| 摘要 |
A fire damper comprising a plurality of interconnected blades is provided with a pair of primary negator type springs which are attached to the leading blade and a pair of auxiliary negator type springs which are attached to an intermediate blade. The blades are normally maintained in a folded condition with the springs exerting a biasing force urging movement of the blades to an extended closed position. Upon release of the blades in response to detection of fire or smoke conditions, the springs cooperate to move the blade assembly to the completely closed position. The auxiliary springs increase the rate of closing of the assembly and facilitate unfolding of a portion of the blade assembly to enhance the closing of the assembly even under high air flow conditions.
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