Patent Publication Number: US-2009218347-A1

Title: Releasable locking mechanism for packaging articles

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/029,901, filed Feb. 19, 2008, which is incorporated herein by reference. 
    
    
     FIELD 
     The invention generally relates to a novel packaging article. 
     BACKGROUND 
     Various types of rigid and semi-rigid containers are used to package food items and non-food items, such as medical supplies and devices. In general, these containers provide at least one shaped cavity defined by a base and a cover within which a product is supported and may be protected against environmental contamination when the container is sealed. 
     Such containers are often subject to treatments under various temperatures, such as, heating in a microwave or storing in a refrigerator. It is not uncommon for a food container to be subject to microwave heating immediately after it is taken out of a refrigerator. Such treatments could mechanically damage the structure of the container and affect its functionality (e.g., the function of providing proper sealing to the food in the container). For example, when the cover and the base of the container have different thermal expansion coefficients, when heated, the cover and the base expend or grow at different rates. Thus, the expansion of the one with larger thermal expansion coefficient may cause mechanical stress to the one with smaller thermal expansion coefficient. 
     In addition, under various circumstances, end user may prefer clear, transparent, or semi-transparent covers for containers, such as, clear covers made from regular plastics which do not degrade or bioplastics which do degrade. In most cases, a change in the moisture content of the environment does not change the size and/or the shape of these lids. However, some widely-used packaging systems have bases, such as, container bases which contain a high percentage of starch and pulp molded containers, which tend to grow and shrink in size based on the moisture content. These containers may be affected by the moisture content or temperature variation of the environment. Thus, current available packaging systems, which are not designed to allow or compensate for the growth/shrinkage differences between the lids and the bases, tend to have difficulty to provide sufficient sealing for their content. 
     Therefore, there is a need in the art for novel packaging articles where the change of temperature and/or moisture does not substantially affect their functionality and/or structural integrity. 
     SUMMARY 
     One embodiment of the present invention provides a packaging article, which includes a cover comprising a first structure and a base comprising a second structure, wherein connecting the first structure and the second structure causes the cover and the base to form an assembled packaging article, wherein the first structure and the second structure are not localized on the edge of the cover and the base, respectively. In said embodiment, the first structure may be a protrusion and the second structure may be a receptacle cavity. In another embodiment, the first structure may be a receptacle cavity and the second structure may be a protrusion. In yet another embodiment, at least one of the first structure and the second structure may comprise a locking structure (e.g., without limitation, a snap or snap fit structure). In some embodiments the locking structure can be releasable. 
     In addition, the cover and the base may have different thermal expansion coefficients such that, when subject to heating (e.g., microwave heating) or cooling (e.g., refrigerated storage), the cover and the base do not expand or shrink to the same degree. In one embodiment, the cover may have a smaller thermal expansion coefficient than that of the base. 
     Furthermore, the cover and the base may expand and/or shrink differently with a change of the moisture content and/or a change of moisture content in the environment. 
     Also provided is a packaging article having a cover and/or a base, which may comprise a biodegradable or edible material, such as, without limitation, starch, and/or pulp. 
     Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating the preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       FIGURES 
         FIG. 1  shows three perspective views of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 2  shows a perspective view of the base of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 3  shows the cover and the base of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 4  shows the packaging article of  FIG. 3 , indicating the snap on the cover and the matching hole on the base of the packaging article. 
         FIG. 5  shows the cover and the base of a representative packaging article having two snaps and two holes, respectively, in accordance with embodiments of the present invention. 
         FIG. 6  shows the base of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 7  shows a representative assembled packaging article having a cover and a base in accordance with embodiments of the present invention. 
         FIG. 8  shows a cross-section view of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 9  shows the cover of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 10  shows the snap on the cover of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 11  shows a representative packaging article having double snaps and double holes in accordance with embodiments of the present invention. 
         FIG. 12  shows a perspective view of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 13  shows a cross-section view of a representative packaging article having double snaps and double holes in accordance with embodiments of the present invention. 
         FIG. 14  shows the cover and the base of a representative packaging article in accordance with embodiments of the present invention. 
         FIG. 15  shows a cross-section view of the representative packaging article of  FIG. 14 . 
