Abstract:
A container for food and beverage products, and more specifically, a substantially metallic container with a microwavable transparent portion and a selectively removable metallic lid, wherein the container can be used in a conventional microwave oven.

Description:
FIELD OF THE INVENTION 
   The present invention relates to food and beverage containers, and more specifically metallic containers used for perishable foodstuffs which can be heated in a microwave oven. 
   BACKGROUND OF THE INVENTION 
   With the introduction of the microwave oven, a huge demand has been created for disposable food and beverage containers which may be heated in conventional microwave ovens. These containers eliminate the necessity of utilizing a separate microwavable bowl and the inconvenience related thereto, and provide a container which is used for both storing food and beverage items, heating those items, and subsequently using the container as a serving bowl or tray. Following use, the microwavable bowl may be conveniently discarded or recycled rather than cleaned. As used herein, the term“foodstuffs” applies to both solid and liquid food and beverage items, including but not limited to pasteurized liquids such as milk products, soups, formula, and solids such as meats, vegetables, fruits, etc. 
   In general, metal containers have not been utilized for heating foodstuffs in microwave ovens due to the likelihood of electrical“arcing”, and the general public misconception that metal materials are incapable of being used in conventional microwave ovens. Although previous attempts have been made to design microwavable metal containers, these products have generally been very limited and impractical in their design and use. 
   For example, U.S. Pat. No. 4,558,198 and 4,689,458 describe microwavable metal containers which have height limitation of less than about 1 inch, and are thus not practical for storing any significant volume of foodstuffs. 
   U.S. Pat. No. 5,961,872 to Simon et al, (the &#39;872 patent”) discloses a microwavable metal container which utilizes a microwavable transparent material. However, the &#39;872 patent does not utilize a hermetic seal which is sufficient to safely store food items under a vacuum for long periods of time, and which requires that the entire lower portion and sidewall oft he metal container be enclosed within an electrical insulation material to prevent arcing. Further, the device requires that the side walls of the container have a height less than about 40 percent of the wavelength of the microwave radiation used to heat the object, which is not overly practical or functional. 
   More recent attempts to store and cook food in microwavable containers have been accomplished by using non-metallic plastic and foam type materials. Although these products are suitable for use in microwave ovens, and are generally accepted by the consuming public, they have numerous disadvantages when compared to metallic containers. More specifically, non-metallic foam and plastic containers have very poor heat transfer characteristics, and these types of containers require significant more time to heat and cool in a food processing plant. Thus, these types of containers are very time-consuming and expensive to fill and sterilize during filling operations, and are thus inefficient for mass production. 
   Further, non-metallic containers are not as rigid as metal containers, and thus cannot be stacked as high as metal containers which limits the volume which can be shipped, and thus increases expenses. Additionally, non-metallic containers are not durable, and are prone to damage and leaking during shipment and placement for sales, thus adding additional expense. Furthermore, multi layer barrier plastics and foams are generally not recyclable like metal containers, which fill landfills and are thus not environmentally friendly. 
   Finally, foodstuffs cooked in non-metallic plastic and foam containers in a microwave oven generally overheat and burn next to the container surface, while the foodstuffs in the center of the container heat last, and thus require stirring or remain cold. Further, there are general health concerns regarding the possible scalping of chemicals and the subsequent altered taste when cooking foods in non-metallic containers, especially since non-metallic plastics and foams can melt and deform when overheated. 
   Thus, there is a significant need in the food and beverage container industry to provide an economical metallic container which may be used for cooking foodstuffs in a microwave oven and which eliminate many of the health, shipping and filling problems described above. 
   SUMMARY OF THE INVENTION 
   It is thus one aspect of the present invention to provide a metallic, microwavable metal container which is hermetically sealed and capable of storing foodstuffs for long periods of time. Thus, in one embodiment of the present invention, a metallic container is provided with a lower end of a sidewall sealed to a non-metallic microwavable transparent material. Preferably, the microwavable transparent material and sidewall are double seamed to a reinforcing material and may additionally utilize a sealant material to create a hermetic, long lasting, airtight seal. 
   It is a further aspect of the present invention to provide a microwavable metal container which generally heats foodstuffs contained therein from the “inside out”, rather than the “outside in” as found with conventional plastic and foam containers. Thus, in one embodiment of the present invention a container with a unique geometric shape is provided, and while the microwavably transparent material on the lower end of the container has a surface area of at least about 1.25 square inches. More specifically, the metallic container in one embodiment has an upper portion with a greater diameter than a lower portion of the container, and thus has a substantially conical geometric shape which facilitates efficient cooking of the foodstuffs contained therein. 
