wind turbine blades

Abstract

In a first aspect of the present invention, a wind turbine blade is provided that includes a blade shell extending from a root end to a tip end in a spanwise direction and from a leading edge to a trailing edge in a chordwise direction. The blade shell includes a spar cap formed from a plurality of substantially planar strips of reinforcement material, the strips being arranged in a plurality of stacks that extend longitudinally in the spanwise direction and are arranged side by side in the chordwise direction. In each stack, an uppermost strip defines an upper surface of the stack, a lowermost strip defines a lower surface of the stack, and longitudinal edges of the stacked strips define side surfaces of the stack. The blade also includes a retaining clip that includes a plurality of side-by-side substantially U-shaped segments. The U-shaped segments each include a pair of spaced-apart sides defining a stack-receiving area therebetween, and the sides are joined by a bridging portion. At least some of the stacks are positioned in the stack-receiving area of ​​the retaining clip such that the sides of the U-shaped segments abut the side surfaces of the stacks. Each U-shaped segment of the retaining clip is inverted relative to its adjacent U-shaped segment such that the bridges of the respective U-shaped segments extend alternately across the upper and lower surfaces of the stack in a chordwise direction.

Description

Technical Field

[0001] The present invention relates generally to wind turbines, and more particularly to wind turbine blades and methods for manufacturing wind turbine blades. Background Art

[0002] Modern wind turbine blades typically include a shell that defines the blade's aerodynamic profile and one or more longitudinally extending spars that serve as the blade's primary load-bearing structure. The spars typically include a shear web connected between opposing spar caps, which are disposed on the windward and leeward sides of the blade, respectively. The spar caps are configured to absorb the bending loads experienced by the blade in use and, therefore, typically comprise a material with high tensile strength, such as carbon fiber reinforced plastic (CFRP). In some wind turbine blades, the spar caps are formed from a plurality of strips of reinforcement material arranged in a plurality of side-by-side stacks to allow the spar caps to conform to the chord curvature of the blade.

[0003] The aerodynamic profile of modern wind turbine blades often twists along the blade's length to most efficiently capture energy from the wind. Consequently, the molds constructed to form the blade shells typically include mold surfaces with varying inclinations along their length. However, the varying inclination of the mold surfaces introduces challenges when manufacturing blades with spar caps formed from stacked strips. Specifically, the stacked strips have a tendency to shift or slide across the steeply inclined sections of the mold due to gravity, and maintaining the strips in their intended position can be difficult.

[0004] It is against this background that the present invention has been developed. Summary of the Invention

[0005] In a first aspect of the present invention, a wind turbine blade is provided, comprising a blade shell extending from a root end to a tip end in a spanwise direction and from a leading edge to a trailing edge in a chordwise direction. The blade shell includes a spar cap formed from a plurality of substantially planar strips of reinforcement material arranged in a plurality of stacks extending longitudinally in the spanwise direction and arranged side by side in the chordwise direction. In each stack, the uppermost strip defines an upper surface of the stack, the lowermost strip defines a lower surface of the stack, and the longitudinal edges of the strips in the stack define side surfaces of the stack. The blade also includes a retaining clip comprising a plurality of side-by-side substantially U-shaped segments. Each U-shaped segment includes a pair of spaced-apart sides defining a stack-receiving area therebetween, and the sides are joined by a bridge. At least some of the stack are positioned in the stack-receiving area of ​​the retaining clip such that the sides of the U-shaped segments abut the side surfaces of the stack. Each U-shaped segment of the retaining clip is inverted relative to its adjacent U-shaped segment such that the bridges of the respective U-shaped segments extend alternately across the upper and lower surfaces of the stack in the chordwise direction.

[0006] During manufacture of the blades, the retaining clips maintain the position of the strips in their respective stacks and prevent the strips from sliding or otherwise moving relative to each other.

[0007] The inverted arrangement of adjacent U-shaped sections means that a U-shaped section of the retaining clip having a bridge extending across the upper surface of the stack will be immediately adjacent to at least one U-shaped section having a bridge extending across the lower surface of the stack. Similarly, a U-shaped section having a bridge extending across the lower surface of the stack will be immediately adjacent to at least one U-shaped section having a bridge extending across the upper surface of the stack. The retaining clip may resemble a square waveform.

[0008] The "uppermost" and "lowermost" bars of a stack are those at the spanwise location of the retaining clips. It will be appreciated that the number of bars in a stack may vary at different spanwise locations of the blade, for example the number of bars may decrease towards the ends of the stack such that the height of the spar cap tapers towards its ends.

