内置的止动装置为动力执行机构提供行程保护，并且作为参考坐标在开启和关闭位置定位阀瓣。

Internal stops provide positive over travel protection for power actuated valves and act as a reference to position the discs in the open and closed positions.

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根据阀瓣的这种形动形式，阀座通口的变化就是与阀瓣行程成正比例关系。

The diametre of seat turns bigger when flap moves higher and smaller when flap lower.

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