BOLTED ATTACHMENT FOR ATTACHING WIND TURBINE PARTS

Abstract

A bolted attachment having opposite threaded sections between which a shank is provided having at least two shank sections with different diameter located at a length from the threaded section of at least three times the difference between a diameter of a threaded section and a minimum diameter of the shank. At least one conical transition is formed between two adjacent shank sections where the ratio of its length to a difference between a diameter at one end of the transition and a diameter at the opposite end of the transition is of at least 0.85.

Claims

1. A bolted attachment for attaching at least a first part to at least a second part in a wind turbine, wherein the first part and the second part are subjected to variable loads acting in different planes, the bolted attachment comprising: at least one bolt comprising having a shank, at least one threaded section, wherein the shank comprises at least two shank sections having different diameter, with at least one of said shank sections being located at a length from the threaded section of at least three times the difference between a diameter of a threaded section and a minimum diameter of the shank.

2. The bolted attachment according to claim 1, wherein at least one transition is formed between two adjacent shank sections.

3. The bolted attachment according to claim 2, wherein the transition is conical in shape.

4. The bolted attachment according to claim 3, wherein the ratio of the length of the transition to a difference between a diameter at one end of the transition and a diameter at the opposite end of the transition is of at least 0.85.

5. The bolted attachment according to claim 4, wherein the ratio of the length of the transition to a difference between a diameter at one end of the transition and a diameter at the opposite end of the transition is shank is 1.3.

6. The bolted attachment according to claim 3, wherein the conical shape of the transition has a curved generatrix.

7. The bolted attachment according to claim 1, wherein the bolt comprises two threaded sections between which the shank is provided.

8. The bolted attachment according to claim 1, wherein the diameter of a shank section closest to a threaded section is larger than the diameter of a shank section furthest from a threaded section.

9. The bolted attachment according to claim 1, wherein the first part and the second part belong to at least one of a wind turbine rotor hub, a wind turbine blade extender, a wind turbine yaw mechanism and a wind turbine blade pitch mechanism.

10. The bolted attachment according to claim 9, wherein the first part is, or is part of, a wind turbine hub and the second part is, or is part of, a wind turbine pitch bearing.

11. The bolted attachment according to claim 9, wherein the first part is, or is part of, a wind turbine pitch bearing and the second part is, or is part of, a wind turbine blade.

12. The bolted attachment according to claim 9, wherein the first part is, or is part of, a wind turbine pitch bearing and the second part is, or is part of, a wind turbine blade extender.

13. The bolted attachment according to claim 9, wherein the first part is, or is part of, a wind turbine nacelle and the second part is, or is part of, a wind turbine yaw bearing.

14. The bolted attachment according to claim 1, wherein the minimum diameter in a shank section is in the range of 65-70 percent of the diameter of threaded section.

15. The bolted attachment according to claim 1, wherein the total length of a minimum diameter shank section is in the range of 70-75 percent of the total length of the shank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Particular embodiments of the present bolted attachment will be described in the following by way of non-limiting examples, with reference to the appended drawings in which:

[0023] FIG. 1 diagrammatically shows one example of a bolt that is part of the present bolted attachment; and

[0024] FIG. 2 diagrammatically shows a bolted attachment including the bolt illustrated in FIG. 1 for attaching a wind turbine blade to a wind turbine hub.

DETAILED DESCRIPTION

[0025] The bolted attachment in the example illustrated in the figures comprises a number of bolts, one of which is shown in FIG. 1 and designated by reference numeral 100 as a whole. Bolt 100 has a shank 110 extending between two opposite cylindrical threaded sections 120. In the specific example shown in FIG. 1, bolt 100 is symmetrical about an axis perpendicular to its longitudinal axis X. Other constructions where bolt 100 is not symmetrical are also conceivable according to the present disclosure.

[0026] The shank 110 of the bolt 100 comprises a first shank section 130 having a first diameter D1 and a second shank section 140 having a second diameter D2. The diameter D1 of the first shank section 130 is larger than the diameter D2 of the second shank section 140. In general, a diameter D1 of a shank section that is located closest to a threaded section 120 is larger than a diameter D2 of a shank section that is located furthest from a threaded section 120. As stated above, bolt 100 is symmetrical about an axis perpendicular to its longitudinal axis X, so that the shank 110 of the bolt 100 has two first shank sections 130, as shown in FIG. 1, between which one second shank section 140 extends.

[0027] In the example shown, the first shank section 130 is located at a length L from threaded section 120. Here, the value for such length is L=3×(DT−D2), wherein DT is a diameter of the threaded section and D2 is the above mentioned second diameter of the second shank section 140, which is the minimum diameter of the shank 110. Such value L for the positioning of at least one of the different diameter sections 130, 140 provides good fatigue behaviour while extreme load strength of the bolt 100 can be efficiently controlled.

[0028] In the example shown, the diameter D2 of the second shank section 140, which is the minimum diameter of the shank 110, is in the range of 65-70 percent of the diameter DT of threaded section, that is, D2=0.65-0.70×DT. Here, the total length of the shank section 140 with diameter D2, which is the minimum diameter of the shank 110, is in the range of 70-75 percent of a total length of the shank 110.

[0029] This allows an optimal distribution of the rigidity to be provided in the particular wind turbine parts 170, 180 being attached, as it will described further below.

[0030] In the example shown, respective conical transitions 150 are formed between the shank sections 130, 140 of the bolt 100. Here, the ratio of the length 1 of the conical transitions 150 to a difference between a diameter at one end of the transition 150 and a diameter at the opposite end of the transition 150 such as, for example, the difference between said first and second diameters D1, D2 of the first and second shank sections 130, 140, is 1.3 in the example shown. A conical connecting portion 160 is also provided between the threaded section 120 and the corresponding first shank section 130 adjacent thereto.

[0031] Conical transitions 150 in the shank 110 avoid stress concentrations. This results in that the structural behaviour of the bolt attachment is optimized. This is very important in the field of wind turbines where the parts to be attached are subjected to variable loads acting in different planes both when in use and even when the wind turbine is not in operation.

[0032] Referring now to FIG. 2 of the drawings, an example is shown in which the bolted attachment comprising the bolt 100 described above is used for attaching a wind turbine blade 170 to a wind turbine hub 180 through a bearing arrangement 190. In this case, and as shown in the right hand side of FIG. 2, a first threaded section 120 of the bolt 100 is screwed on one end of the wind turbine blade 170 while a second threaded section 120 of the bolt 100 is screwed on a female thread element 200. Between said female thread element 200 and the bearing arrangement 190, a spacer 210 is provided. The spacer 210 may or may not be present in the bolted attachment. If a spacer 210 is provided as in the embodiment shown in FIG. 2, the spacer 210 may be provided in at least one of the bolts 100 in the bolted attachment. The spacer 210 may comprise, for example, one or a plurality of bushings which may be e.g. cylindrical bushings. In the particular embodiment shown in FIG. 2, the spacer is a single ring or flange 210 that is applied to the entire bolted attachment. The ring 210 is provided with a number of through bores formed therein for receiving corresponding bolts 100. The ring 210 serves the purpose of adding length to the bolted attachment. In the particular embodiment shown in FIG. 2, the ring 210 also provides stiffness to the attachment.

[0033] Although only a number of particular embodiments and examples of the present bolted attachment have been disclosed herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses, obvious modifications and equivalents thereof are possible. Furthermore, the present disclosure covers all possible combinations of the particular embodiments described herein so it should not be limited by particular embodiments but only by a fair reading of the claims that follow.

[0034] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.