HK1189558B - A container and blank - Google Patents

Description

Containers and blanks

The present invention relates to a container, in particular, but not exclusively, to a container for containing food, such as a sandwich container. The invention also relates to a blank for such a container and to a method for forming such a container.

It is known to package some foods (e.g. sandwiches) in airtight sealed containers formed from blanks of folded material such as cardboard. For the purposes of this specification, "cardboard" will be taken to include paper, paperboard and similar materials.

To extend the shelf life of these packaged foods, it is desirable to reduce the amount of oxygen trapped in the sealed container, preferably to zero. This can be achieved through vacuum packaging, where the air is simply removed from the package, or through gas flushing, where the air is squeezed out of the package by adding one or more gases (e.g., nitrogen, argon, or carbon dioxide). Most preferably, a technique called "modified atmosphere packaging" is used, where the air in the container is first removed and then replaced with one or more of the gases mentioned above. This initial step of sucking out the air prevents residual oxygen from remaining in the container, a typical problem associated with gas flushing.

In order for any of the above techniques to be effective, it is important that the sealed container is as airtight as possible. In particular, the success of modified atmosphere packaging depends largely on the quality of the seal provided on the container.

Several attempts have been made to improve the design of packaging, particularly paperboard containers, in such a way that a proper seal can be formed, and numerous patent applications have been filed relating to these improvements. One important development has been the use of a continuous plastic film to provide an impermeable layer over the entire interior surface of the paperboard container/blank. The increasing use of heat sealing technology has also been helpful, as has better design on the blank itself. However, if modified atmosphere packaging is to be viable, there remains a need to further improve the integrity of such containers.

For example, it is difficult to completely eliminate discontinuity with the container body, particularly at the corners of the container opening, and it is also difficult to completely eliminate discontinuity with the interface between the body of the container and/or the lid/closure. Container blanks are typically provided with panels to create an outwardly extending flange around the opening of the finished container, with which the cover plate is combined to close the container. However, because the blank must be folded into its final structure, the flange-forming portion must be provided as several discrete parts. When the cover plate is combined with the flange of the container, the gap between the flange portions is not effectively sealed as with the rest of the flange and the lid. This compromises the integrity of the seal of the finished container.

Typically, the gaps described above can be minimized by careful design of the container blank, in particular by extending the length of one or more flange-forming panels. However, in some other preferred blank configurations, it is not possible to extend the panels in this way, and therefore, a relatively large gap will remain.

It is an object of the present invention to provide a container and blank that address the above-mentioned problems, thereby providing an improved seal. It is an object of the present invention to provide a container formed from a blank that provides an improved seal for modified atmosphere packaging of the container contents, thereby extending the useful life of the product (e.g., food) placed therein. It is another object of the present invention that the container should be simple to form.

The present invention provides a container for food, the container comprising a body and a lid, the body having an opening for receiving food and closure forming means around the opening, the closure forming means comprising a flange disposed around at least a portion of the opening, the lid engaging a first surface of the flange to close the container in use, wherein the lid is connected to a portion of the flange by a fold line, and wherein the fold line connecting the lid to a portion of the flange is an angled extension of a fold line connecting the lid to the container body. A blank for forming the container is also provided.

Further advantageous features of the container and the blank are described in the associated dependent claims.

Connecting the lid to a portion of the flange can help avoid gaps in the flange at the corners of the container at either end of the lid.

Providing a foldable portion of the lid that is foldable over at least a portion of the container flange allows gaps that may exist in the flange to be effectively sealed.

The container may comprise a paperboard substrate and a liquid-impermeable layer, which preferably comprises a film layer. The film layer may extend beyond the edge of the paperboard substrate to form one or more film projections. In particular, the film projections may be provided at the foldable portion of the lid, but may also be provided in other areas to improve the seal of the container.

The foldable portion of the lid may, for example, include a corner of the lid or an edge portion of the lid.

The lid can be a component separate from the container body, or can be connected to the container body. In particular, it is possible to connect the lid to a portion of the flange of the container via a fold line.

Preferably, the container is formed from a folded blank. Each corner of the container opening may be formed at the end of a fold line located between two body panels of the container body forming adjacent wall portions, and the container may further include closure forming means around the opening, which is continuous around each corner of the opening. Continuous means that the closure forming means is continuous, for example, by a seam between non-adjacent parts of the blank. Alternatively, the blank may include a strip section between the panels forming adjacent wall portions of the finished container, which is folded and bonded to the outside of the container. This avoids the presence of any cut edges on the interior of the finished container, which improves integrity by reducing the chance of grease or other liquids entering the container material.

Preferably, the blank used to form the container described above comprises a paperboard substrate and a liquid-impermeable layer, such as a film layer. The film layer may extend beyond the edge of the paperboard substrate to form one or more film projections in the area that will serve as the free edge of the finished container. Projections may also be provided in other areas to improve the general seal of the container body formed from the blank, such as between adjacent strip-like portions, at the free ends of one or more strip-like portions, and/or beyond the free edge of at least one flange portion, such as between two adjacent flange portions. In some embodiments, one or more portions of the flange, particularly the portion that connects to the container's closure, may be provided solely by the film layer extending beyond the paperboard substrate. If desired, the film may be heat-sealable.

