Patent Description:
Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A conventional wind turbine installation includes a foundation, a tower supported by the foundation, and an energy generating unit positioned atop of the tower. The energy generating unit typically includes one or more nacelles to house several mechanical and electrical components, such as a generator, gearbox, and main bearing, and the wind turbine also includes a rotor operatively coupled to the components in the nacelle through a main shaft extending from the nacelle. Single rotor wind turbines and multi-rotor wind turbines (which may have multiple nacelles) are known, but for the sake of efficiency, the following description refers primarily to single rotor designs. The rotor, in turn, includes a central hub and a plurality of blades extending radially therefrom and configured to interact with the wind to cause rotation of the rotor. The rotor is supported on the main shaft, which is either directly or indirectly operatively coupled with the generator which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator. Wind power has seen significant growth over the last few decades, with many wind turbine installations being located both on land and offshore.

As noted above, blades interact with the wind to generate mechanical rotation of the rotor, which can then be converted into electrical energy. A wind turbine blade is a complex structure that must be constructed to withstand long-term service in an abusive environment, while also maximizing lift and minimizing drag forces. The blades move at varying speeds through the ambient environment surrounding the wind turbine, but often this movement is at high speed, especially near the tip of the blades. Consequently, the blades will typically experience erosion and damage over time in operation as a result of friction from the air as well as potential impacts from particulate matter, debris, or other items in the air, especially along the leading edge facing the direction of movement through the wind. The erosion or damage along the leading edge of the blade adversely affects the aerodynamic qualities of the blade over time, resulting in lower power production for given incoming wind speeds. Such erosion and damage on the blades can be corrected by routine maintenance and repair procedures.

The blades are typically formed from a shell of layered fibre composite, aluminium, or similar material with an outer skin defined by a series of layers of coatings (polymeric elastomers, paint, etc.) surrounding and covering an outer surface of the shell. The shell encloses internal components of the blade and isolates the internal components from the environment, including shear webs and spar caps, for example. The outer skin may be defined by several different layers of material, including at least an outermost topcoat, a second layer underneath the outermost topcoat, and a third layer underneath the second layer. Other layers are typically present underneath the third layer as well, including base materials typically made from fibre composites and the like. Damage to the blade outer skin can be categorized into several different levels of severity based on which layer the damage extends to, e.g., an erosion to the third layer would be a "category <NUM>" level of severity, which would be higher than a cut to the second layer, which would be a "category <NUM>" level of severity. For low levels of damage or erosion, such damage can be repaired by depositing a coating onto the area to fill in the damage and restore the blade to the original condition along the leading edge thereof.

These types of repairs of the wind turbine blades have typically been conducted in three manners conventionally. First, the blade can be disassembled from the remainder of the wind turbine and lowered to the ground for the repair to be completed. Such a repair process is time-consuming and costly as a result of needing to disassemble, move, and reassemble the blade relative to the top of the tower. Thus, this approach is generally not favoured. In a second approach, a human operator with rope access can rappel along the wind turbine blade while still attached to the rotor hub to evaluate and make repairs as needed to the blade. In a third approach, a repair action can be taken by an operator on a platform hoisted into position adjacent the blade on the wind turbine, either extending from the nacelle or hub of the wind turbine or extending from a cherry picker or boom-style lift. Although the blade may remain attached to the wind turbine in the latter two approaches, a significant amount of skill and time are required to apply and shape the coating to the damaged area of the wind turbine blade properly. If the coating is not properly applied or misshapen, the aerodynamic performance of the blade may be adversely affected, requiring the wind turbine to be taken back out of service and a further maintenance and repair process performed on the blade.

<CIT> discloses the preamble of claim <NUM>; it shows a nozzle assembly for spreading material on curved surfaces, in the field of repairing services for wind turbine blades.

In recent years, a desire has emerged to allow for some automated maintenance of wind turbine blades, to improve the speed and/or precision of such a process. However, such automated maintenance devices are not always designed for reliable use on a wind turbine blade still connected to the rotor and hub of a wind turbine, and such systems are very slow in operation. Furthermore, such systems may be prone to uneven or misshapen coatings similar to that of manual processes. Thus, further improvements for automated maintenance and repair systems are desired.

Accordingly, wind turbine manufacturers and operators continue to seek improved options for conducting maintenance and repair on the wind turbine blades of modern wind turbine designs.

An applicator tool for repairing damage to a wind turbine blade is disclosed. The applicator tool includes a spatula including a flexible extrusion plate and one or more spacers positioned proximate the inner surface of the extrusion plate. The extrusion plate includes a front edge, a rear edge, opposed side edges, an outer surface, and an inner surface. The extrusion plate further includes a central region defined by a central axis. The one or more spacers are configured to define a gap between an outer surface of the wind turbine blade and the inner surface of the extrusion plate for dispensing of a coating material. The applicator tool further includes a feed tube for supplying the coating material to the spatula. The spatula is configured to shape the coating material into a coating over a damaged area of the wind turbine blade. The spatula is configured to apply a uniform and even coating of material that in cross section is generally thickest adjacent a leading edge of the blade and decreases in thickness in a generally continuous and smooth manner along the upper and lower surfaces of the blade and in a direction toward a trailing edge of the blade.

The one or more spacers define a height profile that generally corresponds to the shape of the coating from the applicator tool. By way of example, the height profile may have a maximum adjacent the central region of the extrusion plate and decay to substantially zero adjacent the side edges of the extrusion plate. In one embodiment, the extrusion plate may be movable relative to the one or more spacers. For example, the extrusion plate may be slidable relative to the one or more spacers. The relative movement between the extrusion plate and the one or more spacers is configured to vary the height profile.

