Blade for a wind turbine and connection method for connecting a blade to a hub of a wind turbine

Abstract

A wind turbine blade for a wind turbine has a tip (10) and a root (8) and extends along a first longitudinal axis (A1), the root (8) being suitable for mounting on a hub (5) of a wind turbine (1), the root (8) being of cylindrical shape and defining a crown (27) extending about the first longitudinal axis (A1), the base (26) having a plurality of first connection openings (12) spaced apart along the crown (27). Each first opening (12) has an inner surface (28) defining a first helical coupling portion (29), in particular the first helical coupling portion (29) having a groove (30) that develops in a helical manner and that is adapted and allows for the mounting by screwing a connecting device (13) suitable for mounting the root (8) of the blade (6) on the hub (5).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Italian Patent Application No. 102022000005123, filed March 16, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a blade for a wind turbine and to a connection method for connecting the blade to a hub of a wind turbine. [Background technology]

[0003] As is well known, wind turbines are used to convert the energy of airflow into electrical energy. Typically, a wind turbine comprises a rotor with a hub and a number of blades connected to the hub, a nacelle connected to the rotor, and a support tower for supporting the nacelle and the rotor. In particular, each blade extending along its longitudinal axis is hollow, has an end called a "root", and is configured to be connected to the hub of the rotor. More specifically, the end of the blade has a crown-like shape and is configured to contact the outer surface of the hub when the blade is connected to the hub.

[0004] During the assembly process of a wind turbine, it is necessary for each blade to be securely connected to the hub, so such connection of the blade ends to the hub is generally performed with the aid of a connection device.

[0005] A currently known connection process provides for embedding, at the blade end manufacturing stage, a number of tubular bodies of the type described in WO 2015 / 130162 at each blade end, in particular with an internal thread formed in each of the tubular bodies to allow connection with a respective tie rod.

[0006] The tie rods are inserted into respective holes formed in the outer surface of the hub and screwed into each tubular member so as to press the root of the blade against the hub of the wind turbine.

[0007] However, the manufacturing process of the blades by the second connection step is complex, costly and requires a considerable amount of work time. Moreover, during the manufacturing process there is a risk that the tubular body may move out of its position, resulting in a misalignment and impairing the assembly process of the blades to the hub. In particular, in such a process, the tubular body is embedded in the blades at an intermediate stage of the manufacturing process of the blades, for example before the injection of the blades or in any case when the resin from which the blades are manufactured has not yet completely hardened. This often involves a misalignment of the tubular body. Summary of the Invention

[0008] The object of the present invention is to make a blade for a wind turbine which makes it possible to alleviate the drawbacks of the prior art presented herein.

[0009] According to the invention a wind turbine blade for a wind turbine is produced, the wind turbine blade extending along a first longitudinal axis from the tip to the root with a tip and a root, the root being suitable for mounting on a hub of a wind turbine, being of cylindrical shape and in particular preferably with a hollow base defining a substantially circular or elliptical or oblong crown.

[0010] The hollow base and / or crown extend about a first longitudinal axis, and a surface of the hollow base and / or crown defines a plurality of first connecting openings spaced apart along the hollow base and / or crown, each opening extending substantially parallel to the axis or longitudinal direction of the extension of the blade.

[0011] Each first connection opening has an inner surface defining a first helical coupling portion, in particular the first helical coupling portion having a helically extending groove adapted to accommodate and allow attachment by threading a connection device suitable for attaching the root of the blade to the hub.

[0012] The present invention provides a reliable, cost-effective and rapid method of connecting wind turbine blades to their respective hubs.

[0013] In this way, the connecting devices can be inserted into the blade after its manufacture is complete, in particular when the resin from which it is manufactured has already hardened and / or the surface of the blade is hard, and it is also possible to subsequently select the point on the crown of the base of the blade at which each connecting device is inserted.

[0014] Furthermore, the connections between the blades and the hub can be made without weakening the structure of the blades.

[0015] A further object of the present invention is to provide a connection method for connecting a blade of a wind turbine to a hub of a wind turbine, which makes it possible to mitigate the drawbacks of the prior art presented herein.

[0016] According to the invention, a connection method for connecting a blade of a wind turbine to a hub of a wind turbine is provided, comprising the steps of: providing a wind turbine blade, in particular with a hollow, preferably circular, elliptical or oval crown-shaped base, forming a plurality of first openings in a surface of the base and / or the crown by a tapping machine and spaced apart along the base and / or the crown; Each of the first openings has an inner surface that defines a first helical coupling portion.

