Note: Descriptions are shown in the official language in which they were submitted.
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FOOD CONTAINER HAVING
IMPROVED VENTILATION
FIELD OF INVENTION
[0001] This invention relates generally to ventilated plastic food
containers. The
invention is more specifically related to disposable plastic food containers
designed to
hold heated or freshly-cooked crisp, crunchy or texture-sensitive foods that
require
significant amounts of humidity removal.
BACKGROUND OF THE INVENTION
[0002] It is known to use disposable plastic containers in the food
preparation and
restaurant industry to package prepared or take-out foods. The typical food
container of
the prior art consists of a clear or solid color base and a clear lid. The
clear lid of the
prior art plastic food container allows visible inspection of the container
contents. The lid
and base of the prior art plastic food container may be separate articles or
may be
hingedly attached to each other.
[0003] The lid and base of the prior art plastic container have
complementary
interlocking rim structures that seal the container. This interlocking rim
arrangement is
beneficial in preventing spillage of food contents from the container. In
addition, this
interlocking rim arrangement promotes heat build-up inside the container
during
microwaving and retains the temperature of hot foods placed in the container.
When
warm foods are placed in a closed container, steam and condensation can
develop inside
the container. This is particularly so when the container with warm food is
placed into a
storage area at room temperature or less. Steam and condensation may also form
inside a
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container holding food when the container is stored in an environment where
external
heat is applied to it (for example through microwaving, heat plates, heat
lamps, warming
tunnels, etc.). The build up of condensation and steam inside the container
can result in
the over-moistening of the contained food. This build up is particularly
unwanted in the
case of any food of sensitive texture, especially crisp or crunchy foods. In
addition,
undesirable food moistening is exacerbated when condensation drips down onto
the food
contents. In extreme cases, the condensate may pool at the bottom of the
container
leaving desirably crisp foods (e.g., vegetables) or crunchy foods (e.g., fried
chicken or
fried seafood) unpalatably soggy.
[0004] In the case of supermarket fried chicken (or seafood) for example,
the
supermarket prepares the fried chicken in its deli department, resulting in a
cooked food
product having a temperature of about 190 degrees Fahrenheit. After cooking,
the hot
fried chicken is placed into the container. The container may be sold
immediately. If not,
the container containing the fried chicken is typically placed in a heated
display area and
made available for sale as a "hot" food item for up to 4 hours. In the prior
art container,
the heat from the hot chicken builds up in the container and, in turn, causes
moisture
build-up in the container. As a consequence to this moisture build-up, the
fried chicken's
crisp battered coating becomes soggy.
[0005] The solution to preventing over-moistening of cooked food, however,
is not
simply a case of providing unregulated venting. In the first respect,
unregulated venting
allows the food to dry out and over-harden. More importantly, in addition to
palatability
concerns, containers for cooked foods must address safety issues. If the
container is
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vented too much, the temperature of the fried chicken can drop below the
minimum
temperature required by health departments or good food serving practice.
These same
concerns hold true for other establishments like restaurants and with respect
to other
texture sensitive foods like unbreaded cooked crab that can degrade if heat
and moisture
are not properly removed from the container:
[0006] In order to maintain the crispness of food contents within a closed
container, it is known to provide the prior art food container with exhaust
ventilation
means. In this regard, the lid of the prior art plastic food container
typically contains one
or two surface vents in the form of cruciate slits. The cruciate slits form
near-circular
tabs that can be deformed upward to permit egress of steam formed inside the
container.
The one or two slits are located on the surface of the container lid, not in
relation to other
venting structures of the container, but instead in a manner that detracts
least from the
aesthetic appeal of the container. Though these slits assist in the exhaust
venting of steam
gases from the container, moisture build-up inside the container still occurs.
