Note: Descriptions are shown in the official language in which they were submitted.
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PATENT
FN 44191CANlA
MICROWAVE FOOD PACKAGE
TECHNI CAL F IELD
The present invention relates to food packages for use
in a microwave oven and in particular, it relates to food
package# for foodstuffs that are to be dispensed from the
package in a flowable state after heating in a microwave
oven.
B~CKGROUND ART
Numerous package designs and utensils have been
devised for cooking various foodstuffs in microwave ovens.
However, certain foodstuffs are difficult to heat uniformly
in a microwave oven and dispenæe the foodstuff after
heating in the microwave oven. This is particularly true
for foodstuffs such as processed cheese that i6 to be
melted and dispensed in a flowable state. Conventional
microwave food packages for processed cheese include rigid
cup like receptacles. In such designs the outer portions of
the processed cheese contained in the cup like receptacle
tend to heat faster than the interior portion. Thus, in
order to reduce the cheese to a flowable (e.g. liquid)
state, the outer portions of the cheese tend to burn and
stick to the sides of the receptacle, while the interior
port~on "pool~" at the bottom of the receptacle. This is
inefficient and undesirable in terms of the energy and food
wasted, and the reduced amount of melted cheese available
after heating in the microwave oven. It is also difficult
1 to easily and completely dispense all of the melted cheese
from the receptacle without a utensil and thus more of the
' foodstuff tends to be wasted when utensils are not
3 5 avai lable .
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Further, it would be tedious and time consuming to
clean such a package and/or a utensil, if reuse were
desired.
Another problem associated with some foodstuffs, ~uch
as processed cheese for use as a sauce, are the gasses,
such as steam, that may be released from the foodstuff
during heating in a microwave oven. If the package is open
during cooking, the foodstuff may spill from the package,
with evident undesirable results. Conversely, if the
package is sealed during cooking to prevent the loss of the
foodstuff, the gasses released during heating may create an
undesirably high level of pressure within the package,
again with potentially undesirable results if the package
is unexpectedly breached.
Yet another problem associated with such food packages
is that of handllng the package and foodstuff after heating
in a microwave oven, since the package tends to be too hot
for direct manual contact. Further, the foodstuff not only
heats rapidly, but also tends to cool and lose heat too
rapidly for convenient dispensing after heating. If the
foodstuff is not flowable in an unheated state, the too
rapid cooling of the foodstuff may prevent dispensing of
the foodstuff from the package.
DISCLOSURE OF INVENTION
,.~
According to the present invention there is provided a
package for containing a quantity of a foodstuff for
heating the foodstuff in a microwave oven and dispensing
the foodstuff in a flowable state. The package includes a
bag having a chamber for receiving the foodstuff, having
3~ opposed end~ and an upper side and an opposing lower side
adapted for generally horizontal placement of the foodstuff
1 within the microwave oven. Means are provided ~or forming
an orifice in the bag communicating with the chamber $or
' dispensing the foodstuff in a flowable state after heating
in the microwave oven. Means are provided for venting the
chamber when the foodstuff iæ heated in the microwave oven
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to release vapor pressure within the chamber. Means are
also provided for insulating at least part of the upper
side of the bag to enable the bag to be handled after the
foodstuff is heated in the microwave oven.
Further, the present invention provides for the above
microwave food package in combination with a foodstuff.
BRIEF DESCRIPTION OF DRAWINGS
The present ~nvention will be further described with
reference to the accompanying drawing wherein l~ke
reference numerals refer to like parts in the several
views, and wherein:
Figure 1 is an isometric view of a microwave food
package according to the present invention.
Figure 2 is a magnified partial cross sectional view
along plane 2-2 of the microwave food package of Figure 1
containing a quantity of a foodstuff.
Figure 3 is a magnified partial cross sectional view
of the microwave food package of F~gure 2 after the
food~tuff has been heated to a flowa~le state in a
microwave oven and the venting member has been ruptured.
Figure 4 is a magnified partial cross sectional view
along plane 4-4 of the microwave food package of Figure 2.
Figure 5 is a plan v~ew of the microwave food package
of Figure 1, partially broken away.
