Patent ID: 8167161

Claim:
A metallic container closure comprising a metallic shell having a circular top panel wall made of a thin metal sheet having a tensile strength of 200 to 230 N/mm 2 and a cylindrical skirt wall hanging down from a circumferential edge of the top panel wall, and a synthetic resin liner arranged in the shell, the skirt wall of the shell having a thread-forming region and an annular groove positioned at an upper end portion of the thread-forming region, wherein: an internal pressure release line extending in the circumferential direction at an angle of 40 to 95 degrees is arranged in the skirt wall at a portion over the annular groove, the internal pressure release line being constituted by a plurality of slits arranged in the circumferential direction maintaining a distance and low-strength bridging portions present among the slits and having a small width in the circumferential direction so as to be broken by an elevated pressure in the container, wherein a fixing line is formed over an angle of 25 to 180 degrees in the portion on an opposite side of the internal pressure release line in the direction of diameter on an extension thereof, the reinforcing lines are formed over an angle of 10 to 55 degrees neighboring both ends of the internal pressure release line in the circumferential direction, the internal pressure release assist line is formed between the reinforcing line and the fixing line, the internal pressure release assist line being constituted by a plurality of slits extending in the circumferential direction and high-strength bridging portions positioned among the slits and having a width in the circumferential direction larger than that of the low-strength bridging portions, the fixing line being constituted by an ultra-high-strength bridging portion having a width in the circumferential direction larger than that of the high-strength bridging portion, and the reinforcing line being constituted by reinforcing bridging portions having a width larger in the circumferential direction than that of the high-strength bridging portion but is shorter in the circumferential direction than that of the ultra-high-strength bridging portion.