Blanks for packing containers.

The present invention relates to packing containers, e.g. of the ridge roof type (so-called gable-top package). Packages of this kind are typically manufactured from a plane, substantially rectangular blank of a cardboard material or a comparably rigid but foldable material which is provided with a suitable crease line pattern and is formed to a tube, one end of which is given a bottom closure of any chosen kind and the other end of which is closed by means of so-called bellows folding with a sealing fin arranged on top of it formed of the edge zone of the packing container, that is to say a top closure which below the sealing fin consisting of the edge zone comprises four rectangular end panels, of which two are preferably placed obliquely to each other whilst each of the other two is divided into three triangular panels and folded in under the sealing fin to form so-called bellows folds, the sealing fin consisting, at least to the greater part, of four material layers which are joined to one another by means of a sealing operation.

In packing containers of the aforementioned type it has been a problem to make them tight and at the same time openable. It has been found impossible up to now to fulfil both these requirements in a satisfactory manner and it has been more or less unavoidable to sacrifice the tightness of the container in favour of making it easily openable.

There is a need therefore, to eliminate the said problem of the known packing containers and make available a packing container which is both easily openable and at the same time satisfactorily tight.

The present invention provides a packing container having wall portions which are folded and sealed together to form an end closure for the container comprising a fin, wherein the fin is provided with a line of weakening running longitudinally therealong and the wall portions forming the fin are sealed to one another substantially more strongly above the line of weakening than immediately below the line of weakening.

The invention includes a blank for folding and sealing to form a container, which blank has at one end a transverse running strip for folding and sealing to form a fin, within which strip is provided a line of weakness running along the strip, wherein a seal inhibiting composition is provided on said strip on the container interior side of the line of weakness.

The invention further includes a web of such blanks.

Preferably, in the sealing fin above one of the said bellows folds, a tearing indication weakening the materials layers is provided along a line between, and preferably parallel with, the top line and the foot of the sealing fin, and the seal between the material layers below this tearing indication is made substantially weaker or almost negligible compared with the seal between the material layers above the tearing indication.

The invention will be described in more detail in the following with reference to the attached drawings which by way of example show an embodiment of a packing container in accordance with the same. <ul id="ul0001" list-style="none"><li>Figure 1a shows the part of a plane rectangular blank which is intended to form the top of a packing container;</li><li>Figure 1b shows a raised but not yet closed packing container manufactured from the blank shown in Figure 1a;</li><li>Figure 1c shows the closed top of the packing container;</li><li>Figure 1d represents the packing container during an opening stage; and</li><li>Figure 1e shows the container fully opened.</li></ul>

The packing container shown in Figure 1b is made from a substantially rectangular blank of a cardboard material or a comparable rigid, but foldable material coated with plastics on both sides. The crease line and tearing indication pattern is evident from Figure 1a which thus shows the part of the blank which is intended to form the top part of the packing container. After the blank has been provided with the crease line pattern, as shown in Figure 1a, it is formed into a tube (Figure 1b) by sealing together its two longitudinal edges in, for example, a so-called overlap join. In Figure 1a the overlap lug required for the formulation of the overlap join is designated 1a. One end of the tube formed is given an optional kind of bottom closure which, however, is of no vital importance for the invention and is not shown, therefore, in greater detail.

