Wind turbine blade

Abstract

A wind turbine blade has a tubular root portion having a proximal end defining a root end of the blade and a distal end located at a spanwise distance from the proximal end. The root portion includes a metal section extending from a proximal end to a distal end of the root portion, a fiber composite section extending from the distal end to a proximal end, and a transition section between the metal section and the fiber composite section. The metal section includes one or more metal sheets extending beyond the metal section into the transition section. The portion of the metal sheet located in the transition section is encapsulated within a fiber composite material that is continuous with the fiber composite material of the fiber composite material section. The metal section is connectable to a pitch bearing of a wind turbine hub.

Description

Technical Field

[0001] The present disclosure relates to a wind turbine blade and a method of manufacturing a root ring for a wind turbine blade. Background Art

[0002] Wind turbine blades for large horizontal axis wind turbines have a significant mass, which may be in the range of 10 tons or more, up to 30 tons or more.The wind turbine blades are fastened to a pitch bearing of the hub to form a rotor, which rotates on a main shaft to drive a generator.

[0003] The blades are typically connected to the inner or outer ring of the pitch bearing using a plurality of circumferentially spaced bolts extending into the root end of the blade in a direction parallel to the central axis of the root end of the blade. The stresses on the connection of the blade to the pitch bearing are considerable, mainly due to the effects of the blade mass and wind forces, and the permanent rotation of the rotor, which tends to change the degree and direction of the forces on the blade with each rotation of the rotor. Vibrations in the system may also be considerable.

[0004] With an expected life of 20 years or more, the fatigue performance of the blade to pitch bearing connection is critical. The bolt is usually connected to the blade root via a threaded metal bushing embedded in the fiber composite material at the root end of the blade. This bushing is usually cylindrical and usually made of steel. The bushing transfers the load from the composite material of the blade to the bolt, which then transfers the load to the hub via the pitch bearing.

[0005] The manner in which the blade root is connected to the pitch bearing is critical, given the load bearing and fatigue requirements imposed on the connection of the blade to the pitch bearing. However, in the known attachment methods, the best way to use the component parts is to not lead to over-engineering and use large safety factors. For example, the above-mentioned bushings are usually held in place by adhesives, which are subjected to constantly changing tensions in use. It is well known that adhesives are not best suited to such conditions. Similarly, the bolts connecting the pitch bearing to the blade are subjected to tensile and bending loads, rather than the shear loads for which they are more suitable.

[0006] It is desirable to increase the length of wind turbine blades so that each wind turbine can extract more energy from the wind to help reduce our reliance on fossil fuels. However, current methods of blade / hub connection as described above limit the extent to which this can be achieved.

[0007] A schematic diagram of a prior art wind turbine blade construction is shown in Figure 1. The wind turbine blade 10 shown in Figure 1 comprises a blade shell 13 consisting of a windward shell 17 and a leeward shell 18, which are connected together to form the blade shell 13. Both half shells comprise a fiberglass composite root 9, wherein the remainder of the half shells 17, 18 is made of balsa and / or polyurethane foam core material, which is adhered to a fiberglass composite skin.

[0008] Each half shell 17, 18 includes one or more spanwise extending beams or spar caps 22 to provide bending strength to the wind turbine blade 10. The spar caps 22 typically include carbon fiber composite materials due to their light weight and rigid material properties. Shear webs (not shown) extend between opposing spar caps 22 on the windward side 17 and the leeward side 18 of the blade shell 13 and may be made of glass fiber composite materials. The shear webs bear the shear loads of the wind turbine blade 10.

[0009] Most of the loads carried by the wind turbine blade 10 are carried by the spar cap 22 in a substantially straight load path. These loads must be transferred to the wind turbine hub via the root 9 and the pitch bearing. The root 9 is attached to the pitch bearing by a plurality of circumferentially spaced bolts 15 located in a ring around the root end 12 of the root 9. In order to avoid undesirable load peaks that may cause material failure, it is necessary to gradually disperse the load from the spar cap 22 around the entire circumference of the root end 12. In order to achieve this, a large amount of glass fiber composite material is required in the area between the end 24 of the spar cap 22 and the root end 12. In addition, the end 24 of the spar cap 22 must be located at a sufficient spanwise distance away from the root end 12 so that the load can be adequately distributed around the entire circumference of the root end 12. This is schematically shown in Figure 1 by the load line 20.

[0010] It would be desirable to increase the amount of load that the root of a wind turbine blade can carry. However, current methods of wind turbine blade design and construction limit the extent to which this can be achieved.

[0011] It is against this background that the present invention has been developed. Summary of the invention

[0012] The present invention provides a wind turbine blade, which has a root end, a tip end, a leading edge and a trailing edge, the blade extending from the root end to the tip end in the span direction, the blade comprising a tubular root portion, the tubular root portion having a proximal end defining the root end of the blade and a distal end located at a span-wise distance from the proximal end, wherein the root portion comprises: a metal section extending from the proximal end of the root portion toward the distal end of the root portion; a fiber composite material section extending from the distal end of the root portion toward the proximal end of the root portion; and a transition section extending between the metal section and the fiber composite material section, wherein the metal section comprises one or more metal sheets, a portion of the one or more metal sheets extending beyond the metal section into the transition section, wherein a portion of the one or more metal sheets located in the transition section is encapsulated in a fiber composite material, the fiber composite material being continuous with the fiber composite material of the fiber composite material section, wherein the metal section can be connected to a pitch bearing of a wind turbine hub.

[0013] The wind turbine blade of the present invention provides a number of advantages over the prior art. In particular, the strength and stiffness of the root can be adjusted for a specific application by varying the size and profile of the metal sheets and / or the number of metal sheets. Thus, wind turbine blades with roots of different capacities can be designed and manufactured without the need to change the overall dimensions of the root. This is beneficial for the purpose of standardization and overcoming design restrictions imposed by road transport considerations, such as the height of bridges.

[0014] Additionally, because the metal section of the root is much stiffer than the prior art fiberglass root, the spanwise innermost end of the carbon fiber spar cap within the blade shell can be positioned closer to the root than was possible in the prior art. Thus, the stiffness of the entire wind turbine blade can be increased when the carbon fiber spar cap can extend closer to the stiffer root. The metal section of the root can withstand higher peak loads than is possible with the prior art fiberglass root, which means that less glass can be used in the construction of the root, resulting in cost and environmental benefits.

[0015] Optionally, the cross-sectional area of ​​the metal segment in a direction perpendicular to the spanwise extension axis of the metal segment comprises at least 90% of metal to allow the preload (e.g. bolts if used) to be generated and maintained throughout the service life of the wind turbine blade. Preferably, the cross-sectional area of ​​the metal segment in a direction perpendicular to the spanwise extension axis of the metal segment comprises at least 95% of metal, more preferably at least 98% of metal, most preferably at least 99% of metal.

