| 摘要 |
PROBLEM TO BE SOLVED: To prevent or suppress partial breakage and separation of an outer cylindrical seal piece (32) extended downwardly from an inner surface of a top wall, and generation of broken pieces thereof, even when considerable shocks are applied to a boundary area between the top wall (4) and a skirt wall (6) in a vessel lid (2) or an upper end of the skirt wall. SOLUTION: Six to twenty-four ribs (44, 46, 48, 50 and 52) for connecting an inner circumferential surface of the skirt wall to an outer circumferential surface of the outer cylindrical seal piece are disposed with equal intervals in the circumferential direction. |
