CA2003975C - T.v. dinner tray - Google Patents

Abstract

A lid for a T.V. dinner tray is constructed to provide a more uniform heating of the frozen prepared foodstuffs by controlling the flow of microwave radiation to the foodstuff, to effect a decreased flow of microwave energy to the foodstuffs in certain zones of the tray and an enhanced flow of microwave energy to the foodstuffs in the remainder of the tray.

Description

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 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 B

3 20(~3975 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 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 200397~
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.

5a 2003975 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 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 B

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 intensities of microwave heating to different portions of food products. Modifications are possible within the scope of this invention.

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Claims (6)

1. 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 enhancing 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 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.

2. The cover of claim 1 wherein the polymeric material layer is rigid.

3. The cover of claim 2 wherein the polymeric material layer is flexible.

4. The cover of claim 1 wherein said layer of microwave-reflective material is a layer of aluminum foil having a thickness of about 1 to about 15 microns.

5. The cover of claim 4 wherein said aluminum foil has a thickness of about 3 to about 10 microns.

6. The cover of claim 1 wherein said layer of microwave reflective material has an approximately kidney-shaped outline.