[0017] The invention allows the connection between the blades and the hub to be performed in a simple, fast and automated manner, in particular after the manufacture of the blades is completed and the resin from which they are manufactured has hardened, allowing the selection of the positions of the blade ends for mounting each connection device, without at the same time weakening the blades by drilling too many holes at their bases. [Brief description of the drawings]

[0018] Further features and advantages of the invention are defined in the appended independent claims and will become apparent from the following description of non-limiting exemplary embodiments thereof with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a perspective view of a wind turbine constructed in accordance with the present invention, with parts separated for clarity. [Diagram 2] FIG. 2 is a schematic front view of the wind turbine of FIG. 1 with parts removed for clarity. [Diagram 3] FIG. 3 is a cross-sectional view of the first opening of the blade of FIG. 2 taken along the line III-III. [Figure 4] FIG. 4 is a perspective view of the wind turbine connection device of FIG. [Diagram 5] FIG. 5 is a side view of the connection device of FIG. [Figure 6] 6 is a cross-sectional view of the connection device of FIG. 5 taken along the line IV-IV. [Figure 7] FIG. 7 is a flow chart of a connection method for connecting a blade of the wind turbine of FIG. 1 made in accordance with the present invention to a hub of the wind turbine of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] With reference to FIG. 1, the reference number 1 indicates as a whole a wind turbine according to the invention for converting the energy of an air flow into electrical energy.

[0020] The wind turbine 1 comprises a support tower 2, a nacelle 3 rotatably mounted atop the support tower 2, and a rotor 4 rotatably coupled to the nacelle 3 and comprising a hub 5 and a number of blades 6 connected to the hub 5. In particular, the hub 5 comprises a connection portion with a number of openings (not shown in the accompanying drawings). In the non-limiting case of the invention described or illustrated herein, the wind turbine 1 comprises three blades 6.

[0021] Each blade 6 extends radially from hub 5 along its own longitudinal axis A1. In particular, each blade 6 has a sidewall 7 extending between an end connected to hub 5, commonly referred to as a "root" 8, and an end 9 opposite root 8 and including a tip 10.

[0022] 2, the root 8 is adapted for attachment to the hub 5, is cylindrically shaped, and defines an interior cavity 11. In particular, the root 8 includes a base 26 defining a hollow surface. The base 26 defines a substantially circular crown 27 that extends about the longitudinal axis A1. More specifically, the base 26 of the root 8 is configured to contact an outer surface of the hub 5 when the blade 6 is connected to the hub 5.

[0023] According to further embodiments of the invention, not shown in the accompanying drawings, the crown 27 may take various shapes, such as an elliptical or oval shape.

[0024] According to the invention, the base 26 is provided with a plurality of connecting openings 12 spaced along the crown 27. Each opening 12 extends in a direction substantially parallel to the longitudinal axis A1 of the blade 6 or longitudinal to the extension of the blade 6.

[0025] 3, each opening 12 has an inner surface 28 that defines a helical coupling portion 29. In particular, the helical coupling portion 29 includes a helically extending groove 30 adapted to accommodate and permit threaded attachment of a connecting device 13 (FIGS. 3-5) suitable for attaching the root 8 of the blade 6 to the hub 5.

[0026] More specifically, the cross section of the helical coupling portion 29 taken along the cutting plane III-III containing the longitudinal axis A1 has a substantially trapezoidal shape, preferably an isosceles trapezoid.

[0027] According to a non-limiting embodiment of the present invention, the lower base of the substantially trapezoidal shape has a length between 2 millimeters and 50 millimeters. The upper base of the substantially trapezoidal shape has a length between 1 millimeter and 40 millimeters. The height of the substantially trapezoidal shape has a length between 3 millimeters and 80 millimeters.

[0028] In particular, the substantially trapezoidal shape has a perimeter having a length between 20 millimeters and 300 millimeters.

[0029] More specifically, each of the corners of the substantially trapezoidal shape is chamfered.

[0030] It should be understood that different shapes of said cross section are contemplated according to the invention, for example, according to alternative embodiments of the invention, said cross section is substantially triangular, preferably isosceles triangular, or alternatively sawtooth shaped.

[0031] Furthermore, the helical coupling portion 29 has a pitch P1 having a length between 5 millimeters and 150 millimeters.

[0032] The term "pitch," when referring to the helical coupling portion 29, should be understood to mean the length of the distance measured along the longitudinal axis A1 between one portion of the groove 30 and the next succeeding portion of that groove 30.

