GB2277080A - Tamper evident closure and container with thread positioning means - Google Patents

Abstract

A closure (1) for a container (20) e.g. of the push-on, screw-off type has a cap portion (2) with a dependent skirt (3) having a screw-thread (8) for engagement with a corresponding screw thread (22) on the container (20). The skirt (3) has a frangible removable annular tear band (4) having a plurality of teeth (13) for engagement with at least one tooth (24) on the container (20). At least one of the tear band teeth (13) has a leading edge (14) which is angled so that, as the closure (1) is pushed onto the container (20), said tear band tooth (13) engages with said at least one container tooth (24) to cause the closure (1) to rotate backwards to ensure proper relative orientation between the threads on the closure and container to effect a seal. A dependent plug 7 may be provided within the cap to seal against the wall of the neck 21. Sealing may be effected with the closure as much as one full rotation short of fully home. <IMAGE>

Description

A CLOSURE AND CONTAINER The present invention relates to a closure for a container and a combination of a closure and container.

There are numerous types of closures for containers for holding milk, orange juice or the like. Many of these closures generally have a cap portion with a dependent skirt. Tear bands are frequently provided on the skirt and have ratchet teeth which engage with corresponding teeth around the base of the neck of the container so that removal of the closure necessitates fracturing of the thin web or bridges between the tear band and the closure skirt, which therefore provides evidence that the container seal has been broken, allowing detection of tampering.

There has been a recent demand for closures of the "push-on, screw-off" type. In this type of closure, the closure can be pushed onto the container by the dairy or other bottler, which is convenient as the machines for applying the closures can be relatively simpler as no rotation of the closure is required. The consumer unscrews the closure, which breaks the tear band allowing removal of the closure, and can replace the closure by screwing as normal.

Because the screw thread in the closure skirt must ride over the screw threads on the container neck as the closure is pushed onto the container, and are not screwed onto the container threads, it is necessary to ensure that the threads are correctly radially and axially orientated with respect to one another to ensure that the closure and container threads fully engage.

According to the present invention, there is provided a closure for a container, the closure having a cap portion with a dependent skirt having a screw-thread for engagement with a corresponding screw thread on a container, the skirt having a frangible removable annular tear band having a plurality of teeth for engagement with at least one tooth on the container, at least one of the tear band teeth having a leading edge which is angled so that, as the closure is pushed onto a container, said tear band tooth engages with said at least one container tooth to cause the closure to rotate backwards to ensure proper relative orientation between the threads on the closure and container to effect thread engagement.

Because it is unlikely that the threads are correctly positioned as the closure is pushed onto the container, since this only happens over a relatively small range, it is often necessary to rotate the closure slightly on the container neck to ensure that the threads on the container and closure are correctly orientated with respect to each other and do not sit one directly on top of the other.It is not desirable to overtighten the closure on the container and therefore the leading edge of said at least one tooth on the tear band is angled so that the closure rotates backwards (i.e. in an anti-clockwise direction) if the threads are not correctly orientated; the radial position of the leading edge of said tooth is preferably set relative to the vertical position of the thread on at least the closure to ensure that the correct orientation is achieved in turn to ensure reliable sealing and closure retention. The degree of angling of said tooth is also preferably set to ensure that the proper orientation is achieved between the screw threads.

Each of the closure teeth may have a leading edge which is similarly angled.

The cap portion of the closure may have a dependent plug for sealing engagement with the interior of the neck of the container.

The present invention also includes, in combination, a closure as described above and a container having a neck and at least one tooth for engagement with said at least one tooth on the tear band.

The or each container teeth may be angled similarly to the or each teeth on the closure.

The container neck may have an annular bead which engages between the skirt and the dependent plug in the example referred to above, the annular bead urging the wall of the neck of the container into sealing engagement with the dependent plug.

An example of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective cut-away view of a closure; and, Figures 2 to 5 are perspective views showing the closure being fitted to and removed from the container.

A closure 1 is of generally circular cross-section shape and consists of a disk-like cap portion 2 having a dependent skirt 3. An annular tear band 4 is integrally fixed to the lower edge 5 of the skirt 3 by a plurality of radially spaced bridges or webs 6.

The cap portion has an annular dependent wall 7 within the skirt 3 which forms a plug which fits inside the interior of the neck of a container to be described below.

