Collapsible bulk containers are known comprising a base, two side walls, two end walls, and optionally, a lid. The walls may be being detachably mounted on the base by means which are separable to allow the containers to be collapsed or dismantled for secure and low cost empty return. Such containers will hereinafter be referred to as"containers of the kind set forth".

According to one aspect of our invention in a bulk container of the kind set forth at least one of the walls comprises at least one panel which slidably co-operates at opposite ends with opposite ends of adjacent walls.

Preferably that wall comprises at least two separate panels which can be withdrawn in sequence by sliding movement relatively away from the base.

Removal of the panels in turn reduces the effective height of the container locally in stages. This facilitates the discharge or unloading of the contents.

This is particularly advantageous when a container is transporting content which tend to compact within the container during transit, such as resilient blocks. Such compacting causes wedging to take place within the container and hinders discharge at a final destination. Removal of the

panels, in turn, allows the load to be released in stages, with discharge taking place in a controlled manner.

Preferably the wall is constructed from three panels which co-operate at adjacent edges. The lower panel may enclose a corresponding side of the base.

Conveniently each side wall is constructed from removable panels, and each end wall comprises a single panel.

In one construction the base is provided with four upstanding corner brackets to receive the lower corners of each of the walls, and the upper corners of the end walls each carry similar corner brackets arranged to co-operate with and receive the upper corners of the side walls, and the corners of a removable lid.

The base may be adapted to accommodate the side walls and the end walls when the container is dismantled.

Where a first one of the panels slidably co-operates with an adjacent panel, the edge of the first panel may be wholly accommodated within an elongate channel provided on the second panel.

Alternatively, the first panel may be provided with one or more lugs which slidably engage the channel.

The channel may include one or more cut-outs in the side of the channel which are adapted to allow movement of the lugs into or out of the channel in a direction substantially orthogonal to the channel when aligned with the cut-outs. The channel may then prevent movement of the panel

by limiting the lugs to sliding along the channel. The cut-outs preferably permit the lugs to be removed from the channel by outward movement of the panel after the panel has been slid upwards relative to the sides. This is especially advantageous where the content of the container may have slumped during transit.

Thus, at least one end of the first panel may be released by sliding the panel away from the base and pulling the panel outwards away from the contents. The panel may then hinge outwards about a pair of four lugs which remain in the channel.

It is preferred that each panel has two lugs spaced apart along an edge that co-operate with correspondingly spaced apart cut-outs on the channel.

This allows the panel to be hinged relative to the container by only engaging either the upper or lowermost lugs in the channel.

Preferably, the cut-outs are located in the channel so that the first panel must be raised slightly from its normal (assembled) position to align the lugs with the cut-outs. Hence, at rest the panel is retained by the sliding engagement of the lugs with the channel. The cut-outs may extend outward from the channel (towards the outside of the container) so that the panel can be removed by outwards movement of the lugs along the cut-outs.

It is preferred that each wall has at least an upper and lower lug or block along each edge to correspond with cut-outs in the channel. However, more than two could be provided to increase strength as appropriate.

The or each cut-out may extend from an open side of the channel towards the base of the channel. A further retaining lip may be provided on the

cut-out which accommodates and retains part of the corresponding block or lug when it is lowered into the assembled position.

In another construction a bracket at each end of a wall is slidably received in a slot in an adjacent face of the adjacent panel.

Conveniently the slot is defined between complementary members secured to the panel.

The lid may comprise a rigid panel.

However, when a container of the kind set forth includes a flexible liner for the transport of particulate, according to another aspect of our invention, the lid is inclined with respect to the base of the container to define a chute through which the particulate can be discharged when the container is tilted.

Such a lid replaces a conventional planar lid for discharge purposes and, in turn, is replaced by the conventional lid for transport and storage.

The chute may be of arcuate outline to define a hopper pouring lid.

The provision of such a lid has the advantage over conventional constructions in which the base is shaped like an inverted pyramid which discharges by means of a diaphragm or tap through the base of the unit.

Such a known construction has several drawbacks as follows: a) Space taken up at the back of the container means that a tall unit must be used precluding double stacking. In addition the centre of gravity is high leading to instability.

b) If the product is contained with a liner it is often difficult to breach the liner to effect a discharge and even as the product flows out of the liner can result into the product eventually blocking the outlet; and c) the common problem of"ratholing"and blockages requires agitation of the container to achieve a continuous flow.

Replacing a conventional planar lid for discharge purposes with the inclined lid has the advantage that only a minimum number of inclined lids are required and remain on the site where they are to be used.

