U.S. patent application number 10/796924 was filed with the patent office on 2004-11-25 for microwaveable food storage container with freshness indicator and steam vent.
Invention is credited to Goeking, Harold J., Paul, Joseph M., Thompson, Carl R..
Application Number | 20040232026 10/796924 |
Document ID | / |
Family ID | 33032666 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040232026 |
Kind Code |
A1 |
Goeking, Harold J. ; et
al. |
November 25, 2004 |
Microwaveable food storage container with freshness indicator and
steam vent
Abstract
A microwaveable food storage container including a unitary base
having a generally planar bottom portion and a sidewall extending
generally upwardly therefrom, the sidewall of the base including
base sealing means for cooperating with a lid to form a seal; an
injection-molded lid provided with resettable freshness indicator
means at least in part integrally formed with the lid; a resealable
vent preferably with a hinged vent panel integrally formed in the
lid; and lid sealing means for cooperating with the base sealing
means to form an annular interference-fit seal when the lid and
base are joined. Preferably the base is an injection-molded base
formed from a polypropylene resin such as isotactic polypropylene.
In other embodiments, the polypropylene resin composition comprises
a propylene/ethylene copolymer. Preferably, the base has a
chamfered guide shoulder as well as an inwardly projecting annular
sealing protuberance at the upper sidewall to define a notch
wherein a sealing band in the lid is wedged when the base and lid
are joined to form a closed container.
Inventors: |
Goeking, Harold J.;
(Oshkosh, WI) ; Thompson, Carl R.; (Westport,
CT) ; Paul, Joseph M.; (Thomaston, CT) |
Correspondence
Address: |
FERRELLS, PLLC
P. O. BOX 312
CLIFTON
VA
20124-1706
US
|
Family ID: |
33032666 |
Appl. No.: |
10/796924 |
Filed: |
March 10, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60454230 |
Mar 13, 2003 |
|
|
|
60454268 |
Mar 13, 2003 |
|
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Current U.S.
Class: |
206/459.1 |
Current CPC
Class: |
A47J 36/027 20130101;
B65D 2543/00527 20130101; B65D 2543/00296 20130101; B65D 51/245
20130101; B65D 2543/00101 20130101; B65D 2543/00555 20130101; B65D
2543/00759 20130101; B65D 2543/00842 20130101; B65D 2543/00648
20130101; B65D 2543/0037 20130101; B65D 43/0212 20130101; B65D
2543/0099 20130101; B65D 2543/00537 20130101; B65D 51/1672
20130101; B65D 2543/00472 20130101; A47J 47/10 20130101; B65D
2543/00657 20130101; B65D 2543/00796 20130101; B65D 2543/00685
20130101 |
Class at
Publication: |
206/459.1 |
International
Class: |
B65D 085/00 |
Claims
What is claimed is:
1. A microwaveable food storage container comprising: (a) a unitary
base having a generally planar bottom portion and a sidewall
extending generally upwardly therefrom, the sidewall of the base
including base sealing means for cooperating with a lid to form a
seal; (b) an injection-molded lid provided with: (i) resettable
freshness indicator means at least in part integrally formed with
the lid; (ii) a resealable vent integrally formed in the lid; and
(iii) lid sealing means for cooperating with the base sealing means
to form an annular interference-fit seal when the lid and base are
joined to form a closed container.
2. The microwaveable food storage container according to claim 1,
wherein the base is an injection-molded base.
3. The microwaveable food storage container according to claim 2,
wherein the lid and base are formed from a polypropylene resin.
4. The microwaveable food storage container according to claim 3,
wherein the polypropylene resin composition comprises isotactic
polypropylene.
5. The microwaveable food storage container according to claim 3,
wherein the polypropylene resin composition comprises a
propylene/ethylene copolymer.
6. The microwaveable food storage container according to claim 1,
wherein the resettable freshness indicator means comprises a
plurality of bistable, eversible domed regions integrally formed on
the lid.
7. The microwaveable food storage container according to claim 6,
wherein the domed portions are generally thinner at their junctions
with adjacent portions of the lid than the adjacent portions of the
lid.
8. The microwaveable food storage container according to claim 7
wherein the bistable, eversible domed portions of the lid have a
peripheral portion which is less than about 50% of the thickness of
adjacent areas of the lid.
