Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"MULTI-STAGE HOOD FILTER"
FIELD OF THE INVENTION
[0001] The present invention relates generally to filters for use in exhaust
hoods and,
more particularly, to multi-staged filters for use within such hoods.
BACKGROUND
100021 In a typical restaurant kitchen, a plurality of cooking units are lined
up side by
side in a row under common exhaust hoods. The cooking units may include, for
example,
ranges, griddles, fryers, and broilers. The cooking processes performed on
such
equipment all produce air laden with grease, smoke, fumes, moisture, heat, and
other
particles in varying amounts and temperatures. The air is drawn in to the
exhaust hood,
where it is filtered. One known filtration system i s disclosed in U.S. Pat,
No. 7,581,539
B2 to Aviles at al., the disclosure of which is hereby incorporated by
reference.
BRIEF SUMMARY
100031 In accordance with a paiticular embodiment, a multi-staged grease
filtration
system is designed to completely fit inside of a standard two inch wide baffle
filter
channel in a ventilation hood. The system includes a first filter and a second
filter,
operatively disposed in series, The first filter includes a filter material
with an upstream
surface and a downstream surface, an external support element abutting either
the
upstream or downstream surface, and is configured to be mounted within the
upstream
side of the second filter. The external support may attach to the filter
material without the
use of any additional support on the opposite side of the filter material. The
second filter
is configured to be mounted within the ventilation hood, has a perforated air
diffuser in a
middle portion of a housing of the system, a flame barrier, and an upstream
opening that
holds the first filter.
100041 The first filter may be disposed upstream or downstream of the second
filter.
100051 The first filter may comprise: a filter material comprising a first and
second
surface opposite the first surface; an exterior support structure abutting one
of the first
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surface and the second surface of the filter material; one or more fastening
elements
disposed adjacent the periphery of the side of the exterior support structure
that is
abutting the one of the first surface and the second surface, the one or more
fastening
elements configured to hold the filter material substantially in place with
respect to the
exterior support structure, wherein the exterior support structure gives
rigidity to the filter
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] For a more complete understanding of the embodiments of the present
invention,
needs satisfied thereby, and the objects, features, and advantages thereof,
reference now
is made to the following description taken in connection with the accompanying
drawings.
100071 FIG. 1 is a perspective view of filter assemblies mounted in an exhaust
hood
above a cooking apparatus, according to an embodiment of the invention.
10008] FIG. 2 is a perspective view of a filter assemblies being lifted by a
mounting tool
into an opening in the exhaust h.00d, according to an embodiment of the
invention.
100091 FIG. 3 is perspective view of the components of the filter assembly
with the
external support structure removed and the filter material folded back inside
of the
opening within the second filter, according to an embodiment of the invention.
[0010] FIG, 4 is a front isometric view of the filter assembly, according to
the
embodiment of the invention.
[0011] FIG. 5 is a schematic cross-sectional view of the filter assembly,
according to an
embodiment of the invention
[0012] FIG. 6 is a back isometric view of the filter assembly, according to an
embodiment of the invention.
[0013] FIG. 7 is an enlarged front view of the first filter, according to an
embodiment of
the invention.
100141 FIG. 8 is perspective view of the bottom of the filter assembly,
according to an
embodiment of the invention.
[OHS] FIG, 9 is an exploded perspective view of the filter assembly, according
to an
embodiment of the invention.
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100161 FIG. 10 is an exploded perspective view of the filter assembly,
according to an
embodiment of the invention.
DETAILED DESCRIPTION
100171 Commercial exhaust hoods manufactured to be installed in the U.S. must
comply
with certain codes and standards, such as the -National Fire Protection
Associates (NFPA)
Standard 96. This standard requires that all hoods used in commercial cooking
establishments that are installed over cooking equipment that creates
effluents other than
heat and steam, such as gease, during the cooking process include grease
removal
devices that are individually listed in accordance with Underwrites
Laboratories (UL)
Standard 1046, or as components of UL 710 listed hoods This standard requires
grease
removal devices to be able to prevent the spread of fire from the upstream
face of the
filter to an area downstream of the filter.
[0018] Since standard exhaust hoods have a two inch wide filter channel for
the standard.
two inch thick baffle filters, other embodiments of disposable grease filters
that are fiber
based may require welding or drilling to modify the exhaust hood and/or
existing baffle
filters since there is no space within the filter channel to fit the
additional disposable
grease filter adjacent the baffle filters.
[0019] Example embodiments of this disclosure include a multi-staged grease
filtration
system designed to completely fit inside of a standard two inch wide baffle
filter channel
in a ventilation hood including a first filter with high efficiency grease
filtration
capabilities, and at least one second filter located downstream (with respect
to the
direction of air flow through the filter and hood) of the first filter. The
first filter includes
filter material attached to an external support structure that is made of
relatively more
rigid material. The second filter is preferably effective at preventing the
spread of fire
from the upstream face of the filtration system to an area downstream of the
system.
