Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a packaging container
provided with a leakproof tear-open perforation. Said packaging
container is of the kind produced from a laminate comprising a
relatively stiff and unmalleable basic layer, at least one side
of said basic layer being turned towards the inside of the package
has a leakproof unbroken plastic coating, said tear perforation
being so arranged that it completely pierces or substantially
penetrates the basic layer but without penetrating the plastic
layer turned towards the inside of the package.
Modern packages for liquids for single use are often
produced from a packaging laminate having a relatively stiff and
unmalleable basic layer, for example, paper, and a leakproof
homogeneous plastic layer arranged on either side around the basic
layer. A frequently used method for producing packaging containers
from this kind of packaging laminate lies in that the packaging
material is formed by folding and sealing logether the sides
turned towards each other by heat-sealing so that a closed
packaging container with an unbroken inner leakproof plastic layer
is obtained. Various shapes can be imparted to the packaging
containers mentioned hereinbefore and tetrahedral as well as
parallelepipedic packaging containers are thus found on the
market. However, they have one thing in common, namely, the aim
to provide them with an opening mechanism which can be easily
broken and makes the goods in the packaging container readily
accessible. This problem has been solved in a number of different
ways. It is also known, that an opening which is covered with a
cover strip is provided in the package wall and that said cover
strip can be torn off, thus exposing said opening, or the
packaging container can be provided with a tear perforation with
the aid of which a portion of the packaging container can be
torn open in order to expose an opening through which the content
can be poured out.
0
The opening mechanisms with said cover strips which can
be torn off function satisfactorily but unfortunately they have
the drawback that they are relatively expensive to use in
association with single-use packages for daily goods such as
milk. The reason for this is that the manufacture of these
opening mechanisms requires of course additional material and
additional stages of operation. However, openlng mechanisms
based on the principle of a tear perforation arranged in the wall
of the packaging material have the drawback that the tear per-
foration which must be installed in the packaging material priorto the latter's shaping cannot be rendered easily tearable through-
out since the packaging material is exposed to great tensile
stresses and compressive stresses in connection with the shaping
and folding of the packaging container. This requires a com-
promise, which means that the tear-open perforations are made in
such a way that they withstand the stresses to which the packaging
material is exposed while the package is formed but, on the other
hand, they must be so readily tearable that they can be torn open
without difficulty when the package is to be opened and the goods
are to be made accessible.
This compromise of course implies that the tear-open
perforations of the kind described hereinbefore cannot be rendered
as easily tearable as desired and that, therefore, these tear-
open perforations have a relatively unsatisfactory function.
A way of solving the above problem and avoiding the
drawbacks of the known tear-open notches has been found according
to the present invention, which is characterized in that along
the region of the packaging container where the packaging material
is exposed to folding or other processing which intensely stresses
the packaging material said tear perforation is sparsely per-
forated or not at all or it is made in such a way that the
packaging material is not weakened to such an extent that the
Z~
tear perforations break up but that that the tear perforation
along non-bent surfaces of the packaging container or along
surfaces stressed in some other way have a more readily tearable
perforation.
An embodiment of the invention is described hereafter
with reference to the attached drawings.
Figure 1 shows a parallelepipedic packaging container
provided with a tear mechanism according to the invention;
Figure 2 shows the same packaging container after the
tear perforation has been torn open.
Figure 3 shows a portion of a flat material for the
packaging containers shown in Figure 1 and 2.
Figure 4 shows a diagram representing the relationship
~ between tensile strength and punched perforation length (in
j percent) for different lengths of notching or punching.
The packaging container shown in Figure 1 has a parallel-
epipedic shape and consists of side walls 1, an upper end wall 2
and a bottom portion (not shown). As mentioned in the intro-
duction the package is produced from a relatively rigid, unmalle-
able but foldable, web-like material. A rational method of
- producing the packaging containers lies in that the web-like
packaging material is so shaped that a tube is obtained and by
pressing said tube flat and sealing it across the tube is closed
in transverse narrow zones. If the tube is filled with the
intended goods in advance, then the goods will be enclosed in
the sealed packaging containers, which will obtain the intended
parallelepipedic shape by folding. By repeatedly pressing the tube
; flat and sealing it across along zones disposed at intervals a
sealing fin 3 is formed. In the subsequent shaping process said
sealing fin is folded down towards the upper end wall 2 of the
packaging container. During the shaping operation which is
required for obtaining the parallelepipedic shape shown additional
ZO
four triangular double-walled lugs 4 are formed, they are located
in corner sections of the packaging container. Three of the four
corner lugs 4 are folded in towards the bottom portion and the
gable wall (not shown in the Figure, only a lug 4 is visible in
Figure 1). This corner lug 4 is folded over about the straight
edge 6 of the side wall and fixed by means of an easily breakable
bond to one edge 6 belonging to the side wall 1. The sealing fin
3 extends over both the lug 4 and the end wall 2 as well as over
the lug (not shown) folded down at the opposed side of this end
wall. The packaging container shown as a practical example is
also provided with curves 5, which extend from the ends of the
side edges over the end wall 2 to a point of intersection at the
base line 7 on the sealing fin 3.
