GB2617594A

GB2617594A - Packaging

Info

Publication number: GB2617594A
Application number: GB2205497.7A
Authority: GB
Inventors: Matthews Kristian; Cousins David; Brierley Caroline; Godfrey Jonathan; Johnson Paul
Original assignee: Princes Ltd
Current assignee: Princes Ltd
Priority date: 2022-04-13
Filing date: 2022-04-13
Publication date: 2023-10-18
Also published as: WO2023199033A1; GB202205497D0

Abstract

Disclosed is a stack (40) comprised of a plurality of food containers (10a, 10b, 10c, 10d), preferably cans or tins, each comprising a first face (16a, 16b, 16c, 16d) and a second face (18a, 18b, 18c, 18d), arranged such that the food containers are stacked one on top of another by an adhesive material (30) between a second face of one container and a first face of another container. The individual food containers of a stack (40) are configured to be difficult to separate axially yet easily detachable by twisting. The adhesive may be a length of bead (31) on the peripheral edge of one of the faces and may be pressure sensitive. The length of bead of the adhesive material preferably has a diameter no larger than 4.5mm and is preferably applied at at least four spots. The stack may specifically comprise ring pull cans or foil top cans. A method of manufacturing such a stack is also disclosed.

Description

Packaging arrangement and method of manufacture thereof

Field of the Invention

The present invention relates to a packaging arrangement for canned food products, in particular for "tin" can products of the type having low mantle height in relation to their diameter that are typically transported and sold in the form of a stack of three or four such cans. More specifically, the present invention relates to a product consisting of a stack of such cans and a method of manufacturing such a stack.

Background

It has become customary to sell food items such as tuna in the form of cans (tin cans or "tin tuna") that are shipped and sold as a sales unit of several such cans stacked on top of each other, e.g. as a three-can or four-can stack. One common form of such a stack uses shrink wrap material in sleeve form to hold the cans of a stack together for handling and transport. In a drive to reduce the amount of plastic packaging, efforts have been made to replace the plastic material by cardboard.

More recently, it has been suggested to hold a plurality of beverage cans e.g. four or six cans ("six packs") together by a glue material strip provided along and between the mantles of the beverage cans, wherein a can in an array can be attached to at least two adjacent cans. The pack of cans so glued together are provided with a carry-handle, e.g. of plastic form, glued to a few of the cans.

The present disclosure seeks to provide an alternative solution better suited for tin can stacks.

Summary of the Invention

In accordance with a first aspect of the invention, there is disclosed a stack of food containers as defined in claim 1. The stack comprises a plurality of food containers each comprising a first face and a second face, the food containers seated one on top of another by location of a respective second face of one container on a first face of another container, wherein the first and second faces are attached to another by adhesive material.

It will be understood that each food container may be an individual unit to be opened and/or consumed individually by a consumer. Typically, the food containers may contain the same type of product although this is not necessarily a requirement of the invention. The containers are usually made from a sturdy material such as food grade metal that may be provided with a surface treatment. Each food container comprises its own lid, or opening surface for opening e.g. with a can opener, that can be opened independently of the other food containers once removed from the stack. Such food containers may be stacked, one on top of another, to form a stack. In the absence of adhesive material, individual ones of the food containers may be lifted off containers underneath unless otherwise held together.

The adhesive material provides a bond between the faces of the food containers by which the food containers remain attached to each other, providing a stack that can be handled as a unit.

The first face of the food container may be the top side, in use, provided with a lid. The first face comprises a first edge that may be constituted by a seam such as a weld or formed-and-ironed seam. The first face may comprise a pull tap to facilitate opening without the aid of tools. The second face comprises a second edge that may be constituted by a seam as the first face, although this is not necessarily the case in all can designs. The second face may comprise a smaller periphery (circumference) than the first face edge, such as a stepped, curved, or bevel edge, so as to allow the second face to be nested within a circumferential seam of the first face of another can of similar proportions. However, the invention may also be used with other can configurations, provided a face of one container can be brought into contact with, or seated on, a face of another container provided with adhesive material.