In one embodiment, the one or more spacers include a plurality of ribs coupled to the inner surface of the extrusion plate and extend from the front edge toward the rear edge, wherein the plurality of ribs defines grooves between adjacent ribs. The plurality of ribs may be integrally formed with the extrusion plate in this embodiment. The plurality of ribs may be positioned on the inner surface of the extrusion plate about the central region and the regions of the inner surface adjacent the side edges may be void of the ribs. In one aspect, a height of the plurality of ribs may vary across the extrusion plate and the plurality of ribs may be symmetric about the central axis. In an exemplary embodiment, the height of the plurality of ribs may be at a maximum adjacent the central region of the extrusion plate and decrease in height away from the central region and toward the side edges.

In another embodiment, the one or more spacers include one or more spines having a front edge, a rear edge, an upper edge, and a lower edge. The lower edge may be angled relative to the upper edge by an acute angle, and the lower edge may be configured to engage the outer surface of the wind turbine blade during use. In this embodiment, the extrusion plate is separate from the one or more spines and is also movable relative to the one or more spines. The one or more spines may be positioned proximate the inner surface of the extrusion plate about the central region and the one or more spines may extend in a direction generally parallel to the central axis. In one embodiment, the extrusion plate may be coupled to a rigid support, the one or more spines may be coupled to the feed tube, and the rigid support may be slidable relative to the feed tube.

In a further embodiment, a method of repairing damage to a wind turbine blade is disclosed. The method includes providing an applicator tool; engaging the applicator tool to the outer surface of the wind turbine blade; supplying the coating material to the applicator tool; moving the applicator tool along the outer surface of the wind turbine blade; and dispensing the coating material from the applicator tool to form the coating over the damaged area of the wind turbine blade.

In one embodiment, the step of engaging the applicator tool may further include engaging the applicator tool to a leading edge of the wind turbine blade. The step of supplying the coating material may further include supplying the coating material to a funnel-shaped space between the outer surface of the wind turbine blade and the inner surface of the extrusion plate. Additionally, the step of moving the applicator tool may include manually moving the applicator tool along the outer surface of the wind turbine blade or moving the applicator tool along the outer surface of the wind turbine blade using a robotic device. In one embodiment, dispensing the coating material may further include dispensing the coating material onto the outer surface of the wind turbine blade in strips, wherein the strips eventually merge together to form the coating.

The applicator tool is configured to dispense the coating material to form a coating having a first profile and the method may further include reconfiguring the applicator tool to dispense the coating material to form a coating having a second profile different from the first profile. In one embodiment, the step of reconfiguring the applicator tool may further include removing the spatula from the applicator tool and inserting another spatula into the applicator tool. The second spatula may have a different height profile that alters the profile of the coating from the applicator tool. In an alternative embodiment, the step of reconfiguring the applicator tool may further include selectively moving the extrusion plate relative to the one or more spacers. This relative movement also alters the profile of the coating from the applicator tool.

The steps and elements described herein can be reconfigured and combined in many different combinations to achieve the desired technical effects in different styles of wind turbines, as may be needed in the art.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more examples of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

With reference to <FIG>, examples of a coating applicator tool configured to be used with a hand tool or with a robotic maintenance device and a method for repairing damage around a leading edge of a wind turbine blade are shown in detail. The applicator tool for repairing so-called category-<NUM> and category-<NUM> damage to the outer skin of a wind turbine blade includes a spatula for shaping the coating material on the leading edge of the wind turbine blade as the applicator tool is moved along the blade. The spatula is configured to apply a uniform and even coating of material that in cross section is generally thickest adjacent the leading edge of the blade and decreases in thickness in a generally continuous and smooth manner along the upper and lower surfaces of the blade and in a direction toward a trailing edge of the blade. In this way, the coating may smoothly merge with the existing blade surfaces at locations away from the leading edge. The shape of the coating material applied by the applicator tool is configured to repair adequately the damaged area of the blade while also minimizing aerodynamic disruptions of the air flow over the blade. Thus, a repair is achieved with minimal impact on the aerodynamic performance of the blade. A method of using the applicator tool may include scanning the blade to image the damaged area, sanding down a surface of the blade around the damaged area and cleaning the same, and then applying one or more layers of coating with the applicator tool to repair the damage. The spatula and associated method produce a high quality and precise repair of the damaged area of the wind turbine blade that overcomes many of the drawbacks of existing repair devices and processes. Other advantages and effects of the examples of this invention will be evident from the following description.

Throughout this application, the correction of erosion damage on wind turbine blades is typically referred to as a "repair" of those damages. In some contexts, "damage" refers to more significant damages to the blade (perhaps beyond what is described as "category-<NUM>" and "category-<NUM>" damage herein), and so the operation of the applicator tool may be deemed a routine maintenance action that occurs before a blade is "damaged" in such contexts. In this regard, the applicator tool is capable of providing preventative maintenance to remove wear and erosion effects before such effects cause "damage" that must be repaired on the wind turbine blade, and the applicator tool is also capable of providing more thorough repairs after damage is caused on the blade.

