Abstract: An improved pivot assembly operable on an air flow controlling disk, initially to move the disk from a closed position over a damper opening to an intermediate open position away from the opening and subsequently to pivot the disk to a fully open position normal to the opening. The assembly includes stationary support plates and carriage plates carrying the disk. The carriage plates are coupled to the support plates by a system including one axle member received in a bore in the carriage plates for movement with the carriage plates dictated by contact of the axle member with camming slots in the support plates. A piston rod to move the carriage plates relative to the support plates is coupled to the axle member.