The present invention also provides a container formed from a folded blank, the container comprising a container body having a plurality of wall portions, the wall portions being formed by body panels of the blank and defining an opening having a plurality of corners, each corner of the opening being formed at the end of a fold line located between two body panels forming adjacent wall portions of the container body, and the container further comprising a closure forming device around the opening, wherein the closure forming device is connected to each panel of the container body and is continuous around each corner of the opening. The present invention also provides a blank for forming such a container. Other advantageous features are described in the relevant dependent claims.

Further advantageous features of the invention are described in the dependent claims.

As mentioned above, the corners of a container opening are typically some of the most difficult parts of a container to seal. Various approaches have been proposed to overcome this problem, but most often require a complex arrangement of additional panels or film areas to seal the corners, or require forming the corners at fold lines between adjacent panels of the blank. However, containers formed from blanks most often have at least one corner formed by a seam between two non-adjacent panels of the blank, which prevents the use of these solutions. The present invention ensures that each corner of the container is formed by a fold line, rather than by a seam between the ends of the container blank. Thus, sealing of all corners of a container is simplified.

The container is formed from a folded blank, wherein each corner of the container opening is formed at the end of a fold line located between two body panels of the container body forming adjacent wall portions, and the container further includes closure-forming means surrounding the opening and being continuous around each corner of the opening. Continuous means, for example, that the closure-forming means is continuous through a seam between non-adjacent portions of the blank.

The closure forming means may comprise a flange around at least a portion of the container opening.Preferably, the flange is formed from a plurality of outwardly folded panels of the blank, each of the plurality of outwardly folded panels being connected to the body panel by a fold line.

The container may include a paperboard substrate and a liquid-impermeable layer, which preferably includes a film layer. The film layer may extend beyond the edge of the paperboard substrate to form one or more film projections. In particular, the film projections may be provided at the foldable portion of the lid, but may also be provided in other areas to improve the seal of the container.

An impermeable film may span the gap between the outwardly folded panels, preferably, the film being stretchable. Since each corner of the container opening is formed at a fold line of the blank, the spanning film can be easily positioned at any corner of the container opening.

Preferably, the impermeable film is a plastic film, for example comprising multiple layers of plastic material which may be coextruded. A suitable film may comprise a layer of ethylene vinyl alcohol (EVOH) between two layers of low density polyethylene (LDPE).

Preferably, the plastic film is provided over the entire inner surface of the container.

The closure forming means for the container may further comprise a cover panel, which may be connected to the body panel and the remainder of the closure means by a fold line.

Connecting the cover panel to an adjacent portion of the closure device (eg, the flange) can help avoid gaps in the flange at the corners of the container at either end of the lid.

Providing a foldable portion of the cover panel that is foldable over at least a portion of the container flange allows for effective sealing of gaps that may be present in the flange.

For example, the foldable portion of the cover may include a corner of the cover or an edge portion of the cover.

Preferably, one wall portion of the container body includes a seam formed between two body panels of the blank. The closure-forming means may then include a continuous piece of material surrounding the container opening, beginning and terminating at the ends of the seam. The seam may, but need not, be in the middle of the wall panels. Importantly, by relocating the seam from a corner of the container to a single point in the planar wall portion, sealing around the seam is significantly simplified.

The seam can be formed by joining a first tab (which is connected to the first body panel and folded back against the first body panel) to another body panel, thereby forming an additional panel on the exterior of one container wall (which overlaps a portion of the first body panel). The additional panel provides additional strength to the container, and the folding back of the tab ensures that a good seal is achieved.

Preferably, the first body panel is connected to the first closure-forming panel by a fold line, and the other body panel is connected to the other closure-forming panel by a fold line, and the edge of the first closure-forming panel abuts the edge of the other closure-forming panel. This arrangement ensures that there is no overlap of the panels in the flange of the finished container, which advantageously ensures that the lid can reliably seal on the container opening.

If the edges of the first closure-forming panel and the further closure-forming panel are beveled relative to the seam in the container body, a tortuous seam/joint can be provided in the container. This tortuous seam can advantageously prevent gas from leaking into or out of the finished container.

An area of unsupported plastic film is provided between the edge of the first closure-forming panel and the first flap, and preferably, a further closure-forming panel is bonded to the unsupported area of plastic film. This arrangement provides a good seal at the seam. A particularly good seal is provided if the film area extends over the fold line between the first body panel and the first flap, such that a double layer of film is provided when the first flap is folded back to form the container. Preferably, for example, as a result of the arrangement of the closure-forming panel described above, the unsupported film layer is covered by the material of the blank substrate to protect the film from direct heat application during the heat sealing process.

