BOTTOM DESIGN OF PACKING CONTAINERS

Abstract: A bottom design for packing containers of the type manufactured by folding and sealing of plastic laminated packing material. To prevent the absorbtion of liquid contents by the fibrous carrier layer of the material on unprotected cut edges a folding pattern is created in accordance with the invention which ensures that all cut edges (11) at the bottom (4) of the packing container are situated under protecting parts of the packing material.

Description: The following invention relates to a bottom design of a package container manufactured by folding and subsequent sealing of a packing laminate provided with crease lines delimiting four side panels, a top part and a bottom part, said bottom part consisting of a number of material panels which comprise two main bottom panels connected to opposite side walls, two fold-in bottom panels connected to intermediate side walls and four fold-back panels joining together the main bottom panels and the fold-in bottom panels, whereby each fold-in bottom panel has a primary panel which constitutes a continuation of the fold-in bottom panel and is double-folded with the free bottom edge in a protected position between the fold-in bottom panels and the fold-back panels (known from e.g. DE-A-2 632 914). The invention also relates to a bottom design on laminated packing container blanks of the type comprising four side panels as well as a number of top and bottom panels separated by crease lines, the bottom wall panels comprising two main bottom panels, two fold-in bottom panels and four fold-back panels joining together the main bottom panels and the fold-in bottom panels, whereby the bottom wall panels along a free bottom edge have primary panels which are divided from the fold-in bottom panels by means of crease lines (known from e.g. DE-A-2 632 914). In the manufacture of packing containers for e.g. milk and juice, a laminated packing material is used which usually comprises a carrier layer of paper which is coated on either side with thermoplastic material, e.g. polyethylene. The thermoplastics imparts to the material good liquid-tightness and makes it possible at the same time in a simple manner with the help of heat-sealing to obtain liquid-tight joins. The packing laminate also can include further layers of other materials, e.g. aluminium foil, in order to give the material better gas tightness. The packing container blanks are manufactured from weblike packing laminate which after application of the different layers is cut out so as to form blanks which, either in connection with the cutting out or later, are converted through folding and sealing to finished packing containers. To facilitate the conversion of the blanks to finished packing containers the packing laminate is also provided with a pattern of folding lines, usually crease lines, along which the materials can simply be folded with the help of automatic packing machines. The packing laminate can also be provided with different types of opening arrangements, perforation lines or the like, but the design and detailed layout of the laminate are well-known in principle within the packaging branches and do not have to be described, therefore, in any more detail. During the cutting out mentioned earlier of the individual blanks from a coherent, thermoplastic coated laminate web the inner layer will be exposed in the cut edges formed in the process. Since the carrier layer often consists of a material with good absorption capacity, e.g. paper, it is essential that these cut edges should be placed in such a manner that they will not come into contact with the contents when the packing container has been completed. In certain types of packing containers, e.g. ridge packages (also with plane top) parts of the cut edges, on folding according to a conventional pattern, will come to be located inside the packing container and these parts of the cut edges have to be protected, therefore, from contact with the packed contents if high demands on tightness and hygiene are to be maintained, since otherwise the contents will be absorbed into the fibrous layer of the packing laminate. In gas-tight material, that is to say packing laminate which comprises layers of e.g. aluminium foil, the gas-tightness too will be impaired, since the gas-tight layers will not be closely adjoining one another in the areas where the cut edges are exposed. In a packing container of the conventional ridge-type which is manufactured from preformed blanks, cut edges will appear inside the packing container on the one hand along a vertical longitudinal join, on the other hand in a central area of the bottom where folded-in material lugs meet. The longitudinal join can be provided with a covering strip or be realized as a so-called crimped-over longitudinal join which prevents contact with the contents. These solutions have been known earlier, but no solution has been offered until now which in a simple manner makes possible a complete sealing also of the exposed cut edges present at the bottom of the packing container. Earlier solutions suggest, among other things, different types of foldings which deviate from the normal folding pattern and on the other hand, therefore, become more complicated to realize, and involve larger consumption of material (US patent specification 3412922). A further known bottom design in this category (DE-A-26 32 914) involves double-folded flaps protecting the major parts of the cutting edge but leaving corner areas unprotected and exposed to the filling goods. Another solution proposes that on a substantially conventional bottom design different types of seals are