Wind turbine blades

Abstract

A method of making a wind turbine blade in a blade mould is described. The wind turbine blade comprises a plurality of elongate reinforcing structures each comprising a stack of strips of fibre-reinforced polymeric material, and the method comprises: stacking strips of fibre-reinforced polymeric material to form a plurality of stacks (40), each defining a longitudinal axis; aligning the stacks relative to one another in an alignment zone outside the blade mould; supporting the stacks to maintain their relative alignment; transferring the plurality of stacks into the blade mould simultaneously while maintaining the relative alignment of stacks as the stacks are transferred; and integrating the stacks with other blade materials forming the blade in the blade mould. An apparatus for use in the method is also described.

Claims

1. A method of making a wind turbine blade in a blade mould, the wind turbine blade comprising a plurality of elongate reinforcing structures each comprising a stack of strips of fibre-reinforced polymeric material, and the method comprising: stacking strips of fibre-reinforced polymeric material to form a plurality of stacks, each defining a longitudinal axis; aligning the plurality of stacks relative to one another in an alignment zone outside the blade mould; supporting the plurality of stacks to maintain their relative alignment; transferring the plurality of stacks into the blade mould simultaneously while maintaining the relative alignment of the plurality of stacks as the plurality of stacks are transferred; and integrating the plurality of stacks with other blade materials forming the blade in the blade mould, wherein transferring the plurality of stacks further comprises lifting the plurality of stacks from the alignment zone and lowering the plurality of stacks into the blade mould, and wherein the method further comprises supporting the plurality of stacks during the lifting process by means of a plurality of strops arranged at intervals along the length of the plurality of stacks.

2. The method of claim 1, wherein the relative alignment of the plurality of stacks in the alignment zone corresponds to the required alignment of the plurality of stacks in the finished blade.

3. The method of claim 1, further comprising positioning the plurality of stacks in the alignment zone such that the stacks of the plurality of stacks are spaced apart from one another by a predetermined separation distance and the method further comprising maintaining the predetermined separation distance between the stacks of the plurality of stacks as the plurality of stacks are transferred into the mould.

4. The method of claim 3, wherein the predetermined separation distance corresponds to the required separation between the plurality of stacks in the finished blade.

5. The method of claim 1, comprising coupling a support structure to each stack of the plurality of stacks in the alignment zone, the support structure being configured to maintain the relative alignment of the plurality of stacks as the plurality of stacks are transferred into the mould.

6. The method of claim 5, comprising coupling the support structure to respective end regions of each stack of the plurality of stacks.

7. The method of claim 5, comprising clamping the support structure to each stack of the plurality of stacks.

8. The method of claim 5, comprising decoupling the support structure from each stack of the plurality of stacks after the plurality of stacks have been transferred to the mould.

9. A method of making a wind turbine blade in a blade mould, the wind turbine blade comprising a plurality of elongate reinforcing structures each comprising a stack of strips of fibre-reinforced polymeric material, and the method comprising: stacking strips of fibre-reinforced polymeric material to form a plurality of stacks, each defining a longitudinal axis; aligning the plurality of stacks relative to one another in an alignment zone outside the blade mould; supporting the plurality of stacks to maintain their relative alignment; transferring the plurality of stacks into the blade mould simultaneously while maintaining the relative alignment of the plurality of stacks as the plurality of stacks are transferred; and integrating the plurality of stacks with other blade materials forming the blade in the blade mould, wherein transferring the plurality of stacks further comprises lifting the plurality of stacks from the alignment zone and lowering the plurality of stacks into the blade mould, and wherein the method further comprises primarily supporting the plurality of stacks at their respective end regions so that when the plurality of stacks are lifted, the plurality of stacks droop such that a central portion of each stack is below the end regions of the respective stack, and lowering the plurality of stacks into the blade mould such that the central region of each stack makes contact with the blade mould before the end regions of the respective stack.

10. The method of claim 1, comprising integrating the plurality of stacks with other blade materials in the blade mould by means of a resin infusion process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a to 1c have already been described above by way of background to the invention. In order that embodiments of the invention might be more readily understood, reference will now be made, by way of example only, to the accompanying drawings, in which:

(2) FIG. 2 is a schematic plan view of apparatus for making a wind turbine blade;

(3) FIG. 3 is a perspective view of a support structure forming part of the apparatus of FIG. 2 in use in supporting two stacks of strips;

(4) FIG. 4 is an end view of the support structure of FIG. 3;

(5) FIG. 5 is a side perspective view of an end region of the support structure of FIG. 3;

