Air duct valve for shelter

Claim 1

AN AIR DUCT VALVE FOR A SHELTER COMPRISING A SYMMETRICAL HOUSING HAVING TWO FLANGED OPEN COUPLINGS IN HORIZONTAL CENTER LINE ALIGNMENT WITH ONE ANOTHER FOR INSERTING SAID HOUSING INTO AN AIR DUCT, AND THUS PROVIDING A STRAIGHT-LINE AIR PASSAGE THROUGH SAID HOUSING, TWO VALVE SEATS, ONE TOWARD AND ONE AWAY FROM THE SHELTER, RESPECTIVELY, POSITIONED ACROSS SAID CENTER LINE WITH EACH SEAT BEING LOCATED AT THE TRANSITION FROM SAID HOUSING TO ONE OF SAID COUPLINGS, A SHAFT MOUNTED IN THE CENTRAL VERTICAL PLANE OF AND HORIZONTALLY TRANSVERSING SAID HOUSING AND SAID AIR PASSAGE, A BEAM OF BALANCE PIVOTALLY SUPPORTED AT ITS CENTER POINT ON SAID SHAFT, SAID BEAM BEING BENT SO THAT ITS ENDS LIE BELOW THE CENTER LINE OF SAID PASSAGEWAY, TWO VALVE HEADS, MEANS FOR PIVOTALLY SUPPORTING SAID VALVE HEADS, RESPECTIVELY, IN OPPOSITELY FACING DIRECTIONS ON EACH END, RESPECTIVELY, OF SAID BEAM OF BALANCE, SAID BEAM OF BALANCE AND SAID VALVE HEADS CONSTITUTING A TILTABLE VALVE HEAD DEVICE NORMALLY RESTING IN BALANCED OPEN POSITION WITH SAID VALVE HEADS SUBSTANTIALLY VERTICAL WITH RESPECT TO SAID STRAIGHT-LINE AIR PASSAGE AND PARTIALLY PROJECTING INTO SAID PASSAGE, SAID TILTABLE VALVE HEAD DEVICE, UPON AN AIR BLAST STRIKING THE FRONT FACE OF ONE VALVE HEAD AS WELL AS THE REAR SIDE OF THE OTHER VALVE HEAD, BEING MOVABLE BY SAID AIR BLAST IN A DIRECTION WHERE BY ONE VALVE HEAD CLOSES SAID AIR PASSAGE UPON BEING SEATED ON THE VALVE SEAT TOWARD THE SHELTER, AND SAID TILTABLE VALVE HEAD DEVICE ALSO BEING MOVABLE IN THE OPPOSITE DIRECTION BY THE SUCTION FOLLOWING THE AIR BLAST TO SEAT SAID OTHER VALVE HEAD ON THE VALVE SEAT AWAY FROM THE SHELTER AND THUS PROTECTING THE SHELTER AGAINST SHOCK WAVES RESULTING FROM A DETONATION.