| 摘要 |
PURPOSE:To enhance the sealing reliability by eliminating the warps after press processing by a method wherein a rectangular recess is formed at the bottom of the recessform section of a cap. CONSTITUTION:A punch 30, a pressing device, makes a columnar form having a cross-section of the same form as that of the recessform section of the cap 18, and its bottom projects out in a polygonal form: a form of projection toward the center whose cross-section is polygonal. The punch 30 of such a form is pressed on a flat plate of a hoop material fixed on a die 22 having a recess, and thus the cap 18 is provided with a recess of the same form as the projection 31 of the punch 30. As a result, stress disperses to the corners of the bottom, resulting in the elimination of the warp of the whole body. |
