Abstract:
A tamper-evident rigid plastic food container system wherein the outer periphery of the mating surfaces of the lid and tray are permanently bonded together after the food product has been placed in the tray, a set of perforated rows at an inner periphery, the interconnect of which needs to be torn into order to open the lid. Intentional, inadvertent or malicious ingress into the container can only be made by tearing at the perforations thereby evidencing the potential tampering and contamination of the packaging contents. The lid and tray edges may further include mechanical interference fits, including snap-fit grips that may be of the releasably lockable kind to permit sealing, release and re-sealing multiple times without deterioration in reliability, and which can further prevent or minimize leakage of liquid food product.

Description:
PRIORITY 
     Pursuant to 35 U.S.C. Section 119(e) and 37 C.F.R. Section 1.78, the present application claims priority to the provisional application entitled “Versatile Tamper-Evident Food Container” by Terry Vovan (application Ser. No. 60/698,736) filed on Jul. 13, 2005. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to rigid food packaging containment that preserves and facilitates the displaying of contents. More particularly, the invention relates to a food packaging containment system that visually evidences unauthorized ingress if interfered either inadvertently or with the intent to cause harm. 
     BACKGROUND OF THE INVENTION 
     Retail markets have utilized rigid and flexible plastic containers to contain and display perishable and fragile food items both hot and cold, such as sandwiches, salads and bakery items. These traditional roles of plastic packaging are now the minimum expected standards, and the requirements placed on plastic food packaging continue to expand as increasing demands are placed upon it. Presentation, brand presence, consumer desires, added value to enhance commercial competitiveness, differentiation, imagery and psychology has resulted in the design and application of plastic packaging becoming more challenging. Convenience continues to shape the future of packaging, with consumers gravitating toward packaged convenience items that minimize the impact on their behavior forcing packaging manufacturers to include social and environmental considerations into their development process. 
     Rigid plastic food containers are typically manufactured from Polystyrene, Polypropylene, Polyethylene Terephthalate (PET), Polylactide, Polyvinyl Chloride (PVC), or other rigid polymers. They generally comprise either of two-parts—a tray and lid—or they may be a one-piece construction with a hinge that modifies one portion of the container to act as the tray and the other connected portion to act as a lid. This general configuration of food containers in a large variety of shapes and cross-sections (circular, rectangular, square, and elliptical, etc.) has been available in the marketplace for many years. 
     However, a limitation or concern has been undisclosed potentially malicious ingress into such containers that can lead to inadvertent or intentional contamination of the contents of the food container. This has created an increased awareness of and demand for tamper-resistant and tamper-evident food packaging systems. Product tampering has been in existence for as long as there have been packaged consumer goods. The causes of tampering are varied but generally take one of two forms: the first is malevolent tampering, and the second is for personal gratification, where one samples a product and puts it back on the shelf and the next customer is unaware of the contamination. Both modes of tampering compromises the safety and quality of food package contents. The costs of tampering are enormous. In addition to the recalling of tampered, as well as un-tampered product, the resulting negative publicity can lead to reduction in revenue and brand equity, with retailers being forced to stop purchasing from one or more products form the affected company or even litigation. 
     In 1982, Johnson and Johnson (J&amp;J) experienced such a situation when numerous bottles of its Extra-Strength Tylenol capsules had been laced with cyanide. By the end of the crisis, J&amp;J had spent $100 million recalling 31 million bottles, they ceased production of the product and further pursued redesign of its bottles. Seven people died from the ingestion of the cyanide-laced pills. The threat of tampering has been amplified in the wake of the terrorist attack of Sep. 11, 2001. Possible contamination of food product on a potentially larger scale been envisioned. 