         FIG. 16  shows a cross-section view of the representative packaging article of  FIG. 14 . 
         FIG. 17  shows a perspective view of the representative packaging article of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     In order to fully understand the manner in which the above-recited details and other advantages and objects are obtained, a more detailed description will be rendered by reference to specific embodiments. 
     One embodiment of the present invention provides a packaging article, which includes a cover comprising a first structure and a base comprising a second structure, wherein connecting the first structure and the second structure causes the cover and the base to form an assembled packaging article, wherein the first structure and the second structure are not localized on the edge of the cover and the base, respectively. 
       FIGS. 1-17  depict a number of exemplary packaging articles that may be formed according to the present invention. The exemplary packaging articles have regular, symmetrical shapes and configurations. However, it should be understood that other shapes and configurations are contemplated by the present invention. Examples of other shapes encompassed hereby include, but are not limited to, polygons, circles, ovals, cylinders, prisms, spheres, polyhedrons, ellipsoids, and any other shape that may be formed into a three-dimensional package, e.g., for receiving a food item therein. The shape of the package may be determined by the shape of the product intended for use therewith, and it should be understood that different packages are contemplated for different products. 
     According to one embodiment of the present invention as shown in  FIG. 1 , the packaging article comprises a cover  10  and a base  20 . The cover  10  has a first structure  30 , a snap protrusion, which further comprises a locking structure  50 . The base  20  has a second structure  40 , a receptacle cavity, for receiving the snap protrusion. Both the first structure  10  and the second structure  20  are located in the inner section of the cover and the base, respectively. 
     The term “located in the inner section” or “in the inner section” as used herein refers to localizing a structure to a position on the cover or the base other than the edge thereof. In one embodiment, the first structure  10  and the second structure  20  are both localized in the center of the cover and the base, respectively. In another embodiment, first structure  10  and the second structure  20  may be located in a non-center, inner section of the cover or the base of the packaging article of the present invention. 
     In other embodiments of the present invention, the first structure may be a protrusion and the second structure may be a receptacle cavity. In other embodiments, the first structure may be a receptacle cavity and the second structure may be a protrusion. In yet additional embodiments, both the first and the second structures may be protrusions (e.g., protrusions with interactive locking features). 
     When functionally connected, the first structure and the second structure hold the cover and the base together to form an assembled packaging article and prevent the separation of the cover and the base during ordinary handling or processing of the packaging article. To secure the mechanical connection, in one embodiment, at least one of the first structure and the second structure may comprise a locking structure (e.g., without limitation, a snap or snap fit). Locking or interlocking structures suitable for the purposes of the present invention may include, but is not limited to, annular, cantilever, and torsion snap fits. 
     The cover and the base may be made of any materials suitable for the purposes of the packaging article. Examples of suitable materials include, without limitations, starch, paper, natural fibrous materials, a homopolymer or copolymer of polyethylene (PE), polypropylene (PP), polyester, polystyrene (PS), polyvinylchloride (PVC), polycarbonate (PC), polyamide, nylon, ethylene/vinyl alcohol copolymer, such as, high-density polyethylene (HDPE), cyclic olefin copolymer (COC), polyethylene terephthalate (PET), amorphous polyethylene terephthalate (APET), glycol-modified polyethylene terephthalate (PETG), polylactic acid (PLA), polystyrene (PS), high-impact polystyrene (HIPS), polyvinylchloride (PVC), polycarbonate (PC), or mixtures thereof. 
