Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a rotor with a rotor hub and a plurality of blades. The rotor is set into rotation under the influence of the wind on the blades. The rotation of the rotor shaft drives the generator rotor either directly ("directly driven") or through the use of a gearbox. The gearbox (if present), the generator and other systems are usually mounted in a nacelle on top of a wind turbine tower.

An auxiliary system generally provided on wind turbines is the pitch system. Pitch systems are employed for adapting the position of a wind turbine blade to varying wind conditions. A pitch system normally comprises a pitch bearing comprising an outer ring, an inner ring and, between these two rings, one or more rows of rolling elements which allow both rings to rotate relative to each other. Lubricant, e.g. oil or grease, is provided between the rings to prevent excessive wear of the rings and of the rolling elements. The rolling elements, e.g. balls or rollers, may be arranged between an inner race of the inner ring and an outer race of the outer ring for reducing the friction between these rings.

Depending on the type of rolling elements, the pitch bearing may be for example a ball bearing or a roller bearing. The rolling elements of ball bearings are balls that rotate between the inner and outer races. In roller bearings, the rolling elements arranged between the races have a generally cylindrical or conical shape and are generally called rollers.

Alternatively, plain bearings or sliding bearings may also be used. In these bearings, a lubricant film may be provided between planar surfaces of the inner and the outer ring to reduce friction.

A wind turbine blade may be attached either to the inner ring or to the outer ring, whereas the hub is connected to the other of the (inner or outer) rings. A blade may perform a relative rotational movement with respect to the hub when a pitch system is actuated. The bearing inner ring may therefore perform a rotational movement with respect to the bearing outer ring.

Pitch bearings may comprise a bearing sealing element to reduce lubricant leaks from the pitch bearing. For example, a bearing sealing element may be provided to close a bearing gap formed between the inner ring and the outer ring. Lubricant may generally spill out through the bearing gap between the rings.

Furthermore, a groove may be machined in one or in both rings to accumulate lubricant. This groove widens the bearing gap between the inner and the outer rings so as to increase the lubricant stored. The bearing sealing element may also cover the groove to reduce lubricant spillage. The bearing sealing elements are generally known as primary seals.

However, bearing sealing elements do not completely avoid lubricant leaks from the pitch bearings. Lubricant leaks may thus end on the ground which may generate a risk of potential environmental pollution.

Furthermore, the volume of the groove to accumulate lubricant is relatively small and fills up quickly. Maintenance operations to empty the lubricant out of the cavity thus have to be frequently performed.

Brush seals having a bundle of bristles may be used to absorb grease leaking from the pitch bearing. These brush seals are generally arranged relatively close to the bearing gap between the outer and the inner ring of the pitch bearing. However, the bristles may get saturated relatively quickly. The capacity to retain the grease of brush seals may decrease with time. Consequently, maintenance operations to clean these brush seals must be periodically performed. Cleaning and reuse of the brush seal may not be feasible in some cases and thus full replacement of the brush seal may be required. Cleaning the brush seals may commonly involve replacing the complete brush seal. Accordingly, these maintenance operations may be labor-intensive. In addition, brush seals may be difficult to install in existing wind turbine blades. Document <CIT> describes a seal arrangement for sealing a bearing component that includes brush seal having an annular brush body and a bundle of resiliently bendable bristles.

The present disclosure provides examples of systems and methods that at least partially resolve some of the aforementioned disadvantages.

In a first aspect, a lubricant retention system for a pitch bearing of a wind turbine is provided. An example of such a pitch bearing comprises a first bearing component to be coupled to a wind turbine blade and a second bearing component to be coupled to a rotor hub of a wind turbine. The first bearing component is to rotate with respect to the second bearing component.

The lubricant retention system comprises a base and a plurality of annular seal segments. The base is to be connected to a wind turbine blade. The base comprises a base outer surface to fit a surface of the wind turbine blade. The plurality of annular seal segments is to be connected to the base. The annular seal segments of the plurality of annular seal segments are to be connected to each other to form an annular seal assembly. In addition, the plurality of annular seal segments comprises a distal end portion. When the lubricant retention is mounted on the wind turbine blade, the distal end portion extends towards the second bearing component for defining a chamber for retaining lubricant from the pitch bearing. The plurality of annular seal segments further comprises a releasable annular seal segment to be releasably connected to another of the annular seal segments of the plurality of annular seal segments.

According to this aspect, retention of lubricant, e.g. oil and/or grease, leaking from the pitch bearing is improved. Therefore, the risk of lubricant leaking from the pitch bearing reaching the ground is reduced. Consequently, the risk of environmental pollution may be minimized. A bearing gap between the first bearing component and the second bearing component is enclosed by the lubricant retention system when the distal end portion of the plurality of annular seal segments extends towards the second bearing component of the pitch bearing. A sealing arrangement is thus formed between the distal end portion of the plurality of annular seal segments and the second bearing component. As a result, a cavity to accumulate lubricant leaks from the pitch bearing is formed. This cavity allows storing a volume of lubricant greater than in grooves machined in the bearing components or grease absorbed by bristles of seal brushes arranged to directly cover the bearing gap between the first bearing component and the second bearing component. The frequency of maintenance operations of emptying the cavity may thus be reduced.

Connecting the base of the lubricant retention system to the wind turbine blade allows installing the lubricant retention system in existing wind turbines in an easy manner. Attaching a lubricant retention system to the pitch bearing may be more complex since the available space of the pitch bearing for attaching the lubricant retention is more limited. Accordingly, the base of the lubricant retention system may be attached to the blade in a production plant, on the ground before lifting the blade or even in blades already connected to the rotor hub. The plurality of annular sealing segments may thus be coupled to the blade when the base is attached to the wind turbine blade.

In addition, the pitch bearing may suffer structural problems or may require a design change if a lubricant retention system is connected to the pitch bearing. For example, it may be necessary to machine holes on one bearing component to screw the lubricant retention system into this bearing component. This may adversely affect the structural behavior of the pitch bearing. The risk of creation and propagation of cracks on the pitch bearing may thus be increased.

As explained before, the plurality of annular sealing segments is connected to each other to form the annular seal assembly. The annular sealing segments are thus connected edge-to-edge to form a complete annular seal assembly. The plurality of annular sealing segments may be first positioned around the blade and then joined together. This simplifies the installation of the lubricant retention system. The size of these annular sealing segments is smaller than if the annular seal were made from a single piece. Instead of a single-piece annular seal, the plurality of annular sealing segments may be lifted with the existing lifting or hoisting equipment of the wind turbine. Logistics are thus also improved.

At least one of the annular seal segments is releasable. A releasable annular seal segment is an annular seal segment of the plurality of annular seal segments that may be attached and detached from the remaining annular seal segment or segments of the annular seal assembly in an easy manner. The releasable annular seal segment may thus be easily removed from the annular seal assembly. Inspection of the level of lubricant contained within the cavity formed by the annular seal assembly may thus be easily performed. Furthermore, the lubricant contained within this cavity may be extracted by an aperture caused when the releasably annular seal segment is removed. Therefore, maintenance and inspection operations may be simplified and optimized.

In a further aspect, a blade root portion of a wind turbine blade is provided. The blade root portion comprises a blade shell and a blade root attachment portion. The blade shell comprises an inner blade shell surface and an outer blade shell surface. The blade root attachment portion is configured to attach the blade root portion to a first bearing component of a pitch bearing. The blade root portion further comprises a lubricant retention system according to any of the examples herein disclosed. The base of the lubricant retention system is coupled to the blade shell and/or to the blade root attachment portion.

