Damper assembly

Claim 1

A LOUVER OR DAMPER BLADE UNIT COMPRISING, IN COMBINATION, A RELATIVELY ELONGATED BLADE MEMBER INCLUDING A CENTRAL SECTION WHICH IS SUBSTANTIALLY FLAT AND LIES SUBSTANTIALLY IN A FIRST PLANE, AND A PAIR OF LONGITUDINAL EDGE SECTIONS EACH SUBSTANTIALLY FLAT AND EXTENDING AT AN ANGLE TO SUCH FIRST PLANE, SAID EDGE SECTIONS EXTENDING IN OPPOSITE DIRECTIONS FROM SAID FIRST PLANE; SAID CENTRAL SECTION HAVING A CIRCULARLY ARCUATE OFFSET EXTENDING ALONG ITS LONGITUDINAL CENTERLINE AND CENTERED AT AN AXIS MIDWAY BETWEEN THE OPPOSITE SURFACES OF SAID CENTRAL SECTION AND CYLINDRICAL OPERATING SHAFT MEANS FOR SAID BLADE MEMBER EXTENDING ALONG SUBSTANTIALLY THE LONGITUDINAL CENTER LINE OF SAID CENTRAL SECTION; SAID CENTRAL SECTION AND SAID SHAFT MEANS HAVING COOPERATING INTERLOCKING FORMATIONS INTERLOCKED BY RELATIVE LONGITUDINAL MOVEMENT OF SAID BLADE MEMBER AND SAID SHAFT MEANS; SAID COOPERATING INTERLOCKING FORMATIONS COMPRISING AT LEAST A PAIR OF ANGULARLY RELATED RIBS EXTENDING RADIALLY FROM THE INNER SURFACE OF SAID CIRCULARLY ARCUATE OFFSET, AND AT LEAST A PAIR OF ANGULARLY RELATED SLOTS IN SAID CYLINDRICAL SHAFT MEANS EACH RECEIVING ONE OF SAID RIBS UPON RELATIVE LONGITUDINAL MOVEMENT OF SAID BLADE MEMBER AND SAID SHAFT MEANS; SAID EDGE SECTIONS, WHEN SAID UNIT IS MOUNTED IN A FRAME BETWEEN ADJACENT BLADE UNITS ALSO MOUNTED IN SAID FRAME, OVERLAPPING AND INTERLOCKING WITH THE CORRESPONDING EDGE SECTIONS OF THE ADJACENT BLADE UNITS TO PROVIDE A TIGHT SEAL AGAINST AIR OR GAS FLOW THROUGH THE ASSEMBLY OF THE FRAME AND THE BLADE UNITS.