Patent Publication Number: US-2006000076-A1

Title: Method of using a container assembly

Description:
RELATED APPLICATION  
      This application claims benefit of U.S. Provisional Application Ser. No. 60/581,403 entitled “Method of Using A Container Assembly”, filed on Jun. 21, 2004; this application is a continuation-in-part of application Ser. No. 10/840,974 entitled “Containers and Container Assemblies With Releasable Locking Feature” filed on May 7, 2004, which is a continuation of application Ser. No. 10/277,303 entitled “Containers and Container Assemblies With Releasable Locking Feature” filed on Oct. 22, 2002 that issued as U.S. Pat. No. 6,886,704. 
    
    
     FIELD OF INVENTION  
      The present invention relates generally to methods of using a container assembly. More particularly, the present invention relates to methods of using a releasably lockable container assembly.  
     BACKGROUND OF THE INVENTION  
      The use of inexpensive polymeric, paper or metal packaging containers has become popular, especially for preparing and serving various food products. Polymeric, paper and metal containers generally have been used for heating the food product(s) disposed therein. These containers typically comprise a cover or lid and a base.  
      It would be desirable to have a method of using a container assembly that would be easy for the customer to close and open. This is especially important for users who may have difficulty in closing and opening a container assembly. It would also be desirable to provide a container assembly that is releasably lockable and prevents or inhibits material, such as liquid, from leaving the container assembly.  
     SUMMARY OF THE INVENTION  
      According to one method of using a container assembly, a first container and a second container are provided. The first container includes a first continuous body portion and a first rim. The first rim encompasses and projects laterally outwardly from the first body portion. The rim has a first plurality of ribs projecting generally upwardly therefrom such that first spaces are formed between adjacent ribs. The second container includes a second continuous body portion and a second rim. The second rim encompasses and projects laterally outwardly from the second body portion. The rim has a second plurality of ribs projecting generally upwardly therefrom such that second spaces are formed between adjacent ribs. The first container is shaped substantially the same as the second container. It is contemplated that the first and second container may be shaped differently, but the first and second rims are shaped substantially the same.  
      The first plurality of upwardly-projecting ribs is fitted into respective second spaces and the second plurality of upwardly-projecting ribs is fitted into respective first spaces such that the first container and the second container are releasably lockable to each other. The container assembly is disassembled by exerting downward pressure on either the first or second continuous body portion that results in separation of the first and second rims. Such a process enables easy disassembly of the container. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a container to be used in one embodiment of the invention;  
       FIG. 2  is a top view of the container of  FIG. 1 ;  
       FIG. 3  is an enlarged cross-sectional view taken generally along lines  FIG. 3 - FIG. 3  in  FIG. 2 ;  
       FIG. 4  is an enlarged top view of generally circular region  FIG. 4  of  FIG. 2 ;  
       FIG. 5 . is a perspective view of generally circular region  FIG. 5  of  FIG. 2  depicting two adjacent projecting ribs;  
       FIG. 6  is a sectional view of generally circular region  FIG. 6  of  FIG. 1  according to one embodiment.  
       FIG. 7   a  is a side view of a container assembly in a releasably lockable position using the container of  FIG. 1  and a second identical container of  FIG. 1  according to one embodiment of the present invention;  
       FIG. 7   b  is a top view of the container assembly of  FIG. 7   a;    
       FIG. 8  is an enlarged cross-sectional view taken generally along lines  FIG. 8 - FIG. 8  in  FIG. 7   b;    
       FIG. 9  is a side view of a container to be used in another embodiment of the invention;  
       FIG. 10  is a top view of the container of  FIG. 9 ;  
       FIG. 11  is an enlarged top view of generally circular region  FIG. 11  of  FIG. 10 ;  
       FIG. 12  is a perspective view of generally circular region  FIG. 11  of  FIG. 10  depicting two adjacent projecting ribs;  
       FIG. 13  is an enlarged cross-sectional view taken generally along lines  FIG. 13 - FIG. 13  in  FIG. 12 ;  
       FIG. 14   a  is a side view of a container assembly in a releasably lockable position using the container of  FIG. 9  and a second identical container of  FIG. 9  according to another embodiment of the present invention;  
       FIG. 14   b  is a top view of the container assembly of  FIG. 14   a;    
       FIG. 15  is an enlarged cross-sectional view taken generally along lines  FIG. 15 - FIG. 15  in  FIG. 14   b;    
       FIG. 16   a  is a top view of yet another container to be used in the present invention; and  
       FIG. 16   b  is an enlarged cross-sectional view taken generally along lines  FIG. 16   b - FIG. 16   b  in  FIG. 16   a.   
