Two-piece metal can and manufacturing method thereof

A two-piece metal can,

• wherein a cylindrical trunk section is formed integrally with a bottom section closing a lower end of the trunk section,
• the bottom section includes
• a rim section whose diameter is smaller than a diameter of the trunk section, and which is shaped entirely into a circular shape protruding downwardly,
• a counter section extending upwardly from a lower end of the rim section toward an inner circumferential side to serve as an inner circumferential wall of the rim section, and
• a domed section formed continuously from an upper end of the counter section in which a top portion is formed at a central portion thereof,
• the domed section includes
• a first arcuate portion that is formed around a center of the domed section whose cross-section is an arcuate cross-section having a predetermined first curvature radius, and
• a second arcuate portion that is formed between the first arcuate portion and the counter section while being joined smoothly to the first arcuate portion, and whose cross-section is an arcuate cross-section having a predetermined second curvature radius, and
• a ratio between the first curvature radius and the second curvature radius (the first curvature radius/the second curvature radius) falls within a range between a lower limit value and an upper limit value expressed as:
• Lower
• ⁢
• limit
• ⁢
• value
• =
• -
• (
• 0.
• 1
• ⁢
• 48
• ·
• Y
• )
• +
• (
• 0
• .
• 0
• ⁢
• 25
• ·
• DP
• )
• +
• 1.92
• ;
• and
• Upper
• ⁢
• limit
• ⁢
• value
• =
• (
• 0
• .
• 1
• ⁢
• 40
• ·
• Y
• )
• -
• (
• 0
• .
• 0
• ⁢
• 54
• ·
• DP
• )
• +
• 3.97
• ,
• given that a height of the domed section from an outer circumferential end of the second arcuate portion to the top portion is Y, and that an outer diameter of the domed section is DP.

A manufacturing method of a two-piece metal can,

• wherein a bottom section is formed integrally with a trunk section by drawing and ironing a metal sheet,
• the bottom section includes
• a rim section whose diameter is smaller than a diameter of the trunk section, and which is shaped entirely into a circular shape protruding downwardly,
• a counter section extending upwardly from a lower end of the rim section toward an inner circumferential side to serve as an inner circumferential wall of the rim section, and
• a domed section formed continuously from an upper end of the counter section in which a top portion is formed at a central portion thereof,
• the domed section includes
• a first arcuate portion that is formed around a center of the domed section whose cross-section is an arcuate cross-section having a predetermined first curvature radius, and
• a second arcuate portion that is formed between the first arcuate portion and the counter section while being joined smoothly to the first arcuate portion, and whose cross-section is an arcuate cross-section having a predetermined second curvature radius, and
• the bottom section is formed by a doming punch such that a ratio between the first curvature radius and the second curvature radius (the first curvature radius/the second curvature radius) falls within a range between a lower limit value and an upper limit value expressed as:
• Lower
• ⁢
• limit
• ⁢
• value
• =
• -
• (
• 0.
• 1
• ⁢
• 48
• ·
• Y
• )
• +
• (
• 0
• .
• 0
• ⁢
• 25
• ·
• DP
• )
• +
• 1.92
• ;
• and
• Upper
• ⁢
• limit
• ⁢
• value
• =
• (
• 0
• .
• 1
• ⁢
• 40
• ·
• Y
• )
• -
• (
• 0
• .
• 0
• ⁢
• 54
• ·
• DP
• )
• +
• 3.97
• ,
• given that a height of the domed section from an outer circumferential end of the second arcuate portion to the top portion is Y, and that an outer diameter of the domed section is DP.