DESCRIPTION

The present invention relates to a cycloturbine with oscillating mobile blades, in particular a cycloturbine of the type with a vertical-axis rotor, and falls within the field of generating machines for converting the energy of a fluid stream (preferably wind energy but, alternatively, also the energy of marine currents) into electricity.

There are presently known vertical-axis wind generators comprising a supporting frame (rotor) rotatable about the axis and a plurality of blades angularly distributed about the axis and designed to receive a push from the wind such as to cause the frame to rotate about the axis.

There are known solutions which, with the aim of optimizing efficiency, are equipped with mechanisms for moving the blades, which are thus orientable.

The known solutions attempt to minimize the impact with the air/fluid during the recovery phase (that is, during the return movement of the blade, against the wind), for example by seeking to render the blades mobile or flexible by providing mechanisms of a mechanical type for orienting the blades, as shown in US4383801 , which teaches to use symmetrically shaped blades (airfoils) directed by a vane that is mounted on the machine and transmits movement mechanically.

Patent application US2011/0116924 envisages a rotation of the blades having a frequency equal to half the rotation frequency and employs a vane and a transmission of movement achieved with a pair of chains. The two blades can be of the airfoil type, elliptical and symmetrically shaped, since each wing offers its ends to the wind alternatively.

The main problems involved in the operation of cycloturbines of the above- described type are the following:

- the development of a driving torque is generally confined within a portion of a turn having a very limited amplitude: the combined motion of the wind and wing produces a useful torque within an arc of about 30 degrees out of the whole turn;

- triggering of vibrations generated by the intermittence of the forces generated by the combination of the circular movement and wind flow: this prevents such machines from being made to work at high speeds;

- negative effects of centrifugal forces which, in the particular solution of vertical-axis machines, are exerted perpendicularly to the blades, unlike in horizontal-axis wind generators, in which the centrifugal forces are directed parallel to the blades;

- substantial inability to start from a stationary position: this makes it necessary to keep the blades always moving or to adopt specific control circuits.

The combination of the above-mentioned problems forces designers to oversize the structures, so that it is very difficult to construct machines with powers comparable to those of horizontal-axis wind turbine blades.

The object of the present invention is therefore to provide a cycloturbine with oscillating mobile blades capable of remedying the aforesaid problems.

In particular, it is an object of the present invention to provide a cycloturbine with oscillating mobile blades which has high efficiency in exploiting wind energy.

It is likewise an object of the present invention to provide a cycloturbine with oscillating mobile blades which has a high structural strength with reduced overall dimensions (and thus a reduced environmental impact). It is a further object of the present invention to provide a cycloturbine with oscillating mobile blades which has low noise levels, in particular at high rotation speeds.

It is a further object of the invention to provide a cycloturbine with oscillating mobile blades which has excellent properties of starting up autonomously from a stationary position, particularly in the absence of specific control systems. The technical features of the invention, as per the aforesaid object, are clearly deducible from the contents of the claims set forth below, and the advantages of the same will be more apparent from the detailed description that follows, made with reference to the appended drawings, which represent a purely illustrative, non-limiting embodiment thereof, wherein:

- figure 1 illustrates a side view of a cycloturbine according to the present invention;

- figure 2 shows a section view, along a transverse plane, of a blade used in the cycloturbine of figure 1 ;

- figures 3-5 are schematic representations of the operation of the cycloturbine of figure 1 ;

- figure 6 represents a support arm belonging to the cycloturbine of figure 1 , in a first operating configuration;

- figure 7 represents the support arm of figure 6 in a different operating configuration;

- figure 8 represents a partially schematized section view, along a vertical plane, of the support arm of figure 6;

- figure 9 illustrates a schematized side view of a cycloturbine according to the present invention, and in accordance with a variant embodiment;

- figure 10 is an enlarged representation of a detail of the cycloturbine in figure 9.

With reference to the appended figures, 1 represents overall a cycloturbine in accordance with the present invention.

The cycloturbine 1 is adapted to be coupled to an electric generator (alternator), not illustrated.

The cycloturbine 1 is usable in a fluid stream, preferably wind, but could alternatively be used immersed in a liquid, for example to generate electricity from marine currents.

The cycloturbine 1 comprises a rotor 2 able to rotate about a vertical rotation axis "X" and comprising, in the embodiment illustrated, a shaft 3 disposed along the axis "X" (and connected to an alternator, not illustrated) and a plurality of arms 4 fixed to the shaft 3 and oriented in a radial direction. The shaft 3 rests upon the ground by means of a base 5. In the embodiment illustrated in figure 1 , the arms are horizontal and their number can be any whatsoever, preferably greater than four, and they are angularly equally spaced about the axis "X" of the rotor 2.

