CONTAINERS

Abstract: A blank (1) of cardboard, corrugated board or the like, for forming a container (15) having side walls (2, 3, 4, 5) and at least one of the side wall panels is predisposed to deflect in a predetermined direction upon failure through vertical loading.

Description: "Containers" This invention relates to containers made of cardboard, corrugated board or similar lightweight foldable sheet material and to blanks for making the same. It is usual for such containers to undergo vertical loading during their everyday use. However, the amount of loading can vary considerably depending on their intended role and thus it is well known to produce different containers to withstand different loadings. In many situations it is desirable for manufacturers to increase the maximum vertical failure load which a given container can withstand and also to be able to accurately predict the loading at which a container, made to a particular specification, will fail. This latter requirement is especially desirable in allowing the manufacturer to specify a minimum failure load for a particular container design while allowing for the possible variations which may occur for individual containers. However, to achieve these goals has typically required significant changes to the container's design or the use of different materials, for example increasing the thickness or quality of board used to make the container. Such techniques have been implemented with varying degrees of success, but these techniques have, in turn, resulted in their own problems. For example, changes to the container's design generally involve the introduction of complex features which are more difficult to manufacture or which require additional materials to implement. Equally, the use of higher quality or thicker materials requires the use of additional raw materials which is environmentally unfriendly and increases the cost of the containers . Furthermore, even with very careful control of materials and manufacturing processes, the variability in the failure loading of containers is much greater than can be accounted for by the variability in materials and corrugated board performance. Thus, there remains a need to produce containers with improved consistency and reliability and consequently which offer less chance of unexpected failures when under loads below their designed failure loading. It is also preferable if containers for a given role can be supplied which are lighter, and require less material . Viewed from one aspect the present invention provides a blank of cardboard, corrugated board or similar lightweight semi-rigid sheet material, for forming a container having side walls, wherein at least one of the side wall forming panels of the blank is predisposed to deflect in a predetermined direction upon failure through vertical loading. We have discovered that the failure mode of a side wall panel in a container has a significant influence on both the failure loading of the container and also on the consistency of the load at which containers of a given type fail. Thus, by predisposing at least one of the side wall panels of the container to fail in a predetermined direction (i.e. inwards or outwards) the failure mode of t.he container may be beneficially influenced. In contrast, the side wall panels of a conventional container, when exposed to vertical loading exceeding the maximum failure load, may fail inwards or outwards but there is no way of predicting, or controlling, the direction of failure. Preferably, at least one fold line which defines a boundary of the or each said predisposed side wall forming panel is non-rectilinear to bring about said predisposition. It is further preferred that the fold lines which define two opposite boundaries, the top and bottom or left and right vertical boundaries, of the or each said predisposed side wall forming panel are non- rectilinear to bring about said predisposition. Alternatively, the fold lines which define each of the boundaries of the or said predisposed side wall forming panel may be non-rectilinear to bring about said predisposition . The failure modes of each of the side wall panels of the container may be tailored to suit the intended role of the container. For example, in one arrangement two adjacent side wall panels of a four-sided container may be predisposed as aforesaid to allow four of the containers to be packed together on a palette with all of the predisposed side wall panels facing outwards. In an alternative arrangement, only two opposite side wall panels of a four-sided container may be so predisposed. It is, however, preferable that all of the side wall panels are so predisposed as this favourably influences the failure mode of all of the panels . The arrangement in which all of the side wall panels of a container are predisposed to deflect outwardly is advantageous as the mean failure loading for the container is greater than for a container in which the side wall panels fail in a combination of inwards and outwards directions. Furthermore, this arrangement advantageously provides greater consistency in the failure loading for a container made to a particular specification than for conventional, containers. Thus, the failure loading for a container may be more accurately predicted. This advantageously allows containers for specific tasks to be produced using lower quality or thinner board, for example recycled materials in place of Kraft (virgin paper) , than was previously possible . The mean failure loading for containers in which all of the side wall panels fail in an outwards direction is also greater than that for containers in which all of the side wall panels fail inwards. However, we have discovered that the failure loading for containers in which all of the side wall panels fail inwards is