TAMPER INDICATING SECURITY BAG
A method of manufacturing tamper indicating security bags (e.g for the transportation of cash) from plastic film The method comprises (a) forming an elongate rectangular strip of plastics film material; and (b) folding the opposed long edges of the strip towards the centre to form a pair of flaps with a gap between their inside edges, which leaves the central area of the strip exposed; or the method comprises (a) forming an elongate flattened tube of plastics film material; (b) cutting the tube longitudinally to form a pair of flaps in the overlying material of the flattened tube; and (c) exposing a central area of the underlying material in a gap between the pair of flaps. In either case the method also includes (i) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area; (ii) slitting the strip down the middle of the central area to form a pair of elongate folded strips; and (iii) cutting the folded strips transversely at equal intervals, to form individual folded sections of material which can be turned into bags for example by heat sealing the cut edges.
This invention relates to tamper indicating security bags, and particularly to security bags for the transportation of cash or other valuable items. Generally speaking, such bags comprise a body having a closure lip which is adapted to seal the bag in such a way that the contents cannot be accessed, without damaging the seal or the bag in such a way as to render any tampering obvious.
Conventionally, high security bags of this type are constructed with a separate tamper evident tape which is attached to the bag during the manufacturing process, and in a typical example, the tape may be welded to the bag by a heat sealing or sonic welding process, in the case of a thermoplastic bag, or attached by means of an adhesive.
The reason for this method of construction is that it allows the relatively complex layer structure of the tamper evident seal to be pre-formed on a separate tape, rather than on the bag itself.
However, this also has the disadvantage that it creates an inevitable weakness at the junction of the bag and the tape, where the would-be tamperer can potentially disguise the point of entry, by rewelding or regluing after the unauthorised entry. In other words, since there is already a discontinuity in the structure at this point, it will subsequently be difficult to determine whether the discontinuity was part of the original seal, or has been introduced later.
In addition, this construction places a high level of responsibility on the manufacturer, to ensure that the tape is consistently attached to each bag, since again, any variation in manufacturing standards at this point could be difficult to distinguish from an unauthorised attempt at detaching and reattaching the seal.
Similarly, depending on the method of attachment, it may be possible for the tamperer to completely remove the tamper evident tape at its point of attachment and subsequently replace it with tape taken from another similar product. Again, issues of consistency of manufacturing construction will also affect the degree of “tamper evidence” that can be achieved in such circumstances.
Accordingly, the present invention provides a method of forming tamper evident security bags, including a closure with a tamper evident seal comprising a combination of ink and adhesive layers which are formed directly on the material of the bag itself, the method defined in claims 1 and 4 and preferably carried out in order from (a) to (e). It will be appreciated that the layers may be formed on an integral closure lip, or on an area of the body of the bag on which the closure lip is to be sealed, or alternatively, some of the layers may be formed on the closure lip whilst some are formed on the sealing area of the body.
Preferably, in order to ensure that printing ink reliably adheres to a substrate such as polythene, or other similar film material, the surface of the material is treated using known techniques such as corona discharge, gas plasma, or chemicals which effectively etch the surface. In one embodiment of the invention, the surface treatment is made discontinuous, for example by covering the surface with a discontinuous barrier prior to treatment, so as to create predetermined areas of untreated material, and so that a subsequent overall coating of ink or adhesive will not be uniformly attached to the surface, causing a clear pattern to be revealed, in the event that a tamperer tries to reopen the closure.
Alternatively, in another embodiment, the initial surface treatment is applied uniformly, but a discontinuous release layer is formed on top of the surface treatment, so that once again, subsequent layers of ink and/or adhesive will be attached with higher bonding strengths in some areas, and lower bonding strengths in others.
It will be appreciated that the areas of increased release effect may, for example, be in the form of a message or symbol so as to render the evidence of tampering much more obvious.
The seal may also incorporate one way temperature reactive inks, such as thermo-chromic ink, which also enables the bag to show evidence of tampering if it is subjected to heat, cold, or the like, as well as mechanical manipulation or chemical attack. Preferably, the arrangement of the tamper evident ink layers is such that they are enclosed on both sides, that is to say, by the film substrate on one side, and by a layer of adhesive on the other side, so that it is also possible to reduce the risk of pre-tampering. This refers to a scenario in which the would-be tamperer pre-treats the closure device by interfering with the tamper-evident layers before the bag is closed, so that it can be subsequently opened without tamper evidence.
According to a further preferred feature of the present invention, the bag is formed from a strip of material which is folded over, to form a bag having a front and a rear wall of material connected by a fold forming the inner end, whilst one of the wall sections is left longer than the other, so as to form a closure lip. The side edges of the bag may be heat sealed or otherwise welded together, with the heat seals incorporating so-called “security printing”. Similarly, by starting with an elongate strip whose width is at least four times the intended bag length, it is possible to produce bags in “two-up” formations by folding both free edges of the strip inwards towards the middle. In this way, a continuous fold is formed along each of the opposite edges, providing respective overlap portions. This enables a series of pairs of bags to be formed, which are then separated by slitting the assembly lengthwise down the middle. Preferably, in either case, before the folded portions forming the individual bags are finally cut from the entire length, any required printing of adhesive, or ink, or other pre-treatment of the surface, can be carried out in a continuous fashion, on the central area in the region of the folded over edges.
