EP1560759A1

EP1560759A1 - Collapsible container

Info

Publication number: EP1560759A1
Application number: EP03758347A
Authority: EP
Inventors: Robert Edward Fowler
Original assignee: Corrugated Design Ltd
Current assignee: Corrugated Design Ltd
Priority date: 2002-10-22
Filing date: 2003-10-22
Publication date: 2005-08-10
Also published as: AU2003274363A1; WO2004037659A1

Abstract

A blank (10) for assembly into a container comprises first (12), second (14), third (16) and fourth (18) wall panels arranged in series along a principal axis (A) of the blank, a first base panel (30) adjoining the first wall panel (12) along a first transition line (32) extending substantially parallel to the principal axis, a first wall reinforcing panel (36) adjoining the first base panel (30) along a second transition line (34) extending in a direction substantially transverse to the principal axis, a second base panel (40) adjoining the third wall panel (16) along a third transition line (42) extending substantially parallel to the principal axis, and a second wall reinforcing panel (46) adjoining the second base panel (40) along a fourth transition line (44) extending in a direction substantially transverse to the principal axis. At least one of the first (30) and second (40) base panels has a further transition line (64, 72) extending at a diagonal to the principal axis. At least one of the first (30) and second (40) base panels covers substantially the entire area of the base of the container when assembled. The first (30) and second (40) base panels are provided with complementary engagement means (60, 70) which are capable of engaging on the application of external pressure only on assembly of the blank into a container. This avoids the need for the end user to reach inside the container and manipulate the engagement means to enable them to interlock.

Description

COLLAPSIBLE CONTAINER

Field of the Invention

This invention relates to a container. It further relates to a blank for assembly into a container and a partially assembled blank ready for erection into a container.

Description of the Prior Art

Containers, such as boxes, assembled from pre-cut blanks are known in the art. Typically, the blanks for such containers comprise a plurality of panels which may be folded and interlocked together to assemble the container. The blank is usually made of corrugated fibreboard, cardboard or the like.

One such blank known in the art is that disclosed in GB 792261. The blank comprises first, second, third and fourth wall panels arranged in series along a principal axis of the blank (the principal axis defining the width and breadth of the container when assembled), a first base panel adjoining the first wall panel along a first transition line extending substantially parallel to the principal axis, a first wall reinforcing panel adjoining the first base panel along a second transition line extending in a direction substantially transverse to the principal axis, a second base panel adjoining the third wall panel along a third transition line extending substantially parallel to the principal axis, and a second wall reinforcing panel adjoining the second base panel along a fourth transition line extending in a direction substantially transverse to the principal axis. A diagonal fold line is provided on each base panel, the diagonal line running from the inner corner of the cut-away portion of each base panels (described below) to the corner of each base panel where it meets the adjoining wall panel and wall reinforcement panel. This allows the container to be folded substantially flat when partially assembled (when the first and fourth wall panels are attached together to provide an endless series of walls and the wall reinforcement panels are attached to overlie the corresponding wall panels).

A portion of each of the base panels is cut away in identical fashion such that approximately 60% of the area of each base panel remains. The cuts extend in the axial direction from the edge of the base panel furthest from the transition line where it meets the wall reinforcing panel approximately 70% of the distance towards said transition line. At this point the cuts change direction to an angle substantially transverse to the axial direction, leading to a point where, on assembly of the blank into a container, meet at the centre point of the base. The cuts then extend diagonally, at an angle substantially transverse to the diagonal fold line, to the corner of the base panel furthest from the wall panel where it meets the wall reinforcing panel.

On assembly of the blank disclosed in GB 792261 into a container, the first and fourth wall portions are attached together by gluing, stapling or another appropriate method known in the art. After this, the partially assembled container is folded outwards such that the two base panels unfold and the corners of the cut-away portions slide past each other and interlock.

However, a number of problems exist with the container disclosed in GB 792261. Firstly, the manner in which the cut-away portions of the base panels interlock makes the container difficult to re-fold to put away after use. Secondly, neither of the two base panels occupy the entire area of the container once assembled - each base panel only covers a part of the area. This makes the base of the finished container weak and can cause it to give way when containing a heavy internal load.

An embodiment of the blank disclosed in GB 792261 may have a base panel extending across substantially the full width (although not the full length) of the container once assembled. However, problems are encountered with such a blank in that it is difficult to assemble such a blank into a container while allowing such base panels to avoid one another during the assembly process. Therefore, such a blank is only suitable for manufacture from flexible material: a blank made from more rigid material, such as corrugated fibreboard or cardboard, would be damaged during assembly into a container by the need to partially fold back the base panel during assembly. This would also weaken the base of the finished container and make it unsuitable for bearing heavy internal loads.

GB-A-2350602 discloses an attempt to alleviate the above problems. This document discloses a blank for assembly into a container, the blank comprising first, second, third and fourth wall panels arranged in series along a principal axis of the blank (as defined above), a first base panel adjoining the first wall panel along a first transition line extending substantially parallel to the principal axis, a first wall reinforcing panel adjoining the first base panel along a second transition line extending in a direction substantially transverse to the principal axis, a second base panel adjoining the third wall panel along a third transition line extending substantially parallel to the principal axis, a second wall reinforcing panel adjoining the second base panel along a fourth transition line extending in a direction substantially transverse to the principal axis. Both base panels occupy substantially the entire area of the base of the container once assembled. Both base panels are additionally provided with diagonal fold lines of a broadly similar construction to those of the blank of GB 792261 (although extending substantially across the entire diagonal of the base panels) which also allow the container to be folded substantially flat when partially assembled.

To enable the container to be assembled, the base panels of the blank of GB-A-2350602 are also provided with flaps, typically triangular in shape, which are capable of interacting with one another on assembly of the blank into a container. This allows the first and second base panels to overlap with one another to form a reinforced base panel having a double base layer across much of the area of the base.

The blank of GB-A-2350602 addresses some of the problems of GB 792261 by providing a finished container having a double base layer, thus strengthening the container and allowing it to carry heavier internal loads without the risk of the base giving way. However, assembly of the container disclosed in this document is difficult, as interlocking of the two flaps on the base panels requires the end user to reach inside the container and manipulate the flaps to enable interlocking. This is frequently inconvenient for the end user and, for containers of larger dimension, may not be possible.

In addition, once the container of GB-A-2350602 is interlocked, it is difficult to disengage the two base flaps to allow the container to be refolded after use without actually folding back the flaps themselves. This is inadvisable as it leads to weakening of the base.

