Field of the Invention

The present invention relates to a blank for an article of packaging for a foodstuff, an article of packaging assembled from the blank, methods of making the same, and a method of packaging a foodstuff using the article.

Background of the Invention

Various articles for packaging foodstuffs are known. Articles of packaging comprising synthetic plastics materials are extremely light and strong, but are not biodegradable. As a result of the need for recyclable and biodegradable materials, packaging formed from card, board and similar substances are becoming increasingly popular. Unfortunately, card and board and other cellulose-based materials are generally not as strong as synthetic plastics materials and are far less impermeable. Accordingly card and board packaging must be thicker than synthetic plastics packaging and typically must be treated with thin films of moisture-resistant coatings to prevent the packaged foodstuff from becoming dehydrated and/or prevent the ingress of water into the package during storage and/or transit.

In addition there is a need to improve the impermeability of food packaging to moisture to extend shelf-life, especially for sandwiches. At present the relatively short short-life of many food items leads to excessive amounts of waste. Longer shelf-life can be obtained by using synthetic plastics packaging materials, but as explained above, these do not meet the need for re-cyclability and/or biodegradability.

Current card and board packaging for sandwiches, for example, typically confers a 2 day shelf-life, and such packaging is known to those skilled in the art as "P2" packaging. If improved packaging could be provided to confer a three day shelf-life ("P3" packaging), then the amount of food wasted would be considerably reduced.

There is thus a great need for an article for packaging foodstuffs, formed from a cellulose-based material, such as card or board, which is of reduced mass, yet retains sufficient rigidity and structural strength, and is resistant to the passage of water and water vapour and which can confer longer shelf-life than existing card or board-based packaging. The present invention seeks to provide a blank for an article of packaging which simultaneously meets both of these objectives.

WO2008/025982 discloses a method of preparing a reel of laminated card material, the material having defined therein a plurality of packaging blanks. The laminate is a heat-sealable plastics material. The blanks comprise apertures formed therein, by stamping or cutting, the apertures being covered by the plastics laminate, so as to form a transparent window in the blank.

WO2008/025982 also discloses a laminated blank for a sandwich carton. In one embodiment described therein, very small notches may be formed in the periphery of the blank, and the laminated film bridges the gaps left by the cut-out notches, "to ensure that a hermetic seal is formed between the lid and flanges" when the pack is heat-sealed. These embodiments are depicted in Figures 9 & 14 of WO2008/025982.

In fact, the present Applicant has found that the embodiments depicted in Figures 9 & 14 are not viable. By way of explanation, the laminated film is shown bridging the notches in outward-turned flange portions of the blank. These flange portions are turned outwards during assembly of the carton in order to provide a surface which can be heat-sealed to the periphery of the lid portion of the carton. In practice, the Applicant has found that the act of folding the flange portions outwards causes the outermost parts of the film, bridging the notches, to become strained, such that the film tends to tear.

The present invention aims to avoid this problem and, inter alia, to provide a carton in which viable heat seals can be effected using a laminated film. Blanks for articles of packaging are assembled by folding and, typically, gluing and/or heat sealing. Usually the process of assembling the article of packaging from the blank involves folding one portion of the blank over another portion. In particular, where edges of the blank meet at an angle (e.g. 90°), it is known to include a small flap or 'web' of card between the edges, which flap or web is typically bisected by a fold line. Folding this flap along the bisecting fold line creates a convenient way of bringing the edges of the blank into abutment and forming a closure therebetween. This is a standard technique widely used in the packaging industry.

The present applicant has, however, identified certain disadvantages associated with this standard technique, and has proposed an improvement thereto, as elaborated below.

The standard 'folding web' technique used in conventional packaging manufacture can create portions of the article, during folding, which comprise multiple (3 or 4) overlapping portions of the blank. Whilst this can give good leak-proofing to the seam of the assembled article of packaging, the multiple thicknesses of card can be difficult to fold using an automated machine. As a result this greatly reduces the speed at which the machine can be run. This is a considerable disadvantage in such circumstances, as it is usually required to produce many thousands of such packaging articles during a production run. The present invention aims to ameliorate this problem.

