Patent Description:
An example of a known wind turbine <NUM> is shown in <FIG>. The wind turbine <NUM> comprises a rotor <NUM> connected to a generator (not shown) arranged inside a nacelle <NUM>. The nacelle <NUM> is arranged at the upper end of a tower <NUM> of the wind turbine <NUM>. The rotor <NUM> comprises three blades <NUM>. Rotors <NUM> of this kind may have diameters ranging from, for example, <NUM> to <NUM> meters. The blades <NUM> are subjected to high wind loads. At the same time, the blades <NUM> need to be lightweight. For these reasons, blades <NUM> in modern wind turbines <NUM> are manufactured from fiber-reinforced composite materials. Therein, glass fibers are generally preferred over carbon fibers for cost reasons. In addition, the blades <NUM> each comprise one or more core members of a light material to reduce the weight of the blades.

For example, <CIT> describes a method for manufacturing a rotor blade <NUM> using a vacuum-assisted resin transfer molding (VARTM)-process. This process is partially illustrated in <FIG> showing a section view.

In a first step of the manufacturing process, a vacuum distribution layer <NUM> is laid onto a mold surface <NUM> of a mold <NUM>. The mold <NUM> may be a lower part of a closed mold <NUM>, the upper part of the mold <NUM> not being shown in <FIG>.

In a further step, a layup <NUM> of fiber material is arranged on top of the vacuum distribution layer <NUM>.

Then, a layer of non-woven fiber glass material <NUM> is laid on top of the layup <NUM>. The fiber glass material <NUM> has a lower air permeability than the layup <NUM>.

The vacuum distribution layer <NUM> is connected to a vacuum pump <NUM>. As the layers <NUM>, <NUM> are being arranged on the mold <NUM>, the vacuum ensures that said layers <NUM>, <NUM> are firmly positioned against the mold <NUM>. Thus, especially in cases where the mold <NUM> has deeply concave shapes, the vacuum ensures that the layers <NUM>, <NUM> follow the actual curvature of the mold <NUM>. Thus, a phenomenon called "hovering glass" is prevented.

<FIG> shows a portion of the non-woven fiber glass material <NUM> used in the process of <FIG>.

The non-woven glass fiber material <NUM> comprises a plurality of glass fiber rovings <NUM> held together by a stitching yarn <NUM>. The stitching yarn <NUM> causes local constrictions or deformations of a respective roving <NUM> resulting in cavities or openings <NUM> formed between the rovings <NUM>.

When the vacuum is applied as shown in <FIG>, air flows through the openings <NUM> shown in <FIG>. Hence, the vacuum that can be generated underneath the layer <NUM> in order to force the layup <NUM> against the mold <NUM> may not be sufficient for some applications.

<CIT> describes a non-stitched fiber material with unidirectional arranged first fibers being bonded to second fibers that are arranged perpendicular to the first fibers.

<CIT> describes a fiber material with fibers that are arranged parallel and which are interconnected by resin bridges.

<CIT> describes a non-woven warp yarn fabric material with a plurality of yarns that are substantially parallel and equally spaced apart.

<CIT> describes a method for producing parts based on composite materials. The method makes use of a vacuum bag which is arranged on a fiber layup to press it against a mold.

One objective of the present invention is to provide an improved method for manufacturing a component for a wind turbine.

A method according to the present invention includes the features of claim <NUM>.

Accordingly, a non-stitched fiber material configured tc produce a pressure drop sufficient to force a layup of fiber material against a mold surface when vacuum is applied to the space between the non-stitched fiber material and the mold surface is provided. The non-stitched fiber material comprises a plurality of fibers bonded together by an adhesive to improve the air tightness of the non-stitched fiber material, wherein openings or cavities between adjacent fibers are avoided, such that it is configured to produce the pressure drop sufficient to force the layup of fiber material against the mold surface when vacuum is applied to the space between the non-stitched fiber material and the mold surface. The fibers are arranged in an airtight or closely airtight manner next to one another on the layup. The adhesive takes the shape of at least one bead bonding the fibers together, wherein the at least one bead has a zigzag shape.

