GB2504459A

GB2504459A - Hinge for wind turbine blades

Info

Publication number: GB2504459A
Application number: GB1210382.6A
Authority: GB
Inventors: Brian Ash; Shane Caher; Richard Caldow
Original assignee: Kingspan Renewables Ltd
Current assignee: Kingspan Renewables Ltd
Priority date: 2012-06-12
Filing date: 2012-06-12
Publication date: 2014-02-05
Also published as: GB201210382D0; EP2859221A1; KR20150022980A; WO2013186276A1

Abstract

A hinge 20 for connecting a wind turbine blade 16 to a hub 18, eg in a 15kW wind turbine, comprises a body 26 which is capable of hinging movement about at least one hinge axis. The body is formed from flexible, resilient material, eg elastomeric material such as cast polyurethane or synthetic rubber, in which reinforcing material is distributed. The reinforcing material may be polymeric, eg polyamide, glass or metallic fibres. The hinge may have a coning hinge axis 22 a non-parallel base hinge axis 24 to allow the blade to adopt a base pitch under centrifugal force. The reinforcement may be in the form of as rope (40, fig.6), eg of aramid fibres, wound around locating members (30, 32) in the mould (42) such that the rope (40) traverses both hinge axes 22, 24 several times. The reinforcement may be in the form of a mesh (44, fig.5).

Description

Improved Hinge for Wind Turbine Blades

Field of the Invention

The present invention relates to wind turbines, and especially to hinges for wind turbine blades.

Background to the Invention

International PCT patent application WO 91/1 2429 discloses a wind turbine wherein each blade is connected to a hub assembly by a flexible, resilient hinge. The hinge defines two, non parallel hinge axes and made from a sheet of plastics material such as PVC or polyethylene. In this instance, the hinge is integrally formed with the blade, although other similar known hinges are separately formed from the blade and hub.

Such hinges work well with relatively small wind turbines, for example for use with 3kW or 6kW wind turbines. However, when used with larger blades, for example for use with 15kW wind turbines, the forces experienced by the hinge during use can cause hinge failure. In particular, fatigue can cause cracks to appear in the hinge, especially at any sharp corners caused by inserts, holes or other inclusions that may be present.

Also, the relatively large flexural strains experienced by the hinge are considered to be too large for the conventional plastics materials used to make the hinge.

It would be desirable to provide a hinge that mitigates these problems.

Summary of the Invention

A first aspect of the invention provides a hinge for a wind turbine, the hinge comprising a body capable of hinging movement about at least one hinge axis, wherein said body is formed from flexible, resilient material in which reinforcing particulate material is distributed.

Preferably, said reinforcing particulate material comprises synthetic fibres, preferably polymer fibres, most preferably aramid fibres.

Preferably, said particulate material is sized (length or diameter as applicable) between approximately 0.1mm and approximately 2.5mm.

In preferred embodiments, the reinforcing particulate material is present in quantities of between approximately 0.5% and approximately 10% by weight of the material that forms the hinge.

Typically, said flexible, resilient material comprises an elastomer, for example a polyurethane elastomer.

In preferred embodiments, said hinge includes at least one reinforcing mesh incorporated into said body. The preferred mesh comprises a plurality of spaced apart, and preferably substantially parallel, reinforcing strands extending in a first direction, and a plurality of spaced apart, and preferably substantially parallel, linking strands extending in a second direction that is non-parallel with, and preferably substantially perpendicular to, the first direction.

The reinforcing strands are preferably formed from synthetic fibres, especially polymer fibres, for example aramid fibres, typically formed as yarn. The link strands may be formed from synthetic fibres, for example glass fibres, and are configured to keep the reinforcing strands in a desired arrangement. In preferred embodiment, the link strands do not provide appreciable support or reinforcement to the hinge and the material from which they are made and/or their thickness and/or their inter-spacing is selected accordingly. Typically, therefore, the link strands are relatively lightweight and the reinforcing strands are relatively heavyweight.

