Self-folding propeller
A propeller assembly includes propeller blades that self-fold when not in use, which reduces the overall footprint of the propeller assembly and enables efficient storage. During flying conditions, the propeller blades unfold and extend to a flight configuration that enables the generation of lift on the propeller blades and consequently to an attached aerial vehicle. In various embodiments, the transitioning of the propeller blades between a flight and folded configuration may be enabled by torsion springs coupled to each propeller blade. For example, the torsion springs cause each propeller blade to rotate and self-fold when no external forces are applied. Alternatively, during flying conditions, centrifugal forces that arise as the propeller assembly rotates counteract the torsion springs, enabling each propeller blade to achieve an extended flight configuration. Therefore, the propeller blades of the propeller assembly are optimally oriented without the need for human intervention.
1. An unmanned aerial vehicle comprising:
a first propeller blade comprising a first projection, a first hole, and a first shoulder;
a second propeller blade comprising a second projection, a second hole, and a second shoulder; and
a central hub comprising:
a first opening configured to receive the first projection,
a first portion of a face, the first shoulder engaging with the first portion of the face in a first rotational position of the first propeller blade,
a first hub hole extending through the first portion of the central herb;
a second opening configured to receive the second projection,
a second portion of the face, the second shoulder engaging with the second portion of the face in a first rotational position of the second propeller blade; and
a second hub hole extending through the second portion of the central hub;
a right-hand wound torsion spring comprising:
a first spring hole;
a left-hand wound torsion spring comprising:
a second spring hole;
a first hinge pin extending through the first hole in the first propeller base, the first hub hole, and the first spring hole to moveably connect the first propeller blade to the central hub and the right-hand wound torsion spring; and
a second hinge pin extending through the second hole in the second propeller base, the second hub hole, and the second spring hole to moveably connect the second propeller blade to the central hub and the left-hand wound torsion spring.
2. The unmanned aerial vehicle of claim 1 , further comprising:
a first connector located at a root of the first propeller blade, the first connector including the first projection and the first shoulder; and
a second connector located at a root of the second propeller blade, the second connector including the second projection and the second shoulder.
3. The unmanned aerial vehicle of claim 2 , wherein
the right-hand wound torsion spring comprises:
a first spring arm coupled with the first connector; and
a second spring arm coupled with the central hub through the first opening of the central hub, wherein the right-hand wound torsion spring is configured to rotate the first propeller blade in a first direction relative to the central hub; and
the left-hand wound torsion spring comprises:
a first spring arm coupled with the second connector, and
a second spring arm coupled with the central hub through the second opening of the central hub, wherein the left-hand wound torsion spring is configured to rotate the second propeller blade in a second direction relative to the central hub.
4. The unmanned aerial vehicle of claim 3 , wherein the right-hand wound torsion spring applies a clockwise torque onto the first propeller blade and wherein the left-hand wound torsion spring applies a counter-clockwise torque onto the second propeller blade.
5. The unmanned aerial vehicle of claim 3 , wherein
the first hinge pin is configured to restrict translational displacement between the first propeller blade, the central hub, and the right-hand wound torsion spring, and
wherein the second hinge pin configured to restrict translational displacement between the second propeller blade, the central hub, and the left-hand wound torsion spring.
6. The unmanned aerial vehicle of claim 1 , wherein the first opening and the second opening of the central huh further comprise a cavity, and wherein a second spring arm of the left-hand wound torsion spring couples with the central hub within the cavity of the first opening of the central hub and a second spring arm of the right-hand wound torsion spring couples with the central hub within the cavity of second opening of the central hub.
7. The unmanned aerial vehicle of claim 1 , wherein the first propeller blade and the second propeller blade are in the first rotational position relative to the central hub when experiencing below a threshold amount of centrifugal forces, and wherein the first propeller blade and the second propeller blade are in a second rotational position relative to the central hub when experiencing above the threshold amount of centrifugal force.
8. The unmanned aerial vehicle of claim 7 , wherein when the first propeller blade and the second propeller blade are in the second rotational position, the right-hand wound torsion spring applies a directional torque that is in an opposite direction of a spin of the central hub and the left-hand wound torsion spring applies a directional torque that is in a same direction of the spin of the central hub.
9. The unmanned aerial vehicle of claim 7 , wherein at least a portion of the first propeller blade and at least a portion of the second propeller blade overlap a common footprint when the first propeller blade and the second propeller blade are in the first rotational position.
10. The unmanned aerial vehicle of claim 9 , wherein the common footprint is enabled by an angle of attack design of the first propeller blade and the second propeller blade.
11. A propeller assembly comprising:
a first blade comprising a first projection and a first shoulder;
a second blade comprising a second projection and a second shoulder; and
a central hub comprising:
a first opening configured to receive the first projection, wherein the first opening comprises:
a first cavity configured to receive a spring element of a first wound torsion spring, and
a first slot configured to receive and couple with an arm of the first wound torsion spring,
a first portion, wherein the first shoulder engages with the first portion,
a second opening configured to receive the second projection, wherein the second opening comprises:
a second cavity configured to receive a spring element of a second wound torsion spring, and
a second slot configured to receive and couple with an arm of the second wound torsion spring, and
a second portion, wherein the second shoulder engages with the second portion.
12. The propeller assembly of claim 11 , further comprising:
a first connector located at a root of the first blade, the first connector including the first projection and the first shoulder; and
a second connector located at a root of the second blade, the second connector including the second projection and the second shoulder.
13. The propeller assembly of claim 12 , wherein the first wound torsion spring comprises:
a second arm coupled with the first connector, and
the arm coupled with the central hub through the first opening of the central hub, wherein the first wound torsion spring is configured to rotate the first blade in a first direction relative to the central hub; and
wherein the second wound torsion spring comprises:
a second arm coupled with the second connector, and
the arm coupled with the central hub through the second opening of the central hub, wherein the second wound torsion spring is configured to rotate the second blade in a second direction relative to the central hub.
14. The propeller assembly of claim 11 , wherein the slots are coupled with the arms through adhesives and/or mechanical connectors.