The container can therefore be smaller and more compact than traditional hopper based units which allows for better utilisation of transport.

Moreover such containers can be used for a wider range of products, not just particulate.

Preferably, one or more of the base, the side walls, the end walls and the lid comprise a metallic frame structure encapsulated within a plastic material.

This constructions is advantageous as the metal frame provides support to the plastic material yet since it is encapsulated in the plastic material individual portions of the frame do not need to be welded together. The finished product may have no visible parts of the metal frame making it more hygienic.

The metal frame may comprise one or more strips or bars of suitable metal, such as steel, which may optionally be fastened together prior to encapsulation with plastic material. Otherwise, they may simply be laid out in the required configuration prior to encapsulation.

It is most preferred that all of the base, the side walls and the end walls are constructed as a metal frame encapsulated by plastic.

The metal bars or strips may be provided towards the perimeter of the base, walls and/or end panels.

The frame may be encapsulated by a plastic moulding process.

One embodiment of our invention and a modification are illustrated in the accompanying drawings in which:- Figure 1 is an exploded perspective view of a collapsible bulk container; Figure 2 is an exploded layout of the components illustrated in Figure 1; Figure 3 is a view on an enlarged scale showing the co-operation between an end wall and the base; Figure 4 shows the co-operation between the lid and a side end wall; Figure 5 is a side elevation of the container provided with a modified lid; Figure 6 is an end view of the lid; Figure 7 is a partial view of an end panel and side panel which engage through lugs locating in a channel;

Figure 8 is a plan of a corner of the container showing a sliding engagement between ends of adjacent panels.

The collapsible bulk container 10 illustrated in the accompanying drawings comprises a base 1 of rectangular outline provided at the upper end of each of its corners with an upstanding L-shaped bracket 2, a pair of opposed side walls 3 and 4, and a pair of opposed end walls 5 and 6 all upstanding from the base. L-shaped brackets 7 similar to the brackets 2 are upstanding from the sides of the end walls 5 and 6 and are arranged to receive a removable lid 9.

All the walls 3-6 and the lid 9 are removable to dismantle the container.

The side walls 3 and 4 each comprise three lower, middle, and upper panels 10,11 and 12, respectively. Each of these panels, each end wall 5 and the lid 9, are constructed from square hollow metal tube welded together to form a rectangular rim which is reinforced by cross braces.

In use the container is assembled by inserting the end wall 5 and 6 into the brackets 2 on the base 1 and then sliding the middle panel 11 and the side panel 10 into the bracket in opposite directions. Finally the upper panel 12 is slid between the brackets 7 until it abuts against the upper face of the panel 11. The assembly is then completed by fitting the lid 9 between the brackets 7.

Lugs 15,16 extending upwardly from the upper panels 12 and the end walls 5 and 6 co-operate with the edges of the lid 9. Similarly lugs 17 and 18 on end walls 5 and 6 co-operate with, and receive, steel tongues 20, see Figure 3.

The brackets 7 may be provided with notches 21 to receive a projection 22 on the lid 9 in order to prevent the side walls 3 and 4 and the end walls 5 and 6 from bursting.

In use the container is assembled as described above without the lid 9. It is then stacked or filled with components or a liner is filled with liquid or particulate. The lid 9 is then placed in position to complete the assembly and hold the container rigid.

Upon reaching the destination the lid 9 is first removed. If the container is carrying blocks which tend to compact within the container during transit, upper panel 12 for each side wall 3 and 4 is removed by withdrawing it from the end walls. This facilitates the removal of the blocks. Thereafter the middle panels 3 can be removed in a similar manner so that the remainder of the block can be released from the container. Finally the end walls are removed from the base and can be stacked on the base to facilitate storage.

Each of the side walls 3,4, end walls 5 and 6, and the lid 9 are provided with steel fittings and may be panelled in plastics, steel, aluminium sheet or other suitable sheet materials.

When the container is being used with the liner to transport particulate or liquids and when it is desired to empty the container at its destination, the conventional lid 9 may be replaced by a modified lid 25 illustrated in Figures 5 and 6 of the drawings. As illustrated the lid is inclined with respect to the plane of the base and is of arcuate cross-section to define an open mouth 27. Tilting the container in the direction of the mouth 27 by the use of a lift truck enables the contents to pour from the container with the lid 25 acting as a chute.

The lid 25 can be attached to the container by a series of clamps 28.

After the container has been emptied it can then be dismantled as described above with the lid 25 removed and replaced by the conventional lid 9 for transit purposes.

