Note: Descriptions are shown in the official language in which they were submitted.
200397~
"Gour-Met"
T.V. DINNER TRAY
The present invention relates to a novel T.V. dinner
tray which is provided with a novel lid arrangement which
enables more uniform microwave heating of foodstuffs in
compartments of the tray to be achieved.
In T.V. dinners, a complete prepared dinner is
packaged in separate compartments in a tray. Typically,
separate compartments are provided for meat, potato,
vegetables and desert. The foodstuffs are prepared for
serving and frozen for reconstitution for consumption.
A problem which has been encountered with such products
is uneven heating of the foodstuffs in the compartments
upon reconstitution for consumption by microwave energy,
since they often cook at different rates when exposed to
microwave energy. This lack of uniformity of heating is
often considered undesirable by the consumer.
Various attempts have been made to improve the
uniformity of heating of the foodstuffs in the
compartments by the application of microwave energy
thereto. In this regard, a search of the records of the
United States Patent and Trademark Office has revealed
the following U.S. Patents as the closest prior art:
U.S. Patents 3,079,913;
3,219,460;
3,240,610;
3,271,169;
3,398,041;
3,615,713;
3,672,916;
3,799,143;
4,013,798;
4,555,605;
4,626,641;
4,656,325;
4,703,148;
4,676,857; and
4,703,149.
These prior art references describe a variety of
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microwave energy shielding and focussing devices for the
purposes of redistribution of microwave energy to the
prepared foodstuffs in the T.V. dinner tray.
One proposal for dealing with the problem of uneven
heating is described in the aforementioned U.S. Patent
No. 4,656,325. In this patent, there is described the
provision of a lid structure having a plurality of metal
islands and which is arranged to be spaced from the
foodstuff in the holding pan so as to permit microwave
energy to pass through the cover onto the package without
interfering with internal reflections of the microwave
energy within the package by the metal islands.
This prior art structure is expensive to manufacture
and cumbersome to employ. Others of the prior art
structures simply are not effective to produce the
desired result.
The present invention provides a relatively simple
structure, different from the prior art, which,
nevertheless, is able to achieve the desired more uniform
degree of heating upon application of microwave energy to
a multicompartment T.V. dinner tray containing prepared
foodstuffs for cooking to consumption.
On examining a reconstituted T.V. dinner upon
conventional microwave heating, it has been observed
that, when aiming for a desired meat temperature,
vegetables heat the most and potato the least and there
is often a considerable differential of temperature
between the top and bottom of the tray.
In accordance with the present invention, it has
surprisingly been found thatl by providing a microwave
energy reflector of specific structure over those regions
tPn~;ng to heat more, a much more uniform degree of
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heating to the different foodstuffs is possible together
with an enhanced degree of uniformity of temperature
between the top and the bottom of the foodstuff in the
individual compartments.
For a multicompartment T.V. dinner tray containing a
meat course, vegetable, dessert and potato, the microwave
energy reflector is placed over the vegetable and dessert
compartments. This positioning has the affect of
shielding microwave energy from the compartment and
diverting it into the other compartments.
Accordingly, in one aspect, there is provided a
cover for a contAiner having at least one compartment for
prepared foodstuff for reconstitution for consumption by
microwave energy, which consists essentially of:
a planar continuous polymeric material layer;
a microwave-reflective pattern supported on and in
adhered relation with one surface of the polymeric
material layer comprising a continuous layer of microwave
reflective material within a periphery thereof, the
microwave reflecting material inhibiting the flow of a
microwave energy through the cover within the periphery
of and in the location of the pattern on the polymeric
material layer and e~hAncing the flow of microwave energy
through the cover outside the periphery of the pattern
and in the region of the polymeric material layer from
which the continuous layer of microwave reflective
material is absent whereby there is controlled the degree
to which prepared foodstuff positioned in the at least
one compartment is subjected to microwave energy through
the cover when the container is exposed to microwave
energy; and
a layer of paperboard material coextensive in
dimension with the flexible polymeric material layer and
adhered to the polymeric material layer outside the
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periphery of the pattern and to the pattern within the
periphery, so as to sandwich the layer of microwave-
reflective material between the polymeric film layer and
the paperboard material layer.
The microwave energy reflector may be provided of
any convenient material, generally an electroconductive
material, such as a metal, for example, aluminum. The
reflector may vary in thiC~CC from one at which the
metal is partially reflective and partially transmissive
of microwave energy to a thickness at which the metal is
wholly reflective of incident microwave energy.
The thickness required to provide the required
microwave reflective effect d~pen~c on the metal chosen.
For the preferred metal aluminum, a thickness ranging
from that co~ex~ond to an optical density of about 0.70
up to foil-thickness can be employed. It has further
been found that a thickness down to that corresponding to
an optical density of about 0.2 can be employed and still
have the required effect of diverting the microwave
energy into the non-covered areas, so as to ~nhAnce the
heating effect therein, although some microwave
transmission also occurs at that thickness level.
