Tamper-evident container

Abstract: Provision is made on a container to indicate whether the container has been tampered with. Release of a vacuum from within the container causes a lid (4) of the container to become convex. This causes a coating (7) on the lid to craze and therefore produce a visible change.

Description: The present invention relates to a container, particularly one whose contents are to remain safely sealed from the environment, and especially to one having means for rendering tampering evident. There is a great need for some means of reliably determining whether a seal on a container has broken, either through mere failure or by deliberate tampering. This is particularly so in the case of containers for food, drinks and medicines (which term includes medicaments not taken by mouth). If a seal is broken the container or its contents could be contaminated by environmental bacteria by oxidation by deliberate poisoning or by adding glass etc. Whilst in many cases simple failure of a seal may be noticeable, tampering may be more difficult to detect. This is because an attempt may be made to reform the seal to avoid detection. The presence of a vacuum within a container is an accepted indication that an environmental seal has been maintained. In the simple case of a lid being deformed by a vacuum within the container, the conformational change may be reversible. In itself therefore, the presence of a concave lid is no guarantee that the container has not been tampered with. This is simply because the tamperer could reheat the container, replace the lid and let it cool thus recreating the concave lid. Many attempts have been made to design containers such that a broken seal will be permanently observable. The following examples may be noted. In US 4,747,497 a container is disclosed having a closure sealingly applied to the body and a tamper indicating system incorporated within the closure. However, this tamper-indicating system is not irreversible. Some containers, such as beer cans, are made such that they are in effect destroyed when they are opened. Unobservable tampering is difficult, but such containers cannot be resealed by the legitimate user after partial use of their contents. Various proposals have been made for containers, such as bottles, with screw-caps. For example, a cap may be provided with a band at its base, joined to the remainder of the cap through a line of weakness. The band is prevented from rotating or from rising up the screw thread when the cap is unscrewed, and as a result it becomes detached from the remainder of the cap. In another technique a paper label is stuck across a stopper such that the movement of the stopper causes the paper to be torn. Heat-shrink sleeves have been shrunk around the tops of bottles so as to enclose the stopper. Removal of the stopper requires the shrunk sleeve to be cut away. A more expensive technique is to trap the stopper by means of a wire frame around the bottle top, the ends of the wire being locked by means of a solder seal. Unfortunately, each of these techniques has its disadvantages, such as cost or ease of repair after tampering. We have now discovered that a conformational change in a part of a container may be made to occur when an attempt is made to open the container to the environment, and that conformational change can result in an irreversible observable indication. Thus, the present invention provides a container and a method of packing food in a container as defined in the claims. The indication provided by the container may be an optical and/or tactile change that is not reversed if the indicating area is returned from its non-seal indicating position to its seal indicating position. The first part of the container may be a lid, by which term we include caps and stoppers etc. The second part may be a can, box, jar, flexible pack or bottle. The induced optical or tactile change may be a change in light-scattering and/or light-reflectance at a visible or machine-readable portion (which need not be an external surface) of the article. In general, the portion at which scattering or reflectance occurs will be an intermediate surface or layer of a multi-layer coating on the article. Apparatus, such as production line may be provided for use in the methods of the invention. Such apparatus preferably includes means for closing a container, means for applying a label or material in other form, and means for treating the material for example with UV or other irradiation to make it brittle etc. The apparatus may also include means for fitting the container and for making a vacuum inside. The material may be applied as part of a label or as a three-dimensional pre-form, formed for example by injection-moulding. An embodiment of the invention is further illustrated with reference to the accompanying drawings in which: Figure 1 is a cross-section through a bottle; Figure 2 is a cross-section through a can; Figure 3 is a cross-section through a vacuum-packed plastics container; Figures 4(a) and 4(b) show conformational change of a lid; Figures 5(a) and 5(b) are perspective views of the top of a can; Figures 6(a) and 6(b) are plan views of the top of a can; Figure 1 is a schematic sectional view showing an embodiment of the container based on the present invention. In Figure 1, 1 is a bottle made of glass, plastic, etc, 2 is a cap, 3 shows a foodstuff in the bottle, 4 shows a concave shape, 5 shows a vacuum (which term of course includes a partial vacuum), 6 shows a transparent cover and 7 shows a brittle layer. The foodstuff 3 is placed in the bottle 1, the bottle and the foodstuff therein are then sterilised by heating, a cap 2 is then sealed on to the bottle and the bottle and the foodstuff are left to cool. On cooling a vacuum 5 is created within the bottle causing the outside of the lid to become concave 4. The outer surface of the cap has been coated with a material 7, such as a laquer, capable of undergoing an optical and/or tactile change, such as crazing or stress-clouding, when the cap 2 is released from its concave