Package assembly and method for storing and microwave heating of food

A packaged arrangement (1) contains a tray (4) which is convertible into a heating stand by inversion thereof. The walls of the tray are of a material that is transparent to microwave energy, but a support wall (10) which forms a bottom of the tray and top of the stand is provided with a liner of a microwave interactive layer that is formed of a material capable of converting microwave energy into heat. The tray (4) is configured so as to define a storage space for a predetermined quantity of food and to possess sufficient strength as to be able to support the predetermined quantity of food upon the support wall (10) in the inverted, heating stand condition thereof. A second packaged arrangement (1') comprises a recloseable package body (2') that may be used, at least in part, to form the enclosed air space and stand. In accordance with methods of use, food is removed from the package, at least one of the components of the packaged arrangement is formed into an air space enclosing heating stand, upon the floor of a microwave oven, and the food is placed upon this stand during microwave heating thereof.

DESCRIPTION 
1. Technical Field 
This invention relates generally to microwave food packages and more 
particularly to food packages of the type which include an element that 
will produce a heating effect when exposed to microwave energy for the 
purpose of crisping or browning food contained thereon. 
2. Background Art 
In recent years the percentage of homes containing microwaves ovens has 
grown dramatically. This has resulted in an associated growth in the 
demand for microwaveable prepared foods, such as frozen pizzas and the 
like. However, when the manufacturers of prepared foods attempted to meet 
this marketplace demand, they found that a difficulty existed in 
overcoming the common complaint of consumers to the effect that food 
cooked by microwave energy lacked the desired degree of browning or 
crispness that such foods normally have when cooked in a conventional 
oven. This problem is particularly acute with respect to foods that are 
required to be selectively exposed to microwave radiation to a greater or 
lesser extent in certain portions thereof. Furthermore, while auxiliary 
implements are known to facilitate heating and cooking of such difficult 
to microwave foods (see, for example, U.S. Pat. Nos. 3,539,751; 3,941,967 
and 3,965,323), it is undesirable, from a commercial standpoint, for 
manufacturers of frozen prepared foods and the like to have the success of 
a product depend on the availability, in the home, of such auxiliary 
cooking devices. Additionally, requiring the use of such auxiliary devices 
detracts from one of the reasons why consumers buy ready-prepared foods in 
that such auxiliary devices, not being disposable, create the 
inconvenience of an item that must be washed for later use. 
In view of the foregoing, various specialized packages have been developed 
which are designed to achieve microwave browning of food contained 
therein. Specifically, such packaging involves the preparation of a 
package body into which is incorporated a film or element that will 
convert microwave energy into thermal energy so as to produce a browning 
and/or crispening of an item of food situated in heat exchange contact 
therewith. Furthermore, such packages have been designed so as to produce 
a selective heating of various portions of the food to a greater or lesser 
extent than other portions. 
A first type of such packaging is represented by Brastad, U.S. Pat. No. 
4,267,420 and Brastad et al, U.S. Pat. No. 4,230,924 wherein flexible 
sheets of microwave interactive materials are wrapped closely about 
individual items of food so that when the package is exposed to microwave 
energy, the interactive material will convert at least a portion of the 
impinging microwave energy into heat for browning the food surface. 
However, such packages pose problems with various types of food, in that, 
during heating, grease or vapor driven out of the food may create leakage 
and/or venting problems, and such packaging is totally unsuitable for 
foods, such as pizza, which have components which will adhere to a 
contacting wrapping paper and thus be rendered unappetizing when the 
packaging material is removed. 
A second approach is represented by Turpin et al U.S. Pat. No. 4,190,757, 
which discloses a microwaveable package which does not require the product 
to be closely wrapped. In accordance with this patent, a microwave 
interactive layer is supported on or adjacent one of the inside container 
walls for browning food which is positioned therein. However, when the 
microwave interactive layer is directly on the inside container wall, the 
amount of heat transferred between the interactive layer and the food 
being browned, may vary over the surface area of the foods due to surface 
or dimensional irregularities of the food and non-uniform size variation 
of the food. 
