Field of the Invention

The present invention relates generally to the field of wind turbines, and more particularly to a working platform system for a wind turbine, the wind turbine comprises a wind turbine tower, a nacelle arranged on top of the wind turbine tower, and a rotatable rotor with at least two wind turbine blades, where the working platform system comprises a working platform having a platform base, a platform floor and a railing attached to the platform base.

The invention also relates to a method for mounting a working platform system for a wind turbine, the wind turbine comprises a wind turbine tower, a nacelle arranged on top of the wind turbine tower, and a rotatable rotor with at least two wind turbine blades, where the working platform system comprises a working platform having a platform base, a platform floor and a railing attached to the platform base, where the method comprises the steps of:

assembling the platform base, the platform floor and the railing at ground lev- el,

- bringing the assembled platform base, the platform floor and the railing in a position close to the nacelle cover.

Background of the Invention

Today, a working platform is used for effecting work in relation to the cover of the nacelle or the opening in the nacelle which is hanging in a crane. The system is difficult to use in harsh weather. Moreover, it is difficult to secure the platform in relation to the nacelle when working on different elements at the nacelle, e.g. when mounting the bearings.

There is a general desire to obtain more secure working conditions for people working at the nacelle. This security could be obtained when it is possible to have a more stable platform. There is also a desire to obtain a working platform which may be used also during harsh weather conditions in order to effect a more efficient work. Especially in connection with mounting of moment bearings, there has been a desire to have a more secure platform at the upwind side of the nacelle where the moment bearing is mounted in the main structure through an opening in the cover of the na- celle.

A system and a method of the type mentioned by way of introduction have been disclosed in US 2013/0074337. However this document does not disclose beams for attaching the working platform to the main structure of the nacelle. Object of the Invention

It is an object of the present invention to provide a working platform system which is more efficient to use and a method for mounting such working platform system which makes it possible to provide the working platform in an efficient way.

Description of the Invention

This object is obtained with a working platform system mentioned by way of introduction which is peculiar in:

that the working platform system further comprises:

first fastening means arranged at the working platform,

first counterpart fastening means at the main structure of the nacelle, and that first fastening means and first counterpart fastening means are arranged for re- leasable cooperation to releasable fasten the working platform to the main structure of the nacelle and

- that the working platform system further comprises two main beams,

- that said main beams are provided with first connection means arranged in a first part of each main beam for releasable cooperation with first counterpart connection means in the main structure of the nacelle to releasable fasten the main beams to the main structure of the nacelle, with the first part of each main beam arranged inside the nacelle and with a second part of each main beam extending outside an opening in a nacelle cover,

- that the two main beams are provided with second connections means arranged in the second part of each main beam for releasable cooperation with second counterpart connection means in the platform base to releasable fasten the platform base to the main beams, and that the first fastening means and the first counterpart fastening means comprise the first connection means and the first counterpart connection means.

The method according to the present invention is peculiar in that the method further comprises the steps of:

- providing first fastening means in the working platform,

providing first counterpart fastening means in the main structure

providing two main beams either at ground level or in the nacelle,

possible hoisting the main beams from ground level to the nacelle,

arranging the main beams with a first part of each main beam arranged inside the nacelle and with a second part of each main beam extending outside an opening in a nacelle cover,

- bringing the first fastening means and the first counterpart fastening means into a releasable engagement by releasable fastening the main beams to the main structure of the nacelle by means of first connection means arranged in the first part of each main beam and arranged for releasable cooperation with first counterpart connection means in the main structure of the nacelle,

hoisting the assembled platform base, the platform floor and the railing to the nacelle,

arranging the platform base on the second parts of the main beams extending outside an opening in a nacelle cover, and

securing the engagement between the first fastening means and the first counterpart fastening means and thereby releasably fastening the working platform to the main structure of the nacelle by releasable fastening the platform base to the main beams by means of second connection means arranged in the sec- ond part of each main beam and arranged for releasable cooperation with second counterpart connection means in the platform base.

With the present invention it is possible to prepare the working platform at ground level and after this hoist the working platform to the nacelle.

The working platform is arranged in front of the nacelle by a crane. Technicians who are in the nacelle can position the working platform, e.g. by grabbing straps being mounted on the working platform or directly by gripping the platform and guiding the fastening means into engagement. For this, boat hooks are normally used.

