Patent Description:
Wind is an increasingly popular clean source of renewable energy with no air or water pollution. When the wind blows, wind turbine blades capture energy, which is transformed to electrical power in a generator. Wind turbine blades are typically made of a fibre-reinforced polymer material and comprise a pressure side shell half and a suction side shell half. As wind turbines increase in size, so do blade lengths, often resulting in higher tip speeds. The higher speeds increase the risk of erosion of leading edges of the wind turbine blades due to the continued impact from for instance wind, rain, hail, and sand, which cause material to be removed from the blade surface, resulting in a rough surface that impacts the aerodynamic performance and the structural integrity of the blade adversely. Such erosive processes can affect the maximum rotational speed of the wind turbine blades, hence reducing the power output of the wind turbine. The negative effects are exacerbated in harsh environmental conditions, such as at remote offshore sites, mountain regions, and other challenging climates. Leading-edge erosion results in reduced annual energy production and increased need for maintenance and repairs. Protective devices are applied to the leading edge of wind turbine blades to reduce the need for maintenance and repairs.

A prior art method and system for cutting a leading-edge protection element are known from <CIT>.

It is desirable that the manufacturing of leading-edge protective devices is as efficient as possible. It is therefore an object of the present invention to provide an improved method for obtaining a fibre-reinforced composite product such as a cap for protecting a leading edge of a wind turbine blade.

In a first aspect, the invention provides a method for trimming a side portion of a pre-manufactured leading-edge protection element for protecting a leading edge of a wind turbine blade, the leading-edge protection element extending in a longitudinal direction between a first longitudinal end and a second longitudinal end, the leading-edge protection element comprising a first side portion and a second side portion, the first side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a pressure side of the wind turbine blade, and the second side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a suction side of the wind turbine blade, or vice versa. The method comprises:.

Embodiments of the first aspect allow more precise and efficient manufacturing of leading-edge protection products such as leading-edge caps. The invention provides for high product consistency, reducing the amount of additional modifications required for the product to meet specifications.

The first predetermined length is a transverse length in a direction transverse to the longitudinal direction of the leading-edge protection element.

In some embodiments, the first side portion is cut along the predetermined cutting path, such that the first side portion is trimmed to the first predetermined length, L<NUM>.

In some embodiments, the second side portion is cut along a second predetermined cutting path, such that the second side portion is trimmed to a second predetermined length, L<NUM>. The first cutting tool may be used to trim the second side portion, or a separate (second) cutting tool may be used. In some embodiments, two cutting tools are operated simultaneously. In some embodiments, the first cutting tool is operated starting from the first longitudinal end of the leading-edge protection element and the second cutting tool is operated starting from the second longitudinal end of the leading-edge protection element.

The first and second predetermined lengths L<NUM>. and L<NUM>. may, and typically do, vary in the longitudinal direction, reflecting that airfoil profile of wind turbine blades, including the airfoil width and the airfoil thickness, generally decrease from a shoulder <NUM> to a tip end <NUM>, as illustrated in <FIG>.

The leading-edge protection element may be pre-manufactured such that the leading-edge protection element after trimming extends along any desired portion of the leading edge of the wind turbine blade.

In some embodiments, fixating the leading-edge protection element to the support structure comprises fixating at least the first side portion of the leading-edge protection element or both the first side portion and the second side portion of the leading-edge protection element to the support structure.

In some embodiments, fixating the leading-edge protection element comprises clamping a part of the pre-manufactured leading edge protection element to the support structure using clamping means. The clamping means may include one or more clamps and may also include one or more devices, such as one or more boards, arranged to distribute the clamping effect of one or more of the clamps across the first flange. Boards can increase product portion consistency because the outcome of the trimming is less sensitive to the precise position of the clamps relative to the leading-edge protection element during trimming.

