A propeller includes a rotatable hub and at least two propeller blades coupled to the rotatable hub. Each of the propeller blades is formed from a combination of a first material having a negative Poisson's ratio (NPR) and a second material having a positive Poisson's ratio (PPR). The first material and the second material can be layered or can be formed as a matrix with one of the first or second material embedded in the other. In a layered configuration, a layer of the first material is positioned between adjacent layers of the second material, and the layers can be connected by tabs of NPR material. The combination of the NPR and PPR materials improve the strength and impact resilience of the propeller blades compared to conventional materials.

A propeller includes a rotatable hub and at least two propeller blades coupled to the rotatable hub. Each of the propeller blades is formed from a combination of a first material having a negative Poisson's ratio (NPR) and a second material having a positive Poisson's ratio (PPR). The first material and the second material can be layered or can be formed as a matrix with one of the first or second material embedded in the other. In a layered configuration, a layer of the first material is positioned between adjacent layers of the second material, and the layers can be connected by tabs of NPR material. The combination of the NPR and PPR materials improve the strength and impact resilience of the propeller blades compared to conventional materials.

A method of mounting a metal blade root to a composite propeller blade body includes inserting a connection portion of the blade body into a bore formed in the blade root, wherein the connection portion comprises at least one depression formed in an outer surface thereof, and applying pressure to the outer surface of the blade root to cause it to deform and engage with the depressions, thereby mechanically coupling the blade root to the propeller blade body.

A propeller system combines innovative strategies to create a new methodology to reduce propeller or rotor noise. The propeller is specifically aimed for ultra-quiet electrically powered aircraft for use in high proximity aviation, but its low-noise advantages will extend to other purposes. The propeller blade includes geometries, along with size and operational limitations that minimize rotational and vortex noise, vibration and span-wise air flow on the blade. To further reduce noise, the propeller provides greater relative thrust on the inboard portions of the blade than do conventional propellers and provides less than conventional relative thrust including negative thrust at the outermost portions of the blade. The propeller blade includes stepped changes in shape at calculated intervals that can reduce resonant blade vibrations and their resultant noise. This ultra-quiet propeller design can also be used for quieting hovercraft, drones, surveillance aircraft, indoor fans, wind tunnels and other applications.

A propeller system combines innovative strategies to create a new methodology to reduce propeller or rotor noise. The propeller is specifically aimed for ultra-quiet electrically powered aircraft for use in high proximity aviation, but its low-noise advantages will extend to other purposes. The propeller blade includes geometries, along with size and operational limitations that minimize rotational and vortex noise, vibration and span-wise air flow on the blade. To further reduce noise, the propeller provides greater relative thrust on the inboard portions of the blade than do conventional propellers and provides less than conventional relative thrust including negative thrust at the outermost portions of the blade. The propeller blade includes stepped changes in shape at calculated intervals that can reduce resonant blade vibrations and their resultant noise. This ultra-quiet propeller design can also be used for quieting hovercraft, drones, surveillance aircraft, indoor fans, wind tunnels and other applications.

Aerial vehicles may be equipped with propellers having pivotable blades that are configured to rotate or fold when the propellers are not rotating under power. A pivotable blade may rotate about an axis of a propeller with respect to a hub in the presence of wind flow until the pivotable blade is coaligned with a fixed blade, in a direction opposite to the wind flow. A pivotable blade may also fold over a hub of a propeller in the presence of wind flow, with the pivotable blade and a fixed blade being oriented in directions opposite to the wind flow. A center of mass of the pivotable blade may be caused to be on the same side of an axis as a center of mass of a fixed blade, even where the axis is not normal to the wind flow, thereby reducing an amount of drag generated by the propeller.

A fan blade comprising a blade body spanning from a blade root to a blade tip in a longitudinal direction and a fluid passageway formed within the blade body and extending from the blade root to the blade tip. The blade body spanning from a leading edge to a trailing edge in a lateral direction. The fluid passageway allowing fluid to flow out of the blade.

A fan is disclosed. The fan includes a base mountable to a ceiling; a base motor contained in the base; a multi-section shaft operably connected to the base motor and moveable between a collapsed position and an extended position; and a fan assembly connected to the multi-section shaft and including a fan motor and at least one fan blade operably connected to the fan motor, wherein in response to a signal, the base motor raises or lowers the fan assembly by moving the multi-section shaft between the collapsed position and the extended position

In one embodiment, a method may comprise heating a composite material into a viscous form, wherein the composite material comprises a thermoplastic and a plurality of reinforcement fibers, wherein the plurality of reinforcement fibers is randomly arranged within the thermoplastic. The method may further comprise extruding a plurality of strands of the composite material, wherein extruding the plurality of strands causes the plurality of reinforcement fibers within each strand to align. The method may further comprise arranging the plurality of strands of the composite material to form an assembly fixture, wherein the assembly fixture comprises an anisotropic thermal expansion property, and wherein the anisotropic thermal expansion property is based on an orientation of the plurality of reinforcement fibers within the assembly fixture.