Variable-pitch impeller for wind turbines defined by a sliding ring
An impeller for wind turbines comprises a rear ring having a central axis. The impeller comprises a front ring having an inner peripheral surface. The front ring is arranged coaxially and is slidably associated with the rear ring. The front ring is movable along the central axis and switches between a close configuration and a spaced apart configuration, with respect to the rear ring. The impeller comprises a plurality of blades connected to the front ring and defining a variable-pitch propeller. The blades being adjustable between a minimum pitch when the front ring is in the close configuration and a maximum pitch when the front ring is in the spaced apart configuration.
1. An impeller for wind turbines comprising:
a rear ring having a central axis;
a front ring having an inner peripheral surface; the front ring being arranged coaxially with respect to the rear ring; the front ring being slidably associated with the rear ring and movable along the central axis between a close configuration and a spaced apart configuration with respect to the rear ring;
a plurality of blades connected to the front ring and defining a variable-pitch propeller, the blades being adjustable between a minimum pitch when the front ring is in the close configuration and a maximum pitch when the front ring is in the spaced apart configuration;
a shaft extending along the central axis; the shaft comprising a rear portion connected to the rear ring and a front portion connected to the front ring; the front portion of the shaft being configured to perform a rotational translation movement with respect to the rear portion to switch the front ring between the close configuration and the spaced apart configuration; the front portion of the shaft having a front cavity extending along the central axis; the rear portion of the shaft being at least partially inserted in the front cavity,
wherein the front portion comprises at least one spiral guide arranged on an inner surface of the front portion; the rear portion comprising at least one slider associated with the spiral guide and arranged on an outer surface of the rear portion.
2. The impeller according to claim 1 , wherein the rear portion of the shaft has a rear cavity extending along the central axis; the impeller comprises an actuator inserted inside the cavities; the actuator comprising a fixed end connected to the rear ring and a movable end connected to the front ring; the actuator being operable to reversibly switch the rings between the close and spaced apart configurations.
3. The impeller according to claim 1 , wherein the front portion has an outer surface; the outer surface of the front portion having a plurality of flat surfaces; each blade having an inner edge placed in contact with a respective flat surface of the plurality of flat surfaces of the front portion.
4. The impeller according to claim 1 , wherein the front ring comprises a plurality of front radial elements connected to the front portion; each blade having a front edge hinged to a respective front radial element of the plurality of front radial elements.
5. The impeller according to claim 1 , wherein the rear ring comprises a plurality of rear radial elements; each rear radial element having a slot; each blade being slidably inserted in a respective slot of the plurality of slots.
6. The impeller according to claim 1 , wherein the inner peripheral surface of the front ring has a plurality of flat surfaces; each blade having an outer edge placed in contact with a respective flat surface of the plurality of flat surfaces of the inner peripheral surface.
7. A wind turbine comprising a frame, transmission means and an impeller according to claim 1 ; the rear ring of the impeller being connected to the transmission means and being fixed along the central axis.