On the other hand, while the supporting of the microwave interactive layer 
above the inside container wall creates an air space which has the effect 
of more evenly distributing the heat to the underside of the product, the 
provision of a supporting stand for the interactive layer and food has a 
significant effect upon the cost of packaging a given food item, since the 
size of the package is significantly increased beyond that which otherwise 
would be required to package the food item. This, in turn, increases the 
size of the box that will be required to ship a number of packages to the 
retailer, not to mention the increased cost associated with producing a 
complex package, as opposed to a simple box-type structure. 
Moreover, a disadvantage exists with the packages constructed in accordance 
with the teachings of the Turpin et al patent since they are provided with 
holes or openings which are used to regulate the amount internal heating 
and to vent vapor and moisture. That is, since the food is heated in the 
same package in which it is displayed, some vaporization of the inks used 
in the package graphics may occur causing ink vapors to become absorbed 
into the foods themselves. Such an effect can adversely affect the taste 
of the food, and a consumer would be less likely to purchase or use a 
dirty package. 
Presently known approaches to the packaging of foods for microwave cooking 
all focus on the "cook-in" disposable package of the above-noted types 
that are subject to the aforementioned problems. However, no package 
assembly or packaged arrangement has been disclosed wherein simple, 
package design concepts as applied to non-microwaveable foods can be 
utilized while obtaining the benefits, without the detriments, of the the 
more sophisticated microwave package designs incorporating microwave 
interactive layers. 
DISCLOSURE OF THE INVENTION 
It is an object of the present invention to provide a novel and improved 
package assembly and packaged food arrangement for use in association with 
the heating or cooking of the food item in a microwave oven that enables 
the use of a simple package body of the type utilized in packaging food 
products that are to be cooked or heated by non-microwave means. 
It is a general object of the invention to provide a dual food packaging 
assembly for use in a microwave oven having a support surface, comprising 
outer packaging body means initially operable in a packaging mode in which 
food may be retained within an enclosed food storage space for shipment 
and storage and subsequently operable in a cooking mode after the food 
originally located within the enclosed food storage space is removed and 
the outer packaging means is mechanically manipulated to form a heating 
stand means for supporting the removed food at a predetermined distance 
above the microwave oven support surface in heat transfer relation with 
said microwave interactive layer and for enclosing an air filled space 
beneath said microwave interactive layer for promoting even cooking of the 
removed food. 
It is another object of the present invention to provide a novel and 
improved package assembly and packaged food arrangement for use in the 
storing and microwave heating of a food item wherein the package includes 
a disposable, combination food storage tray and heating stand which, in a 
first condition, serves for receiving the food item and holding it within 
the package body, and in a second, inverted, condition functions as an 
auxiliary heating member independent of the package body. 
It is a specific object of the present invention to provide a disposable 
paperboard tray which has a flat support wall bounded perimetrically by 
upwardly projecting walls so as to define a food receiving space, a thin 
microwave interactive layer being attached on a side of the support wall 
which faces away from the food receiving space so that, upon opening of 
the package, the tray may be removed from the package, the food moved from 
the food receiving space, and the tray inverted and placed within a 
microwave oven so as to serve as a heating stand upon which the food item 
is placed for heating and/or cooking. 
it is a further object of the present invention to provide a package 
assembly for microwave cooking use comprised of an outer package and an 
inner tray, at least one of which is provided with a microwave interactive 
layer and is usable, after removal of the food from the outer package, to 
create a stand enclosing an air space within a microwave oven upon which 
the food may be cooked. 
In connection with the preceding object, specific objects include enabling 
only the outer package, only the inner tray, or a combination of the outer 
package and tray, to create the air space enclosing stand having a 
microwave interactive layer upon which food may be cooked in a microwave 
oven. 
It is also an object of the present invention to provide a method of 
cooking or heating packaged food whereby the food is removed from the 
package, at least one of the components of the package is formed into an 
air space enclosing heating stand, with a microwave interactive heating 
layer, upon the floor of a microwave oven, and the food is placed on this 
stand during microwave heating thereof. 
