[0001] This invention relates to the capture and exhaust of smoke, grease-laden fumes, etc.,
emanating from cooking equipment, and particularly to hood systems positioned above
a cooking surface for exhausting such fumes, smoke, etc.
[0002] It has long been desired that all smoke, fumes, etc., emanating from a cooking surface
such as in a commer cial kitchen or the like be captured and exhausted from the kitchen
or other room within which the cooking surface is disposed, with minimum escape of
the fumes, etc. into the kitchen area. Heretofore, there have been provided hoods
with exhuast fans that pull air from the kitchen or other room, into the hood where
the moving air entrains the smoke, fumes, etc., emanating from the cooking surface,
with the air and the entrained fumes being thereafter exhausted to the atmosphere
externally of the room. This prior art concept is of simple construction, thereby
involving relatively low costs for initial manufacture of the equipment, its installation
and operation. In this prior art device, however, all of the air passing through the
hood is drawn from the interior of the room so that if this air has been tempered,
i.e. heated or cooled, there is a substantial energy loss, and resultant economic
loss, by reason of this tempered air being pulled from the room and exhausted to the
atmosphere.
[0003] To minimize the loss of tempered air, it has been suggested that the volume of air
pulled from the coom and through the hood be minimized. This economy measure has been
found to result in inadequate velocities such that grease entrained in the flowing
air is not completely exhausted, but rather, the grease deposits on the interior walls
of the hood and/or ductwork due to the low velocity of the air flow. This, among other
things, has led to the establishment of minimum air flows through hoods. For example,
various fire protection agencys have established a minimum standard of air flow through
a hood of 2.8 cu. m. of air per cu. m. (cfm/cu. m.) of hood face entrance area for
wall mounted hoods and 4.25 cfm/cu. m. of hood face entrance area for island style
hoods. Employing the prior art concept of pulling air from the room through the hood
to the atmosphere
', at a velocity that will meet the minimum standards referred to above, the result
is a flowing air stream that uses enormous amounts of energy.
[0004] It has also been suggested heretofore to bring in air from outside the room or building
("make-up" air curtain) and introduce the same into the space surrounding the hood
and the cooking surface in an attempt to reduce the amount of tempered air extracted
from the room. One of the major problems involved in this concept is inadequate entrainment
of the smoke, fumes, etc., emanating from the cooking surface. One concept has proposed
to jet the incoming air toward the cooking surface from whence it is withdrawn through
the hood. This and similar concepts have resulted in inordinate cooling of the cooking
surface by reason of the air passing thereover. Other problems associated with this
concept involve slow and/or indirect movement of the vapors to the filter such that
grease in the vapors cooled and deposited on the walls of the hood, etc. thereby developing
a situation that is unsanitary, unsightly and a potential-fire hazard. Still further,
these prior art devices tended to blow the make-up air onto a user of the equipment
with resultant discomfort.
[0005] Commercial or industrial cooking facilities such as ovens and steamers are termed
"high profile" cooking equipment, and ranges, char broilers, and deep fat fryers are
termed "low profile" cooking equipment in that the latter commonly introduce relatively
greater volumes of grease and smoke into the atmosphere. Hence heretofore it has been
common to position a hood closer to the cooking surface of the equipment in the case
of the "low profile" equipment to ensure capture of the exhaust gases without their
escape into the room that contained the equipment. In those prior art devices, known
to applicant, that were used with low profile cooking equipment, it is not common
to use make-up air due to the problems associated with the introduction of the air,
from a physical standpoint i.e. size and shape of equipment, from an air flow control
standpoint, etc..Also there has existed the problem of user discomfort due to the
flowing air.
[0006] In accordance with the present disclosure, there is provided a system for the withdrawing
of cooking vapors from above a cooking surface disposed in a room or the like, comprising
a hood disposed above the cooking member. The hood preferably has a horizontal cross-sectional'area
substantially equal to the horizontal cross-sectional area of the cooking surface
so that the hood substantially covers the area of the cooking surface. The hood is
spaced apart from the cooking surface so that there is defined between the hood and
cooking surface an open space. A substantial portion of the peripheral edge of the
hood defines an air inlet through which air is introduced to the space between the
hood and the cooking surface. The air for introduction into this space is drawn from
outside the room, and preferably from the ambient atmosphere outside the building.
