Patent Publication Number: US-5423453-A

Title: Microwaveable container

Description:
This is a continuation of application Ser. No. 08/226,229, filed on Apr. 11, 1994, now abandoned, which is a continuation of application Ser. No. 08/065,737, filed on May 21, 1993, now abandoned. 
    
    
     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® 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 &#34;hot spots&#34; 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 than Ragusa et al. 
     CROSS REFERENCE TO RELATED APPLICATIONS 
     U.S. patent application Ser. Nos. 065,738, now U.S. Pat. No. 5,377,182 and 065,739, now abandoned, are also directed to improved deli-type containers, multi-compartmented and single-compartmented, respectfully. 
     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 container structure which is constituted of a microwave transparent material, wherein the container base is configured in a manner to produce 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 the side wall including a curvilinear transition wall surface joining the side wall with the 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 &#34;single-use&#34; container. 
     Accordingly, it is a primary object of the present invention to provide a 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and advantages of the invention may now be more readily ascertained from the following detailed description of an exemplary embodiment of the microwaveable container, taken in conjunction with the accompanying drawings; in which; 
     FIG. 1 illustrates a top plan view of a microwaveable container pursuant to the present invention; 
     FIG. 2 illustrates an end elevational view of the container; 
     FIG. 3 illustrates a side elevational view of the container; 
     FIG. 4 illustrates a bottom plan view of the container. 
    
    
     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 base 12 which, 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 container base or bowl, portion 12, as shown in FIGS. 1 and 4 of the drawings, essentially consists of an upwardly curved (see FIGS. 2 and 3) bottom wall structure 16 in which the center of the bottom 16 is raised relative to the circumferential bottom edge 20 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. 
     The upwardly extending opposing peripheral side walls 18 and 22 of the container base 12, which are also outwardly sloped or inclined towards the upper end thereof, are connected with the bottom edge 20 through an oblong perimeter base portion which provides a smooth fairing or essentially a curvilnear transition wall surface between peripheral edge 20 of the bottom 16 and the peripheral side walls 18 and 22 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 &#34;hot spots&#34; 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 4, peripheral side (end) walls 18 curve inwardly into the body 17 of the container 10 while the peripheral (lateral) side walls 22 of the container curve outwardly from said body 17 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. 
     The upper edge or rim of the peripheral side walls 18 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 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 body 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. shipping. 
     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 or 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 wall 16 of the container base 12, and the raised center 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.