A screw thread 8 is provided internally of the skirt 3. A twin-start or other multi-start thread may alternatively be used.

The skirt 3 flares out at a point about 1/3 of the way down the skirt. The outer surface of the lower portion of the skirt 3 has serrations 9 or is otherwise profiled to provide a better grip for the user.

The tear band 4 has a deep generally V-shape notch 10 with a small bridge 11 at the bottom of the notch 10 at which the tear band 4 can be easily broken for removal. A portion 12 of the tear band 4 adjacent the notch 10 has a number of serrations 12 or is otherwise profiled also to provide a better grip for the user.

The tear band 4 is provided internally with a number of regularly spaced teeth 13. The teeth 13 extend the full height of the tear band 4. In the example shown, each of the teeth 13 has a leading edge 14 which, on moving down the teeth 13 in Figure 1, is angled backwards (i.e. in an anticlockwise direction). The base 15 of the leading edge 14 of one of the teeth 13 may coincide with the start 16 of one of the threads 8 as shown in Figure 1.

A container 20 has a neck 21 having a screw thread 22 which engages with the screw thread 8 on the closure 1.

The upper portion of the screw thread 22 is interrupted as shown to provide two pairs of diametrically opposed thread portions 23. The radius of this upper portion 23 of the thread 22 may be very slightly less than that of the lower portion of the thread 22. Around the base of the neck 21, a plurality of wedged teeth 24 are provided. These teeth 24 are angled similarly to the teeth 13 in the closure 1.

It will be seen from the drawings that the teeth 24 are not regularly spaced around the whole neck 21 as this simplifies moulding of the container.

An annular externally projecting bead 25 may be provided on the neck 21 closely adjacent to the mouth 26 of the container 20. The neck 21 of the container is flared similarly to the skirt 3 of the closure 1.

The closure 1 and container 20 are preferably each made of a resilient material such as plastics, relatively high density plastics being preferred for at least the closure 1.

The closure 1 is fitted to the container 20 simply by pushing the closure 1 down onto the neck 21 of the container, usually by machine. The resilience of the material of the closure 1 allows the thread 8 on the closure 1 to ride over the thread 22 on the container 20 as the closure 1 is pressed down. Initial engagement between the closure 1 and the container 20 is facilitated by the upper portion of the container thread 22 being interrupted as the closure 1 can bow outwards slightly at positions corresponding to the thread portions 23. This initial engagement may be achieved using light pressure applied by unpowered rollers under which the container 20 may pass and is sufficient to hold the closure 1 on the container 20 during movement of the container 20 downstream in a production line whilst preventing entry of foreign bodies into the container 20.

The closure 1 is then pressed fully home on the container 20 by a larger force applied by powered rollers for example. As the closure 1 moves further down the container neck 21, the leading edges 14 of the teeth 13 on the tear band 4 engage with the leading edges 27 of the teeth 24 on the container 20.Because of the relative angling of the leading edges 14, 27 of the respective teeth 13, 24, unless the closure teeth 13 happen to fall precisely between the container teeth 24 (which in practice is unlikely), the respective leading edges 14, 27 interact to drive the closure 1 backwards (i.e. in an anti-clockwise direction) slightly which, by virtue of the relationship between the position of the teeth 13, 24 relative to the respective threads 8, 22 ensures that the threads 8, 22 are correctly radially and axially positioned with respect to one another so that the closure 1 can be pressed fully home ensuring good attachment of the closure 1 to the container 20 for reliable sealing and closure retention.

As the closure 1 is moved towards the fully home position on the container neck 21, the wall of the neck 21 enters the space between the dependent plug 7 and the skirt 3. At this point, the plug 7 bears against the inner surface of the container neck 21 providing a good seal.

This seal is further strengthened by the annular bead 25 on the container neck 21 pressing against the outer wall 3 of the closure 1, the reaction force pressing the container neck 21 into stronger engagement with the plug 7.

