Damper control and linkage therefor

Claim 1

AIR FLOW CONTROL APPARATUS COMPRISING: CONDUIT STRUCTURE HAVING WALL MEANS DEFINING A PAIR OF SIDE-BY-SIDE FLUID PASSAGES; A DAMPER BLADE UNIT FOR EACH PASSAGE RESPECTIVELY, EACH UNIT HAVING A SHAFT JOURNALLED IN SAID WALLS MEANS FOR ROTATION IN OPPOSED DIRECTIONS RELATIVE THERETO, SAID UNITS BEING MOVABLE INTO AND OUT OF AT LEAST PARTIALLY BLOCKING RELATIONSHIP TO RESPECTIVE PASSAGES AS SAID SHAFTS ROTATE IN SAID DIRECTIONS; MEANS INTERCONNECTING THE SHAFTS ON SAID UNITS FOR ROTATING SAID SHAFTS TOGETHER IN ONE DIRECTION THROUGH A PRESELECTED ARC ONLY AFTER ONE OF THE SHAFTS HAS BEEN ROTATED IN SAID DIRECTION THROUGH A PREDETERMINED DISTANCE; STRUCTURE MAINTAINING SAID SHAFTS INTERCONNECTED TOGETHER UNTIL THE SAME HAVE ROTATED THROUGH SAID ARC IN THE OPPOSITE DIRECTION; SAID INTERCONNECTING MEANS INCLUDING A SLOTTED ARM RIGID TO AND EXTENDING OUTWARDLY FROM SAID OTHER SHAFT, AND LEVER MEANS PIVOTALLY COUPLING SAID ONE SHAFT TO SAID ARM, SAID MAINTAINING STRUCTURE INCLUDING A PROJECTION ON SAID LEVER MEANS, SAID PROJECTION BEING DISPOSED IN SAID SLOT AS SAID SHAFTS ROTATE IN SAID OPOPOSITE DIRECTION THROUGH SAID ARC, AND MEANS FOR SHIFTING THE PROJECTION OUT OF THE SLOT AS SAID SHAFTS APPROACH THE END OF SAID ARC ROTATING IN SAID OPPOSITE DIRECTION; AND MEANS COUPLED WITH SAID ONE SHAFT FOR ROTATING THE SAME.