At one end of each arm 2 opposite the axis "X" a blade 6 is rotatably applied in a configuration such as to make the blade 6 rotatable about a respective axis of oscillation "Y" parallel to the axis "X" of the rotor 2.

The conformation of each blade 6 (the blades are identical to one another) is illustrated in detail in figure 2. In accordance with the figure, each blade 6 has two opposite vertices 6a, 6b defining a chord "C" joining them, and a curved shape defining on one side a convex back 6c ("suction surface") and on the opposite side a concave belly 6d.

Moreover, the blades 6 are symmetrical relative to a vertical plane parallel with the respective axis of oscillation Ύ" and preferably containing tale axis of oscillation Ύ". This feature has a particular function that will be illustrated below. The axis of oscillation "Y" coincides with a main direction of extension of the blade 6.

In the particular embodiment illustrated in figure 1 , pairs of blades 6 are provided in which the two blades 6 of each pair are placed one on top of the other and preferably aligned with the respective coinciding axes of oscillation "Y". However, it is possible to envisage solutions with single blades 6 (thus not stacked) or with blades 6 stacked in groups of three or more.

As can be seen in figure 1 , the blades 6 of each pair are positioned on opposite sides of the respective arm 4, in particular one above and one below.

Furthermore, in order to improve the stability of the cycloturbine 1 with particular reference to centrifugal forces, horizontal and/or inclined ties "T" are provided to connect opposite sides of the cycloturbine 1, in particular axial ends of specific supports 7 of the blades 6, on which the latter are rotatably applied.

The cycloturbine 1 further comprises movement means acting on the blades 6 so as to vary the orientation of the blades 6 relative to the rotor 2 about the respective axes of oscillation "Y".

Advantageously, the movement means are configured in such a way that they cause an alternating oscillation of each blade 6 about the respective axis of oscillation "Y" according to a frequency which is double the frequency of rotation of the rotor 2.

In the context of the present invention, the term "oscillation" means a continuous alternating movement, preferably (but not limitedly) of sinusoidal amplitude, which leads the blades 6 to move in rotation between two extreme positions.

In accordance with the invention, the movement means are configured in such a way as to impart to a each blade 6 an angle of oscillation, about the respective axis Ύ", having an amplitude of between +45° and -45°, and preferably with a maximum travel of +45° and -45°, relative to a radial direction with reference to the axis of rotation "X" of the rotor 2 (the angle and radial direction are determined making reference to the above- mentioned chord "C" of the blade 6).

In other words, the configuration taken on by the blades 6 is obtained as the sum of a dragging movement, given by the rotation of the rotor 2 about the axis of rotation "X", and a relative movement of rotation of each blade 6 about the respective axis of oscillation "Y" between the two extreme positions of amplitude.

Figures 3 and 4 show some of the positions taken on by a blade 6 during rotation of the rotor 2, in particular every 45°.

In accordance with figure 3, the movement means cause the following movements of each blade 6:

- in a first and a third quadrant (quadrants I and III in figure 3), in which the angular position of the blade 6 about the axis of rotation "X" of the rotor 2 defines an angle of absolute value (that is, without the sign) of less than 45° relative to the wind direction "D", the blade 6 is made to rotate in one direction (which in figure 3 is indicated as anticlockwise, discordant with the direction of rotation of the rotor 2) about the respective axis of oscillation "Y";

- in a second and a fourth quadrant (quadrants II and IV in figure 3), in which the angular position of the blade 6 about the axis of rotation of the rotor 2 defines an angle of absolute value between 45° and 90° relative to the wind direction "D", the blade 6 is made to rotate in the opposite direction (which in figure 3 is indicated as clockwise, concordant with the direction of rotation of the rotor 2) about the respective axis of oscillation

As shown in figure 4, it follows that, in the angular positions of the blade 6 about the axis of rotation "X" of the rotor 2 defining an angle of 0° or of 90° relative to the wind direction "D" (indicated with A, C, E, G), the movement means position the blade 6 with the respective chord "C" substantially in a radial direction relative to the axis of rotation "X" of the rotor 2, i.e. with an orientation which defines an angle of 0° formed between the chord "C" and the radial direction.

Moreover, as further shown in figure 4, in the angular positions of the blade 6 about the axis of rotation of the rotor defining an angle of absolute value equal to 45° relative to the wind direction "D" (indicated with B, D, F, H), the movement means position the blade 6 with the respective chord "C" according to an orientation forming, relative to the aforesaid radial direction, an angle "a" equal to ± 45° (the + or - sign is determined by the specific quadrant considered, since the direction of oscillation varies four times in a complete rotation cycle of the rotor 2).