Similar to the first aspect, lubricant leaks from the pitch bearing may be retained with an easy-to-install system. Furthermore, inspection and maintenance operations of the lubricant retention system may be improved.

In further aspects, a wind turbine blade having the blade root portion with the lubricant retention system according to any of the examples herein disclosed is provided. A rotor having a rotor hub and one or more blades having the lubricant retention system according to any of the examples herein disclosed is also provided. Furthermore, a wind turbine having such a rotor is provided.

In a further aspect, a method for mounting a lubricant retention system for a pitch bearing of a wind turbine blade is provided. The pitch bearing comprises a first bearing component and a second bearing component, the first bearing component is to rotate with respect to the second bearing component.

The method comprises connecting a base of the lubricant retention system to a blade root portion of the wind turbine blade configured to be coupled to the first bearing component. In addition, the method comprises connecting a plurality of annular seal segments to the base in such a way that a distal end portion of the plurality of annular seal segments extends towards the second bearing component for defining a chamber for retaining lubricant from the pitch system. The method further comprises connecting the plurality of annular seal segments to each other to form an annular seal assembly, wherein connecting the plurality of annular seal segments comprises releasably connecting a releasable annular seal segment of the plurality of annular seal segments to the another of the annular seal segments of the plurality of annular seal segments.

In yet a further aspect, a method for performing maintenance operations in a wind turbine is provided. The method comprises removing a releasable annular seal segment from an annular seal assembly formed by a plurality of annular seal segments of a lubricant retention system for a pitch bearing. In addition, the method comprises inspecting a level of lubricant leaked from the pitch bearing retained in a chamber defined by the annular seal assembly.

Advantages derived from these aspects may be similar to those mentioned regarding the previous aspects.

In these figures the same reference signs have been used to designate matching elements.

<FIG> illustrates a perspective view of one example of a wind turbine <NUM>. As shown, the wind turbine <NUM> includes a tower <NUM> extending from a support surface <NUM>, a nacelle <NUM> mounted on the tower <NUM>, and a rotor <NUM> coupled to the nacelle <NUM>. The rotor <NUM> includes a rotatable hub <NUM> and at least one wind turbine blade <NUM> coupled to and extending outwardly from the rotor hub <NUM>. For example, in the illustrated example, the rotor <NUM> includes three wind turbine blades <NUM>. However, in an alternative embodiment, the rotor <NUM> may include more or less than three blades <NUM>. Each wind turbine blade <NUM> may be spaced from the rotor hub <NUM> to facilitate rotating the rotor <NUM> to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the rotor hub <NUM> may be rotatably coupled to an electric generator <NUM> (<FIG>) positioned within the nacelle <NUM> or forming part of the nacelle to permit electrical energy to be produced.

<FIG> illustrates a simplified, internal view of one example of the nacelle <NUM> of the wind turbine <NUM> of the <FIG>. As shown, the electric generator <NUM> may be disposed within the nacelle <NUM>. In general, the generator <NUM> may be coupled to the rotor <NUM> of the wind turbine <NUM> for generating electrical power from the rotational energy generated by the rotor <NUM>. For example, the rotor <NUM> may include a main rotor shaft <NUM> coupled to the rotor hub <NUM> for rotation therewith. The generator <NUM> may then be coupled to the rotor shaft <NUM> such that the rotation of the rotor shaft <NUM> drives the generator <NUM>. For instance, in this figure, the generator <NUM> includes a generator shaft <NUM> rotatably coupled to the rotor shaft <NUM> through a gearbox <NUM>. In other examples, the generator may be directly coupled to the rotor hub or to the rotor shaft.

It should be appreciated that the rotor shaft <NUM>, gearbox <NUM>, and generator <NUM> may generally be supported within the nacelle <NUM> by a bedplate or a support frame <NUM> positioned atop the tower <NUM>.

The nacelle <NUM> is rotatably coupled to the tower <NUM> through a yaw system <NUM>. The yaw system comprises a yaw bearing (not visible in <FIG>) having two bearing components configured to rotate with respect to the other. The tower <NUM> is coupled to one of the bearing components and the bedplate or support frame <NUM> of the nacelle <NUM> is coupled to the other bearing component.

Blades <NUM> are coupled to the rotor hub <NUM> with a pitch bearing <NUM> in between the blade <NUM> and the rotor hub <NUM>. The pitch bearing <NUM> comprises an inner ring and an outer ring (shown in <FIG>). A wind turbine blade may be attached either to the inner bearing ring or to the outer bearing ring, whereas the hub is connected to the other. A blade <NUM> may perform a relative rotational movement with respect to the rotor hub <NUM> when a pitch system <NUM> is actuated. The inner bearing ring may therefore perform a rotational movement with respect to the outer bearing ring. The pitch system <NUM> of <FIG> comprises a pinion <NUM> that mesh with a pitch annular gear <NUM> provided on the inner bearing ring to set the wind turbine blade into rotation.

<FIG> illustrates an example of a wind turbine blade <NUM>. The wind turbine blade <NUM> extends in a longitudinal direction or spanwise direction <NUM> from a blade root end <NUM> to a blade tip end <NUM>. The blade <NUM> comprises a blade root region or portion <NUM> closest to the rotor hub, a profiled or an airfoil portion <NUM> furthest away from the rotor hub and a transition portion <NUM> between the blade root portion <NUM> and the airfoil portion <NUM>. The blade <NUM> comprises a leading edge <NUM> facing the direction of rotation of the blade <NUM> when mounted on the rotor hub, and a trailing edge <NUM> facing the opposite direction of the leading edge <NUM>.

The airfoil portion <NUM> has a shape designed to generate lift, whereas the blade root portion <NUM> has a circular or elliptical cross-section for structural considerations and for easy mounting the blade to the rotor hub. The diameter or the chord of the blade root portion <NUM> may be constant along the entire blade root portion <NUM>. At the transition portion <NUM>, the profile gradually changes from the circular or elliptical cross-section of the blade root portion <NUM> to the airfoil profile of the airfoil portion <NUM>.

The wind turbine blade <NUM> comprises a blade shell <NUM>. The blade shell may comprise two blade shell parts, for example, a pressure side blade shell and a suction side blade shell. The pressure side blade shell may be joined, e.g. glued or bonded, to the suction side blade shell along joining lines along the leading edge <NUM> and the trailing edge <NUM>. The blade shell <NUM> comprises an outer side or surface that defines the external shape of the blade, e.g. the outer shape at the blade root portion and the outer shape at the airfoil portion. The blade shell <NUM> also comprises an inner side or surface that defines the internal volume of the blade and faces a load-carrying structure (not shown). The blade shell <NUM> may be made of fiber-reinforced polymer, e.g. glass-fiber and/or carbon fiber.

The blade root portion <NUM> comprises a blade root attachment portion <NUM> configured to attach the blade root portion to a first bearing component of the pitch bearing, e.g. a bearing ring. The blade root attachment portion may comprise a plurality of fastening members distributed along the root end. In some examples, the blade root end comprises a blade flange to face the first bearing component. The blade root end may comprise a structural stiffener, e.g. a stiffening plate or a stiffening ring, at the blade root attachment portion to increase the structural resistance of the blade root portion.

