Collapsible containers are becoming increasingly common for use in storing papers etc in office environments. Such containers must be rigid and strong for repeated use over a period of years, but, for storage prior to use, are collapsible to reduce the amount of storage space required.

Summary of the Invention It is an object of the present invention to provide a collapsible container, which is strong and rigid in the erected condition but which can be collapsed to a flat condition for storage.

The present invention provides a collapsible container comprising a body member comprising a first pair of opposing side walls and a second pair of opposing side walls, the side walls being pivotally joined to one another, and the body member including a base comprising at least first and second base flaps pivotally connected at the base edges of the first side walls, and at least one flap extending substantially the full distance between the first pair of side walls, and at least one U- shaped reinforcement member with its side arm portions coupled to the side walls of one of the pairs of side walls and its base portion extending across the base, whereby in use to provide reinforcement for the container, but to permit collapse of the container when the base flaps are pivoted away from the base forming position.

Thus, in accordance with the invention a rigid container is provided when the container is erected since the base flaps define the base and are supported and reinforced by the U-shaped member which is coupled to the side walls. However, when it is desired to collapse the container, all that is necessary is for the base flaps to be moved from the base forming position, normally upwardly by pressing from beneath so as to permit the side walls to be folded towards one another, the U- shaped member pivoting with the side walls to permit the folding movement.

As preferred, each base flap extends the full extent across the base so as to provide maximum strength. Whilst the U-shaped member may be coupled to either

pair of side walls, in a preferred configuration where the container is adapted to hold paper, the first side wall will be of a size to hold a predetermined size of paper, say A4, and the second pair of side walls will be considerably narrower to define the amount of paper that can be stored, and in this case, the U-shaped member is coupled to the first side walls and extends across the narrower dimension of the base. As preferred, more than one U-shaped member may be provided, spaced apart from one another.

The body member is preferably formed from a blank of sheet material, for example plastic, cardboard or metal foil. In one preferred construction the sheet material is corrugated plastics (for example polypropylene). With such corrugated material, the U-shaped member, preferably formed of steel wire, can be forced through apertures formed at the lower edge of the side walls, up into the interior of the side walls in the interior corrugations. This provides a particularly simple and strong securing of the U-shaped members, but permits rotation of the wires within the corrugations and thus pivoting of the U-shaped members relative to the base, when the container is collapsed.

Brief Description of the Drawings A preferred embodiment of the invention will now be described with reference to the accompanying drawings wherein:- Figure 1 is a perspective view of an assembled collapsible container according to the invention; Figure 2 is a plan view of the blank of sheet material for forming the container of Figure 1; and Figure 3 is an enlarged fragmentary sectional view of a wire within interior corrugations of the sheet material.

Description of the Preferred Embodiment Referring to the drawings, a rectangular box container 2 is formed from a blank 4 of sheet material comprising approximately 3 mm square channel corrugated

polypropylene board. The container comprises a first pair of opposing side walls 6 measuring 37.5 cm long and 26.5 cm high, and a second pair of opposing side walls 8 measuring 15.5 cm wide by 26.5 cm high. A base 10 is formed from two base flaps 12.

Referring to Figure 2, the base flaps 12 are connected along the lower edges of side walls 6 by fold lines 14, and the side walls 6 are connected along fold lines 16 to side walls 8. A further side wall flap 18 is provided, so that in the assembled box, the side wall flap 18 is welded to the overlapping side wall 8 in order to fix the side walls together. The base flaps 12 are not secured together, but as shown in Figure 1 are folded over, with each flap extending the full width of the base so that the edge of the inner flap abuts against the opposing side wall to provide the box with some rigidity.

Apertures 20 are formed along fold line 14 for receiving a first and second U-shaped steel metal wires 22. Wires 22 have a circular cross-section and the side arm portions 24 extend at right angles to the base portion 26. The steel wires are of approximately 3 mm diameter and are inserted into and friction retained by opposing vertically corrugated channels 32, as schematically illustrated in Figure 3. Thus when the box is collapsed to an approximately flat position or is erected from the flat position, the wires 24 rotate within the channels 32. The U-shaped members 22 are thereby rotated through approximately 90°.

The upper portions of the side walls have handle slots 30 formed therein, and the handle slots together with the upper edge have plastics reinforcing edging strips 32.

To assemble the container, the base flaps are folded to define the base, and the U-shaped members 22 are inserted through slots 20 so that the side arm portions 22 extend fully into the side walls 6. Commonly, the container will be stored prior to its use for holding paper. To enable the container to be collapsed, base flaps 12 are folded upwardly against the inner sides of side walls 6 to permit the side walls to be folded flat against one another. The U-shaped support members pivot within the side walls relative to the base, since the round cross-section of the wires permits

their rotation within the side walls during the flattening operation.

When the container is to be used for storage, the side walls are folded back to a rectangular configuration with the U-shaped members pivoting to a position at right angles to the base, and the base flaps are folded downwardly, with the inner base flap engaging against the opposite side wall and the lower base flap engaging against the base portions 26 of the U-shaped members. There is thus provided a very strong and rigid container, which can hold a large quantity of paper stored in files or loosely and is suitable for robust use over a period of years.