In some embodiments, the first and second faces are attached to another by a plurality of spots of adhesive material.

The plurality of spots of adhesive material are understood to be discrete spots, or "dots", spaced apart from each other. Herein, a spot or dot is understood as a generally round shape of material. It will be appreciated that, during the production of a stack, the adhesive spots may be deposited onto one of the faces before another can is attached thereto. Being discrete, the glue spots are spaced apart from each other by areas free of adhesive.

In some embodiments, at least some of the adhesive material is provided as a length of a bead.

In the context of adhesive material, herein a bead is understood as a length of adhesive deposited as a line. A bead may be applied as a single continuous bead or as a series of beads. Beads (lines of glue) and spots (generally round dots) may be mixed e.g. by alternating application of beads and spots separated from each other along a line.

In some embodiments, the adhesive material is applied with a diameter of no more than 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm or 1 mm (prior to compression). For a bead line, the diameter is understood as an extension perpendicular to its elongate extension.

In some embodiments, at least one face comprises a peripheral edge, the adhesive material being positioned peripherally along the peripheral edge.

The peripheral edge may be defined by a seam structure, e.g. an inner wall of the seam structure corresponding to a mantle perimeter. In embodiments comprising discrete glue spots or lengths of beads as the adhesive material, the glue spots may be angularly spaced apart by periphery regions free of adhesive. In embodiments comprising a single continuous bead, the ends of the bead may be spaced apart by a periphery region free of adhesive.

In some embodiments, the adhesive material is located within 13 mm, 12 mm, 11 mm, mm, 9 mm, 8 mm, 7 mm or 6 mm of the peripheral edge.

The adhesive material is preferably located close to the peripheral edge of the food container.

In some embodiments, the adhesive material is radially spaced at least 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm from the peripheral edge.

While the adhesive material may be preferably located close to the container peripheral edge, it may also be preferred for the adhesive material to avoid contact with seam structures. This may be achieved by maintaining a minimum distance radially inward from the peripheral edge.

For consistency, herein measurements provided with reference to a peripheral edge in relation to a nesting-type can are defined with reference to a "mantle perimeter line", which usually corresponds to the wider (usually upper) peripheral edge of a can. Respectively, for glue applied to the underside of a can, the peripheral edge reference corresponds to a can mantle circumference or perimeter defined by the peripheral edge of the lid-comprising (i.e., in use upper) face. For instance, a spacing of 3 mm radially inward of a peripheral edge, on the top face of a can, may be 1 mm radially inward of a bevelled edge if this is 2 mm recessed or rounded relative to the top face peripheral edge.

One of the faces, typically the first face that constitutes a top face, may comprise a weld seam and a recessed annular groove, or countersunk area, inward of the weld seam immediately between the weld seam and the plateau portion of the face. The recessed annular groove may be a fold generated as part of the beading or seam-folding process. The peripheral edge may be constituted by a seam directly adjacent a recessed annular groove. In embodiments, the adhesive material is positioned such that it, while being close to the peripheral edge, avoids contact with the peripheral edge. To this end, adhesive material may be located inward of the annular groove. The adhesive material may be spaced at least 1.5 mm, 2 mm, 2.5 mm, 3 mm or 3.5 mm from the peripheral edge. The adhesive material may be located close to or on a ridge of a reinforcing structure of the first face.

In some embodiments, the stack comprises at least four discrete spots of adhesive material.

The stack may comprise at least five, six, seven, eight, nine or ten discrete spots.

In some embodiments, the food containers are of generally cylindrical shape having a cylinder diameter and a mantle height, the mantle height less than the cylinder diameter.

The food container is of generally cylindrical shape, having a mantle, a base and a top surface. Food containers such as tin tuna cans are usually characterised by a mantle height considerably less than the cylinder diameter, and have a generally flat appearance compared to other "upright" food cans.