Turning with reference to <FIG>, a wind turbine <NUM> is shown to include a tower <NUM>, a nacelle <NUM> disposed at the apex of the tower <NUM>, and a rotor <NUM> operatively coupled to a generator (not shown) housed inside the nacelle <NUM>. The rotor <NUM> of the wind turbine <NUM> includes a central hub <NUM> and a plurality of wind turbine blades <NUM> that project outwardly from the central hub <NUM> at locations circumferentially distributed around the hub <NUM>. As shown, the rotor <NUM> includes three wind turbine blades <NUM>, but the number of blades <NUM> may vary from one wind turbine to another. The wind turbine blades <NUM> are configured to interact with air flow to produce lift that causes the rotor <NUM> to spin generally within a plane defined by the wind turbine blades <NUM>. As the rotor <NUM> spins, the wind turbine blades <NUM> pass through the air with a leading edge <NUM> leading the respective wind turbine blade <NUM> during rotation. The wind turbine blades <NUM> in use are spaced apart from the ground surface by a significant distance, which normally renders maintenance and repair actions difficult. However, the coating applicator tool in accordance with examples disclosed herein improves the repair process to make such maintenance and repairs easy and less time-consuming as will be set forth in detail below.

As the wind turbine <NUM> ages, one or more of the wind turbine blades <NUM> may experience erosion from prolonged, continuous exposure to the environment. One example of such erosion damage <NUM> is shown in <FIG> and better shown in the detailed view of <FIG>. While not being particularly limited to any source, erosion damage <NUM> may occur due to particulates in the air that abrade the leading edge <NUM> of the wind turbine blade <NUM> during operation. Erosion therefore may occur in an erosion zone that includes the leading edge <NUM>, but it may also occur in other areas in the surface of the blade <NUM>. Accordingly, while the applicator tool is configured to repair damage and move along the leading edge <NUM> of the blade <NUM>, this device may also be capable of conducting maintenance and repair actions elsewhere along the outer surface of the blades <NUM>.

Erosion damage <NUM> is generally characterized as a loss of material from the wind turbine blade <NUM>. Material loss may be uniformly distributed but is often non-uniform across the leading edge <NUM> or any other surface of the wind turbine blade <NUM>. Rather than losing a uniform skin of material from a surface, erosion may include localized surface imperfections, such as random pitting and shallow gouges or crack-like features that may be a result of localized, connected pitting (as a result of impacts with debris or other matter in the environment). In any case, if erosion damage <NUM> is not repaired in a timely fashion, the wind turbine blade <NUM> may become less efficient at rotating the rotor <NUM> and ultimately, the structural integrity of the wind turbine blade <NUM> may be significantly impaired.

With reference to the detailed view in <FIG>, it will be understood that the erosion damage <NUM> may define differing levels of severity based on how deep the damage extends inwardly into the material layers defining the outer shell of the blade <NUM>. In the example shown, the erosion damage <NUM> includes some areas with an erosion or cut of material through the outer topcoat layer into a second layer of material underneath the topcoat, which is categorized as a "category <NUM>" level of severity, and further areas with an erosion or cut of material through the outer topcoat layer and the second later of material into a third layer of material underneath the second layer, which is categorized as a "category <NUM>" level of severity. For reference, deeper cuts and erosions defining more significant damage is typically categorized at higher levels such as category <NUM>, <NUM>, or <NUM>. In <FIG>, the topcoat is shown at 28a, the revealed areas of second layer are shown at 28b, and the revealed areas of third layer are shown at 28c. By identifying and correcting such lower levels of erosion damage <NUM> promptly, more significant damage of the blade <NUM> can be avoided along with higher operational downtime caused by the more significant damage.

<FIG> illustrates a repaired section of a wind turbine blade <NUM> having damage <NUM> on the leading edge <NUM> of the blade <NUM>. The repaired section includes a coating <NUM> of material over the damage <NUM> on the leading edge <NUM> of the blade <NUM>. The coating <NUM> is configured to define a new outer surface <NUM> that interacts with the air flowing over the blade <NUM>. As such, the coating <NUM> protects the damage <NUM> on the wind turbine blade <NUM> and prevents or reduces the likelihood of the damage <NUM> further advancing, such as to a higher category of damage. In addition, the coating <NUM> is preferably shaped so as to minimize any negative impacts of the repair on the aerodynamic performance on the wind turbine blade <NUM> during use. Thus, the new outer surface <NUM> is configured to minimize disruptions of the air flow over the blade <NUM>. In this regard and as illustrated in <FIG>, the coating <NUM> is configured to be at a maximum thickness at or about the leading edge <NUM> of the blade <NUM> and then decrease in thickness in a direction away from the leading edge <NUM> and toward the trailing edge (not shown) of the blade <NUM> along both of the outer surfaces <NUM> (i.e., leeward and windward sides) of the blade <NUM>. Ideally, the thickness of the coating <NUM> should decay to substantially zero at the outer edges <NUM> of the coating <NUM>. This allows the coating <NUM> to merge into the existing surfaces <NUM> of the blade <NUM> in a smooth manner, thereby minimizing the disruption of the air flow in the transition from the outer surface <NUM> of the coating <NUM> to the original outer surfaces <NUM> of the blade <NUM>. In an example, the coating <NUM> may be formed from an epoxy or a polyurethane, but other materials may also be possible. The applicator tool aids in providing a precise and high-quality coating <NUM> on the leading edge <NUM> of the wind turbine blade <NUM> having the shape and features as described above.