In some embodiments, the leading-edge protection element comprises a first flange, and fixating the leading-edge protection element comprises clamping the first flange to the support structure using clamping means. In some embodiments, fixating the leading-edge protection element to the support structure includes arranging a board such as to distribute across the first flange a force provided by one or more of the clamps, as also described above.

In some embodiments, the leading-edge protection element comprises a first flange as described above, and fixating the leading-edge protection element comprises arranging the first flange in contact with one or more suction supports on the support structure and providing suction in the one or more suction supports. The suction supports may for instance include a tabletop with openings connected to a vacuum pump or discrete pads with respective openings connected to a vacuum pump.

In some embodiments, the first cutting tool comprises a saw, such as a rotatable saw blade attached to a cutting tool motor.

In some embodiments, the first cutting tool is supported directly by the leading-edge protection element during cutting.

In some embodiments, the leading-edge protection element is an elongate structure having a convex side and a concave side, but the leading-edge protection element may have other shapes.

In some embodiments, the leading-edge protection element is a leading-edge cap for protecting a leading edge of a wind turbine blade.

The leading-edge protection element may be made for instance of fibre-reinforced composite material, polymer material, such as polyurethane polymer material, metal, thermoplastic material, ceramic material, epoxy-infused composite, or a combination of two or more thereof.

In some cases, the leading-edge protection element to be trimmed can be seen as comprising a product portion to be used and sacrificial portions connected to the product portion, where a first sacrificial portion of the sacrificial portions comprises the first side portion, and a second sacrificial portion of the sacrificial portions comprises the second side portion. Fixating the leading-edge protection element to the support structure may comprise fixating the first sacrificial portion to the support structure, and cutting along the first predetermined cutting path at least partially separates the first sacrificial portion from the product portion, trimming the first side portion to the desired predetermined length.

In some embodiments, the first sacrificial portion comprises a first flange, and fixating the first sacrificial portion comprises clamping the first flange to the support structure using clamping means. The clamping means may include one or more clamps and may also include one or more devices, such as one or more boards, arranged to distribute the clamping effect of one or more of the clamps across the first flange. Boards can increase product portion consistency because the outcome of the trimming is less sensitive to the precise position of the clamps relative to the first sacrificial portion during trimming. The advantageous effect of the board or boards is particularly important if the flange does not conform to the shape of the support structure, such as a planar tabletop.

In some embodiments, the first cutting tool comprises rolling means for rolling the first cutting tool so as to cut along the first predetermined path. Rolling means make the moving of the cutting tool easier, in part because it eliminates a sliding friction that may exist between the cutting tool and the leading-edge protection element (or a board arranged on a flange).

In some embodiments, a surface of the leading-edge protection element acts as a guiding fence for the first cutting tool during the moving of the first cutting tool. The guiding means on the cutting tool engage with the leading-edge protection element. Such an embodiment has a higher cutting tool stability during cutting, which results in further improved product consistency.

In some embodiments, the support structure comprises a support part that has a shape that conforms to an inner side of the leading edge protection element. For instance, in some embodiments, the support structure comprises one or more product portion supports that support the product portion during the moving of the first cutting tool during cutting. In case the leading-edge protection element is somewhat flexible, the support part can help dampen vibrations that occur during the trimming process. A product portion support that conforms to a shape of a product portion also has the advantage that the product portion is supported by the product portion support after trimming.

In some embodiments, the support part is reconfigurable to more easily allow support of leading-edge protection elements of different shapes.

In some embodiments, the method comprises the first cutting tool being guided by a guide system. The leading-edge protection element or a board supporting the first cutting tool may for instance have a groove that cooperates with a corresponding flange (or other suitable protrusion) on the first cutting tool. In other embodiments, the first cutting tool comprises a groove that cooperates with a flange (or other suitable protrusion) on the leading-edge protection element or on a board supporting the first cutting tool. The flange-groove parts may be configured with a guide system that prevents the first cutting tool from being easily removed during the cutting. For instance, the motor may be fitted with a dove tail portion that engages with a corresponding groove on the leading-edge protection element or a board supporting the first cutting tool. The dove tail and groove may for instance be engaged from an end of the groove by inserting the dove tail portion into the groove. Such a locking system may improve both safety and product consistency. Equivalent locking mechanisms may be used instead.