In some embodiments, one or more of the food containers are constituted by cans.

In some embodiments, one or more of the food containers are constituted by ring pull cans.

In some embodiments, one or more of the food containers are constituted by foil top cans, e.g. with integral tab to facilitate manual opening.

In some embodiments, the adhesive material comprises a pressure sensitive adhesive.

Several compositions of pressure sensitive adhesive are known, including food grade adhesives. The use of a pressure sensitive adhesive allows the adhesive material to be deposited in relatively small amounts, to locate a relatively thin bead and/or to locate discrete small spots at desired locations with high-precision. Once deposited in the desired quantity or quantities at the desired locations, and appropriate pressure is applied by pressing can faces against each other, the adhesive properties come into play or activate. This practically bonds the cans together.

In accordance with a second aspect of the invention, there is disclosed a method of manufacturing a stack of any one of the embodiments of the first aspect, as defined in claim 14. The method comprises providing a first food container, applying adhesive material on a first face of the first food container, providing a second food container, and seating the second food container on the first face of the first food container.

It will be understood that the method of the second aspect results in the manufacture of a stack of axially aligned food containers, seated, when in an upright configuration, one on top of another such that the mantles of the food containers are arranged coaxially, in a series.

In some embodiments, the method comprises applying, further, adhesive material on a first face of the second food container, providing a further food container, and locating the further food container on the first face of the second food container.

In this manner, a stack of two, three, four, five, six or more food containers may be manufactured. Such a stack can be handled as a single cylindrical unit.

In some embodiments, the method comprises applying the adhesive material in the form of a plurality of discrete spots.

In some embodiments, the method comprises applying at least some of the adhesive material in the form of a continuous bead.

In some embodiments, the method comprises applying all of the adhesive material in the form of a continuous bead.

The material may be applied along a line, or along a linear path extending close to an edge of the food container.

In some embodiments, the step of applying adhesive material to a face of a food container is carried out within no more than 30 seconds, 25 seconds, 20 seconds, 15 seconds, or 10 seconds.

In this manner, if adhesive material is of a hot melt form to be deposited above a softening temperature, some cooling of adhesive material applied first to a face may be tolerated, such that the adhesive material cools no lower than a softening temperature while the remaining adhesive material of a desired quantity is being applied. As such, it is believed that a faster application of adhesive allows thinner spots or beads to be deposited.

In some embodiments, the step of applying adhesive material comprises providing a pressure sensitive adhesive material.

In some embodiments, the step of locating the second food container on the first face of the first food container comprises pressing the second container against the first container.

In the embodiments, pressure is applied temporarily by pressing the second (or subsequent) container against the respective preceding container when, or while, the adhesive exhibits pressure-sensitive properties.

In some embodiments, the method comprises depositing the adhesive material on the first face in a spaced-apart arrangement.

In some embodiments, the method comprises depositing the adhesive material along a peripheral edge of the first container.

In some embodiments, the method comprises depositing the adhesive material radially within 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm or 6 mm of the peripheral edge.

In some embodiments, the method comprises depositing the adhesive material radially spaced at least 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm from the peripheral edge.

As set out above, for cans of nesting type a reference to a peripheral edge is a reference to a mantle perimeter line, e.g. usually the upper edge, even though adhesive material may be applied to an underside of a can.

A plurality of stacks according to the first aspect may be provided on a tray or pallet such as a cardboard tray. In accordance with a further aspect of the invention, at least one stack in accordance with the first aspect is provided on a pallet or tray. Several or all of the stacks on such a pallet or tray may be stacks according to the first aspect. The stacks may be manufactured according to any one of the embodiments of the second aspect.

Features described in relation to the first, second and further aspects may be used or applied with, correspondingly, in any one of the embodiments of each one of the other aspects.

Description of the Figures

Exemplary embodiments of the invention will now be described with reference to the Figures, in which: Figure 1 is a schematic side view cutaway illustration of a can; Figure 2 is a schematic top view of the Figure 1 can; Figure 3 is a schematic top view of another variant; Figure 4 is a schematic side view of a multi-can embodiment; and Figure 5 illustrates exemplary steps of method of manufacturing a multi-can stack.