     In the packaging industry, tampering is the interference with the package contents, and the risk of tampering is a phenomenon that we have come to accept as a necessary evil when making purchases. Today, it is impossible to find food packaging that does not have a security feature. Virtually every packaged food product is enclosed or is attached to a tamper-evident or tamper-proof security feature. Tamper-evident means that a package that has undergone tampering will show some readily observable sign that the tampering has taken place; the sign may be audible or visible. It is the opinion of the inventor that in addition to its functions of protecting the product inside against physical and microbiological harm and oxygen ingress, and of providing brand recognition and product differentiation in the marketplace, packaging should also be designed to protect the consumer against tampering, whether deliberate or accidental. 
     Methods developed and currently used to combat tampering have included bonding the edges of existing packages. The advantage of such an approach is that a barrier against tampering could be achieved without changing the packaging design. Alternatively, addition of clear or printed shrink-wrap over the neck edge joint between the lid and tray or the entire package that keeps the packaging and its contents secure have been used. These methods provide some assurance to the consumer that the product has not been interfered with. Similarly, other attempts developed to combat packaging product tampering include of under-lid barriers (e.g. heat-sealed pop-up lids, glued boxes and tape seals). 
     A limitation associated with these methods, however, is that they achieve only a low level of tamper-evident packaging. They are either not sufficiently or distinctively visible to the consumer, or they can be return to its original condition with a glue gun and a hair dryer. This further makes disposal of unused sealing material a security issue as unused, intact seals may be used to reseal contaminated product. 
     It would be advantageous to consumers if there were a simple method that would rapidly indicate if a rigid plastic food package had been interfered with, that is, opened and then re-closed prior to purchase. 
     As it is extremely difficult to develop product packaging that is regarded as fully tamper-proof, the packaging industry&#39;s efforts have been directed to develop solutions that would ensure that any tampering can be clearly visible to the potential consumer. In response to the evolving demands of consumers, retailers continue to seek novel plastic packaging solutions to improve on the safety, convenience and therefore marketability of food product. 
     As such, the inventors recognizes that greater utility of such rigid plastic containers would be obtained through improved tamper-evident containerization methods and designs to increase the safety to the consumer but yet retains both the functional aspects required from rigid plastic packaging. The present invention fulfills this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to tamper-evident solutions for rigid plastic food containers. In one embodiment, the mating surfaces of the lid and tray of the food container systems is sealed using radiation curing of light-sensitive adhesives, as well as one or more of pre-existing mechanical interference fit sealing methods. Tamper-evidence of rigid plastic packaging is achieved by irreversibly bonding the mating surfaces of the lid and tray of the container system and the use of perforated rows adjacent to the periphery of the lid. Once sealed, the tray and the lid cannot be separated without tearing the material. In order to ingress the sealed container, the consumer will need to tear the lid along the perforated rows. It is not possible for undisclosed ingress to occur since such tampering would be clearly visible without visual aid. An improved tamper-evident product packaging as compared with existing rigid plastic containerization systems results. 
     In another embodiment, additional mechanical interference retaining mechanisms that further mate the lid and tray is added. One or more may be commonly used but highly effective snap-fit grip mechanisms. 
     The bonding of the lid to the tray of the container system is an important element of this invention. Once bonded at the mating surfaces of the lid/tray interface, the two parts cannot be separated without damaging the container. In one embodiment, the method of bonding of the lid and tray mating surfaces is selected from the group consisting of radiation light curing of adhesives including ultraviolet (UV) light and infrared (IR) light, ultrasonic (US) welding, radio frequency (RF) welding, and any combination thereof. In one embodiment, UV light is used to initiate the curing of photo-initiators and/or photosensitizes in the adhesive. The photo-initiators that, when exposed to UV light create polymer chains that change the material from a liquid to a solid. In another embodiment, IR light-sensitive adhesives are used for the curing process. As with UV light curing, the benefits of using IR are low space requirements and costs, rapid heating rate, as well as focused lighting to dry/cure only selected areas. There is a uniform drying of adhesive, without the risk of blisters. In one embodiment, UV or IR light-sensitive adhesive is pre-applied to the mating surfaces to be bonded of the lid and/or tray prior to shipping the food containers to the food processors. This is possible since UV or IR light-sensitive adhesives will not cure for a substantial period of time without exposure to light. At the food processor facility, the final food product can be placed into the tray prior to closing and then conveyed into the light chamber for sealing. 