9. The microwaveable food storage container according to claim 8,
wherein the bistable, eversible domed portions have a generally
planar central portion.
10. The microwaveable food storage container according to claim 6,
wherein the bistable, eversible domed portions are generally
thinner than adjacent portions of the lid over their profiles.
11. The microwaveable food storage container according to claim 10,
wherein the bistable, eversible domed portions of the lid have a
thickness which is 50% or less than the thickness of the adjacent
portions of the lid.
12. The microwaveable food storage container according to claim 11,
wherein the bistable, eversible domed portions of the lid have a
generally planar central portion.
13. The microwaveable food storage container according to claim 1,
wherein the resealable vent comprises a hinged vent panel
integrally formed in the lid and secured to the lid at the lid's
periphery.
14. The microwaveable food storage container according to claim 13,
wherein the resealable vent comprises a vent conduit integrally
formed in the lid and extending therethrough and the vent panel
includes a sealing element integrally formed therewith adapted to
seal the conduit.
15. The microwaveable food storage container according to claim 14,
wherein the sealing element includes terminal projections
configured to provide an audible indication sealing or unsealing
the vent.
16. The microwaveable food storage container according to claim 15,
wherein the sealing element is a segmented closure element.
17. The microwaveable food storage container according to claim 14,
wherein the vent conduit and closure elements have sealing
shoulders configured to engage each other to form a seal.
18. The microwaveable food storage container according to claim 1,
comprising: (a) a unitary base having a generally planar bottom and
a sidewall extending generally upwardly therefrom, (i) the sidewall
defining an upper sidewall portion including an inwardly projecting
annular sealing protuberance; (ii) the base further including a rim
extending outwardly from the upper sidewall portion of the base;
and (b) a unitary lid having a generally planar upper surface as
well as: (i) a downwardly extending sealing band adapted to
cooperate with the inwardly projecting annular sealing protubernace
of the upper sidewall of the base to form an annular
interference-fit seal; and (ii) a lid rim extending outwardly with
respect to the sealing band, the lid rim having a downwardly
projecting outer wall provided with an undercut on its lower edge
extending around the lid, the undercut being adapted to cooperate
with the outer edge of the base rim to audibly indicate secure
closure of the container.
19. The microwaveable food storage container according to claim 18,
wherein the sealing protuberance of the uppermost sidewall portion
of the base is at least about 1.25 times the thickness of the
adjacent sidewall portions of the base.
20. The microwaveable food storage container according to claim 18,
wherein the annular interference-fit seal formed between the
sealing band and the sealing protuberance of the upper sidewall of
the base is a continuous annular seal.
21. The microwaveable food storage container according to claim 18,
wherein the downwardly projecting wall of the lid rim and the
sealing band of the lid generally define an inverted U-shaped
profile.
22. The microwaveable food storage container according to claim 21,
wherein the lid further comprises a downwardly extending
intermediate spacer projection between the sealing band and the
downwardly projecting outer wall of the lid rim.
23. The microwaveable food storage container according to claim 22,
wherein the rim of the base is an inverted U-shape.
24. The microwaveable food storage container according to claim 23,
wherein the downwardly extending intermediate projection of the lid
is configured to adjust the clearance of a downwardly projecting
outer leg of the lid rim and a locking bead on the outer leg of the
base rim to a clearance between about 0 and about 5% when the lid
and base are joined together.
25. The microwaveable food storage container according to claim 23,
wherein the inverted U-shape of the lid rim is sized to compress
the inverted U-shape of the base rim to form a second
interference-fit seal around at least a portion of the container
when the lid and base are joined together.
26. The microwaveable food storage container according to claim 18,
wherein the undercut on the lid rim cooperates with the outer edge
of the base rim to form another leakage barrier.
