Abstract:
A reclosable blister container in which a backing card is slidably and removably retained in the blister without requiring staples or adhesives. The blister includes elongated grooves on opposite sides thereof that slidingly receive the backing card. The blister includes a step that is preferably curved, which facilitates slidable entry of the backing card into the blister. Protrusions may be formed in the blister that extend into corresponding openings in the backing card in order to further retain the backing card within the blister. The present invention provides a more attractive and more economical alternative to prior art “flange-folded” products.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to packaging and more specifically to thermoformed reclosable blister packs. 
     BACKGROUND 
     Clear plastic display packages are commonly used in retail sales environments where it is desired to present merchandise for visual inspection by the customer. Blister packages feature a transparent bubble, typically produced through a thermoforming process, which is sealed to a backing card. One conventional method of attaching the card is to place a heat-activated adhesive on it and heat the card to adhere the flanges of the thermoformed bubble thereto. Display packages with blisters adhered to paperboard backing cards are effective in showcasing the merchandise. Undesirably, however, adhesive backed cards are expensive and require an additional process step, viz., heating, to seal the package. Furthermore, once opened, these packages cannot be easily reclosed because the backing card is typically ripped apart and destroyed during opening. 
     Thermoformed plastic packages having integrally hinged covers with positive snap locking mechanisms are also known in the art and are commonly referred to as “clam-shells.” These packages provide an attractive and functional container, but can require high initial tooling costs and high material costs not always justified by the product to be carried in the package. The tooling for these clam-shell designs also has size limitations in modern production equipment. Further, the clam-shell package requires a separate insert card to communicate the contents of the package. 
     Another popular and inexpensive blister-card design includes the blister having a flange around its periphery that folds unto itself, commonly referred by those skilled in the art as a “flange-fold.” The flange-fold, which is essentially a 180 degree fold, forms a groove or channel into which the backing card is slidably inserted. The backing card is then typically stapled to the blister to hold it in place, thereby eliminating the need for adhesives. This design has at least two drawbacks. First, the staple lends a cheap or chintzy appearance to the package which, undesirably, may also be imported to the contents. Further, forming the flange-fold requires an additional, time-consuming process step after thermoforming and requires an additional costly piece of equipment to perform the flange fold. 
     What is needed is an economical reclosable display package which uses cost-effective materials and an economy thereof, and whose manufacture can be performed cost-effectively. 
     SUMMARY OF THE INVENTION 
     The present invention is a reclosable blister container in which a backing card is slidably and removably retained in the blister without requiring staples or adhesives. The blister includes elongated grooves on opposite sides thereof that slidingly receive the backing card. The blister includes a step that is preferably curved, which facilitates slidable entry of the backing card into the blister. 
     In one form thereof, the present invention provides a reclosable container comprising a thermoplastic blister having a bubble defining a container cavity. A flange extends laterally from the bubble. A side wall extends upwardly from the flange. The side wall defines an elongated groove extending along at least one third of its length. A skirt extends laterally from the sidewall, the skirt defining a plane spaced from the flange. A backing card is slidably and removably received in the groove and abuts the flange. 
     In a preferred form, the flange comprises a step connecting it to the skirt, and the step is angled relative to the flange. With this arrangement, the step facilitates slidable receipt of the backing card into the blister. More preferably, the step is curved. 
     In a further preferred form, either the skirt or the flange, or both, include a protrusion that mates with the backing card and retains the backing card in the blister. In a further preferred form, the protrusion fits into a complementary opening in the backing card. In another preferred form, the protrusion extends from the skirt and projects over the step such that an edge of the backing card fits under the protrusion and is held against the step. 
     The reclosable container is preferably and conveniently integrally formed as one piece. 
     In another form thereof, the present invention provides a reclosable container comprising a thermoplastic blister having a bubble defining a container cavity. A flange extends laterally from the bubble and a side wall extends upwardly from the flange. The side wall defines a groove at a lower end thereof, and a backing card is slidably and removably retained in the groove and abuts the flange. The flange is curved upwardly at an end thereof, which facilitates slidable receipt of the backing card into the blister. 
     In a preferred form thereof, the groove extends continuously along at least one third of the length of the side wall. More preferably, the blister is integrally formed in one piece. 
