WO2011129709A2

WO2011129709A2 - Cup, cup forming apparatus and related methods

Info

Publication number: WO2011129709A2
Application number: PCT/NZ2011/000051
Authority: WO
Inventors: Eduard Sean Scott
Original assignee: Tarvis Tech Ltd
Current assignee: Tarvis Tech Ltd
Priority date: 2010-04-12
Filing date: 2011-04-11
Publication date: 2011-10-20
Anticipated expiration: 2012-10-12
Also published as: WO2011129709A3

Abstract

The invention relates to a method of manufacture of a plug (100) for use in a plug assisted forming process to manufacture an article (300) from a sheet of material (200). The method comprising the steps of establishing formed reinforced zones (330) of the article to be manufactured, mapping the reinforced zones to a corresponding pre-formed reinforcement zone on the sheet (260) of material and creating a plug having a configuration for initial impingement on the sheet of material at the pre-formed reinforcement zone of the plug (160) and recesses not having an initial impingement to prevent contact with the sheet of material.

Description

CUP, CUP FORMING APPARATUS AND RELATED METHODS

The present invention relates to a vacuum forming plug and methods therefor. More particularly but not exclusively it relates to an apparatus and. method for vacuum forming plastic containers.

The process of vacuum forming of plastic containers is widely known. This typically involves drawing a heated deformable thermoplastic plastic sheet into a mould by means of vacuum, and letting it set in the shape of the mould.

In the past, plugs have been used to assist in depressing the heated sheet of plastic into the mould. These plugs loosely correspond in shape to that of the inside periphery of the mould, although they are typically of a smaller size. Once the plug has been used to depress the plastic sheet down into the mould, the vacuum (or a positive pressure from the other side) is used to move the plastic sheet against the mould shape.

However, problems are encountered where such plugs are used. One problem is created when the plug acts as a heat sink to slightly cool the plastic sheet to a slightiy cooler temperature than the plastic sheet. Where the plastic sheet is cooled down, this results in the plastic sheet at the portions making contact with the plug becoming less stretchable than the other portions of the plastic sheet that did not make contact with the plug. The portions which did not make contact with the plug end up being stretched more than the cooler portions, and can end up being stretched very thin.

Particularly for the creation of non-circular vacuum moulded containers, having straight corner edges, these edges are typically required to be load bearing for stacking of containers on top of each other. For this reason, these edges need to be thicker and stiffer than the remaining walls of the container. However, predicting the correct shape of the plug to be used to provide correct wall thicknesses of the containers may be a problem.

This is amplified by the manufacture of containers having irregular shapes, and/ or collapsible walls such as that described in publication WO 2006/068523 by, the present applicant, which publication is hereby incorporated by reference.

In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

For the purposes of this specification, the term "plastic" shall be construed to mean a general term for a wide range of synthetic or semi-synthetic polymerization products, and generally consisting of a hydrocarbon-based polymer, and the term "mermoforrning plastics" shall be construed as any plastic rendered more formable by the application of heat to the plastic.

For the purposes of this specification, where a formation is described as extending from a plug, the meaning shall be construed to mean that the formation is extending relative to the remaining surface areas of the plug, and can include the possibility of the remaining features of the plug being recessed.

It is an object of the present invention to provide apparatus and method for vacuum forming which overcomes or at least ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

In a first aspect, the present invention broadly consists in a method of manufacture of a plug, said plug for use in a plug assisted forming process (eg vacuum forming and/ or mermoforming vacuum) to manufacture an article from a sheet of material, said method comprising the steps of

• establishing those formed reinforced zones of said article to be manufactured that are required to be of an increased thickness relative to other non-reinforced zones of said article when the article is in its formed state;

• mapping said formed reinforced zones of said formed article to a corresponding pre-forming reinforcement zone on said sheet of material before forming; and

• creating a plug having a proximal end and a distal end, the distal end of the plug comprising a cross sectional shape that corresponds substantially to the shape of the preforming reinforcement zone, and wherein those zones not corresponding to the formed reinforced zones is recessed, thereby to prevent or delay contact with the sheet of material during the plug assisted forming process.

