Microwave container

A container constituted of a microwave transparent material for the heating or cooking of foods or comestibles through the intermediary of microwaves at a high degree of efficiency and with an enhanced temperature uniformity. The present invention is directed to the provision of a simple and inexpensive multi-compartmented container structure which is constituted of a microwave transparent material, wherein the multi-compartmented container base is configured in a manner to produce in each compartment a generally upwardly curved bottom wall and inwardly curved and outwardly curved grooved lateral end walls and lateral side walls, respectively, with the lower end of each side wall including a curvilinear transition wall surface joining the respective end and side walls with the respective bottom wall, which will disperse the food or comestible within the container to an optimum extent so as to increase the heating and cooking efficiency thereof and to provide a more uniform temperature distribution throughout the container contents, thereby enabling the rapid and even heating and/or cooking of the food by microwave energy.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a microwaveable container and, more 
particularly, relates to a container constituted of a microwave 
transparent material for the heating or cooking of foods or comestibles 
through the intermediary of microwaves at a high degree of efficiency and 
with an enhanced temperature uniformity. 
In recent years, the heating and cooking of foods through the utilization 
of microwaves has immensely gained in popularity with homemakers in view 
of the simplicity and rapidity in the preparation and cooking of various 
kinds of foods in this manner. Generally, the foods, which may be in a 
frozen state or at ambient temperature, are heated or cooked in suitable 
containers, which may be reusable in nature, i.e. Pyrex.RTM. or other 
non-metallic cookware, or disposable, such as foamed plastic material or 
the like. Such containers are formed from a material which is transparent 
to microwaves to enable the foods within the container to be raised to 
suitable heating or cooking temperature in the absence of any undue 
heating of the container itself, tending to possibly cause distortions 
adversely affecting the integrity of the container. Furthermore, during 
the heating or cooking of the foods in the container through microwaves, 
the heating of the foods is frequently generally irregular or uneven in 
nature; in essence, various locations within the container are raised to 
higher or non-uniform temperatures, causing the formation of so-called 
"hot spots", thereby resulting in an uneven heating or cooking of the 
foods and adversely affecting the taste and appearance thereof to a 
consumer. 
In order to attain a high degree of efficiency and temperature uniformity 
in cooking the foods in containers through the intermediary of microwaves, 
various steps have been undertaken in the development of microwaveable 
containers in order to solve the encountered problems. Among these 
solutions are the use of laminated or complex types of materials for the 
containers, such as special susceptor materials which will improve upon 
the microwave efficiency. Furthermore, in order to further ameliorate 
problems encountered in the nonuniform heating or cooking of foods in 
containers which are constituted from microwave transparent materials, 
consideration has been given in the technology towards suitable 
configuring of the containers, such as raising at least portions of the 
bottom surfaces thereof such as to distribute the contents of the 
container in a more optimum or expedient manner, and to thereby obtain a 
greater degree of temperature uniformity during the microwave heating or 
cooking process. Although the various measures which have been undertaken 
in the technology in order to improve upon efficiency and temperature 
uniformity during microwave cooking of various comestibles, these will 
still have not proven to be entirely adequate; necessitating, either the 
employment of expensive materials or container constructions, or 
configuring microwave-transparent containers in a manner which has still 
proven to be somewhat elusive in providing the required degree of 
temperature uniformity during the cooking of the foods. 
2. Discussion of the Prior Art 
Thus, Matsui U.S. Pat. No. 4,704,510 discloses a container for food service 
which is adapted to withstand heating in a microwave oven, wherein the 
container is formed from a laminate sheet material consisting of a 
non-stretched polyethylene terephthalate film laminated to the interior of 
a foamed plastic sheet. Moreover, the bottom of the container is raised to 
curved concavely towards the center thereof in order to distribute the 
container contents and thereby improve upon the heat distribution within 
the container during the heating or cooking of the contents with 
microwaves. However, the laminated container material employed herein is 
of a complex and resultingly expensive construction. 
Bowen, et al. U.S. Pat. No. 4,486,640 pertains to a utensil for cooking 
and/or baking foods in a microwave oven in which a generally flat bottomed 
container base incorporates a removable tray and a closure lid possessing 
apertures to enable the escape of steam which is generated during cooking. 
This microwaveable container structure is relatively complex and 
expensive, while it does not enable the optimum distribution of foods or 
comestibles within the container to allow for a more uniform temperature 
distribution therethrough during cooking with microwave energy. 
