| 摘要 |
<p>A device for closing a fluid flow passage in response to a decrease in vacuum pressure existing in the passage. The device comprises a fluid flow passage with a seating therein. A diaphragm is located so that one face thereof can locate on the seating to close the passage. A chamber is formed partially by the or at least part of the other face of the diaphragm. In use the diaphragm is maintained away from said seating by a higher pressure in the chamber due to a pressure differential existing between chamber and passage. Venting means open the chamber to atmosphere, and means are provided to seal said venting means. Actuating means are provided and engage with said diaphragm when the pressure differential exists. Accordingly when the pressure differential is altered by a decrease in the vacuum in said passage, the resultant movement of the diaphragm causes the actuating means to operate the sealing means such that the venting means vent said chamber and enables the diaphragm to locate on the seat.</p> |