Said at least one mesh extends across at least the region of the body corresponding to at least one of said at least one hinge axis. Optionally, said at least one mesh is shaped and dimensioned to cover substantially the entire major cross sectional area of said body.

Advantageously, said at least one mesh is arranged such that the first strand direction is substantially perpendicular with, or at least non-parallel with, at least one of said at least one hinge axis.

In preferred embodiments, said at least one mesh is embedded in the body such that does not break the obverse or reverse faces of the body, typically located between, and preferably being substantially parallel with, the obverse and reverse faces of the body. Preferably, said at least one mesh is substantially located in a plane in which the or each neutral axis of the hinge lies. In preferred embodiments, said at least one mesh lies substantially in a plane that is located substantially mid-way between and substantially parallel with the obverse and reverse faces of the body.

Optionally, a flexible line, conveniently comprising a rope, is embedded in said flexible resilient material. Advantageously, the line is not tensioned.

Preferably, said line is arranged in a generally sinusoidal manner and is preferably arranged such that it traverses said at least one hinge axis, preferably multiple times. Locating members may be provided in the body around which the line is wound.

Advantageously, said line is formed from a material that is suitable for adhesion with said flexible, resilient material. For example said line may comprise a Kevlar or aramid fibre rope. Alternatively or in addition said line may be treated with a suitable polymer, e.g. polyurethane, dispersion.

Advantageously, the line is pre-dried before use.

In preferred embodiments, said hinge includes first and second hinge axes, which are typically spaced apart and usually non-parallel.

A support member, for example comprising a plate, may be provided on one or both of the obverse and reverse faces of the body, advantageously not extending across the, or each, hinge axis.

A second aspect of the invention provides a blade assembly for a wind turbine, said blade assembly comprising a plurality of blades connected to a hub by a respective hinge according to the first aspect of the invention.

A third aspect of the invention provides a wind turbine comprising an electric generator coupled to a blade assembly according to the second aspect of the invention.

A fourth aspect of the invention provides a method of manufacturing a hinge for a wind turbine, the method comprising forming, form flexible resilient material, a body capable of hinging movement about at least one hinge axis, and causing reinforcing particulate material to be distributed in said flexible, resilient material.

Typically said method involves forming said body in a mould. Said forming may comprise casting, for example hot casting, said flexible resilient material in said mould. In preferred embodiments where said material comprises an elastomer, said forming may involve adding a curative, typically in liquid form, to a prepolymer (typically in liquid form), and putting the mixed curative and prepolymer into said mould. Advantageously, said method involves adding said reinforcing particulate material to said curative prior to mixing with said prepolymer. Preferably, said method involves drying said reinforcing particulate material prior to adding it to said curative.

In preferred embodiments, said method involves providing one or more supports in said mould to hold said line away from the major mould surfaces. The supports may comprise tensioned lines traversing the mould. It is preferred that one or more supports are provided in the region of at least one of said at least one hinge axis.

In preferred embodiments, said method involves providing one or more supports, for example one or more tensioned lines traversing the mould, the mould for holding said at least one mesh in its desired location. In embodiments where both said at least one mesh and said flexible line are present, the arrangement may be such that the supports hold said at least one mesh against said flexible line.

A fifth aspect of the invention provides a mould for forming the hinge of the first aspect of the invention.

Further advantageous aspects of the invention will be apparent to those ordinarily skilled in the art upon review of the following description of a preferred embodiment and with reference to the accompanying drawings.

Brief Description of the DrawinQs

An embodiment of the invention is now described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a wind turbine suitable for use with hinges embodying the invention; Figure 2 shows a hinge embodying one aspect of the present invention; Figure 3 is a table providing data on the physical properties of Hyperlast 100/90 Pu; Figure 4 is a table providing data illustrating the effect of adding fibres to Hyperlast PU; Figure 5 shows a preferred mesh reinforcement structure for incorporation into preferred hinges embodying the invention; and Figure 6 shows a mould for use in making a preferred hinge.