Figure 6 is a side view of the microwave food package
of Figure 5 after heating in microwave oven and with the
package folded about a transverse line on the lower side
thereof.
Figure 7 is an isometric view of the foodstuff of the
microwave food package of Figure 1 being dispensed after
heating in microwave oven.
I Figure 8 is an isometric view of an alternate
embodiment of the microwave food package of this invention.
Figure 9 is side view of the microwave food package of
Fig~r~ 8.
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Figure 10 is a side view of the microwave food package
of Figure 9 after the foodstuff has been heated in a
microwave oven and the orifice has been opened.
Figure 11 is a magnified partial view of the
stiffening sheet of Figure 10.
Figure 12 is a maqnified partial view of an alternate
embodiment of the stiffening sheet of Figure 11.
Figure 13 is a plan view of yet another alternate
embodiment of the microwave food package of this invention.
Figure 14 is a side view of the microwave food package
of Figure 13.
Figure 15 is a bottom view of yet another alternate
embodiment of the microwave food package of this invention
having a microwave shielding member.
Figure 15a i8 a partial cross sectional view of the
microwave food package of Figure 15.
Figure 16 is a plan view, partially broken away, of
another alternate embodiment of the microwave food package
of this invention.
Figure 17 is a cross sectional view along plane 17-17
of the microwave food package of Figure 16.
Figure 18 is an isometric view of another alternate
embodiment of the microwave food package of this invention.
Figure 19 is a transverse cross sectional view along
plane 19-19 of the microwave food package of Figure 18.
Figure 20 is a longitudinal cross sectional view along
plane 20-20 of the microwave food package of Figure 18.
Figure 21 i8 an isometric view of the microwave food
package of Figure 18 with the foodstuff being dispensed.
Figure 22 is a side view of the microwave food package
of Figure 18 folded about a transverse line on the lower
side aligned with the dispensing orifice.
DETAILED DESCRIPTION
' Referring now to Figures 1-4, there is shown a
3~ mlcrôwave fo~d pac~age ac~ording to the present invention
~enerally designated by the reference numeral 10.
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~ enerally, the microwave food packa~e 10 comprises a
bag or pouch 12 constructed from flexible, microwave
transparent polymeric material. Preferably, the material is
such that bag 12 may be formed by folding the sheet over on
itself and bonding aligned portions of fac~ng surfaces
ad~acent side edges 14a and 14b and end edges 16a and 16b
to form an enclosed chamber 18. The bonding may be
accomplished such as by heat sealin~ the sheet material
together or by use of a suitable adhesive, or by any other
suitable means. Alternatively, bag 12 may be constructed in
other arranqements, such as by sealing two or more separate
sheets (not shown) together to form the chamber 18, or by
sealing the ends of a tube like structure.
In the preferred embodiment of the invention, the bag
is constructed from a polymeric film having two layers, an
lS inner layer (not shown) that is heat sealable to itself,
and an outer layer (not shown) that provides strength and
support to the heat sealable layer and also acts as a
moisture barrier to protect the foodstuff. The following is
a non-limiting list of materials suitable for use in
constructing the heat sealable layer: polypropylene, medium
density polyethylene, ionomers, heat sealable polyesters,
copolyesters, or blends of polyester and copolyester. The
following is a non-limiting list of material suitable for
use in constructing the support layer: polypropylene,
polyester, and nylon.
~ n some applications, it may be desirable to
incorporate an oxygen barrier layer (not shown) into the
film to prolong the shelf life of the foodstuff when placed
within the package, such as for "shelf stable" foodstuffs
that don't require refrigeration. Preferably the oxygen
barrier layer is located intermediate the heat sealable
I layer and the support layer, to protect the oxygen barrier
layer from abrasion or other damage. Preferably, the oxygen
barrier layer ha~ an oxygen transmission rate o~ no gr~at~r
than 15.5 cc per squ~re me~er per 24 hour~ at one (1)
atmosphere and at room temperature. The oxygen barrier
~ ~ 2 ~ J )
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layer may be constructed of any suitable material such as
polyvinylidene chloride (PVDC) or ethylene vinyl alcohol
(EVOH).
