EP0259068A1

EP0259068A1 - Improvements in or relating to containers

Info

Publication number: EP0259068A1
Application number: EP87307368A
Authority: EP
Inventors: David Watson
Original assignee: MARDON WRAPPINGS Ltd
Current assignee: MARDON WRAPPINGS Ltd
Priority date: 1986-08-26
Filing date: 1987-08-20
Publication date: 1988-03-09
Also published as: GB8620636D0

Abstract

A container is formed of sheet material and has an opening to enable access to be gained to the interior of the container. The container includes a flap portion and a layer of adhesive for adhering the flap portion to another portion of the container to close the opening. The adhesive is associated with a solvent-soluble dye wherein any attempt to gain access to the interior of the closed container by treating the adhesive with such a solvent results in dissolution of the dye and the resultant dye solution causes staining which makes it visibly apparent that said attempt has been made. An adhesive layer may be provided on both of said portions.

Description

This invention relates to containers and is concerned with containers which exhibit a visible indication if an attempt has been made to gain access to the contents of the container.
It is known for banking establishments and the like to use containers for transmitting specified sums of money from one department to another. The system operated by the establishment is ordinarily such that it can readily ascertain if such a container is stolen in transit. Ordinarily, however, it is not readily possible to ascertain whether the container has been opened in transit and then resealed after some of the money has been removed. With a view to overcoming this problem, tamper-evident containers have been devised wherein any attempt to gain access to the interior of the container is visibly apparent.
It is also known to use containers for storing personal belongings in prison establishments and the like in such a manner that it is visibly apparent if any attempt has been made to open the container and steal some or all of the belongings.
It is an object of the present invention to provide a container which provides a novel indication of attempted opening.
According to the present invention there is provided a container formed of sheet material and having an opening to enable access to be gained to the interior of the container, the container including a flap portion and adhesive for adhering the flap portion to another portion of the container to close the opening, said adhesive being associated with a solvent-soluble dye whereby an attempt to gain access to the interior of the closed container by treating the adhesive with such a solvent results in dissolution of the dye and the resultant dye solution causes staining which makes it visibly apparent that said attempt has been made.
Any suitable adhesive, such as a hot melt adhesive or a solvent soluble adhesive may be used.
The dye is present in an amount which is effective to produce a dye solution which causes a visibly apparent stain to be produced on the container. In a particularly preferred embodiment of the invention, the dye is incorporated in the adhesive. The adhesive may be coated onto a masking tape which has been treated with a release agent and which is adhered to one of said portions by the adhesive. In this case, in use the masking tape is removed to expose the adhesive and the portions are then superposed so that they become adhered together by means of the adhesive. In accordance with a particularly preferred embodiment, adhesive may be provided on both of the portions in order to improve the adhesive bond. In this case, both adhesive layers may be associated with a solvent soluble dye for the purpose above specified. Alternatively, it may be sufficient for one only of the adhesive layers to be so associated with the dye.
However, in the case where two such adhesive layers are used, it is envisaged that neither layer may be associated with such a dye since it is a further object of the present invention to provide a container having a flap portion to be adhered to another portion to close the container wherein the adhesive bond between the portions is improved.
Accordingly, a second aspect of the present invention provides a container formed of sheet material and having an opening to enable access to be gained to the interior of the container, the container including a flap portion carrying a first adhesive layer and another portion carrying a second adhesive layer, the arrangement being such that the flap portion may be adhered to said other portion to close the opening by means of said first and second adhesive layers.
In accordance with either aspect of the present invention, the container may be formed by superimposing portions of the sheet material and joining the same around their edges. If desired, security printing or coded seals may be provided at the edges to make it evident if access to the container has been gained by cutting the edges and subsequently resealing them. Similarly, security printing may be provided in the vicinity of the opening of the container.
Any suitable sheet material may be used to form the container such as paper, cardboard, thermoplastic plastics film, and combinations of the same.
The container is useful in any fields where tamper evident containers are needed such as in banking establishments, prison establishments, retailing, hospitals, examining boards, forensic laboratories, government departments, and the like.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:

Figure 1 is a plan view of an open container in accordance with one aspect of the present invention,
Figure 2 is a section through the container of Figure 1 along the line II-II but with the container in its closed configuration and the thickness dimensions greatly exaggerated,
Figures 3 to 7 show in diagrammatic form the steps involved in producing the container of Figures 1 and 2, and
Figure 8 is a section corresponding to that of Figure 2 but showing a container in accordance with another aspect of the present invention.

