Anti-blast flap for inlet of ventilation system - has flap held by solenoid and released by time switch to close automatically via gravity hinge with horizontal axis

摘要

The anti-blast flap is designed to protect building ventilation systems from the effect of external explosions and automatically descends to seal the ventilation duct inlet. The flap pivots about a horizontal axis aligns horizontally when open and at 45 deg. below the horizontal when closed. Two alternative types of lock hold the flap open, and a third time-switch controlled lock holds the flap closed. A jack acts automatically to re-open the flap. The locks holding the flap open may be a jack operated bolt and an electro-magnetic contact. The former is deployed under normal circumstances and is replaced by the latter in times of emergency. A blast is detected by remote sensors, the magnetic lock de-energised and the flap drop closed. A solenoid operated bolt holds the flap closed, with draws when authorised by the time switch, and the jack lifts the flap back to the open station.