27. A microwaveable storage container according to claim 1,
comprising: (a) a unitary base having a generally planar bottom
portion and a sidewall portion extending generally upwardly
therefrom; (i) the sidewall defining an upper sidewall portion
including a sealing notch disposed on an interior side of the
sidewall having an inwardly projecting annular sealing protuberance
at the outward side of the notch and an inner notch wall at the
inward side of the notch; (ii) the base further including a rim
extending outwardly from the upper sidewall of the base; (b) a
unitary lid having a generally planar upper surface as well as: (i)
a downwardly extending sealing band adapted to cooperate with the
inwardly projecting annular sealing protuberance of the upper
sidewall of the base to form an annular interference-fit seal; and
(ii) a lid rim extending outwardly with respect to the sealing
band, the lid rim having a downwardly projecting outer wall
optionally provided with an undercut adapted to cooperate with the
outer edge of the base rim to audibly indicate secure closure of
the container.
28. The microwaveable food storage container according to claim 27,
wherein the downwardly extending inner notch wall includes a
substantially vertical portion and an upper chamfered portion which
extends downwardly and outwardly.
29. The microwaveable food storage container according to claim 28,
wherein the annular sealing protuberance at the outer side of the
notch includes a substantially vertical portion.
30. The microwaveable food storage container according to claim 27,
wherein the sealing protuberance is thicker than adjacent portions
of the base sidewall immediately above the sealing
protuberance.
31. The microwaveable food storage container according to claim 27,
wherein the inner notch wall of the sealing notch is thicker than
the sidewall of the base immediately below the inner sealing notch
wall.
32. A microwaveable storage container according to claim 1,
comprising: (a) a unitary base having a generally planar bottom
portion and a sidewall portion extending generally upwardly
therefrom; (i) the sidewall defining an upper sidewall portion
including a sealing notch disposed on an interior side of the
sidewall having an inwardly projecting annular sealing protuberance
at the outward side of the notch and an inner notch wall with a
downwardly extending inner surface at the inward side of the notch;
(ii) the base further including a rim extending outwardly from the
upper sidewall of the base; (b) a unitary lid having a generally
planar upper surface as well as: (i) a downwardly extending annular
sealing band adapted to cooperate with the inwardly projecting
annular sealing protuberance of the upper sidewall of the base to
form an annular interference-fit seal; and (ii) wherein the annular
sealing band of the lid and the sealing notch of the base are
configured so that the sealing band becomes wedged in the notch
when the lid and base are joined together to form a closed
container; and (iii) a lid rim extending outwardly with respect to
the sealing band, the lid rim having a downwardly projecting outer
wall optionally provided with an undercut adapted to cooperate with
the outer edge of the base rim to audibly indicate secure closure
of the container.
33. The microwaveable storage container according to claim 32,
wherein the downwardly projecting wall of the lid rim and the
sealing band of the lid generally define an inverted U-shaped
profile and the rim of the base is an inverted U-shape.
34. The microwaveable storage container according to claim 32,
wherein the lower edge of the sealing band is configured to
cooperate with the downwardly extending inner surface of the inner
notch wall of the base to form another leakage barrier when the lid
and base are joined together to form a closed container.
Description
CLAIM FOR PRIORITY
[0001] This non-provisional application claims the benefit of the
filing dates of U.S. Provisional Patent Applications Ser. Nos.
60/454,230 and 60/454,268, both filed on Mar. 13, 2003.
TECHNICAL FIELD
[0002] The present invention relates generally to food storage
containers and more particularly to a food storage container having
a lid and base with sealable portions operable to form an
interference-fit seal as well as a lid vent and freshness
indicators.
BACKGROUND
[0003] Food storage containers as well as containers with lids and
bases having deformable interlocking rims are well known in the
art. Such containers may include stacking shoulders as is seen, for
example, in U.S. Pat. No. 6,467,647 to Tucker et al. as well as
U.S. Pat. No. 6,170,696 also to Tucker et al. The '647 and 696
patents are directed to plastic containers including a lid and base
wherein the rim of the lid and rim of the base have cut back
portions around their periphery to form at least two continuous
seals around the periphery of the container. So also, there is
shown in U.S. Pat. No. 6,460,716 to Wong a plastic container
including a lid and a base each of which has a flange and an
inverted U-shaped rim. The flanges and rims mate to form four
seals. A large horizontal seal is provided and two air pockets
between seals allow for easy opening.
[0004] U.S. Pat. No. 6,196,404 to Chen shows a container with a lid
and base which form a series of three self reinforcing seals. A
protrusion on the lid reinforces the triple seal between the lid
and base by applying force to the base, locking the lid and base
together.