A second aspect of the invention provides a system for trimming a leading-edge protection element for a wind turbine blade, the leading-edge protection element comprising a first side portion and a second side portion, the first side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a pressure side of the wind turbine blade, and the second side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a suction side of the wind turbine blade, or vice versa. The system comprises:.

In some embodiments, the fixating means comprises clamping means and/or comprises one or more suction supports for fixating at least the first side portion by suction.

The considerations above in relation to the first aspect may be applicable to the second aspect as well. For instance, the fixating means may comprise clamping means and/or one or more suction supports, such as pads, for fixating the leading-edge protection element by suction. A position and/or a posture (e.g. angling) of each of the one or more of the suction supports may be adjustable.

As another example, in some embodiments, the first side portion is cut along the predetermined cutting path, such that the first side portion is trimmed to the first predetermined length, L<NUM>.

As another example, in some embodiments, the second side portion is cut along a second predetermined cutting path, such that the second side portion is trimmed to a second predetermined length, L<NUM>. The first cutting tool may be used to trim the second side portion, or a separate (second) cutting tool may be used. In some embodiments, two cutting tools are operated simultaneously. In some embodiments, the first cutting tool is operated starting from the first longitudinal end of the leading-edge protection element and the second cutting tool is operated starting from the second longitudinal end of the leading-edge protection element.

As another example, the first and second predetermined lengths L<NUM>. and L<NUM>. may, and typically do, vary in the longitudinal direction, reflecting that airfoil profile of wind turbine blades, including the airfoil width and the airfoil thickness, generally decrease from a shoulder <NUM> to a tip end <NUM>, as illustrated in <FIG>.

Embodiments of this disclosure will be described in more detail in the following with reference to the accompanying figures. The description and figures are not to be construed as limiting the scope of the claims to the illustrated embodiments.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM> and three blades <NUM> extending radially from the hub <NUM>, each having a root end <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

The wind turbine blade <NUM> has the shape of a conventional wind turbine blade with a root end and a tip end and comprises a root region <NUM> closest to the hub, a profiled or airfoil region <NUM> furthest away from the hub <NUM>, and a transition region <NUM> between the root region <NUM> and the airfoil region <NUM>. The airfoil region <NUM>, also called the profiled region, has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region <NUM> due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade <NUM> to the hub <NUM>. The blade <NUM> has a pressure side <NUM> and a suction side <NUM>, which, during use - i.e. during rotation of the hub <NUM> - normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The width of the chord in the airfoil region <NUM> typically decreases with increasing distance r from the hub.

The wind turbine blade <NUM> comprises a blade shell comprising two blade shell parts, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fibre-reinforced polymer. The first blade shell part <NUM> is typically a pressure side or upwind blade shell part. The second blade shell part <NUM> is typically a suction side or downwind blade shell part. The first blade shell part <NUM> and the second blade shell part <NUM> are attached to one another with adhesive, such as glue, along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> have a semi-circular or semi-oval outer cross-sectional shape.

Similar to <FIG>, <FIG> schematically illustrates a wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a wind turbine blade part <NUM> similar to the wind turbine blade <NUM> shown in <FIG>. The wind turbine blade <NUM> further comprises a protective cap <NUM> extending along a part of a leading edge <NUM> of the wind turbine blade <NUM>. The protective cap is located near the tip end of the blade part <NUM>. Like all other parts, it is important that the cap <NUM> be manufactured in an efficient way, which the trimming methods in accordance with embodiments of the invention contribute to.