The tubular part of the packing container consists of four side walls 3 which are delimited by side edge lines 4, the bottom edge lines 4 and upper boundary lines 6. The upper end of the blank, and hence of the tube, has been provided beside the crease lines 6 with crease lines 7 running parallel with these and further crease lines 8a, b and c which form two letter Y turned upside down. As a result the upper end of the packing container can be closed by means of a so-called bellows folding with a sealing fin 10 arranged above it, formed of the upper edge zone 9 of the packing container (Figure 1c), that is to say a closure which below the sealing fin consisting of the edge zone comprises four rectangular end panels 11,11,12 and 12 of which two panels 11 are placed obliquely and the panels 12 are divided into three triangular, smaller panels 13a, b and c folded in under the sealing fin 10 to form so-called bellows folds (one of which is shown at B in Figure 1c). The sealing fin consequently will comprise, at least in its greater part, four material layers which are joined to one another by means of a sealing operation to form the configuration shown in figure 1c. In case both sides of the blank are coated with a plastics layer, e.g. polyethylene, this seal can be brought about, for example, by heat sealing which means that the material layers in the sealing fin 10 of the finished folded packing container are pressed against each other with the help of heating sealing jaws in a packing machine of the conventional type, as a result of which the plastic coatings on the heated sealing surfaces facing each other are fused together to form a liquid-tight seal.

In accordance with the present invention a tearing indication 15 weakening the material layers is arranged above the bellows fold B formed along a line between, and preferably parallel with, the top line 10a and the foot line 10b of the sealing fin 10. The tearing indication 15 is formed in accordance with Figure 1a by a perforation 15p whose length on the example chosen substantially corresponds to the length of two whole package widths. On closing the packing container by means of bellows folding, symmetrical in relation to a crease line 8c, the different portions of the perforation 15p are made to adjoin each other, so that the tearing indication 15 will extend from the front edge 10c of the fin 10 substantially to the centre of the fin (Figure 1c).

The perforation 15 preferably can be arranged in the central cardboard layer before the same is coated with plastics layers and possibly with other layers such as e.g. aluminium foil. The advantage gained from such a procedure is that the packing material will be liquid-tight, since the perforation holes or perforation slots included will be covered by a plastics layer.

The packing container shown in Figure 1c is opened by means of folding out again the bellows fold B so as to form an emptying opening 16 in the shape of a pouring spout which is shown in Figure 1e. The procedure here is that one pushes one's finger into the openable bellows fold B and breaks the package outwards towards the sides, as a result of whichthe perforation 15 is broken up and the sealing fin 10 in the region below the tearing perforation 15 is delaminated, whereas the corresponding region above this perforation remains non-delaminated to attain the condition shown in Figure 1d. Subsequently the parts of the sealing fin 10 so delaminated are pressed together, as a result of which seals between these parts are broken and the bellows fold B bulges outwards so as to form the emptying opening 16 in the shape of a pouring spout shown in Figure 1e.

With a view to facilitating the breaking up of the seal between the inside surfaces 17-20 adjoining one another of the bellows fold B folded flat (Figure 1d) and thereby facilitating the subsequent bulging out of this bellows fold, these adjoining surfaces are reduced in their sealing capacity in accordance with the invention by a pretreatment of the corresponding portions on the packing blank shown in Figures 1a. These pretreated parts correspond to the hatched region C in Figure 1a and comprise the part of the edge zone 9 which is located between the tearing perforation 15p or 15 and the upper crease line 7 and are marked 17 to 20 in the figures shown. This seal-reducing pretreatment may involve, for example, the covering of the plastics layer with a coating inhibiting or weakening a seal (a so-called abhesive) consisting of some siliceous compound, e.g. polysiloxane rubber or a wax mateial of a type known in itself.

In accordance with the invention it is preferred to reduce the seal of all adjoining surfaces below the tearing perforation 15 in the sealing fin 10, that is to say, not only the inside surfaces (17-20) on the part of the sealing fin 10 forming the emptying opening 16 but also the two outside surfaces 21,22 of the rectangular end panel 12 above the fold-out bellows fold B. As a result of this, on opening the packing container, the folding out of the bellows fold to the plane condition shown in Figure 1b, is facilitated.

Through the combination of the tearing perforation 15 arranged in the sealing fin 10 and the said weakening of the seal of the inside surfaces 17-20 sealed in a detachable manner in the region C below the tearing perforation a packing container is obtained in accordance with the present invention which eliminates the conflicting requirements mentioned earlier with regard to easy openability and at the same time reliable liquid-tightness and which instead makes both these requirements well compatible with each other.