[0009] The retaining clip may have a first U-shaped section at a first end and a second U-shaped section at a second end. These U-shaped sections are also referred to as "end-most" U-shaped sections. The retaining clip may have any number of intermediate U-shaped sections between the end-most sections. The total number of U-shaped sections preferably corresponds to the number of side-by-side stacks. In this case, each U-shaped section of the retaining clip can accommodate a single stack. In other examples, each U-shaped section can accommodate multiple stacks.

[0010] At least one U-shaped section of the retaining clip, preferably the end-most section, may include a return flange extending from a side of the U-shaped section. The return flange may extend substantially parallel to and spaced apart from a bridge portion of the U-shaped section. The stack may be positioned between the bridge portion and the return flange, such that the bridge portion extends across one of the upper or lower surfaces of the stack, and the return flange extends at least partially across the other of the upper or lower surfaces of the stack. During manufacture of the blade, the stack may be clamped between the return flange and the bridge portion.

[0011] The ends of the retaining clips may include locating flanges. The locating flanges may extend chord-wise below the blade shell component positioned adjacent the spar cap. The blade shell component is preferably a face sheet of core material. For example, the core material may include a material such as structural foam, polystyrene, or balsa wood.

[0012] The locating flange may extend from the side of the most terminal U-shaped section. The locating flange may be substantially coplanar with the return flange. The two flanges may extend from the side of the most terminal U-shaped section in opposite directions along the chord.

[0013] The side-by-side stacks may be spaced slightly apart in the chord-wise direction by the sides of the U-shaped sections of the retaining clips.

[0014] The wind turbine blade may include one or more pairs of retaining clips arranged side by side in the span direction. The U-shaped section of one retaining clip in each pair may be inverted relative to the U-shaped section of the other retaining clip in the pair.

[0015] Preferably, each stack is located within a U-shaped section of one retaining clip of the pair and a corresponding U-shaped section of the other retaining clip of the pair. Thus, the bridge portion of the U-shaped section of one retaining clip of the pair can extend across one of the upper or lower surfaces of the stack, while the bridge portion of the U-shaped section of the other retaining clip of the pair can extend across the other of the upper and lower surfaces of the stack.

[0016] The wind turbine blade may include a plurality of retaining clips or a plurality of pairs of retaining clips. The plurality of retaining clips or a plurality of pairs of retaining clips may be spaced apart from each other in the span direction.

[0017] One or more of the stacks may comprise a tapered end region.The or each retaining clip may be positioned externally of the tapered end region.

[0018] The shape of the chord cross-sectional profile of the stack receiving area of ​​the retaining clip preferably corresponds substantially to the chord cross-sectional profile of the stack.Preferably, the stack of the retaining clip and the chord cross-section of the stack receiving area are substantially rectangular.

[0019] The sides of the U-shaped sections can have a height substantially corresponding to the height of the stack. The stack comprises a plurality of planar strips of reinforcement material arranged in multiple layers. The stack can also include layers of material (such as glass or carbon fabric) interlaced between the planar strips. The height of the stack is the distance between the topmost layer of the stack and the bottommost layer of the stack.

[0020] The bridge of the U-shaped section may have a length substantially corresponding to the chord width of the stack.

[0021] The or each retaining clip may be formed from a fiber-reinforced polymer material. The or each retaining clip may be a pre-cured component. Thus, the retaining clip may comprise a resin that has been cured before the strips are positioned relative to the stack. The retaining clip may also be molded from a high-strength plastic.

[0022] In a second aspect of the present invention, a method for manufacturing a wind turbine blade is provided. The method includes providing a blade shell mold extending from a root end to a tip end in a spanwise direction and from a leading edge to a trailing edge in a chordwise direction, and providing a plurality of substantially planar strips of reinforcement material. The method also includes arranging the strips in a plurality of stacks in the mold to form at least a portion of a spar cap, the stacks extending in the spanwise direction and arranged side by side in the chordwise direction. In each stack, an uppermost strip defines an upper surface of the stack, a lowermost strip defines a lower surface of the stack, and longitudinal edges of the strips in the stack define side surfaces of the stack. The method also includes providing a retaining clip including a plurality of side-by-side substantially U-shaped segments. Each U-shaped segment includes a pair of spaced-apart sides defining a stack-receiving area therebetween, the sides being joined by a bridging portion. The method also includes arranging at least some of the stacks in the stack-receiving area of ​​the retaining clip such that the sides of the U-shaped segments abut the side surfaces of the stacks. Each U-shaped segment of the retaining clip is inverted relative to its adjacent U-shaped segment such that the bridges of the respective U-shaped segments extend alternately across the upper and lower surfaces of the stack in a chordwise direction.

[0023] In another aspect of the present invention, a retaining clip for a wind turbine blade spar cap is provided. The retaining clip is configured to retain strips of reinforcement material in a stacked configuration and to restrict movement of the plurality of stacks of strips relative to one another. The clip comprises a series of substantially U-shaped segments, each having a pair of spaced-apart sides joined by a bridge. Each U-shaped segment is inverted relative to its adjacent U-shaped segments.

