GB2550841A

GB2550841A - Tamper-evident closures for flexible bags

Info

Publication number: GB2550841A
Application number: GB1608002.0A
Authority: GB
Inventors: Orman Kevin
Original assignee: Cm Packaging Ltd
Current assignee: Cm Packaging Ltd
Priority date: 2016-05-06
Filing date: 2016-05-06
Publication date: 2017-12-06
Also published as: GB201608002D0

Abstract

A tamper evident closure for a flexible bag comprising: a zip-fastener having a rib engaging with an opposed groove; a pair of sliders 17,18, each slider causing engagement or disengagement of the groove and rib; and a tamper evident locking member 19 projecting from one slider and receivable in a socket 25 of another slider, so that the slider may be separated by breaking locking member into separate parts. Preferably, locking member comprises separate tabs 21 joined by a frangible narrow neck portion 22. Preferably, sliders comprise windows 25 to indicate presence of tab and tabs are a contrasting colour to slider. Preferably, tab forms step and slider forms shoulder to retain tab in socket. Preferably, sliders are identical.

Description

TAMPER-EVIDENT CLOSURES FOR FLEXIBLE BAGS

This invention relates to a tamper-evident closure in the form of a zip-fastener, for a flexible bag. In particular, but not exclusively, this invention concerns a tamper-evident closure for a bag intended to contain produce, such as grapes, for resale in a retail outlet. The invention further relates to a flexible bag when provided with a tamper-evident zip-fastener closure.

Zip fasteners for the opening to a plastic bag are well known, such fasteners having a projecting rib along one edge of a bag side at the opening, a re-entrant groove along the edge of the opposed side at the opening, and a slider fitted to the edges at the opening, whereby movement of the slider towards a closed position forces the rib to inter-engage into the groove, and movement of the slider towards an open position pulls the rib out of the groove to open the bag. Various rib and groove profiles are possible to achieve the required functionality, in particular to prevent the rib from being pulled out of the groove simply by pulling apart the opposed edges of the bag at the opening. Such zip-fasteners for plastic bags are well known in the art and will not be described in further detail here.

It is known to add a tamper-evident seal to a zip fastener of the kind described above, such that once the bag has been loaded and the slider is moved to the closed position, the tamper-evident seal can be activated whereafter it will be apparent if the slider is moved away from the closed position so opening the bag. Such a tamper evident seal should be designed such that it cannot be re-activated if the slider is moved back to the closed position, whereby it will be apparent for all time that the bag has been opened by moving the slider away from the closed position.

Several examples of tamper-evident zip fasteners for plastic bags are described in EP1096868. In some of these, a cover for the slider is adhered to the bag sides once the slider has been moved to the closed position and that cover must be torn or cut away before the slider can be moved away from the closed position.

In other examples, a blocking member is affixed to the bag on the side of the slider away from its fully closed position and which must be cut, broken or otherwise removed from the bag before the slider can be moved away from the closed position. These examples have the disadvantage that the affixing of the tamper-evident seal requires a positive activity once the bag has been closed, which may be inconvenient, especially when large numbers of bags are to be handled.

Figures 14 and 15 of EP1096868 describe two examples of a tamper-evident closure for a flexible bag which activate automatically when the slider is moved to the closed position. In these, a barb on an end stop (Figure 14) or a barb on the slider (Figure 15) engages in a correspondingly-shaped recess in the other of the slider or the end stop, whereby the barb must be broken away for the component from which it projects before the bag can be opened by moving the slider away from the closed position. Though more useful where large numbers of bags have to be handled, the manufacture of the bag is complex and requires several different components, so that bags incorporating these examples of tamper-evident closures are relatively expensive. Further, if the bag is opened following closure and activation of tamper-evident closure, it is not very easy to see if the bag has been opened by breaching the tamper-evident feature.

It is a principal aim of this invention to provide a tamper-evident closure for a flexible bag which addresses the disadvantages of the closures described in EP1096868, and so which is relatively cheap to manufacture and which, in its preferred forms, provides immediate visual information as to whether the tamper-evident feature has been activated by fully closing the bag, and if the bag has been opened by breaking that tamper-evident feature.

