METHOD OF MASKING A MOULD FOR MOULDING A WIND TURBINE BLADE SHELL PART

Abstract

A method of masking a mould for moulding a wind turbine blade shell part, the method comprising the steps of: arranging a masking device in a mould so that the masking device covers the non-coating zone of the mould surface, spraying a coating onto a mould surface of the mould so that the coating is applied to a coating zone of the mould surface and prevented from being applied to a non-coating zone of the mould surface by the arrangement of the masking device, and removing the masking device from the mould so that the non-coating zone is exposed. The masking device is configured so that, upon terminating spraying of the coating at the first longitudinal boundary of the coating zone, a lip portion of the masking device is separated from the coating applied on the coating zone by a gap.

Claims

1-15. (canceled)

16. A method of masking a mold for molding a shell part for a wind turbine blade, the wind turbine comprising an aerodynamic shell body with a suction side shell part and a pressure side shell part that extends in a longitudinal direction between a root and a tip and in a transverse direction between a leading edge and a trailing edge, the method comprising: providing for molding a shell part, the mold comprising a mold surface having a longitudinal mold edge, a coating zone, and a non-coating zone, wherein the coating zone has a first longitudinal boundary arranged towards the non-coating zone, and wherein the non-coating zone extends longitudinally from the longitudinal mold edge to a second boundary towards the coating zone, and a masking device comprising a lip portion including a longitudinal masking edge; arranging the masking device in the mold so that the masking device covers the non-coating zone of the mold surface and so that the longitudinal masking edge of the masking device delimits the first longitudinal boundary of the coating zone; spraying a coating onto the mold surface so that the coating is applied to the coating zone, wherein the coating is prevented from being applied to the non-coating zone by an arrangement of the masking device; and removing the masking device from the mold so that the non-coating zone is exposed, wherein the masking device is configured so that, upon terminating spraying of the coating at the first longitudinal boundary of the coating zone, the lip portion of the masking device is separated from the coating applied on the first longitudinal boundary of the coating zone by a gap.

17. The method of claim 16, wherein the mold surface comprises a transition zone extending longitudinally from the first longitudinal boundary of the coating zone to the second boundary of non-coating zone.

18. The method of claim 17, wherein the lip portion is arranged so that during spraying of the coating at the first longitudinal boundary, the coating is partially applied through the gap to the transition zone beneath the lip portion of the masking device, wherein coverage or thickness of the coating applied to the transition zone gradually decreases from the first longitudinal boundary of the coating zone to the second boundary of the non-coating zone.

19. The method of claim 16, further comprising biasing the masking device to urge the lip portion away from the mold surface so that, upon terminating spraying of the coating at the first longitudinal boundary of the coating zone, the lip portion returns to a position in which the lip portion of the masking device is separated from the coating applied on the first longitudinal boundary of the coating zone by the gap.

20. The method of claim 16, wherein the lip portion has a resting position in which the lip portion extends non-parallel to and is angled away from the mold surface.

21. The method of claim 16, wherein the masking device comprises a body portion and a separation element arranged between the body portion and the lip portion of the masking device and at a distance to the longitudinal masking edge.

22. The method of claim 21, wherein arranging the masking device in the mold comprises contacting the separation element with the non-coating zone of the mold surface so that the gap separating the lip portion of the masking device and the coating applied on the first longitudinal boundary of the coating zone is provided by the separation element.

23. The method of claim 21, wherein the separation element is formed by a protrusion of the masking device and wherein the separation element contacts the mold surface non-adhesively.

24. The method of claim 21, wherein the separation element is formed separately from the masking device, and wherein the separation element adhesively contacts the mold surface.

25. The method of claim 16, further comprising arranging one or more clamps on the masking device so as to clamp the masking device to the mold surface.

26. The method of claim 16, wherein the gap between the lip portion of the masking device and the coating applied on the first longitudinal boundary of the coating zone is at least 0.1 mm.

27. The method of claim 16, wherein the gap between the lip portion of the masking device and the mold surface is at least 1.0 mm.

28. The method of claim 16, wherein a width of the non-coating zone from the longitudinal mould edge to the second boundary is in the range of 100-500 mm.

29. The method of claim 16, wherein the masking device comprises a plurality of individual masking elements each having a lip portion with a longitudinal masking edge.