    
    
      While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawing and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
      Referring to  FIGS. 1-5 , a container (e.g., plate  10 ) to be used in one embodiment of the present invention is shown. The plate  10  is used with a second plate  110  (see  FIGS. 7 and 8 ) that may be substantially the same or, alternatively, identical to the plate  10  to form a container assembly that is releasably lockable.  
      It is contemplated that other container assemblies may be formed besides those using plates. For example, container assemblies may be formed, but are not limited to, using plates, bowls, platters, tubs, single-serve and family-size containers, single-serve and family-size ovenware, and combinations thereof. One such combination is a bowl and a plate that forms a container assembly. The remainder of the application will discuss container and container assemblies with respect to plates although it is recognized by one of ordinary skill in the art that other container assemblies, such as those discussed above, may be formed.  
      The height and shape of the container assembly may vary from that shown without departing from the scope of the invention. For example, the container assemblies of  FIGS. 7   a  and  14   a,  as will be discussed, are depicted as being generally circular. It is contemplated that the container assemblies and containers used herein may be other shapes such as rectangular, square, hexagonal, octagonal, other polygonal shapes, or oval.  
      The container assemblies of the present invention are typically used with respect to food, but may be used in other applications such as with medical applications, cosmetics or other items. Food container assemblies may be used for serving, storing, preparing and/or re-heating the food.  
      Referring back to  FIGS. 1-2 , the container  10  includes a continuous body portion  12  and a continuous rim  14  encompassing and projecting laterally outwardly from the body portion  12 . The body portion  12  includes a bottom  16  and a continuous sidewall  18  encompassing and projecting upwardly and outwardly from the bottom  16 . It is contemplated that the sidewall may project only upwardly from the bottom  16  or even project upwardly and inwardly from the bottom  16 . It is also contemplated that the rim may not be continuous, although it is preferred to be continuous.  
      Referring specifically to  FIG. 2 , the continuous rim  14  includes a plurality of ribs  20  that project generally upwardly therefrom. The plurality of ribs  20  is spaced around the general periphery of the container  10  and assists in forming a releasably lockable container assembly. The orientation of the plurality of ribs  20  creates a pattern that is generally normal to the direction of the rim  14 . More specifically, the orientation of the plurality of ribs  20  may create a pattern that is normal to the direction of the rim  14 . In a radial configuration with a pattern that is normal to the direction of the rim, each of the plurality of ribs  20 , if extended inwardly, would pass through the general center of the plate.  
      The plurality of ribs  20 , however, may be formed in different patterns than shown in  FIG. 2  with respect to the rim  14  (e.g., diagonally). It may be desirable to form the plurality of ribs  20  in a decorative pattern for aesthetic reasons. Such a decorative feature may assist in “hiding” or disguising the releasable lockable feature in the container  10 . The container  10  of  FIG. 2  has exactly 60 ribs formed in the continuous rim  14 . It is contemplated that the number of ribs may vary from that shown in  FIG. 2 . For example, a container may have from about 3 to about 10 ribs. A container may have greater than about 20 or about 40 ribs, and may even have up to or greater than about 120 ribs. The desired number of ribs formed on the container will often vary depending on factors such as the size or shape of the container assembly, the material(s) type and thicknesses of the container assembly, and the desired holding strength of the container assembly. The desired holding strength depends on factors such as the weight of item(s) placed in the container assembly and its perceived usage.  