[0016] The one or more metal sheets are optionally thinner relative to their spanwise dimension in a direction parallel to the spanwise extension axis of the metal section, such that the thickness of the one or more metal sheets is no more than 25% of the spanwise dimension, preferably no more than 10% of the spanwise dimension, more preferably no more than 5% of the spanwise dimension, still more preferably or no more than 1% of the spanwise dimension, and most preferably no more than 0.1% of the spanwise dimension. The use of thin metal sheets is beneficial in manufacturing because they can be more easily shaped and manipulated.

[0017] Portions of one or more metal sheets located in the transition section may taper toward the fiber composite section to help reduce stress risers caused by material discontinuities.

[0018] In one example, the portion of one or more metal sheets located in the transition section includes a plurality of radially extending features relative to the spanwise extension axis of the metal section.Such radial features are beneficial because they help improve the integrity of the connection between the fiber composite metal sheets or sheets.

[0019] Optionally, the radially extending formations comprise a plurality of protrusions located on the surface of the portion of the one or more metal sheets located in the transition section.Such protrusions help to anchor the fiber composite material to the one or more metal sheets.

[0020] The metal segment optionally comprises a continuous spiral of metal sheet material which is bent to form the multiple layers of metal sheet material.By using a continuous spiral of metal sheet material, multiple layers of metal sheet can be easily formed.

[0021] The metal section may comprise multiple layers of metal sheets arranged on top of each other. This arrangement is beneficial because the number and surface area of ​​metal to fiber composite interfaces increases with the number of layers of metal sheets, thereby providing a stronger connection between the metal section and the fiber composite section. The number of layers of metal sheets may be selected depending on the intended use and size of the wind turbine blade.

[0022] In one example, each layer of metal sheet includes formations that engage with complementary formations on metal sheets located in adjacent layers.Such formations are advantageous because they increase friction between the layers and may also provide an interlocking function depending on the configuration of the formations.

[0023] Optionally, a portion of some or all of the layers of the metal sheet extend beyond the metal section into the transition section, so that some layers may end at the intersection of the metal section and the transition section, while other layers extend from the metal section into the transition section, thereby providing greater design options for optimization of the blade structure according to the use requirements of the blade structure.

[0024] Each portion of the layer of metal sheet extending into the transition section optionally extends into the transition section by the same amount, or optionally extends into the transition section by a different amount than adjacent portions of the metal sheet, thereby providing adjustability for optimization of the blade design.

[0025] In one example, the fiber composite section tapers toward a distal end of the tubular root portion to facilitate integration of the root portion into a wind turbine blade by providing a spanwise extended surface for a fiber composite to fiber composite interface and reduction of geometric stress concentrations.

[0026] Optionally, the wind turbine blade comprises a plurality of bolt holes extending radially through the metal segment from an inner circumferential surface of the metal segment to an outer circumferential surface of the metal segment relative to a spanwise extension axis of the metal segment. The root metal segment facilitates the use of radially extending bolts rather than spanwise extending bolts. This is beneficial because radially extending bolts are able to withstand shear loads rather than tensile and bending loads.

[0027] The inner circumferential surface and the outer circumferential surface of the metal segment are surfaces extending in the span direction.

[0028] In another aspect, the invention provides a component for a wind turbine, comprising: a wind turbine blade according to any of the preceding claims; and an inner ring or outer ring of a pitch bearing connected to a metal section of the wind turbine blade, wherein a circumferential surface of the inner ring or outer ring is in contact with a circumferential surface of the metal section of the wind turbine blade. The connection of the circumferential surface of the metal section to the ring of the pitch bearing is advantageous because the surface area of ​​the interface can be larger than that possible with a butt connection of the prior art, thereby allowing a greater load distribution and reducing load peaks. Such a connection allows loads to be transferred in shear in addition to tension and bending.

[0029] The circumferential surfaces of the inner ring and the outer ring are surfaces extending in the span direction.

[0030] Optionally, the inner ring or outer ring includes an annular groove in which the metal segment is received. In another option, the inner ring or outer ring, whether it includes an annular groove or not, may include one or more parts connected together. Each option is beneficial for design optimization and construction purposes.

[0031] The metal segments may optionally be connected to the inner or outer ring by a friction connection, which may be a shrink fit connection.Such a connection may be used alone or in addition to a bolt connection.

[0032] In one example, the assembly comprises a plurality of bolts extending through the metal segment into the inner ring or the outer ring. Optionally, the bolts extend radially relative to the spanwise extension axis of the metal segment.

[0033] The circumferential surface of the inner or outer ring may include a surface configuration that engages with a complementary surface configuration on the circumferential surface of the metal segment. Such configurations are beneficial because they increase the friction between the ring and the metal segment and may also provide an interlocking function depending on the configuration of the surface configuration.

[0034] In one example, the inner or outer ring includes a proximal end defining a hub end of the ring and a distal end located at a spanwise distance from the proximal end, wherein the ring includes: a hub section extending from the proximal end of the ring toward the distal end of the ring; and a bladewards section extending from the distal end of the ring toward the proximal end of the ring; wherein the circumferential surface of the ring in contact with the circumferential surface of the metal section is completely located in the bladewards section of the ring, and wherein the hub section of the ring is configured to operably engage the inner or outer ring of the pitch bearing. In this way, loads transmitted from the blades to the ring can be at least partially separated from loads transmitted from the ring to the hub via bearing elements (e.g., spherical rollers) and another ring of the pitch bearing.

[0035] In another aspect, the present invention provides a wind turbine comprising: a hub; a pitch bearing connected to the hub; and a plurality of wind turbine blades as described above, which are connected to an inner ring or an outer ring of the pitch bearing via a circumferential surface of a metal segment, or a plurality of assemblies as described above, which are operably engaged with the inner ring or the outer ring of the pitch bearing.