<FIG> illustrate an applicator tool <NUM> in accordance with one example. In accordance with this example, the applicator tool <NUM> includes a spatula <NUM> for shaping the coating <NUM> applied to the leading edge <NUM> of the wind turbine blade <NUM>. Details of the spatula <NUM> are illustrated in <FIG> and <FIG>. In an example, the spatula <NUM> may include a generally flexible or bendable extrusion plate <NUM> made from, for example, rubber or other generally flexible engineering plastics. The extrusion plate <NUM> may be generally rectangular in shape and include a front edge <NUM>, a rear edge <NUM>, and opposed side edges <NUM>, <NUM> that extend between the front and rear edges <NUM>, <NUM>. The extrusion plate <NUM> may further include an outer surface <NUM> and an inner surface <NUM> of the spatula <NUM>. The outer surface <NUM> is configured to face away from the leading edge <NUM> of the wind turbine blade <NUM> during use and the inner surface <NUM> is configured to face toward the leading edge <NUM> of the blade <NUM> during use (see <FIG> and <FIG>). In an example, the extrusion plate <NUM> may be about <NUM> millimetre (mm) to about <NUM> in thickness between the outer and inner surfaces <NUM>, <NUM>. More preferably, the extrusion plate <NUM> may be about <NUM> in thickness. Other thickness values, however, may be possible depending on the particular application. The extrusion plate <NUM> may be formed from a low-friction material or include a coating, such as a polytetrafluoroethylene coating, that provides at least the inner surface <NUM> with low-friction characteristics.

In an example, the spatula <NUM> may include a spacer to provide a gap between the outer surface <NUM> of the blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. In this example, the spacer may include a plurality of ribs <NUM> disposed beneath the inner surface <NUM> of the extrusion plate <NUM>. In one example, the plurality of ribs <NUM> may extend from the inner surface <NUM> of the extrusion plate <NUM> of the spatula <NUM> in a spaced-apart manner. The ribs <NUM> may be generally parallel to each other and extend from the front edge <NUM> and toward the rear edge <NUM> of the extrusion plate <NUM>. In one example, the plurality of ribs <NUM> extends all the way to the rear edge <NUM> of the extrusion plate <NUM> (<FIG>). In an alternative example, however, the plurality of ribs <NUM> stops short of the rear edge <NUM> of the extrusion plate <NUM> (not shown). The plurality of ribs <NUM> may extend away from the front edge <NUM> and along the inner surface <NUM> substantially perpendicular to the front edge <NUM> of the extrusion plate <NUM>. The substantially right angle between the front edge <NUM> and the plurality of ribs <NUM> is merely exemplary and other angles may be possible in alternative examples.

The plurality of ribs <NUM> are spaced apart from each other to define grooves <NUM> between adjacent ribs <NUM>. The grooves <NUM> are formed by side surfaces of adjacent ribs <NUM> and a section of the inner surface <NUM> of the extrusion plate <NUM> between the adjacent ribs <NUM>. In an example, the plurality of ribs <NUM> are uniformly spaced apart from each other by a fixed distance. By way of example and without limitation, the ribs <NUM> may be spaced from each other between about <NUM> and about <NUM>. More preferably, the ribs <NUM> may be spaced from each other about <NUM>. Other values, however, remain possible and remain within the scope of the present invention. In an alternative example, the spacing between the ribs <NUM> may be non-uniform across the width of the spatula <NUM> (not shown). For example, the spacing between adjacent ribs <NUM> may be at a minimum adjacent a central region <NUM> of the spatula <NUM>, as generally defined by an area about a central axis <NUM>, and increase in a direction toward the side edges <NUM>, <NUM> of the extrusion plate <NUM>. In an example, the plurality of ribs <NUM> may be integrally formed with the extrusion plate <NUM> such that, for example, the spatula <NUM> may be formed by a monolithic body. In an alternative example, however, the plurality of ribs <NUM> may be separately formed and fixedly coupled to the inner surface <NUM> of the extrusion plate <NUM> of the spatula <NUM>. The plurality of ribs <NUM> may also be made from a low-friction material or be coated with a low-friction material.

As will be explained in detail below, the applicator tool <NUM> may be moved along the leading edge <NUM> of the wind turbine blade <NUM> to apply the coating <NUM> to the blade <NUM>. In this regard, the spatula <NUM> is configured to engage with the wind turbine blade <NUM> and extrude coating material applied to the blade <NUM> immediately behind of the spatula <NUM> such that after the spatula <NUM> passes over the deposited coating material, the coating <NUM> has the desired smoothness and shape, such as that described above. As noted above, the plurality of ribs <NUM> are configured to operate as spacers so that a gap <NUM> is provided between the outer surfaces <NUM> of the wind turbine blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. The gap <NUM> generally corresponds to the desired shape of the coating <NUM>, and as the applicator tool <NUM> is moved along the leading edge <NUM> of the blade <NUM>, the coating material is essentially extruded from the gap <NUM> to define the coating <NUM>, as will be explained in more detail below. Thus, it is the plurality of ribs <NUM> in combination with the extrusion plate <NUM> that define the shape of the coating <NUM> on the blade <NUM>. More particularly, it is a height profile <NUM> (<FIG>) of the plurality of ribs <NUM> that generally defines the shape of the coating <NUM> applied to the leading edge <NUM> of the blade <NUM>.

