Receptacles – Closures – With closure opening arrangements for means
Patent
1995-10-02
1999-09-14
Cronin, Stephen K.
Receptacles
Closures
With closure opening arrangements for means
220617, 220619, 220624, B65D 1734
Patent
active
059508582
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to metal containers and more particularly to an end closure for carbonated drink cans, and which may have an easy-open aperture.
2. Description of the Prior Art
Carbonated drinks are commonly contained in cylindrical metal containers having a top end closure of sheet material which is provided with a ring pull or tab for the easy opening of an aperture prescored in the end closure. In the manufacturing process, the cylindrical containers are filled and then fitted with their top end closures to enclose the drink, whereafter the containers may be subjected to heat in order to pasteurise the contents. This heating process causes a temporary increase in the pressure within the containers. Also if subsequently the container is stored in a warm environment or is severely shaken, its internal pressure will greatly increase. In order to withstand increased internal pressure, it is common for the top end closure of these containers to be formed with a circumferential valley or countersink adjacent its periphery. Although the containers may be designed to withstand an industry standard pressure of 100 p.s.i., it is possible for the countersink to invert at a localised point under internal pressure created within the container. There has hitherto been a tendency to minimise the thickness or gauge of the sheet material used to make the end closure, because the cost of the sheet material used in the end closure forms a substantial proportion of the overall manufacturing cost of the container. However in order that the gauge of the sheet material used for the end closure can be reduced, it has been necessary to take measures to prevent the countersink locally inverting under the internal pressure within the container. One proposal is given in U.S. Pat. No. 4,093,102 and relates to providing the countersink with a specific cross-sectional profile, such that the opposite walls of the countersink will move in response to internal pressure, the countersink thus adopting a modified profile having increased resistance to inverting. Another proposal is given in U.S. Pat. No. 4,832,223 and relates to coining the end closure around an annular region at the junction of the countersink with the centre panel of the end closure.
SUMMARY OF THE INVENTION
I have now devised a container end closure having an improved arrangement for resisting internal pressure within the container.
In accordance with this invention as seen from one aspect, there is provided a sheet material end closure for a container, the end closure having a centre panel optionally provided with an easy-opening means, a circumferential countersink formed around the centre panel and adjacent the periphery of the end closure, and a fold formed at the junction between the countersink and the centre panel, said fold having opposite side walls which lie closely adjacent or in contact with each other and which project upwards from the end closure, or the fold being formed at the base of the countersink, the fold forming an annular rigid zone in the end closure.
The fold which is provided in accordance with this invention forms a rigid annular zone at an area of potential deformation, by increasing the volume of metal which has to be deformed if the countersink is to invert. Therefore the fold provides effective resistance against the countersink inverting, even at localised points around its circumference.
In embodiments having the fold formed at the junction between the countersink and the centre panel, the fold may be left projecting upwards from the centre panel. In another embodiment the fold may be bent radially inwardly, either to lie at an acute angle to the centre panel or to lie flat against the centre panel. In a further embodiment the fold may be bent outwardly, e.g. to lie flat against the radially inner side wall of the countersink.
The facing surfaces of the fold may have adhesive applied to them so that the opposite side walls of the fold bond together, to improve the
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Cronin Stephen K.
Schindler Edwin D.
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