A patent for Self-Folding Propellers, by Ryan Goldstein of GoPro Inc. has recently been assigned. It’s classified under the category ‘Blades foldable to facilitate stowage of aircraft’. Back in January 2018 GoPro abandoned its Karma drone business, so it’s not clear whether this patent is residue from that product’s development.
The patent (US20180257769A1) describes the structure and parts of a propeller mechanism that has self-folding capabilities. Labeled drawings are included in the patent along with a detailed description of how all the parts come together to achieve the self-folding.
The blades of a propeller are extended in flight in order to provide sufficient thrust to achieve flight in UAVs. When at rest, propeller blades are often large and unwieldy in the extended configuration and thereby require significant space to adequately store the propeller blades and corresponding UAV. Conventional strategies to try to reduce an at rest propeller footprint have involved folding the propellers. However, these strategies require human intervention to fold and unfold the propeller. For example, an individual applies a force to extend the propeller blades for a flight configuration. In each instance, human intervention increases a likelihood of potential issues such as human error and/or subsequent improper mechanical setup of the propeller assembly. Therefore there is a need for a mechanism that can avoid human interaction and thus prolong the life of the blades.
Torsional springs have been utilized in order to provide the springy motion required for the self-folding of the blades. When the drone is not in flight, these springs exert a force on the propeller blades which makes them rotate and fold up, when no external forces are applied. However, 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.