In an example, the height profile <NUM> defined by the plurality of ribs <NUM> may be configured to have a maximum height in the central region <NUM> of the extrusion plate <NUM> and decreases in height away from the central region <NUM> and towards the side edges <NUM>, <NUM> of the extrusion plate <NUM>. In a preferred example, the height of the ribs <NUM> decay to substantially zero in a direction away from the central region <NUM> and toward the side edges <NUM>, <NUM> of the extrusion plate <NUM>. The height profile <NUM> may have a wide range of configurations such that the height is a maximum near the central region <NUM> and then decays to substantially zero near the side edges <NUM>, <NUM>. For example, the region of maximum height in the height profile <NUM> may extend over several of the ribs <NUM> (e.g., <NUM>, <NUM>, or <NUM> ribs) in the central region <NUM>, and then start decreasing in height outside of this region. Moreover, the decrease in the rib height may have different configurations. For example, the rib height may decrease from the maximum height in the central region <NUM> to substantially zero in a linear, parabolic, or exponential fashion. Other decaying configurations may also be possible. In any event, the height profile <NUM> of the plurality of ribs <NUM> operates to define generally the cross-sectional shape of the coating <NUM> applied to the wind turbine blade <NUM>. In one example, a plurality of spatulas <NUM> may be provided wherein each spatula <NUM> will have a different height profile <NUM>. Thus, the particular height profile <NUM> may be selected based on the needs or desires of the coating <NUM> for a particular application. In an example, the height profile <NUM> of the plurality of ribs <NUM> is preferably substantially symmetric about the central axis <NUM> of the extrusion plate <NUM> such that the resulting coating <NUM> is substantially symmetric about the leading edge <NUM> of the blade <NUM>.

<FIG> illustrate the use of the applicator tool <NUM> for making a repair to the leading edge <NUM> of the wind turbine blade <NUM> in greater detail. The applicator tool <NUM> generally includes a frame <NUM> having a front support <NUM> and a rear support <NUM>. The front support <NUM> includes a pair of arms <NUM> that terminate in respective compression pads <NUM>. One or more springs <NUM> or other biasing mechanisms may be coupled to the arms <NUM> and/or pads <NUM> for pressing the spatula <NUM> against the outer surface <NUM> of the wind turbine blade <NUM> as indicated by arrows F. The rear support <NUM> may include a feed tube <NUM> that is operatively coupled (e.g., such as by a pump or the like) to a source of coating material (not shown) and is configured to supply the coating material onto the outer surface <NUM> of the wind turbine blade <NUM>. The spatula <NUM> may be positioned on the frame <NUM> so as to be supported by the front and rear supports <NUM>, <NUM>. For example, the compression pads <NUM> may be adhered or otherwise selectively and removably coupled to the outer surface <NUM> of the extrusion plate <NUM> adjacent the front edge <NUM> and side edges <NUM>, <NUM> of the spatula <NUM>. Moreover, the central region <NUM> of the spatula <NUM> adjacent the rear edge <NUM> may be supported by rear support <NUM> such as with a tab, hook or possibly by the feed tube <NUM>. The feed tube <NUM> is generally positioned beneath the spatula <NUM>. As illustrated in <FIG> and <FIG>, the frame <NUM> or the spatula <NUM> may be angled relative to the leading edge <NUM> of the blade <NUM> such that the rear edge <NUM> of the spatula <NUM> is above the blade <NUM> a greater distance than the front edge <NUM> of the spatula <NUM>. This defines a funnel-shaped space <NUM> between the blade <NUM> and the spatula <NUM> wherein the area between the blade <NUM> and the spatula <NUM> decreases in a direction toward the front edge <NUM> of the spatula <NUM>. The feed tube <NUM> is configured to extend into the funnel-shaped space <NUM> and deliver the coating material within this space to form the coating <NUM>.

As illustrated in <FIG>, to effectuate maintenance and repair of damage <NUM> on the leading edge <NUM> of the wind turbine blade <NUM>, the applicator tool <NUM> may be positioned on the blade <NUM> such that the plurality of ribs <NUM> confront the surface <NUM> of the blade <NUM> and the ends of the ribs <NUM> engage the outer surface <NUM> of the blade <NUM>. The compression pads <NUM> may press the spatula <NUM> against the outer surfaces <NUM> of the blade <NUM> at some distance from the leading edge <NUM>. Moreover, the central axis <NUM> of the extrusion plate <NUM> may be configured to be aligned with the leading edge <NUM> of the blade <NUM>. This arrangement is shown, for example, in <FIG> and <FIG>. The coating material may then be directed to the feed tube <NUM> for deposit in the funnel-shaped space <NUM> between the surface <NUM> of the blade <NUM> and the spatula <NUM>. This is illustrated, for example, in <FIG>.

As the coating material fills the funnel-shaped space <NUM>, the applicator tool <NUM> may be moved along the leading edge <NUM> of the blade <NUM> as demonstrated by arrow A in <FIG> and <FIG>. As the applicator tool <NUM> moves, the coating material is forced into the funnel toward the front edge <NUM> of the spatula <NUM> and is essentially extruded from the grooves <NUM> at the front edge <NUM> of the extrusion plate <NUM>. In this example, the coating material is applied to the outer surface <NUM> of the blade <NUM> in strips <NUM> separated from each other due to the presence of the ribs <NUM> at the front edge <NUM> of the extrusion plate <NUM>. The height of the strips <NUM> is dictated by the height profile <NUM> of the spatula <NUM>. After the coating material is applied to the outer surface <NUM> of the wind turbine blade <NUM> in strips <NUM>, the coating material flows under the influence of gravity, surface tension, or other effects to form a smooth and continuous coating <NUM> having a profile dictated by the height profile <NUM> of the spatula <NUM> (e.g., see <FIG>). In this example, the coating material must be generally flowable (i.e., having a suitable viscosity) that allows the coating material to merge together to form the continuous coating <NUM> but without having the material simply flow uncontrollably over the outer surface <NUM> of the blade <NUM>, as might happen with a coating material with a too low of a viscosity. It should be understood that after the coating <NUM> has dried or cured, the applicator tool <NUM> may be used to make additional passes over the damage <NUM> on the leading edge <NUM> of the blade <NUM>. In this way, the final coating <NUM> may be comprised of a plurality of layers, with each layer applied using the applicator tool <NUM> as described above.

