| 摘要 |
A fluid conveying system includes a fluid conveying conduit which is under vacuum and which has an air opening for admission of air from the atmosphere. Apparatus is provided for periodically admitting air through the opening into the conduit and includes a valve assembly, a solenoid having a movable armature for actuating the valve assembly, and an adjustable timer for controlling energization of the solenoid. The valve assembly includes a stopper plug connected to a rod and seatable against the air opening and held there by vacuum, a bushing member connected to and movable by the solenoid armature, and a compression spring connected between the bushing member and plug rod. In operation, energization of the solenoid causes armature movement which initially effects compression of the spring and application of a loading force on the plug. Subsequent armature movement effect opening movement of the plug and allows the pre-loaded opening force to further assist in rapid opening movement of the plug.
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