The fiber material is advantageous in that by bonding the fibers together rather than using a stitching yarn, openings or cavities between adjacent fibers are avoided. This in turn improves the air tightness of the fiber material allowing a greater pressure drop to be generated across said fiber material.

"Fibers bonded together by an adhesive" in particular comprises embodiments where the adhesive directly connects individual fibers to each other, as well as embodiments where the adhesive bonds a respective fiber to a support layer, the fibers thus being connected to each other by the adhesive as well as the support layer.

The fibers of the non-stitched fiber material may comprise glass fibers, carbon fibers and/or aramid fibers, for example. The term "fibers" used herein encompasses, preferably, fibers, rovings and/or fiber filaments.

The adhesive of the non-stitched fiber material is in a cured or hardened state. This is to say that molecular chains within the adhesive are fully cross-linked or cross-linked to an extent where the shape of the adhesive will not or not significantly change any more.

By "to produce a pressure drop sufficient to force a layup of fiber material against a mold surface" it is meant that the force produced will prevent phenomena like "hovering glass" or similar phenomena where the layup or fiber material is not following the curvature of the mold surface to a desired extent. In some examples, the force produced by the pressure drop may be sufficient to turn the mold, for example, the mold <NUM> of <FIG> by <NUM>°, the force holding the layup against the mold surface counteracting gravity.

According to the invention the fibers are parallel to each other.

This simplifies producing the non-stitched fiber material in a continuous process.

The adhesive takes the shape of at least one bead bonding the fibers together.

Applying a bead to the fibers may be automated easily. The term "bead" herein, preferably, also encompasses a strip, a string or a band. The bead may have, for example, a circular, square or rectangular cross-section. The length of the bead is at least <NUM>, preferably <NUM> and more preferably <NUM> times its diameter (in the case of a circular cross-section) or its diagonal (in the case of a square or rectangular cross-section).

According to the disclosure, the at least one bead is arranged crosswise with respect to the lengthwise direction of the fibers.

In particular, the bead may extend perpendicularly to a respective fiber. Herein, "perpendicularly" preferably includes angles between the bead and a respective fiber of <NUM>° ± <NUM>°, more preferably <NUM>° ± <NUM>°, and even more preferably <NUM>° ± <NUM>°.

According to the disclosure, multiple beads are provided and arranged parallel to each other.

Two respective beads may be spaced from each other by a distance of <NUM> - <NUM>, for example.

According to the invention the at least one bead has a zigzag shape. "Zigzag shape" herein is also to include an "S"-shape.

According to the disclosure, the non-stitched fiber material comprises a support layer, the fibers being bonded by the adhesive to the support layer.

For example, the support layer may be a mesh of fiber material, fiber felt or fiber fabric.

According to the disclosure, the support layer is an adhesive tape.

A self-adhesive mesh tape is preferred, in particular.

According to a further embodiment, the adhesive comprises a resin.

Examples of a resin which may be used are epoxy, polyester, vinylester or any other suitable thermoplastic or duroplastic material. Instead, the adhesive may also comprise a glue.

According to a further embodiment, the pressure drop produced across the thickness of the non-stitched fiber material at a through flow of air of, preferably, <NUM><NUM>/h is larger than <NUM> mbar, preferably <NUM> mbar and more preferably <NUM> mbar.

A pressure drop of this kind will be sufficient to lift a layup of fiber material having an area density of <NUM>/m<NUM>. This ensures a secure lift as this would be <NUM> times the weight of a typical layup of fiber material.

According to a further embodiment, the non-stitched fiber material has an area density of <NUM> - <NUM>/m<NUM>.

Preferred area densities may range from <NUM> - <NUM>/m<NUM>.

These values particularly apply when the fibers of the non-stitched fiber material are glass fibers.

Further, a method for manufacturing a component for a wind turbine is provided, according to the features of claim <NUM>.

According to the disclosure, fibers or bundles of fibers are laid next to one another on top of the layup of fiber material while vacuum is applied to the layup of fiber material. Thus, the vacuum maintains the position of the fibers. Thus, this represents a further method of producing a non-stitched fiber material.

