| 摘要 |
A seal is provided comprising two parts and is made of synthetic material. An upper part has an internal thread, a continuous surface area and an axial external cylinder section. A valve tube is positioned above the cylinder section and is held in place by means of a conical intermediate piece. A lower part has an external thread, a continuous surface area and an axial internal cylinder section. A sealing bulge faces the external cylinder section and a valve pin held in place above it by means of connecting bars. By turning the upper part in relation to the lower part, the upper part is displaced axially in relation to the lower part. A sealing piece is fitted axially to the upper end of the valve pin. As the seal is screwed down, the sealing piece blocks the upper opening of the upper part. Its upper end is flush with or rising above the upper part, and the valve pin is enclosed by the valve tube. When the seal is screwed down on entirely the valve pin will be located outside the valve tube. A rib at the lower part and a baffle at the upper part cooperate to limit the rotation of the upper part in relation to the lower part to less than a full revolution.
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