FIELD OF THE INVENTIONS

The inventions described below relate to the field of nautical and aeronautical propellers.

BACKGROUND OF THE INVENTIONS

Most propellers use blades which conform to the shape of a screw. These are referred to as helicoidal propellers. Helicoidal propellers create a large amount of turbulence compared to the thrust they generate, and various modifications are employed to decrease turbulence and increase thrust. Other forms of propellers have been proposed, but not widely adopted.

Conical propellers described in the prior art include Entat, Method of Producing Propeller Blades and Improved Propeller Blades Obtained by Means of this Method, U.S. Pat. No. 4,135,858 (Jan. 23, 1979). Entat's propeller blades conform to the surface of a reference cone, and the axis of rotation of his propeller is coincident with a vertex of the reference cone. The blades of Entat span a large circumference of the reference cone (about 135° at the root). Moreover, the faces of Entat's propeller blades are angled toward the axis of rotation. This results in large inefficiencies as much of the fluid flow caused by rotation of the propeller blades is directed radially inward, rather than axially away from the thrust surface.

SUMMARY

The propellers described below provide for increased thrust and decreased turbulence with blades shaped to conform to the surface of a cone. Each blade is characterized by a blade center axis which corresponds to a generator line of a cone to which the blade, or blade thrust surface, conforms. The propeller hub is fixed to each blade at the root, in line with the blade center axis, such that the hub axis and blade center axis lie in the same plane, and the leading edge of the blade is positioned forward (referring to the upstream direction of movement caused by the propeller) of the trailing edge of the blade.

The conical propeller may be modified such that each blade subtends 90° or less of the reference cone circumference, and more preferably 45° or less of the reference cone circumference. The conical propeller may also be modified such that the blade's axis of rotation intersects a generator line at a distance of at least half the length of the distance from the blade root to tip as measured along the generator line that passes through the axis of rotation, and up to approximately the length of the blade's radial axis away from the cone's vertex.