[0020] The second filter may be any filter that drains grease out of the
filter, and is
preferably also an effective fire barrier. One example of a filter for a
ventilation hood that
drains grease to a grease drain and is an effective fire barrier is a baffle-
type filter, such
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as that disclosed in U.S. Pat. No. 3,910,782 to Struble et al, the disclosure
of which is
hereby incorporated by reference.
[0021] It is understood that other grease-draining and fire barrier filters
are within the
spirit and scope of the embodiments of the present disclosure.
[0022] A baffle filter is very effective at preventing fire from traveling
downstream as
required by UL Standard 1046. However, while the baffle filter is satisfactory
at filtering
out grease with a particle size of greater than about 10 micrometers ([tm),
but it is less
effective with smaller particles. Therefore, embodiments of the present
invention further
include a first disposable or permanent filter, located upstream of the second
filter in the
airflow direction, the second filter being separate to the first filter.
Moreover, baffle
filters are difficult to clean and re-use so it is beneficial to have a
disposable filter
upstream from the baffle filter.
[0023] In particular embodiments, the filter material is made, in whole or in
part, of
fibers, such as natural, synthetic, and/or hybrid fibers, with or without a
stabilizer frame,
such as, for example and without limitation, the filter disclosed in U.S. Pat.
No,
8,277,530 B2 to Alexander et al., the disclosure of which is hereby
incorporated by
reference. In other embodiments, the filter material is made, in whole or in
part, of wool
fiber, such as, for example and without limitation, the filter disclosed in
U.S. Patent No.
6,293,983 to More, the disclosure of which is hereby incorporated by
reference.
[0024] A recent change in the UL 1046 standard now allows for testing of so-
called
"multi-stage" filters. Materials that cannot and could not pass the fire
safety requirement
of the standard individually may be utilized if the filter assembly as a whole
can pass the
tests mandated by the standard.
[0025] Embodiments of the present disclosure thus provide a filtration system
with both a
first filter and a second filter, in which the second filter is a very
effective fire barrier, and
the first filter is very effective at entrapping particulates. The resulting
combination
provides superior performance in both respects, while simplifying the
installation
procedure and reducing the renewable costs associated with disposable filter
material.
[0026] In some embodiments, the first filter is made, in part, of metal mesh
or fibers,
such as natural, synthetic, and/or hybrid fibers, such as, for example and
without
limitation, wool fibers, wood-based viscose fibers, and cellulose-based
synthetic fibers.
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The blend of fibers may include blending wool fibers with flame resistant
viscose fibers;
carding the blend into a fiber web; spraying the fiber web with a binder;
needle punching
the fiber web into a non-woven blanket; and applying a bonding emulsion to the
wool
fibers. Particular embodiments may further comprise applying a vacuum to the
non-
woven blanket and/or passing the non-woven blanket through an oven at over 280
degrees Fahrenheit. In some embodiments, the first filter is made of organic
material,
such as natural organic material. In some embodiments, the second filter is
made of
animal-derived organic material, such as wool.
[0027] Other filter materials are within the scope of the appended claims.
[0028] The material of the first filter may be disposed adjacent to or
attached to an
external support structure made of relatively more rigid material. While fiber
filters are
advantageous for their particle filtration abilities, their rigidity is
similar to that of paper
towels if an internal frame, or an external housing that sandwiches the filter
material
between two surfaces, is not present. Internal frame options result in
expensive
manufacturing costs, while a sandwiching external housing that sandwiches the
filter
material between two surfaces compresses the filter material resulting in less
grease
loading capabilities while increasing airflow resistance. For this reason,
their use is
limited despite their filtration properties.
[0029] By attaching a single surface of the fiber material to one surface of
an external
support structure, the drawbacks caused by the fiber material's lack of
rigidity may be
rectified. In a particular embodiment, the external support structure may
contain fastening
elements that grip the filter material to hold it in place. In this way, the
material may gain
rigidity for easier installation and removal, while mounting its original
loft, density,
grease loading abilities and minimal airflow resistance.
[0030] As set forth above, the first filter may be installed upstream of the
second filters in
an exhaust hood canopy according to a particular embodiment, as depicted in
FIG. 1.
There are at least two alternative configurations for positioning the first
filter with respect
to the external support structure. First, the first filter may be positioned
with the filter
material on the downstream side of the external support structure in an
airflow direction,
similar to those depicted in FIG. 8. Second, the first filter may be
positioned with the
filter material on the upstream side of the external support structure similar
to those
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depicted in FIG. 9. The
additional benefit when the external support structure is
positioned on the upstream side of the filter material would be that the
external support
structure would provide better aesthetics over the appearance of a soiled
filter material.