Summary of the Invention

In a first aspect the invention provides a blank for an article of food packaging, the blank comprising a foldable substrate of card or board or the like, a surface of the substrate being overlaid by a relatively water-impermeable layer of a film material; the blank comprising at least one webbed region where there is provided two adjacent portions of substrate which, when the blank is assembled into a folded configuration, are folded such that at least part of one of the adjacent portions overlies at least part of the other adjacent portion, to provide at least a double thickness of substrate; the webbed region of the unfolded blank being such that there is a space between the adjacent portions which is devoid of substrate but which is spanned by the relatively water-impermeable layer of film material.

The space between the adjacent portions is conveniently provided by cutting out a part of the substrate, which typically will create an essentially triangular space between the adjacent portions of the webbed region, which space is bridged by the relatively water-impermeable film layer. Although an essentially triangular cut-out is typical, it is by no means essential, and any shape cut-out is permissible.

In a conventional prior art blank, without such a space between the adjacent portions, when folded there will be three overlying thicknesses of substrate. This increased thickness of substrate is relatively difficult to fold and manipulate in an automated process, and reduces the speed at which blanks can be folded and assembled. In contrast, the blank of the present invention, when folded, will have a webbed region comprising only two thicknesses of substrate and an extra thickness of the relatively water-impermeable layer of film material. However, the layer of film material is relatively much thinner than the substrate, and also much more flexible and easier to fold. As a consequence, the blank of the invention is much easier to manipulate than a conventional blank, and allows a higher throughput speed in automated processes. The presence of the relatively water-impermeable layer ensures that a good seal if formed at the webbed region e.g. reducing ingress or egress of fluids, especially liquids.

The invention is such that, in the webbed portion of the assembled blank, the laminate film is, in the area of the webbed portion, doubly folded, (i.e. folded back on itself) so that it reverses direction twice. This is illustrated in Figure 4a, which is a schematic representation of a webbed portion of an assembled blank in accordance with the present invention, and contrasted with Figure 4b, which is a schematic representation of part of an assembled blank of the sort disclosed in WO2008/025982.

In a second aspect, the invention provides an assembled article of packaging for a foodstuff, especially but not necessarily for packaging a sandwich, the article being formed, inter alia, by folding, gluing and optionally heat-sealing a blank in accordance with the first aspect of the invention.

In a third aspect the invention provides a method of forming a blank for an article of food packaging, the method comprising the steps of: (a) creating creases or fold lines in a web of foldable substrate; (b) removing a portion of the substrate at a webbed region, to leave two adjacent portions of substrate separated by a space; (c) applying a layer of relatively water-impermeable film material to a surface of the substrate, said layer spanning the space between adjacent portions of the substrate at the webbed region; and (d) cutting out or otherwise separating the blank from the web of foldable substrate.

A webbed region of an unfolded blank in accordance with the invention comprises a space, devoid of substrate, which is spanned by the relatively impermeable layer of film material. In any one webbed region (and there may be more than one such region in any particular unfolded blank), the film spanning the space devoid of substrate will typically have a surface area (on one surface) of at least 2cm ² , preferably at least 3cm ² , more preferably at least 4cm ² , and most preferably at least 5cm . A typical maximum surface area (on one surface) for the film in one webbed region will be 20cm ² , preferably no more than 18cm ² , and most preferably a maximum of no more than 17cm ² .

In the method of the third aspect of the invention, defined above, step (a) is preferably performed before steps (b)-(d), because folds, cuts, score lines, creases, perforations etc. cause weaknesses in the substrate which tend to reduce the water-impermeability thereof, increasing the rate at which water vapour can be lost by the packaged foodstuff. The same is true if a relatively water-impermeable film is applied to the substrate, and then folded, scored, cut etc. These processes reduce the integrity and barrier properties of the film. Thus, by folding, creasing, scoring, perforating etc. the substrate before applying the relatively water-impermeable film thereto, the film layer is left undamaged and intact, thereby preserving the barrier properties thereof. Typical films for use in the present invention will have a permeability to water vapour of less than 3 grams/m per 24 hours, preferably less than 2 grams/m per 24 hours, more preferably less than 1 gram/m ² per 24 hours, and most preferably less than 0.5 grams/m ² per 24 hours as determined according to standard ASTM F 1770-97 under condition of 85% relative humidity and at a temperature of 23 ⁰ C. The term "relatively water-impermeable" should be construed with this in mind.