The same features described above can also be applied to the seal at the container apex. First and further tabs can be provided on the edges of the first and further body panels opposite the edges on which the first and further closure-forming panels are provided, and can have the same beneficial features as described above. The first and further closure-forming panels are then joined to the cover panel in the finished container, and the first and further tabs can be joined to a third tab provided on a third body panel of the blank.

The above features serve to prevent the need to apply a heat seal through a double layer substrate, whilst still providing a layer to protect the delicate plastic film. Similar features may be provided to achieve the same effect on other parts of the container, for example where other flaps connected to the body panel by a fold line need to be sealed together to form the container.

The container may be a sandwich container, in particular, a generally triangular sandwich container for diagonally cut sandwiches. In this case, it is generally preferred to provide a seam in the generally rectangular wall portion of the container (rather than in the triangular wall portion). The container may also be a container for a variety of other foods and other products. It is also possible to provide a seam in the triangular wall portion, and if desired, as described above, more than one seam may be provided.

The invention also provides a blank for forming a container as previously described.

Preferably, the blank comprises a substrate layer, such as paperboard, having a plurality of body panels and a plurality of closure-forming panels connected to edges of the body panels, the closure-forming panels defining an opening of the container in use. The body panels and closure-forming panels may be defined by fold lines or score lines in the substrate layer, and the impermeable film preferably covers the entire substrate layer and spans the gaps between adjacent closure panels.

A closure panel can be provided as a cover panel connected to a body panel and two other closure forming panels by fold lines. Connecting the cover panel to the other closure forming panels by fold lines can eliminate gaps that exist at the corners of the container opening where the lid is provided.

Preferably, the first body panel of the blank is provided with a first flap which, in use, is connected to the other body panel so that the two body panels together form a single wall portion of the container body. It is also possible to provide an additional fold line in one of the body panels (preferably the body panel which, in use, forms the container wall opposite the container wall formed by the two body walls). This fold line may be located in the middle of the body panel, but this is not required.

A method of forming a container from the blank comprises the steps of folding the blank, possibly at the additional fold line, so that a first flap overlaps an edge of the further body panel, joining the first flap to the further body panel, and folding the first flap back against the first body panel to unfold the container body. The remaining flaps provided on the first and further body panels may then be joined to similar flaps provided on a third body panel to form the container body. The joining is preferably achieved by heat sealing.

In all cases, the container may further include a frangible opening, such as a score line in the lid and flange. Alternatively, or in addition, the container may include a heat-activated sealing device, such as a resin dot, located at the vertex of the container, such as at the interface of the lid and the container opening. If desired, where a film layer is provided, it may be perforated or otherwise breathable.

The present invention will be better understood from the following detailed description, which is described by way of example only with reference to the accompanying drawings, in which:

FIG1 is a plan view of a blank for forming a container according to the present invention;

FIG2 is a perspective view of a container formed from the blank of FIG1 , in an open configuration;

FIG3 is a plan view showing the blank of FIG1 folded in half;

FIG4 is a perspective view showing a container formed from the folded blank of FIG3 ;

FIG5 is a view from the apex of the container of FIG2 showing the container in a closed/sealed configuration;

FIG6 is a plan view of a container blank according to another embodiment of the present invention;

Figures 7a to 7c illustrate folding the blank of Figure 6 into a sandwich container;

FIG8 is a perspective view of a container formed from the blank of FIG6;

FIG9 is a perspective view of the container of FIG8 after sealing;

FIG10 is a plan view of a container blank according to yet another embodiment of the present invention;

FIG11 is a perspective view of a container formed from the blank of FIG10; and

12 is a perspective view of the container of FIG. 11 after sealing.

The container blank 1 shown in FIG1 is used to form a triangular sandwich package for diagonally cut sandwiches. The blank 1 comprises a substrate layer of paperboard divided into a plurality of panels by fold lines. Some of these panels (4, 6, 8, 10, 12) will form the walls defining the finished container body, some of the panels (14, 16, 18, 20, 22) will form the closure of the finished container, and the remaining panels (2, 24, 28, 32) will serve as flaps that hold the container body together.

With the blank 1 in the state shown in FIG1 and processed in a counterclockwise direction, the large flap 2 is shown connected to the first long side of a generally rectangular first body panel 4. The second long side of the first body panel 4 is connected to the first short side of a second body panel 6, which is an isosceles triangle with two short sides and one long side. The second short side of the second body panel 6 is connected to the first long side of a third body panel 8. Similar to the first body panel 4, the third body panel 8 is generally rectangular, but its shorter side is twice the length of the shorter side of the first body panel 4. The first short side of a triangular fourth body panel 10 is connected to the second long side of the third body panel 8. The fourth body panel 10 is an isosceles triangle, similar to the second body panel 6, and its second short side is connected to the first long side of a generally rectangular fifth body panel 12. The shorter side of the fifth body panel 12 is longer than the shorter side of the first body panel 4, but shorter than the shorter side of the third body panel 8.

