Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to a folding box for liqulds, the box being
folded from a packaging web and having an overlapping seam with a protected
edge, the thickness of the material of the packaging web being reduced along
the protected edge.
When producing seams on packages for liquid consisting of composite
material, for example fibrous material coated with syntehtic material, a
protected edge is regarded as necessary, so that the edge of the fibrous
material does not come into contact with the liquid. For this purpose, the
- edge with the layer of synthetic material is bent over towards the outside.
This causes the problem of a double thickness of material being present along
the edge, and where seams cross, it is even possible to have a quadruple
thickness of material. These thicknesses of material are undesirable 9 since
they make processing difficult and may cause leakage. For this reason~ the
thickness of the material has been reduced, for example to half the thickness,
along the marginal edges in the form of a step, so that after folding over
the edge outwards, the normal initial thickness in the folded part of the
material edge is achieved. The removal of material has been carried out by
milling.
; The object of the present invention is to develop a folding box
~0 for liquids, in which the protected edge :Ls constructed in a particularly
simple manner and high liquid-tightness can be achieved even with a slight
thickness of the overlapping seam.
The invention provides a folding box for liquids, said box having
an overlapping seam with a protected edge and being formed by folding from a
packaging web material the opposite surfaces of which have relatively thin and
thick coatings of heat-sealable synthetic material, referred to as the inner
coating and the outer coating respectively; said seam being formed between an
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underneath edge part and an overlapping edge part of said packaging web
material; said underneath edge part being pre-formed as a wedge-shaped
scarfed edge which tapers in thickness initially sharply from the side of
the thin outer coating and then less sharply towards the side of the thick
inner coating which extends to said scarfed edge, said scarfed edge being
folded back upon itself so that said inner coating extends around said under-
neath edge part and back towards the edge of the thin outer coating; said
overlapping edge part extending across said underneath edge part and having
its thick inner coating heat-sealed to said folded-back thick inner coating
and to the thin outer coating of said tnderneath edge part so as to form a
sealed and compLetely covered protected edge.
The wedge point preferably has a thickness of 20 to 60~. For the
relatively sharp tapering it is preferred if there is a reduction in thickness
of the material of the packaging web of more than 50% over the initial third
of the length of the wedge. For the sharper tapering over a wedge length of --
one third to one half of the overall wedge length, it is preferred if there
is a reduction in thickness of 55 to 70% of the initial material thickness.
The remaining shallower or less sharply tapered part of the wedge length then
passes gradually into the wedge point with the given minimum thickness. It
has been found that with the aforesaid wedge profile, advantages are achieved
since in the thicker part of the wedge, high rigidity is ensured, whereas
the shallow wedge point allows folding back of the wedge point or scarfed
edge to form the protected edge in a particularly satisfactory manner.
The liquid-tight folding box with a protected edge, proposed
according to the invention, is of particular advantage in the case of liquid-
tight packaging materials consisting of composite material in which the thick-
er coating is normally provided ad~acent the llquid and the thinner coating
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on the side remote from the liquid. The main material in the centre may be
fibrous material, for example cardboard with a weight of 200 to 300 grams/
square metre (corresponds to a thickness of 300 to 450~, whereas a thick
coating of synthetic material of 20 to 60~is provided adjacent the liquid
and a coating of synthetic material of 10 to 20~ is provided on the side
remote from the liquid. Polyethylene (PE) in particular is known as the
synthetic material coating. ~owever, other conventional synthetic coatings
may be used, even combinations with plastics sheeting or aluminium foils.
In place of the Eibrous material in the centre, foam material or a self-
supporting synthe~ic material can also be provided. It has proved advantage-
ous to fold back at least one third of the length of the wedge, on the one
hand in order to form the protected edge and on the other hand in order to
' achieve a good seal of the underneath part to the overlapping part.
Alternatively, the margin having a profile tapering in a wedge
shape offers the possibility of forming a liquid-tight folding box with a
-~ very thin overlapping seam, in that both the o~erlapping part as well as the
underneath part have a marginal profile tapering in the shape of a wedge and
the two parts are interconnected along the wedge surface. In this embodiment,
the two wedge surfaces may taper in the same direction, i.e. in both cases
the wedge surface ends in the thicker coating.