applied over the parts of the cut edges which otherwise would come into contact with the contents (US patent specification 3913825). This solution too is comparatively complicated and disadvantageous, since it makes necessary the application and use of additional material. The previously known bottom designs, where it was endeavoured to avoid direct contact between exposed cut edges and contents, are thus relatively complicated in that the design involves increased material consumption and consequently higher costs. Moreover, the bottom designs are difficult to fold with automatic machines of a conventional type and give thick, uneven results which increase the risk of channel formation and leakages between the different layers. It is an object of the present invention to provide a bottom design which is not subject to the aforementioned disadvantages but which in comparatively simple manner provides an effective sealing of the cut edges. It is a further object of the present invention to provide a bottom design with protected cut edges, where the folding pattern substantially coincides with a conventional folding pattern, at the same time as the material consumption is reduced to a minimum and any need of additional material in the form of strips, hot-melt or the like does not arise. These and other objects have been achieved in accordance with the invention in that a bottom design of the type described in the introduction has been given the characteristic, that triangular secondary panels are connected to opposite sides of the primary panel by means of secondary crease lines and serve as fold-back panels between the primary panels and the main fold-back panels of the container bottom. Corresponding bottom designs on a blank for conversion to a packing container of the type mentioned at the beginning have been given the characteristic in accordance with the invention that triangular secondary panels serving as fold-back panels are situated on opposite sides of the primary panel and divided from the primary panel and from adjoining fold-back panels by means of secondary crease lines which extend at an angle to the free bottom edge of the bottom wall panel. Preferred embodiments on the bottom design in accordance with the invention on a finished packing container as well as on a blank for the manufacture of packing containers have been given the characteristics in accordance with the invention which are evident from the subsidiary claims. The bottom design in accordance with the invention makes it possible to achieve with limited material consumption a bottom design in which the cut edges of the packing laminate are completely covered so that all contact between the cut edges and contents packaged in the packing container can be avoided. Since the cut edges are protected by folding in of, or covering with, material present already, no application of any additional material of any kind is required either which facilitates appreciably the manufacture of packing containers of this bottom design. Two preferred embodiments of the bottom design in accordance with the invention will now be described in more detail with special reference to the attached drawings which schematically show the bottom design in different stages during the conversion of a packing container blank to a finished packing container. Fig.1 shows in perspective a bottom design in accordance with the invention during formation on an otherwise conventional packing container. Fig.2 shows the bottom design according to Fig.1 from underneath. Fig.3 shows a part of a packing container blank where a first embodiment of the bottom design in accordance with the invention is used. Fig.4 shows a part of a packing container blank where a second embodiment of a bottom design in accordance with the invention is used. Fig.5 shows in section a packing container with a bottom designed in accordance with the second embodiment of the bottom design in accordance with the invention. Fig.6 shows the bottom design in accordance with Fig.5 from the side and in section. Two embodiments of the bottom design in accordance with the invention are described in the following and are illustrated in the figures partly in form of flat packing container blanks, partly in the form of blanks wholly or partly converted to finished packing containers and sealed. Furthermore, the bottom design is applied generally to the type of packing containers which are called ridge packages but which also can be realized with a flat top part. This main type of package is well-known and described in more detail e.g. in Swedish patent specification No.377.313 to which reference is made. Figure 1 shows how the bottom design in accordance with the invention is realized on a known packing container of the flat ridge-type, this packing container comprising four rectangular side panels 1 which are divided from one another and folded along four side crease lines 2 so that a tubular packing container body of substantially square cross section is produced. The packing container furthermore comprises a top part 3 which is of the flat ridge type and a bottom part 4 which is designed in accordance with the invention. The packing container which, apart from the bottom part 4 is of a known type, therefore is also manufactured from conventional packing material, e.g. a laminate which comprises a central carrier layer of fibrous material coated on either side with a layer of liquid-tight and heat sealable material, e.g. a thermoplastics such as polyethylene. Further layers may also be present e.g. gas-tight layers of aluminium foil or the like. The packing laminate is manufactured by means of a conventional