      Turning to  FIGS. 3-5 , the plurality of ribs  20  is shown in greater detail. Specifically, a cross-sectional view of  FIG. 3  shows two adjacent ribs that project upwardly from the continuous rim  14 .  FIG. 3  depicts a first rib  20   a  and a second rib  20   b  with a space  22  being formed therebetween. The first rib  20   a  of  FIG. 3  comprises a generally flat surface  24  that bridges two sidewalls  26 ,  28 . The first rib  20   a  is shown as being generally perpendicular to the plane of the remainder of the continuous rim  14 . Specifically, the first rib  20   a  is shown as being generally perpendicular to plane CC formed along the remainder of the rim  14  in  FIG. 3 . More specifically, the rib may be perpendicular to the plane of the remainder of the rim. The sidewalls  26 ,  28  are spaced apart from each other and are shown as being generally perpendicular to the plane CC of the remainder of the rim  14 . The sidewalls  26 ,  28 , however, do not necessarily have to be generally perpendicular or perpendicular to the remainder of the rim  14 .  
      Similarly, second rib  20   b  of  FIG. 3  comprises a generally flat surface  30  that bridges two sidewalls  32 ,  34 . The second rib  20   b  is also shown as being generally perpendicular to the plane CC of the remainder of the rim  14 . The sidewalls  32 ,  34  are spaced apart from each other and are shown as being generally perpendicular to the plane CC of the remainder of the rim  14 .  
      To provide an improved locked container assembly, at least one of the rib sidewalls may have an undercut. Such an optional undercut formed in the rib sidewall engages a similar undercut in a corresponding space formed between adjacent ribs of a second container when the container assembly is formed. This is discussed below in further detail with respect to  FIGS. 7-8 . For example, in  FIG. 3 , optional undercuts  26   a,    28   a  are formed in respective sidewalls  26 ,  28 . The size and shape of the undercut will often vary depending on factors such as the size or shape of the container assembly, the material(s) type and thicknesses of the container assembly, and the desired holding strength of the container assembly. The desired holding strength may depend on factors such as the weight of item(s) placed in the container assembly and its perceived usage.  
      The number of undercuts formed in the rib sidewalls, if any, depends on factors such as the desired leak-resistant, the type of closure mechanism, manufacturability of the container assemblies, and the material(s) type and thicknesses used in forming the container assemblies. For example, if the container assemblies are made of a first material that has a higher coefficient of friction than a second material, then the container made of the first material will likely need less undercuts in its sidewalls than the same container made with the second material to have the same holding strength. The number of undercuts used also depends on the fitness of use of the container assembly, including the holding strength thereof.  
      It is contemplated that the ribs may have sidewalls with no undercuts or at least one undercut (e.g., first rib  20   a  with optional undercuts  26   a,    28   a  in  FIG. 3 ). It is also contemplated that some ribs within the same container may have no undercuts, while other ribs may have one or more undercuts.  
      Referring to  FIGS. 4 and 5 , adjacent ribs  36 ,  38  of a portion of the rim  14  are shown in more detail. In  FIG. 4 , a top view of the ribs  36 ,  38  shows that the ribs  36 ,  38  generally taper inwardly toward the center of the container.  FIG. 4  also shows a generally flat area  36   a  of rib  36  and a generally flat area  38   a  of rib  38 . To improve the sealability of the container assembly, the generally flat areas  36   a,    38   a  may contact similar sized flat areas formed in the respective spaces between adjacent ribs of a second container that form the container assembly. An example of a similar sized flat area formed in a space between adjacent ribs is shown in  FIG. 4  with generally flat area  40 .  
       FIG. 5  shows adjacent ribs  42 ,  44  with respective generally flat areas  42   a,    44   a.  The ribs  42 ,  44  are spaced apart with a generally flat area  46  that is formed between generally flat areas  42   a,    44   a.  To maintain clearances on radial designs (e.g., oval or circular shaped), the generally flat areas may grow proportionally with the diameter (i.e., increase in size as the distance increases from the center of the container). For example, in  FIG. 5 , the width W 1  of generally flat area  42   a  may be smaller than width W 2 . With, for example, rectangular-shaped containers, the size of the generally flat areas typically remains constant as the distance increases from the center of the container. It is contemplated that this area of the ribs may be sized and shaped differently than shown in  FIGS. 4 and 5 .  