When aligning the fastening means it is possible to bring the fastening means into engagement whereby the working platform is mounted in a fixed position in relation to the main structure of the nacelle.

Different embodiments for fastening means can be used. This will be explained later.

A common advantage of all fastening means is that they are intended for releasable cooperation. Hereby, the fastening can be brought into engagement in order to fasten the working platform to the main structure of the nacelle, and after the platform has been used it is possible in an easy way to disengage the fastening means and bring the working platform to ground level, where after it is easy to demount or to reuse the working platform in connection with another wind turbine.

The present invention makes it possible to obtain the advantages of assembling the working platform at ground level and also the advantages of having a working platform which is fixed to the main structure of the nacelle when the working platform is used.

Typical work to be done from the working platform would be maintenance, mounting and demounting of moment bearings. However, also work on generators and other equipment in the nacelle can be effected from the working platform.

Accordingly, the working platform would normally be arranged in front of the nacelle in a position in front of the opening through which the main shaft is extending when the wind turbine is in use. However, it is also possible to have an embodiment in which the working platform is attached in relation to other openings in the nacelle structure where work is intended to be formed through the opening.

After having brought the first fastening means and the first counterpart fastening means into engagement, there will be effected a securing of the engagement. Hereby, it is ensured that there will not be any accidental and unintended release of the en- gagement during use. Accordingly, there will be obtained a secure fixation of the working platform to the main structure of the nacelle. However, the securing means used for securing the engagement between the fastening means would be releasable. Different securing means will be explained in the following.

The working platform is especially efficient due to the use of the two main beams fastened to the main structure of the nacelle. The main beams may be stored in the nacelle or may be hoisted to the nacelle when mounting a working platform.

The two main beams may be positioned in the correct way with technicians being inside the nacelle during the positioning of the main beams. The main beams will be attached to the main structure of the nacelle as the first part of a main beam is connected to the main structure of the nacelle.

When the two main beams are attached through the first part of the main beams, the second of each main beam will extend outside the opening in the nacelle cover. The opening might be the opening in which the moment bearing is to be mounted.

After having arranged the main beams with the second part extending outside the nacelle it is possible with the crane to hoist the working platform system which has been assembled at ground level. The working platform system is hoisted and arranged with the platform base in contact with the second part of the main beams. After this, the working platform system is connected to the second part of the main beams, e.g. with use of bolts or security pins or a combination thereof.

In this situation, bolts will constitute the security means which, in a detachable way, makes it possible to have secure engagement between the beams and the working platform and the main structure respectively.

When using the main beams it is possible to consider that the main beams constitute a part of the nacelle. In this situation, the fastening means would be considered to be the second connection means arranged in the second part of the main beam and which in a releasable way cooperate with the second counterpart connection means in the platform base. However, in a situation where the main beams are considered to be a part of the working platform, then the fastening means would be constituted of the first connection means which are in the first part of each main beam and which are intended for releas- able cooperation with the first counterpart connection means in the main structure of the nacelle.

As occurring above, one could consider the main beams as a part of the nacelle or a part of the working platform. In both situations, the embodiment will benefit of the advantages already explained above, namely to have an easy and quick procedure to attach the working platform to the main structure of the nacelle.

After the attachment, one would normally secure the main beams to the working platform and the nacelle by bolts. However, also other security members, like security pins etc., may be used for securing the individual elements together during use of the working platform.

The platform base has two channels in which the parallel second parts of the two main beams can enter. After the main beam parts are arranged in the channels, the connection is provided by bolting the parts together.

After this, the working platform may be provided with a cover. Otherwise, a cover might be provided on the sides of the working platform at ground level. This will depend on the weather conditions.

The two main beams will be identical and will be mounted one by one according to a well-defined procedure.

If the main beam is hoisted to the nacelle, then the hoisting will be effected in the following way.

In both ends of the beams a strap is mounted. The crane must grab the second end of the main beam, and the strap in the first end of the beam is going to be caught by the technicians which are positioned in the nacelle. This catching could be effected by the use of a boat hook. When the end of the beam is near the main frame of the nacelle, then the main beam is orientated into the correct position. This could be assisted by having signs on the beam. These signs may e.g. state that it is a left hand or right hand side beam and having a marking for the upwards side as well as a marking for the direction against the center.

