GB2234958A - Container and blank therefor - Google Patents

Abstract

A blank for a food container is constructed with corners each comprising a triangular central panel (36) and two triangular side corner panels (38, 40). Each side corner panel has profiled flange panel (44, 46) with lateral tab extensions (48, 50). When the corner is folded, the inner surface of one of the side corner panels (38) contacts the inner surface of the central corner panel (36) and the outer surface of the central corner panel (36) contacts the outer surface of the other side corner panel (40). The profiled flange panels (44, 46) overlap one another, while their tab extensions (48, 50) overlap the flange panels of the adjacent wall panels. The corner is stronger than existing blank corners, less prone to leakage and does not present sharp edges. <IMAGE>

Description

CONTAINER AND BLANK THEREFOR This invention relates to a container erected from a blank i.e. a sheet of laminar material cut to a certain shape and formed with fold lines. The invention also extends to the blank of or for the container.

Tray-like food containers are known, the blanks of which are formed of a board material which is coated on what is to be the inside surface of the container with a plastics substance combining impermeability to fluids at cooking temperatures with the ability to be heat-sealed to itself or to another surface to hold the container erected and receive a heat-sealed lid by which the container is closed.

A known corner of a blank for such a container is shown in Figure 1. The blank is generally rectangular and has fold lines defining a base panel 1, opposed pairs of wall panels 2, 4 (only one each of which is shown), and elongate flange panels 6, 8 along the free margins of the wall panels. For securement purposes each flange panel has an end tab extension 6A, 8A at each of its ends.

Each corner of the blank is defined by two substantially triangular and adjacent corner panels 10, 12 between adjacent wall panels 2, 4. During erection the blank is folded so that, simultaneously at its four corners, the inner face of the corner panels 10 is made to contact the inner face of the corner panel 12, the corner panels 10, 12 being folded together as a composite gusset fold against the outside surface of the adjacent wall panels 4. The corner panel 12 has a cut-out 13 which then allows part of the inner surface of corner panel 10 to be heat-sealed to the outer surface of corner wall panel 4 at the area 14 shown outlined by a broken line; at the same time the adjacent surfaces of the corner panels 10, 12 are heat-sealed to one another.

In this way the wall panels 2, 4 and the corner panels 10, 12 are formed as an upstanding, downwardly and inwardly tapering peripheral wall which surrounds the base panel 1. To complete the erection of the container the flange panels 6, 8 are moved to generally coplanar positions parallel to the base panels 1, with the end tabs 6A of the flange panels 6 overlying the end tabs 8A of the flange panels 8. The end tabs 6A, 8A are then heat-sealed together where they overlap, so as to form a continuous peripheral flange to which a lid for the container can be secured.

The only regions which are secured together and which contribute to securing the container are the area 14 outlined by the broken line and the end tab 8A of the rim portion 8.

As the container is not secured along the full depth of the wall there is a real risk of leakage during cooking.

Further, since reliance is placed on a small area to secure a fairly bulky corner (three layers of the board) having a large area of unsecured contact, the corner is prone to failure.

One partial solution to these problems would be to secure the corner along the full depth of the wall using an additional sealant. However this negates all the advantages to be gained from using a fusible plastics-coated box blank. In addition it would not overcome the inherent weak points caused by cutting away one sector at the upper edge of the container.

According to one aspect of the present invention there is provided a blank for a container, which comprises a substantially rectangular base panel, wall panels attached by fold lines to the base panel, corner panels between and attached by fold lines to the wall panels, the wall and corner panels being adapted to form for the erected container a peripheral wall having faceted corners, the blank further including flange panels adapted to form for the container an outturned flange carried by the said peripheral wall and to which a closure for the container may be attached, wherein for forming each said faceted corner the blank has a central said corner panel and a further said corner panel on each side of the central corner panel, the central and further corner panels being substantially triangular and foldable against one another in pleated relationship to form the corner, the central corner panels having no flange panel attached thereto but the further corner panels having respective corner flange panels formed with mutually inwardly projecting extensions which lie adjacent to, but free of, the central corner panel, for the formation of the said flange the corner flange panels being disposable in partially mutually overlapping relationship, with the extension of the uppermost corner flange panel disposed in overlying relation to a first said flange panel carried by the respectively adjacent wall panel and with the extension of the lowermost corner flange panel disposed in underlying relation to a second said flange panel carried by the respectively adjacent wall panel.