[0007] In the case of microwavable storage containers (as opposed to deli
case
containers) manufacturers have chosen to deal with removal of moisture
damaging steam
by constructing container rims whereby the lid rim can assume two different
positions on
the base rim. One position keeps the container sealed. The other position
allows exhaust
venting. In the case of these latter containers, the sealed lid assumes a
second fixed
exhaust venting position on the base either through manual repositioning or by
the lifting
action of rising pressure inside the container. Once the lid is in the fixed
exhaust venting
position, steam can escape the container by flowing along and between the
contour of the
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rim structures and out through the container. The contour of these rim
structures can
require egressing steam to undergo flow restricting direction changes
(including direction
reversals). The drawback to these exhaust venting solutions is that they still
result in the
creation of interior vapors and condensation in the container, particularly in
the case of
the self-activating lid Also, because air must flow around the contour of
rims, these
containers promote only the egress of air out of the container and do not
allow drying air
into the container.
[0008] U.S. Patent No. 6,257,401 discloses a thermoplastic container for
food with
a cover that is removably attached to the base to define a food storage
chamber. A
downwardly extending rib formed in the cover rim is intermittently provided
with a
plurality of notches that are aligned with respective notches formed in an
upwardly
extending elongated rib of the base. With the cover in place atop the base,
the
conjunction of the base notches and the cover notches define apertures.
However, as is
best shown in FIG. 11 of that patent, the notches of the lid rim and base rim
are offset,
such that air flow into the container is directed upward toward the upper
apertures of the
lid. Another set of apertures for additional ventilation are provided in the
side walls of
the cover.
[0009] Because of the venting drawbacks of the prior art container with
respect to
desirably crisp or crunchy foods, container manufacturers have designed
containers
having textured surface grids on the container floor that keep the food
contents raised
above pooled food juices or condensate. These grids can create pooling areas
that collect
the condensate and juices. The container of U.S. Patent No. 6,257,401 includes
a plurality
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of small wells in the container bottom, the function of which is to
purposefully retain food
juices via capillary action or surface tension. These solutions, however, do
not completely
remedy the creation of food-damaging steam and fluids inside the container. In
fact, they
can make it worse. In particular, the condensate and juices may drip into and
pool in the
wells of the container's floor grid and be retained. This pooled liquid
absorbs heat and
creates rising steam that infuses the lower portion of the container's food
contents with
texture damaging moisture.
[0010] There is thus a need in the art for a plastic food container
that reduces steam
creation and enhances container venting to prevent over-moistening of
desirably crisp or
crunchy foods.
SUMMARY OF THE INVENTION
[0011] The present invention satisfies the need in the art and
provides an
aesthetically appealing food container that is easy to use, while providing
for improved
moisture removal. In this respect the present invention container achieves
balanced vapor
removal by incorporating structures that enhance the exhaust venting of the
container with
structures that allow for efficient air intake. The container uses convection
and guided
flow of inducted air to prevent the over-moistening of food product.
[0011a] According to an aspect of the present invention, there is
provided a plastic
food container comprising: a lid and a base; the lid and base each having a
peripheral rim;
the lid rim adapted for closing engagement with the base rim; when the lid rim
and base
rim are in closed engagement, the lid and base forming an interior of the
container, a first
intake port disposed between the two rims and a first counterpart intake port
disposed
between the two rims; the first intake port and the first counterpart intake
port being further
disposed between the two engaged rims such as to permit air to enter directly
and generally
horizontally into the container; the first intake port and the first
counterpart intake port
defining a line in the interior of the container that extends from the first
intake port to the
first counterpart intake port; the base comprising a floor, the floor having a
plurality of ribs
projecting upwardly into the interior of the container; the plurality of
upwardly projecting
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ribs forming at least one channel within the interior of the container and
aligned with the
line defined by the first intake port and the first counterpart intake port;
the lid including a
top surface and one or more outermost side surfaces, the one or more outermost
side
surfaces having no vents disposed on them; and the top surface of the lid
having a plurality
of exhaust vents disposed on it.
[0012] The present invention comprises a plastic food container
including a lid and
a base. The lid and base each have a peripheral rim. The lid rim is adapted
for sealing
engagement with the base rim. When the container is sealed with hot food
contents, the
heat load created by the food causes the moisture laden air to rise and exit
through
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selectively positioned and numbered exhaust vents in the top surface of the
container lid.
