BLANKS FOR FORMING CARTONS

Abstract: A blank for erecting into a carton having a base (1) and side walls (2, 3), the blank being formed of a foamed plastics material which has been extruded and subsequently thermoformed, and formations being panels, ridges, etc. (11, 12, 112, 13, 113, 14, 17) being provided in the plane of the blank at least some of said formations being arranged such that they cooperate and interlock when the blank is erected into a carton. The blank may additionally have top wall portions (5) also provided with panels (15). The various parts of the blank are suitably hinged by integral thin strips of plastics (10). The blank is preferably provided with feet (201) which in the erected carton project downwards from the bottom corners thereof to space the erected carton from another carton stacked therewith.

Description: BLANKS FOR FORMING CARTONS This invention relates to a blank, for forming cartons, crates, boxes and the like (herein referred to for convenience as cartons), for holding produce of various types such as fruit and vegetables. Disposable cartons are presently made, principally, of either corrugated board or of fibreboard. Cartons made of these materials suffer from three problems. When moist, humid or damp the rigidity of the board diminishes and the board, in certain cases, disintegrates. Another problem lies with the fact that most cartons are made from a single sheet of board which is cut and scored. In the cutting process a significant amount of board (' 'scrap 1 ') is left after cutting out the carton shape. This ' 'scrap' 1 is collected and reprocessed into pulp first and then into board and this process adds significantly to the cost of the carton. Another problem with cardboard cartons are that they are generally beige to brown in colour due to the low cost pulp used in the board's manufacture and this detracts from the overall presentation of the carton. Cartons can be made in white or other colours through lamination or through the use of higher quality wood or other pulps but these increase the cost of the cartons significantly. A further problem of cardboard cartons is their inability to withstand heavy loads unless relatively thick, and therefore, costly board is used in their construction or unless the carton is designed in such a way that various planes fold over and reinforce each other in the carton construction. Most cartons use this method to create the necessary resistance to loads. Another type of board used for cartons is made of extruded foamed plastic which is subsequently laminated with either a kraft paper on both sides of the board or with a plastic film on one side or both sides of the board. A further type is made of extruded foam plastic and which is, generally, extrusion coated on one side with an unfoamed plastic film. The foamed plastic board with the kraft paper lamination suffers from two main disadvantages. The first is that, as with corrugated cardboard cartons, a significant amount of scrap is created in the cutting and forming which, unlike the cardboard cartons, can not be easily or readily recovered since the kraft paper cannot be separated from the foamed plastic. This inability to reprocess the scrap increases the costs very significantly. A second problem is that when the kraft lamination gets wet a lot of the strength of the carton is lost. A further problem is the unattractive colour of the kraft paper. It is also known to form a skin on one or both faces of a foamed plastics material by collapsing the foam at the outside surfaces. The process(es) and materials used to laminate or extrusion coat foamed board are expensive and this makes the board generally uncompetitive with wood pulp based boards and cartons. There are known various blanks for containers which are strengthened by the provision in certain portions thereof of for example ribs, such as is described in British Patent Specification Nos. 2138782A, 1416891, 1361501 and 1347989. However, none of these prior specifications describes the main features of the present invention as is defined below, that ridges, panels or the like formed on one portion of the blank cooperate with corresponding ridges or panels formed on another portion of the blank, when the blank is erected into a carton, so that said ridges or panels interlock to impart strength and rigidity to the erected carton. Also, of said prior specifications, at least the blanks described in Nos. 1416891 and 1361501 are produced by injection moulding, in contrast to the present invention as defined below wherein the blanks are produced from extruded and formed foamed plastics material. Reference is also made to U.S. Patent Nos. 3675808, 4235346. 3829004 and 3973721. Again, none of these prior specifications describes the provision of ridges. panels or the like formed on one portion of the blank to cooperate with corresponding ridges or panels formed on another portion of the blank, when the blank is erected into a carton, so that such ridges interengage to impart strength and rigidity to the erected carton. The present invention aims to provide a carton, and specifically a blank therefor, which overcomes the various disadvantages of the prior art as described above, and which has in particular the advantage of improved strength and rigidity. The invention provides a blank for erecting into a carton having a base and side walls, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, preferably thermoformed. wherein formations (as herein defined) are provided in the plane of the blank, at least some of said formations being arranged such that they cooperate and interengage when the blank is erected into a carton. The said forming of the extruded blank may be suitably carried out by ther oforming, but vacuum forming or pressure forming may be alternatively employed. Said formations are to be understood as providing areas of the blank which deform or disturb the otherwise flat surface thereof, and may take for example the form of ridges, troughs, ribs, panels, recesses, undulations and the like. Angular troughs/ridges/ribs (subsequently referred to as ridges) and/or panels are formed in different planes to create strong resistance to loads, and according to the invention at least some of such ridges and/or panels cooperate and interengage with each other when the blank is erected into a carton so as to considerably add to the strength and rigidity of the carton by virtue of the interlocking of the respective portions of the blank In particular, on the sides of the carton ridges and/or panels may be formed in a vertical plane to create strength and resistance to stacking loads. Ridges and/or panels may be formed in