      It is contemplated that the shape and size of the plurality of ribs  20  may vary from that shown in  FIGS. 2-5 . It is preferred that the plurality of ribs be shaped and sized to minimize the stacking height of the containers used to form container assemblies. It is desirable to minimize the stacking height of the containers to (a) reduce transportation costs and packaging, and (b) provide space efficiency in retail and consumer settings. It is also desirable to maximize the holding strength of the container assembly. The desired holding strength is often a balance between making the container assembly easy for a consumer to open and close, while still preventing or inhibiting an inadvertent opening of the container assembly.  
      It is contemplated that the upwardly projecting features may be shaped differently than the ribs shown in  FIGS. 2-5  and  11 - 13 . For example, the upwardly projecting features may be a plurality of round, oval, square, or polygonal features. It is contemplated that many shapes and sizes may be formed by the upwardly projecting features used in the present invention.  
      Referring to  FIGS. 5 and 6 , an optional seal feature  50  formed on the rim  14  is depicted. In  FIG. 6 , the optional seal feature  50  is located outwardly from the rib  52  with respect to the center of the container  10 . In other words, the optional seal feature  50  is located farther away from the center of the container  10  than the rib  52 . The optional seal feature  50  in conjunction with a corresponding optional seal feature on another container (not shown), along with the locked ribs of the container assembly, assist in preventing or inhibiting material from leaving or entering the container assembly. The optional seal feature is especially useful in preventing or inhibiting product leakage that may occur due to tolerances within the manufacturing process. To provide an efficient seal, the height H 1  of the optional seal feature  50  should be at least one-half of the rib height H 2 .  
      The optional seal feature, however, may be located inwardly from the ribs such that the seal is formed nearer the center of the container assembly as compared to the releasably lockable ribs. For example, in  FIGS. 16   a  and  16   b,  a container  510  includes a plurality of ribs  520  and also includes an optional seal feature  550 . In  FIGS. 6 and 16   b,  the optional seal feature  550  is located inwardly from the plurality of ribs  520  with respect to the center of the container  510 . The optional seal feature  550  in conjunction with a corresponding seal feature on another container (not shown), along with the locked ribs of the container assembly, assist in preventing or inhibiting material from leaving or entering the container assembly. The optional seal feature may be formed in a variety of shapes, including a general conical shape.  
      A container assembly  100  according to one embodiment of the present invention is depicted in  FIGS. 7   a,    7   b.  The container  100  comprises the first container  10  and a second container  110 . In one embodiment, the second container  110  is shaped substantially the same as the first container  10 . Alternatively, the second container  110  may be identical to the first container  10 . It may be desirable to have containers identically shaped to reduce waste by a consumer when the top container or lid is not used. As discussed above, the container assembly may be formed with different first and second containers than plates.  
      The container assembly  100  of  FIGS. 7   a,    7   b  may be formed according to one method by providing the first container  10  and the second container  110 . The second container  110  includes a continuous body portion  112  and a continuous rim  114  that encompasses and projects laterally outwardly from the body portion  112 . Similarly, the first container  10 , as discussed above, includes the continuous body portion  12  and the continuous rim  14  that encompasses and projects laterally outwardly from the body portion  12 . Both of the rims  14 ,  114  include a respective plurality of ribs with spaces therebetween (not shown in  FIGS. 7   a,    7   b ). Each of the plurality of ribs may be shaped and sized similarly to the ribs  20  shown above in  FIGS. 2-5 . Each of the plurality of ribs projects generally upwardly therefrom (i.e., in a direction away from the continuous body portion).  