[0005] In U.S. Pat. No. 6,168,044 to Zettle et al. there is
disclosed a resilient microwaveable container including a bowl and
a detachable snap on lid. The lid includes a plurality of
protrusions which snap over a pair of annular flanges extending
outwardly from the bowl whereby a distinct clicking sound can be
heard to verify the lid is properly attached.
[0006] In U.S. Pat. No. 6,056,138 to Chen there is disclosed a
triple seal container including both a base and a lid. The base is
a unitary component including a bottom portion attached to an
upwardly extending perimeter wall which is further connected to a
peripherally extending rim having an inner and outer edge. The lid
also consists of a unitary component with a downwardly extending
wall which is connected to a peripherally extending rim also having
an inner and outer edge. Upon contact, the edges of the rims form
three main seals.
[0007] Numerous means have been employed to form rim seals between
lids and bases of containers. For example, there is seen in U.S.
Pat. No. 6,260,729 to Mitchell et al. a highly elastic sealing
cover for covering food containers or dishes which includes an
accordion like construction so as to be adaptable to a variety of
bases.
[0008] In U.S. Pat. No. 6,021,917 to Lovell et al. there is
disclosed a plastic lid for a pail. The lid has a substantially
planar central section and a peripheral channel. The channel fits
over the pail to effect closure thereof. The central section is
spaced from the channel by a groove and a ridge each of which
extend around the lid juxtaposed to the channel with a groove being
adjacent to the channel. Another pail/lid combination is seen in
U.S. Pat. No. 5,328,047 to Smith. In the '047 patent there is
disclosed a double locking cover which has a substantially J-shaped
locking tip which fits into locking engagements with a ring on the
pail.
[0009] U.S. Pat. No. 5,377,860 to Littlejohn et al. discloses a
food container which is a combination of base portion and a lid
portion made from resilient polymeric material. The base is a
unitary component including an upwardly projecting peripherally
extending sealing rim having inner and outer sealing regions. The
lid is also a unitary component including a peripherally extending
sealing channel correspondingly shaped to receive the sealing rim
of the base and particularly to engage the rim at the inner and
outer sealing areas.
[0010] In addition to sealing rims, various features have been
incorporated into food sealing containers such as vents, freshness
indicators and the like. As to vents the following art is
representative: U.S. Pat. No. 6,305,546 to Saunders et al.; U.S.
Pat. No. 5,780,824 to Matos; U.S. Pat. No. 5,750,967 to Sprauer,
Jr.; U.S. Pat. No. 5,039,001 to Kinigakis et al.; U.S. Pat. No. Re.
32,739 to Terauds; U.S. Pat. No. 4,261,504 to Cowan; U.S. Pat. No.
4,574,174 to McGonigle; and U.S. Pat. No. 3,873,735 to Chalin et
al.
[0011] Indicators for identifying container contents and/or
freshness indicators for containers are known in the art. There is
shown for example in U.S. Pat. No. 3,974,916 to Bartolucci a cup
cover with a plurality of raised, dome-shaped portions each of
which is capable of manual eversion. Visible indicia associated
with each raised portion and identifying a variety of contents
which can be placed in the cup around the raised dome-shaped
portions. Manual eversion of a selected raised portion thus alters
the appearance of the portion to provide a visual indication of the
identity of the particular contents of the cup. Other containers
associated with identifying indicia are shown in the following
patents: U.S. Pat. No. 5,642,605 to Tenner et al.; U.S. Pat. No.
5,790,718 also to Tenner et al.; U.S. Pat. No. 5,839,581 to
Vagedes; U.S. Pat. No. 4,762,248 to Uhlig; and U.S. Pat. No.
3,818,858 to Kramer et al. See, also, U.S. patent application Ser.
No. 09/277,270 of Ferretti et al., filed Mar. 26, 1999.
SUMMARY OF INVENTION
[0012] There is provided in accordance with the invention a
microwaveable food storage container including a unitary base
having a generally planar bottom portion and a sidewall extending
generally upwardly therefrom, the sidewall of the base including
base sealing means for cooperating with a lid to form a seal; an
injection-molded lid provided with resettable freshness indicator
means at least in part integrally formed with the lid; a resealable
vent integrally formed with the lid; and lid sealing means for
cooperating with the base sealing means to form an annular
interference-fit seal when the lid and base are joined to form a
closed container. Preferably the base is an injection-molded base
formed from a polypropylene resin such as isotactic polypropylene.
