| 摘要 |
A screw top has a long, thin annular sealing washer which extends from the ring part of the top to the container opening over its outer edge. During the final phase of screwing down, it is pressed on to the surface around the container opening by a pressure rib attached to the cap part. As the base or root of the washer moves further downwardly, while the contact line between the pressure rib and the packing washer remains fixed, the intermediate portion is expanded. It is therefore pressed against the opening and particularly against the outer edge of the container.
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