a horizontal plane to create resistance to spreading loads from the contents of the carton and to resistance to bowing of the sides under pressure. Further ridges and/or panels can be formed in the base and lid, or a separate cover, to create a secure stacking method. The blank according to the invention is made of extruded foamed plastics material which is subsequently formed, preferably thermoformed. More particularly, the blank of the invention is essentially manufactured by a three-stage process, as follows: firstly, there is extruded a foamed plastics material; secondly, the extruded sheet is formed in which step there is imparted to it the desired formation of ridges, panels etc., in which step there are also formed the required hinge portions; and thirdly, the extruded and formed blank is cut out from the sheet. It is important for the purposes of the present invention that the blank can be made of a foamed plastics material and can be made relatively thin, so that the blank may be manufactured relatively cheaply and the carton formed therefrom may be treated as a disposable item. This would not be practicable if the blank were formed by injection moulding instead of by extrusion, since the blank would have to be made thicker and would be relatively expensive to manufacture. The blank according to the invention acquires the required strength and rigidity by virtue of the ridges, panels etc. formed therein at least some of which interengage and interlock when the blank is erected into a carton. While a blank for erecting into a carton, as described above, has many advantages, a problem may occur when the cartons are stacked upon one another, with the consequence that there may be virtually no air flow between the stacked cartons. This is particularly a problem when the cartons contain soft fruit for example, where the lack of adequate air flow may cause the contents of the cartons to perish, a problem which is accentuated in that the cartons themselves have a heat insulating effect by virtue of being formed of a foamed plastics material. We have found that this problem may be overcome by providing means on either the upper or lower edge of a carton, in particular by providing projections (herein referred to as feet) at the lower corners of the carton, whereby when such cartons are stacked together they are vertically spaced apart by the said feet or other means to permit air flow between the stacked cartons. Accordingly, there is provided a blank according to the invention, as previously- defined, wherein means are provided in or on the blank such that in the erected carton said means act to space the erected carton from another carton stacked therewith. As indicated above, the means provided for spacing stacked cartons will most preferably comprise feet provided to project downwards from the bottom corners of the erected carton. The spacing of stacked cartons by the means provided leads to another problem in that the stacking strength of the erected cartons is reduced and it therefore becomes most desirable to support the feet provided, and this is most preferably achieved by providing internal ribs at the corners of the erected carton which are arranged and adapted to support the said feet. It is envisaged that such internal ribs will most preferably be created from the blank itself when it is erected into a carton. The foamed plastics material constituting the blank preferably has a skin formed on one or more preferably both faces thereof, such skin being suitably formed by the known technique of collapsing the foam at the outside surfaces so as to give a smooth surface to the blank. The blank of the invention may be of any thickness suitable to the purpose for which the erected carton is to be employed, but is preferably from about 2.5 mm to about 8 mm thick. The blank may be of relatively simple form and comprise essentially a base portion and side wall portions, which side wall portions are hinged to the base portion, and the side walls being interlockable together by virtue of the cooperating ridges and/or panels when the blank is erected to form a carton, or more preferably the blank may be of more complicated form as will be described subsequently with reference to the accompanying drawings. In either case, the side walls are preferably hinged to the base by means of an integral thin strip of plastics material which can be bent when the side walls are folded up. In a more complicated form of blank the other portions thereof are suitably similarly hinged together. The hinges preferably form generally a 'V shape in the blank, the gap defined by the hinge closing up when the respective parts of the blank are hinged together. Further preferred features and advantages of the blank according to the invention are described below. 1. The extruded foamed material of which the blank is made may be suitably polystyrene, styrene copolymer, PET, polypropylene or polyethylene. 2. The provision of cooperating ridges, panels etc., suitably of circular, square or other shape, create interengaging formations which interlock to give the carton erected from the blank greater stability. Such interengaging formations, not only give the carton vertical strength, i.e. greater rigidity in vertical planes, but also assist in assembly of the carton. 3. Indented handles may be provided in the carton from suitable cooperating formations, most preferably, at least one pair of opposite side wall portions are provided with panels arranged to constitute indented handles for the erected carton. 4. The cooperating ridges, panels etc. may permit improved stacking of the cartons, whether column stacking or cross-stacking. 5. There will usually be provided top wall portions of the blank respectively hinged to a pair of opposite side wall portions. Such top wall portions may each have a width somewhat less than half the width of the base portion of the blank so that the erected carton is partly open at the top thereof, or alternatively the top portions may each have a width substantially equal to half the width of the base portion so that the lid may completely close the erected carton. The provision of such top wall portions also helps to prevent outward bowing of the erected carton. 6. There may be suitably provided on such top wall portions tabs arranged and adapted to snap-fit into appropriate openings in the other pair of opposite side wall portions of the carton, to assist in interlocking of the erected carton. Such locking tabs are preferably tapered for ease of insertion. The provision of such tabs and corresponding openings in. the blank can only be satisfactorily achieved by forming, especially thermoforming. 