[0036] Within the scope of the present application, it is expressly intended that the various aspects, examples and alternatives set forth in the preceding paragraphs, claims and / or the following description and drawings, and in particular the individual features thereof, may be understood independently or in any combination. That is, all examples and / or features of any example may be combined in any manner and / or combination, unless these features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Examples of the present invention are described below with reference to the accompanying drawings, in which:

[0038] FIG1 shows a schematic diagram of a portion of a prior art wind turbine blade configuration;

[0039] Figure 2 A schematic diagram of a wind turbine is shown;

[0040] Figure 3 A schematic diagram of a wind turbine blade is shown;

[0041] Figure 4 A schematic cross-sectional view showing the root end of a wind turbine blade attached to an inner ring of a pitch bearing;

[0042] Figure 5a schematic partial cross-sectional view showing an alternative root end configuration attached to an outer ring of a pitch bearing;

[0043] Figure 6 A schematic partial cross-sectional view showing another alternative root end configuration;

[0044] Figures 7a to 7c a schematic partial cross-sectional view showing a further alternative root end configuration attached to an alternative example of a pitch bearing;

[0045] Figure 8 A schematic diagram showing a portion of a wind turbine blade configuration;

[0046] Figure 9a A schematic isometric view showing a manufacturing method for a root portion of a wind turbine blade;

[0047] Figure 9b Shows Figure 9a A schematic cross-sectional view of a manufacturing method of ;

[0048] Fig.9c Shown for Figure 9a A schematic cross-sectional view of a sheet material layer of a manufacturing method of the invention; and

[0049] Fig.10 A schematic partial cross-sectional view of the root of a wind turbine blade is shown. DETAILED DESCRIPTION

[0050] The following detailed description refers to the accompanying drawings, which show by way of illustration specific details and examples in which the present invention may be practiced. These embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the present invention. Other examples may be utilized, and structural changes may be made without departing from the scope of the present invention as defined in the appended claims.

[0051] Figure 2 A wind turbine 1 is shown. The wind turbine 1 comprises a nacelle 2 supported on a substantially vertical tower 4, which itself comprises a plurality of tower sections 5. The nacelle 2 houses a plurality of functional components, including a gearbox and a generator (not shown), and supports a main rotor arrangement 6. The main rotor arrangement 6 comprises a hub 8 and a plurality of wind turbine blades 10 connected to the hub 8. In this example, the wind turbine 1 comprises three wind turbine blades 10.

[0052] Figure 3A schematic diagram of a wind turbine blade 10 is shown. The wind turbine blade 10 comprises a blade shell 13 consisting of a windward half shell 17 connected to a leeward half shell 18. The wind turbine blade 10 extends from a root end 12 to a tip end 11, and each half shell 17, 18 has a tip end 19 and a hub end 21. The root end 12 is configured to be attached to a hub 8. A leading edge 14 and a trailing edge 16 extend between the root end 12 and the tip end 11 in the span direction.

[0053] Figure 4 A schematic cross-sectional view of a root 29 of a wind turbine blade attached to an inner ring 41 of a pitch bearing 40 is shown. The root 29 comprises a tubular root portion having a proximal end 35 defining a root end 12 of the blade and a distal end 25 located a spanwise distance X from the proximal end 35. The root 29 comprises a metal section 30 extending from the proximal end 35 of the root 29 towards the distal end 25 of the root 29, and a fiber composite section 32 extending from the distal end 25 of the root 29 towards the proximal end 35 of the root 29. A transition section 31 extends between the metal section 30 and the fiber composite section 32.

[0054] The metal section 30 is defined by a first portion 34 of a metal sheet 33. A second portion 36 of the metal sheet 33 extends from the first portion 34 into the transition section 31 such that the metal sheet 33 extends from a proximal end 35 of the root 29 to an outermost spanwise end 37 of the transition section 31, the outermost spanwise end 37 being located a spanwise distance Y from the proximal end 35. The metal sheet 33 is bent about the spanwise axis 28 of the root 29 such that the metal sheet follows the circumferential bend of the root end 12.

[0055] The first portion 34 of the metal sheet 33 may have a constant thickness and the second portion 36 may have a varying thickness that tapers away from the first (or constant thickness) portion 34 toward the outermost spanwise end 37 of the transition section 31 .

[0056] The second portion 36 of the metal sheet 33 in the transition section 31 is encapsulated in a fiber composite material 38 that is continuous with the fiber composite material 38 of the fiber composite section 32. The thickness of the fiber composite material 38 in the transition section 31 varies along the length of the transition section 31, such that the total thickness of the fiber composite material 38 at the innermost spanwise end 39 of the transition section 31 is less than the total thickness of the fiber composite material 38 at the outermost spanwise end 37 of the transition section 31. Thus, the minimum thickness of the fiber composite material 38 in the transition section 31 is located near the thickest section of the metal sheet 33 in the transition section 31, and the maximum thickness of the fiber composite material 38 in the transition section 31 is located near the thinnest section of the metal sheet 33 in the transition section 31. In this example, the thickness of the root 29 may remain constant from the innermost spanwise end 39 of the transition section 31 to the outermost spanwise end 37 of the transition section 31. In other examples, the thickness of the root portion 29 may vary from the innermost spanwise end 39 to the outermost spanwise end 37 of the transition section 31 , depending on design choice.

[0057] It should be understood that for the sake of clarity, the Figure 4 The thickness of the fiber composite material 38 shown in FIG. 1 and the thickness of the transition section 31 along its span may be largely the same as the first portion 34 of the metal sheet 33 forming the metal section 30. However, it should also be understood that this is not required and that the relative thicknesses of the metal section 30, transition section 31 and fiber composite section 32 need not be the same, depending on design choice.

[0058] The fiber composite material 38 is a glass fiber composite material, which is a commonly used material in the manufacture of wind turbine blades. However, any suitable fiber composite material may be used. In one example, the fiber material is a pre-impregnated fiber material. In another example, the fiber material is a dry fiber material that is infused with resin and cured to form the composite material 38.

[0059] The metal sheet 33 is relatively thin relative to its spanwise dimension Y. For example, the thickness of the metal sheet 33 at the root end 35 may be 30 mm, and its spanwise dimension may be 650 mm. Preferably, the thickness of the metal sheet 33 is no more than 25% of its spanwise dimension. Preferably, the thickness of the metal sheet 33 is no more than 10% of its spanwise dimension, more preferably no more than 5% of its spanwise dimension, more preferably still no more than 1% of its spanwise dimension, and most preferably no more than 0.1% of its spanwise dimension. It is conceivable that the thickness of the metal sheet 33 at the root end 35 may be up to about 50 mm, and its spanwise dimension may be up to about 1000 mm. However, if the thickness of the metal sheet 33 does not exceed 25% of its spanwise dimension, dimensions outside this range may be used.

[0060] As will be described in more detail below, the metal sheet 33 can be formed by a metal sheet wound around a mandrel to form a tubular structure. Alternatively, the metal sheet 33 can be one of a plurality of metal sheets 33 positioned side by side to form a tubular structure. In each case, one or more metal sheets can be connected together by any suitable method, such as by welding or by an interlocking structure located on the spanwise edges of the metal sheets. Alternatively, one or more metal sheets can be held in place by a fiber composite material 38 that encapsulates a variable thickness portion 36 of one or more metal sheets located in the transition section 31.