FIG2 shows a container 51 formed from the blank 1 shown in FIG1 . The second and fourth body panels 6, 10 form the triangular wall portion of the container, with one generally rectangular end wall formed by the third body panel 8 and the other formed by the first and fifth body panels 4, 12, which are connected together by joining the large flap 2 to a portion of the fifth body panel 12. Importantly, this arrangement means that the seam in the body of the container 51 (i.e., where the blank 1 is joined together) is located in the middle of the wall portion of the container 51, rather than at the corner of the container body 51 between the container vertex 30 and its opening. This means that a single fold line 5, 7, 9, 11 between adjacent body panels forms each corner of the container body 51. Another vertex fold line 25 can be seen extending from the vertex toward the midpoint of its long side on the triangular fourth body panel 10 to a position approximately halfway along the length of the long side. FIG1 shows that the second body panel 6 of the blank 1 is also provided with a vertex fold line 25 as described above. Vertex fold line 25 is advantageous when forming the container, as will be explained later.

Another fold line 3 exists between the large flap 2 and the first body panel 4 and is shown as a dashed line in Figure 2. Although not visible in Figure 2, the large flap 2 is folded back toward the first body panel 4 at the fold line 3 so that the large flap 2 is sandwiched between a portion of the fifth body panel 12 and the first body panel 4. The formation of the container 51 from the blank 1 will be described in more detail later.

Although described as generally rectangular, each of the first, third and fifth body panels 4, 8, 12 actually incorporates a slight taper such that the opening of the container 51 is wider than the container apex 30. This is preferred to allow stacking of multiple empty containers 51 and to simplify the act of placing a sandwich in the container 51, but is not required.

The blank 1 of Figure 1 also includes a plurality of closure-forming panels 14, 16, 18, 20, and 22 for forming the closure of the finished container 51. A closure-forming panel is provided at the edge of each body panel 4, 6, 8, 10, and 12, and, in use, defines the opening of the finished container 51 of Figure 2. Specifically, the four flange-forming panels 14, 18, 20, and 22 are connected to the edges of the first body panel 4, the third body panel 8, the fourth body panel 10, and the fifth body panel 12, respectively, via fold lines; and the cover panel 16 is connected to the edge of the second body panel 6 via a fold line.

Small tabs 24, 28, 32 are provided at the edges of the first, third, and fifth body panels 4, 8, 12 opposite their respective flange-forming panels 14, 18, 22. For convenience, the small tab 24 connected to the first body panel 4 will be referred to as the first small tab, the small tab 28 connected to the third body panel 8 will be referred to as the third small tab, and the small tab 32 connected to the fifth body panel 12 will be referred to as the fifth small tab. Similar nomenclature will be applied to the flange-forming panels 14, 18, 20, 22.

The blank 1 also includes a layer of plastic film applied over the entire paperboard substrate. The plastic film has several benefits, most notably preventing liquids from entering the paperboard substrate, providing a substantially airtight layer to enable gas flushing, and serving as a heat-sealable medium to hold the finished container 51 together.

Experiments have determined that a particularly suitable film comprises a layer of ethylene vinyl alcohol (EVOH) between two layers of low-density polyethylene (LDPE). In a preferred embodiment of the present invention, the total thickness of the film is 40 microns. This represents a top layer of LDPE 18.5 microns thick, a middle layer of EVOH 3 microns thick, and a bottom layer of LDPE also 18.5 microns thick. Suitable coextruded films are available from the French company Leygatech and exhibit the following properties:

- Breaking stress (MD/TD): 27/16Mpa

-Elongation at break (MD/TD): 410/470%

-Tear strength (MD/TD): 95/205Nmm ^-1

The film also exhibits a water vapor transmission rate of less than 7.5 gm ^-2 /24h (at 38°C and 90% relative humidity), and an oxygen permeability of 2 ^{cm3m -2} /24h or less (at 23°C and 0% relative humidity).

Unsupported areas of plastic film are placed where there are gaps in the paperboard substrate. Specifically, a triangular first plastic film 19 is placed between the third flange-forming panel 18 and the fourth flange-forming panel 20, and a triangular second plastic film 21 is placed between the fourth flange-forming panel 20 and the fifth flange-forming panel 22. A triangular third film 13 is placed at the end of the fold line 3 between the large flap 2 and the first body panel 4, adjacent to the first flange-forming panel 14. A triangular fourth film 23 is placed at the opposite end of the fold line 3, adjacent to the first small flap 24. Finally, the plastic film provides the window 26 in the cover panel 16.

Typically, the flange of a container formed from a blank is formed into several discrete sections. This is necessary to allow the flange to be folded outward from the container wall without tearing the blank material. A problem with this typical arrangement is that gaps will inevitably exist between the various sections of the flange at the corners of the finished container, which is undesirable for ensuring a good seal. In the blank 1 of FIG. 1 , the triangular first and second plastic films 19 , 21 are stretchable so that the third, fourth, and fifth flange-forming panels 18 , 20 , 22 can be folded outward to form a continuous flange without tearing the blank 1 at the corners of the container 51 .

