Patent Description:
Devices for producing wind energy, including horizontal-axis wind turbines, are known in the state of the art. These devices comprise a rotor comprising blades, e.g., three. The rotor is connected to a nacelle, which is positioned on top of a tower. The nacelle is capable of rotating with respect to the tower, so as to align itself with the direction of the wind. The rotor shaft is placed inside the nacelle, and is arranged to transmit the rotary motion of the blades to a gear transmission box. The gear transmission box transfers the movement to a further shaft, called the high-speed shaft, which drives an electric generator.

<CIT> describes a windmill configured to operate a pump. The windmill comprises a pair of coaxial rings spaced apart from each other and blades arranged radially between the pair of rings, with an arcuate shape. Furthermore, the windmill comprises springs which connect the pair of rings and which are configured to contract, bringing the pair of rings closer together. Furthermore, during the contraction of the springs, the blades are reoriented, increasing the exposed area.

Disadvantageously, the energy production according to the prior art depends on two factors: wind speed and the actual area of the disc formed by the blades during rotation. To optimize the performance of the device, a considerable wind speed is necessary, not present at ground level: therefore, the blades must be installed at considerable heights. Furthermore, large blades must be used to maximize the actual disc area. Due to these operating conditions, the transportation and installation of the device are complicated.

In this context, the technical task underlying the present invention is to propose an impeller for wind turbines which overcomes the drawbacks of the prior art mentioned above.

In particular, it is an object of the present invention to provide an impeller for wind turbines whose power produced is maximized even when the wind speed is not optimal.

A further object of the present invention is to provide an impeller for wind turbines which, for the same power produced, requires smaller blades.

The mentioned technical task and the specified aims are substantially achieved by an impeller for wind turbines, comprising the technical specifications set out in one or more of the appended claims.

In particular, an impeller for wind turbines according to the present invention comprises a rear ring having a central axis.

A front ring has an inner peripheral surface and is arranged coaxially with respect to the rear ring and is slidably associated with the rear ring. The front ring is movable along the central axis; it varies between a close configuration and a spaced apart configuration, with respect to the rear ring.

A plurality of blades is connected to the front ring and define a variable-pitch propeller. The blades are 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 extends along the central axis. Said shaft includes a rear portion connected to the rear ring and a front portion connected to the front ring. The front portion of the shaft is 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 and has a front cavity extending along the central axis. The rear portion of the shaft is at least partially inserted in the front cavity.

The front portion comprises at least one spiral guide arranged on an inner surface. The rear portion comprises at least one slider associated with the spiral guide and arranged on an outer surface.

Such an impeller for wind turbines solves the technical problem, as the impeller is capable of optimizing its configuration according to the wind speed. In fact, the front ring, translating along the central axis, changes the pitch of the blades. Thereby, the angle of incidence of the air flow is adjusted, allowing a maximized energy production even at reduced wind speeds. Advantageously, the impeller does not need large blades: being able to optimize the inlet air flow, the impellers can be built with smaller dimensions with the same power produced.

Further features and advantages of the present invention will become more apparent from the description of an exemplary, but not exclusive, and therefore nonlimiting preferred embodiment of an impeller for wind turbines, as illustrated in the appended figures, in which:.

With reference to the appended <FIG> refers to an impeller for wind turbines according to the present invention.

As shown in <FIG>, the impeller <NUM> comprises a front ring <NUM>, from which the air flow enters, and a rear ring <NUM>, from which the air flow flows outwards. The impeller <NUM> also has a central axis X.

As shown in <FIG>, the front ring <NUM> has a converging portion <NUM>, with a truncated cone shape, for conveying the air flow towards the inside of the impeller <NUM>. In particular, the converging portion <NUM> has an inlet section <NUM> defined at the front edge of the front ring <NUM>. The converging portion <NUM> has an intermediate section <NUM>, positioned inside the front ring <NUM> and having a smaller area with respect to the inlet section <NUM>. A cylindrical portion <NUM> is connected to the converging portion <NUM>. The cylindrical portion <NUM> has the same diameter as the smaller section <NUM> of the converging portion <NUM> and extends along the central axis X.

As shown in <FIG>, the front ring <NUM> comprises a front portion <NUM> and a rear wall <NUM>. The front portion <NUM> has a cylindrical shape and has substantially the same diameter as the larger section <NUM> of the converging portion <NUM>. The rear wall <NUM> comprises an inner peripheral surface <NUM> and an outer peripheral surface <NUM>. The outer peripheral surface <NUM> has a cylindrical shape and has substantially the same diameter as the cylindrical portion <NUM>. The inner peripheral surface <NUM> is opposite with respect to the outer peripheral surface <NUM>. Furthermore, the inner peripheral surface <NUM> comprises a plurality of flat surfaces <NUM>, alternated with intermediate surfaces <NUM> which can have a different geometry, for example portions of cylinder side surfaces. As shown in <FIG>, generally the rear wall <NUM> has a dimension L in the direction of the central axis X, which is larger with respect to a dimension D in the direction of the central axis X of the front portion <NUM>.