[0033] 4 and 5, there is shown a connection device 13 for connecting each blade 6 to the hub 5. The connection device 13 extends along a longitudinal axis A2 and includes an outer portion of a cylindrical surface 15 having a helical coupling portion 16 configured to mate with a helical coupling portion 29 formed in at least one of the openings 12.

[0034] In particular, the elongated body 14 is cylindrical in shape and extends about a longitudinal axis A2.

[0035] More specifically, the helical coupling portion 16 protrudes from a portion of the cylindrical surface 15. In this manner, the helical coupling portion 16 can slide within the groove 30 of the helical coupling portion 29 when the connecting device 13 is screwed into the respective opening 12.

[0036] 6, the cross section of the helical coupling part 16 along the section plane IV-IV containing the longitudinal axis A2 has a substantially trapezoidal shape. In particular, said cross section has an isosceles trapezoidal shape.

[0037] According to a non-limiting embodiment of the present invention, the lower base of the substantially trapezoidal shape has a length between 2 millimeters and 50 millimeters. The upper base of the substantially trapezoidal shape has a length between 1 millimeter and 40 millimeters. The height of said substantially trapezoidal shape has a length between 3 millimeters and 80 millimeters.

[0038] In particular, said substantially trapezoidal shape has a perimeter length between 20 mm and 300 mm.

[0039] More specifically, each of the corners of said substantially trapezoidal shape is chamfered.

[0040] It should be understood that different shapes of the cross section are contemplated according to the invention, for example, according to alternative embodiments of the invention, the cross section is substantially triangular, preferably isosceles or sawtooth shaped.

[0041] Furthermore, the elongated body 14 has an inner side of the cylindrical surface 17, in which helical coupling portions 18 are adapted to mate with complementary coupling portions of a tie rod (not shown in the accompanying drawings). In particular, each helical coupling portion 18 is adapted to mate with a tie rod inserted into a respective opening 12 and a respective opening in the connecting portion of the hub 5.

[0042] In accordance with an embodiment of the present invention, not shown in the drawings, strip 14 is substantially cylindrical in shape. In such a configuration, portion of cylindrical surface 15 and portion of cylindrical surface 17 are located at opposite ends of strip 14.

[0043] According to the invention, the helical coupling part 16 has a pitch P2 and the helical coupling part 18 has a pitch P3. The pitches P2 and P3 have different lengths. In particular, the length of the pitch P2 is greater than the length of the pitch P3.

[0044] More specifically, the helical coupling portion 16 has a pitch P2 having a length between 5 millimeters and 50 millimeters.

[0045] More specifically, the helical coupling portion 16 has a pitch P3 having a length between 1 millimeter and 20 millimeters.

[0046] The term "pitch," when referring to the helical coupling portions 16, 18, should be understood to mean the length of the distance measured along the longitudinal axis A2 between a protrusion from the helical coupling portion 16 or the helical coupling portion 18, respectively, and the next succeeding protrusion from the helical coupling portion 16 or the helical coupling portion 18.

[0047] As described and illustrated herein, elongated body 14 has a length L1 measured along longitudinal axis A2. Helical coupling portion 16 extends over a portion of cylindrical surface 15 a length L2 measured along longitudinal axis A2, which is less than length L1.

[0048] In other words, the helical coupling portion 16 extends over only a portion of the total length L1 of the elongated body 14 on a portion of the cylindrical surface 15.

[0049] Furthermore, the helical coupling portion 18 extends at the cylindrical surface 17 by a length L3 measured along the longitudinal axis A2, the length L3 being less than the length L1.

[0050] In other words, the helical coupling portion 18 extends over only a portion of the total length L1 of the elongated body 14 on a portion of the cylindrical surface 17.

[0051] According to a non-limiting embodiment of the present invention, the cylindrically shaped elongated body 14 has an inner diameter D1 between 15 and 120 mm. Moreover, the cylindrically shaped elongated body 14 has an outer diameter D2 between 17 and 170 mm, in particular between 19 mm and 160 mm. In other words, the thickness of the cylindrically shaped elongated body 14 is comprised between 1 and 25 mm, in particular the thickness measured in terms of the tubular shape of the elongated body 14.

[0052] With reference to FIG. 7, a flow chart of a connection method for connecting each blade 6 of the wind turbine 1 to the hub 5 is shown.

[0053] The connection method includes a step of manufacturing the root 8 of the blade 6 (block 31), preferably such that the base 26 of the root 8 of the blade 6 extends in a crown shape centered on the longitudinal axis A1.