In the intermediate positions between the ones shown, there will be an angle of oscillation "a" of each blade 6 having an absolute value of less than 45°, continuously variable depending on the angular position instantaneously assumed by the blade 6 about the axis of rotation "X" of the rotor 2.

The movement means, therefore, ensure that:

- each blade, when it is in the first quadrant Ί", will exploit the effect of the "suction surface" 6c, using the lift of the airfoil shape of the blade 6 itself while maintaining the blade 6 oriented in such a way as to maintain a constant/optimal angle relative to the wind direction;

- in the second quadrant "II" each blade 6 is oriented with the back 6c in the same direction as the wind in order exploit the effect CX (the wind presses on the concave belly 6d of the blade 6, thus obtaining maximum thrust efficacy);

- in the third quadrant "III", the blade 6 is oriented in such a way as once again to exploit the effect of the "suction surface" 6b (which has an opposite direction relative to the first quadrant, but which, being on the opposite of the axis "X" of the rotor 2, contributes in a direction that is concordant with generation of torque) while maintaining a constant/optimal angle relative to the wind direction; and

- in the fourth quadrant "IV", in which the blade 6 is moving against the wind, the blade 6 offers its back 6c to the wind, hence the side opposite the one offered to the wind in the second quadrant "II".

The effect of the "suction surface" 6c created in the first and third quadrants advantageously serves to impart to the cycloturbine according to the invention a marked torque even from a stationary position and at any angle assumed by the rotor 2 when it starts.

Thanks to the above-mentioned logic of movement, the blades 6 rotate continuously about the respective axes of oscillation "Y", in particular with an angular speed equal to double the angular speed of rotation of the rotor 2, in such a way that a double frequency of rotation cycles is obtained relative to the rotor 2.

Figure 5 shows the (symmetrical) pattern of the angle of oscillation "a" according to the angular position assumed by the blade 6 about the axis "X" of the rotor 2. One may note, in particular, the presence of two "negative correction" (-) areas in which the blade 6 is rotated anticlockwise ("backward"), opposite the direction of rotation of the rotor 2, and two "positive correction" areas (+) in which the blade 6 is rotated clockwise ("forward"), in the same direction as the direction of rotation of the rotor 2.

5 Figures 6-8 show a preferred embodiment of the movement means.

In accordance with that embodiment, the movement means comprise, for each blade 6, a respective connecting rod - crank mechanism 8, 9 mounted on the rotor 2, wherein the crank 8 is rotatable about a respective axis "X", fixed relative to the rotor 2 and parallel to the axis of rotation "X"

3 of the rotor 2, while the connecting rod 9 is rotatably connected to the blade 6 in a position which is off-centre relative to the axis of oscillation "Y" of the blade 6. In this manner, a continuous rotational movement of the crank 8 is converted into an oscillating movement of the blade 6.

In the specific embodiment illustrated, the crank 8 is defined by a gear wheel upon which one end of the connecting rod 9 (opposite the other end of the connecting rod 9, hinged to the blade 6 in an off-centre position) is rotatably applied in an off-centre position.

Preferably, the crank 8 is driven in rotation by the rotor 2, directly by engaging with a gear wheel 10 (or a rack) which is stationary and coaxial

) with the rotor 2 in such a way that the rotation of the rotor 2 about the respective axis of rotation "X" drives the rotation of the crank 8 at an angular speed which is double that of the rotor 2. Therefore, the diameter of the gear wheel defining the crank 8 is equal to half the diameter of the gear wheel 10 (or rack).

j The term "stationary", in reference to the gear wheel 10, means that the gear wheel 0 does not rotate together with rotor 2 but is on the contrary fixed, preferably removably fixed to a fixed part of the cycloturbine 1.

As shown in figures 6 and 7, each arm 4 has a diametrical extent and supports a pair of diametrically opposed blades 6. The same arm 4 thus

) supports both connecting rod-crank mechanisms 8, 9 (which have a common crank 8 and two connecting rods 9 connected to it) of the two blades 6 and determines a simultaneous and opposite movement of the two blades 6.

The rotation of the arm 4 about the axis "X" of the rotor 2 determines a revolution movement of the gear wheel defining the crank 8, which, being engaged with the gear wheel 10, rotates at a double speed, driving the blades 6 at a frequency that is double the frequency of rotation of the rotor 2.

Alternatively, it is in any case possible to envisage that the two blades 6 are moved independently of each other or else envisage the use of mutually independent arms 4 (one arm 4 per blade 6).

