Patent Publication Number: US-6210038-B1

Title: Closure arrangement having a peelable seal indicator

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to closure arrangements for polymeric packages and, in particular, to a closure arrangement having a peelable seal. 
     BACKGROUND 
     In many consumer packaging applications, it is important to prevent air or water from passing out of or into a package containing certain products. This is particularly true with respect to meat packages, cheese packages, and the like, for which the contained product must be kept in a constant environment to prevent spoilage. In order to preserve the product contained within such a package, the periphery of the package must be hermetically sealed. Hermetic seals can be provided by both permanent seals and temporary seals, known as peelable seals. Peelable seals are usable to provide a hermetic seal and, at the same time, provide a consumer with access to the contents of the package. A consumer breaks a peelable seal of a package by first grabbing onto opposing film faces to which peelable seal materials are adhered and then pulling the film faces apart. 
     A common method of packaging foods, such as sliced luncheon meats and the like, is by use of horizontal form, fill, and seal procedures. These procedures involve shaping a portion of film (“form”), placing the food article inside or upon the formed film portion (“fill”), completing the closure of the film portion around the food article and “sealing” open edges to complete the packaging process. 
     In some implementations, one sealing station is used to seal all the edges of a package and, at the same time, make a peelable seal from a strip of peelable materials. The sealing station has a set of seal bars, protruding from a sealing head, that press the package edges in the peelable strip against a resilient backing, such as rubber, to form both the permanent edge seals and the peelable seal. The strength of the seals is determined by the temperature, pressure, size of the seals, and dwell time of the seal bars. 
     Many packaging applications use resealable containers to store various types of articles and materials. These packages may be used to store and ship food products, non-food consumer goods, printed matter, correspondence, medical supplies, waste materials, and many other articles. 
     Resealable packages are convenient in that they can be closed and resealed after the initial opening to preserve the enclosed contents. The need to locate a storage container for the unused portion of the products in the package is thus avoided. As such, providing products in resealable packages appreciably enhances the marketability of those products. 
     The “sealing” stage of the form, fill, and seal procedure often involves using a resealable closure mechanism. The resealable closure mechanism and peelable seal are often produced as separate items fiom the package and are attached to and made integral with the package at a later point in the manufacturing process by a heat and pressure sealing process. Each separate closure profile includes a base strip and an interlocking member. In some conventional implementations, the closure profiles are formed by two separate extrusions or through two separate openings of a common extrusion die. One closure profile may have a rib or male member and the other, a mating groove or female member. The male or female member extends from the front face of the base strip. The rib and groove form a pressure-fastenable and releasable closure mechanism. The back side, or sometimes an extended portion of the front face of the base strip, is sealed to the package film so that the closure mechanism is disposed between the package walls adjacent to the openable side of the package. In some implementations, the packages are made of polymeric materials, since these materials inhibit the migration of air and water from and into the package. The packages can be either flexible or rigid. 
     To provide a peelable seal on a package with a resealable closure mechanism, the package typically uses permanent seals at its side edges and bottom edge and a peelable seal above or below the resealable closure mechanism at the mouth end of the package. In addition, the peelable seal may be arranged on either the flange/base portions of the closure mechanism or on the packaging film adjacent to the flange portions. 
     There are a couple of common implementations for forming peelable seals on resealable packages having a top and bottom film. One implementation adheres a multi-layered film to each of the opposing inner surfaces of the packaging film along the length of the mouth end of the package. This results in a first multi-layered film on the inner surface of the top film and a second multi-layered film on the inner surface of the bottom film. A peelable seal is formed by heat-sealing the first and second multi-layered films to one another. When a consumer breaks the peelable seal, one or more layers of the second multi-layered film will disengage from the other layers of the second multi-layered film and remain adhered to the first multi-layered film. As a result, the first multi-layered film will include at least one additional layer when the peelable seal is broken. The above layer disengagement upon breaking the peelable seal is accomplished by using film layers composed of different polymeric materials and by exploiting the varying bond strengths between the layers. 
     Another implementation adheres a layer of film to each of the opposing inner surfaces of the packaging film and introduces contaminants to one or both of the film layers. When the peelable seal is formed by heat-sealing the layers to one another, the bond between them is weak due to the surface contamination. Breaking the peelable seal detaches the layers from one another. 
