| 摘要 |
<p>An air pressure stabilising device comprises a flow control device mounted in a generally rectangular duct (6) between a generally controlled environment (8), and an exterior environment (10). The flow control device comprises a flow control member (14) mounted for rotation about an axis (12), counterbalancing means being provided to cause the flow control member (14) to adopt a closed position in normal use, and to move to an open position in the event that air pressure within the environment (8) rises to a level above a predetermined excess pressure. A closure means is provided to cause the flow control member (14) to move to its closed position in the event of a hazard condition being detected, conveniently by a sensing means. The closure means may be provided by a spring (22, 40) held in a rest condition in which it is operationally separate from the flow control member so as to exert no force on the flow control member as may interfere with its normal operation. When the temperature rises above a threshold temperature, the spring (22) enters into an operative engagement with the flow control member to cause the flow control member to move to its closed position.</p> |
