SECURITY BAGS

Abstract: A security bag (6) is formed from sheet material (1) and has a first portion (3) including an opening (8) by means of which access is gained to the interior of the bag and a closure portion (7, 14) which is superposable with the first portion (3) to seal the opening by virtue of a band of adhesive (9). An indicator means (11) is provided which is disposed adjacent the opening (8) on sealing of the opening and which provides a visible and durable indication of heating or cooling of the bag.

Description: Securitv Bags The present invention relates to bags, and more particularly to security bags in which a visible indication is provided of any attempt to gain access to the contents of the bag. It is know for banking establishments and the like to use bags for transmitting valuables, for example specified sums of money, from one department to another. The system operated by such establishments is such that it is readily possible to ascertain whether a bag has been stolen in transit. However, it is ordinarily more difficult to ascertain whether the bag has been opened in transit and then resealed after some of the contents have been removed. In order to overcome this problem, tamper-evident bags have been provided wherein any attempt to gain access to the interior of the bag becomes visibly apparent. Typically, the walls of such bags are formed of sheet material including a portion having an opening which gives access to the interior of the bag. The bags include a closure portion arranged to be superposed on the portion having the opening, to close the bag. Closure is effected by means of a band of high-tack adhesive which is applied across the closure portion or the portion having the opening, for example from the molten state or in the form of a tape. The adhesive may be pressure sensitive adhesive, and suitable adhesives include thermoplastic hot melt adhesives, cured silicone rubber adhesives, acrylic pressure sensitive adhesives and the like. Such adhesives are required to have high initial tack with respect to the surface of the sheet material and also to have high adhesive and cohesive strength. In order to provide a visible indication of any attempt to open the bag by separating the closure portion and the portion having the opening, the adhesive should be strong enough to cause stretching or tearing of the portions. If desired, perforations may be provided in the closure portion to indicate tearing and emphasise the effect in the manner described in our British patent specification no. 2149381. With the exception of the cured silicone rubber adhesive described in our British patent application no. 9008276.9, pressure sensitive adhesives suitable for the closure of security bags have a softening temperature which is below the melting point of the closure portion and of the sheet material. The softening temperature is commonly in the range of 90 to 100°C. Accordingly, by the local application of heat, the security bags can be opened and resealed without any visible indication that the bag has been opened. Also, the non-silicone adhesives may be rendered glass¬ like by cooling. Such cooling may be effected by means of a spray from aerosol cans containing halogenated hydrocarbons, such as Freons. Such sprays are intended for use in cleaning electrical contacts and are widely available. Consequently by local cooling of the closure portion, the bags can be opened and resealed without any indication that the bags have been opened. Our European Patent Specification No. 0396428 and British Patent Application No. 9024177.9 describe methods for making such tampering evident. However, the methods described therein are dependent upon subjective assessment of layer separation or degradation of print quality. Inspection of bags for evidence of tampering may therefore take longer than is desired by the banking establishment or the like. The present invention seeks to provide a security bag incorporating means of determining unequivocally whether the bag has been subjected to heating or cooling. Desirably, an indication is provided not only of whether an attempt has been made to open the closure of the bag by heating or cooling, but also the method used. Even in the case that the adhesive used was the cured silicone rubber adhesive in our above patent application no. 9008276.9, the indicating means would ensure that even unsuccessful attempts to open the bags are detected. Accordingly, the present invention provides a bag formed of sheet material which bag comprises a first portion of the sheet material having an opening to enable access to be gained to the interior of the bag, a closure portion arranged to be superposable with the first portion and a band of adhesive arranged so as to seal the opening on superposition of the first portion and the closure portion, wherein an indicating means is provided which, on superposition of the first portion and the closure portion, is disposed adjacent to the opening and which provides a durable visible indication of heating or cooling of the bag. In an embodiment of the invention, the closure portion comprises a flap portion