US20070092166A1

US20070092166A1 - Reclosable pouches or bags having front panel containment zipper

Info

Publication number: US20070092166A1
Application number: US11/257,856
Authority: US
Inventors: David Anzini; Rusty Koenigkramer; David Matthews; Lars Wihlborg
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2005-10-25
Filing date: 2005-10-25
Publication date: 2007-04-26
Also published as: WO2007050695A1

Abstract

Flexible containers that are hermetically resealable after initial opening. The resealable containers are of a type that comprises front and rear panels forming an interior volume that is accessible by means of a resealable plastic zipper attached to the front panel only. Each zipper comprises a pair of extruded plastic zipper strips. The zipper strips are flattened and joined to each other at the ends and are further joined to each other, without substantial deformation of the closure profiles, in respective transition areas substantially contiguous with the flattened ends. These transition areas of zipper strip joinder assist in providing a leakproof transition from the openable section of the zipper to where the closure profiles have been fused and flattened (i.e., crushed).

Description

BACKGROUND OF THE INVENTION

This invention generally relates to flexible containers, such as pouches, bags or other packages, having a reclosable plastic zipper. In particular, the invention relates to reclosable bags, pouches or other packages for containing vacuum, pressure or liquid.
To ensure hermeticity or airtightness, packagers have typically sealed their flexible containers to an extent that they are not reclosable after the seal is broken. Many flexible containers that were reclosable typically did not retain the desired vacuum, pressure or liquid containment feature that existed prior to the container being opened for the first time.
In many different applications, it is desirable to provide a reclosable container that, under normal or expected conditions of usage, will not leak fluid when the zipper is reclosed. Such a container should maintain a leakproof condition even when there is a large differential in pressure between the interior and exterior of the container. As used herein, the term “leakproof” does not mean free of leaks under all temperature/pressure conditions, but rather free of leaks over a range of temperatures and pressures expected to occur during normal usage of the reclosable container.
One use for hermetically resealable containers is in the field of food product packaging. After a package of food has been opened and a portion of the food product removed, the remaining food product can be stored by closing the reclosable feature and then evacuating the interior space of the package via a fixture that penetrates a package wall. It is highly desirable that such packages, containing perishable food product in a vacuum, be leakproof, i.e., hermetic. By preventing exposure to air, the life span of the perishable food product can be extended.
In other situations, it is desirable to provide a reclosable package capable of holding liquid without leaking during normal usage when the zipper is reclosed. Preferably such a package would be able to withstand a predetermined pressure differential (interior/exterior) without liquid leaking out of the package.
In accordance with another product application, a reclosable bag may be filled at ambient atmosphere instead of being evacuated. If such a bag were placed under extremely low pressure, e.g., while being air-lifted via a cargo plane having a depressurized cargo bay, then a large differential in pressure would exist between the interior and exterior of the bag. In this situation, the internal pressure may be about 15 psi, while the external pressure is negligible. It is desirable that the bag not develop a leak and that the zipper not pop open under such conditions.
Many existing form-fill-seal (FFS) machines operate on bag making film and do not incorporate equipment for attaching zipper assemblies to the bag making film. Although zipper application machines are available that can be coupled to the FFS machine to provide the zipper application function, operators of FFS machines who do not wish to purchase a zipper applicator require that bag making film with pre-attached zippers be available for purchase. This film can then be run through the FFS machine. Although the packager may need to modify his FFS machine to handle bag making film with pre-attached zippers, the major capital investment of a zipper application system can be avoided.
There is a need for improvements in the construction of hermetically resealable flexible containers that can withstand a large pressure differential (internal versus external) without leaking and that can be formed, filled and sealed without the FFS machine needing to perform any zipper application step.