The film may be constructed such as by co-extruding
the layers, laminating the layers with a suitable adhesive
or a combination of coextrusion and laminating.
The chamber 18 is generally uniform in thickness,
broad, flat and relatively thin and is adapted for the
receipt of foodstuff 20. The bag 12 includes an upper side
22 and an opposing lower side 24. Preferably, the side
edge~ 14a and 14b are bonded adjacent the end edges 16a and
16b such that a flap 26 is formed in a generally medial
position on the upper side 22 transverse to the side edges
14a and 14b.
The chamber lB in the bag may be filled with any
suitable foodstuff 20 that is desired to be heated in a
microwave oven and dispensed through the orifice 30. By
necessity, when the foodstuff 20 is dispensed through the
orifice 30, it must be in a flowable state. ~or the
purposes of this invention, the term "flowable" includes
substances that are liquid, fluid or solid but having a
consistency enabling the foodstuff to be poured or extruded
through an orifice. The following is a non-limiting list of
foodstuffs that may be used in the microwave food package
of the present invention: processed cheese, ice cream
toppings, hollandaise sauce, barbecue sauce, oriental hot
sauces, hot breakfast cereal, syrup, pasta sauce, cream
sauce, gravy, salad dressing, chili, butter, soups.
The bag includes means for forming an orifice in the
microwave food package communicating with the chamber and
exteriorly of the package for dispensing the foodstuff from
the package after heating in a microwave oven. In the
1 illustrated embodiment of the invention, the bag 12
includes preformed orifice 30 for dispensing the foodstuff
' after heating in a microwave oven. The orifice oomprises a
passageway 32 communicating wi~h chamber 18 and extendlng
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through flap 26 exteriorly of the baq. Alternatively, the
bag may be constructed with an orifice formed anywhere on
the bag, in which case flap 26 of the bag may be omitted.
Alternatively, the bag may be constructed without a
preformed orifice, but with means for forming an orifice in
the bag during or after heating of the foodstuff.
Means are provided to enclose the preformed orifice 30
during heating of the foodstuff, to protect the foodstuff
from contamination or degradation during storage and to
prevent the foodstuff from escaping from the bag, and to
enable the orifice to be opened for dispensing of the
foodstuff, when desired. Preferably, the enclosing means
provides a hermetic seal to prevent degradation of the
foodstuff during storage. For instance, the end edges 16a
and 16b of the bag 12 at the flap 26 may be sealed from
side edge 14a to side edge 14b. The side edges of the bag
may include aligned notches or the like (not shown) spaced
from the end edges 16a, 16b to facilitate tearing of the
film to open the orifice. Alternatively, a perforated or
weakened line (not shown) may be formed in the flap 26
spaced from the end edges also to facilitate removal of the
end edges of the flap and open the orifice, or a tape or
like member ~not shown) may be adhered to the exterior of
the bag transversely across the neck portion, or a tear
strip (not shown) may be adhered within the flap to assist
in opening the orifice. Also, a piece of pressure sensitive
adhesive tape ~not shown) may be applied to the bag over
the orifice, and then removed to dispense the foodstuff.
Means are also provided to automatically vent the
chamber of the bag during the heating of the foodstuff to
release vapor pressure that is created when the foodstuff
exudes moisture and other gasses. The venting means will
1 provide a controlled exhaustion of gases from the chamber
lB to prevent premature rupture of the chamber and the
' escape of the foodstuff.