Description

Referring to Figures 1 and 2, a can 10 is schematically illustrated, the can 10 being of the type used for tin tuna or similar products, although the invention is not necessarily so limited. The can 10 constitutes a food container of the invention. The can 10 comprises a generally cylindrical body 12 comprising a mantle surface 14, a base 16 and a top 18, the base 16 constituting a second face of the can 10 and the top 18 constituting a first face of the can 10. In some forms, the top 18 and the base 16 may have the same shape, however in the present embodiment the can 10 is of a nesting configuration, the top 18 comprising a peripheral rim portion 19 (constituting an upper circumferential edge or peripheral edge) and the base 16 comprising a peripheral taper 17 (constituting a lower circumferential edge or peripheral edge) having an outer diameter relatively narrower, compared to a mantle line 15, than the inner diameter of the rim portion 19, for nested location on top of another. When nested in this manner, this reduces the likelihood of an upper can sliding sideways relative to a can underneath. As the first and second faces are generally circular, individual cans of a stack may be rotated axially relative to other cans of a stack when nested, unless they are otherwise held together in a manner resisting rotation. Measurements with reference to a peripheral edge, e.g. 3 mm radially inward of the peripheral rim, are understood to be with reference to the mantle perimeter line 15, when adhesive is applied to a base of a can rather than a top face.

The top 18 is characterised by the presence of a lid formation 20. The lid formation 20 may be integral with the cylindrical body 12 and/or integrally formed with the top 18, to be opened with the aid of a tool such as a can opener. Alternatively or in addition, the lid formation 20 may be of a type facilitating tool-less opening, for instance, comprising a score line 22 to provide a pre-determined break line defining a lid portion of the top 18. The lid formation 20 may be constituted by a foil top. The top 18 may be provided with an integral pull ring (not shown in the drawings).

The top 18 comprises a plateau face 24 that may comprise an arrangement of ridges, stepped terraces and/or grooves extending for instance concentrically to provide stability to the structure of the top 18. The ridges and/or grooves may be arranged in other patterns, for instance to surround a pull ring and/or to provide a flat region for labels or product information to be printed thereto. However, several other lid formations are known, one common lid formation being in the form of a so-called foil top with a plateau face 24 of concavely recessed, or dished, form. Herein, for ease of illustration, the lid structure 18 is shown as a generally flat plateau 24, even though it will be understood that the plateau face 24 may comprise a dished appearance, and/or strength-imparting structures, and/or functional structures, as set out above.

Typical tin cans of this type are manufactured and closed off using an ironed or weld seam 26 extending circumferentially, along the periphery of the edge of the top 18.

Respectively, the seam 26 may be considered as constituting the circumferential edge of the top 18. The seam 26 for a nesting-type can may be an outward weld seam, with a bead portion extending outwardly relative to the cylinder mantle surface 14 (and outside the mantle perimeter line 15). Inward of the seam 26, a groove 28 in the form of an annular fold, constituting a countersunk recess, extends between the seam 26 and the remaining area of the plateau face 24. To provide illustrative values, the deepest region of the groove 28 may be spaced radially about 1, 1.5 or 2 mm from the mantle perimeter line 15 or inside wall of the weld seam 26. The score line 22 may be about 2.5, 3 or 3.5 mm from the inside wall of the weld seam. The score line 22 may be generally circular although may comprise a pull region 22a where the generally circular shape is altered to accommodate of a pull tab. The spacing from the inside wall in the pull region 22a may be more than the 2.5, 3 or 3.5 mm set out above.

