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 whilst maintaining specified buckle pressure performance. In one embodiment, the control feature 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 comprising a center panel, a countersink bead, a chuck wall portion, a seaming panel, and a peak triggering strain-limiting shelf, the shelf extending around an arc of at least part of an outer wall of the countersink bead and located below the height of the center panel.
2. An end shell according to claim 1 , in which the shelf extends around the whole circumference of the end shell.
3. An end shell according to claim 1 , in which the shelf extends over an arc behind the heel of a tab fixed to the can end, and centered on a diameter through a tab central axis.
4. An end shell according to claim 1 , in which a shelf is disposed on each side of a diameter through a tab central axis and each extending around an arc of the can end.
5. An end shell according to claim 3 , in which the arc length is 90° or less.
6. An end shell according to claim 1 , in which said end shell includes two or more strain-limiting shelves extending around an arc centered on the same diameter of the can end.
7. An end shell according to claim 1 , further comprising an indentation in the chuck wall, extending around an arc centered on the same can diameter.
8. An end shell according to claim 1 , in which an indentation or coined region is positioned at least partially in the upper half of the chuck wall, extending either internally or externally, or a combination of these.
9. An end shell according to claim 1 , further comprising coining of a shoulder between the inner wall of the countersink and the center panel over an arc or pair of arcs.
10. An end shell according to claim 1 , in which the shelf is made in either a shell press or a conversion press or a combination of these.
11. An end shell according to claim 4 , wherein the arc length is 90° or less.
12. An end shell according to claim 1 , wherein the chuck wall portion is inclined relative to an axis perpendicular to the exterior of the center panel by an angle of between 30 degrees and 60 degrees.
13. An end shell according to claim 1 , wherein (i) the outer wall of the countersink bead includes an upper half and a lower half, and (ii) the shelf is in the lower half.
14. An end shell according to claim 1 , wherein (i) the outer wall of the countersink bead includes an upper half and a lower half, and (ii) the shelf is in the upper half.
15. An end shell according to claim 1 , wherein the shelf is located proximate the region of force concentration in the countersink bead.
16. A can end shell comprising:
a center panel;
a countersink bead about the periphery of the center panel;
a chuck wall portion located radially outwardly from the countersink, the chuck wall inclined relative to an axis perpendicular to the exterior of the center panel by an angle of between 30 degrees and 60 degrees;
a seaming panel located radially outwardly from the chuck wall; and
a peak triggering strain-limiting shelf the shelf extending around an arc of at least part of an outer wall of the countersink bead and located proximate the region of force concentration in the countersink bead.