Apparatus for surface heating an object by microwave energy

An apparatus for surface heating of an object, such as a food object, in an oven by microwave energy which requires only a microwave interactive heater material and a support for it that is designed to obtain higher temperatures via a contact wall formed of stacked layers. In particular, in accordance with various embodiments, a primary panel defines a contact surface against which an object is disposed, and a secondary panel which is coextensive in area with at least an object heating portion of the primary panel is disposed adjacent to the primary panel at an opposite side thereof from the contact surface. Each of the primary panel and secondary panel is formed of a layer of microwave interactive heater material that is applied to a microwave transparent support material, such as paperboard. The layer of heater material applied to the primary panel covers at least the object heating portion thereof, and the layer of microwave interactive heater material applied to the secondary panel covers at least a part of a surface which faces toward the primary panel to an extent that is substantially coextensive with at least the object heating portion of the primary panel.

DESCRIPTION 
I. Technical Field 
This invention relates generally to the packaging of food products to be 
heated in a microwave oven through a direct surface heating effect, in 
addition to the heating produced by exposure to microwave energy, 
particularly for crispening or browning of food. 
II. Background Art 
Attempts to increasingly expand the number and types of prepared foods 
which can be heated within a microwave oven without losing the desired 
degree of browning or crisping that such foods normally have when cooked 
in a conventional oven or stove top implement have led to the development 
of numerous specialized packages and package components which are designed 
to achieve microwave browning or crispening of food contained therein. 
More specifically, these specialized packages incorporate a film or 
element that will convert microwave energy into thermal energy in order to 
produce a surface heating effect upon the food which will result in 
browning and/or crispening thereof. 
Typically, the heating film or element is applied directly to an internal 
wall surface of an outer package body (see, for example, Brown, et al. 
U.S. Pat. Nos. 4,555,605 and 4,590,349). In other cases, the microwave 
browning film is applied to a tray contained within the outer package body 
(see, for example, the noted Brown, et al. U.S. Pat. No. 4,555,605) or to 
an insert element that is disposed on or under the food object within a 
tray member located in an outer package body (see, for example, the other 
Brown, et al. U.S. Pat. No. 4,590,349 and Mikulski, et al. U.S. Pat. No. 
4,703,148). Still further, for items which require browning or crispening 
of multiple surfaces, open-ended sleeves, formed from a unitary paperboard 
blank that is covered with a microwave interactive heating material and 
having plural panels hingedly interconnected along fold lines about which 
the blank is folded, are known for surface heating of a food item inserted 
therein (see, for example, Brown U.S. Pat. No. 4,780,587 and Pawlowski, et 
al. U.S. Pat. No. 4,775,771). 
Generally, such specialized "cook-in" packaging has served to improve 
consumer acceptance of a wider range of prepared food products for heating 
in microwave ovens. However, in many cases, due to the nature of the food 
object to be heated, a single layer of heater material is unable to 
achieve high enough temperatures to produce the desired degree of browning 
and/or crispening of the food object within the time constraints necessary 
to thoroughly heat the food object without overheating it. 
In the case of one embodiment of the Brown, et al. U.S. Pat. No. 4,555,605, 
a food item is heated within a microwave oven in a pan-shaped tray that 
has a microwave interactive heating layer affixed on its bottom wall by 
placing the tray upon the top or top half of a reclosed carton-type outer 
package, the underside of which may, optionally, have a microwave 
interactive heating layer joined thereto as well. However, such an 
arrangement wherein the heating layer on the bottom of a pan is separated 
from the food object by the wall of the pan itself, and an optional, 
second interactive heating layer is disposed on the underside of a support 
surface of a stand created by a carton or carton half is not a suitable 
solution to the noted problem of a need for higher contact heating 
temperatures. That is, in such an arrangement the thermal contact heating 
effects are diminished by the facts that the microwave interactive 
layer(s) face(s) away from the food object, and both the bottom of the 
pan-shaped tray and the supporting wall of the carton or carton half 
produce an insulating effect relative to the transference of heat from the 
heating layer(s) to the food object. 
