A bistable pitch propeller includes a ball, a spring, and a clutch module where the clutch module has a range of rotational movement between a locked end position and a released end position. The clutch module includes a detent, where the ball sits inside and outside of the detent when the clutch module is in the locked end position and released end position, respectively. In response to an input torque and a spring force from the spring, the clutch module rotates toward the released end position and the locked end position, respectively. The bistable pitch propeller also includes an aircraft blade where the aircraft blade is at the first pitch angle and the second pitch angle when the clutch module is in the locked end position and the released end position, respectively.

A system having a variable diameter impeller device that is operable for reducing an energy consumption of a rotating fluid or gas pump by increasing said impeller diameter as a speed of said rotating fluid or gas pump increases and decreasing the impeller diameter as the speed decreases. An extendable vane mechanism is configured to move along an elongated curved or sloping slot, said movement along the elongated curved or sloping slot is operable for increasing and decreasing a diameter of the impeller device. A spring mechanism having a first end and a second end extends and retracts to dynamically increase or decrease a diameter of the impeller device.

A linear actuator for use with a fan with deployable fan blades to deploy the fan blades when in use and stow the fan blades when not in use. The linear actuator utilizes a drive element having a driver that moves linearly along a shaft of the linear actuator. Linear movement of the driver causes radial movement of arms connected to the linear actuator and the fan blades. Radial movement of the arms causes rotational movement of gears attached to the ends of the fan blades to cause the fan blades to rotate into the deployed or stowed configuration.

A bistable pitch propeller includes a ball, a spring, and a clutch module where the clutch module has a range of rotational movement between a locked end position and a released end position. The clutch module includes a detent, where the ball sits inside and outside of the detent when the clutch module is in the locked end position and released end position, respectively. In response to an input torque and a spring force from the spring, the clutch module rotates toward the released end position and the locked end position, respectively. The bistable pitch propeller also includes an aircraft blade where the aircraft blade is at the first pitch angle and the second pitch angle when the clutch module is in the locked end position and the released end position, respectively.

A double-layer blade ceiling fan capable of adjusting the arrangement of blades includes a motor and at least two blades. The motor has a stationary part and two rotating parts. The rotating parts are spaced apart from the stationary part. The rotating parts each have a plurality of mounting portions that are arranged around a central axis of the motor. The stationary part has an upper connecting portion and a lower connecting portion. The mounting portion is configured for connection of one of the blades. At least one of the blades is fixed to each of the rotating parts. The blades mounted to the rotating parts are selectively arranged in a same or different pattern for regulating air flow. When the blades and the rotating parts are rotated, the upper connecting portion and the lower connecting portion are not affected.