Hinged rotor blade to provide passive variable pitch
A hinged propeller comprising a hub and one or more blades is disclosed. In various embodiments, a blade is connected to the hub via a hinge, wherein at least a substantial part of the blade has a longitudinal axis that is substantially parallel to a line extending radially from a center of the hub, and wherein the hinge has an axis of hinge rotation that is oriented at a non-zero acute angle to a line that is perpendicular, in a plane of rotation of the hub, to said longitudinal axis.
1. A propeller for an aircraft, comprising:
a hub;
a blade including:
a primary airfoil portion; and
a neck portion angled away from a plane of rotation of the hub, wherein the blade has a longitudinal axis extending through a center of the blade and running from a tip of the blade to an end of the neck portion; and
a hinge having a pivotal link and connecting the blade to the hub, wherein:
the hinge has an axis of hinge rotation that is offset by a non-zero angle from a line perpendicular to the longitudinal axis of the blade; and
the hinge varies a pitch of the blade as the hinge rotates about the axis of hinge rotation, including by a combination of centrifugal force and thrust force to cause the blade to be at a lower pitch and higher dihedral angle in a vertical flight mode relative to a forward flight mode, the dihedral angle being an angle of the blade relative to the plane of rotation of the hub.
2. The propeller of claim 1 , wherein said hinge comprises a single pivotal link.
3. The propeller of claim 1 , wherein said hinge comprises a pin positioned on said axis of hinge rotation.
4. The propeller of claim 1 , wherein said hinge is integrated with a structure mounted fixedly to said hub.
5. The propeller of claim 1 , wherein said hub comprises a nose cone.
6. The propeller of claim 1 , wherein said hub comprises a nose structure.
7. The propeller of claim 1 , wherein the hinge is oriented in a plane that is in the plane of rotation of the hub.
8. The propeller of claim 1 , wherein the hinge comprises a forward end associated with a leading edge of the blade and a rearward end associated with a trailing edge of the blade, and wherein the forward end lies further from a geometric center of the hub than the rearward end.
9. The propeller of claim 1 , wherein the neck portion has a neck portion longitudinal axis that is substantially orthogonal to the axis of hinge rotation and wherein a substantial part of the blade is coupled to the hub by the neck portion.
10. The propeller of claim 1 , wherein a substantial part of the blade comprises the primary airfoil portion of the blade.
11. The propeller of claim 1 , wherein the neck portion is positioned between the primary airfoil portion and the hinge.
12. The propeller of claim 1 , wherein in a first propeller orientation associated with a first mode of flight, the blade deploys to a first stable position associated with a first pitch, and in a second propeller orientation associated with a second mode of flight the blade rotates about the axis of hinge rotation to a second stable position associated with a second pitch.
13. The propeller of claim 12 , wherein the first propeller orientation comprises a substantially horizontal plane of rotation.
14. The propeller of claim 12 , wherein the second propeller orientation comprises a substantially vertical plane of rotation.