The above and other objects and advantages of the invention are achieved by 
a package assembly, in accordance with a preferred embodiment of the 
invention, which includes a package body in the form of a simple 
paperboard carton within which a disposable combination food storage tray 
and heating stand is fully received. The combination tray and stand forms 
a food storage space that is bounded by a support wall on which a food 
item or predetermined quantity of food is located and upstanding 
perimetric walls which laterally enclose the food positioned on the 
supporting wall. These walls are formed of a material, such as paperboard, 
which is transparent to microwave energy, and a microwave interactive 
layer formed of a material capable of converting microwave energy into 
heat is disposed in association with the support wall, such as by being 
laminated to an underside thereof. The combination tray and heating stand, 
so formed, is designed such that the perimetric walls coact with the 
support wall for converting the food storage space into an enclosed air 
space when the combination storage tray and heating stand is placed on the 
floor of a microwave oven in an inverted heating stand condition and is of 
sufficient strength to support the predetermined quantity of food or food 
item upon the support wall when the combination storage tray and heating 
stand is in the inverted heating stand condition with the interactive 
layer closely associated positionally in heat transfer relationship with 
respect to the food thereon. 
In accordance with modified embodiments, the package body is designed to be 
recloseable and to be usable alone or in combination with an inner food 
receiving tray to create an air space enclosing heating stand, with a 
microwave interactive heating layer, upon the floor of a microwave oven. 
In accordance with methods of use of the various embodiments, the food is 
removed from the outer package, and the outer package and/or the inner 
food tray is rearranged into an air space enclosing heating stand on the 
floor of a microwave oven. The food is then placed upon the heating stand, 
over the enclosed air space, so as to be in heat exchange relationship 
with a microwave interactive heating layer of the heating stand. 
Thereafter, the microwave oven is turned on so as to heat the food.

BEST MODE FOR CARRYING OUT THE INVENTION 
With reference to FIG. 1, the packaged arrangement designated generally by 
the reference numeral 1 is shown. This packaged arrangement includes a 
package assembly formed of a package body 2 defining a receiving space 3 
and a disposable, combination food storage tray and heating stand 4, as 
well as a predetermined quantity of food 5, for example, an item of food 
such as a pizza. Furthermore, the item of food itself may be wrapped 
within a plastic wrapping, such as a bag 6. 
The package body 2 preferably is a paperboard carton and any conventional 
carton blank may be utilized for the purposes of forming the schematically 
depicted carton 2. However, while a paperboard carton is preferred, since, 
in accordance with this embodiment of the present invention, the package 
body merely serves the function of defining a receiving space for the 
remainder of the packaged arrangement, the present invention encompasses 
the use of any form of package body that is known for use in the packaging 
of "ready-to-heat" foods, such as a plastic bag. 
The disposable combination food storage tray and heating stand 3 must 
possess the following requisites. Firstly, it must be constructed so as to 
form a food storage space of a size and shape within which the 
predetermined quantity of food (food item) may be stored and must be sized 
relative to the receiving space of the package body in order to be fully 
receivable within the receiving space thereof. 
In addition to forming a tray means within which the food may be received, 
the combination food storage tray and heating stand 3 must be able to 
function in an inverted condition as a heating stand. To this end, the 
food storage space is bounded by a support wall 10 and at least one 
perimetric wall which, together are sized and shaped so as to convert the 
food receiving space 11 into an enclosed air space when the combination 
storage tray and heating stand is placed on the floor of a microwave oven 
in an inverted heating stand condition. While a circular tray would have 
only a single perimetric wall extending about the periphery of the support 
wall 10, in the illustrated arrangement for use with a rectangular carton, 
four perimetric walls 12 are provided. It should also be appreciated that 
the at least one perimetric wall and the support wall must be of 
sufficient strength to support the predetermined quantity of food (food 
item) upon the support wall when the combination storage tray and heating 
stand is in the inverted heating stand condition as illustrated in FIG. 3. 