The reflective metal layer may be sandwiched between
paper and polyester substrates to provide a lid for the
T.V. dinner tray. The reflective metal layer may be
provided on the substrate in any convenient manner. For
example, the reflective metal layer may be provided as
die-cut foil, cut to the desired shape and then laminated
or otherwise attached to the substrate in any convenient
manner.
Alternatively, the reflective metal layer may be
provided on the substrate by any convenient transfer
procedure, such as hot stamping or, preferably, the
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procedures described in U.S. Patents Nos. 4,963,424 and
4,936,935.
The present invention may also be employed in
combination with a structure such as described in U.S.
Patent No. 4,230,924. As described therein a pattern of
islands of metal foil may be provided on a dielectric
substrate. When such an arrangement is employed with a
T.V. dinner tray, with a part being left clear an
~nhAnC~ heating effect is achieved in the zone covered
by the island structure as compared with the clear area.
When this experiment is repeated with a solid foil
replacing the patterned foil, then an enhanced heating is
observed in the clear area but not as great as the
patterned area in the previous experiment.
With the combination of the solid foil and patterned
foil, a greater enhanced heating effect is observed in
the patterned foil area than is observed in the first
experiment, while a greater shielding effect is observed
in the solid foil area is observed than in the second
experiment.
These effects may be used in a T.V. dinner tray to
achieve degrees of enhanced heating and shielding as
desired by appropriate manipulations of clear, continuous
foil and patterned foil coverings.
In addition, the reflective metal layer may be
applied to the substrates by laminating to it on
polymeric film generally polyester, bearing the metal on
its surface. The metal first usually is subjected to
demetallization to provide the desired metal pattern such
as by employing one of the selective demetallizing
procedures described in U.S. Patents Nos. 4,398,994,
4,552,614 and 4,610,755.
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In one embodiment, the substrate layer is completely
covered with the reflective metal layer, except for
regions of the surface thereof corresponding to the meat
compartment and the potato compartment from which the
metal layer is absent. This arrangement effects, not
only reflection of microwave energy in the region of the
metal, but, for certain patterns, also effects focussing
of the microwave energy into certain of the regions from
which the metal is absent thereby enhAncing the heating
in such regions and contributing to the uniformity of
heating achieved.
The focussing effect may be further enhanced by
providing a small strip or pattern of the microwave
reflective material within the periphery of the openings
in the metal layer.
The metal layer-substrate layer combination may be
laminated or otherwise associated with other elements to
provide a complete lid for the T.V. dinner tray, so that
the metal tray is not exposed outwardly of the tray nor
is in contact with the food. The metal pattern also may
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be provided on the underside of the tray, if desired.
Another application of the principles of the invention
is with respect to foodstuffs packaged in plastic
containers., generally of box-like construction
("Tupperware").
When microwave heating such products, for example,
lasagna, uneven heating occurs. Typically, while outside
portions may be satisfactorily heated, inner portions are
not. In accordance with the invention, microwave
reflective material is employed on the walls of the
container as well as its lid and possibly the bottom of
the container, with a circular opening being provided at
approximately the central portion of the reflective
material on each wall. The opening area may be provided
with a pattern of the reflective microwave material, such
as a regular pattern of circles. By providing the
container with the layers of microwave reflective
material, enhanced uniformity of heating of the food
product is obtained.
The present invention, therefore, provides a lid
structure for T.V. dinners which does not require the
spacing from the food of U.S. Patent No. 4,656,325, but
rather is employed as a conventional planar lid, but is
able to achieve satisfactory microwave reconstitution of
frozen T.V. dinners and provide even heating in all food
compartments in a single rapid cooking operation, which
does not require any interruptive intermediate
procedures, such as changing the cooking power and/or
rotating the dinner tray during cooking.
As noted earlierl the principles of the invention may
be applied to the microwave heating of a variety of food
products where it is desired to provide a greater
intensity of heating of the food product or a combination
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of several different food products in one region thereof
from another, in order to achieve a microwave-heated food
product having a uniform temperature.
EXAMPLE
Commercial frozen Swanson-brand Salisbury steak
dinners were cooked by the application of microwave
energy for 10 minutes at half power (the cooking
instructions provided with the T.V. dinner) in a 450 watt
0.5 cu ft. Sanyo-brand microwave oven without and with
a lid according to the invention and as structured as
described above. The heating effect obtained was
compared to that obtained with a conventional lid. The
results are set forth in the following Table I:
Table
Compartment Temp.
Veg. Desert Potato Steak Spread
(corn)
Inventive
Lid-top 60 70 65 60 12
-bottom 63 71 72 60 12
Prior Art
(No Lid)
-top 80 73 32 65 48
-bottom 72 72 18 60 54
As may be seen from the results set f orth in the
above Table I, by employing the lid structure of the
invention, very even heating of the contents of the T.V.
dinner tray is achieved, in contrast to the prior art.
In summary of this disclosure, the present invention
provides, in particular, a novel T.V. dinner tray lid
which enables uniform heating of the different types of
the food in the multi-compartment tray to be achieved,
and, in general, a means for effecting differential
200397S
intensities of microwave heating to different portions of
food products. Modifications are possible within the
scope of this invention.
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