A GRIPPING DEVICE FOR LIFTING A PREFORM FOR A WIND TURBINE BLADE

Abstract

A gripping device (76) is provided for lifting a preform for a wind turbine blade from a preform mould (71). The gripping device (76) comprises a base frame (62), a plurality of arms (78) slidably mounted on the base frame (62), each arm (78) having a proximal end and a distal end, a plurality of gripping members (86) for gripping a top surface (75) of the preform. The vertical position of one or more arms (78) of the gripping device (76) relative to the base frame (62) may change when lowering the gripping device (76) towards a preform to reflect the top surface (75) of the perform.

Claims

1. A gripping device (76) for lifting a preform (98) for a wind turbine blade from a preform mould (71), the gripping device (76) comprising a base frame (62), a plurality of arms (78) slidably mounted on the base frame (62), each arm (78) having a proximal end and a distal end, a plurality of gripping members (86) for gripping a top surface (75) of the preform, each gripping member (86) being attached to the distal end of at least one of the arms (78), a plurality of lock members (90), each lock member being engaged with at least one of the arms (78) for allowing sliding motion of the arm (78) relative to the base frame (62) in a first direction while preventing sliding motion of the arm (78) relative to the base frame (62) in a second direction.

2. A gripping device (76) according to claim 1, wherein the first direction is an upward direction and wherein the second direction is a downward direction.

3. A gripping device (76) according to claim 1, wherein the lock member comprises a ratchet or a brake.

4. A gripping device (76) according to claim 1, wherein sliding motion of the arms (78) relative to the base frame (62) is achieved exclusively by the force of gravity.

5. A gripping device (76) according to claim 1, wherein the position of the arms (78) relative to the base frame (62) is not controlled by a computer or a control unit.

6. A gripping device (76) according to claim 1, wherein the gripping member (86) is a needle gripper.

7. A gripping device (76) according to claim 1, wherein the gripping member (86) releasably attaches to the preform upon contact with the top surface (75) of the preform.

8. A gripping device (76) according to claim 1, wherein each arm (78) is slidably arranged in a bracket or fixture mounted on the base frame (62).

9. A gripping device (76) according to claim 1, wherein the base frame (62) is suspended from a lifting device such as a crane or a hoist.

10. A gripping device (76) according to claim 1, wherein the base frame (62) further comprises one or more pivot connectors adapted for being received in a socket member attached to a wind turbine blade mould.

11. A method of transferring a preform for a wind turbine blade, the method comprising suspending a gripping device (76) according to claim 1 over the preform, lowering the gripping device (76) towards a top surface (75) of the preform until one or more of the gripping members (86) engage the top surface (75) of the preform, raising the gripping device (76) with the engaged preform, arranging the engaged preform within a wind turbine blade mould, and disengaging the preform.

12. A method of transferring a preform for a wind turbine blade according to claim 11, wherein one or more of the arms (78) of the gripping device (76) are pushed upwards relative to the base frame (62) by the engaged preform top surface (75) during the step of lowering the gripping device (76).

13. A method of transferring a preform for a wind turbine blade according to claim 11, wherein the vertical position of one or more arms (78) of the gripping device (76) relative to the base frame (62) changes during the lowering step.

14. A method of transferring a preform for a wind turbine blade according to claim 11, wherein downward movement of one or more of the arms (78) relative to the base frame (62) is prevented by the lock members.

15. A method of manufacturing a wind turbine blade part, the method comprising: manufacturing one or more preforms of a wind turbine blade part in a preform mould (71), transferring each preform to a blade mould using the method of claim 11, infusing resin into the blade mould, curing or hardening the resin in order to form the blade part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0070] The invention is explained in detail below with reference to embodiments shown in the drawings, in which corresponding components are identified by the same reference numerals, wherein

[0071] FIG. 1 shows a wind turbine,

[0072] FIG. 2 shows a schematic view of a wind turbine blade,

[0073] FIG. 3 shows a schematic view of an airfoil profile through section I-I of FIG. 4,

[0074] FIG. 4 shows a schematic view of the wind turbine blade, seen from above and from the side,

[0075] FIG. 5 is a perspective drawing of a blade mould for producing a wind turbine shell part according to the present invention,

[0076] FIG. 6 is a perspective drawing of a base frame of a gripping device according to the present invention,

[0077] FIG. 7 is a perspective drawing of a gripping device according to the present invention,

[0078] FIG. 8 is an enlarged perspective view of a gripping member and a lock member according to the present invention,

[0079] FIG. 9 is a perspective view of a socket arrangement for mounting on a blade mould according to the present invention,

[0080] FIG. 10 is a schematic view of different steps of a method of transferring a preform for a wind turbine blade according to the present invention, and

[0081] FIG. 11 is a schematic drawing illustrating the arrangement of a preform in a blade mould using the gripping device of the present invention.