     One advantage of the present invention is that it eliminates the costly adhesive-backed cards employed in prior art containers and it also avoids the concomitant process steps of heating the card and adhering it to the blister. Instead, with containers embodying the present invention, the card is simply fed into the blister and is retained by the blister alone. With the present invention, no staples, glue, adhesives, tape or any other tools are necessary to secure the backing card to the blister. 
     Another advantage of the present invention is that containers embodying it can be opened and closed as many times as desired without destroying the container. To open the container, the backing card is simply pried away from the blister and slid therefrom. The container can be easily re-closed by reinserting the card and sliding it back into the blister. 
     Yet another advantage of the present invention is that it avoids the time-consuming and costly process step of “flange-folding” the blister. The present invention also obviates the costly piece of equipment whose sole purpose is to flange-fold the blisters. Further, the present invention eliminates the unsightly staple and process step to install it which is typically associated with flange-folded blisters. Indeed, the present invention fulfills a long-felt need for an inexpensive replacement to the flange-folded blister design. 
     Still another advantage of the present invention is that it provides a reasonable alternative for clam-shell containers. As mentioned above, clam-shell type containers provide an attractive and functional reclosable container, but their high cost is not always justified by the cost of the product being packaged therein. Flange-folded containers, on the other hand, are often not perceived in the industry as a suitable replacement for clam-shells because the poor quality perceived by the consumer of the flange-folded container can be transferred to the product, thereby negatively affecting sales. Of course, with any product, the packaging effects the perceived quality of the product. Because containers in accordance with the present invention provide a high quality appearance, they offer a plausible alternative to costly clam-shells for many packaging applications. 
     Amazingly, containers made in accordance with the present invention not only provide a more attractive package than one which is flange-folded, but they also provide a significant cost savings over a flange-folded product. Specifically, it is estimated that a container made in accordance with the present invention would cost approximately 25% less than its flange-folded counterpart. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The above-mentioned and other advantages of the present invention, and the manner of obtaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a reclosable container in accordance with the principles of the present invention, illustrating the backing card separated from the blister; 
     FIG. 2 is a sectional perspective of the container illustrated in FIG. 1; 
     FIGS. 3 a - 3   j  are fragmentary sectional views of various embodiments of the side wall, flange and groove of blisters in accordance with the present invention. 
     FIGS. 4 a - 4   e  are fragmentary perspective views of alternate embodiments of blister containers in accordance with the present invention, illustrating various configurations of protrusions which engage and retain the backing card; 
     FIGS. 5 a - 5   c  are schematic side views illustrating alternate embodiments of a step which facilitates installation of the backing card into the blister; and 
     FIG. 6 is a perspective view of a container in accordance with an alternate embodiment of the present invention. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. 
     DETAILED DESCRIPTION 
     The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention. 
     Referring now to FIG. 1, container  20  includes thermoformed blister  22  and a paper board backing card  24 . One suitable backing card  24  would be a 21 point blister card with an optional heat activated adhesive. Backing card  24  may be formed of any stiff single or multi-ply paper or other suitable material and may be printed on one or both sides. Blister  22  is integrally formed in a single piece from 0.020 inch stock polyvinyl chloride (PVC) stock sheets, commercially available from Klockner Co. and American Mirrex Co. Blister  22  can be formed by a conventional thermoforming processes, wherein a thermoplastic sheet is heated and pulled down onto a mold surface to be shaped into blister  22  as shown 
     As shown in FIG. 1, blister  22  includes bubble  26  which defines a container cavity into which the product to be displayed and sold is placed. A flange  28  extends laterally away from the bottom (or top, depending on how the package is viewed) of bubble  26 . Flange  28  is substantially planar, with the exception of one of its ends which curves upwardly, as described in more detail below. Along three sides of flange  28 , sidewall  34  extends upwardly, generally orthogonally from the major plane defined by flange  28 . Along the periphery of the top of sidewall  34 , skirt  32  extends laterally outwardly and generally defines the outer confines of container  20 . Skirt  32  defines a plane that is spaced from the plane defined by flange  28  and is substantially parallel thereto. 
     As just alluded to, on one of the four sides of blister  22 , curved portion  30  integrally connects flange  28  to skirt  32 . Curved portion  30  facilitates slidable receipt of backing card  24  into blister  22  and also facilitates nesting of multiple blisters  22 . Further, curved portion  30  facilitates thermoforming blister  22 , in that the curved portion eliminates the gap between the plastic and the mold when hang tab  54  is being punched, which thereby eliminates undesirable whitening or bulging of the blister. Curved portion  30  also allows the blisters to be more easily pulled from the mold. 