      The second container  110  is flipped 180 degrees relative to the first container  10  such that the containers  10 ,  110  are generally aligned and the rims  14 ,  114  are adjacent to each other. This flipped position of container  110  relative to the container  10  is shown in  FIG. 7   a.  To fit the ribs into respective spaces, the container  110  may have to be rotated slightly such that the ribs are offset (i.e., the ribs and spaces are aligned). It is desirable that the consumer can assembly the containers so as to form a container assembly of the present invention.  
      Referring to  FIG. 8 , adjacent ribs  120   a,    120   b  of the container  110  are fit into respective second spaces  22   a,    22   b  of the container  10  and ribs  20   a,    20   b  of the container  10  are fit into respective spaces  122   a,    122   b  such that the container assembly  100  is releasably lockable. To fit the ribs into respective spaces, the container  110  may have to be rotated slightly such that the ribs are offset (i.e., the ribs and spaces are aligned).  FIG. 8  also depicts interference areas  124   a,    124   b  formed between the first rib  20   a  and the space  122   a  created between ribs  120   a,    120   b  of the container  110 .  
      The strength of this lockable closure is dependent on many variables such as the number of the projecting ribs, the height of those ribs, whether undercuts are included, the size of the contact areas, the clearance needed between spaces and ribs, and the material(s) type and thickness used in forming the container assemblies. To improve the lockability of the container assembly, as discussed above, an optional sealing feature may be added.  
      The lockable closure feature of formed container assembly  100  of  FIGS. 7   a,    7   b  may be opened, disassembling container assembly  100  into separate first and second containers  10 ,  110  according to one method by providing pressure on continuous body portion  112 . For example, exerting downward pressure on body portion  112  results in separation of the rims  14 ,  114 , thereby enabling the easy disassembly of container assembly  100  into containers  10 ,  110 . In a preferred embodiment, the downward pressure is applied in a substantially uniform manner across the surface area of body portion  112  that comprises the horizontal top of container assembly  100  as depicted in  FIG. 7   a.  Such pressure may be applied, for example, by the palm of a user&#39;s hand. However, as part of the ergonomic design of this embodiment, pressure may be applied by any suitable means, including for example by the user&#39;s forearm or elbow or by using any device that is capable of applying pressure to body portion  112 . In this manner, the ergonomic design of this embodiment enables release or opening of the lockable closure feature of the formed container assembly  100  in a manner that does not require use of one&#39;s hands and/or manual dexterity with one&#39;s hands or fingers.  
      The ease with which the lockable closure feature may be released or opened by using this pressure method depends upon several variables such as the degree of contour or arc of continuous body portion  112 , the design and geometry of rims  14 ,  114 , and the material(s) type and thickness used in forming the containers  10 ,  110 .  
      According to one method of using a container assembly, a first container and a second container are provided. The first container includes a first continuous body portion and a first rim. The first rim encompasses and projects laterally outwardly from the first body portion. The rim has a first plurality of ribs projecting generally upwardly therefrom such that first spaces are formed between adjacent ribs. The second container includes a second continuous body portion and a second rim. The second rim encompasses and projects laterally outwardly from the second body portion. The rim has a second plurality of ribs projecting generally upwardly therefrom such that second spaces are formed between adjacent ribs. The first container is shaped substantially the same as the second container. It is contemplated that the first and second container may be shaped differently, but the first and second rims are shaped substantially the same.  
      The first plurality of upwardly-projecting ribs is fitted into respective second spaces and the second plurality of upwardly-projecting ribs is fitted into respective first spaces such that the first container and the second container are releasably lockable to each other. The container assembly is disassembled by exerting downward pressure on either the first or second continuous body portion that results in separation of the first and second rims. Such a process enables easy disassembly of the container.  
      Referring to  FIGS. 9-10 , a container (e.g., plate  210 ) includes a continuous body portion  212  and a continuous rim  214  encompassing and projecting laterally outwardly from the body portion  212 . The body portion  212  includes a bottom  216  and a continuous sidewall  218  encompassing and projecting upwardly and outwardly from the bottom  216 . It is contemplated that the sidewall may project only upwardly from the bottom  216  or even project upwardly and inwardly from the bottom  216 . It is also contemplated that the rim may not be continuous, although it is preferred to be continuous.  