In both embodiments described above, the fibers or bundles of fibers may be placed with a robot onto the layup of fiber material.

The fiber material used for the layup may comprise fiber material of different shapes and composition. For example, the fiber material may comprise a layup of fibers, rovings, a fiber mat, a fiber fabric, woven fibers or a fiber felt. The fibers may be arranged unidirectionally, in a biax-configuration or in any other configuration. The fibers may comprise glass fibers, carbon fibers and/or aramid fibers, for example. Preferably, the layup of fiber material is arranged on top of the mold surface in a dry, i.e. unimpregnated state. Yet, in other embodiments, the layup of fiber material may be provided in a at least partially wetted, i.e. pre-impregnated state (so-called prepreg material).

Step c) may be followed by a vacuum bag being arranged on top of the non-stitched fiber material and resin being injected into the space between the vacuum bag and the mold surface. After the resin has set or has been cured - typically by the addition of external heat - the vacuum bag and/or mold is removed and the final component is obtained. Of course, when using a prepreg material, there is no need to inject the fiber material with resin.

Generally speaking, the mold may be an open or a closed mold. For example, the mold may comprise one or more parts, in particular a lower part and an upper part.

"Cured" or "set" refers to the resin being hardened and/or cross-linked to an extent where a shape of the resin including the fiber material will not or not significantly change any more.

Examples of a resin which may be used for impregnating the layup of fiber material are epoxy, polyester, vinylester or any other suitable thermoplastic or duroplastic material.

The term "layup" is to be understood as one or more layers of fiber material. The fiber material can be of a shape and a configuration as described in the above.

"a)", "b)" and "c)" are not to imply a fixed order of the method steps. Rather, the steps a) - c) may be carried out in a different order where appropriate in the mind of the skilled person.

According to a further embodiment, the mold having the mold surface is turned by <NUM>°, the non-stitched fiber material holding the layup against the mold surface counteracting gravity.

Furthermore, an apparatus for manufacturing a non-stitched fiber material is provided. The non-stitched fiber material has the features described above, in particular. The apparatus comprises a feeding unit and an application unit. The feeding unit is configured to, preferably continuously, feed the fibers to the application unit and the application is configured to, preferably, continuously apply the adhesive to the fibers for bonding the fibers together.

According to the disclosure, the apparatus comprises a heating unit for curing the adhesive, the heating unit being configured as a rotating drum.

The rotating drum continuously or certain areas of the rotating drum intermittently contact the fibers including the adhesive. Thus, heat is transferred from the rotating drum to the adhesive. The heat transferred cures the adhesive in order to permanently bond the fibers together.

"Wind turbine" presently refers to an apparatus converting the wind's kinetic energy into rotational energy, which may again be converted to electrical energy by the apparatus.

The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention, as defined by the claims.

Further objects, features and advantages of the present invention become apparent from the subsequent description and the pending claims, taken in conjunction with the accompanying drawings, in which:.

<FIG> shows a top view of a non-stitched fiber material <NUM> to be used instead of the fiber material <NUM> in the process illustrated in <FIG>, for example. Even though explained herein after with reference to the embodiment of <FIG>, the non-stitched fiber material <NUM> may be used in any other manufacturing process for manufacturing a component, in particular a rotor blade <NUM> (<FIG>).

The non-stitched fiber material <NUM> is configured to produce a pressure drop sufficient to force the layup <NUM> of fiber material against the mold surface <NUM> when vacuum is applied to the space between the non-stitched fiber material <NUM> and the mold surface <NUM>. The pressure drop across the thickness t of the non-stitched fiber material <NUM> is preferably larger than <NUM> mbar at a through flow of air of <NUM><NUM>/h in the direction <NUM> normal to the surface of the non-stitched fiber material <NUM> as shown in <FIG>. This kind of pressure drop will be sufficient to prevent "hovering glass" as explained in the introductory section above. Further, this kind of pressure will be sufficient to hold the layup <NUM> firmly against the mold surface <NUM> when the mold <NUM> is turned by a <NUM>° such that gravity tends to pull the layup <NUM> away from the mold surface <NUM>. Thus, the pressure drop is sufficient to counteract gravity. In one embodiment, the layup <NUM> may have an area density of <NUM>/m<NUM>. Even in this case, the pressure drop will be sufficient to maintain close contact between the fiber layup <NUM> and the mold surface <NUM> (via the vacuum distribution layer <NUM> in cases where a vacuum distribution layer <NUM> is used).