Furthermore, it has been found that when microwave interactive heating 
layers are disposed in back-to-back relationship on opposite sides of a 
board layer, severe scorching of the board layer results. In particular, 
this scorching problem has been noted in attempts to laminate a microwave 
interactive layer in back-to-back relationship on the same board layer to 
produce a heating element which heats to higher temperatures. Likewise, as 
described in the above-mentioned Brown Pat. No. 4,780,587, a problem of 
package scorching has also been found to result when a double heater area 
is created when the ends of a blank are joined to create a sleeve, unless 
the double heater area is positioned so as to be sufficiently shielded 
from microwave energy by the food item itself. 
Thus, the described scorching problems have caused package manufacturers to 
find the goal of obtaining a heating apparatus which will heat to a higher 
temperature than a single layer of microwave interactive heating material 
elusive. In this regard it is noted that, unlike reuseable implements for 
conventional and microwave ovens, microwave interactive heating materials 
of the type used on food packages cannot be preheated prior to use, 
thereby imposing yet another limitation upon a solution to achieving a 
contact heating surface which will reach higher temperatures than a single 
layer. 
DISCLOSURE OF THE INVENTION 
It is an object of the present invention to provide a novel and improved 
apparatus for surface heating an object, such as a food product, in a 
microwave oven wherein the apparatus is capable of achieving higher 
surface heating temperatures than is possible through the use of a single 
layer of microwave interactive heater material without scorching or 
burning of the material upon which it is supported. 
It is another object of the present invention to enable a double layer of 
heater material to be achieved which not only meets the foregoing object, 
but also minimizes the number of additional pieces required per package. 
It is a specific object, in accordance with preferred embodiments of the 
present invention, to enable one or more stacked layers of heater material 
to be produced from structural designs formed of a one-piece blank of 
paperboard material. 
Yet another object in accordance with the present invention is to enable 
double heater material layers to be produced, consistent with the 
preceding objects, in a manner that is applicable to various forms of 
microwave interactive heating element apparatus, such as cook-in cartons 
and sleeves as well as inserts therefor. 
Still a further object of the present invention is to provide an improved 
apparatus for surface heating of an object in a microwave oven via a 
microwave interactive heater material, wherein the apparatus is formed of 
a unitary blank which is inexpensive, simple to manufacture, and 
disposable. 
A specific object in accordance with preferred embodiments of the present 
invention is to provide an apparatus for surface heating of an object in a 
microwave oven wherein primary and secondary panels, formed by unitary 
sections of a single paperboard blank upon which a microwave interactive 
heater material is applied, may be brought into a stacked configuration 
wherein the primary panel is a contact surface against which the object to 
be surface heated is disposed and has the microwave interactive heater 
material applied to at least the object heating portion thereof, and 
herein the secondary panel is disposed adjacent to the primary panel at an 
opposite side thereof from the contact surface and with a second layer of 
the microwave interactive heater material being applied to the secondary 
panel, covering at least that part of its surface which is directed toward 
the primary panel so that a stacked arrangement of similar structures 
results. 
Another object of the present invention is to facilitate cost savings 
through reductions in the amount of microwave interactive heater material 
and/or paperboard material required through the use of focused patterns of 
microwave interactive heater material applied to one or more panels of a 
supporting blank and/or by shaping of a panel to use less supporting board 
material. 
An additional object of the present invention is to enable stacked layers 
of surface heating panels to be achieved through overlapping of one or 
more panels of a single blank and securing the panels in overlapping 
relationship such as by the use of adhesive. 
