Abstract:
A reclosable package ( 10 ) for the retail display of a food product and for the purchase and storage thereof by a consumer has tamper-evident features to enable the consumer to discern whether the package has been opened prior to purchase. The package ( 10 ) includes a header ( 26 ) formed by attaching the front and back sheets ( 12,14 ) of the package ( 10 ) to one another above the interlocking profiles ( 20,22 ) of the zipper ( 18 ) of the package ( 10 ) with a peel seal. Below the interlocking profiles ( 20,22 ), the front sheet ( 12 ) has a line of weakness ( 32 ), such as a line of perforations extending transversely across the package ( 10 ) below the interlocking profiles ( 20,22 ). A tear in the line of weakness ( 32 ) or a breach of the peel seal would readily indicate that the integrity of the package ( 10 ) has been compromised.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates, in general, to the packaging art, and, more particularly, is concerned with a package having a reclosable plastic zipper at its mouth and including tamper-evident features which provide a clear visual indication of the integrity of the package.  
           [0003]    2. Description of the Prior Art  
           [0004]    When using plastic bags and packages in the retail sale of foodstuffs, it is important that the bags or packages be hermetically sealed until consumers purchase them and their contents, take them home and open them for the first time. It is then commercially attractive and useful for the consumer for the bag or package to be reclosable so that its contents may be protected and their shelf lives extended. Flexible plastic zippers have proven to function with excellent results in reclosable plastic bags, because they may be manufactured on high-speed equipment and continue to work reliably after repeated reuse.  
           [0005]    A typical plastic zipper has a groove along one side of the bag mouth and a rib along the other side, the rib interlocking into the groove when the two sides of the mouth of the bag are pressed together. Alternatively, a member having a plurality of ribs may be on one side of the bag mouth, while a member having a plurality of channels may be on the other side, the ribs locking into the channels when the sides of the mouth of the bag are pressed together. In such a case, there may be no difference in appearance between the two members, as the ribs may simply be the intervals between the channels on a strip which may lock into one of the same kind.  
           [0006]    In general, and in short, some form of male/female interengagement is used to join the two sides of the bag mouth together. The so-called members, or strips, which are commonly referred to as profiles, are bonded in some manner to the material from which the bags themselves are manufactured. In recent years, plastic zippers of this general type have been equipped with sliders, which separate the profiles from one another when moved in one direction and join the profiles to one another when moved in the opposite direction, in the manner of a zipper on an article of clothing.  
           [0007]    Although flexible zippers of this variety have become quite popular with consumers, the inadvertent or deliberate opening of a bag or package within a store or supermarket prior to purchase is possible. In order to alert prospective consumers that the integrity of a package has been breached prior to purchase, various tamper-evident features may be incorporated into the packages.  
           [0008]    The most common feature of this type is the tamper-evident non-reclosable peel seal. Typically, seals of this type are formed across the mouth of the package by polymeric resin materials which seal the opening closed, but which are easily broken when the two sides of the package are pulled apart at the opening. Ideally, the material used to form the peel seal, that is, the peel-seal material, whitens or otherwise discolors when broken, thereby giving a visual indication that the integrity of the package has been compromised.  
           [0009]    The present invention represents an alternate approach toward providing a reclosable package with a tamper-evident feature.  
         SUMMARY OF THE INVENTION  
         [0010]    Accordingly, the present invention is a reclosable package for the retail display of a food product and for the purchase and storage thereof by a consumer. The package comprises a front sheet and a back sheet of thermoplastic sheet material. The front and back sheets define the package having a top, a bottom, a first side and a second side. The front sheet has a line of weakness running transversely thereacross at the top of the package. The front and backs sheets are connected to one another along the bottom and first and second sides of the package. The back sheet may be thermoformed to provide a compartment for a food product within the package.  
           [0011]    A zipper is disposed transversely across the package between the front and back sheets and sealed thereto at the top of the package to provide it with a reclosable opening. The zipper comprises two interlocking profiles, each of which is integrally formed with a web, one of the webs being sealed to the front sheet and the other being sealed to the back sheet. The zipper is disposed such that the interlocking profiles are above the line of weakness relative to the top of the package, while the web sealed to the front sheet is so sealed below the line of weakness. The front and back sheets are connected to one another above the zipper with a peel seal to form a header from which the package may be hung for retail display. The peel seal and the line of weakness in the front sheet below the interlocking profiles provide the package with tamper-evident features.  