7. Each top wall portion preferably has formed therein a panel corresponding to a panel formed in the carton base portion, whereby when two like cartons are stacked the panel of the top wall portion of a lower carton may cooperate and interengage with the panel of the base portion of an upper carton. In particular, in the embodiment of the invention wherein feet are provided for spacing apart stacked cartons, each top wall portion preferably has formed therein panels corresponding to panels formed in the feet of the carton base portion, whereby when two like cartons are stacked the panel of the top wall portion of a lower carton may cooperate and interengage with the panel of the foot extending down from the base portion of an upper carton. 8. Preferably each of the side wall portions is provided with a pair of flaps, each arranged to cooperate with an adjacent side wall portion, each flap having a ridge arranged to cooperate with a corresponding ridge of the adjacent side wall portion. 9. Each side wall portion is preferably provided with at least one panel. 10. One pair of opposite side wall portions may each comprise an inner and an outer side wall portion connected by a narrow top wall portion, the respective inner and outer side wall portions having cooperating ridges. The gap between such inner and outer side wall portions in the erected carton is preferably exactly the same as the thickness of side flaps provided on the other pair of opposite side wall portions which are folded in between such inner and outer side wall portions; this forms a 3-layer, compact "sandwich" structure which is particularly strong, especially when the foamed material of the blank is provided with a rigid skin on each face thereof. Such alternating layers of different density provide an especially rigid structure. 11. Ridges may be suitably provided at the ends of the base portion adjacent the double wall side portions referred to in paragraph 10 above so as to secure the folded over inner side wall portions. 12. Horizontal ridges provided in opposite side wall portions of the erected carton also act to prevent outward bowing of the erected carton, and may be employed for this purpose instead of, or as well as, the top wall portions mentioned in paragraph 5 above. 13. In the erected carton, the stacking strength is always transferred through the side wall portions, i.e. not through the base portion, especially where the side wall portion is 2 or 3 planes thick as described in paragraph 10 above and where ridges are provided in vertical planes. 14. Ridges or panels (as described in paragraph 7 above) provided in the carton base portion considerably enhance the strength and rigidity of the carton in the horizontal plane. 15. The erected carton according to the invention may be firmly interlocked together, especially at the corners thereof. 16. Cells, indentations or the like may be formed in the carton base portion for receiving individual items of produce, such as fruits etc., for example apples or oranges. The foamed plastics material of which the blank is formed may also provide thermal insulation to keep the contents of the carton cool. The blank itself is preferably a solid structure, but some parts thereof may be open if required. Because the blank itself is foamed it is extremely light-weight but nevertheless extremely strong, and therefore it is also of low cost. A carton formed from a blank according to the invention is particularly suitable for transporting and warehousing fresh fruit and vegetables at a competitive cost, while avoiding the problems of the prior art as mentioned above. The blank will lie generally flat with the base, side walls and other portions thereof in substantially the same plane, and the blanks may be stacked together for easy transport thereof. The invention in another aspect provides a blank for erecting into a carton having a base portion and side wall portions, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein the said base portion is shaped to receive individual items of produce. For example the part of the blank which will form the base portion of the erected carton may be provided with a series of indentations or cells formed therein for receiving fruit such as apples or oranges for example. In this alternative aspect of the invention the blank is not otherwise formed with cooperating and interengaging formations such as ridges, panels etc. The blank may, however, suitably include one or more preferred features of the blank according to the first aspect of the invention as described above, e.g. the preferred material of which the blank is made may be as described above, and/or the side wall portions may be hinged to the base portion by respective integral thin strips of plastics material, and/or the blank may additionally comprise top portions hinged to respective opposite side wall portions. The invention in a further aspect provides a blank for erecting into a carton having a base portion and side wall portions, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein flaps provided on at least some of the said side walls are arranged to be connected or to cooperate with other said side walls when the blank is erected into a carton, and wherein the side wall portions are hinged to the base portion by respective integral thin strips of pLasτ,ics material. The hinges of integral thin strips of plastics material preferably form generally a 'V shape in the blank, the gap defined by the hinge closing up when the respective parts of the blank are hinged together. The apex of the V shape may be rounded. When the hinge is folded together the top edges of the V shape will come together. Displacement of material of the blank so as to define the hinges may be suitably effected during forming, especially thermoforming, of the blank. Top wall portions may be suitably provided as described previously, and such top wall portions will be hinged to the respective side wall portions as described above. Again, in this further aspect of the invention, the blank is not otherwise formed with cooperating and interengaging formations such as ridges, panels etc., although the blank may suitably include one or more preferred features of the blanks as previously described, e.g. the preferred material of which the blank is made may be as described above, and/or the base portion may be shaped with indentations, cells or the like for receiving individual items of produce. The invention in a yet further aspect provides a blank for erecting into a carton having a base and side walls, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein means are provided in or on the blank such that in the erected carton said