In order to facilitate the opening of the package, it
is provided with a tear perforation consisting of linear or curved
perforation lines 8 only partially passing through the packaging
material. Said perforations lines 8 originate from a common
point _ located on the inside of the lug 4 at a distance from the
base line 7 of the fin 3. They then pass through symmetric point
_ on the free side edges of the lug and end at a point _ at the
base line 7 somewhat within the lug 4.
The tear perforation described hereinbefore is attained
simply because prior to the shaping of the package the packaging
material is provided with a perforation to such an extent that the
desired tear perforation 8 on the packaging container shown in
Figure 1 is obtained. Figure 3 shows diagrammatically a piece
of a packaging material web having an inverted perforation
pattern, which, in the case described here, is formed by a slightly
U-shaped perforation line 8 so located on the web of the packag-
ing material that when the package is shaped said line 8 isfound at the intended place on the packaging container.
Figure 2 shows the packaging container according to
21~
Figure 1 in the open state, a discharge opening 9 being formed in
that the portion of the sealing fin 3 which extends over the lug
4 is torn away along with an additional smaller portion of the
fin, partly a portion of the material in the fin itself, i.e.,
the material between the tear perforation 8 and the fin 3.
As is evident from Figure 1 the tear perforation 8 has
a plurality of cut-off points b, d at which the tear perforation
is exposed to substantial stresses in connection with the shaping
of the package. It can be seen easily that a leakage will be
caused if the tear perforation along with its region is so easily
tearable that it breaks on being exposed to said stresses.
In order to avoid this drawback without simultaneously
rendering the tear perforation difficulty tearable, the tear
perforation according to Figure 3 is designed with differentiated
tear strength. The tear perforation shown in Figure 3 consists
of two angle-positioned straight lines but if another tear
, perforation is desired for the packaging container, then the
shape of the tear perforation produced on the packaging material
can of course be varied and adapted to the tear perforation on
the finished packaging container. It is thus possible to design
the tear perforation as a straight or curved line or also as a
plurality of continuous straight or curved tear-perforation lines.
In the present case the tear perforations 8 is so designed that
certain portions b and d which correspond to the parts of the
tear perforation shown in Figure 1 and are located on parts of
the packaging material which is exposed to folding. The per-
foration line 8 shown in Figure 3 consists of a series of notches
or punchings in the packaging material web 10, said notches or
punchings 11 being separated from each other by a non-broken
portion 12. The unbroken portions 12 can be advantageously made
of the same size along the entire perforation line, whereas the
length of the notches 13 along the regions b and d are made
94~0
substantially shorter than the notches 11 along the other portions
of the tear perforation. Th s means that the tear perforation
will be less readily tearable and that the strength within the
regions b and d increases while the remaining region of the tear
~ perforation will be readily breakabie.
- Since in the finished packaging container the tearing
of the tear perforation starts either at point c or at point a,
i.e., points having readily breakable tear perforation it is
merely a matter of initiating the tearing and when this has
properly started the portions b and d in readily tearable tear
perforations offer only a slight resistance, which is barely
noticeable in most cases.
Said differentiated tear strength of the tear perfor-
ation 8 is also illustrated in Figure 1, where the tear perfor-
ation along the portions b and d have notches or punchings 11
of substantially smaller length than that of the notches or
` ~ punchings 12 along the other portions of the tear perforation 8.
,,
~ The packaging container 1 shown in Figure 1 and provided
-- with tear perforation has double-walled triangul~ar lugs 4 as
mentioned hereinbefore. Said tear perforation is arranged along
one of these lugs 4. The tear perforation 8 in Figure 1 actually
is concealed to a great extent since on passing the edge of the
triangular lug 4 at b the perforation extends along the underside
of the lug 4 to the region b', where the perforation 8' is
visible again along the surface of the lug 4 along the portions
not covered by the folded down sealing fin 3. However, large
portions of the perforation 8' along the side of the lug 4 of the
packaging container and the surface 2 against which the sealing
fin 3 is folded down will be covered by the fin 3. In order to
indicate the fact that certain portions of the tear perforation
are concealed by the material layer overhead or by the superposed
sealing fin 3, the concealed portions of the tear perforation
1~3420
have been marked with primes, i.e., 8', b', d'. At the same time
said concealed portions of the tear perforation have been marked
with thinner lines as compared with the visible portions.