     Sources of starch may include, but are not limited to, plant sources such as tubers, roots, seeds, and/or fruits of plants, and specific plants sources may include corn, potato, tapioca, rice, or wheat or similar, or animal sources, namely glycogen. In some embodiments, starch is a combination of both pregelatinized and uncooked or native starches. In some embodiments, the pregelatinized starch has a concentration in the range of about 0% to about 30% by weight of total starch in the formulation, and more preferably 3% to 20%, and most preferably 5% to 15%. Food-grade starches (pregelatinized or uncooked) that have been modified by cross-linking, stabilization, or addition of lipophilic functional groups may be included to increase resistance of the products to softening when exposed to aqueous foods. In some embodiments, the starch can be a water-resistant starch, and these starches can be a modified starch, an unmodified starch such high-amylose starch, or a combination thereof. In some embodiments, the starch component can include a high-amylose starch. For example, the starch component can comprise natural starch, pre-gelatinized starch, high-amylose starch, or a combination thereof. In some embodiments, a portion of the starch component can be comprised of one or more water-resistant starches. The water-resistant starches may either be standard starches that have been chemically modified to be water resistant, or high amylose starches that are water resistant in their native, unmodified state. In these embodiments, the water-resistant fraction of the starch component may consist of chemically modified water-resistant starch, naturally water resistant high amylose starch, or a combination thereof. Use of water-resistant starches as a portion of the starch component increases the moisture resistance of the finished products. 
     As used herein, the terms “polyamide” and “nylon” are used synonymously herein and refer to a homopolymer or copolymer having an amide linkage between monomer units which may be formed by any method known to those skilled in the art. The amide linkage can be represented by the general formula: [C(O)—R—C(O)—NH—R′—NH] n  where R and R′=the same or different alkyl (or aryl) group. Examples of nylon polymers include, but are not limited to, nylon 6 (polycaprolactam), nylon 11 (polyundecanolactam), nylon 12 (polyauryllactam), nylon 4,2 (polytetramethylene ethylenediamide), nylon 4,6 (polytetramethylene adipamide), nylon 6,6 (polyhexamethylene adipamide), nylon 6,9 (polyhexamethylene azelamide), nylon 6,10 (polyhexamethylene sebacamide), nylon 6,12 (polyhexamethylene dodecanediamide), nylon 7,7 (polyheptamethylene pimelamide), nylon 8,8 (polyoctamethylene suberamide), nylon 9,9 (polynonamethylene azelamide), nylon 10,9 (polydecamethylene azelamide), nylon 12,12 (polydodecamethylene dodecanediamide), and the like. Examples of nylon copolymers include, but are not limited to, nylon 6,6/6 copolymer (polyhexamethylene adipamide/caprolactam copolymer), nylon 6,6/9 copolymer (polyhexamethylene adipamide/azelaiamide copolymer), nylon 6/6,6 copolymer (polycaprolactam/hexamethylene adipamide copolymer), nylon 6,2/6,2 copolymer (polyhexamethylene ethylenediamide/hexamethylene ethylenediamide copolymer), nylon 6,6/6,9/6 copolymer (polyhexamethylene adipamide/hexamethylene azelaiamide/caprolactam copolymer), as well as other nylons which are not particularly delineated here. Exemplary of aromatic nylon polymers include, but are not limited to, nylon 4,1, nylon 6,1, nylon 6,6/61 copolymer, nylon 6,6/6T copolymer, nylon MXD6 (poly-m-xylylene adipamide), poly-p-xylylene adipamide, nylon 61/6T copolymer, nylon 6T/61 copolymer, nylon MXDI, nylon 6/MXDT/I copolymer, nylon 6T (polyhexamethylene terephthalamide), nylon 12T (polydodecamethylene terephthalamide), nylon 66T, nylon 6-3-T (poly(trimethyl hexamethylene terephthalamide). 
     As used herein, the phrase “ethylene/vinyl alcohol copolymer” (EVOH), refers to copolymers composed of repeating units of ethylene and vinyl alcohol. Ethylene/vinyl alcohol copolymers can be represented by the general formula: [(CH 2 —CH 2 ) m —(CH 2 —CH(OH))] n . Ethylene/vinyl alcohol copolymers may include saponified or hydrolyzed ethylene/vinyl acrylate copolymers, and refers to a vinyl alcohol copolymer having an ethylene comonomer, and prepared by, for example, hydrolysis of vinyl acrylate copolymers or by chemical reactions with vinyl alcohol. The degree of hydrolysis is preferably at least 50%, and more preferably, at least 85%. Non-limiting examples of ethylene/vinyl alcohol copolymers include the family of EVOH sold under the trademark SOARNOL™ from Nippon Gohsei, Tokyo, Japan. 
     As used herein, the term “polypropylene” refers to a homopolymer or copolymer having at least one propylene monomer linkage within the repeating backbone of the polymer. The propylene linkage can be represented by the general formula: [CH 2 —CH(CH 3 )] n . 