[0024] Optional features described in relation to the first aspect of the invention are equally applicable to any other aspect of the invention and repetition of these features is avoided for reasons of clarity only. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0026] Figure 1 is a schematic exploded view of a wind turbine blade comprising a shell formed from two half-shells, each half-shell comprising a spar cap formed from a stack of reinforcement material strips;

[0027] Figure 2 is a cross-sectional view of a blade mould during the manufacture of the half-shells, illustrating the many difficulties caused by the use of strips of reinforcing material;

[0028] Figure 3a is a schematic perspective view of a retaining clip for maintaining the position of the strips and stack relative to each other during manufacture of the half-shells;

[0029] Figure 3bis a schematic cross-sectional view of a plurality of stacks of strips arranged in a U-shaped section of a retaining clip;

[0030] Figure 4 is a schematic perspective view of a spanwise portion of a spar cap with a stack of strips arranged with a pair of retaining clips; and

[0031] Figure 5a and Figure 5b is a schematic cross-sectional view of a retaining clip in another example. DETAILED DESCRIPTION

[0032] Figure 1 A schematic exploded view of a wind turbine blade 10 is shown. The blade 10 includes a first shell half 12a and a second shell half 12b, each of which extends from a root end 14 to a tip end 16 of the blade 10 in the spanwise direction (S) and extends between a leading edge 18 and a trailing edge 20 in the chordwise direction (C). The first shell half 12a and the second shell half 12b are joined together to form a blade shell 22. The blade shell 22 defines an aerodynamic profile and is configured to capture energy from wind incident on the blade 10. The blade shell 22 can be twisted along its spanwise length to most efficiently capture wind energy.

[0033] The blade 10 further includes longitudinally extending spar caps 24 to absorb bending loads experienced by the blade 10 in use. The half-shells 12 include spar caps 24 that may be embedded in the laminated layers of the half-shells 12 to form a so-called structural shell. The spar caps 24 are formed from a plurality of substantially planar strips of reinforcement material 26 arranged side by side in a stack 28 that extends longitudinally in the spanwise direction (S). The blade 10 may further include shear webs 30 that are bonded between the mutually opposed spar caps 24 of the first and second half-shells 12a, 12b to form a spar structure that provides structural support to the blade 10 in use.

[0034] As described above by way of background, the reinforcement strips 26 may comprise a relatively rigid material, such as carbon fiber reinforced plastic (CFRP). As such, due to the tensile properties of the reinforcement material, the strips 26 may comprise an inherent elastic restoring force, which provides the strips 26 with a degree of resistance to twisting along their longitudinal length. This may present a problem during manufacture of the blade 10, as will now be described with reference to the Figure 2 Descriptive.

[0035] Figure 2 A plurality of strips 26 of reinforcement material are shown arranged in a plurality of stacks 28 on a mould surface 32 of a blade shell mould 34 to form a spar cap 24. The longitudinal edges 36 of the strips 26 in the stacks 28 define side surfaces 38 of the stacks, and the uppermost strip 40 and the lowermost strip 42 in each stack 28 define an upper surface 44 and a lower surface 46 of the stack. Figure 2The chord cross-section of the stack 28 shown in FIG should be substantially rectangular. However, the strips 26 in the stack 28 are not constrained and can therefore move relative to each other in the mold 34.

[0036] To form a blade shell 22 that twists along its spanwise length, a mold 34 may include a mold surface 32 having a slope that varies between a root end of the mold 34 and a tip end of the mold 34. In some cases, the elasticity of the reinforcing material may constrain the twisting of the strips 26 such that the strips 26 do not conform to the variations in slope of the individual mold surfaces 32. The transition between the relatively flat outer portions of the mold surface 32 and the relatively steeply sloped surface 32 in the root portion may be particularly problematic.

[0037] The internal stresses created by twisting the strips 26 act to pull the strips 26 back to their flat, neutral state. As the strips 26 attempt to untwist themselves, these torsional stresses cause the first longitudinal edge 36a of each strip 26 to be pressed downwardly toward the mold surface 32, while the second longitudinal edge 36b of each strip 26 is lifted from the mold surface 32. Figure 2 As shown, this may result in a step being formed between adjacent stacks 28 where the upper surfaces 44 of adjacent stacks 28 are not flush, ie, not coplanar.

[0038] The steps between adjacent stacks 28 may cause wrinkling of material, such as a fiberglass mat, that is disposed on top of the stacks 28 in the mold 34. Such wrinkling may cause stress concentrations in the laminate structure of the shell 22 and also present an uneven surface for the shear web 30 to bond to, thereby reducing the strength of the connection between the web 30 and the half shell 12.