BRIEF DESCRIPTION OF THE INVENTION

Flexible containers that are hermetically resealable are disclosed herein. The disclosed resealable containers are of a type that comprises front and rear panels forming an interior volume that is accessible by means of a resealable plastic zipper attached to the front panel only. Each zipper comprises a pair of extruded plastic zipper strips. The zipper strips are flattened and joined to each other at the ends and are further joined to each other, without substantial deformation of the closure profiles, in respective transition areas substantially contiguous with the flattened ends. These transition areas of zipper strip joinder assist in providing a leakproof transition from the openable section of the zipper to where the closure profiles have been fused and flattened (i.e., crushed).
One aspect of the invention is a reclosable package comprising: a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, the first zipper strip comprising a length of a first closure profile having at least two projecting elements and first and second flanges extending in opposite directions and connected to the first closure profile, respective portions of the first and second flanges being flattened within the boundaries of the first and second zipper end seals, and the second zipper strip comprising a length of a second closure profile having at least one projecting element that fits between the at least two projecting elements of the first closure profile and a third flange connected to the second closure profile, respective portions of the third flange being flattened within the boundaries of the first and second zipper end seals, the first and second zipper end seals respectively comprising first and second substantially flat portions and first and second transition areas respectively connected to the first and second substantially flat portions on first, second and third sides, wherein along the first and third sides of each of the first and second transition areas, each of the two projecting elements of the first and second closure profiles that are furthest apart from each other is fused to some portion of the one of the first and second zipper strips of which the respective one of the furthest-apart projecting elements does not form a part; and wherein along a second side of and within each of the first and second transition areas, the first and second closure profiles are deformed and fused together but not flattened, the respective ends of the fused material along the second side being integrally connected to the fused material of the first and third sides, respectively, the third flange being longer than the first flange and extending beyond the first and second zipper end seals in an elevational direction; and a receptacle comprising top and bottom seals, a first panel connected to and extending between the top and bottom seals, and a second panel connected to and extending between the top and bottom seals, the first and second panels bounding an interior volume of the receptacle, wherein each of the first through third flanges is joined to the first panel and not joined to the second panel.
Another aspect of the invention is a reclosable package comprising: a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, the first zipper strip comprising a length of a first closure profile and first and second flanges extending in opposite directions and connected to the first closure profile, respective portions of the first and second flanges being flattened within the boundaries of the first and second zipper end seals, and the second zipper strip comprising a length of a second closure profile interlockable with the first closure profile and a third flange connected to the second closure profile, respective portions of the third flange being flattened within the boundaries of the first and second zipper end seals, the first and second zipper end seals respectively comprising first and second transition areas disposed at opposite ends of the first and second closure profiles, and first and second substantially flat portions that respectively border the first and second transition areas on three sides thereof, the first transition area comprising first sections of the first and second closure profiles that have been deformed and at least partially fused together but not flattened, and the second transition area comprising second sections of the first and second closure profiles that have been deformed and at least partially fused together but not flattened, the third flange being longer than the first flange and extending beyond the first and second zipper end seals in an elevational direction; and a receptacle comprising top and bottom seals, a first panel connected to and extending between the top and bottom seals, and a second panel connected to and extending between the top and bottom seals, the first and second panels bounding an interior volume of the receptacle, wherein each of the first through third flanges is joined to the first panel and not joined to the second panel.
A further aspect of the invention is a reclosable package comprising: a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, the first zipper strip comprising a length of a first closure profile and first and second flanges extending in opposite directions and connected to the first closure profile, respective portions of the first and second flanges being flattened within the boundaries of the first and second zipper end seals, and the second zipper strip comprising a length of a second closure profile interlockable with the first closure profile and a third flange connected to the second closure profile, respective portions of the third flange being flattened within the boundaries of the first and second zipper end seals, the first and second zipper end seals respectively comprising first and second transition areas disposed and connected to opposite ends of the first and second closure profiles, and first and second substantially flat portions that respectively border the first and second transition areas on three sides thereof, the first transition area comprising first sections of the first and second closure profiles that have been deformed and at least partially fused together but not flattened, and the second transition area comprising second sections of the first and second closure profiles that have been deformed and at least partially fused together but not flattened, wherein third and fourth sections of the first and second closure profiles that are respectively adjacent the first and second sections form channels therebetween, the channels within the third section being either sealed at one end thereof by the first transition area or communicating with channels formed by the first section that are sealed except where they communicate with the channels formed by the third section, and the channels within the fourth section being either sealed at one end thereof by the second transition area or communicating with channels formed by the second section that are sealed except where they communicate with the channels formed by the fourth section, the third flange being longer than the first flange and extending beyond the first and second zipper end seals in an elevational direction; and a receptacle comprising top and bottom seals, a first panel connected to and extending between the top and bottom seals, and a second panel connected to and extending between the top and bottom seals, the first and second panels bounding an interior volume of the receptacle, wherein each of the first through third flanges is joined to the first panel and not joined to the second panel.
