Abstract:
A foldable or collapsible ovenware container that maintains a rigid shape while in use and can be folded into a smaller size for storage. The ovenware container includes rigid top and bottom portions separated by a flexible middle portion. The flexible middle portion includes thick and thin wall sections. Pressure applied to the top portion causes the flexible middle portion to collapse in an orderly manner toward the bottom portion, with the middle portion folding at each of the thin wall sections to create a plurality of folds or pleats in the middle portion in the collapsed configuration.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to ovenware containers and particularly to an ovenware container that includes an elastomeric portion that enables the container to be folded or collapsed when not in use to enable easy and more efficient storage. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional ovenware containers are usually of rigid structure and are typically constructed of metal, ceramics, or glass such as Pyrex®. Most kitchens, commercial and residential, typically stock a large range of types and sizes of ovenware containers in order to be prepared for the myriad cooking tasks that are encountered. 
         [0003]    Conventional ovenware containers, as a result of their rigid construction, typically occupy a significant amount of space in the kitchen. All kitchens, especially residential kitchens that are typically limited in space, would benefit from ovenware containers that occupy less space when not in use. 
         [0004]    Recently, non-rigid or soft ovenware containers have been introduced. The prior art soft ovenware containers are typically constructed of soft silicone rubber and are so soft, typically having a Shore A hardness of approximately 40, that they can be flexed or bent out of shape. Although soft ovenware containers can be flexed or bent into a smaller size to conserve space, they have the disadvantage that they must be supported by a rigid pan or similar object for stability when lifted or transported from one area to another. Soft silicone is not practical for large ovenware containers having deep sides or including a large volume as the soft sides lack rigidity and, when filled with a liquid or semi-liquid food such as cake batter, can buckle or have the sides deflect and cause spillage of the contents. 
         [0005]    What is needed therefore is ovenware container that maintains a rigid shape when in use, without the use of a supporting pan, and can be folded to a smaller size to conserve space during storage. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the present invention, there is provided a collapsible ovenware container which maintains a rigid shape while in use and which can be folded into a smaller size for storage. The ovenware container includes rigid top and bottom portions separated by a flexible middle portion. The flexible middle portion includes thick and thin wall sections. Pressure applied to the top portion causes the flexible middle portion to collapse in an orderly manner toward the bottom portion, with the middle portion folding at each of the thin wall sections to create a plurality of folds or pleats in the middle portion in the collapsed configuration. 
       OBJECTS AND ADVANTAGES 
       [0007]    Several advantages are achieved with the ovenware container of the present invention, including:
       (1) The foldable ovenware container of the present invention has the advantage that it can be folded into a compact shape for storage. This greatly reduces the need for storage space for the ovenware container when it is not in use.   (2) The foldable ovenware container of the present invention maintains its shape when placed in its unfolded state. This is a big advantage over prior art soft ovenware containers.   (3) In its unfolded state, the ovenware container of the present invention is capable of supporting unstable foods such as liquids or batters without collapse caused by errant bumping or jostling by a handler.   (4) Unlike soft ovenware containers, the foldable ovenware container of the present invention does not need to be supported by a separate pan or other rigid object when being moved from one location to another.   (5) The foldable ovenware container of the present invention can be used in high temperature environments such as conventional ovens.   (6) An ovenware container constructed entirely of silicone rubber according to the present invention can be used in microwave ovens.       
 
         [0014]    These and other objects and advantages of the present invention will be better understood by reading the following description along with reference to the drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a side view of an ovenware container according to the present invention. 
           [0016]      FIG. 2  is a sectional view of the ovenware container taken along line  2 - 2  of  FIG. 1 . 
           [0017]      FIG. 3  is a side view of the ovenware container of  FIG. 1  in a collapsed or folded state. 
           [0018]      FIG. 4  is a sectional view of the ovenware container taken along line  4 - 4  of  FIG. 3 . 
           [0019]      FIG. 5  is a sectional view of a second embodiment of the ovenware container of the present invention. 
           [0020]      FIG. 6  is a sectional view of a third embodiment of the ovenware container of the present invention. 
           [0021]      FIG. 7  is a sectional view of a fourth embodiment of the ovenware container of the present invention. 
           [0022]      FIG. 8  is a bottom view of the ovenware container depicted in  FIG. 1 . 
       