Referring to Figures 1 to 7, the container is in the form of a bag formed of flexible thermoplastic plastics material such as polyethylene. The bag is produced by folding longitudinally a continuous length of the thermoplastic plastics material (after it has been optionally printed as appropriate), into a J-form wherein it includes a first portion 1 folded longitudinally at 2 so as to be superposed on part of a second portion 3 so as to leave a flap portion 4 exposed (Fig. 3). The first portion 1 is heat sealed to the second portion 3 by a longitudinally extending heat seal denoted by reference numeral 5 (Fig. 4). Thereafter, a longitudinally extending region of the flap portion 4, which region is generally parallel to the heat seal 5, is subjected to a corona discharge to improve its adhesion characteristics and three longitudinally extending lines of perforations 6 are provided in that region (Fig. 5).
A masking tape 7 formed of a base film of thermoplastic plastics material and coated with a layer of a silicone resin release agent is then coated with a composition 8 comprising a hot melt adhesive and a solvent soluble dye. The adhesive may be a synthetic rubber based pressure sensitive hot melt adhesive of the type known under the designation 089-2505 and marketed by National Adhesives and Resins Limited. This is a pale beige odourless material of 100% solids content. It has a viscosity (Brookfield Thermosel) at 120°C of about 63000 cps and its viscosity at 200°C is . about 3500 cps. The dye may be of the type known as Kenawax Blue AS marketed by Durham Chemicals Limited of Bradford and it may constitute about 2% by volume of the composition. The composition 8 may be applied at a temperature of from about 150°C to 180°C to the masking tape 7 by means of, for example, a hot melt slot coater.
The thus coated masking tape is then adhered to the perforated region of the flap portion 4 which had been treated by the corona discharge so that it adheres thereto by means of the composition layer 8 (Fig.6). Thereafter, the first portion 1 is provided with a longitudinally extending cut 9 and this cut 9 serves as the opening to the container proper. Also, a further longitudinal perforation 10 is provided in the flap portion 4 equidistant between the heat seal 5 and the masking tape 7 (Fig.7).
The continuous length of film material is then cut transversely using a double heat sealing device comprising two pairs of heat sealing jaws between which is located a cutting blade so that the material is cut into adjacent transverse portions wherein each of the transverse portions has heat sealed edges 12. Each of these transverse portions constitutes a bag and if desired, each transverse portion may be given a sequential number for security purposes.
In use, articles are inserted into the interior 11 of the bag through the cut 9. Then, when it is desired to seal the bag, the masking tape 7 is removed from the adhesive layer 8 and the flap portion 4 is folded over the first portion 1 (perforations 10 constituting the fold line) so that the layer 8 is superposed over the cut 9 as shown in Figure 2 and adheres portions 1 and 4 together. - The interior 11 of the bag is thus completely sealed.
In the event that any unauthorised person attempts to gain access to the interior 11 by applying a solvent for the adhesive of the layer 8, the solvent will cause the dye to be leached out of the composition and the resultant dye solution will exude through the perforations 6 in the flap portion and also between the flap portion 4 and the first portion 1 and cause visible staining. Moreover, if an attempt is made to gain access by pulling the flap portion 4 and portion 1 apart, the flap portion 4 will tend to tear along the outermost perforation 6 before the portions 1 and 4 separate.
If desired, the inner marginal area of the bag adjacent to heat seals 12 may be provided with security printing i.e. printed characters very close to the seals 12 so that any attempt to gain access to the interior 11 by cutting off the seal 12 and subsequently resealing them will be immediately apparent.
Referring now to Figure 8, there is shown an exaggerated section through a bag according to a second aspect of the invention wherein parts corresponding to parts of Figures 1 to 7 are denoted by like reference numerals. In this case, the first portion 1 is not heat sealed to the second portion 3 so that access to the interior 11 is gained through a conventional mouth formed between first and second portions 1 and 3. In this embodiment, masking tape carrying adhesive composition 8 is applied to the flap portion 4 in the same way as in the previous embodiment. However, a similar masking tape carrying an adhesive composition 8ʹ is applied to the first portion 1 so that when the masking tapes are removed and the bag is closed by folding over the flap portion 4 the two adhesive layers 8 and 8ʹ are superposed and adhere together. Because of the double layer of adhesive, a strong bond is produced between portions 1 and 4.
Again, as in the case of the previous embodiment, any attempt to use a solvent to dissolve the adhesive composition 8 would cause exudation of dye and resultant staining. If desired, however, in accordance with this second embodiment, the dye may be omitted. Although this may mean that an attempt to open the bag by applying a solvent may not be detected, the bond between the first portion 1 and the flap portion 4 will be equally as strong.
In the case where this second embodiment is applied to a container having an opening line 9 of the type shown in Figures 1 to 7, the second tape (7ʹ) carrying masking composition 8ʹ will preferably be of reduced width, compared to tape 7 and will be located adjacent to the opening line 9 on the side remote from the heat seal 5 (as shown by dotted lines in Figure 7).

Claims

1. A container formed of sheet material and having an opening (9) to enable access to be gained to the interior (11) of the container, the container including a flap portion (4) and an adhesive layer (8) for adhering the flap portion (4) to another portion (1) of the container to close the opening (9), characterised in that said adhesive (8) is associated with a solvent-soluble dye whereby an attempt to gain access to the interior (11) of the closed container by treating the adhesive (8) with such a solvent results in dissolution of the dye and the resultant dye solution causes staining which makes it visibly apparent that said attempt has been made.

2. A container as claimed in claim 1 wherein the dye is incorporated in the adhesive

3. A container as claimed in claim 1 or 2 wherein the adhesive is coated onto a masking tape (7) which has been treated with a release agent and which is adhered to one of said portions by the adhesive.

4. A container as claimed in claim 1, 2 or 3 wherein adhesive is provided on both of said portions in order to improve the adhesive bond.

5. A container as claimed in claim 4 wherein the adhesive on each portion is associated with said solvent soluble dye.

6. A container formed of sheet material and having an opening (9) to enable access to be gained to the interior (11) of the container, the container including a flap portion (4) carrying a first adhesive layer (8) and another portion (1) carrying a second adhesive layer (8ʹ), the arrangement being such that the flap portion (4) may be adhered to said other portion (1) to close the opening by means of said first and second adhesive layers.

7. A container as claimed in any preceding claim wherein the container is formed by superimposing portions of the sheet material and joining the same around their edges.

8. A container as claimed in claim 7 wherein security printing or coded seals is provided at the edges.

9. A container as claimed in any one of the preceding claims wherein security printing is provided in the vicinity of the opening (9) of the container.

10. A container as claimed in any one of the preceding claims wherein the sheet material is thermoplastic plastics film.