[0039] The portion of mold surface 32 configured to form the root portion of blade shell 22 having a substantially circular cross-sectional profile may be relatively steeply inclined. The steep inclination of mold surface 32 in this area may cause strips 26 in stack 28 to slide relative to one another. This undesirable sliding may result in a so-called "book effect," whereby stack 28 resembles a book with its spine standing upright. This may lead to misalignment of strips 26 and may also cause other shell components arranged adjacent to stack 28 to be incorrectly positioned in mold 34.

[0040] To overcome at least some of the above-mentioned difficulties involved in manufacturing the wind turbine blade 10 , the strips 26 may be held in place by retaining clips 48 , such as those shown in the remaining figures.

[0041] Now refer to Figure 3a and Figure 3b The retaining clip 48 according to an example of the present invention includes a plurality of substantially U-shaped sections 50 configured to receive the stack 28 of strips 26 forming the spar cap 24 . Figure 3a and Figure 3b The retaining clip 48 shown in FIG. 4 includes three side-by-side U-shaped sections 50. The U-shaped sections 50 are formed by spaced-apart sides 52 connected by bridges 54 extending transversely between the sides 52. Each U-shaped section 50 is inverted relative to one or more of its adjacent U-shaped sections. Thus, the bridges 54 of adjacent U-shaped sections 50 extend between opposite ends of the sides 52.

[0042] The first U-shaped section 50a defines a first end 56 of the retaining clip 48, and the second U-shaped section 50b defines a second end 58 of the retaining clip 48. The first U-shaped section 50a and the second U-shaped section 50b may therefore be referred to as endmost U-shaped sections. Figure 3a and Figure 3b The retaining clip 48 in the embodiment of the present invention further includes an intermediate U-shaped segment 50c between the endmost U-shaped segments 50a, 50b. The retaining clip 48 may include any number of intermediate U-shaped segments 50c between the endmost U-shaped segments 50a, 50b, including no intermediate U-shaped segment 50c. For example, Figure 5a and Figure 5b The retaining clip 48 shown in FIG includes a first U-shaped section 50 a and a second U-shaped section 50 b , but lacks an intermediate U-shaped section 50 c .

[0043] The U-shaped section 50 defines a stack receiving area 60 in which the stack 28 of strips 26 is arranged, as shown. Figure 3b Each stack receiving area 60 may be configured to receive a single stack 28 of strips 26. The shape of the stack receiving area 60 preferably corresponds to the cross-sectional profile of the stack 28 when viewed in chordal section, as shown in FIG. Figure 3b For example, where the stack 28 of strips 26 is substantially rectangular in cross-section, the cross-sectional shape of the corresponding stack-receiving area 60 in which the stack 28 is arranged is preferably also substantially rectangular.

[0044] The retaining clip 48 is configured to form a tight fit around the stack 28. As such, the sides 52 of the U-shaped section 50 preferably have a height that substantially corresponds to the height of a stack 28 disposed in a given receiving area 60. Similarly, the length of each bridge 54 preferably corresponds to the chord width of the stack 28 disposed in the corresponding receiving area 60. The bridges 54 fix the distance between the sides 52. Thus, substantially matching the length of the bridges 54 to the width of the stack 28 means that the stack 28 is clamped in the stack receiving area 60 between the sides 52 with an interference fit.

[0045] When the stack 28 is arranged in the receiving area 60 of the retaining clip 48, the side surfaces 38 of the stack 28 abut the sides 52 of the U-shaped sections 50. The sides 52 abutting the side surfaces 38 of the stack 28 prevent the strips 26 from sliding, thereby avoiding the previously described "book effect" and maintaining the position of the strips 26 relative to each other in the chord-wise direction (C).

[0046] The side-by-side stacks 28 are slightly spaced apart in the chord-wise direction (C) by the sides 52 of the U-shaped sections 50 of the retaining clips 48. In this manner, the retaining clips 48 ensure that gaps are maintained between adjacent stacks 28. During manufacture of the half shells 12, the gaps between the stacks 28 can help promote thorough injection of resin throughout the material disposed in the mold 34.

[0047] With the stack 28 disposed in the stack receiving area 60 of the retaining clip 48, the inverted orientation of adjacent U-shaped segments 50 relative to each other results in the bridges 54 of the U-shaped segments 50 extending alternately across the upper and lower surfaces 44, 46 of the stack 28 in the chordwise direction (C). Figure 3b As shown in FIG, the bridge portion 54 alternately extends across which surface 44, 46, meaning, for example, the bridge portion 54a of the first U-shaped segment 50a extends across the upper surface 44 of the stack 28, the bridge portion 54c of the adjacent middle U-shaped segment 50c extends across the lower surface 46 of the stack 28, and the bridge portion 54b of the adjacent second U-shaped segment 50b again extends across the upper surface 44 of the stack 28. When viewed in chord-wise cross-section, the retaining clip 48 can thus substantially resemble a square wave. The retaining clip 48 can be considered to be interwoven between the side-by-side stacks 28 in the chord direction (C).

