GB2269372A

GB2269372A - Cap with tamper-evident band

Info

Publication number: GB2269372A
Application number: GB9216692A
Authority: GB
Inventors: Henryk Dudzik
Original assignee: Lawson Mardon USA Inc
Current assignee: Amcor Specialty Cartons Americas LLC
Priority date: 1992-08-06
Filing date: 1992-08-06
Publication date: 1994-02-09
Also published as: GB9216692D0

Abstract

A cap (10) for a container, eg a glass container, has a top (11) and a skirt (14), the end of the skirt (14) remote from the top (11) being attached by a plurality of frangible means (30) to a ribbed tamper-evident band (20). The band (20) has faces (22) for engaging a formation on the container and has sufficient flexibility to allow the faces (22) to be pushed over the formation. A plurality of axially extending ribs (40) are provided on the band (20) to which the frangible means (30) are connected, the ribs (40) being less flexible than the remainder of the band (20). Preferably the ribs are triangular in cross section and the band is rebated at (50) between the ribs to increase flexibility. The top (11) of the cap may carry sealing projections (12) and (13). The cap is moulded in one piece. <IMAGE>

Description

CAP WITH TAMPER-EVIDENT BAND This invention relates to a cap with a tamper-evident band.

It is well known to provide a moulded plastics cap for a container, the cap having a top and a skirt, in which the end of the skirt remote from the top is attached to a tamper-evident band by a plurality of frangible connections. The cap is not removable from the container without breaking the frangible connections so that the cap is separated from the band. In this way, an indication of tampering is provided since the cap cannot be re-attached to the band once the frangible connections have been broken.

Such bands are usually provided on screw caps in which the band has one or more projections which extend inwardly towards the axis of the band. As the cap is screwed onto the container, the skirt resiliently expands as the projections pass over a collar present on the neck of the container, and snaps back so that the projections engage under the collar to resist removal of the cap, while the frangible connections are still intact.

A cap has to be matched to a particular container and the outer diameter of the collar, the radial extent of the projections on the cap and the flexibility of the band have to be predetermined within manufacturing tolerances for effective operation.

For a given manufacturing tolerance of the outer diameter of the collar, the radial extent of the projections and the flexibility of the band should be sufficient to ensure that the cap and band cannot be pulled off the container and replaced without breaking the frangible connections. If this were to take place, then there would be no evidence that tampering had occurred. The radial extent of the projections and the flexibility of the band must also be adapted so that the band does not break as it is pushed over the collar during fitting of the band to the container.

These considerations are easily accommodated when the container is made from a plastics material because plastics can be moulded with small tolerances. There are problems with using caps and tamper-evident bands with glass containers, however, because the manufacturing tolerances of glass are much larger than those of plastics. Hence, the outer diameter of the collar on glass containers tends to vary over a relatively large range. The cap and band may be capable of being slipped off the container, without breaking the frangible connections, when the collar has an outer diameter at the lower end of the range, or the band may break during fitting of the cap on the container when the collar's outer diameter is at the upper end of the range.

There have been proposals in the prior art to overcome this problem, but each involves use of an additional manufacturing process. One such proposal is that the band should be oversized to fit over the largest diameter collar without difficulty. A separate process of heat-shrinking the band on the container is then carried out.

The present invention overcomes the problem without the need for an additional processing step.

GB-2172239 discloses a method for moulding caps with tamperevident bands, wherein the cap, band and frangible means are formed as part of a single, one-piece injection moulding. The mould used in the method has separable parts, which leave the moulded cap and band on a male core for axial stripping of the cap from the core in a single operation. The stripping step imposes restrictions on the degree of flexibility of the band that can be tolerated when removing the cap and band from the mould. If the band is too flexible, then the stripping means tends to slide between the band and the core without effecting stripping. In addition to the problems discussed above, it is also necessary, therefore, to ensure that the cap can be stripped from the mould.It is also necessary to ensure that the projections are sufficiently deep to engage the collar throughout the tolerance range, without being so deep that the cap cannot be stripped from the mould.