Detailed Description of the Drawings

Referring now to Figure 1 of the drawings there is shown a wind turbine 10 for generating electricity, mounted on a post 12. An electrical generator (not visible) is provided in a housing 14 and is driven in use by a plurality of blades 16 which emanate from a rotatable hub 18. The hub 18 is coupled to the generator by a rotatable shaft (not visible). During use, wind drives the blades 16 to rotate the hub 18 and shaft. Rotation of the shaft causes the generator's rotor to rotate and so causes electricity to be produced.

Each blade 16 is connected to the hub 18 by a respective hinge 20. The hinge 20 is configured to have first and second hinge axes 22, 24 about which the blade 16 can pivot with respect to the hub 18. The hinge 20 comprises a body 26 that is hingedly coupled to the hub 18 along the first hinge axis 22 and hingedly coupled to the blade 16 along the second hinge axis 24. The hinge axes 22, 24 are non-parallel but preferably substantially co-planar. The body 26 may be substantially planar, although in preferred embodiments has an end portion 28 (Figure 2) that is non-coplanar, typically oblique, with respect to the rest of the body 26, the second hinge axis 24 running between the end portion 28 and the rest of the body 26. Typically, the body 26 is generally triangular.

At the first hinge axis 22, which may be referred to as a coning hinge axis, the hinge 20 allows the blade 16 to pivot with respect to the hinge body 26. This is known as coning. Typically, coning occurs as a result of transient environmental conditions, in particular wind speed and/or strength.

At the second hinge axis 24, which may be referred to as the base hinge axis, the hinge 20 allows the blade 16 to adopt a base pitch with respect to the hub 18 under the centrifugal force caused by rotation of the hub 18 during use. Hence, the base pitch may be said to be centrifugally regulated.

The 2-axis hinge configuration allows the wind turbine to regulate its rotational speed in order to maximise output. During use, as the wind gets stronger the blades 16 pitch and cone, protecting the turbine 10 and allowing continual operation during the fiercest of storms.

In more detail, as the wind turbine 10 increases its rotational speed (RPM), the centrifugal forces created by each blade 16 tensions the respective hinge 20. The hinge position may be regulated by damper springs (not shown). The more the blade 16 pulls on its hinge 20 the further it pitches towards stall. At a certain point the turbine 10 reaches equilibrium,

B

rotating fast enough to keep the hinge pulled into stall, but stalled enough not to speed up any further. The blade coning reduces any stresses on the rotor (the blades 16 adjust themselves) and smoothes the turbine's response to gusty conditions. It also decreases the load on the turbine by decreasing its rotor disc size in very high winds. This is only the peak power regulation; at all times when the turbine is connected to the grid the RPM is also regulated by the amount of load applied by an inverter (power taken from the generator). This configuration allows continued generation in all wind speeds, unlike alternative wind turbines which are required to brake themselves in high wind conditions.

Figure 2 shows a specific embodiment of the hinge 20. The hinge 20 may be fixed to the blade 16 and to the hub 18 by any convenient means, e.g. screws, bolts, rivets, adhesive, bonding agent, welding or any other tixing means or combination thereof. In the illustrated embodiment, end portion 28 is provided with sockets 30 for receiving suitable mechanical fixings (not shown), the sockets 30 preferably being arranged along a notional line running substantially parallel with hinge axis 24. Similarly, the body 26 has an opposite end portion 32, the first hinge axis 22 running between the end portion 32 and the rest of the body 26, provided with sockets 34 for receiving suitable mechanical fixings (not shown), the sockets 34 preferably being arranged along a notional line running substantially parallel with hinge axis 22.

In preferred embodiments, a support member, typically comprising a plate (visible in Figure 1 but not shown in Figure 2), is fixed to one or both faces of the body 26, being dimensioned to substantially cover the area between the axes 22, 24. As such, the plate(s) help to define the axes 22, 34. The or each support member may for example be formed from metal or carbon fibre. The or each support member may be fixed to the body 26 by any suitable fixing means. e.g. screws, bolts, rivets, adhesive, bonding agent, welding or any other fixing means or combination thereof. In the embodiment illustrated in Figure 2, the body 26 is provided with sockets between the axes 22, 24 for receiving suitable mechanical fixings for this purpose.