Figure 1 shows a blank 1 from the outside as it will be located in use on a finished container 51. The plastic film layer will be provided in use on the inside of the finished container 51. For simplicity, the respective surfaces of the blank will be referred to simply as the inner surface and the outer surface below.

To ensure that there are no gaps at the corners of the container 51 at opposite ends of the cover panel 16 , the cover panel 16 is connected to the first and third flange forming panels 14 , 18 by two angled extensions 15 , 17 of the fold line between the cover panel 16 and the second body panel 6 .

FIG3 illustrates the first step in forming the container 51 shown in FIG2 from the blank 1 shown in FIG1 . The blank 1 is shown folded in half along fold line 33, which is located between the third body panel 8, the third flange-forming panel 18, and the third tab 28. The fourth and fifth body panels 10, 12 have been folded under the second and first body panels 4, 6, and the large tab 2, so that the inner surfaces of the two halves of the blank are in contact. The fifth flange-forming panel 22 is located under the first flange-forming panel 14 and the triangular-shaped third film 13, while the fifth tab 32 is located under the first tab 24 and the triangular-shaped fourth film 23. The fourth flange-forming panel 20 is visible through the window 26 in the cover panel 16.

After the blank 1 is folded as shown in FIG3 , heat is applied to bond the large flap 2 to the edge of the underlying fifth body panel 12. Specifically, heat is applied to the underside of the folded blank as shown, to the outer surface of the fifth body panel 12 in the area below the large flap 2, and to the ends of the triangular third and fourth plastic films 13 and 23 that lie beyond the fold line 3. Heat is not applied directly to the triangular third and fourth films 13, 23, visible in the view of FIG3 , to avoid damaging the plastic films. This will be described further below. However, in most cases, the heat applied to the fifth body panel 12 is sufficient to seal the overlapping portions of the triangular third and fourth plastic films 13, 23 to the fifth body panel 12.

The next stage in forming the container 51 is to separate the triangular second and fourth body panels 6, 10, flatten the third body panel 8, and fold the large flap 2 back against the first body panel 4 at the fold line 3 between the large flap 2 and the first body panel 4. FIG4 attempts to illustrate this opening process. The large flap 2 is folded back against the first body panel 4, and this results in the triangular third and fourth films 13, 23 being folded twice. The fifth body panel 5 is not apparent from the view, but it should be noted that the angled edges of the paperboard substrate of the fifth flange-forming panel 22 and the fifth small flap 32 coincide with the angled edges of the triangular third and fourth films 13, 14, which can be seen in FIG4.

The heat sealing process used to seal the apex 30 of the container 51 typically involves separating the triangular body panels 6, 10 as described above and clamping the tabs 24, 28, 32 together between heated rollers. Problems can arise if this action of clamping the apex 30 of the container 51 is blocked by the triangular walls 6, 10 of the container 51. There is a risk that the tabs 24, 28, 32 will not be held together tightly enough during heat sealing, or that the process will stress the material in the triangular walls 6, 10. Both of these problems are alleviated by providing an apex fold line 25 extending from the apex of each triangular wall 6, 10. When the tabs 24, 28, 32 are heat sealed, the apex fold line 25 allows the triangular walls 6, 10 to deform in a controlled manner when the package 51 is clamped at the apex 30. The exact length of the apex fold line 25 is not critical and can be shorter than shown. Preferably, the vertex fold line does not extend more than halfway along the triangular wall panels 6, 10, so that the wall of the finished container 51 maintains a certain rigidity.

When the container 51 is fully unfolded and the large flap 2 is fully folded flat against the exterior of the first body panel 4, as clearly shown in Figures 1 and 3, the angled edges of the fifth flange-forming panel 22 and the fifth small flap 32 abut the angled edges of the first flange-forming panel 14 and the first small flap 24. This is best seen in Figure 5, which shows a view from the vertex 30 of the completed container 51. As a result, when the container 51 is fully formed, there is no exposed film on the exterior of the container 51. This improves the outward appearance of the container 51 and provides other benefits as described below.

The plastic film of the blank 1 is easily heat-sealed, but it can also be damaged if subjected to excessively high temperatures during the heat-sealing process. Typically, heat sealing of the container occurs at approximately 200°C, but it has been found that temperatures exceeding 100°C can damage any exposed plastic material. Any loss of integrity in the plastic film can lead to a loss of integrity in the finished container and is therefore to be avoided.

As can be seen in FIG. 5 , there is no exposed plastic film at the apex 30 of the container 51 where the tabs 24, 28, 32 are heat-sealed together, nor is there any exposed plastic film where the first and fifth flange-forming panels 14, 22 are heat-sealed to the cover sheet to close the container. Thus, when forming the container 51, heat can be applied to the exterior of the container on both sides of the area to be sealed. During the heat-sealing process, the paperboard backing layer protects the film from direct heat application and prevents damage and/or loss of integrity.

