| 摘要 |
A differential-vacuum alarm device is disclosed. The device comprises a housing divided into three chambers by two walls. One wall isolates one chamber from the other two. The other wall, preferably transverse to the first wall and integral therewith, substantially isolates the second chamber from the third. The second wall preferably carries a vibratable reed which is activatable when air, moving via effects of differential vacuum, passes from the second chamber into the third. The housing further includes a cover, preferably snap engageable with the housing. The walls are preferably integral with, and depend from, the cover. Inner surface portions of the housing preferably include integral, U-shaped channels for receiving edge portions of the walls. With the wall edge portions engaged in the channels and the cover snap engaged with the housing, the three chambers are substantially isolated, one from the other. A housing bottom, forming a floor common to the three chambers, includes three through apertures. Each aperture provides a respective chamber with communication outside of the housing. One of the three chambers further includes another through aperture, preferably connectible to a vacuum source. One of the other two chambers similarly includes another through aperture, preferably connectible to a second vacuum source. A flapper valve, preferably carried along the underside of the housing floor, has sufficient surface area for substantially covering each one of the three chamber-floor apertures simultaneously. The valve is pivotable about an axis thereof in response to a predetermined vacuum-differential condition existing between vacuum sources. |