The can 10 is provided with a plurality of glue spots 30, each constituting a discrete location for an amount of adhesive. The adhesive may be a pressure-sensitive adhesive the adhesive properties of which become stronger as it is squeezed between two can surfaces. An example composition is a pressure sensitive adhesive available under the trade name "Technomelt (RTM)" (available Henkel Ltd, Wood Land End, HP2 4RQ, United Kingdom), such as Technomelt EM598 MP which is a food grade adhesive based on a hydrocarbon resin with a softening temperature range between 90°C and 102°C. The pressure sensitive adhesive may be a hot melt adhesive that is deposited onto a can surface in a warmed or heated condition, e.g. to a temperature above its softening range, so as to be sufficiently liquid for small volume deposition of a spot no wider than 2 mm and no higher than 2 mm, or for small volume deposition of a bead of any length (practically a few centimetres length) having a diameter of no more than 2 mm and a height of no more than 2 mm. When using hot melt material, the deposition temperature may be selected sufficiently high to tolerate cooling of adhesive material to a temperature that remains above its softening temperature or range, such that the adhesive material on the surface of a can remains in a soft condition until the desired quantity of adhesive has been applied and until another can has been attached. For instance, for a material with a softening range of up to 102°C, the adhesive may be heated to a temperature exceeding 120°C, 130°C, 140°C or 150°C so as to be able to tolerate a cooling of the first-deposited adhesive to a temperature no lower than the softening temperature, e.g. no lower than around 105°C, during the time additional adhesive material is applied and another food can is pressed against it.

It will be appreciated that the hot melt deposition parameters will depend to some extent on the choice of material, and/or dimensions (width, height and surface-tovolume ratio) of the spot or bead, as well as the operation speed of the adhesive applicator and can handling equipment. For a food container application, it is preferable for the adhesive to be a food grade adhesive, for instance to comply with EU Regulation (E) No 1272/2008 (CLP), although it will be understood this is not necessarily a requirement for the invention to be put into practice.

In Figure 2, a plurality of (here: six) discrete glue spots 30a,b,c,d,e,f is illustrated. For simplicity, the glue spots are referenced herein by a common numeral 30. The glue spots 30 are located radially between the score line 22 and the groove 28, on a generally flat annular portion of the top 18. The glue spots 30 are equi-angularly spaced apart (here, about 60 degrees) so as to be evenly distributed along the periphery of the can 10, while avoiding being located in the groove 28 or on the score line 22. Alternatively, (not shown in Figure 2), the glue spots may be located radially inward of the score line 22, within a few millimetres distance of the score line 22, so as to be located on a removable lid portion.

While not believed to be essential to all embodiments of the invention, the equi-angular distribution is believed to facilitate providing an evenly distributed adhesive strength.

The adhesive material may be located on or along a ridge of the plateau face 24. It has also been observed that a number of at least four, five or six glue spots achieves a near-isometric resistance to attempts to lever one can from a can underneath.

The glue spots are small in size, no larger in diameter than 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm or 1 mm when applied to a surface. It will be understood that the spots may flatten and have a somewhat larger diameter when compressed between two cans. Initial trials in the development of an adhesive-bonded stack were directed to locating a glue spot centrally, so as to avoid and practically minimise the risk of adhesive material cooling too quickly during the manufacture of a stack.

However, the adhesive area of the glue spots 30 is distributed over a wider area than a single glue spot applied centrally on the top of a tin.

Figure 3 shows a top view of a can 11 that is a variant of the can 10 depicted in Figures 1 and 2. Like numerals are used for like features to avoid a repetition of the description. In Figure 3, the can 11 comprises a top surface 18 to which a generally continuous adhesive bead 31, or length of adhesive material is applied. The adhesive bead 31 is arranged generally following the contour of a rim portion 19 (constituting a peripheral edge). Although indicated as a linear bead, the bead could be applied in other forms, e.g. in an undulating or meandering form, however it is believed that a linear bead is more practical to apply. The adhesive bead 31 has a width of 2 mm and a height of no more than 2 mm when applied. It will be understood that the dimensions may be flatter once compressed. The bead is applied in a region between, measured radially inward from the rim portion 19, of between 3 to 6 mm, and generally in a region no closer than 1 mm to the peripheral edge and within 10 mm, 11 mm, 12 mm, or 13 mm of the peripheral edge. The ring may be located on or along a ridge or elevated location of the top surface 18. While the adhesive bead 31 is applied to follow a generally circular contour, corresponding to the circular contour of the can face, a region 23 may be free of adhesive. For instance, region 23 may be reserved for a pull tab. The Figure 3 arrangement using a continuous bead 31 is believed to allow adhesive material to be applied in a less thick (less high) manner when used for can designs with a relatively thick pull tab.