<FIG> shows a cross-sectional view of a lubricant retention system according to one example of the present disclosure and <FIG> is a zoomed-in view of the lubricant retention system of <FIG>. The lubricant retention system <NUM> of this example is coupled to a blade root portion <NUM>. The blade root portion <NUM> comprises a blade shell <NUM> comprising an inner blade shell surface <NUM> and an outer blade shell surface <NUM>. The outer blade shell surface <NUM> defines the outer shape of the blade.

The blade root portion <NUM> further comprises a blade root attachment portion <NUM> configured to attach the blade root portion <NUM> to a first bearing component <NUM> of a pitch bearing <NUM>. The second bearing component <NUM> is coupled to the rotor hub <NUM>. Accordingly, the first bearing component <NUM> is configured to be coupled to a wind turbine blade <NUM> and the second bearing component <NUM> is configured to be coupled to a rotor hub <NUM> of a wind turbine. The blade root portion <NUM> of this example comprises a circular cross-section.

In this example, the first bearing component <NUM> is an outer ring and the second bearing component <NUM> is an inner ring. However, in other examples, the first bearing component is the inner ring and the second bearing component is the outer ring.

The blade root attachment portion <NUM> comprises a receiver to secure a blade fastener <NUM>. The receiver may be for example an insert with an inner thread or a T-bolt connector. The first bearing component <NUM> of this figure comprises a through-hole. The fastener <NUM> may pass through the hole of the first bearing component <NUM> and may be secured to the receiver of the blade root attachment portion <NUM> to connect the blade <NUM> to the first bearing component <NUM>. A plurality of fasteners or bolts may be distributed along the circumference of the first bearing component <NUM> to connect the pitch bearing <NUM> to the blade.

In this figure, the blade root attachment portion <NUM> comprises a mounting flange <NUM> to face an upper surface <NUM> of the first bearing component <NUM>. In some examples, the blade root attachment portion <NUM> comprises a stiffener element to increase the radial stiffness of the blade. The stiffener element may be a stiffening ring. A stiffening ring may be arranged between the mounting flange and the laminate.

In <FIG>, the rotor hub <NUM> comprises a threaded hole. A fastener, e.g. a bolt, may pass through a hole of the second bearing component <NUM> and may be secured, e.g. threaded, in the threaded hole of the rotor hub <NUM>. This fastener may thus connect the rotor hub <NUM> to the second bearing component <NUM>. A plurality of fasteners may be threaded in a plurality of threaded holes formed at the rotor hub <NUM> to connect the second bearing component <NUM> to the rotor hub <NUM>. In other examples, the rotor hub and the second bearing component may comprise a plurality of through holes. Bolts may be inserted into these through holes and secured with nuts to connect the second bearing component to the hub.

The pitch bearing <NUM> of this example is a ball bearing and a bearing gap <NUM> is formed between the first bearing component <NUM> and the second bearing component <NUM>. Lubricant, e.g. grease and/or oil, may be provided between the bearing components to reduce friction. This lubricant may flow through the bearing gap <NUM> between the first bearing component <NUM> and the second bearing component <NUM>. In this example, a groove <NUM> is machined on the upper sides of the first and second bearing components. Lubricant may be accumulated in this groove <NUM>. The pitch bearing <NUM> of this figure further comprises a bearing seal element <NUM> covering the groove <NUM>. The bearing seal element <NUM> may help to reduce the lubricant leaks from the bearing gap <NUM>. However, the bearing seal element <NUM> does not completely avoid lubricant leaks from the pitch bearing <NUM>. The bearing seal element <NUM> of this example is an example of a primary sealing element.

The lubricant retention system <NUM> comprises a base <NUM> connected to the blade root portion <NUM>. The base <NUM> is thus configured to be connected to the wind turbine blade <NUM>. The base <NUM> comprises a base outer surface <NUM>. In this figure, the base outer surface <NUM> fits the inner blade shell surface <NUM>. In other examples, the base outer surface <NUM> fits the outer blade shell surface <NUM>. The base outer surface <NUM> is thus configured to fit a surface of the wind turbine blade <NUM>, e.g. the blade shell <NUM> and/or a blade root attachment portion <NUM>. The base <NUM> of this example further comprises a base inner surface <NUM> opposite to the base outer surface <NUM>.

The base <NUM> of this example extends from a base root end <NUM> to a base tip end <NUM> in a base longitudinal direction <NUM>. When the base <NUM> is coupled to the wind turbine blade, the base longitudinal direction <NUM> is parallel to the longitudinal direction of the wind turbine blade. In this example, the base root end <NUM> of the base <NUM> is apart from the upper surface <NUM> of the first bearing component <NUM>. However, in other examples, the base root end <NUM> may rest on the upper surface <NUM> of the first bearing component <NUM>. In these examples, the base outer surface <NUM> may be coupled to the blade shell <NUM>, e.g. to the inner blade shell surface <NUM>, and/or to the blade root attachment portion <NUM>, e.g. to an inner surface of the mounting flange <NUM>.

The base <NUM> of this example may be connected to the blade according to any of the examples herein disclosed. For example, glue or an adhesive may be used for fixing the base outer surface <NUM> to the blade shell <NUM>. However, other suitable connecting methods may be alternatively used. For example, a pressure element may be used for exerting an outwards pressure against the base inner surface <NUM> for fixing the base <NUM> to the blade shell <NUM>. The pressure element may be a disc with a variable diameter that may be arranged inside the wind turbine blade to exercise an outwards radial pressure onto the base.

In further examples, a portion of the base, e.g. the base outer surface, may be integrated within the blade shell. The base may be arranged between fibers of the blade shell during blade manufacturing.

The base <NUM> of this example extends <NUM>°. In some examples, the base <NUM> may comprise a plurality of annular base segments that forms a base <NUM> extending <NUM>°. In some examples, the base may be formed by a single annular element extending <NUM>°. The segments may be connected to each other by e.g. glue, adhesive or through a bolted connection.

The base <NUM> may comprise a plastic material. For example, the base <NUM> may be manufactured from glass-reinforced plastic. The base may be made from a flexible material to adjust the base <NUM> to the diameter of the blade root portion <NUM>.

The lubricant retention system <NUM> further comprises an annular seal assembly <NUM>. Although not shown in <FIG>, the annular seal assembly <NUM> is formed by a plurality of annular seal segments <NUM> connected to each other. The annular seal segments <NUM> extend from a proximal end portion <NUM> to a distal end portion <NUM>. The proximal end portion <NUM> is connected to the base <NUM> and the distal end portion faces the second bearing component <NUM>.

The annular seal assembly <NUM> extends <NUM>°. The angular extension of each of the annular seal segments <NUM> depends on the number of segments. For example, an annular seal assembly <NUM> may be formed by two annular seal segments <NUM>. These two annular seal segments <NUM> may thus substantially extend about <NUM>°. The annular seal assembly may be formed by any suitable number between two and twenty annular seal segments, e.g. between two and six annular seal segments. For example, when the annular seal assembly is formed by joining six annular seal segments, each of the annular seal segments substantially extends <NUM>°.

The annular seal segments <NUM> are connected edge to edge to form a complete annular seal assembly <NUM>. One edge of one annular seal segment <NUM> is connected to one edge of an adjacent annular seal segment <NUM>, and so on. At least one of the annular seal segments of the plurality of the annular seal segments is removably connected to the adjacent or adjacent annular seal segments. For example, the releasable annular seal segment is configured to be releasably connected to a first adjacent annular segment and to a second annular seal segment of the plurality of annular seal segments. For example, the removable annular seal segment or segments may be connected to the adjacent annular seal segments through a bolted connection. In other examples, snap-fit connectors may be used for removably connecting one edge of one annular seal segment to one edge of an adjacent annular seal segment.

