Abstract A damper that is normally biased toward open position against the pressure of air flowing through the damper and rapidly closed by the increase of such pressure resulting when pressure exteriorly of the damper abruptly drops to a predetermined level. The damper comprises a plurality of parallel blades mounted on parallel axes and coupled to each other for movement between a closed position with the blades lying generally in a vertical plane across the damper and normally open position with the blades lying in parallel spaced planes inclined into the air flow. Means are connected to the blades for biasing them inwardly toward open position against the pressure interiorly of the damper caused by the air flow which tends to swing the blades in an outward direction toward closed position. When the atmospheric pressure on the outside of the damper drops, as by the presence of the negative phase of a tornado, the damper closes immediately.
A protective damper for a gas exhaust opening, said damper comprising, in combination, a. an open rectangular frame defining an exhaust opening to atmosphere, b. a plurality of rectangular essentially planar damper blades, extending across such opening, said blades being mounted on parallel, spaced axes extending along corresponding edges thereof for angular movement between closed position with all of said blades lying generally in a plane transverse to the flow of gas through said frame and with said blades engaging each other and open position with all of said blades swung inwardly against such flow of gas and lying in spaced parallel planes inclined into such gas flow, c. means coupling said blades for movement together, d. means biasing said blades inwardly away from closed position to open position against such flow of gas and the force of gravity, and e. wherein said damper blades are responsive solely to atmospheric pressure drop to move to closed position.
Claim 2
Dependent Claim
157 words
A protective damper for a gas exhaust opening, said damper comprising, in combination, a. an open rectangular frame defining an exhaust opening to atmosphere, b. a plurality of rectangular essentially planar damper blades, extending across such opening, said blades being mounted on parallel, spaced axes extending along corresponding edges thereof for angular movement between closed position with all of said blades lying generally in a plane transverse to the flow of gas through said frame and with said blades engaging each other and open position with all of said blades swung inwardly against such flow of gas and lying in spaced parallel planes inclined into such gas flow, c. means coupling said blades for movement together, d. means biasing said blades inwardly away from closed position to open position against such flow of gas and the force of gravity, and e. wherein said damper blades are responsive solely to atmospheric pressure drop to move to closed position.
Claim 3
Dependent Claim
27 words
A damper according to claim 1 in which the means for biasing the blades comprises a constant tension spring means and which has adjustable force applying means.
Claim 4
Dependent Claim
25 words
A damper according to claim 1 and stop means for limiting the angular movement of said blades away from closed position to a predetermined maximum.