In this regard, the top surface exhaust vents are numbered and positioned in
relation to the
expected temperature and humidity of the container's contents. The convection
movement of warm moist air upwardly in the container and through the top
surface
exhaust vents causes the induction of air through the intra-rim intake ports
hereinafter
described.
[0013] It is a further feature of the present invention container that the
lid rim and
base rim when in closed engagement form at least one first intake port
disposed between
the two rims. To achieve optimum balanced venting and eliminate humidity dead
zones
in the container, each first intake port has a counterpart intake port
disposed between the
two rims. Additionally, the first intake port and its counterpart intake port
are oriented
such as to permit air to enter, directly and generally horizontally, into the
container
through them and not encounter obstructing rim structures or have to change
directions or
angles while traveling through the rims.
[0014] The first intake port and its counterpart intake port define a line
inside the
container. The container's floor can have at least one channel formed in it,
which is
aligned with the line defined by the first intake port and a counterpart
intake port. By
aligning the floor channels with at least one intake port, a cross flow of
inducted ambient
air is allowed whereby the container promotes the flow of relatively drier air
under the
container's food contents. This flow of air not only helps evaporate collected
condensate
and food juices, it removes the vapor away from the underside of the food
content,
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preventing its damaging absorption. The container floor may comprise channels
aligned
with two or more sets of intake ports.
[0015] In more specific summary, the present invention plastic food
container
comprises a lid adapted for sealing arrangement with a base. The lid has a
peripheral rim
structure that complementarily engages the peripheral rim structure of the
base. The base
has a floor and a sidewall extending between the floor and the rim. In
contrast to prior art
containers utilizing through-the-rim exhaust or intake venting, it is a
feature of the present
invention that when the lid is fully closed to the base, the mating rim
structures create at
least two intake ports that allow generally horizontal and direct
(unrestricted) flow of air
into the container through the closed rims. Preferably, each intake port is
located on the
rim in opposing relationship to another intake port. Hence, each intake port
is located
such that it is across from another intake port on the other side of the
container. The
positioning of the intake ports allows for the cross-flow of air through the
container.
[0016] In the preferred embodiment, the rim structure of the lid has a
channel
shaped to receive spaced apart projections on the base rim structure. When the
lid is
closed to the base, the channel of the lid rim structure receives the
projections on the base
rim structure. The height of the projections emanating from the base rim
structure
prevents the lid flange from sealing completely against the base flange. As a
result, when
the lid is fully engaged to the base, the spaces between the base rim
projections create rim
air intake ports.
[0017] The present invention container further comprises elevated
(preferably
embossed) projecting ribs from the base floor. These ribs create one or more
channels on
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the container floor that compared to the prior art are specifically aligned
with a line
defined by at least two intake ports located within the engaging container
rims. These
ribs and channels provide for several beneficial effects. First, as in the
case with the grid
or textured surface of the prior art container, the ribs keep the food
contents elevated from
the base floor and away from collecting liquids. However, in combination with
the intake
ports, the aligned channels act like baffles and allow for the free passage of
gases and
vapors underneath the food contents. Thus, should pooled liquids in the
container start
steaming, the channels of the present invention container allow for the
evacuation of
steam out through the top surface exhaust vents in the lid instead of into the
food. In
addition, by virtue of their alignment with the intake ports, the channels of
the present
invention container allow for the end-to-end cross flow of moisture-removing
air
underneath the container's food contents in the event a pressure differential
exists
between the ends of the channels. This arrangement not only enhances the
removal of
pooled moisture, but also aids in drying of the bottom of the food contents.
Thus, the
convective movement of warm air inside the container causes induction of air
through the
rim intake ports. That air, being relatively cooler than the existing vaporous
air inside the
container, drops to the floor of the container. This drop is effected, in
part, by the
generally horizontal (not upwardly angled) orientation of the rim intake
ports. Once the
cool, dry air reaches the container floor, it flows as guided by the channels.
Thus, the
intake ports along with the aligned, one or more channels allow the direct,
unimpeded
flow of relatively dry air to enter into the container from the intake ports
and pass under
the food contents. While passing under the food contents, heat is transferred
from the
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= food contents to the incoming air. That heated air rises, scavenging
moisture from the
existing air in the container as it rises.