The body 26, including end portions 28, 32, is elastomeric and typically formed from flexible, resilient plastics, for example polyurethane or synthetic rubber. The material from which the body is made preferably comprises at least one elastomer, for example a polyurethane elastomer.

In preferred embodiments, the material comprises a cast elastomer, preferably a cast polyurethane elastomer. The cast elastomer may be formed by adding a suitable curative, or chain extender, (typically in liquid form) to a suitable prepolymer (typically in liquid form), for example by adding a polyether based curative to a polyurethane or urethane prepolymer. The mixed prepolymer and curative is added to a suitably shaped (and typically open) mould whereupon the prepolymer and curative react to form the elastomer. The casting process is typically a hot casting (or hot curing) process. The body 26 may alternatively be formed by other casting or moulding techniques.

By way of example Hyperlast 100/90 (trade mark), as provided by Hyperlast Limited of Staines, United Kingdom (http://www.dow.com/hypedast/). Hyperlast 100/90 comprises a polyether based curative which reacts with Hyperlast 100 (trade mark) prepolymer to produce a high performance polyurethane elastomer. Figure 3 provides data describing the physical properties of Hyperlast 100/90. It will be understood that other substances having the same or similar properties could alternatively be used as would be apparent to a skilled person.

Hence, in preferred embodiments, the hinge 20, and in particular the body 26, is made by a cast moulding process. Typically this involves mixing the polyether (or other) curative and the Hyperlast (or other) prepolymer through a dynamic mixer which then allows the mixed chemicals to pour into a mould (not shown). Once in the mould the mix reacts through an exothermic reaction and forms an elastomer, in this example a polyurethane elastomer, in particular a hot cast polyurethane elastomer.

Investigations and analysis carried out in arriving at the present invention indicate that Hyperlast 100/90 does not have sufficient strength properties to withstand the forces the hinge 20 is subjected to when used in, for example, a 1 5kW wind turbine. The fatigue performance of the material is the main property which is not high enough for the application. Also, during operation the blades 16 may experience a significant amount of bending that transmits a bending moment along the length of the blade, the resultant force being dampened by the hinge 20. This force causes stress on the hinge and it would therefore be desirable to improve the damping properties of the hinge. A problem with modifying the hinge for these purposes is that the hinge should remain sufficiently flexible and resilient to perform the pitching and coning described above.

Fibres may be used to reinforce elastomer materials by dispersing the fibres into the material during vulcanization, or during an injection moulding stage. This allows the fibre orientation to be controlled and allows for good dispersion of the material. A problem with incorporating fibres into the Hyperlast 100/90, or similar, material is the two part process whereby the polyether based curative and Hyperlast 100 material are both in liquid form until the reaction occurs in the cast mould.

In preferred embodiments of the invention, reinforcing particulate material, preferably comprising fibres, are introduced into the elastomer during the casting or other manufacturing process. Typically synthetic fibres are used, preferably polymer fibres. In particular aromatic polyamide :ii (commonly known as Aramid (which is intended to include meta-aramid and para-aramid)) fibres are preferred. For example, Aramid fibres provided by Teijin Limited, Chuo-ku, Osaka, Japan (e.g. under the trade name Twaron), or Kelvar fibres, which are para-aramid fibres produced by DuPont of Wilmington, Delaware, USA, may be used. Other particulate material, especially synthetic particulate material (e.g. plastics, polymeric, glass and/or metallic) may be used for reinforcement.

By way of example, any one or more of the following fibres may be used.

* Twaron 1088, an aramid fibre with a length of 0.25mm (Teijin).

* Twaron 1189, an aramid fibre with a length of 1.5mm (Teijin).

* Kevlar Pulp Merge 1 F543, a Kevlar Pulp (Dupont).

Kelvar pulp is a fibrillated pulp comprising chopped fibres, typically 0.25 to 1mm in length.

