WO2022112151A1

WO2022112151A1 - Blade part for a wind turbine blade

Info

Publication number: WO2022112151A1
Application number: PCT/EP2021/082450
Authority: WO
Inventors: Mark Hancock
Original assignee: Blade Dynamics Limited
Priority date: 2020-11-25
Filing date: 2021-11-22
Publication date: 2022-06-02
Also published as: GB202018493D0

Abstract

Disclosed is a method for manufacturing a blade part, such as a shear web, for a wind turbine blade, the method comprising the steps of providing a panel section as a sandwich construction made of a fibre-reinforced thermoplastic material and comprising a core material sandwiched between a first fibre-reinforcement sheet and a second fibre-reinforcement sheet to form a blade part having a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side; and shaping at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part.

Description

BLADE PART FOR A WIND TURBINE BLADE

The present disclosure relates to wind turbine blades and manufacture of wind turbine blades. More specifically, the present disclosure pertains to the field of manufacturing of a blade part for wind turbine blades, such as manufacturing of shear webs of wind turbine blades.

BACKGROUND

As the demand for sustainable energy increases, the demand for recyclable material in the wind turbine blades increases. Furthermore, there is a constant demand for a shorter manufacturing time for wind turbine blades.

The conventional shear webs are typically made of a fibre-reinforced material and manufactured in a mould. The body of the shear webs are often manufactured as a sandwich construction with a core material and fibre skins on each side. Web foot flanges may be arranged at the ends of the body for attaching the shear web to for instance a spar cap of a wind turbine blade. This way of manufacturing is time consuming and requires large areas for the moulds.

Thermoplastic material provides a higher flexibility in terms of the final shape of the blade parts. Furthermore, thermoplastic shear webs can be manufactured without the need for large moulds.

Thus, there is a need for more sustainable materials in parts of the wind turbine blades. Furthermore, the need for an optimization of the manufacturing of blade parts would reduce the manufacturing time of blade parts and ultimately reduce the manufacturing time for wind turbine blades.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide a blade part, in particular a shear web, of a wind turbine blade and a wind turbine blade comprising such a blade part which overcome or ameliorate at least some of the disadvantages of the prior art.

In particular, it is an object of the present invention to provide a blade part, such as a shear web, for a wind turbine blade comprising a thermoplastic material and a method for manufacturing a blade part for a wind turbine blade comprising a thermoplastic material.

Thus, the present invention relates to a method for manufacturing a blade part, such as a shear web, for a wind turbine blade. The method comprises the steps of providing a panel section made of a fibre-reinforced thermoplastic material to form a blade part having a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side. The method comprises the step of shaping at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part.

According to a preferred embodiment the panel section may be provided as a sandwich construction and comprising a core material sandwiched between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet.

However, in an alternative embodiment, it may be sufficient to have panel section comprising only a single fibre-reinforcement sheet or plurality of fibre-reinforcement sheets, at least at the first side segment.

The blade part may be a shear web, a part of a shear web, a blade part comprising a mounting flange for a shear web or similar. The blade part may be an internal part of a wind turbine blade.

Also disclosed is a shear web made of made of a fibre-reinforced thermoplastic material. The shear web has longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side. The shear web comprises a first side segment at the first side. The first side segment is shaped and forms a mounting flange configured for mounting to another blade part.

In a preferred embodiment the shear web may be made of a sandwich construction made of a fibre-reinforced thermoplastic material and comprising a core material sandwiched between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet.

However, in an alternative embodiment, it may be sufficient to have a shear web comprising only a single fibre-reinforcement sheet or plurality of fibre-reinforcement sheets, at least at the first side segment.

The other blade part may be a shear web, a part of a shear web, a spar cap, a blade shell part or a mounting flange. The other blade part may be an internal part of a wind turbine blade or a blade shell part.

It is an advantage of the present disclosure that a better method for manufacturing blade parts is provided due to an easier and faster manufacturing method requiring reduced manufacturing space. It is a further advantage of the present disclosure, that the manufacturing cost may be reduced. Particularly, the panel sections for manufacturing the blade parts may be standard sandwich panels delivered from sub-contractors and the material may be recycled due to the thermoplastic composition of the panel sections. The method may comprise cutting the panel section to the desired size, e.g. a size corresponding to the internal dimensions of a wind turbine blade between a first spar cap and a second spar cap. The panel section may be cut before shaping the first side segment.

The method may comprise removing at least a part of the core material at the first side of the panel section before shaping the first side segment. The core material may be removed by cutting out, routing out or melting out.

The method may comprise attaching a first fibre-reinforcement part to the first side segment to form a part of the mounting flange. The first fibre-reinforcement part may be attached to the first fibre-reinforcement sheet. A second fibre-reinforcement part may be attached to the second fibre- reinforcement sheet. A part of the first fibre-reinforcement part and/or the second fibre- reinforcement part may be attached to another blade part. The fibre-reinforcement part may be attached by applying an adhesive or by welding. The fibre-reinforcement part may be plasma or heat treated before being attached. Alternatively, the fibre-reinforcement part may be treated with sanding, peel ply application or chemical treatment before being attached. The fibre-reinforcement part may be treated before adhesive is applied. The fibre-reinforcement part may be treated after adhesive is applied.

