Means for protecting ventilating ducts and flue ducts against air shock waves

摘要

875,912. Ventilating air raid shelters; chimneys and flues. BERGMAN, S. G. A., and STALFORS, J. B. Feb. 10, 1960 [March 4, 1959], No. 4671/60. Classes 25 and 137. A device for protecting the air ventilating channels of air raid shelters against air shock waves comprises a channel 1 which widens at 2 to house a conical valve 3 which slides on a shaft 4 and is normally kept in an open position by springs 5 and 6. A shock wave from the direction of the arrows impinges on the valve to close it against a seating 7 and a support grid 8 as shown in position 3a. In the advent of back pressure the valve closes the passage in the position 3b. In a modification in which the shock wave is totally excluded from the ventilating channel, the part of the wave which operates the valve is made to travel along a straight tube whereas the part which would communicate with the valve opening travels along a longer helical path so that the valve has time to close before the wave can pass through it. In a further modification the longer path to the valve opening is formed through a separate ventilation opening. A pin and spring device for automatically locking the valve in a closed position is also described.