DETAILED DESCRIPTION

[0082] FIG. 1 illustrates a conventional modern upwind wind turbine 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.

[0083] FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to the invention. The wind turbine blade 10 has the shape of a conventional wind turbine blade 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] FIGS. 3 and 4 depict parameters which are used to explain the geometry of the wind turbine blade according to the invention. FIG. 3 shows a schematic view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use—i.e. during rotation of the rotor—normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber (or suction side camber) and lower camber (or pressure side camber), which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

[0088] Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position d.sub.f of the maximum camber f, the maximum airfoil thickness t, which is the largest diameter of the inscribed circles along the median camber line 62, the position d.sub.t of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c. Thus, a local relative blade thickness t/c is given as the ratio between the local maximum thickness t and the local chord length c. Further, the position d.sub.p of the maximum pressure side camber may be used as a design parameter, and of course also the position of the maximum suction side camber.

[0089] FIG. 4 shows other geometric parameters of the blade. The blade has a total blade length L. As shown in FIG. 3, the root end is located at position r=0, and the tip end located at r=L. The shoulder 40 of the blade is located at a position r=L.sub.w, and has a shoulder width W, which equals the chord length at the shoulder 40. The diameter of the root is defined as D. The curvature of the trailing edge of the blade in the transition region may be defined by two parameters, viz. a minimum outer curvature radius r.sub.o and a minimum inner curvature radius r.sub.i, which are defined as the minimum curvature radius of the trailing edge, seen from the outside (or behind the trailing edge), and the minimum curvature radius, seen from the inside (or in front of the trailing edge), respectively. Further, the blade is provided with a prebend, which is defined as Δy, which corresponds to the out of plane deflection from a pitch axis 22 of the blade.

[0090] As illustrated in FIG. 5, a manufacturing process for manufacturing a blade part, such as a blade half, may involve laying a number of preforms 98a, 98b, 98c in a blade mould 96. For example, the preforms 98a, 98b, 98c are used for a blade section starting from the root end of the blade, such as the root region. The preforms 98a, 98b, 98c are arranged in the blade mould cavity 97, usually together with additional fibre material 94. Then, resin is infused to the blade mould cavity 97, which is subsequently cured or hardened in order to form the blade part, such as a blade half.

[0091] FIG. 6 illustrates a base frame 62 for a gripping device of the present invention. The base frame 62 may advantageously be suspended from a lifting device such as a crane or a hoist (not shown). The base frame of FIG. 6 comprises a plurality of vertically extending beams 64, a plurality of horizontally extending beams 66 in the longitudinal direction of the base frame 62, and a plurality of horizontally extending beams 68 in the transverse direction of the base frame 62.

[0092] Two horizontally extending sheath members 70 are arranged to receive respective angled support members 72, each support member 72 carrying a pivot connector 74 in the form of a ball member at its distal end. The pivot connector 74 is adapted for being received in a socket member 77 attached to a wind turbine blade mould of the type illustrated in FIG. 9. The socket member 77 may be affixed to a pole member 79 for attachment to a blade mould. Thus, when the preform held by the gripping device is suspended above a blade mould, one or more of the pivot connectors 74 may be received in one or more socket members 77 attached to the blade mould, such that the perform can be pivoted (turned) by simply lowering the same with a crane, without the need for further turning devices.

[0093] FIG. 7 illustrates an embodiment of the gripping device 76 of the present invention for lifting a preform for a wind turbine blade from a preform mould. The gripping device 76 comprises a base frame 62 of the type illustrated in FIG. 6 and a plurality of arms 78 slidably mounted on the base frame 62. The arms 78 may be mounted to the base frame 62 via one or more horizontally extending transverse support members 80. Alternatively, the arms could be mounted directly on the frame 62, for example on the horizontally extending beams 68 in the transverse direction of the base frame 62.

[0094] Each arm 78 has a proximal end 82 and a distal end 84, as also seen in the enlarged with of FIG. 8. The gripping device 76 further comprises a plurality of gripping members 86, such as needle grippers, for gripping a top surface of the preform, each gripping member being attached to the distal end 84 of at least one of the arms 78, either directly or via a connection member 88. The needle gripper 86 preferably releasably attaches to the preform upon contact with the top surface of the preform.