US patents 5887782, 6135347 and 6149052, all to Charles J. Mueller, disclose containers formed from blanks of similar construction. The base panels of the Mueller blanks also occupy substantially the entire area of the base of the container when assembled, thereby providing the extra reinforcing effect of a double base layer. The Mueller blanks principally differ from those described above in that the first base panel lacks any diagonal fold lines and the second base panel has two converging fold lines. On unfolding the flat, partially assembled Mueller container, the second base panel flattens along the two fold lines to form the bottom of the container, and the first base panel overlies this. However, the same problems are encountered with the Mueller containers as with those disclosed in GB-A- 2350602, namely the need for the end user to reach inside the container to assemble it and the difficulty in refolding the container after use without weakening it.

Summary of the Invention

It is an objective of the present invention to provide a blank capable of straightforward assembly into a container. In particular, it is an objective of the present invention to provide a blank possessing engagement means on the base panels capable of being engaged with minimal manual effort as the partially assembled container is opened.

It is a further objective of the present invention to provide a container formable from a blank, the base of the container being of sufficient strength such that it is capable of fully supporting substantial internal loads without giving way.

In addition, it is an objective of the present invention to provide a blank capable of being easily assembled into a container, and a container capable of being easily refolded to its former substantially flat state after use, without weakening or damaging the container.

With these objectives in mind, there is provided according to a first aspect of the present invention a blank for assembly into a container, the blank comprising: first, second, third and fourth wall panels arranged in series along a principal axis of the blank, a first base panel adjoining the first wall panel along a first transition line extending substantially parallel to the principal axis, a first wall reinforcing panel adjoining the first base panel along a second transition line extending in a direction substantially transverse to the principal axis, a second base panel adjoining the third wall panel along a third transition line extending substantially parallel to the principal axis, a second wall reinforcing panel adjoining the second base panel along a fourth transition line extending in a direction substantially transverse to the principal axis, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the principal axis, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, the first and second base panels having complementary engagement means which are capable of engaging on the application of external pressure only on assembly of the blank into a container.

There is also provided according to a second aspect of the present invention a partially assembled container comprising: first, second, third and fourth wall panels arranged in series, the first and fourth wall panels being attached to form an endless series of wall panels, a first base panel adjoining the first wall panel along a first transition line and adjoining a first wall reinforcing panel along a second transition line, the first wall reinforcing panel being attached to the second wall panel, a second base panel adjoining the third wall panel along a third transition line, the second base panel adjoining a second wall reinforcing panel along a fourth transition line, the second wall reinforcing panel being attached to the fourth wall panel, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the axes of the base panel, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, the first and second base panels having complementary engagement means which are capable of engaging on the application of external pressure only when the partially assembled container is assembled from a state where the panels lie substantially flat to an assembled state where the wall panels are substantially perpendicular to the base panels.

There is further provided according to a third aspect of the present invention a container comprising: first, second, third and fourth wall panels arranged in series, the first and fourth wall panels being attached to form an endless series of wall panels, a first base panel adjoining the first wall panel along a first transition line and adjoining a first wall reinforcing panel along a second transition line, the first wall reinforcing panel being attached to the second wall panel, a second base panel adjoining the third wall panel along a third transition line, the second base panel adjoining a second wall reinforcing panel along a fourth transition line, the second wall reinforcing panel being attached to the fourth wall panel, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the axes of the base panel, the first and second base panels having complementary engagement means which are engaged by the application of external pressure only on assembly of the container.

Detailed Description of Preferred Embodiments

The blank of the present invention may typically be formed from sheet material. Typical examples of such sheet material include cardboard and fibreboard (which may have a corrugated cross-section to provide improved strength and rigidity to the assembled container), plastics, wood or metal.

The blank may advantageously be formed from a sheet of the desired material by any suitable means known in the art, such as stamping or cutting. Suitably, the blank may be manufactured by die-cutting. As is known in the art, this method involves bending and folding lengths of a cutting blade, typically a metal knife to the required shape and then housing in a suitable shell, typically made from plywood or metal. This is applied to the sheet of material under pressure to cut the sheet to the required shape. This method is particularly suitable for manufacturing large quantities of blanks. Smaller quantities could be cut by hand, using a scalpel or craft knife.

The base panels, wall panels and wall reinforcement panels adjoin one another along transition lines, by which is meant the lines forming the transition between the respective panels. Such transition lines are also present at diagonals of one or more of the base panels, as described in more detail below. The transition lines are preferably fold lines, ie pre-formed crease lines impressed on the blank. These fold lines form lines of weakness about which the respective panels can hinge so as to allow the blank to fold into a container. This allows a degree of flexibility to be introduced into the blank, which is particularly advantageous when the blank is made from a substantially rigid material such as fibre board or corrugated cardboard. However, the transition lines may be formed by other ways readily apparent to those skilled in the art, such as by the use of perforations.

When the blank is formed by die-cutting as described above, the fold lines may be impressed on the blank at the same time as the blank is die-cut, by the inclusion of blunt cutting blades at the appropriate locations in the die. When the blank is pre-assembled into a partially assembled container, the blank is folded along the transition lines, as described in more detail below, such that the first and fourth wall panels adjoin one another and are preferably attached together. The first wall reinforcement panel is then attached to the second wall panel. Similarly, the second wall reinforcement panel is then attached to the fourth wall panel.

In the partially and fully assembled containers of the present invention, the panels may be attached together by any suitable means known in the art, such as stapling or stitching (the staples or stitches being formed from any suitable material, such as metal or plastic), preformed clips, rivets or ties, suitably formed folding tabs or other locking mechanism (which may advantageously be die-cut directly into the material of the blank during manufacture), or the use of an adhesive (which may take any suitable form, such as glue, adhesive pads or tape). Preferably, the panels are attached together by glueing, as this enables the containers to be mass produced most efficiently and economically. The appropriate panels may be glued together by a suitable machine which automatically folds and glues the blank to assemble it into a partially assembled container. The nature of such machines is readily known to those skilled in the art. Examples of suitable glueing machines include the "NC80 Folder Gluer" multi-point gluing machine available from J&L Industries Inc, Keithville, Louisiana, USA, and the "Tanabe 2200", a product of Tanabe Company, Japan, available via Andrew and Suter Ltd., Hertfordshire, UK.