In another aspect, the present invention broadly consists in a method of manufacture of a plug, said plug for use in a plug assisted forming process (eg vacuum forming and/or thermoforming vacuum) to manufacture an article from sheet of material, said method comprising the steps of • establishing those formed reinforced zones of said article to be manufactured that are required to be of an increased thickness relative to other non-reinforced zones of said article when the article is in its formed state;

• mapping said formed reinforced zones of said formed article to a corresponding pre-formed reinforcement zone on said sheet of material before forming; and

• creating a plug having a shape that is configured and adapted for initial impingement on the sheet of material at the pre-formed reinforcement zone, and wherein the surface area of the plug that do not correspond to the formed reinforced zones is recessed, thereby to prevent or delay contact with the sheet of material during the vacuum forming process.

Preferably, the mapping of the formed reinforced zones of the formed article to preformed reinforcement zones on the sheet of material is carried out by dividing the sheet material into visible discrete indexed regions and subjecting the sheet of material to the forming process to see the extent that the sheet of material is stretched during the forming process.

Preferably, the method includes the step of installing said plug in a vacuum forming production line.

Preferably the article to be manufactured is a container.

Preferably, the container includes a plurality of sides.

Preferably, the container includes collapsible formations along at least one side of said container.

Preferably, the container includes collapsible formations disposed at opposed sides. Preferably, the collapsible formations are concertina formations.

Preferably, the collapsible formations are also reinforcing formations for reinforcing the container for increased stackability.

Preferably, the plug comprises at least one corner reinforcing extension formation extending from its distal end at a position corresponding to a position on the pre-forming reinforcement zone that will come into contact with the sheet material that will form the base of the container at at least each corner of the container.

Preferably, the plug comprises at least one collapsible formation reinforcing extension formation extending from its distal end, corresponding to a position on the pre-forming reinforcement zone that will come into contact with the sheet material that will form at least one of the collapsible formations of the container. In another aspect the present invention broadly consists in a plug for use in a vacuum forming process, said plug having been manufactured by a method as described above.

In another aspect the present invention broadly consists in a method of manufacture of an article in a vacuum forming process, said method including the steps of

• providing a heated sheet of material;

• providing a vacuum forming mould having a recess corresponding at least loosely to the shape of the article to be manufactured;

• providing a plug;

• moving the heated sheet of material between the plug and the vacuum forming mould; and

• inserting said plug into the recess of the vacuum forming mould, thereby causing the heated sheet of material to be plastically deformed into the recess;

• wherein the plug is configured and adapted so that those zones of the plug impinge on the heated sheet of material at pre- formed reinforcement zones that correspond to the zones of reinforcement required in the formed article, thereby to pre-cool the pre-formed reinforcement zones to allow for reduced thinning of said pre-formed reinforcement zones during formation of the article.

Preferably, the plug is as described above.

Preferably, the method of manufacture includes the step of creating a differential pressure on either side of the sheet material to thereby cause the sheet material to conform to the shape of the vacuum forming mould.

In another aspect the present invention broadly consists in a plug for assisting in the formation of an article from a sheet of material by a vacuum or thermo- forming process, said article comprising a base, a plurality of side walls extending from the base to define a plurality of corner edges extending upwards from the base, with at least one side wall defining at least one reinforcing formation extending from the base, said plug comprising

a plug body including a proximal end and a distal end, wherein the plug body is configured and adapted to impinge upon said sheet material in a forming process and includes, at a point between the plug body's proximal end and distal end, a cross sectional shape including plug body corner zones configured and adapted for impingement on preformed corner edge zones on the surface area of the sheet material that will be formed into the base adjacent the corner edges and the corner edges themselves; and

at least one plug body reinforcement zone configured and adapted for impingement on pre-formed reinforcement zones on the surface area of the sheet material that will be formed into the reinforcing formation.

Preferably, the plug body is recessed from the plug body corner zones and the plug body reinforcement zones around at least part of the remaining surface area of the plug.

Preferably, the plug comprises connecting formations configured for mounting the plug body to a reciprocating machine.

Preferably, the container has at least two opposed sides.

Preferably, the container is four sided container.

Preferably, the container has at least one reinforcing formation at each opposed side of the container.