Within the hood and in the space between the hood and the cooking surface, there is
provided a filter.at a vertical height that is less than the height of the air inlet
means above the cooking surface. The air introduced into the space through the air
inlet is directed toward the filter. In the preferred embodiment, the air is injected
into the space along an inwardly and downwardly oriented path toward the filter. The
velocity of the air entering the space is not sufficient to allow the air to reach
the cooking surface before it is withdrawn from the hood through the filter by an
exhaust fan.
[0007] .In a preferred embodiment of the present system, the quantity of air exhausted from
the hood through the filter is greater than the quantity of air entering the space
between the hood and cooking surface by'at least about 10 per cent and not more than
50 per cent. By this means, there is assurance that fumes will not escape capture
and eventual exhaust through the hood. This relatively small quantity of air drawn
from the room minimizes the economic loss.and other undesirable effects such as drafts.
[0008] It is therefore an object of this invention to provide an improved system for the
capture and exhaust of vapors emanating from a cooking surface. It is another object
to provide a system of the type disclosed wherein there is minimal removal of tempered
air from the room that contains the cooking equipment. It is another object to provide
a system of the type described wherein air is drawn from a source outside the room
containing the cooking surface and directed into a space between a hood and a cooking
surface along an inwardly and downwardly oriented path to a filter that is disposed
at a vertical height above the cooking surface less than the vertical height of the
inlet above the cooking surface. Other objects and advantages of the invention will
be recognized from the following description, including the drawings in which:
FIGURE 1 is a schematic representation of a system employing various features of the
invention;
FIGURE 2 is a schematic representation, partly fragmentary and partly cut-away, of
a hood and cooking surface as employed in the disclosed system.
FIGURE 3 is a front elevational view of a system
[0009] ![](https://data.epo.org/publication-server/image?imagePath=1979/08/DOC/EPNWA1/EP78100625NWA1/imgb0001)
moving air from outside the room through the ducts 52, 5
0, and 48 into the plenum 44. The panels 30 and 34 of the partition 28 are provided
with a plurality of perforations 56 so that these panels define an inlet 57 for the
introduction of air from outside the room 14 to the space 20 between the hood and
the cooking surface 12. In the drawings, the size of the individual perforations 56
is exaggerated for purposes of illustration. In a preferred embodiment, the individual
perforations are circular and about 4.76 mm. in diameter.
[0010] The plenum 44 is divided into an upper portion 43 and a lower portion 45 as by an
opposed blade damper 47 of the type available from Reliable Metal Peoducts of Geneva,
Alabama. -By means of this damper, the incoming air flow is redirected toward the
space 20 and selected portions thereof are caused to exit the plenum through the perforations
in each of the panels 30 and 34. That is, more or less air is caused to exit through
each panel. In one embodiment, the individual blades of the damper are adjustable
in groups along the length of the damper to adjust the volume of air entering the
space 20 from one end of the hood to the other end thereof.
[0011] Still further, interiorally of the hood there is provided a further partition 58
comprising a first panel 60 that depends from the lower surface 32 of the cover 22
generally vertically downwardly within the hood so that in combination with the cover
22 and the rear wall 24 of the hood, there is defined an exhaust plenum 62 that extends
along the rear wall of the hood. The bottom of this plenum 62 is closed as by one
or more filters 64 that are mounted in this bottom opening. As seen in the several
figures, the filter 64 is preferably inclined at an angle "B" with respect to the
vertical so that the exposed face 65 of the filter receives thereagainst the incoming
air as admixed with tempered air from the room and with entrained vapors from the
cooking surface.
[0012] In the preferred embodiment, and as illustrated in the. several figures, the vertical
height of the perforated panels 30 and 34 of the partition 28 is greater than the
vertical height of the filter 64. This positions the inlet 57 higher than the filter
64. Further, as noted above, the angular disposition of these panels is chosen such
that air entering through the perforations 56 in the panel 34 is directed inwardly
and downwardly of the hood into the space 20 between the hood and the cooking surface
and generally toward the filter 64. As further noted above, the angular disposition
of the filter 64 is such as to receive the incoming air against the face of the filter
64. Simultaneously, outside air enters the top interior area of the hood through the
perforations 56 in the panel 30 to fill and sweep this area of vapors.