Yet another aspect of the invention is a method of manufacture comprising the following steps: (a) interlocking first and second zipper strips of a plastic zipper tape, the first zipper strip comprising a first closure profile and first and second flange extending from the first closure profile in opposite directions, the second zipper strip comprising a second closure profile and a third flange extending further from the second closure profile than the first flange extends from the first closure profile, the first and second closure profiles in combination comprising at least three projecting elements; (b) applying heat and pressure or ultrasonic vibrations and pressure in first and second zones of the interlocked zipper strips, each of the first and second zones extending from an elevation lower than the first and second closure profiles to an elevation higher than a top edge of the first flange, and having a predetermined dimension in first and second areas of overlap with the interlocked first and second closure profiles, whereby the first and second closure profiles are flattened in first and second sections having a length equal to the predetermined dimension, the midpoints of the first and second sections being separated by one zipper length, the first and third flanges are flattened at least in respective areas directly above the first and second sections of the first and second closure profiles, and the second flange is flattened at least in respective areas directly below the first and second sections of the first and second closure profiles; (c) before step (b) is performed, applying heat and pressure or ultrasonic vibrations and pressure in first and second transition regions having intermediate portions that will be respectively overlapped by the first and second zones in step (b), heat and pressure or ultrasonic vibrations and pressure being applied to an extent that upon completion of step (c), the projecting elements of the first and second closure profiles that are furthest apart from each other will become fused to respective portions of the other zipper strip in the first and second transition regions, and the first and second closure profiles will be heated but not flattened in the first and second transition regions, wherein upon completion of steps (b) and (c), the unflattened portions of the first and second closure profiles in the first transition region form first and second transition areas on opposite sides of a first flattened section of the first and second closure profiles, and the unflattened portions of the first and second closure profiles in the second transition region form third and fourth transition areas on opposite sides of a second flattened section of the first and second closure profiles; (d) after step (b) has been performed, applying pressure in the first and second transition regions to an extent that surface irregularities formed on the first through third flanges during step (b) are flattened without flattening the first through fourth transition areas; and (e) cutting the first and second zipper strips along first and second lines that respectively intersect the first and second zones to create an individual zipper.
Other aspects of the invention are disclosed and claimed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing a schematic representation of the cross section of a reclosable pouch or bag for vacuum, pressure or liquid containment in accordance with one embodiment of the invention.
FIG. 2 is a drawing showing a cross-sectional view of a zipper that is suitable for use as a containment zipper in pouches or bags of the type schematically depicted in FIG. 1.
FIG. 3 is a drawing showing in detail the closure profiles of the zipper depicted in FIG. 2.
FIG. 4 is a drawing showing an isometric view of various stations in a machine that is set up to perform operations in a predetermined sequence in accordance with one method of manufacture.
FIG. 5 is a drawing showing an isometric view of a grooved bar suitable for heating and pressing a portion of a zipper without flattening the closure profiles.
FIG. 6 is a drawing showing an isometric view of a grooved bar suitable for flattening some portions of a zipper while providing clearance for portions of the closure profiles not to be flattened.
FIG. 7 is a drawing showing a stage in the manufacture of the reclosable pouch or bag depicted in FIG. 1.
FIG. 8 is a drawing showing (on an enlarged scale) a front view of a portion of a plastic zipper tape, having the cross section shown in FIG. 2, that has been formed into a zipper end seal structure. That structure can be bisected to form zipper end seals of respective zippers suitable for incorporation in pouches or bags of the type depicted in FIGS. 1 and 9. The dashed line indicates the cut line.
FIG. 9 is a drawing showing a front view of the reclosable pouch or bag depicted in FIG. 1 and having a zipper cut from the zipper tape shown in FIG. 8.
FIG. 10 is a drawing showing an isometric view of portions of a conventional vertical form-fill-seal machine suitable for making pouches or bags of the type depicted in FIGS. 1 and 9.
It should be appreciated that the elements depicted in the various drawings are not drawn to scale (except for FIG. 3, which is based on a shadowgraph of an actual sample). In particular, for purposes of illustration, the containment zipper has been shown out of proportion (i.e., enlarged relative to the bag) in FIGS. 1 and 9.
Reference will now be made to the drawings in which similar elements in different drawings bear the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to hermetically resealable pouches or bags having an interior volume bounded by front and rear panels, with a containment zipper attached to the front panel only. In accordance with the embodiments disclosed herein, the containment zipper has three flanges joined to the front panel only of the completed reclosable pouch or bag. The zipper strips are flattened and joined to each other at the ends and are further joined to each other, without substantial deformation of the closure profiles, in respective transition areas substantially contiguous with the flattened ends. These transition areas of zipper strip joinder assist in providing a leakproof transition from the openable section of the zipper to where the closure profiles have been fused and flattened (i.e., crushed).
With the ends of the zipper sealed using the techniques disclosed hereinafter, the bag or pouch with front panel containment zipper can be rendered suitable for containing vacuum, pressure or liquid without leaking, even after the bag or pouch has been opened and reclosed. By sealing the zipper to the front panel instead of to both panels, the zipper will be exposed to less stress under pressure. More specifically, by placing the zipper on the front panel, forces due to internal pressure will act perpendicularly to the zipper and all in one direction. With all the force acting on the zipper in one direction, resistance to opening will be maximized. The front panel design is also effective in transferring the stresses of the internal pressure to the film and away from the zipper. Higher internal pressures can be accommodated to the point where the package film fails before the zipper closure fails.
Further, in order to produce a reclosable pouch, bag or package that will contain vacuum, pressure and/or liquids, it was determined that there should be hard and intimate contact between the closure profiles when the zipper is closed. More specifically, it was determined that, in order to ensure that the zipper performs its containment function in an acceptable manner, the percentage of the area of intimate contact between closure profiles should lie within a predetermined range. As used herein, the term “intimate contact”, in the context of a close zipper, means those portions of the area at the interface of the interlocked closure profiles that do not show any clearance between the respective closure profile elements, such as hooked elements and posts or backup elements, which viewed under a microscope. The areas without clearance can be displayed by cutting the zipper with a razor blade and placing the cross section under magnification. A magnified image of the closure profiles (i.e., a so-called “shadowgraph”) is produced, and then the portions of the profiles that display intimate contact can be marked on the image.
The minimum and maximum intimate contact area may be expressed as percentage, whereby the area of lineal contact is divided by the total available lineal surface of one profile. It was determined that the minimum percentage of intimate contact area that would still enable the zipper to perform satisfactorily as a containment zipper was 33%, whereas the maximum percentage of intimate contact area that would still enable the zipper to open and reclose was 76%. It is believed that any zipper having an intimate contact area percentage in the range of 33 to 76% can be effectively placed in a reclosable package that will contain vacuum, pressure and/or liquid during normal usage. Once a containment zipper has been selected, the package designer must then select a proper film strength and film seal integrity for the specific application.
In addition, the respective closure profiles of the zipper should have the same shape and configuration of elements, so that thermoplastic zipper material is substantially symmetrically and evenly distributed across the interlocked profiles. This will facilitate the formation of zipper end stomps or joints having flat surfaces and constant thickness.