           [0012]    The present invention will now be described in more complete detail with frequent reference being made to the drawing figures identified blow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a frontal plan view of the thermoform-fill-and-seal (TFFS) package of the present invention;  
         [0014]    [0014]FIG. 2 is a cross-sectional view taken as indicated by line  2 - 2  in FIG. 1;  
         [0015]    [0015]FIG. 3 is a schematic illustration of a method for manufacturing the package shown in FIGS. 1 and 2;  
         [0016]    [0016]FIG. 4 is a schematic illustration of a method for making a similar package on a horizontal form-fill-and-seal (HFFS) machine;  
         [0017]    [0017]FIG. 5 is a schematic illustration of a method for making a similar package on a vertical form-fill-and-seal (VFFS) machine;  
         [0018]    [0018]FIG. 6 is a schematic illustration of a method for making a similar package having a zipper in the transverse direction; and  
         [0019]    [0019]FIG. 7 is a schematic illustration of a method for making a similar package on a horizontal form, vertical fill-and-seal (HFVFS) machine. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Turning now to these figures, FIG. 1 is a frontal plan view of the thermoform-fill-and-seal (TFFS) package  10  of the present invention, and FIG. 2 is a cross-sectional view thereof taken as indicated by line  2 - 2  in FIG. 1. The package  10  comprises a front sheet  12  and a back sheet  14 , the latter of which may be thermoformed to provide a compartment  16  for a food product. Both the front sheet  12  and the back sheet  14  may be extruded from a thermoplastic resin material, such as polyethylene, and may, depending on the process used to manufacture the package, have been physically part of a single sheet at the beginning of the manufacturing process. A zipper  18 , comprising two interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , and having a slider  24 , runs across the top of the package  10  and provides it with a reclosable opening.  
         [0021]    At the top of the package  10 , the top being at the left-hand side of the views presented in both FIGS. 1 and 2, the front sheet  12  and the back sheet  14  form a header  26 , from which the package  10  may be hung for display at a retail outlet. To facilitate the hanging, a hole  28  may be punched through the header  26 .  
         [0022]    At the header  26 , the front sheet  12  and the back sheet  14  are attached to one another with a peel seal, except at one corner  30 , where the two sheets  12 , 14  are not joined to one another. This allows the consumer to grasp the front and back sheets  12 , 14  separately at the corner  30  to pull the two sheets  12 , 14  apart to gain access to the zipper  18  and ultimately to the contents of the package  10 . Alternatively, instead of leaving the two sheets separated from one another at corner  30 , they may be separated, that is, not peel-sealed to one another, at some other portion of the header  26 , such as across the top of the header  26 .  
         [0023]    Across the front sheet  12 , at a point below the interlocking profiles  20 , 22 , that is, to the right of the interlocking profiles  20 , 22  in both FIGS. 1 and 2, is a line of weakness  32 , which may be a line of perforations, a score formed by some cutting device, or a line of reduced thickness. The line of weakness  32  enables the front sheet  12  portion of the header  26  to be torn from the package  10  when the package  10  is first being opened by the consumer in the manner described in the preceding paragraph. Both the peel seal joining the front and back sheets  12 , 14  at the header  26  and the line of weakness  32  provide the package  10  with tamper-evident features to alert the consumer that the package  10  may have been opened prior to purchase.  
         [0024]    Optionally, the front sheet  12  and the back sheet  14  may be joined to one another by hermetic peel seal  34  within the package  10  to provide an additional tamper-evident feature, as well as to ensure that no air can be exchanged between the inside and outside of the package  10 . Once the zipper  18  is opened, hermetic peel seal  34  may be broken by pulling the front and back sheets  12 , 14  apart at the mouth of the package  10 , giving the consumer access to its interior.  
         [0025]    To complete the description of the package  10 , both of the interlocking profiles  20 , 22  of the zipper  18  are integrally formed with webs  36  extending toward the interior of the package  10 . Each of the front and back sheets  12 , 14  is sealed to the web  36  immediately adjacent thereto with seal  38 , the web  36  attached to the front sheet  12  being so attached below (to the right of) line of weakness  32 . Moreover, the package  10  is sealed along the sides and the bottom, which is on the right-hand side of both FIGS. 1 and 2, with seals  40 , 42 , 44 .  
         [0026]    It will be noted in FIG. 2 that the front and back sheets  12 , 14  wrap around the zipper  18  to form a pocket  46 . The size of the pocket  46  may be chosen advantageously to minimize any wrinkling of the front and back sheets  12 , 14 . The pocket  46  may also be sized advantageously to provide easy finger access by which to operate the slider  24  on the interlocking profiles  20 , 22 . In addition back sheet  14  may be sealed to web  36  extending from profile  22  at a point close to interlocking profiles  20 , 22  to make it easier for a consumer to hold and pull the slider  24 .  
         [0027]    A method for making the TFFS package  10  of the present invention is shown schematically in FIG. 3, where the process proceeds from left to right. Starting at the left-hand side of FIG. 3, back sheet  14  is dispensed from roll  48 . Heating device  50  heats the back sheet  14  so that it may be thermoformed at point  52  to provide the compartment  16 . A food product may be dispensed into the compartment  16  at point  54 .  