<FIG> illustrate an applicator tool in accordance with another example. The applicator tool is similar to that described above in that the tool is configured to apply a coating to damage on the leading edge of the wind turbine blade in an improved manner. However, there are a number of distinctions between the applicator tool of this example and that described above that will be highlighted by the following description. By way of example, one difference is the manner in which the coating is applied to the wind turbine blade. More particularly, the applicator tool described above applies strips of the coating material onto the surface of the wind turbine blade as a result of the rib/groove configuration of the spatula. The rib/groove configuration of the spatula is, in turn, a consequence of defining the height profile of the spatula, which ultimately defines the shape of the coating on the blade. In any event, after the strips are applied to the blade, the coating material has to possess a suitable viscosity that allows the material to flow under the influence of gravity and surface tension effects to form a smooth and continuous coating.

The applicator tool in an alternative example described below, however, is configured to operate in a different way. As described in more detail below, the applicator tool is configured to shape the coating material being extruded from the applicator tool more directly. In other words, the coating material extruded from the applicator tool is in a shape that substantially and more directly corresponds to the final shape of the coating on the leading edge of the wind turbine blade. Thus, the application of the coating material in strips and merging of the strips to form the final coating is avoided with this alternative applicator tool. This distinction may have particular relevance when working with coating materials with a high viscosity, such that the strips of the coating material using the applicator tool described above would not flow together under gravity and other effects to form a smooth and continuous coating on the blade. Thus, the alternative applicator tool described below may be ideally suited for high viscosity coating materials.

Another distinction between the applicator tool described above and the alternative applicator tool below is the ability to more dynamically change the profile of the coating applied to the blade. As discussed above, the profile of the coating is dictated primarily by the height profile of the plurality of ribs on the extrusion plate. Recall that if a different profile is desired, then a different spatula is generally required to provide that new profile. The applicator tool in the alternative example is configured to have some ability to selectively adjust the profile of the coating provided by a pass of the applicator tool along the blade. This adjustable feature as well as other features of the alternative applicator tool will now be described in detail.

The applicator tool <NUM> includes a spatula <NUM> for shaping the coating <NUM> applied to the leading edge <NUM> of the wind turbine blade <NUM>. In an example, the spatula <NUM> may include a generally flexible or bendable extrusion plate <NUM> made from, for example, rubber or other generally flexible engineering plastics. The extrusion plate <NUM> may be generally rectangular in shape and include a front edge <NUM>, a rear edge <NUM>, and opposed side edges <NUM>, <NUM> that extend between the front and rear edges <NUM>, <NUM>. The extrusion plate <NUM> may further include an outer surface <NUM> and an inner surface <NUM> of the spatula <NUM>. The outer surface <NUM> is configured to face away from the leading edge <NUM> of the wind turbine blade <NUM> during use and the inner surface <NUM> is configured to face toward the leading edge <NUM> of the blade <NUM> during use (see <FIG> and <FIG>). In an example, the extrusion plate <NUM> may be about <NUM> to about <NUM> in thickness between the outer and inner surfaces <NUM>, <NUM>. More preferably, the extrusion plate <NUM> may be about <NUM> in thickness. Other thickness values, however, may be possible depending on the particular application.

Similar to the above, the spatula <NUM> may include one or more spacers to provide a gap between the surface <NUM> of the blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. In this example, the one or more spacers may include a rigid blade or spine <NUM> disposed beneath the inner surface <NUM> of the extrusion plate <NUM>. Unlike the applicator tool described above, the spine <NUM> is not integrally formed with the extrusion plate <NUM> but is a separate element that works in conjunction with the extrusion plate <NUM> in operation of the applicator tool <NUM>. The spine <NUM> includes a front edge <NUM>, rear edge <NUM>, upper edge <NUM> and lower edge <NUM>. In an example, the front edge <NUM> forms a substantially right angle relative to the upper edge <NUM> and the lower edge <NUM> forms an acute angle relative to the upper edge <NUM> (see <FIG> and <FIG>). For example, the lower edge <NUM> may be angled between about <NUM> degrees and about <NUM> degrees relative to the upper edge <NUM>. As explained in more detail below, the lower edge <NUM> is configured to engage with the leading edge <NUM> of the wind turbine blade <NUM> during use and the configuration of the spine <NUM> provides a gap between the outer surface <NUM> of the blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. The spatula <NUM> further includes a feed tube <NUM> that is coupled to the rear edge <NUM> of the spine <NUM> at one end thereof and is operatively coupled (such as by a pump or the like) to a source of coating material (not shown) at another end thereof for supplying the coating material onto the outer surface <NUM> of the wind turbine blade <NUM>. In one example, the spine <NUM> may be integrally formed with the end of the feed tube <NUM>. In an alternative example, these elements may be separate and subsequently coupled together.