If the minimum design criteria for the closure profiles are met, the reclosable package will only be limited by the material strength of the package components, i.e., the web material, the web-to-web and web-to-zipper seals, and the zipper material.
Many different types of zippers are suitable for use as containment zippers. In accordance with various embodiments disclosed hereinafter, a containment zipper is incorporated into a pouch or bag in such a way that the pouch or bag is able to withstand a large pressure differential between the interior and the exterior of the pouch or bag without leaking or popping open. Alternatively, the pouch or bag is suitable for containing liquid without leaking or popping open under the expected conditions of normal usage.
A reclosable pouch or bag in accordance with one embodiment of the invention is schematically represented in cross section in FIG. 1. The pouch or bag comprises a receptacle 2 with a three-flange containment zipper installed on the front panel 2 a of the bag. A top seal 20 joins respective marginal portions of the front and rear panels 2 a and 2 b at the top of the bag; a bottom seal 21 joins respective marginal portions of the front and rear panels 2 a and 2 b at the bottom of the bag.
Still referring to FIG. 1, one strip of the containment zipper comprises a closure profile 10 and upper and lower flanges 12 and 14 extending in opposite directions from closure profile 10. The other zipper strip comprises a closure profile 16 and an upper flange 18 having a length substantially greater than upper flange 12. The lower flange 14 of zipper strip 6 is heat sealed to the front panel 2 a in a band-shaped zone 24 that extends the length of the zipper strip. The upper flanges 12 and 18 are heat sealed to the front panel 2 a in a racetrack-shaped zone 26, best seen in FIG. 9. In the sectional view of FIG. 1, items 26 a and 26 b represent the straight portions of the racetrack seal, the straight portion 26 b being a zone where upper flange 18 is joined to the front panel 2 a, while the straight portion 26 a is a zone where upper flange 12 is joined to the front panel 2 a. The portion of the front panel 2 a that is bounded by the racetrack seal 26 is provided with a line 118 of weakened tear resistance, e.g., a line of spaced perforations or a laser scoreline, which extends generally parallel to the zipper. The tear line 118 is best seen in FIG. 9. After the consumer tears open the front panel along the tear line 118, access to the zipper is blocked by a peel seal 36, which joins opposing portions of the upper flanges 12 and 18 along the length of the zipper. To gain access to the contents of the package, the consumer must peel open the peel seal 36 and then pull apart the zipper strips 6 and 8.
The structure of the containment zipper attached to front panel 2 a is only schematically represented in FIG. 1. The structure of an exemplary containment zipper, suitable for incorporation in the bag seen in FIG. 1, is shown in detail in FIG. 2. The intimate contact area between the respective closure profiles lies within the aforementioned percentage range that is suitable for use as a containment zipper. One zipper strip 6 comprises a closure profile 10 and upper and lower flanges 12 and 14 extending in opposite directions therefrom. The upper flange 12 is longer than the lower flange 14 in the elevational direction. The closure profile 10 comprises a pair of monohook elements and a post or backup element devoid of a hook. A portion of the outer surface of upper flange 12 is coated with a sealant layer 30 to facilitate heat sealing of the upper flange 12 to the front panel 2 a. The lower flange 14 has a similar sealant layer 28 on its outer surface. The other zipper strip 8 comprises a closure profile 16 and an upper flange 18 having a length substantially greater than the length of upper flange 12. Zipper strip 8 has no lower flange. The closure profile 16 also comprises a pair of monohook elements and a post or backup element devoid of a hook. In this particular containment zipper embodiment, the respective posts are the profile elements that are furthest apart from each other. A portion of the inner surface of upper flange 18 is coated with a sealant layer 32 to facilitate heat sealing of the upper flange 18 to the front panel.
The zipper shown in FIG. 2 further comprises a layer 36 a of peelable sealing material applied on the interior surface of upper flange 12 of zipper strip 6 and a layer 36 b of peelable sealing material applied on the interior surface of upper flange 18 of zipper strip 8. The layers of peelable sealing material have the same width and extend the full length of the zipper strips, and are placed in mutual opposition to each other. These layers are pressed together and heat-activated to form the peel seal 36 seen in FIG. 1.
The three-flange zipper seen in FIG. 2 is shown on an enlarged scale in FIG. 3. The closure profile 16 comprises three profiled closure elements 42, 44 and 46 projecting from a base 38, the upper flange 18 (shown only in part) having an end integrally formed with base 38. Elements 44 and 46 are monohook elements, while element 42 is a post having no hook. Similarly, the closure profile 10 comprises three profiled closure elements 48, 50 and 52 projecting from a base 40, the upper flange 12 and the short extension 14 having respective ends integrally formed with base 40. Elements 50 and 52 are monohook elements, while element 48 is a post having no hook. When the closure profiles are fully interlocked, as shown in FIG. 3, monohook element 52 of closure profile 10 is disposed in a recess defined by and is in contact with post 42 and monohook element 44 of closure profile 16; the monohook element 44 of closure profile 16 is disposed in a recess defined by and is in contact with monohook elements 50 and 52 of closure profile 10; and so forth. The intimate contact area between the respective closure profiles lies within the aforementioned percentage range that is suitable for use as a containment zipper.
Before pouches or bags of the type shown in FIG. 1 can be made on an FFS machine, the thermoplastic zipper material must be processed into containment zippers suitable for transverse attachment to a web of packaging film. Zipper material is typically supplied in the form of a great length of zipper tape comprising interlocked zipper strips unwound from a reel or spool. The zipper tape will become many zippers of equal length.
In accordance with the embodiments disclosed herein, the zipper tape is subjected to heat and pressure and/or ultrasonic vibrations and pressure in so-called “transition regions” spaced along the zipper tape at regular intervals, one transition region per length of zipper tape equal to one zipper. A system for forming such transition regions on a zipper tape is schematically depicted in FIG. 4.
As seen in FIG. 4, the zipper processing system comprises a plurality of stations, each of which performs work on each transition region, the stations being spaced along an automated production line at regular intervals. Each transition region on the zipper tape 4′ must pass in succession through the stages depicted in FIG. 4. The direction of zipper advancement is indicated by the arrow. FIG. 4 shows the case where the spacing of the work stations is constant, i.e., one station per zipper length, meaning that during each cycle the zipper tape 4′ is indexed forward by a distance equal to one zipper length, successive stations operating on the same transition region during successive dwell times. However, the person skilled in the art of setting up such equipment for processing plastic zipper tape will recognize that the distance between the centerlines of the work stations may be varied, so long as each such distance is one or multiple zipper lengths.
At station 90, a transition region on zipper tape 4′ is pressed between a first set of mutually opposing heated grooved bars (only one of which is visible in FIG. 4, the other being underneath the zipper tape). Each grooved bar at station 90 preferably has the same structure. FIG. 5 shows an exemplary grooved bar 70 having coplanar flat rectangular surfaces 78 and 82, with a groove 74 therebetween. In this example, the groove 74 has a trapezoidal cross-sectional shape; however, the shape of the groove may be varied as a function of the outer profile of the particular zipper being employed.