Alternatively, when the external support structure is configured on the
downstream side
of the filter material, the external support structure would remain cleaner
for longer
periods of time which results in reduced labor and associated cleaning costs.
[0031] As depicted in FIG. 1, the filter assemblies 200 mounted within a hood
102 over
cooking equipment 100. A fryer 101 is illustrated for exemplary purposes.
Alternatively,
the cooking equipment may include, for example, ranges, griddles, fryers,
broilers, or the
like.
[0032] FIGS. 2 depicts a filter assembly 200 being lifted by sliding the head
501 of a
mounting tool 502 under the top lip 401 of the filter assembly 200, and
maneuvering the
filter assembly up into the an opening 105 and top channel 103 within the hood
200
where it will rest down into the bottom channel 104.
[0033] FIG. 3 shows the exterior support structure 300 removed from the
housing 400,
while the filter material 303 has been inserted behind the top lip 401 and
bottom lip 402
of the second filter 202. The filter material 303 has been folded back to
reveal the
downstream perforated air diffuser 409.
[0034] FIG. 4 shows a front isometric view of the filter assembly 200 and a
reference line
used to indicate a cross-sectional view as depicted in FIG. 7.
[0035] FIG. 5 illustrates one of the cross-section views of the filter
assembly 200 that
was referenced in FIG. 4, wherein the filter assembly 200 may include the
following
components: a first filter 201 and a second filter 202. The first filter 201
may include an
exterior support structure 300 and filter material 303. The second filter 202
may include
middle divider tabs 408 (optional), a perforated air diffuser 409, and a
baffle assembly
404 all enclosed within the housing 400. The baffle assembly 404 by comprise
of an
upstream row of vertical baffle ribs 405 and a downstream row of vertical
baffle ribs 406,
each being offset from the other to define an airflow spacing 407. Optional
vertical bail
handles 410 may be added to the housing 400. The filter assembly 200 may
define
tortuous paths "P" 106 that may enter the filter assembly 200 via the first
filter 201, then
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through the perforated air diffuser 409, then through the airflow spacing 407
provided by
the baffle assembly 404.
[0036] The majority of the grease may be filtered from the airflow by the
filter material
303 within the first filter 201. Any remaining grease carried in passing air
may adhere to
upstream row of vertical baffle ribs 405 and a downstream row of vertical
baffle ribs 406.
Thereafter, baffles assembly 404 may function as a channel, or gutter, and
direct the
accumulation of grease under the force of gravity to the bottom of the filter
assembly 200
as further described in FIG.8
[0037] FIG. 6 shows the back side of the second filter 202 revealing a baffle
filter
assembly 404 comprising of a upstream row of vertical ribs 405, a downstream
row of
vertical ribs 406 and airflow openings 407.
[0038] The embodiments of FIGURES 4-6 may be configured such that the baffle
assembly 404 and the perforated air diffuser 409 are fixed within housing 400,
and the
exterior support structure 300 and filter material 303 are removable from
housing 400.
This allows the filter material to be replaced periodically, without having to
remove the
entire housing from the kitchen hood. The filter material 303 may simply be
placed
against the exterior support structure 300 and then the exterior support
structure inserted
within the housing 400. Upper lip 400a and lower lip 400b of housing 400 hold
exterior
support structure 300 in place within housing 400.
[0039] When installed in this manner within hood 102, gravity will pull
exterior support
structure 300 away from diffuser 409 such that the filter material will not be
compressed
between diffuser 409 and exterior support structure 300. This allows for an
air gap 420
between filter material 303 and diffuser 409. This air gap and the lack of
compression of
filter material 303 allows filter material 303 to operate more efficiently at
removing
grease particulates from the air. Removable exterior support structure may
also be
perforated to allow for sufficient air flow there through.
[0040] FIG. 7 shows an embodiment of this invention where the filter material
303 is
attached the exterior support structure 300 with the use of independent
fastening elements
301 which can be located on any one or more sides of the external support
structure 300,
and are designed like velcro or hooks to adhere or penetrate directly to the
filter materials
303 woven or nonwoven surface. The fastening elements 301 can be any size or
shape,
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and attached to external support structures 300 using either adhesive,
welding, riveting,
sewing, screwing or any combination thereof.
[0041] Other independent fastening elements 301 are within the scope of the
appended
claims. For example, in particular embodiments, the filter material may be
attached to
the external support structure using clasps, hook and loop fasteners, clamps,
adhesive,
stick tacks, hooks or other similar means.
[0042] FIG. 8 shows the bottom of the housing 400 of the filter assembly 200
which may
comprise of a series of drainage apertures 411 and 412, for the first filter
and second filter
respectively, through which the grease may travel on its way to a ventilation
hoods
holding reservoir (not shown).
