Inventors: John E. Rusnak, Lawrence John Racana and Richard Miller

FIELD OF THE INVENTION

[0001] The present invention relates generally to storage devices having a cover adapted to seal an inner and an outer container. Multiple covers of the plastic containers may be aligned together when stacked in a first position and may be locked together in a second position.

BACKGROUND OF THE INVENTION

[0002] Rigid, thermoplastic food containers are generally known. Users often accumulate a large number of these containers in different sizes and shapes. When not in use, the containers are often stored haphazardly into drawers. In this case, the unused containers take up a great deal of room, and finding a matching base and cover in a disarranged drawer may be difficult. To avoid this, some users stack the containers in cabinets. While the bases of the containers usually nest and therefore take up less room than in a disorganized drawer, it may still be difficult to match a base with a cover. In addition, the covers may not stack and the covers may tend to topple down. When the containers are in use to store food, the containers are often stacked one on top of another in cabinets or in a refrigerator. These stacks may be precarious, and their fall may cause food to spill from the containers. Many users would find it desirable if the containers, whether empty or in use, could be stored in a manner space efficient, less precarious, and more structurally rigid. Related U.S. Patent Publication No. 2009/0166369, describes a system of interlocking covers for sealable plastic containers and is hereby incorporated by reference in its entirety.

[0003] During large-scale manufacturing, the covers may be transported in bulk before being separated out for individual packaging. During bulk handling, manufacturers would find it desirable if the covers would form a stack stable enough to resist the vertical and lateral movements caused by forces typically encountered during manufacturing operations.

[0004] Consumers often desire to carry two separate items in a storage container. For example, a consumer may store a salad in one storage container and salad dressing in a separate container. Conventional solutions for providing a single storage device for holding multiple items have been proposed. U.S. Patent Publication No. 2007/0102319 describes a one-piece container having a first vessel and a second vessel permanently secured to and inside the first vessel. In this design, the user may not be able to, for example, pour salad dressing out of the inner vessel without spilling the contents of the outer vessel. U.S. Patent No. 6,302,268 describes a container having an insert chamber that may release its contents into the container through a hole in the bottom of the insert chamber. To fill the insert chamber, it must be removed from the lid of the container, filled, capped and inserted, cap side down, back into the container. When the insert chamber is not in use, it must remain in place in the lid of the container, else the lid of the container would have an opening and not seal the contents within the container.

[0005] The present invention has as a general aim to provide containers that satisfy both users and manufacturers.

[0006] Users would find it desirable to provide containers that advantageously create a partial vacuum within the sealed storage area of the container during use. Still further, users would find it desirable a cover that holds items in place within the container or that expands somewhat to accommodate larger items. Still further, users would find it desirable to have covers that provide for cover interlocking while at the same time allow for stacking of additional containers on top of the cover of a first container. Still further, users would find it desirable for a cover that may cover both an outer container and an inner container, fitting inside the outer container, simultaneously. What is needed is a container of improved flexibility that can provide these advantages. SUMMARY OF THE INVENTION

[0007] In view of the foregoing, the present invention provides containers whose covers can be stacked together in two different ways. First, the covers can be stacked into an "aligned" stack. The aligned stack provides enough structural rigidity for bulk handling during manufacturing. Second, the covers can be stacked into a "locked" stack. The locked stack provides even more structural rigidity than does the aligned stack and is useful when storing unused covers.

[0008] The present invention further provides a container whose cover may secure an outer container while simultaneously securing an inner container positioned inside the outer container. The inner container may sealingly engage with an inner closure mechanism in the container cover. The outer container may sealingly engage with an outer closure mechanism in the same container cover. The inner closure mechanism may form a portion of a means for stacking the covers together.

[0009] In some embodiments, the cover may include a first closure portion, a third closure portion, an engagement portion, and an alignment portion. The outer container may include a second closure portion and the inner container includes a fourth closure portion. The first closure portion of the cover may be sealingly engageable with the second closure portion of the outer container to form a substantially sealed, leak-proof, and re-sealable storage area for items such as food. The outer surface of the alignment portion of the cover is engageable with the inner surface of the alignment portion of a second cover to form an aligned cover stack. The outer surface of the engagement portion of the cover may be engageable with the inner surface of the engagement portion of a second cover to form a locked cover stack. The third closure portion of the cover may be sealingly engageable with the fourth closure portion of the inner container to define a substantially sealed, lead- proof, and re-sealable storage area for items such as food, condiments, or the like. The third closure portion of the cover may be formed from the inner surface of the alignment and engagement portions of the cover.