In other cases, the polypropylene resin composition comprises a
propylene/ethylene copolymer.
[0013] A preferred resettable freshness indicator means comprises a
plurality of bistable, eversible domed regions integrally formed on
the lid. The domed regions are generally thinner at their junctions
with adjacent portions of the lid than the adjacent portions of the
lid; typically less than about 50% of the thickness of adjacent
areas of the lid and have a generally planar central portion.
Preferably, the bistable, eversible domed portions are generally
thinner than adjacent portions of the lid over their profiles and
have a thickness which is 50% or less than the thickness of the
adjacent portions of the lid over their entire profiles.
[0014] The resealable vent preferably comprises a hinged vent panel
integrally formed in the lid preferably secured to the lid at the
lid's periphery which is adapted to cooperate with a vent conduit
integrally formed in the lid and extending therethrough wherein the
vent panel includes a sealing element integrally formed therewith
adapted to seal the conduit. The sealing element includes terminal
projections configured to provide audible feedback such as a snap
or click indicating the container is sealed upon sealing or
unsealing the vent. Most preferably, the closure element is a
segmented closure element. The vent conduit and closure elements
have sealing shoulders configured to engage each other to form a
seal in a preferred construction.
[0015] A preferred embodiment is a microwaveable food storage
container provided with a unitary base having a generally planar
bottom portion and a sidewall extending generally upwardly
therefrom, the sidewall defining an upper sidewall portion
including an inwardly projecting annular sealing protuberance. The
base further includes a rim at the upper and outer edge of the
uppermost sidewall portion preferably in the shape of an inverted
U. A lid which is adapted to join with the base to form a sealed
enclosure is a unitary lid having a generally planar upper surface
as well as:
[0016] a downwardly extending sealing band adapted to cooperate
with the inwardly projecting annular sealing protuberance of the
upper sidewall of the base to form an annular interference-fit
seal; and
[0017] a lid rim extending outwardly with respect to the sealing
band, the lid rim having a downwardly projecting outer wall
provided with an undercut on its lower edge extending around the
lid, the undercut being adapted to cooperate with the outer edge of
the base rim to optionally provide a leakage barrier as well as
audibly indicate secure closure of the container.
[0018] Preferably, the inwardly projecting sealing protuberance of
the upper sidewall of the base is at least about 1.25 times the
thickness of the adjacent sidewall portions of the base. Most
preferably, the annular interference-fit seal formed between the
sealing band and the sealing protuberance of the upper sidewall of
the base is a continuous annular seal.
[0019] In typical embodiments, the downwardly projecting wall of
the lid rim and the sealing band of the lid generally define an
inverted U-shaped profile and the lid further comprises a
downwardly extending intermediate spacer projection between the
sealing band and the downwardly projecting outer wall of the lid.
Preferably, the downwardly extending intermediate projection of the
lid is configured to adjust the clearance of a downwardly
projecting outer leg of the lid rim and a locking bead on the outer
leg of the base rim is between about 0 and about 5% when the lid
and base are joined together. This may be accomplished by sizing
the downwardly extending intermediate projection of the lid such
that the height of the projection is from about 100% to about 105%
of the clearance between the lid rim and base rim at the location
of the downwardly extending intermediate projection when the lid
and base are joined together.
[0020] In some embodiments, the inverted U-shape of the lid rim is
sized to compress the inverted U-shape of the base rim to form a
second interference-fit seal around at least a portion of the
container when the lid and base are joined together. In
particularly preferred embodiments, the sidewall of the base
defines a sealing notch disposed on an interior side of the
sidewall having an inwardly projecting annular sealing protuberance
at the outward side of the notch and an inner notch wall at the
inward side of the notch. The annular sealing protuberance and the
inner notch wall may both include a substantially vertical portion.
The inner wall most preferably has an upper chamfered portion which
extends outwardly and downwardly with respect to the center of the
container. Both the sealing protuberance and the inner notch wall
are thicker than immediately adjacent portions of the base
sidewall.