Preferably, the plug body includes a pair of plug body reinforcement zones for impingement on a pre-formed reinforcement zones on the surface area of the sheet material that will be formed into the reinforcing formations.

Preferably, the reinforcing formations are concertina formations.

Preferably, the reinforcing formations are adapted and configured to collapse when the container is squeezed from opposing sides.

In another aspect the present invention broadly consists in a plug for use in a plug assisted forming process (eg vacuum forming and/or thermoforming vacuum) to form an article from a sheet of material, said plug comprising a distal end that defines an initial contact zone of the plug with the sheet material that has a plurality of discrete initial contact points.

Preferably, the plug includes one or more selected from

• at least two

• preferably three and

• preferably 4 discrete initial contact points.

Preferably, the plug comprises a plug body and connecting means.

Preferably, the discrete initial contact points correspond to and during the forming process are aligned with pre-formed' reinforcing zones of said sheet of material that will become formed reinforced zones that are required to be of an increased thickness relative to other non-reinforced zones of said article when the article is in its formed state.

Preferably either the plug and/ or sheet of material is heated.

Preferably, the article comprises

a base,

a plurality of side walls extending from the base to define

a plurality of corner edges extending upwards from the base, and

at least one side wall defining at least one reinforcing formation extending from the base.

Preferably, at least one of the discrete initial contact points of the plug is a plug body corner zone configured and adapted for impingement on pre-formed corner edge zones on the surface area of the sheet material that will be formed into the base adjacent the corner edges and the corner edges themselves.

Preferably, one of the discrete initial contact points of the plug is a plug body reinforcement zone configured and adapted for impingement on pre-formed reinforcement zones on the surface area of the sheet material that will be formed into the reinforcing formation at a side of an article.

In another aspect the present invention broadly consists in a plug for use in a plug assisted forming process (eg vacuum forming and/ or thermoforrning vacuum) to manufacture an article from a sheet of material, said plug comprising a castellated distal end.

Preferably, the castellated distal end includes raised zones that extend from a plug body.

Preferably, the plug comprises a plug body and connecting means.

Preferably each of the raised zones of the castellated distal end correspond to, and during the forming process are aligned with, pre-formed reinforcing zones of said sheet of material that will become formed reinforced zones that are required to be of an increased thickness relative to other non-reinforced zones of said article when the article is in its formed state.

Preferably, the article comprises

a base,

a plurality of side walls extending from the base to define

a plurality of corner edges extending upwards from the base, and at least one side wall defining at least one reinforcing formation extending from the base.

Preferably, one of the raised zones of the plug is a plug body corner zones configured and adapted for impingement on pre-formed corner edge zones on the surface area of the sheet material that will be formed into the base adjacent the corner edges and the corner edges themselves.

Preferably, one of the raised zones the plug is a plug body reinforcement zone configured and adapted for impingement on pre-formed reinforcement zones on the surface area of the sheet material that will be formed into the reinforcing formation at a side of an article.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

As used herein the term "and/ or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/ or singular forms of the noun.

The term "comprising" as used in this specification means "consisting at least in part of. When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention will now be described by way of example only and with reference to the drawings in which:

Figure la, b, c & d: shows a side schematic view of a plug in use in a plug assisted forming process where figures la and lb illustrate the process before the vacuum is applied and figures 1 c and 1 d illustrate the process during and after the vacuum has been applied; Figure 2: shows

Figure 3: shows

Figure 4: shows

the preformed reinforcement

Figure 5: shows

of material;

Figure 6: sshhoowwss a perspective end view of the distal end of one embodiment of a plug;

Figure 7: shows

Figure 8: shows

Figure 9: shows

Figure 10: shows

of a plug; and

Figure 11: shows

10.

With reference to the above drawings, in which similar features are generally indicated by similar numerals, a vacuum plug according to one aspect of the invention is generally indicated by the numeral 100.

In one embodiment, there is provided a plug 100 comprising a plug body 110 and connecting means. The connecting means could be in the form of a connecting mechanism or a connecting formation 120 (as shown in figures 9 and 11) to enable the plug 100 to be mountable to a machine (not shown) or other mounting point 500. It is anticipated that the machine can be a reciprocating machine, but this need not necessarily be the case.