technique, that is to say a web of fibrous carrier layer is being coated successively with different material layers as desired, whereupon it is provided with crease lines in the required pattern and divided up into individual blanks. The conversion of the packing laminate to individual packing containers may be done either whilst the packing laminate continues to be in form of a web, directly after the dividing up into individual sheets or on a later occasion. The manufacturing process as well as the composition of the packing laminate, the crease line pattern and the cutting out are conventional and well-known to those versed in the art, so that they are not described in more detail in the present context. For the same reason only the bottom part of the packing container or the packing container blank is illustrated in certain figures and it is assumed that any parts not shown are of any conventional type. The bottom design in accordance with the invention is shown in general in figures 1 and 2 from which it is evident that the bottom part 4 comprises two substantially rectangular main bottom panels 5 which are connected in foldable manner to two opposite side panels via a transverse bottom crease line 6, which extends substantially at a right angle to the vertical side crease lines 2 of the packing container and runs along the whole circumference of the packing container, that is to say transversly over the whole width of the packing container blanks (Fig.3,4) The bottom crease line 6 delimits on the other pair of opposite side panels 1 two fold-in bottom panels 7 which along the bottom crease line 6 are of a width which corresponds to the width of the adjoining side panel 1 but which tapers in the direction away from the side panel. Between each fold-in bottom panel 7 and the main bottom panels 5 situated nearby two fold-back panels 8 are provided, which are connected in foldable manner to the fold-in bottom panels 7 via oblique crease lines 9 and to the main bottom panels 5 via parts crossing the bottom crease lines 6 of the side crease lines 2. On a bottom part formed in conventional manner the fold-in bottom panels 7 as well as the fold-back panels 8 are triangular and the oblique crease lines situated between the said panels meet, therefore, in a common point at the lower end of the panel, that is to say at the free edge remote from the side panel 1. When the bottom is formed through folding-in of the fold-in panels under the main panels of the bottom this point will be critical since here the cut edges will be exposed and accessible to the contents. In the bottom design in acordance with the invention the previously triangular fold-in bottom panels and fold-back panels have been given a four-sided form in that their corner facing towards the free bottom edge 11 of the bottom part 4 has been delimited by means of crease lines and divided into a number of foldable edge panels 10. More precisely, the fold-in bottom panel 7 is divided from an edge panel, situated centrally called primary panel 12, with the help of a primary crease line 13 which extends parallel with the free bottom edge 11 and is of a length which substantially corresponds to a quarter of the distance between two adjoining side crease lines 2. The primary panel 12 thus constitutes a rectangular continuation of the fold-in bottom panel 7 and is limited on either side by further triangular edge panels which are called secondary panels 14. The secondary panels 14 serve as fold-back panels and are divided from the primary panel 12 and the adjoining fold-back panel 8 respectively by means of secondary crease lines 15 which extend at an angle to the free bottom edge 11. More precisely, the two secondary crease lines 15 which delimit the side of the primary panel 12 extend substantially at a right angle to the bottom edge 11, whilst the two secondary crease lines 15 which divide the secondary panels 14 from the fold-back panels 8 extend substantially at a right angle to the crease line 9, which separates the fold-in bottom panels 7 from the fold-back panels 8. All the above information on angles and directions relate to the flat state of the packing container, e.g. as illustrated in figure3. On conversion of the packing container blank to finished packing containers the bottom design is folded along the crease lines in such a manner, that the two fold-in bottom panels 7 form part of the inside of the bottom, that is to say, they end up inside the packing container whereas the main bottom panels 5 form the outside of the bottom and the remaining parts of the inside. On folding of the main bottom panels the fold-back panels 8 will be placed between the fold-in bottom panels 7 and the main bottom panels 5, whereas when the forming of the packing container has been completed the edge panels 10, will be located, folded back over 180°, in a protected position between the fold-in bottom panels 7 and adjoining fold-back panels 8, so that the free bottom edge 11 of the edge panels is completely isolated from any contents subsequently filled into the packing container. The folding of the edge panels 10 in connection with the forming of the bottom part 4 of the package is evident most clearly from Figures 1 and 2 which show the bottom design in an intermediate position during the forming of the bottom. During the conversion of the packing container blank from the flat condition to the finished packing container the blank is folded first in conventional manner over 90° around each side crease line 2, so that the two outer side panels 1 will meet and be sealed to each other with the help of a longitudinal sealing panel 16. Then the top and bottom parts