The method may comprise compressing at least a part of the first side segment such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side. At least a part of the first side segment of the shear web may be compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side. The first side segment may be compressed by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

The method may comprise folding at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction. At least a part of the first side segment of the shear web may be folded so that said part forms a part of a mounting surface of the mounting flange and such that said part is folded to a first flange direction to form a first angle relative to the transverse direction. The first side segment may be folded by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

Folding at least a part of the first side segment may comprise folding at least a part of the first fibre-reinforcement sheet to a first flange direction forming the first angle relative to the transverse direction, and folding at least a part of the second fibre-reinforcement sheet to a second flange direction forming a second angle relative to the transverse direction. At least a part of the first fibre-reinforcement sheet may be folded to a first flange direction to form a first angle relative to the transverse direction. At least a part of the second fibre-reinforcement sheet may be folded to a second flange direction to form a second angle relative to the transverse direction.

Alternatively, folding at least a part of the first side segment may comprise folding at least a part of the first fibre-reinforcement sheet and the second fibre-reinforcement sheet to the same flange direction to form the first angle relative to the transverse direction. At least a part of the first fibre- reinforcement sheet and the second fibre-reinforcement sheet may be folded to the same flange direction to form a first angle relative to the transverse direction. The first fibre-reinforcement sheet and the second fibre-reinforcement sheet may be folded to the first flange direction or the second flange direction. The first fibre-reinforcement sheet and the second fibre-reinforcement sheet may be connected before folding, e.g. connected during compression.

The first angle and/or second angle may be variable along the longitudinal direction of the blade part, e.g. a direction corresponding to the longitudinal direction of the wind turbine blade. The first angle and/or second angle may change where the local slope of the other blade part changes. The first angle and the second angle may be different.

The first angle and/or second angle may be an acute angle, e.g. the first angle may be up to 88 degrees. The first angle and/or second angle may be an obtuse angle, e.g. the first angle may be at least 92 degrees.

The first angle and/or the second angle may be between 30-88 degrees, such as between 45-85 degrees. The first angle and/or the second angle may be between 92-150 degrees, such as between 110-135 degrees.

The first angle may be an acute angle while the second angle may be an obtuse angle. The first angle may be an obtuse angle while the second angle may be an acute angle.

At least a part of the first side segment and at least a part of the second side segment may form a plane mounting surface, e.g. the angle between at least a part of the first side segment and at least a part of the second side segment may be around 180 degrees.

The first angle and/or the second angle may be different than a right angle.

The method may comprise compressing at least a part of a second side segment of the panel section such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second side. The shear web may comprise a second side segment at the second side. At least a part of the second side segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second side. The second side segment may be compressed by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

The method may comprise folding at least a part of the second side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction. The second side segment may be folded by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

Folding at least a part of the second side segment may comprise folding at least a part of the first fibre-reinforcement sheet to a first flange direction forming the first angle relative to the transverse direction, and folding at least a part of the second fibre-reinforcement sheet to a second flange direction forming a second angle relative to the transverse direction. At least a part of the first fibre-reinforcement sheet may be folded to a first flange direction to form a first angle relative to the transverse direction. At least a part of the second fibre-reinforcement sheet may be folded to a second flange direction to form a second angle relative to the transverse direction.

Alternatively, folding at least a part of the second side segment may comprise folding at least a part of the first fibre-reinforcement sheet and the second fibre-reinforcement sheet to the same flange direction to form the first angle relative to the transverse direction. At least a part of the first fibre-reinforcement sheet and the second fibre-reinforcement sheet may be folded to the same flange direction to form a first angle relative to the transverse direction. The first fibre- reinforcement sheet and the second fibre-reinforcement sheet may be folded to the first flange direction or the second flange direction. The first fibre-reinforcement sheet and the second fibre- reinforcement sheet may be connected before folding, e.g. connected during compression.

The first angle of the second side segment and the second angle of the second side segment may be different than the first angle of the first side segment and the second angle of the first side segment.

The first flange direction of the first side segment may be the same as the first flange direction of the second side segment. The second flange direction of the first side segment may be the same as the second flange direction of the second side segment.

The method may comprise compressing at least a part of a first end segment of the panel section such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the first end. The shear web may comprise a first end segment at the first end. At least a part of the first end segment may be compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first end.

The method may comprise compressing at least a part of a second end segment of the panel section such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second end. The shear web may comprise a second end segment. At least a part of the second end segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second end.

The first end segment and/or the second end segment may be compressed by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

At least a part of the first side segment and/or the second side segment and/or the first end segment and/or the second end segment may be heated before applying pressure during compression and/or folding. Alternatively, the shaping unit may be heated such that the heating unit provides heat and pressure simultaneously.

During compression of the first side segment and/or the second side segment and/or the first end segment and/or the second end segment the first fibre-reinforcement sheet and the second fibre- reinforcement sheet may be attached or adhered together.

The blade part may be a sectionised blade part. The method may comprise manufacturing a primary blade part and a secondary blade part and connecting the first end of the primary blade part with the second end of the secondary blade part. The shear web may be a sectioned shear web comprising a primary shear web and a secondary shear web. The primary shear web and the secondary shear web may be connected by connecting the primary first side of the primary shear web with the secondary second side of the secondary shear web. The primary blade part and the secondary blade part may be connected by means of an overlapping joint, a joining strap, welding or adhesive. The primary shear web and the secondary shear web may be connected by means of a joining strap, welding or adhesive.