While, as mentioned above, it is important to protect the plastic film from very high temperatures, it is still necessary to transfer the heat applied to the package to the film in order to form a reliable film. Therefore, it is undesirable to have excess material between the applied heat source and the heat-sealable film (especially if the excess is only in certain areas) because this would require applying heat to different portions of the container 51 for different lengths of time. The blank 1 of FIG. 1 does not present this problem because, as mentioned above, the angled edges of the fifth flange-forming panel 22 and the fifth tab 32 abut the angled edges of the first flange-forming panel 14 and the first tab 24. Thus, when formed, the corresponding portion of the container comprises only one layer of paperboard overlapping a double layer of plastic film.

The overlap of each of the triangular shaped third and fourth films 13, 23 also provides an improved seal for the container. Straight seals or seams between portions of the container can act as "rat runs" to allow gas to flow into or out of the container. The folding of the triangular films 13, 23, along with the angled lines at the seams between the first and fifth flange-forming panels 14, 22 and between the first and fifth tabs 24, 32, provide a more tortuous route for any gas attempting to enter or exit the container 51, further improving the integrity of the container 51.

FIG5 also illustrates how the triangular-shaped first and second films 19, 21 are stretched to span the respective gaps between the third and fourth flange-forming panels 18, 20, and between the fourth and fifth flange-forming panels 20, 22. At opposite corners of the container 51, the angled extensions 15, 17 of the fold lines where the lid panel 16 connects to the first and third flange-forming panels 14, 18 can be seen. Referring briefly again to FIG2, it can be seen that when the lid panel 16 is in the open position, the connection between the lid panel 16 and the first and fifth flange-forming panels 14, 18 causes the first and fourth flange-forming panels 14, 18 to extend outward from the container opening. When the lid is closed, the flange-forming panels 14, 18 fold outward and then, possibly, seal to the interior of the lid panel 16, as shown in FIG5. The angles of the fold line extensions 15, 17 allow the lid panel 16 to be permanently attached to the first and third flange-forming panels 14, 18 without placing undue strain on any portion of the blank 1 during its folding to form the container 51. Even if folding results in damage to the cardboard around the angled extensions 15, 17 of the fold line, the continuous layer of plastic film on the interior of the container 51 will maintain the integrity of the seal.

The finished container 51 comprises four walls, with the folded-over large flap 2 and the edge of the fifth body panel 12 connected to the large flap providing a further fifth panel. This further panel provides additional strength and rigidity to the wall portion that, in use, will form the bottom of the finished container 51. The additional material in this further panel also provides additional weight to the bottom wall, which may slightly improve the stability of the container 51 in use.

The present invention should not be considered to be limited to the above-described structures and materials. For example, it will be apparent from the above description that providing a fold line 33 in the third body panel 8 of the blank 1 can simplify the initial stages of forming the container 51 by allowing the entire blank 1 to be folded in half so that the large flap 2 can be easily joined to the fifth body panel 12. However, it should be noted that, conversely, the same container 51 can be formed without the fold line 33 in the third body panel 8 by folding each panel 2, 4, 6, 8, 10 in sequence and joining the same parts together.

Furthermore, it should be noted that an advantage of the present invention is that if the container is provided with a flange around its entire opening and the cover is provided as a separate component, then ensuring that all corners of the container opening are provided by fold lines will further improve the sealing of the container.

Figures 6 to 12 show a blank for another sandwich container in an unassembled, partially assembled and assembled state. It will be understood that in many cases, the features shown and described will also be applicable to blanks for containers for a variety of other purposes, and to the containers and blanks shown in Figures 1 to 5.

FIG. 6 shows a blank 100 which, in use, is folded to form a sandwich container 101 as shown in FIG. 8 .

For purposes of this description, the terms "left" and "right" and their derivatives will relate to the invention as oriented as in Figure 6, as if blank 100 were placed on a table and viewed from above. However, it will be understood that the invention may assume various alternative orientations, except where expressly indicated to the contrary.

The blank 100 of Figure 6 includes left and right triangular side panels 102, 103, and generally rectangular first and second end panels 104, 105. As shown in Figure 6, the end panels 104, 105 include a slight taper so that the finished container 101 has an opening slightly larger than its apex, but this is not required.

Left and right triangular side panels 102 and 103 extend perpendicularly from the left and right edges of first end panel 104, respectively. Second end panel 105 extends from the narrow end of rectangular first panel 104 below rectangular first panel 104. Triangular side panels 102 and 103 are the same size as one another and are both right-angled triangles. End panels 104 and 105, which are generally rectangular, are also the same size as one another.

Left and right webbing sections 106 and 107 extend on each side of the second end panel 105 and connect the left and right edges of the second end panel 105 to the bottom edges of the left and right side panels 102 and 103, respectively. The webbing sections 106 and 107 each include two parts indicated by the suffixes "a" and "b" in FIG6 , with a webbing fold line 108 between the webbing parts 106a and 106b and a webbing fold line 109 between the webbing parts 107a and 107b.