means act to space the erected carton from another carton stacked therewith. As indicated above, such means may be provided on either the upper or lower edge of a carton, in particular by providing projections (feet) at the lower corners of the carton, whereby when such cartons are stacked together they are vertically spaced apart by the said feet or other means to permit air flow between the stacked cartons. Most preferably the means provided for spacing stacked cartons will comprise feet provided to project downwards from the bottom corners of the erected carton. In order to improve the stacking strength of the carton, the feet provided may be supported by providing internal ribs at the corners of the erected carton which are arranged and adapted to support the said feet. Such internal ribs will most preferably be created from the blank itself when it is erected into a carton. In ' this yet further aspect of the invention the blank is not otherwise formed with cooperating and interengaging formations such as ridges, panels etc. The blank may, however, suitably include one or more preferred features of the blank according to the invention as described above, e.g. the preferred material of which the blank is made may be as described above, and/or the side wall portions may be hinged to the base portion by respective integral thin strips of plastics material, and/or the blank may additionally comprise top portions hinged to respective opposite side wall portions. Also, flaps provided on at least some of the side walls are arranged to be connected or to cooperate with the other side walls when the blank is erected into a carton. The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of one embodiment of a blank according to the invention for erecting into a carton; Figures 2, 3, 4 and 5 are sections respectively taken along the lines A-A, B-B, C-C and D-D in Figure 1. Figure 6 is a perspective view of a carton assembled from the blank shown in Figure 1; Figure 7 is a sectional side view of a part of the assembled carton shown in Figure 6, for the purpose of illustrating how like assembled cartons may be stacked one upon the other; Figure 8 is a plan view of another embodiment of a blank according to the invention for erecting into a carton; Figures 9 and 10 are enlarged sections respectively taken along the lines B-B and C-C in Figure 8 of the assembled carton; Figure 11 is a plan view of a further embodiment of a blank according to the invention for erecting into a carton; Figure 12 is an enlarged detail of the part A indicated in Figure 11; Figure 13 is a section taken along the line F-F in Figure 12; Figures 14 and 15 are enlarged sections respectively taken along the lines B-B and C-C in Figure 11, of the assembled carton; Figure 16 is a section taken along the line E-E in Figure 14; Figure 17 is a plan view of a yet further embodiment of a blank according to the invention for erecting into a carton; Figure 18 is a section taken along the line D-D in Figure 17, of two crates stacked together; Figures 19a and 19b are sectional views illustrating preferred hinge portions of the blank according to the invention; Figures 20a and 20b are sectional views illustrating left-hand and right-hand folds respectively of a preferred hinge portion of the blank; Figures 21 and 22 are vertical sectional views of modified blanks of the invention erected into cartons; Figure 23 is a vertical section of a further modified blank of the invention erected into a carton having a domed base; Figure 24 is a plan view of one embodiment of a blank according to the invention for erecting into a carton; Figure 25 is a half section taken along the line A-A in Figure 26, and is essentially a plan view of an erected carton formed from the blank shown in Figure 24; Figure 26 is a half section taken along the line C-C in Figure 25, and is essentially a side view of the erected carton formed from the blank shown in Figure 24; Figure 27 is a half section taken along the line B-B in Figure 25, and is essentially an end view of the erected carton formed from the blank shown in Figure 24; Figure 28 is a section taken along the line D-D in Figure 25; Figure 29 is a section taken along the line E-E in Figure 25; Figure 30 is a detailed side view showing the manner of interconnection of the top portions of the erected carton with the side walls thereof; Figure 31 is a section taken along the line F-F in Figure 30; and Figure 32 is a sectional side view showing two cartons of the type shown in Figures 24 to 31, stacked one upon the other. The blank shown in Figure 1 essentially comprises the following elements. In the following description the various parts of the blank will be referred to in terms of the respective parts of the carton which they constitute when the blank is assembled. That is, the blank comprises a base 1, a pair of long side walls 2 and a pair of shorter side walls 3. Each of the side walls 3 is a double wall formed of side wall portions 3a and 3b joined together by a narrow top portion 3c. Each of the side walls 2 has a pair of flaps 4. Attached to the edges of the side walls 2 remote from the base 1 are respective partial top or lid portions 5. The top portions 5 each have a pair of tapered tabs 6. The side wall portions 3b each have a pair of flaps 7. A pair of openings 8 are provided in each of the portions 3c for receiving the tabs 6. The blank as a whole is formed of foamed plastics material which has been extruded and subsequently formed, preferably thermoformed, the surfaces of which are formed with skins, suitably obtained by causing the cells of the foam to collapse at the surfaces thereof. The various parts of the blank are hinged together by means of a series of hinges 10, each formed of a thin integral strip of plastics material. The hinges 10 are best seen in Figures 2 to 5, and it will be apparent that the hinges form generally a 'V shape in the blank. the gap defined by the hinge closing up when the respective parts of the blank are hinged together. The various parts of the blank are provided with ridges and panels etc. for the purpose of imparting greater rigidity to the assembled carton in the vertical and horizontal directions, some of such formations in the blank being arranged and adapted to cooperate so as to assist in interlocking the assembled carton together, and some of such formations being arranged to cooperate with corresponding formations in a like carton so as to assist in stacking of the cartons. Specifically, in the blank shown in the drawings, the base 1 is provided with a pair of panels 11; the side walls 2 are each provided with a pair of panels 12 and a pair of ridges 112; the side wall