Alternatively such pairs of bags can also be produced starting with a continuously extruded tube of film which is flattened and then slit longitudinally, so as to form a pair of facing overlap portions.
Some embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which:
Referring to the drawings,
In order to produce bags with an integral security feature, on the other hand, as shown in
It will be clear, however, from the illustration on
A similar result of C-shaped film with a central gap between two flaps can be achieved from an extruded “tube” of film, by cutting it longitudinally down one side. There are two methods starting with at tube, in both cases, the tube is flattened and stored on a roll. Then, either a longitudinal strip is cut from the centre of the overlying material to expose the central area of the underlying material, or a longitudinal slit could be cut down the length of overlying material of the tube and the inside edges of the material along the slit could be urged apart, for example by “ploughing”.
In order to make the bag according to the invention, having formed the C-shaped web shown in
A first layer of ink 51 is applied in a pattern (in this case in the form of a pair of lines spelling void) directly onto the (preferably transparent/translucent) central area of the lower web (see
Next the central area 26 is treated to improve the adhesion of ink, for example by corona treatment 52 (see
Third, as shown in
Fourth an ink 54 is applied over the release layer as shown in
In a sixth step (shown in
The seventh step is shown in
In the eighth step shown in
Once the security features have been applied, the web is cut and sealed laterally to attach the flaps to the web underneath, such that the web forms a rear wall and the flaps become the front walls of the bags. The lateral cutting and sealing (e.g. heat welding) would normally take place at equal intervals to form bags of equal width.
Of course, as mentioned above a layer of hot melt adhesive 57 has been applied over the whole area of the closure lip, and also extends into the opening of the bag, but the adhesive is clear and cannot be seen in
In this way, a “double seal” is formed at the mouth of the bag, which greatly improves the “tamper evident” capability of the assembly.
It will be noted that
1. A method of forming tamper-evident security bags from plastics film material, the method comprising:
- (a) forming an elongate rectangular strip of plastics film material, the formed strip having opposed long edges, a center, and a central area having a middle;
- (b) folding the opposed long edges of the strip towards the center to form a pair of flaps with a gap between the opposed long edges, which leaves the central area of the strip exposed;
- (c) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area;
- (d) slitting the strip down the middle of the central area to form a pair of elongate folded strips; and
- (e) cutting the elongate folded strips transversely at equal intervals, to form individual folded sections of material.
2. A method according to claim 1, wherein cutting the elongate folded strips transversely further includes heat-sealing edges created by the cutting, so that the individual folded sections are formed into individual open-ended bags.
3. A method according to claim 1, wherein layers of adhesive or ink are also applied to the opposed long edges of the strip in a region adjacent to the central area of the strip.
4. A method of forming tamper-evident security bags from plastics film material, the method comprising:
- (a) forming an elongate flattened tube of plastics film material, the flattened tube comprising an overlying material and an underlying material;
- (b) cutting the tube longitudinally to form a pair of flaps in the overlying material of the flattened tube;
- (c) exposing a central area of the underlying material in a gap between the pair of flaps;
- (d) selectively applying layers of adhesive and ink, adapted to form a tamper-evident sealing means, to the central area;
- (e) slitting the central area to form a pair of elongate folded strips; and
- (f) cutting the folded strips transversely at equal intervals, to form individual folded sections of material.
5. A method according to claim 4, wherein (b) cutting the tube and (c) exposing the central area of the underlying material are completed by cutting a strip of material out of the central area of the overlying material.
6. A method according to claim 4, wherein (b) cutting the tube further comprises cutting a slit along the center of the overlying material of the tube and wherein (c) exposing the central area further comprises urging the edges of the pair of flaps apart.
7. A method according to claim 4, wherein cutting the folded strips transversely further includes heat-sealing edges formed by cutting, so that the folded sections are formed into individual open-ended bags.
8. A method according to claim 4, wherein layers of adhesive or ink are also applied to the central area of the underlying material underneath an edge of the overlying material adjacent to an opening of the bags.
10. A tamper evident security bag comprising:
- a mouth;
- an integral closure lip; and
- a tamper evident feature on the closure lip, the tamper evident feature comprising: a patterned release layer,
- a coating ink layer applied over the release layer, a thermochromic ink applied in a region away from the release layer and the coating ink layer, and an adhesive,
- wherein the adhesive is applied to the closure lip covering the tamper evident feature and in a region under the mouth of the bag which faces a side of the bag opposite the closure lip.
11. A tamper evident bag according to claim 10, wherein the patterned release layer is formed by a first layer of ink applied in a pattern directly onto the closure lip prior to corona treatment.
12. A tamper evident bag according to claim 10, further comprising a mask of text applied to a region of the release layer to mask any shadow of a release pattern formed by the patterned release layer.
13. A tamper evident security bag according to claim 10, further comprising a second layer of coating ink to improve opacity of the coating ink covering the patterned release layer and to thicken the coating ink layer, so that a more significant air gap is produced when tampering occurs which leaves some ink attached to the closure lip and some of the ink coating the patterned release layer adhered to an opposing surface of the closure lip.
14. A tamper evident security bag according to claim 10, further comprising a release liner, applied over the adhesive.
International Classification: B65D 33/34 (20060101);