Surprisingly, by locating the glue spots 30 or adhesive bead 31 radially outward, away from the centre of the top 18, close to the periphery of the can 10 or 11, less glue material is needed while still providing a suitable bonding strength. An observation during the development of the invention was that the peripheral positioning of the adhesive material addresses several intended use-scenarios for can stacks of the invention. The intended use includes picking up a can stack (comprising, for instance, 4 tins) by a user or customer holding the top can only, including the levering of a stack held at the top can only from within a shopping shelf, the remaining (e.g. three) cans being supported only by the glue spots to bond to the respective adjacent cans in a stack. The stack should withstand, i.e. its cans should maintain connected, when a stack is placed or thrown, with varying degree of care, into a shopping trolley, or accidentally dropped from a height of about 1.6 metres. It will be appreciated that using a sufficient amount of glue on the top surface will provide a correspondingly robust stack of individual cans.

A practical problem with a robust stack using any amount of glue is that this will also hinder intended removal of a can by a consumer, which is undesirable. For a consumer, each individual can of a stack must be easily removable from the stack when they intend to do so.

It was a discovery leading to the present invention that positioning adhesive material along the periphery of the can face combines the adhesive strength required for a robust attachment, while allowing a consumer to detach a can by turning, or twisting, a can relative to a can underneath. By locating the adhesive material on a plateau area laterally of the score line 22 (where present), or in a region where otherwise a score line would be located, the likelihood of glue spots falling from the edge of a can is removed and practically eliminated. It was further observed that the glue, in the relatively small amounts in which it is deposited on the top, may in some instances collect inside the annular recess 28 where it is more or less retained, preventing it from falling into a can when opened. However, in other variants the adhesive may be applied inward of a lid edge so as to remain on the lid after removal.

Figure 4 shows an schematic illustration of a stack 40 comprising a plurality of (here: four) cans 10a, 10b, 10c, 10d, each generally corresponding to a can 10 described with reference to Figure 1, although Figure 4 may also be considered representative of a stack comprised of cans 11 described in Figure 3. To better illustrate relevant aspects of the interfaces between the cans, the cans of Figure 4 are illustrated geometrically simplified as transparent wireframe cylinders. The base 16a of the first (here: lowest) can 10a constitutes the base of the stack 40. The top 18a of the first can 10a is provided with a plurality of (here: six) glue spots 30, in the manner described with reference to Figure 2. The base 16b of the second can 10b is located on the top 18a of the first can 10a, and bonded to it by the glue spots 30. In the same manner, the base 16c of the third can 10c is located on the top 18b of the second can 10b and base 16d of the fourth can 10d is located on the top 18c of the third can 10c, each bonded to the respective can underneath by an arrangement of glue spots 30. The top 18d of the fourth can constitutes a top of the stack 40. The base 16a and the top 18d of the stack 40 are free of glue spots. The stack 40 comprised of cans bonded together by glue spots in this manner can be handled as a unitary item, of generally cylindrical form, the cans being axially aligned in a series of co-axially aligned cylinders (e.g. on top of each other when placed upright). In trials, a stack 40 of this type could be handled by holding it at one end, e.g. the top (here: fourth) can 10d, the stack remaining intact after dropping from 1.6 metres height and remaining intact, as a stack, when being thrown by a tester into a shopping trolley.

The individual cans of a stack 40 stick strongly together and are very difficult to separate axially or by levering manually with a typical manual force of an average user.

