Reclosable Bag

Abstract

The bag has an elongate opening 20 in a front panel 10 of the bag. The opening 20 is openable and reclosable by a zipper 22 located in the opening 20 and consisting of first and second profiles, having interengagable male and female formations, and a slider for engagement and release of the formations. Each profile further has a flange which is secured to the front panel of the bag adjacent the opening 20. The flanges extend in opposite directions from the interengagable parts of the profiles. A closure sheet 60 covers the zipper to form a tamper-evident feature and is releasable along a line-of-weakness 64.

Description

The present invention relates to reclosable bags, and other containers, having reclosable fasteners of the type known as “zippers”.

“Zippers” are a particular type of reclosable fastener which consist of first and second lengths of material, usually plastics, which are shaped to engage with each other along their lengths and can be released from engagement and repeatedly re-engaged and re-released. The zipper can thus form a reclosable fastener for a container, for example a plastics bag. The individual lengths of material making up the zipper are known as “profiles”. The profiles can be engaged by pressing them together and released by pulling them apart. Alternatively, the zipper may be fitted with a slider which is moveable along the zipper to cause engagement and release the profiles upon movement of the slider in first and second opposite directions. These zippers are known as “slider zippers”. The present invention is concerned with bags and other containers having reclosable slider zipper fasteners.

A particular concern with the bags and other containers to which this invention relates is to provide a “tamper evident” feature. This is a feature which makes it evident that the container has been opened subsequently to the putting into place of the tamper-evident feature.

The present invention provides a reclosable container having a wall portion having therein an elongate opening in which is located a zipper closure which comprises first and second interengagable profiles and a slider mounted on the profiles and slidable therealong to engage and disengage the profiles upon sliding movement in respective opposite directions, wherein each zipper profile comprises a longitudinally-extending body portion and a longitudinally-extending lateral flange portion, the body portions overlapping each other and being shaped to interengage when pressed together by movement of the slider in one of its directions of movement and to be separated from each other by movement of the slider in the other, opposite direction, and the flange portions extend from the respective body portions in directions opposite to each other.

Conveniently, the body portions are substantially identical to each other in cross-sectional shape.

Advantageously, the flange portions are substantially coplanar with each other.

Preferably the reclosable container has a closure sheet which encloses the zipper closure and provides a tamper-evident feature.

Advantageously, the closure sheet is attached to the flange portions of the zipper along their lengths.

Preferably, the closure sheet is attached to at least one flange portion along a line of weakness.

The reclosable container is preferably a reclosable bag. Advantageously, the elongate opening is formed in a major planar surface of the bag.

An embodiment of the invention will now be described by way of example with reference to the drawings, in which:

FIG. 1 is a front view of an upper portion of a bag having an opening in which a reclosable fastener is located;

FIG. 2 is a perspective view of the bag of FIG. 1;

FIG. 3 is a section on the line III-III of FIG. 1, on an enlarged scale;

FIG. 4 is a section on the line IV-IV of FIG. 1, also on an enlarged scale;

FIG. 5 is a section on the line V-V of FIG. 4, on an enlarged scale;

FIG. 6 is a section on the line VI-VI of FIG. 3, on a reduced scale; and

FIG. 7 is a schematic drawing showing the manufacture of the bag of FIG. 1.

Referring first to FIGS. 1 and 2 of the drawings, these show a bag formed from a suitable plastics film material, such as polyethylene, and having a rectangular front panel 10, a rectangular rear panel 12 and two gusset-forming side panels 14. The front and rear panels 10, 12 are joined to the side panels 14 by respective side welds 16 formed by the application of heat and pressure to the plastics film material. The bag may be constructed from individual panels 10, 12, 14 joined by the welds 16 which are then seams or, as is preferred, folded from a single piece of film material. In the latter case, the bag may have a longitudinal back seam where the longitudinal edges of the film overlap and are heat sealed to each other. When present, the back seam is preferably located centrally of the rear panel 12. In an alternative construction, also formed from a single piece of material, longitudinal edges of the film are joined to each other at one of the side welds 16. When the bag is constructed from more than one piece of film, the pieces of the film are preferably joined to one another at the side welds 16. In all the constructions mentioned, those side welds 16 which do not form a join between separate pieces of film material are formed by welding the folded film to itself each side of the respective fold line. The top of the bag is shown open in FIGS. 1 and 2.

