WO1998022355A1

WO1998022355A1 - Can lid with depression to avoid its separation and apparatus for making the same

Info

Publication number: WO1998022355A1
Application number: PCT/US1997/019000
Authority: WO
Inventors: Richard O. Wahler; Robert A. Winkless
Original assignee: Crown Cork & Seal Technologies Corporation
Priority date: 1996-11-18
Filing date: 1997-10-21
Publication date: 1998-05-28
Also published as: AU4825697A

Abstract

An apparatus for forming a score line (14) within a metal can end (12) is provided. The apparatus comprises a score die (50) without a ground notch for forming a score line (14) in a metal can end (12). The score die has a corner radius area (30). A score anvil (70) having a top surface that mates with the score die (50) is also provided. The score anvil (70) has at least one relief notch cavity (90) formed therein at a location proximate to where the score die corner radius area (30) mates with the score anvil (70). The anti-missile relief notch cavity defines a groove that increases the score line area in a metal can end (12) when the score die (50) and score anvil (70) mate with a metal can end (12) therebetween.

Description

CAN LID WITH DEPRESSION TO AVOID ITS SEPARAΗON AND APPARATUS FOR MAKING THE SAME

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to beverage containers and more particularly to beverage containers having a can tear panel end and apparatus for making the same .

2. Description of the Related Technology Easy opening containers are well known in the beverage industry. Typically, a beverage container comprises a body and a separate can end made of a thin aluminum material . The can end is attached to the body after a tear panel is formed in the can end and a tab is attached using an integral rivet. The tear panel is defined by a score line or a tear line. A tab member is attached above the tear panel and is used to force the tear panel open by tearing or rupturing the score line to create a pour opening . Conventional apparatus employed to form a can end having a tear panel defined by a score line include a score die and mating anvil. Typically, the score die comprises an outer surface having a protruding member formed thereon that corresponds to the shape of the score line that is formed in the can end. The usual anvil has a surface that mates with the protruding member to form the score line in the can end as the score die is brought down upon the can end and anvil. The most common operation for forming a can end having a tear panel defined by a score line consist of the step of maneuvering a metal material between a score die and mating anvil. Thereafter, the score die is brought down upon the metal blank and anvil with a force sufficient to crush the metal blank therebetween to create the score line. The thickness of the crushed area along the can end is routinely referred to as the score residual.

One apparatus and method employed in forming a can end having a tear panel defined by a score line is taught in U.S. Patent No. 4,027,612 to Herbst . The tear panel forming apparatus employed comprises a curved preforming punch with flat score anvil, and score die having a depression formed therein. In forming the tear panel, the can end is drawn between the preforming punch and the die thereby forming an outwardly open convex configuration in the can end. Simultaneously, the can end is placed on top of the anvil with the convex drawn portion positioned within the score die depression to allow the scoring punch to be brought down upon the can end to create the score line in the can end. Conventional apparatus and methods employed to form beverage cans having tear panels defined by a score line have, however, produced tear panels that are subject to failure. The tear panel member of a beverage can is subject to "missiling" . Missiling occurs when the tear panel and/or tab member ruptures and dislodges from the can end. The beverage can may also fail when being stored, as it is likely that the fluid contained within the beverage can will leak around the score line. The cause of the leakage is discussed in more detail below.

The main reason that missiling occurs and the tear panel member completely dislodges from a can end is that the tear panel member is insufficiently secured by the metal in the score residual. To rupture the score line, the tab must overcome the relatively high internal pressure produced by the fluid contained within the container. If during opening the score tearing propagates too rapidly, then it is likely that the tear panel member will dislodge from the can end.

One method that has been employed in an attempt to prevent the tear panel member from dislodging from the can end is to increase the score line cross-sectional area which slows down the rate of score line tearing while the gas pressure in the can is being equalized to atmospheric pressure. Currently, the beverage can industry employs a score die comprising a protruding member that corresponds to the shape of the score line and a ground notch formed proximate to the protruding member. The ground notch, which is also called an anti-missile slot, creates the additional area along the score line when the score die is brought down upon the metal can material and anvil. The conventional ground notched score dies, however, produce abrupt changes along the score line path which may create stress risers along the base of the residual and lead to the development of stress corrosion along the residual, dislodging of the tab member from the can end, or leakage along the score line.