      Referring to  FIGS. 10 and 11 , the continuous rim  214  includes a plurality of rib sets  220  that project generally upwardly therefrom. The plurality of rib sets  220  is spaced around the general periphery of the container  210  and assists in forming a releasably lockable container assembly. The orientation of the plurality of rib sets  220  creates a pattern that is generally parallel or generally concentric with the general direction of the rim  214 . In other words, each of the plurality of rib sets  220 , if extended outwardly, would be no closer to the general center of the container  210 . The plurality of rib sets  220  is in the opposite direction of the plurality of ribs  20  in  FIGS. 2-5 .  
      The plurality of rib sets  220 , however, may be formed in different patterns than shown in  FIG. 10  with respect to the rim  214  (e.g., diagonally). It may be desirable to form the plurality of rib sets  220  in a decorative pattern for aesthetic reasons. Such a decorative feature may assist in “hiding” or disguising the releasable lockable feature in the container  210 .  
      The container  210  of  FIG. 10  has exactly 60 sets of ribs formed in the continuous rim  214 . As will be discussed in more detail below, each of the plurality of rib sets  220  has a first set of ribs on a raised portion and a second set of ribs on a recessed portion. It is contemplated that the number of rib sets may vary from that shown in  FIG. 10 . For example, a container may have from about 2 to about 30 sets of ribs. A container may have greater than about 40 or about 80 sets of ribs, and may even have up to or greater than about 120 sets of ribs. The desired number of ribs formed on the container will often vary depending on factors such as the size or shape of the container assembly, the material(s) type and thicknesses of the container assembly, and the desired holding strength of the container assembly. The desired holding strength may depend on factors such as the weight of item(s) placed in the container assembly and its perceived usage.  
      Turning to  FIGS. 11-13 , two adjacent sets of ribs are shown in greater detail. The number of ribs in a set varies in  FIGS. 11 and 12  depending on whether the ribs are located in a recessed area or a raised area formed in the rim  214 . For example, in  FIGS. 11 and 12 , recessed area  240  has a first rib  242  and a second rib  244  with spaces  246 ,  248  and  250 . Raised area  260  of  FIGS. 11 and 12 , however, has a first rib  262 , a second rib  264 , and a third rib  266  with spaces  268 ,  270  therebetween. Each of the ribs of  FIGS. 11 and 12  projects upwardly from the continuous rim  214 .  
      Referring specifically to  FIG. 13 , a cross-sectional view of the recessed area  240  is depicted and includes the ribs  242 ,  244 . A cross-sectional view of the raised area  260  (not shown) would depict three ribs. The first rib  242  of  FIG. 13  comprises a generally flat surface  288  that bridges two sidewalls  290 ,  292 . The first rib  242  is shown as being generally perpendicular to the plane of the remainder of the continuous rim  214 . Specifically, the first rib  242  is shown as being generally perpendicular to plane DD formed along the remainder of the rim  214  in  FIG. 13 . More specifically, the rib may be perpendicular to the plane of the remainder of the rim. The sidewalls  290 ,  292  are spaced apart from each other and are shown as being generally perpendicular to the plane DD of the remainder of the rim  214 . The sidewalls  290 ,  292 , however, do not necessarily have to be generally perpendicular or perpendicular to the remainder of the rim  214 .  
      Similarly, second rib  244  of  FIG. 13  comprises a generally flat surface  298  that bridges two sidewalls  300 ,  302 . The second rib  244  is also shown as being generally perpendicular to the plane DD of the remainder of the rim  214 . The sidewalls  300 ,  302  are spaced apart from each other and are shown as being generally perpendicular to the plane DD of the remainder of the rim  214 .  
      To provide an improved locked container assembly, at least one of the rib sidewalls may have an optional undercut. As discussed above, such an undercut formed in the rib sidewall engages a similar undercut in the spaces formed between adjacent ribs when the container assembly is formed. For example, in  FIG. 13 , optional undercuts  290   a,    292   a  are formed in respective sidewalls  290 ,  292 . The size and shape of the undercut will often vary depending on factors such as the size or shape of the container assembly, the material(s) type and thicknesses of the container assembly, and the desired holding strength of the container assembly. The desired holding strength may depend on factors such as the weight of item(s) placed in the container assembly and its perceived usage.  