Advantageously, the cycloturbine 1 further comprises means for detecting the wind direction and correcting means acting on the movement means so as to angularly translate, about the axis of rotation "X" of the rotor and depending on the wind direction "D", the distribution of the configurations taken on by the blades (Y) during the rotation of the rotor 2.

In other words, the correcting means have the function of orienting the blades 6 always in the optimal direction relative to the wind, since the latter is changeable and a logic of fixed oscillation of the blades 6 would not ensure sufficient effectiveness in capturing wind energy.

In particular, the correcting means have the effect of angularly translating, about the axis "X" of the rotor 2, each instantaneous configuration taken on by the blades 6, thus rendering it optimal relative to the current wind direction "D".

By way of example, considering figure 4, a change in the direction "D" of the wind (which instead of coming from the left could arrive with an inclination of 45°) would lead the blade 6 in position "B" to work with an orientation that is unsuitable for generating the maximum efficiency, and the same applies for the blades 6 in the other positions.

Going into greater detail, as can be seen in figures 6-8, the correcting means comprise an electric motor 11 acting on the stationary gear wheel 10 (or rack) so as to vary the angular position of the gear wheel 10 itself about the axis of rotation "X" of the rotor 2. This rotation of the stationary gear wheel 10 has the effect of correcting the inclination of the blades 6 about the respective axes of oscillation "Y", adapting it to the current wind direction "D".

In figure 8 it may be noted that the electric motor 11 acts directly on a respective driving gear wheel 12 solidly joined to the gear wheel 10, by means of a pinion "P" which is solidly joined to the electric motor 11.

The electric motor 11 as well, like the stationary gear wheel 10, is mounted on a fixed structure that is not rotatable together with the rotor 2.

Preferably, the movement means (gear wheels, etc..) are enclosed within a volume filled with an oil bath 12, as can be seen in figure 8.

Preferably, as shown in figures 6-8, specific means are provided to detect the angular position of the stationary gear wheel (10) or rack, realized for example by means of an auxiliary gear wheel (15) engaged with the stationary gear wheel (10) or rack and connected to a detector (16) rotationally coupled to the auxiliary gear wheel (15).

In one embodiment, the wind direction "D" is detected by means of a detached apparatus (for example, common to a plurality of cycloturbines making up a same installation) which transmits, to a control unit, the wind direction in the form of an electric signal that ranges from a minimum value to a maximum value. The angular position of the blades 6 is detected by means of a respective electrical sensor which transmits to the control unit a corresponding electric signal that ranges from a minimum to a maximum. The control unit then actuates the electric motor 11 so as to ensure that the values of the two signals are equal or in any case compatibly close, thus optimizing the efficiency of the cycloturbine.

Figure 9 (schematically) shows a variant embodiment of the invention, which differs from the previously described embodiment in that the arms 4 are not horizontal, but rather form an acute angle relative to the horizontal, despite being arranged in a spoke-like fashion about the shaft 3.

In this configuration, as better illustrated in figure 10, the blades 6 (not shown in figure 9) are positioned with their axis of oscillation "Y" parallel and preferably coinciding with the direction of extension of the arms 4. In other words, the blades 6 extend along the arms 4.

In order to move the blades 6 in the above-described manner (the control logic is identical to the one previously described), the movement means (and in particular the connecting rod-crank mechanism 8, 9) have an additional joint 14 positioned on the connecting rod 9 in such a way as to obtain a solution with a double hinged connecting rod, wherein the two connecting rods 9a, 9b are inclined relative to each other (the first connecting rod 9a positioned horizontally and the second connecting rod 9b positioned perpendicularly to the axis of oscillation "Y" of the respective blade 6).

In this case as well, it is envisaged to use top ties "T" to endow the rotor with greater resistance to the centrifugal forces acting on the arms 4.

The present invention achieves the proposed objects, overcoming the drawbacks complained of it the prior art.

The operating logic of the cycloturbine according to the present invention, in particular a double oscillation frequency of the blades relative to the rotor frequency, makes it possible to optimize efficiency in the interaction between blades and fluid stream (wind, marine currents) and hence to maximize the specific output capacity.

Furthermore, the cycloturbine according to the invention, being able to vary the orientation of the blades four times during a complete revolution of the rotor, enables the output torque to be distributed over at least three quarters of the revolution, with a beneficial impact on the vibrations generated (and consequently on the sizing of the members).

Thanks to the use of the lift/downforce effect of the airfoil shape of the blades (symmetrical and with a suction surface), the cycloturbine according to the invention is capable of self-starting from a stationary position without require additional starting apparatus.