Watkins U.S. Pat. No. 4,416,906 discloses a microwave food heating 
container having a central raised core in the container bottom to 
essentially distribute the food contained therein about an annulus to 
improve upon the uniform heating thereof. As in the other above-mentioned 
patents, there is no optimum distribution of the food within the container 
so as to allow for a greater efficiency during cooking and a degree in the 
uniformity of the temperature which will meet the demands of the 
technology for cooking with microwave energy. 
Isakson, et al. U.S. Pat. No. 4,640,838 describes a vapor-tight microwave 
oven package incorporating a vent enabling the escape of steam or vapor 
which is generated during cooking, and does not provide for an optimum 
distribution of foods within a generally rigid microwaveable container to 
attain uniform temperatures during microwave cooking or heating of the 
food contents of a container. 
Levendusky, et al. U.S. Pat. No. 4,560,850 discloses a microwave container 
with a cover incorporating a port for the release of steam, and with a 
raised container bottom to distribute the foods therein for more even 
cooking or heating. This structure also fails to provide for the optimum 
dispersion of a food within a specially configured container and does not 
allow for an adequately uniform temperature distribution through the food 
as it is cooked by microwave energy with a resultant higher degree of 
efficiency. 
Ragusa et al. U.S. Pat. No. 4,859,822 assigned to a common assignee 
overcomes all of the above problems. The present application similarly not 
only also solves all of the aforementioned problems, but is also an 
improvement over said U.S. Pat. No. 4,859,822 in that the present shape is 
more functional for deli-type containers and is more readily acceptable by 
the industry, and moreover is multicompartmented. 
CROSS REFERENCE TO RELATED APPLICATIONS 
U.S. patent application Ser. Nos. 08/065,737 and 08/065,739 filed 
concurrently herewith are also directed to an improved deli-type 
containers which are single compartmented. 
SUMMARY OF THE INVENTION 
In order to ameliorate or obviate the shortcomings and limitations 
encountered in prior art microwaveable containers which are adapted for 
the heating and/or cooking of foods in a microwave oven, the present 
invention is directed to the provision of a simple and inexpensive 
multi-compartmented container structure which is constituted of a 
microwave transparent material, wherein the multi-compartmented container 
base is configured in a manner to produce in each compartment a generally 
upwardly curved bottom wall and inwardly curved and outwardly curved 
lateral end walls and lateral side walls, respectively, with the lower end 
of each side wall including a curvilinear transition wall surface joining 
the respective end and side walls with the respective bottom wall, which 
will disperse the food or comestible within the container to an optimum 
extent so as to increase the heating and cooking efficiency thereof and to 
provide a more uniform temperature distribution throughout the container 
contents, thereby enabling the rapid and even heating and/or cooking of 
the food by microwave energy. 
Pursuant to the foregoing concept, the inventive microwaveable container 
may be constituted of simple materials which are inexpensive and are 
essentially microwave transparent; for instance, foamed thermoplastic 
materials, so as to enable the container to be employed as a disposable, 
so-called "single-use" container. 
Accordingly, it is a primary object of the present invention to provide a 
multi-compartmented microwaveable container possessing a novel 
configuration enabling an optimum distribution or dispersion of foods 
contained therein so as to achieve a high degree of efficiency and 
temperature uniformity during the heating and/or cooking of the contents 
of the container with microwave energy.

DETAILED DESCRIPTION 
Referring now in more specific detail to the drawings, FIG. 1 illustrates a 
microwaveable container 10 which is constructed pursuant to the present 
invention. In essence, the container includes a generally bowl-shaped 
multicompartmented base 12 divided into (in this embodiment) a main 
compartment 13 at one end and two smaller compartments 15 and 15' at the 
other end. It is to be understood that the relative sizes of the 
compartments may vary depending on the ultimate use of the container. In 
this particular embodiment the main compartment 13 is large enough to hold 
an entree type portion while the two smaller compartments 15 and 15' may 
hold so-called side dishes. Moreover, there need be only two compartments 
if desired, of equal size or otherwise, when desired, is adapted to be 
sealingly closed by a conventional cover (not shown) as described in U.S. 
Pat. No. 4,859,822, during the heating and/or cooking of foods or 
comestibles by means of microwave energy in a suitable microwave oven (not 
shown). 
In essence, the container base 12 (and the cover) may each be constituted 
of any kind of suitable heat resistant material which is substantially 
transparent to microwaves, while concurrently being liquid-impervious, 
such as foamed polystyrene or the like, and in which the container base 12 
(and the cover) may suitably and inexpensively be produced through the 
intermediary of thermoforming or the like, as is well-known in the 
plastics molding technology. 