The annular seal segments <NUM> may be made from a flexible material to adjust the length of the distal end portion <NUM> to the shape of the second bearing component <NUM>. One example of flexible material is rubber. In some examples, the annular seal segments may comprise an internal stiffener to provide stiffness to the rubber so as to maintain a specific shape of the annular seal segments <NUM>.

In further examples, the annular seal segments <NUM> may comprise a plastic material, e.g. glass reinforced plastic.

In some examples, each of the plurality of annular seal segments is a releasable annular segment. The annular seal segments may thus be releasably connected to the adjacent annular seal segments. The annular seal assembly may thus be easily dismounted for performing maintenance or inspection operations.

In some examples, one or more of the annular seal segments <NUM> are removably coupled to the base <NUM>. In some examples, the releasable annular seal segments may be removably coupled to the base <NUM>. In some examples, the plurality of annular seal segments <NUM> is removably coupled to the base <NUM>.

In some examples, the base may comprise a base engaging portion and the one or more annular seal segments a seal segment engaging portion for removably coupling the base to the annular seal segment. One of these engaging portions may comprise a receiver and the other a protrusion that fits the receiver. The annular seal segments <NUM> may be pressed against the base <NUM> to lock the protrusion onto the receiver. A non-permanent connection may thus be formed. Snap-fit connectors may be employed for removably connecting one or more annular seal segments <NUM> to the base <NUM>. In further examples, one or more annular seal segments <NUM> may be bolted to the base <NUM>.

The distal end portion <NUM> of the annular seal segments <NUM> that form the annular seal assembly <NUM> extends towards the second bearing component <NUM>. In this example, the distal end portion <NUM> contacts the second bearing component <NUM>. In other examples, the distal end portion <NUM> does not contact the second bearing component <NUM>. A gap may thus be defined between the distal end portion <NUM> and the second bearing component <NUM>.

In this example, the annular seal segments <NUM> extend from a radial direction <NUM> (perpendicular to the base longitudinal direction <NUM>) to a direction substantially parallel to the base longitudinal direction <NUM>. The annular seal segments <NUM> extend back from the proximal end portion <NUM> towards the distal end portion <NUM>. The plurality of annular seal segments <NUM> defines a seal inner surface <NUM> that faces the bearing gap <NUM> between the first bearing component <NUM> and the second bearing component <NUM>. In this example, the seal inner surface <NUM> comprises a concave shape. The annular seal assembly may further comprise a seal outer surface <NUM> opposite to the seal inner surface <NUM>.

In use, the distal end portion <NUM> of each of the annular seal segments extends beyond the base root end <NUM>. Thus, the distal end portion <NUM> is closer to the rotor hub <NUM> than the base root end <NUM>.

In this example, the distal end portion <NUM> of the plurality of annular seal segments <NUM> contacts the upper surface <NUM> of the second bearing component <NUM>. The plurality of annular seal segments <NUM> thus extends from the blade <NUM> that is connected to the first bearing component <NUM> towards the second bearing component <NUM>. The lubricant retention system <NUM> rotates together with the first bearing component <NUM>. The distal end portion <NUM> of the plurality of annular seal segments <NUM> may exert pressure against the upper surface <NUM> of the second bearing component <NUM> but allows the rotation of the first bearing component <NUM> with respect to the second bearing component <NUM>.

In some examples, a retention member may be connected to the distal end portion <NUM>. The retention member may be employed for reducing a gap between the distal end portion <NUM> and the second bearing component. For example, the gap may be formed between the upper surface <NUM> of the second bearing component <NUM> so as to extend along a direction substantially parallel base longitudinal direction <NUM>. This gap may be formed when the distal end portion <NUM> is not in contact with a surface of the second bearing component <NUM>. The retention member may comprise a flexible material, e.g. rubber or brush with a plurality of bristles. The retention member may alternatively or additionally comprise a material such as an absorbent material, a textile material, a felt-type material, a hydrophobic material, a hydrophilic material, a combination of hydrophobic and hydrophilic materials, a sponge material, a porous material, and/or a filtering material or any combination thereof.

The retention member <NUM> may have material properties such that it retains certain types of fluids while repelling others, for example, based on viscosity or other physical or chemical properties of the fluid to be contained or repelled. For example, the material may absorb lubricant such pitch bearing lubricant, e.g. grease while allowing water to pass through and leave the chamber <NUM>.

The retention member <NUM> may have structural (e.g. geometrical, porosity) properties such that it retains certain types of fluids while repelling others. For example, the material may absorb grease such pitch bearing grease while allowing water to pass through and leave the chamber <NUM>.

The retention member may extend substantially perpendicular to the upper surface <NUM> of the second bearing component <NUM>. Alternatively, the retention member may have a curved or arcuate profile, for example, forming a concavity facing towards the inside of the formed chamber <NUM>. The retention member may be a separate element from the distal end portion <NUM>, or may be integrally formed with the distal end portion <NUM>.

As in this example the distal end portion <NUM> contacts the upper surface <NUM> of the second bearing component <NUM>, a chamber <NUM> is formed enclosing the bearing gap <NUM> of the pitch bearing <NUM>. Lubricant spilling out from the groove <NUM> covered by the bearing seal element <NUM> may be retained within the chamber <NUM>. Accordingly, the leaking point of the pitch bearing <NUM> is enclosed or substantially enclosed. The sealing effect is consequently improved. Lubricant leaks from the pitch bearing <NUM> may be stored within the chamber <NUM>. The volume of lubricant leaks retained by the chamber may thus be increased. In this example, the chamber <NUM> is arranged inside the wind turbine blade <NUM>. The chamber <NUM> of <FIG> and <FIG> is thus substantially delimited by the seal inner surface <NUM>.

<FIG> shows a lubricant retention system according to some examples of the present disclosure. Contrary to the lubricant retention system <NUM> of <FIG> and <FIG>, the lubricant retention system <NUM> of <FIG> is connected to the outer blade shell surface <NUM>.

In this example, the first bearing component <NUM> comprises an inner ring and the second bearing component <NUM> comprises an outer ring. The diameter of the second bearing component <NUM> of this figure is greater than the diameter of the first bearing component <NUM>. As explained before, the first and/or the second bearing component may comprise a stiffener element to increase the radial stiffness of the blade-hub connection.

The lubricant retention system <NUM> of this figure is similar to the examples described with respect to <FIG> and <FIG>. However, in this figure, the base outer surface <NUM> of the base <NUM> fits the outer blade shell surface <NUM>. Furthermore, the base root end <NUM> of the base <NUM> of this figure rests on the upper surface <NUM> of the first bearing component <NUM>. The base outer surface <NUM> of this example also fits the outer surface of the mounting flange <NUM>. In other examples, there may be a gap between the base root end <NUM> and the upper surface <NUM> of the first bearing component <NUM>.

In <FIG>, the base <NUM> surrounds the outer blade shell surface <NUM>. Glues or adhesives may be used for connecting the base outer surface <NUM> to the outer blade shell surface <NUM>. In some examples, a pressure element may be used to exert an inward pressure against the base <NUM>. For example, a ring arranged around the base may press the base to the blade shell <NUM>. Steel wires may be arranged around the base to secure the base to the outer blade shell surface <NUM>, e.g. by wrapping the base and the blade.

