Abstract:
A tamper resistant thermoformed container having a tray and a lid, where the tray has an inside shelf between the cavity floor and a second shelf that extends to a cavity rim, where the lid has a sealing slot formed to engage the inside shelf of the tray, and where the lid also has a latching tab formed to fit into a matching latching hole on the tray. This structure keeps the lid on the tray by a combination of friction between the lid sealing slot and the tray inside shelf, plus interference between the latching tab and the latching hole.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the field of containers. More particularly, the present invention relates to thermoformed containers having features that enhance the container&#39;s ability to resist tampering, and to make evident any tampering which does occur. 
     BACKGROUND OF THE INVENTION 
     Thermoformed plastic containers are well known as inexpensive and highly customizable containers for the sale of a wide variety of products, everything from cell phones to deli meats. Thermoformed plastic containers can be transparent and rigid, to let a consumer examine a product closely. They can be lightweight, and may be efficiently stored or shipped together in a nested fashion. It is easy to include product information and cosmetic features in these types of containers, for example with stickers or cards glued to the outside of the containers, with embossing molded into the containers, or with paper inserts inside the containers. For these and other reasons, thermoformed plastic containers can be superior to other available options for product containers, such as cardboard or metal boxes, bags, metal cans, or paper cartons. 
     Thermoformed containers can include features that make it more difficult to access the contents of the container without being noticed, to form a tamper-resistant container. In a retail electronics setting, for example, tamper-resistance can reduce shoplifting. 
     In a retail food setting, tamper-resistance can improve food safety by reducing the risk that the product could be partially consumed or contaminated. In retail food settings like a deli counter in a grocery store or in a conventional fast-food or takeout restaurant, it can also be beneficial to provide a container that can be assembled when needed at the point of use, for example after putting a sandwich or other food in the container. 
     What is needed is a thermoformed container system that includes tamper-resistant features that make it difficult to open without detection, yet easy to open by the end consumer, and preferably allowing assembly on demand by unskilled personnel without specialized machinery or tools. 
     SUMMARY OF THE INVENTION 
     A first embodiment of the invention is a thermoformed container system using thermoformed plastic containers, each container having a tray and a lid mounted on the tray, where the tray has a first peripheral shelf between the cavity floor and a second peripheral shelf that extends to a cavity rim, where the lid has a sealing slot formed to engage the first peripheral shelf of the tray, and where the lid has a latching tab formed to fit into a matching latching hole on the tray, so that the lid is retained on the tray by friction between the lid and the tray, plus interference between the latching tab and the latching hole. 
     In a second embodiment of the invention, the latching tab is formed as part of the tray (instead of being part of the lid), and the latching hole is formed as part of the lid (instead of being part of the tray). 
     A third embodiment of the invention is a method of forming a container by providing a tray with a first peripheral shelf between the cavity floor and a second peripheral shelf that extends to a cavity rim, where the lid has a sealing slot formed to engage the first peripheral shelf of the tray, and providing a lid for mounting on the tray, where the lid has a latching tab formed to fit into a matching latching hole on the tray, and inserting the tab of the lid into the slot of the tray to form a container with the lid retained on the tray by friction between the lid and the tray and by interference between the latching tab and the latching hole. 
     Further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIGS. 1A, 1B, and 1C  are top, bottom, and perspective views, respectively, of an exemplary tray for use in a container according to the invention; 
         FIGS. 1D and 1E  are enlarged views of the region marked  1 D in  FIG. 1A  and the region marked  1 E in  FIG. 1B , respectively; 
         FIGS. 1F and 1G  are enlarged views of the regions marked  1 F and  1 G, respectively, in  FIG. 1C ; 
         FIGS. 2A, 2B, and 2C  are top, bottom, and perspective views, respectively, of an exemplary lid for use in a container according to the invention; 
         FIGS. 2D and 2E  are enlarged views of the regions marked  2 D in  FIG. 2A  and the region marked  2 E in  FIG. 2B , respectively; 
         FIGS. 2F and 2G  are enlarged views of the regions marked  2 F and  2 G, respectively, in  FIG. 2C ; 
         FIGS. 3A and 3B  are perspective and top views, respectively of a container according to the invention, comprising the tray of  FIGS. 1A-1G  and the lid of  FIGS. 2A-2G , with tab of the lid inserted into slot of tray; 
         FIG. 3C  is an enlarged top view of the region marked  3 C in  FIG. 3B , with the tear-off portion of the tray intact; 
         FIG. 3D  is an enlarged bottom view of the region marked  3 D in  FIG. 3B , with the tear-off portion of the tray intact; 
         FIG. 3E  is an enlarged top view of the region marked  3 E in  FIG. 3B , with the tear-off portion of the tray separated from the remainder of the tray; 
         FIG. 4  is a cross-section of the latch region of the container, taken along the line  4 - 4  in  FIG. 3C , with the tear-off portion of the tray intact; 
         FIG. 5  is a cross-section of the latch region of the container, taken along the line  5 - 5  in  FIG. 3E , with the tear-off portion of the tray removed; and 
         FIG. 6  is a cross-section of the joint between the tray and the lid of the container, taken along the line  6 - 6  in  FIG. 3B . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1A-1G  provide various views of an exemplary tray  20  for a container according to the invention. For purposes of illustration and not as a limitation, the names of the walls of the tray  20  (e.g. floor, top, side, bottom, rear, etc.) assume that the tray  20  is positioned in an upright standing position with the cavity (concave) side of the tray facing upward and with the tray floor  22  on the bottom. 