     In order to preserve the product contained within a package, it is important that the peelable seal provides a hermetic seal. Peelable seals are highly susceptible to small variations that might occur during manufacture; ie., the peelable seals have low manufacturing tolerances. Given these manufacturing variations, it is possible for a peelable seal to not be hermetically sealed. In the current manufacturing process, it is difficult for the manufacturer to know which peelable seals are hermetically sealed and which are not. Furthermore, one purpose of the peelable seal is to provide a tamper resistant package to the consumer. With current peelable seals, it is difficult for the consumer to detect if the package has been tampered. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, one example embodiment involves a closure arrangement for use with a polymeric package. The closure arrangement includes a first and second base strip. Each base strip has an inner and an outer surface. The outer surfaces are adapted for attachment to the polymeric package. The closure arrangement further includes a peelable seal. The peelable seal has a first and second layer for attachment to the first and second base strips. The peelable seal further has a third layer attached to the first layer, and a fourth layer attached to the second layer. The third and fourth layers have colored ribs. These ribs indicate to the manufacturer that a hermetic seal has not been achieved. 
     In another embodiment of the present invention, a closure arrangement includes a first and second base strip. Each base strip has an inner and an outer surface. The outer surfaces are adapted for attachment to the polymeric package. The closure arrangement further includes a peelable seal. The peelable seal has a first and second layer for attachment to the first and second base strips. The first and second layers also have a pattern printed on the them. These patterns indicate to the manufacturer that a hermetic seal has not yet been achieved. 
     According to another aspect of the present invention, a method of manufacturing a polymeric package is provided. The method includes placing a first film panel adjacent to a second film panel, sealing tree edges of the first film panel to three corresponding edges of the second film panel, placing a peelable seal between a fourth edge of the first film panel and a corresponding fourth edge of the second film panel, and heat sealing the peelable seal to both the first film panel and the second film panel while simultaneously fusing the peelable seal. 
     The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description that follow more particularly exemplify these embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more completely understood in consideration of the detailed description of various embodiments of the invention that follows in connection with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a flexible, resealable package according to an example embodiment of the present invention; 
     FIG. 2 is a perspective view of a rigid, resealable package according to an example embodiment of the present invention; 
     FIG. 3 is a fragmented, cross-sectional view of a particular type of resealable closure mechanism, according to an example embodiment of the present invention, showing its male and female closure profiles; and 
     FIG. 4 is a fragmented, cross-sectional, somewhat schematic view of a resealable closure mechanism with a peelable seal, also according to an example embodiment of the present invention. 
    
    
     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     The present invention is believed to be applicable to a variety of packaging arrangements. The invention has been found to be particularly advantageous for use in sealing mechanisms for polymeric packages. An appreciation of various aspects of the invention is best gained through a discussion of an application example for such a packaging arrangement. 
     According to an example embodiment of the present invention, a package includes a peelable seal indicator to allow the manufacturer to inspect for a hermetic or airtight seal and to provide the consumer a way of checking for a tamper resistant package. FIGS. 1 and 2 illustrate example types of packages  17 ,  24  that benefit from use of such peelable seal indicators. 
     FIG. 1 illustrates an example packaging arrangement in the form of a resealable, flexible package  17  having a zipper-type closure mechanism  26  constructed in accordance with the present invention. The flexible package  17  includes first and second opposed panel sections  15 ,  16  made from a flexible, polymeric film. For some manufacturing applications, the first and second panel sections  15 ,  16  are heat-sealed together along two edges and meet at a fold line in order to form a three-edged containment section for a product within the interior of the package  17 . The fold line comprises the bottom edge  29 . Alternatively, two separate panel sections  15 ,  16  of polymeric film may be used and heat-sealed together along the two edges  25 ,  27  and at the bottom  29 . Access is provided to the interior of the package  17  through a mouth  31 . In other implementations, the package  17  includes tear strings and/or notches at the mouth  31  to assist with opening the package  17 . 
     FIG. 2 is a perspective view depicting a rigid resealable package  24 . The rigid resealable package  24  has the same basic features as the flexible resealable package  17  of FIG.  1 . The package  24 , however, has one flexible top side  21 . The remaining five sides are rigid or a combination of rigid and flexible. 
     The flexible package  17  and the package  24  may be used to hold a variety of products. Such products may be a variety of edible food products such as cheese, meat, crackers, sugar, powdered sugar, flour, salt, and baking soda, or non-food products such as laundry detergent, sand, medical supplies, and other products. Resealable packages are convenient in that they can be closed and resealed after the initial opening to preserve the enclosed contents. The need to locate a storage container for the unused portion of the products in the package is thus avoided. As such, providing products in resealable packages appreciably enhances the marketability of those products. 