Also disclosed is a shear web for a wind turbine blade manufactured according to the steps of the method for manufacturing a blade part.

Also disclosed is a wind turbine blade extending from a root to a tip. The wind turbine blade comprises a root region, an airfoil region with the tip, a pressure side, a suction side and a chord line extending between a leading edge and a trailing edge. The wind turbine blade comprises a primary shear web arranged between a first spar cap arranged at a suction side blade shell part and a second spar cap arranged at a pressure side blade shell part.

The primary first side of the primary shear web may be attached to the first spar cap and the primary second side of the primary shear web may be attached to the second spar cap. The primary first side section of the primary shear web may be attached to the first spar cap and the primary second side section may be attached to the second spar cap.

The wind turbine blade may comprise a secondary shear web arranged between the first spar cap and the second spar cap. The secondary first side of the secondary shear web may be attached to the first spar cap and the secondary second side of the secondary shear web may be attached to the second spar cap. The secondary first side section of the secondary shear web may be attached to the first spar cap and the secondary second side section may be attached to the second spar cap. The primary first end of the primary shear web and the secondary second end of the secondary shear web may be connected.

The primary shear web and/or the secondary shear web may be attached to the spar caps of the wind turbine blade by plastic welding or adhesive, e.g. by means of a joining strap.

It is envisaged that any embodiments or elements as described in connection with any one aspect may be used with any other aspects or embodiments, mutatis mutandis.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described in more detail in the following with regard to the accompanying figures. Like reference numerals refer to like elements throughout. Like elements may, thus, not be described in detail with respect to the description of each figure. 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. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

Fig. 1 is a schematic diagram illustrating an exemplary wind turbine,

Fig. 2 is a schematic diagram illustrating an exemplary wind turbine blade, Fig. 3 is a schematic diagram illustrating a cross section of an exemplary wind turbine blade,

Figs. 4a-4d are schematic diagrams illustrating an exemplary panel section and an exemplary blade part,

Figs. 5a-5d are schematic diagrams illustrating an exemplary segment of a blade part,

Figs. 6a-6d are schematic diagrams illustrating an exemplary segment of a blade part,

Fig. 7 is a schematic diagram illustrating an exemplary blade part,

Figs. 8a-8d are schematic diagrams illustrating an exemplary blade part, and

Fig. 9 is a block diagram illustrating an exemplary method for manufacturing a blade part.

DETAILED DESCRIPTION

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.

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. 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.

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 blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

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 area 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.

A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

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.

The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together with adhesive, such as glue, along bond lines or glue joints 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 have a semi-circular or semi-oval outer cross-sectional shape.

Fig. 3 is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade 10, e.g. a cross-sectional view of the airfoil region of the wind turbine blade 10. The wind turbine blade 10 comprises a leading edge 18, a trailing edge 20, a pressure side 24 and a suction side 26. The shell parts 24, 26 may comprise glass fibres. The wind turbine blade 10 comprises a chord line 38 between the leading edge 18 and the trailing edge 20. The wind turbine blade 10 comprises blade parts 58, such as shear webs 42, such as a leading edge shear web and a trailing edge shear web. The shear webs 42 could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The shear webs 42 are made of a panel section made of a thermoplastic material.

The shear webs 42 are arranged between spar caps 44, 46, such as a pressure side spar cap 44 and a suction side spar cap 46 arranged in or on the blade shell parts 24, 26. The spar caps 44, 46 may alternatively be referred to as main laminates. The spar caps 44, 46 may comprise pultruded elements of carbon fibres or fibre-reinforced composite material. The spar caps 44, 46 may comprise a thermoplastic material or be covered at least partly by a sheet of thermoplastic material.

Figs. 4a-4d are schematic diagrams illustrating an exemplary panel section 56 for forming a blade part 58, such as the shear web 42 of Fig. 3. The panel section 56 is a sandwich construction made of a fibre-reinforcement thermoplastic material and comprises a core material 50 sandwiched between a first fibre-reinforcement sheet 52 and a second fibre-reinforcement sheet 54. The panel section 56 is used to form a blade part, such as a shear web.

In Fig. 4b the panel section 56 is first cut by a cutting tool into the desired size of a blade part 58, e.g. the size of a shear web, which tapers in the spanwise direction of the wind turbine blade. In Fig. 4b the panel section 56 is cut into two blade parts 58, but the panel section 56 may be cut into one or more blade parts 58. The blade parts 58 have a longitudinal direction L between a first end 60 and a second end 62 and a transverse direction T between a first side 64 and a second side 66. The panel section 56 cut to have a height FI and a width W. The height FI and width W may correspond to the height of a shear web, wherein the height FI corresponds to the distance between a first blade shell part and a second blade shell part. Alternatively, the height FI may correspond to more than the distance between a first blade shell part and a second blade shell part. The height FI may vary along the longitudinal direction L of the panel section 56.