formed integrally with a portion of the sheet material of the bag. In another embodiment of the invention, the closure portion comprises a transparent plastics substrate to which the band of adhesive is applied, which substrate is adhered to the sheet material of the bag by means of adhesive which may be the same as, or different from, that of the band of adhesive. In still another embodiment of the invention, a releasable cover-strip is provided on the free surface of the band of adhesive. In use, the cover strip is removed prior to the closure of the bag. In a further embodiment of the invention, the indicating means is applied to or affixed on the closure portion. In a still further embodiment of the invention, the indicating means is applied or affixed to the portion having an opening. In a yet further embodiment of the invention, the indicating means provides a colour change on heating or cooling of the bag and in a still further embodiment, the indicating means provides a visible change of phase or state on heating or cooling of the bag. If desired, individual means may be provided to show heating or cooling, respectively. 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 only, to the following drawings in which: Figure 1 is a diagrammatic front view of an open security bag in accordance with a first embodiment of the present invention, Figure 2a is a diagrammatic section through a part of the bag of Figure 1 on an increased scale when the bag is open, Figure 2b is a diagrammatic section through a part of the bag of Figure 1 when the bag is closed, Figures 3a and 3b are respectively diagrammatic sections through a variation of the bag of the embodiment of Figure 1 when open and closed. Figure 4 is a diagrammatic section through a part of a bag of a second embodiment of the invention, Figure 5 is a diagrammatic section through a variation of the bag of Figure 4 showing optional additional security features, and Figure 6 is a diagrammatic section through a precursor of a security bag of the first embodiment of the invention when the bag is open, during an exemplary production process. Referring now to Figures 1 and 2, the bag is formed from a single strip 1 of flexible thermoplastics sheet material such as polyethylene or polypropylene which is folded laterally along a fold line 2 to form a first portion 3 and a second portion 4. The thermoplastics sheet material is preferably transparent, partially transparent or translucent, or a combination of opaque and transparent so as to make it easier to see evidence of tampering. The folded portions 3 and 4 are heat welded to each other in a zone 5 which extends parallel with and close to each of the longitudinal and each of the lateral edges of the portions to produce an envelope-like bag 6 wherein the second portion 4 is longer than the first portion 3. The second portion 4 has a closure portion in the form of a flap 7. The flap portion 7 is at least translucent, and preferably is transparent. At an end region of the bag 6 closer to the flap portion 7, an opening line in the form of a slit 8 extends across the first portion 3 terminating at each end at the weld zone 5. The slit 8 provides access to the interior of the bag 6. A band of adhesive 9 is provided on the flap portion 7. The choice of adhesive is not limited, although the adhesive should be a high tack adhesive having high cohesive and adhesive strength, such that any attempt to open the bag by separating the first portion and the closure portion will result in stretching or tearing of the closure and/or first portions, and can include all those mentioned above. The adhesive 9 may be applied from the molten state or in the form of a tape, or by any other suitable method. As can be seen from Figure 2a, a releasable cover strip 10 is provided to cover the free surface of the adhesive 9 when the bag is open. An indicating means 11, comprising a band of a substance exhibiting a change of colour, phase or state when subjected to heating or cooling is provided on the flap portion 7 and is covered by the adhesive 9. The indicator means is visible through the flap portion 7. In use of the security bag, the items to be held in the bag are introduced through the slit 8. The cover strip 10 is then removed from the adhesive 9 and the flap portion 7 is folded over onto the portion 3, with the fold line being close to the proximal laterally extending part of the weld zone 5. The disposition of the adhesive layer 9 relative to the fold line of the flap portion 7 is such that when the flap portion 7 is brought down onto the first portion 3, the part of the flap portion 7 carrying the adhesive 9 straddles the slit 8 so that the slit 8 is completely overlain by the * "said adhesive 9. Thus, the slit 8 is completely sealed and there is no access opening whatsoever to the interior of the bag 6 (see Figure 2b). Advantageously, the parts of the first portion 3 adjacent to the slit 8 have previously been subjected to Corona discharge to assist adhesion. The indicator means 11 overlies at least that part of the portion 3 adjacent to the slit 8 which is distant from the lateral weld zone 