Blower impeller and method of lofting their blade shapes

An impeller blade for a blower comprising:

• i. an elongated blade with first and second opposite ends, a substantially uniform thickness, and a substantially uniform width, and
• ii. a first curved portion extending from said first end toward said second end, and
• iii. a second curved portion extending from said second end and joining said first curved portion with a faired alignment thereby forming a continuous smooth curve from said first end to said second end, and wherein said first curved portion being defined as a segment of an Archimedes spiral, and said second curved portion having increased concave curvature, and
• iv. said blade being adaptable for use in a plurality of equally angularly spaced blades mounted on a rotating circular disk having a center and outer rim with the said blades extending from the interior of the disk with said second end being proximal to the outer edge of the disk, thereby forming an impeller for a blower, and
• iv. said curved portions adapted to define a space having substantially constant width between adjacent blades in the plurality of blades, and
• vi. each blade of the plurality of blades extending over an arc chord angle of approximately 55 to 70 degrees.

A method of lofting an impeller blade for a blower comprising the steps of:

• a. drawing an outer circle scaled to represent the radial extent of an impeller blade,
• b. drawing an inner concentric circle at least ⅓ the diameter of the outer circle, scaled to represent the starting point of an impeller blade,
• c. drawing four concentric evenly spaced circles between the inner and outer circles, thereby defining six circles with diameters increasing by equal amounts, and
• d. drawing at least 7 radials from the common center to the outer circle, spaced apart by 10 degrees,
• e. designating one radius as 0 degrees, and the next 6 radii as 10 through 60 degrees, and designating the inner circle as 1, and the others as 2 through 6 as references for locating points in the form 1,20 on the polar graph drawn thusly, where the first number is the circle and the second number is the radius,
• f. locating the progressive points of intersection of the first 4 circles and the first four radii;
• the coordinates of these points are 1,00, 2,10, 3,20, and 4,30
• g. skipping over the point at 5,40,
• h. locating points at the progressive intersections of the 5th circle and the 50 radius, and the outer circle and the 60 radius, the coordinates of these 2 points are 5,50, and 6,60,
• i. optionally locating the point on the 40 radius midway between the 4th and 5th circles, the coordinates of this point are 4.5, 40, and
• j. drawing a smooth curve between the 4 points located in step f, thereby drawing a segment of an Archimedes spiral,
• k. drawing a smooth compromise curve between the points located in steps h and i and the point located in step f designated as 4,30, said compromise curve starting in the proximity of point 6,60 and ending in the proximity of point 3,20, and
• l. joining the curve of steps j and k with a smoothly faired alignment.