         [0028]    Zipper  18  including interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , is dispensed continuously from spool  56 , and, at point  58 , deformed at intervals equal to the width of the package  10  being produced to limit the movement of the sliders  24  that are being added at point  60 . The sliders  24  may optionally be moved to some preselected position on the zipper  18  at point  62  if desired.  
         [0029]    The zipper  18  is united with the thermoformed back sheet  16  at point  64  and attached by sealing the web  36  of one of the interlocking profiles  20 , 22  thereto. Optionally, the ends of the zipper  18  may be deformed at the sides of the packages  10  being manufactured at point  66 .  
         [0030]    Front sheet  12  is dispensed from roll  68 . Device  70 , which may be a perforator, scorer or laser heating device, is used to provide a lengthwise line of weakness  32  on front sheet  12 . Thereafter, the front sheet  12  is united with the zipper  18  and back sheet  14  at point  72 , air is evacuated from the package  10  and the front and back sheets  12 , 14  are sealed together as previously described. Specifically, the front sheet  12  is disposed such that the line of weakness  32  is adjacent the zipper  18  with the interlocking profiles  20 , 22  being above the line of weakness  32  relative to the tops of the packages  10  being produced, and the web  36  of the other of the interlocking profiles  20 , 22  is sealed to the front sheet  12  below the line of weakness  32 . The front and back sheets  12 , 14  are also sealed to one another above the interlocking profiles  20 , 22  with a peel seal. Subsequently, the packages  10  are trimmed in the machine direction, if necessary, and are cut from one another in the cross-machine direction, the machine direction being the direction in which the process proceeds and the cross-machine direction being transverse thereto.  
         [0031]    While the present invention is primarily directed toward a method of making a thermoform-fill-and-seal (TFFS) package and toward the TFFS package itself, it may be applied to the manufacture of packages according to other methods used in the industry. For example, a method for making a similar, although not thermoformed, package on a horizontal-form-fill-and-seal (HFFS) machine is shown schematically in FIG. 4. Starting from the left-hand side of FIG. 4, thermoplastic sheet  80  is dispensed from roll  82 . A lengthwise line of weakness  84  is provided along one side of the sheet  80 , or a sheet  80  already having a lengthwise line of weakness  84  is used. Alternatively, the lengthwise line of weakness  84  could be provided substantially down the center of the sheet  80 , or a sheet  80  already having such a lengthwise line of weakness  84  could be used. A food product  86  is placed on the sheet  80  at intervals corresponding to the width of the packages being produced. The sheet  80  is then folded lengthwise over the food product  86  at point  88 .  
         [0032]    As above, zipper  18  including interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , is dispensed continuously from spool  90 , and, at point  92 , deformed at intervals equal to the width of the packages being produced to limit the movement of the sliders  24  that are being added at point  94 . The sliders  24  may optionally be moved to some preselected position on the zipper  18  so produced at point  96  if desired.  
         [0033]    At point  98 , zipper  18  is fed between the front sheet and back sheet obtained by folding sheet  80 , and thereafter, at point  100 , is attached to the front and back sheets as previously described. Specifically, the zipper  18  is fed such that the line of weakness  84  is adjacent the zipper  18  with the interlocking profiles  20 , 22  being above the line of weakness  84  relative to the tops of the packages  10  being produced, and with the sheet having the line of weakness  84  being sealed to the web of one of the two interlocking profiles  20 , 22  below the line of weakness  84 , while the sheet not having the line of weakness  84  is sealed to the web of the other of the two interlocking profiles  20 , 22 . The front and back sheets are also sealed to one another above the interlocking profiles  20 , 22  with a peel seal. Subsequently, cross seals  102  are formed, and the packages so obtained are separated from one another at the cross seals  102 .  
         [0034]    A method for making a similar package on a vertical-form-fill-and-seal (VFFS) machine is shown schematically in FIG. 5. Starting from the left-hand side of FIG. 5, thermoplastic sheet  104  is dispensed from roll  106 . A lengthwise line of weakness  108  is provided along one side of sheet  104 , or a sheet  104  already having a lengthwise line of weakness  108  is used.  
         [0035]    The sheet  104  is formed into the shape of a tube by the collar  110  of the fill tube  112  of the vertical form-fill-and-seal machine  114 . As above, and as shown in FIG. 4, zipper  18  including interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , is dispensed continuously from a spool, and is deformed at intervals equal to the width of the packages being produced to limit the range of movement of the sliders  24  that may be added. As before, the sliders  24  may optionally be moved to some preselected position on the zipper  18 .  