[0021] In particularly preferred embodiments, the sealing band of
the lid and the notch in the upper sidewall of the base are
configured such that the sealing band is wedged into the notch when
the base and lid are joined together to form a sealed
container.
[0022] Preferably the polymeric composition from which the
inventive containers are made is a resilient composition based on
polypropylene. While any suitable polypropylene polymer may be
used, the polypropylene polymers are perhaps most preferably
selected from the group consisting of isotactic polypropylene, and
copolymers of propylene and ethylene, for example, wherein the
ethylene moiety is less than about 10% of the units making up the
polymer, and mixtures thereof. Suitable polymers are isotactic
polypropylenes with melt-flow indices of from about 20 to about
100, usually between about 30 and 60. In some preferred
embodiments, the resin from which the containers are made includes
polypropylene melt blended with a polyethylene component. The
polyethylene component may be any suitable polyethylene such as
HDPE, LDPE, MDPE, LLDPE or mixtures thereof.
[0023] The various polyethylene polymers referred to herein are
described at length in the Encyclopedia of Polymer Science &
Engineering (2d Ed.), Vol. 6; pp: 383-522, Wiley 1986; the
disclosure of which is incorporated herein by reference. HDPE
refers to high density polyethylene which is substantially linear
and has a density of generally greater that 0.94 up to about 0.97
g/cc. LDPE refers to low density polyethylene which is
characterized by relatively long chain branching and a density of
about 0.912 to about 0.925 g/cc. LLDPE or linear low density
polyethylene is characterized by short chain branching and a
density of from about 0.92 to about 0.94 g/cc. Finally,
intermediate density polyethylene (MDPE) is characterized by
relatively low branching and a density of from about 0.925 to about
0.94 g/cc.
[0024] Instead of the above noted polypropylene based resinous
compositions, polypropylene/polyethylene copolymers with more
significant polyethylene content could be used or a polyethylene
based composition could be used or polyethylene terephthalate based
compositions may be used. In still further embodiments, any other
suitable polymeric composition is used so long as the composition
is sufficiently resilient.
[0025] As used herein the terminology polypropylene resin or
polypropylene composition or like terminology refers to a
composition which is predominately (more than 50 mole %) made up of
propylene repeat units and includes melt blends with other resins
and additives. Likewise, polyethylene resins are mostly ethylene
repeat units while polyethylene terephthalate resins are mostly
ethylene terephthalate repeat units. An ethylene/propylene
copolymer contains both ethylene and propylene repeat units in the
resin and may be made up primarily of repeat units of either
species.
[0026] The terminolopgy "interference-fit seal" refers to a seal
between sealing members which are configured such that they are
urged into engagement by their geometries. One sealing member thus
has a larger dimension or dimensions in the free state than the
dimension or dimensions of the cooperating part with which it forms
a seal. When the interference-fit seal is formed, the sealing
members become the same size and develop a seal through elastic
compression, plastic movement of material, or both, much like
interference-fit class 5 threads. See Machinery's Handbook, R.
Green, Ed., 24.sup.th edition, Industrial Press.
[0027] The foregoing features and advantages of the present
invention will be further appreciated from the drawings and
description which follows.
BRIEF DESCRIPTION OF DRAWINGS
[0028] The invention is described in detail below with reference to
the various drawings wherein like numbers designate similar parts
and wherein:
[0029] FIG. 1 is an exploded view in perspective of a microwaveable
food storage container provided in accordance with the present
invention;
[0030] FIG. 2 an enlarged schematic view showing partial profiles
of the inventive lid and container base prior to joining the lid to
the base;
[0031] FIG. 2A is a further enlarged schematic view showing the
annular sealing notch profile of the base;
[0032] FIG. 3 is an enlarged schematic view showing the lid of the
invention attached to the base wherein the sealing band engages the
sealing notch of the container, the outer sealing bead of the lid
grips the lower edge of the container base rim and the intermediate
spacer projection engages the arcuate rim of the container
base;
[0033] FIG. 3A is a further enlarged schematic view showing the
annular sealing band wedged into the sealing notch when the lid and
base are joined to form a closed container;
[0034] FIG. 4 is an enlarged schematic view showing the resealable
vent of the inventive container in an open position; and
[0035] FIG. 5 is an enlarged view in cross section of an eversible
indicator dome of the present invention.