35Wh~le the p~ckag~ accord~ ng to the pre~ent ~nvention
could be vented by puncturing, as with a fork, to allow the
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escape of steam and other vapors during cooking, preferably
the package includes means that will automatically vent the
package during heating of the foodstuff. That means for
venting the bag could compr~se pre-formed opening~ (such
orifice 30~ in the bag that are initially closed by a
manually removable cover (e.g., a piece of pressure
sensitive adhesive coated tape). Preferably, however, that
means for venting comprises venting member 34 including a
deposit of microwave susceptor material adhered at or in
the vicinity of a heat sensitive material forming at least
a portion of the bag 60 as to be in thermal communication
with that portion of the bag, which microwave susceptor
material will be heated by exposure tc microwave radiation
and will automatically cause a vent to form or open in or
around the venting member during microwave heating of the
foodstuff. The deposit of microwave susceptor material for
2,450 megahertz radiation normally used in household
microwave ovens can comprise nonmetallic, microwave
absorbing particles (e.g., graph$te, carbon black, iron
oxide or ferrite) dispersed in a nonmetallic ~e.g.,
polymeric) binder, which deposit has a thickness within the
range from 10 to 300 micrometers, with the particles
comprising at least 10~ by weight of the deposit as is
taught in U.S. Patent No. 4,640,83B, entitled "Self-venting
Vapor-tight Microwave Oven Package" issued February 3, 1987
and incorporated herein by reference. Other configurations
and/or materials may be employed, extending the range of
thicknesses of the deposit to between 5 to 1000
micrometer8, or even greater.
Preferably, however, the susceptor material is a metal
vapor coating of aluminum with a surface resistance in the
range of 50 to 300 ohms per square (about 100 ohms per
I square preferred) either coated directly on the bag or
coated on a polymeric film adhered to the bag ~y a suitable
' adhesive. When the bag 12 comprises heat sen6itive material
6uch as thermoplastic film and the 6usceptor material
comprises metal adhered by vapor deposition or susceptor
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particles adhered by adhesive directly to the film, heating
of the deposit by microwaves can soften and weaken that
portion of the film to which the deposit is adhered, thus
causing that portion to rupture and vent the package under
the influence of steam or vapor pressure within the bag.
When an adhesive layer adheres the susceptor material to
the heat sensitive material which is to be weakened by heat
from the particles, that adhesive layer hould be thin to
afford good heat transfer, preferably from 10 to 20
micrometers.
When the susceptor material is adhered on a polymeric
film adhered to the bag, rupturing of the softened and
weakened portions of the bag 12 caused by heating of the
deposit by microwaves can occur under the influence of
steam or vapor pressure within the bag, or because one or
both of the films shrink when they are heated causing
tearing of the films under the deposit, or because of both
causes.
When the susceptor material itself or a polymeric film
to which it is adhered and the adhesive by which the film
is adhered to a bag are impervious to vapors, but the
susceptor material or adhesive will soften and weaken when
heated; the susceptor material or film can be positioned
over a weakness in the bag such as an opening, a slit, or a
score. When so used, such a susceptor material may be
covered with a vapor-impervious thermoplastic film. Upon
doing so, heating of the susceptor material may either
soften and weaken the covering thermoplastic film or film
on which the susceptor material is coated, or venting may
occur laterally through the susceptor material or through
3~ an unfilled adhesive layer by which the film and susceptor
material are adhered over a weakness of the bag 12.
I The susceptor material itself or a polymeric film to
which the susceptor material is adhered can also be adhered
along a seal between layers of material forming the bag 12
th~t iB h~t eoftenabl~ 60 that héatLng of the layer during
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cooking of foodstuff within the packa~e by microwave energy
will cause the seal to rupture because of vapor pressure in
the bag 12.
The susceptor material can form an alpha numeric
message or a distinctive pattern that informs the user of
the self-venting nature of the package. Whether directly
placed on the bag 12 or cut from a pre-formed sheet that i6
adhered to the bag, the susceptor material may be shaped to
concentrate the microwave energy. The susceptor material
may have a distinctive shape to remind the user by its very
appearance that the package is self venting and to position
the pac~age in the oven so that nothing spills when the
vent forms. For such reasons, the susceptor material or
other portions of the venting member may be highly
conspicuous or indicia may be placed on the bag or package
to direct attention of the user to the venting member. The
susceptor material or the venting member may have the shape
of a logo or trademark to identify the company marketing
the package.
The microwave susceptor material may take the form of
a rectangular piece of metal vapor coated film adhered by a
suitable adhesive to the bag. The vapor coated film and top
sheet of polymeric film forming the bag will be softened by
heating of the metal vapor coating to cause rupturing of
that top sheet of film and vapor coated film due to steam
or vapor pressure within the bag during heating of the
foodstuff by microwave energy so that the vent member will
allow excess steam or vapor pressure within the bag to
escape, while retaining sufficient steam or vapor within
the bag to enhance heating of the foodstuff.
