Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

In order to extract more energy from the wind, the size of the rotor diameter is increased by increasing the dimensions of the wind turbine blades. The larger size of the blades introduces higher physical loads to the blade and related components. Wind turbine rotor blades generally comprise a body shell formed by two shell haves of a composite material. The body shell is relatively lightweight and has structural properties that are not designed to withstand the bending moments and other loads acting on the blade during operation. To improve the structural properties of the rotor blade such as stiffness and strength, the blade is generally reinforced with structural components, e.g. one or more spar caps at the suction and pressure side of the blade with a shear web connecting them.

The spar caps can be manufactured using several materials such as glass fiber laminate composites and carbon fiber laminate composites. Modern spar caps may be manufactured using pultruded composites, particularly carbon fiber based pultruded composites. Composites manufactured by pultrusion may have a constant cross-section that can be easily stacked to form a larger composite part. They may be referred to as pultruded "plates". A plurality of pultruded plates may be stacked and infused together in a mold to form a larger (i.e. longer, thicker, wider) composite part, e.g. a spar cap.

Due to the benefits of using pultruded plates for the manufacture of composite parts in terms of cost and others, the industry is developing new approaches to integrate them in composite manufacturing processes. Known approaches include the placement of pultruded plates in a mold to later infuse them. However, the pultruded plates may be difficult to align with respect to each other and to the mold, and this may lead to imperfections in the final product. To mitigate the aforementioned misalignments, a considerable amount of manual labor is required, which leads to an increase in the average cost of the composite part and a reduction in the overall composite manufacture throughput.

Further, approaches known in the art employ supports located in the mold to guide the pultruded plates coming from, for example, a lifting device, such as a crane or similar. After resin infusion and unmolding, the resin infused stack of pultruded plates may need to be treated by qualified operators to improve the quality of the product and e.g. remove excess resign. This results in a time-consuming and complex task that requires manual labor and hinders the production rate and quality of the final product.

<CIT> discloses a method for manufacturing a spar cap for a wind turbine blade, the spar cap comprising a stack of pultruded plates, the method comprising laying the stack of pultruded plates between a first and a second porous infill blocks on a mold; infusing the stack of pultruded plates with resin; and unmolding the infused stack of pultruded plates from the mold.

The present disclosure provides examples of assemblies and methods that at least partially overcome some of the drawbacks of existing molds for spar cap manufacturing and methods for manufacturing spar caps comprising pultrusion plates.

In a first aspect, a mold assembly is provided. The mold assembly is configured for manufacturing a spar cap comprising a stack of pultruded plates. The mold assembly comprises a mold surface having a longitudinal direction and a transverse direction, and at least two sidewalls. The sidewalls are arranged substantially in the longitudinal direction. Further, at least one of the sidewalls is configured to be adjusted along a transverse direction of the mold surface.

According to this first aspect, the mold assembly allows placement of the pultruded plates relative to the mold surface and to align the pultruded plates by adjusting the position of at least one sidewall along a transverse direction. Therefore, the mold assembly considerably reduces manual supervision and labor during the positioning and alignment of the pultruded plates. This results in a, at least, partially automatized process with high reproducibility. At the same time, it brings down production costs and increases the production rate of composite parts. Moreover, a draft angle which is usually employed for placement of the pultruded plates and for unmolding of the resin infused component may be reduced or eliminated. There will thus be less excess of resin on the side of the components, requiring less labor afterwards.

Further, the fact that at least one sidewall can be adjusted allows the use of the same mold assembly for pultruded plates of different dimensions. Further, said sidewall aids on the unmolding step after resin infusion, e.g. the sidewall may be move away from the spar cap to ease the collection of the same.

In another aspect, a method for manufacturing a spar cap comprising a stack of pultruded plates is provided. The method comprises laying the stack of pultruded plates between a first and a second sidewall on a mold surface. Further, the method comprises infusing the stack of pultruded plates with resin and unmolding the infused stack of pultruded plates from the mold. Additionally, at least one of the sidewalls is adjusted along the transverse direction relative to the stack of pultruded plates at least after the laying or prior the unmolding of the stack of pultruded plates.

According to this aspect, the method allows placing the stack of pultruded plates in a mold and then displacing a sidewall relative to the stack of pultruded plates. Thus, the alignment of the pultruded plates can occur during the translation of the sidewall. Further, the fact that a sidewall can be moved allows manufacturing spar cap with different dimensions, e.g. widths and can reduce the draft angle usually employed for unmolding. The sidewall(s) can be translated after infusing the stack of pultruded plates with resin, which simplifies considerably the unmolding process and reduces the risk of damaging the spar cap during extraction.