[0048] The stack 28 arranged in the U-shaped section 50 having the bridge 54 extending across the lower surface 46 of the stack 28 applies downward pressure on the bridge 54 of the retaining clip 48. The retaining clip 48 uses this downward pressure to counteract the upward pressure caused by the previously described internal torsional stresses exerted by the adjacent stack 28 on the bridge 48 extending across the upper surface 44 of the stack. Thus, the alternating bridges 54 ensure that the strips 26 of the stack 28 cannot come loose because the bridges 54 abut against the upper surface 44 and press the stack 28 against the mold surface 32.

[0049] The retaining clip 48 may also include a return flange 62 to further secure the strips 26 in their respective stacks 28 and to secure the stacks 28 in position relative to the other stack(s) 28. The return flange 62 may extend in the chord-wise direction (C) from the side 52 of the U-shaped segment 50 (preferably the endmost U-shaped segment 50a, 50b) and at least partially across the upper surface 44 or lower surface 46 of the stack 28 disposed in the receiving area 60, as shown. Figure 3a As shown in Figure 3aand Figure 3b As shown, the retaining clip 48 may include two return flanges 62 , ie, each endmost U-shaped section 50 a , 50 b of the retaining clip 48 may include a return flange 62 extending from the respective side 52 .

[0050] The return flanges 62 extend from opposite ends of the respective side portions 52 to the ends from which the bridge portion 54 extends. Thus, the return flanges 62 are spaced apart from the bridge portion 54 of a given U-shaped segment 50. One or more of the return flanges 62 may be substantially parallel to the bridge portion 54 of a given U-shaped segment 50. Figure 3b , the bridge portions 54a, 54b of the first and second U-shaped segments 50a, 50b extend across the upper surface 44 of their respective stacks 28, and the return flange 62 thus extends partially across the lower surface 46 of the stack 28. The stack 28 of strips 26 located between the bridge portion 54 and the return flange 62 can be clamped between the flange 62 and the bridge portion 54 to restrict movement of the strips 26 in the stack 28 relative to each other. The return flange 62 further helps to secure the retaining clip 48 in position relative to the stack 28. By clamping around one or more of the endmost strips 26 in the stack 28, the retaining clip 48 is better equipped to withstand the spring forces in the strips 26 that act to spring the strips 26 apart in the stack 28.

[0051] The retaining clip 48 may also include a locating flange 64 extending from the side 52 of the endmost U-shaped section 50a, 50b in the chord-wise direction (C). Such a locating flange 64 may be configured to be arranged below a blade shell component 66 arranged adjacent to the stack 28 during manufacture of the blade shell 22, as will be described in greater detail later. The locating flange 64 extends in the chord-wise direction (C) in a direction opposite to the return flange 62 (i.e., away from the stack receiving area 60). Where the return flange 62 is configured to engage against the lower surface 46 of the stack 28, the locating flange 64 may be substantially coplanar with the return flange 62 so that the retaining clip 48 rests flush against the mold surface 32.

[0052] Still refer to Figure 3a and Figure 3b , the strips 26 may be arranged individually in the stack 28 and arranged with the retaining clips 48 in the mold 34 during manufacture of the blade shell 22. Alternatively, the strips 26 of reinforcement material may be arranged in the side-by-side stack 28 as a subassembly off-line (i.e., outside the blade shell mold 34) to reduce time in the mold during manufacture of the blade shell 22. Regardless of where the strips 26 are arranged, the process for arranging the strips 26 with the retaining clips 48 to form the spar cap 24 is the same.

[0053] The reinforcement strips 26 are arranged into a stack 28 that, when arranged in the mold 34, extends longitudinally in the spanwise direction (S). The stack 28 is arranged in a stack receiving area 60 of a retaining clip 48 configured with U-shaped sections 50 adjacent to each other in the chordwise direction (C). The stack 28 arranged in the U-shaped sections 50 is thus arranged side by side in the chordwise direction (C). In the case where the retaining clip 48 includes a return flange 62, the stack 28 is clamped in the receiving area 60 and held in place by the bridge 54 of the U-shaped section 50 and the return flange 62 engaging against the opposing surfaces 44, 46 of the stack 28.