   It is a further aspect of the present invention to provide a microwavable metallic container which utilizes well known materials and manufacturing processes which are well accepted by both the container industry and consumers alike. Thus, in one aspect of the present invention a microwavable metallic container is provided which is compiled of steel, aluminum, tin-coated steel, and which utilizes a microwavable transparent material comprised of materials such as polypropylene/EVOH, polyethylene, polypropylene and other similar materials well known in the art. Furthermore, the microwavably transparent material may be interconnected to the sidewall of the metallic container with a metallic or plastic reinforcing member by a double seaming process that is well known in the metallic container manufacturing industry, and which is capable of interconnecting multiple layers of materials. Alternatively, or in conjunction with the double seaming process the microwavable transparent material may be welded or chemically adhered to a flange portion of the container sidewall or reinforcing member. 
   Alternatively, it is another aspect of the present invention to provide a microwavable metallic container which utilizes a microwavable transparent material which is welded or chemically sealed to a lower end of the metallic container sidewall. Thus, in one embodiment oft he present invention there is no double seaming required to interconnect the metallic container sidewall to the microwavable transparent material, nor is a reinforcing member necessary for support since sufficient rigidity is obtained with the metallic sidewall and microwavable transparent bottom portion. 
   It is another aspect of the present invention to provide a bowl or container shape which is more efficient with regard to heating the foodstuffs within the container. Thus, in one aspect of the present invention a container is provided which utilizes an upper portion with a greater diameter than a lower portion, or alternative a lower portion with a greater diameter than an upper portion. Alternatively, a container which has an upper portion with substantially the same diameter upper portion and lower portion may be utilized. 
   Thus, in one aspect of the present invention, a microwavable metallic container is provided, and which comprises: 
   A substantially metallic container adapted for cooking foodstuffs in a microwave oven, and including a metallic sidewall defined by an upper end and a lower end; 
   a selectively removable lid operably interconnected to said upper end of said metallic sidewall; and 
   a microwavable transparent bottom portion seamed to said lower end of said metallic sidewall to create a hermetic seal, wherein the foodstuffs may be stored or subsequently cooked in said substantially metal container upon removal of said selectively removable lid. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front exploded perspective view of a metallic microwavable bowl; 
       FIG. 2  is a front perspective view of the lid configuration of the embodiment shown in  FIG. 1 ; 
       FIG. 3  is a bottom perspective view of one embodiment of the invention identified in  FIG. 1 , and identifying a metallic microwavable bowl with a microwavable transparent material on a bottom portion; 
       FIG. 4  is a cross-sectional view of the container shown in  FIG. 1 ; 
       FIG. 5   a  is a front cut-away perspective view of the lower portion of the metal microwavable bowl shown in  FIG. 4 , and identifying the various components therein; 
       FIG. 5   b  is an enlarged view of the container shown in  FIG. 5   a.    
       FIG. 6  is a bottom perspective view of an alternative embodiment of the present invention; 
       FIG. 7  is a cross-sectional front elevation view depicting an alternative embodiment of a lower portion of the present invention; 
       FIG. 8  is a cross-sectional front elevation view of an alternative embodiment of a lower portion of a metal microwavable bowl; 
       FIG. 9  is a cross-sectional front elevation view of a lower portion of a metal microwavable bowl, and identifying an alternative embodiment; 
       FIG. 10  is a cross-sectional front elevation view of a lower portion of a metal microwavable bowl and identifying an alternative embodiment; 
       FIG. 11  is a cross-sectional front elevation view of a lower portion of a metal microwavable bowl, and identifying an alternative embodiment; 
       FIG. 12  is a bar graph identifying the average temperature comparison of a soup heated in the hybrid bowl of the present invention, as compared to a typical microwavable plastic bowl; 
       FIG. 13  is a bar graph identifying the middle top temperature of a soup material heated in a conventional plastic bowl, and the hybrid bowl of the present invention; 
       FIG. 14  is a bar graph identifying the middle bottom temperature of a soup cooked in the microwavable hybrid bowl of the present invention as compared to a conventional plastic bowl; 
       FIG. 15  is a bar graph identifying the top side temperature comparison of a soup cooked in the hybrid bowl of the present invention and a conventional plastic bowl; 
       FIG. 16  is a bar graph depicting the bottom side temperature of the hybrid microwavable bowl oft he present invention as compared to a conventional plastic bowl; and 
       FIG. 17  is a graph depicting the temperature versus time of a soup cooked in the hybrid metal microwavable bowl oft he present invention compared to a conventional plastic bowl, and identifying temperatures taken over time at the middle, top and bottom of the container. 
   