Throughout this disclosure, the terms "pultruded composites", "pultruded plates", "pultrusions" or similar terms are generally used to define reinforced materials (e.g. fibers or woven or braided strands) that are impregnated with a resin and pulled through a heated die such that resin cures.

Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation.

<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 blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

The wind turbine blade <NUM> comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fiber-reinforced polymer. The wind turbine blade <NUM> may comprise additional shell parts, such as a third shell part and/or a fourth shell part. 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 fastened together 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> has a semi-circular or semi-oval outer cross-sectional shape.

<FIG> is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade <NUM>, e.g. a cross sectional view of the airfoil region of the wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM>, a suction side <NUM> a first spar cap <NUM>, and a second spar cap <NUM>. The wind turbine blade <NUM> comprises a chord line <NUM> between the leading edge <NUM> and the trailing edge <NUM>. The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web and a trailing edge shear web. The shear webs <NUM> could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps <NUM>, <NUM> may comprise carbon fibers while the rest of the shell parts <NUM>, <NUM> may comprise glass fibers.

<FIG> is a schematic diagram illustrating an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system <NUM> comprises a first mold <NUM> and a second mold <NUM>. The first mold <NUM> is configured for manufacturing a first blade shell part of a wind turbine blade, such as an upwind shell part of the wind turbine blade (forming the pressure side). The second mold <NUM> is configured for manufacturing a second blade shell part of the wind turbine blade, such as a downwind shell part of the wind turbine blade (forming the suction side). The mold system <NUM> further comprises surfaces <NUM>, <NUM> for depositing fibers.

<FIG> schematically illustrates a top perspective view of a mold assembly <NUM> according to one example. The mold assembly <NUM> is configured to manufacture a spar cap comprising a stack of pultruded plates <NUM>. The mold assembly <NUM> comprises a mold surface <NUM> having a longitudinal direction and a transverse direction. Further, the mold assembly <NUM> also comprises at least two sidewalls <NUM>, <NUM> arranged substantially in the longitudinal direction. At least one of the sidewalls <NUM>, <NUM> is configured to be adjusted along a transverse direction of the mold surface <NUM>. This allows an accurate adjustment of the distance between sidewalls <NUM>, <NUM> that serves both to guide the stack of pultruded plates <NUM> while these are laid on the mold surface <NUM>, and to push the stack of pultruded plates <NUM> in the transverse direction and align them relative to each other and to the mold surface <NUM>.

In the illustrated example, only one of the sidewalls <NUM> can be adjusted, but in other examples both sidewalls <NUM>, <NUM> could be adjustable. Note that in the present example the stack of pultruded plates <NUM> has been illustrated elevated with respect to the mold surface <NUM>, as if the stack of pultruded plates <NUM> was still descending down to the mold <NUM>. Once the pultruded plates <NUM> have been positioned in the mold, the (final) adjustment of the sidewalls of the mold may occur.

Also referring to <FIG>, in some examples the mold assembly <NUM> may comprise guides <NUM> extending in the transverse direction. The guides <NUM> may be configured to guide at least one of the sidewalls <NUM>. The connection between the guides <NUM> and the sidewalls <NUM>, <NUM>, may be a male-female connection. The guides <NUM> may define the female connection and the sidewall <NUM> the male connection or vice versa. Further, the guides <NUM> may be embedded in the mold surface <NUM>. Additionally, the guides <NUM> may comprise a sealing cap to at least partially seal the guide opening that is below the stack of pultruded plates <NUM> and avoid the accumulation of resin.

In examples, the sidewalls of the mold may be substantially parallel to each other i.e. the draft angle may be 0º. After resin infusion, the adjustable sidewall(s) may be displaced in the transverse direction to allow unmolding.

In examples, at least one of the sidewalls <NUM> may comprise a sliding element configured to slide along the guide <NUM> in the transverse direction. The sliding element and guide <NUM> may define a low friction coupling to promote a smooth adjustment. Besides, said sidewalls <NUM> may also comprise a clamping or fixing element to secure the position of the sidewall <NUM> along the guide, as for example a locking lever. The clamping (or fixing) element may be manual or automatic.

In further examples, the mold assembly <NUM> may further comprise a drive unit configured to adjust at least one of the sidewalls <NUM> along the transverse direction. The drive unit may be operated autonomously or by a qualified operator. The drive unit may comprise pneumatic, and/or hydraulic, and/or electronic components, such as for example, pistons, pumps, encoders, stepper motors, and others. Thus, the drive unit may displace the sidewalls <NUM>, <NUM> prior to laying the stack of pultruded plates to provide more room for the descent of the same. In other examples, the drive unit may displace the sidewalls <NUM>, <NUM> after laying the stack of pultruded plates to secure them and align them relative to each other and to the mold <NUM>. Additionally, the mold assembly <NUM> may comprise a sensor unit configured to determine the pressure exerted by at least one of the sidewalls <NUM>, <NUM> to the stack of pultruded plates <NUM>. The sensor unit may feed the driver so that it stops the displacement after reaching a giving pressure threshold. Additionally, the sensor unit may also comprise a processing and control unit that process the data from the sensor and provides controlling parameters to the driver.

