Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2166498
ADJUSTABLE EXHAUST HOOD WITH AIR CURTAIN
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an exhaust hood for removing air laden with grease,
smoke or other contaminants from a working environment, and more specifically
to such
an exhaust hood with mechanisms for adjusting the volume of air passing
through the
hood and generating an air curtain beneath the hood.
Description of Related Art
Exhaust hoods are used in a variety of environments such as kitchens,
laboratories
and factories for exhausting heated or contaminated air from a working
environment. In
a restaurant kitchen, for example, there are usually a number of cooking units
aligned in
a row. Some of these units, broilers and fryers for example, may produce
considerable
quantities of smoke, fumes, grease particles and moisture, while other units
such as
ranges and griddles may generate such pollutants in considerably smaller
amounts.
Kitchen exhaust ventilators have traditionally been designed with enough
airflow capacity
to remove pollutants from broilers, fryers and other more active pollution-
generating
cooking units. This results in excessive ventilation for those cooking units
which
generate less pollution, such as the ranges and griddles.
A typical exhaust hood comprises a housing in the form of a box-like structure
with an intake comprising an open underside, and an exhaust duct leading
outwardly
from its upper side. Air from the kitchen environment passes into the housing
through a
series of grease filters, and into an exhaust plenum above the grease filters.
From the
exhaust plenum, it is drawn out of the hood through the exhaust duct. In a
kitchen the
hoods are typically horizontally elongated to accommodate a row of cooking
units.
An elongated hood may give rise to uneven distribution of air across the width
of
the hood. The portion of the hood directly beneath the exhaust duct tends to
remove air
at the greatest volume-rate, while portions of the hood displaced from the
exhaust duct
tend to exhaust air at lower volume-rates. A common solution to this problem
is to
situate the most active of the pollution-generating cooking units directly
beneath the
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exhaust duct and to place the least active pollution-generating units furthest
from the
exhaust duct. However, such an arrangement may not promote optimal efficiency
of the
cooks working at the equipment, and many chefs prefer to experiment with
different
equipment locations to achieve maximum efficiency within the kitchen.
To improve the flow distribution across a given exhaust hood, prior designs
have
incorporated a flow restriction strategically located in the path of the
exhaust air to
provide a desired flow distribution. For example, U.S. Pat. 4,281,635, issued
August 4,
1981 to E. C. Gaylord, discloses a kitchen ventilator or exhaust hood mounted
over an
arrangement of kitchen equipment which includes a broiler, a fryer, a range
and a
griddle. Air and grease pass from the equipment through an inlet opening and
take a
circuitous path through a series of opposing horizontal baffles to extract
grease and other
contaminants. A damper baffle mounted on a horizontal pivot at the inlet
opening is
pivotable toward and away from the lowest baffle to vary the width of a gap
between the
damper and the baffle, whereby to vary the volume of air flowing past the
damper. To
accommodate the varying exhaust requirements of different pieces of kitchen
equipment,
additional baffling is provided to reduce the rate of air flow into portions
of the
ventilator positioned above the range and griddle units. The additional
baffling
comprises choke plates attached to the hood in strategic locations and
extending into the
path of the exhaust air passing through the grease baffles. Several of the
choke plates
are bolted in place and others are spot-welded in place. To rearrange
equipment
beneath the exhaust hood, the choke plates must be removed and repositioned.
To
remove those choke plates which are spot-welded, the welds must be burned off.
The volume of air exhausted through the hood must be replenished from some
source. if the exterior air is drawn into the kitchen area, it is typically
tempered,
particularly in northern climes. Such systems require additional energy
expenditures. It
is also known to draw air (often called "make-up" air) from adjacent rooms in
restaurants, for example, but such systems require additional ducting and
sometimes
result in uneven air distribution from room to room.
Sometimes air curtains are generated across the front of a hood to "seal"
smoke
and grease-laden air beneath the hood and prevent it from entering the kitchen
area.
Many such air curtains are generated by structure mounted to the front of a
hood and
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obtain source air from the exterior of a building, or from make-up air. Both
sources
require costly installations of extra ductwork.
SUMMARY OF THE INVENTION
The exhaust hood of the present invention provides a simpler and more
effective
solution to the problem of providing air distribution across the exhaust hood
which
accommodates the requirements of various arrangements of equipment beneath the
hood.
More particularly, the invention provides an exhaust hood in which a housing
and
a grease filter cooperate to define an exhaust plenum and a flow path through
the grease
filter, and in which the improvement comprises a shutter panel slidable into
the flow
path adjacent to the grease filter to block a portion of the flow path and
thereby adjust
the volume of air flowing through the exhaust hood.
The height of the shutter panel varies between its ends, whereby the amount of
flow restriction effected by the panel varies correspondingly between the
ends. In a
preferred embodiment the upper and lower edges of the panel converge so that
the
height of the panel tapers uniformly from one end to the other. Also in the
preferred
embodiment the panel is reversibly mounted within the housing.