      As discussed above, the number of undercuts formed in the rib sidewalls, if any, depends on several factors. It is contemplated that the ribs may have sidewalls with no undercuts or at least one undercut (e.g., first rib  242  with optional undercuts  290   a,    292   a  in  FIG. 13 ). It is also contemplated that some ribs within the same container may have no undercuts, while other ribs have one or more undercuts.  
      Referring back to  FIG. 12 , the raised and recessed areas  240 ,  260  have a plurality of ribs with generally flat areas. For example, the rib  242  includes a top surface or generally flat area  242   a.  Similarly, the rib  264  includes a top surface or generally flat area  264   a.  To improve the sealability of the container assembly, the generally flat areas  264   a,    242   a  may contact similar sized flat areas formed in the spaces formed between adjacent ribs of a second container that forms the container assembly. An example of a similar sized flat area formed in a space is depicted in  FIG. 12  with space  246 . As shown in  FIG. 12 , a generally flat area  282  is formed between adjacent sets of ribs (i.e., the raised and recessed portions) to assist in releasably locking the container assembly. It is contemplated that this area of the ribs may be sized and shaped differently than shown in  FIGS. 11-13 . It is contemplated that the numbers of ribs in a set of ribs may vary from that shown in  FIGS. 11 and 12  (two ribs in the recessed areas and three ribs in the raised areas)  
      It is contemplated that the shape and size of the plurality of ribs  220  may vary from that shown in  FIGS. 10-13 . It is preferred that the plurality of ribs be shaped and sized to minimize the stacking height of the containers. It is desirable to minimize the stacking height of the containers to (a) reduce transportation costs and packaging, and (b) provide space efficiency in retail and consumer settings. It is also desirable to maximize the holding strength of the container assembly. The desired holding strength is often a balance between making the container assembly easy for a consumer to open and close, while still preventing or inhibiting an inadvertent opening of the container assembly.  
      Referring specifically to  FIG. 12 , an optional seal feature  350  formed on the rim  214  is depicted. The optional seal feature  350  is located outwardly from the ribs  242 ,  244 ,  262 ,  264  and  266  with respect to the center of the container  210 . In other words, the optional seal feature  350  is located farther away from the center of the container  210  than the ribs. The optional seal feature  350  in conjunction with a corresponding seal feature on another container (e.g., optional seal feature  450  shown in  FIG. 15 ), along with the locked ribs of the container assembly, assist in preventing or inhibiting material from leaving or entering the container assembly. The optional seal feature is especially useful in preventing or inhibiting product leakage that may occur due to tolerances within the manufacturing process. To provide an efficient seal, the height of the optional seal feature should be at least one-half of the rib height. This is shown in  FIG. 15  where the optional seal features  350  and  450  contact each other.  
      As discussed above with respect to  FIGS. 16   a, b  above, the optional seal feature, however, may be located inwardly from the ribs such that the seal is formed nearer the center of the container assembly as compared to the releasably lockable ribs.  
      A container assembly  400  according to one embodiment of the present invention is depicted in  FIGS. 14   a,    14   b.  The container  400  comprises the first container  210  and a second container  410 . In one embodiment, the second container  410  is shaped substantially the same as the first container  210 . Alternatively, the second container  410  may be identical to the first container  210 . As discussed above, the container assembly may be formed with different first and second containers than plates. For example, the container assembly may be formed using a bowl and a plate.  
