FIELD OF THE INVENTION
[0001] The present invention relates to a closure for a packaging container, primarily for
pressure creating or pressurized filling goods, for instance carbonated drinks. With
advantage the closure is useful also in general for containers having relatively thin
walls. Additionally, the closure is of a heat sealable type providing an adequate
sealing pressure in the sealing area.
BACKGROUND OF THE INVENTION
[0002] The problem behind the invention is to provide a closure having strain resisting
sealing characteristics and an inherent controllable deformation resistance against
internal pressure as well as handling.
[0003] The problem is also to provide means allowing expansion, created by pressure, of
the volume of the package such that a volume in excess to the nominal filling volume
may be assumed.
[0004] A most important sub-problem is to provide a closure allowing sealing with an acceptable
counter-pressure, meaning the provision of a sufficient sealing pressure in the sealing
area.
[0005] In for instance the European patent specification No. 0029039 there is described
an end closure for a sleeve shaped packaging container manufactured from a relatively
thin material. As such, the end closure reinforces the packaging construction, but
for the rest there is no solution to the main problem or the sub-problems of the present
invention.
SUMMARY OF THE INVENTION
[0006] In order to eliminate such lack the invention in general provides a closure for a
packaging container comprising at least one panel of a relatively thin and flexible
material for substantially covering an opening in the packaging container, and a marginal
part surrounding the panel and attachable to the edge of the opening. The closure
is characterized in that the marginal part comprises a sealing area having a fold
formed in the panel and exposed to the internal region of the package, said sealing
area at least partially consisting of the said flexible material and having a sealing
strength in the interval zero to less than the sealing strength of the marginal part
against the edge.
[0007] In one embodiment the closure forms the end piece of a sleeve shaped container casing,
and the sealing area comprises a fold having radially inner and outer rims and extending
circumferentially around the panel. The radially outer rim of the fold is integral
with a lip of the marginal part that is attachable to the casing.
[0008] In said embodiment preferably the radially outer rim forms said lip.
[0009] In another embodiment the lip comprises a double layer of the flexible material.
[0010] In a manner known per se, in order to increase the deformation resistance, the layers
of the lip preferably are sealed against each other.
[0011] In the actual embodiment the sealing strength between the layers of the lip is higher
than the sealing strength of the fold.
[0012] In order to "hide" the "cut edge" of the double layer, this layer preferably comprises
at least the lower portion of the rim and a skirt folded around the rim.
[0013] The extension of the skirt preferably is such that at least one edge is hidden behind
the rim and/or in the wall of the packaging container.
[0014] In either one of said embodiments the marginal part with advantage comprises a conical
region acting as an entering part.
[0015] The marginal part and/or the panel preferably also comprises a material suitable
for induction sealing or high frequency welding or a combination thereof, at least
in the sealing area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
Figure 1 in a partial section view shows a first embodiment of an end closure of a
container together with a portion of a container wall,
Figure 2 in a partial section view shows another embodiment of an end closure of a
container together with a portion of a container wall,
Figure 3 in a partial section shows a third embodiment of an end closure of a container
together with a portion of the wall of the container,
Figure 4 in a partial section view shows a fourth embodiment of an end closure of
a container together with a portion of a container wall,
Figure 5 in a partial section view shows a container closure according to the principles
of the invention provided with a conical entering portion,
Figure 6 shows a trapezoid strip which is to be formed into a truncated conical funnel
for forming an essentially smooth abutment surface against the inside of the packaging
container,
Figure 7 shows an injection moulded closure having a foil laminated thereto,
Figure 8 shows a closure having a conical double rim,
Figure 9 shows the closure in a sealed state,
Figure 10 shows an injection moulded closure having an overdimensioned sealing label,
and
Figure 11 shows an injection moulded closure consisting of two parts, also having
an overdimensioned sealing label.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] In Figure 1 the reference numeral 10 generally relates to a container closure shown
in a partial section view and comprising a lid panel 11 and a marginal part 12. In
the embodiment that has been shown the closure 10 is manufactured from a relative
thin flexible material, for instance a laminate comprising an aluminium foil having
a thickness in the interval 10 to 200 µm and having a coating of a thermoplastic material,
preferably a polyolefine, on one or both sides thereof. Other type of material/material
combinations are of course possible, for instance plastic laminates/plastic film having
a suitable additive for giving the required tightness degree and/or for allowing a
specific sealing method.