The extrusion plate <NUM> is carried by a rigid support <NUM> having a tubular portion <NUM> and a finger <NUM> coupled to and extending forward of the tubular portion <NUM>. For example, the rigid support <NUM> may include a tab that is received in a hole in the extrusion plate <NUM>. Other attachment means, however, may be possible. The tubular portion <NUM> is generally disposed about an end of the feed tube <NUM> in, for example, a coaxial and telescoping manner. The finger <NUM> extends from an upper region of the tubular portion <NUM> and includes a generally arcuate central portion <NUM> and a pair of wings <NUM> extending on both sides of the central portion <NUM>. The extrusion plate <NUM> is coupled to the rigid support <NUM> and generally disposed between the finger <NUM> of the support <NUM> and the spine <NUM>. In an example, the extrusion plate <NUM> may be movable relative to the spine <NUM>. More particularly, the rigid support <NUM> is slidable over the feed tube <NUM>, which in turn moves the extrusion plate <NUM> relative to the spine <NUM> generally along a direction illustrated by arrows B (<FIG>). The relative movement between the extrusion plate <NUM> and the spine <NUM> (which may be permitted for only a limited distance) allows the height profile of the coating material extruded from the applicator tool <NUM> to be varied. For example, in a forward position of the extrusion plate <NUM> relative to the spine <NUM>, the height of the coating material (e.g., at the central axis <NUM> of the extrusion plate <NUM>) may be at a minimum, and in a rearward position of the extrusion plate <NUM> relative to the spine <NUM>, the height of the coating material at the central axis of the extrusion plate <NUM> may be at a maximum. In other words, while the applicator tool <NUM> is configured to provide a coating <NUM> similar to that shown in <FIG>, for example, the thickness of the coating (such as at the leading edge <NUM> of the blade <NUM>) may be varied depending on the position of the extrusion plate <NUM> relative to the spine <NUM>. In any event, when the desired thickness of the coating <NUM> is determined, a set screw may be used to fix the relative positions of the extrusion plate <NUM> and the spine <NUM> to thereby fix the thickness of the coating <NUM> at the leading edge <NUM>, for example. Additionally, the feed tube <NUM> and the rigid support <NUM> may have a keying feature <NUM> (e.g., key and corresponding keyway) to prevent relative rotations between the feed tube <NUM> and the rigid support <NUM>.

As will be explained in detail below, the applicator tool <NUM> may be moved along the leading edge <NUM> of the wind turbine blade <NUM> to apply the coating <NUM> to the blade <NUM>. In this regard, the spatula <NUM> is configured to engage with the wind turbine blade <NUM> and extrude coating material applied to the blade <NUM> immediately behind the extrusion plate <NUM> of the spatula <NUM> such that after the spatula <NUM> passes over the deposited coating material, the coating <NUM> has the desired smoothness and shape. As noted above, the spine <NUM> is configured to operate as a spacer so that a gap <NUM> is provided between the outer surfaces <NUM> of the wind turbine blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. The gap <NUM> in this example more directly corresponds to the desired shape of the coating <NUM>, and as the applicator tool <NUM> is moved along the leading edge <NUM> of the blade <NUM>, the coating material is essentially extruded from the gap <NUM> to ultimately define the coating <NUM>, as will be explained in more detail below. Thus, it is the spine <NUM> in combination with the extrusion plate <NUM> that defines the shape of the coating <NUM> on the blade <NUM>. More particularly, it is the position of the extrusion plate <NUM> relative to the spine <NUM> that defines a height profile which generally defines the shape of the coating <NUM> applied to the leading edge <NUM> of the blade <NUM>.

In an example, the height profile <NUM> defined by the spine <NUM> may be configured to have a maximum height in the central region <NUM> of the extrusion plate <NUM> and decrease in height away from the central region <NUM> and towards the side edges <NUM>, <NUM> of the extrusion plate <NUM>. In a preferred example, there is but a single spine <NUM> in the central region <NUM> of the spatula <NUM>. Due to the lack of other spines away from the central region <NUM>, the height profile <NUM> defined by the spine <NUM> decays to substantially zero in a direction away from the central region <NUM> and toward the side edges <NUM>, <NUM> of the extrusion plate <NUM>. The height profile <NUM> may have a wide range of configurations such that the height is a maximum near the central region <NUM> and then decays to substantially zero near the side edges <NUM>, <NUM>. The height profile <NUM> of provided by the spine <NUM> operates to define the cross-sectional shape of the coating <NUM> applied to the wind turbine blade <NUM>. As explained above, the relative position of the extrusion plate <NUM> and the spine <NUM> may be adjusted to vary the height profile <NUM> provided by the spatula <NUM>. The particular height profile <NUM> may be selected based on the needs or desires of the coating <NUM> for a particular application. In an example, the height profile <NUM> provided by the spine <NUM> is substantially symmetric about the central axis <NUM> of the extrusion plate <NUM> such that the resulting coating <NUM> is substantially symmetric about the leading edge <NUM> of the blade <NUM>.

As illustrated in <FIG>, to effectuate maintenance and repair of damage <NUM> on the leading edge of the wind turbine blade <NUM>, the applicator tool <NUM> may be positioned on the blade <NUM> such that the spine <NUM>, and more particularly the lower edge <NUM> thereof, engages the surface <NUM> of the blade <NUM> substantially along the leading edge <NUM>. The applicator tool <NUM> may further include compression pads <NUM> or other biasing mechanisms that press the extrusion plate <NUM> against the outer surfaces <NUM> of the blade <NUM> at some distance removed from the leading edge <NUM>. Moreover, the central axis <NUM> of the spatula <NUM> may be configured to be aligned with the spine <NUM> (and leading edge <NUM> of the blade <NUM>). This arrangement is shown, for example, in <FIG> and <FIG>. The coating material may then be directed to the feed tube <NUM> for deposit in the funnel-shaped space <NUM> between the outer surfaces <NUM> of the blade <NUM> and the inner surface <NUM> of the extrusion plate <NUM>. This is illustrated, for example, in <FIG>.

