Ventilators

Claim 1

A POWERED VENTILATOR COMPRISING A HOUSING DEFINING AN AIR EXIT PASSAGE FOR EXTRACTED AIR, AN EXTRACTION FAN MOUNTED IN THE HOUSING WHICH FAN, IN OPERATION, IMPELS AIR EXTRACTED BY THE FAN THROUGH SAID AIR EXIT PASSAGE WITH A SWIRLING MOTION AND A NONRETURN SHUTTER ASSEMBLAGE DOWNSTREAM OF THE FAN IN THE SWIRLING AIRSTREAM AND OPERABLE TO CLOSE SAID AIR EXIT PASSAGE WHEN THE EXTRACTION FAN IS NOT OPERATING, THE NONRETURN SHUTTER ASSEMBLAGE COMPRISING A PLURALITY OF HINGED SHUTTERS HINGED ON AXES RADIATING FROM THE CENTER OF THE ASSEMBLAGE, SAID SHUTTERS BEING MOVABLE ABOUT THEIR HINGE AXES BETWEEN OPEN AND CLOSED POSITIONS, TO OPEN FROM THEIR CLOSED BETWEEN OPEN AND SHUTTERS IN THE SAME ROTATIONAL DIRECTION AS VIEWED FROM THE CENTER OF THE NONRETURN SHUTTER ASSEMBLAGE LOOKING RADIALLY OUTWARDLY ALONG THE RESPECTIVE HINGE AXES OF THE SHUTTERS, THE ROTATIONAL DIRECTION OF MOVEMENT OF THE SHUTTERS WHEN MOVING FROM THEIR CLOSED POSITION TO THEIR OPEN POSITION CORRESPONDING TO THE DIRECTION OF ROTATION OF THE FAN AS VIEWED FROM UPSTREAM OF THE FAN, MEANS WHEREIN SAID HOUSING IN FORMED AS PART OF A COWL HAVING A HOOD COVERING OVER SAID EXIT PASSAGE AND WEATHERING THE NONRETURN SHUTTER ASSEMBLAGE, THE ASSEMBLAGE COMPRISING STOPS LIMITING THE OPENING OF THE SHUTTERS WHEREBY THE SHUTTERS WHEN ENGAGING THE STOPS ACT TO GUIDE AIR DISCHARGED BY THE FAN THROUGH THE ASSEMBLAGE IN PART TOWARDS THE EDGE OF THE HOOD.