The present invention overcomes these problems by providing a cap for a container, the cap having a top and a skirt, the end of the skirt remote from the fop being attached by a plurality of frangible means to a tamper-evident band in which the band has faces for engaging a formation on the container, the band having sufficient flexibility to allow the faces to be pushed over the formation, characterised in that the band has a plurality of axially extending ribs to which the frangible means are connected, the ribs being less flexible than the remainder of the band.

The cap may be made in a simple injection moulding operation, e.g. as disclosed in GB-2172239, the band being sufficiently flexible to be usable with a glass container having the usual manufacturing tolerances. The ribs act as pivot points for intervening flexible parts of the band that lie therebetween.

The flexible parts are, thus, able to pivot and move radially as the band is fitted over a collar of a container, while the ribs provide sufficient rigidity for the band to snap back under the collar and resist removal. The ribs also act as a platform for the mould stripper to ensure effective stripping of the cap from the core of a mould.

Reference is now made to the accompanying drawing, wherein the sole figure shows a sectional view of a cap with a tamper-evident band according to the present invention.

The cap 10 has a top 11, formed with inner sealing projections 12 and 13, and a skirt 14 formed with screw threads 15. A tamper-evident band 20 is joined to the skirt 14 by circumferentially spaced, thin, frangible connections 30, so that a space 31 is provided between the cap 10 and the band 20.

The cap 10 and the band 20 are moulded together as a single unit from a plastics material, e.g. by the method disclosed in GB2172239, wherein the cap and band are stripped from the mould by a stripping means.

The band 20 is formed with engaging members 21, projecting inwardly towards the axis of the cap 10 and band 20, and having faces 22 for engaging a collar provided on the neck of the container to which the cap 10 and band 20 are to be fitted.

The band 20 is provided with a plurality of axially extending ribs 40. The ribs are equally spaced around the circumference of the band 20, with the engaging members 21 provided therebetween. The engaging members 21 are rebated on their outer circumferential surfaces, so that the engaging members are more flexible than the ribs 40. The rebates 50 give the band 20 sufficient flexibility to allow the faces to be pushed over the formation. As shown in the figure, the ribs 40 are wedge-shaped, although they can be any other suitable shape. Circumferential beading 45, which is radially aligned with the inner and outer diameters of the cap 10, is defined by the rebating at the axial end of the band 20 furthest from the skirt 14. The beading 45 ensures that the band 20 is not undesirably fragile.

In addition, since each rib 40 is connected to the skirt 14 by a thin and flexible frangible connection 30, the ribs 40 act as pivot points which allow radial movement of the rebated portions 50 that lie therebetween as the band 20 is pushed over the collar of a container.

The ribs 40 also provide the band 20 with sufficient rigidity to ensure that, once engaged with the collar, the faces 22 cannot be disengaged therefrom by pulling the cap 10 and band 20 off the container without breaking the frangible connections 30. In this way, evidence of tampering with the cap 10 and band 20 can be provided.

The provision of ribs 40 provide the band 20 with sufficient rigidity to ensure that the stripping means pushes the cap 10 and band 20 from the mould and is prevented from sliding between the mould and the band 20.

Claims

1. A cap for a container, the cap having a top and a skirt, the end of the skirt remote from the top being attached by a plurality of frangible means to a tamper-evident band in which the band has engagement faces for engaging a formation on the container, the band having sufficient flexibility to allow the faces to be pushed over the formation, characterised in that the band has a plurality of axially extending ribs on the band to which the frangible means are connected, the ribs being less flexible than the remainder of the band.

2. A cap according to claim 1, wherein portions of the band lying circumferentially between the ribs are rebated to increase flexibility.

3. A cap according to claim 2, wherein a circumferential bead is defined by the rebating at the axial end of the band furthest from the skirt.

4. A cap according to claim 3, wherein each rib is elongate and has a triangular cross section, with one of the side faces of the rib lying on the inner circumference of the band.

5. A cap according to any preceding claim, wherein the engagement faces lie circumferentially between the ribs and the ribs extend closer to the skirt than the engagement faces.

6. A cap according to any preceding claim, wherein the ribs are equally spaced around the circumference of the band.

7. A cap as herein described with reference to the accompanying drawing.