   DETAILED DESCRIPTION 
   Referring now to the drawings,  FIGS. 1–11  depict various embodiments of a metallic microwavable bowl. Referring now to  FIG. 1 , a microwavable container  2  of the present invention is provided in an exploded view, and which identifies a metal lid  4  with interconnected pull tab  26 , as well as a removable plastic lid  6  which is positioned thereon. In use, the metal lid  4  is hermetically sealed to the metallic side wall upper portion  10  of the container after the foodstuff is placed in the container during filling operations. During use, the metal lid  4  is removed from the metallic sidewall  8 , and the removable plastic lid  6  is positioned on an upper end of the metallic side wall  8 , to prevent splattering and to improve the heating of the foodstuff contained in the microwavable container  2 . 
   Referring now to  FIG. 2 , a detailed drawing of the upper portion of one embodiment of the microwavable container  2  is provided herein and which depicts the interconnection of the metal lid  4  which is used in conjunction with a sealant material  20 , and further identifying a seam with a lower lip used to retain the removable plastic lid  6 . Alternatively, the metal lid  4  is interconnected to the metallic side wall upper portion by a conventional double seam commonly used in the container manufacturing industry. 
   Referring now to  FIG. 3 , the microwavable container  2  of  FIG. 1  is provided herein as viewed from a bottom perspective view. More specifically, the microwavable container  2  comprises a metallic side wall  8  which includes a sidewall upper portion  10 , a metallic sidewall lower portion  12 , and a reinforcing member  16  which is used to interconnect the microwavable transparent bottom portion  14  to the metallic sidewall  8 . In one embodiment of the present invention the microwavable transparent material is comprised of a polyethylene or a polypropylene/EVOH, nylon, PET or other plastics, and as appreciated by one skilled in the art can comprise any number of materials which allow the passing of microwavable energy. 
   Furthermore, in a preferred embodiment of the present invention, the microwavable transparent bottom portion  14  has a cross sectional area of at least about 1.25 square inches, to allow optimum heating of the foodstuff contained within the microwavable container  2 . The bottom reinforcing member  16  is used for interconnecting the metallic sidewall lower portion  12  to the microwavable transparent bottom portion  14 , and is generally comprised of a metal material such as aluminum, or steel. However, as appreciated by one skilled in the art this material may also be comprised of a plastic material such as polypropylene, polyethylene or other well known materials in the art. 
   Referring now to  FIG. 4 , a cut-away sectional view of one embodiment of a microwavable container  2  is provided herein, and depicts additional detail oft he double seam used to interconnect the microwavable transparent bottom portion  14  to the metallic sidewall lower portion  12  and the bottom reinforcing member  16  as further provided in  FIG. 5 . As shown in  FIG. 5 , a conventional double seam  30  is used in one embodiment of the present invention and which efficiently interconnects the bottom reinforcing member  16  to the peripheral edge of a microwavable transparent material  18  and to a lower portion of the metallic sidewall  12 . Additionally, a sealant material  20  may be positioned between at least  2  of either the metallic sidewall lower portion  12 , the microwavable transparent material  18 , or the bottom reinforcing member  16  to improve and assure the hermetic seal of the microwavable container  2 . Preferably the sealant is comprised of an elastomer, a silicon or a latex based material. 
   Referring now to  FIG. 6 , an alternative embodiment of the present invention is provided herein which depicts a bottom perspective view of a microwavable container  2  which utilizes an alternative geometric pattern for the microwavable transparent material  18 . Although in this embodiment additional rigidity is provided with the bottom reinforcing member  16 , and which creates  4  individual pieces of the microwavable transparent material  18 , any variety of geometric shapes and configurations may be used as appreciated by one skilled in the art. Preferably, and as stated above, the microwavable transparent material  18  has a surface area sufficient to efficiently heat the foodstuffs contained within the microwavable container  2 , and thus is preferably at least about 1.25 square inches, and more preferably about 3.0 square inches. 
   Furthermore, and again referring to  FIG. 6 , the upper portion of the container  2  has a greater diameter than a lower portion, which appears to have superior heating qualities when compared with a traditional food container with a generally cylindrical shape. Alternatively, the lower portion of the container  2  may be designed to have a larger diameter than an upper portion of the container, or a generally cylindrical shape may be utilized. 