The invention also provides a method of adjusting air flow in an exhaust hood
having an open underside, a grease filter and means defining a flow path
extending from
the open underside through the grease filter, the method comprising the steps
of
mounting a panel adjacent to the grease filter for slidable movement across a
face of the
grease filter, and reducing the air flow through the exhaust hood by sliding
at least a
portion of the panel into the flow path to restrict a portion of the flow. The
latter step
may be performed by varying the shape of the portion of the panel within the
flow path
to vary the volume of air flow across the width of the flow path.
In another aspect of the invention, the hood is provided with a plenum toward
its
front, with a diffused opening facing downwardly at the front of the hood, and
a second
opening elsewhere which is open to the room air. A fan is disposed in the hood
in a
position to draw air into the plenum through the second opening and force it
out through
the diffused opening.
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Other features and advantages of the invention will be apparent from the
ensuing
description in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a partial sectional perspective view of an exhaust hood according to
the
invention;
FIG. 2 is a side elevational view in cross-section of the exhaust hood of FIG.
1
taken along line 2--2 of FIG. 1;
FIG. 3 is a sectional view of the hood of FIG. 1 taken along line 3--3 of FIG.
2
and illustrating grease baffles and an adjustable flow restriction panel
according to the
invention;
FIG. 4 is a sectional view of a portion of the hood of FIG. 1 taken along line
4--4
of FIG. 2 and illustrating a mounting arrangement for the adjustable flow
restriction
panel of FIG. 3;
FIG. 5 is a perspective view of the adjustable flow restriction panel of FIG.
3;
FIG. 6 is a partial sectional perspective view of a second embodiment of a
hood
according to the invention; and
FIG. 7 is a cross sectional view of the hood taken along line 7--7 of FIG. 6.
DESCRIPTION
Referring now to the drawings and to FIG. 1 in particular, an exhaust hood 10
is
shown which includes a housing comprising upper rear front and side panels 12,
14, 16
and 18 forming a generally rectangular box-like structure having an open
underside 20.
A dividing wall 22 slopes from a rear portion of the underside 20 upwardly and
forwardly
towards the top panel 12 to define an exhaust plenum 24 within the exhaust
hood 10
above the dividing wall 22. An exhaust duct 26 extends upwardly and outwardly
from
the exhaust plenum 24 through the top panel 12. Suction applied to the exhaust
duct 26,
as by an exhaust fan (not shown), draws air from the exhaust plenum 24 out of
the
exhaust hood 10 through the exhaust duct 26.
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A portion of the dividing wall 22 comprises a grease filter 28 of a type
ordinarily
used in the art. Typically, an exhaust hood such as the hood 10 will have
several grease
filters 28 arranged in side-by-side arrangement to span the full width of the
exhaust
hood. The grease filters 28 are mounted in upper and lower U-shaped
horizontally
disposed channels 30 in the ordinary fashion.
Turning to FIG. 2, the grease filters 28 thus slope upwardly and forwardly at
an
approximately 45 angle. A flow adjusting mechanism 32 is disposed immediately
behind
the grease filters 28. The flow adjusting mechanism 32 comprises one or more
shutter-
like panels 34 slidably mounted behind and parallel to the grease filters 28.
Preferably,
a pair of elongated U-shaped channels 36 are provided for slidably receiving
the panel
34. The panel 34 slides within the channels 36 parallel to the grease filters
28 to
selectively cover and uncover portions of the grease filters 28 and thereby
adjust the
quantity of air flowing through the hood. Preferably, the components of the
flow
adjusting mechanism 32 are formed of stainless steel or aluminized steel.
Turning to FIG. 3, it can be seen that the panel has the shape of an
elongated,
truncated right triangle providing a first end 38 (corresponding to the base
of the
triangle) and a second end 40 (corresponding to a truncated edge of the
triangle). An
upper edge of the panel 42 is essentially horizontal, while a lower edge 44
slopes slightly
upwardly toward the panel second end 40. Preferably, the height of the panel
34
(distance between the upper and lower edges 42 and 44) at the first end 38
will be
approximately twice the height at the second end 40. Thus, the panel first end
38 blocks
a larger portion of the grease filters 28 than the panel second end 40 and
provides for a
correspondingly larger volume of air passing through the grease filter 28
adjacent to the
panel second end 40.
Turning to FIG. 4, it can be seen that the U-shaped channels 36 are oriented
along lateral edges 46 of the grease filters 28 with the open edges of the
channels 36
facing each other. U-shaped return flanges 48 are provided at the first and
second ends
38 and 40 of the panel 34. Each flange 48 comprises a lip 50 extending normal
to the
panel 34 and a second lip 52 extending from the first lip parallel to the
panel 34. (See
also FIG. 5). The flanges 48 are designed to slide freely within the channels
36. Some
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form of locking mechanism, such as a lock nut or pin (not shown), is
preferably provided
for holding the panel 34 at a desired location within the channels 36.