The blank of the present invention may preferably be provided with means to facilitate attachment of the panels during partial assembly, particularly means for facilitating attachment of the fourth wall panel to the first wall panel (especially by glueing). In one embodiment, the fourth wall panel may have an edge flap adjoined thereto along a further transition line to facilitate attachment to the first wall panel. In another embodiment, the first wall panel may have an edge flap adjoined thereto along a further transition line to facilitate attachment to the fourth wall panel. In this embodiment, the second wall reinforcing panel may additionally be provided with a cut-away section on the side remote from the wall panels, in order to avoid accidental glueing of the edge flap to the second wall reinforcing panel. In a yet further embodiment, the first base panel may be provided with a cut-away section at the corner where it meets the first wall panel, opposite to the side where it meets the first wall reinforcing panel. Such a cut-away section may take the shape of a right- angled isosceles triangle, such that the shape of the base panel is defined by two parallel edges. Alternatively, the cut-away section may take the shape of a thin isosceles or scalene triangle (ie where the length of two of the sides greatly exceeds that of the third), such that the shape of the base panel is defined by two edges, the first edge subtending a greater angle to the first transition line than the second edge.

In the blank and partially and fully assembled containers of the present invention, the first and second base panels are provided with complementary engagement means which are capable of engaging on the application of external pressure only on assembly of the blank into a container. This conveys a considerable advantage over the prior art, particularly GB- A-2350602 and the Mueller patents, in that the blank may be assembled into a container much more easily than the blanks disclosed in these documents, as the engagement means on the base panels enable assembly with the bare minimum of manual effort, without the need to reach inside the container to guide the engagement means into place.

It is preferred that the complementary engagement means comprises one or more tongues or tabs present on one of the base panels (preferably the first base panel) arranged for engagement with one or more complementary slots, cut-away portions or the like on the other base panel (preferably the second base panel). This type of engagement means is particularly advantageous in that, when the flat, partially assembled container is opened out by the application of external pressure, the tongue may automatically feed into the complementary slot without the need for manual guidance from within the container.

Typically, a single tongue on the first base panel is arranged for engagement with a single complementary slot on the second base panel. However, the engagement means may comprise a plurality of tongues (preferably two) on the first base panel arranged for engagement with the same number of complementary slots on the second base panel. Such an arrangement is advantageous when the length of the assembled container greatly exceeds its width, when the presence of one long slot may weaken the base.

In the blank and container of the present invention including the tongue/slot engagement means described above, the tongue-bearing base panel (including the tongue) typically occupies at least 50%, preferably 50% to 70%, more preferably 50% to 60%, and still more preferably 50% to 55%, of the base area of the container once assembled. The area of the tongue-bearing base panel (without the tongue) may be at least 50%) of the base area of the container once assembled. The area of the tongue may vary depending on factors such as the material and dimensions of the container to be assembled, and is typically up to 20%), preferably up to 10%, more preferably up to 5%, of the base area of the container once assembled. In one embodiment, the boundary line between the tongue and the remainder of the base panel bearing it may be substantially parallel to the principal axis of the blank. Suitably, the boundary may be about halfway along the width of the tongue-bearing base panel. When the base panel bears one tongue, the transverse axis of the tongue (an imaginary line dividing the tongue in two in a direction transverse to the principal axis of the blank), may preferably be located about halfway along, preferably 45% to 55% along, the length of the base panel. When the base panel bears two tongues, the transverse axes of the tongues may preferably be located at about 30% to 70%, preferably 25% to 35% and 65% to 75%, along the length of the base panel. In these embodiments, the principal axis of the slots is also substantially parallel to the principal axis of the blank. The skilled reader will therefore appreciate that, on erection of the partially assembled blank into a container, the tongue will move diagonally towards the slot to engage therewith.

In another embodiment, the boundary line between the tongue or tongues and the remainder of the base panel bearing the tongue or tongues may be substantially parallel to the free edge of the base panel (ie that edge bearing the tongue, which does not adjoin the wall panel and the wall reinforcing panel). In this embodiment, the boundary line is, of course, at an angle to the principal axis of the blank, and the principal axis of the complementary slot or slots is also at an angle to the principal axis of the blank. This embodiment is particularly advantageous when the base panels approximate to a square shape, as this alleviates the problem caused in this case by the lack of material available to form the tongue. The skilled reader will therefore appreciate that, on erection of the partially assembled blank into a container, the tongue will move directly towards the slot to engage therewith.

In the above embodiment, when the base panel bears one tongue, the transverse axis of the tongue may preferably be located about 55% to 70%) of the way along, preferably 60% to 65% of the way along, the edge of the base panel. In this embodiment, the edge of the base panel (other than the tongue) runs directly from the corner where it meets the respective wall panel to the corner remote from the wall panel where the base panel meets the wall reinforcing panel. When the base panel bears two tongues, the transverse axis of the first tongue may preferably be located about 20% to 40% of the way along, preferably 25% to 35%) of the way along, the edge of the base panel, and the transverse axis of the first tongue may preferably be located about 60% to 80% of the way along, preferably 65% to 75%) of the way along, the edge of the base panel. In this embodiment, the edge of the base panel (other than the tongue) runs from the corner where it meets the respective wall panel to the end of the boundary line with the first tongue, continues in a direction substantially parallel to the principal axis of the blank up to the beginning of the boundary line with the second tongue, and then continues to the corner remote from the wall panel where the base panel meets the wall reinforcing panel.

However, the skilled reader will appreciate that the location of the tongues and slots may vary depending on factors such as the load to be borne by the container and the type and thickness of the material from which it is assembled.

The one or more tongues may preferably be substantially trapezoidal in shape. However, tongues of other shapes, such as a polygon (for example, a triangle, a rhombus, a rectangle, or a pentagon or higher polygon) or a segment, are also encompassed within the scope of this invention. The shapes described above for the tongue exclude any partial cutaway portions or cut-off corners, such as those which may be cut off in order to provide a locking means. Furthermore, the corners of the tongue may be rounded.

In the embodiment where the boundary line between the tongue and the base panel bearing it is substantially parallel to the principal axis of the blank, the tongue is preferably trapezoidal, the long edges of the trapezoid being parallel. In the embodiment where the boundary line between the tongue and the base panel bearing it is substantially parallel to the edge of the base panel, the tongue is preferably trapezoidal, the short edges of the trapezoid being parallel.

