Easy-Open Metal End for a Container, and Method for Making Same

Abstract

An easy-open metal end and a method for making same, in which a pre-score coining operation is performed, followed by an operation to form a score line. The coining step uses gentle-radius tooling designed not to crack or cut a protective coating on the metal end. Between the coining step and the score line-forming step, a paneling step is performed to pull out the loose metal generated in the coining step, such that end tension can be controlled more easily than in a conventional process. The coining operation thins the metal, so the score line can have less penetration than, and therefore can be narrower than, a conventional score line. Consequently, even if the score line does rust, it will be very small in width and thus relatively unnoticeable.

Description

BACKGROUND OF THE INVENTION

The present disclosure relates to easy-open metal ends for containers.

An easy-open (EZO) metal end is produced by conversion of a sheet metal “shell” in a progressive die press, via a series of operations performed with dies. The shell, which typically comprises a sheet metal layer coated on its interior and/or exterior with a protective non-metallic coating, is moved progressively through a series of stations. At each station, one or more features are created in the shell via tooling at that station. In particular, a score line is formed in the metal end to define a tear portion that can be at least partially separated from the remainder of the end by severing along the score line.

EZO metal end production is inherently harmful to the protective coatings on the metal ends, in many cases requiring a two-pass approach. Specifically, the formation of the score line typically breaks or thins the protective coating(s) on the metal end and may expose bare metal. Thus, a post-manufacturing repair operation is usually necessary. This is normally accomplished in a completely separate, dedicated piece of equipment that applies a new coating onto one or both surfaces of the newly manufactured EZO metal ends, and then cures the coating in an oven through which the coated ends are carried. If it were possible to manufacture EZO ends in a single-pass process, productivity would be significantly enhanced.

Conventional score processes also produce considerable amounts of loose material that must be pulled tight again. If enough of the loose metal is not removed, the end will be difficult to open. If too much is removed then the score line is placed under tension. If too much tension is applied, then the score line is susceptible to formation of cracks or micro-fractures, which can significantly impair the drop performance of the container.

BRIEF SUMMARY OF THE INVENTION

The present disclosure describes an easy-open metal end, and a method for making an easy-open metal end, in which cracking of polymeric coatings and resulting exposure of bare metal are substantially reduced or eliminated. The method entails performing a pre-score coining operation, followed by a second operation to form a score line. The coining step uses more gentle-radius tooling designed not to crack or cut the coatings, in contrast to conventional “sharp” tooling that forms a score line and breaks the coating on the scored surface.

Between the coining step and the score line-forming step, a paneling step is performed to pull out the loose metal generated in the coining step. By forming a metal-gathering panel to at least partially pull out the loose metal, end tension can be controlled more easily than in a conventional process. This is because, compared to a conventional score line, the coined region is much less susceptible to cracking from being over-stretched.

Additionally, because the coining operation thins the metal in the coined region, the score line can be of the conventional style but can have less penetration than, and therefore can be narrower than, a conventional score line. Consequently, even if the score line does rust, it will be very small in width and thus relatively unnoticeable. It is also possible that the surface friction and tension of water will not allow the water to get into the narrow score line, and hence rust may not even form.

In accordance with one embodiment of the invention, a method for making an easy-open metal end comprises the steps of:

(a) providing a metal end comprising at least a metal layer, the metal end comprising a central panel, a countersink surrounding the central panel, and a chuck wall extending generally upwardly and outwardly from the countersink;

(b) engaging an upper coining tool with an upper surface of the central panel and a lower coining tool with a lower surface of the central panel, the upper and lower coining tools each defining a coining portion that is generally convex in a direction toward the respective surface of the central panel, and advancing the upper and lower coining tools so as to coin the upper surface to form an upper coined region that is generally concave in an upward direction and to coin the lower surface of the central panel to form a lower coined region that is generally concave in a downward direction, thereby thinning the metal layer between the coined regions and generating loose metal in the central panel as a result of metal flow away from the coined regions, the coined regions extending about a predetermined area of the central panel;

(c) forming a first metal-gathering panel in the central panel, thereby at least partially pulling out the loose metal generated in step (b); and

(d) forming a score line in at least one of the upper and lower coined regions, the score line extending about the predetermined area of the central panel so as to delineate a tear portion that is at least partially separable from a remainder of the central panel by severing the central panel along the score line.