The above and other objects and advantages of the present invention are 
achieved by preferred embodiments of an apparatus for surface heating an 
object in an oven by microwave energy which requires only a microwave 
interactive heating means for surface heating the object by converting 
microwave energy to heat and a support means for supporting the microwave 
interactive heating means and for engaging the object to be surface heated 
by the microwave interactive heating means by virtue of the facts that the 
support means has at least one contact wall, with a contact surface 
against which the object is disposed, that is comprised of a primary 
panel, which defines the contact surface, and a secondary panel, which is 
coextensive in area with at least an object heating portion of the primary 
panel and which is disposed adjacent to the primary panel at an opposite 
side thereof from the contact surface. In this regard, for purposes of 
this application, the term "object heating portion" is being used to mean 
that portion of the primary panel of the contact surface that is 
positioned in sufficient proximity to the object being heated to produce a 
surface heating browning and/or crispening effect thereon, and the 
terminology "at least coextensive in area" with the "object heating 
portion" is being used to indicate an area that, at a minimum, is 
congruent with the object heating portion, although it may be larger so as 
to cover additional areas as well. 
Moreover, the microwave interactive heating means can comprise a first 
layer of microwave interactive heater material on the primary panel and a 
second layer of microwave interactive heater material applied to the 
secondary panel without producing scorching or burning of the support 
means. This result is achievable by virtue of the fact that the first 
layer of heater material is applied to the primary panel so as to cover at 
least the object heating portion thereof, and the second layer of 
microwave interactive heater material is applied to the secondary panel so 
as to cover at least a part of a facing surface thereof that is directed 
toward the primary panel, the part of the facing surface that is covered 
by the microwave interactive heater material being substantially 
coextensive with at least the object heating portion of the primary panel. 
Surprisingly, an arrangement, in accordance with the present invention, 
which possesses the characteristics noted in the preceding paragraph, 
avoids the scorching and burning problem that has been found to occur when 
only small portions of similar interactive heater material covered panels 
are overlapped and the overlap is not positioned to be maximally shielded 
from microwave energy by the object to be surface heated when the object 
and apparatus are located in an operative position within a microwave 
oven. 
While the reasons for such success in the face of the failures of somewhat 
similar structures are not entirely clear, it appears that two 
characteristics are of particular significance. Firstly, keeping in mind 
that typical microwave interactive heater material is formed of a 
metallized plastic laminate wherein a metal layer is deposited upon a 
plastic film and the metallized film is laminated to a paperboard support 
material with the metal layer between the plastic film and support 
material, evidently the sandwiching of the paperboard support material and 
metal layers between the plastic layers of such a heater material causes 
too much of the heat generated, upon conversion of the microwave energy 
into heat by the metallized plastic, becomes trapped between the plastic 
layers so as to result in severe scorching and burning of the board. 
Similarly, it seems that when panels, that are covered with a microwave 
interactive heater material on like facing sides, are only overlapped to a 
small extent, scorching and burning also occurs (if the area of overlap is 
not adequately shielded for microwave energy) because the double layer of 
interactive heater material at the overlap serves as a focus for the 
microwave energy and the overlapped layers of heater material convert 
substantially more microwave energy into heat than can be effectively 
transferred from them (considering that paperboard and many foods, as well 
as air, are thermally relatively insulative). As a result, heat builds up 
in the overlap to the point that severe scorching and burning of the 
paperboard support material, as well as the food, can occur. 
Thus, the present invention seeks to provide an apparatus wherein an 
undesirable buildup of heat within the support material will be avoided. 
In particular, the invention ensures that the area of overlap is at least 
coextensive with the object heating area in order to provide sufficient 
heat distribution. 
Consistent with the foregoing, the preferred embodiments of the present 
invention form a primary panel and a secondary panel of a surface heating 
apparatus as unitary sections of a single paperboard blank, each section 
of the blank being connected to an adjoining section by a fold line, so 
that the sections forming the primary panel and the secondary panel are 
disposed relative to each other in a manner enabling them to be brought 
into a superimposed relationship by folding of the blank about the fold 
lines. In this manner, the apparatus may be formed into browning and 
crispening sleeves by folding of the blank so as to bring at least 
opposite end sections thereof into an overlapping relationship forming one 
or more double-layered contact walls. 
Alternatively, the blank may be comprised of first and second polygonal 
main wall sections with a side wall section situated at each edge of the 
first main wall section and with a primary panel forming wall section 
joined to one of the side wall sections at an edge thereof that is 
disposed opposite its edge that is joined to the first main wall section. 
