CA1262702A

CA1262702A - Container end closure

Info

Publication number: CA1262702A
Application number: CA000458500A
Authority: CA
Inventors: Arne Andersson; Lars-Eric Plitz; Bo Ullman
Original assignee: Akerlund and Rausing AB
Current assignee: Akerlund and Rausing AB
Priority date: 1983-11-07
Filing date: 1984-07-10
Publication date: 1989-11-07
Also published as: SE8306088L; SE8306088D0; ZA842496B; SE448858B

Abstract

ABSTRACT OF THE DISCLOSURE
An end closure for a packaging container, comprising a panel for covering an opening in the container end. The closure comprises a panel and a marginal portion and is provided with radially adjacent portions of the panel having mutually different wall thickness, providing concentric grooves or a sprial shaped groove and a ridge, for forming pressure sensitive deformation zones.

Description

i7~

The present invention relates to container end closures, preferably manufactured completely or partially from a material that is sensitive to a pressure difference between the interior region and the exterior region of the container. Such a container may, for instance, comprise a casing of a supporting layer of plastic having a suitable foil or laminate thereon and a pair of end closures to be applied onto the ends of the casing.

The idea behind the invention is to master, in a lo controlled manner, the "panelling" problems that arise in such packaging containers havlng a deformation tendency. By the term llpanellingl' is meant the deformation inwardly of the wall o~ a packaging container that occurs when an under-pressure is obtained ln the sealed container. Such an under-pressure may for instance arise from the fact that the container has beerl hot filled or due -to consumption of oxygen by the product packed in the container.

It has previously been suggested to arrange specific pressure sensitive closure panels, of the membrane type, operating between two "stable" end positions.

AS su~h, the conventional arrangements for controlled pressure difference elimination form a solution to the problem according to the present inventlon. However, the solution implies that an extremely unreliable and instable state is created as soon as the arrangement departs from either of the two natural "stable" end positions until the stable second end posltion is assumed. The conventional solution operates with a too large "stroke". In practice this may resul-t in a state where the pressure difference is not compensated in the manner that was intended. There may, for instance, arise an "equilibrium~' state where an under-pressure exists in the container, implying a forced suction in of contamination and bacteria to the product, if the relatively weak seal breaks up due to the pr~ssure difference.

It is of a great impor ance to provide an arrangement that g.ives a quick acting ~panelling~ and an exact pressure compensation.

In the broadesk sense thereof, the present invention provides an end closure for a packaging container, comprising a panel arranged to generally cover an openlng ln a container end, and a marginal portlon merging into the panel in which radially ad~acent portions of the panel have a mutually different wall o thickness for forming pressure sensitive deformation zones.
The radially, close to each other, deformation zones are formed over substantially the whole area of the end closure.

In one embodiment the radially ad;acent portions are formed by a spiral shaped groove in the panel giving a first ~all thickness and leaving a splral shaped ridge in the p~nel of a second wall thickness.

Preferably, the spiral shaped groove is formed in that side of the end closure which is to be turned towards the interior of the container.

The arrangement is such that the first wall thickness is considerably less than the second wall thickness.
In a specific embodiment that is obtainable by in~ection mouldable plastics, the groove starts in the region of the centre portion of the end closure and extends generally out to the marginal portion.
In an alternative embodiment the radially ad~acent portions are obtained by concentric grooves in the panel leaving a first wall thickness in the panel and concentric ridges of a second wall thickness.

The grooves are preferably arranged oYer substantially the entire area of the end closure.

Preferably, the grooves are formed in that slde of the end closure -that is to be turned towards the interior of the container.