The plug 100 is for assisting in the formation of an article, such as a container shown in patent application WO2006/068523 by the present applicant, from a sheet of material 200 in a vacuum forming process. The different stages of the vacuum forming process are shown in figures 1 a, b, c & d. The process involves layering a heated sheet of material over a vacuum mould 600, pushing the heated sheet of material 200 into the mould cavity 610. The plug 100 is slightiy smaller than the mould cavity 610 and does not cause the sheet of material 200 to make contact with the mould cavity 610. When the sheet of material has been sufficiendy depressed, a differential fluid pressure is created on either side of the sheet of material 200, (either by creating a vacuum on the mould 600 side of the sheet of material 200, or by creating a positive pressure on the plug 100 side of the sheet of material 200). This differential pressure pushes or sucks the sheet of material 200 against the mould, and the sheet of material is cooled to set in this position. Such vacuum forming processes are well known to those skilled in the art and will not be discussed further in this specification.

In a preferred embodiment, the finally manufactured container 300 (shown in figures 2 and 5) comprises a base 310, four side walls 340 extending from the base 310 to meet at four corner edges 320 that also extend upwards from the base 310. At one pair of opposed side walls 340, a reinforcing formation 330 is defined on each sidewall 340 that extends upwards from the base 310.

In the particular container shown 300, the reinforcing formations 330 also function as concertina-type collapsing formations for allowing the collapse or concertinaing of the container when the container is squeezed together from its opposed side walls not having such reinforcing formations 330. However, such a configuration is not necessarily required, and a plug for manufacturing any container having reinforcing formations along at least one sidewall is contemplated.

The plug body 110 features a proximal end 130 and a distal end 140. The plug body 110 is configured and adapted to impinge upon the sheet of material 200 during the forming process. The plug body 110 defines, at at least one point between the plug body's proximal end 130 and distal end 140, a cross sectional shape including plug body corner zones 150. The plug body corner zones 150 are configured and adapted for impinging on pre-formed corner edge zones 250 on the surface area of the sheet material 200. The pre-formed corner edge zones 250 will be formed into a zone on the base 310 of the container 300 adjacent the corner edges 320, as well as the corner edges 320 themselves.

The plug body 110 also comprises at least one plug body reinforcement zone 160 configured and adapted to impinge on pre-formed reinforcement zones 260 on the surface area of the sheet material 200. The pre-formed reinforcement zones 260 will be formed into the reinforcing formation 330 of the formed container 300.

It should be understood that both the plug body corner zones 150 and the plug body reinforcement zone 160 are intended to create a heat sink from the heated sheet material 200 at the interface between the plug 100 and the sheet material 200 when the plug 100 impinges on the sheet material 200 during the forming process, thereby to reduce the amount of stretching of those aresas that have lost heat, resulting in those areas being thicker and hence stronger, to reinforce those zones in the finally formed container 300. In this sense, both the plug body corner zones 150 and the plug body reinforcement zone 160 are there to reinforce the zones of the sheet material 200 they make contact with during forming.

The plug body corner zones 150 and the plug body reinforcement zone 160 together make up an initial contact zone 170.

The raised areas of the plug 00 that are intended to make initial contact with the sheet material 200, and to act as a heat sink, are shown in two embodiments in figures 6-11 as a castellated distal end 140. The distal end 140 defines an initial contact zone 170 of the plug 100 with the sheet material 200 that has a plurality of discrete initial contact points. However, it should be noted that the initial contact zone need not necessarily be raised at a distal end of the plug body 110, but can be raised relative to the rest of the plug body 110 (in the direction of insertion of the plug body into the mould cavity) at any point between the distal end 40 and the proximal end 130.

It is envisaged that in one embodiment, the surface of the plug body 10 can be recessed from the initial contact zone 170, while in another embodiment; the initial contact zone 170 can be raised from the remainder of the plug body 110.

In a preferred embodiment, and as shown in figures 6-9, the plug 100 comprises four corner reinforcing extension formations 180 extending from its distal end 140 at a position corresponding to a position on the pre-formed reinforcement zone 270 that will come into contact with the sheet material 200 that will form the base 310 of the container 300 at at least each corner of the container 300.

