Powered extract ventilator

Claim 1

A POWERED VENTILATOR INCLUDING POWERED FAN IMPELLER MEANS FOR PROMOTING A FLOW OF AIR, PASSAGE MEANS THROUGH WHICH EXTRACTED AIR IS CAUSED TO FLOW BY SAID IMPELLER MEANS DURING OPERATION OF THE VENTILATOR, SAID IMPELLER MEANS BEING LOCATED IN SAID PASSAGE MEANS AND SAID PASSAGE MEANS HAVING A MOUTH THROUGH WHICH THE EXTRACTED AIR IS IMPELLED BY SAID IMPELLER MEANS FOR DISCHARGE TO THE OUTSIDE ATMOSPHERE, A WEATHER HOOD COVERING OVER AND WEATHERING THE MOUTH OF SAID PASSAGE MEANS, A DAMPER COMPRISING A PLATE AND MEANS FOR GUIDING THE DAMPER PLATE FOR SUBSTANTIALLY PARALLEL MOVEMENT BETWEEN A CLOSED POSITION IN WHICH IT SEATS ON THE MOUTH OF SAID PASSAGE MEANS AND AN OPEN POSITION IN WHICH IT IS HELD DISPLACED AWAY FROM SAID MOUTH BY THE DISCHARGE OF EXTRACTED AIR THERETHROUGH, SAID PLATE BEING FLAT SO AS NOT TO PENETRATE INTO SAID PASSAGE MEANS WHEN IN ITS CLOSED POSITION; AND MEANS WHEREIN SAID DAMPER PLATE IS GUIDED ON AN INCLINED GUIDE ROD WHEREBY THE PLATE OR DISC MAY SLIDE DOWN THE ROD TO ITS CLOSED POSITION UNDER THE ACTION OF ITS OWN WEIGHT WHEN THE VENTILATOR IS SHUT DOWN AND SLIDE UP THE ROD TO AN OPEN POSITION UNDER THE INFLUENCE OF THE AIRSTREAM DISCHARGING THROUGH THE MOUTH OF SAID PASSAGE MEANS WHEN THE VENTILATOR IS OPERATED.