Two heated grooved bars of the type shown in FIG. 5 are arranged in mutual opposition at station 90. FIG. 7 shows two such grooved bars 70 and 72 in their respective positions at the start of retraction. For the purpose of illustration, gaps have been exaggerated. Respective sections of closure profiles 10 and 16 are captured between the mutually confronting grooves 74 and 76 of bars 70 and 72 when they are extended. The grooves may be designed to apply a gentle force to the profiles without substantial deformation and, in particular, without flattening the closure profiles. The mutually confronting flat surfaces 82 and 84 of the grooved bars press intervening portions of the upper flanges together with a temperature sufficient to melt the upper flanges together, forming fused upper flanges 54. The height of each grooved bar is generally coextensive with the transition region 110 seen in FIG. 8, which shows a processed portion of the zipper tape. More precisely, the transition region comprises the cross-hatched area in FIG. 8 as well as the areas 114, which are not cross hatched. These areas form a rectangular transition region 110. As indicated by the hatching in FIG. 8, the grooved bars at station 90 are placed so that one edge of the grooved bars is disposed lower than the closure profiles, while the opposing edge is disposed at the level of the edge of upper flange 12.
The grooved bars at station 90 may be designed to apply heat and light pressure to the flanges in the transition region 110 (see FIG. 8) while clearance is provided for the section of the closure profiles within the transition region, which section may be shaped but not flattened. The temperature of the grooved bars is sufficiently high to melt the upper flanges during the allotted dwell time. The portions of the flanges trapped between the flat faces of the grooved bars are melted, while the portions of the closure profiles trapped between the opposing grooves of the grooved bars are shaped and partially fused, but not flattened. In particular, it is desirable that the projecting elements of the closure profiles which are furthest away from each other be melted and later fused to opposing melted portions of the other zipper strip.
Such a state is depicted in FIG. 7, which depicts a cross section of a portion of the closure profiles in the transition region after operation of station 90. FIG. 7 shows two areas 56 and 58 where the zipper strips 6 and 8 have been fused or melded together. Although the separate components are no longer visible in FIG. 7, each fused region 56 and 58 represents a region where a post and an adjoining portion of one zipper strip has been fused with confronting portions of the other zipper strip. For example, the fused region 58 seen in FIG. 7 was formed by fusing portions of post 48 and flanges 12 and 18 seen in FIG. 3. Similarly, the fused region 56 seen in FIG. 7 was formed by fusing portions of post 42 and flange 14 seen in FIG. 3. FIG. 7 shows that the hooks of the monohook elements of zipper strips 6 and 8 have not been fused together in the area where the section was taken. In this particular example, the spaces between undeformed portions of the closure profiles form a plurality of channels 60, 62, 64 and 66 that run lengthwise along the zipper. (Portions of the undeformed closure profiles in the transition region will in turn become respective transition areas, as explained hereinafter.) These channels will not produce leakage through the end of the zipper because they will be closed off during the subsequent profile flattening operation.
However, in the alternative, the transition areas may be formed in a manner such that the hooks of the monohook elements are fused together and there are no channels such as those depicted in FIG. 7.
If necessary, the formation of transition areas may involve one or more operations performed by respective sets of heated grooved bars located at different stations in the machine. The temperatures and pressure at those stations may be varied as required. For example, the state of fusion depicted in FIG. 7 may be attained by station 90 alone or in conjunction with a similarly constructed station downstream from station 90.
At the start of the next work cycle, the zipper tape 4′ is indexed forward until the same zipper section that was pressed at station 90 arrives at ultrasonic welding 92. Station 92 comprises an ultrasonic horn (seen in FIG. 4) and an opposing anvil (not visible in FIG. 4 because it is underneath the zipper tape 4′. The horn and anvil may each comprise a bar constructed as seen in FIG. 6. The bar 98 may have the same size and shape as bar 70 seen in FIG. 5, except that instead of a groove extending across the full width of the bar, the bar 98 has two grooves 103 and 105, separated by a neck portion 104. The flat surface of neck 104 is coplanar with and connected to flat faces 100 and 102, which are disposed on opposite sides of the grooves. The width of the neck portion 104 must be less than (e.g., ⅔) the width of the grooved bars at station 90.
Two bars of the type shown in FIG. 6 can be arranged in mutual opposition at station 92, one of the bars being coupled to an ultrasonic transducer (not shown) that converts electrical current into vibrations. The horn and anvil are extended while the horn is activated. In their extended positions, the horn and anvil will impinge upon the transition region 110 seen in FIG. 8. As the flat surfaces of the horn press intervening portions of the zipper tape 4′ against the flat surfaces of the anvil, those intervening portions are melted and flattened, with some of the material being displaced sideways. At the same time, the portions of the closure profiles that lie between the mutually opposing grooves are not flattened. These unflattened portions of the closure profiles will become transition areas 114 as depicted in FIG. 8. The transition areas 114 are separated by an area 112 in which the closure profiles have been flattened.
If further flattening of the flanges above and below the transition areas is not desired, a horn and an anvil having rectangular faces without grooves and having a width equal to the width of neck portion 104, seen in FIG. 6, could be used to flatten the zipper tape 4′ in an intermediate portion of the transition region 110, thereby flattening the closure profiles between areas 114 seen in FIG. 8.
Welding and sealing of thermoplastic material by ultrasonic vibrations is an established process. A typical ultrasonic welding apparatus in which a workpiece is fed through an ultrasonic weld station comprises an anvil and an oppositely disposed resonant horn. The frontal surface of the horn and the anvil are urged toward mutual engagement, for coupling the ultrasonic vibrations from the activated horn into the thermoplastic material of the workpiece, thereby effecting ultrasonic welding. The horn is energized from a power supply that provides electrical high-frequency power at a predetermined ultrasonic frequency to an electro-acoustic transducer, which, in turn, provides mechanical vibrations at that frequency to a booster or coupling horn for coupling these vibrations to the horn.
Alternatively, station 92 could employ heated bars having the same size and shape seen FIG. 6, thereby avoiding capital investment in ultrasonic welding equipment. In that event, the portions of the closure profiles intervening between the necked portions of the heated bars would be thermally crushed.
At the start of the next work cycle, the zipper tape 4′ is again indexed forward until the same zipper section that was partially flattened at station 92 arrives at station 94, where it is pressed between a set of mutually opposing heated grooved bars (only one of which is visible in FIG. 4). The grooved bars at station 94 may be arranged and configured substantially identically to the grooved bars at station 90, but are heated to a lower temperature and apply a higher pressure than were in effect for the grooved bars at station 90. During operation of the grooved bars at station 94, any dams of plastic created by the ultrasonic welding apparatus on the flanges of the zipper are flattened. Again, the portions of the closure profiles trapped between the opposing grooves of the grooved bars at station 94 (namely, the transition areas 114 seen in FIG. 8) are not flattened. The area contacted by the grooved bars at station 94 approximately overlies the area that was previously contacted by grooved bars at station 90 (namely, the transition region 110 seen in FIG. 8). During the application of heat and pressure by the third set of grooved bars, the transition areas will reside in the gap between the mutually confronting grooves on the bars, and thus will not be flattened.
