Buckle resistant can end

In a metallic end closure for a tubular container body wherein said closure prior to being secured to a container body includes a central panel extending laterally from a central longitudinal axis of rotation thereof merging downwardly at its periphery into an upwardly-facing countersink groove having a lowermost central portion, the outer extremity of said groove merging into an upwardly and outwardly-extending countersink wall and thence into a terminal peripheral flange,

• the improvement therein prior to be secured to a container body to enhance buckle resistance thereof when secured to a container body and subjected to substantial internal container pressures, comprising:
• (a) said countersink groove having inner and outer arcuate groove wall portions with said inner wall portion at its innermost extremity merging with said central panel and said outer wall portion at its outermost extremity merging with said countersink wall, with said arcuate groove wall portions extending respectively therefrom toward said groove lowermost central portion to merge together thereat at the groove root;
• (b) said outer arcuate groove wall portion having a predetermined arc radius with an origin located on an axis normal to said groove at said root, said normal axis being parallel to said longitudinal axis of rotation of said end closure;
• (c) said inner arcuate groove wall portion having a predetermined radius substantially greater than said outer groove wall portion radius with the inner portion arc radius having origin located on said normal axis and spaced further from said root than said outer radius origin;
• (d) said outer arcuate groove wall portion extending from said root to a line substantially perpendicular to said normal axis at the inner radius origin whereat its merges with said countersink wall, and said inner arcuate groove wall portion extending from said root substantially to said line;
• (e) said countersink wall above its merge with said groove wall portion defining a continuous curve reverse to that of said countersink groove between said groove and said flange thereby to tension the inner surface thereof and to compress the outer surface thereof when said closure is secured by said flange to a container body;
• (f) said end closure is aluminum and wherein further said central panel is stretched beyond its yield point to define a taut profile-stable, upwardly-domed configuration of greater radius than that of said reversely-curved wall portion at said central panel periphery.