Abstract: A fail-safe HVAC damper apparatus comprises a duct channel with a closure comprising one or more quadri-panel hinged elements, each with four panels connected by four parallel hinge pins. A gear shaft with a toothed gear is controllably rotated to linearly drive a spring-biased plate to move one of the hinge pins of each quadri-panel element between an open and a closed position. A damper may use blades of different sizes and be driven to begin an opening and/or closing action sequentially and/or very gradually. A drive motor may be activated to open or close the closure, e.g. by a smoke detector or other controller. Melting of a fuse in the duct channel serves to disengage a gear from a gear shaft, enabling a spring mounted plate to move the hinged elements to a default closed (or alternative open) safety position. Various gear shaft and gear structures are shown.

Abstract: A fail-safe HVAC damper apparatus comprises a duct channel with a closure comprising one or more quadri-panel hinged elements, each with four panels connected by four parallel hinge pins. A gear shaft with a toothed gear is controllably rotated to linearly drive a spring-biased plate to move one of the hinge pins of each quadri-panel element between an open and a closed position. A damper may use blades of different sizes and be driven to begin an opening and/or closing action sequentially and/or very gradually. A drive motor may be activated to open or close the closure, e.g. by a smoke detector or other controller. Melting of a fuse in the duct channel serves to disengage a gear from a gear shaft, enabling a spring mounted plate to move the hinged elements to a default closed (or alternative open) safety position. Various gear shaft and gear structures are shown.

Abstract: A fail-safe HVAC damper apparatus comprises a duct channel with a closure comprising one or more quadri-panel hinged elements, each with four panels connected by four parallel hinge pins. A gear shaft with a toothed gear is controllably rotated to linearly drive a spring-biased plate to move one of the hinge pins of each quadri-panel element between an open and a closed position. A drive motor may be activated to open or close the closure, e.g. by a smoke detector or other controller. A meltable fuse in the duct channel may be connected to a disconnect which uncouples the gear shaft and toothed gear, and a spring moves the closure to a default closed or open position.