DETAILED DESCRIPTION
[0036] The invention is described in detail below with reference to
the various Figures. Such discussion and illustration is for
purposes of exposition only and is not intended to limit in any way
the scope of the present invention which is set forth in the
appended claims.
[0037] Referring generally to FIGS. 1 through 5 there is shown an
embodiment of the inventive microwaveable food storage container 10
which includes a lid 12 and a base 14. Base 14 has a generally
planar bottom portion 16 as well as a sidewall 18 which extends
upwardly and outwardly to an upper sidewall portion. Upper sidewall
portion 20 defines a notch 25 between an inner annular notch wall
27 and an annular sealing protuberance 23 at the outer side of the
notch. Inner notch wall 27 preferably defines a chamfered surface
22 as well as a substantially vertical surface 27a. Annular sealing
protuberance 23 has a sealing corner 29 and a substantially
vertical surface 23a.
[0038] Preferably, both the sealing protuberance 23 and the inner
notch wall 27 are thicker than the immediately adjacent portions of
the sidewall of the base. In the embodiment illustrated, the
sidewall of the container generally has a thickness A, whereas
protuberance 23 has a thickness B and inner notch sidewall 27 has a
thickness C. B and C may be 1.25 times or more the thickness A in
order to fortify the sealing notch. For example, B and C could be
1.5 times A or twice A in some embodiments. This fortified
construction is readily achieved by injection molding the base and
is appreciated by reference to FIG. 2A in particular, which is a
further enlarged schematic view of the interior sealing region of
the container.
[0039] Upper sidewall portion 20 of the base continues upwardly and
outwardly with respect to notch 25 and defines a rim 24 which
terminates at a lower peripheral edge 26.
[0040] Lid 12 includes a generally planar central portion 28 as
well as a curved rim 30 shaped like one leg of an inverted U. The
lid also includes a downwardly extending sealing band 32 as well as
an intermediate spacer projection 34 and an undercut or bead 36 to
provide audible and tactile feedback that the lid is securely
snapped in place on a downwardly extending portion of the rim of
the base such as edge 26. Bead 36 is located on the lower edge of
rim 30 and preferably forms a leakage barrier with edge 26 when
snapped in place as is seen in FIG. 3, wherein there is represented
an annular leakage barrier at 7.
[0041] The lid and base fit together to form an interference-fit
seal as is shown schematically in FIGS. 3 and 3A in particular.
Band 32 is generally disposed in notch 25 when lid 12 and base 14
are joined as shown in FIGS. 3 and 3A. Sealing band 32 has a slight
inward draft and is configured to bear upon inwardly projecting,
annular sealing protuberance 23 at corner 29 to form an
interference-fit seal therewith. Preferably, that seal is
substantially liquid proof and extends around the entire periphery
of the container, as is indicated at 3 on FIG. 3A; that is, seal 3
is preferably a continuous annular interference-fit seal.
[0042] The various features are sized as shown and are further
understood by reference to FIG. 2. The height of the bottom of
projection 34 above the bottom of sealing band 32 is shown as
H.sub.LB, while the height of the bottom of projection above bead
36 is denoted H.sub.LR. The height of the base rim, H.sub.BR, is
from about 0.95 to about 1.0 times the height, H.sub.LR, such that
the clearance of the outer leg of the lid rim with the locking bead
36 is from about 0 to about 5% when the lid and base are joined
together. Sealing band 32 is sized and notch 25 is positioned such
that the height of the base rim above the top of notch 25,
H.sub.RN, is less than H.sub.LB. H.sub.LB, in turn, is typically
less than the height of the top of the base rim above the bottom
notch 25, H.sub.RB. In summary, the lid and base features are
suitably sized such that:
[0043] H.sub.BR.apprxeq.(0.95-1.0)H.sub.LR
[0044] and
[0045] H.sub.RN<H.sub.LB.ltoreq.H.sub.RB
[0046] Preferably both the lid and base are injection molded from a
polyolefin such as polyethylene or polypropylene, copolymers or
melt blends thereof.
[0047] In some embodiments, rim 24 may have a span 24a which is
larger than the interior span of the inverted U-shaped rim 30 of
the lid such that the rim of the base is compressed in the
direction of arrow 33 when the lid and base are joined. In such
cases, a second annular interference-fit seal 9 is formed between
rim surfaces.