More generally, it is preferred to use particles/fibres sized (length or diameter as applicable) between approximately 0.1mm and approximately 2.5mm.

When adding the fibres during the casting process a number of issues must be considered. Aramid fibres and Kevlar are prone to water absorption. Water reacts with the Hyperlast material and can produce carbon dioxide when reacted. As a result the fibres are advantageously pre-dried, for example at >80° for at 6-8 hours, prior to processing. The fibres is preferably added to the curative since the prepolymer should not be exposed to moisture and as a result should not be exposed to atmospheric conditions. When the fibres/pulp are added to the curative it increases the viscosity of the curative. This can have an effect on the processing properties of the material, including its amenability to being moulded or otherwise handled. For example, the viscosity of a base polyether curative is approximately 300cps and the maximum viscosity that would still be able to react with the prepolymer is approximately l500cps.

The following results are presented by way of example: * Incorporating approximately 2% of Twaron 1088 gives a viscosity of about 96Ocps.

* Incorporating approximately 0.75% of Twaron 1189 gives a viscosity of about 1 500cps.

* Incorporating approximately 0.5% of Kevlar Pulp 1 F543 gives a viscosity of about l45Ocps.

It will be apparent that the respective fibres may be added to the curative, e.g. the polyether curative, in quantities up to the respective percentage levels indicated whilst still enabling the desired reaction with the prepolymer to occur.

More generally, in preferred embodiments, the reinforcing particulate material is present in quantities of between approximately 0.5% and approximately 10% by weight of the elastomeric material used to form the hinge 20.

It is preferred that the fibres or other particulate material are substantially evenly distributed throughout the body.

It is found that the inclusion of fibres, for example the fibres identified above, produces a significant improvement in the properties of the elastomer. Figure 4 provides data indicating how various quantities and combinations of fibres affect the strength of Hyperlast PU. It can be seen in particular that the inclusion of Twaron fibres yields substantial improvements in the strength properties of the material. For example, with the inclusion of 2% (by weight) Twaron 1088 and 0.5% (by weight) Twaron 1189 the strength of the material increased by 75% over its original strength.

The tensile properties of the samples of Figure 4 reveal that with the inclusion of the respective fibre reinforcements, the properties of the PU changes. The tensile strength of the PU is improved at relatively low modulus levels, e.g. at 50% modulus the tensile strength is increased from 4Mpa to 6.5 Mpa. This trend is observed up to approximately 250% or 300% modulus whereupon the tensile strength of the PU material performs better than the samples with the various fibres. Hence, in the present example, the tensile strength of the PU material is increased by approximately 40% in the modulus range from 0-250% approximately.

Above 250% modulus the tensile properties are reduced. In the context of a wind turbine blade hinge the expected maximum strain rate is typically in the less than 25% modulus and so these results indicate that the by adding the fibre reinforcements the properties of the PU material are improved for the preferred application.

In the context of a wind turbine blade hinge, the tear properties of the material used to make the hinge 20 are important. A tear tests, e.g. a trouser test, on the respective samples of Figure 4 reveal that the inclusion of the fibres improves the tear strength of the PU material by as much as 130% from 18 to 41 N/mm. This is a substantial improvement that helps prevent tear propagation which is a cause of hinge failure.

Optionally, a flexible line in the convenient form of a rope 40 (Figure 6), for example a polyester or other synthetic rope, may be embedded in the hinge 20 material. The rope 40 may be located in the mould 42 prior to addition of the curative and prepolymer mix. Typically the rope 40 is arranged in a generally sinusoidal manner and is preferably arranged such that it traverses both hinge axes 22, 24 (preferably multiple times).

Locating members may be provided in the mould 42 around which the rope 40 may be wound to help position and shape the rope 40.

Conveniently, the sockets 30, 32 (which may comprise sleeves provided in the mould 42) may be used for this purpose.