[0061] like Figure 4 As shown, the metal segment 30 includes an outer circumferential surface 48 in contact with the inner circumferential surface 49 of the inner ring 41 of the pitch bearing 4. The metal segment 30 includes a plurality of bolt holes 46, which extend radially from the inner circumferential surface 47 of the metal segment 30 through the metal segment 30 to the outer circumferential surface 48 relative to the spanwise extension axis 28 of the metal segment 30. The metal segment 30 can be connected to the inner ring 41 of the pitch bearing 40 by radially extending bolts 45, which extend through the bolt holes 46 and enter the bearing ring 41. In this way, the bolts 45 are mainly subjected to shear loads, rather than tension and bending loads as in the prior art connection method.

[0062] In reference Figure 4 In the depicted example, the root 29 is connected to an inner ring 41 of a pitch bearing 40. It will be appreciated that this is not essential and the root 29 may be connected to an outer ring 42 of a pitch bearing 40 depending on the particular pitch bearing design.

[0063] Four bolts 45 in Figure 445 are shown aligned with each other in the cross-sectional view of the root 29. However, it should be understood that this is only an example and there may be only two bolts 45 or more than four bolts 45 in any particular spanwise cross-section of the root 29. It should be understood that the metal section 30 of the root 29 is connected to the inner ring 41 of the pitch bearing 40 by a plurality of bolts 45 spaced around the entire periphery of the metal section 30. There is also a friction connection between the outer peripheral surface 48 of the metal section 30 and the inner peripheral surface 49 of the inner ring 41. This friction connection is generated by the tension generated by the bolts 45 when tightening. Since the metal section 30 and the bolts 45 are made of elastic metal material, both the metal section 30 and the bolts 45 are slightly deformed when the bolts are tightened, so that residual force is generated due to the elastic material of the metal section 30 and the bolts 45 trying to restore their original shape. This is called "preload". The preload force causes the inner ring 41 and the metal section 30 to be pulled tightly together, generating friction between them. This frictional force serves to securely fix the metal section 30 of the root 29 to the inner ring 41. This is an important enabler for the successful design and use of wind turbine blades of greater lengths than prior art connection methods.

[0064] In an alternative example, the metal section 30 may be fully or partially covered by the fiber composite material 38, so that the inner ring 41 of the pitch bearing 40 contacts the fiber composite material 38 instead of the metal sheet material 33 of the metal section 30. In this case, the cross-sectional area of ​​the metal section 30 in a direction perpendicular to its spanwise extension axis 28 may comprise at least 90% metal to generate and maintain the preload of the bolt 45 throughout the service life of the wind turbine blade 10. Preferably, the cross-sectional area of ​​the metal section 30 may comprise at least 95% metal, more preferably at least 98% metal, and most preferably at least 99% metal.

[0065] If the cross-sectional area of ​​the metal section 30 comprises less than 90% metal, the above and Figure 4 , because the root 29 is still securely fixed to the inner race 41 by the bolts 45 which mainly bear the shear load.

[0066] In the above example, the root 29 may be connected to the inner ring 41 or the outer ring 42 of the pitch bearing 40. It should be understood that the inner ring 41 or the outer ring 42 may include one or more components connected together to form a complete ring 41, 42. For example, the pitch bearing ring 41, 42 may include a plurality of components connected together to form a complete ring 41, 42. Figure 4The first and second portions of the pitch bearing rings 41, 42 may be connected to each other by any suitable method, including by connecting circumferential surfaces in a manner similar to the connection between the root end 29 and the first portion of the inner ring 41 or the outer ring 42. Alternatively, the first portion may be connected to the second portion by a stud bolt extending in the span direction. The use of pitch bearing rings 41, 42 comprising two or more component parts connected together is contemplated and applicable to all examples described herein.

[0067] Figure 5 Shows something like Figure 4 Schematic cross-sectional view of the root structure of an example of , in which the metal sheet 33 is replaced by a plurality of metal sheets 33. Thus, Figure 5 An example construction of Figure 4 A preferred example of an example construction.

[0068] Just as an example, Figure 5 The root 29 of the pitch bearing 40 is attached to the outer ring 42 of the pitch bearing 40. It should be understood that in an alternative configuration, the root 29 may be attached to the inner ring 41 of the pitch bearing 40. Note that like reference numerals are used throughout this specification to indicate like components.

[0069] Figure 5 The root 29 is identical in all respects to Figure 4 The root 29 is the same as Figure 5 The root 29 of the present invention comprises a plurality of metal sheets 33 arranged one above the other. Thus, the root 29 comprises a metal section 30 extending from a proximal end 35 of the root 29 toward a distal end 25 of the root 29, and a fiber composite material section 32 extending from a distal end 25 of the root 29 toward a proximal end 35 of the root 29. A transition section 31 extends between the metal section 30 and the fiber composite material section 32.

[0070] The metal section 30 is defined by a first portion 34 of the metal sheet 33. The second portion 36 of the metal sheet 33 extends into the transition section 31 such that each metal sheet 33 extends from a proximal end 35 of the root 29 to an outermost spanwise end 37 of the transition section 31, the outermost spanwise end 37 being located a spanwise distance Y from the proximal end 35. The metal sheet 33 is bent about the spanwise axis of the root 29 such that the metal sheet follows the circumferential bend of the root end 12.

[0071] The first portion 34 of each metal sheet 33 may have a constant thickness, and each second portion 36 may have a varying thickness that tapers away from the constant thickness portion 34 toward the outermost spanwise end 37 of the transition section 31 .

[0072] The second portion 36 of the metal sheet 33 located in the transition section 31 is encapsulated in a fiber composite material 38 which is continuous with the fiber composite material 38 of the fiber composite material section 32. The second portion 36 of each metal sheet 33 is interlaced with the fiber composite material 38 in the transition section 31. Figure 5 In the example shown, the fiber composite material forms the outermost layer of the transition section 31. In an alternative example, the second portion 36 of the metal sheet 33 may form the outermost layer of the transition section 31.

[0073] The metal sheets 33 are thin relative to their spanwise dimension Y. For example, the thickness of the metal sheets 33 may be 3 mm, and their spanwise length may be 650 mm. Preferably, the thickness of the metal sheets 33 is no more than 25% of their spanwise dimension. More preferably, the thickness of the metal sheets 33 is no more than 10% of their spanwise dimension, more preferably still no more than 5% of their spanwise dimension, further more preferably no more than 1% of their spanwise dimension, and most preferably no more than 0.1% of their spanwise dimension. It is conceivable that the thickness of the metal sheets 33 may be as low as 0.5 mm, and their spanwise dimension may be as low as 100 mm. However, if the thickness of the metal sheets 33 does not exceed 25% of their spanwise dimension, dimensions outside this range may be used.