configuration. This will, of course, occur when the container is opened, at the cap or elsewhere and the vacuum is released. The cap may be provided alone or it may be used with another closure part such as a cover 6. Cover 6 may be transparent such that the state of the laquer 7 may be viewed without its removal. To ensure that the material 7 undergoes an optical and/or tactile change when the cap 2 is released from its concave configuration, it must be brittle. If it is not brittle when it is applied to the cap, it can be made brittle by a process such as cross-linking. This may be carried out by irradiation with ultra-violet light or by chemical means etc. Techniques other than irradiation by ultra-violet light can be used. For example, the lacquer or other material 7 may be melted by the application of heat and allowed to cool to become a brittle solid which can be caused to craze in a way that is not reversible by any reasonable treatment. In a further alternative the material 7 is applied in solution and on evaporation of the solvent, whilst the lid 2 is in the concave conformation, the material cures. A variety of chemical formulations may be used as the material that provides the optical and/or tactile change. At present a preferred material comprises a wax/resin blend. A variety of such materials are available and the desired melting point, brittleness, hardness and colour may be chosen. At present preferred blends are those marketed by Wilkins Cambell & Co Ltd under the trade marks 6565, 6545 and 6566. Other materials may be used depending upon the technique by means of which they are applied to the container. Melting and resolidification may be used in the case of hot-melt adhesives, such as polyamides and ethylene vinylacetates etc. Various cross-linkable or curable materials may be used, such as epoxy materials which may be chemically cross-linked and polyimides which may be cross-linked using ultra-violet light. Other suitable polymeric materials include polystyrenes, polypropylenes and polyurethanes. These materials are preferably used without plasticizers, and with inert fillers such as talc or chalk. Figure 2 is a schematic sectional view showing a second embodiment of the container according to the present invention. Figure 2 shows a tin can 8 having a lid 2 sealed to it by means of a sealed seam 9. The tin contains a perishable foodstuff 3 under vacuum 5. The lid is in a first conformation having a concave portion 4 due to the vacuum 5. Before generation of the vacuum 5 the lid was in a second conformation, which is substantially flat or convex. On release of the vacuum the elastic energy in the lid causes it to return to this second conformation. The concave portion 4 has on it a mark 10 such as a bar code or a visual message. The mark is then covered with a material 7, such as a laquer, that will craze when the lid 2 is released from its first conformation. If desired, a transparent layer may be provided over the material 7 as shown by the dotted line. This transparent layer may be provided to prevent fragmentation and removal of the material 7 after crazing. Figure 3 is a schematic sectional view showing a third embodiment of the container according to the present invention. Figure 3 shows a plastics vacuum pack 11 containing perishable goods 3 under vacuum 5. An insert 12 is placed on the goods 3. The insert has perforations or is otherwise constructed such that pressure within it equals the pressure within the pack 3. The insert has a concave portion 4 resulting from the vacuum 5 within the pack 11. On release of the vacuum 5 the presently concave portion of the insert 12 pops outwards and becomes substantially flat or convex. This causes the lacquer 7 to craze as described above. Preferably the top of the insert is aligned with the top edges of the pack 11 in order that the film 2 can cause concave portion 4 to be formed in the insert as the vacuum 5 develops in the pack 11. Figure 4(a) demonstrates a method of curing a material 7, in this case a laquer. Figure 4(a) shows a lid 2, having a coating of a laquer 7, in its concave conformation brought about by the vacuum 5. The arrows 13 represent some agency such as ultra-violet light which causes the laquer 7 to cure and become brittle after the concave conformation has been achieved. In Figure 4(b) the vacuum 5 has been released and the lid has popped upwards and become convex. This has caused the laquer 7 to become crazed and to scatter or reflect light. The concave portion of the lid may bear some mark, as mentioned above, or it may merely be coloured in a colour that is distinctive from that of the crazed or otherwise altered material 7. The optical change may be enhanced by the provision of a colourant, such as a micro-encapsulated dye that is dispersed by the conformational change. The dye may then travel along cracks in the material by capillary action. Figure 5(a) shows the presence of a bar code 14 on a lid 10 of a can 8. The material 7 may be coated above or below the bar code 14. When the material 7 is clear the code can be read easily, but after crazing, as shown in Figure 5(b) at 15, the code 14 can no longer be read. This lack of ability of the bar code to be read will cause the goods to be rejected at the point of sale. The fault in the goods will be readily apparent to both buyer and seller and the crazing will not be reversed on resealing. Figures 6(a) and 6(b) show how a message can be altered in meaning by crazing of material 7 to produce a generally opaque covering 15. A first mark 7 and two second marks 17 are shown on a lid 2. Before the conformational change the message read "tamper not evident" and after the conformational change, brought about by loss of vacuum within the container, the message reads "tamper evident". The invention may be used together with one or more other means of detecting or resisting tampering, for example, a heat-shrink sleeve or a label or other layer etc may at least partially cover the second part of the container such that its rupture is required to separate the first and second parts.