It should be noted that the impeller <NUM> comprises a shaft <NUM>, shown in <FIG>, which extends along the central axis X. The shaft <NUM> comprises a rear portion <NUM>, connected to the rear ring <NUM>, and a front portion <NUM>, connected to the front ring <NUM>. More details on the shaft <NUM> will be provided later in the present description.

The front ring <NUM> comprises a plurality of front radial elements <NUM>, shown in <FIG>. Each front radial element <NUM> comprises a first end <NUM> fixed to the front portion <NUM> of the shaft <NUM> and a second end <NUM>, connected to the cylindrical portion <NUM> of the inner peripheral surface <NUM>. Furthermore, each radial element <NUM> comprises a rear edge <NUM>, shown in <FIG>, identified as the edge facing the rear ring <NUM>.

Referring now to the rear ring <NUM>, shown in <FIG>, it has a cylindrical shape and comprises an inner surface <NUM>. Furthermore, the rear ring <NUM> extends along the central axis X, passing through the centre of the rear ring <NUM>. The front ring <NUM> is arranged coaxially with respect to the rear ring <NUM>. The rear ring <NUM> has a larger diameter of the rear wall <NUM> and a smaller diameter of the front portion <NUM> of the front ring <NUM>.

The rear ring <NUM> comprises a plurality of rear radial elements <NUM>. Each rear radial element <NUM> comprises a first end <NUM> fixed to the rear portion <NUM> of the shaft <NUM> and a second end <NUM> connected to the inner surface <NUM> of the rear ring <NUM>. Furthermore, each radial element <NUM> comprises a slot <NUM>, shown in detail in <FIG>. The distance between two consecutive radial elements is greater than the width of the slot <NUM>.

As shown in <FIG>, the impeller <NUM> comprises a plurality of blades <NUM>, preferably eight, connected to the front ring <NUM>. The number of front radial elements <NUM> and rear radial elements <NUM> corresponds to the number of blades <NUM>. The blades <NUM> define a variable-pitch propeller <NUM>. Each blade <NUM> has an outer edge <NUM>, an inner edge <NUM> and a front edge <NUM>, shown in <FIG>. The outer edge <NUM> is in contact with a respective flat surface <NUM> of the inner peripheral surface <NUM>. The inner edge <NUM> is in contact with the shaft <NUM> of the impeller. The front edge <NUM> is identified as the edge of each blade <NUM> closest to the entrance of the incident air flow. The front edges <NUM> of each blade <NUM> are hinged with a respective rear edge <NUM> of the front radial elements <NUM>.

In greater detail, each blade has a main body <NUM> and a tail portion <NUM>. The tail portion <NUM> forms an angle with the main body <NUM>. Each tail portion <NUM> is inserted inside a respective slot <NUM> of the rear radial elements <NUM>. Furthermore, as shown in <FIG>, the tail portion <NUM> has an intermediate edge <NUM>, identified between the tail portion <NUM> and the main body <NUM> of the blade <NUM>, and a rear edge <NUM>, opposite with respect to the front edge <NUM>.

It should be noted that the front <NUM> and rear <NUM> portions of the shaft <NUM> have, respectively, a front cavity <NUM> and a rear cavity <NUM>, shown respectively in <FIG> and <FIG>. The front cavity <NUM> and the rear cavity <NUM> extend along the central axis X. The rear portion <NUM> of the shaft <NUM> is inserted inside the front cavity <NUM> at least partially.

It should be noted that the front portion <NUM> of the shaft <NUM> has an inner surface <NUM>, shown in <FIG>, on which at least one spiral guide <NUM> is comprised. The rear portion <NUM> comprises an outer surface <NUM>, shown in <FIG>, on which there is at least one slider <NUM>, associated with the spiral guide <NUM> of the front portion <NUM>. The front portion <NUM>, shown in <FIG>, has an outer surface <NUM>, on which a plurality of flat surfaces <NUM> are present. The flat surfaces <NUM> of the front portion <NUM> are alternated with side surfaces <NUM> which can have a different geometry, for example portions of cylinder side surfaces. Furthermore, each flat surface <NUM> of the front portion <NUM> is in contact with a respective inner edge <NUM>, shown in <FIG>, of a blade <NUM>.