As the coating material fills the funnel-shaped space <NUM>, the applicator tool <NUM> may be moved along the leading edge <NUM> of the blade <NUM> as demonstrated by arrow A in <FIG> and <FIG>. As the applicator tool <NUM> moves, the coating material is forced into the funnel toward the front edge <NUM> of the spatula <NUM> and is essentially extruded from the front edge <NUM> of the extrusion plate <NUM>. In this example, the coating material is applied to the outer surfaces <NUM> of the blade <NUM> as a whole (e.g., instead of in strips) to form a smooth and continuous coating <NUM> having a profile that corresponds to the height profile <NUM> of the spatula <NUM> (e.g., see <FIG>). It should be understood that after the coating <NUM> has dried or cured, the applicator tool <NUM> may be used to make additional passes over the damage <NUM> on the leading edge <NUM> of the blade <NUM>. In this way, the final coating <NUM> may be comprised of a plurality of layers, with each layer applied using the applicator tool <NUM> as described above.

<FIG> illustrates an applicator tool <NUM> very similar to that described above. The primary difference is that the spatula <NUM> includes a plurality of spines <NUM> instead of a single spine, as described above. The additional spines <NUM> not only help define the height profile <NUM>, but are also configured to provide stability to the applicator tool <NUM> as the tool is moving along the leading edge <NUM> of the wind turbine blade <NUM>. For instance, with a single spine <NUM>, the applicator tool <NUM> may be susceptible to movements (e.g., slips) away from the leading edge <NUM> of the blade <NUM>. The plurality of spines <NUM> now engage the surface <NUM> of the blade <NUM> in multiple locations about the leading edge <NUM>, and thereby reduces the likelihood of the applicator tool <NUM> from slipping away from the leading edge <NUM> as the applicator tool <NUM> is moved.

The example of the applicator tool described above improve maintenance and repairs for erosion damage at the leading edge of the wind turbine blade. More particularly, the applicator tool provides an apparatus and method for applying a coating over the damage at the leading edge so as to arrest further deterioration of the wind turbine blade. Additionally, the applicator tool provides a coating that has an ideal profile, i.e., having a maximum thickness at the leading edge of the blade and then decaying in thickness to substantially zero thickness away from the leading edge so as to smoothly merge into the outer surfaces of the wind turbine blade. The profile provided by the applicator tool minimizes disruptions of the airflow over the blade and any resulting reduction in aerodynamic performance as a result of those disruptions. The applicator tool is particularly advantageous when repairing wind turbine blades in field conditions when, for example, the blades remain attached to the rotor hub at the top of the tower of the wind turbine. Thus, even in less than ideal field conditions, the applicator tool is able to provide a high quality and precise repair of the damaged area of the wind turbine blade. In addition, the applicator tool may be adapted to be used to repair the leading edge of a wind turbine blade in a variety of ways. In one example, for example, the applicator tools may be adapted to be used manually, such as by an operator that is positioned adjacent to the damage on the blade during the repair process. For example, the operator may have rope access to the blade from, for example, the nacelle of the wind turbine. Alternatively, the operator may be positioned in a platform or the like and the platform positioned adjacent the damaged area of the blade. In any event, the applicator tool is arranged to be manipulated by the operator's hands in order to move the applicator tool along the leading edge of the blade. In an alternative example, the applicator tool may be adapted for use with a robotic maintenance device that is configured to replace the human operator and move the applicator tool along the leading edge of the blade. Exemplary robotic maintenance devices are, for example, disclosed in <CIT> and <CIT>, which are owned by the same Assignee as the present invention.

Accordingly, a further description of such robotic maintenance devices will not be provided herein.

Claim 1:
An applicator tool (<NUM>) for repairing damage (<NUM>) to a wind turbine blade (<NUM>), comprising:
a spatula (<NUM>) comprising:
a flexible extrusion plate (<NUM>) having a front edge (<NUM>), a rear edge (<NUM>), opposed side edges (<NUM>, <NUM>), an outer surface (<NUM>), and an inner surface (<NUM>), the extrusion plate (<NUM>) further having a central region (<NUM>) defined by a central axis (<NUM>); and
a feed tube (<NUM>) for supplying a coating material to the spatula (<NUM>), characterized in that it further comprises
one or more spacers (<NUM>, <NUM>) positioned proximate the inner surface (<NUM>) of the extrusion plate (<NUM>), wherein the one or more spacers (<NUM>, <NUM>) are configured to define a gap between an outer surface (<NUM>) of the wind turbine blade (<NUM>) and the inner surface (<NUM>) of the extrusion plate (<NUM>);
wherein the spatula (<NUM>) is configured to shape the coating material into a coating (<NUM>) over a damaged area (<NUM>) of the wind turbine blade (<NUM>), wherein the spatula (<NUM>) is configured to apply a uniform and even coating (<NUM>) of material that in cross section is generally thickest adjacent a leading edge (<NUM>) of the blade (<NUM>) and decreases in thickness in a generally continuous and smooth manner along the upper and lower surfaces of the blade (<NUM>) and in a direction toward a trailing edge of the blade (<NUM>).