Claims: A method for packing food in a container which is tamper-indicating, which comprises the steps of: providing a container including a body (1) and a closure (6) for application to the body (1) which closure includes a flexible end panel having a sealing state indicating area which is capable of flipping from a seal indicating position (4) to a non-seal indicating position due to the release of energy stored in the panel; placing food inside the body (1) and heating the body (1) and the food therein; applying the closure (6) to the body (1) while the container and food are hot and allowing them to cool and develop a vacuum therein, whereby the sealing state indicating area is caused to flip to its seal indicating position in which energy is stored in the panel; and wherein the sealing state indicating area has applied to it a hardenable material which is caused to become brittle after the sealing state indicating area has flipped to its seal indicating position so as to provide a brittle layer (7) which provides an irreversible tamper indicating system which is actuable by the indicating area flipping to its non-seal indicating position whereupon the brittle layer (7) is caused to rupture and provide an indication that the container has been opened. The method of claim 1, in which in the seal indicating position, the end panel (2) is concave or substantially flat when viewed from the outside of the container and the non-seal-indicating position is respectively substantially flat or convex. The method of claim 1 or 2, wherein the brittle layer (7) comprises a material which has been cross-linked in order to render it brittle. The method of claim 3, wherein the brittle layer comprises a material which is a photo-curable resin or lacquer. The method of any preceding claim, wherein the brittle layer (7) has a colourant therein that is dispersed when the area flips from its seal indicating position (4) to the non-seal-indicating position. The method of any preceding claim, wherein the tamper-indicating system includes indicia means underlying the brittle layer so that when the brittle layer ruptures the visibility of the indicia is altered. The method of any preceding claim, wherein the food within the container is heat sterilised. The method of any preceding claim, wherein the body is a glass bottle and the closure is a cap seal to the bottle. The method of any of claims 1 to 6, wherein the body is a plastics bottle and the closure is a cap sealed to the bottle. The method of any of claims 1 to 7, wherein the body is a can and the closure is a lid sealed to the can. A container including a body (1), a closure (6) sealingly applied to the body (1), a flexible end panel (2) comprised in the closure (6) that has an area that when the container is opened flips from a seal-indicating position (4) to a non-seal-indicating position due to release of internally stored energy within the end panel (2), and a tamper indicating system carried by the end panel that comprises a brittle layer (7) irreversibly rupturable in response to flipping of the end panel area to provide an indication that the container has been opened; characterised in that: the brittle layer (7) comprises a material which is a ultra-violet-light-photo-curable resin or lacquer and has been cross-linked to render it brittle. A container including a body (1), a closure (6) sealingly applied to the body (1), a flexible end panel (2) comprised in the closure (6) that has an area that when the container is opened flips from a seal-indicating position (4) to a non-seal-indicating position due to release of internally stored energy within the end panel (2), and a tamper indicating system carried by the end panel that comprises a brittle layer (7) irreversibly rupturable in response to flipping of the end panel area to provide an indication that the container has been opened; characterised in that: the brittle layer (7) has been cross-linked to render it brittle and has a colourant therein that is dispersed when the area flips from its seal indicating position (4) to the non-seal-indicating position. A container including a body (1), a closure (6) sealingly applied to the body (1), a flexible end panel (2) comprised in the closure (6) that has an area that when the container is opened flips from a seal-indicating position (4) to a non-seal-indicating position due to release of internally stored energy within the end panel (2), and a tamper indicating system carried by the end panel that comprises a brittle layer (7) irreversibly rupturable in response to flipping of the end panel area to provide an indication that the container has been opened; characterised in that: the brittle layer (7) has been cross-linked to render it brittle and the tamper-indicating system includes indicia means underlying the brittle layer so that when the brittle layer ruptures the visibility of the indicia is altered. The container of claim 11, 12 or 13, in which in the seal indicating position, the end panel (2) is concave (4) or substantially flat when viewed from the outside of the container, and the non-seal-indicating position is respectively substantially flat or convex. The container of any of claims 11 to 14, wherein the seal indicating position (4) is unstable and the non-seal-indicating position is stable. The container of any of claims 11 to 15, in which there is present food, drink or medicine. The container of any of claims 11 to 16, which is under vacuum. The container of any of claims 11 to 17, the contents of which are sterile. The container of any of claims 11 to 18, wherein the body is a glass bottle and the closure is a cap sealed to the bottle. The container of any of claims 11 to 18, wherein the body is a plastics bottle and the closure is a cap sealed to the bottle. The container of any of claims 11 to 18, wherein the body is a can and the closure is a lid sealed to the can.

Inventors: GAYLOR IAN MICHAEL DAINES, LIVESLEY DAVID JOHN, GAYLOR, IAN MICHAEL DAINES, LIVESLEY, DAVID JOHN
Applicants: CONTINENTAL WHITE CAP INC, CONTINENTAL WHITE CAP, INC.
Application year: 1990
Main classification: B65D55
IPC codes: B65D55, B65D43, B65D79