[0018] A sealing area comprising a fold 13 extending around the panel 11 is formed in the
end closure and exposed to the internal region of the package, which here merely has
been shown as a portion of a sleeve wall 14. In this case the fold is formed by folding
the margin of the blank forming the closure 10. The fold has an outer rim 15, which
is this case alone forms a lip for sealing against the sleeve wall. The seal 16 between
the rim and the sleeve is formed with a sufficient sealing pressure for obtaining
an acceptable sealing. This pressure is obtained in that a counter-pressure is created
by means of a support 17 which is displaceable in the directions of the double arrow
18 and for instance expandable in the directions of the double arrow 18' and which
co-operates with a stationary support 19. The sealing technique used may for instance
comprise induction welding or high frequency welding, and in this case the material
of the end closure 10, at least in the welding area comprises an additive well suited
for the actual welding technique. For rational reasons the end closure generally is
laminated with a metal foil (not explicitely shown in Figures 1 to 5) along the entire
surface thereof. In the embodiment according to Figure 1 the seal 16 preferably extends
along the entire height of the rim 15 and continously around the sleeve 14.
[0019] In order to protect the free edge of the rim, the cut edge, a lacquer layer 20, alternatively
a tape or other protective means is arranged along the edge facing the internal region
of the package.
[0020] Alternatively, it is possible to press the edge into the material of the casing 14,
as shown by the reference numeral 21 in Figure 1.
[0021] The fold 1.3, which is exposed to the internal region of the package, has a seal
22 of so called peelable type. The seal 22 is thus weaker than the seal 16.
[0022] If for some reason, for instance due to a pressure increase originating from the
filling goods, the internal pressure increases within the container, the seal 22 will
break (if such a seal exists, i.e. a seal having a strength higher than zero). The
flexible end closure 10 (cover panel 11) then assumes its natural shape according
to the broken lines 23 in Figure 1. Due to the increase of volume the pressure decreases
inside the container. The seal is protected by this construction, meaning that the
risk for leakage and destruction of the contents of the package is reduced at the
same time as the fold construction, in the manner mentioned, allows the creation of
an acceptable sealing pressure.
[0023] In Figure 2 there is shown a lip 15 comprising double material layers 15' and 15".
The layer 15' forms a skirt which is folded and sealed against the rim 15" in order
to reinforce the end closure. The seal 15"' preferably is of the same strength as
the seal 16 and has an extension in the height direction for instance equal to the
height of the rim 15". The seal may also be accomplished dot-wise, alternatively along
a certain part of the height of the rim. In the same manner as previously, the fold
13 has a peelable seal 22, which at a strain exceeding the maximum load allows resetting
of lid panel 11 to the natural position 23 thereof.
[0024] The free edge of the skirt 15' is turned away from the internal region of the container
and in Figure 1 the skirt is located at the same level as the upper edge of the sleeve
14 and the uppermost portion of the lip 12.
[0025] An extension of the skirt 15' according to the broken line 24 is also possible.
[0026] I Figure 3 the edge part 12 is placed in a position below the top edge of the sleeve
14. Such placement implies that the lid panel 11, in the natural position 23 thereof,
is protected by the sleeve 14 and/or the skirt 15'.
[0027] In Figure 4 there is shown a version of an end closure where the skirt 15' is shortened
and the upper portion of the rim 15" of the marginal part 12 is sealed against the
sleeve 14. This seal together with the seal 16 forms the actual sealing of the end
closure 10. In the same manner as previously there is a peelable seal 22 in the fold
13 exposed to the internal region of the package.
[0028] In Figure 5 there is shown a conical marginal part 12 for facilitating the entering
operation. The rim 15 of the marginal part may be formed from or covered by a banderol
25 according to Figure 6. Such a banderol, punched out to a trapezoid shape, almost
provides an essentially smooth sealing area.
[0029] Although the end closures in the embodiments shown have been manufactured from a
flexible, foldable material it is realized that other processing techniques, for instance
injection moulding, may be used as an alternative for manufacturing of certain parts,
for instance the marginal part, of the end closure.
[0030] In Figure 7 there is shown a version where the lid panel 11 comprises a relatively
thick material and for instance is injection moulded and thereafter laminated by an
aluminium foil 11' or corresponding. The idea is to provide a double layer 12 which
may be pressed together and pressed against the walls of the sleeve or the opening
edge against which the closure should be placed. The pressing together may for instance
be accomplished by pressing the panel 11 axially inwards the container at the same
time as the rim 15 is prevented from moving into the sleeve.