     As used herein, the term “polyester” refers to a homopolymer or copolymer having an ester linkage between monomer units which may be formed, for example, by condensation polymerization reactions between a dicarboxylic acid and a diol. The ester linkage can be represented by the general formula: [O—R—OC(O)—R′—C(O)] n  where R and R′=the same or different alkyl (or aryl) group and may be generally formed from the polymerization of dicarboxylic acid and diol monomers containing both carboxylic acid and hydroxyl moieties. The dicarboxylic acid may be linear or aliphatic, i.e., lactic acid, oxalic acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like; or may be aromatic or alkyl substituted aromatic, i.e., various isomers of phthalic acid, such as paraphthalic acid (or terephthalic acid), isophthalic acid and naphthalic acid. Specific examples a useful diol include, but not limited to, ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butane diol, neopentyl glycol, cyclohexane diol and the like. Suitable polyesters may include, a homopolymer or copolymer of alkyl-aromatic esters, such as, for example, but not limited to, polyethylene terephthalate (PET), amorphous polyethylene terephthalate (APET), crystalline polyethylene terephthalate (CPET), glycol-modified polyethylene terephthalate (PETG), and polybutylene terephthalate; copolymers of terephthalate and isophthalate, such as, for example, but not limited to, polyethylene terephthalate/isophthalate copolymer; and a homopolymer or copolymer of aliphatic esters such as, for example, polylactic acid (PLA) and polyhydroxyalkonates, such as, for example, but not limited to, polyhydroxypropionate, poly(3-hydroxybutyrate) (PH3B), poly(3-hydroxyvalerate) (PH3V), poly(4-hydroxybutyrate) (PH4B), poly(4-hydroxyvalerate) (PH4V), poly(5-hydroxyvalerate) (PH5V), poly(6-hydroxydodecanoate) (PH6D) and blends of any of these materials. 
     As used herein, the term “polystyrene” refers to a homopolymer or copolymer having at least one styrene monomer (benzene, i.e., C 6 H 5 , having an ethylene substituent) linkage within the repeating backbone of the polymer. The styrene linkage can be represented by the general formula: [CH 2 —CH 2 (C 6 H 5 )] n . Polystyrene may be formed by any method known to those skilled in the art. Suitable polystyrenes include, for example, but are not limited to, oriented polystyrene (OPS) film and resins, i.e., polystyrene (PS), syndiotactic polystyrene (SPS), acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), ethylene/styrene copolymers, styrene/acrylic copolymers, styrene block copolymers (SBC), and the like. Other non-limiting examples of polystyrene suitable for use in the present invention include high-impact polystyrene (HIPS). 
     As used herein, the term “polyethylene” refers to a homopolymer or copolymer having at least one ethylene monomer linkage within the repeating backbone of the polymer. The ethylene linkage can be represented by the general formula: [CH 2 —CH 2 ] n . Polyethylenes (PE) may be formed by any method known to those skilled in the art. Suitable polyethylenes may include, but is not limited to, high-density polyethylene (HDPE), ultra high-density polyethylene (UHDPE), and cyclic olefin copolymers (COC). Exemplary of commercially available cyclic olefin copolymers suitable for use in the present invention include, but are not limited to, the TOPAS™ family of resins which is supplied by Celanese-Ticona, Summit, N.J., U.S.A. 
     As used herein, the term “polyvinylchloride” refers to a homopolymer or copolymer having at least one vinyl chloride monomer linkage, i.e., ethylene moiety having a chlorine atom substituent on a carbon atom, within the repeating backbone of the polymer. Polyvinylchloride (PVC) can be represented by the general formula: [CH 2 —CH(Cl)] n . 
     As used herein, the term “polycarbonate” refers to a homopolymer or copolymer having at least one carbonate monomer linkage within the repeating backbone of the polymer. Polycarbonate (PC) can be represented by the general formula: [O—R—OC(O)] n . 