As shown in <FIG>, the non-stitched fiber material <NUM> comprises a plurality of fibers <NUM> arranged parallel to each other (so-called unidirectional orientation). The fibers <NUM> are bonded together by an adhesive. In this particular case, the adhesive takes the shape of a plurality of parallel beads <NUM> of cured resin. The beads <NUM> may be arranged crosswise with respect to the fibers <NUM>, thus extending at an angle with <NUM>° with respect to the fibers <NUM>.

The beads <NUM> are spaced apart from each other in the lengthwise direction <NUM> of the fibers <NUM>. In particular, a distance <NUM> between adjacent beads may range between <NUM> and <NUM>, for example <NUM> in the present embodiment.

The fibers <NUM> may, for example, be configured as glass fibers with an area density ranging from <NUM> - <NUM>/m<NUM>. In this particular case the area density may be <NUM>/m<NUM>.

<FIG> illustrates an enlarged perspective view from <FIG>.

<FIG> illustrates a bead <NUM> having a circular cross-section <NUM>, for example. However, the cross-section <NUM> may also be of a rectangular or square shape. The bead <NUM> may be produced, in particular, by moving a nozzle in the crosswise direction <NUM> of the fibers <NUM>, the nozzle (not shown) depositing the bead material on the fibers <NUM>. Once cured, the bead <NUM> firmly connects the fibers <NUM>. In the example of <FIG>, the fibers <NUM> are directly connected to one another by a respective bead <NUM>.

Thus, the mold surface <NUM> - having no stitches - does not have openings <NUM> and is therefore more airtight than some conventional fiber materials <NUM>. In particular, the non-stitched fiber material <NUM> has a lower air permeability than the layup <NUM>.

<FIG> illustrates in a top view a non-stitched fiber material <NUM>.

The non-stitched fiber material <NUM> has a single bead <NUM> having a zigzag shape and connecting individual fibers <NUM> to each other. Instead of the zigzag shape, the bead <NUM> may also have an "S"-shape.

<FIG> illustrates a top view of a non-stitched fiber material <NUM>.

The non-stitched fiber material <NUM> comprises parallel fibers <NUM>. A support element configured as a self-adhesive glass mesh tape <NUM> is bonded to the fibers <NUM>.

The mesh <NUM> is shown in more detail in a perspective view in <FIG>. The mesh tape <NUM> comprises a mesh of fibers <NUM> each coated in adhesive <NUM>, for example resin, as illustrated in the cross-sectional view of <FIG>. The fibers <NUM> may, for example, be configured as glass fibers.

<FIG> illustrates a process of manufacturing a non-stitched fiber material <NUM>.

According to the disclosure the layup <NUM> of <FIG> is sprayed with a hot melt <NUM>. The hot melt <NUM> is a glue or resin, for example. While the hot melt <NUM> is still soft, a robot <NUM> arranges fibers <NUM> or bundles of fibers next to one another on the hot melt <NUM>. The fibers <NUM> are positioned in such close relationship that a non-stitched fiber material <NUM> of low air permeability is produced as explained with reference to <FIG> in the above.

According to the disclosure instead of the hot melt <NUM>, vacuum is applied to the layup <NUM> in <FIG>, for example via the vacuum pump <NUM>. As the robot <NUM> deposits fibers or fiber bundles <NUM> on the layup <NUM>, the vacuum secures the fibers <NUM> or fiber bundles in close relationship to each other. Thus, a non-stitched fiber material <NUM> having a low air permeability as described above is obtained.

<FIG> illustrates a top view of an apparatus <NUM> for manufacturing the non-stitched fiber material <NUM> described with reference to <FIG> in the above. <FIG> shows the apparatus <NUM> of <FIG> in a side view.