     To close container  20 , edge  36  of backing card  24  is placed against curved portion  30  and slid therealong until edge  36  fits into grooves  38  that are disposed on opposite of the longer sides of blister  22 . Grooves  38  slidingly receive backing card  24  and retain same in an abutting relationship against flange  28  of blister  22 . As also shown in FIG. 1, edge  36  is received in optional groove  42  disposed at end  40  of blister  22  and retained against flange  28  when backing card  24  is fully inserted into blister  22 . Groove  42  is formed in the same shape and configuration as grooves  38 . To further aid retention of backing card  24  in blister  22 , protrusion  44  is received into complementary opening  46  formed in backing card  24  Protrusions  48  formed in skirt  32  abut against edge  50  of backing card  24  when fully inserted into blister  22  to also help retain backing card  24  in blister  22 . Backing card  24  is removably retained by blister  22 . To remove the backing card, one or more fingers or fingernails are used to pull upward on edge  50  of card  24 . Once edge  50  is pulled sufficiently away from the blister, it can be easily slid from the blister to allow access to the contents. 
     Matching hang tabs  54  and  56  in blister  22  and card  24 , respectively, allow the closed container  20  to be hung from a display hanger (not shown), which usually takes the form of a thin metal rod extending from the display and having its end bent upwardly, as is widely known in the art. Typically, many containers of an identical item are hung from the same rod such that the consumer takes as many containers as needed, the remainder being left for future customers. 
     Turning now to FIG. 2, the further details of grooves  38  can be appreciated. As shown, sidewall  34  forms a bulge  52  along a portion thereof. Vertical portion  35  of sidewall  34  serves to space bulge  52  away from flange  28  sufficiently such that backing card  24  is slidably retained therebetween. Bulge  52  extends inwardly toward bubble  26  and projects over flange  28  as shown in FIG.  2 . Preferably, bulge  52  has a semicircular shape shown in FIG.  2  and shown more closely in FIG. 3 a . However, bulge  52  can take any of a variety of shapes such as shown in FIGS. 3 b - 3   j.    
     Referring now to FIGS. 2 and 3 a , it can be appreciated that bulge  52  and the portion of flange  28  which bulge  52  projects over form groove  38  therebetween. Groove  38  is preferably formed continuously along side wall  34  for at least one-third of the total length of side wall  34 , more preferably at least one-half of the total length of side wall  34 . It has been found that the integrity of the fit and retention of card  24  in blister  22  is improved with increased continuous length of groove  38 , as one of ordinary skill in the art might expect. However, forming a long groove  38  presents problems in the molding process because the blister has an increased propensity to stick to the mold as the length of groove  38  increases. To combat this problem, it has been found that the geometric configuration of bulge  52  and sidewall portion  35  inherently facilitates removal of the blister after molding. Indeed, one of the achievements of the present invention is the ability to form a long, continuous groove like groove  38  without the blister sticking to the mold and the part becoming damaged upon removal of the blister from the mold. While less preferable than a long, continuous groove, it is also possible to form a series of discrete bulges spaced along a portion of side wall  34  (not shown). Such a thermoformed product would be easier to mold. 
     It is to be understood that the specific dimensions of groove  38  could vary widely depending upon thickness, stiffness and other characteristics of backing card  24 , the type and thickness of the thermoformed plastic used for blister  22 , and the overall size of the container. Nonetheless, it has been found that for a 0.020 inch plastic blister  22  and a 21 point backing card  24 , specific dimensions for groove  38  having a semicircular bulge  52  have been proved satisfactory. For the preferred embodiment known at the time of this writing, as shown in FIG. 3 a , the Height, H of side wall  34  is preferably about 0.1875 inches. Height, h, of groove  38 , radius, R, of bulge  52  and depth, d, of groove  38  are all about 0.0625 inches in this preferred embodiment. Again, it cannot be overstated that these dimensions recited herein are merely descriptive of the preferred embodiment known at the time of this writing, and are in no way to be construed as limiting the invention defined by the appended claims. 