[0054] The connection method then comprises the steps of placing the blade 6 in a drilling / tapping station (block 19) so as to center the blade 6 relative to the drilling / tapping machine, and drilling holes in the base 26 of the blade 6 (block 20) ​​so as to obtain a number of openings 12 along the crown 27 (FIG. 2). By way of example, the drilling step can be performed by a numerically controlled machine, or by a robot, or by hand.

[0055] In other words, the drilling / tapping step is performed on the blade when the resin has already hardened and when all the parts defining the blade's outer surface are assembled, i.e. when the blade already has a hollow shape and the outer surface already defines a circular outer surface. In other words, when the blade is defined by gluing two half-shells together, the drilling / tapping step is performed after gluing the two half-shells. On the other hand, when the blade is defined in a single blade outer surface manufacturing step, the drilling / tapping step is performed after the single blade manufacturing step is completed and the blade surface already defines a cylindrical body.

[0056] Subsequently, a helical coupling 29 is produced in each opening 12 by means of a tapping tool (block 21).

[0057] In particular, the fabricated helical coupling portion 29 has a helical groove 30 that complements the helical coupling portion 16 of the connecting device 13 .

[0058] More specifically, each helical coupling portion 29 is fabricated by a numerically controlled machine, or a robot, or by hand.

[0059] Once the drilling and tapping operations are completed, each connecting device 13 (FIGS. 3-5) is preferably threaded into each opening 12 (block 22) such that the longitudinal axis A2 of each connecting device 13 is substantially parallel to the longitudinal axis A1 of the blade 6.

[0060] In particular, during threading of the connecting device 13 into each opening 12 , the helical coupling portion 16 slides within the groove 30 of the helical coupling portion 29 of each opening 12 .

[0061] Preferably, prior to threading connector 13 into each aperture 12 , an interface material is disposed on coupling portion 16 to act as a thread locking agent during threading of connector 12 into each aperture 12 .

[0062] When the connection device 13 is screwed in, the root 8 of the blade 6 is placed in the connection part of the hub 5 with the further opening so that the opening 12 is aligned with said further opening (block 23).

[0063] Subsequently, a tie rod, not shown in the accompanying drawings, is inserted into each opening 12 and into each of the further openings (block 24) and screwed into the elongate body 14 of each connecting device 13 so as to press the root 8 of the blade 6 against the hub 5 of the wind turbine 1.

[0064] Finally, it is evident that the invention comprises further modifications of the described embodiments, which fall within the scope of protection of the appended claims.

Claims

1. 1. A wind turbine blade for a wind turbine, comprising: The wind turbine blade (6) has a tip (10) and a root (8) and extends along a first longitudinal direction from the tip (10) to the root (8); said root (8) is suitable for being attached to the hub (5) of the wind turbine (1) and is of cylindrical shape, preferably defining a crown (27) of, in particular, substantially circular, or elliptical or oblong shape, in particular comprising a base (26) extending laterally, preferably vertically, about a first longitudinal axis (A1); A plurality of first connection openings (12) are spaced along the crown (27); each of said first openings (12) extends in a direction substantially parallel to said first longitudinal axis (A1) or along the longitudinal direction of extension of said blade (6); Each of the first openings (12) has an inner surface (28) that defines a first helical coupling portion (29); In particular, said first helical coupling part (29) is provided with a groove (30) which develops in a helical manner and which is adapted for and allows the attachment by screwing in a connecting device (13) suitable for attaching the root (8) of said blade (6) to said hub (5).

2. 2. The wind turbine blade according to claim 1, wherein a cross-section of the first helical coupling part (29) along a first cutting plane (III-III) containing the first longitudinal axis (A1) is substantially trapezoidal, preferably isosceles trapezoidal, or substantially triangular, preferably isosceles triangular, or sawtooth shaped.

3. Wind turbine blade according to claim 1 or 2, wherein the first helical coupling part (29) comprises a first pitch (P1) with a length between 5 mm and 150 mm.

4. a connecting device (13) for each of said openings (12) configured to connect said roots (8) of said blades (6) to said hub (5); The connection device (13) An elongate body (14) extending along a second longitudinal axis (A2); The elongated body (14) a first portion of a cylindrical surface (15) having a second helical coupling portion (16) configured to mate with the first helical coupling portion (29) formed in the at least one first opening (12) of the blade (6); A wind turbine blade according to any of the previous claims, comprising a second portion of the cylindrical surface (17) in which a third helical coupling portion (18) is formed to mate with a complementary coupling portion of a tie rod.