5a. If desired, the flap portion 7 may include a receipt portion 12 which is detachable by means of perforations 13. The nature of the indicator means 11 is not limited, and the indicator means may, for example, comprise a temperature indicating paint (such as Thermindex 0/G 87, supplied by Synthetic and Industrial Finishers Ltd of Cheam, Surrey), or temperature indicating ink, temperature indicating labels El or NE1 or other temperature indicating materials such as "Colour Change" and "Thermal Melt" crayons supplied by Thermographics Ltd of Burton, South Wirral. Thermal transfer printing labels, such as those available from Kanzaki Label Technologies, Ricoh Ltd and Armour Ltd (from the latter under part nos. 479 and F 52 622) and heat-sensitive paper as used for facsimile machines and heat copiers are also suitable. Also, suitable are coated papers and coated films such as those sold under the trade names RIVATAC T5206 and RIVATAC AT231/67HG and the coating materials of such papers and films sold under the trade names T902 and T903 by Smith & McLaurin Ltd of Kilbarchan, Scotland. Furthermore, the dye systems included in heat-sensitive papers can advantageously be incorporated into printing inks. The temperature indicating paints and inks and the temperature indicating labels and paper provide a visible indication of heating or cooling by changing colour at a specified temperature, which is preferably below the softening temperature of the adhesive or above the temperature at which the adhesive becomes glass-like, as appropriate. It is essential however, that the colour change of such materials is irreversible. Advantageously, temperature indicating inks may be applied directly to the adhesive in the form of a pattern or design by means, for example, of an ink jet printing technique. Where, for example in the case of the thermal melt crayons, the indication of heating or cooling is provided by a change of state, it will also, in general, be necessary for the change of phase or state to be irreversible. However, where, for example, the indication is provided by a change from the solid to the liquid state, the indicator means may be applied in a pattern or design to the sheet material or directly on the adhesive. Thus, any change from the solid to the liquid state of the indicator means can provide a disruption or distortion of the applied pattern or design which will be immediately apparent, even is the indicator re-solidifies. Referring to Figures 3a and 3b, in which parts corresponding to those of Figures 1 and 2, are indicated by like reference numerals, it v 11 be seen that the indicator means can also be provided on at least that part of the portion 3 which is immediately adjacent the opening 8 distant from the lateral weld zone 5. After closure of the bag, the adhesive 9 completely overlies the opening slit 8 and the indicator 11. In this embodiment, the adhesive 9 must be translucent, or preferably transparent, to ensure that the indicator means 11 is visible through the flap portion 7. Referring to Figure 4, in which parts corresponding to parts in Figures 1 to 3 have the same reference numerals, the bag 6, which is shown in the open state, can be sealed by a closure member 14. The closure member 14 comprises a plastics material substrate 15 which is at least translucent and preferably is transparent and which is adhered to at least a part of the section 16 of the first portion 3 along the whole lateral width of the bag, and optionally to the second portion 4, by an adhesive layer 9. A releasable cover strip 10 prevents adhesion of the closure member 15 to the first portion 3 adjacent to the opening 8 prior to the filling of the bag. In use, the items to be held in the bag are introduced through the slit 8, the cover strip 10 is removed and the closure member 14 seals the opening 8 by completely overlying the same. The free surface of the adhesive 9 which is exposed on removal of the cover strip 10 adheres the substrate 15 to the first portion 3,16. An indicator means 11 is provided on the transparent plastics material substrate 15 in such a position that, when the bag is sealed, the indicator means overlies the opening 8, or at least that part of the first portion 3 which is adjacent to the opening 8 and distant from the lateral weld zone 5a. The indicator means 11 may equally be applied to the adhesive 9 (by for example ink jet printing) or to the part of the first portion 3 adjacent the slit opening 8 and distant from the weld zone 5a. Further security features may be incorporated into the security bags as is particularly illustrated in Figure 5, which is a variation of the embodiment of Figure 4. These security features can also be incorporated into the embodiments of Figures 1 to 3. In Figure 5, the closure member 14 comprises a transparent plastics material substrate 15 which carries a discontinuous weakly bonded adhesive layer 17 such as ethyl cellulose and a strongly bonded adhesive layer 18 such as epoxy cellulose acetate propionate. Because of the layers 17 and 18, any attempt to gain access to the interior of the bag 6 by lifting the substrate 15 will result in