Motor operated fire damper

A protective damper for controlling the flow of fluid through a ventilation conduit for a building, said damper comprising:

• a frame adapted to be mounted in said conduit;
• a barrier carried by the frame and movable between an open position permitting fluid flow through the damper, and a closed position blocking said flow;
• spring means operably coupled with the barrier biasing the latter into said closed position;
• electric motor means operably coupled with the barrier and adapted to be coupled with a source of power for moving the barrier to said open position against the bias of said spring means when the motor is energized,
• thermal responsive switch means mounted on the frame and exposed to the fluid flowing therethrough, said switch means being operably coupled with the motor means to permit the latter to remain energized to hold the barrier in said flow permitting position when the ambient temperature at the switch is below a predetermined level and to deenergize the motor to permit the barrier to be moved to said flow blocking position when the ambient temperature at the switch is elevated to said predetermined level;
• and
• an overriding switch operably coupled with the motor means and adapted to be coupled with said power source, whereby to permit optional energizing of the motor to open the barrier irrespective of operation of the thermal responsive switch to deenergize the motor.