[0074] The metal sheet 33 can be formed by a continuous metal sheet, which is spirally wound around a mandrel to form a tubular structure. Alternatively, the metal sheet 33 can include a plurality of metal sheets 33, which are positioned side by side and one on top of another to form a tubular structure. In this case, the metal sheets 33 can be offset relative to each other around the periphery of the tubular structure so that the edge of the metal sheet 33 in one layer is not aligned with the end of the metal sheet 33 in the adjacent layer. The metal sheets 33 can be connected together by any suitable method, such as by welding or by an interlocking structure located on the spanwise edge of the metal sheet 33. Alternatively, the metal sheet 33 can be held in place by a fiber composite material 38, which encapsulates the second portion 36 of the metal sheet 33 located in the transition section 31.

[0075] As mentioned above about Figure 4 As described, Figure 5 A preferred example of comprises a plurality of bolt holes 46 extending through the metal section 30. The metal section 30 is connected to the outer ring 42 of the pitch bearing 40 by bolts 45 extending radially.

[0076] As mentioned above Figure 4As discussed in the example of , friction connection also exists between the inner surface 47 of the metal segment 30 and the outer surface 50 of the outer ring 42. Friction connection also exists between the contact surfaces of the plurality of metal sheets 33. As described above, when the bolt 45 is tightened, friction connection is generated by the preload of the bolt 45.

[0077] In an alternative example, the metal segment 30 may include a small amount of composite material 38 located between one or more metal sheets of the metal segment 30 and / or on the outermost metal sheets. In this case, the cross-sectional area of ​​the metal segment 30 in a direction perpendicular to the spanwise extension axis of the metal segment 30 must include at least 90% metal to generate and maintain the preload of the bolt 45 throughout the service life of the wind turbine blade 10. Preferably, the cross-sectional area of ​​the metal segment 30 may include at least 95% metal, more preferably at least 98% metal, and most preferably at least 99% metal. As described above with respect to Figure 4 As discussed above, if the cross-sectional area of ​​the metal section 30 comprises less than 90% metal, the above and Figure 5 The connection method shown, because the root 29 is still securely fixed to the outer ring 42 by the bolts 45 which mainly bear the shear load.

[0078] Figure 6 Another example of a root 29 is shown, which is similar in all respects to Figure 5 The root 29 is the same as that of Figure 5 Thus, Figure 6 An example construction of Figure 5 A preferred example of an example construction.

[0079] exist Figure 6 In the example of FIG. 3 , the first sections 34 of the metal sheet 33 may each have a constant thickness and a textured second portion 36 extending into the transition section 31 .

[0080] In this example, the outer surface of the second portion 36 of the metal sheet 33 includes a plurality of formations 53 extending radially relative to the spanwise extension axis of the metal segment 30. The radially extending formations 53 include a plurality of discrete protrusions having a generally spike-like configuration. It should be understood that the formations 53 may have any suitable form, including, for example, cylindrical, round, or square sides. In another example, the formations 53 may be formed by roughening the surface of the second portion 36 of the metal sheet 33. In another example, the formations 53 may include parallel or intersecting grooves, such as may be seen on a rasp or file.

[0081] The second portion 36 of the metal sheet 33 located in the transition section 30 is encapsulated in a fiber composite material 38 that is continuous with the fiber composite material 38 of the fiber composite material section 32 of the root 29. The second portion 36 is interleaved with the fiber composite material 38 in the transition section 31. The formation 53 helps to improve the integrity of the connection between the fiber composite material 38 and the second portion 36 of the metal sheet 33. However, it should be understood that the formation 53 is not required, and that a portion or all of the metal sheet 33 located in the transition section 31 may not include the formation 53. Similarly, each side of the second portion 36 does not have to include the formation 53, and in some examples, only one side of the second portion 36 may include the formation 53.

[0082] In one exemplary construction method, the depth of the fiber material can match the depth of the step 51 in the metal sheet 33 located at the spanwise outermost end 54 of the metal segment 30, and match the depth of the spanwise outermost end 52 of the second portion 36, so that the fiber material can be easily interleaved with the second portion 36 during layup. For example, the step 51 can have a depth of 0.5 mm, the second portion 36 can have a depth of 0.5 mm (excluding the construction 53), and the fiber material can have a depth of 0.5 mm. However, this is not required, and any other suitable dimensions and layup methods can be used.

[0083] The metal sheets 33 are thin relative to their spanwise dimensions. For example, the metal sheets 33 may be 1.5 mm thick at the proximal end 35 of the root 29 and their spanwise dimensions may be 650 mm.

[0084] Figures 7a to 7c Shows Figure 5 A schematic partial cross-sectional view of another example variation of the root structure of. Figure 7a In the example of Figure 4 and Figure 5 The inner ring 41 of the pitch bearing 40 is attached to the inner ring 41 of the pitch bearing 40 in the same manner as discussed. In this example, the metal sheet 33 of the metal segment 30 includes a formation 56 that engages with a complementary formation 56 located on an adjacent layer of the metal sheet 33. In addition, the inner surface of the inner bearing ring 41 may include a complementary surface formation 57 that engages with the surface formation 56 of the metal segment 30.

[0085] The surface texture 56 provides an interlock between adjacent layers of the metal sheets 33 and between the outer surface of the metal portion 30 and the inner surface of the inner ring 41 of the pitch bearing. Figure 7a In the example shown, radially extending bolts 45 are shown connecting the metal portion 30 to the inner ring 41. However, the bolts 45 may be omitted, with the connection between the root 29 and the inner ring 41 being provided entirely by the interlocking formations 56,57.

[0086] exist Figure 7a In the example of FIG. 5 , the innermost surface 47 of the metal segment 30 is shown as having a formation 56 thereon. It should be understood that the surface may alternatively not include the formation 56.

[0087] like Figure 7a The portion of the metal sheet 33 shown in the transition section 31 of the root 29 can be compared with the above description of Figure 5 In an alternative example, the portion of the metal sheet 33 located in the transition section 31 may also include a formation 56 to help improve the connection between the metal sheet 33 and the fiber composite material 38. The formation 56 in the metal section 30 and optionally in the transition section 31 may include the above-mentioned Figure 6 The discrete structures 53 described may be continuous structures, such as curves or waves. Alternatively, the structures 56 may be formed by roughening the surface of the metal sheet 33 (e.g., by abrasive / sandblasting). In another example, the structures 56 may include parallel or intersecting grooves, such as may be seen on a wood rasp or file.