those parts of the layer 18 which are in registry with layer 17 remaining adhered to portions 3 and 4 whilst other parts of the layer 18 will remain adhered to substrate 15. This results in the formation of a visible pattern constituted by the split layer 18 which pattern cannot be obliterated by re-sealing the closure member. Soluble transparent or translucent dye may be carried in a layer 19. Layer 20 comprises a high tack adhesive in which the indicator means 11 is disposed. It is not essential, however, for the indicator means 11 to be disposed in the layer 20. Layer 21 is an optional second layer of adhesive which carries optional ink jet printing 22. Referring now to Figure 6% the bag is produced by folding longitudinally a continuous length 101 of thermoplastic sheet material (after it has been optionally printed as appropriate) into a J-form where it includes a first portion 103 folded longitudinally at 102 so as to be superposed on a part of a second portion 104 so as to leave a flap portion 107 of the second portion 104 exposed. The first portion 103 is heat sealed to the second portion 104 by a longitudinally extending heat seal denoted by a reference numeral 105. Preferably, a longitudinally extending region of the flap portion 107, which region is generally parallel to the heat seal 105, is subjected to corona discharge to improve its adhesion characteristics in that region. A band of high-tack adhesive 109 is applied to that region and is covered by a removable cover strip 110 optionally after having been provided with a security code by means of an ink jet printing technique. An indicating means 111 may be applied to the flap portion 107 prior to the application of the adhesion 109. Alternatively, the indicating means may be applied generally at region 113. The region indicated generally by 113 may also be subjected to corona discharge to improve its adhesion. The continuous length 101 of sheet 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 sheet material is cut into adjacent transverse sections each having heat sealed edges. Each of these sections constitutes a bag in accordance with the invention. It will be appreciated that a similar method can be applied for the production of the bags in accordance with Figures 4 and 5. It is particularly advantageous to apply the closure member as a pre-made tape which will desirably incorporate the indicating means.

Claims: CLAIMS : 1. A bag formed of sheet material which bag comprises a first portion of the sheet material having an opening to enable access to be gained to the interior of the bag, a closure portion arranged to be superposable with the first portion and a band of adhesive having a free surface so arranged as to seal the opening on superposition of the of the first portion and the closure portion, characterised in that at least one indicating means is provided which, on superposition of the first portion and the closure portion, is disposed adjacent to the opening and which provides a durable visible indication of heating or cooling of the bag. 2. A bag as claimed in claim 1 wherein the closure portion comprises a flap portion formed integrally with a portion of the sheet material of the bag. 3. A bag as claimed in claim 1 wherein the closure portion comprises a transparent plastics substrate to which the band of adhesive is applied, which substrate is affixed to the sheet material of the bag. 4. A bag as claimed in claim 3 wherein the plastics substrate is affixed to the sheet material by means of an adhesive. 5. A bag as claimed in claim 3 wherein the plastics substrate is heat welded to the sheet material. 6. A bag as claimed in any preceding claim wherein a releasable cover-strip is provided on the free surface of the band of adhesive. 7. A bag as claimed in any preceding claim wherein an indicating means is applied to or affixed on the closure portion. 8. A bag as claimed in any preceding claim wherein an indicating means is applied or affixed to the portion having the opening. 9. A bag as claimed in any preceding claim wherein an indicating means provides a colour change on heating the bag. 10. A bag as claimed in any preceding claim wherein an indicating means provides a colour change on cooling the bag. 11. A bag as claimed in any preceding claim wherein an indicating means provides a visible change of phase or state on heating of the bag. 12. A bag as claimed in any preceding claim wherein an indicating means provides a visible change of phase or state on cooling the bag. 13. A bag as claimed in any preceding claim including a temperature indicator selected from the group comprising temperature indicating paints, temperature indicating inks, temperature indicating labels, heat sensitive papers, thermal coated papers, themal coated films, thermal melt crayons and thermal colour change crayons. 14. A bag as claimed in any preceding claim wherein an indicator means is applied to the sheet material in a patter or design.

Inventors: TODMAN VICTOR, TODMAN, VICTOR
Applicants: TRIGON CAMBRIDGE LTD, TRIGON CAMBRIDGE LIMITED
Application year: 1992
Main classification: B65D33
IPC codes: B65D27, B65D33