| 摘要 |
An inner peripheral portion (31) of a receiving frame (30) includes: a receiving-frame first surface part (40) with a gentle gradient, and a receiving-frame second surface part (42) which is formed below the receiving-frame first surface part and with a steeper gradient than that of the receiving-frame first surface part by reducing a diameter toward a downward direction of the receiving frame, and an outer peripheral portion (11) of a lid body (10) includes: a lid first surface part (16) with a gentle gradient; and a lid second surface part (18) which is formed below the lid first surface part and vertically toward a downward direction of the lid body, or with a steeper gradient than that of the receiving-frame second surface part by reducing a diameter toward the downward direction of the lid body, in which in a closed-lid state of the lid body, the lid first surface part (16) is supported by the receiving frame first surface part (40), and the lid second surface part (18) and the receiving-frame second surface part (42) are pressed against each other by a pressing force caused by elastic deformation of at least either one of the outer peripheral portion (11) of the lid body (10) and the inner peripheral portion (31) of the receiving frame (30). |