According to this invention there is provided a tamper-evident closure for a flexible bag having opposed sides and an opening between two adjacent edges of opposed sides, the closure comprising a zip-fastener having a rib extending along one edge at the opening and engageable with a groove extending along the opposed edge at the opening, and a pair of sliders each engaged with and arranged to run along the zip-fastener, each slider being configured to cause inter-engagement of the rib and groove when slid towards the other slider and to cause disengagement of the rib and groove when slid away from the other slider, and a tamper-evident locking member projecting from one of the sliders and receivable in a socket in the other slider when the two sliders are slid together to close the opening to the bag, the locking member and socket being configured to resist removal of the locking member from the socket whereby the two sliders may be separated to open the bag only by breaking the locking member into separate parts.

It will be appreciated that with the closure of this invention, there are two sliders each capable of separating or closing the opening; advantageously the sliders are therefore identical but mounted on the rib and groove opposite ways round, for sliding therealong. During manufacture, the locking member may be fitted into one of the sliders, and then when the bag is closed by moving the two sliders fully together the locking member is engaged in the socket of the other slider. Thereafter, the bag can be opened only by breaking the locking member into separate parts, to leave a part of the member in each slider.

In a preferred embodiment, the locking member has a tab part which is received in the socket of said other slider and a weakened zone adjacent the tab part, whereby the locking member can be broken more easily at said weakened zone. The weakened zone may comprise a region of reduced cross-section at which the tab part may be separated from said one of the sliders.

It is highly preferred for the other slider includes a window in register with the socket, whereby the presence of the tab part of the locking member in the socket may be observed. At least the tab part of the locking member may be of a contrasting colour to that of the other slider, in order that the presence of the tab part in the socket may easily be observed. For example, the slider may be “natural” coloured plastic and so essentially transparent, and the locking tab of a bright, readily apparent colour such as red. A step may be formed on the tab part, in which case the socket may have a shoulder behind which the step locates on inserting the tab part into the socket, thereby to restrain the tab part in the socket. Such a step and shoulder may be formed to interlock so as positively to restrain removal of the tab part from the socket, whereby separation is possible only by breaking the tab part from the remainder of the locking member.

As mentioned above, the one and other sliders may be essentially identical, and the locking member comprises a component separate from the sliders and having two tab parts respectively receivable in the sockets of the one and other sliders. In this case, the weakened zone is advantageously disposed between the two tab parts of the locking member. Breaking the member then leaves a tab part in each of the two sliders, to show that the bag has been closed with the two sliders locked together and then has been opened.

This invention extends to a flexible plastic bag having opposed sides and an opening between two adjacent edges of opposed sides, wherein the opening is provided with a tamper-evident zip closure of this invention as described above.

By way of example only, one specific embodiment of a tamper-evident closure provided on a flexible plastic bag for containing produce will now be described in detail, reference being made to the accompanying drawings in which:

Figure 1 is a side view of the bag, being used to contain grapes and with the two sliders of the zip fastener locked together;

Figures 2 to 5 show the sequence of steps in sliding together the two sliders of the zip fastener (Figure 2), the two sliders locked together (Figure 3), breaking apart the two sliders (Figure 4) and opening the bag by moving the two sliders away from each other (Figure 5);

Figures 6A and 6B show one of the sliders from two different angles;

Figure 7 is an underplan of the slider;

Figure 8 is a side view of the slider;

Figure 9 is a sectional view of the slider, taken on line 9-9 marked on Figure 8, but with the locking member received in the slider socket; and

Figure 10 is a sectional view of the slider, taken on line 10-10 marked on Figure 9 and so with the locking member received in the slider socket.

Referring initially to Figure 1, there is shown a flexible plastic bag 10 having two opposed sides 11 (only one of which is visible in Figure 1) joined together at their side edges 12 and the bottom edge 13. Extending along the top edges 14 of the two sides 11 is a zip-fastener 15 having one part on one side edge and the other part on the opposed side edge. When the two parts of the zip fastener are interlocked the bag is closed and when the two parts are separated, the bag is open and access can be gained to the interior. Bags of this kind are very well known and are provided with a slider which is configured to force the two parts of the zip-fastener together when moved in one direction to a closed position, and to pull apart the two parts of the zip-fastener when moved in the opposed direction to an open position. Very often, such bags are used to contain produce of various kinds but a particular usage finding a very large market is for holding grapes, as shown.

