Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. TITLE OF THE INVENTION:

“CORNER LEG FOR A LATTICE STRUCTURE OF A TOWER OF A WIND TURBINE”
2. APPLICANT:

(a) Name : Suzlon Energy Limited
(b) Nationality : Indian
(c) Address : Shrimali Society, Near Shri Krishna
Complex, Navrangpura, Ahmedabad 380 009, Gujarat, India

3. PREAMBLE TO THE DESCRIPTION:

The following specification particularly describes the invention and the manner in which it is to be performed.

TITLE OF INVENTION

CORNER LEG FOR A LATTICE STRUCTURE OF A TOWER OF A WIND TURBINE

FIELD OF INVENTION

The present invention is directed to corner leg for a lattice structure of a tower of a wind turbine, a lattice structure having said corner leg and a tower having a lattice structure as well as a wind turbine having said tower.

BACKGROUND

Hybrid towers, especially hybrid lattice towers, for wind turbines are well-known in prior art. However with increasing height of the hybrid tower itself and at same time increasing of length of rotor blades the loads will increase too. Additional to this, in the area of the rotor blade the hybrid tower has to be designed with a small diameter so that a collision of the rotor blade tip with the hybrid tower is avoided. These make the hybrid tower construction challenging.

For handling increasing loads different solutions are disclosed, namely in DE102013221681B4 and DE102006056274B4 directed to an adapter for a hybrid tower of a wind turbine. However, the prior art only provides solution for the transition from the lattice section of the tower to a tubular section or connection to the nacelle of the wind turbine. Disadvantageous is that the prior art doesn’t provide a solution for handling the loads for the lattice section with limited diameter especially of the area at rotor blade tip.

OBJECT OF THE INVENTION

One object of the present invention is to provide a solution which overcomes the disadvantages of the prior art, especially to provide a lattice structure which can manage increased loads.

SUMMARY OF THE INVENTION

The above-mentioned objection is solved by the present invention.

One aspect of present invention is directed to a corner leg for a lattice structure of a tower of a wind turbine.

The corner leg for a lattice structure of a tower of a wind turbine, characterized by
- a plate which is bent to form a L-shaped corner leg or
- at least two plates which are kinked or straight, wherein the plates are welded together such a way to form an X-shaped corner leg.

Advantageously, the welded or bent and welded and bent and screwed corner legs in the lattice structure overcome the different inclinations at the kink area and the required connection. Said corner legs are screwed to the lattice structure below and above the kink by using plates. Thus, a cross section of the corner leg can be designed individually to transfer loads. Furthermore, clamping areas – necessary to connect secondary bracings by screws – can be designed with appropriate space where they are needed. In context of this invention the term "bent" means that a component is bent parallel to the longitudinal axes of the component and the term "kink" means that a component is kinked essential perpendicular to the longitudinal axes of the component.
More advantageously, the adapted corner legs in the lattice structure of a wind turbine reduce the amount of parts that need to be screwed according to the structural calculation, enable the individual design of the corner legs according to the structural calculation and enable an optimum force transmission. So the total weight and the cost can be reduced compared to the use of standard profiles. The lattice structure can be part of a hybrid tower or lattice tower.

According to a preferred embodiment said corner leg can be designed according to three alternatives:
- one or two bent plates have a kink to form a kinked L-shaped corner leg or
- the at least two plates which are kinked welded together such a way to form kinked X-shaped corner leg or
- the at least two plates which are straight and welded together such a way to form kinked X-shaped corner leg.

Advantageously, the kink is arranged at middle section of the of the L-shaped or X-shaped corner leg, preferred kink is arranged in middle of the L-shaped or X-shaped corner leg.

According to a preferred embodiment said the X-shaped corner leg comprises three or six or eight plates.

According to a preferred embodiment of said X-shaped corner leg can be de-signed according two alternatives:
- if the X-shaped corner leg comprises three plates then the three plates are kinked and welded together to form the X-shaped corner leg or
- if X-shaped corner leg comprises six or eight plates then the six plates are straight and welded together to form the X-shaped corner leg.

According to a preferred embodiment said L-shaped corner leg or said X-shaped corner leg has unequal flange width for increasing area of screwed connection and for increasing blade tip distance.

According to a more preferred embodiment the unequal flanges of the L-shaped corner leg or the X-shaped corner leg having a longer flange width side for screwing a cross brace to the corner leg.

According to a preferred embodiment said corner leg comprises at least one clamping area for connecting secondary bracing by screws.