[0054] Manufacturing the blade shell 22 may further include arranging other blade shell components 66, such as core material panels of structural foam, adjacent to the stack 28 in the mold 34. If the retaining clip 48 includes a locating flange 64 extending along the chord from the side 52 of the U-shaped section 50, the method may further include arranging the retaining clip 48 and / or the stack 28 in the mold 34 so that the locating flange 64 is positioned between the blade shell component 66 and the mold surface 32. For example, this may include sliding the retaining clip 48 and / or the stack 28 in the chord-wise direction (C) to arrange the locating flange 64 below the shell component 66. Alternatively, the retaining clip 48 and / or the stack 28 may be arranged in the mold 34 first, and then the shell component 66 may be arranged on top of the locating flange 64 and adjacent to the stack 28 in the mold 34.

[0055] The retaining clips 48 hold the position of each strip 26 in its respective stack 28 during manufacture of the blade shell 22. The sides 52 of the retaining clips 48 prevent the strips 26 from sliding or otherwise moving relative to each other, and the bridges 54 extending over the upper surface 44 of the stack 28 prevent the strips 26 from loosening or pulling away from the mold surface 32. Thus, the retaining clips 48 ensure that the reinforcement material strips 26 are accurately aligned in the blade shell mold 34 and that other blade shell components 66 arranged adjacent the stack 28 are accurately positioned.

[0056] The blade material arranged in the mold 34 can be injected with resin to form the half-shell 12. In another example, the blade material can include pre-impregnated fibers. The retaining clip 48 holds the strips 26 in the stack 28 throughout the manufacture of the blade 10 and remains embedded in the blade shell 22 even after manufacture of the blade 10 is complete, for example, after the resin has cured. The retaining clip 48 preferably has a span width that is very small compared to the overall length of the spar cap 24. Therefore, including the clip 48 in the laminated structure of the half-shell 12 does not adversely affect the load-bearing capacity of the spar cap 24. Furthermore, the retaining clip 48 is preferably lightweight so as not to excessively increase the mass of the blade 10. The retaining clip 48 preferably has as little thickness as possible (such as 1 mm thick or less) to avoid deviation relative to the fabric layers subsequently placed on the clip.

[0057] Figure 4 A pair of retaining clips 48 are shown, arranged with the stack 28 of spar caps 24. The retaining clips 48 are arranged side by side in the spanwise direction (S), and the stack 28 of strips 26 is arranged in U-shaped sections 50 of the two retaining clips 48. The retaining clips 48 can be arranged so that the U-shaped section 50 of the first clip 48a of the pair is inverted relative to the corresponding U-shaped section 50 of the second retaining clip 48b of the pair. The retaining clips 48a and 48b can be constructed in a substantially identical manner, with each clip 48 simply being inverted in orientation relative to the other. The upper surface 44 of each stack 28 engages the bridge portion 54 of the retaining clip 48, ensuring that each stack 28 is pressed down onto the mold surface 32.

[0058] The bridge portion 54 of the first retaining clip 48a or the second retaining clip 48b extends across each of the upper surface 44 and the lower surface 46 of the stack 28. Figure 4 As shown, the bridge portion 54a of the first retaining clip 48a extends across the upper surface 44 of the first stack 28, and the bridge portion (not shown) of the second retaining clip 48b extends across the lower surface 46 of the stack 28. A pair of retaining clips 48 arranged in this manner effectively serves to lock the strips 26 in place in each stack 28 by clamping the stack 28 between the respective bridge portions 54 of the clips 48. Where both the first retaining clip 48a and the second retaining clip 48b include locating flanges 64, the locating flanges 64 may extend over and under a portion of an adjacent blade shell component 66, thereby also locking the adjacent blade shell component in place.

[0059] The wind turbine blade 10 may include a plurality of retaining clips 48 arranged along the spanwise length of the spar cap 24. Similarly, the blade 10 may include a plurality of pairs of retaining clips 48 arranged along the length of the spar cap 24. The retaining clips 48 or pairs of clips 48 may be spaced apart from one another in the spanwise direction (S) of the blade 10. For example, the clips 48 or pairs of clips 48 may be spaced apart at intervals of between 3 m and 5 m along the length of the spar cap 24. Spacing the clips 48 or pairs of clips 48 apart in the spanwise direction (S) minimizes any adverse effects of the bridges 54, including the clips 48, in the glueline between the shear web 30 and the spar cap 24.

[0060] Preferably, retaining clips 48 are arranged along the spar caps 24 in the spanwise region where the inclination of the mold surface 32 changes, thereby introducing twist into the reinforcement material strips 26. As described above, the retaining clips 48 abut against the upper surface 44 of the stack 28 to ensure that the strips 26 and stack 28 are held in place despite the changing inclination of the mold surface 32.