In the blank and container of the present invention, one or more of the base panels may advantageously be provided with locking means. Such locking means may secure the engagement means of the base panel in place on assembly of the blank into a container, thereby preventing unintentional re-folding of the container. In the embodiment wherein the engagement means comprises a tongue / slot means and the boundary line between the tongue and the base panel bearing it is substantially parallel to the principal axis of the blank, the locking means may take the form of an edge on one side of the tongue, the edge being substantially transverse to the principal axis of the blank. This allows the tongue to locate easily in the slot, but then "wedges" against the slot end and resists unintentional refolding of the container. In this embodiment, the edge is preferably located on the side of the tongue closer to the transition line between the base panel and the wall reinforcing panel to which it is attached. In the embodiment wherein the engagement means comprises a tongue / slot means and the boundary line between the tongue and the base panel bearing it is substantially parallel to the edge of the base panel, the locking means may take the form of a rounded edge on one side of the tongue, the edge being substantially transverse to the edge of the base panel. In this embodiment, friction between the tongue and the slot may be sufficient to maintain the container in an erect state.

Alternatively, the slot may taper towards one or both of its ends to aid retention of the tongue. The tongue may include further engagement means, such as projections or recesses, which engage complementary engagement means on the slot to further aid retention of the tongue.

In the blank and partially and fully assembled containers of the present invention, the first and second base panels have, in addition to the transition lines dividing the various panels forming the blank, at least one transition line extending at a diagonal to the principal axis of the blank (ie at a diagonal to that axis defining the width and breadth of the container when assembled). As is known in the art, this diagonal transition line allows the partially assembled container to be folded into a flat state with wall reinforcement panels attached to the corresponding wall panels. In preferred embodiments, each base panel is provided with a diagonal transition line extending from the corner of the blank where the base panel meets its adjoining wall panel and wall reinforcement panel (in the case of the first base panel, at the junction of the first and second transition lines; in the case of the second base panel, at the junction of the third and fourth transition lines) at least to a position bordering the engagement means.

When the engagement means comprises the tongue / slot means described above, the diagonal transition line on the tongue-bearing base panel (preferably the first base panel) may extend from the junction of the appropriate transition lines to the edge of the tongue. Similarly, the diagonal transition line on the slot-bearing base panel (preferably the second base panel) may extend from the junction of the appropriate transition lines, past the edge of the slot, across the entire width of the base panel to its edge.

In the assembled container of the present invention, at least one of the first and second base panels covers substantially the entire area of the base of the container. This strengthens the container and allows it to carry heavier internal loads than those of the prior art (particularly that of GB 792261 ) without the risk of the base giving way. When the engagement means comprises the tongue / slot means described above, the second base panel covers substantially the entire area of the base of the container, the first base flap having some cut-away sections including the tongue.

One or both of the base panels may advantageously include a small cut-away section. This facilitates re-folding of the container after use into the partially assembled state where the panels lie substantially flat. When the engagement means comprises the tongue / slot means described above, the cut-away section may be present on the second base panel. The cut-away section may suitably face the first wall reinforcing panel. Alternatively, the cutaway section may be present on the edge of the second base panel opposite to the third transition line. The cut-away section is usually small enough only for a human finger to pull up the base panel of which it forms part: this, even when it is present on the second base panel, it does not remove sufficient area from said panel to affect the load bearing capacity of the assembled container.

The first wall reinforcing panel is preferably separated from the second wall panel by a first cut-away portion. Similarly, the second wall reinforcing panel is preferably separated from the fourth wall panel by a first cut-away portion. This prevents bunching of the wall reinforcing panel with the wall panels when the blank is folded to form the partially assembled container. The cut-away portion is removed prior to partial assembly of the blank into the partially assembled container. Suitably, the portion is cut away when the blank is prepared from a sheet of material. Alternatively, the cut-away portion may comprise a detachable portion retained on the blank, the portion being removed before partial assembly of the blank into the partially assembled container.

The first wall reinforcing panel is preferably attached to the remainder of the blank solely along the second transition line. Similarly, the second wall reinforcing panel is preferably attached to the remainder of the blank solely along the second transition line.

The container of the present invention may be further provided with a closure. The nature of such closures is well known to those skilled in the art and is not the subject of this invention. The closure may form part of the blank (typically an additional panel or panels adjoining one of the wall panels), such as that disclosed in GB 792261. Alternatively, the container of the present invention may be provided with a separate closure. The invention will now be described in detail by way of example with reference to the accompanying drawings, in which:

Fig. 1 illustrates a blank according to a first embodiment of the invention;

Fig. 2 illustrates a blank according to a second embodiment of the invention, with the edge flap in an alternative position;

Fig. 2a illustrates an alternative wall reinforcing panel for the embodiment of Fig. 2;

Fig. 3 illustrates a blank according to a third embodiment of the invention, wherein the first base panel has a cut-away section;

Fig. 3a illustrates an alternative cut-away section for the first base panel of the embodiment of Fig. 3;

Fig. 4 illustrates a blank according to a fourth embodiment of the invention, provided with two tongues and two complementary slots;

Fig. 5 illustrates a blank according to a fifth embodiment of the invention, with the edge flap in the same position as that of Fig. 2;

Fig. 5a illustrates an alternative wall reinforcing panel for the embodiment of Fig. 5;

Fig. 6 illustrates a blank according to a sixth embodiment of the invention, having a similar cut-away section to that of Fig. 3;

Fig. 6a illustrates an alternative cut-away section for the first base panel of the embodiment of Fig. 6;

Fig. 7 illustrates a blank according to a seventh embodiment of the invention, wherein the tongue is positioned at an angle to the principal axis of the blank;

Fig. 8 illustrates a blank according to an eighth embodiment of the invention, with the edge flap in an alternative position;

Fig. 8a illustrates an alternative wall reinforcing panel for the embodiment of Fig. 8;

Fig. 9 illustrates a blank according to a ninth embodiment of the invention, wherein the first base panel has a cut-away section;

Fig. 9a illustrates an alternative cut-away section for the first base panel of the embodiment of Fig. 9;

Fig. 10 illustrates a blank according to a tenth embodiment of the invention, provided with two tongues and two complementary slots;

Fig. 11 illustrates a blank according to an eleventh embodiment of the invention, with the edge flap in the same position as that of Fig. 8;

Fig. 11a illustrates an alternative wall reinforcing panel for the embodiment of Fig. 11 ;

Fig. 12 illustrates a blank according to a sixth embodiment of the invention, having a similar cut-away section to that of Fig. 9; Fig. 12a illustrates an alternative cut-away section for the first base panel of the embodiment of Fig. 12;

Figs. 13a to 13h illustrate how a partially assembled container formed from the blank of Fig.