[0010] Further, the covers of the present invention may include articulation elements that allow the covers to easily flex upwardly or downwardly, sometimes referred to as articulate, either alone or when engaged with the base of the container. A protruding engagement portion of the cover may be articulated downwardly to the level of the top of the remaining portions of the cover.

[0011] The covers and bases (e.g., inner and outer containers) can be economically constructed from relatively thin-gauge plastic so that the user can either wash them after use or dispose of them with the view that their purchase price allows them to be used as a consumable good. The container can be readily manufactured, for example, with conventional vacuum thermoforming equipment. The cover can be made from a semi-transparent material to ensure satisfactory visibility of the container's contents. The container can be suitable for refrigerator, freezer, microwave, and machine dishwasher use.

[0012] The features of the present invention will become apparent to one of ordinary skill in the art upon reading the detailed description, in conjunction with the accompanying drawings, provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is an isometric view of a container with a cover and a base according to an embodiment of the present invention;

[0014] Figure 2 is a partially cut-away view of a container, showing an inner container nested inside the base, according to an embodiment of the present invention;

[0015] Figure 3 is a cross-sectional isometric view of a round container of the invention;

[0016] Figure 4 is a cross-sectional isometric view of the rectangular-shaped container of Figure 2;

[0017] Figure 5 is a top plan view of the cover of Figure 1; [0018] Figure 6 is a bottom plan view of the cover of Figure 1; [0019] Figure 7 is an isometric view of the base of Figure 1; [0020] Figure 8 is an isometric view of the inner container of Figure 2;

[0021] Figure 9 is a partial isometric sectional view with the engagement portion of the cover of Figure 1 locking engaged with and engagement portion of a second cover;

[0022] Figure 10 is an isometric view of a container base;

[0023] Figure 11 is a top plan view of the container base of Figure 10;

[0024] Figure 12 is a top plan view of a container cover;

[0025] Figure 13 is a side sectional view of the container base of Figure 10 and the container cover of Figure 12; and

[0026] Figure 14 is an enlarged, detail view of a portion of Figure 13.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Turning to the drawings, wherein like reference numerals refer to like elements, an embodiment of the present invention is illustrated in Figures 1 through 8. A container 100 includes a continuous, flexible cover 102 sealingly engaged to a outer container 104. In the example of Figures 1 through 3, the container 100 is depicted as substantially circular in top plan view. In other embodiments of the present invention, for example Figure 4, the container 100 can have other shapes such as rectangular, square, or elliptical.

[0028] The cover 102 includes an engagement portion 106 that is lockingly engageable with the engagement portion of a second cover (not shown in Figure 1, see Figure 9). As described more fully below with reference to Figures 10A through 13C, circumscribing the engagement portion 106 of the cover 102 is at least one articulation element 108. The engagement portion 106 of the Figures is depicted as circular but, as with the shape of the container 100 itself, other shapes are possible. In some embodiments, a standard shape and configuration of the engagement portion 106 is used with covers 102 of various shapes and sizes. This enhances storage flexibility by allowing different types of covers 102 to be stored together in a locked stack. [0029] The continuous cover 102 includes a first closure portion 310 (Figure 6). The first closure portion 310 is sealingly engageable with a second closure portion 416 (Figure 7) of the outer container 104. The first closure portion 310 of the cover 102 can be sealingly engaged with a second closure portion 416 of the outer container 104 to provide a leak-resistant, re-sealable closure. When the first closure portion 310 of the cover 102 and the second closure portion 416 of the outer container 104 are abutted and sealingly engaged with each other, the cover 102 and the outer container 104 define a substantially sealed storage area within container 100 (Figure 1).