Still further, while the support wall 10 and the perimetric walls 12 must 
be formed of a material that is transparent to microwave energy, in 
accordance with the present invention, a microwave interactive layer 
formed of a material capable of converting microwave energy into heat is 
disposed in association with the support wall 10 so as to be able to heat 
the predetermined quantity of food when it is supported on the support 
wall in the inverted heating stand condition of FIG. 3. In this regard, it 
is noted that, in addition to the direct heating effect of the microwave 
energy upon the food and transferance of heat from the interactive layer 
to the food, the enclosed air space 11 will serve to store heat that is 
produced and act to distribute the heat evenly to the underside of the 
product in order to facilitate production of a more satisfactorily cooked 
product. 
With reference to FIG. 2, a blank for formation of a combination food 
storage tray and a heating stand is illustrated of a configuration 
suitable for use with a carton of the type illustrated in FIG. 1. This 
blank is formed from a paperboard material having sufficient strength and 
heat and moisture resistance and is totally free of printing. Such 
paperboard materials are known, per se, and in and of themselves form no 
part of the present invention apart from their use in the overall 
combination. As can be seen, the support wall 10 is disposed centrally in 
the blank and is connected at its edges, defined by score lines 13, to the 
perimetric walls 12, so that the perimetric walls can be folded into an 
upstanding position projecting upwardly from the support wall in order to 
laterally define the food storage space. In order to form a stable tray 
configuration, tabs 14 are formed by score lines 15 such that a tab is 
provided on the edge of one of every pair of adjacent edges of walls 12. 
Thus, the tabs 14 of one wall can be folded at right angles to that wall 
and secured to the inner side of the other adjacent wall (see right front 
corner, FIG. 1) such as by an adhesive. 
In order to obtain a browning or crisping of the food item, such as a 
pizza, a microwave interactive layer 16 is bonded or laminated to the 
support wall 10 on a side, relative to the score lines 13, such that, when 
the combination tray and heating stand is in an assembled condition, the 
interactive layer 16 is disposed on a side of the support wall 10 which 
faces away from the food storage space 11, whereby the predetermined 
quantity of food (food item) is positionable thereon when the combination 
storage tray and heating stand is in the noted inverted stand condition of 
FIG. 3. The material of which the microwave interactive layer is formed in 
order to be capable of converting microwave energy into heat does not, per 
se, form part of the present invention and any known interactive material, 
such as those described in the background art, may be utilized. One 
suitable type of interactive material is disclosed in Canadian Pat. No. 
1,153,069, issued Aug. 30, 1983. 
In order to maximize the cost efficient attributes of the present 
invention, as illustrated in FIG. 1, the packaged arrangement of the 
present invention utilizes a combination tray and stand whose perimetric 
walls have their height set so as to correspond to the height of the 
interior receiving space 3 of the package body and both are coordinated to 
the height of the predetermined quantity of food (food item) disposed 
therein. Thus, the minimum amount of packaging materials need be used and 
the package can be formed as small as practical for the amount of food 
involved. This is made possible by the fact that there is no need for any 
heating spaces to be designed into the package arrangement because the 
food is not cooked within the package body itself, but rather the package 
assembly is utilized in the following matter. 
In particular, a consumer desiring to heat or cook the contents of the 
package assembly 1 would open up the package body 2 and remove the tray 4 
(containing the food item 5) from the receiving space 3 of the package 
body 2. Then, the consumer would move the food item 5 from the food 
storage space 11 of the combination tray and stand 4 and then remove any 
wrapping 6 within which it might be packaged. Next, the tray would be 
converted into a heating stand by inverting of the combination tray and 
stand and placing it on the floor of the microwave oven. The interactive 
layer 16, which had been disposed in the package body, substantially 
without clearance, upon the bottom wall of the package body 2 would then 
be in an upwardly directed, exposed condition. The walls of the 
combination tray and stand, in this converted heating stand condition, 
will then define the above-noted enclosed air space in conjunction with 
the floor of the microwave oven. The consumer, thus, need only place the 
food item upon the support wall, and because of the heat exchange 
relationship that, thus, would exist between the interactive layer 16 and 
the food, as well as the heat distributing effect of the enclosed air 
space, a satisfactorily heated and crisped or browned food item will be 
produced when the microwave oven is operated in accordance with the proper 
time and power requirements for the particular food. 