Preferably, and as shown in Figure 1, a venting member
34 is located at or adjacent one side of the distal end of
1 passageway 32 of orifice 30. This end is presealed after
the foodstuff is placed within chamber 18. During heating
' in the microwave oven, the venting members 34 weaken the
bond between facing sealed surfaees of the d~tal end of
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the passageway so that the orifice i6 opened, as
illustrated hereinafter, a venting member 34 may be applied
to both sides of flap 26, if desired.
Means are also provided to insulate the package, to
enable handling of the bag and its contents immediately
after heating in a microwave oven, and also to enhance the
heat retention ability of the package after the foodstuff
has been heated, and until the foodstuff is dispensed. In
the illustrated embodiment, the insulation means takes the
form of a continuous flexible sheet 36 of polypropylene
foam. However, any material having the desired insulative
properties may be utilized. The foam sheet 36 is applied to
the lower side 24 of the bag and with either end extending
about the ends 38 and 40 of the bag 12 and over the upper
side 22 of the bag towards the flap 26. The insulating
sheet 36 may be secured to bag 12 by a suitable adhesive
capable of withstanding the elevated temperatures
encountered in a microwave oven, or by any other means,
such as mechanical clips.
In any of the embodiments of the invention described
herein, one or more labels tnot shown) may be adhered or
attached to the exterior of the microwave food package in
one or more locations for advertising, identification,
instructional, or other purposes. Alternatively, indicia,
logos or the like may be imprinted directly on the
outermost layer of the package, including the insulating
layer.
In use, the illustrated embodiment of the microwave
food package 10 is placed in a microwave oven with the
lower side 24 of the bag 12 placed downward. This positions
the chamber 18 and the foodstuff 20 therein in a generally
horizontal position and the foodstuff having a generally
uniform thickness. Upon heating, the build up of vapor
pressure in the chamber may lift the upper side of the bag.
' Since the orifice 30 is located medially on the upper s~de
22 of the bag, the orifice i8 lifted and i8 positioned at a
high point of the bag. Thus, when orifice 30 is opened, the
' ?. ~ J j
foodstuff 20 is prevented by gravity from escaping from the
package 10. The horizontal position and generally uniform
thickness of the foodstuff 20 in the bag enables the
foodstuff to be evenly heated by the microwave oven,
without the burning and uneven heating of conventional cup
like containers, as previously discussed.
As utilized herein, the term "susceptor" refers to
substrates which include a layer of microwave interactive
mater~al capable of absorbing microwave enerqy and
converting the microwave energy to sensible heat.
As utilized herein, the term "microwave interactive"
refers to materials which absorb and/or reflect a
substantial proportion of the microwave energy striking the
material.
As utilized herein, the term "microwave shield" refers
to microwave reflective materials which can be configured
about a food item so as to reduce the amount of microwave
energy directly transmitted to the food item.
As utilized herein, the term "microwave transparent"
refers to materials which allow microwaves to be
transmitted therethrough without a substantial alteration
in the intensity or direction of the microwaves.
Figures 5 and 6 illustrate the configuration of the
package after heating and removal from a microwave oven.
Since orifice 30 has been opened, the preferred method for
dispensing the foodstuff is to fold the bag 12 and the
chamber 18 about a transverse line on the lower side 24 of
the bag aligned with the flap 26. The folded chamber 18 may
then be squeezed, as shown in Figure 7, to force the
foodstuff 20 to flow from the chamber and through the
orifice 30. The package 10 may then be discarded. This
enables substantially all of the foodstuff to be heated and
dispensed from the package without the use of a utensil.
Although the venting member 34 is illustrated as
' mounted at or near the distal end of the pa6sageway 32, it
16 withln the 6pirit and BCope of thi6 ~nvention to mount
the venting member 34 at any location along the length of
~ J ~
the passageway, such as the end proximate the chamber 18.
In such a case, other means, such as the tear strips,
perforated or weakened lines or the like previously
described herein, may be employed to open the distal end of
the passageway to dispense the foodstuff.