It is preferred that the rope 40 be embedded in the body 26 such that does not break the obverse or reverse faces of the body 26, e.g. located substantially mid-way between the obverse and reverse faces. To this end, it is preferred not to hold the rope 40 under tension in the mould since this tends to urge the rope 40 towards the bottom surface of the mould and so to cause the rope to break the corresponding surface of the body 26. One or more supports 38 may be provided in the mould 42 to hold the rope 40 away from the mould surfaces. In Figure 6, the supports 38 comprise tensioned lines, e.g. thread, traversing the mould 42. It is preferred that one or more supports 38 are provided in the region of the hinge axis 24 since this corresponds, in the illustrated embodiment at least, to a bent portion of the mould 42 where it is otherwise more difficult to keep the rope 40 from contacting the mould surface.

It is found through FEA analysis that the rope 40 provides support to the elastomer material of the hinge 20 and increases the damping properties of the hinge 20. For example, the rope 40 may have a diameter of between approximately 5mm and 15mm.

If the rope does not provide a satisfactory bond with Hyperlast PU or other hinge material (which can be the case for a polyester rope), then during operation of the hinge 20, movement of the PU material can causes a break to occur in the bond between the Hyperlast PU material and the polyester rope. The break can propagate to the surface of the hinge 20 and create a weak point which can lead to hinge failure. It is preferred therefore that the rope 40, or other reinforcing line, is formed from a material that is suitable for adhesion with the hinge material. For example a Kevlar or aramid fibre rope may be used. Alternatively or in addition the rope may be treated with a suitable polymer, e.g. polyurethane, dispersion.

Advantageously, the rope is pre-dried before use.

In order to provide the hinge 20 with improved damping properties, it is preferred to incorporate a mesh 44 into the hinge 20. In the preferred embodiment, the mesh 44 is provided in the mould 42 prior to the addition of the curative/prepolymer mix. The mesh 44 comprises a plurality of substantially parallel reinforcing strands 46 extending in a first direction (known as the 0 direction) and a plurality of substantially parallel linking strands 48 extending in a second direction (which may be referred to as the 90 direction) that is non-parallel with and preferably substantially perpendicular to, the first direction. The respective strands 46, 48 may be fixed to each other using any suitable means, e.g. adhesive or bonding, to form the mesh 44. The mesh 44 provides a substantially planar or two dimensional support structure for the body 26.

The mesh 44 is shaped and dimensioned to extend across at least the region of the second hinge axis 24, since this is typically the region that requires support, but may alternatively be shaped and dimensioned to cover substantially the entire plan area defined by the hinge 20, e.g. traversing both hinge axes 22, 24. The mesh 44 may alternatively be shaped and dimensioned to extend across at least the region of the first hinge axis 22. Separate meshes may be used to traverse respective hinge axes, or a single mesh may be shaped and dimensioned to traverse both.

It is preferred that the mesh 44 is arranged with respect to the hinge 20 such that the first strand direction is substantially perpendicular with, or at least non-parallel with, the or each hinge axis 22, 24 (as applicable). This allows the reinforcing strands 46 to support and provide damping to the hinge 20 during use without unduly inhibiting the flexibility of the hinge 20.

The reinforcing strands 46 are preferably formed from synthetic fibres, for example polymer fibres e.g. aramid fibres, conveniently formed as yarn.

The thickness of strands 46 may be selected depending on the material from which the strands 46 are formed and on the level of reinforcement that they are required to provide, but may typically be between approximately 0.5mm and approximately 3mm. By way of example, the spacing between adjacent strands 46 may typically be between approximately 0.5mm and approximately 3mm. The link strands 48 may be formed from any suitable material, conveniently synthetic fibres, e.g. glass fibres, that serve to keep the strands 46 in the desired orientation. In the preferred embodiment, the link strands 48 do not provide appreciable support or reinforcement to the hinge 20 and the material from which they are made and/or their thickness and/or their inter-spacing is selected accordingly. Typically, therefore, the strands 48 may be described as relatively lightweight and the strands 46 as relatively heavyweight.

By way of example, the mesh 44 may comprise a Kevlar mesh such as the RUBAN 9081 FK (trade mark) Kelvar mesh. This mesh consists of an aramid yarn in the o direction and a glass fibre in the 90 direction which keeps the aramid yarns in the correct direction.