more consistent than for containers in which the side wall panels fail in any combination of inwards and/or outwards directions and thus may be more accurately specified (providing the same benefits as detailed above) . Thus, the or each non-rectilinear fold line preferably predisposes its associated side wall forming panel to deflect outwardly. In one arrangement, the predisposition for the or each of the side wall panels to fail outwardly is brought about by the or each non-rectilinear fold line being convex towards its associated side wall forming panel. In this arrangement the side wall panels are initially deflected outwards. In an alternative arrangement, the or each non- rectilinear fold line is concave towards its associated side wall forming panel causing the side wall panels to be initially deflected inwards. In one such arrangement, when the upper fold lines are concave towards their associated side wall forming panels, the central regions of the upper boundaries of the side wall panels tend to project above the upper corners of the container. Thus, vertical loading on the container, from for example other containers stacked on top thereof, generally occurs first at the central region of each side wall panel and this causes the loading of the container to be distributed between the side wall panels and the corners. This load distribution is advantageous as the loading on the corners is, at least initially, reduced. (In conventional containers, the corners take almost all the load, as they are more rigid, and are where failure through vertical loading commences.) The central loading on the inwardly projecting side wall panels can be arranged so as to cause the side wall panels to "pop" into an outwardly projecting configuration before failure. Thus, although the side wall panels are initially deflected inwards they tend to fail outwards and therefore provide the same beneficial failure characteristics as discussed above. The maximum displacement from rectilinearity of the or each said curved fold line, according to any of the arrangements discussed herein, is preferably in the range of 1% to 6% of its length, more preferably between 3% and 4%. Displacements from rectilinearity of between 1% and 3% and between 4% to 6% may also be advantageously employed. Indeed, displacements in the range of 1% to 10% or even up to 15% may be beneficially employed. Furthermore, the maximum displacement, and indeed the direction of displacement, of different fold lines formed in the blank need not all be the same. The maximum displacement from rectilinearity for the fold lines of a container is dependent on both the material from which the blank is formed and on the machinery used to form the blank and, subsequently, the container. For example if the container is to be formed from cardboard, Kraft board or higher weight papers would allow the lower displacements to be selected as would the use of precision equipment such as modern flat bed die-cutters, whereas rotary die-cutters or in-liners would require larger displacements to be adopted. A fold line of any of the arrangements discussed herein may be non-rectilinear by comprising two or more straight lines or a combination of curves and straight lines. Preferably however it is curved. The container of any of the arrangements described herein may also be provided with a top and/or a base. An embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figure 1 is a plan view of blank according to the present invention; Figures 2 and 3 are perspective views of a container made from the blank of Figure 1; Figures 4, 5 and 6 show plan, side and end views, respectively, of the container; and Figure 7 is a perspective view of an alternative arrangement of a container according to the present invention. Referring first to Figure 1, a blank 1 for making a container comprises side wall forming panels 2 to 5, top closure flaps 6 to 9 and base closure flaps 10 to 13. The blank 1 is formed from a mid-range recycled board box in B-flute (flute height 2.46mm, 154 flutes/metre, approximately 120gsm liner and fluting papers) although a range of sheet materials are equally suitable. Curved top fold lines 2T to 5T are formed between the side wall forming panels 2 to 5 and the top closure flaps 6 to 9 connected thereto. The curved top fold lines 2T to 5T are concave towards the associated top closure flaps 6 to 9, i.e. they curve inwardly from the top closure flaps 6 to 9 towards the centre of the side wall panels 2 to 5 and have a maximum displacement from rectilinearity of between 3% and 4% of their length. Curved lower fold lines 2L to 5L are formed between the side wall forming panels 2 to 5 and the base closure flaps 10 to 13 connected thereto. The curved lower fold lines 2L to 5L are also concave towards the associated base closure flaps 10 to 13, i.e. they curve inwardly from the base closure flaps 10 to 13 towards the centre of the side wall panels 2 to 5, and have the same maximum displacement from rectilinearity as the top fold lines 2T to 5T. A series of vertical fold lines 14 are also formed on the blank 1 between each of the side wall forming panels 2 to 5. A container 15, as shown in Figure 2, is erected from the blank 1 by folding the side wall forming panels 2 to 5 about the vertical fold lines 14. The base closure flaps 10 to 13 are folded inwards about the respective lower fold lines 2L to 5L, causing the side wall panels 2 to 5 to deflect outwards. (Conversely, the base closure flaps 10 to 13 deflect inwards.) The container 15 is secured in this erected position. The top closure flaps 6 to 9 may now be folded about the respective upper fold lines 2T to 5T, as shown in Figure 3. The curvature of the upper fold lines 2T to 5T causes the respective side wall panels 2 to 5 to deflect outwards and the top closure