The relatively water-impermeable film may comprise, for example, a plastics film such as polypropylene (especially biaxially-oriented polypropylene or "BOPP") or cellulose-based materials. Cellulose-based materials include derivatised celluloses, such as hydroxyethyl cellulose or other chemically-modified celluloses. Suitable films are available under the trade names PropaFresh™ (BOPP-based) and NatureFlex™ (cellulose-based) and are sold by Innovia Films (Wigton, Cumbria, UK; Tecumseh KS 66542 USA; Merelbeke B9820 Belgium; and 19 Potter Street, Craigieburn, Victoria 3064, Australia). Preferably at least one surface of the film is treated with substances to render the film heat-sealable and/or mist-resistant (i.e. to inhibit formation of condensation on the surface of the film). If desired, both surfaces of the film may be so-treated. Substances suitable for conferring a heat-sealable and/or mist-resistant finish to the film are known to those skilled in the art and include, for example, aqueous dispersions of polyvinylidene chloride (PVdC) copolymers, polyolefins and the like. Again, suitably treated films are available from Innovia Films.

The relatively water-impermeable film may be applied to the inner surface of the substrate (i.e. that surface which, when the packaging article is assembled, lies on the inside of the packaging), or to the outer surface, or to both. Advantageously the film is applied to at least the inner surface, so as to prevent loss of moisture into the substrate from the packaged foodstuff, which might otherwise result in significant dehydration of the foodstuff. In a preferred embodiment, the relatively water- impermeable film is applied solely to the inner surface of the substrate.

In order to provide a good barrier to the passage of water and water vapour, which might otherwise lead to unacceptable dehydration of the packaged foodstuff, it is desirable that the relatively water-impermeable film is substantially continuous and should preferably be applied to essentially all of the inner surface of the blank which when in use in the assembled article of packaging is in gaseous flow contact with the packaged foodstuff. It will be apparent to those skilled in the art that there may, depending on the design of the blank, be portions of the blank which, topologically speaking, form part of the inner surface but which are not in gaseous flow contact with the foodstuff. Such portions need not be covered with the relatively water- impermeable film in order to attain all the advantages of the invention. However, in terms of ease of manufacture, it will usually be preferred simply to cover substantially the entire inner surface of the blank with the relatively-impermeable film. Thus, in preferred embodiments, the invention relates to a blank in which the entire inner surface is substantially so-covered, and to a corresponding assembled article of packaging.

Preferably all of the folds, creases, cuts, perforations etc. which need to be present in the blank, and which need to be on a portion of the substrate to be covered by the film, will be formed before the film is applied to the substrate. This applies especially to such folds etc. which are present on the inner surface, and also, in preferred embodiments, to such folds etc. which may be formed on the outer surface.

The blank, the assembled article of packaging, and the method of the invention, are applicable to essentially any design of food packaging utilising a foldable substrate, such as salad boxes, sandwich cartons and the like. The invention is especially applicable to sandwich cartons, of the type used to package triangular cut sandwiches, and blanks for such cartons accordingly constitute a preferred embodiment of the invention.

In preferred embodiments of the invention (blanks, and corresponding assembled articles of packaging, adapted to package triangular cut sandwiches), the blank and assembled article of packaging, respectively, may conveniently additionally comprise a foldable webbed substrate region (not necessarily comprising a film layer) which, when the blank is folded, projects inside the assembled article, the foldable webbed region being located between two adjacent walls of the blank. Preferably a foldable flap is provided along substantially an entire edge of the foldable webbed region within the container. This arrangement forms a sort of secondary lid or closure over the edge of the foldable web and, in conjunction, these features render the assembled article of packaging more tamper-proof than conventional designs. Suitable arrangements are disclosed in GB2447127. In addition, frangible connections may be provided between the foldable webbed substrate region and a wall of the assembled article of packaging, as disclosed in GB2447128.