In Fig. 4c the panel section 56 is shaped to form a blade part 58 using a shaping tool 90. The shaping tool 90 may comprise a plurality of shaping units 96, 98 and actuators 94. The plurality of shaping units 96, 98 may come in pairs such that one shaping unit is arranged on each side of the panel section 56 e.g. one shaping unit 96, 98 is configured to contact the first fibre-reinforcement sheet 52 and one shaping unit 96, 98 is configured to contact the second fibre-reinforcement sheet 54. The shaping units 96, 98 may be rollers 98, shoes 96, clamps or the like. The illustrated combination of shaping units 96, 98 is one example, but other combinations are also possible. The surface of the shaping units 96, 98 is preferably of low friction such that the panel section may move freely across the shaping units 96, 98. The shaping units 96, 98 may be controlled by the actuators 94. In Fig. 4c actuators 94 are illustrated with the shoe 96, however, the rollers 98 may also be controlled by actuators 94. The actuators 94 may be computer controlled and programmed to form the panel section 56 to a predetermined shape. The actuators 94 control the shaping units 96, 98 to apply heat and/or pressure to the panel section 56. The shaping units 96, 98 may move in a direction according to the arrows D5.

The panel section 56 may move in a direction according to the arrow D3 to engage with the shaping tool 90, which may be stationary. Alternatively, the panel section 56 is removably fixed to a holder, i.e. the panel section 56 is stationary, and the shaping tool 90 moves along the first side of the panel section 56 or blade part 58 in a direction according to the arrow D4.

The shaping units 96, 98 may shape at least a first side segment 74 of the panel section 56 at the first side 64. The first side segment 74 may be shaped by compressing with the roller 98 such that the thickness between the first fibre-reinforcement sheet 52 and the second fibre-reinforcement sheet 54 decreases towards the first side 64. The first side segment 74 may be shaped by folding with the shoe 96 to form a mounting flange 80 of the blade part 58. The mounting flange 80 has a mounting surface 82 configured to be attached to another blade part, e.g. a blade shell part, a spar cap or a shear web.

Fig. 4d is a schematic diagram illustrating the first side segment 74 of a blade part 58, such as the first side segment 74 of Fig. 4c. The first side segment 74 is shaped by compressing and folding the first side segment 74. The mounting flange 80 of the blade part 58 is formed by folding to a first flange direction D1 to form a first angle F1 relative to the transverse direction T. The transverse direction T is still the same after folding of the first side segment 74.

Figs. 5a-5d are schematic diagrams illustrating an exemplary segment, such as a first side segment 74 or a second side segment 76 of a blade part, such as the blade part 58 of Fig. 4. Figs. 5a-5d illustrate steps for shaping a side segment 74, 76 of the blade part. The steps may comprise providing a panel section, such as the panel section of Fig. 4, and removing at least a part of the core material 50 with a shaping unit 99, such as a drill or mill, rotating in a direction according to the arrow D5. Other suitable means for removing core materials may also be used.

In Fig. 5b the side segment 74, 76 is further shaped by compressing and folding. Compressing and folding may be performed simultaneously, or one step may be performed before the other. The side segment 74, 76 is compressed using a shaping unit, such as a shoe 96 or a pair of shoes 96. Other suitable means for shaping may alternatively be used, such as rollers. The side segment 74, 76 is shaped by folding the first fibre-reinforcement sheet 52 and the second fibre-reinforcement sheet 54. In Fig. 5b the first fibre-reinforcement sheet 52 is folded towards a first flange direction D1 (see Fig. 5c) and the second fibre-reinforcement sheet 54 is folded towards a second flange direction D2 (see Fig. 5c) as indicated by the arrows D5. Flowever, the sheet 52, 54 may alternatively be folded to the same flange direction, such as illustrated in Fig. 4. The sheet 52, 54 may be folded using shaping units 93, 96. The shaping units 93, 96 may provide pressure and heat simultaneously, or the panel section may be heated before the shaping units 93, 96 provide the pressure. Fig. 5c illustrates the situation where the shaping units 93, 96 have folded and compressed the side segments 74, 76. The shaping units 93, 96 may be held at position for a period of time, e.g. until the core 50 and the sheet 52, 54 have cured.

Fig. 5d illustrates a further step of folding a part of the side segment 74, 76. The first fibre- reinforcement sheet 52 is folded to a first flange direction D1 forming a first angle F1 relative to the transverse direction T. The second fibre-reinforcement sheet 54 may be folded to a second flange direction D2 forming a second angle F2 relative to the transverse direction T. As seen in Fig. 5c and 5d the transverse direction is still the same after folding of the side segment 74, 76. The first angle F1 and the second angle F2 correspond to the local slope of another blade part, such as a blade shell part or a spar cap, which the first side segment 74 or second side segment 76 is configured to be attached to. The first angle F1 and/or the second angle F2 may vary along the longitudinal direction, e.g. a direction corresponding to the longitudinal direction of a wind turbine blade, such that the angle F1, F2 changes where the local slope of the other blade part changes.

Figs. 6a-6d are schematic diagrams illustrating an exemplary segment of a blade part, such as the first side segment 74 or the second side segment 76 of Figs. 4-5. The side segments 74, 76 illustrate alternative embodiments of the mounting flange 80 and the features illustrated may be combined in other ways than illustrated.