     In another embodiment, a lifting tab that is a part of the lid is located at one end of the lid of the food container and facilitates the tearing of the lid at the perforations. The lifting tab may optionally include a discrete snap-fit grip to allow the lid to be further releasably lockable to the tray. The invention can include various types of opening tabs or tamper-evident seals either at the corner or on any side of polygonal container. 
     In another embodiment, a continuous interlocking snap-fit grip retaining mechanism along the periphery of the lid and tray provides the consumer the ability to close and re-opening the package, and further provide a leak resistant groove to accommodate semi-liquid products (i.e. fruits juices, sauces). 
     One advantage of using radiation light curing is that the floor space needed to accommodate the requisite equipment is low, the power requirements are low and production speed may be enhanced through automation. 
     In one embodiment, bonding of the lid to the tray is achieved using RF welding. Sometimes referred to as Dielectric welding or High Frequency welding, RF welding may be used to fuse the lid and tray together by applying radio frequency energy to the area to be bonded. Only certain materials can be RF welded as it relies on certain properties of the material, e.g. thermoplastics, to cause the generation of heat in the alternating electromagnetic field. Normally applied between two metal bars, these bars may also act as pressure applicators over the lid and tray edges during the heating and cooling phases. The RF welding process may be used on a variety of materials including PVC and polyurethanes, nylon, PET, Ethyl Vinyl Acetate and some Acrylonitrile Butadiene Styrene resins. 
     In another embodiment, bonding is achieved using ultrasonic vibratory energy welding. In this approach, the mating surfaces at the lid and tray edges of the food container system are melted by the vibrating ultrasonic tool. When the tool is removed, the material solidifies and a weld is achieved. The resultant bond is therefore irreversibly bonded with a strength that approaches that of the parent material. The advantage of ultrasonic and RF welding over other bonding methods described here are that they utilize no consumables in their processes. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is an isometric view of the container system that shows one embodiment of the invention. 
         FIG. 1A  is an enlarged view of the corner of the lid of the container system in  FIG. 1 . 
         FIG. 2  is a plan view of another embodiment of the invention. 
         FIG. 3  is a side view of the cross-section taken substantially along the line X-X of the container system in  FIG. 2 . 
         FIG. 4  is an enlarged view of the lift tab and releasably lockable snap-fit grip of the container system in  FIG. 3 . 
         FIG. 5  is an enlarged side view of the cross-section taken substantially along the line Y-Y of the container system in  FIG. 2 . 
         FIG. 6  is an isometric view of the container system of  FIG. 1  but showing the lid torn at the rows of perforations in order to open the food container. 
         FIG. 7  is a plan view of the hinge portion of an embodiment of the invention similar to that in  FIG. 2  but with the row of perforations in the lid extending to the edge of the lid and the absence of any bonding at the hinge side of the container. 
         FIG. 8  is an isometric view of an embodiment of the invention showing the hinge portion illustrated in  FIG. 7  and the annular releasably lockable snap-fit mechanisms of the container system. 
         FIG. 9  illustrates is the container system of  FIG. 8  but with the mating surfaces of the lid and tray engaged. 
         FIG. 10  is an enlarged view of the cross-section taken in substantially along the line XX-XX of the container system in  FIG. 9 . 
         FIG. 11  is an enlarged view of the cross-section taken in substantially along the line Z-Z of the container system in  FIG. 9 . 
         FIG. 12  is a perspective view of another embodiment of the invention. 
         FIG. 13  is a perspective view of another embodiment of the invention 
         FIG. 14  is a perspective view of another embodiment of the invention. 
