| 摘要 |
The lid, esp. for use in sand filter vessels for water consists of an assembly of an exterior lid resting around the mouth of the container and an interior lid connected axially with the first lid at a variable distance by means of a screw with an upper rotary control. An O-ring joint fits in a throat defined by the peripheral skirt on the lid, and is compressed in the closed position by operating the control screw. In this position the joint is compressed between the skirt of the exterior lid, the edge of the container mouth and the skirt of the interior lid which forms a projecting inclination.
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