In this case, the blank is erectable into a carton having the first and 
second main wall sections disposed in facing relationship to each other 
with the side wall sections extending therebetween to define an object 
receiving space and with the primary panel wall section being disposed in 
overlapping relationship to an inner side of one of the wall sections that 
define the object receiving space so that the primary panel wall section 
and the wall section overlapped thereby form the primary panel and 
secondary panel of a surface heating contact wall. 
Still further, for those situations wherein a planar surface heating insert 
is required, the paperboard blank support material may be comprised of an 
insulating section that is free of microwave interactive material, with 
sections of the blank that form the primary panel and the secondary panel 
of the contact wall being connected together with the insulating section 
in a hinge-like manner by fold line means for enabling the primary panel 
to be stacked upon the secondary panel at one side of the insulating 
section. Such a heating element may use sections that have a disk-like 
shape, and wherein the microwave interactive material completely covers 
the sections forming the primary and secondary panels on the same side of 
the blank, the insulating section being connected between the sections 
forming the primary and secondary panels. 
Other and more specific objects, features, and advantages of the present 
invention will become more apparent from the following "Brief Description 
of the Drawings" and from the detailed description of the preferred 
embodiments contained in the description of The "Best Mode for Carrying 
Out the Invention".

BEST MODE FOR CARRYING OUT THE INVENTION 
FIG. 1 illustrates an apparatus for surface heating of an object, such as a 
food item, in a microwave oven that is in the form of a browning and 
crispening sleeve of the type described in Brown U.S. Pat. No. 4,780,587 
and is normally packaged as an insert (in a collapsed form) within a 
package of prepared food for shipping, storage, and sale as shown in 
Pawlowski, et al. U.S. Pat. No. 4,775,771. As for the blanks for the 
sleeves described in both of these patents, the sleeve 1 of the present 
invention is formed from a unitary blank 3 (FIG. 3) of microwave 
transparent material, such as paperboard. Furthermore, as is the case for 
the blanks of the known sleeves, blank 3 has a layer of microwave 
interactive heater material 5 on one side. This heater material 5 is 
comprised of a plastic layer 5a upon which a metal film layer 5b has been 
deposited, the metal film layer 5b being laminated to a surface 7a of the 
paperboard material 7 of the blank 3. 
In addition, the blank 3 is subdivided into a plurality of sections by fold 
lines which serve to hingedly interconnect the sections of the blank in a 
manner which allows it to be folded into an open-ended sleeve of the 
desired size and configuration, also, in the manner of the known sleeves. 
A sleeve 1 of the rectangular configuration shown as an illustrative 
embodiment of the surface heating apparatus of the present application, if 
constructed in accordance with known techniques, would be formed from a 
blank having four panels separated by fold lines and would be assembled in 
a manner causing the opposite end sections to slightly overlap (or an 
additional attachment flap would be provided) for enabling the opposite 
ends of the blank to be connected in an end-to-end manner, such as by 
gluing. However, in contrast, the blank 3, in accordance with the present 
invention, is subdivided into five sections, 9, 11, 13, 15, 17, by fold 
lines 19a-19d, with the first and last sections 9, 17 being of essentially 
the same size and configuration so that, upon folding of the blank along 
the fold lines 19a-19d, the blank is assembled into a sleeve which, as 
shown in FIGS. 1 and 3, has section 17 superimposed upon section 9 so as 
to almost totally overlap it. 
It can be appreciated from FIG. 4 that the overlapped sections 9, 17 form a 
contact wall C having a contact surface against which an object, such as 
the food item F, is disposed for heating in a microwave oven. The contact 
surface is defined by the inner surface of section 17, which forms a 
primary panel of the contact wall C, while the underlying section 9 forms 
a secondary panel that is coextensive in area with not only the object 
heating portion of the primary panel, but also the surrounding areas 
thereof. In addition to the first layer of microwave interactive heater 
material that is applied over the surface of primary panel section 17, a 
second layer of microwave interactive material covers the secondary panel 
section 9 on the facing surface thereof that is directed toward section 
17, i.e., stacked layers of paperboard-heater material-paperboard-heater 
material, are produced. 