   Referring now to  FIGS. 7–11 , sectional front elevation views of a lower portion of alternative embodiments of a microwavable container  2  are provided herein. More specifically, various embodiments are provided herein which show the interconnection oft he microwavable transparent material  18 , the bottom reinforcing member  16 , and the lower portion of the sidewall  12 . More specifically, as shown in  FIG. 7 , a weld  22  is provided which effectively interconnects the microwavable transparent material  18  to the bottom reinforcing member  16  along an upper edge oft he bottom reinforcing material  16 . As shown in  FIG. 8 , the weld  22  in this embodiment extends over a portion of the bottom reinforcing member  16  and along a portion of the bottom edge. Referring now to  FIG. 9 , yet another embodiment of the seal between the microwavable transparent material  18  and the bottom reinforcing member  16  is shown herein and wherein the weld  22  extends downwardly along the bottom reinforcing member  16  in a slightly different configuration. 
   Referring now to  FIGS. 10–11 , two alternative embodiments of the present invention are provided, wherein a double seam is not utilized to interconnect the microwavable transparent material  14  to a lower portion of the container sidewall  12 . Further, in both of the embodiments depicted in  FIG. 10  and  FIG. 11  the microwavable container  2  rests completely on the microwavable transparent material  14 , and there is no requirement for a bottom reinforcing material  16 . Rather, the lower portion of the container sidewall  12  is merely welded  22  directly to the microwavable transparent material  14  to create an airtight seal, thus eliminating entirely the requirement for the reinforcing material  156  and the step of double seaming these materials together. Further, based on the inherent rigidity of the metallic sidewall  12  and microwavable transparent material  18 , there is no need of the bottom reinforcing member  16 , and thus a significant cost savings. 
   Although each of the geometric configurations provided in  FIGS. 7–11  have proven to be effective, numerous other variations may be provided as appreciated by one skilled in the art and which may be dictated by preferred geometric shapes, material costs, and/or manufacturing concerns. 
   Referring now to  FIGS. 10–14 , bar graphs are provided herein which summarize test data taken during development to compare the heating efficiency oft he hybrid microwavable container  2  of the present invention with respect to a typical plastic or foam microwavable bowl, and more specifically a container comprised of a polypropylene EVOH thermo formed barrier sheet material. As depicted in the graphs, each of the containers were filled with a beef with country vegetable soup, and heated over a period of time up to 150 seconds at a power rating of 1100 watts. During this time period, the temperatures of the soup were taken at various positions within the containers, and the data collected and provided herein. More specifically,  FIG. 10  depicts the average temperature comparison oft he soup within the hybrid microwavable container  2  and the plastic bowl, while  FIG. 11  represents the middle top temperature of the soup in the containers.  FIG. 12  represents the middle bottom temperature, while  FIG. 13  represents the top side temperature, while the bottom side temperature is depicted in  FIG. 14 . A line graph further depicting the comparisons between the heating in the microwavable container  2  and a typical plastic container is further shown in  FIG. 15 , which shows the various temperature over time in different portions of the container. 
   As supported by the data shown in  FIGS. 10–15 , the metal microwavable container  2  of the present invention is shown to have superior heating characteristics for the middle portions of the container, which is advantageous compared to typical plastic and foam microwavable containers which typically overheat the contents near the sidewall and lower portions of the container, thus causing burning of the foodstuffs contained therein, as well as potential deformation of the plastic container and an alteration in taste. 
   With regard to the test data used to plot  FIGS. 10–15 , Table 1 is provided herein, and which identifies the temperatures taken at various locations within the containers, and comparing both a conventional microwavable plastic bowl and the hybrid metallic microwavable bowl of the present invention. For example, after 60 seconds the middle bottom of the hybrid bowl has a temperature of 173° F., while a conventional plastic/foam bowl comprised of a polypropylene EVOH thermo formed barrier material has a temperature of only 107° F. Furthermore, the top side of the conventional bowl has a temperature of 163° F., as compared to the hybrid bowl of the present invention, which has a temperature of 83° F. Similar readings may be found at times of 90 seconds and 150 seconds, which clearly show the advantage of the hybrid bowl which heats from the “inside out” as opposed to the “outside-in”, and thus substantially reducing the likelihood of inconsistent heating and deformation of the container along the sidewalls. 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
                 