Advantageously said clamping area can be designed with appropriate space where it’s needed.

A further aspect of present invention is directed to a lattice structure for a hybrid tower of a wind turbine.

The lattice structure for a hybrid tower of a wind turbine comprising at least one said corner leg, wherein the at least one said corner legs is screwed to lattice structure.

Advantageously, the lattice structure needs to be adapted at the kink/blade tip area.

According to a preferred embodiment said lattice structure for a hybrid tower of a wind turbine, the longer flange width side of L-shaped corner leg or of the X-shaped corner leg is screwed to a cross girder and/or cross braces of lattice structure.

According to a preferred embodiment said lattice structure for a hybrid tower of a wind turbine, wherein the lattice structure comprises a kink area and the at least one corner leg screwed below and above kink area to lattice structure by using plates.

Advantageously, a cross section of the corner leg can be designed individually to transfer loads.

According to a preferred embodiment the lattice structure for a hybrid tower of a wind turbine, wherein the corner leg is screwed to the lattice structure with a connecting plate. Advantageously, the connecting plate can have any suitable shape to connect the corner leg with lattice structure, in particular K-shape or T-shape.

Another aspect of the present invention is directed to a tower of a wind turbine.

The tower, in particular a hybrid tower or lattice tower, of a wind turbine comprises said lattice structure which comprises at least three corner leg assemblies comprising at least one said corner leg.

Another aspect of the present invention is directed to a wind turbine.

The wind turbine comprises said tower.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be explained in more detail with respect to exemplary embodiments with reference to the enclosed drawings, wherein:

Figure 1 shows a wind turbine according to prior art;

Figure 2 shows a hybrid tower having kink area for a wind turbine according to Fig. 1

Figure 3 shows a detailed side view of kink area;

Figure 4 shows a detailed top view of kink area according Fig. 3;

Figure 5 shows a side view of corner leg according to a welded embodiment;

Figure 6 shows a side view of corner leg according to a further welded embodiment;

Figure 7 shows a detailed top view of corner leg according to Fig. 6 or 7;

Figure 8 shows a top view of corner leg according to a bent embodiment;

Figure 9 shows a top view of corner leg assembly with corner legs according to Fig. 8;

Figure 10 shows a side view of an alternative assembly of corner leg and cross braces;

Figure 11 shows a top view of a further alternative assembly of corner leg and cross braces and

Figure 12 shows a top view of another corner leg assembly.

The foregoing and other aspects will become apparent from the following de-tailed description of the invention when considered in conjunction with the ac-companying drawing figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 depicts a schematic view of a wind turbine 1 with a tower 2 and a nacelle 3. Depending on given requirements the wind turbine 1 can be used for off-shore or onshore applications. The nacelle 3 is rotatable mounted on the tower 2 which is indicated by a double arrow at the tower 2. The nacelle 3 incorporates a number of components like a drive train chain 4 comprising a rotor shaft 5 (also known as slow-speed-shaft) connecting a rotor 6 with a gear box 7. A high-speed-shaft 8 connects the gear box 7 with a generator 9. The generator 9 is connected with a plurality of electrical components indicated by box 10. Further the nacelle 3 comprises a yaw system 11 for rotating the nacelle 3 indicated by double arrow at tower 2. The rotor 6 comprises three rotor blades 12 which are mounted to a hub body (not shown). Latter is connected to the rotor shaft 5 of the drive train chain 4. The rotor blades 12 are adjustably mounted on the hub body indicated by double arrows at the rotor blade 12. This is realized by means of pitch drives 13, said pitch drives (not shown) being part of a pitch system 13. The pitch system controls the rotor speed to given set points. By means of pitch-drives, the rotor blades 12 may be moved about a rotor blade axes into different pitch positions which is indicated by double arrows at the rotor blade 13. Said rotor blade 6 axis extends in an axial direction of the rotor blades 13. Each rotor blade 13 is connected to the hub body via its blade bearing (not shown). The nacelle 3 is covered by a nacelle cover 14. The hub body is covered by a spinner 15, wherein the hub body and spinner 11 forming a hub 16.

