Under-body ventilating fan units

Claim 1

AN UNDER-BODY VENTILATING UNIT COMPRISING AN UNSTABLE, HIGH PITCH TYPE OF AXIAL FLOW FAN ROTOR IN A STATOR SHROUD RING FORMING PART OF AN OUTER CASING FOR THE UNIT, AN INNER, MOTOR-HOLDING PORTION RIGIDLY CONNECTED TO SAID SHROUD RING AND HAVING THEREIN AN ELECTRIC MOTOR WITH A SHAFT AT ONE AXIAL END, A GENERALLY CUP-LIKE ROTOR HUB PORTION SECURED ON SAID MOTOR SHAFT AND EXTENDING OVER AT LEAST THE SHAFT END OF SAID MOTOR, AND AIRFOIL FAN BLADES FIXED TO SAID ROTOR HUB PORTION, EACH BLADE INCLUDING A THIN SHEET WHOSE SURFACES CONTAIN STRAIGHT LINES EXTENDING GENERALLY ACROSS THE CHORD WIDTHS OF THE BLADE SUBSTANTIALLY FROM ITS LEADING EDGE TO ITS TRAILING EDGE, SAID SURFACES BEING TILTED TO THE FAN''S AXIS OF ROTATION TO PROVIDE EFFECTIVE PITCH AS WELL AS EFFECTIVE CHAMBER CURVATURE THROUGHOUT A MATERIAL PORTION OF THE RADIAL AIR FLOW SECTIONS THROUGH THE BLADE, THE AXIAL LENGTHS OF AT LEAST THE TIP PORTIONS OF SAID BLADES BEING WITHIN THE AXIAL LENGTH OF SAID SHROUD RING CASING.