Alternatively, the work done at stations 90 and 94 could be accomplished using ultrasonic vibrations instead of heated bars. Or, alternatively, the work done at station 92 could be accomplished using heated bars instead of ultrasonic vibrations.
In accordance with the preferred method of manufacture, the heated areas are then cooled by being placed in contact with surfaces of chilled or unheated bars. The zipper tape 4′ is again indexed forward until the same zipper section that was pressed at station 94 arrives at the cooling station 96, where it is pressed between a set of mutually opposing chilled or unheated grooved bars (only one of which is visible in FIG. 4). The grooved bars at station 96 may be arranged and configured substantially identically to the grooved bars at station 92 (one of which is shown in FIG. 6). Again, the portions of the closure profiles trapped between the opposing grooves of the grooved bars at station 96 are not flattened. The area contacted by the grooved bars at station 96 approximately overlies the area that was previously contacted by grooved bars at station 92. During the application of pressure by the chilled or unheated bars, the transition areas will reside in the gap between the mutually confronting grooves on the bars, and thus will not be flattened. The grooved bars at station 96 act as heat sinks, extracting heat from the previously heated thermoplastic material. The material thus cooled would include the upper and lower flanges in the heat-treated zipper section as well as the transition areas. The cooling stations achieve the desired final formation of the transition areas and adjacent areas.
The transition area between crushed and non-crushed closure profiles needs to be correctly formed for containment applications. To successfully form a tight transition area, the zipper processing machine can be set up with grooved bars that are specially designed for the particular zipper being employed. Although FIG. 4 shows two stations 90 and 94 having heated grooved bars for softening and/or melting portions of the zipper profiles and flanges, the number of stations used to form the leakproof zipper end seal will not be the same for all machines and zipper structures. Moreover, the temperature and pressure settings for the heated grooved bars will be based on different line speeds, available dwell times, zipper structures and machine types.
The result of the foregoing operations is seen in FIG. 8, which shows a processed portion of a zipper tape having the cross section generally shown in FIG. 2. Each transition area 114, comprising respective sections of the closure profiles that are at least partly joined together, is connected at one end to an uncrushed portion of the closure profiles 8, 10 and is substantially contiguous at the other end with the flattened area 112. The areas above and below the transition areas 114 and the flattened area 112 form a flattened area generally indicated by cross hatching in FIG. 8. The zipper tape will later be cut along dashed line 111 to form respective zipper end seals for respective individual zippers.
During the zipper formation by the apparatus depicted in FIG. 4, leakproof transition regions are formed. Thereafter, the zipper tape can be fed directly to a zipper applicator on site, which attaches successive zipper-length zipper tape segments to a web of packaging film, each zipper being oriented transverse to the lengthwise direction of the web. Alternatively, the zipper tape can be rolled up and transported for feeding into a zipper applicator located at a different site. Zipper application equipment for attaching three flanges of a three-flange front panel zipper to a web of packaging film is well known. A zipper guide is used to guide a distal portion of the zipper tape into a transverse position overlying the web. Then the distal portion is cut off and heat sealed to the web using two sets of mechanically linked sealing bars, at least one sealing bar of each set being heated. If the zipper was not produced with a pre-activated peel seal, the peel seal would be formed at this time in conjunction with the zipper-to-film sealing operation. The sealing bars of the set that makes zone of web-zipper joinder 24 (see FIG. 9) are straight; the sealing bars of the set that makes zone of web-zipper joinder 26 (see FIG. 9) are racetrack shaped, i.e., two semicircles connected by two straight lines. A tear line 118 (e.g., a line of spaced perforations) is formed in the web before zipper application.
The web with attached containment zippers can be fed directly to an FFS machine (vertical or horizontal) on site or, in the alternative, the web with attached containment zippers can be rolled up and transported for feeding into an FFS machine located at a different site.
In accordance with one embodiment of the invention, the web 2 of bag making film with zippers 4 attached at intervals therealong is fed to a VFFS machine 120 (shown in FIG. 10). The web 2 is fed downwardly over a forming collar 126 and is folded around a filling tube 122. The edges of the web are brought together and pressed by a pair of rollers 124 a and 124 b. These edges of the web are then sealed together by a pair of opposing longitudinal sealing bars 128 a and 128 b to form a longitudinal fin seal 25 (behind the bag in FIG. 9). Contents are then dropped through the tube 122 into the bag 132 that is currently being made. At the time of filling, bag 132 has a bottom seal 22 that was formed when the immediately preceding bag 136 was completed by making a top seal 20. After filling, the top of the instant bag 132 and the bottom of the next succeeding bag 134 are sealed by the action of cross sealing jaws 130 a and 130 b. Each cross sealing jaw 130 a and 130 b comprises a respective pair of mutually parallel sealing bars, the sealing bars of jaw 130 a being aligned with and opposed to the respective sealing bars of jaw 130 b. Both cross sealing jaws 130 a and 130 b are heated to a temperature that causes the front and rear panels to seal together during a preset dwell time (controlled by a programmable controller not shown) in their extended positions, thereby forming a top seal 20 of the just-filled bag and a bottom seal 22 of the immediately preceding unfilled package. The temperature of the sealing bars is controlled by a programmable heat controller (not shown). A knife (not shown in FIG. 10) is incorporated in cross sealing jaw 130 a, while a backing member (not shown) for supporting the film during cutting is incorporated in cross sealing jaw 130 b. When the cross sealing jaws are in their respective extended position, the opposing panels of web 2 are cut by the knife. When the sealing jaws 130 a and 130 b are retracted, the severed bag 136 will proceed to the next stage.
A completed package having a containment zipper attached to the front panel only is shown in FIG. 9. Flange 14 is attached to the front panel by means of heat seal 24; flanges 12 and 18 are attached to the front panel by means of racetrack heat seal 26, which is formed in part by portions of the sealant layers 30 and 32 on flanges 12 and 18. Access to the interior volume of the package is through the portion of the front panel bounded by the racetrack seal 26. A tear line 118 facilitates opening of that portion. The containment zipper has zipper end seals comprising a respective transition area 114 and the flat fused area (indicated by cross hatching) that connects to the transition area 114 on three sides thereof. Those fused areas include area 112 where the closure profiles were flattened. The pre-activated peel seal 36 is disposed between the tear line 118 and the closure profiles 10, 16.
While the invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
As used in the claims, the term “joined” means fused, welded or heat sealed. As used in the claims, the term “package” means a bag, pouch or other flexible container. As used in the claims, the term “panel” includes, but is not limited to, a discrete piece of web material, a portion of a folded piece of web material or two portions of a folded piece of web material joined at a seam. Further, in the absence of explicit language in any method claim setting forth the order in which certain steps should be performed, the method claims should not be construed to require that steps be performed in the order in which they are recited.