Given sufficient force, or the use of tools, the stack could be separated axially, as is also the case for a stack of cans held together by a sleeve material. However, compared to relatively difficult separation using axial force, individual ones of the cans are comparatively easily detachable by twisting a can relative to an adjacent can, e.g. the fourth can 10d relative to the third can 10c. Without wishing to be bound by theory, it is believed that the detachment is facilitated at least in part by the application of a torque perpendicular to the glue-can interfaces, in the plane of the squeezed glue spots, in combination with a better rotational leverage achieved by gripping a can mantle. The twisting separation is a mechanism that is expected to differ from forces a stack experiences during transport and handling in a retail environment. Interestingly, it was observed that the twisting motion causes a detachment from the adhesive material in a sudden, near-simultaneous manner, the force of the detachment resulting in an audible noise characterised in trials as a popping or "pop" sound. The "pop" sound, in combination with a suddenly discontinued resistance to twisting, is believed to provide helpful audible and haptic feedback for a consumer that the detachment was successful. While the pop sound may not be present with all adhesive types, where observed, the pop sound may provide an indication that the bonding method described herein was used to manufacture the stack.

After detachment of a can from a can underneath, it has been observed that adhesive material may remain either on the top of the can underneath, or on the base of the can lifted away, and/or adhesive material may separate with parts remaining attached to both cans. Adhesive material remaining on the underside may exhibit sufficient bonding strength to adhere to a surface such as a kitchen surface underneath, which may be undesirable. By providing the adhesive material with a relatively small diameter, the strength was found to be not as strong so as to hinder handling of the can in a test environment.

Referring now to Figure 5, described is a method 50 of manufacturing a stack of food containers as illustrated in Figure 4. The method 50 comprises a first step 52 of providing a first food container, such as a can 10a illustrated in Figure 4. In step 54, adhesive material is applied to a first face (e.g. the top face) of the first food container, in a region radially spaced at least 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm inward of the mantle perimeter line, and within 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm or 6 mm of the mantle perimeter line. In step 56, adhesive material is deposited in the manner of the glue spots 30 (Figure 2) or in the manner of a bead 31 (Figure 3). Steps 54 and 56 may be carried out concurrently. When the adhesive material is a hot-melt adhesive material, the step 56 may be carried out such that all adhesive material for a face is applied before it cools below its softening temperature. In step 58, a second (or further) food container is provided. In step 60, the second food container is located, with its second face against the first food container, such that the adhesive material is sandwiched between the second face of the second food container and the first face of the first food container. In embodiments in which the adhesive material has pressure sensitive properties, the step of locating a food container on another food container may comprise applying pressure during a phase the adhesive is in a pressure sensitive condition, or in an activated condition. For instance, the step 60 may be carried out, when used with hot-melt adhesive, while the adhesive material temperature is above a softening temperature. In an optional step 62, steps 54 to 60 are repeated to attach a further food container on top of the stack underneath.

The steps of the method 50 may be repeated to obtain a stack of three, four, five, six, or more cans. It is believed that stacks of three or four tins are those in most common use, however the invention is not so limited and may be used for stacks of five, six or more tins.

In some embodiments, the amount of adhesive material, such as the number of glue spots or the length of a bead, may be altered between different interfaces of a stack. For instance, a stack may comprise fewer glue spots between the first (lowest) and second cans and relatively more glue spots between the uppermost can and the can directly underneath. The number of spots or amount of adhesive material may have to be adjusted for a given can geometry or weight.

Whilst an embodiment of the invention has been described as using six discrete glue spots, other numbers of glue spots, such as 3, 4, 5, 6, 7, 8, 9, or 10 glue spots are also believed to result in viable embodiments. Likewise, in some embodiments a single continuous bead, or a series of discrete beads or even a combination of lengths of beads and circular spots may be provided. It will be understood that the glue strength may affect the number of glue locations and size of glue spots required.