portions 3a are each provided with a panel 13a and a pair of ridges- 113a; the side wall portions 3b are each provided with a pair of ridges 13b arranged to cooperate with the. ridges 113a; the flaps 4 are each provided with a ridge 14 arranged to cooperate with a respective ridge 113a and/or 13b; the top portions 5 are each provided with a panel 15; and the flaps 7 are each provided with a ridge 17 arranged to cooperate with a respective ridge 112. Also in each side wall portion 3a and 3b are formed respective cooperating panels 23a and 23b which may function as indented handles. A pair of formations 223a are also provided in each of the side wall portions 3a. The blank shown in Figure 1 may be assembled to form the carton as shown in Figure 6, with the flaps 4 being inserted between the respective side wall portions 3a and 3b, with the flaps 7 being arranged along the inside of the respective side walls 2, and with the tabs 6 being inserted in the respective openings 8. It will be apparent from Figure 7 that like assembled cartons may be stacked one upon the other, with a panel 11 of the base of an upper carton resting in a panel 15 of a top portion 5 of a lower carton. In the assembled form of the carton, the panels 12 and 13a provide greater rigidity in vertical planes, adding to the stacking strength of the carton. While the forming of interlocking panels and ridges, as previously shown, helps to reinforce the strength of the side walls of the carton when assembled, the strength may be further improved by ensuring that the load bearing walls, and especially the ridges, are kept in the same plane or that any part of the load bearing walls that is not in a direct vertical plane is supported in some way. This can be accomplished in a number of ways and two of these are described below, with reference to the embodiments of Figures 8 to 10 and 11 to 16 respectively. The blanks shown in Figures 8 and 11 are similar to each other and also to the blank shown in Figure 1. Each of the blanks shown in Figures 8 and 11 comprises a base 1, a pair of long side walls 2 and a pair of shorter side walls 3. Each of the side walls 3 is a double wall formed of side wall portions 3a and 3b joined together by a narrow top portion 3c. Each of the side walls 2 has a pair of flaps 4. Attached to the edges of the side walls 2 remote from the base 1 are respective partial top or lid portions 5. The top portions 5 each have a pair of tapered tabs 6. The side wall portions 3b each have a pair of flaps 7. A pair of openings 8 are provided in each of the portions 3c for receiving the tabs 6. The blank is formed of foamed plastics material as described in the embodiment of Figure 1, and the various parts of the blank are hinged together by means of a series of hinges 10, again as described in the embodiment of Figure 1. The base 1 is provi ' ded with a series of three panels 11; the side walls 2 are each provided with a single elongate panel 12a and a pair of ridges 112; the side wall portions 3a are each provided with a panel 13a and a pair of ridges 113a; the side wall portions 3b are each provided with a pair of ridges 13b arranged to cooperate with the ridges 113a; the flaps 4 are each provided with a ridge 14 (of reduced length as compared with the flap 4) arranged to cooperate with a respective ridge 113a and/or 13b; the top portions 5 are each provided with a panel 15; and the flaps 7 are each provided with a ridge 17 (of reduced length as compared with the flap 7) arranged to cooperate with a respective ridge 112. the flaps 7 being additionally each provided with a panel 117 arranged to cooperate with a portion of a respective panel 12a. Also in each side wall portion 3a and 3b are formed respective cooperating panels 23a and 23b which may function as indented handles. The blanks shown in each of Figures 8 and 11 may be assembled in a manner similar to the blank of Figure 1 to form a carton, with the flaps 4 being inserted between the respective side wall portions 3a and 3b, with the flaps 7 being arranged along the inside of the respective side walls 2, and with the tabs 6 being inserted in the respective openings 8, said insertion of the tabs 6 being facilitated by the provision of cut-out portions 140 in the flaps 4. In the embodiment of Figures 8 to 10 small ridges 130 and 131 are formed respectively in the base 1 and in the narrow top portion 3c adjacent the ridges 113a and 13b. Similarly, small ridges 132 and 133 are formed in the base 1 and in the top portions 5 adjacent the ridges 112. In the embodiment of Figures 11 to 16 cut-out sections 135 are formed at the respective ends of the ridges 113a and 112. One such alternative way of supporting the vertical loads is shown in Figures 9 and 10. Interlocking ridges are formed in the side walls as in the embodiment of Figure 1. At the point where the vertical ridge deviates from the vertical plane, a corresponding ridge 130-133 is formed to interface with the deviation so as to form a structure that will transmit any vertical load down through the vertical plane of the rib. The angle formed by the ridges 130-133 is approximately 45° as shown in Figures 9 and 10, but this angle may be a different value provided that the ridge 130-133 forms an interface with the corresponding vertical ridge 13b, 113a, 17, or 112. Another alternative way of supporting vertical loads is shown in Figures 11 to 16. By cutting and punching out a section 135 the approximate width of the vertical re-inforcing ridges (Figure 13) at the point where the plane changes when assembled (i.e. at the hinges) and allowing for the thickness of the material as shown (see Figures 11 and 12) the vertical stacking ridges are kept in a vertical plane but also touch the horizontal planes (i.e. the base 1 and the top portions 5). This ensures, that when crates are stacked on top of each other, that the vertical load is supported by ridges that are in a totally vertical plane. The features described above benefit both column stacking crates or cross-stacking crates, as described subsequently. The embodiment shown in Figures 17 and 18 is generally similar to that shown in Figures 11 to 16, except that the panels 11 in the base 1 are replaced by a series of small panels 110 and the panels 15 in the top portions 5 are replaced by a series of small panels 150, as shown in Figure 17. Detail A and sections B-B and C-C shown in Figure 17 correspond to Figures 12 to 16 described with reference to Figure 11. The interfacing angles of the panels 110 formed in the base and the panels 150 formed in the top portions can be created in various angle profiles so that they naturally slip or slide into each other even when placed on