1 is opened to assemble the container;

Figs. 14a to 14d illustrate how a partially assembled container formed from the blank of Fig.

10 is opened to assemble the container; and

Figs. 15a to 15d illustrate how a partially assembled container formed from the blank of Fig.

7 is opened to assemble the container.

With reference to Fig. 1 , a blank 10 according to a first embodiment of the present invention comprises first 12, second 14, third 16 and fourth 18 wall panels arranged in series along a principal axis A of the blank. The four wall panels 12, 14, 16, 18 are rectangular in shape, with the length of the edge of each wall panel along direction A defining the width and breadth of the assembled container. The height of each wall panel in the direction transverse to axis A defines the height of the assembled container. The fourth wall panel 18 has attached at one end an edge flap 20 to facilitate attachment to the first wall panel during assembly. A number of fold lines are illustrated by dashed lines in Fig. 1 , the fold lines being suitably provided by impression with a blunt cutting edge during cutting of the blank. Fold lines 22, 24, 26, 28, extending in a transverse direction to axis A, define the areas of each wall panel and the edge flap.

A first base panel 30 adjoins the first wall panel 12 along fold line 32 which extends in a direction substantially parallel to axis A. A first wall reinforcing panel 36 adjoins the first base panel 32 along fold line 34 which extends in a direction substantially transverse to axis A. The first wall reinforcing panel 36 is separated from the second wall panel 14 by means of cut-away portion 48.

Similarly, a second base panel 40 adjoins the third wall panel 16 along fold line 42 which extends in a direction substantially parallel to axis A. A second wall reinforcing panel 46 adjoins the second base panel 40 along fold line 44, which extends in a direction substantially transverse to axis A. The second wall reinforcing panel 46 is separated from the fourth wall panel 18 by means of cut-away portion 50. In this way, both wall reinforcing panels are separate from the wall panels which they reinforce in the assembled container.

The shape of the base panels is complex. To aid understanding of the shape of the base panels, points on the base panels remote from the edges are defined by the coordinates: ( B, yC)

wherein x is the distance of the point described from the point O in the direction perpendicular to axis A, as a proportion of the total width of the base panel (B), and y is the distance of the point described from the point O in the direction of axis A, as a proportion of the total length of the base panel (C). The skilled reader will appreciate that, while the coordinates are quoted to two or three decimal places in this description, they may vary within an appreciable tolerance range (preferably up to 10%, more preferably up to 5%) without affecting the workability of the present invention. Similar tolerance ranges apply to the angles of the lines described below.

In this embodiment, the length of the base panel (C) is about 1.5 times the width of the base panel (B). The skilled reader will understand that the particular dimensions described hereinbelow may be varied depending on the general dimensions of the container to be assembled.

The first base panel 30 occupies roughly 54 % of the total area of the container once assembled, and comprises five straight edges 52, 54, 56, 58, 62 which together define substantially trapezoidal tongue 60. Edge 52 extends from point O in a direction roughly 45° to the direction of axis A, away from fold line 32, to the point (0.65B, 0.43C). Edge 54 then extends in the direction of axis A to the point (0.65B, 0.57C), edge 56 then extending from this point in a direction roughly 45° to the direction of axis A, towards fold line 32, to the point (0.55B, 0.67C). Edge 58 extends from this point towards fold line 32 in a direction parallel to fold line 34, perpendicular to axis A, to the point (0.5B, 0.67C). Edge 62 then extends from this point O in a direction roughly 45° to the direction of axis A, away from fold line 32, to the point (B, C) at the corner of first base panel 30 and wall reinforcing panel 36 remote from fold line 32. The portion of the tongue 60 defined by edges 56, 58 and 62 provide a locking means which aid retention of the tongue 60 in the slot 70 when the blank is assembled into a container. The first base panel 30 further comprises a diagonal fold line 64 extending from the point (0.5B, 0.65C) in a direction roughly 45° to the direction of axis A, towards fold line 32, to the point (0, C) where fold lines 22, 32 and 34 coincide. The transverse axis 66 of the tongue extends along the line 0.5C.

The second base panel 40 will hereinafter be described using a similar coordinate system, the origin being the point P wherein fold lines 24 and 42 meet. The second base panel 40 occupies almost the entirety of the area of the container once assembled, and includes a slot 70 suitable for receiving tongue 60 from the first base panel 30 on assembly of the partially assembled container. The slot 70 comprises a cut-away portion defined by the points (0.5B, 0.33C), (0.525B, 0.33C), (0.525B, 0.67C) and (0.5B, 0.33C). The second base panel 40 further includes a diagonal fold line 72 extending from the point (B, 0.33C) in a direction roughly 45° to the direction of axis A, towards fold line 42, to the point (0, C) where fold lines 26, 42 and 44 coincide. The second base panel 40 further includes a semicircular cut-away portion 74 centred on the point (B, 0.2C). The cut-away portion is small enough only for a human finger to pull up the second base panel 40 and does not remove sufficient area from said panel to affect the load bearing capacity of the assembled container.

Fig. 2 illustrates a blank according to a second embodiment of the invention, which differs from that illustrated in Fig. 1 in that the edge flap 20 is attached to the first wall panel 12 along transition line 29, rather than to the fourth wall panel 18.

Fig. 2a illustrates a modification of the blank according to Fig. 2, having a modified second wall reinforcing panel 47 which is provided with an additional cut-away section 51 on the side remote from the fourth wall panels. This modification avoids accidental glueing of the edge flap 29 to the second wall reinforcing panel. The size and shape of cut-away section 51 may vary depending on the size and shape of edge flap 20. In addition, cut-away section 74 is omitted.

Fig. 3 illustrates a blank according to a third embodiment of the invention, which differs from that illustrated in Fig. 1 in that the first base panel 30 is provided with a cut-away section 68, so that the first base panel 30 does not meet the first wall panel 12 at the point O. The cutaway section 68 takes the shape of a thin scalene triangle, such that edge 52 subtends a greater angle (q-i) to first transition line 32 than edge 62 (q₂). In addition, cut-away section 74 faces the first wall reinforcing panel 36. The cut-away section 68 occupies roughly 2.9% of the area of the base panel.