Further, and as shown in figure 6-9 in a preferred embodiment, the plug 100 includes at least one or more reinforcing extension formations 190 extending from its distal end. These reinforcing extension formations 190 correspond to a position on the pre-formed reinforcement zone 270 that will come into contact with the sheet material to form at least one of the reinforcing formations 330 of the formed container.

- The plug 100 described above is for assisting in the formation of an article such as a container shown in patent application WO2006/068523 by the present applicant, but it is anticipated that the method used to create the plug 100 (and described in more detail below) could also be used to create plugs 100 for use in the formation of a wide variety of vacuum formed containers (not shown) or other articles (not shown) that include a base and at least one reinforcing formation extending from the base.

In order to form a plug for use in a forming process as described above, and for manufacture of an article from a sheet of material as described above a particular method of manufacture of the plug 100 is used. This will result in a plug 100 of a kind intended to reinforce particular areas of a finally formed article such as a container.

The method includes the steps of first establishing where reinforcing is required at reinforced zones 370 (by means of an increased thickness of wall) in the finished formed article. Next, each of the reinforced zones 370 are mapped to a corresponding pre-formed reinforcement zone 270 on a sheet of material 200 to be formed.

Mapping of the reinforced zones 370 to pre-formed reinforcement zones 270 is carried out by dividing the sheet material 200 into discrete indexed regions 280 such as squares as shown in figure 4 and 5. When such an indexed sheet of material 200 is formed by a vacuum forming process, the extent of stretch of the sheet material 200 can be clearly seen.

Those regions of the formed article that require reinforcement can then be readily mapped back to their original starting location on the flat planar sheet of material 200 as preformed reinforcement zones 270. In the example given above, the pre-formed corner edge zones 250 and pre-formed reinforcement zones 260 would make up the pre-formed reinforcement zones 270.

The initial contact zone 170 of the plug can then be manufactured to correspond to the pre-formed reinforcement zones 270, so that the pre-formed reinforcement zones 270 are initially cooled by contact with the plug 100. To prevent the extent that these pre-formed reinforcement zones 270 stretch, and thereby prevent reduction of their wall thickness.

It should be noted that parts of the pre-formed reinforcement zones 270 that are impinged upon by the initial contact zone 170 do not necessarily stay in that position relative to the initial contact zone 170 of the plug 100, and can stretch out of contact with it. Those zones of the sheet material 200 that are not pre-formed reinforcement zones 270 (i.e. do not correspond to the formed reinforced zones) are recessed relative to the preformed reinforcement zones 270, thereby to prevent or delay contact of these zones with the sheet of material 200 during the forming process.

The result of utilising such differential cooling of the sheet material 200 is that different parts of the formed article can be engineered with differing wall thicknesses. For example, the concertina formations as shown in figure 3 can have a wall thickness at an outer edge 332 larger than the wall thickness at an inner edge 334. This means that the outer edge 332 is more resistant to buckling from side impacts, and is capable of resisting increased stacking loads. It has been found by intensive research by the applicant that such differential cooling to create engineered wall thicknesses can result in significant increases in ability to bear top loads and resist buckling, while using the same thickness sheet material.

Alternately, thinner sheet material may be used as a base, with similar stackability and bucking resistance. Where economies of scale are in play, such as in the FMCG market (for example for yoghurt containers) then these differences can result in significant commercial opportunity. Not least, the practice of a thinner sheet material as a base can mean less consumption of plastic and more sustainable use of plastics raw material.

Where in the foregoing description reference has been made to elements or integers having known equivalents, then such equivalents are included as if they were individually set forth.

Although the invention has been described by way of example and with reference to particular embodiments, it is to be understood that modifications and/ or improvements may be made without departing from the scope or spirit of the invention.

In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognise that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

Claims

1. A method of manufacture of a plug, said plug for use in a plug assisted forming process to manufacture an article from a sheet of material, said method comprising the steps of

^• establishing formed reinforced zones of said article to be manufactured that are required to be of an increased thickness relative to other non-reinforced zones of said article when the article is in its formed state;

^• mapping said formed reinforced zones of said formed article to a corresponding pre-formed reinforcement zone on said sheet of material before forming; and

^• creating a plug having a shape that is configured and adapted for initial impingement on the sheet of material at the pre-formed reinforcement zone, and wherein the surface area of the plug that do not correspond to the formed reinforced zones is recessed, thereby to prevent or delay contact with the sheet of material during the plug assisted forming process.