[0048] Most preferably, sealing band 32 and notch 25 are configured
so that annular band 32 is wedged into annular notch 25 as is seen
in FIG. 3A, preferably between surfaces 23a and 27a. In such cases,
the profile of band 32 undergoes a direction change with respect to
its line of contact with corner 29 of protuberance 23. That
direction change may be inward or outward with respect to the upper
profile of the sealing band, but is most preferably inward as shown
in FIG. 3A, wherein an additional annular leakage barrier is formed
at 11.
[0049] The containers of the invention are particularly suitable
for storing food and later microwaving the food in a microwaveable
oven. During this process, steam may be generated as the food is
heated to an elevated temperature. To accommodate the vapor, the
inventive containers are provided with a resealable steam vent in a
preferred embodiment. The resealable vent may take any suitable
configuration. One preferred embodiment is shown schematically in
FIG. 4. The resealable vent shown in FIG. 4 is integrally formed
with the rest of the lid 12 and includes a circular conduit 40
extending through the base as well as a hinged vent panel 42
attached to the remainder of the lid by an integral hinge 44. Vent
panel 42 includes a segmented cylindrical closure element 46 having
a sealing shoulder 45 which is adapted to seal vent conduit 40 at
shoulder or ledge 47. To close the vent hinged panel 42 is swung in
the direction of arrow 48 such that its edge 50 aligns generally
with a recess 52 formed in the top of the lid. Most preferably, the
closure element is further provided with a plurality of terminal
outward radially extending projections 49 which snap into place
when pressed through conduit 40. These projections are sized to
securely seal the vent and provide audible and tactile feedback
upon sealing or unsealing the vent. The recess is provided so that
when the vent panel is closed a user may readily insert a finger to
swing the panel to the open position as is shown in FIG. 4.
[0050] In preferred embodiments, the containers of the invention
are preferably provided with freshness indicators. Such indicators
may be eversible domed portions integrally formed in the lid as is
shown in FIGS. 1 and 5. Generally the eversible domed portions are
bistable in the sense that they can be pressed either inwardly to a
stable position or outwardly to a stable position. In the
embodiment shown in FIG. 1 there are provided seven domed portions
such as shown at 54 each of which is adjacent indicia indicating a
day of the week. In this way a user can mark or record the day that
a given entree or other food was stored. The eversible dome
portions are generally thinner than adjacent portions of the lid
and have a planar central portion as will be appreciated
particularly from FIG. 5.
[0051] There is shown in FIG. 5 a cross section of an eversible
domed portion integrally formed in lid 12, the domed portion 54
includes a generally planar central portion 56 as well as a
downwardly extending sidewall 58 as shown in the diagram. It is
noted that the adjacent portion of lid 12 has a thickness 60 which
is more than twice the thickness of the eversible dome portion of
the microwaveable container. Typically the domed portion is less
than 50% of the thickness of the adjacent areas of the lid as is
shown in FIG. 5. This thinning may extend over the entire domed
portion of the containers or may be localized at the boundaries
between the domed portion and the remainder of the lid indicated
generally at 62. That is to say, it is important that at least the
parts of the domed eversible indicators that are next to the
adjacent lid portions are thinner than the adjacent lid portion so
that the eversible domes may be readily inverted to indicate a date
or other pertinent information.
[0052] Additional features of the inventive containers may include,
for example, arcuate tabs 64, 66, 68 which are configured to have
an appearance similar to vent panel 42 in the closed position. The
tabs project outwardly from the corners in order to facilitate
opening and closing of the container. Arcuate tabs 64, 66 and 68
project outwardly and facilitate removal of lid 12 from base 14 by
providing a levering action when pressed upwardly urging bead 36
out of engagement with edge 26 of base 14.
[0053] While the invention has been described in connection with
several examples, modifications to those examples within the spirit
and scope of the invention will be readily apparent to those of
skill in the art. In view of the foregoing discussion, relevant
knowledge in the art and references including co-pending
applications discussed above in connection with the Background and
Detailed Description, the disclosures of which are all incorporated
herein by reference, further description is deemed unnecessary.
* * * * *