[0088] exist Figure 7b In the example, root 29 is consistent with the above Figure 5 Same as described above and with Figure 4 and Figure 5 The inner ring 41 of the pitch bearing 40 is attached to the inner ring 41 of the pitch bearing 40 by bolts 45 in the same manner as discussed above. In this example, the inner ring 41 is elongated and includes a proximal end 60 defining a hub end of the inner bearing ring 41 and a distal end 61 located at a spanwise distance from the proximal end 60. A hub-facing section 62 of the inner bearing ring 41 extends from the proximal end 60 toward the distal end 61, and a blade-facing section 63 of the inner bearing ring 41 extends from the distal end 61 toward the proximal end 60.

[0089] The circumferential outer surface 48 of the metal section 30 contacts the circumferential inner surface 49 of the inner ring 41 only in the blade-facing section 63 of the inner ring 41, so that the contact circumferential surfaces 48, 49 are completely located in the blade-facing section 63. The hub-facing section 62 of the inner ring 41 operably engages the outer ring 42 of the pitch bearing via bearing elements (e.g., spherical rollers) 43 located between the inner ring 41 and the outer ring 42 of the pitch bearing 40. This arrangement helps to decouple the loads transmitted from the root 29 to the inner ring 41 from the bearing elements 43, thereby reducing the forces they encounter in use.

[0090] Figure 7c An example similar to Figure 7bThe example of the present invention is shown in Figure 1, except that the inner bearing ring 41 includes an annular groove 70, in which the metal segment 30 of the root 29 is received. In this example, the metal segment 30 of the root 29 can be attached to the inner ring 41 by bolts 45 alone (bearing mainly shear forces), or the bolts 45 can be preloaded as described above to generate friction between multiple layers and the circumferential outer surface of the metal segment 30 and the circumferential inner surface of the groove 70.

[0091] In this example, and in all the examples described above, the metal section 30 of the root 29 may be attached to the inner ring 41 or outer ring 42 of the pitch bearing 40 by a shrink fit connection, wherein the inner ring 41 or outer ring 42 is heated so that it expands, the metal end 30 of the root 29 is positioned in or around the inner ring 41 or outer ring 42, as the case may be, or in the groove 70, and the rings 41, 42 are allowed to cool so that a shrink fit connection is formed between the rings 41, 42 and the metal section 30 of the root 29. This may also be achieved by cooling the metal section 30 of the root 29 and allowing it to preheat before positioning it in or around the rings 41, 42. If a shrink fit connection is used, the bolts 45 may be omitted. Alternatively, the bolts 45 may be used for additional security.

[0092] Reference now Figure 8 , shows a schematic diagram of a wind turbine blade 10 including a root portion 29 connected to a blade shell 13. The root portion 29 is as described above with reference to Figures 4 to 7c Because the metal section 30 of the root 29 is much stiffer than the glass fiber root of the prior art, the spanwise innermost end 24 of the carbon fiber spar cap 22 can be located closer to the root 29 than was possible in the prior art. Therefore, as the carbon fiber spar 22 can extend closer to the stiffer root 29, the stiffness of the entire wind turbine blade 10 is increased. This is beneficial to the efficiency of the wind turbine blade 10. The metal section 30 of the root 29 is able to withstand higher peak loads than the glass fiber root of the prior art could withstand. This is advantageous because it allows less glass to be used in the construction of the root 29, thereby providing cost and environmental benefits.

[0093] In addition to these advantages, the above-described root configuration has an additional benefit in that the integrity of the bond between the various layers of the root wall can be checked throughout the depth of the root wall by ultrasonic non-destructive testing (NDT) methods. This is not possible with a root that includes conventional spanwise extending bolt holes because the ultrasonic NDT equipment cannot "see" the void formed in the glass fiber composite material in which the insert for the stud bolt insert is received.

[0094] Figure 9a A schematic diagram showing a method of manufacturing the root ring 80 (see Fig.10 ), Figure 9b Shows Figure 9a Schematic cross-sectional view of the manufacturing method. Fig.10 Shown by Figure 9a and Figure 9b A schematic cross-sectional view of a root ring 80 manufactured by the method.

[0095] As will be described in more detail below, the root ring 80 is incorporated into a stack of blade shells 13 to form the root 29 of the completed wind turbine blade 10. Thus, the root ring 80 includes a hub-toward end 81 and a tip-toward end 82 (relative to the position of the root ring 80 in the completed wind turbine blade 10), the root ring 80 extending in the spanwise direction from the hub-toward end 81 to the tip-toward end 82.

[0096] The root ring 80 is formed with multiple layers of metal sheets 33, which are arranged one on top of another, so that the root ring 80 forms the root 29 when incorporated into the blade shell 13, as described above with respect to Figures 5 to 7c The completed root ring 80 comprises the metal section 30 , the transition section 31 and the fiber composite material section 32 .

[0097] Reference Figures 9a to 9c , the root ring 80 is manufactured on the mandrel 90 by interlacing and winding the metal sheet material 33 and the sheet fiber material 98 around the mandrel 90. Once wound onto the mandrel 90, the metal sheet material 33 forms the metal sheet layer of the root ring 80. Figure 9b Only the metal sheet material 33 wound around the mandrel 90 is shown in FIG. 8 , as the cross section is taken through a plane of the mandrel 90 corresponding to the location of the metal segments 30 forming the root ring 80 .

[0098] like Fig.9c As shown, the metal sheet material 33 may include a first constant thickness portion 34 and a second variable thickness portion 36. The metal sheet material 33 is wound onto the mandrel 90 in multiple layers so that the first portion 34 forms the metal section 30 of the root ring 80 and the second portion 36 is located in the transition section 31 of the root ring 80.

[0099] The metal sheet material 33 may have a thickness of 3 mm throughout the first portion 34 and a spanwise dimension Y of 650 mm. For example, if ten layers of such metal sheet material 33 are wound onto the mandrel 90, the metal section 30 of the root ring 80 will have a radial depth (relative to the spanwise extension axis of the root ring 80) of 30 mm, and the transition section 31 will include eighteen to twenty metal to composite fiber interfaces 83 (depending on the material forming the outermost layer of the transition section 31).

[0100] In another example, the metal sheet material 33 may have a thickness of 0.5 mm throughout the first portion 34 and a spanwise dimension Y of 650 mm. If sixty layers of such metal sheet material 33 were wound onto the mandrel 90, the metal section 30 of the root ring 80 would have a radial depth of 30 mm as previously described, but the transition section 31 would include six times the number of metal to composite fiber interfaces 83 of the previous example.

