GB2243825A

GB2243825A - Sealing member and container sealed therewith

Info

Publication number: GB2243825A
Application number: GB9009689A
Authority: GB
Inventors: Robert Peter Sunman
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-30
Filing date: 1990-04-30
Publication date: 1991-11-13
Anticipated expiration: 2010-04-30
Also published as: GB2243825B; GB9009689D0

Abstract

A tamper evident member for sealing a container comprises a sheet (12) formed from two layers (13) and (15) integrally secured to one another around the edges. One of the layers has a reactive substance (14) printed or sprayed thereon preferably in the form of a message such as "danger", the reactive substance being reactive on exposure to the atmosphere eg to change colour and reveal the message. The layers define a pocket (16) between them which preferably in use extends completely over the join between the container (20) and its closure member (25). The layers (13) and (15) are preferably of heat shrinkable thermoplastics material having different directions of shrinkage or different shrinkage rates. The sealing member may incorporate substances which are reactive over different periods of time which are able to indicate to a user that a product has passed its useful life. <IMAGE>

Description

TAMPER EVIDENT SEALING MATERIAL AND CONTAINER SEALED THEREWITH This invention relates to a tamper evident sealing member, particularly intended for forming a seal around the closure member of a container and providing an indication that such sealing member has been tampered with in an attempt to penetrate the container, and to containers sealed with such sealing members.

The invention is particularly concerned with a sealing member incorporating a reactive substance, hermetically sealed from the ambient atmosphere but which changes appearance, normally by a colour change, on exposure to the atmosphere. The only known disclosure of such a sealing means is that of U.S. Patent Specification 4511052 which discloses such a reactive substance sealed in a frangible envelope which in operation is associated with a closure member of a container so that it will be ruptured by normal opening of the container. However, in this arrangement an annular envelope containing the reactive substance is first adhered around the neck of the container below the container closure member and then a strip of transparent sealing material is adhesively attached over the envelope, the lower part of the closure member and the neck of the container.It is stated that removal of the strip of sealing material necessarily breaks the frangible envelope.

However in practice, as the envelope does not extend over the join of the closure member and the container and as the envelope and sealing strip are formed as two separate entities, careful softening of the adhesive and/or prising away of the strip from the closure member above the envelope allows the closure member to be fairly easily removed from the container and replaced and the strip readhered to the closure member without rupturing the frangible envelope or giving any evidence of tampering.

An object of the present invention is to provide a more secure sealing device for a container and a container so sealed.

According to the present invention, a sealing member comprises a sheet formed from two layers integrally secured to one another around their edges, at least one of the layers having a reactive substance printed or sprayed thereon, the reactive substance being reactive on exposure to the atmosphere to change appearance, preferably colour, the layers defining a pocket between them which is free of substances to which the reactive substance reacts, the material being attachable to a container by heat shrinkage and/or adhesive so that the pocket extends completely over the join between the container and its closure member and preferably over a substantial part or all of the container and its closure member.

In another aspect, the invention provides a container sealed by such a sealing member.

Where the container, for example in the form of a jar or bottle, has a body ending in a neck defining an opening closable by a closure member, the sealing member preferably extends at least partially over the top of the closure member as well as over the neck and preferably over at least part of the body of the container and with advantage over a part of the base of the container.

The container could be a bag or envelope with no specific closure member and the sealing means act as the closure With any such arrangements it is extremely difficult to remove the seal without rupturing one of the layers and thus indicating by a colour change that the seal has been broken.

The sealing member may be formed as a wrap around strip or as a tube and the term "sheet" is intended to cover either such form. Where the sealing member is a wrap around strip, the edges should overlap sufficiently that the relevant portion of the container is completely surrounded by the pocket between the layers.

The layers are preferably made of heat shrinkable thermoplastics material and are heat shrunk on to the container. Alternatively to or preferably in addition to the heat shrinkage, adhesive is applied over the whole of the back of the base layer of the sheet, such adhesive preferably having a higher softening temperature than that of the base layer so that the adhesive cannot be softened to a temperature at which the sealing material could be removed without rupturing the lower layer. Solvents of the adhesive will also destroy the base layer.

In a preferred form, the layers are made of materials having different shrinkage rates or different shrinkage directions. Most heatshrink thermoplastic materials are highly directional and if the layers have their shrinkage directions at an angle, normally perpendicular, to one another any attempt to expand one layer will cause the collapse of the other layer. While the sealing member can, with reasonable industrial practice, be shrunk on to the container in the first place, the degree of temperature control necessary to soften and expand the outer layer without softening the inner layer to a point where it ruptures would be very high.