<FIG> illustrates a leading-edge cap having a first side portion <NUM> that extends from the leading edge <NUM> and along a part of the pressure side <NUM> of the blade <NUM>. Similarly, <FIG> illustrates a leading-edge cap second side portion <NUM> that extends from the leading edge <NUM> and along a part of the suction side <NUM> of the blade <NUM>.

<FIG> illustrates a pre-manufactured leading-edge protection element <NUM> that is an intermediate product for manufacturing a leading-edge cap, such as the cap <NUM> shown in <FIG>. In the present example, the leading-edge protection element <NUM> has been manufactured in a mould, which has given the element <NUM> its shape. The leading-edge protection element <NUM> is an intermediate product having a product portion to be used - the cap <NUM> - and sacrificial portions that will be discarded or used for another purpose if possible. The sacrificial portion or portions are those portions that are trimmed off the leading-edge protection element <NUM> to achieve the product portion <NUM>, i.e. the cap <NUM> in this case. The product portion may be subjected to additional processing steps after being separated from the sacrificial portions. In <FIG>, the reference <NUM> also points to a leading-edge protection element crest that defines the leading edge <NUM> when the cap <NUM> is mounted on the wind turbine blade <NUM>, as illustrated in <FIG>. <FIG> illustrates the first and second side portions <NUM>, <NUM> extending from the crest <NUM>. At this point in the process, the side portions <NUM>, <NUM> are longer than on the final cap <NUM>, but are trimmed in accordance with an embodiment of the invention as described below to achieve desired predetermined lengths L<NUM> and L<NUM> in the direction transverse to the crest. The leading-edge protection element (and crest) extends in a longitudinal direction from a first longitudinal end to a second longitudinal end.

In the present example, the leading-edge protection element <NUM> has an arcuate portion comprising the first and second side portions <NUM>, <NUM> of the cap <NUM>, and two flanges <NUM>, <NUM> that are integrally formed with the first and second side portions <NUM>, <NUM>. The flanges may for instance result, when fibre material is arranged, in a mould and on edges of the mould and later resin-infused. During resin infusion, the fibre material on the mould edges may receive resin as well, resulting in an element <NUM> with flanges <NUM>, <NUM>.

In the present example, the leading-edge protection element <NUM> is subsequently arranged on a support, in this case a table-like support with a flat tabletop <NUM> and legs <NUM>, as shown in <FIG>. The flanges <NUM>, <NUM> initially rest freely on the tabletop <NUM>. In the present example, the flanges are planar and conform to the tabletop. The tabletop <NUM>, or more generally the support structure, may instead or additionally be adapted to accommodate flanges that are not planar, for instance by having reconfigurable pads that can be reconfigured to support non-planar flanges.

In a subsequent step, the flanges <NUM>, <NUM> are fixated to the tabletop <NUM> using clamps, as illustrated in <FIG>. Flange <NUM> is clamped on one side of the tabletop using three clamps <NUM>. Similarly, flange <NUM> is clamped on the other side of the tabletop using three clamps <NUM>. In addition, this embodiment makes use of two intermediate boards <NUM>, <NUM> arranged to hold down the flanges <NUM>, <NUM> along the length of the leading-edge protection element <NUM>. This ensures that two elements of the type <NUM> are held onto the support <NUM> in a consistent way even if the shape of the flanges deviate from planar or differ somewhat from one leading-edge protection element to another due to unavoidable minor process variations during manufacturing of the leading-edge protection elements. The boards <NUM>, <NUM> thereby improve product consistency.

In a subsequent step, shown in <FIG>, the flange <NUM> is separated from the rest of the leading-edge protection element <NUM> using an activated cutting tool <NUM>. The cutting tool <NUM> comprises a rotating saw <NUM> connected to a motor <NUM>. The saw <NUM> is engaged with the leading-edge protection element <NUM> and moved along a first predetermined path on the leading-edge protection element <NUM> as indicated with the straight arrow originating from the motor <NUM>, thereby producing a separation as indicated by arrow <NUM>. In the present example, the motor rests on the board <NUM>, meaning it is indirectly, not directly, supported by a sacrificial portion, such as the flange <NUM>. In some embodiments, boards <NUM>, <NUM> are not used, and the motor <NUM> is arranged directly on a sacrificial portion, such as on the flange <NUM>.