Close to its upper edge, the front panel 10 of the bag is formed with a slot 20 which is rectangular, apart from rounded end portions 21. The slot 20 extends across a major portion of the width of the bag, being close to the side welds 16 at each end. A length of zipper 22 is located in the slot 20 and serves to open and close the slot. The zipper 22 is shown in more detail in FIGS. 3 to 6 of the drawings. It consists of first and second profiles 24, 26 which are substantially identical in cross-sectional shape, and a slider 28 which is mounted on the profiles 24, 26 and is slidable longitudinally along the profiles. The slider 28 consists of a body 30 having first and second cavities 32, 34 and a central partition 36. The slider 28 further has a pivoted tab 38 which can conveniently be grasped between thumb and finger for movement of the slider 28 along the profiles 24, 26 of the zipper 22.

One zipper profile 24 consists of a flange 40 and a body portion 44 respectively. The other profile 26 consists of a flange 42 and a body portion 46. The flanges 40, 42 extend in opposite directions from the body portions 44, 46. Each body portion 44, 46 has two longitudinal ridges 48 and two longitudinal grooves 50 which provide male and female formations which are shaped to engage one with the other and to form a closure between the profiles. The slider 28 is slidable along the zipper profiles 24, 25. Each slider body portion 44, 46 is received in a respective cavity 32, 34 of the slider 28. Sliding of the slider along the profiles results in the ridges and grooves 48, 50 of the respective body portions 44, 46 being brought into and out of engagement with each other upon movement of the slider in respective opposite directions. This is achieved by the partition 36 of the slider which is shaped in section as shown in FIG. 5 and serves to separate the profiles 24, 25 upon movement in one direction (left-to-right in FIG. 5) and to bring the profiles into engagement upon movement in the opposite direction.

The flanges 40, 42 of the zipper 22 are secured by heat or pressure, or a combination of heat and pressure, to respective inner surface portions 50, 52 of the front panel 10 of the bag adjacent the opening 20.

A closure strip 60 is secured to the flanges 40, 42 of the zipper 22 adjacent their outer edges. The closure strip 60 is formed from polythene having a polyester or nylon layer laminated thereto. The strip is thus formed from a barrier laminate material. The closure strip 60 is further secured to the zipper flanges 40, 42 across their ends adjacent the rounded slot end portions 21. Securement is such that the closure strip 60 is joined by a heat and/or pressure seal 62 to the upper zipper flange 40 and across the ends of the flanges 40, 42. It is secured by way of a line-of-weakness forming material 64 to the lower zipper flange 42. The line-of-weakness forming material may be formed by a longitudinally extending coated strip of a polymer which is a blend of polyethylene and polybutylene. The inclusion of the polybutylene component reduces the effectiveness of the polyethylene as a seal-forming material, the greater the polybutylene component, the less the sealability. By selection of the amount of polybutylene component, a desired sealability can be obtained.

The zipper 22 may be applied to a web of the plastics film material from which the bag is eventually made by use of what is known as “cross-web technology”. This means that individual lengths of zipper are applied to the web to external transversely, usually perpendicularly, to the longitudinal direction of the web and spaced at longitudinal intervals. Our international patent application WO-A-03/097341 describes and claims a method of and apparatus for applying the zipper to the web whilst the web is moving; our co-pending UK application 0401500.4 claims further methods and apparatus, also for applying the zipper to the moving web.

The slider 40 may be mounted on the zipper profiles prior to their being cut to length and applied to the web. Our copending UK patent application 0406626.2 describes and claims an apparatus for and method of achieving this. Slider applicators for use in such apparatus and methods are available from Supreme Plastics limited of Supreme House, 300 Regents Park Road, London, N3 2TL, UK.