The strip fold lines 108 and 109 extend approximately 45 degrees from the upper left corner and the upper right corner of panel 105, respectively, so that the strip fold line 108 is equidistant from the left edge of panel 105 and the bottom edge of panel 102. Similarly, the strip fold line 109 is equidistant from the right edge of panel 105 and the bottom edge of panel 103.

A panel fold line 110 is provided between each webbing section 106, 107 and the adjacent panel, and a flange 111 is shown around the edge of the blank 100. The flange 111 is formed into a plurality of discrete portions 121, 122, 123, 124, which are connected to the first end panel 104, the right side panel 103, the second end panel 105, and the webbing portion 106a, respectively, via flange fold lines 112. Additional panel fold lines 113 are provided at the seam between the first and second end portions 104 and 105, between panels 102 and 104, and between panels 103 and 104. In this embodiment, fold lines 108, 109, 110, 112, and 113 are all formed as creases.

A generally rectangular closure/lid panel 114 for closing the finished container extends from the hypotenuse of the triangular side panel 102 and is connected thereto by a lid fold line 115. Notably, the closure 114 is connected to adjacent flange portions 121, 124 by angled extensions at each end of the fold line 115.

A diagonal fold line 116 is provided at a free corner 117 of the closure panel 114 so that the corner 117 can be folded back after the finished container 101 is closed. The closure panel also includes a window portion 118.

In the illustrated embodiment, blank 100 comprises a paperboard substrate with a liquid-impermeable film coating. The film coating covers the entire substrate and also forms a window 118 in closure panel 114. Small areas of film projections 125 are provided around corners 117 of closure panel 114, and additional areas of film projections 126 are provided along the short sides of each flange portion 121 and 123. Although not shown, it is contemplated that additional areas of film projections may be provided, for example, extending beyond fold line 108 between adjacent strip portions 106a and 106b and/or beyond fold line 109 between strip portions 107a and 107b. Film projections may also be provided at the free ends of strip portions 106b and 107b, on the exterior of flange portion 123, and/or at the ends of flange portion 122. The film layer may even bridge the gap between the adjacent panels (e.g., adjacent flange portions) of the container blank in the same manner as the triangular films 19 and 20 of the blank 1 shown in Figure 1. In this case, the film layer should be able to stretch so as not to prevent the flange portions from folding outwards when forming a container. Tests have determined that a particularly suitable film comprises a deck of ethylene vinyl alcohol (EVOH) between two layers of low-density polyethylene (LDPE). A suitable coextruded film can be obtained from French company Leygatech. Yet, other films that show similar elongation and tear strength can also be used.

In another embodiment, flange portion 124 may be provided solely as a film layer extending beyond the edge of the paperboard substrate. The edge of film flange portion 124 may terminate as shown in FIG6 , or it may extend beyond the edge shown to provide a larger flange area, as in the case of providing a film projection around paperboard flange 124. Furthermore, another flange portion similar to portion 124 may be provided at the free edge of strip-like portion 107a. This additional flange portion may also be provided with a film projection, or may be provided solely as a film layer in the same manner as flange portion 124. When provided solely as a film layer, this additional flange-forming portion may be connected to the adjacent flange portion 122.

Figures 7a through 7c illustrate the folding of blank 100 to form finished container 101, shown in Figure 8. First, as shown in Figure 7a, blank 100 is folded at right angles along fold lines 110 between side panels 102, 103 and webbing portions 106a, 107a, and along fold line 113 between end panels 104, 105. Next, as shown in Figure 7b, the blank is folded along fold line 113 between first end panel 104 and right side panel 103, so that right side panel 103 bridges the gap between first and second end panels 104, 105. As a result, oppositely directed fold lines are also formed at fold line 109 between webbing portions 107a, 107b, with webbing portions 107a, 107b overlapping and extending from the exterior of the now partially formed container. A similar folding operation is then performed between first end panel 104 and left side panel 102, resulting in the structure shown in Figure 7c. To complete the container body, the strip sections 106 and 107 are folded flat against and bonded to the exterior of the second end panel 105, and the flange portions 121, 122, 123, and 124 are folded outward to form a flange 111 around the container opening. During this process, flange portion 124 overlaps flange portion 123 on the container exterior. The stiffness of flange portion 123 allows flange portion 124 and another optional flange portion at the end of the strip section 107a to consist solely of film, as described above. The flexibility gained by omitting the paperboard layer from these flange portions helps provide an improved seal at this end of the finished container.

FIG8 shows the finished container 101 as seen from its apex at fold line 113 between first and second end panels 104, 105, and shows flange 111 folded back at flange fold line 112 around the edge of the container. A generally rectangular closure 114 has been folded along fold line 115 and bonded to flange 111 to close container 101. As described above, closure 114 is connected to adjacent flange portions 121, 124 by an angled extension extending to fold line 115, resulting in no gaps in flange 111 at the side of the finished container 101 where lid fold line 115 is located. However, gaps 127 do exist in flange 111 at the corners of container 101 between flange portions 121 and 122, and between portions 122 and 123.