The multi-compartmented container base or bowl, portion 12, as shown in 
FIGS. 1 and 5 of the drawings, essentially consists of an upwardly curved 
(see FIGS. 2 and 4) divided bottom wall structure 16, 31 and 31' in which 
the respective centers of the bottoms 16, 31 and 31' are raised relative 
to the circumferential respective bottom edges 20, 33 and 31', on which 
the container base 12 is adapted to be supported on a flat surface, such 
as in a microwave oven, at its respective corners 30 and 40, 40'. 
The upwardly extending opposing peripheral side walls 18 and 22 and 18' and 
22' of the compartments 13, 15 and 15', respectively, which are also 
outwardly sloped or inclined towards the upper end thereof, are connected 
with the bottom edges 20 and 30 and 31' through an oblong perimeter base 
portion which provides a smooth fairing or essentially a curvilnear 
transition wall surface between peripheral edges 20, 33 and 33' of the 
bottoms 16, 31 and 31' and the peripheral side walls 18, 22 and 18' and 
22', respectively, such as to, in essence, elevate the container base in 
order to improve upon the uniform heating to cooking of the container 
contents and to concurrently prevent the formation of so-called "hot 
spots" or localized regions of elevated temperature tending to unevenly 
cook or heat the contents or food in the container which will adversely 
affect the taste and appearance of the food. 
As may be clearly ascertained from FIGS. 1 and 5, peripheral side (end) 
wall 18 curves inwardly into the body 17 of the container 10 while the 
peripheral side walls 18', 22 and 22' of the container curve outwardly 
from bodies 17 and 17', respectively, which will improve upon the heating 
efficiency and uniform temperature distribution within the container 
during microwave heating or cooking of the foods in the container. 
As can be seen from FIGS. 1, 3 and 4, compartments 13, 15 and 15' are 
divided by interior sloped walls 50, 51 and 51', respectively, to form in 
this case, three separate compartments. 
The upper edge or rim of the peripheral side walls 18 and 18' and 22 and 
22' extends into a generally preferably oblong flange 24, which may have 
rounded corners 26, and which projects horizontally outwardly from the 
upper rim of the container side walls 18, 18', 22 and 22' so as to enhance 
the rigidity and strength of the container; in effect, its resistance to 
bending and distortion, to enable handling thereof without deforming the 
container, and to allow for an improved storage and orientation when the 
container is intended to be packaged in a carton or the like for wholesale 
and retail display or shipping. 
Extending upwardly from the generally oblong flange 24 is an oblong flange 
portion 28, formed integrally therewith about the upper opening of the 
bodies 17, 17' and which is adapted to be introduced into a suitable 
complementary oblong recess provided in a cover (not shown) for mating 
engagement therewith, and which will facilitate the sealing mounting of 
the cover on the container base 12 without the need for having to 
ascertain the correct angular orientation therebetween. 
The foregoing unique inwardly curved and outwardly curved design or shape 
of the end wall and lateral side walls, respectively, and the upwardly 
curved bottom wall of the container base 12 allows for an optimum 
distribution or dispersion of the foods contained therein, and will 
considerably increase the efficiency and temperature uniformity within the 
container during microwave heating o cooking of the contents in a 
microwave oven without, in any manner, adversely affecting the integrity 
or strength of the container. 
Furthermore, the configuration of the bottom walls 16, 31 and 31' of the 
container base 12, and the raised centers thereof relative to the bottom 
of the microwave oven or support surface further increases the efficiency 
in the heating or cooking of the container contents by causing the 
microwaves to be evenly distributed throughout the food, thereby 
eliminating temperature and heating non-uniformities. 
From the foregoing, it becomes readily apparent that due to the unique 
shape of the container there is attained a considerable increase in the 
uniformity and efficiency in the microwave heating of foods, without the 
necessity of having to provide special materials for the microwaveable 
container, inasmuch as any inexpensive material which is substantially 
transparent to microwaves can be readily employed in achieving the 
desirable results pursuant to the invention, thereby rendering the 
container expendable even after a single use. 
While there has been shown and described what is considered to be a 
preferred embodiment of the invention, it will of course be understood 
that various modifications and changes in form or detail could readily be 
made without departing from the spirit of the invention. It is therefore 
intended that the invention be not limited to the exact form and detail 
herein shown and described, nor to anything less than the whole of the 
invention herein disclosed as hereinafter claimed.