30. The method of claim 29, wherein arranging the masking device in the mold comprises arranging the plurality of masking elements so that longitudinal masking edge of each masking element extend in parallel and substantially coincide to delimit the first longitudinal boundary of the coating zone.

31. The method of claim 16, wherein the masking device comprises a polymer material.

32. The method of claim 16, wherein arranging the masking device in the mold comprises attaching the masking device to the mold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments of this disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0039] FIG. 1 is a schematic perspective view of a wind turbine.

[0040] FIG. 2 is a schematic perspective view of a wind turbine blade for a wind turbine as shown in FIG. 1.

[0041] FIG. 3 is a schematic perspective view of a mould for moulding a wind turbine blade shell part.

[0042] FIG. 4 is schematic perspective view of a root region of the mould as shown in FIG. 3 including a masking device and illustrating a detail view A.

[0043] FIG. 5 is a schematic view of a root region of the mould as shown in FIG. 3 after application of coating.

[0044] FIGS. 6A-6D are schematic cross-sectional views at the detail view A of masking devices arranged in the mould.

DETAILED DESCRIPTION OF THE INVENTION

[0045] In the following figure description, the same reference numbers refer to the same elements and may thus not be described in relation to all figures.

[0046] FIG. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called Danish concept with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft which may include a tilt angle of a few degrees. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.

[0047] FIG. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The airfoil region has a tip region 36 closest to the tip 15 of the blade. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub 8, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0048] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root region 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0049] A shoulder 38 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 38 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0050] It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0051] The blade 10 is typically made from a pressure side shell part 24 and a suction side shell part 26 that are glued to each other along bond lines 28 at the leading edge 18 and the trailing edge 20 of the blade to form an aerodynamic shell body of the wind turbine blade 10.

[0052] FIG. 3 illustrates a mould 40 for moulding a shell part, such as the suction side shell part 26 or pressure side shell part 24 of the wind turbine blade 10 (as shown in FIG. 2). The mould 40 has a root region 30 for moulding the root 16 of the wind turbine blade 10 and a tip region 36 for moulding the tip 14 of the wind turbine blade 10. The mould 40 comprises a mould surface 41 with a longitudinal mould edge 42, a coating zone 44, a transition zone 48, and a non-coating zone 46. The coating zone 44 has a first longitudinal boundary 45 arranged towards the non-coating zone 46. The non-coating zone 46 extends longitudinally along the mould 40 and further extends from the longitudinal mould edge 42 to a second boundary 47 towards the coating zone 44. The transition zone 48 extends from the first longitudinal boundary 45 of the coating zone 44 to the second boundary 47 of non-coating zone 46.

[0053] Before applying a coating to the coating zone 44, the mould 40 is masked. This is performed by providing a masking device 50 comprising a lip portion 52 including a longitudinal masking edge 53 extending along the longitudinal direction of the mould 40. The masking device 50 is then arranged in the mould 40 as shown in FIG. 4. In the present embodiment, the masking device 50 is divided into separate masking elements 57 but the masking device 50 may in other embodiments be formed in one piece. A plurality of clamps 60 that reaches around the mould flange 43 and forcing the masking device 50 onto the mould surface 41 thereby attaching the masking device to the mould 40. In this arrangement, the masking device 50 covers the non-coating zone 46 of the mould surface 41 by overlapping the transition zone 48 and extending to the first longitudinal boundary 45 of the coating zone 44 as best seen in FIGS. 6A-6D. Thus, the longitudinal masking edge 53 of the masking device 50 delimits the first longitudinal boundary 45 of the coating zone 44. Further, a gap G separates the lip portion 52 of the masking device 50 and the first longitudinal boundary 45 of the coating zone 44. The gap G as measured from the mould surface 41 to the longitudinal masking edge 53 is at least the maximum coating thickness together with a safety tolerance, such as between 1.0-10 mm. The masking device is configured so that, upon terminating spraying of the coating at the first longitudinal boundary 45 of the coating zone 44, the lip portion 52 of the masking device 50 is separated from the coating 70 (as shown in FIG. 5) applied on the first longitudinal boundary 45 of the coating zone 44 by the gap G. This can be achieved by the masking devices 50 as shown in FIG. 6A-6D which are discussed in more detail below. In principle, the gap G needs only be present while the coating has not yet dried. Thus, in some embodiments, the lip portion 52 is forced to contact the mould surface 41 by the spray force of the coating being applied but once the spray force stops, the lip portion returns to its original shape to provide the gap G between the lip portion 52 and the mould surface 41. After application of the coating and even after the coating has dried, the masking device 50 can be removed from the mould 40 to reveal the zones 44, 46, 48 of the mould surface 41. As shown in FIG. 5, a full layer of coating has been applied onto the coating zone 44, while a layer of coating that gradually decreases in thickness and/or coverage has been applied to the transition layer 48 (which is often seen as a cloudy or spotted layer), and no coating has been applied to the non-coating zone 46. The coverage of the coating applied to the transition zone 48 decreases from 100% at the first longitudinal boundary 45 to 0% at the second boundary 47. The first longitudinal boundary 45 and the second boundary 47 are parallel and may in some cases be distanced from each other by 2-3 cm.