     A resealable closure mechanism  26  is illustrated in FIG. 1 at the opening of the flexible package  17 . A similar closure mechanism  26 ′ is illustrated in FIG.  2 . Each closure mechanism  26  or  26 ′ extends the width of the package  17  or  24 . In the particular embodiment illustrated in FIG. 3, the resealable closure mechanism  26  of FIG. 1 is shown in the specific form of a zipper-type mechanism. 
     Attention is directed to FIG.  3 . The resealable closure mechanism  26  is shown in expanded form to include an elongated male closure profile  28  and an elongated female closure profile  30 . The male closure profile  28  is comprised of a base strip  42 , a rib or male interlocking closure member  44  at a free end, and a stem  43 . The male interlocking member  44  is generally T-shaped. In one embodiment, the base strip  42  is attached to the first panel section  15  of the flexible package  17  by a heat and pressure seal process. 
     The female closure profile  30  includes one of many types of interlocking structures for interlocking with the male closure profile  28 . This particular example of a locking structure of the female closure profile  30  includes first and second legs  45 ,  47 . The first and second legs  45 ,  47  have a J-shaped cross section and interlocking closure members  46 ,  49 . Interlocking members  46 ,  49  mechanically engage the interlocking member  44  of the male profile  28  in order to reseal the package  17  at the mouth  31 . The first and second legs  45 ,  47  are joined by a common base strip  51  that is attached to the second panel section  16  by, for example, a conventional heat and pressure seal process. 
     A mating groove  53  functions to contain the interlocking member  44  of the male closure profile  28 . When pressure is applied to the closure profiles  28 ,  30 , they engage and form a resealable closure mechanism  26 . Pulling the male closure profile  28  and female closure profile  30  away from each other causes the two profiles to disengage, opening the package. 
     In some applications, the profiles are formed by two separate extrusions or through two separate openings of a common extrusion. Typically, the resealable closure mechanism  26  is made of a flexible polymeric material. Generally, the closure profiles  28 ,  30  are manufactured separately from the package and are subsequently attached to the package, such as the flexible resealable package  17  of FIG. 1 or the rigid resealable package  24  of FIG. 2, using a conventional heat and pressure seal process. 
     FIG. 4 illustrates a cross-sectional view of an example peelable seal according to an embodiment of the present invention. The elongated male closure profile  28  of FIG. 3 is shown attached to the first package film  15  of FIG.  1 . The elongated female closure profile  30  of FIG. 3 is also shown attached to the second package film  16  of FIG.  1 . The male closure profile  28  includes corresponding base strip  42 , and the female closure profile  30  includes corresponding base strip  51 . 
     In FIG. 4, the peelable seal  40  includes a first peelable layer  32  and a second peelable layer  34 . The first peelable layer  32  is bonded to the base strip  42  of the male closure profile  28 . The second peelable layer  34  is likewise bonded to the base strip  51  of the female closure profile  30 . The peelable seal  40  further includes a third peelable layer  36  and a fourth peelable layer  38 . The third peelable layer  36  is bonded to the first peelable layer  32 . The fourth peelable layer  38  is bonded to the second peelable layer  34 . In the example embodiment shown in FIG. 4, the third and fourth peelable layers  36 ,  38  have ribs. In another example embodiment, only one of the third and fourth peelable layers  36 , 38  has ribs, and the other peelable layer is a flat surface in a variation of the preceding, either or both layer  32  and layer  34  may be omitted. 
     In one example embodiment, the closure arrangement illustrated in FIG. 4 is manufactured using conventional extrusion and heat sealing techniques. In particular, the closure profiles  28 ,  30  and the peelable layers  32 , 34 ,  36 ,  38  are co-extruded through a die plate fed by a plurality of extruders. These extruders carry the different molten materials for forming the closure profiles  28 ,  30  and the peelable layers  32 ,  34 ,  36 ,  38 . As is well-known in the art, the die plate includes input ports, output ports, and channels connecting these input ports to output ports. The extruders feed the different molten materials to different input ports, and the channels are designed to configure the molten materials into the shapes of the closure profiles  28 ,  30  and peelable layers  32 ,  34 ,  36 ,  38 . In this process, the first peelable layer  32  is bonded to the base strip  42 , and the third peelable layer  36  is bonded to the first peelable layer  32 . Furthermore, the second peelable layer  34  is bonded to the base strip  51 , and the fourth peelable layer  38  is bonded to the second peelable layer  34 . 
     Generally, the closure profiles  28 ,  30  and peelable layers  32 ,  34 ,  36 ,  38  are extruded from a polymeric resin such as polyethylene, polybutylene or polypropylene. In one example embodiment, the peelable layers  32 ,  34 ,  36 ,  38  are extruded from a polymeric material with a lower bond strength than the package films  15 ,  16  or the closure profiles  28 ,  30 . In another example embodiment, the peelable layers  32 ,  34 ,  36 ,  38  are extruded from the same polymeric material but are weakened by adding contaminants to the resin. This causes the peelable layers  32 ,  34 ,  36 ,  38  to have a lower bond strength than the package films  15 ,  16  or the closure profiles  28 ,  30 . 
