METHOD FOR PREPARING A CONTAINER AND A BLANK FOR FORMING THE SAME

Abstract: A method for preparing a container with sharp corners at the bottom out of a cardboard material. In the method, first a box blank (17) is prepared, in which the corners (16) at the top edge are rounded. A lid blank prepared by cutting is mounted at the top end, and the blanks are sealed together. The container is filled through the end placed next to the bottom edge, and finally the bottom edge is closed and folded to make a bottom with sharp corners.

Description: METHOD FOR PREPARING A CONTAINER AND A BLANK FOR FORMING THE SAME The present invention is concerned with a method for preparing a cardboard container with sharp corners at the bottom and with a box blank to be used for the container. In the commonest cardboard container system in use at present, a board web is fed from a roll into the package and filling machine to make a hose. The longi- tudinal seam is closed by hot-sealing, and the hose is filled with liquid. The containers are formed by hot- sealing the transverse joints in the hose through the liquid. Finally, the bottom and the cover are folded so that a container shaped as a right-angled prism is formed. Usually these containers are made openable by cutting or tearing, and the opening is in practice quite difficult.. Another drawback is poor rigidity of the container, which results from the fact that in the con¬ tainer the direction of the fibres in the cardboard is parallel to the hose. In order to make it easier to open the con¬ tainer, it is possible to provide the cover with per¬ forations, but they do not provide an essential improve¬ ment. Moreover, it is usually necessary to prepare the perforations in the packaging machine itself, which makes the packaging more complicated. If an easily openable opening system is con¬ structed for such a container, the cardboard must be perforated in the packaging machine and the machine must be provided with two or three additional material lines, in which case the system becomes quite complicated and difficult, e.g., from the aseptic point of view. Nor is it possible to handle liquids that contain particles in this packaging system, because the sealing takes place through the liquid. In the German published Patent Applications DE 3,043,134 and DE 3,343,629, methods for preparing containers have been suggested, wherein a tubular blank is first formed of a hose. Then, an injection-moulded lid is mounted on the mouth of the blank, which said lid is provided with an opening construction, whereinafter the container is filled through the bottom, and finally the bottom is closed by sealing and by folding it to rectangular form. This method is quite expensive and difficult to carry out, in particular if the lid is injection-moulded in connection with the packaging machine. It is also known in prior art to prepare similar containers while starting from a ready-cut cardboard blank, in which case the direction of running of the fibres in the board can be made optimal in view of the rigidity of the package. However, the problem still remains that the container cannot be provided with a simple opening construction without a highly com¬ plicated packaging machine. • A packaging system is also in use in which the cardboard is introduced into the packaging machine as blanks sealed at the side joint, wherein the fibre direction can be made parallel to the bottom. The con¬ tainer may be provided with a ridge-shaped lid fold by hot-sealing, a pouring spout being formed by opening the fold. The package can be opened quite easily if the joint is not made- very tight. In aseptic containers, the lid joint must, however, be closed tightly, and its opening is no longer very easy. This packaging system is not particularly practical, because the blanks sealed at the side require an abundance of transportation space, the ridge fold requires a lot of extra material, and the ready container requires extra space and is even otherwise difficult to store and to transport. A packaging system is also known in prior art in which a cardboard tube is prepared which has a square section and is rounded at the corners and to whose ends a lid and a bottom are attached by hot-sealing partly inside and partly outside the edge, the said lid and bottom being made of separate plastic/aluminium laminate. Thus, it is possible to provide the lid in advance with an opening construction of the desired sort', which makes the packaging process itself easier. The package is also favourable in transportation, A drawback is, how¬ ever, the very high cost of the package. In the method now invented, the lid part of the container, together with the opening and closing con- struction included in it, is prepared out of a separate film-like material. All the rest of the container, including the bottom, is made of one blank. In the first stage, the cardboard blank is sealed at the side joint so that the corners at the • mouth of the container become rounded. The lid part made of a film-like material, for example cardboard or plastic or aluminium laminate, is .attached to the mouth of the. container, whereby, owing to the rounded corners,. a tight, liquid-proof joint is obtained at the edge of the lid material. The container is filled through the bottom, and finally the bottom is closed by sealing and folded to sharp-cornered form. The ready container is rectangular in shape, its bottom and lid are plane, and therefore it is favourable for distribution systems. The lid material makes about 10 to 15 per cent of the material of the whole container. The lid blanks are prepared preferably so that the desired opening and closing constructions are formed in the material roll as appropriately spaced. The lid blanks are introduced into the packaging machine from a roll, from which a piece slightly larger than the mouth of the container is cut, which said piece is hot-sealed onto the inner edge of the container mouth with the edges of the lid outwards. In this way, the container is provided with an opening construction of desired sort in a simple way, without making the packaging machine complicated. Only two lines of material have to be passed into the packaging machine, whereby it is easier, for example, to maintain aseptic conditions. The blank which forms the main part of the container is fed into the packaging machine preferably as a plane open sheet, into which the grooves have been pressed which form the side edges as well as the folds and joints at the bottom. The grooves for the side edges do, however, not extend up to the upper edge of the sheet, but their extensions are provided with form pressings facilitating the rounding. The fibre direction in the cardboard is pre¬ ferably perpendicular to the side edges, in which case the container becomes rigid. The container is intended in particular for liquid products, but it is also, better than the prior- art containers, -suitable for liquids of high viscosity, liquids that contain particles or liquids that solidify upon filling as well as for dry products. In accordance with the present invention, it is possible to solve the great problem of the present-day cardboard liquid containers, in particular of aseptic liquid containers: how to make the container easily openable and reclosable. Further advantages of the method are low con- sumption of raw-material as well as little requirement of transportation space for the raw-material. An embodiment of the invention will be de¬ scribed in more detail ' with reference to the accompanying drawings. Figure 1 shows a grooved blank sheet. Figure 2 the sealing of the side joint of the blank. Figure 3 the cutting of the lid blank. Figures 4 to 6 the folding of the bottom, and Figure 7 a finished container. The side walls and the bottom of the container are made out of a box blank in accordance with Fig. 1. The blank is made of cardboard coated with polyethene film, and it is provided with grooves arranged in a suitable way. In a finished container, the side edges 1 and 2 of the blank are hot-sealed overlapping each other. In order that liquid could not penetrate into the paper via the lower edge 1 in the overlapping joint, the edge is protected by a plastic tape, or it is folded into the joint. The blank is provided with grooves 4 -parallel to the side edges, which said grooves form the side edges of the container so that a finished container has a rectangular section. At the top edge 5 of the blank (i.e. at the edge placed next to the lid of the con¬ tainer to be formed) the grooves 4 do not extend up to the edge, but, as an extension of each groove, there is a form-pressed zone 6 between the groove and the edge. In this way, rounded corners 16 are formed at the top edge 5 of the container (Fig. 2) . In the bottom part of the blank, near the bottom edge 7, there is a groove 8 parallel to the bottom edge, along which the bottom is hot-sealed, a groove 9, which forms the bottom edge of the container, as well as, between them, at the narrow sides of the container, grooves 10 for the projecting tongues. The bottom of the container is formed by folding along the grooves in the bottom part (Figures 4 to 6) . In the first stage of the packaging process, the blank is folded along the grooves 4 around a mandrel 11 to make a tubular blank 17, so that the top edge of the blank is placed at the side next to the end of the mandrel, whereupon the edges 1 and 2 are joined by hot- sealing so that they overlap each other and that the edge 1 remains inside. Fig. 3 shows a rolled lid-blank band, which is made of the same material as the side-wall and bottom blank. The band 12 is provided with holes 13 spaced in accordance with the dimensions of the lid and closed by means of an opening construction 14. In the second stage of the process, a lid blank 15 is cut out of the band 12, which said blank is shaped like the lid of the container but is slightly larger than the lid. The lid blank 15 is pressed into the top end 5 of the folded and side-sealed box blank so that the edges of the lid blank become directed outwards. If desired, the joint is sealed, and it is closed by hot-sealing. If desired, it is also possible to fold or roll the joint, whereby it becomes stronger. In the next stage, the container is turned so that its lid is facing downwards, and filled (Fig. 4) Thereupon the bottom joint is closed by heating, and the folds are bent so as to make a plane bottom (Figs. 5 and 6) .