[0018] To further enhance the convection flow in the container, the
preferred
embodiment container includes a plurality of exhaust vents disposed about the
top surface
of the container lid and not along any of the lid's outermost side surfaces.
This
arrangement of top-surface-only vents removes the dead-air effect caused by
having
apertures on the side of the lid in close proximity to the rim intake ports.
By removing
this dead-air effect, convection in the container is enhanced. In addition, by
removing the
vents from the extreme side of the lid by the intake ports, rising air in the
container does
not intercept the inducted air from the intake ports and push it out of the
container.
[0019] While the invention is susceptible to various modifications
and alternative
forms, a specific embodiment thereof has been shown by way of example in the
drawings
and will herein be described in detail. It should be understood, however, that
it is not
intended to limit the invention to the particular forms disclosed. Quite to
the contrary, the
intention is to cover all modifications, equivalents, and alternatives falling
within the
scope of the invention as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a perspective view of a preferred embodiment of the
present
invention container in the open arrangement.
[0021] FIG. 2 is a perspective view of a preferred embodiment of the
present
invention container in the closed arrangement.
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[0022] FIG. 3 is a plan view of the present invention container in the
open
arrangement.
[0023] FIG. 4 is a cross-section view taken along line A-A of FIG. 3.
[0024] FIG. 5 is a side elevation view of the preferred embodiment present
invention container in the closed arrangement.
[0025] FIG. 6 is a perspective view of the inside of the base of the
preferred
embodiment present invention container.
[0026] FIG. 7 is a perspective view of the inside of the lid of the
preferred
embodiment present invention container.
[0027] FIG. 8 is a side elevation view of the lid of the preferred
embodiment
present invention container.
[0028] FIG. 9 is a side elevation view of the base of the preferred
embodiment
present invention container.
[0029] FIG. 10 is an enlarged view of detail area Z of FIG. 4.
[0030] FIG. 11 is an enlarged view of detail area Y of FIG. 4.
DETAILED DESCRIPTION
100311 A preferred embodiment container 10 of the present invention in the
open
and closed arrangement is shown in FIGS. 1 and 2. In practical use, the outer
surface of
floor 31 of base 25 will normally rest upon a surface (such as a table top)
considered
horizontal in reference to the user. Thus, the directional terms "vertical"
and "horizontal"
and the like are used to describe the container 10 and its components with
respect to the
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orientation illustrated in FIG. 2 and are employed merely for the purposes of
clarity and
illustration. For example, in the orientation shown in FIG. 2, lid 11 of
closed container
is spaced "vertically" from the base 25. The directional terms "inner,"
"outer," and the
like are used herein with respect to the described container to refer to
directions along the
directional component toward and away from the geometric center of the
container.
[0032] Container 10 is preferably thermoformed. As shown by the figures,
container 10 is composed of lid 11 and base 25. Lid 11 includes top surface
12,
descending surface (sidewall) 19 and multi-segment rim 14. Lid 11 and base 25
are
manufactured from a conventional plastic material. Lid 11 is preferably clear.
Top
surface 12 may include levels or features of varying height, but is preferably
flat. It may
also be contoured and have ribs 16 in accordance with the prior art to enhance
such
factors as container volume, strength, nesting of multiple lids, stackability
of closed
containers and see-through visibility. In the preferred embodiment, lid top
surface 12
includes top plateau 15. Sidewall 19 extends from top surface 12 to horizontal
segment
17 and may include ribs 13 for strength. Horizontal segment 17 extends from
sidewall 19
to vertical inner wall 18. Sidewall 19 preferably includes ribs 7 for strength
and, in the
depicted preferred embodiment, represents an outermost side surface of the
lid.
[0033] The structure of preferred embodiment lid rim 14 will now be
discussed in
further detail. As best shown in FIG. 10, lid rim 14 includes peripherally
projecting
segment 20, which extends between inner wall 18 and outer wall 21, creating
channel 23.