As previously described, in some examples, the plurality of annular seal segments <NUM> that forms the annular seal assembly <NUM> extends to contact (or substantially contact) the upper surface <NUM> of the second bearing component <NUM> so as to form the chamber <NUM> to collect lubricant leaks from the pitch bearing <NUM>.

In other examples, the distal end portion <NUM> may contact (or substantially contact) a lateral surface <NUM> of the pitch bearing. Fasteners connecting the second bearing component <NUM> to the rotor hub <NUM> may thus be covered by the annular seal assembly <NUM>. These fasteners may thus be protected from environmental conditions, e.g. rain. Corrosion of the fasteners may thus be reduced.

<FIG> shows a cross-sectional view of a lubricant retention system mounted on a wind turbine blade according to one example of the present disclosure and <FIG> is an enlarged view of the connection of the base to the blade shell of <FIG>.

The blade root portion <NUM> comprises a blade root attachment portion <NUM> having a mounting flange <NUM> facing the upper surface <NUM> of the first bearing component <NUM>. In this example, the first bearing component <NUM> is an inner ring and the second bearing component <NUM> is an outer ring. In other examples, the first bearing component <NUM> may be an outer ring and the second bearing component <NUM> may be an inner ring. The first bearing component <NUM> and the second bearing component <NUM> may be respectively connected to the blade <NUM> and to the rotor hub <NUM> according to any of the examples herein disclosed.

The pitch bearing <NUM> of this example comprises a bearing seal element <NUM> arranged in a groove defined between the first bearing component <NUM> and the second bearing component <NUM>. The bearing seal element <NUM> is a primary seal for the pitch bearing <NUM>.

The base <NUM> of this example comprises a substantially cylindrical shape. The base <NUM> extends from a base root end <NUM> to a base tip end <NUM> along a base longitudinal direction <NUM>. The base <NUM> of this example comprises a base outer surface <NUM> that fits the outer shape of the blade shell <NUM>. The base <NUM> further comprises a base inner surface <NUM> that faces the annular seal assembly <NUM>. The base <NUM> encloses the outer shape of the blade <NUM>.

In this example, the base <NUM> is bonded to the outer blade shell surface <NUM>. For example, glue and/or adhesive may be used for bonding the base <NUM> to the outer blade shell surface <NUM>. In these figures, a pair of double-sided tapes <NUM> are arranged between the base outer surface <NUM> and the outer blade shell surface <NUM>. In this example, one double-sided tape is arranged at the base root end <NUM> and the other one at the base tip end <NUM>. In these figures, glue <NUM> is provided between the pair of double-sided tapes <NUM>. Glue <NUM> may be injected into the annular recess defined between the pair of double-sided tapes <NUM>. The combination of glue <NUM> and the double-sided tapes <NUM> provides a bonding force to retain the base <NUM> joined to the outer blade shell surface <NUM>. The double-sided tapes <NUM> may be used to position the base <NUM> and then glue may be applied to permanently bond the base outer surface <NUM> to the outer blade shell surface <NUM>.

In other examples, the base <NUM> may be connected to the blade according to any other suitable method. For example, the base may also be integrated with the blade shell during blade manufacturing.

The base <NUM> may be formed by a plurality of base segments. These base segments may be joined together edge to edge. This may simplify the connection of the base <NUM> to the blade <NUM>, in particular, in existing wind turbine blades. In other examples, the base <NUM> may be formed by a single member. The opposite edges of this single member may be arranged to enclose the blade shell and may then be connected to each other.

The lubricant retention system <NUM> comprises a plurality of annular seal segments <NUM>. In these figures, each of the plurality of annular seal segments <NUM> is removably coupled to the base <NUM>. In other examples, some annular seal segments <NUM> may be fixedly coupled to the base <NUM> and some annular seal segments <NUM> may be removably coupled to the base <NUM>. A seal inner surface <NUM> faces the base inner surface <NUM>. The seal inner surface <NUM> defines the inner surface of the annular seal assembly <NUM>, i.e. the surface configured to define the chamber <NUM> for retaining lubricant leaks.

In this example, a fastener <NUM> may be used for connecting the base <NUM> to a proximal end portion <NUM> of each of the plurality of annular seal segments <NUM>. The fastener may be a bolt, e.g. a T-bolt. The fastener may pass through corresponding holes provided at the base <NUM> and at the proximal end portion <NUM>. A thread may be secured to the fastener. To ensure the fluid-tightness of the chamber <NUM>, a pair of gaskets <NUM> may be provided between the base outer surface <NUM> and the seal inner surface <NUM> at the proximal end portion <NUM> of the annular seal segments <NUM>.

Each of the plurality of annular seal segments <NUM> that form the annular seal assembly extends from the proximal end portion <NUM> to the distal end portion <NUM>. The distal end portion <NUM> extends towards the second bearing component <NUM>. In this example, the distal end portion <NUM> further extends alongside (that is, along a direction <NUM>) a portion of a lateral surface <NUM> of the second bearing component <NUM>. The distal end portion <NUM> thus extends beyond the upper surface <NUM> of the second bearing component <NUM>. The lubricant retention system <NUM> may thus define a chamber <NUM> to enclose the bearing gap <NUM> of the pitch bearing so as to accumulate lubricant leaks. In addition, as the annular seal assembly <NUM> covers the pitch bearing <NUM> and the fasteners connecting the second bearing component <NUM> to the rotor hub <NUM>, the lubricant retention system <NUM> prevents water and/or dust from entering the pitch bearing. A seal outer surface <NUM> may act as a cover for the pitch bearing. Protection of the pitch bearing is consequently increased. Corrosion of the pitch bearing and/or of the fasteners connecting the second bearing component <NUM> to the rotor hub <NUM> is prevented.

The lateral surface <NUM> extends between the upper surface <NUM> and the lower surface <NUM> of the second bearing component <NUM>. The lower surface <NUM> of the second bearing component <NUM> faces the rotor hub <NUM>, whereas the upper surface <NUM> faces the blade <NUM>.

The proximal end portion <NUM> of these figures extends substantially parallel to the base <NUM>. The proximal end portion <NUM> thus extends substantially parallel to the base longitudinal direction <NUM>. When the plurality of annular seal segments <NUM> are joined to each other to define the annular seal assembly, the proximal end portion <NUM> of the plurality of annular seal segments defines a cylindrical shape. The proximal end portion <NUM> of the plurality of annular seal segments <NUM> defines a proximal end portion diameter. In this example, the proximal end portion <NUM> of the plurality of annular seal segments <NUM> encloses the base <NUM>.

In this example, when the plurality of annular seal segments <NUM> are joined to each other to form the annular seal assembly <NUM>, the distal end portion <NUM> of the plurality of annular seal segments <NUM> defines a cylindrical shape having a distal end portion diameter. When assembled and mounted on the blade, the distal end portion <NUM> of the plurality of annular seal segments <NUM> extends substantially parallel to the base longitudinal direction <NUM>. The distal end portions <NUM> of this example substantially enclose the second bearing component <NUM>.

The distal end portion diameter of this example is greater than the proximal end portion diameter. The diameter of the annular seal assembly thus increases from the proximal end portion diameter to the distal end portion diameter. This increase in diameter allows defining the chamber <NUM> to store lubricant leaking from the pitch bearing.