(6) FIG. 6a is a cross-sectional view of a clamping bracket forming part of the support structure of FIG. 3;

(7) FIG. 6b is a cross-sectional view of a strap in use in securing a stack of strips

(8) FIGS. 7 to 11, 12a and 13a are perspective views of the apparatus of FIGS. 3 to 6 at different stages in use in the process of making a wind turbine blade;

(9) FIGS. 12b and 13b are end views of FIGS. 12a and 13a respectively;

(10) FIGS. 14a to 14d are side views of another support structure in use in making a wind turbine blade; and

(11) FIG. 14e is a perspective view of a strop forming part of the support structure of FIGS. 14a to 14d.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(12) FIG. 2 illustrates an apparatus 50 according to the present invention used in the manufacture of wind turbine blades 10 of the type described above by way of introduction to the present invention. More specifically, the apparatus 50 is used for making wind turbine blades comprising spar caps that extend along a longitudinal axis L, and that comprise a plurality of strips 18 of fibre reinforced polymeric material arranged one on top of another in a stack.

(13) Referring to FIG. 2, the apparatus 50 comprises an alignment zone, generally indicated at 60, which is defined on the factory floor adjacent a wind turbine blade mould 20.

(14) Pultruded strips 18 made from carbon-fibre reinforced plastic (CFRP) are fed to the alignment zone 60 from a down-stream strip manufacturing station or strip feed station (not shown) in a feed direction F. At the alignment zone 60, the strips 18 are stacked up to form two stacks 40 that will later form spar caps 15a, 15b, 16a, 16b. The stacks 40 are arranged side-by-side and are aligned relative to one another in the configuration that they will adopt in the finished wind turbine blade 10. Once aligned, the stacks 40 are supported in that configuration by a support structure 70. The stacks 60 are lifted using the support structure 70 from the alignment zone 60 and transferred to a blade mould 20 in a transfer direction 200, and then lowered onto a surface 21 of the mould 20. During the transfer, the support structure 70 maintains the configuration of the stacks 40, such that no, or relatively little, further alignment is required once the stacks 40 have been lowered into the mould 20.

(15) The support structure 70 will now be described in further detail, with reference to FIGS. 3 to 5 and FIGS. 6a and 6b.

(16) As best seen in FIG. 3, the support structure 70 comprises a longitudinal beam 72 that extends parallel to the longitudinal axis L of each stack 40. The beam 72 is suspended from a lifting means such as a crane (not shown) by a pair of cables 74 attached to the respective ends 76 of the beam 72.

(17) First and second transverse beams 78 are suspended respectively from the respective ends 76 of the longitudinal beam 72. Each transverse beam 78 is suspended by a respective pair of cables 80. As best seen in FIG. 4, and considering one of the transverse beams 78, a lower end of each cable 80 in a pair is fixed to a fixing point 84 at a respective end 77 of the transverse beam 78 whilst an upper end of each cable 80 in the pair is connected to a common fixing point 82 at the end 76 of the longitudinal beam 72. The suspension arrangement of the other transverse beam 78 at the other end of the longitudinal beam 72 is substantially identical.

(18) FIG. 5 illustrates the relative positions of the fixing points 82, 84 at one end of the support structure 70. The arrangement at the other end of the support structure 70 is a mirror image of this arrangement. FIG. 5 reveals that the common fixing points 82 on the longitudinal beam 72 are not located directly above the corresponding fixing points 84 on the transverse beams 78. Instead, the longitudinal distance between the respective common fixing points 82 is greater than the longitudinal distance between the respective transverse beams 78, such that the cables 80 extend inwardly (in the longitudinal direction) from the longitudinal beam 74 to the transverse beam 78. This suspension arrangement serves to minimise the movement of the stacks 40 in the longitudinal direction during transfer by reducing the ability of the transverse beams 78 to swing back and forth on the cables 80.

(19) Referring again to FIG. 4, first and second brackets 86, which in this example are in the form of clamps, are attached respectively to the ends 77 of the transverse beams 78. Each clamp 86 is suspended directly beneath a respective end 77 of the transverse beam 78 by a respective clamp cable 88. The clamps 86 are the primary load-bearing elements of the support structure 70, and bear the load of the stacks 40 during lifting. Referring to FIG. 6a, each clamp 86 comprises upper and lower plates 90, 92 joined at one edge by a sidewall 94, to form a structure that is C-shaped in cross-section. The plates 90, 92 and side wall 94 embrace the stack 40 from one side, and the plates 90, 92 are held together on the other side of the stack 40 by a bolt 96 or other suitable fixing means. The clamps 86 ensure that the strips in the stacks are held firmly together and prevent the strips sliding or otherwise moving relative to one another. The upper plate 90 is provided with a hook 98 or other attachment means, for easy attachment to the cables 88.

