Air flow control damper

Claim 1

THE COMBINATION WITH AN AIR DUCT HAVING A FLAT WALL, A DAMPER VANE WITHIN THE DUCT INCLUDING A GENERALLY RECTANGULAR PLATE PERFORATED BY A PLURALITY OF LATERALLY SPACED APERTURES EXTENDING THERETHROUGH, MEANS PROVIDING A HINGE EXTENDING ALONG ONE EDGE OF SAID PLATE AND SUPPORTING THE LATTER FOR SWINGING OF THE OPPOSITE FREE EDGE TOWARD AND AWAY FROM A CLOSED POSITION AGAINST SAID WALL TO VARY THE WIDTH OF THE INTERVENING AIR PASSAGE OR TO CLOSE THE SAME, A SECOND PLATE LYING AGAINST AND MOUNTED ON SAID FIRST PLATE TO SWING THEREWITH AND FOR EDGEWISE SHIFTING RELATIVE THERETO AND HAVING HOLES THERETHROUGH ADAPTED TO REGISTER WITH SAID APERTURES, AND MECHANISM FOR SHIFTING SAID SECOND PLATE EDGEWISE RELATIVE TO SAID FIRST PLATE IN RESPONSE TO SWINGING OF THE LATTER ABOUT SAID HINGE AND OPERABLE TO MAINTAIN SAID APERTURES COVERED WHEN THE FIRST PLATE IS IN SAID CLOSED POSITION AND TO UNCOVER THE APERTURES PROGRESSIVELY AS THE PLATE IS MOVED AWAY FROM SUCH POSITION TO INCREASE THE WIDTH OF SAID AIR PASSAGE.