     In other words, the names assume the tray  20  is viewed as in  FIG. 1A . In that orientation, the exemplary tray  20  can be said to include a floor  22  and multiple first side walls  24  extending from a perimeter  26  of the floor  22  to a cavity rim  46  that surrounds an interior cavity  30 . The floor  22  may have a floor indentation  27 , however this is not required. The multiple first side walls  24  meet at corners  28 , which may include embossed features for rigidity or other structural purposes or for entirely cosmetic purposes. 
     As perhaps best shown in the cross-sectional view of  FIG. 6  and in the zoomed perspective views of  FIGS. 1F and 1G , the multiple first side walls  24  extend to a first peripheral shelf  32 . The first peripheral shelf  32  has a first peripheral shelf inside boundary  34  and a first peripheral shelf outside boundary  36 . The first peripheral shelf  32  extends from the multiple first side walls  24  to the multiple second side walls  38 . 
     The multiple second side walls  38  extend from the first peripheral shelf outside boundary  36  to a second peripheral shelf  40 . The second peripheral shelf  40  has a second peripheral shelf inside boundary  42  and a second peripheral shelf outside boundary  44 , and extends from the multiple second side walls  38  to the cavity rim  46 . 
     The cavity rim  46  has a cavity rim inside wall  48 , a cavity rim top surface  50 , and a cavity rim outside wall  52 , and terminates in a cavity rim outside wall flange  54 . 
     As perhaps best shown in  FIGS. 1D, 1E, and 1G , at least one portion of the tray, preferably a corner  28 , includes a hole  96 . The tray may include a tear-off portion  98 , for example located between the hole  96  and the periphery of the tray formed by the rim  46  and/or the outside flange  54 . At least part of the boundary of the tear-off portion  98  may include perforations  100 . The tear-off portion  98  or any other portion of the tray  20  may include text  102 . 
     Any of the walls may include one or more embossed wall features for decoration or for structural purposes. Any of the walls may also include one or more raised engravings, for example brand markings, informational messages, or decorations. The engravings can be placed inside a frame. 
     The exemplary tray  20  can have (by way of example, and not as a limitation) an interior cavity  30  that is between 0.5-2 inches deep from the top surface  50  of the rim  46  to the floor  22  that forms the bottom of the cavity  30 . Similarly, the tray  20  can be about 3-8 inches wide to fit typical products such as electronics or foods. However these exact dimensions are not required—the tray could be bigger or smaller, and/or could have different relative dimensions. While the exemplary tray  20  is approximately square when viewed from the top, this particular shape is not required, and the tray  20  could be a different shape, for example rectangular, triangular, ovoid, circular, pentagonal, trapezoidal, etc. 
       FIGS. 2A-2G  provide various views of an exemplary lid  60  for use in a container according to the invention. In  FIG. 2A  the lid  60  is positioned with the convex side of the central portion  62  of the lid  60  facing upward, as if to cover the tray  20  of  FIG. 1A . 
     The lid  60  includes a central portion  62  that may include engravings, such as brand markings, informational messages, or decorations. The lid  60  has an exterior surface  66  that faces outwardly when the lid  60  is fitted on a tray  20 , and an interior surface  68  that faces the interior cavity  30  of the tray  20 . 
     As perhaps best shown in the cross-sectional view of  FIG. 6  and in the zoomed perspective views of  FIGS. 2F and 2G , the lid  60  includes a lid sealing slot  72 , with a sealing slot first side wall  74 , a sealing slot floor  76 , and a sealing slot second side wall  78 . The lid side wall  70  extends from the lid central portion  62  to the sealing slot first side wall  74 . The sealing slot floor  76  extends from the sealing slot first side wall  74  to the sealing slot second side wall  78 . A lid sealing slot outside flange  80  extends from the sealing slot second side wall  78 , and forms the perimeter of the lid  60 . 
     As perhaps best shown in  FIGS. 2D, 2E, and 2G , at least one portion of the lid  60 , preferably a corner, includes a tab  92  which may include one or more barbs  94 . 
     The lid  60  is preferably sized to fit the tray  20 . Like the tray  20 , the lid  60  can be roughly square and about 3-8 inches wide, and about 0.5-2 inches high. However, as with the tray, this shape and these exact dimensions are not required—the lid could be a different shape, and it could be bigger or smaller or have different relative dimensions. 
