Rotor for passively stable helicopter

1. A rotor generating lift, at least comprising a rotor shaft having a central axis and two flexible rotor blades having longitudinal axis, each rotor blade extending outwards from the rotor shaft, ending in a tip, the tips being connected to a ring encircling the rotor, wherein an inner part of the rotor blades have pitch angles generally fixed relative to a reference plane perpendicular to the rotor shaft axis, wherein at least one of said rotor blades is separately connected to the rotor shaft or to a hub by a hinge having a hinge axis generally perpendicular to both the rotor shaft axis and to the longitudinal axis of the separately connected blade,

and further wherein the ring comprises two or more interconnectable tubular elements connected to the tip of the rotor blades.

2. A rotor generating lift, at least comprising a rotor shaft having a central axis and two flexible rotor blades having longitudinal axis, each rotor blade extending outwards from the rotor shaft, ending in a tip, the tips being connected to a ring encircling the rotor, wherein an inner part of the rotor blades have pitch angles generally fixed relative to a reference plane perpendicular to the rotor shaft axis, wherein at least one of said rotor blades is separately connected to the rotor shaft or to a hub by a hinge having a hinge axis generally perpendicular to both the rotor shaft axis and to the longitudinal axis of the separately connected blade, wherein the hinge comprises a flexible material connecting the rotor blade and an arm extending generally horizontally outwards from the rotor shaft.

3. A rotor generating lift, at least comprising a rotor shaft having a central axis and two flexible rotor blades having longitudinal axis, each rotor blade extending outwards from the rotor shaft, ending in a tip, the tips being connected to a ring encircling the rotor, wherein an inner p art of the rotor blades have pitch angles generally fixed relative to a reference plane perpendicular to the rotor shaft axis, wherein at least one of said rotor blades is separately connected to the rotor shaft or to a hub by a hinge having a hinge axis generally perpendicular to both the rotor shaft axis and to the longitudinal axis of the separately connected blade, wherein the hinge is comprising two parts, a first part having a V-shaped edge resting inside a V-shaped grove in a second part, the first part with the edge and the second part with the grove being able to tilt with respect to each other.

4. A rotor according to any of the claims 1 - 3 , wherein the hinge is comprising two parts, a first part being an inner shaft and a second part being an outer tube mounted on the inner shaft, the shaft and the tube being able to rotate with respect to each other.

5. A rotor according to any of the claims 1 - 3 , wherein the generally perpendicular hinge axis is offset or angled with respect to a reference axis going trough and being perpendicular to both the rotor shaft axis and the longitudinal axis of the rotor blade.

6. A rotor according to any of the claims 1 - 3 , wherein the number of rotor blades are three.

7. A method of manufacturing a rotor at least comprising a rotor shaft having a central axis and two flexible rotor blades having longitudinal axis where at least one rotor blade is separately connected to the rotor shaft or to a hub by a hinge having a hinge axis generally perpendicular to both the rotor shaft axis and to the longitudinal axis of the separately connected blade, wherein the method comprises the steps of:

utilizing an injection molding machine to mould at least the hinge and the blade as one part and

utilizing a material having properties that will form a strong flexible hinge when molded into a thin layer.

8. A rotor according to any of the claims 1 - 3 , wherein the rotor blades can be disconnected from the ring encircling the rotor and folded up parallel with the rotor shaft axis for easy transportation.