Stock material or miscellaneous articles – Sheet – web – or layer weakened to permit separation through...
Patent
1996-09-03
1998-06-23
Watkins, William
Stock material or miscellaneous articles
Sheet, web, or layer weakened to permit separation through...
428131, 428137, 428132, 428 359, 428213, 428214, 428215, 428457, 428458, 428461, 220266, 220267, 220268, 220269, 220270, 220276, 215253, 215256, 413 15, 413 12, 413 17, B65D 1728, B65D 7562, B32B 330
Patent
active
057702900
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention belongs to the technical area of the application of layered metal-plastic material construction to packaging and more precisely to the fabrication of easy open ends used for closing containers containing food or beverage products.
More precisely still, the metal-plastic construction applied is of the type metal-polymer-metal, that is in which a foil of polymer is surrounded by two metal foils to which it is adhered.
In the text of the present patent application, we will use, without distinction for these constructions, the terms metal-plastic-metal, metal-polymer-metal, or more simply in an abbreviated fashion, MPM.
1. Problem Posed
Easy-open ends for food or beverage cans are generally constituted of a metal foil covered on the inside of the can by a protective varnish avoiding contact of the foods or of the beverage with the metal of the end and preserving the cover from corrosion and the contents from contaminations.
These easy open ends possess a system of perforation and a tearing line. The system of perforation is constituted most frequently by a ring connected to a punch. When one pulls on the ring to move it from a position parallel to the end to a position perpendicular to the end, the punch perforates the cover at a place located on the line of weakness corresponding to which the tearing continues when one continues to pull on the ring. The line of weakness or of tearing can have various designs according to whether one wishes to achieve an opening in the form of a pour panel (the case of the beverage can) or a full panel opening of the can (the case of food cans).
In both cases, the line of weakness or tearing is obtained by scoring the outside or the inside face of the end. It is not unusual in fact, notably for steel food can ends to score the internal face and later repair the damaged internal varnish layer. This method presents two advantages: the first is that it is easier to achieve in this manner the balance between ease of opening and the resistance to accidental opening; the second is that even with an outside score, the deformation of the metal induces small cracks in the internal varnish. But these small cracks are practically impossible to repair whereas the larger notches resulting from the internal scoring can be easily repaired by electrophoresis. The weakening in both cases is caused by the smaller quantity of metal present under the base of the score, as this is shown in cross-section in FIG. 1 where (1) designates the metal, (2) the external incision, and (3) the layer of inside varnish.
The problem posed initially to the inventors was that of improving the beverage can. Of a capacity in general of 33 centiliters, of a cylindrical shape, this can is closed by an easy open end, coated internally by a food approved varnish and externally by one or several layers of decoration indicating the nature and the brand of the contents. These coatings are in general applied after the forming of the can.
Among the elements of cost of the beverage can, the cost of the metal, despite its slight weight, constitutes a preponderant portion. The idea had therefore occurred to the researchers of replacing a part of the metal by a less costly material: plastic.
The inventors have found a solution to this problem consisting of a metal-plastic construction composed on a foil of thermoplastic polymer coated on each of its faces with a metal foil with an intermediate adhesive layer. They have then asked themselves if such a metal-plastic construction would not also be able to replace the metal sheet used for the preparation of the ends. Aside from the economic advantages, this solution would facilitate the recycling of the ends which would be made starting from a product identical to or similar to that of the metal-plastic cans of a similar type of MPM structure.
But even with the conventional easy open ends having a thin protective organic coating, it is difficult to arrive at an acceptable balance of easy opening and the protection against an accidental ope
REFERENCES:
patent: 4126244 (1978-11-01), Elser
patent: 4313996 (1982-02-01), Newman et al.
patent: 4504181 (1985-03-01), Khoury
McHenry Robert J.
Petit Dominique
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