     Indeed, it is contemplated that many of the designs for side wall  34  depicted in FIGS. 3 b  through  3   j  would perform suitably. Two primary considerations factor into the design choice for side wall  34 —first, the extent and quality with which the backing card is releasably retained in the blister, and second, the ease with which the bulge/groove can be formed in the thermoforming process and the molded part easily removed. As shown in FIGS. 3 b - 3   j , the shape of the bulge/groove formed in side wall  34  can be polygonal (FIGS. 3 b ,  3   c  and  3   h ), square or rectangular (FIGS. 3 e  and  3   g ) or mostly round (FIGS. 3 a ,  3   f  and  3   j ). Further, the groove, itself, can be rounded (FIGS. 3 b ,  3   d ,  3   f , and  3   g ), pointed.(FIG. 3 c ) or rectangular (FIGS. 3 a ,  3   e ,  3   h , and  3   i ). Certain designs of the bulge and groove may result in the blister undesirably sticking to the mold. In such cases, one solution envisioned is a spring-loaded, pivotable mold which allows the part of the mold that forms the bulge  52  to pivot upwardly when removing the blister. Other modifications to the mold may also be made by one of ordinary skill. Or, as in the case of the presently preferred design shown in FIG. 3 a , the inherent configuration of semicircular bulge  52  and sidewall portion  35  inherently facilitates removal of the blister from the mold. It can now be readily appreciated by one of ordinary skill in the art, that while dimensions for a currently preferred embodiment have been recited herein, many other shapes, sizes and configurations of side wall  34 , which defines groove  38 , are possible. 
     Turning now to FIGS. 4 a - 4   e , alternate embodiments of the projections or protrusions that aid retention of the backing card are illustrated. As shown in FIG. 4 a , substantially rectangular protrusions  100  extend upwardly from skirt  32  and are formed with rectangular cut-out sections  102  which further define ledges  104  that project over curved portion  30  and sandwich the backing card (not shown in FIG. 4 a ) therebetween. Protrusions  100  represent the preferred embodiment. However, other configurations of the protrusions are possible. FIG. 4 b  illustrates substantially rectangular protrusions  106  that extend upwardly from skirt  32 . Protrusions  106  have a width that substantially coincides with the width of skirt  32 . As shown in FIG. 4 c , substantially rectangular protrusions  108  extend upwardly from skirt  32  and “hang over” curved portion  30  such that the backing card (not shown in FIG. 4 c ) is pinched between curved portion  30  and protrusions  108 . FIGS. 4 d  and  4   e  illustrate that the protrusions can be formed on curved portion  30  instead of skirt  32 . Substantially rectangular protrusions  110  extend from curved portion  30  shown in FIG. 4 d  whereas substantially cylindrical protrusions  112  extend from curved portion  30  shown in FIG. 4 e . In the alternate embodiments shown in FIGS. 4 d  and  4   e , the backing card would be formed with complementary openings to receive the respective protrusions. 
     While portion  30  which connects skirt  32  to flange  28  has been described hereinabove as being curved, other configurations are possible. More generally, embodiments incorporating the present invention will include a “step” connecting skirt  32  to flange  28  and which facilitates slidable engagement of the backing card into the blister. Advantageously, the step is angled relative to the flange as shown, which encourages the edge of the backing card to easily slide into the blister. Turning to FIG. 5 a , the step is formed as the preferred curved portion  30 . In FIG. 5 b , the step is shown as substantially flat ramp  114  and in FIG. 5 c , the step is formed as staircase  116 . These and many other embodiments are envisaged as possible for the step which connects skirt  32  to flange  28  and facilitates insertion of card  24 . 
     The blister depicted in FIG. 6 is similar to that depicted in FIG. 1, except FIG. 6 depicts an alternate embodiment of the protrusion  48  illustrated in FIG.  1 . With reference to FIG. 6, flange  28  includes two ramp-shaped protrusions  120  which fit through complementary shaped openings in backing card  24  (not shown in FIG. 6) and help retain backing card  24  in blister  22 . The ramp shape of protrusions  120  allows the backing card to slide into the blister without getting stuck against the protrusions, such that the end of the backing card need not be lifted upwardly in order to fully insert the card into the blister. 
     It can now be appreciated that the present invention provides a cost-effective reclosable container that addresses the high costs and disadvantages associated with prior art reclosable blister containers. 
     While a preferred embodiment incorporating the principles of the present invention has been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.