[0030] The cover 102 includes a third closure portion 311 (Figure 6) which may be an inner surface of the engagement portion 106. The third closure portion 31 1 is sealing engageable with a fourth closure portion 417 (Figure 8) of the inner container 105. The third closure portion 311 of the cover 102 can be sealingly engaged with the fourth closure portion 417 of an inner container 105 to provide a leak-resistant, re- sealable closure. When the third closure portion 311 of the cover 102 and the fourth closure portion 417 of the inner container 105 are abutted and sealingly engaged with each other, the cover 102 and the inner container 105 define a substantially sealed storage area within the inner container 105.

[0031] As shown in Figures 2 through 4, the inner container 105, once sealed to the cover 102, may fit inside the outer container 104 and the first closure 310 of the cover 102 and the second closure portion 416 of the outer container 104 may sealingly engage with each other. This configuration may provide a substantially sealed storage area within the inner container 105 removably nested inside a substantially sealed storage area within the outer container 104.

[0032] The inner container 105 may have its own lid (not shown) that may sealingly engage with the inner container 105. In this configuration, an item, for example, salad dressing, may be stored in the inner container 105 and covered with its lid. When a user desires, the lid of the inner container 105 may be removed and the inner container may be sealingly engaged with the cover 102 (Figures 2 through 4).

[0033] The inner container 105 may be pre-filled with an item, such as a dip, dressing, condiment, or the like, and sealed at the time of manufacturer. A user may unseal the inner container 105 and sealingly engage the inner container to the cover 102 at the appropriate time. For example, salad dressing may be pre-filled into the inner container 105 and sealed with a foil seal. When the user prepares a salad in the outer container 104, the user may remove the seal on the inner container 105, attach the inner container 105 to the cover 102 and seal the cover 102 on the outer container 104. This configuration provides a convenient way to carry a salad and salad dressing separately. When the user desires to mix the salad and dressing, they may simply remove the cover 102 from the outer container 104 and remove the inner container 105 from the cover 102. The user may then simply pour the contents of the inner container 105 onto the contents within the outer container 104.

[0034] In an alternate embodiment, the inner container 105 may be used to hold, for example, crushed ice. When the inner container 105 is sealed to the cover 102 and the cover 102 is sealed to the outer container 104, the ice in the inner container 105 may help keep cold the contents within the outer container 104. The same concept may be used for keeping items warm. Alternatively, other substances may be stored in the inner container 105, such as an odor or moisture absorber. The inner container 105 may be gas permeable to allow air to pass between the inner container and the outer container 105.

[0035] The size of the inner container 105 may vary depending on the desired use. In some embodiments, the inner container 105 may, when sealingly engaged to the cover 102 and the cover 102 is sealingly engaged to the outer container 104, come close to or contact the bottom of the outer container 104 (Figure 2). In other embodiments, the inner container 105 may, when sealingly engaged to the cover 102 and the cover 102 is sealingly engaged to the outer container 104, be shorter and a gap 107 may be present between the outer container 104 and the inner container 105 (Figure 3).

[0036] As shown in Figure 7, the outer container 104 of the container 100 includes a bottom 410 and a peripheral sidewall 412 extending upwardly from the peripheral edge of the bottom 410. The top of the outer container 104 is open. The second closure portion 416 of the outer container 104, which, as noted above, is adapted to sealingly engage with the first closure portion 310 of the cover 102 (Figure 6), is positioned at the open end of the peripheral sidewall 412 of the outer container 104. In one embodiment, the second closure portion 416 of the outer container 104 is a raised locking ring that extends from an upper edge of the peripheral sidewall 412 of the outer container 104.

[0037] More particularly with reference to the engagement portion 106, the cover 102 illustrated in Figures 1, 5, 6 and 9 includes the engagement portion 106 that allows the cover 102 to lockingly engage with the engagement portion 506 of a second cover 502 to form a locked stack of covers (Figure 9). This locking feature makes the resultant stack of covers more structurally rigid and thus less precarious than a traditional, non-interlocked, stack of covers.