In alternative examples, adjusting the sidewall(s) may be a manual process.

<FIG> illustrate a cross-section view of the mold assembly according to another example of the present disclosure.

<FIG> schematically illustrates a mold assembly <NUM> with a stack of pultruded plates <NUM> at a given height prior to being deposited onto the mold surface <NUM>. Additionally, <FIG> illustrates that at least one of the sidewalls <NUM>, <NUM>, comprises a sidewall surface <NUM> configured to contact a lateral surface (reference <NUM> in <FIG>) of the stack of pultruded plates <NUM>. In examples, the sidewall surface <NUM> may be rotatable about the longitudinal direction of the mold surface <NUM>. Thus, the rotation of the sidewall surface <NUM> allows defining a variable draft angle delimits the distribution of resin during infusion.

Additionally, <FIG> also shows that the mold surface <NUM> may comprise one or more receptacles <NUM> to receive sidewall fasteners <NUM>. Having a plurality of receptacles distributed along the transverse direction allows locating the sidewall <NUM> at discrete locations depending on, for example, the dimensions of the pultruded plates or the stage of the molding process. It will be clear that a plurality of receptacles and fasteners may be provided along the longitudinal direction as well.

The receptacles <NUM> and corresponding fasteners <NUM> may provide a threaded connection, but other couplings can also be employed. In some examples, the sidewalls <NUM>, <NUM> may have elongated holes to receive the sidewall fasteners <NUM>. The elongated holes may provide a variable positioning of the sidewall <NUM> with respect to the mold surface <NUM>. In other examples, the receptacles in the mold <NUM> may be elongated and the fasteners <NUM> may be introduced in them at a desired transverse position.

<FIG> schematically shows the mold assembly <NUM> with a stack of pultruded plates <NUM> already deposited on top of the mold surface <NUM>. Further, in <FIG>, one of the sidewalls <NUM> is located next to the stack of pultruded plates <NUM> and fixed to the mold <NUM>. In this example, the mold assembly <NUM> also comprises fasteners <NUM> that match the inner geometry of the receptacles <NUM> in the mold <NUM>. As discussed with respect to <FIG>, the sidewalls <NUM>, <NUM> may comprise a lateral surface <NUM> that is rotatable about the longitudinal direction of the mold <NUM>. As shown, this may lead to a lateral surface <NUM> that is substantially parallel to the lateral surface of the stack of pultruded plates <NUM>.

Note that although the sidewalls <NUM>, <NUM> have been represented as L profiles, these may have any other suitable cross-section.

<FIG> illustrates two infused pultrusion stacks <NUM>. The infused pultrusion stacks <NUM> define a longitudinal direction and a transverse direction. Further, the infused pultrusion stacks <NUM> and define two lateral surfaces <NUM> that limit the infused pultrusion stacks <NUM> in the transverse direction. The two lateral surfaces <NUM> extend along the longitudinal direction and are substantially parallel to each other.

In examples, the infused stack <NUM> comprises a plurality of pultruded plates <NUM> infused with resin. The stack of pultruded plates <NUM> may comprise carbon fiber, glass fiber, aramid fiber or other suitable fibers. Besides, the infused stack of pultruded plates <NUM> may comprise epoxy resin, polyester resin, vinylester resin or other suitable resins.

As illustrated in <FIG>, the infused pultrusion stack <NUM> may have a rectangular cross section (embodiment on the left) or it may have a curved cross section (embodiment on the right). Thus, the external surface <NUM> of the infused pultrusion stack <NUM> may be either flat or curved. The dimensions and geometry of the infused pultrusion stack <NUM> may be adapted depending on the geometry or mechanical requirements of the composite product.

In both these examples, the draft angle of the sidewalls may have been <NUM>° or close to 0º. Resin build-up on the sides of the stacks may thus be avoided. This can reduce the weight of the product and can also reduce the need for post-processing. Additionally, a draft angle of 0º or close to <NUM>° may also reduce the cost of other components adjacent to the pultrusion stack <NUM>. For example, core panels that are configured to be assembled next to the pultrusion stack <NUM> may be cut with straight angles that substantially match the sidewalls of the pultrusion stack <NUM>. This may result in a faster and cheaper manufacturing process.

In some examples, the infused pultrusion stacks <NUM> may be obtained by a method that will be further discussed in relation with <FIG>.