The stacks formed in trials were sufficiently strong for manual handling without requiring any additional strap or packaging material to provide a handle.

For ease of visualisation, the embodiments illustrate adhesive material applied to a top surface for another can to be seated on top. Adhesive material may be applied from other directions. For instance, adhesive may be applied from underneath to an underside of a can, such that another can is attached from underneath. As another example, the adhesive may be applied laterally to a first face of a can (facing sideways) and another can be pushed or pressed against it.

Whilst the principle of the invention has been illustrated using exemplary embodiments, it will be understood that the invention is not so limited and that the invention may be embodied by other variants defined within the scope of the appended claims.

Claims

CLAIMS: 1. A stack of food containers, the stack comprising a plurality of food containers each comprising a first face and a second face, the food containers seated one on top of another by location of a respective second face of one container on a first face of another container, wherein the first and second faces are attached to another by adhesive material.
2. The stack according to claim 1, wherein the first and second faces are attached to another by a plurality of spots of adhesive material.
3. The stack according to claim 1 or 2, wherein at least some of the adhesive material is provided as a length of a bead.
4. The stack according to claims 2 or 3, wherein the adhesive material is applied with a diameter of no more than 4.5 mm, 4 mm, 3.5 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm or 1 mm prior to compression.
5. The stack according to any one of the preceding claims, wherein at least one face comprises a peripheral edge, the adhesive material being positioned peripherally along the peripheral edge.
6. The stack according to claim 5, wherein the adhesive material is located within 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm or 6 mm of the peripheral edge.
7. The stack according to claim 5 or 6, wherein the adhesive material is radially spaced at least 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm from the peripheral edge.
8. The stack according to any one of the preceding claims, comprising at least four discrete spots of adhesive material.
9. The stack according to any one of the preceding claims, wherein the food containers are of generally cylindrical shape having a cylinder diameter and a mantle height, the mantle height less than the cylinder diameter.
10. The stack according to any one of the preceding claims, wherein one or more of the food containers are constituted by cans.
11. The stack according to any one of the preceding claims, wherein one or more of the food containers are constituted by ring pull cans.
12. The stack according to any one of claims 1 to 10, wherein one or more of the food containers are constituted by foil top cans.
13. The stack according to any one of the preceding claims, wherein the adhesive material comprises a pressure sensitive adhesive.
14. A method of manufacturing a stack according to any one of the preceding claims, the method comprising providing a first food container, applying adhesive material on a first face of the first food container, providing a second food container, and seating the second food container on the first face of the first food container.
15. The method according to claim 14, comprising applying, further, adhesive material on a first face of the second food container, providing a further food container, and locating the further food container on the first face of the second food container.
16. The method according to claim 14 or 15, comprising applying the adhesive material in the form of a plurality of discrete spots.
17. The method according to any one of claims 14 to 16, comprising applying at least some of the adhesive material in the form of a continuous bead.
18. The method according to any one of claims 14 to 17, wherein the step of applying adhesive material to a face of a food container is carried out within no more than 30 seconds, 25 seconds, 20 seconds, 15 seconds, or 10 seconds.
19. The method according to any one of claims 14 to 18, wherein the step of applying adhesive material comprises providing a pressure sensitive adhesive material.
20. The method according to claim 19, wherein the step of locating the second food container on the first face of the first food container comprises pressing the second container against the first container.
21. The method according to any one of claims 14 to 20, comprising depositing the adhesive material on the first face in a spaced-apart arrangement.
22. The method according to claim 21, comprising depositing the adhesive material along a peripheral edge of the first container.
23. The method according to claim 22, comprising depositing the adhesive material radially within 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm or 6 mm of the peripheral edge.
24. The method according to claim 22 or 23, comprising depositing the adhesive material radially spaced at least 0.5 mm, 1mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm from the peripheral edge.
25. A pallet of stacks comprising at least one stack according to any one of claims 1 to 13 or at least one stack bonded according to a method of any one of claims 14 to 24.