Claims

1. A reclosable package comprising:

a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, said first zipper strip comprising a length of a first closure profile having at least two projecting elements and first and second flanges extending in opposite directions and connected to said first closure profile, respective portions of said first and second flanges being flattened within the boundaries of said first and second zipper end seals, and said second zipper strip comprising a length of a second closure profile having at least one projecting element that fits between said at least two projecting elements of said first closure profile and a third flange connected to said second closure profile, respective portions of said third flange being flattened within the boundaries of said first and second zipper end seals, said first and second zipper end seals respectively comprising first and second substantially flat portions and first and second transition areas respectively connected to said first and second substantially flat portions on first, second and third sides, wherein along said first and third sides of each of said first and second transition areas, each of the two projecting elements of said first and second closure profiles that are furthest apart from each other is fused to some portion of the one of said first and second zipper strips of which said respective one of said furthest-apart projecting elements does not form a part; and wherein along a second side of and within each of said first and second transition areas, said first and second closure profiles are deformed and fused together but not flattened, the respective ends of the fused material along said second side being integrally connected to the fused material of said first and third sides, respectively, said third flange being longer than said first flange and extending beyond said first and second zipper end seals in an elevational direction; and

a receptacle comprising top and bottom seals, a first panel connected to and extending between said top and bottom seals, and a second panel connected to and extending between said top and bottom seals, said first and second panels bounding an interior volume of said receptacle,

wherein each of said first through third flanges is joined to said first panel and not joined to said second panel.

2. The reclosable package as recited in claim 1, wherein said first and second closure profiles have a contact area in the range of 33 to 76%.

3. The reclosable package as recited in claim 1, wherein each of said first and second closure profiles comprises two hooked projecting elements and a hookless projecting element.

4. The reclosable package as recited in claim 1, further comprising a peel seal joined to said first and third flanges along their length.

5. The reclosable package as recited in claim 1, further comprising a line of weakness formed in a portion of said first panel that connects the respective portions of said first panel that are joined to said first and third flanges.

6. The reclosable package as recited in claim 5, further comprising a racetrack-shaped zone in which said first panel is joined to said first and third flanges by means of sealant material having a melting point lower than the melting point of the zipper material.

7. The reclosable package as recited in claim 6, wherein each of said first and second zipper end seals extends from an elevation lower than said first and second closure profiles to an elevation higher than a top edge of said first flange, and overlaps a respective portion of said racetrack-shaped zone of joinder.