[0013] The exhaust plenum 62 is connected through an opening 64 to a duct 66, thence to
an exhaust fan 68 that perferably is disposed exteriorally of the room 14 to exhaust
the air from the hood to the atmosphere outside the room.
[0014] It will be recognized that the system shown in the figures is a "wall-type" system
in which the rear wall 24 of the hood lies against the room wall and the hood projects
from the wall in a cantilevered fashion over the cooking equipment. It will be readily
recognized by a person skilled in the art that two of the hood systems shown in the
figures and described herein can be placed back to back and suspended from the ceiling
or the like to provide an "island style" system. The function and operation of the
system is identical in either the wall style or island style system, the island style
merely comprising a duplication of components.
[0015] It has been found that the present system accomplishes essentially complete entrainment
of the cooking vapors without their escape into the adjacent room while minimizing
the withdrawal of tempered air from the room. Contrary to the prior art devices which
employ the use of "make-up" air from outside the.room, the present system does not
interfere with the accessibility to the cooking surface by an employee nor does the
flow of the make-up air create a discomfort to the employee. Among other things, these
advantages are accomplished in the present system by positioning the filter, hence
the exhaust outlet of the hood, relatively close to the cooking surface and at a location
across the cooking surface from the.position of a user of the equipment so that the
filter is relatively close to the cooking surface where the vapors are generated but
out of the way of'the cooking operation and/ or the user. Contrary to the prior art
devices, in the present system the make-up air is introduced into the space between
the hood and the cooking surface in a diffuse manner, i.e., through a plurality of
perforations 56, and along a path that is oriented inwardly of the hood and downwardly
across the cooking surface with the path terminating at the filter that is disposed
at a lower vertical height above the cooking surface than the height of air inlet.
By reason of this arrangement of the elements of the present system,' the velocity
of the tempered air drawn from the room into the space between the hood and the cooking
surface and eventually exhausted through the filters is relatively great in the area
immediately adjacent the hood and cooking equipment by reason of the minimizing of
the open area between the hood and cooking surface. This velocity of the flow of the
tempered air from the room, however, reduces precepitiously as the distance increases
away from the hood and cooking euqipment. This produces the desirable result of being
able to use relatively low volumes of make-up air and low-volumes of tempered air
while the respective velocities of the make-up air and the tempered air are maintained
relatively high. The result has been found to be an almost immediate entrainment of
cooking vapors as they emanate from the cooking surface, with the entrained vapors
being conveyed quickly to the filter before the greases, etc., in the vapors can cool
and deposit on the walls of the hood etc. Rather, the greases are trapped in the filter
as is desired and the other vapors are exhausted from the hood to the atmosphere out
side the room.
[0016] It further appears that in the present system the introduction of make-up air into
the space between the hood and cooking surface and through differently oriented perforated
panels 30 and 34 generates different air flow patterns within the space such that
the upper interior area of the space 20 is filled with make-up air and the same area
is swept clear of vapors etc., such sweeping action apparently tending to prevent
vapors from accumulating in the upper interior of the hood where they have time to
cool and condense grease, etc. onto the hood walls. The second flow path of the air,
i.e. the air entering the space 20 through the perforations in the panel 34, is along
a path directed inwardly of the hood and downwardly across the cooking surface with
the path intercepting the face of the filter 64. This flow of air appears to develop
a type of air curtain that intersects the upwardly flowing vapors from the cooking
surface to entrain the vapors and sweep them toward the filter 64. These de- sirabl
'e results have been found to occur when the filters are within about 91.4 cm. above
the cooking surface and the air inlet is at a greater height from the cooking surface,
e.g. about 104.1 cm. from the cooking surface to the lower edge of the air inlet 57.
Not only does this physical arrangement provide for desired air flow, it also provides
for ready and unobstructed accessability to the cooking surface by a user. As noted
hereinabove, by means of the damper 47, the relative quantities of air exiting the
plenum 44 through the panels 30 and 34 is selectable to effect the desired air flow
patterns within the space 20. The selection of these air flows is accomplished in
the field after installation of the system to accommodate the extant room air flow
patterns and either actual or anticipated vapor generation.
