Patent ID: 7682231

Claim:
An exhaust fan assembly which comprises: an outer enclosed wall that defines a substantially cylindrical cavity therein having an air inlet formed at its bottom end; an inner enclosed wall fastened to the outer enclosed wall and positioned in the cylindrical cavity to divide it into a centrally located bearing chamber and a surrounding annular space, the inner enclosed wall being spaced upward from the air inlet to form a fan chamber at the bottom of the cylindrical cavity, wherein the annular space is constricted at its top to form a nozzle; a bottom plate fastened to the bottom end of the inner enclosed wall; a rotatably mounted shaft located in the bearing chamber and extending downward through the bottom plate into the fan chamber; a fan attached to the shaft and being disposed in the fan chamber to draw exhaust air in through the air inlet and blow it upward through the annular space; a motor coupled to the shaft in the bearing chamber for rotating the fan; and a windband mounted to an upper end of the outer enclosed wall, the windband having a frustum-shape body with a straight cylindrical ring at an upper end and an inlet bell at a lower end that flares radially outward from the body and defines a circular opening which is coaxial with the nozzle and substantially coplanar with the nozzle.