The cross-section profile of segment 20 is generally horizontal. The profile,
however, can
be shaped to include structure such as ribbing, curves or bends to modulate
rim rigidity or
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flexibility so as to enhance the closing, sealing and opening functions of the
rim as
needed. The drawings depict a preferred embodiment cross-section profile of
this
peripherally projecting segment. As viewed in FIG. 10 outer wall 21 extends
downwardly between peripherally projecting segment 20 and peripheral flange
22. Outer
wall 21 is preferably angled to frictionally engage projection 35 further
described below.
[0034] The structure of preferred embodiment rim structure 30 of base 25
is best
shown in FIG. 11. Base 25 includes a bottom-most level or floor 31 adjoined to
sidewall
32. Sidewall 32 extends between base floor 31 and multi-segment rim 30.
Sidewall 32
preferably includes ribs 41 for strength. The structure of base rim 30 is
adapted to
complementarily engage the structure of lid rim 14 when lid 11 and base 25 are
placed in
sealing arrangement. In this respect, the lower portion of base rim 30
includes sidewall-
to-rim transition segment 33. Transition segment 33 flares outwardly from the
top of
sidewall 32 and curves upwardly into base shelf 34. Base shelf 34 extends
outwardly
from base 25 and curves upwardly to form sealing projection 35. Preferred
embodiment
container 10 has at least two sealing projections 35. As viewed in FIG. 11,
sealing
projection 35 comprises outer vertical segment 36 and inner ascending segment
37. Top
sealing segment 38 spans between segments 36, 37. Peripheral flange 42 extends
outwardly from segment 36.
[0035] As shown in FIG. 9, projections 35 are located at spaced apart
intervals on
shelf 34 so as to create base rim gaps 39 between two adjacent projections.
Each base rim
gap 39 is preferably located so as to geometrically oppose a counterpart base
rim gap 39
located on the container. For example, in the disclosed embodiment square
container
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depicted in FIG. 1, base rim gaps 39 are disposed in opposing relationship on
each pair of
parallel container sides. Lid rim structure 14 preferably contains similar
projections 26
located on horizontal segment 17. Projections 26 are complementarily located
on rim
structure 14 such that they align with and frictionally contact projections 35
when lid 11
is closed to base 25. Projections 26 serve to buttress projections 35 and keep
lid 11 from
twisting about base 25. Lid rim gaps 27 are disposed between projections 26 on
lid rim
14. In addition, by frictionally engaging projections 35, projections 26 make
the
engagement between lid 11 and base 25 stronger. As shown in the drawings, the
height
of projections 35 emanating from the base rim structure prevents lid flange 22
from
sealing completely against base flange 42. As a result, when the lid is fully
engaged to
the base, projections 35 of base rim 30 are engaged by channel 23 and
projections 26 of
lid rim 14. However, the height of engaged projections 35 is such that flange
22 and
flange 42 do not meet when the lid is engaged by the base. In this regard,
when the
container is closed, one or more lid rim gaps 27 between projections 26 of the
lid align
both vertically and horizontally with a base rim gap 39 of the base rim.
Hence, base rim
gaps 39 between the base rim projections are now roofed by rim 14 and create
at least two
rim intake ports 40 that allow air to directly enter the container generally
horizontally.
[0036] In carrying out the invention it is not important which rim, lid or
base, is
provided with the projections 35 or the engaging channel 23. Accordingly, in
another
embodiment, base rim 30 could be provided with channel 23 and lid rim 14 could
be
provided with projections 35. In fact, other rim engaging methods could be
used as long
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as the sealing rim structures of the lid and base create intake ports 40 when
the rims are in
sealing arrangement.
[0037] When the lid rim and base rim are in sealing arrangement, the
container
comprises at least one set of counterpart intake ports 40 (a first intake port
and a first
counterpart intake port). More specifically, in the present invention
container, the lid rim
and base rim when in closed engagement form at least one first intake port
disposed
between the two rims. In addition, it is a feature of the invention that each
first intake
port has at least one first counterpart intake port disposed between the two
rims. In
contrast to prior art containers, the intake ports of the present invention
allow air to flow
directly through the rims of the container and not travel a serpentine course
through rim
structure. In addition, in comparison to prior art containers, the intake
ports of the present
invention allow air to flow directly into the container in a generally
horizontal manner
without having to travel an angled path. Hence, in the present invention
intake ports 40
are not angled toward the container top.