The apparatus <NUM> comprises a feed unit <NUM>, an application unit <NUM>, a heating unit <NUM> and a storage unit <NUM>.

The feeding unit <NUM> is, for example, configured as multiple bobbins with fiber materials or rovings. The fibers <NUM> are fed from the feeding unit <NUM> to the application unit <NUM>. The application unit <NUM> applies the beads <NUM> to the fibers <NUM>. For example, the application unit <NUM> may comprise a nozzle moving crosswise with respect to the length of fibers to deposit a respective bead <NUM> on the fibers <NUM>.

Optionally, a rotating drum <NUM> may be provided supporting the fibers <NUM> as the beads <NUM> are deposited.

After the application unit <NUM>, there is a heating unit <NUM> provided. The heating unit <NUM> is configured for curing the beads <NUM> (resin).

The storage unit <NUM> may be configured as a drum for winding up the finished non-stitched fiber material <NUM>.

In one embodiment, the heating unit <NUM> is integrated into the drum <NUM>. As the drum rotates <NUM>, the area in contact with the fibers and beads <NUM> transfers sufficient heat to cure the beads <NUM>.

Thus, a process of manufacturing the non-stitched fiber material <NUM> in a continuous process is provided. This is beneficial to a high degree of automation.

Last, a flow diagram of an embodiment of a method for manufacturing a rotor blade <NUM> for a wind turbine <NUM> is illustrated.

Again, reference is made to <FIG> for illustration purposes only.

In a first step S1, a layup <NUM> of fiber material is arranged on top of a mold surface <NUM>. Optionally, a vacuum distribution layer <NUM> is laid on the mold surface <NUM> beforehand.

In a step S2, the layup <NUM> is covered with a non-stitched fiber material <NUM> as explained above.

In another preferred embodiment, the vacuum distribution layer <NUM> is arranged on top of the layup <NUM>, i.e. between the non-stitched fiber material <NUM> and the layup <NUM>.

In a step S3, a vacuum is applied to the space between the non-stitched fiber material <NUM> and the mold surface <NUM>. The non-stitched fiber material <NUM> thus forces the layup <NUM> of fiber material against the mold surface <NUM>.

In a step S4, the mold <NUM> may be turned by <NUM>°, the layup <NUM> thus facing downwards. The non-stitched fiber material <NUM> will hold the layup <NUM> against the mold <NUM> due to the applied vacuum.

In a step S5, a web (not shown) or a core member of the blade <NUM> is arranged on top of the non-stitched fiber material <NUM>, for example.

In a step S6, the non-stitched fiber material <NUM> and, as the case may be, the web or core member is covered with a vacuum bag (not shown), then vacuum is applied to the space between the vacuum bag and the mold surface <NUM>. Then resin is injected into said space. In a further step, external heat is applied, and the resin is cured.

Claim 1:
A method for manufacturing a component (<NUM>) for a wind turbine (<NUM>), in particular a rotor blade (<NUM>), comprising the steps of
a) arranging (S1) a layup (<NUM>) of fiber material on top of a mold surface (<NUM>),
b) covering (S2) the layup (<NUM>) with a non-stitched fiber material (<NUM>) comprising a plurality of fibers (<NUM>) bonded together by an adhesive (<NUM>, <NUM>) to improve the air tightness of the non-stitched fiber material (<NUM>), wherein openings or cavities between adjacent fibers (<NUM>) are avoided, such that it is configured to produce a pressure drop sufficient to force a layup (<NUM>) of fiber material against a mold surface (<NUM>) when vacuum is applied to a space between the non-stitched fiber material (<NUM>) and the mold surface (<NUM>), wherein the adhesive takes the shape of at least one bead (<NUM>) bonding the fibers (<NUM>) together, the at least one bead (<NUM>) has a zigzag shape, and wherein the non-stitched fiber material (<NUM>) comprises fibers (<NUM>) being arranged parallel to each other, and
c) applying (S3) a vacuum to a space between the non-stitched fiber material (<NUM>) and the mold surface (<NUM>), the non-stitched fiber material (<NUM>) forcing the layup (<NUM>) of fiber material against the mold surface (<NUM>).