[0043] FIGS. 9-10 show two configuration options in which the first filter 201
is placed
in the upstream of a second filter 202.
[0044] FIG. 9 shows that within the first filter 201, the external support
structure 201 is
oriented downstream of the filter material 303. This may be done so that the
filter
material 303 filters the air before it come into contact with the external
support structure
300, reducing the need for the external support structure 300 to be cleaned
nightly and
still giving rigidity to the filter material 303.
[0045] FIG. 10 shows that within the first filter 201, the external support
structure 201 is
oriented upstream of the filter material 303. This may be done so that the
external support
structure 300 offers better aesthetics while maintaining rigidity to the
filter material 303.
This configuration is further illustrated in the embodiment of FIGS. 1-5.
[0046] In accordance with a particular embodiment of the present invention,
components
of the filter assembly may be made from stainless steel. For example, re-
usable
components of the system including the baffle assembly, air diffuser, housing
and
exterior support structure may be made of stainless steel. The filter material
that
comprises the disposable filter may be made from a variety of different
materials,
including a combination of wool and viscose materials. In certain embodiments,
it is
advantageous to have wool comprise more than 50% and in some cases more than
75%
of the blend of materials of the filter material. For example, wool may
account for 60% to
90%, or 70% to 80% of the blend. In such embodiments, viscose may be the only
other
material in the blend and account for the balance of the material. In other
embodiments,
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it is more advantageous to include more than 50% and in some case more than
75% of
viscose material in the blend. Similarly, viscose may comprise 60% to 90%, or
70% to
80% of the blend. In such embodiments, wool may be the only other material in
the blend
and account for the balance of the material.
[0047] It is advantageous to size the filter assembly to allow it to be
inserted into a hood
to replace a two inch baffle filter. Accordingly, the thickness of the housing
and in some
embodiments the entire filter assembly may be within the range of one and one-
half to
two inches thick. In certain embodiments, in order to allow the best "fit"
within the hood,
the total thickness would be within a range of 1.65" to 1.95". In certain
illustrated
embodiment herein, a 1.75" thick assembly is illustrated.
[0048] In particular embodiments, the filter assembly of Figures 4-6 may be a
square
configuration with sides of a length within a range of 14" to 16". This would
allow the
multi-stage filter to replace a standard baffle filter in a standard hood. In
the illustrated
embodiment, the sides of the filter are approximately 15.5" long.
[0049] In order to fit within the housing of the filter assembly, the exterior
support
structure is configured to be a square or rectangular configuration that is
slightly smaller
than the filter assembly. In the illustrated embodiment, the exterior support
structure is
approximately 14.5" by 15". The "short" side corresponds to the side that will
engage the
top and bottom lips of the housing. In other embodiments, the sides of the
exterior
support structure may be from 13.5" to 15.5" with the "short" side being
approximately
1/2 inch shorter than the long side.
[0050] Figures 4-6 are generally illustrated to scale. Thus, the baffle filter
takes up
greater than 50% of the thickness of the filter assembly. In various
embodiments, the
baffle filter may comprise 55% to 75% of such thickness. The exterior support
structure
and filter material together comprise less than 1/3 of the thickness. In
various
embodiments, the exterior support structure may comprise 15% to 40% of the
thickness.
In particular embodiments, the filter material (e.g., filter pad) may be
slightly longer than
the exterior support structure in at least one dimension to allow for the
filter assembly to
lap over the exterior support structure on at least two sides of the exterior
support
structure, and in some embodiments on all four sides.
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100511 In accordance with a particular embodiment, the rigidity provided by
the exterior
support structure may be advantageous for more easily handling the filter
material during
the installation and removal of the filter material, thereby shortening the
time and effort
required for installation and removal.
100521 The first filter may be orientated with the external support element
either on the
upstream or downstream side of the filter material for aesthetics and
maintenance
purposes benefits.
100531 The external support structure may not require any additional support
on the
opposite side of the filter material.
100541 The first filter may be attached, such as removably attached, to the
second filter.
100551 The filter material of the first filter may be natural fibers, hybrid
fibers, synthetic
fibers or any combination thereof.
100561 The second filters elements may cooperate to define an opening for the
first filter.
100571 The second filter may comprise: a housing, top lip, bottom lip, hanging
clips,
flame barrier, drain holes, middle divider tabs and a perforated air diffuser.
100581 The flame barrier within the second filter may be one or more baffle
filters, metal
mesh filters or any other known flame barrier.
100591 The ventilation hood may include a track, and the second filter may be
configured
to be inserted and possibly clipped onto the hood with the use of the filter
assembly's
hanging clips and be moved along the track. The first filter may also be
configured to be
inserted the second filter and into the hood by being moved along the track.