Claims: WHAT IS CLAIMED IS: 1. Method for preparing a container with sharp corners at the bottom out of a cardboard material, in which method - a tubular box blank (17) of substantially rectangu¬ lar cross-section is prepared out of a cardboard material, in which said blank there is a bottom edge (7) and an upper edge (5) and in which the corners (16) at the upper edge are rounded, a lid blank, which is provided with an opening construction, is attached to the end of the box blank that is placed next to the upper edge , the container is filled through the end placed at the bottom edge, as well as the end placed at the bottom edge is closed and folded to make a sharp-cornered bottom, c h a r a c t e r i z e d in that - a lid blank (15) , which is cut out of a film-like material and which is provided with an opening con¬ struction (14) , is attached to the end of the box blank that is placed next to the upper edge, by placing the lid blank into the end of the box blank and by sealing the blanks together. 2. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that, before the lid blank (15) is attached, grooves (4) for the side edges are formed into the box blank (17) , which said grooves (4) end before the top edge (5) of the blank. 3. Method as claimed in claim 2, c h a r ¬ a c t e r i z e d in that side-edge grooves (4) are formed, which begin from the bottom edge (7) of the blank. 4. Method as claimed in claim 1, c h a r - a c t e r i z e d in that form pressings (6) are formed at the top edge (5) of the box blank facing the side edges (4) . 5. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the box blank (17) is made of a cardboard sheet (1) . 6. Method as claimed in claim 1 , c h a r - a c t e r i z e d in that a box blank (17) is prepared in which the fibre direction of the cardboard material is perpendicular to the s-ide edges of the blank. 7. Method as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the lid blank (15) is made by cutting from a roll. 8. Box blank for preparing a cardboard container with sharp corners at the bottom, which said blank is a rectangular sheet that has side edges (1 and 2) as well as a top edge (5) and a bottom edge (7) ; side-edge grooves (4) which are parallel to the side edges, which start from the bottom edge, and which form the side edges of the finished container so that the side- edges of the blank can be joined together; grooves (8, 9 and 10) along which the bottom of a ready container is formed and closed, c h a r a c t e r i z e d in that the side-edge grooves (4) end before the top edge (5) of the blank and that extensions of the side-edge grooves consist of form pressings (6) .

Inventors: KLEEMOLA PERTTI, KLEEMOLA, PERTTI
Applicants: YHTYNEET PAPERITEHTAAT OY
Application year: 1986
Main classification: B31B3
IPC codes: B65B3, B65D5