Sheet metal container making – Method – Forming or treating metallic closure
Reexamination Certificate
1999-07-15
2001-11-13
Vo, Peter (Department: 3721)
Sheet metal container making
Method
Forming or treating metallic closure
C413S008000, C413S015000
Reexamination Certificate
active
06315511
ABSTRACT:
RELATED PATENT APPLICATIONS
None.
1. Field of the Invention
This invention relates in general to the forming of end panels for food and beverage containers and relates in particular to a method and apparatus for coining the end panel thereof, particularly with regard to easy-open containers.
2. Background of the Invention
In the container industry, the so-called easy-open container is well known. These containers, whether two- or three-piece, consist of a top end panel which has a displaceable panel and, generally, a finger-engaging ring or lever tab affixed to the end panel which can be engaged or grasped by the finger so that lifting of the tab about its point of affixation causes the displaceable panel to fracture about a score line and provide an opening in the end closure for access to the contents after removal of the displaceable panel. In many instances, the tab can be formed integrally with the displaceable panel so that the displaceable panel is not totally removed but folded inwardly to provide an opening, but here, too, the juncture between the displaceable panel and the end panel per se is characterized by a score line which facilitates separation. It is well known that this general principle of operation and design can be employed with either full or partial openings, and regardless of whether the displaceable panel is fully or partially separated from the end panel. In general, these are designed for easy opening by the user without the utilization of any implement such as a can opener.
Examples can be seen in Langseder U.S. Pat. Nos. 4,361,251; Saunders 4,367,996; Baumeyer 4,386,713; Zysset 4,394,927; and Guimarin 4,397,403.
In the prior art, as previously noted, it is known to provide the end panel with a score or severing line about the periphery or at least part of the periphery of the displaceable panel so that it will fracture easily upon activation of the tab. Of necessity, forming the score line is a delicate operation inasmuch as the material from which these containers are formed is generally in the nature of 0.010 of an inch thick and the score line must be sufficiently deep to enable easy separation of the displaceable panel from the remainder of the container end while retaining sufficient strength to contain the contents of the container, which is often filled under pressure, in order to prevent premature rupture of the end and thereby leakage or spoilage of the contents.
In the prior art, it has been known to offset the main surface of the container end panel per se from the displaceable panel by raising and/or depressing at least a portion of the perimeter surface of the displaceable panel above the plane of the top surface, thus creating an offset. This offset reduced the deformation of the score line caused by the residual stress after the scoring operation. That is, when the scoring knife was retracted, there was a tendency for the metal to flow back to the scored area and deform it. Usually, it has been attempted to compensate for this by providing a bulge or raised area spaced from the score line to compensate for this flow. However, there was a serious lack of precision with this method. This is generally accomplished in a press with a punch and die and presents a radiused transition surface between the depressed displaceable panel and the remainder of the top panel.
Also, these containers are generally fabricated from steel or aluminum and additional problems are encountered in connection with providing the score both during and after the scoring operation. Specifically, steel containers in general are coated on both sides with a thin plastic coating because it is generally considered desirable to separate the contents of the container from the metal or other material from which it is fabricated. Examples of these coatings can be seen in Das U.S. Pat. Nos. 4,381,064; Marcus 4,452,375; and Smith 4,457,450.
The difficulty is that, in creating the score, the coating is often perforated or broken, thereby defeating its purpose. This generally occurs because of the high tooling pressures required to displace the material creating the score line and because this is fabricated around a radiused corner of the periphery of the punch and the die. Also, generally, the end panel is held between the punch and the die and a scoring tool is pressed into the panel in the appropriate area. However, the metal displaced in this manner tends to flow away from the score area and, when the holding pressure is released, tends to flow back due to the residual stresses thus created, again often causing distortion.
It has been found that, by coining this critical area, applying pressure over a larger surface area, and controlling the metal flow, the operation can be performed providing the necessary offset without disturbing the coating or distorting the finished product.
SUMMARY OF THE INVENTION
It accordingly becomes a principal object of the invention to fabricate a container end with a full or partial removable panel and having an offset portion in its surface which includes the displaceable panel by coining the transition area between the normal plane of the container end and the displaceable panel surface.
It has been found that this and other objects of the invention can be facilitated by providing a coining die having a flat surface at the juncture of the die top and side periphery disposed at an angle between its top surface and its side surface and providing a mating tooling punch having a complemental edge surface about its periphery, again between its end and side surfaces.
It has further been found that the objects of the invention can be facilitated by providing a pressure pad which will engage a first portion of the top surface and hold it against the top of the coining die, engaging the remainder of the top surface of the container end, i.e., the displaceable panel portion, with a coining punch which holds it against the top of a control die. As noted, the periphery of the coining punch and the coining die can be provided with chamfered or angled peripheral edges which, when the press is in the closed position, are disposed in juxtaposed relationship to each other.
In this fashion, the metal flow can be controlled and the integrity of the coating can be preserved by directing the metal being displaced into a contained area.
The method of operation of the invention includes positioning the end panel on the coining die and the control die and engaging the first portion of the top surface of the panel with a pressure pad and engaging the remainder with a tooling punch. This is achieved by coining an area of the top surface of the panel between the peripheral edges of the coining punch and the coining die while holding the remaining end portions so as to compress the metal and thin it.
Accordingly, production of an improved method and apparatus for forming an end panel for a container becomes the principal object of this invention with other objects thereof becoming more apparent upon a reading of the following brief specification considered and interpreted in view of the accompanying drawings.
REFERENCES:
patent: 4361251 (1982-11-01), Langseder et al.
patent: 4367996 (1983-01-01), Saunders
patent: 4381064 (1983-04-01), Das et al.
patent: 4386713 (1983-06-01), Baumeyer et al.
patent: 4394927 (1983-07-01), Zysset
patent: 4397403 (1983-08-01), Guimarin
patent: 4452375 (1984-06-01), Marcus
patent: 4457450 (1984-07-01), Smith et al.
Huynh Louis K.
Renner Kenner Greive Bobak Taylor & Weber
Vo Peter
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