The first part of the main beam is guided into the opening in the main frame concurrently with the crane lowering the second part. This is effected until the beam is substantially horizontal and, thereby, able to be slided into the final position in the nacelle. In order to obviate the risk of damaging the nacelle cover in the front of the opening in the nacelle there could be provided smaller support beams in the opening. These support beams will ensure that the main beams do not come into contact with the nacelle cover.

The main beams are orientated in such a way that the second parts extend outside the nacelle and are parallel.

The distance between the two beams will be fixed and determined by the fixation points inside the nacelle and the form of the main beams.

A connection could be effected by using holes already provided in the main structure of the nacelle and using bolts for fixation of the main beams to such existing holes. Alternatively, specific mounting holes may be provided in the main structure of the nacelle.

After the main beams are positioned and fastened, the working platform in assembled form is hoisted to the nacelle.

A crane hooking to four straps arranged in the assembled working platform and tag lines are controlled by technicians on the ground. When the platform comes close to the nacelle then technicians being in the nacelle would use boat hooks to catch the rope and guide the platform to slide over the two main beams which enter into channels in the platform base. When the platform is in the final position the platform may be temporarily fastened with straps to the nacelle. Then the crane can be unhooked. After this, the platform is connected to the main beams by use of bolts entering through holes in order to fixate the platform base to the main beams.

It is preferred that the platform railing is arranged and three sides leaving one side opened for work at the nacelle. The platform has removable sides which can be demounted when needed. In such situation, the railing can be stored inside the nacelle.

Moreover, it is preferred that the platform has a doubled floor in the center of the platform. Hereby, different heights of the platform could be obtained depending of the type of work going on at the nacelle. The removable floor can be stored in the platform or in the nacelle when not used.

The working platform system could also comprise a roof. The roof may be attached to the railings of the platform.

Alternatively, the roof may be connected directly to the nacelle. The roof will then be mounted through openings in the nacelle cover. Support legs will then enter through the openings and be attached to the main part of the nacelle.

When using a roof it is preferred that it can be adjusted in height in order to obtain the smallest gab between the roof and the nacelle cover when the roof is arranged directly on the nacelle.

The construction of the working platform is explained primarily in connection with the use of two main beams. However, also embodiments of the platform where hooks are used will have the same structure of the working platform. In such situation, the working platform will not have the channels in the platform.

Instead, the platform may have hook members arranged at the platform base. Such hooks would constitute the first fastening means. However, the working platform system could also have further fastening means in the working platform and further counterpart fastening means in the main structure of the nacelle. Such further fastening means and further counterpart fastening means could also be hooks. Such further fastening means could e.g. be provided in the platform base or in the platform floor or in the railing attached to the platform base.

Besides the fastening means mentioned above, it is also possible to have other embodiments. E.g. magnets may be used as fastening means. With the magnet-technology today it is possible to have sufficient strength to obtain a secure attachment of a working platform to the main structure of the nacelle. The magnets could be permanent magnets or electro magnets.

According to a further embodiment, the system according to the present invention is peculiar in that each main beam comprises a foot arranged at each end of the first part of the main beam and that said feet are provided with the first connection means.

When the system is based on the main beams it is preferred that the feet are arranged in order to have a precise and well defined attachment surface between the beam and the platform base or the main structure of the nacelle. It would often be that the main structure of the nacelle would be a part of the floor in the nacelle.

According to a further embodiment, the system according to the present invention is peculiar in that the second parts of the main beams are parallel.

It is already mentioned that at least the part extending outside the nacelle would be parallel. This makes it easier that a working platform is slid over the parallel beams being attached to the nacelle.

According to a further embodiment, the system according to the present invention is peculiar in that the railing is provided with third connections means for releasable cooperation with third counterpart connection means in the platform base to releasable fasten the railing to the platform base.

Having third connection means in the railing cooperating with third counterpart connection means in the platform base it is possible to dismount the platform for easy storing when not in use. Also, it is possible with such construction to provide different railings with one and same platform base. Hereby it is possible to adapt a working platform system to different kinds of nacelles and to different openings.