[0031] Such a controlled pressing operation may be obtained by overdimensioning the double
layer relative the opening, at least in certain areas of the double layer, for instance
by forming said layer with a truncated conical shape as in Figure 8.
[0032] Figure 9 shows the effect of the pressing together pressure - between the layers
and against the sleeve - after folding. Frequently, the "void space" will not occur,
but in Figure 9 it has been indicated for illustration purposes as a result obtainable
by a controlled application of pressure in the welding area.
[0033] In Figure 10 there is shown a pressure resistant closure obtained by over-dimensioning
the foil/sealing label 11' relative the opening in the sleeve 14. When pressure occurs
or strain occurs in the weld 16, the strain is transferred by the relatively stiff
rim 15, meaning an advantageous "line load" (along a line in the height direction)
in the welding area (contrary to a strain along a peripheral line).
[0034] Still increased strain resistance is possible by the two-part closure in Figure 11
comprising a separate panel 11 and a separate marginal part 12.
1. A closure for a packaging container (14), comprising at least one panel (11) of
a relatively thin and flexible material for substantially covering an opening in the
packaging container and a marginal part (12, 15) surrounding the panel and attachable
to the edge of the opening, characterized in that the marginal part comprises a sealing
area (22) having a fold formed therein and exposed to the internal region of the package,
said sealing area at least partially consisting of the flexible material and having
a sealing strength in the interval from zero to a strength lower than the sealing
strength of the marginal part to be attached against said edge of the opening.
2. A closure according to claim 2, where the closure consists of an end piece (10)
for a sleeve shaped container casing (14), characterized in that the sealing area
comprises a fold (13) having radially inner and outer rims and extending around the
panel, said radially outer rim (15, 15") of the fold being integral with a lip (15)
of the marginal part of the closure attachable to the casing.
3. A closure according to claim 2, charac- terized in that the radially outer rim
(15) forms said lip (Figure 1).
4. A closure according to claim 2, charac- terized in that the lip comprises a double
layer (15', 15") of the flexible material.
5. A closure according to claim 4, charac- terized in that the layers of the lip are
sealed (Figure 2) against each other.
6. A closure according to claim 5, charac- terized in that the sealing strength between
the layers of the lip is higher than the sealing strength of the fold (12).
7. A closure according to anyone or any of the preceding claims 4 to 6, characterized
in that the double layer (15, 15") comprises at least the lower portion of the rim
and a skirt (Figure 4) folded around said rim.
8. A closure according to claim 7, charac- terized in that the extension of the skirt
(15') is such that at least the edge thereof is hidden behind the rim (15") and/or
in the wall (at 21) of the packaging container.
9. A closure according to anyone or any of the preceding claims, characterized in
that the marginal part (12) comprises a conical portion (Figure 5) formed as an entering
part.
10. A closure according to anyone or any of the preceding claims, characterized in
that the marginal part and/or the panel comprises a material suited for induction
welding/high frequence welding, at least in the sealing areas.
11. A closure for a packaging container (14), comprising at least one element (11,
11') substantially covering an opening in the packaging container and a marginal part
surrounding said element and attachable to the edge of the opening, characterized
in that the marginal part is formed as a double layer (12, 15) arranged for being
pressed together and pressed against said edge by the edge of the opening.
12. A closure according to claim 11, charac- terized in that said double layer comprises
a substantially truncated conical envelope surface.
13. A closure according to claim 12, charac- terized in that said marginal part, at
least in the sealing areas thereof is laminated with a metal foil or corresponding
arranged for induction welding and/or high frequency welding.
14. A closure for a packaging container (14), comprising at least one element (11;
11, 11") substantially covering an opening in the packaging container and a marginal
part surrounding said element and attachable to the edge of the opening, characterized
in that said element comprises a flexible material which is over-dimensioned relative
said opening and with at least a portion thereof arranged for abutment against the
marginal part (12, 15) and/or the element (11).
15. A closure according to claim 14, charac- terized in that the element covering
said opening is placeable by snap action into the marginal part.
16. A closure according to claim 14, charac- terized in that the panel is positioned
such that it receives the flexible material without streching.