GB2544743B

GB2544743B - Stackable box

Info

Publication number: GB2544743B
Application number: GB1520716.0A
Authority: GB
Inventors: Timpson Simon
Original assignee: TRI-PACK PLASTICS Ltd; TRI PACK PLASTICS Ltd
Current assignee: TRI-PACK PLASTICS Ltd; TRI PACK PLASTICS Ltd
Priority date: 2015-11-24
Filing date: 2015-11-24
Publication date: 2019-06-26
Anticipated expiration: 2035-11-24
Also published as: GB2544743A; GB201520716D0; WO2017089742A1

Description

STACKABLE BOX

Field of the Invention

This invention relates to a stackable box, for example suitable for the transportation of whole fish such as salmon.

Background to the Invention

Whole fish such as salmon are typically transported to market packed in ice in a thermally-insulated box formed from expanded polystyrene or from expanded polystyrene beads. The boxes are intended to be single-use boxes that are disposed of when the fish reach the market. Such boxes are light in weight and relatively cheap to manufacture, but have a number of disadvantages. Firstly, polystyrene is difficult to recycle, both because of the nature of the plastics material and because of contamination by fish protein, which tends to be absorbed into the material, and so the material is of relatively low value; indeed there is typically a cost involved in its disposal after use. Secondly, because the material is relatively brittle, it is readily broken into small fragments, or into the individual beads from which the boxes are formed, thus presenting a pollution hazard during disposal. Thirdly, it is necessary to manufacture the boxes close to the source of the fish, because transporting the empty boxes would be costly. The capital and running costs of the necessary manufacturing plant add to the overall price of the fish.

Since the boxes contain melting ice, they must be capable of retaining strength when wet and, especially when transported by air freight, of resisting leakage of water. These requirements limit the choice of alternative materials that might be more readily recycled.

It has been proposed to use extruded fluted double-walled polypropylene sheet materials to form fish boxes. The sheet material can be cut and creased to form a blank which can be transported to the packing place and then readily assembled into a box for use. After use, the boxes can readily be flattened for transport to a recycling plant, for example in the vehicle that transported the fish. Since the material is smooth and impervious, it can be easily washed before being melted down to produce reusable plastics materials which can, for example be used to produce new sheet materials. The recycling of the boxes is therefore more economically viable than with conventional polystyrene fish boxes.

One problem with the twin-walled fluted polypropylene sheet materials is that they are more easily bent from the plane of the sheet than the corresponding portions of the polystyrene boxes, so that provision has to be made to resist lateral movement of the sides under load. GB2471268A discloses a fish box formed of the double-walled polypropylene sheet materials and provided with positioning tabs engageable with indentations in the next box above when stacked. This required careful stacking to pack the desired number of boxes on a pallet, for example, and the height of stacking could still be limited.

Summary of the Invention

According to the invention, there is provided a stackable box having side walls and end walls upstanding from a base, the length of the side walls being greater than that of the end walls, the box being formed of plastics sheet material cut and creased to provide side walls of double thickness with a portion along the uppermost edge of each side wall configured to provide a hollow triangular cross-section presenting an upwardly-facing horizontal surface, and the end walls are connected to each side wall by a folded web extending between the two thicknesses of the side wall, wherein the two thicknesses of the side wall are secured together by welding in a plurality of locations, and wherein each end wall includes a flap along the upper edge thereof which is folded over on to and welded to the upwardly-facing horizontal surfaces of the side walls.

The sheet material is preferably a twin wall olefin plastics material.

Welding is suitably achieved by the use of an ultrasonic welder to form spot welds.

The portion along the uppermost edge of each side wall suitably occupies no more than a third of the height of the side wall. The portion is preferably formed so as to extend on the inside of the box.

The stackable box of the invention may be stacked, when loaded with fish, up to at least ten high without significant distortion, compared with a maximum of seven or eight for conventional polystyrene boxes of the same general capacity. The boxes are readily recycled after use, and can be assembled be fore use from shaped and pre-creased blanks, for example using a suitable sequential folding and welding machine.

Twin wall plastics sheet conventionally has parallel webs or flutes extending between the walls, thereby providing a fixed air space between the walls. This ensures that the sheets have good thermal insulating properties and high strength for a given weight of material, properties which are especially useful when transporting fish or the like.

Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the invention:

Figure 1 is a perspective view of a flat cut and creased blank for forming the box; and

Figures 2 to 5 illustrate successive stages in shaping the box from the blank.

Detailed Description of the Illustrated Embodiment A sheet of twin-walled fluted polypropylene is cut and creased by pressing the sheet on to a first tool having a predetermined pattern of knives and heated creasing bars upstanding therefrom, thereby forming a box blank 1 as shown in Figure 1. In the Figure, the cut edges are represented by solid lines, while the creases are represented by broken lines. The heated creasing bars serve to provide permanently indented lines along which folds can be formed when the box is erected. It will be appreciated that while heated creasing bars will be suitable for forming creases in plastics sheet material, other materials may require different configurations for forming creases, for example knives to form scored lines in the material.