Fig. 3a illustrates a modification of the blank of Fig. 3, in which the cut-away section 69 takes the shape of a right-angled isosceles triangle, such that edges 52 and 62 are substantially parallel fa = q₂). The cut-away section 69 occupies roughly 1.9% of the area of the base panel. Fig. 4 illustrates a blank 10' according to a fourth embodiment of the invention wherein the length of the base panel (E) is roughly 2.5 times the width of the base panel (D). Portions of the blank 10' which correspond to those in the embodiment described in Fig. 1 are numbered with corresponding reference numerals followed by a prime (') and are not described in further detail.

A similar coordinate system is used to describe the shape of the base panels 30' and 40' of this embodiment of the invention, the values being the distance of the relevant point from the point O' or P' (as appropriate) as a proportion of the distance D and E.

The first base panel 30' occupies roughly 54% of the total area of the container once assembled, and comprises nine straight edges 80, 82, 84, 86, 88, 90, 92, 94, 96 which together define substantially trapezoidal tongues 100, 102. Edge 80 extends from point O' in a direction roughly 45° to the direction of axis A, away from fold line 32', to the point (0.65D, 0.26E). Edge 82 then extends in the direction of axis A to the point (0.65D, 0.32E), edge 84 then extending from this point in a direction roughly 45° to the direction of axis A, towards fold line 32', to the point (0.5D, 0.38E). Edge 86 then extends in the direction of axis A to the point (0.5D, 0.62E). Edge 88 extends from this point in a direction roughly 45° to the direction of axis A, away from fold line 32', to the point (0.65D, 0.68E). Edge 90 then extends in the direction of axis A to the point (0.65D, 0.74E), edge 92 then extending from this point in a direction roughly 45° to the direction of axis A, towards fold line 32', to the point (0.55D, 0.8E). Edge 94 extends from this point towards fold line 32' in a direction parallel to fold line 34', perpendicular to axis A, to the point (0.5D, 0.8E). Edge 96 then extends from this point in a direction roughly 45° to the direction of axis A, away from fold line 32', to the point (D, E) at the corner of first base panel 30' and first wall reinforcing panel 36' remote from fold line 32'. The first base panel 30' further comprises a diagonal fold line 64' extending from the point (0.5D, 0.8E) in a direction roughly 45° to the direction of axis A, towards fold line 32', to the point (0, E) where fold lines 22', 32' and 34' coincide. The transverse axes 104,106 of tongues 100, 102 extend along the lines 0.3E and 0.7E respectively.

The base panel 40' occupies almost the entirety of the area of the container once assembled, and includes two slots 110, 112 suitable for receiving tongues 100, 102 from the first base panel 30' on assembly of the partially assembled container. Slot 110 is defined by the points (0.5D, 0.2E), (0.525D, 0.2E), (0.525D, 0.38E) and (0.5D, 0.38E), and slot 112 by the points (0.5D, 0.62E), (0.525D, 0.62E), (0.525D, 0.8E) and (0.5D, 0.8E). The second base panel 40' further includes a diagonal fold line 72' extending from the point (D, 0.62E) in a direction roughly 45° to the direction of axis A, towards fold line 42', to the point (0, C) where fold lines 26', 42' and 44' coincide. The second base panel 40 further includes a semicircular cut-away portion 74' centred on the point (D, 0.5E).

Fig. 5 illustrates a blank according to a fifth embodiment of the invention, having the same modification as that described above in relation to Fig. 2.

Fig. 5a illustrates a modification of the blank illustrated in Fig. 5. The modification is the same as that described above in relation to Fig. 2a.

Fig. 6 illustrates a blank according to a sixth embodiment of the invention, which differs from that illustrated in Fig. 4 in that the first base panel 30' is provided with a cut-away section 68', so that the first base panel 30' does not meet the first wall panel 12' at the point O'. The cut-away section 68' takes the shape of a thin scalene triangle, such that edge 80 subtends a greater angle (q^ to first transition line 32' than edge 96 (q₂). In addition, cut-away section 74' faces first wall reinforcing panel 46'.

Fig. 6a illustrates a modification of the blank of Fig. 6, in which the cut-away section 69' takes the shape of a right-angled isosceles triangle, such that edge 80 is substantially parallel to edge 96 (not shown) fa = q₂).

The double tongue / slot arrangement illustrated in Figs. 4 to 6 is advantageous when, as in these embodiments, the length of the assembled container (E) greatly exceeds its width (D), when the presence of one long slot may weaken the base of the container once assembled.

Fig. 7 illustrates a blank 10" according to a seventh embodiment of the invention wherein the length of the base panel (G) is roughly 1.4 times the width of the base panel (F). Portions of the blank 10" which correspond to those in the embodiment described in Fig. 1 are numbered with corresponding reference numerals followed by a double prime (") and are not described in further detail.

A similar coordinate system to that adopted above is used to describe the shape of the base panels 30" and 40" of this embodiment of the invention, the values being the distance of the relevant point from the point O" or P" (as appropriate) as a proportion of the distance F and G. The skilled reader will understand that the particular dimensions described hereinbelow may be varied depending on the general dimensions of the container to be assembled.

The first base panel 30" occupies 50%> (excepting the area of the tongue) of the total area of the container once assembled, and comprises edges 152, 154, 158, 162 and 164 and rounded corners 156 and 160 which together define substantially trapezoidal tongue 60". Edge 152 extends from point O" along axis Q in a direction roughly 35° to the direction of axis A, away from fold line 32", to the point (0.59F, 0.59G). The tongue 60" is further defined by edge 154 which extends in a direction perpendicular to edge 152, rounded corner 156, edge 158 (which is generally at a slightly smaller angle to the axis A, compared to edge 152), rounded corner 160 and edge 162, which meets edge 164 at the point (0.71 F, 0.71 G). Edge 164 then extends from this point along axis Q in a direction parallel to edge 152, to the point (F, G) at the corner of first base panel 30" and wall reinforcing panel 36" remote from fold line 32". The skilled reader will therefore appreciate that, in the absence of tongue 60", edges 152 and 164 would form a continuous line extending along axis Q.

The shape of the tongue 60" defined by edges 154, 158 and 162 and rounded corners 156 and 160 provide a locking means which aids retention of the tongue 60" in the slot 70" when the blank is assembled into a container. The first base panel 30" further comprises a diagonal fold line 166 extending from the point (0.59F, 0.59G) in a direction roughly 45° to the direction of axis A, towards fold line 32", to the point (0, G) where fold lines 22", 32" and 34" coincide.