In place of the L-shaped brackets 7 which restrain the panels, continuous channels could be provided along the edge of one panel which receive a corresponding edge of an adjacent panel. For instance, the edges of the side panels 5,6 may include a C-section elongate channel into which the tubular box section of the end panels is slidably received.

The L-shaped brackets may, of course, still be retained in order to hold the end panels and/or side panels in place relative to both the base and/or the lid during assembly.

A modification to the container is shown in Figure 7 of the accompanying drawings. This figure is a partial view of one side channel and a corresponding edge portion of a side wall 3,4.

Whilst in the embodiment of Figures 1 to 6 the side walls slidably engage the channel by inserting the whole edge of the wall into a channel, in the modification each side edge of the end walls (10,11,12) are provided with two lugs or blocks 20,21 which engage the channel. The outermost edge 31 of the channel 30 is provided with cut-outs 32,33 that allow the walls to engage the channel or be removed from the channel when the blocks align with the cut-outs. When the panel is slid with the blocks in the channel to a position in which they are not aligned with the cut-outs then it is prevented from either inward or outward movement.

In practice, the cut-outs in the channel wall are positioned such that the walls must be pushed into the channels whilst being held slightly above (say one inch) their nominal position when in use. After inserting the blocks, 20,21 through the cut-outs into the channel the wall is then allowed to drop down into its nominal position where it is restrained.

To remove the wall it is necessary to first lift it slightly until the blocks 20,21 align with the cut-outs 32,33. It can then be lifted outwards unto the blocks clear the channel. Alternatively, and if preferred, only the uppermost blocks may be cleared of the channel whereafter the wall can be hinged down away from the channel. To dismantle the container, the panel then must be raised slightly to align the lugs with the cut-outs. This is advantageous when compared to having an entire edge of the panel co- operating with the channel (or lugs but without the channel cut-outs) as it means the panel need not be slid as far for removal.

To allow removal of the panel in a simple outward movement the cut-outs should be provided on the outer face of the channel with the open side of the channel facing along the plane of the panel when in place.

In a further modification, the channels are defined by corner posts which are separate from the panels. They may be mounted relative the base prior to installing the panels. Of course, it is preferred that the channels form an integral part of the panels as this eases assembly.

A modified cut-out is shown in Figure 7 (b) for co-operation with an L- shaped block as shown in Figure 7 (c) comprising a block with a small protruding lug.

In this arrangement, the block 20 extends horizontally from the panel to enter the side panel channel. The small lug 20a, which is welded to the side (outermost) of the block 20 is arranged so as to engage a cut-out part of the side wall of the channel when the panel is lowered into its assembled position. This lug co-operates with the L-shaped cut-out to resist outwardly directed forces acting on the end walls. To remove, the panel is lifted freeing the lug from the cut out. The whole panel is then removed freeing the block from the channel. Figure 7 (d) shows the lug locked in place.

It will of course, be readily appreciated that the channel may have different cross-sections from the simple C-shaped channel shown. This will depend on the direction of loading and forces that will be applied to the container in use. A simple C-shaped channel as shown requires the lid and base to remain (at least partially) in place as the end panels are removed to stop the side panels falling outwards. In this case, a sliding portion may be provided in the lid which can be removed to allow the sliding side panels to be raised for release.

In the modified construction illustrated in Figure 8 of the drawings the end walls 5 and 6 are each provided at opposite ends with a vertical slot 40 defined between the internal faces of a right-angle member 41 and a right-angle bracket 42.

The angle member 41 comprises flanges 43 and 44 which are normal to each other. The angle member 41 extends also from the top to the bottom of the respective wall 5 and is notched into the horizontal members of the wall 5, so that the flange 44 is normal to the face of the panel 5.

The bracket 42 comprises flanges 45 and 46 at right-angles to each other.

The flange 45 is secured to the free end of the wall 5 with the flange 46 spaced from and parallel to the wall 5 and with its free end spaced from the flange 44 of the member 41.

Opposite ends of each panel 10,11, and 12 are each provided with a hook-shaped bracket 48 slidably received in the slots 40 to assemble the container as described above.

The internal faces of the walls 5,6 and each panel 10,11,12 are lined with a plastics sheet 50 and 51 respectively. Preferably the sheet 51 is of a similar thickness of that of the flange 44 of the member 41.

Alternatively, the walls and each panel may be constructed as a metallic frame encapsulated by a plastic material. The finished panel or wall appears as a solid plastic panel whilst the metal frame provides reinforcement.