- 2a -Pre~erably, the wall thickness is such that the first wall thickness is considerably less than the second wall thickness.
In order to Eacilltate axial movement the groove width preferably is relatively large, within the interval oE some millimetres.
In either embodiment the end closure preferably is formed as a domed panel.
For instance, the end closure is manuEactured from an injection mouldable/thermoformable material, preEerably a thermoplastic material.
The invention will now be exemplified by reference to the accompanying drawings, where Figure 1 seen from the thought inside of a packaging con-tainer shows an end closure according to a first embodiment, Figure 2 is a section along line II-II in Figure 1, Figure 3 shows a second embodiment of an end closure, and Figure 4 is a section along line IV-IV in Figure 3.
The end closure 10 in Figure 1 basically comprises a closure panel 11 and a marginal portion 12. Said parts are formed integrally, or instance by injection moulding or thermoforming, from an injection mouldable and thermoEorm-able, respectively, mate7ia~,~ Eor instance a thermoplastic material, preferably a ~r~r~sn, for instance polypropy-lene.
In the side 13 oE the panel 11 - the thought inside oE
the closure - there is formed a spiral shaped groove 14 having one end in the area oE the central por-tion 15 of the closure and a seconcl end adjacent^~o the~ ~g~ 12. I'he groove leaves a wall thickness 16 ~ considerably less than -the wall thickness 17 oE the spiral shaped ridge 18 tha-t is Eormed on -the closure 10.
As appears from Fig1lre , the ck)sllre has a domed shape.
The spirals 18, 14 having radia]ly adjacent portions of rnutually different wall ~ ickness along the entire area o~
the clo~sure 10 give evenly clistributed de~ormatlon zones alon-~ ~he e-ntire area of -the closure. This dlstributiol- of a larger n-llnber of zones imply a quick reaction -to a pressure difference in the con-tainer (not shown) which is to be closed by the closure 10 at one or both ends thereof. The quick reaction implies a momen-taneous pressure compensa-tion and this is extremely advantageous Eor minimizing stress in the weld/sealing areas.
The embodiment according -to Figures 3 and 4 comprises concentric grooves/ridges 14, 18. The groove width is pre-ferably selected somewhat wider than in the first embodiment in order to obtain a quicker reaction. For the same reason it may be feasible to place in an angle, for instance as a parallelogram or as a cone, the sides of the groove, as has been shown by the re~erence numeral l9.
The marginal portion of the closure has been shown as a single rim, but it is o:~ course possible to have a double rim and this has been indicated by the broken lines 20 in Figures 2 and 4.
It is further to be understood that the closure, speci-~ically if it is manu~actured ~rom plastics, may be provided with a foil that is gas and vapour tight, for instance a metal ~oil 21.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A packing container end closure comprising a panel for generally covering an opening in the container end, and a marginal portion merging into the panel, radially adjacent por-tions of the panel having mutually different wall thickness for forming pressure sensitive deformation zones over a substantially the entire area of the end closure, said radially adjacent por-tions being obtained by a spiral shaped groove in the panel that leaves a first wall thickness in the panel and forms a spiral shaped ridge in the panel of a second wall thickness.

2. A closure according to claim 1, in which the spiral shaped groove is formed in that side of the end closure that is to face the interior of the container.

3. A closure according to claim 3, in which the first wall thickenss is considerably less than the second wall thick-ness.

4. A closure according to claim 3, in which the grooves starts in the area of the central portion of the end clo-sure and extends generally to the marginal portion.

5. A packing container end closure comprising a panel for generally covering an opening in the container end, and a marginal portion merging into the panel, radially adjacent por-tions of the panel having mutually different wall thickness for forming pressure sensitive deformation zones over substantially the entire area of the end closure, said radially adjacent por-tions are obtained by concentric grooves in the panel leaving a first wall thickness and concentric ridges in the panel of a sec-ond wall thickness.

6. A closure according to claim 5, in which the grooves are formed over substantially the entire area of the end closure.

7. A closure according to claim 6, in which the con-centric grooves are formed in that side of the end closure which is to be turned towards the interior of the container.

8. A closure according to claim 7, in which the first wall thickness is considerably less than the second wall thick-ness.

9. A closure according to claim 8, in which the groove width is relatively wide, within the interval of some millime-ters.

10. A packing container end closure comprising a panel for generally covering an opening in the container end, and a marginal portion merging into the panel, radially adjacent por-tions of the panel having mutually different wall thickness for forming pressure sensitive deformation zones over substantially the entire area of the end closure, said radially adjacent por-tions being obtained by a spiral shaped groove or concentric grooves in the panel having a first wall thickness and ridges in the panel of a second wall thickness.