5. 5. The wind turbine blade according to claim 4, wherein the elongated body (14) is cylindrically shaped and extends about the second longitudinal axis (A2), the first portion of the cylindrical surface (15) being external and the second portion of the cylindrical surface (17) being internal.

6. the second helical coupling portion (16) has a second pitch (P2) and the third helical coupling portion (18) has a third pitch (P3); 6. The wind turbine blade according to claim 4 or 5, wherein the second pitch (P2) and the third pitch (P3) have different lengths, preferably the length of the second pitch (P2) being greater than the length of the third pitch (P3).

7. 7. Wind turbine blade according to any of claims 4 to 6, wherein the second helical coupling part (16) protrudes from the first part of the cylindrical surface (15).

8. The wind turbine blade according to any of claims 4 to 7, wherein a cross-section of the second helical coupling part (16) along a second cutting plane (VI-VI) containing the second longitudinal axis (A2) is trapezoidal in shape, preferably an isosceles trapezoid, or substantially triangular, preferably an isosceles triangle, or a sawtooth shape.

9. The wind turbine blade according to any one of claims 4 to 8, wherein the second helical coupling part (16) and the third helical coupling part (18) are arranged at opposite ends of the elongated body (14).

10. The wind turbine blade according to any of claims 4 to 8, wherein the second helical coupling part (16) and the third helical coupling part (18) are arranged at the same end of the elongated body (14).

11. A rotor for a wind turbine comprising a wind turbine blade according to any of the preceding claims, a rotor comprising a hub (5) having a connection portion with a plurality of second openings that are coupled with a plurality of said connection devices (13), said connection portion connecting each of said blades (6) to said hub (5).

12. A support tower (2); a nacelle (3) supported on the support tower (2); A rotor (4) according to claim 11, The rotor (4) is rotatably coupled to the nacelle (3).

13. 1. A method for connecting a blade of a wind turbine to a hub of the wind turbine, comprising: - providing a wind turbine blade (6) having a root (8) with a base (26) preferably in the shape of a crown (27), in particular in the shape of a circle, or in the shape of an ellipse or an oval; creating, by means of a tool, preferably a tapping machine, a plurality of openings (12) on a surface of the crown (27) and at intervals along the crown (27) having an inner surface (28) defining a first helical coupling portion (29).

14. The method of claim 13, wherein the second helical coupling part (29) is fabricated by a numerically controlled machine, a robot, or by hand.

15. 15. The method according to claim 13 or 14, wherein the first helical coupling part (29) preferably has a helical groove (3) with a pitch (P1) having a length between 5 mm and 150 mm.

16. The method according to any of claims 13 to 15, further comprising the step of screwing a connecting device (13) comprising an elongated body (14) into each said opening (12), in particular into said first helical coupling part (29).

17. positioning the base (26) of the root (8) of the blade (6) at a connection part of the hub (5) provided with a second opening such that the first opening (12) is aligned with the second opening; Inserting a tie rod into the aligned first opening (12) and second opening; 17. The method according to claim 16, further comprising: screwing the tie rod into the elongated body (14) of each of the connection devices (13) in such a way as to press the root (6) of the blade (6) against the hub (5) of the wind turbine (1).

18. The method according to any one of claims 13 to 17, further comprising the step of drilling holes in the base (26) of the blade (6) to obtain a plurality of said first openings (12) before fabricating each said first helical coupling part (29).

19. The method according to any of claims 13 to 18, further comprising the step of positioning the blade (6) at the drilling / tapping station such that the blade (6) is centred relative to a drilling / tapping machine.

20. completing the manufacture of the root (8) of the blade (6) such that the root (26) of the root (8) of the blade (6) preferably extends in a crown shape centered on the first longitudinal axis (A1) of the blade (6) and preferably such that the resin of the manufactured blade is already hardened; Next, the first helical coupling portion (29) is manufactured. The method of any of claims 13 to 19, further comprising:

21. The connection device (13) further comprises an elongated body (14) having a cylindrical shape, The elongated body (14) an outer, first portion of the cylindrical surface (15) having a second helical coupling portion (16) configured to mate with the first helical coupling portion (29) of each of the first openings (12); The method according to any one of claims 14 to 20, wherein a third helical coupling portion (18) comprises an inner, second portion of a cylindrical surface (17) configured to mate with a complementary coupling portion of the tie rod.

22. The method of claim 21, wherein the second helical coupling portion (16) protrudes from the first portion of the cylindrical surface (15).

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