[0038] A shown in Figure 9 the cover 102 is locked together with the second cover 502 by their engagement portions 106 and 506 respectively. In the example of Figure 9, the engagement portion 106 of the cover 102 includes an upper protrusion 118 (see also Figure 1) and a lower protrusion 120. Further, the engagement portion 506 of the second cover 502 likewise includes an upper protrusion 518 and a lower protrusion 520. Each protrusion 118, 518, 120, and 520 is convex on one side and concave on the other. The lower protrusion 120 of the cover 102 fits over and receives the upper protrusion 518 of the second cover 502, thus locking the covers 102 and 502 together. In this manner, the covers 102 and 502 are held together and form a structurally stable cover stack. A third cover (not shown) may be lockingly engaged with the second cover 502, a fourth cover with the third and so on to form a stack of any number of covers.

[0039] The engagement portion 106 can also be chosen to have a shape or otherwise include elements that provide an aligned or locked stack of covers 102 with rotational alignment. Rotation, as used herein, is defined about an axis A (Figure 1) normal to the plane formed by orthogonal midlines, i.e., first midline 205A and second midline 205B at the top surface of the cover 102 as shown in Figure 5. The origin of the rotational axis is at the center point 207 at which the orthogonal midlines intersect. For instance, shapes that inherently require alignment prior to engagement or that may be self-aligning during the process of connecting engagement portions would be shapes with linear or curvilinear sides, vertices or lobes such as triangular, square, rectangular, or multi-petal shapes. Additionally, the cover may have one or more elements on or about the engagement portion that require alignment prior to connection of engagement portions or elements that may be self-aligning during the process of connecting engagement portions.

[0040] Other embodiments of the engagement portion may include one or more of the following features to enable engagement: convex portions or ribs, concave portions or ribs, linear or curvilinear undercuts, discrete snap elements or buttons, interference fits, textured surfaces, or elements that modify surface friction or tackiness at or around the point of engagement. The engaging areas that create a locking condition can be continuous about the engagement portions or discretely segmented about the engagement portions. In some embodiments, the force required to connect the cover and the second cover may differ substantially from the force required to disengage the covers. For instance, it may be beneficial during manufacturing that the force needed to connect the covers is less than the force required to separate the covers. As a result, the covers are relatively easy to connect during manufacturing, yet they will lock securely and not undesirably separate during the manufacturing process. To accomplish this, the protrusions on the engagement portion may be designed where, for a given protrusion, the upper protrusion edge comprises a gradual taper whereas the lower protrusion edge comprises a more abrupt shape. For example, in one embodiment, the shape of the protrusion may be similar to a barbed hook with gradual taper on the upper edge of the barb that would impart little resistance during engagement and with an abrupt shape on the lower edge of the barb that would impart relatively high resistance during disengagement. Conversely, it may be beneficial to design the engagement portion so that the force that needs to be applied to connect the covers is more than the force required to separate the covers, since the user may perceive that a high connecting force equates to satisfactory locking integrity, whereas a weak connecting force may lead the user to perceive that the cover stack lacks the integrity required to insure the expected organizational benefit. Thus, the high connecting force provides the perceived benefit, yet a lower disengagement force does not require that the user untowardly struggle during separation of covers. To accomplish this, the protrusions on the engagement portion may be designed where, for a given protrusion, the upper protrusion edge comprises an abrupt shape whereas the lower protrusion edge comprises a more gradual taper. For example, in one embodiment, the shape of the protrusion may be a reversed barb with an abrupt shape on the upper edge of the barb that would impart relatively high resistance during engagement and with a gradual taper on the lower edge of the barb that would impart little resistance during disengagement. Furthermore, during the process where the user applies force to aligned covers in a direction normal to the general cover plane so as to lock the covers together, the engagement portion can provide tactile or audible feedback upon locking. In this way, the user would sense that the covers are connected and that no further force need be applied