flaps 6 to 9 to deflect inwards . The outward curvature of the side wall panels 2 to 5 can clearly be seen in plan in Figure 4. Similarly, the waisted nature of such panels can be seen in Figures 5 and 6. In use, the container 15 may undergo a vertical loading, for example when a number of such containers are stacked on top of each other. If this vertical loading exceeds the failure loading of the container 15, one or more of the side walls 2 to 5 will fail. However, unlike conventional containers, the curvature of the upper and lower fold lines, and the resulting outward deflection of the side walls 2 to 5 , causes the side walls to be predisposed to deflect outwards when they fail. This outward deflection is the strongest failure mode of the container 15 and thus the container can withstand a greater vertical loading than equivalent conventional containers before failure. An alternative arrangement of the container 15 is shown in Figure 7. In this arrangement, the vertical fold lines 14 have each been replaced by two curved vertical fold lines 16 and 17 which are convex towards their respective side wall panels 2 to 5. The curved vertical fold lines 16 and 17 cause the side wall panels 2 to 5 to deflect outwards, in addition to the outwards deflection caused by the upper fold lines 2T to 5T and the lower fold lines 2L to 5L, when the container 15 is erected. Furthermore, the curved vertical fold lines 16 and 17 may be used in addition to, or instead of, the curved upper fold lines 2T to 5T and/or the curved lower fold lines 2L to 5L. Of course, for those arrangements in which the side wall panels are initially deflected inwards the orientation of the two curved vertical fold lines 16 and 17 may be reversed, i.e. so they are concave towards their respective side wall panels 2 to 5. In a modification of the above arrangements each of the curved upper fold lines 2T to 5T, curved lower fold lines 2L to 5L and vertical fold lines 16 and 17 may be replaced by two or more rectilinear fold lines, or a combination of rectilinear fold lines and curves, which are angled relative to each other, for example to form an obtuse isosceles triangle. This arrangement again induces an outwards deflection of the side walls 2 to 5. Thus, the same beneficial outward failure mode of the container 15, as described above, is obtained. Furthermore, any combination of curved upper fold lines 2T to 5T, lower fold lines 2L to 5L and curved vertical fold lines 16 and 17 may be employed to predispose any of the side wall panels 2 to 5 of the container 15 to fail in a predetermined direction. In a further possible arrangement, the curved vertical fold lines 16 and 17 are convex and the curved upper fold lines 2T to 5T and/or the lower fold lines 2L to 5L are concave towards common associated side walls. The reverse of this arrangement, whereby the vertical fold lines 16 and 17 are concave and the upper fold lines 2T to 5T and/or the lower fold lines 2L to 5L are convex, is equally applicable. It will be appreciated by those skilled in the art that a number of variations and modifications may be made without departing from the scope of the present invention. For example, folds may be formed internally of the side wall panels to predispose the panels to fail in a predetermined direction, rather than at their edges. Furthermore, the present invention is not limited to containers having four sides and it can equally be applied to containers having less than or more than four sides. Indeed, the present invention may be applied to very many box styles or combinations of box components, with opening on top or at the side, to sleeves, covers, high-sided trays, 3-part boxes and the like.

Claims: Claims : 1. A blank of cardboard, corrugated board or similar lightweight semi-rigid sheet material, for forming a container having side walls, wherein at least one of the side wall forming panels of the blank is predisposed to deflect in a predetermined direction upon failure through vertical loading. 2. A blank as claimed in claim 1, wherein at least one fold line which defines a boundary of the or each said predisposed side wall forming panel is non-rectilinear to bring about said predisposition. 3. A blank as claimed in claim 2, wherein two opposite boundaries of the or each said predisposed side wall forming panel are each defined by a non-rectilinear fold line . 4. A blank as claimed in claim 2, wherein the boundaries of the or each said predisposed side wall forming panel are each defined by a non-rectilinear fold line . 5. A blank as claimed in any of claims 2 to 4 , wherein the or each non-rectilinear fold line predisposes its associated side wall forming panel to deflect outwardly upon failure . 6. A blank as claimed in claim 5, wherein the or each non-rectilinear fold line is convex towards its associated side wall forming panel . 7. A blank as claimed in claim 5, wherein the or each non-rectilinear fold line is concave towards its associated side wall forming panel . 8. A blank as claimed in any of claims 2 to 7, wherein the maximum displacement from rectilinearity of the or each said non-rectilinear fold line is in the range of 1% to 6% of its length. 9. A blank as claimed in any of claims 2 to 8 , wherein the or each said non-rectilinear fold line is curved. 10. A blank substantially as herein described and with reference to the accompanying drawings. 11. A container made from a blank as claimed in any preceding claim.

Inventors: KYNASTON-PEARSON ANTHONY WILLI, STREEFLAND WILBERT, KYNASTON-PEARSON, ANTHONY, WILLIAM, NIGEL, STREEFLAND, WILBERT
Applicants: KYNASTON PEARSON ANTHONY WILLI, SCA PACKAGING LTD, STREEFLAND WILBERT, KYNASTON-PEARSON, ANTHONY, WILLIAM, NIGEL, SCA PACKAGING LIMITED, STREEFLAND, WILBERT
Application year: 2001
Main classification: B65D5
IPC codes: B65D5