Fig. 2 shows a hybrid tower 2, wherein an upper section of the hybrid tower 2 is designed as a tubular section 17 and a lower section of the hybrid tower 2 is de-signed as a lattice section 18. The tubular section 17 and the lattice section 18 are connected with each other by means of an adapter arrangement 19 according to prior art. The lattice section 18 comprises at least three, in this embodiment four, corner leg assemblies 22 which are connected to each other by a number of cross girders 20 and cross braces 21 and the corner leg assemblies 22 are arranged in an angle a to a longitudinal axis 23 of the hybrid tower 2. The corner leg assemblies 22 are designed for dissipating the bending moments acting perpendicularly to the tower axis 23 as well as for dissipating forces acting in the tower axis 23. The corner leg assemblies 22 will be described in detail later. The cross braces 21 of the lattice section 18 are designed for dissipating torsional moments acting around the tower axis 23 as well as for dissipating forces acting perpendicularly to the tower axis 23. The corner leg assemblies 22 are arranged with an inclination angle to the tower axis 23. The tubular section 17 is connected to the lattice section 18 via the adapter arrangement 19. For the tubular section 17 already existing tubular segments 24 from the known tubular section 17 can be used; here, for instance, the two uppermost segments 24 of the known tubular section 17 are used. The hybrid tower 2 is designed very slimly in the section of the rotor 6 so that it is ensured that the rotor blades 12 can freely move in relation to the hybrid tower 2 even at high deflection of the rotor blades 12. Below the rotor 6 the width of the lattice section 18 can be freely increased so that a large platform and thus a stable standing of the hybrid tower 2 can be guaranteed. In area of blade tip the lattice section 18 has a kink area 25 for increasing the diameter of hybrid tower 2. This kink area 25 will be explained in detail with help of Fig. 3 and 4. The kinked area 25 can also applied for lattice towers.

Fig. 3 and Fig. 4 depict the kink area 25 of hybrid tower 2. The kink area 25 comprises a lattice structure 26, which comprises at least one corner leg assembly 22 having at least one corner leg 27. Two or more corner legs 27 can be screwed, in particular with help of plates. At least one cross girder 20 and/or at least one cross brace 21 is screwed to the corner leg 27. Therefore each corner leg 27 has a corner leg flange 28. At this corner leg flange 28 the cross girder 20 and/or at least one cross brace 21 is screwed via a plurality of bolts. The cross girder 20 and cross brace 21 are standard profiles already known in prior art. The shown kink area 25 comprises four corner leg assemblies 22. These corner leg assemblies 22 are kinked so that the diameter of the lattice structure 26 decreases from down to top. In the area at rotor blade the lattice section 18 has limited diameter with increased loads. To manage these loads the corner legs 27 have to be de-signed in novel way as described as follows.

Fig. 5 depicts a corner leg 27 made of three plates 29 which are bent and welded together. Each kinked plate 29a is bent such a way to form a kink 31 in middle section of the corner leg 27. One kinked plate 29a has a width which is same as the sum of width of the two remaining kinked plates 29a. The kinked plates 29a are welded together such a way that the wider kinked plate 29a provides two flanges 28 and each remaining kinked plate 29a provides one flange 28. In result, an X-shaped corner leg 27a with four flanges 28 is formed. The size of the flang-es 28 of X-shaped corner leg 27a can be equal or unequal. Latter will be de-scribed in more detail in Fig. 7. On top end and bottom end of X-shaped corner leg 27a are arranged a plurality of bore holes 30 for connecting a further corner leg of any type. In middle section of X-shaped corner leg 27a are arranged a plurality of further bore holes 30 for connecting cross girder 20 or cross brace 21 (not shown).

Fig. 6 depicts a corner leg 27 made of six plates 29 which are straight and welded together. In a not shown embodiment up to 8 straight plates 29b are possible. Two straight plates 29b have a width which is same as the sum of width of two remaining straight plates 29b. Each straight plate 29b has essential equal width. One end of each straight plate 29b is formed such a way that a kink 31 is formed when the straight plates 29b are welded together. The straight plates 29b are welded together such a way that each of two wider straight plates 29b provides two flanges and welded together at one end. Two remaining straight plates 29b are welded to one of the wider straight plate 29b and the other two remaining straight plates 29b are welded to the other wider straight plate 29b. The aligned remaining straight plates 29b are welded together at one end. In result, an X-shaped corner leg 27b with four flanges is formed. The size of the flanges of X-shaped corner leg 27b can be equal or unequal. Latter will be described in more detail in Fig. 7. On top end and bottom end of X-shaped corner leg 27b are ar-ranged a plurality of bore holes 30 for connecting a further corner leg of any type. In middle section of X-shaped corner leg 27b are arranged a plurality of further bore holes 30 for connecting cross girder 20 or cross brace 21 (not shown).