The blank 1 consists of a rectangular base panel 2 having along two opposed longer edges rectangular side panels 3 and 4 which can be folded up at right angles to the base panel. Each side panel 3 and 4 has along its outer edge a series of three additional rectangular panels 5-7 and 8-10 respectively whose combined extent outwardly of the side panes 3 and 4 is greater than the depth of the side panel. Panels 5 and 8 are each dimensioned to form a narrow ledge along the top edge of the respective side panel 3, 4, while panels 6 and 9 outwardly thereof form diagonally-extending supports, the outermost panels 7 and 10 being of the greatest area of the three and serving to double the thickness of the greater part of each side panel when the box is erected as hereinafter described. It is important for the strength of the box that the flutes in the polypropylene sheet material are oriented in the direction of the arrow in Figure 1 so that the sides of the resultant box offer the greatest resistance to crushing when subjected to a vertical load, thereby permitting the greatest possible stacking height for the boxes in use.

The base panel 2 also has rectangular end panels 11 and 12 along the opposed narrower sides thereof, each end panel being provided with a flap 13 and 14 along the outer edge thereof. Each side panel 3 and 4 is joined to each end panel 11 and 12 through a respective corner panel 15, 16, 17, 18, each of which is of generally square shape with a diagonal reverse crease extending from the corner of the base panel 2 outwardly.

Referring to Figures 2 to 5, the box is erected by first raising the side 3, 4 and end 11,12 panels from the plane of the base 2, causing the corner panels to fold along the diagonal creases so as to move inwardly of the box as illustrated particularly in Figure 3. During further movement of the side and end panels towards the upright position illustrated in Figure 4, the folded corner panels 15-18 are turned to lie flat against the respective side panels. The additional panels 5 and 8 are then folded over so as to extend inwardly of the upper edges of the side panels 3 and 4 and parallel to the base panel 2. The outer additional panels 7 and 10 are brought into contact with the inner face of the respective side panels 3 and 4, sandwiching the corner panels between the two layers. This arrangement ensures that the resulting box cannot leak liquid. Where drainage is desired, it will be necessary to cut drainage holes in the base 2, the sides 3 and 4, or the end panels 11 and 12. A series of welds is formed along each side panel using an ultrasonic welder, to secure the two layers together, thus holding the box in shape. The intermediate additional panels 6 and 9 extend obliquely between the respective panels 5 and 8 and the welded panels 7 and 10 and thus serve to strengthen and support the sides of the box, providing a triangular section reinforcement.

Finally, the flaps 13 and 14 are folded over, as shown in Figure 5, into contact with the additional panels 5 and 8 and welded to them to form a rigid stackable structure.

In use, the box may be provided with a lid to close the box and protect the contents. The lid may be in the form of a simple open box structure of the same material, which fits over the box with side panels extending over the side panels of the box, thereby providing and additional support when the loaded boxes are stacked. However, it may be sufficient to form the lid as a plain rectangle of the polypropylene sheet which is then spot-welded on to the upper rim of the box using an ultrasonic welder.

It will be appreciated that the steps of assembling from a blank could be carried out by a machine, for example employing pneumatically-operated paddles to push the panels into their correct positions and configurations. The preformed blanks can thus be supplied to the fish-packing location for erection and welding to form the boxes. After the fish (or other content) have been delivered to the desired destination and removed from the boxes, the boxes can readily be washed and flattened to be recycled; the cost of returning the flattened boxes to a recycling centre being relatively low (possibly using the otherwise empty vehicles that delivered the fish).

While the invention has been described with reference to plastic sheet material for forming boxes suitable for packing and transporting fish, the boxes may serve a wide range of uses.

Claims

1. A stackable box having side walls and end walls upstanding from a base, the length of the side walls being greater than that of the end walls, the box being formed of a plastics sheet material cut and creased to provide side walls of double thickness with a portion along the uppermost edge of each side wall configured to provide a hollow triangular cross-section presenting an upwardly-facing horizontal surface, and the end walls are connected to each side wall by a folded web extending between the two thicknesses of the side wall, wherein the two thicknesses of the side wall are secured together by welding in a plurality of locations, and wherein each end wall includes a flap along the upper edge thereof which is folded over on to and welded to the upwardly-facing horizontal surfaces of the side walls.

2. A stackable box according to Claim 1, wherein the plastics sheet material is a twin wall olefin plastics sheet material.

3. A stackable box according to Claim 2, wherein the twin wall plastics sheet is arranged with internal webs or flutes between the twin walls extending vertically in the side walls of the box.

4. A stackable box according to any preceding claim, wherein the two thicknesses of the side wall are secured together.

5. A stackable box according to any preceding claim, wherein the portion along the uppermost edge of each side wall occupies no more than a third of the height of the side wall.

6. A stackable box according to any preceding claim, wherein the portion along the uppermost edge of each side wall is formed so as to extend on the inside of the box.