         FIG. 15  is side cross-section view of the container system illustrating how the food containers may be stacked. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following descriptions of the preferred embodiments are merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Turning now in detail to  FIGS. 1 ,  3 ,  4  and  5 , therein illustrated is a single rigid polymer plastic construct food container system  10  that includes a lid  12  and a tray  14  that are flexibly connected together at a hinge  16  at which the lid  12  may rotate relative to the tray  14 . When shut, the container system will enclose food contents placed in the tray.  14 . Sealing of the contents would be achieved by bonding the lid  12  to the tray  14  at outer periphery faying surfaces  20 ,  22  between points  21  to  23  and  17  to  19  respectively to form a bonded regions  33 ,  33 ′. Such bonding may achieved by a variety of methods including, but not necessarily limited to, radiation light-based curing, ultrasonic welding or radio frequency welding. 
     As illustrated in  FIGS. 4 and 5 , as well as in  FIGS. 10 and 11 , the lid  12  is further defined by an inner periphery that is a raised channel  13  into which a complementary raised edge  15  of the tray fits into thereby forming a dovetail interlocking joint and releasably fastening the lid  12  and the tray  14 . Fastening of the lid  12  to the tray  14  is achieved by virtue of a squeeze fit between the raised channel  13  of the lid  12  and the complementary mating raised edge  15  of the tray  14 . The lid  12  is further held in place by a reversibly lockable discrete snap-fit grip  26  that is adjacent to a lift tab  24  that is a contiguous element of the lid edge  20  except that it is marginally extended to facilitate easy grasping by thumb and fingers. The reversibly lockable discrete snap-fit grip  26  and lift tab  24  is generally placed at a distal end from the hinge  16  to provide leverage in raising and pivoting the lid  12  around the axis of the hinge  16 . As depicted in  FIGS. 1 ,  1 A,  2 ,  6 ,  7 ,  8 ,  9 ,  12 ,  13  and  14 , the lid  12  includes perforations  28  that are located at an intermediate periphery of the lid  12  from the inner periphery of the lid  12  as defined by squeeze fit raised edge and groove  13 ,  15  of the lid  12  and tray  12  respectively. As depicted in  FIGS. 1 and 2 , the line of perforations  28  are discontinuous beginning at point  17 ,  21  of the lift tab  24  and extending only along the intermediate periphery of the lid  12  terminating at points  19 ,  23  distal from the location of the lift tab  24 . It is intended that ingress of the container will be achieved through raising of the lid by lifting the lift tab  24  and tearing along the perforations  28  and rotating the lid  12  around the axis of the hinge  16 . Turning to  FIG. 2 , therein is illustrated an embodiment that after tearing at the perforations  28  to release the lid  12 , the detached portion of the lid  12  can pivot along an edge defined by the fold line  25  approximately connecting the points  19  and  23 . In the one embodiments illustrated in  FIGS. 1 ,  6 ,  7 ,  8  and  11 , the fold line  25  is the hinge  16 . It is an intent of this invention that once the broken interconnect between the perforations  28  is torn, it would not be possible for the broken interconnect to be reconnected again; additionally, and as importantly, such tearing, however, minimal will be visible to the naked eye or touch. It is anticipated that the consumer will be provided added assurance that the food product purchased is unlikely to have been tampered with. 
       FIG. 1  illustrates a food container systems constructed from a single piece of rigid plastic, however, other embodiments of the invention may include a lid  12  and a tray  14  that are of a two-piece construction. Additionally,  FIGS. 1 ,  2 ,  6 ,  7  and  8  illustrate a food container system of the present invention wherein the shape of the food container is rectangular when viewed from above. This is merely exemplary and not a limitation of the present invention. As illustrated by  FIGS. 12 ,  13  and  14 , the food container system may take the form of a large variety of shapes. 