In Fig. 6a and 6c the mounting flange 80 is formed by attaching a first fibre-reinforcement part 84 and a second fibre-reinforcement part 86 to the side segment 74, 76 with a bonding 88, e.g. an adhesive, such as a thermoplastic compatible adhesive, or by plastic welding. The mounting surface 82 is configured to be attached to another blade part with a bonding (not illustrated), e.g. an adhesive or by plastic welding, and may be treated by plasma treatment before bonding with the other blade part. Alternatively, the mounting surface 82 may be treated before bonding, e.g. by heat or chemical treatment, peel ply application or sanding before attachment or boding.

Figs. 6b and 6d illustrate that the first fibre-reinforcement sheet 52 and the second fibre- reinforcement sheet 54 of the side segments 74, 76 of the blade part may be configured to attach to another blade part with a bonding 88, e.g. an adhesive or by welding. The bonding 88 may be activated, e.g., by plasma, chemical or heat treatment, peel ply application or sanding before attachment.

In Figs. 6a and 6b the side segment 74, 76 is shaped by removing some of the core material 50 and by folding the sheet 52, 54. The core material 50 may be removed such as illustrated in Fig. 6a or 6b. In Figs. 6c and 6d the side segments 74, 76 are shaped by compressing and folding at least a part of the side segment 74, 76.

Fig. 7 is a schematic diagram illustrating an exemplary blade part 58, such as the blade part of Figs. 4-5 or the shear web of Fig. 3. The first side segment 74 and the second side segment 76 of the blade part 58 are shaped by compressing at least a part of the side segments 74, 76. The first side segment 74 of the blade part 58 is shaped by folding at least a part of the first side segment 74. The first side segment 74 is shaped by folding at least a part of the first fibre-reinforcement sheet 52 to a first flange direction D1 and the second fibre-reinforcement sheet 54 to the second flange direction D2 relative to the transverse direction T. The blade part 58 is also shaped at the second side segment 76 by folding at least a part of the second side segment 76. The second side segment 76 is shaped by folding at least a part of the first fibre-reinforcement sheet 52 to a first flange direction D1 and the second fibre-reinforcement sheet 54 to the second flange direction D2 relative to the transverse direction T.

Figs. 8a-8d are schematic diagrams illustrating an exemplary blade part 58, such as the blade part of the previous figures or the shear web of Fig. 3. The blade part 58 may be a sectionised blade part comprising at least a primary blade part 100 and a secondary blade part 102. The blade part may be a shear web 42 for a wind turbine blade and the primary blade part 100 and the secondary blade part 102 may be sections of the shear web 42. The blade part 100, 102 is made of a panel section comprising a core 50 sandwiched between a first fibre-reinforced sheet 52 and a second fibre-reinforced sheet 54. A part of the first side segment 74 and the second side segment 76 may be shaped, e.g. compressed and/or folded. The said part forms a mounting flange 80 with a mounting surface 82 on each of the first side segment 74 and the second side segment 76.

Fig. 8b is a cross sectional view taken from the line 8b in Fig. 8a. The primary blade part 100 comprises a first end segment 70 at the first end 60 (not illustrated) and a second end segment 72 at the second end 62. The secondary blade part 102 comprises a first end segment 70 at the first end 60 and a second end segment 72 at the second end 62 (not illustrated). The second end 62 of the primary blade part 100 is connected to the first end 60 of the secondary blade part 102. In Fig. 8a and 8b the primary blade part 100 and the secondary blade part 102 are connected using a joint strap 104. Flowever, the blade parts 100, 102 may alternatively be connected by applying an adhesive or by welding. For example, the ends 60, 62 may overlap and be glued or welded together (not illustrated). At least a part of the first end segment 70 and the second end segment 72 of each of the primary blade part 100 and the secondary blade part 102 may be shaped, e.g. compressed using the same method and means as described in relation to Fig. 4. Fig. 8c is a cross-sectional view as seen along the transverse direction of the blade part 100, 102.

In Fig. 8c the side segment 74, 76 is shaped by folding and compressing at least a part of the side segment. The said part forms a mounting flange 80 comprising a mounting surface configured to be mounted to other blade parts. The side segments 74, 76 show examples of how a part may be compressed, e.g. curvilinearly and/or linearly.

Fig. 8d illustrates how sections of blade parts, e.g. a primary blade part 100, a secondary blade part 102 and a tertiary blade part 103 may be arranged to form a blade part 58, such as a shear web 42. The blade parts 100, 102, 103 may be arranged in series such that the second end 62 of the primary blade part 100 is connected to the first end of the secondary blade part 102, etc. The dimensions of each of the blade parts 100, 102, 103 may correspond to the internal dimension of a wind turbine blade where the blade parts 100, 102, 103 are configured to be attached. The first side segment 74 and the second side segment 76 may be shaped to accommodate for the local variations of the surface where the blade parts 100, 102, 103 are configured to be attached, e.g. variations in the surface of spar caps.

Fig. 9 is a block diagram illustrating an exemplary method 200 for manufacturing a blade part, such as the blade part or the shear web of the previous figures.

The method 200 comprises providing 202 a panel section, such as the panel section of Fig. 4, as a sandwich construction made of a fibre-reinforced thermoplastic material and comprising a core material sandwiched between a first fibre-reinforcement sheet and a second fibre-reinforcement sheet to form a blade part. The formed blade part has a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side.