Each of the plurality of annular seal segments <NUM> comprises a central portion <NUM> connecting the proximal end portion <NUM> to the distal end portion <NUM>. The central portion <NUM> of each of the annular seal segments comprises an inclined surface. When the plurality of annular seal segments <NUM> forms the annular seal assembly, the central portions <NUM> comprise a substantially frustum conical shape.

In this example, each of the plurality of annular seal segments <NUM> comprises a retention member <NUM> to reduce a gap (defined in the direction <NUM>) between the distal end portion <NUM> and a lateral surface <NUM> of the second bearing component <NUM> when the lubricant retention system (<NUM>) is mounted on the wind turbine blade (<NUM>). The retention member <NUM> of these figures is connected to the distal end portion <NUM>. The retention member <NUM> of this example extends substantially perpendicular to the lateral surface <NUM> of the second bearing component <NUM>. In other examples, the retention member <NUM> may extend in a curved or arcuate manner, for example, forming a concave area facing the interior of the chamber <NUM>.

In use, a retention member tip <NUM> of the retention member <NUM> may contact the second bearing component <NUM>. In some examples, the retention member <NUM> may exert pressure against the second bearing component <NUM> to prevent lubricant flow between the second bearing component <NUM> and the distal end portion <NUM>. In the example of these figures, the retention member tip <NUM> is configured to contact the lateral surface <NUM> of the second bearing component <NUM>. The retention member <NUM> of these figures faces the lateral surface <NUM> of the second bearing component <NUM>. The retention member <NUM> may extend from the distal end portion <NUM> of the plurality of annular seal segments <NUM> to the retention member tip <NUM> inwardly in a radial direction <NUM>. The retention member <NUM> may thus close a gap defined between the distal end portion <NUM> and the lateral surface <NUM> of the second bearing component <NUM>.

The retention member extends between the edges of each of the annular seal segments. When the annular seal segments are joined together, the plurality of retention members define a ring. The retention members may thus extend along an inner diameter of the annular seal assembly.

In some examples, the retention member <NUM> is detachably connected to the distal end portion <NUM> of the plurality of annular seal segments <NUM>. The retention member may thus be easily removed. As the retention member may be in contact with the second bearing component <NUM>, the retention member tip <NUM> may suffer from wear. Furthermore, the retention member <NUM> may get excessively impregnated by lubricant leaking from the pitch bearing. To maintain a sealing effect, the retention member <NUM> may be replaced by a new retention member. Maintenance operations may thus be simplified.

In some examples, snap-fit connectors may be used for removably or detachably connecting the retention member <NUM> to the distal end portion <NUM>. In some examples, the retention member <NUM> may comprise a protrusion and the distal end portion <NUM> a groove to receive this protrusion. In some examples, the retention member <NUM> may be fastened or bolted to the distal end portion <NUM>.

In the example of these figures, the annular seal segments <NUM> comprise a plastic material. An annular seal assembly with sufficient stiffness to retain the lubricant and relatively low weight may thus be obtained. For example, the plastic material may comprise glass-reinforced plastic. In other examples, the annular seal segments <NUM> may comprise rubber. A stiffener may be provided within the rubber material to prevent excessive deformation of the annular seal assembly.

The base <NUM> may also comprise a plastic material. For example, the base <NUM> may be manufactured from glass-reinforced plastic.

The retention member <NUM> may comprise a flexible material. The pressure exerted by the retention member <NUM> against the second bearing component <NUM>, e.g. against the lateral surface <NUM> of the second bearing component <NUM>, may thus be adjusted. In some examples, the retention member <NUM> may comprise rubber.

In some examples, the retention member <NUM> comprises a brush having a plurality of bristles. The bristles are oriented towards the second bearing component <NUM>, e.g. extend perpendicular to the lateral surface <NUM> of the second bearing component <NUM>. The bristles may bend when contacting the second bearing component <NUM>. The brush may absorb and retain lubricant, e.g. grease. The sealing effect may be enhanced by the combination of the chamber <NUM> formed by the annular seal assembly <NUM> to store lubricant and the brush arranged at the distal end portion <NUM>. Large amounts of lubricant leaking from the pitch bearing may be thus retained with the lubricant retention system according to the present disclosure.

According to some examples, as shown in <FIG>, the retention member <NUM> may comprise a brush having bristles, some bristles may contact the lateral surface <NUM>, while other bristles of the brush may not contact the surface <NUM>. In some examples, the dimensions of the brush are such that none of the bristles contact the lateral surface <NUM> of the second bearing <NUM>.

According to some examples, as shown in <FIG>, the retention member tip <NUM> does not contact the lateral surface <NUM> of the second bearing <NUM>. Thus, a gap <NUM> remains between the retention member <NUM> and the lateral surface <NUM> of the second bearing <NUM>.

<FIG> schematically represents an annular seal assembly of a lubricant retention system according to an example of the present disclosure. The annular seal assembly <NUM> of this figure may be used in the lubricant retention systems <NUM> depicted in <FIG> of the present disclosure.

The annular seal assembly <NUM> of <FIG> is formed by four annular seal segments 120a, 120b, 120c and 120d that extend from a proximal end portion <NUM> to a distal end portion <NUM>. The connection of these annular seal segments defines a seal inner surface <NUM> to face the pitch bearing and a seal outer surface <NUM> opposite to the seal inner surface <NUM>.

Each of these annular seal segments extends a length of an arc of the circumference between a first edge and a second edge. For example, the annular seal segment 120a extends between the first edge 127a and the second edge 128a. In this example, each of these annular seal segments substantially extends <NUM>° between the respective first edge and second edges. In other examples, the annular seal segments may extend any suitable portion of the arc of the circumference.

In this example, the annular seal segment 120a is a removably annular seal segment. The annular seal segment 120a is removably connected to the annular seal segments 120b and 120d. The first edge 127a of the annular seal segment 120a is removably connected to the second edge 128b of the annular seal segment 120b, and the second edge 128a of the annular seal segment 120a is removably connected to the first edge 127d of the annular seal segment 120d. The annular seal segment 120a may thus be easily removed for inspecting the level of lubricant retained by the annular seal assembly <NUM>.

The removable connection may be according to any of the examples herein disclosed. For example, a bolted connection and/or snap-fit connection may be used to removably connect the annular seal segment 120a to the annular seal segments 120d and 120b.

In some examples, the first edge 127a may engage the second edge 128b. For example, one of these edges 127a and 128b may comprise a flat edge portion and the other a stepped edge portion. These shapes may enhance the connection between the annular seal segments 120a and 120b. In other examples, the edges 127a and 128b may comprise interlocking edges. The second edge 128a of the annular seal segment 120a and the first edge 127d of the annular seal segment 120d may be connected in a similar manner.

In this example, the annular seal segment 120c is permanently connected to the annular seal segments 120b and 120d. In other examples, each of the plurality of annular seal segments may be removably connected with the adjacent annular seal segments. The first edge 127b of the annular seal segment 120b and the second edge 128c of the annular seal segment 120c are permanently connected. Similarly, the first edge 127c of the annular seal segment 120c is permanently connected to the second edge 128d of the annular seal segment 120d. Glue or welding methods may be used for establishing a fixed connection.