It should be noted that the front ring <NUM> is slidably associated with the rear ring <NUM> and switches with respect to the rear ring <NUM> along the central axis X between a close configuration and a spaced apart configuration. Indicatively, the maximum stroke of the front ring <NUM> with respect to the rear ring <NUM> is in the order of ten centimetres along the central axis X. When the front ring <NUM> reversibly changes configuration, the rear ring <NUM> is inserted between the rear wall <NUM> and the front portion <NUM>. Furthermore, by varying the configuration of the front ring <NUM>, it is possible to adjust the orientation of the blades <NUM> between a minimum pitch, when the front ring <NUM> in the close configuration, and a maximum pitch, when the front ring <NUM> is in the spaced apart configuration.

When the front ring <NUM> changes its configuration, the blades <NUM> are adjusted. The hinge between each front edge <NUM> of the blades <NUM> and a respective rear edge <NUM> of the front radial elements <NUM> allows the main body <NUM> of the blades <NUM> to tilt, changing the pitch of the propeller <NUM>, optimizing the air flow. When the blades <NUM> are adjusted, the outer edge <NUM> and the inner edge <NUM> slide respectively on the respective flat surface <NUM> of the inner peripheral surface <NUM> and on the flat surface <NUM> of the front portion <NUM>. The edges <NUM> and <NUM> slide in the same direction and maintain contact with the respective flat surfaces <NUM> and <NUM>. Furthermore, each tail portion <NUM> of the blade <NUM> can slide into the respective slot <NUM> in a portion between the intermediate edge <NUM> and the rear edge <NUM>.

It should be noted that the front portion <NUM> of the shaft <NUM> is configured to rotationally translate with respect to the rear portion <NUM>, reversibly switching the front ring <NUM> between the close configuration and the spaced apart configuration. Advantageously, by associating the slider <NUM> of the rear portion <NUM> with the respective spiral guide <NUM> of the front portion <NUM>, a controlled rotational translation of the rear portion <NUM>, and consequently of the front ring <NUM>, is allowed. Furthermore, each inner edge <NUM> is slidable along the flat surface <NUM> of the front portion <NUM> during the switching of the front ring <NUM> between the close configuration and the spaced apart configuration.

It should be noted that the impeller <NUM> comprises an actuator <NUM>, shown in <FIG> and <FIG>, inserted inside the front <NUM> and rear <NUM> cavities. The actuator <NUM> comprises a fixed end <NUM> inserted in the rear cavity <NUM> of the rear portion <NUM> and a movable end <NUM> inserted in the front cavity <NUM> of the front portion <NUM>. In use, the actuator <NUM> is operated and switched between a contracted configuration, for switching the front ring <NUM> into a close configuration, and an extended configuration, for switching the front ring <NUM> into a spaced apart configuration.

Claim 1:
Impeller (<NUM>) for wind turbines comprising:
- a rear ring (<NUM>) having a central axis (X);
- a front ring (<NUM>) having an inner peripheral surface (<NUM>); the front ring (<NUM>) being arranged coaxially with respect to the rear ring (<NUM>); the front ring (<NUM>) being slidably associated with the rear ring (<NUM>) and movable along the central axis (X) between a close configuration and a spaced apart configuration with respect to the rear ring (<NUM>);
- a plurality of blades (<NUM>) connected to the front ring (<NUM>) and defining a variable-pitch propeller (<NUM>), the blades (<NUM>) being adjustable between a minimum pitch when the front ring (<NUM>) is in the close configuration and a maximum pitch when the front ring (<NUM>) is in the spaced apart configuration;
- a shaft (<NUM>) extending along the central axis (X); the shaft (<NUM>) comprising a rear portion (<NUM>) connected to the rear ring (<NUM>) and a front portion (<NUM>) connected to the front ring (<NUM>); the front portion (<NUM>) of the shaft (<NUM>) being configured to perform a rotational translation movement with respect to the rear portion (<NUM>) to switch the front ring (<NUM>) between the close configuration and the spaced apart configuration; the front portion (<NUM>) of the shaft (<NUM>) having a front cavity (<NUM>) extending along the central axis (X); the rear portion (<NUM>) of the shaft (<NUM>) being at least partially inserted in the front cavity (<NUM>),
characterized in that the front portion (<NUM>) comprises at least one spiral guide (<NUM>) arranged on an inner surface (<NUM>); the rear portion (<NUM>) comprising at least one slider (<NUM>) associated with the spiral guide (<NUM>) and arranged on an outer surface (<NUM>).