[0041] More particularly with regard to the first closure portion 310 and the second closure portion 416 forming the sealing engagement of the cover 102 and the outer container 104, and to the third closure portion 311 and the fourth closure portion 417 forming the sealing engagement of the cover 102 to the inner container 105, Figure 6 is a bottom plan view of the cover 102 of Figure 1. Referring to Figures 1, 6, 7 and 8, as noted above, the cover 102 of the container 100 may sealingly engaged with the outer container 104 and the inner container 105 of the container 100. The cover 102 includes the first closure portion 310 (Figure 6) in the form of receiver at the perimeter edge of the cover 102 adapted to sealingly engage the second closure portion 416 in the form of the raised locking ring at the top edge of the peripheral sidewall 412 of the outer container 104. The cover 102 further includes the third closure portion 311 (Figure 6) in the form of receiver at the perimeter edge of the inner surface of the engagement portion 106 adapted to sealingly engage the fourth closure portion 417 in the form of the raised locking ring at the top edge of the peripheral sidewall 413 (Figure 3) of the inner container 105. As a result, when the cover 102 and the inner container 105 are abuttingly engaged, a positive seal is formed between sealing surfaces around the perimeters of the inner container 105 and of the cover 102. In this embodiment, the container 100 uses a locking rim design that includes both inside and outside seals. As would be apparent to one of ordinary skill in the art however, the present invention can be embodied with a variety of closure designs including outer closures and/or inner closures. Related U.S. Patent Publication number 2008/0041850, co-owned with the present invention and incorporated in its entirety herein by reference, further describes the closure portions. However, the closure portions described therein are examples only, and many other types of closure portions could be used with the present invention.

[0042] The first and second closure portions 310 and 416 and the third and fourth closure portions 311 and 417 can be configured to be slightly different in size to form an interference fit therebetween. The interference fit between the first and second closure portions 310 and 416 and the third and fourth closure portions 311 and 417 can provide a sealing engagement between the closure portions. As a result, when the pieces are abuttingly engaged, a positive seal can be formed between the first and second sealing surfaces around the perimeters of the outer container 104 and of the cover 102 and between the third and fourth sealing surfaces around the perimeters of the inner container 105 and the cover 102. The sealing engagement of the closure portions can be accompanied by an audible "snap" indicating that the container is securely closed.

[0043] The outer container 104 and the inner container 105 can be made from any suitable plastic with sufficient thickness to withstand without deforming the heat of microwave cooking and of top-shelf dishwashing. It should also remain sturdy during lifting while laden with hot food. The outer container 104 and the inner container 105 can be made from any suitable plastic and can be made by any suitable technique, such as co-extrusion, lamination, injection molding, vacuum thermo forming, or overmolding. In one embodiment, the outer container 104 and the inner container 105 are formed from polypropylene. As with the cover 102, the nominal wall thickness of the outer container 104 and the inner container 105 can vary somewhat due to the manufacturing process.

[0044] The cover 102 of Figure 1 can be constructed with a wall thickness thinner than that of a outer container 104. The cover 102 can be made from any suitable plastic and can be made by any suitable technique, such as vacuum thermoforming processes described herein. In one embodiment, the cover 102 can be formed from polypropylene. Due to the vacuum thermoforming process, the wall thickness of the cover 102 can vary slightly over its nominal thickness. A cover 102 with a nominal thickness less than the nominal thickness of the outer container 104, however, reduces the cost of material for the container 100. Further, with a thinner cover 102, increased cover flexibility more easily accommodates the removal of the cover 102 from, and the sealing engagement with, the outer container 104. The cover 102 can maintain adequate flexibility for proper sealing even during typical freezer temperatures.

[0044] The container base 104 of Figures 10 and 1 1 includes a bottom 400 and a sidewall 402 extending from the periphery of the bottom 400. The bottom 400 includes a raised lower section 404 to accommodate the engagement portion 200 of a container cover 102 when containers 100 are stacked together. Just as the engagement portion 200 of the cover 102 of Figure 12 can include a central field 300, a similar field for a manufacturer's mark or for user information could be included in the raised portion 404 of the base 104.

[0045] Figures 13 and 14 present embodiments of a container 100 whose cover 102 is sealingly engaged with its base 104. Figure 13 shows the cover 102 cooperating with the base 104 to define a sealed storage compartment 600. The cover 102 can be sufficiently flexible to allow a user to create a vacuum in the container 100 upon sealing. In order to create a vacuum, the user could, for example, depress the cover 102 during the closing of the container 100. A return force imparted upon the cover 102 by the resiliency of the material of the cover 102 will urge the cover 102 to return to its normal position, thereby creating a vacuum. To facilitate convenient sealing engagement of the cover 102 with its base 104, the users can, at their discretion, apply downward force to only the engagement portion 200 of the container cover 102. The engagement portion 200 is located to accept and distribute the force to the first closure portion 700 of the cover 102 during sealing to the base 104. The engagement portion 200 may also act as a convenient handle for grasping the cover 102. [0046] In the embodiments of Figures 13 and 14, the container 100 uses a locking rim design that includes both inside and outside seals as will be described. The present invention can be embodied with a variety of closure designs including outer closures and/or inner closures.