The plug 7 may provide a seal with the inner surface of the container neck 21 over an axial movement of the closure 1 of say x mm. In order to ensure that the tamperevident feature of the tear band 4 is achieved, the respective teeth 13, 24 on the closure 1 and container 20 must be meshed when the closure 1 is pressed onto the container 20 and after any backwards rotation of the closure 1 on the container 20. Now, the closure 1 may be positioned on the container 20 as much as one full rotation of the closure 1 short of the fully home position whilst sealing is still provided by the plug 7.In order to ensure reliable sealing by the plug 7 at all times, i.e. to cover the range from the fully home position up to as much as one full turn from the fully home position, it is therefore necessary to ensure that the relationship between the spacing between adjacent closure teeth 13, and the spacing between the closely adjacent container teeth 24, and the helix angle of the threads 8, 22, is such that the closure 1 rises a distance of less than x mm (the distance over which sealing by the plug 7 is provided) during one complete rotation of the closure 1 on the container 20 whilst ensuring that the respective closure and container teeth 13, 24 remain meshed.In an exemplary embodiment, the plug 7 provides a seal over an axial movement of the closure 1 of 1.47mm; the diameter of the thread 8 on the closure 1 is 38mm; the angle subtended by the closure teeth 13 at the centre of the closure 1 is 120; the diameter of the lower continuous portion of the thread 22 on the container 20 is 37mm; the angle subtended by the container teeth 24 at the centre of the neck 21 is 120 or an integer multiple of 120; and, the height of the closure and container teeth 13, 24 is 4.2mm.

To remove the closure 1 from the container 20, it is necessary to break the small bridge 11 at the notch 10 in the tear band 4, which allows the serrated end of the tear band 4 to be pulled back, thereby allowing subsequent complete removal of the tear band 4 by breaking each of the bridges 6 between the tear band 4 and the lower edge 5 of the skirt 3. It is not possible to remove the closure 1 without breaking the tear band 4 from the skirt 3 as, if the closure 1 is rotated as a whole, the engagement between the teeth 13, 24 is strong enough to cause the bridges 6 to break. Alternatively, it is not possible to lever under the tear band 4 to remove the closure 1 without breaking the bridges 6 because of the engagement between the screw threads 8, 22.

Once the tear band 4 has been removed, the remaining part of the closure 1 can be unscrewed as shown in Figure 4. The closure 1 can be screwed back, or pushed back, onto the container 20 as shown in Figure 5. A good seal is maintained because of the engagement of the plug 7 with the neck 21 of the container 20.

The closure 1 described above can be initially screwed onto the container 20 rather than initially pushed on if necessary so that it can be used in conventional equipment of the screw-on type.

In order to ensure that the closure 1 is not overtightened on the container 20, an end stop, for example in the shape of a small square peg (not shown), may be provided on the container neck 21 against which the end of the thread 8 on the closure 1 bears at the fully home position of the closure 1. The end of the closure thread 8 may be square to abut more completely with the square peg.

Claims (10)

1. A closure for a container, the closure having a cap portion with a dependent skirt having a screw-thread for engagement with a corresponding screw thread on a container, the skirt having a frangible removable annular tear band having a plurality of teeth for engagement with at least one tooth on the container, at least one of the tear band teeth having a leading edge which is angled so that, as the closure is pushed onto a container, said tear band tooth engages with said at least one container tooth to cause the closure to rotate backwards to ensure proper relative orientation between the threads on the closure and container to effect thread engagement.

2. A closure according to claim 1, wherein each of the closure teeth has a leading edge which is similarly angled.

3. A closure according to claim 1 or claim 2, wherein the cap portion of the closure has a dependent plug for sealing engagement with the interior of the neck of the container.

4. In combination, a closure according to any of claims 1 to 3, and a container having a neck and at least one tooth for engagement with said at least one tooth on the tear band.

5. A combination according to claim 4, wherein the or each container teeth is angled similarly to the or each teeth on the closure.

6. A combination according to claim 4, or claim 5, when dependent on claim 3, wherein the container neck has an annular bead which engages between the skirt and the dependent plug, the annular bead urging the wall of the neck of the container into sealing engagement with the dependent plug.

7. A combination according to any of claims 4 to 6, wherein the container has a screw thread the upper portion of which is interrupted to facilitate pushing-on of the closure.

8. A combination according to any of claims 4 to 7, wherein the container has an end stop against which the screw thread on the closure bears at the fully home position of the closure on the container.

9. A closure substantially as described with reference to the accompanying drawings.

10. A closure and container substantially as described with reference to the accompanying drawings.