    
    
     TABLE OF NOMENCLATURE 
       [0023]    The following is a listing of part numbers used in the drawings along with a brief description: 
         [0000]    
       
         
               
               
             
           
               
                   
               
               
                 Part Number 
                 Description 
               
               
                   
               
             
             
               
                 20 
                 ovenware container 
               
               
                 22 
                 bottom portion 
               
               
                 24 
                 middle portion 
               
               
                 26 
                 top portion 
               
               
                 28 
                 thin wall section 
               
               
                 30 
                 thick wall section 
               
               
                 32 
                 top edge 
               
               
                 34 
                 bottom edge 
               
               
                 36 
                 handle 
               
               
                 37 
                 bottom of container 
               
               
                 38 
                 extension 
               
               
                 39 
                 pleat or fold 
               
               
                 40 
                 ovenware container, second embodiment 
               
               
                 50 
                 ovenware container, third embodiment 
               
               
                 60 
                 ovenware container, fourth embodiment 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION 
       [0024]    With reference to a first and preferred embodiment in  FIG. 1 , the present invention is an ovenware container  20  and a method of producing the ovenware container. The ovenware container includes a bottom portion  22 , a middle portion  24  extending from the bottom portion  22 , and a top portion  26  extending from the middle portion  24 . 
         [0025]    Referring to the cross-sectional view in  FIG. 2 , the middle portion  24  of the ovenware container  20  includes one or more thin wall sections  28  separated by thick wall sections  30 . The thin wall sections  28  are planar and arranged parallel with the bottom edge  34  of the container  20 . The thin wall sections  28  render the container foldable, with the container  20  capable of folding at each of the thin wall sections  28 . The container  20  further includes a top edge  32 , a bottom edge  34 , and a handle  36  extending from the top portion  26 . The container  20  can further include extensions  38  extending from the bottom edge  34 . As shown in  FIG. 8 , the extensions  38  extend from the bottom  37  of the ovenware container  20  and provide a set-off for elevating the bottom  37  of the container away from any surface it is placed upon. The extensions  38 , being out of direct contact with the bottom  37  of the container  40 , provide a cooler lower contact surface when placing the container on a surface. 
         [0026]    As shown in  FIGS. 3 and 4 , in which the ovenware container  20  is shown in a folded configuration, the vertical profile of the container  20  can be reduced dramatically for storage purposes, allowing several ovenware containers to be stacked on top of one another (not shown) and thereby reducing the amount of space required for storage. As shown in  FIG. 4 , the container  20  has folded at each of the thin wall sections  28 . As pressure is applied to the top edge  32  of the container  20  the container folds in sequence at each of the thin wall sections  28  until it is folded at all of the thin wall sections  28 . In the folded configuration, the thin wall sections  28  and thick wall sections  30  form pleats  39  or folds in the flexible middle portion  24  of the ovenware container  20 . 
         [0027]    With reference to  FIG. 1 , in addition to the thin wall sections  28 , to enable the folding ability and the self supporting characteristics of the ovenware container  20  the container includes a middle portion  24  that is flexible and slightly softer than the bottom portion  22  or top portion  26 . Preferably the middle portion  24  is constructed with a hardness of between 70 and 85 Shore A hardness and the bottom portion  22  and top portion  26  are constructed with a hardness of greater than 85 Shore A. The middle portion  24  is constructed of a flexible, resilient material, such as silicone rubber, and therefore the container can withstand many repeated folding cycles without any cracking at the thin wall sections  28 . Having the top  26  and bottom  22  portions harder than 85 Shore A enables the top portion  26 , when pressed on the top edge  32 , to maintain its rigidity and thereby allows the middle portion  24  to fold evenly and in a controlled fashion toward the bottom portion  22 . The hard top  26  and bottom  22  portions further promote easier handling of the foldable ovenware container  20 , as the top  26  and bottom  22  do not buckle or flex when grasped. This is a significant advantage over prior art soft ovenware containers, which typically have thin walls and a hardness rating in the range of 40 Shore A, making them very susceptible to buckling and leading to spillage of the contents of the prior art soft ovenware containers. Furthermore, the hard top  26  and bottom  22  portions enable the ovenware container of the present invention to be a stand-alone container. The ovenware container  20  of the present invention is therefore capable of accepting and being carried with any kind of food, including liquids such as soups, without being supported by an external pan or other support. Prior art soft ovenware containers, in contrast, must be supported by a pan or other support device in order to lessen the chance of spillage caused by buckling of the sides, which is very possible with ovenware containers having a hardness rating of about 40 Shore A. The ovenware container  20  of  FIG. 1 , being constructed entirely of silicon rubber, can be used in both conventional and microwave ovens as microwave radiation is not absorbed by the silicon rubber. 