of the packing container are formed, each by itself, through folding in of the respective material panels. On forming a conventional bottom part the two fold-in bottom panels 7 are folded in towards each other by being turned around the corresponding part of the bottom crease line 6 at the same time as the two main bottom panels 5 are folded towards each other and around the bottom crease line 6, so that the main bottom panel will be on the outside of the fold-in bottom panels 7, In so doing the fold-back panels 8 joining together the fold-in bottom panels 7 and the main bottom panels 5 will be folded outwards around the crease line 9 situated between the fold-back panels 8 and the fold-in bottom panels 7, and, in the bottom design in accordance with the invention,the edge panels 10 are also folded at the same time around the primary and secondary crease lines 13,15. More precisely, the central primary panels are folded over 180° outwards around the primary crease lines 13 so that they rest against the outside of the respective fold-in bottom panels 7, at the same time as the triangular secondary panels 14 serving as fold-back panels are folded around the secondary crease lines 15. After completion of the folding process the parts of the bottom edge 11 which delimit the primary panels 12 will be located in a protected position between the fold-in bottom panels 7 and the fold-back panels 8 which rest against each other and are sealed to each other with the help of the outer thermoplastic layers. The edge 11 as a result will no longer be situated inside the packing container, and the risk of an absorption of the contents into the said cut edge has thus been eliminated. However, the part of the bottom edge 11 which is located along the main bottom panel 5, which is overlapped by the main bottom panel situated opposite, will be located inside the packing container and will be in contact with the contents in the space at the bottom of the packing container which is not covered by the two folded-in fold-in bottom panels 7. This part of the bottom edge 11 can be protected in a conventional manner by providing it with a projecting tongue 17 which is folded back over 180° so that it will be located between parts of the two main bottom panels 5 which in the finished state of the bottom part overlap each other and are sealed to each other. This is part of the prior art, though, and need not be described in more detail in the present context. In a second embodiment of the bottom design in accordance with the invention the shape and size of material panels have been modified so that the need for a separate sealing tongue 17 on the bottom edge 11 disappears at the same time as further safety against leakage and absorbtion of the contents into the carrier layer of the packing laminate is achieved. This second, modified embodiment of the bottom design in accordance with the invention is illustrated in more detail in the Figures 4,5 and 6. The parts of the packing container blank and the packing container which agree with the corresponding parts in the first embodiment described of the bottom design in accordance with the invention, have been given corresponding reference numerals and will not be described in detail, since their design and function is identical with what has been described earlier. The greatest difference betweenthe packing container blank in Figure 4 and the packing container blank in Figure 3 consists in that the free bottom edge 11 of the blank is no longer straight in the region of the edge panels 10 and fold-back panels 8, but bends and turns outwards, so that the distance between the free bottom edge 11 and the bottom crease line 6 which joins together appurtenant fold-in bottom panels 7 with adjoining side panels 1 of the packing container is greatest at the central part of the cut edge 11 situated right before the primary panel 12 when the panels are in a common plane, that is to say when the packing container blank is unfolded. The distance between the primary crease line 13 and the corresponding section of the crease line 6 will be greater, here, in this second embodiment and, more precisely, the distance between the bottom crease line 6 and the primary crease line 13 (the distance a) is equal to, or slightly greater (1-5%) than half the width (distance b) of the adjoining main bottom panel 5. After conversion of the packing container blank and folding of the bottom panels to form a flat base the two outer end edges of the fold-in bottom panels 7 defined by the primary crease lines 13 will meet in the centre of the bottom surface of the packing container and they can be made to join tightly to each other, so that after sealing together of the different panels of the bottom design they completely cover and seal off the part of the edge line 11 which previously came into contact with the contents and, therefore, had to be provided with the fold-in tongue 17. As a result the bottom design in accordance with the invention can ensure a completely sealed off bottom which not only protects all cut edges from contact with the contents, but also possesses such evenness that the risk of leakage via channels at the transition between different material thickness etc, is avoided. The finished and sealed bottom design in accordance with the second embodiment of the invention is illustrated in Figures 5 and 6, where the closeness between the fold-in points of the two fold-in bottom panels 7 is clearly illustrated. Figure 6 moreover makes evident how the folded-in primary panels 12 are located between fold-in bottom panels 7 and the main bottom panels 5 forming the outside base of the packing container.