In the orientation shown in FIG. 4, the panel 34 nearly abuts the grease
filters 28,
whereby air cannot flow through the grease filters 28 adjacent to the panel 34
and then
travel parallel to the panel 34 and out through the exhaust duct 26. However,
if the
panel 34 is reversed within the channels 36, the panel 34 will be spaced apart
slightly
from the grease filter 28. With the panel 34 in this orientation and to
prevent air from
flowing through the grease filter 28 adjacent to the panel 34 and travelling
parallel to the
panel 34 to escape into the plenum 24 and out through the exhaust 26, a lip 54
is
provided at the upper edge 42 of the panel 34. If desired, an additional lip
(not shown)
may be provided at the panel lower edge 44.
In a typical kitchen installation, the kitchen equipment will be oriented
underneath the exhaust hood 10. After the kitchen equipment has been placed
into a
desired arrangement, the flow adjusting mechanism 32 is adjusted to provide
appropriate
exhaust quantities across the width of the exhaust hood 10. For instance, the
panel 34
will be inserted into the channel 36 with its narrower second end 40
positioned above the
more active producers of smoke, fumes and grease such as the broilers and
fryers. Then,
the panel 34 will be moved within the channels to a desired location to
produce an
appropriate total volume of exhaust flow through the hood 10. Thus, the flow
control
mechanism 32 provides not only control over the gross volume of air exhausted
through
the exhaust hood 10 but also the lateral distribution of the exhaust air
across the width
of the exhaust hood 10.
If an even distribution of air is desired across the exhaust hood 10, the
exhaust
duct 26 can be located adjacent to one side 18 of the exhaust hood 10 and the
wider first
end 38 of the panel 34 can be located at that same side. Thus, more flow
restriction will
be placed in front of the grease filters 28 adjacent to the exhaust duct 26
and less flow
restriction placed in front of the grease filters 28 away from the exhaust
duct 26 to
provide an even distribution of air exhausted through the grease filters
laterally across
the width of the exhaust hood 10.
As shown in FIG. 3, multiple panels 34 are preferably provided in side-by-side
orientation for increased flexibility in adjusting the air distribution within
the exhaust
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hood 10. Various orientations of side-by-side panels can be provided. For
instance, two
panels 34 can be provided with their wide first ends 38 located in a central
section of the
hood 10 and their narrower second ends 40 located adjacent to the sides of the
hoods 18.
In this orientation, with an exhaust duct 26 located in the center of the hood
10, an even
distribution of air can be provided as the greater suction effect in the
center of the hood
due to the location of the exhaust duct would be negated by the greater
blockage of the
grease filters 28 in the center of the hood. Each panel 34 could be
independently
adjusted. Also, multiple panels can be provided, one behind the other.
By varying the angle of the lower edge 44 relative to the upper edge 42, a
greater
degree of flow restriction is provided on one side of the hood versus the
other. Also,
other shapes may be provided for the panel 34. For instance, the lower edge 44
can be
made parallel the upper edge 42 with one of the upper or lower edges 42 or 44
provided
with a discontinuity to vary the height (distance between the upper and lower
edges 42
and 44) of the panel 34 from one end 38 to the other 40. When employed in a
kitchen,
the exhaust hood 10 could be provided with separate panels 34 in side-by-side
relation
corresponding to each piece of kitchen equipment located beneath the exhaust
hood 10.
However, for most applications, an arrangement having one or two panels 34
shaped as
illustrated in FIG. 3 provides ample adjustability of flow distribution across
the exhaust
hood 10 with a simple and uncomplicated structure.
Turning now to FIGS. 6 and 7, a second embodiment of the invention includes a
hood 100, similar in all salient respects to the hood 10 of FIG. 1, but with
an additional
flow path A to create an air curtain across the front of the hood with make-up
air
directly from the space adjacent the hood. A front panel 102 of the hood 100
has an
opening 104 which is covered by a protective louver 106. A flow-through fan
108,
directly behind the opening, draws air from adjacent the hood, through the
opening, and
into a plenum 110 at a forward portion of the hood.
A diffuser opening 112, preferably extending from one side of the hood to the
other, is disposed at the front edge of a lower panel 114 of the hood. Air in
the plenum
110 is forced by the fan 108 out through the diffuser opening 112 to create a
curtain of
air beneath the front panel 102 of the hood. When the hood 100 is installed
and
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operated in the kitchen, the air curtain is created solely from make-up air
which is
already tempered since it is drawn from adjacent the hood.
The air is expelled, not to a separate receiver, but directly through the
hood.
Hence, it is not a complete air curtain in the sense of fully sealing the
front of the
adjoining work area beneath the hood, but rather curtains primarily the
uppermost space
beneath the hood. However, since warm, smoke and grease-laden air generally
rises, a
partial air curtain effectively seals the contaminated air from the kitchen
area and helps
exhaust it through the hood.
While the invention has been particularly described in connection with certain
specific embodiments thereof, it is to be understood that this is by way of
illustration and
not of limitation, and the scope of the appended claims should be construed as
broadly
as the prior art will permit.
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