; The profile tapering in a wedge shape of the margins is appropri-
ately produced by paring-off the edge by means of a cutter. Particularly
suitable for the production of the wedge surface tapering ln the manner
according to the invention is a hollow cutter rotating at a peripheral speed
of more than 10 metres per second, against which the continuously fed pack-
aging web is pressed by means of compressed air. This construction ensures
that one obtains a cut surface which can be easily sealed or stuck, without
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the sealing operation being impaired by particles of dust. This also has
the advantage that in the case of boxes for packaging liquids for example,
such as milk containers, the milk is not contaminated by undesirable dust.
The inven-tlon is described in detail hereafter, by way of example
only, with reference to the embodiment shown in the accompanying drawings,
w71erein:
Fig~re l is a diagrammatic illustration of a folding box with an
overlapping seam,
Figure 2 shows an example of a particularly preferred edge pro-
file, to an enlarged scale,
Figure 3 shows an example of sealed overlapping seam formed from
the edge profile of figure 2, and
Figure 4 shows an example where the seams cross.
The liquid~t~ght folding box, for example a folding box for milk,
designated generally by the reference numeral l is made from a composite
material (figure 2), which comprises a central layer of cardboard 2 having a
- thickness of 430~, a relatively thick layer of synthetic material 4 ~40~
poqyethylene) adjacent the liquid and a relatively thin synthetie layer 5
(15,~ polyethylene) on the side remote from the liquid. By folding the pack-
aging web, overlapping seams 6 are formed on the olding ~ox l. These over-
lapping seams 6 may cross at intersections 7.
Figure 2 shows the profile of margins forming the wedge surface 9,
which taper in the direction of ~he wedge point lO, Over the first third of
the length of the wedge, the thickness is already reduced to more than 55%
of the total thickness, whereas approaching of the wedge point lO, the re-
duction is slower and more gradual. In the two illustrated parts o the pack-
aging web, the wedge profile is tapered towards the same side, in which case
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an overlapping seam as shown for example in figure 3 can be formed.
Aa shown in detail in figures 3 and 4, ~he folding box 1 comprises
a protected edge 8 at the overlapping seams 6. This protected edge 8 is
necessary in order that the liquid does not come into contact with the end
face of the packaging web. The tapering wedge profile illustrated in figure
2 is the basis for the protected edge 8, the thickness oE the wedge point 10
corresponding approximately to the thickness of the thicker synthetic layer
4 (for example 40~.
In the embodiment of figure 3, the protected edge 8 is formed by
the wedge surface 9 of the underneath part 12 being folded back approximately
at its centre, so that this folded-back wedge point 10 bears against the
relatively thin synthetic layer 5 of the underneath part 12. Bearing against
the folded-back relatively thick synthetic layer 4 of the underneath part 12
is the relatively thick synthetic layer 4 of the overlappirlg part 11, in
which case the front edge 10 of the overlapping part 11 extends above the
relatively thin syn~hetic layer 5 of the underneath part 12, so that the
` ~protected edge 8 is completely covered by the relatively thick synthetic layer
`~ 4 of the overlapping part 11. The adjoining relatively thick coatings 4 of
the underneath part 12 and of the overlapping part 11 are fused by the
- 20 application of heat. In this embodiment, a good bond is achieved upon seal-
ing, but a certain increase in thickness has to be tolerated.
The crossing of a longitudinal seam by a transverse seam illustra-
ted in figure 4 is also particularly advantageous. The upper part of the
figure corresponds to the illustration according to figure 3. The lower part
shows a further layer 14 of the composite material with the layer of card-
board 2, the relatively thick synthetic layer 4 and the relatively thin
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synthetic layer S.
The construction of the wedge surface both on the underneath part
12 as well as on the overlapping part 11 is recommended particularly for the
processing of thick profi].es, since overall, in this way one achieves a
thinner construction of the overlapping seam.
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