       FIGS. 3A and 3B  are perspective and top views, respectively, of an exemplary container according to the invention comprising the lid of  FIG. 2A  mounted on the tray of  FIG. 1A  to form a sealed container  10 . 
     In the container  10 , the tab  92  of the lid  60  is inserted in the hole  96  of the tray  20 , forming a latch  90  between the lid  60  and the tray  20 . (In the present application, the term “sealed” means substantially closed in order to retain contents, not necessarily air tight or completely enclosed.) Additionally, the sealing slot  72  of the lid  60  is nested into the tray  20 , with the peripheral flange  80  of the lid buried behind the rim  46  of the tray  20 , forming a friction fit to retain the lid  60  on the tray  20 . 
     The seal between the lid  60  and tray  20  is perhaps best illustrated in the cross-section view of  FIG. 6 , taken at line  6 - 6  in  FIG. 3B . As shown in  FIG. 6 , the lid sealing slot  72  nests against the first peripheral shelf  32  and second side wall  38  of the tray  20 , with the sealing slot floor  76  against the first peripheral shelf  32  and the sealing slot second side wall  78  against the tray second side wall  38 . The peripheral flange  80  of the lid  60  preferably nests tightly into the corner between the second peripheral shelf  40  and the cavity rim inside wall  48  of the tray  20 . 
     The cavity rim inside wall  48  may also include one or more convex structures protruding outwardly to provide an interference fit with the peripheral flange  80  of the lid  20  locked under the convex structure. The convex structure could be one or of a post, pin, plug, bulge, bump, hump, pyramid, cube, nub, projection, protrusion, protuberance, knob, ridge, or a combination of these structures. 
     These features provide tamper resistance by securely retaining the lid  60  on the tray  20  to require a high level of manual dexterity to open the container  10 . Also, burying the flange  80  of the lid  60  behind the rim  46  of the tray  20  hides the flange  80 , making it difficult to find the edge (i.e. the flange  80 ) of the lid  60  in order to pry the lid  60  off the tray  20 . The friction fit (possibly augmented with an interference fit) helps keep the lid sealed on the tray unless deliberately opened by the consumer, and the serpentine path through this seal between the lid and tray helps to keep any contents inside the cavity. 
     In the condition shown in  FIGS. 3A, 3B, 3C, 3D, and 4 , the latch  90  retains the lid  60  on the tray  20 . In the condition shown in  FIGS. 3E and 5 , the tear-off portion  98  has been separated from the remainder of the tray  20 , facilitating removal of the lid  60  from the tray  20  in order to open the container  10 . The use of a tear-off portion  98  also provides tamper resistance, for example by making it obvious when the latch  90  has been broken and preventing repair of the latch once it has been broken. 
     While the preceding discussion of the exemplary container  10  uses particular embodiments of a tray  20  and lid  60 , the invention could be practiced with other tray and lid configurations. The exemplary container  10  includes a single internal cavity  30 , but this particular structure is not required. For example, a different number of cavities could be provided for particular applications, and the container as a whole or the individual cavities could be different sizes and/or shapes. While the exemplary container includes a tray with a latching hole and a lid with a latching tab, an alternative embodiment of the invention can have a tray with a latching tab and a lid with a latching hole. While the exemplary container includes a tray with a single latching hole located at a corner, and a lid with a single latching tab located at a corner, there could be multiple latching holes and multiple latching tabs, and the latching tabs and latching holes need not be located at corners. 
     While the exemplary container includes a tray with a latching hole and a lid with a latching tab, an alternative embodiment of the invention can have a tray with a latching tab and a lid with a latching hole. While the exemplary container includes a tray with a single latching hole, and a lid with a single latching tab, there could be multiple latching holes and multiple latching tabs. While the exemplary container includes a tray with a latching hole located at a corner, and a lid with a latching tab located at a corner, the latching tabs and latching holes could be located at a different position, for example between corners. 
     The tray  20  and lid  60  of the container  10  are preferably made using thermoforming methods, from a suitable thermoformable material. For example, a tray  20  and lid  60  meant for use with ready-to-eat foods might be formed of a thermoformable plastic such as oriented polystyrene (OPS), talc-filled polypropylene (TFPP), polypropylene (PP), high impact polystyrene (HIPS), polyethylene terephthalate (PET), amorphous PET (APET), crystalline polyethylene (CPET) polystyrene copolymer blends, styrene block copolymer blends, and the like. 
     The materials forming the tray  20  and lid  60  may be different, and those materials are not necessarily homogeneous, but may be, for example, a laminate, co-extruded material, or multilayer material. Additional components could be used, for example a plastic or foil membrane could be positioned on the tray  20  and covering the contents  110  in a way that allows the lid  60  to be fastened on the tray. 
     It is understood that the invention is not confined to the embodiments set forth herein as illustrative, but embraces all such forms thereof that come within the scope of the following claims.