In FIG. 4, a modified packaged arrangement is illustrated, like reference 
numerals being utilized to identify features common to both of the FIGS. 1 
and 4 embodiments, except that a prime designation is utilized to 
distinguish the modified features of FIG. 4. The packaged arrangement of 
FIG. 4 also includes a package assembly, this package assembly 1' 
including an outer package body 2' defining a receiving space 3' and a 
disposable, inner tray 4' upon which a predetermined quantity of food 5 is 
situated. 
The packaged body 2' is preferably of a construction which will enable the 
package body to be reclosed, after removal of the food therefrom, for 
reasons which will become more apparently in connection with the 
discussion of the methods of use of this embodiment. While any form of 
recloseable carton may be used as the outer package body, the construction 
thereof should be one which will not have a high likelihood of being 
damaged by the consumer during opening of the packaged body, and will have 
sufficient structural strength, to be able to support the packaged 
quantity of food 5, with or without the tray 4', thereon. 
One known type of package that is suitable for this purpose is illustrated 
in FIG. 4 and is of the zip-strip opening type. In such a known 
construction, a pair of serrations or perforations are formed along three 
or four of the side walls of the package body 2', so as to create strips 
2'a which may be pulled in a manner ripping a strip from the side walls 
which will result in the package body 2' being divided into an upper half 
2'b and a lower half 2'c. 
Joined to the inner side of the side walls of the lower half 2'c are inner 
side walls 2'd, which extend substantially the full height of the package 
body 2', but which are not affected by the ripping-out of the strip 2'a 
and which are not joined to the upper half 2'b. If zip-strips are placed 
on only three of the side walls, then the package body 2' may be opened in 
the manner of the valise, the fourth wall serving as a hinge and no inner 
side wall 2'd being required in association therewith. 
On the other hand, if zip-strips are provided on all four sides, then four 
inner walls 2'd are utilized. In such a case, after the strips 2'a are 
detached, the top half 2'b can be removed and reapplied in a telescoping 
manner upon the side walls 2'd. With either three or four wall zip strips 
2'a, opening of the package poses a minimal threat of the body of the 
package being damaged in a manner that would preclude reclosing thereof, 
and the inner side walls 2'd will provide support for the top panel 2'e of 
the package body 2'. 
While the inner tray 4 of the FIG. 1 embodiment may be utilized in 
connection with a packaged body 2', an inner tray 4' in the nature of a 
paperboard pie pan having sloped walls is shown in FIG. 4, and a flat tray 
(not shown) may be used as well. 
The method of use of the FIG. 4 embodiment will now be described. Like use 
of the embodiment of FIG. 1, use of the FIG. 4 embodiment involves opening 
of the packaged body and removal of the inner tray and quantity of food 
contained therein. However, instead of rearranging the inner tray within a 
microwave oven so as to form an air space enclosing a heating stand upon 
which the quantity of food is supportable in heat exchange relationship 
with the microwave interactive heating layer and enclosed air space, with 
no use being made of the outer package body for the purpose, the FIG. 4 
embodiment not only has the capability of being used in the same manner as 
the FIG. 1 embodiment, but is capable of various different methods of use, 
all of which utilize at least part of the outer package body, with or 
without the heating tray. 
With regard to the FIG. 5 usage, one half of the outer package body 2', 
such as the lower half 2'c, is placed on the floor 30 of a microwave oven 
with its open end directed downwardly, and the other half, such as the top 
half 2'b, is placed on top of the first half with its open end directed 
upwardly. When this manner of use is intended, the broken line enclosed 
area 20 of wall 2'e (FIG. 4) would be a microwave interactive heating 
layer 16' joined to the underside thereof. The quantity of food 5, thus, 
would be placed within the package half 2'b, in heat exchange relationship 
with the layer 16' and the enclosed space formed by the package half 2'c 
and oven floor 30. The oven would then be turned on for heating or cooking 
of the food in the desired manner. 