The second base panel 40" occupies almost the entirety of the area of the container once assembled, and includes a slot 70" suitable for receiving tongue 60" from the first base panel 30" on assembly of the partially assembled container. The slot 70" comprises a cutaway portion defined by the points (0.31 F, 0.29G), (0.43F, 0.41 G), (0.48F, 0.39G) and (0.36F, 0.27G). The principal axis R of slot 70" is substantially parallel to that of axis Q on first base panel 30". The second base panel 40" further includes a diagonal fold line 72" extending from the point (F, 0.3G) in a direction roughly 45° to the direction of axis A, towards fold line 42", to the point (0, G) where fold lines 26", 42" and 44" coincide. The second base panel 40" further includes a semicircular cut-away portion 74" centred on the point (F, 0.2G).

The skilled reader will appreciate that modifications can be made to the size, shape and positioning of the tongue 60" on the first base panel 30". For example, the tongue 60" may be positioned at different places along the edge of the base panel defined by lines 152 and 164. If the container approximates to a square shape, the tongue may be present on the opposite side of diagonal fold line 166.

Fig. 8 illustrates a blank according to an eighth embodiment of the invention, having the same modifications as those described above in relation to Figs. 2 and 5.

Fig. 8a illustrates a modification of the blank illustrated in Fig. 8. The modification is the same as that described above in relation to Figs. 2a and 5a.

Fig. 9 illustrates a blank according to a ninth embodiment of the invention. The blank has similar modifications to those described above in relation to Figs. 3 and 6, in that the first base panel 30" is provided with a cut-away section 168, so that the first base panel 30" does not meet the first wall panel 12" at the point O". The cut-away section 168 takes the shape of a thin scalene triangle, such that edge 152 subtends a greater angle (f,) to first transition line 32 than edge 164 (f₂). In addition, cut-away section 74" faces first wall reinforcing panel 36".

Fig. 9a illustrates a modification of the blank of Fig. 9, in which the cut-away section 169 takes the shape of a right-angled triangle, such that edge 152 is parallel to edge 164 (not shown) (f-i = f₂).

Fig. 10 illustrates a blank 10"' according to a tenth embodiment of the invention wherein the length of the base panel (I) is roughly 1.4 times the width of the base panel (H). Portions of the blank 10'" which correspond to those in the embodiment described in Fig. 1 are numbered with corresponding reference numerals followed by three primes ('") and are not described in further detail.

A similar coordinate system is used to describe the shape of the base panels 30"' and 40"' of this embodiment of the invention, the values being the distance of the relevant point from the point O"' or P"' (as appropriate) as a proportion of the distance H and I.

The first base panel 30"' occupies roughly 53.5% of the total area of the container once assembled, and comprises nine straight edges 180, 182, 186, 190, 192, 194, 198, 204 and 206 and rounded corners 184, 188, 196, 202 which together define substantially trapezoidal tongues 200, 210. Edge 180 extends from point O"' in a direction roughly 45° to the direction of axis A, away from fold line 32'", to the point (0.33H, 0.231). The shape of the base panel then extends around edges 182, 186 and 190 and rounded corners 184, 188, forming tongue 200, straight edges 190 and 192 meeting at the point (0.51 H, 0.35I). Straight edge 192 then extends in the direction of axis A to the point (0.51 H, 0.64I). The shape of the base panel then extends around edges 194, 198 and 204 and rounded comers 196, 202, forming tongue 210, straight edges 204 and 206 meeting at the point (0.68H, 0.77I). Edge 206 then extends from this point in a direction roughly 45° to the direction of axis A, away from fold line 32'", to the point (H, I) at the corner of first base panel 30'" and first wall reinforcing panel 36"' remote from fold line 32"'. The first base panel 30"' further comprises a diagonal fold line 64'" extending from the point (0.68H, 0.77I) in a direction roughly 45° to the direction of axis A, towards fold line 32'", to the point (0, I) where fold lines 22"', 32'" and 34'" coincide.

The second base panel 40"' occupies almost the entirety of the area of the container once assembled, and includes two slots 220, 222 suitable for receiving tongues 200, 210 from the first base panel 30"' on assembly of the partially assembled container. Slot 220 is defined by the points (0.34H, 0.23I), (0.51 H, 0.361), (0.55H, 0.33I) and (0.38H, 0.2I), and slot 222 by the points (0.51 H, 0.64I), (0.68H, 0.76I), (0.73H, 0.73I) and (0.55H, 0.611). The second base panel 40'" further includes a diagonal fold line 72"' extending from the point (H, 0.31) in a direction roughly 45° to the direction of axis A, towards fold line 42'", to the point (0, I) where fold lines 26'", 42'" and 44'" coincide. The second base panel 40'" further includes a semicircular cut-away portion 74"' centred on the point (H, 0.21).

Fig. 11 illustrates a blank according to an eleventh embodiment of the invention, having the same modifications as those described above in relation to Figs. 2, 5 and 8.

Fig. 11a illustrates a modification of the blank illustrated in Fig. 11. The modification is the same as that described above in relation to Figs. 2a, 5a and 8a.

Fig. 12 illustrates a blank according to a twelfth embodiment of the invention. The blank has similar modifications to those described above in relation to Figs. 3, 6 and 9, in that the first base panel 30'" is provided with a cut-away section 218, so that the first base panel 30"' does not meet the first wall panel 12"' at the point O'". The cut-away section 218 takes the shape of a thin scalene triangle, such that edge 180 subtends a greater angle (a- to first transition line 32"' than edge 206 (a₂). In addition, cut-away section 74'" faces first wall reinforcing panel 36'". Fig. 12a illustrates a modification of the blank of Fig. 12, in which the cut-away section 219 takes the shape of a right-angled triangle, such that edge 180 is substantially parallel to edge 206 fa = a₂).

In use, a container is formed from the blanks as follows.

Firstly, the blank is partially assembled into a partially assembled container by attaching the appropriate panels together, using any of the known methods described above. This is typically done as part of the manufacturing process, so that the container is supplied to the end user in this partially assembled state. As with other containers of this type, the partially assembled container may be folded flat for easy storage and delivery.

In order to fully assemble the container, the end user applies pressure to opposing corners of the partially assembled container, as illustrated by the arrows X and Y in Fig. 13a. As shown in Fig. 13b, as the container begins to open the base flaps automatically begin to unfold.

