| 摘要 |
PROBLEM TO BE SOLVED: To obtain a closure member which can open a take-out port wide by a weak pressing force. SOLUTION: A radial groove 52 formed on a seal disk 34 of a packing is formed with a low strength portion 64 within a predetermined range from the center of the seal disk 34 by cutting the radial groove 52 deep to further reduce thickness of a thin part 62 (thickness T'2). When the center of the seal disk 34 is pressed by a pressing means, first a crack occurs on the low strength portion 64, and then the crack reaches a bent groove 54 and a peripheral groove 56. |