As mentioned hereinbefore, it has been found that it
is favourable to keep an unchanged interval 12 between the
notches or punchings 11 or 13, since in that case an even tear
resistance is obtained when the packaging container is opened.
At the same time a substantially strengthening of the tear per-
foration can be obtained by shortening the notches or punchings
13 substantially. However it is of course also possible and
absolutely in accordance with the idea of the invention that
instead of varying the length of the notches and punchings 11 and
13 the interval between them is varied or the length of the
notches or punchings 11 or 13 and the interval 12 are varied.
As indicated hereinbefore it is even possible to attain the
differentiated tear strength by changing the depth of penetration
i~ of the basic layer of the packaging material but this kind of
tear perforation has been found to be more difficult to produce
with sufficient accuracy in order to attain the intended aim and
moreover it has been shown that no improvement of the tear
function can be obtained.
Tear tests carried out with packaging material consist-
ing of a basic layer of paper with thin surface coatings of
polyethylene, wherein the perforations have completely broken
through the basic layer, have surprisingly shown a tendency that
the strength of the tear perforation is greater for small inter-
vals between the perforations than with slightly greater inter-
vals on the assumption that the ratio between the length of the
punchings and the length of the intervals is the same. This
rule possibly does not apply generally, but the diagram in
Figure 4, which shows diagrammatically the relationship between
the tear strength and the percentage of punch length per unit of
420
length indicates that the rule is applicable for lengths of cut
of approximately 0.5 to 1 mm. The diagram according to Figure
4 shows no tear strength in absolute values since this is
relatively uninteresting in this connection and, for example,
it varies with the paper quality, paper thickness and quality of
plastic coating, etc., but the diagram shows the mutual relation-
ship between tear strengths of different perforations, i.e.,
perforations made with perforating knives having different
' "toothings." Figure 4 also shows diagrammatically a section of
a perforating knive, where the width of the knife blade is marked
with A and the interval between the knife blades with B. As
' mentioned hereinbefore the horizontal axis of the diagram is
divided into percent and illustrates the percentage of perforation
which has been broken through, i.e., the graduation corresponds
to a term for lOOA , referred to hereafter as breakthrough ratio.
A+B
For reasons explained hereinbefore the vertical axis is not
graduated but is intended only to illustrate the tear strength
with the increasing tear strength shown above and the tear strength
20 O in the origin. The diagram contains a dashed-line region which
is intended to illustrate the easily torn region within which
the unknown portions of the tear perforation can be assigned.
However, the portions of the tear perforation are not within this
region of the'diagram since they then break spontaneously during
the deformation. The diagram according to Figure 4 shows three
curves representing B = 0.5 mm, B = 0.7 mm and B = 1.0 mm, wherein
B is the interval between knife portions. For a break-through
ratio of 50% (i.e., A = B) it can be seen that the tear strength
is slightly higher for a perforation with B = 0.5 mm than for
perforations with B = 0.7 mm and B = 1.0 mm. However, the curves
for different values of B tend to converge as the break-through
ratio increases. However, it does not seem that the value of the
8 --
94ZO
factor B has a somewhat greater influence when the break-through
ratio has reached a value of 70 to 75~.
As a result of the tests performed a test was carried
out to optimize the tear perforation and the result of this test
, shows that;
a) for the easily torn region of the tear perforation,
i.e., the region where it is shaped by folding the following
values apply: B = 0.5 to 1.0 mm and A = 1.0 to 3.0 mm
b) for the region within which the tear perforation
will be shaped by folding the following values apply:
B = 0.3 to 0.7 mm and A = 0.3 to 1.0 mm.
j~ ~
As mentioned hereinbefore the perforation had to be
dimensioned with regard to kind and quality of the basic layer
and the strength of the external plastic layer, but the above
values should be representative and a guide for the optimization
of the perforation.
~- By producing tear-open perforations for packaging
t. containers according to the invention it is possible to produce,
r in a simple manner, functional and readily opening tear-open
perforations without the risk of spontaneously breaking the tear
perforations and without resulting in leakage when the package is -~
t. shaped. The embodiments described hereinbefore are intended only
as examples. As mentioned hereinbefore it is possible to apply
~ the invention to any packaging container wherein the tear
,~ perforation will pass an edge or another break while the package
is shaped when it is exposed to increased stresses. Thus, the
application of the invention is not limited to the package
construction or shape shown here but it can be generally applied
to any form of packaging container which has the technical
problem mentioned at the outset.