As fully commented upon in the initial "Description of the Invention," this 
arrangement surprisingly avoids the scorching and burning problem that has 
plagued prior attempts to achieve a microwave interactive heating means 
that will heat to higher temperatures, as well as the scorching and 
burning problem that has been associated with similar stacked structures 
that have had only small edge or flap portions of interactive heater 
material covered panels overlapped. This is, apparently, a result of the 
fact that heat generated by the layers of heater material does not become 
trapped between their associated plastic film layers, and since extending 
the area of overlap, so as to make it at least coextensive with the object 
heating area of the contact wall, ensures that microwave energy is not 
focused into an area that is too small to enable effective distribution 
and transference of the heat produced in the overlapped heater material 
layers. In fact, as shown by the sleeve 1' of FIG. 5, blank 3 could be 
extended so as to have additional sections 19, 21 and 23 which results in 
the food object F being completely surrounded by contact walls formed of 
overlapped primary and secondary panels. In this regard, it is noted that, 
for simplicity, these additional overlapped sections 11, 19; 13, 21; and 
15, 23 have also been referred to as contact walls due to their possessing 
the identical structure as the contact wall formed by the overlapped 
sections 9, 17, even though contact may or may not actually occur to the 
same extent as occurs for the bottom contact wall, or may not even occur 
at all (heating then occurring by radiation instead of conduction). 
As can be appreciated from FIGS. 4 and 5, often times the object heating 
portion of the primary panel of the contact wall C, formed by the 
overlapping sections of the blank, has an area that is smaller than the 
area of the contact wall. As such, economies can be achieved, along with 
avoidance of unnecessary heat production, by confining the metallization 
layer of the microwave interactive heating means to the object heating 
portion of one of the panel sections forming a contact wall C. In FIG. 6, 
a blank 3" is shown for producing a sleeve in which the section 17" is 
provided with a focused covering of microwave interactive heater material 
that conforms essentially to the shape of the object heating portion of a 
contact wall C intended for use with a particular food object F, thereby 
limiting the amount of heat buildup in the paperboard material 17 by 
confining the double heater material layers to the minimum area required 
to produce the desired browning and crispening effect, the microwave 
energy that, otherwise, would unnecessarily be converted to heat being 
able to act directly on the food object F. On the other hand, in FIG. 7, a 
blank 3"' is shown in which the end section 17"' has been given a shape 
that conforms essentially to the shape of the object heating portion of a 
contact wall C, except for the provision of a connecting hinge portion 
17"'a thereof. An arrangement as shown in FIG. 7 is advantageous relative 
to that of FIG. 6 in that it requires the use of less paperboard and 
eliminates the need to utilize the more complicated focus metallization 
technique required to form a panel 17" as shown in FIG. 6. 
Additionally, it should be appreciated from a comparison of FIGS. 4 and 5 
that, in assembling a blank 3", 3"' into a sleeve, the end section 17", 
17"' may be disposed so as to serve as the primary panel of a contact wall 
C (as in FIG. 4) or as the secondary panel of a contact wall C as in FIG. 
5; although, in most cases, it will be preferable to utilize the panel 
having a smaller area of microwave interactive heater material as the 
secondary panel of the contact wall, thereby enabling a more effective 
distribution of heat and less buildup of heat within the paperboard layer 
disposed between the stacked layers of interactive heater material. It 
should also be recognized that the techniques shown for panels 17", 17"' 
need not be confined to only a single end section, but rather can be 
utilized, for example, with respect to the panel sections 19', 21' and 23' 
of the FIG. 5 embodiment. 
FIG. 8 depicts another modified sleeve embodiment 1"" which is designed to 
enable the sleeve to more closely conform to the peripheral contour of 
irregularly shaped food objects F. That is, in comparison to a sleeve as 
shown in FIG. 4, the side sections 11, 15 have been subdivided by 
additional fold lines 19""e, 19""f into half sections 11""a, 11""b, and 
15""a, 15""b. Another feature embodied in the FIG. 8 sleeve 1"" is the 
provision of glue flaps F which may be used, in addition to or instead of 
the overlapped panel sections 19"", 17"" to adhesively join together 
opposite end portions of an elongated blank into the sleeve 1"". 