                 
               Plastic 
               Hybrid 
             
             
                 
                 
                 
               Bowl 
               Bowl 
             
             
                 
                 
                 
               Power = 
               Power = 
             
             
                 
                 
               Time (Sec) 
               1100 watts 
               1100 watts 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               Top Side 
               60 
               134 
               73 
             
             
                 
                 
               60 
               137 
               94 
             
             
                 
                 
               60 
               124 
               74 
             
             
                 
                 
               60 
               123 
               75 
             
             
                 
               Average 
               60 
               129.5 
               79.0 
             
             
                 
               Bottom Side 
               60 
               181 
               112 
             
             
                 
                 
               60 
               173 
               118 
             
             
                 
                 
               60 
               157 
               100 
             
             
                 
                 
               60 
               171 
               123 
             
             
                 
               Average 
               60 
               170.5 
               113.25 
             
             
                 
               Middle Top 
               60 
               76 
               101 
             
             
                 
               Middle Btm 
               60 
               107 
               173 
             
             
                 
               Top Side 
               90 
               163 
               83 
             
             
                 
                 
               90 
               147 
               86 
             
             
                 
                 
               90 
               141 
               91 
             
             
                 
                 
               90 
               146 
               103.0 
             
             
                 
               Average 
               90 
               149.3 
               90.8 
             
             
                 
               Bottom Side 
               90 
               186 
               117 
             
             
                 
                 
               90 
               162 
               93 
             
             
                 
                 
               90 
               172 
               101 
             
             
                 
                 
               90 
               168 
               120 
             
             
                 
               Average 
               90 
               172.0 
               107.8 
             
             
                 
               Middle Top 
               90 
               84 
               134 
             
             
                 
               Middle Btm 
               90 
               121 
               189 
             
             
                 
               Top Side 
               120 
               161 
               113 
             
             
                 
                 
               120 
               178 
               102 
             
             
                 
                 
               120 
               165 
               98 
             
             
                 
                 
               120 
               173 
               103 
             
             
                 
               Average 
               120 
               169.3 
               104.0 
             
             
                 
               Bottom Side 
               120 
               200 
               137 
             
             
                 
                 
               120 
               197 
               103 
             
             
                 
                 
               120 
               159 
               115 
             
             
                 
                 
               120 
               193 
               125 
             
             
                 
               Average 
               120 
               187.3 
               120.0 
             
             
                 
               Middle Top 
               120 
               103 
               151 
             
             
                 
               Middle Btm 
               120 
               123 
               191 
             
             
                 
               Top Side 
               150 
               195 
               112 
             
             
                 
                 
               150 
               198 
               120 
             
             
                 
                 
               150 
               177 
               108 
             
             
                 
                 
               150 
               183 
               103 
             
             
                 
               Average 
               150 
               188.3 
               110.8 
             
             
                 
               Bottom Side 
               150 
               194 
               136 
             
             
                 
                 
               150 
               198 
               146 
             
             
                 
                 
               150 
               181 
               130 
             
             
                 
                 
               150 
               180 
               120 
             
             
                 
               Average 
               150 
               188.3 
               133.0 
             
             
                 
               Middle Top 
               150 
               151 
               161 
             
             
                 
               Middle Btm 
               150 
               124 
               200 
             
             
                 
                 
             
           
        
       
     
   
   For clarity, the following is a list of components and the associated numbering used in the drawings: 
   
     
       
             
             
           
             
             
           
         
             
                 
             
             
               # 
               Components 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               2 
               Microwavable container 
             
             
               4 
               Metal lid 
             
             
               6 
               Removable plastic lid 
             
             
               8 
               Metallic sidewall 
             
             
               10 
               Metallic sidewall upper portion 
             
             
               12 
               Metallic sidewall lower portion 
             
             
               14 
               Microwavable transparent bottom portion 
             
             
               16 
               Bottom reinforcing member 
             
             
               18 
               Peripheral edge of microwavable transparent material 
             
             
               20 
               Sealant material 
             
             
               22 
               Weld 
             
             
               24 
               Insulative material 
             
             
               26 
               Pull tab 
             
             
               28 
               Venting apertures 
             
             
               30 
               Double seam 
             
             
                 
             
           
        
       
     
   
   While an effort has been made to describe various alternatives to the preferred embodiment, other alternatives will readily come to mind to those skilled in the art. Therefore, it should be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. Present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not intended to be limited to the details given herein.