Importance

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Abstract

A motorized fire and smoke damper for an air passage is disclosed. The damper includes a wrap spring clutch used to automatically open and close a multifold curtain to define an opening in the passage. The clutch is normally connected to a stationary member by a fusible link, which restrains a portion of the clutch to enable the clutch to transmit torque to rotate a windup pulley and thereby raise or open the curtain. In the event of fire, the fusible link melts, whereupon the spring clutch no longer transmits torque and the pulley automatically freewheels to lower or close a raised curtain under its own weight or by spring bias. The passage opening is then closed. When desired, the air passage can be reopened by energizing the clutch to rotate it until it engages an adjacent finger, at which point the spring clutch can again transmit torque to the pulley and open the curtain.

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First Claim