8. The reclosable package as recited in claim 1, further comprising food product inside said receptacle.

9. The reclosable package as recited in claim 1, further comprising liquid inside said receptacle.

10. The reclosable package as recited in claim 1, further comprising pressurized gas inside said receptacle.

11. The reclosable package as recited in claim 1, further comprising a vacuum inside said receptacle.

12. A reclosable package comprising:

a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, said first zipper strip comprising a length of a first closure profile and first and second flanges extending in opposite directions and connected to said first closure profile, respective portions of said first and second flanges being flattened within the boundaries of said first and second zipper end seals, and said second zipper strip comprising a length of a second closure profile interlockable with said first closure profile and a third flange connected to said second closure profile, respective portions of said third flange being flattened within the boundaries of said first and second zipper end seals, said first and second zipper end seals respectively comprising first and second transition areas disposed at opposite ends of said first and second closure profiles, and first and second substantially flat portions that respectively border said first and second transition areas on three sides thereof, said first transition area comprising first sections of said first and second closure profiles that have been deformed and at least partially fused together but not flattened, and said second transition area comprising second sections of said first and second closure profiles that have been deformed and at least partially fused together but not flattened, said third flange being longer than said first flange and extending beyond said first and second zipper end seals in an elevational direction; and

13. The reclosable package as recited in claim 12, wherein said first and second closure profiles have a contact area in the range of 33 to 76%.

14. The reclosable package as recited in claim 12, further comprising a peel seal joined to said first and third flanges along their length.

15. The reclosable package as recited in claim 12, further comprising a line of weakness formed in a portion of said first panel that connects the respective portions of said first panel that are joined to said first and third flanges.

16. The reclosable package as recited in claim 15, further comprising a racetrack-shaped zone in which said first panel is joined to said first and third flanges by means of sealant material having a melting point lower than the melting point of the zipper material.

17. The reclosable package as recited in claim 16, wherein each of said first and second zipper end seals extends from an elevation lower than said first and second closure profiles to an elevation higher than a top edge of said first flange, and overlaps a respective portion of said racetrack-shaped zone of joinder.

18. A reclosable package comprising:

a zipper comprising first and second zipper strips that have respective portions fused together in first and second zipper end seals, said first zipper strip comprising a length of a first closure profile and first and second flanges extending in opposite directions and connected to said first closure profile, respective portions of said first and second flanges being flattened within the boundaries of said first and second zipper end seals, and said second zipper strip comprising a length of a second closure profile interlockable with said first closure profile and a third flange connected to said second closure profile, respective portions of said third flange being flattened within the boundaries of said first and second zipper end seals, said first and second zipper end seals respectively comprising first and second transition areas disposed and connected to opposite ends of said first and second closure profiles, and first and second substantially flat portions that respectively border said first and second transition areas on three sides thereof, said first transition area comprising first sections of said first and second closure profiles that have been deformed and at least partially fused together but not flattened, and said second transition area comprising second sections of said first and second closure profiles that have been deformed and at least partially fused together but not flattened, wherein third and fourth sections of said first and second closure profiles that are respectively adjacent said first and second sections form channels therebetween, said channels within said third section being either sealed at one end thereof by said first transition area or communicating with channels formed by said first section that are sealed except where they communicate with said channels formed by said third section, and said channels within said fourth section being either sealed at one end thereof by said second transition area or communicating with channels formed by said second section that are sealed except where they communicate with said channels formed by said fourth section, said third flange being longer than said first flange and extending beyond said first and second zipper end seals in an elevational direction; and

19. A method of manufacture comprising the following steps:

(a) interlocking first and second zipper strips of a plastic zipper tape, said first zipper strip comprising a first closure profile and first and second flange extending from said first closure profile in opposite directions, said second zipper strip comprising a second closure profile and a third flange extending further from said second closure profile than said first flange extends from said first closure profile, said first and second closure profiles in combination comprising at least three projecting elements;

(b) applying heat and pressure or ultrasonic vibrations and pressure in first and second zones of said interlocked zipper strips, each of said first and second zones extending from an elevation lower than said first and second closure profiles to an elevation higher than a top edge of said first flange, and having a predetermined dimension in first and second areas of overlap with said interlocked first and second closure profiles, whereby said first and second closure profiles are flattened in first and second sections having a length equal to said predetermined dimension, the midpoints of said first and second sections being separated by one zipper length, said first and third flanges are flattened at least in respective areas directly above said first and second sections of said first and second closure profiles, and said second flange is flattened at least in respective areas directly below said first and second sections of said first and second closure profiles;

(c) before step (b) is performed, applying heat and pressure or ultrasonic vibrations and pressure in first and second transition regions having intermediate portions that will be respectively overlapped by said first and second zones in step (b), heat and pressure or ultrasonic vibrations and pressure being applied to an extent that upon completion of step (c), the projecting elements of said first and second closure profiles that are furthest apart from each other will become fused to respective portions of the other zipper strip in said first and second transition regions, and said first and second closure profiles will be heated but not flattened in said first and second transition regions,

wherein upon completion of steps (b) and (c), said unflattened portions of said first and second closure profiles in said first transition region form first and second transition areas on opposite sides of a first flattened section of said first and second closure profiles, and said unflattened portions of said first and second closure profiles in said second transition region form third and fourth transition areas on opposite sides of a second flattened section of said first and second closure profiles;

(d) after step (b) has been performed, applying pressure in said first and second transition regions to an extent that surface irregularities formed on said first through third flanges during step (b) are flattened without flattening said first through fourth transition areas; and

(e) cutting said first and second zipper strips along first and second lines that respectively intersect said first and second zones to create an individual zipper.

20. The method as recited in claim 19, further comprising the following step:

(f) attaching said individual to a web of packaging material in a transverse direction,

wherein steps (a) through (f) are repeated to form a zipper-carrying web having a multiplicity of zippers attached thereto, said zippers being spaced apart at regular intervals along the length of said web.

21. The method as recited in claim 20, further comprising the steps of forming, filling and sealing said zipper-carrying web on a form-fill-seal machine to make filled packages.