[0101] Mathematical modeling of the root ring 80 indicates that a root ring having six times the number of metal to composite fiber interfaces 83 will be six times stronger. Thus, the strength of the root ring 80- and by association the strength of the root 29- of the completed wind turbine blade 10- can be varied and tailored for a particular application by varying the dimensions of the metal sheet material 33 and by selecting the number of layers in the root ring 80. This is advantageous because it allows the design and manufacture of roots 29 of varying strengths without requiring changes to the overall dimensions of the root. This is beneficial for the purposes of standardization and overcoming design limitations imposed by road transportation considerations, such as the height of bridges.

[0102] In addition to varying the size and number of layers of sheet metal material 33 , the strength of the connection between root 29 and pitch bearing 40 may be varied by varying the number and location of radially extending bolts 45 (if used) and / or by varying the surface finish and interlocking structure (if present) of sheet metal 33 .

[0103] The method of winding the sheet material 33, 98 onto the mandrel 90 is advantageous because it allows multiple layers to be formed quickly without requiring a large amount of manual labor. In addition, all or part of the metal sheet material 33 can be roughened before being roughly wound onto the mandrel 90 to improve the bond between the metal sheet material 33 and the fiber composite material 38 in the finished root ring 80.

[0104] In one example, the metal sheet material 33 overlaps the sheet fiber material 98 before the overlapping sheets are wound onto the mandrel 90. In this way, the metal sheet material 33 is interlaced with the sheet fiber material 98 in the completed root ring 80 once wound onto the mandrel 90.

[0105] In another example, a layer of metal sheet material 33 is wound onto the mandrel 90 followed by an overlapping layer of sheet fiber material 98 (or vice versa) such that the metal sheet material 33 is interlaced with the sheet fiber material 98 in the completed root ring 80 .

[0106] In each case, the sheet fiber material 98 may overlap the metal sheet material 33 only proximate the second portion 36 of the metal sheet material 33 to form the transition section 31 of the root ring 80 .

[0107] The sheet fiber material 98 may include a pre-impregnated sheet fiber material. Alternatively, the sheet fiber material 98 may include a dry sheet fiber material that is wound onto the mandrel 90 prior to being infused with resin and cured. Fig.10 It will be understood that, prior to curing of the pre-impregnated sheet fiber material, or prior to infiltration and curing of the dry sheet fiber material, the section of the assembled but uncured root ring 80 extending from the transition section 31 of the root ring 80 to the terminal end 82 may be referred to as a fiber section 88. The fiber section 88 becomes the composite fiber section 32 once cured.

[0108] The tapered inner surface 89 of the fiber composite section 32 of the root ring 80 may be formed during the winding process by winding a greater thickness of the sheet fiber material 98 onto the mandrel 90 proximate the transition section 31 than when winding onto the mandrel 90 proximate the distal end 82 of the root ring 80. If desired, the cured fiber composite section 32 of the root ring 80 may be machined to obtain improved dimensional accuracy. In an alternative exemplary method, the fiber section 88 may be wound onto the mandrel 90 in full thickness (i.e., the same or similar thickness as the metal section 30 and transition section 31), cured, and then machined to provide any particular cross-sectional profile, including tapering as desired.

[0109] Above about Figures 4 to 7c Any of the root structures discussed above can be Figures 9a to 9c Made in the manner described.

[0110] Once completed, the root ring 80 is removed from the mandrel 90 and incorporated into the blade shell 13 to form the root 29 of the complete wind turbine blade 10. In one example, this can be done by cutting the root ring 80 in half and incorporating each half into the windward half shell 17 and the leeward half shell 18 of the blade shell 13. In this method, the root ring halves are partially or completely placed into the hub end 21 of the half shells 17, 18, covered with fiber material and cured. Then, the two half shells 17, 18 including the root ring halves are connected together to form a complete wind turbine blade shell 13 with a complete root 29.

[0111] In an alternative example, the finished root ring 80 may be incorporated into the blade shell 13 in one piece by positioning the complete root ring 80 partially or completely into the hub end 21 of the windward and leeward half shells 17, 18, and connecting the root ring 80 to the half shells 17, 18 by covering with a fiber material and curing. This may be done after the windward and leeward half shells 17, 18 have been connected together to form the blade shell 13. Alternatively, the root ring 80 may be connected to one half shell before the other half shell is placed in place, and connected to the root ring 80 by covering with a fiber material and curing as previously described.

[0112] In all of the root loop connection methods described above, the covering fibre material may be a pre-impregnated fibre material or a dry fibre material which is impregnated with resin prior to curing.

[0113] In all examples described herein, the second portion 36 of the one or more metal sheets 33 located in the transition section 31 of the root ring 80 or the root 29 is linearly tapered or has a primarily constant thickness (optionally with a radially extending configuration). It should be understood that the second portion 36 of the one or more metal sheets 33 located in the transition section 31 of the root ring 80 or the blade root 29 may have any suitable cross-sectional profile including a curve. The second portion 36 of the one or more metal sheets 33 located in the transition section 31 may be tapered from one side of the metal sheet 33 so that one side of the curved metal sheet 33 has a linear cross-section. Alternatively, the one or more metal sheets 33 may be tapered from both sides toward a common vertex.

[0114] The example configurations of roots and root rings described above provide a number of advantages over the prior art. In particular, the strength and stiffness of the root / root ring can be tailored for a particular application by varying the size and profile of the sheet metal material and / or the number of layers of sheet metal material. Such modifications affect the strength, stiffness and number / surface area of ​​the metal to fiber composite interfaces contained in the root / root ring. Thus, roots / root rings of varying capacity can be designed and manufactured without the need to change the overall dimensions of the root / root ring. This is beneficial for the purposes of standardization and overcoming design limitations imposed by road transport considerations (such as the height of bridges).

[0115] The strength of the connection between the root and the pitch bearing can also be engineered by varying the number and location of bolts (if used) and / or by varying the surface finish of the sheet metal and the interlocking structure (if present).

[0116] Because the metal section of the root / root ring is much stiffer than the prior art fiberglass root, the spanwise innermost end of the carbon fiber spar cap within the blade shell can be positioned closer to the root than was possible in the prior art. Thus, the stiffness of the entire wind turbine blade can be increased when the carbon fiber spar cap can extend closer to the stiffer root. Furthermore, the metal section of the root can withstand higher peak loads than is possible with the prior art fiberglass root, which means that less glass can be used in the construction of the root, providing cost and environmental benefits.

[0117] The above root configuration also has the benefit that the integrity of the bond between the various layers of the root / root ring can be checked by ultrasonic non-destructive testing (NDT) methods throughout the depth of the root wall. This is not possible with a root that includes conventional spanwise extending bolt holes because the ultrasonic NDT equipment cannot "see" the void formed in the glass fiber composite into which the insert for the stud bolt insert is received.