As illustrated in <FIG>, the trimming provides the desired first predetermined length L<NUM> of the pressure side portion of the cap <NUM>.

As also seen in this example, the cooperation between the cutting tool <NUM> and the board results in a cut having an even height along the leading-edge protection element <NUM>, i.e. along the first predetermined path. It is clear to the skilled person in view of the present disclosure that the leading-edge protection element <NUM> can be formed in such a way that when the step shown in <FIG> is performed, i.e. the leading-edge protection element <NUM> is cut with a uniform height relative to the flange or board, the resulting product portion obtains the desired shape. In other words, the sacrificial portions are designed such that when the cutting takes place, the resulting product portion, such as a leading-edge cap for a wind turbine blade, achieves the desired shape. This means that the method is also suitable for a product portion having dimensions that change along an axis of the product portion, such as the lengths of the first and second side portions <NUM>, <NUM>. This is typically the case for a cap for a leading edge of a wind turbine blade. If the cap is designed to extend to, or substantially to, the relatively small tip region of the wind turbine blade, the present method may in some cases need to be supplemented by an alternative method to finish the trimming.

The method may comprise the cutting tool being guided by a guide system (not illustrated). The flange <NUM> itself or the board <NUM> may for instance have a groove that cooperates with a corresponding flange on the cutting tool <NUM>. In other embodiments, the cutting tool comprises a groove that cooperates with a flange (or other suitable protrusion) on the flange <NUM> or on the board <NUM>. The flange-groove parts may also be configured with a guide system that prevents the cutting tool <NUM> from being easily removed during the trimming. For instance, the motor <NUM> may be fitted with a dove tail portion that engages with a corresponding groove on the board <NUM>. The dove tail and groove may be engaged from an end of the groove by inserting the dove tail portion into the groove, i.e. at the first or second longitudinal end of the leading-edge protection element <NUM>. Such a locking system may improve safety and product portion consistency.

As indicated above, the cutting tool may be used to cut off a sacrificial portion either partly or entirely. In some cases, it is advantageous to perform part of the trimming process using another method, especially where the product has a more intricate shape. In some embodiments, the element <NUM> has been partly trimmed before a method in accordance with the present invention is used.

<FIG> illustrates an end view corresponding to the first longitudinal end of the leading-edge protection element <NUM>, showing the support tabletop <NUM> with the leading-edge protection element <NUM> arranged on it, the flanges <NUM>, <NUM> clamped to the tabletop <NUM> using respective boards <NUM>, <NUM> and clamps <NUM>, <NUM> as described above. <FIG> also illustrates an additional cutting tool <NUM> comprising a saw <NUM> powered by a motor <NUM>.

The additional cutting tool <NUM> may be used to cut off the sacrificial portion comprising flange <NUM>, or the first cutting tool <NUM> may be used. In some embodiments, two cutting tools can be operated simultaneously. In some embodiments, one cutting tool is operated starting from the first longitudinal end of the leading-edge protection element <NUM> and the other cutting tool is operated starting from the second longitudinal end of the leading-edge protection element <NUM>.

As illustrated in <FIG>, the trimming provides the desired first and second predetermined lengths L<NUM> and L<NUM> of the pressure side portion <NUM> and the suction side portion <NUM> of the cap <NUM>, respectively.

<FIG> further illustrates a product portion support <NUM>. The product portion support <NUM> in this example conforms to the shape of the leading-edge protection element <NUM>. In case the leading-edge protection element <NUM> is somewhat flexible, the product portion support <NUM> can help dampen vibrations arising during the trimming process. In some embodiments, the product portion support <NUM> is reconfigurable to more easily allow support of elements <NUM> of different shapes. Another advantage of the product portion support <NUM> is that the product portion <NUM> is supported by the product portion support <NUM> during and also after trimming. This makes it easier to handle the product portion <NUM>, which may have lengths above <NUM> and a weight that cannot be safely handled manually.