It is preferred that the mesh 44 be embedded in the body 26 such that does not break the obverse or reverse faces of the body 26, e.g. located between and preferably substantially parallel with the obverse and reverse faces of the body 26. Preferably, the mesh 44 is substantially located in a plane in which the or each neutral axis of the hinge 20 lies. In preferred embodiments, the mesh 44 lies substantially in a plane that is located substantially mid-way between and substantially parallel with the obverse and reverse faces of the body 26.

One or more supports, e.g. one or more tensioned lines traversing the mould, may be provided in the mould 42 to hold the mesh 44 in its desired location. Conveniently, supports 38 may be used for this purpose. In embodiments where both the mesh 44 and the rope 40 are present, the arrangement may be such that the supports 38 hold the mesh 44 against the rope 40.

By way of example, it is found that hinges having a Kelvar rope and the Ruban 9081 mesh exhibit increased stiffness (approximately a 95% increase in stiffness when compared to conventional hinges). This causes an increase in the damping properties of the hinge 20.

It will be apparent that the invention is not limited to use with a 2-axis hinge.

The invention is not limited to the embodiments described herein, which may be modified or varied without departing from the scope of the invention.

Claims

Claims 1. A hinge for a wind turbine, the hinge comprising: a body capable of hinging movement about at least one hinge axis, wherein said body is formed from flexible, resilient material in which reinforcing particulate material is distributed.
2. The hinge of claim 1, wherein said reinforcing particulate material comprises synthetic fibres.
3. The hinge of claim 2, wherein the synthetic fibres comprise polymer fibres.
4. The hinge of claim 3, wherein the polymer fibres comprise aramid fibres.
5. The hinge of any of claims 1 to 4, wherein said particulate material is sized between approximately 0.1mm and approximately 2.5mm. (0o
6. The hinge of claim 5, wherein the reinforcing particulate material is present in quantities of between approximately 0.5% and approximately 10% by O weight of the material that forms the hinge.
7. The hinge of any of claims ito 6, wherein said flexible, resilient material comprises an elastomer.
8. The hinge of claim 7, wherein said elastomer comprises a polyurethane elastomer.
9. The hinge of any of claims 1 to 8, wherein said hinge includes at least one reinforcing mesh incorporated into said body.
10. The hinge of claim 9, wherein the mesh comprises a plurality of spaced apart reinforcing strands extending in a first direction, and a plurality of spaced apart linking strands extending in a second direction that is non-parallel with the first direction.
11. The hinge of claim 10, wherein the reinforcing strands are substantially parallel to each other and the linking strands are substantially parallel to each other, and wherein the second direction is substantially perpendicular to the first direction.
12. The hinge of claim 10 or claim 11, wherein the reinforcing strands are formed from synthetic fibres.
13. The hinge of claim 12, wherein the synthetic fibres comprise polymer fibres.
14. The hinge of claim 13, wherein the polymer fibres comprise aramid fibres.
15. The hinge of any of claims 10 to 14, wherein the linking strands are formed from synthetic fibres. (0o
16. The hinge of claim 15, wherein the synthetic fibres comprise glass fibres.LUO
17. The hinge of any of claims 9 to 16, wherein said at least one mesh extends across at least the region of the body corresponding to at least one of said at least one hinge axis.
18. The hinge of claim 17, wherein said at least one mesh is shaped and dimensioned to cover substantially the entire major cross sectional area of said body.
19. The hinge of claim 17 or claim 18, wherein said at least one mesh is arranged such that the first strand direction is non-parallel with at least one of said at least one hinge axis.
20. The hinge of claim 19, wherein said at least one mesh is arranged such that the first strand direction is substantially perpendicular with at least one of said at least one hinge axis.
21. The hinge of any of claims 9 to 20, wherein said at least one mesh is embedded in the body such that does not break the obverse or reverse faces of the body.
22. The hinge of claim 21, wherein said at least one mesh is located between the obverse and reverse faces of the body.
23. The hinge of claim 22, wherein said at least one mesh is substantially parallel with the obverse and reverse faces of the body.
