 24
that connect to fabric panel 16. Although end panels 24 may be made of porous
fabric and
may be disposed at an incline (relative to ceiling 26) as shown in Figure 2,
end panels 24
could alternatively be disposed perpendicular to ceiling 26, be impervious to
air, and/or be
made of a rigid, non-fabric material. To evenly distribute the air pressure
across suspended
panel 16, a relatively coarse screen 28 (Fig. 5) may be added to help break
the velocity
pressure of the air traveling from inlet 22 toward panel 16.
[0024] Diffuser 10 can be assembled as shown in Figure 4. End panels 24 can be
sewn or
otherwise joined to fabric panel 16. To help attach and suspend panels 16 and
24 from back
pan 18, a bead 30 extends along the periphery of panels 16 and 24. Bead 30
fits within a slot
32 in a generally rectangular frame 34, and threaded fasteners 36 can be used
to fasten frame
34 to back pan 18, thereby clamping bead 30 between frame 34 and a rim 38 of
back pan 18.
To hold screen 28 in place, additional fasteners 40 can hold four mounting
ears 42 (Fig. 5) of
screen 28 to back pan 18. The assembled diffuser 10 may have, for instance,
nominal
dimensions of two feet by four feet to conveniently fit within a rectangular
opening normally
meant for receiving standard size ceiling tiles. The total area of fabric
panel 16 may be
between three and twenty square feet.
[0025] To thoroughly mix and disperse air 14, the example fabric panel 16
includes two or
more discrete regions that have different flow coefficients so that diffuser
10 releases air 14
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at different flow rates through panel 16, thereby creating an airflow with a
predetermined
pattern and promoting intermixing of adjacent airstreams. In this manner, the
fabric of
diffuser 10 can serve the function of both diffusing the air passing
therethrough as well as
properly separating and directing the airflow. The latter of these functions
is conventionally
achieved with internal guide vanes or louvers behind a diffuser panel. This
conventional
structure can be eliminated by giving the diffuser 10 itself areas of
differing porosity to
thereby separate and direct the airflow to create an airflow of desired
pattern. The areas of
different porosity can be referred to as having differing flow coefficients.
The term, "flow
coefficient" refers to a volumetric flow rate through a given area for a given
pressure drop.
Although the actual units for a flow coefficient may vary, the subject
disclosure will be
described and claimed using units of cubic feet per minute through an area of
one square foot
for an industry-standard pressure drop of 0.5 inches of water. The regions of
different flow
coefficients can be laid out in various locations across panel 16 to program a
certain airflow
pattern that provides a desired effect.
[0026] Referring to Figure 1, in some examples, panel 16 includes a first
region 44 whose
flow coefficient is determined by the inherent porosity of the fabric material
itself Panel 16
can be a polyester fabric with a mock leno weave that provides a flow
coefficient of 80 to
320, and for example, about 160 cubic feet per minute per unit area at a
pressure drop of 0.5
inches of water. A second region 46; comprising areas 46a, 46b, 46c and 46d;
has a flow
coefficient of 130 to 500, and for instance, about 260 cubic feet per minute
per unit area at a
pressure drop of 0.5 inches of water. To ensure thorough air dispersion, a
ratio of the first
region's area to the second region's area may be between one and ten, and a
ratio of the first
region's average flow coefficient to the second region's average flow
coefficient may be
between 0.3 and 0.9.
[0027] Referring to Figure 6, the additional porosity or increased flow
coefficient of region
46 can be produced in various ways including, but not limited to, laser
cutting a plurality of
slits 48 into a fabric sheet 50 that can later be used for making panel 16. To
create slits 48, a
plurality of laser units 52 can be pulsed on and off as sheet 50 is fed across
laser beams 54.
Good airflow characteristics have been achieved, for example, when each slit
is at least three
times longer than they are wide. In some cases, each slit is about 1/8 inch
long, and the slits
are spaced about 1/8 inch apart end-to-end. The slits can run generally
parallel to each other
and be spaced about 3/16 inches apart from side-to-side. The slits can be
grouped to provide
areas 46a, 46b, 46c and 46d of different widths. In some cases, for instance,
areas 46c and
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46d are about 1.5 inches wide (dimension 56), and areas 46a and 46b are about
1.7 inches
wide (dimension 58).
[0028] Areas 46a, 46b, 46c and 46d can be positioned on panel 16 to direct a
disproportionate amount of air in a first general direction (e.g.,
horizontally) near ceiling 26,
thus avoiding the creation of strong currents of air in a second general
direction (e.g..
downward) that might disrupt the operation of a fume hood below diffuser 10.
To accomplish
this, the position of areas 46a, 46b, 46c and 46d can be biased toward a first
upper region 60
and a second upper region 62 of panel 16 (Figs. 1 and 3), wherein a central
lower region 64
has a relatively low average flow coefficient and regions 60 and 62 have a
relatively high
average flow coefficient. Regions 60, 62 and 64 are defined as arced portions
of the panel 16
each comprising one third of panel 16, wherein first upper region 60 lies
along a first lateral
edge 66 of rim 38, second upper region 62 lies along a second lateral edge 68
of rim 38, and
central lower region 64 is interposed between and adjacent to upper regions 60
and 62.
[0029] The nearly horizontal flow at ceiling 26 may be enhanced when panel 16
droops
about 6.5 inches (dimension 70) for a two-foot wide panel as shown in Figure
3. It may also
be helpful to have the wider regions 46a and 46b (which are about 1.7 inches
wide) close to
ceiling 26 and to have the narrower regions 46c and 46d (which are about 1.5
inches wide) a
little farther away from ceiling 26.
[0030] Although the
invention is described with respect to various examples, modifications
thereto will be apparent to those of ordinary skill in the art. For example,
the porosity of the
first region need not be the same as the native porosity of the fabric -
treatment such as
coating and/or perforating the material can be used to set its porosity. The
shape and location
for the areas of different porosity could also be different than those
depicted herein - and
chosen to achieve a desired airflow patterns or characteristics. For example,
while the slits 48
shown on the end panels 24 are parallel to those on the panel 16, they could
be perpendicular
thereto or disposed at some other angle. Given that such modification are
possible without
departing from inventive concepts herein, the scope of the invention, is to be
determined by
reference to the following claims:
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