Damper assembly and blade construction

Claim 1

A DAMPER ASSEMBLY COMPRISING, IN COMBINATION, A GENERALLY RECTANGULAR FRAME INCLUDING SIDE, TOP AND BOTTOM MEMBERS OF CHANNEL SHAPE CROSS SECTION SECURED TOGETHER WITH THE CHANNELS FACING INWARDLY, A SEALING STRIP OF RESILIENT MATERIAL SUPPORTED IN EACH FRAME MEMBER, A PLURALITY OF DAMPER BLADES SUPPORTED AT OPPOSITE ENDS ON THE SIDE MEMBERS OF THE FRAME FOR LIMITED ROTATIVE MOVEMENT ABOUT AXES EXTENDING LONGITUDINALLY AND SUBSTANTIALLY CENTRALLY OF THE BLADES, EACH OF SAID BLADES COMPRISING AN ELONGATED GENERALLY FLAT BODY OF RESILIENT MATERIAL HAVING A THIN RELATIVELY WIDE LONGITUDINAL CHANNEL EXTENDING SUBSTANTIALLY CENTRALLY THROUGH THE BODY AND OTHER CHANNELS EXTENDING LONGITUDINALLY OF THE BODY ADJACENT ITS OPPOSITE EDGES TO DEFINE THIN FLEXIBLE EDGE PORTIONS, A SHEET METAL PLATE DISPOSED IN SAID CENTRAL CHANNEL OPERATIVE TO IMPART SUBSTANTIAL STIFFNESS TO THE BLADE, TANGS RIGID WITH EACH END OF SAID PLATE PROJECTING BEYOND THE RESPECTIVE ENDS OF THE BODY, A SHAFT NONROTATABLY COUPLED TO EACH TANG, BEARING MEMBERS SUPPORTED ON THE SIDE MEMBERS OF THE FRAME FOR ROTATABLY RECEIVING SAID SHAFTS, SAID BEARING MEMBERS BEING POSITIONED SO THAT THE UPPER EDGE OF THE UPPERMOST BLADE AND THE LOWER EDGE OF THE LOWERMOST BLADE ENGAGE THE SEALING STRIPS OF THE TOP AND BOTTOM FRAME MEMBERS AND COMPRESS THEM SUFFICIENTLY TO PRODUCE AN AIRTIGHT SEAL WHEN THE BLADES ARE TURNED TO A CLOSED POSITION, THE BEARINGS ON THE RESPECTIVE SIDE MEMBERS ALSO BEING SPACED FROM EACH OTHER SO THAT THE EDGES OF ADJACENT BLADES MEET WITH A ROLLING ACTION AS THE BLADES ARE TURNED TO CLOSED POSITION, AND SAID BLADE BODIES BEING DIMENSIONED LONGITUDINALLY SO AS TO FRICTIONALLY ENGAGE THE SEALING STRIPS OF THE SIDE MEMBERS WHEN THE BLADES ARE IN CLOSED POSITION.