Claims: A bottom design of a package container manufactured by folding and subsequent sealing of a packing laminate provided with crease lines delimiting four side panels (1), a top part (3) and a bottom part (4), said bottom part consisting of a number of material panels which comprise two main bottom panels (5) connected to opposite side walls, two fold-in bottom panels (7) connected to intermediate side walls and four fold-back panels (8) joining together the main bottom panels and the fold-in bottom panels, whereby each fold-in bottom panel (7) has a primary panel (12) which constitutes a continuation of the fold-in bottom panel (7) and is double-folded with the free bottom edge (11) in a protected position between the fold-in bottom panels (7) and the fold-back panels (8), characterized in that triangular secondary panels (14) are connected to opposite sides of the primary panel (12) by means of secondary crease lines (15) and serve as fold-back panels between the primary panels (12) and the main fold-back panels (8) of the container bottom. A bottom design in accordance with claim 1, characterized in that the primary panel (12), when the packing container is finished, is folded over 180° along a primary crease line (13) extending parallel with the edge and rests against the adjoining fold-in bottom panel (7). A bottom design in accordance with claim 1 or 2, characterized in that the folded edges formed between respective primary panels (12) and adjoining fold-in bottom panels (7), in the finished state of the packing container rest in liquid-tight manner against one another, and are sealed together. A bottom design on laminated packing container blanks of the type comprising four side panels as well as a number of top and bottom panels separated by crease lines, the bottom wall panels comprising two main bottom panels (5), two fold-in bottom panels (7) and four fold-back panels (8) joining together the main bottom panels and the fold-in bottom panels, whereby the bottom wall panels along a free bottom edge (11) have primary panels (12) which are divided from the fold-in bottom panels (7) by means of crease lines (13), characterized in that triangular secondary panels (14) serving as fold-back panels are situated on opposite sides of the primary panel and divided from the primary panel (12) and from adjoining fold-back panels (8) by means of secondary crease lines (15) which extend at an angle to the free bottom edge (11) of the bottom wall panel. A bottom design in accordance with one or more of the preceding claims, characterized in that the free bottom edge (11) common to both the fold-back panels (8) and the edge panels (10) is a straight line when the panels are in a common plane. A bottom design in accordance with one or more of claims 1 to 4 inclusive, characterized in that the free bottom edge (11), common to both the fold-back panels (8) and the edge panels (10), is curved outwards when the panels are in a common plane. A bottom design in accordance with claim 6, characterized in that the distance between the free bottom edge (11) and the bottom crease line (6) which joins together appertenant fold-in bottom panels (7) with adjoining side panels (1) is greatest at the central part of the edge (11) situated right in front of the primary panel (12) when the panels are in a common plane. A bottom design in accordance with claim 7, characterized in that the primary crease line (13) extends parallel with the bottom crease line (6) situated between the fold-in bottom panel (7) and the adjoining side wall (1) of the packing container. A bottom design in accordance with claim 8, characterized in that the distance (a) between the bottom crease line (6) and the primary crease line (13) is equal to or greater than half the width (b) of adjoining main bottom panels (5).

Inventors: DERVING, JACKIE
Applicants: AB TETRA PAK
Application year: 1986
Main classification: B65D5
IPC codes: B65D5