     In the embodiment illustrated in  FIG. 1 , the location of the lift tab  24  and corresponding discrete snap-fit grip  26  are positioned directly across from the hinge  16  of the food container system  10  to facilitate lifting and tearing of the lid  12 . Location of the lift tab  24  and corresponding discrete snap-fit grip  26  need only be at a convenient distal location from the hinge. The embodiment in  FIG. 12  shows the lift tab  24  and discrete snap-fit grips  26  positioned at the corner of the lid  12 .  FIG. 6  illustrates the food container system of  FIG. 1  but with the lid  12  torn along the perforations  28  and pivoted around the hinge  16 . 
     The figures illustrate packaging concepts made from plastic, which is made up principally of a binder together with plasticizers, fillers, pigments, and other additives. There is significant literature on the chemistry and manufacturing processes, as well as applications related to plastics. For the purposes of this invention, plastic trays and matching lids have been available in a variety of designs and has found applications in numerous markets from food and general purpose industrial product to retail products because of its versatility in material characteristics allowing the plastic designer to affect its strength, imperviousness, flexibility, robustness, mold-ability and clarity, among other things. 
       FIGS. 8 ,  9  and  10  show embodiments of invention that include a continuous snap-fit grip  27  along a periphery of the lid  12  and tray  14 . In this embodiment shown, the lid  12  has a continuous raised rib  30  that opposes a matching groove  32  located in the sidewall of the tray  14 . By depressing the lid  12  into the tray  14  and engaging the raised rib  30  into the matching groove  32 , the snap-fit grip effectively provides a leak-proof seal that allows the consumer to open, close and releasably lock the container system  10  multiple times. Some of the advantages of this aspect of the invention are that food freshness can be extended then would otherwise occur without sealing and spillage of the food content is prevented. 
     Bonding of the lid to the tray to the lid may be achieved by a variety of methods, including radiation light sensitive curing such as with ultraviolet (UV) and infrared (IR) light and/or either ultrasonic welding and radio frequency (RF) welding. For radiation light curing, the adhesive can be disposed at any suitable time during the manufacturing process. The adhesive is disposed on one or both of the faying surfaces  20 ,  22  of the lid  12  and tray  14 , and except for the lift tab region, it can be disposed over part or all of the area of the bonding region  33 . In the embodiment illustrated in  FIG. 2 , bonding of the lid  12  and tray  14  includes the entire length of the hinge  16  whereas in the embodiment illustrated in  FIG. 1  and other illustrations, the bonding does not extend the length of the hinge  16  but ends at points  19 ,  23  as previously described. 
     Snap-fit grips as referred to in the above embodiments are a well-known, common assembly method for rigid polymer molded parts, and are not the subject of the invention. A snap-fit is a mechanical joint system where part-to-part attachment is accomplished with locking features (constraint features) that are homogenous with one or the other of the components being joined. Joining requires the flexible, locking features  30 ,  32  to move aside for engagement with its the mating part, followed by return of the locking features  30 ,  32  toward their original positions to accomplish the interference fit required to latch the lid  12  and tray  14  together. The illustrations contained in the  FIGS. 8 ,  9  and  10  show that the snap-fits are molded into the lid  12  and the tray  14 . Since the material of construction of the food container is a rigid polymer, the lid  12  and tray  14  can be assembled, disassembled and reassembled many times over without a decline in reliability. However; in order to enable a quality snap-fit, a high degree of precision is needed to ensure that the force-fitting of the male rib  30  to female groove  32  of the snap-fit is true. The combination of bonding at the faying surfaces  20 ,  22  and snap-fit grips  27  serve to prevent contaminants such as moisture, debris, and other substances from entering the food container system. For the embodiments described, the snap-fit grip joint is meant to be easily detachable as opposed to being made to be inseparable. 
     Turning finally to  FIG. 15 , the sidewall  34  of the tray  14  of the food container system can be either tapered or formed in such a way as to fit snugly into a shallow recess of the lid  12 . In this way food processors are able to stack the food containers and maximize the use of valuable, limited space for both storage and transportation purposes. The same benefit is afforded the retailer whose need to advertise by affixing labels of the product content to the side wall and/or top of the food container for viewing by the prospective consumer remain unaffected. 
     Although particular embodiments of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.