Volume Damper
A round sleeve with one blade, or a rectangular sleeve with a row of blades: the blades cut with their clearance and the sleeve with its shaft holes. A damper to set the flow in a duct: a round sleeve with one round blade, or a rectangular sleeve with a row of blades, the blades cut with their clearance and the sleeve with the holes for the shafts.
How the volume damper is developed, with a worked example · Dampers, doors and attenuators