In one embodiment, the loose metal from the coining step is pulled out in step (c) before the score line is formed in step (d). The method then can comprise a further step (e) in which a second metal-gathering panel is formed in the central panel. Step (e) can be performed after step (d).

In one embodiment, the coined regions formed in step (b) extend in a loop located proximate the countersink, and step (c) comprises forming the first metal-gathering panel at a location spaced radially inwardly from the coined region. The first metal-gathering panel can be formed in a generally C-shaped configuration extending parallel to the score line.

Step (c) can further comprise forming an additional metal-gathering panel spaced radially inwardly from the first metal-gathering panel.

In preferred embodiments, the metal end comprises a polymeric coating on at least an upper surface of the metal layer, and step (b) is carried out such that the forming of the upper and lower coined regions does not break the polymeric coating and expose bare metal.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is a cross-sectional view illustrating a first step of a process for converting a flat sheet metal blank into an easy-open metal end, in accordance with an embodiment of the invention, the first step comprising the conversion of the blank into a shell in a shell press;

FIG. 2 is a cross-sectional view illustrating a second step of the process in accordance with an embodiment of the invention, the second step comprising a coining step;

FIG. 3 is a cross-sectional view depicting a portion of the metal end resulting from the coining step of FIG. 2;

FIG. 4 is a cross-sectional view showing a third step of the process in accordance with an embodiment of the invention, the third step comprising a paneling step;

FIG. 5 is an isometric view of the metal end resulting from the paneling step of FIG. 4;

FIG. 6 is a cross-sectional view illustrating a fourth step of the process in accordance with an embodiment of the invention, the fourth step comprising a score line-forming step;

FIG. 7 shows a portion of FIG. 6 on an enlarged scale;

FIG. 8 is a cross-sectional view showing a portion of the metal end resulting from the score line-forming step of FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention now will be described more fully hereinafter with reference to the accompanying drawings in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. The drawings are not necessarily to scale, and thus the relative proportions of various elements suggested by the drawings is not necessarily indicative of the actual relative proportions.

With reference to FIG. 1, a sheet metal blank is shown being converted into a “shell” 20 in a shell press, as a first step in a process for converting the blank into an easy-open metal end. It will be understood that only an outer peripheral area of the shell 20 is depicted in FIG. 1. The shell comprises at least a metal layer, and optionally can further comprise a protective coating on one or both major surfaces of the metal layer. The shell 20, which is also referred to herein as a “metal end,” is shown being formed by tools T1, T2, T3 to have a central panel 22 that is generally planar, a countersink 24 that surrounds the central panel, a chuck wall 26 that extends generally upwardly and outwardly from the countersink, and a curl 28 (only partially visible in FIG. 1, but see FIG. 2) that extends generally outwardly from an upper end of the chuck wall. These features of the shell 20 are of course typical and well-known features of metal ends in general.

Shells or metal ends produced in the shell press are next transferred to a further conversion press in which easy-open features are formed in the metal ends. FIG. 2 depicts one step in the process carried out in the conversion press, in which a pre-score coining operation is performed on the metal end 20. An upper coining tool T4 and a lower coining tool T5 simultaneously engage upper and lower surfaces, respectively, of the central panel 22 of the metal end. The upper and lower coining tools directly oppose each other and each defines a coining portion that is generally convex in a direction toward the other coining portion. The tools T4 and T5 are advanced toward each other so as to coin the upper surface to form an upper coined region 30 that is generally concave in an upward direction and to coin the lower surface of the central panel to form a lower coined region 32 (FIG. 3) that is generally concave in a downward direction. As used herein, “generally convex” and “generally concave” do not exclude the possibility of there being portions of the shape that are flat or planar, as long as the overall shape is convex or concave when the overall shape is approximated by a smooth curve.

While the illustrated embodiment has coining tools T4 and T5 acting simultaneously to form the upper and lower coined regions, alternatively one coined region can be formed first, and subsequently the other coined region can be formed.

The formation of the coined regions 30, 32 results in a thinning of the metal layer between the coined regions, and also generates loose metal in the central panel 22 as a result of metal flow away from the coined regions. The coined regions 30, 32 are configured to extend about a predetermined area of the central panel, which will become a tear portion that will be removable (or at least partially removable) from the remainder of the central panel once the score line is formed as described below. If the tear portion is to be completely removable, then the score line extends about a closed loop, as do the coined regions. Alternatively, if the tear portion is to be only partially removable (e.g., bending about a hinge line, such as in beverage cans where the tear portion is pushed down into the resulting opening, pivoting about a hinge line formed by an unscored portion of the panel), then the score line forms an open loop, as do the coined regions. The metal end illustrated in the present drawings has a completely removable tear portion.