each other slightly askew. This feature can be further enhanced by making the panels in the base of smaller width than that of the panels in the top portions and allowing space between them in the horizontal plane (see Figure 18). The design of the ridges can be inverted as compared with the structure of Figure 18 so that panels 150 extend upwards into panels 110. The above applies to column stacking of crates or cross stacking of crates as described below. Where cartons are required to be cross stacked, square, round or rectangular panels can be formed in the base and top portions in such positions so that they interface when cartons are stacked in a column formation or in a cross-stacking or "brick-stacking" formation. In such cases the vertical walls of the cartons would be formed with reinforcing ridges at the points, in the vertical plane, where the horizontal planes crossed. The vertical ridges described previously with references to Figures 8 to 10 and Figures 11 to 16 would be especially applicable in this type of cross stacking. The blank according to the present invention can be used to form a so-called self-erecting carton. In this regard, there are already known a number of fibreboard and corrugated carton board boxes that are formed from blanks, then erected and glued, and then collapsed again prior to delivery to the customer. All the customer has to do is to pull them together again - normally in one single motion. Normally the design and collapsing/erection system is achieved by diagonal creases which can hinge in opposite directions as required. These two way creases can be in the walls, base or lid according to the design. The hinges 10 formed in the extruded foam sheet of the blanks of the present invention, can be designed (typically shown in Figure 19a but also as in Figure 19b) in such a way as that they fold to create a right angle in either direction (as shown in Figures 20a and 20b) in order to achieve a self erecting design. As previously, interlocking ridges are formed in the side walls to add vertical stacking strength. In a self erecting carton, however, these ridges might create a problem when the carton is collapsed by preventing the carton from completely collapsing. In order to overcome this, corresponding male or female ridges would be created in the base, side walls, or top to allow the ridges to recess into when in the collapsed position. When the cartons are first erected and assembled the method of securing the side walls to each other or to the top portions or to the base can be, typically, by glue or adhesive; by solvent which dissolves the plastics slightly between the planes and then resets them together; by heating the surfaces to the plastic melting point and then letting them set together; by ultra-sonically welding them together; by welding them together with a laser; or by fixing them together with a metal or plastic staple or rivet. For certain types of delicate fruits, vegetables or other products it might be desirous to protect these with supporting pillars. This can be achieved by thermoforming pillars 16 from the base of the carton up to the underneath of the horizontal top portion (as shown in Figure 22) or, if the carton does not have a top or only has a partial top, to the underneath of the base of the carton stacked on top of it (as shown in Figure 21). or a combination of both. This is also important where the contents of a carton are very heavy and therefore might create a bow in the base thereby damaging the contents of the carton below it. Although the base of the carton made from plastic foam sheet, when skinned, coated or laminated on both sides, will support appreciable loads, certain products are too heavy for the carton to support them and as a result the base bends downwards onto the contents of the carton below. In order to overcome this problem the base may be formed in such a way as to create a dome 26 or upward curve in it, as shown in Figure 23. Downward pressure on the curved base creates a horizontal force against the bottom edge of the side walls. Since the square or rectangular base shape is extremely strong and maintains its shape, the base is kept in its upward dome shape thereby supporting the contents satisfactorily. A further method to support and maintain the upward dome shape is to create troughs along the length, width or diagonals (or a combination of two or more of these directions) of the base. The preferred design of these troughs will be such that the top of the trough will follow the profile of the dome while the bottom of the trough will follow a different profile such as on a plane similar to the direct line between the bottoms of the side walls. Alternatively the profile of the bottom of the trough might be a larger radius than that of the profile at the top of the trough. A further design could be that the radius at the bottom of the trough could be equal to the radius at the top. The trough(s) may start and end at the extremities of the inside or of the outside of the base or they may start and end at any point on the base. 0 The blank shown in Figure 24 comprises a base 1, a pair of long side walls 2 and a pair of shorter side walls 3. Each of the side walls 3 is a double wall formed of side wall portions 3a and 3b joined together by a narrow top portion 3c. 5 Each of the side walls 2 has a pair of flaps 4. Attached to the edges of the side walls 2 remote from the base 1 are respective partial top or lid portions 5. The top portions 5 each have a pair of tapered tabs 6 having barbed portions 6a. The side wall portions 3b o each have a pair of flaps 7. A pair of openings 8 are provided in each of the portions 3c for receiving the tabs 6. The blank as a whole is formed of foamed plastics material which has been extruded and subsequently 5 formed, preferably thermoformed. the surfaces of which are formed with skins, suitably obtained by causing the cells of the foam to collapse at the surfaces thereof. The various parts of the blank are hinged together by means of a series of hinges 10, each formed of a thin integral strip of plastics material, as previously described, and form generally a "V" shape in the blank, the gap defined by the hinge closing up when the respective parts of the blank are hinged together. The various parts of the blank are provided with ridges and panels etc. for the purpose of imparting greater rigidity to the assembled carton in the vertical and horizontal directions, some of such formations in the blank being arranged and adapted to cooperate so as to assist in interlocking the assembled carton together, and some of such formations being arranged to cooperate with corresponding formations