| 摘要 |
<p>A vacuum relay valve for isolating a vacuum operated dependent device from a contaminated vacuum signal source includes a check valve and an atmospheric bleed valve arranged such that a negative-going pressure change in the vacuum source causes the check valve to open and the bleed valve to close, permitting evacuation of the vacuum operated device by flow toward the source, while a positive-going pressure change in the vacuum source causes the check valve to close and the bleed valve to open thereby isolating the vacuum operated device from the signal source and permitting the pressure in the device to rise by infusion of atmospheric air. The relay valve may include a timing restriction arranged for isolation from the signal source, which is purged by unidirectional flow each time the device is evacuated.</p> |