(20) A method of making a wind turbine blade using the support structure 70 will now be described, with particular reference to FIGS. 7 to 11, 12a and 12b and 13a and 13b.

(21) A plurality of strips 18 are stacked one on top of another to form two separate stacks 40. The stacks 40 are strapped together using plastic straps 41. A detailed view of the strapping arrangement is shown in FIG. 6b. A block made from wood or another suitable material that has the same width as the stack 40 is placed on top of the stack 40. The strap 41 is wrapped around the stack 40 and the block 43. Edges of the strap 41 overlap one another and are bonded to one another by an adhesive, so as to secure the strap in place. Straps 41 are fitted to the stack 40 at regular intervals along the stack 40, so as to maintain the strips 18 in the correct position in the stack 40.

(22) Referring to FIG. 7, once the straps have been fitted to each stack 40, the stacks 40 are arranged side-by-side in an alignment zone 60 defined on the factory floor adjacent a wind turbine blade mould 20. As will be described in further detail below, the stacks 40 are aligned relative to one another in the alignment zone 60 in a configuration that matches the eventual configuration of the spar caps 15a, 15b, 16a, 16b in the finished blade 10.

(23) In the alignment zone 60, the stacks 40 are positioned relative to one another so that their relative orientations correspond almost exactly to their relative orientations in the wind turbine blade mould 20. In this example, the relevant alignment parameters include:

(24) (i) the transverse separation between respective stacks 40, as indicated by reference s on FIG. 7; (ii) the relative orientation of the respective longitudinal axes L of the respective stacks 40in FIG. 7 the respective longitudinal axes L are parallel to one another; and (iii) the relative positions of the stacks 40 in the longitudinal directionin FIG. 7 the stacks 40 are arranged such that the corresponding ends of the respective stacks 40 are aligned in the longitudinal direction; in other examples the corresponding ends of the respective stacks 40 could be offset in the longitudinal direction.

(25) Thus, the required stack configuration is a pre-determined combination of the transverse spacing distance s between the stacks 40, the relative orientations of the longitudinal axes L of the stacks 40, and the relative position of the stacks 40 along the longitudinal axes L.

(26) The stacks 40 are then supported in this configuration by the support structure 70 as will now be described.

(27) To couple the stacks 40 to the support structure 70, the clamps 86 are firstly clamped around each end of a respective stack 60, as shown in FIG. 8. Referring also again to FIG. 6a, the upper and lower plates 90, 92 and the sidewall 94 of the clamp 86 are fitted around the stack 40, and the plates 90, 92 are clamped together by the bolt 96. Next, as shown in FIG. 9, the longitudinal beam 72, transverse beams 78 and cables 74, 80, 88 are lowered into place above the stacks 40 as indicated by the arrow 300. The clamp cables 88 are attached to the respective clamps 86 by means of the hook 98 (FIG. 6a), and the stacks 40 are then ready for transfer to the mould 20.

(28) To transfer the stacks 40 to the mould 20, as shown in FIG. 10, the support structure 70 is lifted up by the crane (not shown) in a lifting direction 400, and moved laterally towards the blade mould 20 in a transfer direction 200, until the stacks 40 are generally above their required position in the blade mould 20 (see FIG. 11).

(29) Referring to FIG. 11, the support structure 70 is then lowered towards the mould surface 21 as represented by the arrow 300, until the stacks 40 are arranged in the mould 20, as shown in FIG. 12a.

(30) As best seen in FIG. 12b, the support structure 70 and the attached stacks 40 are lowered into the blade mould 20 such that the stacks 40 are located each side of a foam panel region 24. The foam panel regions 24 eventually form sandwich panel cores in the blade shell structure.

(31) FIG. 12b also illustrates that a positioning block 25 is arranged over the foam panel region 24. In practice a plurality of positioning blocks are spaced at intervals along the length of the foam panel region 24. The positioning blocks 25 are removable wooden blocks in the shape of a trapezium, which each have a width slightly greater than the width of the foam panel 24 and inclined side walls. The positioning blocks 25 shield the foam panel 24 from the stacks 40 as they are lowered into the mould 20 so as to avoid damage to the foam panel region 24. The inclined sidewalls of the blocks 25 serve to guide the stacks 40 to the sides of the foam panel 24 as the stacks 40 are lowered into place.