The panel section may be cut 204 to the desired size, e.g. a size corresponding to the internal dimensions of a wind turbine blade. The method 200 may comprise removing 206 at least a part of the core material before shaping the mounting flange.

The method comprises shaping 208 at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part. The mounting flange may be configured to be mounted to a shear web, a blade shell part, a spar cap or other parts of a wind turbine blade.

Shaping 208 at least the first side segment may comprise attaching 210 a first fibre-reinforcement part to the first side segment to form a part of the mounting flange. The first fibre-reinforcement part may be attached 210 to the first fibre-reinforcement sheet. A second fibre-reinforcement part may be attached to the second fibre-reinforcement sheet. Shaping 208 at least the first side segment may comprise compressing 212 at least a part of the first side segment such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side. The first side segment may be compressed by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

Shaping 208 at least the first side segment may comprise folding 214 at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange and such that said part is folded to a first flange direction forming a first angle relative to the transverse direction. The first side segment may be folded by applying heat and/or pressure, e.g. by controlled actuators with shaping units such as rollers, clamps, shoes or the like.

Folding 214 at least a part of the first side segment may comprise folding 216 at least a part of the first fibre-reinforcement sheet to a first flange direction forming the first angle relative to the transverse direction. Folding 214 at least a part of the first side segment may comprise folding 218 at least a part of the second fibre-reinforcement sheet to a second flange direction forming a second angle relative to the transverse direction.

Alternatively, folding 214 at least a part of the first side segment may comprise folding 220 at least a part of the first fibre-reinforcement sheet and the second fibre-reinforcement sheet to the same flange direction, e.g. first flange direction, to form the first angle relative to the transverse direction.

At least a part of the first side segment may be heated before applying pressure during compression and folding. Alternatively, the shaping unit may be heated such that the heating unit provides heat and pressure simultaneously.

The method 200 may comprise shaping 228 at least a second side segment at the second side of the panel section to form a mounting flange of the blade part for mounting to another blade part. Shaping 228 the second side segment may comprise one or more of the steps attaching 230, compressing 232 and folding 234, wherein folding may comprise folding 236 the first fibre- reinforcement sheet to the first flange direction, folding 238 the second reinforcement sheet to the second flange direction or folding 240 the first sheet and the second sheet to the same flange direction. The steps 230, 232, 234, 236, 238 and 240 for the second side segment may be performed in the same manner as for the first side segment.

The invention has been described with reference to preferred embodiments. Flowever, the scope of the invention is not limited to the illustrated embodiments, and alterations and modifications can be carried out without deviating from the scope of the invention. Exemplary embodiments of the present disclosure are set out in the following items:

1. A method for manufacturing a blade part, such as a shear web, for a wind turbine blade, the method comprising the steps of:

• providing a flat panel section made of a fibre-reinforced thermoplastic material and comprising a first fibre-reinforcement sheet and a second fibre-reinforcement sheet to form a blade part having a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side; and

• shaping at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part.

2. Method according to item 1, wherein the panel section is provided as a sandwich construction and comprising a core material sandwiched between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet.

3. Method according to item 2 comprising removing at least a part of the core material at the first side of the panel section before shaping the first side segment.

4. Method according to any of the preceding items comprising attaching a first fibre- reinforcement part to the first side segment to form a part of the mounting flange.

5. Method according to any of the items 2-4 comprising compressing at least a part of the first side segment such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side, e.g. before shaping at least the first side segment and/or folding at least a part of the first side segment.

6. Method according to any of the preceding items comprising folding at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction,

• e.g. wherein the first angle is an acute or an obtuse angle.

7. Method according to item 6, wherein folding at least a part of the first side segment comprises: • folding at least a part of the first fibre-reinforcement sheet to a first flange direction forming the first angle relative to the transverse direction, and

• folding at least a part of the second fibre-reinforcement sheet to a second flange direction forming a second angle relative to the transverse direction.

8. Method according to item 6, wherein folding at least a part of the first side segment comprises

• folding at least a part of the first fibre-reinforcement sheet and the second fibre- reinforcement sheet to the same flange direction, e.g. first flange direction, to form the first angle relative to the transverse direction.

9. Method according to any of the items 6-8, wherein the first angle is variable along the longitudinal direction of the blade part.

10. Method according to any of the items 2-9 comprising compressing at least a part of a second side segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second side.

11. Method according to any of the preceding items comprising folding at least a part of the second side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction.

12. Method according to any of the items 2-11 comprising compressing at least a part of a first end segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first end.

13. Method according to any of the items 2-12 comprising compressing at least a part of a second end segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second end.

14. Method according to any of the preceding items wherein the blade part is a sectionised blade part and wherein the method comprises manufacturing a primary blade part and a secondary blade part and connecting the first end of the primary blade part with the second end of the secondary blade part, e.g. by means of a joining strap, welding or adhesive.

15. Method according to any of the preceding items, wherein the first angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

16. Method according to any of the items 7-15, wherein the second angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

17. A shear web for a wind turbine blade manufactured according to any of the items 1-16.

18. A shear web made of a fibre-reinforced thermoplastic material, the shear web having longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side, the shear web comprising a first side segment at the first side, wherein the first side segment is shaped and forms a mounting flange configured for mounting to another blade part, e.g. another shear web.