[0038] The at least one first intake port and its one or more first
counterpart intake
ports are disposed between the two rims such as to permit air to enter the
container
through an intake port, cross at least a portion of the interior of the
container under the
food contents and then, as it warms, rise and exit the container through the
exhaust vents
in the top surface of the lid. For balanced moisture removal, each first
intake port 40 is
located in the engaged rims 14, 30 and has at least one first counterpart
intake port 40
similarly located in the engaged rims 14, 30. In the shown preferred
embodiment
container, each first intake port 40 is located on the closed container such
that it
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geometrically opposes (is perpendicularly across from) one counterpart intake
port 40 on
the other side of the container. This arrangement enables the cross-flow of
air underneath
food contents throughout the entire container in the case of a pressure
differential
between the ends of the one or more channels. The invention thus allows drier
air to flow
into the container through an intake port 40, under the container contents and
out through
the exhaust vents 28 in the top surface of the lid. Though the depicted
embodiment
container shows an intake port 40 to have only one counterpart intake port 40,
an intake
port 40 may have more than one counterpart intake port 40.
[0039] Floor 31 includes two or more ribs 50 and may have alternating
levels or
elevations for strength and fluid control. To further enhance food crispness,
floor 31 of
base 25 comprises ribs 50 in floor recess 51. Floor recess 51 is a preferred
embodiment
feature. Ribs 50 project upward from floor recess 51. Spaced apart elongated
ribs 50 are
aligned with the line defined by at least one set of counterpart intake ports
40 and form at
least one channel 55. The one or more channels 55 act as flow paths for the
relatively
drier air inducted into the container through intake ports 40. In this regard,
the formation
of aligned channels 55 on floor 31 differs from the prior art container with
floor bottoms
provided with grids, wells or other structural features intended to capture
and retain
liquid. These structural floor elements, though useful in preventing sloshing
of liquids or
keeping food raised above pooled liquids serve as barriers to air flow
underneath the
container's food contents.
[0040] In the depicted preferred embodiment the one or more channels 55
are
lengthwise centered along one dimension of the floor and extend substantially
across the
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length of the floor. Further, recess 51 is formed in floor 31 so as to guide
incoming air to
the channels and allow incoming air to fan (branch) out to the multiple of
channels
disposed in it. The at least one channel 55 is oriented such that it extends
in the direction
of one set of counterpart intake ports 40 and thus the sides of the channel
act like interior
baffles. In the disclosed embodiment, the container depicts six channels 55
aligned with
intake ports 40 disposed on the ends of the container. By virtue of being
oriented in this
fashion, channel 55 allows steam gases that may form from pooled liquid to
rise and be
conveyed away from food contents by convection, thus reducing the over-
moistening of
the bottom of food. Additionally, by virtue of the intake ports 40, drier air
may flow into
intake ports 40 and around and under the container contents. Specifically, by
virtue of the
baffle effect of channel 55, drier air entering into the container through an
intake port 40
may flow under food contents and exit out through top surface exhaust vents
28. In an
alternative embodiment, floor 31 could comprise a plurality of channels 55, at
least two of
which are aligned in two different directions so as to provide channels that
align with
more than one set of counterpart intake ports 40. Additionally, in the
preferred
embodiment, floor 31 includes textured surface platforms 52. Platforms 52 are
embossed
(raised) above the interior surface of floor 31 (and thus substantially higher
than the
surface of recess 51). By virtue of this arrangement, food contents are lifted
off the
surface of floor 31 and the drier air entering the container from the intake
ports 40 can
more easily flow under the food contents and into the one or more channels 55.