Examples of suitable materials for the layers are PVC and polythene for example having a thickness in the range 10 microns to 1 mm. The adhesive may for example be a methacrylate and the reactive material may be a Leucodye such as methylene blue or any of the other substances disclosed in U.S. Patent 4511052.

With advantage, the melting point of the base layer material should be lower than that of the outer layer.

This ensures that the layers cannot be fused together on a part of the seal which would allow the container to be penetrated with a hypodermic syringe or the like at a part which was fused.

The sealing member will preferably be printed with words indicating that it will change colour on opening and with other distinctive printing such as a manufacturer's Trade Mark to avoid the seal being completely removed by a tamperer and merely resealed with a heat shrinkable clear plastics sheath which will not change colour on opening.

In another aspect, the invention provides a sealing member comprising a sheet formed from two layers of heat shrinkable thermoplastics material the layers having different shrinkage rates or directions of maximum shrinkage and having sealed between them a reactive substance which reacts to change colour on exposure to the atmosphere.

In a preferred form of either aspect of the invention, the reactive substance is printed with a message in the form of words to indicate that the container has been opened, for example "warning: product has been opened". It may be printed with more than one message, which messages appear sequentially after the container has been opened in normal use. While the first message will appear within a few minutes of the container being opened, a second message may appear later, for example after 24 hours, with a warning that the contents of the container have exceeded their useful life after opening. For example "danger: discard: contents now contaminated" or the second message may consist of the whole or part of the sealing means changing colour and the customer will be informed that the contents should not be used after this has happened.

In a further aspect, the invention provides a sealing member for a container and/or a container so sealed incorporating two reactive substances which are reactive after different periods of time to change appearance when contacted by an activating medium (such as the atmosphere) and are normally sealed therefrom, the reactive substances being printed on the sealing means in the form of one or more messages such that the messages appear at different times after the seal has been broken. Preferably one of the messages indicates that the seal has been broken and a second message indicates that the contents have been exposed for a sufficient time that their useful life after opening has been exceeded.

In a further aspect, the invention provides a sealing means for a container and a container sealed with such sealing means in which the sealing means incorporates a reactive substance which is reactive when contacted by an activating medium (such as the atmosphere, and is normally sealed therefrom, the reactive substance being reactive to such activating medium to give a visual indication such as a change of colour after a predetermined delay period following exposure to such activating medium, such period being initiated by normal opening of the container and the length of the period corresponding to the useful life of the container contents after opening.

One embodiment of sealing means and container so sealed will now be described, by way of example only, with reference to the accompanying diagramatic drawings of which Figure 1 is a front view of a sealing member, Figure 2 is a section through the sealing member on the line II-II of Figure 1 with the thicknesses of the layers exaggerated for clarity, Figure 3 is a plan view of the sealing member wrapped round to form a cylinder, Figure 4 is a diagramatic sectional view through a container sealed with a sealing member of the form of Figures 1 to 3 but showing sealing members of exaggerated thickness and different sizes on its two sides, and Figure 5 is a side view of a container on which the sealing means has been ruptured.

A sealing member 12 comprises a sheet of material formed from two layers of heat shrinkable thermoplastics material, a base layer 13 of which has printed or sprayed thereon a reactive substance 14 (indicated in Fig. 1 as saying DANGER but initially invisible) which is covered by an outer transparent layer 15 sealed to the base layer 13 around its edges so that the reactive material is contained in a hermetically sealed pocket or space 16 extending over substantially the entire area of the sheet. The reactive material, such as methylene blue, is reactive to oxygen in the atmosphere to change colour and the printing and sealing of the edges of the layers must therefore take place in an oxygen free atmosphere.The printing, for example, may be done by ink jets, silk screen or spraying and as seen in Figure 5 in this case takes the form of a written message saying "Warning: product has been opened". The sealing means will also preferably be printed with other permanent ink messages such as a manufacturer's label and an indication of the contents. It preferably also includes an indication that the label will change colour or come up with the message when the container is opened. The back of the base layer 13 is coated with an adhesive 17 and the sealing member is mounted on a barrier sheet 18 having a coating from which the adhesive is easily separated. The sealing member is preferably arranged to wrap around a container with the edges 19 overlapping sufficiently that the pocket completely surrounds the container. Alternatively, the sealing member can be constructed in tubular form.