In one example of a microwave food package according
to the present invention, a sheet was constructed by
laminating the PVDC side of a 0.00052 inch (0.013 mm) thick
support layer of Scotchpart~ 2708 brand film available from
Minnesota Mining and Manufacturing Company of St. Paul,
Minnesota to a 0.001 inch (0.025 mm) thick heat sealing
layer of CP136 polypropylene film available from the Crown
Advanced Film Division of James River Corp. of Orange,
Texas with Adcote 76T198 adhesive available from Morton
Thiokol of Chicago, Illinois (dry weight of 2-3 pounds per
3,000 square feet of film). An insulating layer of 0.0625
inch (1.59 mm) thick polypropylene foam available from
Ametek, Inc. of Chadds Ford, Pennsylvania under the trade
mark "Microfoam" was laminated to the exterior of the film
previously described when formed into a bag as shown in
Figure 1, with a Swift No. 48~03 brand pre6sure sensitive
adhesive available from the Swift Adhesives Division of
Reichhold Chemicals, Inc. of Downer's Grove, Illinois to
the outside (polyester) of the bag film. A 0.00057 inch
(0.014 mm) thick layer of Scotchpart~ 86096 brand film may
be sub6tituted for the Scotchpart~ 2708 brand film.
In an alternative arrangement, separate insulating
sheets (not shown) may be àpplied to the upper side of the
bag on either side of the flap. In such an arrangement, the
bag 12 may be removed from a microwave oven by grasping the
flap 26 and lifting the bag so that the bag is
automatically folded over on itself about a transverse line
1 on the lower side 24 generally opposite the flap (as shown
in Figure 6). This places the insulating sheets on opposite
' sides of the exposed surfaces of the bag. The bag may then
3~ be qrasped by the insulating sheets and squeezed to
dispense the foodstuff.
w, ~ ~ ~3
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Figures 8-lO illustrate an alternate embodiment of
this invention in which the insulating sheet 36 also takes
the form of a stiffening sheet~ The stiffening sheet 36
provides sufficient stiffness to the bag to assist in the
squeezing of the chamber during dispensing of the
foodstuff. In the illustrated embodiment, the insulating
sheet take6 the form of a sheet of single faced corrugated
chipboard, with the corrugations facing outwardly. The
sheet ls bent and flexible at the ends 38, 40 of the bag 12
50 that the portions on the upper side 22 of the bag are
hingedly connected to the portion on the lower side of the
bag. Dispensing of the foodstuff is assisted by pushing the
portionfi of the sheet 36 on the upper side of the bag
towards the portion of the sheet 36 on the lower side of
the bag. In this embodiment, the chamber 18 is not folded
over on itself in the manner shown in Figure 6. of course,
if desired, a stiffening sheet may be provided separate
from the insulating sheet and mounted on the package either
above or below the insulating sheet. The corrugations of
the single faced stiffening sheet should preferably either
be directed outwardly (as in Figure 11) or the stiffening
sheet should be double faced (as in Figure 12).
Figures 13 and 14 illustrate an embodiment 10' of the
invention in which the orifice 30 and venting member 34 are
located at one end of the bag 12', with the orifice
communicating with the chamber 18. An insulating and
stiffening sheet 36' is provided that includes ridge 42 to
support the bag in a recumbent (although still generally
horizontal within the meaning of this invention) position,
but with the end 38' of the bag having the orifice 30
tilted slightly upwards, to prevent the escape of foodstuff
from the bag after the venting member 34 is ruptured. The
1 portion of the insulating and stiffening sheet 36' that is
on the upper side 22 of the bag 12 may be pushed towards
' the portion of the sheet 36' on the lower side 24 of the
bag to 6queeze the chamber and dispense the foodstuff
through the orifice.