         [0028]    In the preferred embodiment shown in  FIG. 1 , the ovenware container  20  is preferably constructed of an elastomeric polymer such as food grade silicone rubber. The top portion  26  and bottom portion  22  are preferably each formed in a separate mold by compression molding. The molds are each filled with an uncured silicone rubber composition and are cured to obtain a Shore A hardness of greater than 85 in the resultant cured top  26  and bottom  22  portions. The top  26  and bottom  22  portions are then placed in a third mold for forming the final ovenware container  20 . The bottom portion  22  is placed in the bottom of the mold, an uncured silicone rubber composition is inserted on top of the bottom portion  22 , and the top portion  26  is placed in the top of the mold. The uncured silicone rubber composition introduced to the third mold contains a measured quantity of hardness agent to obtain a Shore A hardness of between 70 and 85 in what will become the middle portion  24  of the ovenware container. The mold includes sufficient uncured silicone rubber to ensure intimate contact of the uncured silicone rubber with the entire periphery of both the bottom  22  and top  26  portions. The curing cycle preferably includes between 5 and 13 minutes of curing time at between 120 and 180 kg force per cm 2  and at a cure temperature of between 140 and 200 degrees Celsius. The parameters of the curing cycle are varied according to the size of container, the grade of uncured silicone rubber introduced to the mold, the thickness of the container, the amounts and types of additives within the uncured silicone rubber composition, and various other factors. After the curing cycle, the ovenware container includes a bottom portion  22  of cured silicone rubber having a Shore A hardness of greater than 85, a middle portion  24  of cured silicone rubber having a Shore A hardness of between 70 and 85, and a top portion  26  having a Shore A hardness of greater than 85. After being cured, the top  26  and bottom  22  portions of the ovenware container  20  are securely bonded to the middle portion to form the integral ovenware container  20  and the ovenware container is oven safe to 530 degrees F. 
         [0029]    The top  26  and bottom  22  portions of the ovenware container  20  shown in  FIG. 1  can also be formed from a ceramic and silicone rubber mixture. Ceramic powders can be mixed with the uncured silicone rubber to further raise the hardness of the top  26  and bottom  22  portions. Aluminum oxide is one example of a ceramic powder that can be added to the uncured silicone rubber to increase the Shore A hardness rating of the cured silicone rubber and ceramic mixture. 
         [0030]    A second embodiment of the ovenware container  40 , shown in  FIG. 5 , includes a bottom portion  22  that is constructed of aluminum. A third embodiment of the ovenware container  50 , shown in  FIG. 6 , has both the bottom portion  22  and top portion  26  constructed of aluminum. As these two embodiments illustrate, the top  26  and bottom  22  portions of the ovenware container can be constructed of other appropriate materials that include the desired Shore hardness of greater than 85. The top portion  26  and the bottom portion  22  therefore can be constructed of metal. Preferably the bottom portion  22  is a metal with a high heat transfer coefficient. A list of preferred metals for the bottom  22  and top portions includes copper, aluminum, and steel. Alternatively, the top  26  and bottom portions can be constructed of ceramic, tempered glass, or borosilicate glass. All of these materials can be bonded securely to the silicone rubber middle portion  24  with an appropriate cycle time, temperature, and pressure in the compression molding procedure described above. The top  26  and bottom  22  portions, whether constructed of metal, ceramic, or glass, are introduced to the mold as described above and uncured silicone rubber composition is introduced to form the middle portion. After the pressure, temperature, and time of the curing cycle are applied in the compression molding operation, the cured silicone rubber middle portion  24  is integrally bonded with the separate top  26  and bottom  22  portions. 
         [0031]    With reference to  FIG. 7 , a fourth embodiment of the ovenware container  60  is shown in which the top  26  and bottom  22  portions are constructed of different products to provide different desired properties at the top versus the bottom of the ovenware container. The top portion  26  is constructed of tempered or borosilicate glass, which has good insulating properties. After it has been removed from the oven, a user can grasp the top portion  26  of the ovenware container  60  with less risk of heat transfer to their fingers. The bottom portion  22  of the ovenware container  60  is constructed of aluminum, which promotes good heat transfer from the oven or stovetop to the contents of the container during cooking. 
         [0032]    Another possible construction for the container of the present invention would include a top and bottom portion constructed of ceramic or tempered or borosilicate glass and a middle portion constructed of silicon rubber. Ovenware containers constructed in this manner would be appropriate for use in both conventional ovens and microwave ovens. 
         [0033]    The present invention includes a method of forming a container including bonding together in a molding operation, including compression molding or injection s molding, a bottom, middle, and top portion. The bottom portion and top portion are each constructed of cured silicone rubber, metal, ceramic, tempered glass, or borosilicate glass. A mold is provided having a cavity for accepting the bottom portion, the top portion, and an uncured silicone rubber composition between the bottom and top portions. The method includes loading the mold with the bottom container portion, the uncured silicone rubber composition, and the top container portion. The uncured rubber composition within the mold is in intimate contact with the bottom container portion and with the top container portion. Heat and pressure are applied to the mold for a length of time to cure the uncured silicone rubber composition and form a container that includes a cured middle container portion bonded to the top and bottom container portions. The container is then removed from the mold and the resultant product includes a container in which the top and bottom container portions are integrally bonded to the middle container portion. 
         [0034]    As should be obvious to a person skilled in the art, several variations can be made in the ovenware container without departing from the scope of the invention. It would be within the scope, for example, to construct the ovenware container of the present invention without a handle rather than with a handle as was shown in the several embodiments shown herein. It would also be within the scope of the present invention to construct ovenware containers according to the present invention with different container widths, heights, and shapes. Depending on the grades of uncured silicone rubber, and the additives to the silicone rubber composition, it would be within the scope of the present invention to vary the level of heat, the pressure, and the cycle time of the curing cycle during the compression molding procedure. It would also be within the scope of the present invention to construct the ovenware container in an injection molding procedure. 
         [0035]    As the invention has been described, it will be apparent to those skilled in the art that the same may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be included within the scope of the appended claims.