FIG. 4 illustrates a subsequent step in the process in accordance with an embodiment of the invention. Only a portion of the central panel 22 of the metal end is shown in FIG. 4. Upper tools T6 and T7, and a lower tool T8, are shown engaging the central panel 22 to pull out “loose” metal generated in the coining step. More particularly, the coining step causes metal of the central panel 22 to “flow” away from the coined regions 30, 32 in radially outward and radially inward directions as a result of the thinning of the metal layer between the upper and lower coined regions. If this loose metal is not pulled taut again, it will be difficult to cleanly sever the score line ultimately formed in the metal end. In order to at least partially pull out this loose metal, one or more metal-gathering panels are formed in the central panel. As depicted in FIGS. 4 and 5, a first metal-gathering panel 34 and a second metal-gathering panel 36 are formed in the central panel 22. The first metal-gathering panel 34 is formed by deforming an area of the central panel upwardly out of the plane of the central panel via the tools T6 and T8. The upper tool T6 defines a recess and the lower tool T8 defines a protrusion that deforms an area of the central panel upwardly into the recess in the upper tool as shown. The second metal-gathering panel 36 is formed by deforming an area of the central panel downwardly out of the plane of the central panel via the tools T7 and T8. The lower tool T7 defines a recess and the upper tool T8 defines a protrusion that deforms an area of the central panel downwardly into the recess in the lower tool. While the illustrated embodiment shows the two metal-gathering panels 34, 36 to be deformed in opposite directions, the direction in which each panel is deformed is not critical.

In the embodiment illustrated in FIG. 5, which shows the metal end resulting from the operation of FIG. 4, the coined regions 30 (and 32, not visible in FIG. 5) are located immediately proximate the countersink 24 and extend in a closed loop about a geometric center point of the metal end. In this embodiment, the first metal-gathering panel 34 is located a little ways radially inwardly from the coined regions and is in a C-shaped configuration rather than being a closed loop (and hence is also called a “C-panel” herein). The C-shaped configuration is adopted because of the necessity (in this particular embodiment as illustrated) of having an integral rivet 38 spaced inwardly from the coined regions by about the same distance that the C-panel 34 is spaced inwardly therefrom. As known in the art, the integral rivet is used for attaching a pull tab (not shown).

The second metal-gathering panel 36 is generally circular and is located at about the center point of the metal end, spaced radially inwardly from the C-panel 34. It will be understood that the illustrated number, configurations, and locations of the metal-gathering panels is exemplary only, and is not limiting with respect to the present invention. Thus, the second panel 36 need not be concentric with the C-panel 34 as illustrated.

FIGS. 6 and 7 depict a further step in the process for forming the easy-open metal end. Upper tools T9 and T10 act in conjunction with a lower tool T11 to form a score line within the upper coined region 30 of the metal end. Specifically, upper tool T10 has a scoring portion of relatively small surface area, and lower tool T11 has a backing portion of relatively large radius of curvature. As examples, the radial width of the scoring portion of the tool T10 that contacts the metal end can range from about 0″ (i.e., a knife edge) to about 0.002″. The lower tool T11 provides support to the metal end in the coined regions so that the scoring tool T10 can score the upper surface without unduly deforming the metal end.

FIG. 8 depicts the metal end 20 resulting from the operation of FIG. 5. The score line 40 is shown in the upper coined region 30. The score line's penetration and width can be relatively small because of the thinning of the metal layer 22 by the formation of the coined regions 30, 32. For example, the score line 40 can have a depth of penetration that ranges from about 0.0002″ to about 0.0020″. In comparison, conventional score lines typically have penetration depths ranging from about 0.0030″ to about 0.0050″. Consequently, even if the score line does rust, it will be very small in width and thus relatively unnoticeable. It is also possible that the surface friction and tension of water will not allow the water to get into the narrow score line, and hence rust may not even form.