When a beverage can end is subject to stress corrosion, it is likely that the beverage can will leak when it is stored at elevated temperatures and there is moisture on the outside surface of the beverage can end. Moisture forms on the beverage can end after the cans are filled with a liquid having one temperature and then subjected to differing storage environment temperatures. After the cans are filled, they should be completly dried of any moisture before being wrapped in the typical plastic wrap and prepared for shipping. When beverage cans are wrapped without being completely dried, the remaining moisture will likely cause leakage around stress corroded areas when the cans are stored at elevated temperatures .

It would, therefore, be desirable to provide an apparatus for making a beverage can having improved integrity and reliability.

SUMMARY OF THE INVENTION An apparatus for forming a score line within a metal can end is provided. The apparatus comprises a score die (without a ground notch) for forming a score line in a metal can end. The score die has a corner radius area for producing a score line with a corner radius area in a metal can end. A score anvil having a surface that mates with the score die is provided. The score anvil has at least one relief notch cavity formed therein at a location substantially close to where the score die mates with the score anvil. The relief notch cavity defines a substaintially smooth groove that increases the score line area in a metal can end when the score die and score anvil mate with a metal can end therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a can end having a score line formed therein in accordance with the present invention;

Figure 2 shows a score die with a protruding rib that corresponds to the score line that is formed in the can end shown in Figure 1;

Figure 3 shows a scoring anvil having a relief notch cavity formed therein in accordance with the present invention which mates with the score die shown in Figure 2 ; and

Figure 4 is a sectional-view taken along section line 4-4 shown in Figure 3 of the relief groove cavity formed in the anvil.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows a metal can tab end 12 that is attached to a beverage can 8. The can tab end 12 has a tear panel defined by a score line 14 in accordance with the present invention. The score line 14 has several sections. The score line 14 comprises a first end 16 having a head portion 18 and a second end 20 having a tail end 22. The first end 16 and the second end 20 are located substantially adjacent to each other. A substantially continuous curved path 24 having a corner radius area 30 is formed between the first end 16 and second end 20. The score line 14 curved path 24 has an outer portion 26, an inner portion 28, and a base 92 therebetween. A substantially smooth notched residual area 32 is proximate to the corner radius area 30. Preferably, the notched residual area 32 intersects the corner radius area 30 proximate to the outer portion 26 of the score line 14. The cross-sectional area along the base 92 of the corner area 30 and notched residual area 32 is greater than a substantial portion of the remaining score line 14 except for the head portion 18 of the first end 16. As an example, for a 12 ounce carbonated beverage can, the substantially smooth notched residual area 32 increases the area along the corner radius area 30 by approximately 31% but, not more than 38%.

The can tab end 12 further includes a reinforcing bead or "D" bead 40, a raised panel bead 42, and a panel bead 44 which strengthen the can end's 12 resistance to the internal pressure created by a carbonated liquid contained within the can. A tab member 46 is secured above the score line 14 by a rivet 47 that is attached in a rivet hole 10. The tab member 46 is positioned above the score line 14 to enable a user to rupture the score line 14 and open the can end to gain access to the liquid contained within the can. In accordance with the present invention, the notched residual area 32 improves the tab panel's ability both to overcome the pressures produced by the container contents during handling and to puncture the score line 14 without causing the tear panel 42 to dislodge from the can end during opening. The notched residual area also eliminates the likelihood, or reduces the tendency, of the metal material developing stress corrosion that may cause the can end to leak. Figure 2 shows a score die 50 employed for manufacturing the can end 12 shown in Figure 1. The score die 50 comprises a protruding member 52 that is formed to correspond with the score line 14 shown in Figure 1. The protruding member 52 includes a first end 16' and a second end 20', which further include a head portion 18' and tail end 22', respectively. A substantially continuous curved path 24' having a corner radius area 30' is formed between the first end 16' and second end 20' . The protruding member 52 has a relative outer portion 26', inner portion 28', and base 92' therebetween.

Dowel holes 54 and 56, and tapped holes 58 are provided for locating and locking the score die 50 on a die shoe (not shown) , such as that provided in the Stolle Conversion System 8, manufactured by the Stolle Corporation. A rivet relief area 60 is provided for aiding in the creation of a rivet hole 10 in the finished can tab end. An anti-rotation pin hole 62 is provided to prevent the "D" bead from rotating. A "D" bead clearance hole 64' is provided to aid in forming the "D" bead 40 in the can tab end 12.