[0095] Each arm 78 also comprises a lock member 90, each lock member 90 for allowing sliding motion of the arm 78 relative to the base frame 62 in an upward direction while preventing sliding motion of the arm relative to the base frame in a downward direction. The lock member 90 may comprise a ratchet or a brake system. As best seen in FIG. 10, each arm 78 is individually slidable relative to the base frame 62. Each arm 78 may be slidably mounted within a slot 91 of a fixture 92 arranged on the base frame 62.

[0096] FIG. 10 illustrates a method of transferring a preform 73 for a wind turbine blade according to the present invention. The method comprises suspending a gripping device 76 according to the present invention over the preform 73, for example from a crane (not shown). In the illustrated embodiment the preform is manufactured in a preform mould 71 and is to be transferred to a blade mould for producing a shell half of a wind turbine blade. The gripping device 76 is lowered towards a top surface 75 of the preform 73 until a first gripping member 86a engages the top surface 75 of the preform 73; see FIG. 10b. the gripping device is further lowered until a second gripping member 86c engages the preform top surface 75; FIG. 10c. Meanwhile, the arm 78a carrying the first, already engaged gripping member 86a is moved upwards relative to the base frame as upward movement of the arms relative to the base frame 62 is allowed. The arms of the gripping device 76 are thus pushed upwards relative to the base frame 62 by the engaged preform top surface during the step of lowering the gripping device.

[0097] In FIG. 10d, also the last gripping member (needle gripper) 86 has engaged the top surface 75 of the preform 73, while the other two arms 78a, 78c have moved further upwards relative to the base frame 62. Subsequently, as seen in FIG. 10e, the gripping device is raised with the engaged preform for transporting and arranging the engaged preform 73 within a wind turbine blade mould (not shown). Downward movement of the arms 78a-c relative to the base frame 62 is prevented by the lock members. The upward direction U and the downward direction D are indicated in FIG. 10e. Thus, as seen in FIGS. 10a-e, the positions of the arms 78a-c relative to the base frame 62 is set by the top surface geometry of the preform.

[0098] FIG. 11 illustrates an arrangement of a preform in a blade mould using the gripping device of the present invention. The gripping device 76 comprises a pivot connector 74 in the form of a ball member 74. The pivot connector 74 is adapted for being received in a socket member 77 attached to an edge of a wind turbine blade mould 96 for moulding a blade shell half. FIG. 11 shows the blade mould 96 seen from its root end. The socket member 77 is affixed to a pole member 79 at the edge of the blade mould. The pole member 77 may be height-adjustable. In FIG. 11a, the preform 73 held by the gripping device 76 is suspended above the blade mould 96 using a rope or strap 89 held by a crane or similar lifting device (not shown). The ball member 74 is received in the socket 77 and subsequently the gripping device is further lowered to tilt the preform and to arrange the preform in the mould cavity 97 (FIG. 11b). Thus, the perform can be pivoted or tilted by simply lowering it using the lifting device, without the need for further turning devices.

[0099] The invention is not limited to the embodiments described herein and may be modified or adapted without departing from the scope of the present invention.

List of Reference Numerals

[0100] 2 wind turbine [0101] 4 tower [0102] 6 nacelle [0103] 8 hub [0104] 10 blade [0105] 14 blade tip [0106] 16 blade root [0107] 18 leading edge [0108] 20 trailing edge [0109] 22 pitch axis [0110] 30 root region [0111] 32 transition region [0112] 34 airfoil region [0113] 40 shoulder/position of maximum chord [0114] 50 airfoil profile [0115] 52 pressure side [0116] 54 suction side [0117] 56 leading edge [0118] 58 trailing edge [0119] 60 chord [0120] 62 base frame [0121] 64 vertical beams [0122] 66 horizontal beams, longitudinal direction [0123] 68 horizontal beams, transverse direction [0124] 70 sheath member [0125] 71 preform mould [0126] 72 angled support member [0127] 73 preform [0128] 74 pivot connector [0129] 75 top surface of preform [0130] 76 gripping device [0131] 77 socket member [0132] 78 arms [0133] 79 pole member [0134] 80 transverse support members [0135] 82 proximal end of arm [0136] 84 distal end of arm [0137] 86 gripping member [0138] 88 connection member [0139] 89 strap [0140] 90 lock member [0141] 91 slot [0142] 92 fixture [0143] 94 fibre material [0144] 96 blade mould [0145] 97 blade mould cavity [0146] 98 preform [0147] c chord length [0148] d.sub.t position of maximum thickness [0149] d.sub.f position of maximum camber [0150] d.sub.p position of maximum pressure side camber [0151] f camber [0152] L blade length [0153] r local radius, radial distance from blade root [0154] t thickness [0155] Δy prebend