Fig. 7 depicts an upper part of corner leg 27 with detailed view of corner leg flange size. Both described X-shaped corner legs 27a, b can have unequal flange size with a wider and smaller flange 28. These flanges 28 are arranged mirror-symmetrically to form X-shape. At the wider flange 28 the at least one cross girder 20 and/or cross brace 21 (not shown) are screwed via a plurality of bolts. Advantageously, if the smaller flange 28 is mounted in direction to the blade tip than the distance to the blade tip is increased.

Fig. 8 depicts a corner leg 27 made of a bent plate 29c. This bent plate 29c comprises a kink in middle section to form an L-shaped corner leg 27c. This kink is provide with any suitable method like bending, welding or screwing one or two bent plates 29c together. The L-shaped corner leg 27c has unequal sized flanges 28, wherein one flange is wider compared to the other. At the wider flange 28 the at least one cross girder 20 and/or cross brace 21 (not shown) are screwed via a plurality of bolts. Advantageously, if the smaller flange 28 is mounted in direction to the blade tip than the distance to the blade tip is increased. Even it is not shown, also the L-shaped corner leg 27c comprises on top end and bottom end a plurality of bore holes 30 for connecting a further corner leg of any type. In middle section of L-shaped corner leg 27c are arranged a plurality of further bore holes 30 for connecting cross girder 20 or cross brace 21 (not shown). Depending on size the bent plate 29c can also vary from shown angle a 90°, in particular the angle a can be between 60° to 120°, preferred a can be between 70° and 110° and more preferred a can be between 80° and 100°.

Fig. 9 depicts a corner leg assembly 22 comprising two L-shaped corner legs 27c connected with a connector 32 which can be a plate or profile. The connector 32 is arranged between the bent edge of the L-shaped corner legs 27c such a way to form an X-shaped corner leg assembly 22a. The L-shaped corner legs 27c have same design as described above, namely each has unequal flange size. At each wider flange of the L-shaped corner leg 27c a cross braces 21 are screwed. In shown embodiment two opposite arranged cross braces 21 are screwed to the wider flange 28. In same way also one or more cross girders 20 can be attached to the wider flange 28 of the L-shaped corner leg 27c.

Fig. 10 depicts an alternative embodiment for connecting cross braces 21 to corner leg 27. In this embodiment a connecting plate 33 is used. This connecting plate 33 can have any suitable shape which is suitable to connect the corner leg 27 with one or more cross braces 21. In preferred shown embodiment the connecting plate 33 is K-shaped. Advantageously, the cross braces 21 has not mounted directly to the flange of the corner leg 27. So the connecting plate 33 increases the area for screwing the corner leg 27 with the cross braces 21. In result higher loads can be managed. Same applies for cross girders 20. The connecting plate 33 can be used for all types of above-mentioned corner leg 27, namely for X-shaped corner leg 27a, b and L-shaped corner leg 27c.

Fig. 11 depicts an alternative embodiment for connecting two cross braces 21 to the L-shaped corner leg 27c. Same as mentioned-above the connecting plates 33 are K-shaped. Each cross brace 21 is connected with one K-shaped connecting plate 33. Between the cross braces 21 a filler plate 34 is arranged. A plurality of bolts are extending through the connecting plate 33, the cross brace 21, filler plate 34 and trough the opposite cross brace 21 as well as opposite connecting plate 33.

Same can also be applied to X-shaped corner leg assembly 22a as described in Fig. 9.

Fig. 12 depicts an alternative embodiment of corner leg assembly 22. The X-shaped corner leg assembly 22b comprises two L-shaped corner legs 27c as mentioned above and an additional angle bracket 36. The wider flange 28 of the L-shaped corner leg 27c is attached to the one flange of the angle bracket 36 and the wider flange 28 of the other L-shaped corner leg 27c is attached to the other flange of the angle bracket 36. They can be screwed and/or welded together. Fur-ther at the flanges of the angle bracket 36 one or more cross braces can be screwed. Therefore the angle bracket 36 is dimensioned such a way that the L-shaped corner legs 27c as well as the cross braces 21 can be attached. Same applies for the cross girders 20 (not shown). So the angle bracket 36 provides an increased area for screwing the cross braces 20 and/or cross girders 20.

Advantageously, all shown embodiments provides an increased area for mounting cross braces as well as cross girders to the corner leg to manage higher loads. At the same time the distance especially to the blade tip can be maximized which reduces the risk of a collision of the blade tip with the hybrid tower.

