| 摘要 |
<p>A drop tube for underground fuel storage tanks and the like has a flow restriction section that includes a plate or disc mounted for rotation and controlled by a float located outside the section. Unlike overfill shut-off valves that slam against a sealing valve seat and require springs and cams for their operation, the subject restrictor simply and slowly rotates the plate between a non-restricting position and one in which the plate closes off the delivery liquid flow. Since the plate and interior wall of the tube are not sealed, liquid above the restrictor can bleed past the plate into the storage tank after the delivery valve on the truck is closed. Overfill is unlikely because it would take several hours to overfill with the plate in the restricting position.</p> |
