Importance

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Abstract

A resettable fail-safe fire door release mechanism which allows normal powered operation of a fire door is disclosed. A solenoid having a first open state in the absence of an applied electric current and a second closed state in the presence of an applied electric current is incorporated into the motor-operator unit of an overhead door. Brake actuator utilizes the spring force of a normally disengaged brake to keep the brake actuator in a first position. The plunger of the solenoid acts through the brake actuator in opposition to the spring so that energizing the solenoid overcomes the force of the spring, moving the brake actuator, and engaging the brake; deenergizing the solenoid causes the spring to again disengage the brake. A normally closed switch having a mechanical actuator is wired in series with the solenoid. The melting of a fusible link releases a spring loaded plunger which depresses the actuator opening the switch. A cable having one end connected to the actuator of the switch and the other end external to the case of the motor-operator allows manual opening of the switch and hence closing of the door.

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First Claim