[0017] In one specific embodiment, a hood 1.8 m. in length and 1.22 m. from its front wall
to its rear wall was positioned above a cooking surface with the filter of the system
being spaced approximately 60.96 cm. above the cooking surface. The inlet 57 for the
make-up air in this embodiment comprised the panel 30 having an area of 5574.18 sq.
cm., and the panel 34 having an area of 6967.73 sq. cm. The angle "A" between these
two panels was 135 degrees. The lower edge of the panel 34 was 104.14 cm. above the
cooking surface. The straight line distance between the center of the panel 34 and
the center of the filter 64 was 132.08 cm. The make-up inlet 46 to the plenum 44 was
30.48 cm. wide and 66.04 cm. long. A supply fan having a capacity of about 35.68 cu.
m. per minute was connected to the duct 52 to supply air to the plenum 44. It will
be recognized that the velocity of the air moved into the hood by the supply fan was
substantially reduced as the air entered the plenum 44 and was distributed along the
length thereof prior to its exiting the plenum 44 through the perforations 56.,
[0018] In this specific embodiment, the exhaust fan 68 had a capacity of about 50.97 µm.
per minute of air flow and was connected through the duct 62 to the exhaust opening
64 which was 25.4 cm. wide and 45.7 cm. long. A 60.7 centimeter x 30.5 centimeter
filter having an exposed face area of 1858.1 sq. cm. was mounted in the open end of
the exhaust plenum at an angle "B" of 45 degrees with respect to the vertical.
[0019] The volume of air introduced into the space between the hood and cooking surface
was about 70 per cent of the total volume of air exhausted by the exhaust fan 68'.
The make-up air entered the space 20 in a plurality of streams through the perforations
56 in the panels 30 and 34. The perforations 56 occupied about 60 percent of the area
of these two panels, each perforation being about 4.76 mm. in diameter. The static
pressure loss through the hood was about 2.54 cm. water gauge.
[0020] In this embodiment, relatively heavy smoke emanating from the cooking surface was
quickly and effectively captured without escape into the room and was fully exhausted
through the filter. No user discomfort due to drafts was experienced. No substantial
quantities of grease or other condensibles were noted to collect on the hood or duct
walls, but rather such were collected by the filter.
[0021] While a preferred embodiment has been shown and described, it will be understood
that there is no intention to limit the invention by such disclosure, but rather,
it is intended to cover all modifications and alternate constructions falling within
the scope of the invention as defined in the appended claims.
1. A system for the capture and withdrawal of cooking vapors from above a cooking
surface disposed in a room or the like comprising hood means disposed above said cooking
surface, said hood means being at least substantially equal in horizontal cross-sectional
area to the horizontal cross-sectional area of said cooking surface and being spaced
apart from said cooking surface whereby there is defined an open space between said
hood means and said cooking surface, a source of air located remotely of said room,
air inlet means located adjacent a substantial portion of the peripheral edge of said
hood means and defining an opening through which air is introduced to said space between
said hood means and said cooking surface, first conduit means connecting said source
of air in fluid communication with said air inlet means, first blower means disposed
in position to move air from said source of air to and through said air inlet means,
filter means disposed within said space between said hood means and said cooking surface
at a vertical height above the cooking surface less than the vertical height of said
air inlet means, said filter means being disposed substantially across said hood means
from said air inlet means and in the path of air entering said hood means through
said air inlet means, second conduit means connected in fluid communication with said
filter means and terminating exteriorly of said room, and second blower means disposed
in position to move air through said second conduit means in a direction away from
said filter means.
2. The system of Claim 1 and including means associated with said air inlet means
and defining a plurality of openings through which air is introduced in a plurality
of streams to said space between said hood means and said cooking member.
3. The system of Claim 1 wherein said air inlet means includes air flow control means
directing said air entering said space between said hood means and said cooking member
along a path that includes a section thereof which extends inwardly of said space
and downwardly toward said filter, said section of said path terminating at said filter.
. 4. The system of ,Claim 1 wherein the quantity of air exhausted through said filter
is greater than the quantity of air entering said space between said hood means and
said cooking surface via said air inlet means.
5. The system of Claim 4 wherein said quantity of air exhausted through said filter
exceeds by at least 10 per cent the quantity of air entering said space between said
hood means and said cooking surface.