As shown in FIG9 , gap 127 is covered by folding back corner 117 of closure panel 114 at fold line 116 and bonding it to the opposite side of flange 111. Raised film 125 provided at corner 117 extends around the corner of container 101 to further improve the seal. The seal of closure 114 to flange 111 in the area of gap 127 is improved by raised film areas 126 at the ends of flange panels 121 and 123 (not shown). The resulting package eliminates any gaps at the interface between flange 111 and closure 114, thereby providing an improved hermetic seal to the finished container.

FIG10 shows a blank 200, which represents an alternative embodiment of the present invention. Many features of blank 200 are identical to those of blank 100 of FIG6 , and therefore, these will not be described again. The key difference is that the closure 214 of alternative blank 200 is wider and has a single fold line 216 along its entire length. The edge portion 217 of closure 214 is located outside fold line 216, and, as in the first embodiment, film projections 225 are provided at the corners of closure 214.

FIG11 shows a container 201 formed from the blank 200 of FIG10 . The container 201 is formed exactly as described above with respect to the first embodiment. However, as can be seen in FIG11 , the edge portion 217 of the closure panel 214 extends beyond the flange 211 so that the fold line 216 is located near the edge of the flange 211. To cover the gap 227 in the flange 211, the edge portion 217 of the closure panel 214 is folded along the fold line 216 and joined to the opposite side of the flange 211, specifically, to the flange portion 222 along the long side of the container 201.

Figure 12 shows a second embodiment of a container 201 in which the closure panels 214 are folded and joined as described above.The film tabs 225 serve essentially the same purpose as described in relation to the first embodiment.

In use, a food item (e.g., a sandwich) is placed inside the container 101, 201, and, as described above, the container 101, 201 is hermetically sealed. Consequently, the sealing of the container 101, 201 can include a "gas flushing" step, or modified atmosphere packaging technology. Gas-flushed containers are capable of retaining an inert atmosphere for at least 14 days, further extending the shelf life of any food item stored therein.

The present invention should not be considered limited to the above-described structures and materials. For example, the lid/closure panel may be integrated with the long side of the flange portion, or it may be provided as a completely separate component. Alternatively, or in addition, other foldable portions may be provided on the closure panel as desired.

Other means for improving the seal may also be provided. For example, discrete, generally circular, heat-activated dots of resin may be located near each of the four corners of the closure 114, 214, on the inner face. The dots of resin should be positioned to coincide with vertices on the container 101, 201 so that, when heated, they can flow into and/or around each vertex to hermetically seal the closure 114, 214 thereat. After the heat source is removed, each dot of resin solidifies and, in combination with the bond of the closure 114, 214 to the flange 111, 211, forms a hermetic seal.

The container may also include a frangible opening, possibly provided by a first score line on the inner surface of the closure panel 114, 214 and a second score line on the outer surface of the flange 111, 211. The portion 117, 217 of the closure 114, 214 that is folded back onto the flange 111, 211 may be used to initiate tearing along the score line to facilitate opening of the container.

While primarily concerned with providing an airtight container, in certain applications it may be preferable for the container to have a degree of permeability to allow the contents to "breathe." This is particularly important for certain food products (e.g., cheese). This can be achieved in any of the above embodiments by using an alternative film layer that has inherent air permeability, or by perforating the plastic film as described above.

Claims (9)

1. A container for food, said container being formed from a folded blank having a cardboard substrate and comprising: The body is formed by folding a blank, and the formed body has an opening for receiving the food. An outwardly projecting flange is disposed around at least a portion of the opening, the outwardly projecting flange comprising cardboard material and including a plurality of outwardly folded panels of the blank, each outwardly folded panel being connected to a body panel by a fold line; and A lid, in use, engages with the outwardly projecting flange to close the formed body, wherein the lid is connected by a fold line to at least one of the outwardly folded panels forming part of the flange. 2. The container of claim 1, wherein the fold line connecting the lid to a portion of the flange is an angled extension of the fold line connecting the lid to the formed body. 3. The container according to claim 2, wherein the container comprises a cardboard substrate and a liquid-impermeable film. 4. The container of claim 3, wherein the film extends beyond the edge of the cardboard substrate to form at least one film protrusion. 5. The container of claim 4, wherein the at least one thin film protrusion forms part of the flange. 6. The container of claim 3, wherein the film comprises a plurality of plastic material layers. 7. The container of claim 6, wherein the film is co-extruded. 8. The container of claim 7, wherein the film comprises an ethylene-vinyl alcohol layer between two layers of low-density polyethylene. 9. A blank for forming a container, the container being formed from a folded blank having a cardboard substrate and comprising: The body is formed by folding a blank, and the formed body has an opening for receiving food. An outwardly projecting flange is disposed around at least a portion of the opening, the outwardly projecting flange comprising cardboard material and including a plurality of outwardly folded panels of the blank, each outwardly folded panel being connected to a body panel by a fold line; and A lid, in use, engages with the outwardly projecting flange to close the formed body, wherein the lid is connected by a fold line to at least one of the outwardly folded panels forming part of the flange.