The sealing member 12 is shown attached to a container 20 having a body 21 with a base 22, a neck 23 defining at its upper end an opening 24 and a closure member 25 intended to close the opening. The sealing member is attached to such a container both by the adhesive layer 16 and by heat shrinkage of the whole sheet about the container so that it is a close fit over part of the top of the closure member, completely around the join between the closure member and the container along the neck and shoulder of the container and extends down over a part of the body of the container. As seen at the left hand side of Figure 4 it preferably extends down to contact the base 22 of the container. When the seal of the sealing material is broken to expose the reactive substance to the atmosphere the reactive substance changes colour to show the message "warning: product has been opened.Alternatively, the sheet may just change colour and the customer be instructed to expect this. Preferably, two forms of reactive substance are included in the sealing member to act at different times.

This can be achieved using metallic catalysts to accelerate or decelerate the colour change by a set time. This can be used to particular advantage to indicate to a customer either by a printed warning message or by a complete colour change that the container has been opened long enough for the contents to have "gone off". Such a warning could be used on its own without the tampering message on any product which has a well defined short life. The manufacturer's label or logo could be arranged to disappear at such time as the danger warning appeared.

As explained above the two layers may be formed from materials having different shrinkage rates or different directions of maximum shrinkage. The layers may, for example, be formed of pvc and polythene with the inner layer having a lower melting temperature than the other layer and the adhesive, where present, having a higher softening temperature than that of the inner layer. One advantage of spraying the inner membrane layer with a permanently sticky adhesive, or a curable one, is that the strength of the membrane becomes much greater when it is supported by the container. It becomes effectively a part of the container.

A tear strip could be incorporated in the sealing member which would increase the printing difficulty but not diminish the security.

The sealing member may be attached to the container only by adhesive without heat shrinkage or vice versa.

Claims

1. A sealing member comprising a sheet formed from two layers integrally secured to one another around their edges, at least one of the layers having a reactive substance printed or sprayed thereon, the reactive substance being reactive on exposure to the atmosphere to change appearance, the layers defining a pocket between them which is free of substances to which the reactive substance reacts, the sheet being adapted to be attached to a container by heat shrinkage and/or adhesive so that the pocket will extend completely over the join between the container and its closure member.

2. A sealing member according to Claim 1 in which the reactive substance changes its appearance by changing colour.

3. A sealing member according to Claim 1 or Claim 2 in which the sheet is in the form of a tube.

4. A sealing member according to any of Claims 1 to 3 in which the layers are of heat shrinkable plastics material.

5. A sealing member according to Claim 4 in which the layers have different shrinkage rates or directions from one another.

6. A sealing member according to any of Claims 1 to 5 in which the base layer has a lower softening temperature than the outer layer.

7. A sealing member according to any of Claims 1 to 6 including a layer of adhesive attached to the base layer.

8. A sealing member according to Claim 7 in which the material of the base layer has a lower softening temperature than the adhesive softening temperature.

9. A sealing member according to Claim 7 or Claim 8 in which the adhesive is selected such that solvents of the adhesive would also destroy the base layer.

10. A sealing member according to any of Claims 1 to 9 in which the reactive substance is printed on the sealing member in a pattern to provide a warning that the product has been opened/tampered with.

11. A sealing member according to any of Claims 1 to 10 in which the sealing member is printed with a message indicating that if the sealing member is coloured the product has been opened/tampered with.

12. A sealing member according to any of Claims 1 to 11 which is printed with a distinctive pattern or other information.

13. A sealing member according to any of Claims 1 to 12 in which the reactive substance has a delayed reaction to contact with the atmosphere so that it changes appearance only after a predetermined time selected to correspond to the life of a product sealed thereby, and the sealng member is printed with information notifying a purchaser that the change in appearance of the sealing member indicates that the product is passed its useful life.

14. A sealing member comprising a sheet formed from two layers of heat shrinkable thermoplastics material, the layers having different shrinkage rates or directions of maximum shrinkage and having sealed between them a reactive substance which reacts to change colour on exposure to the atmosphere.

15. A sealing member incorporating two reacting substances which are reactive after different periods of time to change appearance when contacted by an activating medium and are normally sealed from such activating medium, the reactive substances being printed on the sealing means in the form of one or more messages such that the messages appear at different times after the seal has been broken.

16. A sealing member substantially as described herein with reference to or as illustrated in the accompanying drawings.

17. A container sealed by a sealing member according to any of Claims 1 to 16.

18. A container according to Claim 17 in which the sealing member extends completely over the join between the container and its cloure member and is secured to the container by heat shrinkage and/or adhesive.

19. A container according to Claim 18 in which the sealing member extends over the majority of the container and its closure member.