24. The hinge of claim 23, wherein said at least one mesh is substantially located in a plane in which the or each neutral axis of the hinge lies.
25. The hinge of claim 24, wherein said at least one mesh lies substantially in ¶2 a plane that is located substantially mid-way between and substantially (0 parallel with the obverse and reverse faces of the body.
26. The hinge of any of claims ito 25, wherein a flexible line is embedded in O said flexible resilient material.
27. The hinge of claim 26, wherein the flexible line comprises a rope.
28. The hinge of claim 26 or claim 27, wherein the line is not tensioned.
29. The hinge of any of claims 26 to 28, wherein said line is arranged in a generally sinusoidal manner.
30. The hinge of claim 29, wherein said line is arranged such that it traverses said at least one hinge axis.
31. The hinge of any of claims 26 to 30, wherein locating members are provided in the body around which the line is wound.
32. The hinge of any of claims 26 to 31, wherein said line is formed from a material that is suitable for adhesion with said flexible, resilient material.
33. The hinge of claim 32, wherein said line comprises a Kevlar rope.
34. The hinge of claim 32, wherein said line comprises an aramid fibre rope.
35. The hinge of any of claims 26 to 34, wherein said line is treated with a polymer.
36. The hinge of claim 35, wherein said polymer comprises polyurethane.
37. The hinge of any of claims 26 to 36, wherein the line is pre-dried before use.
38. The hinge of any of claims ito 37, wherein said hinge includes first and (0 second hinge axes.
39. The hinge of claim 38, wherein said first and second hinge axes are O spaced apart.
40. The hinge of claim 39, wherein said first and second hinge axes are non-parallel.
41. The hinge of any of claims 38 to 40, further comprising a support member provided on one or both of the obverse and reverse faces of the body.
42. The hinge of claim 41, wherein the support member does not extend across the, or each, hinge axis.
43. The hinge of claim 41 or claim 42, wherein the support member comprises a plate.
44. A blade assembly for a wind turbine, said blade assembly comprising a plurality of blades connected to a hub by the hinge of any of claims ito 43.
45. A wind turbine comprising an electric generator coupled to the blade assembly of claim 44.
46. A method of manufacturing a hinge for a wind turbine, the method comprising the steps of: forming, from flexible resilient material, a body capable of hinging movement about at least one hinge axis, and causing reinforcing particulate material to be distributed in said flexible, resilient material.
47. The method of claim 46, wherein said forming comprises casting said flexible resilient material in a mould. C')48. The method of claim 47, wherein said casting comprises hot casting.LCD 49. The method of any of claims 46 to 48, wherein said flexible, resilient 0 material comprises an elastomer.50. The method of any of claims 47 to 49, wherein said forming further comprises adding a curative to a prepolymer, and putting the mixed curative and prepolymer into said mould.51. The method of claim 50, wherein said curative and prepolymer are both in liquid form.52. The method of claim 50 or claim 51, further comprising adding said reinforcing particulate material to said curative prior to mixing with said prepolymer.53. The method of claim 52, further comprising drying said reinforcing particulate material prior to adding it to said curative.54. The method of claim 52 or claim 53, further comprising providing one or more supports in said mould to hold said line away from the major mould surfaces.55. The method of claim 54, wherein the one or more supports comprise tensioned lines traversing the mould.56. The method of claim 54 or claim 55, wherein the one or more supports are provided in the region of at least one of said at least one hinge axis.57. The method of any of claims 50 to 56, further comprising providing at least one mesh in the mould prior to the putting the mixed curative and prepolymer into said mould. C')58. The method of claim 57, wherein the method further comprises providing o one or more supports traversing the mould for holding said at least one mesh LCD in its desired location.59. The method of claim 58, wherein the one or more supports comprise one or tensioned lines.60. The method of claim 58 or claim 59, wherein the one or more supports hold said at least one mesh against said flexible line.61. A mould for forming the hinge of any of claims ito 43.