A can end having a countersink bead, an inclined chuck wall and a strong seam, resists distortion from its circular profile when subjected to thermal processing or when packaging carbonated beverages. This high hoop strength affects the manner in which the can end ultimately fails when placed under extreme abuse conditions, even if buckle pressure performance is within industry specified standards. The can end of the invention has control features introduced which control the failure mode while maintaining specified buckle pressure performance. In one embodiment, the can end has a two part wall and a control feature that comprises expansion of the countersink bead to act as a trigger for local peaking, together with a groove in the chuck wall which prevents the peaking force from being concentrated at a single point which could result in leaking by the production of a pin hole.
1. A can end shell adapted to be joined to a can body for packaging beverages under pressure and having improved failure characteristics, said can end shell comprising:
a circumferentially extending peripheral curl including a cover hook, a seaming panel, and a radiused portion;
a wall extending circumferentially and radially inwardly from said radiused portion of said peripheral curl at a first point, said wall including a lower portion, an upper portion, and a juncture therebetween, said lower portion being inclined at least 46° and no more than 60° with respect to a vertical axis;
an annular reinforcing bead extending radially inward from said wall lower portion at a second point, wherein a line between said first and second points is inclined between about 20° and about 60° with respect to the vertical axis; and
a center panel extending radially inward from said annular reinforcing bead.
2. The can end shell of claim 1 wherein said lower wall portion is inclined between 46° and 54°.
3. The can end shell of claim 1 wherein said lower wall portion is inclined between 48° and 54°.
4. The can end shell of claim 1 wherein said lower wall portion is inclined at approximately 52°.
5. The can end shell of claim 2 wherein the lower wall portion is substantially straight.
6. The can end shell of claim 3 wherein the lower wall portion is convex between the second point and the juncture.
7. The can end shell of claim 4 wherein the upper wall is substantially straight.
8. The can end shell of claim 4 further comprising one or more control features, each control feature extending around an arc of at least part of the countersink bead and/or the chuck wall, whereby the failure mode of the can end, when seamed to a can body, is controlled, and in which the or each control feature comprises one or more of: an expansion of the countersink bead, a shelf in the outer wall of the countersink, an indentation in the chuck wall, and/or coining.
9. The end shell according to claim 8 wherein the control feature includes at least one feature which extends around the whole circumference of the end shell.
10. The can end shell according to claim 8 wherein the arc length is 90° or less.
11. The can end shell of claim 8 wherein said end shell includes a combination of different types of control features extending around an arc centered on the same diameter of the can end.
12. The can end shell of claim 8 wherein said control feature comprises at least an expansion of a upper portion of the countersink bead.
13. The can end shell of claim 8 wherein each control feature comprises at least an expansion of an upper portion of the countersink bead and an indentation in the chuck wall.
14. The can end shell of claim 8 wherein the control feature is made in either a shell press or a conversion press or a combination thereof.