The blank of the invention will conveniently comprise an aperture, cut out, stamped or otherwise formed in the substrate. The aperture forms a window which, in the assembled article of packaging, allows a prospective consumer to view the packaged food within the article of packaging prior to purchase.

The aperture will typically be covered by the relatively water-impermeable film which is applied to the surface of the substrate. If desired, an additional film of laminate material (conveniently a synthetic plastics material) may be applied over the aperture to increase the strength or thickness of the closure. The film or films may desirably be heat sealed to the substrate around one or more of the edges defining the aperture.

The method of the second aspect of the invention is advantageously performed, entirely or at least in part, using automated machinery.

The blank is conveniently such that it is substantially compostable or biodegradable, with the substrate typically being formed from a cellulose-based material and the water-impermeable film being substantially compostable also. Suitable materials are know to those skilled in the art.

Advantageously, the method of the invention will preferably comprise other steps to form a finished blank. These may include one cutting or otherwise forming one or more windows or apertures in the substrate (which step is also preferably performed before applying the relatively water-impermeable film). In a preferred embodiment the flat blank is prepared by performing each of the necessary steps using a single automated machine.

An exemplary method of the invention is as follows: an automated machine is supplied with a sheet, roll or reel of foldable substrate material such as card or board; the inner and outer surfaces of the substrate (in terms of which surface will be closer to the packaged foodstuff in the assembled article of packaging) are both cleaned with a reel cleaner to remove dust; the substrate passes through a printing station, typically comprising six printing heads, to apply the desired print pattern to the outer surface of the substrate; the printed substrate then passes through a die station which cuts out a window in the substrate and discards the surplus material, and which makes any desired score lines, folds, creases, cuts, perforations etc. on the inner surface of the substrate, including cutting out those parts of the substrate from the webbed region(s) of the blank. Next the creased, printed substrate is fed to a gluing station which applies spots of a suitable liquid glue to the inner surface. The machine is also supplied with a reel of the relatively water-impermeable film and, at this point in the process, the film or laminate is applied to the spot-glued inner surface and pressure applied e.g. by passage through one or more rollers. The film spans gaps in the webbed region of the substrate where a portion of the substrate has been removed. The glue is then cured or dried e.g. by UV irradiation or gentle heating by a hot air blower or exposure to a source of infra-red irradiation. Lastly the substrate/film combination is fed to a finishing station, in which the outline of the blank is cut out from the reel or sheet of substrate (the waste being discarded) and the finished blank output from the machine.

In a fourth aspect, the invention provides a method of packaging a foodstuff, especially a sandwich, the method comprising the steps of: providing a blank in accordance with the first aspect of the invention, which is folded and glued so as to form a partially assembled article of packaging; opening out the partially assembled article of packaging, if necessary, and inserting the foodstuff into the article of packaging; placing a lid over the opening through which the foodstuff is inserted; and heat sealing the lid closed. The lid may be a separate item of packaging or, more preferably, forms an integral part of the article, such that the "placing" step can be accomplished simply by folding the lid over the opening.

For the avoidance of doubt, it is hereby expressly stated that any feature of the invention described herein as "preferable", "desirable" "advantageous", "convenient" or the like may be present in the invention in isolation, or may be present in any combination with any one or more other features so described, unless the context dictates otherwise.

The various features of the invention will now be described by way of illustrative examples and with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a blank, for a prior art item of food packaging, not in accordance with the invention;

Figure 2 is a plan view of a similar blank, but in accordance with the invention;

Figure 3 is a plan view of a blank, for an item of packaging for a sandwich, in accordance with the invention;

and Figure 4a is a schematic representation of part of webbed region of an assembled blank in accordance with the invention; and Figure 4b is a schematic representation of part of a prior art blank.

Examples

Referring to Figure 1, a prior art blank (2) is shown. The blank comprises a foldable card substrate, coated on its inner surface with a thin film of transparent synthetic plastics material which is relatively water-impermeable. The blank is essentially planar, but has a plurality of fold lines or creases to facilitate folding of the blank into an assembled article of packaging. A few such fold lines are indicated (4).