The example of bag of this invention shown in the drawings has two essentially identical sliders 17 and 18 mounted to the two parts of the zip-fastener in opposition, such that moving slider 17 in the direction of arrow A opens the bag, and moving slider 18 in the same direction (arrow A) closes the bag. Thus, whenever the two sliders are more or less abutting each other (as shown in Figure 1) the bag will be closed, and whenever the two sliders are separated, the bag will be open between the two sliders. Though the two sliders are shown abutting each other at the left hand end of the zip-fastener in Figure 1, the sliders could be anywhere along the length of the zip-fastener and if still abutting the bag will remain closed.

With the arrangement as described above, the two parts of the zip-fastener typically comprise a rib projecting from and extending along the upper edge of one bag side and a groove formed in and extending along the opposed upper edge of the other bag side. The rib and groove can be formed integrally during the manufacture of the bag or could be formed separately and welded or otherwise bonded to the top edges of the two bad sides. Various rib and groove profiles have been developed to optimise the performance of the zip-fastener but as those form no part of this invention, they will not be described in further detail here.

The zip-fastener is given tamper-evident properties such that when the two sliders have been pushed together as shown in Figure 1, it is apparent that the two sliders are locked together. Then, when the bag is to be opened by relatively separating the two sliders, this can be done only by breaking a locking member and then when the two sliders are separated, it will be apparent that the bag had been locked closed and then opened. As such, it will also be apparent that access may have been had to the contents of the bag.

Figures 2 to 5 show the configuration of the two sliders 17 and 18 in more detail, together with a locking member 19 which confers on the sliders the tamper-evident feature. Each slider has a body 20 which is internally profiled either to push together the rib and groove of the zip-fastener or to pull apart the rib and groove, depending on the direction of movement of the slider relative to the two parts of the zip-fastener. The locking member 19 has two similar tabs 21 joined together by a narrow neck 22 and the body defines a socket 23 for receiving one of the tabs 21. The tab and socket are profiled such that when a tab is fully received in a socket, it is restrained therein and cannot be pulled out of the socket without damaging one or both of the tab and socket. The top face 24 of the slider has a window 25 opening to the socket, such that the presence of a tab 21 in the socket 23 may readily be discerned by observing through the window 25.

Figure 2 shows the bag (in part) as manufactured with the two sliders 17,18 separated and a tab 21 of the locking member 19 restrained in the socket of slider 17. As such the other tab 21 projects towards the other slider 18, and the bag is open between the two sliders. The bag is closed by relatively moving the two sliders 17, 18 until they are abutting, as shown in Figure 3. This pushes the tab 19 projecting from slider 17 into the socket of slider 18 and the presence of the tab in that socket can be discerned through the window 25 of slider 18.

When the bag is to be opened, the two sliders are twisted relative to each other, as shown by arrow B in Figure 4. This breaks the locking member at the neck 22 thereof so allowing the two sliders to be relatively separated (Figure 5), but leaving a tab 21 in each slider body. The visual impact of a tab in a socket can be enhanced by having the sliders and locking member of different colours; for example, the sliders as well as the bag may be of natural plastic and so essentially clear, and the locking member of a strong colour such as red.

Figures 6A, 6B and 7 to 10 show the slider 17 or 18 in more detail and also the locking member 21. The slider body 20 is moulded from a plastics material and has curved side flanks 27 provided with external finger-grips 28 to assist the moving of the slider along the zip-fastener. In addition to the socket 23 and window 25, the top face 24 has a recess 29 merely to minimise shrinkage during moulding and ensure the slider can easily be produced to have an accurate profile. A slot 30 is formed in the lower part of the body 20, the slot tapering in width from the front end 31 of the body 20 to the rear end 32. Flanges 33 are provided at the lower edge of the slot to retain the slider on the zip-fastener, and a driving member 34 is arranged to pull the two parts of the zip-fastener apart when the slider is moved in the appropriate direction along the zip-fastener. Conversely, the slider is moved in the opposite direction, the tapering slot forces together the two parts of the zip-fastener, so inter-engaging the rib into the groove as described hereinbefore.