19. Shear web according to item 18, wherein the shear web is made of a sandwich construction made of a fibre-reinforced thermoplastic material and comprising a core material sandwiched between a first fibre-reinforcement sheet and a second fibre- reinforcement sheet.

20. Shear web according to item 19, wherein at least a part of the first side segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side.

21. Shear web according to any of the items 18-20, wherein at least a part of the first side segment is folded so that said part forms a part of a mounting surface of the mounting flange and such that said part is folded to a first flange direction to form a first angle relative to the transverse direction,

• e.g. wherein the first angle is an acute or an obtuse angle.

22. Shear web according to any of the items 19-21, wherein at least a part of the first fibre- reinforcement sheet is folded to a first flange direction to form a first angle relative to the transverse direction and wherein at least a part of the second fibre-reinforcement sheet is folded to a second flange direction to form a second angle relative to the transverse direction. 23. Shear web according to any of the items 19-22, wherein at least a part of the first fibre- reinforcement sheet and the second fibre-reinforcement sheet are folded to the same flange direction, e.g. first flange direction, to form a first angle relative to the transverse direction.

24. Shear web according to any of the items 19-23 comprising a second side segment at the second side wherein at least a part of the second side segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second side.

25. Shear web according to any of the items 19-24 comprising a first end segment at the first end wherein at least a part of the first end segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first end.

26. Shear web according to any of the items 19-25 comprising a second end segment at the second end wherein at least a part of the second end segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second end.

27. Shear web according to any of the claims 18-26, wherein the first angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

28. Shear web according to any of the claims 22-27, wherein the second angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

29. A wind turbine blade extending from a root to a tip, the wind turbine blade comprising a root region, an airfoil region with the tip, a pressure side, a suction side and a chord line extending between a leading edge and a trailing edge, the wind turbine blade comprising a primary shear web according to any of the items 17-28 arranged between a first spar cap arranged at a suction side blade shell part and a second spar cap arranged at a pressure side blade shell part.

30. Wind turbine blade according to item 29, wherein the primary first side of the primary shear web is attached to the first spar cap and the primary second side of the primary shear web is attached to the second spar cap.

31. Wind turbine blade according to any of the items 29-30, wherein the primary shear web and/or the secondary shear web is attached to the spar caps of the wind turbine blade by plastic welding or adhesive. A method for manufacturing a blade part, such as a shear web, for a wind turbine blade, the method comprising the steps of:

• providing a flat panel section made of a fibre-reinforced thermoplastic material and comprising a first fibre-reinforcement sheet and a second fibre-reinforcement sheet to form a blade part having a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side;

• cutting the flat panel section, e.g., such that the flat panel section has a width and a height;

• removing at least a part of the core material at the first side of the panel section before shaping the first side segment; and

• shaping at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part. Method according to claim 30 comprising folding at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction. Method according to claim 31 comprising treating the mounting surface, e.g., with peel ply application, sanding, heat, chemical or plasma treatment. Method according to any of the claims 30-32 wherein the first angle is an acute or an obtuse angle.

LIST OF REFERENCES

2 wind turbine

4 tower

6 nacelle

8 hub

10 blade

12 blade part

14 blade tip

15 tip end

16 blade root

17 root end

18 leading edge

20 trailing edge

24 first blade shell part (pressure side)

25 leading part of pressure side

26 second blade shell part (suction side)

27 leading part of suction side

28 bond lines/glue joints

30 root region

32 transition region

34 airfoil region

36 first shell part flange

38 chord line

40 shoulder

42 shear web or spar side

44 first spar cap (pressure side)

46 second spar cap (suction side)

50 core

52 first fibre-reinforcement sheet

54 second fibre-reinforcement sheet

56 panel section

58 blade part

60 first end

62 second end

64 first side 66 second side

70 first end segment

72 second end segment

74 first side segment

76 second side segment

80 mounting flange

82 mounting surface

84 first fibre-reinforcement part

86 second fibre-reinforcement part

88 bonding

90 shaping tool

92 cutting tool

93 shaping unit

94 actuator

96 shoe

98 roller

99 drill

100 primary blade part

102 secondary blade part

103 tertiary blade part

104 joint strap

L longitudinal direction

T transverse direction

F1 first angle

F2 second angle

D1 first flange direction

D2 second flange direction

D3 moving direction

D4 moving direction

D5 moving direction

H height

W width

200 method for manufacturing a blade part

202 providing panel section 204 cutting

206 removing

208 shaping

210 attaching 212 compressing

214 folding

216 folding first sheet

218 folding second sheet

220 folding first and second sheet 228 shaping

230 attaching

232 compressing

234 folding

236 folding first sheet 238 folding second sheet

240 folding first and second sheet

Claims

• shaping at least a first side segment at the first side of the panel section to form a mounting flange of the blade part for mounting to another blade part; and

• folding at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction wherein the first angle is an acute or an obtuse angle.

2. Method according to claim 1, wherein the panel section is provided as a sandwich construction and comprising a core material sandwiched between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet.

3. Method according to claim 2 comprising removing at least a part of the core material at the first side of the panel section before shaping the first side segment.