Then blank has a larger aperture or window which is covered with a heat sealable transparent film of synthetic plastic material (6) - this is a different material to the laminate film applied to the substrate. The food within the packaging can thus be viewed by a prospective consumer prior to purchase. The film (6) covering the window is also desirably relatively water-impermeable.

The blank has at least four webbed regions (8) at which, when the blank is assembled, a plurality of thickness of substrate are caused to become overlying.

During assembly of the packaging, the front flap (10) of the blank is moved upwards, hinging along fold line (12), which fold line is continued (as 12') into the webbed region denoted generally as 8'. This brings together adjacent portions (14, 16) of the webbed region (which are optionally glued). Portion 14 is then folded backwards about fold line (12), and adjacent portion 16 is folded about fold line (20), such that both portions 14 and 16 come to lie against the side wall (22). In the assembled item of packaging therefore, there are three thicknesses of substrate (14, 16 and 22) in the webbed region 8'. A generally similar process is repeated at each of the three other webbed regions. The folding of multiple layers of substrate in this way, (and gluing thereof) is inefficient and not readily performed at high speed in an automated assembly process.

A similar blank, but without the disadvantages of the prior art blank, is illustrated in Figure 2, which is an embodiment of a blank in accordance with the present invention. Referring to that figure, like components as in Figure 1 are denoted by common reference numerals. In the blank of the invention, the part of the substrate generally corresponding to portion 14 of Figure 1 has been cut out, leaving a gap 24 between otherwise adjacent components, portion 16 and side wall 22. The thin film of substantially water-impermeable material however is continuous over the substrate and is present in the gap 24. In this instance, when the blank is assembled, since there is no portion of substrate corresponding to portion 14 in Figure 1, only two thicknesses of substrate (corner portion 16, and side wall 22) and the relatively very thin film, which are overlying at the webbed region. This is much easier to manipulate at high speed in an automated assembly process, and so allows much higher throughput.

Referring to Figure 3, there is shown a blank for an article of packaging for a triangular cut sandwich, the blank being in accordance with the invention. The shape of the blank is generally in accordance with that of known prior art blanks. However, the inner surface of the blank is coated with a thin film of relatively water- impermeable synthetic plastics material. This film is substantially continuous over the entire inner surface of the substrate and is present in the window or aperture portion of the blank and also forms a web of material at a webbed region of the blank (8"), where a gap (24") has been created between adjacent portions of the blank: foldable portion (16") and side wall (22").

When the blank is assembled, portion 16" and the thin film present in the gap 24" are folded so as to overlie side wall 22". Accordingly there are two thicknesses of overlying or overlapping substrate, rather than the three thicknesses which would be present if gap 24" had not been formed in the substrate.

With reference to Figure 4a, there is shown a schematic representative of part of a webbed region of an assembled blank in accordance with the present invention. The webbed region comprises a first portion of foldable card substrate 30, which is overlaid by an adjacent portion of foldable card substrate 32. an inner surface of the substrate 30, 32 is overlaid by a relatively water-impermeable layer of a laminate film 34. The ends of the two portions of substrate 30, 32 are effectively joined by a continuous layer of the film 34. As shown in Figure 4a, in exaggerated manner for the purposes of clarity, the film 34 is doubly folded, with two reversals of direction; a first fold (with consequent reversal of direction) indicated generally at 36, and a second fold (and consequent reversal of direction) indicated generally at 38. This arrangement is characteristic of what the person skilled in the art understands by "a web", and the term "webbed region", as used herein is to be interpreted accordingly.

Also, again as shown in Figure 4a, the webbed region of the assembled blank, comprises (going from the inner surface of the blank to the outer surface) a "sandwich" of the film 34, substrate 30, two layers of film 34, and then another layer of substrate 30.

In contrast, Figure 4b shows a schematic representation of part of an assembled blank of the sort disclosed in WO2008/025982. The assembled blank comprises a first, outward folded portion of substrate 40 and an adjacent second, outward folded portion of substrate 42, the portions 40 and 42 being separated by a small notch 44 cut in the substrate. The assembled blank also comprises a lid 46, overlying the portions of substrate 40, 42. Both the lid 46 and the portions of substrate 40, 42 are coated on an inner surface with a layer of film material 48. It is apparent that there is no web in the prior art arrangement.