[0047] Figure 14 depicts an embodiment of the closure portions used to engage the cover 102 with the base 104 of the container 100. The cover 102 includes a first closure portion 700 in the form of a raised locking ring. The first closure portion 700 of the cover 102 can be engaged with a second closure portion 702 of the base 104 to provide a leak-resistant, re-sealable closure.

[0048] The first closure portion 700 includes an inner wall 704, a retention bead 706, and an outer wall 708. The inner wall 704, the retention bead 706, and the outer wall 708 define a first sealing surface, which is part of the lower surface of the cover 102. The first closure portion 700 can include one or more locking ridges 710. The outer wall 708 extends between the retention bead 706 and a flange 712. The flange 712 can provide a convenient gripping surface to facilitate the removal of the cover 102 from the base 104.

[0049] As illustrated in Figure 14, the second closure portion 702 of the base 104 is a raised locking ring that extends from an upper edge of the sidewall of the base 104. The second closure portion 702 includes an inner wall 714, a retention bead 716, and an outer wall 718. The inner wall 714, the retention bead 716, and the outer wall 718 define a second sealing surface, which is part of the upper surface of the base 104. The second closure portion 702 can include one or more locking ridges 720. The outer wall 718 extends between the retention bead 716 and a flange 722. The flange 722 can provide a convenient gripping surface to facilitate the removal of the cover 102 from the base 104.

[0050] The first and second closure portions 700 and 702 can be configured to be slightly different in size to form an interference fit therebetween. The interference fit between the first and second closure portions 700 and 702 can provide a sealing engagement between the closure portions. As a result, when the two pieces are engaged, a positive seal can be formed between the first and second sealing surfaces around the perimeters of the base 104 and of the cover 102.

[0051] The engagement of the first and second closure portions 700 and 702 can be accompanied by an audible "snap" indicating that the container is securely closed.

[0052] In the example of Figure 14, the inner wall 704 of the first closure portion 700 of the cover 102 extends to the engagement portion 200. This engagement portion 200 includes an upper protrusion 724 and a lower protrusion 726. The cover 102 includes a ridge 728 on the outer wall 708 of the first closure portion 700.

[0053] The cover 102 can be made by various plastic molding processes, including but not limited to vacuum thermoforming and injection molding. Vacuum thermo forming of the cover 102 is typically the most economical means for forming the cover 102. As is well know in the art, vacuum thermoforming involves the heating a suitable plastic sheet of material to a temperature at which the sheet becomes formable into a shape that is set as the plastic sheet cools. As used herein, a suitable plastic sheet is a plastic sheet that may be readily used by the vacuum thermoforming process. The heated plastic sheet is made to conform to the surface features of a single surface "male" tool by drawing the heated sheet of plastic to the surface of the tool by the force of a vacuum applied to the tool. In vacuum thermoforming, the sealed air space between the heated plastic and mold is evacuated to draw the heated plastic to contact the single male surface of the mold.

[0054] Typically, however, in vacuum thermoforming, the thickness of the finished article formed by the process is nominally uniform. A side cross-section view through the vacuum thermoformed article reveals a substantially uniform thickness profile. The "bottom" surface of the heated plastic sheet that contacts the tool surface conforms to its shape. The "top" surface of the plastic element formed in the vacuum thermoforming process does not contact a tool surface and generally resides at a uniform distance from the bottom surface of the plastic article. Only nominal thinning of the plastic material occurs when it bends and stretches around curved mold features to conform to the path of the curved surfaces of these features. As used herein, a substantially uniform thicknesses in side cross-sectional profile is a thickness in a plastic article that is not sufficiently variable to preclude its manufacture with typical prior art single male surface vacuum thermo forming techniques. Conversely, a non-uniform thickness is a profile thickness in an article that varies enough to preclude the manufacture of the article with standard prior art vacuum thermoforming techniques requiring instead other plastic molding techniques such as injection molding.