<FIG> is a flow diagram of a method <NUM> for manufacturing a spar cap according to one example, wherein the spar cap of method <NUM> comprises a stack of pultruded plates <NUM>. The method <NUM> comprises laying <NUM> the stack of pultruded plates <NUM> between a first and a second sidewall <NUM>, <NUM> in a mold <NUM>. Further, the method <NUM>, at block <NUM>, comprises infusing the stack of pultruded plates <NUM> with resin. Then, the method <NUM> also comprises unmolding <NUM> the infused stack of pultruded plates <NUM> from the mold <NUM>.

During method <NUM> at least one of the sidewalls <NUM>, <NUM> may adjusted along the transverse direction relative to the stack of pultruded plates <NUM>. This may take place at least after the laying <NUM> of the pultruded plates <NUM> or prior the unmolding <NUM> of the stack of pultruded plates <NUM>.

The adjustment of at least one of the sidewalls <NUM>, <NUM> may be done according to any of the examples herein previously illustrated.

As previously discussed, the fact that at least one of the sidewalls <NUM>, <NUM> is adjusted along the transverse direction greatly simplifies the placement of the stack of pultruded plates <NUM> (both by potentially guiding the descent and by providing more room for the plates) and the unmolding. In fact, in some examples adjusting at least one of the sidewalls <NUM>, <NUM> is performed by displacing said sidewall <NUM>, <NUM> in the transverse direction and subsequently fastening said sidewall <NUM>, <NUM> to a receptacle in the mold <NUM> prior to infusing <NUM> the stack of pultruded plates <NUM> with resin.

In some examples, the method <NUM> comprises laying <NUM> the stack of pultruded plates <NUM> substantially adjacent to the first sidewall <NUM>, the first sidewall <NUM> being fixed in the mold <NUM>, and the method <NUM> further comprises adjusting the second sidewall <NUM> in the transverse direction to contact the stack of pultruded plates <NUM>. This results in an improved alignment of the pultruded plates <NUM> and therefore increases the quality of the final product. Additionally, the sidewalls <NUM>, <NUM> may define a draft angle smaller than <NUM> degree, specifically smaller than <NUM>,<NUM> degrees, more specifically a draft angle of approximately <NUM> degrees. This draft angle limits the accumulation of resin between the sidewall <NUM>, <NUM> and the lateral surfaces of the pultruded plates <NUM>, which reduces considerably the amount of post-molding surface treatment that may be required. In other examples, the sidewalls <NUM>, <NUM> may be fixed in the mold at a given location and defining a large draft angle to ease the guiding of the stack of pultruded plates <NUM>. Then, prior to infusing <NUM>, the draft angle may be reduced by rotating a sidewall surface <NUM>.

In examples, the sidewalls <NUM>, <NUM> may be substantially parallel to each other. Since the mold <NUM> may have a curved geometry and the sidewalls <NUM>, <NUM> may be displaced along the surface of the mold <NUM>, the sidewalls <NUM>, <NUM> may be further adjusted by rotating a sidewall surface <NUM> configured to contact the stack of pultruded plates <NUM>. The rotation of the sidewall surface <NUM> may be about the longitudinal direction of the mold surface <NUM>.

As discussed with respect to <FIG>, the stack of pultruded plates <NUM> may comprise carbon fiber, glass fiber, aramid fiber or other suitable fibers and the resin may comprise epoxy resin, polyester resin, vinylester resin or other suitable resins.

In yet a further aspect of the present disclosure, a wind turbine blade is provided. The wind turbine blade comprises a shear web and spar caps, wherein the spar caps comprise an infused stack of pultruded plates <NUM> according to any of the examples illustrated herein, and/or manufactured according to any of the examples illustrated herein. The upwind and downwind shell of the wind turbine blade may be made e.g. in accordance with the process illustrated in <FIG>.

Note that some of the technical features described in relation with the mold assembly <NUM> and infused pultrusion stack <NUM> can be included in the method <NUM> for manufacturing a spar cap, and vice versa.

Claim 1:
A method (<NUM>) for manufacturing a spar cap for a wind turbine blade, the spar cap comprising a stack of pultruded plates (<NUM>), the method comprising:
laying (<NUM>) the stack of pultruded plates (<NUM>) between a first and a second sidewall (<NUM>, <NUM>) on a mold (<NUM>);
infusing (<NUM>) the stack of pultruded plates (<NUM>) with resin; and
unmolding (<NUM>) the infused stack of pultruded plates from the mold (<NUM>),
characterized in that at least one of the sidewalls (<NUM>, <NUM>) is adjusted along the transverse direction relative to the stack of pultruded plates (<NUM>) at least after the laying (<NUM>) or prior to unmolding (<NUM>) of the stack of pultruded plates (<NUM>).