US Patent 7341163 Can shell and double-seamed can end

A drawn aluminum can shell has a peripheral crown which is double-seamed with an end portion of an aluminum can body to provide a can end having a generally flat center panel connected by a curved panel wall to an inner wall of an annular U-shaped countersink. The countersink has a generally cylindrical outer wall and an inner width less than the radius of the panel wall. The outer wall of the countersink connects with a frusto-conical chuckwall at a junction below the center panel, and the chuckwall extends to an inner wall of the crown at an angle of at least 16° with the center axis. The chuckwall has an S-curved intermediate configuration, the inner width of the countersink is less than the radius of the panel wall, and the inner wall of the countersink extends at an acute angle relative to the outer wall.