     The cover and the base may have different thermal expansion coefficients such that, when subject to heating (e.g., microwave heating) or cooling (e.g., refrigerated storage) or other environmental conditions, the cover and the base do not expand or shrink to the same degree. In one embodiment, the cover may have a smaller thermal expansion coefficient than that of the base. Due to the unique and advantageous configuration of the present invention, the differences in the degree of expansion or contraction may not substantially affect the functionality and/or structure integrity of the cover, the base, and/or the assembled packaging article. 
     Furthermore, the cover and the base may expand and/or shrink differently with a change of the moisture content and/or a change of moisture content in the environment. For instance, such covers may be clear, transparent, or semi-transparent covers, e.g., without limitations, clear covers made from regular plastics which do not degrade or bioplastics which do degrade (e.g., PLA), where the changes of the moisture content of the environment generally do not cause significant changes in the size and/or the shape of these covers; while the bases may be bases containing a high percentage of starch and/or pulp, which tend to grow and shrink in size based on the moisture content, which may be affected, e.g., by the moisture content of the environment. Therefore, the packaging article of the present invention provides better sealing to the content, at least partially due to the fact that it allows for the growth/shrinkage differences between the lids and the bases. 
     Packaging articles with enhanced moisture resistance can be provided by coating the article with a moisture resistant coating. Where long term storage of food products requires a sealed moisture and oxygen barrier, conventional coated paper or plastic film materials may be used for barrier materials, with a rigid biodegradable insert acting to hold and protect the food items. 
     A formulation according to the present invention from which the packaging items (containers, plates, trays, bowls, cones, and cups, as well as other novel shapes) can be produced is provided, comprising water; starch; and optionally natural fibrous materials, proteins, natural polymeric compounds, and wax or wax emulsions. 
     Proteins and natural polymeric compounds may include, but are not limited to preparations made from casein, soy protein isolate or concentrate, or similar such preparations. One such preparation can be prepared in the following three steps: 1) cooking a solution of casein or soy protein isolate in water (about 10% by weight) as per usual manufacturer&#39;s recommendations (generally, hydrating the protein by soaking, then gradually raising the temperature and pH of the solution to 180° F. and pH=9 to 9.5, then holding the solution at 180° F. for 15 minutes); 2) cooling the preparation to room temperature; and optionally, 3) adding a preservative and blending thoroughly. The preferred concentration of preservative in the preparation is about 0.1% or less, depending on the shelf life required for the protein solution, the concentration of protein required in the final product, and the limits imposed by government regulations on the dosages of preservative compounds in edible materials. 
     Other proteins may also be used in combination with the casein or soy protein preparation or separately to improve the water-resistant properties of the containers. For example, such proteins may include albumen, gelatin, or the like. 
     Several natural fibrous materials may be used in combination both as structural elements (at several size scales) in the baked items and or as inexpensive organic fillers. Fiber elements are used both to control the molding characteristics of the wet batter and to enhance the structural stability of the finished food service articles. Although there is a continuum of fiber lengths and fiber aspect ratios used in the formulation, the fibrous portion of the formulation can be in a general sense separated into three classes (based on fiber length) that serve different functions. Long or very long (4 to 25 mm or longer) fibers or composite fiber elements are used to form a meshwork that helps prevent defects from forming in the batter as it expands in the mold. Medium-length fibers (0.5 to 5 mm) also help control the flow characteristics of the wet batter, and serve to increase the toughness of the finished food service articles, preventing fracture during handling and during normal use. Short fibers (&lt;0.5 mm) serve mainly as a means to introduce readily biodegradable material into the formulation, i.e., filler material that is more water-resistant than the starch-based matrix that contains them. 
     Optionally, the shorter fibers may be used in conjunction with, or replaced by other filler materials imparting the same advantages as the shorter fibers. For example, such filler materials may include both organic and inorganic aggregates such as calcium carbonate, silica, calcium sulfate, calcium sulfate hydrate, magnesium silicate, micaceous minerals, clay minerals, titanium dioxide, talc, etc. The concentration of aggregate and/or short fibers may be in a range from about 0% to about 25% by dry weight of the formulation, in a range from about 2.5% to about 20% by total dry weight of the formulation, in a range from about 5% to about 15% dry weight of the formulation, in a range from about 5% to about 20% by total dry weight of the formulation, or in a range from about 7% to about 17% dry weight of the formulation. 