      The container assembly  400  of  FIGS. 14   a,    14   b  may be formed according to one method by providing the first container  210  and the second container  410 . The second container  410  includes a continuous body portion  412  and a continuous rim  414  that encompasses and projects laterally outwardly from the body portion  412 . Similarly, the first container  210 , as discussed above, includes the continuous body portion  212  and the continuous rim  214  that encompasses and projects laterally outwardly from the body portion  212 . Both of the rims  214 ,  414  include a respective plurality of ribs with spaces therebetween (not shown in  FIGS. 14   a,    14   b ). Each of the plurality of ribs may be shaped and sized similarly to the ribs  220  shown above in  FIGS. 10-13 . Each of the plurality of ribs projects generally upwardly therefrom (i.e., in a direction away from the continuous body portion).  
      As discussed above with container assembly  100 , the second container  410  is flipped 180 degrees relative to the first container  210  such that the containers  210 ,  410  are generally aligned and the rims  214 ,  414  are adjacent to each other. This flipped position of the container  410  relative to the container  210  is shown in  FIG. 14   a.    
      Referring to  FIG. 15 , adjacent ribs  262 ,  264 ,  266  of one set of the container  210  are fit into respective second spaces  422 ,  424 , and  426  of the container  410  and ribs  418 ,  420  of the container  410  are fit into respective spaces  268 ,  270  such that the container assembly  400  is releasably lockable.  
      The strength of this lockable closure is dependent on many variables such as the number of the projecting ribs, the height of those ribs, whether undercuts are included, the size of the contact areas, the clearance needed between spaces and ribs, and the material(s) type and thickness used in forming the container assemblies. To improve the lockability of the container assembly, as discussed above, an optional sealing feature may be added.  
      The container assemblies of the present invention are typically formed from polymeric materials, but may be formed from materials such as paper or metal. The polymeric containers may be formed from polyolefins. The polymeric food containers are typically formed from orientated polystyrene (OPS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polypropylene and combinations thereof. The containers assemblies may be made from a mineral-filled polymeric material such as, for example, talc or calcium carbonate-filled polyolefin. An example of paper that may be used in forming the container assemblies is paperboard or molded fiber. Paperboard and molded fiber typically have a sufficient coefficient of friction to maintain the first and second containers in a lockable position.  
      As discussed, the materials used in forming the container assembly may assist in releasably locking the container assembly. For example, the material(s) forming the container assembly may have a fairly tacky laminate on one side that corresponds with a fairly tacky laminate on the opposing side, resulting in a desirable releasably lockable container assembly.  
      It is contemplated that the containers used in forming the container assemblies may be made from different materials. It is contemplated that one of ordinary skill in the art will recognize that other polymers or combination of polymers may be used to form the containers.  
      The container assemblies of the present invention are typically disposable, but it is contemplated that they may be reused at a future time. The containers used in forming the container assemblies (e.g., container  10 ) are shown as including one compartment. It is contemplated that the containers may be formed of multiple compartments. Such containers are desirable for placing items (e.g., food items) in different compartments to prevent or inhibit commingling of items. For example, undesirable mixing of food items can corrupt the flavor and the consistency of the food items.  
      As discussed above, the container assemblies may be used with food items. A method of using such container assemblies includes placing the food and locking the containers to form a container assembly with food therein. The container assembly is then placed in a heating apparatus and heated. Typical heating apparatuses include microwaves and conventional ovens. The container assemblies may contain solid food products. The container assemblies may be used for storage in the refrigerator and/or the freezer.  
      The containers to be used in forming the container assemblies of the present invention may be formed using conventional thermoforming (e.g., by pressure, vacuum or the combination thereof), injection-molding processes, or rotational molding. According to one method of thermoforming, pellets of a polymeric resin and additives, if any, are added into an extruder. The pellets of the polymeric resin and additives, if any, are melted to form a blend. The blend is extruded through a die to form an extruded sheet. The extruded sheet is thermoformed to a desired shape of a container to be used in forming the container assembly.  
      The thickness of the container to be used in forming the container assemblies generally ranges from about 0.002 to about 0.15 inch, but is typically from about 0.005 to about 0.04 inch. The container assemblies may be opaque or a variety of colors or color combinations. The container assemblies typically have at least one transparent container if it is desired for the customer to ascertain the nature of the accommodated product and the condition thereof without having to open the container assembly.  
      While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.