15-
Figures 15 and 15a illustrate another embodiment 10~
of the invention in which A microwave shielding member or
layer 44 is applied to the lower side 24 of a bag 12 as
shown in Figure 1. The microwave shielding member 44 may be
constructed from any suitable microwave shielding material,
such as thin metal foils, which may attenuate the microwave
radiation directed at the package, or the microwave shield
be completely opaque to microwave radiation. In any case,
the shield facilities uniform heating of the foodstuff
thought the chamber by reducing the rate of heating at the
edges thereof relative to the middle of the bag. In the
illustrated embodiment, shield 44 is constructed from
0.0003 inch (0.0076 mm) thick layer of aluminum foil
laminated to a supporting paper substrate and the laminate
adhered to the bag with a Swift brand 48803 adhesive. The
paper substrate provides mechanical support to the
relatively thin and weak metal foil during handling and
application to the package. If the foil i6 cracked or
severely wrinkled, arcing may occur during heating of the
foodstuff in a microwave oven. As illustrated, the shield
includes a central opening 46. Alternatively, thicker metal
foils may be employed, such as 0.003 inch ( 0.076 mm)
Aluminum foil.
In conjunction with the flat chamber of generally
uniform thickness, the shield 44 acts to prevent the edges
of the foodstuff from exposure to excessive amounts of
microwave energy while enabling unimpeded heating of the
foodstuff in the middle of the bag. Of course, the size,
shape, thickness, location, and number of the 6hields may
be varied as is found effective for a particular
application-
The following are three comparative examples of
I microwave food packages according to the present inventionto demonstrate the effect of the shielding layer 44 on the
uniform heating of the foodstuff:
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Comparative Example 1 Without Shielding:
A pouch was made by heat sealing 4" x 6" (102 mm x 152
mm) films made of Scotchpak~M Type 5 with the polyethylene
sides together as shown in Figures 1-7. Scotchpak #5 film
is 0.002 inch thick (0.051 mm) and is made of a layer of
polyester and a layer of polyethylene. The pouch was heat
sealed about 0.5 inch (1.2 mm3 around the bottom and two of
the sides and about 1.5 inch (3.8 mm) on the top to form a
chamber that is 3" x 4.5" ~76 mm x 108 mm). Four (4)
ounces ~113 ~rams) of Cheese Whiz brand processed cheese
~available from Kraft, Inc. of Glenview, Illinois) was
placed in the chamber just prior to sealing the top edge.
The top ~as the pouch lays flat) of the filled pouch
was slit in the center with a razor blade to form a 0.5"
(13 mm) long slit to allow steam to escape. The pouch was
then heated in a 600 watt microwave oven at full power for
45 seconds, after which the temperature of the Cheez Whiz
was measured with a Fluke 52 K/J (Type J) thermocouple
available from John Fluke Manufacturing Co., Inc. of
Rolling Meadows, Illinois at the four corners of the pouch
and in the center of the pouch. The sample was then heated
in the 600 watt microwave oven at full power for another 45
seconds and the temperature was again measured at the
corners and center as described above. Results are noted
in Table 1. No shielding was used.
Example 2 With Shielding:
A second pouch was made and filled as described above.
A shielding material consisting of a composite made of
0.0003 inch ~0.0076 mm) aluminum foil laminated to 20 lb.
bleached Kraft paper was cut into a 3.25" x 4.75" ~83 mm x
121 mm~ rectangle and laminated to the pouch with the paper
side to the pouch with a Swift #48803 brand adhesive. The
composite is available as described from Reynolds Metals
' Co. of Richmond, Virginia. The filled pouch was heated and
3~ temper~turQ waB m~a5ured a5 des~r~bed above. The results
2~2~
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are recorded in Table 1. (The slit was made as in Example
1 and the shield was on the bottom of the pouch as in
Fi gure 15 . )
Example 2 With Partial Shielding:
A third pouch was made and filled as described in
Example 1. The shielding material of Example 2 was used
except that an oval hole 1.75" x 3.25" ~45 mm x 83 mm) was
cut about in the middle of the shielding material. The
filled pouch was heated and the temperature was measured at
45 seconds and at 90 seconds as described in Example 1.
Results are recorded in Table 1. (A slit was made as in
Example 1 and the Shield was on the bottom of the pouch.)
Table 1
Averaqe
Time Center Temp. Corner Temp.
