This is achieved in a variety of ways, but essentially involves creating a raised groove or area along the posterior border, on the fitting surface. This is often referred to as the postdam.

这可以通过多种方式达到，但基本上不外乎，在基托组织面沿后缘制作一个突起的沟或区域，这就是常提到的后堤。

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Raised-face seat. A groove around the seat collects particles pushed aside by the knife and prevents clogging. When the valve opens, media pressure cleans the groove.

凸面阀座。阀座周围的槽将颗粒收集起来，并排挤到闸刀旁边，以避免出现堵塞。当阀门开启时，流体介质压力就会清洗槽内的颗粒。

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The pedestal is arranged with a raised column and a groove, and can be connected with a first drive mechanism, therefore, is controlled to move in the horizontal direction.

所述底座上面设有凸柱与沟槽，该底座可以连接于第一驱动机构而被控制在水平方向移动；

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