[0041] The terms "opposing," "opposed" or "opposite" as used herein to
describe
the location of the base rim gaps 39 or intake ports 40 means that the gaps or
portals are
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oriented to allow the flow of ventilation into the container through one port,
through a
certain length or width of the interior of the container and then toward at
least one other
intake port. Hence, in the depicted rectangular container embodiment, a first
intake port
40 is situated on one side of the container and a counterpart intake port 40
is located
across the container on the opposing parallel side of the container. In this
case, the at
least one other counterpart intake port 40 would be preferably, but not
necessarily,
located perpendicularly across from the first intake port 40. Similarly, with
a round
container, the set of counterpart intake ports 40 would be preferably, but not
necessarily,
diametrically across from each other. Variations in the locations of
counterpart ports 40
(and gaps 39) and the alignment of the floor ribs 50 and channel 55 may be
made such
, that air only flows through a portion of the container and not its entire
width or length.
For example, in a rectangular container the intake ports 40 could be located
on adjacent
sides of the container to promote the diagonal flow of cross ventilation. The
cross flow of
ventilation in such an embodiment would be enhanced by having one or more
diagonally
oriented floor channels 55 aligned with the intake ports. Additionally, each
intake port 40
preferably has at least one counterpart intake port 40 to achieve cross flow
ventilation.
Thus, an intake port 40 could have more than one counterpart intake port 40.
[00421 As shown in FIG. 2 to further enhance the convection flow in the
container,
the lid of the preferred embodiment container includes a plurality of exhaust
vents 28
disposed about the top surface 12 of the container lid. For optimum convection
movement in the container, it is critical that exhaust vents 28 be disposed
and arranged on
the top surface 12 of the container and not on any of the outermost side
surfaces of the
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lid. Otherwise, the inductive action on intake ports 40 is lessened or the
inducted air may
not have an opportunity to drop to the container floor before being pushed out
by
convection forces. At the same time, to enhance convective movement inside the
container it is preferable that the plurality of exhaust vents 28 on the top
surface 12 of the
lid be disposed away from the lid center so that they follow the contour (as
viewed from
overhead) of the lid shape. In the depicted embodiment shown in FIG. 2, an
exemplary
number and arrangement of surface exhaust vents is shown on an approximately
9" x 8"
rectangular container. Tests on this exemplary embodiment show that the
optimum
convection movement in the container occurs with a plurality of 14 exhaust
vents
disposed in the shown pattern about the periphery of the top surface of the
lid and located
within the range of 1" to 1-1/4" (measured from the front edge of the vent)
from the
nearest outer edge of the top surface of the container. For most food service
applications
(side dish sized containers to entrée sized containers) a plurality of at
least 8 top surface
exhaust vents 28 works well, with the range of 8 to 14 vents (cruciate slit
type) showing
optimum results. As shown in FIG. 2, it is further preferable that exhaust
vents 28 be
disposed so that they direct rising gases and vapors outward in relation to
the container's
outermost exterior side surfaces. This arrangement of exhaust vents on the lid
top surface
and the absence of vents on the outermost side surfaces of the lid removes the
dead-air
effect caused by having apertures on the side of the lid in close proximity to
(particularly
above) the rim vents. By removing this dead-air effect, convection in the
container is
enhanced.
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[0043] A container constructed in accordance with the present
invention can be
manufactured in a variety of shapes and sizes, and is preferably formed of
resins or plastic
materials including, but not limited to, polyethylene, polypropylene,
polyvinyl chloride or
polyethylene terephthalate ("PET"). The container lid and base can be
transparent or
translucent, and may be colored in either instance. The size and number of
intake and
exhaust vents can be varied to accommodate the food heating environment or the
requirements of the food placed in the container. The container can be made by
a variety
of processes including thermoforming, vacuum forming, blow molding, extrusion
molding or injection molding. Further, the container can be of any shape,
including
round or polygonal. The lid and base of the container may be separate articles
or may
include the depicted hinge such that the lid and base are connected to each
other in a
clamshell configuration.
[0044] Having described the invention in detail, those skilled in the
art will
appreciate that modifications may be made of the invention without departing
from its
scope. Therefore, it is not intended that the scope of the invention be
limited to the
specific embodiment illustrated and described.
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