Configuration Sec. Deg. F Deg. C Deg. F Deg. C
No Shield 45 140 60 lB3 84
(Ex. 1) 90 170 77 204 96
Full Bottom 45 97 36 137 58
Shield (Ex. 2) 90 105 41 165 74
Part Bottom 45 105 41 125 52
Shield (Ex. 3) 90 160 71 159 71
Example's 2 and 3 show that the shield layer prevents the
corner temperature of the foodstuff from getting too high
and causing burning. Example 3 shows uniform heating of
the foodstuff from edge to center.
I Figures 16 and 17 illustrate an embodiment of 10' the
invention similar to that shown in figures 13 and 14, but
' wherein the insulating sheet 36' comprises a sheet of foam,
without 6ignificant 8tiffening propertie8. Further, one
side of the flap 26 is provided with an auxiliary flap 48
2 ~ 3 3
-18-
on the same side as the lower side 24. When placed
horizontally in a microwave oven, the auxiliary flap 48
urges the flap 26 into a ~enerally upright position as
shown. ~n this manner, the foodstuff is prevented from
spilling or "percolating" through the orifice 30 during
heating of the foodstuff and after rupturing caused by
venting member 34.
Figures 18-20 illustrate an embodiment 10'' of the
invention which includes a tray portion 50. The tray
portion may be formed such as ~y vacuum forming, blow
molding, injection molding, embossing, cold forming, or by
any other suitable method. A film 56 is laminated or sealed
to the tray portion 50 to form the enclosed chamber 18 for
receipt of the foodstuff 20. Such an arrangement has
significant manufacturing advantages for filing the chamber
with foodstuff and then sealing the chamber with the film
56. As illustrated, the film 56 comprises two separate
sheets 56a and 56b that are laminated or sealed to the tray
portion 50 and to each other at a medial position to form
flap 26, with the chamber 50 divided into receptacles 52
and 54 communicating with each other adjacent the flap 26.
Venting member 34 and insulating sheets 36' are provided as
previously described. The foodstuff 20 may be dispensed as
shown in Figures 21 and 22 by folding the tray portion 50
over on itself about preformed transverse fold line 5B
opposite the flap 26 and squeezing the receptacles 52, 54
together.
An example of a microwave food package 10''
constructed according to the embodiment shown in Figures
18-20 includes a tray portion constructed of 0.0075 inch
~0.19 mm) thick Curlon HK-28 nylon/ionomer film available
from Curwood, Inc. of New London, Wisconsin and a top film
constructed of 0.003 inch (0.076 mm) thick Curlon MKS
nylon/ionomer film.
' The microwave food package of the present invention
thu6 proYlde~ an effective container for 8torage and
uniform heating of a foodstuff in a microwave oven, and for
~ c~ ;`
--19--
efficiently dispensing the foodstuff in a flowable state
without use of a utensil, after which the package may be
disposed of. The package may be handled and the foodstuff
may be dispensed immediately after heating in the microwave
oven, or the dispensing of the foodstuff may be delayed
while the heated foodstuff is retained in the insulated
package.
The present invention has now been described with
reference to several embodiments thereof. It will be
apparent to those skilled in the art that many changes can
be made in the embodiments described without departing from
the scope of the present invention. For instance, this
invention further includes the microwave food package as
herelnabove described in combination with a quantity of a
foodstuff. Further, the microwave food package of this
invention may be constructed with a longitudinal or
diagonal fold line, or with multiple fold lines or with
fold lines located at any desired location on the package
and specifically, the fold line does not have to be aligned
with the orifice. Similarly, the microwave shielding member
may be located on any portion or portions of the package as
is found advantageous. The orifice 30 may be located
anywhere on the package, and specifically, the orifice may
be positioned at any transverse point along the flap 26.
The orifice may be constructed with a rigid member of
pouring spout to facilitate dispensing the foodstuff, such
as a cylindrical tube or nozzle. Finally, the shape of the
package and/or the bag 12 may be varied as desired, such as
round, triangular, octangonal, cylindrical or the like.
Thus, the scope of the present invention should not be
limlted to the structures described in this application,
but only by structures described by the language of the
claims and the e~uivalents of those structures.