In this example, the annular seal segment 120a is configured to be detachably connected to the base. This may allow completely removing the annular seal segments from the base and from the remaining annular seal segments. In some examples, the set of fixedly connected annular seal segments, in this example 120b, 120c and 120d, may be detachably connected to the base. This set of annular seal segments may thus be disconnected from the base together.

In this example, the annular seal assembly is formed by six annular seal segments 120a, 120b, 120c, 120d, 120e and 120f. These six annular segments defined the annular seal assembly extending from the proximal end portion <NUM> to the distal end portion <NUM> through the central portion <NUM>.

In the example of <FIG>, the annular seal segments extend substantially <NUM>°. The annular seal segments of this example are removably annular seal segments. For example, the annular seal segment 120d may be removably connected to the annular seal segments 120c and 120e. These annular seal segments may be connected to the corresponding edges according to any of the examples herein disclosed. For example, each of the annular seal segments may comprise a stepped edge portion and a flat edge portion. The stepped edge portion of one annular seal segment may fit the flat edge portion of the adjacent annular seal segments. Accordingly, positioning and connecting the annular seal segments may be improved.

The plurality of the annular seal segments of this example is also removably connected to the base. Accordingly, each of the annular seal segments may be independently connected and disconnected from the base and from the adjacent annular seal segments in an easy manner. Inspections or maintenance operations may thus be simplified and more efficiently performed.

<FIG> schematically represents a bottom view of a portion of an annular seal assembly according to an example of the present disclosure. The annular seal segment 120a of this example is removably coupled to the annular seal segments 120b and 120c.

The annular seal segments 120a, 120b and 120c of this figure define a seal inner surface <NUM> to face the pitch bearing and a seal outer surface <NUM> that faces the opposite side, e.g. outside the wind turbine.

A first edge 127a and a second edge 128a of the annular seal segment 120a are, respectively, removably connected to the second edge 128b of the annular seal segment 120b and to the first edge 127c of the annular seal segment 120c.

The annular seal segments of this example comprise a stepped edge portion 161a and 161c and a flat edge portion 162a and 162b. The stepped edge portion of an annular seal segment is configured to overlap the flat edge portion of an adjacent annular segment.

When the annular seal assembly is assembled, the stepped edge portions extend outwards so as to overlap the flat edge portions. The seal inner surface <NUM> may thus remain substantially constant, however, the stepped edge portions generate protrusions on the seal outer surface <NUM>. The stepped edge portions may thus engage the corresponding flat edge portions.

In this example, the annular seal segment 120a comprises a first edge 127a having a stepped edge portion 161a and a second edge 128b having a flat edge portion 162a. The stepped edge portion 161a of the annular seal segment 120a engages the flat edge portion 162b arranged at the second edge 128b of the annular seal segment 120b. Similarly, the annular seal segment 120c comprises a first edge 127a having a stepped edge portion 161c. The stepped edge portion 161c of the annular seal segment 120c engages the flat edge portion 162a of the second edge 128a of the annular seal segment 120a.

A seal fastener <NUM> may be inserted through a hole arranged at the flat edge portion and the stepped edge portion. The seal fasteners, e.g. bolts, may be inserted from the seal inner surface <NUM> towards the seal outer surface <NUM>. A nut may be secured on a thread of the seal fasteners to join the stepped edge portion to the flat edge portion of two consecutive annular seal segments. A bolted connection may thus be established to connect the annular seal segments to each other. A gasket may be provided between the flat edge portion and the stepped edge portion of two consecutive annular seal segments.

In this example, the annular seal segments 120a, 120b and 120c respectively comprise a retention member 150a, 150b and 150c. The retention members 150a, 150b and 150c may comprise a brush with a plurality of bendable bristles. At least some of these bendable bristles may press a lateral surface of a second bearing component to seal the cavity for accumulating lubricant spilling out from the pitch bearing.

The retention members of this figure are removably attached to the annular seal segments. A plurality of retention member fasteners <NUM> may be provided for joining the retention member to the corresponding annular seal segment. For example, the retention member 150a is bolted to the annular seal segment 120a through a plurality of retention member fasteners <NUM>.

The retention members may be connected to the corresponding annular seal segment prior to joining the annular seal segments to form the annular seal assembly. The retention member may thus be mounted at a manufacturing plant. For example, the retention member 150a may be connected to the annular seal segment 120a through the retention member fasteners. Then, the annular seal segment 120a may be connected to the annular seal segments 120b and 120c through the seal fasteners <NUM>. In this example, the seal fastener <NUM> may also connect the retention member to the annular seal member.

<FIG> is a block diagram of a method <NUM> for mounting a lubricant retention system for a pitch bearing in a wind turbine blade according to an example of the present disclosure. The lubricant retention system <NUM> and the wind turbine may be according to any of the examples herein disclosed. In this example, the pitch bearing <NUM> comprises a first bearing component <NUM> and a second bearing component <NUM>, the first bearing component <NUM> configured to rotate with respect to the second bearing component <NUM>.

At block <NUM>, connecting a base <NUM> of the lubricant retention system <NUM> to a blade root portion <NUM> of the wind turbine blade <NUM> configured to be coupled to the first bearing component <NUM> is represented. The base <NUM> may be connected to a blade shell <NUM> and/or to a blade root attachment portion <NUM>, e.g. a mounting flange. <NUM>
In some examples, connecting the base <NUM> to the blade root portion <NUM> comprises positioning a base outer surface <NUM> of the base <NUM> to fit a surface of the wind turbine blade <NUM>. The base outer surface <NUM> may thus be fitted with the surface of the wind turbine blade <NUM>.

When the wind turbine blade <NUM> is coupled to the outer ring of the pitch bearing <NUM>, the method may comprise fitting the base outer surface <NUM> with the inner blade shell surface <NUM> and/or an inner surface of the blade root attachment portion <NUM>, e.g. an inner surface of a mounting flange <NUM>. The base <NUM> is thus positioned within the wind turbine blade <NUM>. In these examples, connecting the base <NUM> to the blade root portion <NUM> may comprise adhering the base outer surface <NUM> to the inner blade shell surface <NUM> and/or an inner surface of the blade root attachment portion <NUM>.

When the wind turbine blade <NUM> is coupled to the inner ring of the pitch bearing <NUM>, the method may comprise fitting the base outer surface <NUM> with the outer blade shell surface <NUM> and/or an outer surface of the blade root attachment portion <NUM>, e.g. an outer surface of a mounting flange <NUM>. The base <NUM> is thus positioned around the wind turbine blade <NUM>.

In some examples, connecting the base <NUM> to the blade root portion <NUM> may comprise adhering the base outer surface <NUM> to the blade shell <NUM> and/or to the blade root attachment portion <NUM>. Adhering or bonding the base outer surface <NUM> to the blade <NUM> may comprise arranging a pair of double-sided tapes <NUM> between the base outer surface <NUM> and the blade <NUM>. Then, glue <NUM> may be inserted between this pair of double-sided tapes <NUM> to increase the adherence of the joint.

In some examples, a fastener <NUM> may be inserted through a hole arranged on the base <NUM> from the base outer surface <NUM> to the base inner surface <NUM>. This fastener <NUM> may be used for removably connecting the base <NUM> to the annular seal segment <NUM>. The fastener <NUM> may be arranged between the double-sided tapes <NUM>. Glue <NUM> may be applied after the insertion of the fastener <NUM>. A head of the fastener <NUM> may thus be fixed to the base outer surface <NUM>.