FIG. 7 shows schematically a method of making a web which can subsequently be used to make a bag as shown in FIG. 1 to 6. The method uses cross-web technology. A supply roll 100 of suitable plastics film material 102. A continuous web of the material 102 is first fed upwardly, around a guide roller 104 and then horizontally, before passing around a further guide roller 106 and thence to a take-up roller 108. Between the guide rollers 104, 106 the web passes through successive stations where the following operations are carried out. At a first station 110, the web is stopped and a punch (shown only schematically in FIG. 7) operates to cut the slot 20 in the material from which the bag is to be made. After cutting of the slot 20, the web is restarted and advanced so that the slot 20 comes to a second station 120 when the web is again stopped. A rotary turret 122 (shown schematically) is located at the second station and is used for applying pre-cut lengths of zipper 124 to the web by use of a heated pressure bar (not shown). The zipper is fed from a supply (shown schematically at 126), through a slider applicator 127 and thence to the turret 122 after passing around a guide roller 129. Sliders are applied to the zipper at a slider applicator 127 as referred to above, to which sliders are fed from a supply 128 thereof.

After application of the zipper strips, the web is advanced to a third station 130 where the closure strip 60 fed from a source 132 thereof is applied by means of a sealing bar applying heat and/or pressure and shown schematically at 130. Such sealing bars are known per se. A knife, shown schematically at 134 severs the closure strip into predetermined lengths. The web is then rolled onto a take-up roller 108 for subsequent use. The process is therefore of the type generally known as a reel-to-reel process.

In an alternative arrangement, the closure strip is sealed to the zipper strip before application of the zipper strip to the web. The closure and zipper strips are then fed to the web from a common source, and applied at a single station replacing the second and third stations 120, 130. The sliders are again mounted on the zipper by a slider applicator.

In further modified apparatus and methods, the take-up reel is replaced by a bag-making machine to produce empty bags which can be filled (through their open bottoms) and sealed subsequently. Such bags are known as “pre-made bags”.

By way of further modification, the bag-making machine is omitted and replaced by a form-fill-seal machine which may be vertically or horizontally operating. Examples of such machines and their use in conjunction with cross-web technology are to be found in international patent application WO-A-03/097341 and UK patent applications 0401500.4 and 0406626.3 referred to above. The web is thus used as part of a “form-fill-seal” process.

When access to the contents of the closed and filled bag is required, the closure strip 60 is peeled away on the line 64 to gain access to the zipper 22 which can thus be opened by means of the slider 28. It will be evident that the closure strip 60 thus contributes a tamper-evident feature.

In a modified bag, the closure strip 60 is on the outside of the front wall 10 and is peeled away to provide access to the zipper.

Claims

1. A reclosable container having a wall portion having therein an elongate opening in which is located a zipper closure which comprises first and second interengagable profiles and a slider mounted on the profiles and slidable therealong to engage and disengage the profiles upon sliding movement in respective opposite directions, wherein each zipper profile comprises a longitudinally-extending body portion and a longitudinally-extending lateral flange portion, the body portions overlapping each other and being shaped to interengage when pressed together by movement of the slider in one of its directions of movement and to be separated from each other by movement of the slider in the other, opposite direction, and the flange portions extend laterally from the respective body portions in directions opposite to each other.

2. A reclosable container according to claim 1, wherein the body portions are substantially identical to each other in cross-sectional shape.

3. A reclosable container according to claim 1, wherein the flange portions are substantially coplanar with each other.

4. A reclosable container according to claim 1, having a closure sheet which encloses the zipper closure and provides a tamper-evident feature.

5. A reclosable container according to claim 4, wherein the closure sheet is attached to the flange portions of the zipper along their lengths.

6. A reclosable container according to claim 5, wherein the closure sheet is attached to at least one flange portion along a line of weakness.

7. A reclosable container according to claim 6, which is a reclosable bag.

8. A bag according to claim 7, wherein the opening is formed in a major planar surface of the bag.

9. (canceled)