[0054] Turning to FIGS. 6A-6D, four embodiments of a masking device 50 are shown. All embodiments of the masking device 50 have an attachment portion 55 which is fixed to the mould 40, in particular the mould flange 43. However, different embodiments are envisioned but not shown in which the masking device is suspended in the mould 40 without being necessarily fixed to the mould 40. The coating is sprayed substantially perpendicularly to the coating zone 44 via a spray nozzle 72 as schematically shown in the figures.

[0055] In FIG. 6A, a first embodiment of the masking device 50 is shown in which both the body portion 51 and the lip portion 52 extend along the longitudinal direction (through the plane of FIG. 6A) and along a transverse direction (in the plane of FIG. 6A). The body portion 51 lies substantially flat against the mould surface 41 and the lip portion 52 curved outwards away from the mould surface 41. The masking device 50 has sufficient weight and stiffness so that during spraying of the coating, the gap G does not substantially diminish and is thus preserved during the application of the coating. Such sufficient weight and stiffness depend on the spray force of the spray nozzle 72 and on the characteristics of the coating.

[0056] The second embodiment shown in FIG. 6B, differs from the first embodiment shown in FIG. 6A in that a body joint 56 is arranged between the body portion 51 and the attachment portion 55. This body joint 56 allows the body portion 51 to flex about the body joint 56 relative to the attachment portion 55. This enables the provision of a relatively rigid body portion 51 and lip portion 52 while allowing the body portion 51 and the lip portion 52 to conform to the changing gradient of the mould surface 41 along the longitudinal direction (through the plane of the FIG. 6B). The body joint 56 can be provided as a hinge, such as a living hinge.

[0057] Turning to FIG. 6C, a third embodiment of the masking device 50 is shown. The third embodiment of the masking device 50 comprises a protrusion 54 arranged between the lip portion 52 and the body portion 51. The protrusion 54 contacts the mould surface 41 at the second boundary 47 and prevents the lip portion 52 from being forced to contact the mould surface 41 when coating is sprayed at the first longitudinal boundary 45 by the spray nozzle 72. Thus, the protrusion 47 maintains the gap G during coating application.

[0058] Lastly, a fourth embodiment is shown in FIG. 6D. The fourth embodiment differs from the first embodiment in that the lip portion 52, in its resting position as shown in FIG. 6D, is angled outwardly, away from the mould surface 41, so that when coating is applied and a spray force urges and deforms the lip portion 52 towards the mould surface 41, the angling of the lip portion 52 ensures that the lip portion 52 resists this deformation towards the mould surface 41. Thus, during coating application, the gap G is reduced but still maintained. In this embodiment, the body portion 51 preferably mates with the non-coating zone 46 of the mould surface 41.

TABLE-US-00001 LIST OF REFERENCES 2 wind turbine 4 tower 6 nacelle 8 hub 10 blade 13 shell 14 blade tip 15 tip end 16 blade root 17 root end 18 leading edge 20 trailing edge 24 pressure side shell part 26 suction side shell part 28 bond line 30 root region 32 transition region 34 airfoil region 36 tip region 38 shoulder 40 mould 41 mould surface 42 longitudinal mould edge 43 mould flange 44 coating zone 45 first longitudinal boundary 46 non-coating zone 47 second boundary 48 transition zone W.sub.NC width W.sub.T width 50 masking device 51 body portion 52 lip portion 53 longitudinal masking edge 54 separation element 55 attachment portion 56 body joint 57 masking element G gap 60 clamp 70 applied coating 71 transitional coating 72 spray nozzle