In accordance with an alternative (unillustrated) embodiment similar to that of FIG. 8, there are both an upper score line 40 in the upper coined region 30 and a lower score line (not shown) in the lower coined region 32. Employing two score lines in this fashion may allow each score line's penetration and width to be reduced even further relative to those of a conventional score line.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for making an easy-open metal end, comprising the steps of:

(a) providing a metal end comprising at least a metal layer, the metal end comprising a central panel, a countersink surrounding the central panel, and a chuck wall extending generally upwardly and outwardly from the countersink;

(b) engaging an upper coining tool with an upper surface of the central panel and a lower coining tool with a lower surface of the central panel, the upper and lower coining tools each defining a coining portion that is generally convex in a direction toward the respective surface of the central panel, and advancing the upper and lower coining tools so as to coin the upper surface to form an upper coined region that is generally concave in an upward direction and to coin the lower surface of the central panel to form a lower coined region that is generally concave in a downward direction, thereby thinning the metal layer between the coined regions and generating loose metal in the central panel as a result of metal flow away from the coined regions, the coined regions extending about a predetermined area of the central panel;

(c) forming a first metal-gathering panel in the central panel, thereby at least partially pulling out the loose metal generated in step (b); and

(d) forming a score line in at least one of the upper and lower coined regions, the score line extending about the predetermined area of the central panel so as to delineate a tear portion that is at least partially separable from a remainder of the central panel by severing the central panel along the score line.

2. The method of claim 1, wherein step (c) is performed before step (d).

3. The method of claim 2, further comprising the step of:

(e) forming a second metal-gathering panel in the central panel.

4. The method of claim 3, wherein step (e) is performed after step (d).

5. The method of claim 1, wherein the coined regions formed in step (b) extend in a loop located proximate the countersink, and wherein step (c) comprises forming the first metal-gathering panel at a location spaced radially inwardly from the coined regions.

6. The method of claim 5, wherein the first metal-gathering panel is formed in a generally C-shaped configuration extending parallel to the score line.

7. The method of claim 6, wherein step (c) further comprises forming an additional metal-gathering panel spaced radially inwardly from the first metal-gathering panel.

8. The method of claim 1, wherein an upper score line is formed in the upper coined region and a lower score line is formed in the lower coined region.

9. The method of claim 1, wherein step (b) comprises forming the upper coined region and forming the lower coined region at different times.

10. The method of 1, wherein step (b) comprises forming the upper coined region and forming the lower coined region simultaneously.

11. The method of claim 1, wherein step (a) comprises:

providing a metal blank comprising a flat, disk-shaped member having at least a metal layer; and

deforming an outer peripheral portion of the blank to form the countersink and chuck wall.

12. The method of claim 1, wherein the metal end comprises a polymeric coating on at least an upper surface of the metal layer, and wherein step (b) is carried out such that the forming of the upper and lower coined regions does not break the polymeric coating and expose bare metal.

13. An easy-open metal end, comprising:

a metal end comprising at least a metal layer, the metal end comprising a central panel, a countersink surrounding the central panel, and a chuck wall extending generally upwardly and outwardly from the countersink;

an upper coined region in an upper surface of the central panel, the upper coined region being generally concave in an upward direction, and a lower coined region in a lower surface of the central panel and directly opposite from the upper coined region, the lower coined region being generally concave in a downward direction, the metal layer being thinned between the coined regions, the coined regions extending about a predetermined area of the central panel;

a first metal-gathering panel in the central panel, loose metal generated by the formation of the coined regions being at least partially pulled out by the formation of the first metal-gathering panel; and

a score line formed in at least one of the upper and lower coined regions, the score line extending about the predetermined area of the central panel so as to delineate a tear portion that is at least partially separable from a remainder of the central panel by severing the central panel along the score line.

14. The easy-open metal end of claim 13, further comprising a second metal-gathering panel in the central panel.

15. The easy-open metal end of claim 13, wherein the coined regions extend in a closed loop located proximate the countersink, and wherein the first metal-gathering panel is at a location spaced radially inwardly from the coined regions.

16. The easy-open metal end of claim 13, wherein the first metal-gathering panel is formed in a generally C-shaped configuration extending parallel to the score line.

17. The easy-open metal end of claim 16, further comprising an additional metal-gathering panel spaced radially inwardly from the first metal-gathering panel.

18. The easy-open metal end of claim 13, having an upper score line formed in the upper coined region and a lower score line formed in the lower coined region.