<FIG> also illustrates guiding means <NUM> on the cutting tool that engage with the leading-edge protection element <NUM>. The leading-edge protection element <NUM> is used as a fence for the guiding means <NUM>. This provides additional support for the cutting tool <NUM>, increasing the stability of the cutting tool during cutting, in turn resulting in further improved product portion consistency.

<FIG> shows an end view similar to <FIG>, but after the product portion <NUM> has been separated from the sacrificial portions, which are labelled <NUM> and <NUM> in <FIG>. The sacrificial portions <NUM>, <NUM> comprise the flanges <NUM>, <NUM> used to fixate the leading-edge protection element <NUM> to the support <NUM>. <FIG> shows how the product portion <NUM> can be removed by simple lifting from the product portion support <NUM> supporting it as shown in <FIG>.

After trimming of the leading-edge protection element <NUM>, thereby obtaining the product portion <NUM>, the sacrificial portions <NUM>, <NUM> can be removed, and another element <NUM> can be trimmed in accordance with an embodiment of the invention.

The product portion <NUM> obtained as described above is shown separately in <FIG>. After suitable additional processing, the product portion is ready to be used. In the example above, the trimming of the leading-edge protection element <NUM> results in a leading-edge cap similar to the cap <NUM> shown in <FIG>. After trimming and after performing any additional steps required, the cap <NUM> is attached to the wind turbine blade, resulting in the blade shown in <FIG>. It is noted that for simplicity, the non-uniform cross-section of the cap <NUM> in <FIG> is not illustrated in <FIG>.

Similarly to <FIG>, <FIG> shows how the trimming provides the desired first and second predetermined lengths L<NUM> and L<NUM> of the pressure side portion <NUM> and the suction side portion <NUM> of the cap <NUM>, respectively.

<FIG> illustrates an alternative way of fixating the leading-edge protection element <NUM> to a support such as a tabletop <NUM>. <FIG> schematically illustrates a number of suction openings <NUM> connected to a vacuum pump <NUM> via tubes <NUM>. Suction produced by the vacuum pump maintains the leading-edge protection element <NUM> fastened on the tabletop <NUM>. The suction openings <NUM> may be higher or lower in number and may have alternative shapes in order to provide suitable suction pressure to hold the leading-edge protection element <NUM> in place during trimming. If necessary, part of the leading-edge protection element <NUM>, such as the flanges <NUM>, <NUM>, may be treated to ensure a vacuum-tight fit.

The leading-edge protection element <NUM> may alternatively be supported by pads rather than a flat surface, such as by adjustable pads, such as by pads that can provide suction. The pads are preferably adjustable with respect to position and/or posture (e.g. adjustable angling), the adjustable posture being implemented for instance using adjustable ball joints.

Claim 1:
A method for trimming a side portion of a pre-manufactured leading-edge protection element (<NUM>) for protecting a leading edge of a wind turbine blade, the leading-edge protection element extending in a longitudinal direction between a first longitudinal end and a second longitudinal end, the leading-edge protection element comprising a first side portion (<NUM>) and a second side portion (<NUM>), the first side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a pressure side (<NUM>) of the wind turbine blade, and the second side portion, when mounted to the wind turbine blade, extending from the leading edge and along a part of a suction side (<NUM>) of the wind turbine blade, or vice versa, the method comprising the steps of:
- providing a support structure (<NUM>, <NUM>);
- providing a first cutting tool (<NUM>), preferably connected to the support structure;
- arranging the leading-edge protection element on the support structure,
- fixating the leading-edge protection element to the support structure, and
- cutting along a predetermined cutting path, whereby the leading-edge protection element is trimmed to a predetermined length.