     The resins for the third and fourth peelable layers  36 ,  38  are pigmented with a color such that after manufacturing, the ribs are easily seen. In one example embodiment, the third and fourth peelable layers  36 ,  38  are pigmented the same color. In another example embodiment, the third peelable layer  36  is pigmented one color while the fourth peelable layer  38  is pigmented a separate color. For example, the third peelable layer  36  is colored blue, and the fourth peelable layer  38  is colored yellow. 
     After manufacturing, the closure profiles  28 ,  30  are interlocked, and the third peelable layer  36  is located opposite and adjacent to the fourth peelable layer  38 . The colored ribs of the third and fourth peelable layers  36 ,  38  are readily visible to the manufacturer, indicating a hermetic seal has not yet been achieved. The spacing of ribs between sides shows that a seal has not been made. The closure arrangement is then attached to the package films  15 ,  16  by a conventional heat and pressure seal process. This process causes the package films  15 ,  16  to heat-fuse with the base strips  42 ,  51 . This process further causes the third peelable layer  36  to heat-fuse with the fourth peelable layer  38  such that one fused layer results providing the hermetic seal. 
     In one example embodiment, the third and fourth peelable layers  36 ,  38  are no longer visible, and the entire resulting layer, resulting from the fusion of the third and fourth peelable layers  36 ,  38 , is colored, leaving a wide band of color rather than individual ribs of color. The lack of colored ribs and the presence of the wide band of color indicates to the manufacturer that a hermetic seal has been achieved. It also indicates to the consumer that the hermetic seal is intact. 
     In another example embodiment, where the third peelable layer  36  is one color (i.e. blue) and the fourth peelable layer  38  is a separate color (i.e. yellow), the resulting layer has a wide band of a third color (i.e. green). The presence of this third color indicates to the manufacturer the hermetic seal has been achieved. It also indicates to the consumer that the hermetic seal is intact. 
     In yet another embodiment, the peelable seal consists of only a first and second peelable layer. The first and second peelable layers are printed with a pattern that, after manufacturing, is visible to the manufacturer indicating the hermetic seal has not yet been achieved. Upon heat-fusing the closure arrangement to the package films, the fusion of the first and second peelable layer causes the pattern to be destroyed. This provides an indication to the manufacturer that the hermetic seal has been achieved and an indication to the consumer that the hermetic seal is intact. 
     In yet another embodiment, the peelable seal exists without the interlocking closure mechanisms. In this embodiment, the peelable seal is co-extruded with the base strips and then heat-fused directly to the package firms. An alternative is strip printing of peelable filn without a closure mechanism or separate strip. 
     The peelable seal  40  provides a hermetic seal at the mouth of the package. The hermetic seal prevents air and water from penetrating the package films. This keeps the contents of the package in a constant environment to prevent spoilage. 
     Prior to initially opening a package incorporating the closure arrangement shown in FIG. 4, the peelable seal  40  is intact, the closure profiles  28 ,  30  are interlocked with each other, and the top and bottom films  15 ,  16  are connected at the mouth end  31  of the bag. The top and bottom films  15 ,  16  are heat-fused together at the mouth end  31  of the bag shown in FIG.  1 . Because the peelable seal  40  already provides a hermetic seal for the package, the top and bottom films  15 ,  16  may alternatively be disconnected from each other at the mouth end  31 . 
     To open the bag, the top and bottom films  15 ,  16  are separated from each other by cutting them apart. Next, the interlocked closure profiles  28 ,  30  are detached from each other by grabbing onto the top and bottom films  15 ,  16  and pulling them apart. Finally, the peelable seal  40  is broken by continuing to pull the top and bottom films  15 ,  16  in opposite directions. The strength of the peelable seal  40  is determined by the composition of the peelable material, temperature, pressure, dwell time of the seal bars, and the size of the peelable seal  40 . Generally, the peelable seal  40  should have a strength ranging from two to six pounds per linear inch. This strength provides an adequate hermetic seal while still allowing the consumer to “peel” the peelable seal apart. 
     The above specification and examples are believed to provide a complete description of the manufacture and use of particular embodiments of the invention. Because many embodiments of the invention can be made without departing from the spirit and scope of the invention, the true scope and spirit of the invention reside in the broad meaning of the claims hereinafter appended.