[0061] The spar cap 24 in some wind turbine blades 10 may include one or more stacks 28 having a tapered end region 68 (e.g., a tapered end region 68) at the tip or root end of the spar cap 24. Figure 1 ). The tapered end region 68 of the stack 28 may be formed by varying the number of strips 26 stacked one above the other in different spanwise regions along the spar cap 24. For example, the number of strips 26 in the stack 28 may decrease near the root end and / or near the tip end of the stack 28, such that the height of the spar cap 24 tapers toward the root end and / or the tip end thereof. The tapered end region 68 may be configured to transfer loads from the spar cap 24 to the blade shell laminate at the root and tip ends of the blade 10.

[0062] Where the blade 10 includes a stack 28 having one or more tapered end regions 68, the one or more retaining clips 48 are preferably positioned outside the tapered end regions 68 to avoid interfering with shear load transfer from the spar cap 24 to the shell laminate. For example, the strips 26 may be formed from a blade shell laminate of carbon fiber and glass fiber, and by placing the clips 48 outside the tapered region, they will not interfere with shear load transfer from the carbon to the glass.

[0063] supply Figure 5a and Figure 5b This is merely to illustrate other examples of the retaining clip 48 according to the present invention. For example, as described above, the retaining clip 48 may include a first U-shaped section 50a and a second U-shaped section 50b without an intermediate section 50c therebetween. Figure 5a and Figure 5b shown. Figure 5a A retaining clip 48 is shown comprising inverted U-shaped sections 50a, 50b, and Figure 5b The retaining clip 48 is shown additionally including the return flange 62 as previously described. It should be understood that the description previously provided with respect to features such as the inverted adjacent U-shaped sections 50, their sides 52 and bridges 54, and the return flange 62 and locating flange 64 also applies to the Figure 5a and Figure 5b Therefore, for the sake of brevity, further description of these features will not be repeated here.

[0064] The retaining clip 48 described with reference to any of the accompanying figures can be formed from any suitable material. Preferably, the retaining clip 48 can be formed from a fiber-reinforced composite material, such as glass fiber reinforced plastic (GFRP). For example, the retaining clip 48 can be formed from one or more layers of biaxial fiberglass laminated with a polymer resin. The resin is preferably cured, i.e., solidified, before the stack 28 of strips 26 and the retaining clip 48 are arranged together. Thus, the retaining clip 48 can be a pre-cured component, i.e., cured before being arranged in the mold 34. The material of the retaining clip 48 preferably has a high tensile strength to resist the elastic forces exerted by the twisted reinforcement strips 26.

[0065] Preferably, the surface of the retaining clip 48 is activated (such as via abrasion or removal of a release layer) so that the clip properly adheres to the surrounding blade material during manufacture of the blade 10 .

[0066] The retaining clip 48 may be configured such that a plurality of stacks 28 may be arranged in a single receiving area 60 defined by the U-shaped section 50 of the clip 48. Alternatively or additionally, the retaining clip 48 may be configured to retain the strips 26 in only some of the stacks 28 that form the spar cap 24. For example, the spar cap 24 may have three side-by-side stacks 28, and the retaining clip 48 as described herein may have only two side-by-side U-shaped sections 50 that are each configured to receive a single stack 28. Thus, the present invention is not limited to matching the number of U-shaped sections 50 to the number of side-by-side stacks 28 that form the spar cap 24 of the wind turbine blade 10.

[0067] It should be understood that terms such as "engage," "abut," and "abut" include direct and indirect "engagement," "abutment," and "abutment." That is, these terms are intended to encompass examples in which one or more intermediate components (such as spacers) may be disposed between the engaged abutting surfaces.

[0068] Many modifications may be made to the examples described above without departing from the scope of the invention as defined in the appended claims. It will be appreciated that the features described with respect to each of the examples above may be easily combined with the features described with reference to the other examples without departing from the scope of the invention as defined in the appended claims.

Claims

1. A wind turbine blade (10), comprising: a blade shell (12) extending in the spanwise direction from a root end (14) to a tip end (16) and in the chordwise direction from a leading edge (18) to a trailing edge (20), the blade shell comprising a spar cap (24) formed from a plurality of substantially planar strips (26) of reinforcement material, the strips being arranged in a plurality of stacks (28) extending longitudinally in the spanwise direction and arranged side by side in the chordwise direction, whereby an uppermost strip (40) in each stack defines an upper surface of the stack, a lowermost strip (42) defines a lower surface of the stack, and longitudinal edges (36) of the stacked strips define side surfaces (38) of the stack; a retaining clip (48) comprising a plurality of side-by-side substantially U-shaped sections (50), each of the U-shaped sections including a pair of mutually spaced sides (52) defining a stack receiving area (60) therebetween, the sides (52) being joined by a bridge (54); wherein at least some of the stack (28) are located in the stack receiving area (60) of the retaining clip (48) such that the side portions of the U-shaped segments (50) abut the side surfaces (38) of the stack, and each U-shaped segment of the retaining clip is inverted relative to an adjacent U-shaped segment thereof such that the bridging portions (54) of the respective U-shaped segments extend alternately across the upper and lower surfaces of the stack in the chordwise direction.