4. Method according to any of the preceding claims comprising attaching a first fibre- reinforcement part to the first side segment to form a part of the mounting flange.

5. Method according to any of the claims 2-4 comprising compressing at least a part of the first side segment such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side, e.g. before shaping at least the first side segment and/or folding at least a part of the first side segment.

6. Method according to any of the preceding claims, wherein folding at least a part of the first side segment comprises: folding at least a part of the first fibre-reinforcement sheet to a first flange direction forming the first angle relative to the transverse direction, and • folding at least a part of the second fibre-reinforcement sheet to a second flange direction forming a second angle relative to the transverse direction.

7. Method according to any of the preceding claims, wherein folding at least a part of the first side segment comprises

8. Method according to any of the preceding claims, wherein the first angle is variable along the longitudinal direction of the blade part.

9. Method according to any of the claims 2-8 comprising compressing at least a part of a second side segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second side.

10. Method according to any of the preceding claims comprising folding at least a part of the second side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction.

11. Method according to any of the claims 2-10 comprising compressing at least a part of a first end segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first end.

12. Method according to any of the claims 2-11 comprising compressing at least a part of a second end segment of the panel section such that the thickness between the first fibre- reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the second end.

13. Method according to any of the preceding claims wherein the blade part is a sectionised blade part and wherein the method comprises manufacturing a primary blade part and a secondary blade part and connecting the first end of the primary blade part with the second end of the secondary blade part, e.g. by means of a joining strap, welding or adhesive.

14. Method according to any of the preceding claims, wherein the first angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

15. Method according to any of the claims 6-14, wherein the second angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

16. A shear web for a wind turbine blade manufactured according to any of the claims 1-13.

17. A shear web made of a fibre-reinforced thermoplastic material, the shear web having longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side, the shear web comprising a first side segment at the first side, wherein the first side segment is shaped and forms a mounting flange configured for mounting to another blade part, e.g. another shear web, wherein at least a part of the first side segment is folded so that said part forms a part of a mounting surface of the mounting flange and such that said part is folded to a first flange direction to form a first angle relative to the transverse direction, and wherein the first angle is an acute or an obtuse angle.

18. Shear web according to claim 17, wherein the shear web is made of a sandwich construction made of a fibre-reinforced thermoplastic material and comprising a core material sandwiched between a first fibre-reinforcement sheet and a second fibre- reinforcement sheet.

19. Shear web according to claim 18, wherein at least a part of the first side segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first side.

20. Shear web according to any of the claims 18-19, wherein at least a part of the first fibre- reinforcement sheet is folded to a first flange direction to form a first angle relative to the transverse direction and wherein at least a part of the second fibre-reinforcement sheet is folded to a second flange direction to form a second angle relative to the transverse direction.

21. Shear web according to any of the claims 18-20, wherein at least a part of the first fibre- reinforcement sheet and the second fibre-reinforcement sheet are folded to the same flange direction, e.g. first flange direction, to form a first angle relative to the transverse direction.

22. Shear web according to any of the claims 18-21 comprising a second side segment at the second side wherein at least a part of the second side segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second side.

23. Shear web according to any of the claims 18-22 comprising a first end segment at the first end wherein at least a part of the first end segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre-reinforcement sheet of said part decreases towards the first end.

24. Shear web according to any of the claims 18-23 comprising a second end segment at the second end wherein at least a part of the second end segment is compressed such that the thickness between the first fibre-reinforcement sheet and the second fibre- reinforcement sheet of said part decreases towards the second end.

25. Shear web according to any of the claims 17-24, wherein the first angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

26. Shear web according to any of the claims 20-25, wherein the second angle is an acute angle of up to 88 degrees or an obtuse angle of at least 92 degrees.

27. A wind turbine blade extending from a root to a tip, the wind turbine blade comprising a root region, an airfoil region with the tip, a pressure side, a suction side and a chord line extending between a leading edge and a trailing edge, the wind turbine blade comprising a primary shear web according to any of the claims 16-24 arranged between a first spar cap arranged at a suction side blade shell part and a second spar cap arranged at a pressure side blade shell part.

28. Wind turbine blade according to claim 27, wherein the primary first side of the primary shear web is attached to the first spar cap and the primary second side of the primary shear web is attached to the second spar cap.

29. Wind turbine blade according to any of the claims 27-28, wherein the primary shear web and/or the secondary shear web is attached to the spar caps of the wind turbine blade by plastic welding or adhesive.

30. A method for manufacturing a blade part, such as a shear web, for a wind turbine blade, the method comprising the steps of: • providing a flat panel section made of a fibre-reinforced thermoplastic material and comprising a first fibre-reinforcement sheet and a second fibre-reinforcement sheet to form a blade part having a longitudinal direction between a first end and a second end and a transverse direction between a first side and a second side;

31. Method according to claim 30 comprising folding at least a part of the first side segment so that said part forms a part of a mounting surface of the mounting flange such that said part is folded to a first flange direction forming a first angle relative to the transverse direction.

32. Method according to claim 31 comprising treating the mounting surface, e.g., with peel ply application, sanding, heat, chemical or plasma treatment.

33. Method according to any of the claims 30-32 wherein the first angle is an acute or an obtuse angle.