Figure 3 shows anvil 70 in accordance with the present invention. The anvil 70 has an upper surface 72 that is formed to mate with the score die 50. The anvil 70 is provided with an anvil rivet hole 74 for forming the rivet hole 10 in the can tab end. A "D" bead punch hole 76 is provided in the anvil top surface 72 for forming the "D" bead 40 in the can tab end 12. Dowel holes 78 and bolt holes 80 are provided to secure the anvil 70 to a support (not shown) such as a support in the Stolle Conversion System 8. A relief notch cavity 90 is formed in the upper surface 72 for forming the notched residual area 32 in the can tab end 12. Preferably, the relief notch cavity 90 is formed as a substantially smooth oblong cavity having at least two generally smooth rounded opposing edges 96. This configuration ensures that a smooth notched residual area 32 is formed in a can tab end 12 when the score die 50 is brought down upon the anvil 70. Preferably, the relief notch cavity 90 is formed at a location on the anvil top surface 72 such that the outer portion 26' of the score die 50 corner radius area 30' intersects the relief notch cavity 90 to form the score line 14 and intersecting notched residual area 32 in the can tab end 12.

A phantom line 82 of the score line 14 is shown superimposed on the top surface 72 of the anvil 70 to illustrate where the score die 50 and score die corner radius area 30 mate with the anvil top surface 72 and relief notch cavity 90 to form the score line 14 in a can tab end 12.

It is noted that the relief notch cavity 90 can be formed at any location on the anvil top surface 72 such that the notched residual area 32 is formed anywhere proximate to the inner portion 28 of the score line 14 corner radius area 30 or outer portion 26 of the score line 14 corner radius area 30 in the can tab end 12. Figure 4 shows the relief notch cavity 90 in more detail. The relief notch cavity 90 has a substantially smooth surface 94 extending therethrough. It is noted that the number of relief notch cavities 90, the location of where a relief notch cavity 90 is placed along the anvil to produce a notched residual area 32 along a score line 14 in a can tab end 12, and the dimensional characteristics of a relief notch cavity 90 may vary depending on the size of the can end and the specific score line configuration.

In operation, the score die 50 and anvil 70 are employed to form a can tab end out of a metal material. The metal material or can tab end 12 is placed on the anvil top surface 72 and adjacent to the relief notch cavity 90 with the score die 50 and protruding member 52 directly above. The score die 50 is then brought down upon the can end such that the "D" bead 40, raised panel 42, panel bead 44, and score line 14 having a corner radius area 30 and a notched residual area 32 intersecting the corner radius area 30 are formed in the can tab end 12. The notched residual area 32 gradually and smoothly increases the score line 14 cross- sectional area without any abrupt changes. This gradual increase in area enhances the strength and integrity of the score line 14 which slows down the rate at which the score tears while the pressure in the can is being lowered or vented. Additionally, these gradual increase in area does not produce any significant stress risers that can cause stress corrosion and, in turn, cause the beverage can to leak when stored at elevated temperatures . It is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

I Claim:

1. An apparatus for forming a score line within a metal can end, said apparatus comprising: a score die for forming a score line in a metal can end, said score die having a corner radius area; and a score anvil, said anvil having a surface that mates with said score die to form a score line in a metal can end, said score anvil having at least one relief notch cavity defining a groove that increases the score line area in a metal can when the score die and score anvil mate with a metal can end therebetween, thereby making a metal can end that substantially prevents missiling and reduces the development of stress corrosion in the metal can end.

2. The apparatus of claim 1, wherein said at least one relief notch cavity is formed at a location where said score die intersects said score line, thereby increasing the area of a score line residual and reducing the development of stress corrosion in this area.

3. The apparatus of claim 1, wherein said at least one relief notch cavity is formed proximate to where said score die corner radius area mates with the score anvil, thereby, increasing the area proximate said score line residual and reducing the development of stress corrosion in this area.

4. The apparatus of claim 1 wherein said at least one relief notch cavity is formed at a location on said anvil where said score die corner radius area intersects said anvil, thereby, increasing the area of the corner radius residual and reducing the development of stress corrosion in this area.

5. The apparatus of claim 1 wherein said score die further comprises a protruding rib having a first tail end, a second tail end, and a substantially continuous curved path therebetween, said corner radius area being at a location distal to said second tail end.

6. A beverage can comprising: a can body; and a can tab end attached to one end of said can body, said can tab end having a score line defining a pour opening, said score line having a base, first tail end, second tail end, generally curved path with a corner radius area therebetween, and relief notch formed in the base proximate said score line, said relief notch having a substantially smooth cross-sectional area for substantially preventing missiling and reducing the development of stress corrosion in the can end.

7. The beverage can in claim 6 wherein said relief notch is proximate said corner radius area.

8. The beverage can in claim 6, wherein said relief notch intersects said corner radius area.