Abstract: A centrifugal fan having a damper control system located away from the air flow path is disclosed. The control system includes a rotatable shaft located outside of a fan housing wherein rotation of the control shaft actuates a plurality of shafts and rods to move an annular damper located within the housing into an open position away from the centrifugal fan blades and to a closed position coaxially over the fan blades thus substantially restricting the flow of air through the centrifugal fan. The dampers are mounted for translation on two support rods located on opposite sides of the centrifugal fan. The dampers ride on a support system including a plurality of ball bearings that are in tangential contact with the support rods thus providing high-pressure contact surfaces between the bearings and the support shafts which act to keep the path of travel of the bearings on the rods free of debris so that the dampers have unobstructed motion between the open and closed positions.

Abstract: An actuator and associated linkage assembly combined to multiply the force applied by the actuator in moving a flow control disk of a centrifugal fan against the air pressure generated by the fan. The actuator includes an internal spring mechanism for closing the disk against the fan air pressure. For some applications the closing force provided by the return spring may be supplemented with an auxiliary spring mechanism that is mounted for providing maximum assistance in closing the control disk, yet not prohibiting the actuator from reopening the disk.

Abstract: A control device for a triple-plenum air conditioning apparatus having a by-pass air duct, a hot air duct and a cold air duct. A first shaft mounted through the by-pass and hot air ducts carries a first by-pass air damper blade and a hot air damper blade at right angles to each other. A second shaft mounted through the by-pass air duct and the cold air duct carries a second by-pass damper blade and a cold air damper blade at right angles to each other. The control device includes a first geneva link on the first shaft, a second geneva link on the second shaft and a third shaft carrying a drive plate with pins for independently actuating the geneva links and a geneva cam for holding one of the geneva links against rotation while the other is being independently actuated. Rotation of the third shaft through one hundred degrees results in rotation of each of the first and second shafts through ninety degrees.