In some examples, a pressing element may be positioned on the base inner surface <NUM> to press the base <NUM> against the blade <NUM>. The pressing element may be a ring with a variable diameter to adjust the pressure against the base.

These connection methods allow connecting the lubricant retention system <NUM> to existing wind turbines. Accordingly, existing wind turbines may be retrofitted.

In further examples, the base <NUM> may be connected to the blade root portion <NUM> during manufacturing. For example, the blade shell <NUM> of the blade root portion <NUM> may be infused together with the base <NUM>. In these examples, the method may further comprise coupling the blade <NUM> having the base <NUM> of the lubricant retention system <NUM> to the first bearing component <NUM>. This may involve lifting the blade <NUM> with the base <NUM> of the lubricant retention system from the ground to attach the blade <NUM> to the first bearing component <NUM>.

The method <NUM> further comprises connecting a plurality of annular seal segments <NUM> to the base <NUM> in such a way that a distal end portion <NUM> of the plurality of annular seal segments <NUM> extends towards the second bearing component <NUM> for defining a chamber <NUM> for retaining lubricant from the pitch bearing <NUM>, as represented at block <NUM>. The annular seal segments <NUM> may be positioned according to any of the examples herein disclosed. For example, the annular seal segment <NUM> may be positioned such that the distal end portion <NUM> faces the upper surface <NUM> or a lateral surface <NUM> of the second bearing component <NUM>.

The annular seal segments <NUM> may be removably connected to the base <NUM>. In some examples, the plurality of annular seal segments <NUM> is removably connected to the base <NUM>. A snap-fit connection or a bolted connection may be employed for removably connecting the annular seal segments <NUM> to the base <NUM>.

In some examples, the fastener <NUM> fixedly connected to the base <NUM> may be inserted through a hole arranged at the proximal end portion <NUM> of an annular seal segment <NUM>. A nut may be threaded on the fastener <NUM> to secure the proximal end portion <NUM>. A gasket <NUM> may be arranged between the base <NUM> and the proximal end portion <NUM> to enhance the sealing effect of the lubricant retention system <NUM>.

In further examples, the annular seal segments <NUM> may be fixedly connected to the base. Glue or adhesive may be used for fixedly connecting the annular seal segments <NUM> to the base <NUM>. In some examples, some annular seal segments of the plurality of annular seal segments <NUM> may be fixedly connected to the base <NUM> and some annular seal segments of the plurality of annular seal segments <NUM> may be removably or detachably connected to the base <NUM>.

At block <NUM>, connecting the plurality of annular seal segments to each other to form an annular seal assembly is represented. Connecting the plurality of annular seal segments comprises releasably connecting a releasable annular seal segment of the plurality of annular seal segments to the other annular seal segment or annular seal segments of the plurality of annular seal segments. At least one of the annular seal segments is thus removably connected to the adjacent annular seal segment or segments.

The releasable annular seal segment or segments may be connected to the adjacent annular seal segments according to any of the examples herein described. For example, a stepped edge portion <NUM> of an annular seal segment <NUM> may be positioned to overlap a flat edge portion <NUM> of an adjacent annular seal segment. Once the stepped edge portion <NUM> engages the flat edge portion <NUM> a seal fastener <NUM> may be inserted through a hole formed at the flat edge portion <NUM> and at the stepped edge portion <NUM> of two consecutive annular seal segments. In some examples, a gasket may be arranged between the flat edge portion <NUM> and the stepped edge portion <NUM>.

In some examples, the annular seal segments <NUM> may be connected to each other to form the annular seal assembly <NUM> before connecting each of the annular seal segments <NUM> to the base <NUM>. In other examples, the plurality of annular seal segments <NUM> may be first connected to the base <NUM> and then the annular seal segments <NUM> may be joined together. In further examples, some annular seal segments of the plurality of annular seal segments <NUM> may be joined together before connecting these annular seal segments <NUM> to the base <NUM>.

In some examples, the method <NUM> may comprise connecting a retention member <NUM> to each of the plurality of annular seal segments <NUM> prior to connecting the plurality of annular seal segments <NUM> to each other and/or connecting the plurality of annular seal segments <NUM> to the base <NUM>. The retention member may be connected to the annular seal segments according to any of the examples herein disclosed. The retention member <NUM> may be removably connected to the annular seal segments <NUM>, e.g. through a bolted connection.

<FIG> is a block diagram of a method <NUM> for performing maintenance operations in a wind turbine. The wind turbine comprises a lubricant retention system <NUM> for collecting lubricant spilling out from the pitch bearing <NUM>. The lubricant retention system <NUM> may be according to any of the examples herein disclosed.

At block <NUM>, removing a releasable annular seal segment from an annular seal assembly <NUM> formed by a plurality of annular seal segments <NUM> of a lubricant retention system <NUM> for a pitch bearing <NUM>. The releasable annular seal segment may be disconnected from the annular seal assembly <NUM> according to any of the examples herein disclosed. For example, fasteners connecting the releasable annular seal segment to the adjacent annular seal segments may be unscrewed.

In some examples, removing the releasable annular seal segment may comprise disconnecting the releasable annular seal segment from the base <NUM>. For example, a proximal end portion <NUM> of the releasable annular seal segment may be unscrewed from the base <NUM>.

The method <NUM> further comprises inspecting a level of lubricant leaked from the pitch bearing <NUM> retained in a chamber <NUM> defined by the annular seal assembly <NUM>, as represented at block <NUM>. The amount of lubricant contained within the chamber <NUM> may thus be observed.

Depending on the amount of lubricant collected by the lubricant retention system, the method may comprise extracting the lubricant retained in the chamber <NUM> of the lubricant retention system <NUM>. In some examples, extracting the lubricant retained in the chamber <NUM> may comprise disconnecting a retention member <NUM> from the distal end portion <NUM> of the releasable annular seal segment. The retention member <NUM>, e.g. brush having a plurality of bristles, may be cleaned to extract the lubricant impregnating the bristles. In some examples, the disconnected retention member <NUM> may be replaced by a new retention member to ensure the sealing effect of the lubricant retention system.

Claim 1:
A lubricant retention system (<NUM>) for a pitch bearing (<NUM>) of a wind turbine, wherein the pitch bearing (<NUM>) comprises a first bearing component (<NUM>) to be coupled to a wind turbine blade (<NUM>) and a second bearing component (<NUM>) to be coupled to a rotor hub (<NUM>) of a wind turbine, the first bearing component (<NUM>) rotatable with respect to the second bearing component (<NUM>); the lubricant retention system (<NUM>) comprising:
a base (<NUM>) to be connected to a wind turbine blade (<NUM>), the base (<NUM>) comprising a base outer surface to fit a surface of the wind turbine blade (<NUM>);
a plurality of annular seal segments (<NUM>) to be connected to the base (<NUM>), wherein the annular seal segments of the plurality of annular seal segments (<NUM>) are to be connected to each other to form an annular seal assembly (<NUM>);
wherein the plurality of annular seal segments (<NUM>) comprises a distal end portion (<NUM>), wherein when the lubricant retention system (<NUM>) is mounted on the wind turbine blade (<NUM>), the distal end portion (<NUM>) extends towards the second bearing component (<NUM>) for defining a chamber (<NUM>) for retaining lubricant from the pitch bearing (<NUM>); and
wherein the plurality of annular seal segments (<NUM>) comprises a releasable annular seal segment to be releasably connected to another of the annular seal segments of the plurality of annular seal segments (<NUM>).