Alternatively, as represented by FIG. 6, either the box 2' is reclosed or 
one half thereof, such as top half 2'b, is placed, open-side down, upon 
the microwave floor 30, thus forming an enclosed air space. The food 5, in 
the tray 4', would then be positioned on top of the box 2' or box half 
2'b. In such a case, a microwave interactive heating layer would be placed 
on the bottom wall of the tray (and optionally also in the area 20 of the 
wall 2'e). Thus, the food will be supported in heat exchange relationship 
with both the enclosed air space and the microwave heat interactive layer 
for heating or cooking purposes. 
For most efficient usage of the present invention, from a packaging 
standpoint, the dimensions of the parts of the package assembly will be 
dictated by the minimums required to enclose a given food item or quantity 
of food. However, it has been determined that the quality of a food 
product that is heated in accordance with the present invention, is a 
function of the height of the air-space confining support wall upon which 
the food is supported in heat exchange relationship. This height will vary 
depending upon the size and type of food products involved, but can be 
determined empirically for any given food product or quantity of food. 
Thus, to the extent that such can be achieved consistent with the noted 
packaging concepts, the appropriate components of the package assembly 
should be dimensioned such that the surface upon which the food will be 
supported and heated will be situated, approximately, at the empirically 
predetermined optimized heating height. However, in certain instances, it 
may not be possible or practical to so dimension the tray, outer package 
or package half, and in such instances use of the arrangement of FIG. 4 in 
the manner illustrated in connection with FIG. 7 is advantageous. 
That is, by constructing the area 20 of wall 2'e as a detachable panel 
(such as through the use of a ring of perforations or serrations), such a 
panel can be removed, after opening of the package body 2', so as to 
create a tray receiving aperture. By dimensioning the size of such an 
aperture relative to the diameter of the sloping wall 4'a of tray 4', the 
height of the bottom of the tray 4'b can be set at any level between a 
fully inserted position of tray 4' within the aperture within top wall 2'e 
(whereat the pan would be supported by its lip 4'c resting on the panel 
2'e) and the height that would be achieved by simply having the tray 4' 
rest on the reclosed package or the package half in the manner shown in 
FIG. 6. As such, regardless of the size of the package, the quantity of 
food can be supported upon a heating surface that is situated, 
approximately, at the empirically predetermined optimized heating height. 
It is now apparent from the foregoing description of the various 
embodiments of this invention that the outer carton and the inner tray or 
the outer carton alone can be considered an outer packaging means which is 
initially operable in a packaging mode in which food may be retained 
within an enclosed food storage space for shipment and storage and 
subsequently operable in a cooking mode after the food originally located 
within the enclosed food storage space is removed and the outer packaging 
means is mechanically manipulated to form a heating stand means for 
supporting the removed food at a predetermined distance above the 
microwave oven support surface in heat transfer relation with a microwave 
interactive layer and for enclosing an air filled space beneath the 
microwave interactive layer for promoting even cooking of the removed 
food. 
It should be recognized that while various embodiments in accordance with 
the present invention have been described, the present invention is 
susceptible to numerous changes and modifications which will have become 
apparent to those skilled in the art from the foregoing disclosure. 
Therefore, the present invention should not be considered to be limited to 
the details shown and described herein, but encompasses all such changes 
and modifications as are within the scope of the claims. 
INDUSTRIAL APPLICABILITY 
This invention has particular utility in the packaging of food for 
distribution and sale in refrigerated and frozen display cases now common 
in most grocery stores. The disclosed package arrangement is ideally 
suited for packaging, shipping, vending and microwave heating of a variety 
of food products, but is especially useful in conjunction with those 
products that are subject to non-uniform heating by microwave energy 
and/or require browning or crisping on only one side thereof, such as is 
the case with pizza.