As illustrated in Figs. 13c to 13h, as the user continues to apply external pressure to the partially assembled container at points X and Y, the container continues to open from its flat state towards its assembled cuboid state. As this process continues, tongue 60 approaches slot 70 diagonally and automatically feeds therein (see in particular Figs. 13f and 13g). This conveys a considerable advantage over the prior art in that there is no need for the end user to reach inside the container and manipulate the tongue and slot to enable them to interlock: the end user simply has to apply pressure to opposite corners of the container as illustrated.

As illustrated in Fig. 13g, the straight edge 58 provided on tongue 60 locks against the end of slot 70 when the container is assembled. This arrangement serves to retain the tongue in place in the slot, thereby preventing unintentional re-folding of the container.

Figs. 14a to 14d illustrate assembly of a partially assembled container formed from the blank of Fig. 10. Application of external pressure to the partially assembled container at points X and Y causes the container to open from its flat state towards its assembled cuboid state. Tongues 200, 210 directly approach corresponding slots 220, 222 and automatically feed therein. Figs. 15a to 15d illustrate assembly of a partially assembled container formed from the blank of Fig. 7. Application of external pressure to the partially assembled container at points X and Y causes the container to open from its flat state towards its assembled cuboid state. Tongue 60" directly approaches corresponding slot 70" and automatically feeds therein.

Claims

CLAIMS:

1. A blank for assembly into a container, the blank comprising: first, second, third and fourth wall panels arranged in series along a principal axis of the blank, a first base panel adjoining the first wall panel along a first transition line extending substantially parallel to the principal axis, a first wall reinforcing panel adjoining the first base panel along a second transition line extending in a direction substantially transverse to the principal axis, a second base panel adjoining the third wall panel along a third transition line extending substantially parallel to the principal axis, a second wall reinforcing panel adjoining the second base panel along a fourth transition line extending in a direction substantially transverse to the principal axis, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the principal axis, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, the first and second base panels having complementary engagement means which are capable of engaging on the application of external pressure only on assembly of the blank into a container.

2. A blank according to claim 1 , wherein the complementary engagement means comprises one or more tongues provided on one of the base panels arranged for engagement with one or more complementary slots on the other base panel.

3. A blank according to claim 2, wherein the one or more tongues are provided on the first base panel and the one or more complementary slots are provided on the second base panel.

4. A blank according to claim 2 or claim 3, wherein the one or more tongues are substantially trapezoidal in shape.

5. A blank according to any one of claims 2 to 4, wherein the boundary line between the one or more tongues and the remainder of the base panel bearing the one or more tongues is substantially parallel to the principal axis of the blank.

6. A blank according to any one of claims 2 to 4, wherein the boundary line between the one or more tongues and the remainder of the base panel bearing the one or more tongues is substantially parallel to the free edge of the base panel.

7. A blank according to any one of claims 1 to 6, wherein one or more of the base panels are provided with locking means.

8. A blank according to claim 7 when dependent on claim 5, wherein the locking means take the form of an edge on one side of the tongue, the edge being substantially transverse to the principal axis of the blank.

9. A blank according to claim 2, wherein the first base panel, including the tongue, covers at least 50% of the area of the base of the container.

10. A blank according to claim 9, wherein the first base panel covers between 50%o and 70%) of the area of the base of the container.

11. A blank according to claim 9, wherein the first base panel covers between 50% and 55%) of the area of the base of the container.

12. A blank according to claim 5, wherein the boundary between the tongue and the remainder of the base panel bearing the tongue is about halfway along the width of the base panel.

13. A blank according to any one of claims 2 to 11 , wherein the second base panel covers substantially the entire area of the base of the container.

14. A blank according to any preceding claim, further provided with means to facilitate attachment of the panels during partial assembly.

15. A blank according to claim 14, wherein the means to facilitate attachment of the panels comprises an edge flap adjoined to the first wall panel.

16. A blank according to claim 15, wherein the second wall reinforcing panel is additionally provided with a cut-away section on the side remote from the fourth wall panel.

17. A blank according to claim 14, wherein the first base panel is provided with a cutaway section at the corner where it meets the first wall panel, opposite to the side where it meets the first wall reinforcing panel.

18. A blank according to claim 17, wherein the cut-away section takes the shape of a right-angled isosceles triangle.

19. A blank according to claim 17, wherein the cut-away section takes the shape of a thin isosceles or scalene triangle.

20. A blank according to any preceding claim, wherein one or both of the base panels includes a small cut-away section.

21. A blank according to any preceding claim, when partially assembled ready for forming into a container.

22. A container erected from a blank according to any preceding claim.

23. A partially assembled container comprising: first, second, third and fourth wall panels arranged in series, the first and fourth wall panels being attached to form an endless series of wall panels, a first base panel adjoining the first wall panel along a first transition line and adjoining a first wall reinforcing panel along a second transition line, the first wall reinforcing panel being attached to the second wall panel, a second base panel adjoining the third wall panel along a third transition line, the second base panel adjoining a second wall reinforcing panel along a fourth transition line, the second wall reinforcing panel being attached to the fourth wall panel, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the axes of the base panel, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, the first and second base panels having complementary engagement means which are capable of engaging on the application of external pressure only when the partially assembled container is assembled from a state where the panels lie substantially flat to an assembled state where the wall panels are substantially perpendicular to the base panels.

24. A container comprising: first, second, third and fourth wall panels arranged in series, the first and fourth wall panels being attached to form an endless series of wall panels, a first base panel adjoining the first wall panel along a first transition line and adjoining a first wall reinforcing panel along a second transition line, the first wall reinforcing panel being attached to the second wall panel, a second base panel adjoining the third wall panel along a third transition line, the second base panel adjoining a second wall reinforcing panel along a fourth transition line, the second wall reinforcing panel being attached to the fourth wall panel, at least one of the first and second base panels covering substantially the entire area of the base of the container when assembled, at least one of the first and second base panels having at least one additional transition line extending at a diagonal to the axes of the base panel, the first and second base panels having complementary engagement means which are engaged by the application of external pressure only on assembly of the container.

25. A container according to claim 24, further provided with a closure.

26. A blank for assembly into a container, substantially as described herein with reference to and as illustrated in the accompanying drawings.

27. A partially assembled container, substantially as described herein with reference to and as illustrated in the accompanying drawings.

28. A container substantially as described herein with reference to and as illustrated in the accompanying drawings.