While, to this point, the present invention has been described exclusively 
with respect to embodiments in the form of open-ended tubular sleeves, it 
should be appreciated that the invention is not so limited. In FIG. 9, an 
embodiment is shown wherein the above-described concepts are incorporated 
into a paperboard carton 30 having at least one primary panel wall section 
which, as depicted in this illustrative embodiment, may form a sleeve-like 
lining 31 for a carton of otherwise conventional construction. 
In particular, with reference to FIG. 10, a blank 33 is shown as one way in 
which a carton 30 can be formed with an integral liner 31. The carton 
forming portion of the illustrated blank 33 is comprised of seven sections 
which include first and second polygonal main wall sections 33a, 33b, four 
side wall sections 33c-33f, that are connected to each edge of the first 
main wall section 33a by fold lines 35ac-35af, respectively, and a closure 
section 33g. The second polygonal main wall section 33b is joined to side 
wall section 33d by a fold line 35bd, so that when the blank is erected to 
form carton 30 (glue flaps F being shown for securing the side walls 
together, but lock type flaps for interlocking in a slot of the adjoining 
side wall section may be used), the first and second main wall sections 
33a, 33b are disposed in facing relationship to each other with the side 
wall sections 33c-33f extending therebetween to define an object receiving 
space. The closure wall 33g is attached at an edge of the second main wall 
section 33b by a fold line 35bg, so that, in use, it will overlap the 
exterior of side wall section 33c and which it may be adhesively secured 
for sealing of a food object within the carton for shipping and storage 
purposes. This closure section 33g may be constructed to provide a 
zip-strip type, tear-open closure to facilitate opening of the carton. 
As can be seen from FIGS. 9 and 10, the liner portions of blank 33 is 
divided by fold lines into sections 31a-31d that are essentially matched 
to the corresponding wall sections 33a-33d of the carton forming section. 
Side wall section 31c is connected by a fold line to the side wall section 
33c that is disposed on the opposite side of the first main wall section 
33a from the side wall section 33d that is connected to the cover-forming, 
second main wall section 33b. As a result, in the in-use configuration of 
FIG. 9, each of the wall sections of the liner portion is disposed in 
superimposed overlapping relationship with respect to a corresponding wall 
section of the carton portion. Thus, in dependence upon the nature of the 
particular food object to be heated within the surface heating apparatus 
formed by carton 30, any or all of the surfaces of the wall sections which 
face the interior of the carton 30 may have microwave interactive heater 
material applied thereover so that one or more contact walls, which 
correspond to the contact walls C of the earlier mentioned sleeve 
embodiments, can be produced. With respect to such contact walls, it 
should be apparent that a primary panel wall section will be formed by 
each liner section that is covered with microwave interactive heater 
material and overlies a carton portion wall section that is similarly 
covered with a microwave interactive heater material to form a secondary 
panel wall section. 
Furthermore, it should be appreciated that the focused heater material 
concept shown for section 17" in FIG. 6 may be utilized in conjunction 
with the layers of heater material applied to any sections of either of 
the carton portion or liner portion, while the configured section concept 
shown for sleeve section 17"' of FIG. 7 is applicable to wall sections of 
the liner portion only. In any case, the covering of heater material 
applied to any wall section will typically be at least as great as the 
object heating area as initially defined in the "Disclosure of the 
Invention" section. 