[0055] Injection molding of a plastic article involves heating suitable plastic material in the form of pellets or granules until a melt is obtained. The melt is next forced into a split-die mold, sometimes referred to as a split-die tool, where it is allowed to "cool" into the desired shape. Both the bottom surface and the top surface of the plastic article are formable by the split-die mold. Thus, articles may by formed by the injection molding process that have side cross-sectional profiles of varying non-uniform thickness. After the plastic melt cools, the split-die mold is opened and the article is ejected. Since, the mold is separable, undercut surface on the plastic article may be relieved from the split-die mold when it is opened. Injection molding, well know in the art, is typically used to form plastic articles that have large undercuts and substantially varying thicknesses in side cross-sectional profile. As used herein undercuts are said to be large if a molded plastic article having undercut features is difficult or impossible to remove from a single-surface vacuum thermoforming mold after it is formed and cooled.

[0056] Since cover 102 as described, contains significant undercuts, such as included in upper protrusion 118 and lower protrusion 120 (Figures 1 and 9) on the engagement portion 106 of the cover 102, injection molding would typically be required to form cover 102. Further, injection molding would typically be required to form articulation elements 108 that are significantly thinner than the rest of cover 102.

[0057] The container 100 can be reusable, but it can also be constructed cheaply enough that consumers see it as a disposable item, with replacement covers 102 and bases 104 available separately for retail sale. The outer container 104 and the cover 102 can be fabricated by vacuum thermoforming a clarified polypropylene homopolymer material. In another embodiment, the container 100 may be fabricated by vacuum thermoforming a clarified random copolymer polypropylene material. Other plastic materials which would be suitable for fabricating the cover 102 and the outer container 104 of the container 100 by vacuum thermoforming include PS (polystyrene), CPET (crystalline polyethylene terephthalate), APET (amorphous polyethylene terephthalate), HDPE (high density polyethylene), PVC (polyvinyl chloride), PC (polycarbonate), and foamed polypropylene. The material used can be generally transparent to allow a user to view the contents of the container.

[0058] The container 100 may include a visual indication of closure between the cover 102 and the outer container 104 and/or between the cover 102 and the inner container 105. The visual indication may be a color change in the area where the cover 102 engages the outer container 104 and/or the inner container 105. In one embodiment, the first closure portion 310 on the cover 102 may be a first color and the second closure portion 416 on the outer container 104 may be a second color. When the closure portions are engaged, the first and second colors produce a third color which is visible to the user to indicate that the container 100 is sealed.

[0059] The container 100 may include a rough exterior surface to reduce slipping and to improve grasping by the user, especially if the user's hands are wet or greasy.

[0060] The container 100 may include a self-venting feature. The pressure in the sealed container 100 may increase when the sealed container 100 and contents are heated in a microwave oven. Thus, the cover 102 may include a self- venting mechanism, which opens when the pressure in the container 100 exceeds a predetermined value.

[0061] The container 100 may be divided to separate foods in the container. A divider may be integral with the container 100 or may be a separate component. Either the outer container 104 only may include a divider or both the outer container 104 and the cover 102 may each include a divider. The divider located in the cover 102 may only partially engage the divider in the outer container 104 so as to provide splash protection, or it may fully engage the divider in the outer container 104 to provide varying degrees of inter-compartmental leak resistance. [0062] The container 100 may include a strip indicating the temperature of the container 100 and its contents.

[0063] The use of the terms "a," "an," "the," and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise indicated.

[0064] While the invention is described herein in connection with certain preferred embodiments, there is no intent to limit the present invention to those embodiments. For example, those of skill in the art would recognize that may be formed such that the vertex of the articulation element 108 is above the top of the cover 108, that is the articulation elements 108 may be pointed upwardly. It is recognized that various changes and modifications to the described embodiments will be apparent to those skilled in the art upon reading the foregoing description, and that such changes and modifications may be made without departing from the spirit and scope of the present invention. Skilled artisans may employ such variations as appropriate, and the invention may be practiced otherwise than as specifically described herein. Accordingly, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention. Moreover, any combination of the above described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.