LIST OF REFERENCE SIGNS

1 wind turbine
2 tower
3 nacelle
4 drive train chain
5 rotor shaft
6 rotor
7 gear box
8 high-speed-shaft
9 generator
10 electrical components
11 yaw system
12 rotor blades
13 pitch system
14 nacelle cover
15 spinner
16 hub
17 tubular section
18 lattice section
19 adapter arrangement
20 cross girders
21 cross braces
22 corner leg assembly
22a X-shaped corner leg assembly
22b X-shaped corner leg assembly
23 longitudinal axis
24 tubular segments
25 kink area
26 lattice structure
27 corner leg
27a X-shaped corner leg
27b X-shaped corner leg
27c L-shaped corner leg
28 corner leg flange
29 plate
29a kinked plate
29b straight plate
29c bent plate
29a kinked plate
29b straight plate
29c bent plate
30 bore holes
31 kink
32 connector?
33 connecting plate
34 filler plate
35 bolts
36 angle bracket

, Claims:We Claim:

1. A corner leg for a lattice structure of a tower of a wind turbine, characterized by
- a plate (29) which is bent to form a L-shaped corner leg (27c) or
- at least two plates (29) which are kinked or straight, wherein the plates (29) are welded together such a way to form an X-shaped corner leg (27a, 27b).

2. The corner leg for a lattice structure of a tower of a wind turbine according to claim 1, wherein
- one or two bent plates (29c) have a kink to form a kinked L-shaped corner leg (27c) or
- the at least two plates (29a) which are kinked and welded together such a way to form kinked X-shaped corner leg (27a) or
- the at least two plates (29b) which are straight and welded together such a way to form kinked X-shaped corner leg (27b).

3. The corner leg for a lattice structure of a tower of a wind turbine according to claim 1 or 2, wherein X-shaped corner leg (27a, 27b) comprises three or six or eight plates (29a, 29b).

4. The corner leg for a lattice structure of a tower of a wind turbine according to claim 3, wherein
- if the X-shaped corner leg (27a) comprises three plates (29a) then the three plates (29a) are kinked and welded together to form the X-shaped corner leg (27a) or
- if X-shaped corner leg (27b) comprises six or eight plates (29b) then the six plates (29b) are straight and welded together to form the X-shaped corner leg (27b).

5. The corner leg for a lattice structure of a tower of a wind turbine according to claim 1 or 2, wherein the L-shaped corner leg (27c) or the X-shaped corner leg (27a, 27b) has unequal flange width for increasing area of screwed connection and for increasing blade tip distance.

6. The corner leg for a lattice structure of a tower of a wind turbine according to claim 5, wherein the unequal flanges of the L-shaped corner leg (27c) or the X-shaped corner leg (27a, 27b) having a longer flange width side for screwing a cross braces (21) to the corner leg (27).

7. The corner leg for a lattice structure of a tower of a wind turbine according to one of the claims 1 to 6, wherein the corner leg (27) comprises at least one clamping area for connecting secondary cross braces (21) by screws.

8. A lattice structure for a tower of a wind turbine comprising at least one corner leg (27) according to one of the claims 1 to 7, wherein the at least one corner leg (27) is screwed to lattice structure (26).

9. The lattice structure for a tower of a wind turbine according to claim 8, wherein the longer flange width side of L-shaped corner leg (27c) or of the X-shaped corner leg (27a, 27b) is screwed to a cross girder (20) and/or cross braces (21) of lattice structure (26).

10. The lattice structure for a tower of a wind turbine according to claim 8 or 9, wherein the lattice structure (26) comprises a kink area (25) and the at least one corner leg (27) screwed below and above kink area (25) to lattice structure (26) by using plates.

11. The lattice structure for a tower of a wind turbine according to one of the claims 8 to 10, wherein the corner leg (27) is screwed to the lattice structure (26) with a connecting plate (33).

12. A tower of a wind turbine comprises a lattice structure according to one of the claims 8 to 11 which comprises at least three corner leg assemblies (22, 22a, 22b) comprising at least one corner leg (27) according to one of the claims 1 to 7.

13. A wind turbine comprises a tower according to claim 12.

Dated this 14th day of March, 2024

For Suzlon Energy Limited

Nandan Pendsey
(IN/PA – 726)
Authorized Agent of the Applicant
To
The Controller of Patents
The Patents Office
Mumbai