Other modifications that can be made to carton 30 include the fact that, as 
reflected by broken lines in FIG. 10, side sections 31e and 31f can be 
connected by fold lines to the opposite sides of wall section 31a of the 
liner portion in order that the end wall sections 33e and 33f also may be 
made into double heater contact walls. Alternatively, as reflected by the 
modified embodiment of a carton 30' illustrated in FIG. 11, a single 
primary panel forming wall section 31'b can be joined to the side wall 
section 33'c that is disposed opposite the wall section 33'd to which the 
main wall section 33'b is connected. Thus, upon sealing of the carton, 
liner wall section 31'b will be disposed in overlapping relationship to 
the main wall section 33'b to form primary and secondary panel wall 
sections of a contact wall. Such a contact wall at the top of a carton can 
be useful with respect to food objects requiring browning or crispening at 
only a top surface thereof, such as for pot pies, or, by inverting of the 
carton, can form a bottom browning contact wall for food objects, such as 
pizzas, which require browning and crispening only at a bottom surface 
thereof. Of course, a primary panel as is formed by wall section 31'b may 
have a focused covering of heater material, as with the embodiment of FIG. 
6, or may be configured to the object heating area, as done for the 
embodiment of FIG. 7. 
While normally it is desired to minimize the number of pieces per package 
which must be handled by the packer, in some cases the use of a separate 
heater insert may be preferable and/or more advantageous than an 
integrally formed one. For example, in situations where stacked heater 
layers are to be used in conjunction with trays or containers that are 
made from materials that will melt when the heater structure is in contact 
therewith, such as trays or containers formed of thin plastic materials, a 
heater insert as illustrated in FIG. 12 can be advantageously utilized. 
In FIG. 12, an apparatus for surface heating of an object in an oven by 
microwave energy in the form of a disk-like insert 40 is shown that is 
formed of a paperboard blank having an insulating section 41 that is free 
of microwave interactive heater material and to which sections 43 and 45 
of the blank are connected in a hinge-like manner by fold lines 47, 49. 
The fold lines 47, 49 enable, for example, section 43 to be folded on top 
of section 41 and section 45 on top of section 43 to create the stacked 
configuration illustrated in FIG. 13, wherein the layers of heater 
material H face upwardly, while the paperboard layers B of sections 43, 45 
face downwardly toward section 41. However, a triple heating layer 
arrangement can be created by applying microwave interactive heater 
material H to section 41 at the opposite side of the blank from that 
having the heater material for sections 43, 45, so that, in the FIG. 13 
configuration, all of the layers of heater material H will face in the 
same direction (this optional layer H being designated by a broken arrow 
in FIG. 13). 
An insert apparatus 40, as described relative to FIGS. 12 and 13, may be 
packaged, for example, in a carton with, for example, a package of 
vegetables (with or without flavoring or sauce ingredients), as well as a 
thin plastic tray 50 (FIG. 14). A consumer can then easily follow 
instructions for folding of the insert apparatus 40 into a contact wall C' 
to be disposed with insulating section 41 protectively resting upon the 
bottom wall 51 of the tray 50, after which the food ingredients can be 
added to the tray and heated in a microwave oven in accordance with 
prescribed cooking directions. The contact wall C' will ensure that the 
vegetables are rapidly exposed to a high enough conductive heating surface 
to produce a crisp food texture, despite the fact that a microwave oven is 
utilized, and without concern for scorching, burning or melting of the 
thin plastic tray 50. 
From the foregoing, it should now be apparent how the present invention 
provides a means for enhanced microwave cooking using multiple stacked 
surfaces of interactive heater material, with or without supportive 
insulation. Furthermore, it should be recognized that the above described 
embodiments are merely illustrative in nature and that those skilled in 
the art should readily perceive how aspects of one embodiment may be 
substituted or added to other embodiments, as well as the virtually 
limitless application of the inventive concepts to package types and 
package inserts beyond those illustrated. Therefore, since the present 
invention is susceptible to numerous changes, modifications, and 
variations that will have become apparent to those skilled in the art from 
the foregoing disclosure, the present invention should not be considered 
to be limited to the details shown and described herein, but rather 
encompasses all such changes, modifications, and variations as are within 
the scope of the appended claims. 
Industrial Applicability 
The present invention has particular utility in the packaging of food 
products for distribution and sale in refrigerated and frozen display 
cases for cooking in a household microwave oven. However, the present 
invention will be applicable to the heating of any object in a microwave 
oven to produce a result, such as browning and crispening of one or more 
surfaces of a food object, where the heat generated by a single layer of 
microwave interactive heater material will not heat to a high enough 
temperature.