Die for stay—on—tab

Details Die for stay—on—tab Die for stay—on—tab

2000-12-21

2003-06-10

Sipos, John (Department: 3721)

Sheet metal container making

Apparatus to form container closure

Having means forming frangible zone on closure

C413S056000

Reexamination Certificate

active

06575684

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to containers, and more particularly to metal containers having a pull type opening tab.
BACKGROUND OF THE INVENTION
Easy opening beverage containers are well known in the beverage industry. Typically, a beverage container comprises a body and a separate can end or lid formed of an aluminum sheet—typically 0.011″ (0.28 mm) to 0.013″ (0.33 mm) thick. A conventional can lid may employ one of several pull-type tabs. A popular type of lid has a tab that is attached to a top plate by a rivet to form a lever. To open the can, a user lifts one end of the tab to urge the other end downward against a tongue or tear panel formed by a score in the top plate. The tab member forces the tongue downward until the score pattern ruptures. The score may be discontinuous to form a hinge area that connects the tongue to the top plate, even after opening.
A common operation for forming a can end having a tongue defined by a score pattern comprises the step of placing a metal material between a score die and mating anvil. Thereafter, the score die is brought down upon the metal material with a force sufficient to depress the metal material to form the score pattern.
Ease of opening and enhanced strength of the lid components are long standing goals of designers and researchers. For example, U.S. Pat. No. 5,563,335 to Tominaga et al. (“Tominaga”) discloses a can lid having a top plate, a tab, a tongue formed by a score, and a hinge area formed in the lid. However, the lid disclosed in the Tominaga patent has several drawbacks. First, the top plate has a center which is a fulcrum point. Such a layout may not be desired in light of tongue size and location, tab length, aesthetics, strength characteristics, and like variables.
Second, the Tominaga patent discloses that the force application point, the fulcrum point, the tab nose, and the depression force point form a straight line. Such an alignment restricts the depression force point to a location that is not optimum with respect to the opening characteristics. Third, the Tominaga patent discloses a recess that is disposed beneath the tab nose having a straight side perpendicular to the straight line as defined above. The straight side yields to an arcuate side generally to form a D-shaped recess. This D-shape inherently requires a large surface area in the critical tongue area, within which space should be conserved, and might position a stress riser at a problematic location. Fourth, a large deboss in the top plate of the Tominaga patent contains and is disposed outside of the score area and tab, which has inherent drawbacks, especially with respect to the score. Furthermore, like many can lid designs, the lid disclosed in the Tominaga patent may be prone to loose metal or excess metal in the tongue area, and may generally not provide optimum accessibility to the finger of the user (that is, mechanical and geometrical characteristics of the tab with respect to the tongue and the top plate).
The present invention is directed to the goals of improving the opening considerations of pull type tabs, as well as possessing other attributes that will be apparent to persons familiar with such technology.
SUMMARY
Accordingly, a can lid is provided that accomplishes the goals. The can lid that has a top plate and a tab that is coupled to the top plate by a rivet. The tab has a nose and an opposing heel. A score, which is formed in the top plate, has a first end and a second end that define a hinge portion therebetween. The score defines a tongue, formed in the top plate, that is coupled to the hinge portion. A first deboss is formed entirely in the tongue within the score. An emboss also is formed in the tongue. An arcuate second deboss is formed in the tongue between the rivet and the emboss. The emboss and the second deboss may be formed within the first deboss.
The first deboss has a first arcuate side and an opposing second arcuate side. The second deboss is capable of receiving a depression force applied by the tab nose. The second deboss may have a bottom surface of varying depth. Specifically, the second deboss may have a sloped bottom surface that has a shallow end and opposing deep end so as to form an incline within the second deboss. Thus, second deboss forms a can.
According to a second embodiment of the present invention, a can lid is provided that has an arcuate contact emboss disposed below the tab nose. According to a third embodiment of the present invention, a can lid is provided that has a contact emboss having opposing straight sides. The can lid according to the second and third embodiments lack a second deboss, but includes a top plate, a tab, a rivet, a tongue, a score, a hinge area, a first deboss, and a primary emboss, as generally described above. The contact emboss may be disposed within the first deboss, which maybe disposed entirely in the tongue. Further, the contact emboss may have a short end and a tall end so that the contact surface on the tab nose contacts the tall end before contacting the short end.
According to another aspect of the present invention, a die insert for forming the first deboss, second deboss, and emboss is provided. The die insert according to the present invention includes these features generally according to the description thereof as above.
The present invention has several inventive and beneficial aspects, including: the emboss and the second deboss may be formed entirely in the tongue; the first deboss is formed entirely within the score; the can lid may comprise an embossed ridge, disposed on the top plate outside of the tongue, such that most of the emboss ridge is spaced equidistant from the score; the second deboss may be formed by two opposing arcuate sides equidistantly spaced apart; and the fulcrum point is not disposed at the center of the lid.
Further, the sloped surface of the second deboss enables the tab nose to contact the shallow end of the second deboss prior to contacting the deep end. Thus, the contact point or depression force point is offset from centerline defined by a centerlines of the tab heel, rivet, and tab nose, thereby providing control of the location, direction, and distribution of forces applied to the tongue by the tab. The sloped surface of the contact emboss provides similar advantages.
Providing the first deboss that is entirely within the tongue eliminates problems associated with loose metal that may be exacerbated in embodiments in which the score area is debossed. The heart shaped second deboss and embossed ridge generally follow the score, and thus provide stress and scratch barriers for the score.


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