(32) During the transfer process, the support structure 70 maintains the relative alignment of the stacks 40 that was defined in the alignment zone 60 outside the blade mould 20. The transverse beams 78 maintain the spacing distance s between the stacks 40 and maintain the relative orientation of the respective longitudinal axes L of the stacks 40. The longitudinal beam 72 maintains the position of the stacks 40 relative to one another along the longitudinal axis. In this way, as the stacks 40 are transferred to the blade mould 20, the relative positions and orientations of the stacks 40 remain fixed. The stacks 40 are therefore pre-aligned before being transferred into the mould 20 so that little, if any, further alignment of the stacks 40 is required once the stacks 40 have been placed in the mould 20.

(33) Referring to FIG. 13a, once the stacks 40 have been positioned in the mould 20, the clamps 86 are detached from the clamp cables 88, and the remainder of the support structure 70 is lifted upwards in the lifting direction 400 and moved away from the blade mould 20, to be stored for use in supporting and transferring further stacks 40. The clamps 86 are then removed from the stacks 40. As best seen in FIG. 13b, once the clamps 86 have been removed, the stacks 40 are in place in the blade mould 20 on each side of the foam panel regions 24 in the required configuration and ready for integration into the blade 10.

(34) Next, other components of the blade 10 are added to the blade mould 20 as required. The components are infused with resin using the resin-infusion process described above, and the resin is cured. Once cured, the stacks 40 form the spar caps 15a, 15b, 15c, 15d of the blade 10.

(35) In one embodiment of the invention, illustrated in FIGS. 14a to 14e, the stacks 40 are allowed to droop at their centres 42 during the lifting process, such that a longitudinal curvature is developed in the stacks 40 as shown in the figures. In this case, as illustrated in FIG. 14e, strops 99 are attached along the length of the stack 40 and are attached to the longitudinal beam 72 by strop cables 100. The strops 99 are spaced at intervals along the length of the stacks 40. The strop cables 100 are of varying length to accommodate the droop developed in the stacks 40, and hence the strop cables 100 are longer near the centre 42 of the stacks 40 than near the ends 46 of the stacks 40. The strops 99 do not act as load-bearing components, since this function is carried out by the clamps 86 and clamp cables 88, but instead the strops 99 merely act to control the droop of the stacks 40.

(36) As the stacks 40 are lowered into the mould 20 (FIG. 14a), the drooping central portion 42 of each stack 40 makes contact with the mould surface 21 first (FIG. 14b). As lowering continues, leading points of contact 44 between the stacks 40 and the mould surface 21 move outwardly towards the ends 46 of the stacks 40, as shown in FIG. 14c. Eventually, the stack 40 is lowered such that the entire stack 40, including the ends 46, are in contact with the mould surface 21, as shown in FIG. 14d.

(37) This method of lowering the stacks 40 into the mould 20 is particularly advantageous because the ends 46 of the stacks 40 are particularly susceptible to damage during handling, and lowering the stacks 40 such that the central region 42 makes contact with the mould surface 21 first reduces impact forces on the ends 46 of the stacks 40, and hence reduces the risk of damage to the ends 46.

(38) Although in the embodiments described above two stacks of strips are aligned and transferred into the mould, any number of stacks may be transferred simultaneously. In particular, three, four, five or six stacks may be transferred.

(39) In some embodiments, a single spar cap may be formed from more than one stack of strips. In this case, the stacks that form the spar cap are arranged side-by-side, and are strapped together by a single strap. This arrangement is useful for creating wider spar caps. A single wooden block may be used in the strapping arrangement, which has a width equal to the total width of the stacks that form the spar cap.

(40) In the embodiments described above, plastic straps are described for holding the stacks in place whilst the stacks are lifted and positioned in the mould. The plastic straps are removed once the stacks have been arranged in place and before the stacks are infused with resin. However, in other embodiments on the invention infusible straps may be employed to hold the stacks together, for example straps made from glass-fibre material. In such cases, the infusible straps can remain in place when the stacks are infused such that the straps are also infused together with the stacks. The straps thereby become an integral component of the elongate reinforcing structure.

(41) The required stack configuration may be any suitable configuration. It need not necessarily be the final configuration that the stacks will adopt when integrated into the blade. For example, the required configuration may be a configuration that can be easily re-adjusted to give the final configuration of the stacks in the blade mould.

(42) The support mechanism need not be fixed to the stacks by clamps, but may be fixed to the stacks using any suitable means.

(43) The present invention is therefore not limited to the exemplary embodiments described above and many other variations or modifications will be apparent to the skilled person without departing from the scope of the present invention as defined in the following claims.