Patent ID: 8371819

Claim:
A quiet propeller driven by a motor, comprising: a boss at a center of the propeller; and a plurality of blades extending from the boss, each of said plurality of blades having a leading edge with respect to a direction of rotation of said plurality of blades and a trailing edge with respect to said direction of rotation of said plurality of blades, a first portion of a back surface of the blade rising centrifugally toward a distal end of the blade from a bend line connecting a distal end of the leading edge to a distal end of the trailing edge, a diagonal line extending from an intersection of the leading edge with the bend line to a proximal end of the trailing edge, a first angle of the back surface of the blade close to the boss with respect to oncoming fluid flow being defined from 0 to four degrees, the leading edge being gradually thinner from the boss to a distal end of the blade, a second portion of the back surface of the blade rising toward the trailing edge between the diagonal line and the trailing edge, a front surface of the blade being planar between the leading edge and the trailing edge, a second angle of the back surface of the blade away from the boss with respect to the oncoming fluid flow ranging from 7 to 25 degrees, whereby fluid from the leading edge is gathered centripetally of the propeller by the tilted portion and the tilted back surface during rotation of the propeller.