Exhaust fan assembly

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 second nozzle assembly mounted to the inner enclosed wall and having a frustum shape with a circular opening at its top end which is coaxial with the inner enclosed wall;
• 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.