In the described embodiment, the first flange panel is carried by the wall panel adjacent the lowermost corner panel and the second flange panel is carried by the wall panel adjacent the uppermost corner panel.

In this way, the corner can be sealed internally for the full depth of the tray, thus strengthening the corner and reducing the possibility of product leakage.

Another feature of the corner is that it does not present extremely sharp edges, i.e. where an angle of 900 is defined between two adjacent wall panels. Instead, the corner presents a triangular face with two edges, one where one wall panel meets one of the corner panels and the other where the other wall panel meets that corner panel after folding. These wall panels meet the corner panels at respective angles greater than 900, preferably at 1200. The elimination of sharp edges improves product cooking in microwave ovens.

Preferably, each corner panel is an isosceles triangle including a vertex angle of 300.

According to another aspect of the invention there is provided a container manufactured from a box blank in accordance with said one aspect of the invention.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings in which: Figure 1 is a plan view of a corner of a known blank adapted to form a nestable tray-like container for a food product; Figure 2 is a plan view of a blank in accordance with one embodiment of the present invention, as seen looking onto its interior surface; Figure 3 is a plan view of the nestable tray-like food container formed using the blank of Figure 2, showing (in particular) the lid of the container; Figure 4 is a perspective view of the container of Figure 3 as seen from above (inside), one corner of the container being visible; Figure 5 is a section along line V - V of Figure 3; and Figure 6 is a plan view of an alternative corner of a nestable tray-like food container embodying the present invention.

Figure 1 has already been described above with reference to the prior art. Referring now to Figure 2, a blank in accordance with one embodiment of the present invention is generally rectangular and comprises fold lines defining side wall panels 20, 22 and end wall panels 24, 26 which in the erected container form the major product-contacting interior surfaces of a downwardly and- inwardly tapering peripheral wall. Elongate rectangular flange panels, 28, 30, 32, 34 are also defined and attached by fold lines to respective ones of the side and end wall panels.

At each corner of the blank there is provided a substantially triangular central corner panel 36 flanked by two substantially triangular side corner panels 38, 40. These triangular corner panels 36, 38, 40 are substantially isosceles, each having a vertex angle of 0 = 300 and a base angle s = 750. As can be seen clearly from Figure 2, the corner panels 36, 38, 40 share a common vertex 42 and the total included angle at that vertex is 900.

Each of the side corner panels 38, 40 has a respective profiled flange panel 44, 46 attached by a fold line along its base. Each of these flange panels has an outer curved part 45, 47 which has a greater depth than the rectangular flange panels 28, 30, 32, 34 so as to provide a projecting corner region by which the container can conveniently be held; it also has a laterally extending tab 48, 50 the depth w of which is substantially the same as the depth w of the rectangular flange panels. The entire inner surface of the blank is coated with a plastics material, for example, polyethylene terephthalate (PET), polypropylene or polyethylene, which, when the blank is folded to form a tray-like container and subjected to suitably high temperatures, can fuse to cause overlapping surfaces to be bonded together.The overlapped interior surfaces (i.e. those not visible from the interior of the container) are those shown shaded in a representative corner of Figure 2. When the blank is erected, the corner might be considered to be pleated; thus the inner surface of the side corner panel 38 is caused to contact the inner surface of the central corner panel 36, while the outer surface of the central corner panel 36 is caused to contact the outer surface of the other side corner panel 40.The folding of the corner in this manner places the corner panels 40, 38 on respectively the inside and outside of the three-ply composite corner 70 (Figure 4) which is one of four created for the tapering side wall of the container; moreover the folding causes the rounded corner regions 45, 47 of the profiled flange panels 44, 46 to overlap one another in register, with the flange panels 46 uppermost, the extension tab 48 of the flange panel 44 being caused to underlie the adjacent end of the rectangular flange panel 32 and the extension tab 50 of the flange panel 46 being likewise caused to overlie the rectangular flange panel 28. At this time the flange panels are generally coplanar with the side or corner panels 20, 22, 24, 26, 38 or 40 which carry them.The flange panels are thereafter bent down to their required flange-forming positions, and all overlapping surfaces are bonded together by the application of heat and pressure in known manner.

