Abstract: The structure of a clinch portion of a mounting cup is provided which can retain a gasket. The clinch portion includes a curl portion continuous with an upper end of an outer circumferential wall at an inner circumferential edge of the curl portion, and a curl skirt portion having an upper end continuous with an outer circumferential edge of the curl portion. The curl portion is made of a plurality of curved planes having different radii extending from the inner circumferential edge to outer circumferential edge. A space a portion of the gasket can enter is formed between a virtual curved plane with a radius constituting the inner plane of the curl portion and an inner curved plane or an outer curved plane, or between the virtual curved plane and both the inner and outer curved planes.

Abstract: The structure of a clinch portion of a mounting cup is provided which can retain a gasket reliably between a curl portion and a can bead, prevent extrusion of the gasket, and obtain a reliable seal. The clinch portion includes a curl portion 7 continuous with an upper end of an outer circumferential wall 6 at an inner circumferential edge of the curl portion, and a curl skirt portion having an upper end continuous with an outer circumferential edge of the curl portion, respectively of the mounting cup 1 and being concentric relative to a center line 2. The curl portion 7 is made of a plurality of curved planes having different radii extending from the inner circumferential edge to outer circumferential edge. A space 31 a portion of the gasket 34 can enter is formed between a virtual curved plane 27 with a radius constituting the inner plane of the curl portion and an inner curved plane 25 or an outer curved plane 26, or between the virtual curved plane and both the inner and outer curved planes.