     The organic filler material may include ground walnut shells. Ground walnut shells results in fibrous matter comprising short fibers. The ground walnut shells may be used alone as the filler material or may be combined with other filler materials. When used alone the preferred concentration is about 8% by dry weight. 
     Fibers from several sources are typically included in the formulation. Relatively high quality fibers from grass or reed species provide the mid-length fibers that contribute most to the structural stability and resilience if the finished articles. The long to very long fibers or fiber composites may come from lightly processed agricultural byproducts, e.g., stalk or husk materials that have been chopped, ground, or milled to an appropriate size, or they can come from traditional sources of long cellulose fiber, e.g., cotton or cotton linters. Under appropriate processing conditions (e.g., hammer milling), these materials can also provide a considerable amount of the very short fiber that serves to replace starch and add water resistance to the finished article. Fibrous material in the form of ground nut shells (or other very hard, lignin-rich plant materials) may also serve as organic, relatively water resistant, biodegradable fibers that replace conventional filler materials. 
     Moreover, these other sources of fiber suitable as structural elements in starch-based food service articles are readily available. Some of these are from fast-growing plants that can be broadly characterized as grasses or reeds, such as kenaf and bamboo, which provide fiber with smaller associated environmental costs than taking fiber from trees. A growing segment of the fiber industry is based on the use of fiber from these plants. In many cases the quality and consistency of fibers taken from these plants (after processing) is as good as that provided by the wood pulp industry. In addition, fiber is also widely available as a by-product of agricultural production. Stalks, stems, and husks from cereal grains, for example, are a ready source of fibrous material that, while not as high in quality as the fiber taken from wood or the better grass species, is extremely cheap and, as a by-product, has essentially no additional environmental cost (beyond whatever environmental costs are associated with the production of the main crop). 
     The fibrous materials included in the formulations described here vary greatly in both fiber length and fiber aspect ratio. Overall, however, it is preferred that the materials have an average fiber length that is less than about 2 mm and an average aspect ratio that is in the range of about 5:1 to 25:1. 
     The preferred wax or wax emulsions in the formulation, used to increase water-resistance, is a stable aqueous emulsion usually made of carnauba, candelilla, rice bran, paraffin, or any other food-grade wax: vegetable waxes are preferred over animal and mineral waxes, and natural waxes are preferred over synthetic varieties. The wax type is selected based on the particular application and desired properties of the final product. The emulsion is usually prepared by means of emulsifying agents and mechanical agitation. Examples of wax emulsions suitable for use in the present formulation include emulsified carnauba wax and emulsified candelilla wax. Emulsifiers include all of those permitted for food applications, including (but not limited to) sorbitan monostearate, Polysorbate 60, Polysorbate 65, Polysorbate 80, food-grade gums (e.g., arabinogalactan, carrageenan, furcelleran, xanthan), stearyl monoglyceridyl citrate, succistearin, hydroxylated lecithin, and many other compounds. In the alternative to wax, one may use an additive component or emulsion thereof in an amount ranging from about 0.5% to about 10% on a dry weight basis. The additive component can comprise an epoxidized vegetable oil, a hydrogenated triglyceride, poly(vinyl acetate), poly(vinylacetate-ethylene) copolymer, poly(ethylene-vinyl acetate) copolymer, or a combination thereof. 
       FIG. 2  depicts an exemplary base  20  in accordance with one embodiment of the present invention. A hole  40  is localized in the center of the base  20 . 
       FIGS. 3 and 4  depict an exemplary packaging article having a cover  10  and a base  20 . In addition,  FIG. 4  shows that, when assembling the cover  10  and the base  20 , protrusion  30  should be connected with the hole  40 . 
       FIG. 5  shows an exemplary packaging article having double protrusions  31  and  32  and double holes  41  and  42 . 
       FIGS. 6-17  further depict a number of exemplary packaging articles that may be formed in accordance to various embodiments of the present invention. 
     Although the invention has been described with respect to specific embodiments and examples, it will be readily appreciated by those skilled in the art that modifications and adaptations of the invention are possible without deviation from the spirit and scope of the invention. Accordingly, the scope of the present invention is limited only by the following claims.