2. The wind turbine blade according to claim 1, wherein: At least one U-shaped section of the retaining clip includes a return flange extending from the side of the U-shaped section substantially parallel to and spaced apart from the bridging portion of the U-shaped section, wherein a stack is located between the bridging portion and the return flange such that the bridging portion extends across one of the upper surface or the lower surface of a stack and the return flange extends at least partially across the other of the upper surface or the lower surface of the stack.

3. The wind turbine blade according to claim 1 or 2, wherein: An end portion of the retaining clip includes a locating flange, and the locating flange extends in the chord-wise direction below a blade shell component positioned adjacent to the spar cap.

4. The wind turbine blade according to claim 3, wherein: The locating flange extends from a side of the endmost U-shaped section.

5. The wind turbine blade according to claim 2, wherein: The end of the retaining clip includes a locating flange, and the locating flange extends in the chord direction below the blade shell member located adjacent to the spar cap, the locating flange extends from a side of the endmost U-shaped section, the locating flange is substantially coplanar with the return flange, and the two flanges extend from the side of the endmost U-shaped section in opposite directions along the chord.

6. The wind turbine blade according to claim 1 or 2, wherein: The side-by-side stacks are spaced apart in the chord-wise direction by the sides of the U-shaped section of the retaining clip.

7. The wind turbine blade according to claim 1 or 2, comprising one or more pairs of retaining clips arranged side by side in the span direction, wherein: The U-shaped section of one of the retaining clips in each pair is inverted relative to the U-shaped section of the other retaining clip in the pair. 8 . The wind turbine blade according to claim 1 , comprising a plurality of retaining clips or a plurality of pairs of retaining clips spaced apart from each other in the span direction.

9. The wind turbine blade according to claim 1 or 2, wherein: One or more of the stacks include a tapered end region, and the retaining clip is positioned exterior to the tapered end region.

10. The wind turbine blade according to claim 1 or 2, wherein: The shape of the chord-sectional profile of the stack receiving area of ​​the retaining clip substantially corresponds to the shape of the chord-sectional profile of the stack.

11. The wind turbine blade according to claim 1 or 2, wherein: The sides of the U-shaped section have a height substantially corresponding to a height of the stack, and the bridge of the U-shaped section has a length substantially corresponding to a chord width of the stack.

12. The wind turbine blade according to claim 1 or 2, wherein: The retention clip is formed from a fiber reinforced polymer material.

13. The wind turbine blade according to claim 1 or 2, wherein: The retaining clip is a pre-cured component.

14. The wind turbine blade of claim 2, wherein: The end-most section of the retaining clip includes the return flange.

15. A method of manufacturing a wind turbine blade (10), the method comprising: Providing a blade shell mold (34), wherein the blade shell mold (34) extends from the root end to the tip end in the span direction and extends from the leading edge to the trailing edge in the chord direction; providing a plurality of substantially planar reinforcing material strips (26); arranging the strips in a plurality of stacks (28) in the mold (34) to form at least a portion of a spar cap (24), the stacks extending in the spanwise direction and arranged side by side in the chordwise direction, whereby an uppermost strip (40) in each stack defines an upper surface of the stack, a lowermost strip (42) defines a lower surface of the stack, and longitudinal edges (36) of the stacked strips define side surfaces (38) of the stack; providing a retaining clip (48) comprising a plurality of side-by-side substantially U-shaped sections (50), each of the U-shaped sections including a pair of mutually spaced side portions (52) defining a stack receiving area (60) therebetween, the side portions (52) being joined by a bridge portion (54); as well as arranging at least some of the stack (28) in the stack receiving area (60) of the retaining clip (48) such that the sides of the U-shaped section abut the side surfaces of the stack, wherein each U-shaped segment (50) of the retaining clip (48) is inverted relative to its adjacent U-shaped segment such that the bridge portion (54) of the corresponding U-shaped segment extends alternately across the upper surface and the lower surface of the stack in the chordwise direction.

16. A retaining clip for a wind turbine blade spar cap, the retaining clip being configured to retain strips of reinforcement material in a stacked configuration and to restrict movement of multiple stacks of strips relative to each other, the clip comprising a series of substantially U-shaped sections, each of the U-shaped sections having a pair of mutually spaced sides joined by a bridge, whereby each U-shaped section is inverted relative to its adjacent U-shaped section.

Images