2. A method of manufacture of a plug as claimed in claim 1 wherein said plug has a proximal end and a distal end, the distal end of the plug comprising a cross sectional shape that corresponds substantially to the shape of the pre-forming reinforcement zones.

3. A method of claims 1 or 2 wherein the process is a vacuum and/or thermo forming process.

4. A method of claim 3 wherein the mapping of the formed reinforced zones of the formed article to pre-formed reinforcement zones on the sheet of material is carried out by dividing the sheet material into visible discrete indexed regions and subjecting the sheet of material to the forming process to see the extent that the sheet of material is stretched during the forming process.

5. A method of claim 2 wherein the method includes the step of installing said plug in a vacuum forming production line.

6. A method of claim 1 wherein the article to be manufactured is a container.

7. A method of claim 1 wherein the container includes a plurality of sides.

8. A method of claim 7 wherein the container includes collapsible formations along at least one side of said container.

9. A method of claim 8 wherein the container includes collapsible formations disposed at opposed sides.

10. A method of claim 8 wherein the collapsible formations are concertina formations.

11. A method of claim 8 wherein the collapsible formations are also reinforcing formations for reinforcing the container for increased stackability.

12. A method of claim 1 wherein the plug includes at least one corner reinforcing extension formation extending from its distal end at a position corresponding to a position on the pre-- forming reinforcement zone that will come into contact with the sheet material that will form, the base of the container at at least each corner of the container.

13. A method of claim 12 wherein the plug comprises at least one collapsible formation, corresponding to a position on the pre-forming reinforcement zone that will come into contact with the sheet material that will form at least one of the collapsible formations of the container.

14. A method of manufacture of an article in a plug assisted forming process, said method including the steps of

• providing a sheet of material;

• providing a vacuum forming mould having a recess corresponding at least generally to the shape of the article to be manufactured;

• providing a plug;

• wherein the plug is configured and adapted so that zones of the plug impinge on the heated sheet of material at pre-formed reinforcement zones that correspond to zones of reinforcement required in the formed article, thereby to pre-cool the pre-formed reinforcement zones to allow for reduced dimning of said pre-formed reinforcement zones during forming of the article.

15. A method of claim 14 wherein the method of manufacture includes the step of creating a differential pressure on either side of the sheet material to thereby cause the sheet material to conform to the shape of the vacuum forming mould.

16. A method of claim 14 wherein the method of manufacture includes the step of heating the sheet of material and/ or the plug.

17. A plug for assisting in the formation of an article from a sheet of material by a vacuum or thermo- forming process, said article comprising a base, a plurality of side walls extending from the base to define a plurality of corner edges extending upwards from the base, with at least one side wall defining at least one reinforcing formation extending from the base, said plug comprising

a plug body including a proximal and a distal end, wherein the plug body is configured and adapted to impinge upon said sheet material in a forming process and includes, at a point between the plug body's proximal end and distal end, a cross sectional shape including

plug body corner zones configured and adapted for impingement on preformed corner edge zones on the surface area of the sheet material that will be formed into the base adjacent the corner edges or the corner edges themselves; and

18. A plug of claim 17 wherein the plug body is recessed from the plug body corner zones and the plug body reinforcement zones around at least part of the remaining surface area of the plug.

19. A plug of claim 17 wherein the plug comprises connecting formations configured for mounting the plug body to a reciprocating machine.

20. A plug of claim 17 wherein the article comprises a container having at least two opposed sides.

21. A plug of claim 20 wherein me container is a four sided container.

22. A plug of claim 20 wherein the container has at least one reinforcing formation at each opposed side of the container.

23. A plug of claim 22 wherein the plug body includes a pair of plug body reinforcement zones for impingement on pre-formed reinforcement zones on the surface area of the sheet material that will be formed into the reinforcing formations.

24. A plug of claim 17 wherein the reinforcing formations are concertina formations.

25. A plug of claim 24 wherein the reinforcing formations are adapted and configured to collapse when the container is squeezed from opposing sides.