Regulator for constant volume of gas flow

Claim 1

FOR MAINTAINING A CONSTANT VOLUME FLOW OF AIR THROUGH A DUCT IN SPITE OF VARIATIONS IN THE SUPPLY PRESSURE, THE COMBINATION WITH SAID DUCT OF, TWO IMPERFORATE SHEETS EXTENDING ALONG AND DISPOSED IN OPPOSED SPACED RELATION WITHIN SAID DUCT SO AS TO DEFINE BETWEEN THEM AN AIR PASSAGE OF SMALLER TRANSVERSE AREA THAN SAID DUCT AND EXTENDING LONGITUDINALLY THEREOF, A SUPPORT FOR SAID SHEETS MOUNTED FOR BACK AND FORTH MOVEMENT ALONG THE AXIS OF SAID DUCT AND SPACING THE UPSTREAM EDGES OF THE SHEETS INWARDLY FROM THE INNER WALL OF THE DUCT, MEANS HINGING THE DOWNSTREAM EDGES OF SAID SHEETS TO AND SEALING THE SAME AGAINST SAID WALL FOR FREE SWINGING OF THE UPSTREAM PORTION OF SAID SHEETS WITHIN SAID DUCT WHEREBY TO DEFINE BETWEEN EACH SHEET AND THE OPPOSED DUCT WALL A CHAMBER WHICH IS OPEN AT THE UPSTREAM END AND CLOSED AT THE DOWNSTREAM END, THE INWARD AND OUTWARD SWINGING OF SAID SHEETS BEING ACCOMPANIED BY MOVEMENT OF SAID SUPPORT ALONG SAID DUCT IN DOWNSTREAM AND UPSTREAM DIRECTIONS RESPECTIVELY, AN EXTENSION SPRING STRETCHED BETWEEN SAID SUPPORT AND SAID DUCT UPSTREAM FROM SAID SUPPORT AND YIELDABLY URGING SAID SUPPORT UPSTREAM, SAID PASSAGE HAVING A RESTRICTED AREA THEREIN TO CREATE A DROP IN THE STATIC PRESSURES BETWEEN SAID CHAMBERS AND THE PASSAGE WHEREBY TO INDUCE INWARD SWINGING OF THE SHEETS AND A CORRESPONDING REDUCTION IN THE AIR FLOW THROUGH SAID PASSAGE UNTIL THE NET INWARD PRESSURE ON SAID SHEETS URGING SAID SUPPORT DOWNSTREAM BALANCES THE FORCE OF SAID EXTENSION SPRING.