in a like carton so as to assist in stacking of the cartons. Specifically, the base 1 is provided with a series of three elongate panels 11, and also with a number of small square panels 11a; the side walls 2 are each provided with a single elongate panel 12a and a pair of ridges 112; the side wall portions 3a are each provided with a pair of ridges 113a; the flaps 4 are each provided with a ridge 14 arranged to cooperate with a respective ridge 113a; the top portions 5 are each provided with an elongate panel 15, with a pair of small square panels 15a, and with a further elongate (half-) panel 15b adjacent the free edge of the portion 5; and the flaps 7 are each provided with a panel 117 arranged to cooperate with a portion of a respective panel 12a. Also in each side wall portion 3a and 3b are formed respective cooperating panels 23a and 23b which may function as indented handles. Respective portions 223a and 223b are also provided in the side walls 3a and 3b, for cooperating with the barbed portions 6a of the tabs 6. as best illustrated in Figure 31. The blank shown in Figure 24 may be assembled to form a carton, with the flaps 4 being inserted between 0 the respective side wall portions 3a and 3b, with the flaps 7 being arranged along the inside of the respective side walls 2, and with the tabs 6 being inserted in the respective openings 8, said insertion of the tabs 6 being facilitated by the provision therein of 5 the barbed portions 6a. For the purpose of permitting adequate air flow between stacked cartons respectively formed from blanks as described above, the blank shown in the drawings is provided at each corner of the base 1 with a foot or o like downward projection 201, which when the blank is erected into a carton may rest upon the corresponding upper corner of a like carton so as to define a space between the respective cartons. This is best illustrated in Figure 32. 5 Each of the feet 201 are suitably shaped as shown in the drawings, and taper from a relatively wide opening portion 202 in the plane of the base 1 via downwardly inclined portions 203 to a base portion 204 of reduced dimensions as compared with the portion 202. The provision of the feet 201 leads to the erected carton having a reduced stacking strength, and this disadvantage is accordingly overcome in the blank shown in the drawings by the provision of internal ribs 210, best illustrated in Figure 25. The ribs 210 are provided by means of respective portions 211a. 211b on each of the flaps 7 and by means of respective portions 212a, 212b on each of the ends of the side walls 3b adjacent thereto. The respective portions 211, 212 are interconnected by portions 213. In the erected carton formed from the blank as shown in Figure 24, respective ribs are formed at each of the internal corners of the carton by the folding deformation of the portions 211, 212, 213. Also, the portions 211, 212 of each of the internal ribs are provided with respective projecting portions 214 and 215, as best illustrated in Figure 24. When the blank shown in Figure 24 is erected into a carton, the projecting portions 214. 215 are folded into the adjacent foot portion 201. to further reinforce the stacking strength of the carton. As best illustrated in Figure 29, in each of the feet 201 the base portion 204 thereof is upwardly recessed as shown, and arranged and adapted to receive an upwardly projecting panel 15a provided on a top portion 5, so as to assist in stacking of the cartons. While the stacking strength of the carton shown in the drawings is particularly assisted by the provision of the internal ribs formed by the portions 211, 212. 213, the stacking strength could alternatively be improved by any other appropriate folding formation or even by the provision of appropriate undulations in the carton side walls. Also, the feet 201 themselves could of course be of any other appropriate configuration, different from that shown in the drawings. While the forming of interlocking panels and ridges, as previously shown, helps to reinforce the strength of the side walls of the carton when assembled, the strength may be further improved by ensuring that the load bearing walls, and especially the ridges, are kept in the same plane or that any part of the load bearing walls that is not in a direct vertical plane is supported in some way, particularly as previously described. For example small ridges may be formed respectively in the base 1 and in the narrow top portion 3c adjacent the ridges 113a. Similarly, small ridges may be formed in the base 1 and in the top portions 5 adjacent the ridges 112. That is, at the point where the vertical ridge deviates from the vertical plane, a corresponding ridge is formed to interface with the deviation so as to form a structure that will transmit any vertical load down through the vertical plane of the rib. The angle formed by the ridges may be approximately 45°, but this angle may be a different value provided that the ridge forms an interface with the corresponding vertical ridge 113a, or 112. Alternatively, cut-out sections may be formed at the respective ends of the ridges 113a and 112. That is. by cutting and punching out a section the approximate width of the vertical re-inforcing ridges at the point where the plane changes when assembled (i.e. at the hinges) and allowing for the thickness of the material as shown the vertical stacking ridges are kept in a vertical plane but also touch the horizontal planes (i.e. the base 1 and the top portions 5). Thus when cartons are stacked on top of each other, the vertical load may be supported by ridges that are in a totally vertical plane. According to one particular embodiment of the invention (not specifically illustrated), the top portion 5 could be made so as to have a width substantially equal to the height of the side walls 2 to which they are attached, so that an intended user of the carton, if it were desired that the erected carton should not have top portions, could instead fold the top portions down parallel and adjacent to the side walls 2, so that a side wall 2 and a top portion 5 together formed a double-wall arrangement similar to that provided by the side wall portions 3a and 3b. This would further increase the strength of the carton. The flaps 7 could then be folded in between the side wall portions 2 and 5. Further, the portions 5 could be cut so that their ends nearest the corners of the carton would lie vertically against the portions 211b, 212b. The feet 201 could be suitably arranged to fit onto the top edges of the side wall portions 2 and 5. Finally, the portions 2 and 5 could be joined together by a narrow portion similar to the top portion 3c.