[0118] The method of winding the sheet material onto a mandrel is advantageous because it allows multiple layers to be formed quickly without requiring extensive manual labor. In addition, all or part of the surface of the metal sheet material may be treated prior to winding onto the mandrel to increase friction between the metal sheet material layers in the metal segment and to help improve the bond between the metal sheet material and the fiber composite material in the finished root ring. The surface treatment may include a mechanical roughening process, such as sandblasting, and / or may include a chemical treatment process.

Claims

1. A wind turbine blade (10) having a root end (12), a tip end (11), a leading edge (14) and a trailing edge (16), the blade extending in a spanwise direction from the root end to the tip end, the blade comprising a tubular root portion having a proximal end (35) defining the root end of the blade and a distal end (25) located a spanwise distance from the proximal end, wherein the root portion comprises: a metal section (30) extending from the proximal end of the root toward the distal end of the root; a fiber composite section (32) extending from the distal end of the root toward the proximal end of the root; and a transition section (31) extending between the metal section and the fiber composite material section, The metal segment (30) comprises one or more metal sheets (33), wherein a portion of one or more of the metal sheets extends beyond the metal segment into the transition segment (31), wherein the portion of the one or more metal sheets located in the transition segment is encapsulated in the fiber composite material (38), the fiber composite material being continuous with the fiber composite material of the fiber composite segment (32), wherein the metal segment is connectable to a pitch bearing (40) of a wind turbine hub (8).

2. The wind turbine blade according to claim 1, wherein: The cross-sectional area of ​​the metal section (30) in a direction perpendicular to the spanwise extension axis of the metal section comprises at least 90% metal, preferably at least 95% metal, more preferably at least 98% metal, and most preferably at least 99% metal.

3. A wind turbine blade according to claim 1 or 2, wherein: The one or more metal sheets (33) are thin relative to their spanwise dimension (Y) in a direction parallel to the spanwise extension axis of the metal segment, so that the thickness of the one or more metal sheets is not greater than 25% of the spanwise dimension (Y), preferably not greater than 10% of the spanwise dimension (Y), more preferably not greater than 5% of the spanwise dimension (Y), still more preferably or not greater than 1% of the spanwise dimension (Y), and most preferably not greater than 0.1% of the spanwise dimension (Y).

4. A wind turbine blade according to any one of the preceding claims, wherein: The portion of the one or more metal sheets (33) located in the transition section (31) tapers toward the fiber composite material section (32).

5. A wind turbine blade according to any one of the preceding claims, wherein: The portion of the one or more metal sheets (33) located in the transition section (31) includes a plurality of radially extending formations (53) relative to the spanwise extension axis of the metal section.

6. The wind turbine blade according to claim 5, wherein: The radially extending formation (53) includes a plurality of protrusions positioned on a surface of the portion of the one or more metal sheets (33) located in the transition section (31).

7. A wind turbine blade according to any one of the preceding claims, wherein: The metal section (30) comprises a continuous spiral of metal sheet material (33) which is bent to form multiple layers of metal sheet material.

8. A wind turbine blade according to any one of the preceding claims, wherein: The metal section (30) comprises a plurality of metal sheets (33) arranged one above the other.

9. The wind turbine blade of claim 8, wherein: Each layer of metal sheet (33) includes formations (53) that engage with complementary formations (56) on the metal sheet of an adjacent layer.

10. A wind turbine blade according to claim 8 or 9, wherein: Portions of some or all of the layers in the multi-layer metal sheet (33) extend beyond the metal section (30) into the transition section (31).

11. The wind turbine blade of claim 10, wherein: Each portion of the multi-layer metal sheet (33) extending into the transition section (31) extends into the transition section by the same amount.

12. The wind turbine blade of claim 10, wherein: Each portion of the multilayer metal sheet (33) extending into the transition section (31) extends into the transition section by an amount different from that of adjacent portions of the metal sheet.

13. A wind turbine blade according to any one of the preceding claims, wherein: The fiber composite material section tapers (32) toward the distal end (25) of the tubular root portion.

14. A wind turbine blade according to any one of the preceding claims, comprising a plurality of bolt holes (46) extending radially through the metal segment (30) from an inner circumferential surface (47) of the metal segment to an outer circumferential surface (48) of the metal segment relative to the spanwise extension axis (28) of the metal segment.

15. An assembly for a wind turbine, the assembly comprising: A wind turbine blade (10) according to any one of the preceding claims; as well as An inner ring (41) or an outer ring (42) of a pitch bearing (40) connected to the metal section (30) of the wind turbine blade, wherein a circumferential surface of the inner ring or the outer ring is in contact with a circumferential surface of the metal section of the wind turbine blade.

16. The assembly of claim 15, wherein: The inner ring (41) or the outer ring (42) comprises one or more parts connected together.

17. An assembly according to claim 15 or 16, wherein The metal section (30) is connected to the inner ring (41) or the outer ring (42) by friction connection.

18. The assembly of claim 17, wherein: The metal section (30) is connected to the inner ring (41) or the outer ring (42) by a shrink-fit connection.

19. An assembly according to any one of claims 15 to 18, comprising a plurality of bolts (45) extending through the metal section (30) into the inner ring or the outer ring.

20. The assembly of claim 19, wherein: The bolts (45) extend radially relative to the spanwise extension axis (28) of the metal section.

21. An assembly according to any one of claims 15 to 20, wherein The inner ring (41) or the outer ring (41) comprises an annular groove (70) in which the metal segment (30) is received.

22. An assembly according to any one of claims 15 to 21, wherein The circumferential surface of the inner ring (41) or the outer ring (42) includes a surface formation that engages with a complementary surface formation on the circumferential surface of the metal segment (30).

23. An assembly according to any one of claims 15 to 22, wherein The inner ring (41) or the outer ring (42) comprises a proximal end (60) defining a hub-end of the ring and a distal end (61) located a span-wise distance from the proximal end, wherein the ring comprises: a hub section (62) extending from the proximal end of the ring toward the distal end of the ring; and a blade-like section (63) extending from the distal end of the ring toward the proximal end of the ring; wherein the circumferential surface (49) of the ring contacts the circumferential surface (48) of the metal section (30) and is completely located in the blade-facing section of the ring, and wherein the hub-facing section of the ring is configured to operably engage an inner ring or an outer ring of a pitch bearing.

24. A wind turbine, comprising: Wheel hub (8); a pitch bearing (40) connected to the hub; as well as A plurality of wind turbine blades (10) according to any one of claims 1 to 14, the wind turbine blades being connected to an inner ring or an outer ring of the pitch bearing via a circumferential surface of the metal section, or a plurality of assemblies according to any one of claims 15 to 23, the assemblies being operatively engaged with the inner ring or the outer ring of the pitch bearing.

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