         [0036]    The zipper  18  is fed between the two edges of the tube formed by folding sheet  104  around the fill tube  112  at point  116 , and is attached to the two edges at point  118  as previously described. Specifically, the zipper  18  is fed such that the line of weakness  108  is adjacent the zipper  18  with the interlocking profiles  20 , 22  being above the line of weakness  108  relative to the tops of the packages  10  being produced, and with the edge having the line of weakness  108  being sealed to the web of one of the two interlocking profiles below the line of weakness  108 , while the sheet not having the line of weakness  108  is sealed to the web of the other of the two interlocking profiles  20 , 22 . The edges of the tube formed by folding sheet  104  are also sealed to one another above the interlocking profiles  20 , 22  with a peel seal. The packages being produced are sealed in the crosswise direction by transverse sealing bars  120 , each package being filled with the food product of interest through fill tube  112  after each cross seal is made. Subsequently, each of the packages so obtained is separated from the next at the cross seals.  
         [0037]    A method for making a similar package with a zipper in the transverse direction of the thermoplastic sheet is shown schematically in FIG. 6. Again starting from the left-hand side of the figure, thermoplastic sheet  122  is dispensed from roll  124 . Lines of weakness  126  are provided transversely across sheet  122  for approximately one half of its width, or a sheet  122  already having such lines of weakness  126  is used. Preferably, the lines of weakness  126  are centered with respect to the two lateral edges of the sheet  122 .  
         [0038]    As above, and as shown in FIG. 4, zipper  18  including interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , is dispensed continuously from spool  128 , and is deformed at intervals equal to the width of the packages to be produced, that is, approximately one half of the width of the sheet  122 , to limit the range of motion of the sliders  24  that are being placed thereon. As before, the sliders  24  may optionally be moved to some preselected position on the zipper  18 .  
         [0039]    The zipper  18  is then cut at the deformed points, and attached to the sheet  122  adjacent to the lines of weakness  126 . Specifically, the cut zipper intervals are sealed to the thermoplastic sheet  122  adjacent and substantially parallel to each of the lines of weakness  126  with the webs  36  being on one side of the lines of weakness  126  and the interlocking profiles  20 , 22  being on the other side of the lines of weakness  126 . The resulting sheet  122  with zipper  18  and lines of weakness  126  may be used on both vertical and horizontal form-fill-and-seal machines, or on premade pouch machines to produce the packages of the present invention.  
         [0040]    Typically, such processes may include the steps of folding the thermoplastic sheet  122  lengthwise over the cut zippers  18 , and sealing the lateral edges of the thermoplastic sheet  122  to one another and the folded thermoplastic sheet  122  to the cut zippers  18 . Then, peel seals would be formed between the thermoplastic sheet  122  and the folded portions thereof adjacent to the interlocking profiles  20 , 22  and opposite the interlocking profiles  20 , 22  from the lines of weakness  126 . Finally, cross seals would be formed at intervals equal to the lengths of the reclosable packages, and the packages would be separated from one another.  
         [0041]    Finally, a method for making a similar package according to a HFVFS (horizontal-form, vertical-fill-and-seal) technique is shown schematically in FIG. 7. Again, starting from the left-hand side of the figure, thermoplastic sheet  130  is dispensed from roll  132 . A lengthwise line of weakness  134  is provided along one side of the sheet  130 , or a sheet  130  already having a lengthwise line of weakness  134  is used.  
         [0042]    Zipper  18  including interlocking profiles  20 , 22 , each of which is integrally formed with a web  36 , is dispensed continuously from spool  136 , and, at point  138 , deformed at intervals equal to the width of the packages being produced to limit the movement of the sliders  24  that are being added at point  140 . The sliders  24  may optionally be moved to some preselected position on the zipper  18  at point  142  if desired.  
         [0043]    Sheet  130  is folded in half vertically at point  144 , and zipper  18  is fed between the two vertically oriented sheets so obtained so as to be adjacent to the lengthwise line of weakness  134  running along one side of the sheet  130 . Alternatively, the lengthwise line of weakness  134  may be provided substantially down the center of sheet  130 , or a sheet  130  already having a lengthwise line of weakness  134  running substantially down its center may be used. In this case, the zipper  18  is fed down to the fold to be adjacent to the lengthwise line of weakness  134 .  
         [0044]    In either case, zipper  18  is fed such that the lengthwise line of weakness  134  is adjacent to the zipper  18  with the interlocking profiles  20 , 22  being above the line of weakness  134  relative to the tops of the packages  10  being produced, and with the side having the lengthwise line of weakness  134  being sealed to the web of one of the two interlocking profiles  20 , 22  below the lengthwise line of weakness  134 , while the side not having the lengthwise line of weakness  134  is sealed to the web of the other of the two interlocking profiles  20 , 22 .  
         [0045]    Subsequently, side seals are made and individual packages are made by cutting one from the next at the side seals. Then, the individual packages are filled and the final package seals are made, including a peel seal above the zipper  18  on the header of the package.  
         [0046]    Modifications to the above would be obvious to those of ordinary skill in the art, but would not being the invention so modified beyond the scope of the appended claims.