The erected container has a tapering peripheral wall, and when empty is nest able with other such containers for transit and storage. After filling with a food product the container is closed with a plane lid 52 which may be of the same material as the container; in known manner the lid is heat-sealed to the container flange formed by the flange panels (28,30,32,34,44 and 46).

The form of each composite corner 70 of the erected container is apparent from Figure 4. It will be understood from this perspective view that by virtue of the provision of its corners 70 the container approximates more fully to circular form than a container having right-angled corners formed at the intersection of its wall panels, as is depicted in Figure 1. The uniformity of the cooking of the food product in a microwave oven is thereby improved.

A further advantage over the corner arrangement of Figure 1 possessed by the blank of Figure 2 is a reduced tendency to leakage of liquid from the food product. The corner formed from the blank arrangement of Figure 1 has a potential leakage site or "pinhole" in the angle of the corner immediately below the peripheral flange. This pinhole is left where the board material of the blank is removed to form the cut-out 13. In contrast, in the container formed from the blank of Figure 2 all three of the corner panels 36, 38 and 40 occupy substantially the full height of the peripheral wall; moreover, the corner flange panels 44, 46 and their attachment to the adjacent flange panels 32, 28 as described above ensure that the flange, both cer se and in its attachment to the container wall, has a high seal integrity along its length.

As shown in Figure 2, for optimum material utilisation the tab extensions 48, 50 at each corner of the blank are preferably of sufficient length so as together to span the whole width of the corner panel 36. For some applications of the invention, however, it may be desirable to foreshorten one or both of the tab extensions in which case they may be separated by a gap in the blank.

Figure 6 shows an alternative form of corner which can be used to save board. In this corner, one of the corner flanges (designated by the reference numeral 44') is shown reduced in size so that its free outer edge adjacent the neighbouring rectangular flange panel is aligned with the free outer edge of that flange panel. The corresponding free edge of the other corner flange panel may additionally or alternatively be treated in the same way if desired.

Claims (6)

1. A blank for a container, which comprises a substantially rectangular base panel, wall panels attached by fold lines to the base panel, corner panels between and attached by fold lines to the wall panels, the wall and corner panels being adapted to form for the erected container a peripheral wall having faceted corners, the blank further including flange panels adapted to form for the container an outturned flange carried by the said peripheral wall and to which a closure for the container may be attached, wherein for forming each said faceted corner the blank has a central said corner panels and a further said corner panel on each side of the central corner panel, the central and further corner panels being substantially triangular and foldable against one another in pleated relationship to form the corner, the central corner panels having no flange panel attached thereto but the further corner panels having respective corner flange panels formed with mutually inwardly projecting extensions which lie adjacent to, but free of, the central corner panel, for the formation of the said flange the corner flange panels being disposable in partially mutually overlapping relationship, with the extension of the uppermost corner flange panel disposed in overlying relation to a first said flange panel carried by the respectively adjacent wall panel and with the extension fo the lowermost corner flange panel disposed in underlying relation to a second said flange panel carried by the respectively adjacent wall panel.

2. A blank as claimed in claim 1, wherein each corner panel is an isosceles triangle including a vertex angle of 300

3. A blank as claimed in claim 1 or 2 which carries a coating of a fusible plastics material.

4. A blank as claimed in any preceding claim in which each corner flange panel has a curved part to provide a projecting corner region by which the container formed from the blank can be held.

5. A blank substantially as hereinbefore described with reference to or as shown in Figures 2 to 6 of the accompanying drawings.

6. A container manufactured from a blank as claimed in any preceding claim.