As best seen in Figures 6B and 10, a transverse wall 36 extends across the entrance to the socket, that wall defining the front edge of the window 25 with the entrance to the socket 23 being below the wall 36. Each tab 21 of the locking member 19 has an upper face 37 lying at a shallow angle to the lower face 38 such that the thickness of the tab tapers towards its free end 39. A shoulder 40 is formed in the upper face 37 such that when the tab is fully inserted in the socket, the shoulder 40 engages behind the transverse wall 36 and prevents the tab being withdrawn. The tapering thickness of the tab serves to facilitate the insertion of the tab into the socket, by springing the transverse wall, thereby giving a snap-fit.

During manufacture of an example of a plastic bag 10 to incorporate the tamper-evident zip-fastener 15, the two parts of the zip-fastener are welded to the two edges of the bag at the opening. The two sliders 17,18 are then fitted to the zip-fastener parts, with the front faces 31 of the sliders confronting each other. The two ends of the zip-fastener are welded together to prevent the sliders running off the zip-fastener. Finally, a tab 21 of the locking member 19 is pressed into the socket 23 of one of the sliders and the bag is thereafter ready for use.

Claims

1. A tamper-evident closure for a flexible bag having opposed sides and an opening between two adjacent edges of opposed sides, the closure comprising a zip-fastener having a rib extending along one edge at the opening and engageable with a groove extending along the opposed edge at the opening, and a pair of sliders each engaged with and arranged to run along the zip-fastener, each slider being configured to cause inter-engagement of the rib and groove when slid towards the other slider and to cause disengagement of the rib and groove when slid away from the other slider, and a tamper-evident locking member projecting from one of the sliders and receivable in a socket in the other slider when the two sliders are slid together to close the opening to the bag, the locking member and socket being configured to resist removal of the locking member from the socket whereby the two sliders may be separated to open the bag only by breaking the locking member into separate parts.

2. A tamper-evident closure as claimed in claim 1, wherein the locking member has a tab part which is received in the socket of said other slider and a weakened zone adjacent the tab part, whereby the locking member can be broken at said weakened zone.

3. A tamper-evident closure as claimed in claim 2, wherein the weakened zone comprises a region of reduced cross-section at which the tab part may be separated from said one of the sliders.

4. A tamper-evident closure as claimed in claim 2 or claim 3, wherein said other slider includes a window in register with the socket, whereby the presence of the tab part of the locking member in the socket may be observed.

5. A tamper-evident closure as claimed in claim 5, wherein at least the tab part of the locking member is of a contrasting colour to that of the other slider, in order that the presence of the tab part in the socket may easily be observed.

6. A tamper-evident closure as claimed in any of the preceding claims, wherein a step is formed on the tab part and the socket has a shoulder behind which the step locates on inserting the tab part into the socket, thereby to restrain the tab part in the socket.

7. A tamper-evident closure as claimed in any of the preceding claims, wherein said one and other sliders are essentially identical.

8. A tamper-evident closure as claimed in claim 7, wherein the locking member comprises a component separate from the sliders, the locking member having two tab parts respectively receivable in the sockets of the one and other sliders.

9. A tamper-evident closure as claimed in claim 2 and claim 7, wherein the weakened zone is disposed between the two tab parts of the locking member.

10. A tamper-evident closure as claimed in claim 9, wherein the weakened zone comprises a narrow neck formed between the two tabs.

11. A tamper-evident closure as claimed in any of claims 8 to 11, wherein the locking member is formed from a frangible material.

12. A tamper-evident closure as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

13. A flexible bag comprising opposed sides and an opening between two adjacent edges of opposed sides, wherein the opening is provided with a tamper-evident closure as claimed in any of the preceding claims.