Claims: CLAIMS : 1. A blank for erecting into a carton having a base portion and side wall portions, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, and wherein formations (as herein defined) are provided in the plane of the blank, at least some of said formations being arranged such that they cooperate and interengage when the blank is erected into a carton. 2. A blank as claimed in claim 1, wherein the blank has a skin formed on both faces thereof by collapsing the foam at the blank surfaces. 3. A blank as claimed in claim 1 or 2, wherein the side walls portions are hinged to the base portion by respective integral thin strips of plastics material. 4. A blank as claimed in any of claims. 1 to 3, which is 2.5 mm to 8 mm thick. 5. A blank as claimed in any of claims 1 to 4, further comprising top portions respectively hinged to a pair of opposite side wall portions. 6. A blank as claimed in claim 5, wherein each said top wall portion has formed therein a panel corresponding to a panel formed in the carton base portion, whereby when two like cartons are stacked the said panel of the top wall portion of a lower carton may cooperate with the said panel of the base portion of an upper carton. 7. A blank as claimed in any of claims 1 to 6, wherein at least one pair of opposite side wall portions are provided with panels arranged to constitute indented handles for the erected carton. 8. A blank as claimed in any of claims 1 to 7, wherein a pair of opposite side wall portions each comprise an inner and an outer side wall portion connected by a narrow top wall portion, the respective inner and outer side wall portions having cooperating ridges. 9. -A blank as claimed in any of claims 1 to 8, wherein each of the side wall portions is provided with a pair of flaps, each arranged to cooperate with an adjacent side wall portion, each flap having a ridge arranged to cooperate with a corresponding ridge of the adjacent side wall portion. 10. A blank as claimed in any of claims 1 to 9, wherein each side wall portion is provided with at least one panel. 11 * A blank as claimed in any of claims 1 to 10, wherein means ' are provided in or on the blank such that in the erected carton said means act to space the erected carton from another carton stacked therewith. 12. A blank as claimed in claim 11, wherein the said means for spacing stacked cartons comprises feet provided to project downwards from the bottom corners of the erected carton. 13. A blank as claimed in claim 12, wherein internal ribs are provided at the corners of the erected carton which are arranged and adapted to support the said feet. 14. A blank as claimed in claim 13, wherein the said internal ribs are adapted to be formed from the blank when the blank is erected into a carton. 15. A blank for erecting into a carton, substantially as herein described with reference to. and as shown in Figures 1 to 7. Figures 8 to 10, Figures 11 to 16, Figures 17 and 18, Figure 21, Figure 22, Figure 23, or Figures 24 to 32 of the accompanying drawings. 16. A blank for erecting into a carton having a base portion and side wall portions, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein the said base portion is shaped to receive individual items of produce. 17. A blank as claimed in claim 16, wherein the said base portion is formed with a series of indentations or cells. 18. A blank as claimed in claim 16 or 17, having the features claimed in any of claims 2 to 5. 19. A blank for erecting into a carton having a base portion and side wall portions, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein flaps provided on at least some of the said side walls are arranged to be connected or to cooperate with other said side walls when the blank is erected into a carton, and wherein the side wall portions are hinged to the base portion by respective integral thin strips of plastics material. 20. A blank as claimed in claim 19, wherein the hinges of integral thin strips of plastics material form generally a 'V shape in the blank, the gap defined by the hinge closing up when the respective parts of the blank are hinged together. 21. A blank as claimed in claim 19 or 20, wherein the hinges of integral thin strips of plastics material are formed by displacement of the material of the blank during thermoforming thereof. 22. A blank for erecting into a carton having a base and side walls, wherein the blank is formed of a foamed plastics material which has been extruded and subsequently formed, wherein means are provided in or on the blank such that in the erected carton said means act to space the erected carton from another carton stacked therewith. 23. A blank as claimed in claim 22, wherein the said means for spacing stacked cartons comprises feet provided to project downwards from the bottom corners of the erected carton. 24. A blank as claimed in claim 23, wherein internal ribs are provided at the corners of the erected carton which are arranged and adapted to support the said feet. 25. A blank as claimed in any of claims 22 to 24, having the features claimed in any of claims 2 to 5. 26. A carton when erected from a blank as claimed in any preceding claim.

Inventors: DEVEREUX CHRISTOPHER PETER, DEVEREUX, CHRISTOPHER, PETER
Applicants: DEVEREUX CHRISTOPHER PETER, PORTAPAX LTD, DEVEREUX, CHRISTOPHER, PETER, PORTAPAX LIMITED
Application year: 1986
Main classification: B65D1
IPC codes: B65D5