Forced flow ventilator

Claim 1

A VENTILATOR COMRPRISING IN COMBINATION: A VENTILATOR STACK ADAPTED TO SURROUND A CURB OF A VENTILATOR OPENING IN A ROOF OF A BUILDING, SAID STACK BEING DEFINED BY A PLURALITY OF CONNECTED VERTICAL FLAT SIDE WALLS, SAID STACK TERMINATING IN AN EXTERNAL FLANGE AT THE UPPER EDGE THEREOF; A FAN MOUNTED WITHIN THE SAID STACK FOR ROTATION ABOUT A FIXED VERTICAL AXIS, DRIVE MEANS FOR ROTATING THE SAID FAN; A VERTICAL SUPPORT MEMBER EXTENDING UPWARDLY FROM EACH JUNCTURE OF ADJACENT ONES OF SAID VERTICAL SIDE WALLS; MEANS FOR SECURING SAID SUPPORT MEMBER TO SAID ADJACENT ONES OF SAID VERTICAL SIDE WALLS; A CAP MEMBER SECURED TO THE UPPER ENDS OF SAID VERTICAL SUPPORT MEMBERS AND HAVING A PLURALITY OF DOWNWARDLY SLOPED CONNECTED SIDE WALLS TERMINATING AT SUBSTANTIALLY THE SME LEVEL AS SAID EXTERNAL FLANGE AND SPACED THEREFROM; A GAS PASSAGEWAY BETWEEN AT LEAST ONE ADJACENT PAIR OF SAID VERTICAL SUPPORT MEMBERS AND ABOVE THE SAID EXTERNAL FLANGE AND BELOW THE SAID CAP MEMBER; A DAMPER DISPOSED EXTERNALLY OF TE SAID GAS PASSAGEWAY, SAID DAMPER BEING SUBSTANTIALLY THE SAME SIZE AS SAID GAS PASSAGEWAY; HINGE MEANS MOUNTED AT THE JUNCTION OF SAID VERTICAL SUPPORT MEMBERS AND SAID CAP MEMBER BENEATH THE SAID DOWNWARDLY SLOPED CONNECTING SIDE WALLS, SAID HINGE MEANS PIVOTALLY SECURING SAID DAMPER AT ITS UPPER EDGE; AND AN OUTWARDLY EXTENDING FLASHING MEMBER ALONG THE BOTTOM EDGE OF SAID DAMPER, SAID FLASHING MEMBER BEING ENGAGED WITH A PORTION OF SAID EXTERNAL FLANGE WHEN THE SAID FAN IS NOT OPERATING.