One piece adjustable damper

A adjustable damper for positioning in an air duct to adjustably restrict flow of air through the duct, the damper comprising:

• a tubular duct section defining first and second diametrically opposed openings;
• first and second sets of detents formed from the material of the duct and extending radially about the respective openings to define a plurality of damper settings, the first detent set being offset angularly relative to the second detent set;
• and
• a valve element having a circular central portion proportioned to fit within the duct section, diametrically opposed first and second shoulders projecting from the periphery of the disc, aligned first and second stub axles formed from the material of the disc and dependent from the respective first and second shoulders, the shoulders being engageable with the respective first and second sets of detents such that in any one selected angular position of the valve element, the element is located by engagement of one of the shoulders in one of the detents of the detent sets, and means attached to one of the stub axles to permit manual operation to change the angular position of the element in the duct section to position one of the shoulders in another of the detents of the detent sets whereby the flow of air through the duct can be controlled in stages by moving the element angularly between fully closed and fully open positions.