According to a further embodiment, the system according to the present invention is peculiar in that at least in a central part of the platform there is provided a double floor.

With the double floor it is possible to have a correct working position for different tasks to be effected. The double floor may be arranged in relation to the platform base in an adjustable way in order to have an adjustable height for the upper floor.

According to a further embodiment, the system according to the present invention is peculiar in that a connection eye is arranged at each end of a main beam for mounting a strap used for hoisting and lowering the main beam to the nacelle.

With a connection eye it is easy to hoist and lover the main beam to the nacelle if it could not be stored in the nacelle when the platform is not in use. One eye could be attached to a strap in a hook on a crane and the other eye could be attached to a strap which is grabbed by a technician in the nacelle when the main beam is in position outside the opening.

Then the end of the main beam could be swung into the nacelle, and by lowering the hook to the other eye the main beam could be swung and slid into the nacelle to be correctly positioned.

The sliding movement could be assisted by the technicians being in the nacelle who would effect a pull in the strap attached to the eye in the end of the main beam which is first swung into the nacelle.

According to a further embodiment, the system according to the present invention is peculiar in that the first and second connection means and the first and second counterpart connection means comprise thread and bolt connections. The first and second connection means and the counterpart connection would normally be thread and bolt connections. Also other connections are possible. However, the use of bolt connection is common in the nacelle and, therefore, the use of thread and bolt connections will have the advantage that tools are already present in the nacelle for providing the connection.

According to a further embodiment, the system according to the present invention is peculiar in that the third connection means and the third counterpart connection means comprise telescopically connected tube profiles provided with holes and bolts for entering through said holes.

It is advantageous that the railing could be dismounted from the platform base. When having third connection means and third counterpart connection means being telescopically connected it is possible to have the element telescopically pushed into each other during storage. Alternatively, the telescopically engagement could only be a partially engagement of a part of the tubes which are used for mounting the railing to the platform base. This is commonly known to provide different diameters in the tubes and, hereby, a secure and correct engagement between different tube elements in the construction will be obtained.

It should be mentioned that the railing not necessarily needs only to be constructed from one single tube profile. The height of the railing could be adjusted by use of more interconnected tube profiles.

When securing the tubes to each other aligned holes would be used for receiving a bolt. This bolt could be secured by means of a screw or, alternatively, security pins as explained above.

According to a further embodiment, the method according to the present invention is peculiar in that the method further comprises the steps of:

- securing the engagement between the first fastening means and the first counterpart fastening means. The step of effecting a securing of the engagement between the first fastening means and the first counterpart fastening means would normally be effected, However, if a system is arranged with fastening means which are self-locking due to gravity, the securing step could be omitted.

This method steps will be necessary to effect in connection with the embodiment explained above which is based on the use of main beams. The method for mounting the working platform system will depend on the position of the main beams whether they are arranged in the nacelle on beforehand or whether they are arranged at ground level.

According to a further embodiment, the method according to the present invention is peculiar in that the step of hoisting the main beams from ground level to the nacelle comprises the steps of:

attaching a strap to each end of a main beam,

hoisting the main beam to the nacelle through the strap attached to the end of the second part of the main beam,

grabbing the strap attached the end of the first part of the main beam - by a person placed in the nacelle,

guiding the first end of the main beam into the opening in the nacelle cover while lowering the second part until the main beam is horizontal,

sliding the main beam to its final position before effecting the fastening step, and

- -repeating the above steps for the second main beam.

The benefit of the swinging and sliding of the main beam to the final position has been explained above. Also here, it should be noted that this method step is only necessary in situations where the main beam are stored at ground level or in a situation where a working platform system should be mounted for the first time in a wind turbine. Accordingly, this method step could be effected only once and, after the dismounting of the working platform, the main beams may be stored in the nacelle for later use. According to a further embodiment, the method according to the present invention is peculiar in that the method further comprises the steps of:

providing a cover for covering three sides of the platform, and

attaching the cover to the railing either before or after hosting the assembled platform base, the platform floor and the railing to the nacelle.

A cover could normally be usable in order to have more extended use of the working platform. The three sides and the roof would be covered and, then, leaving one side opening facing the nacelle and which could be used for work. Accordingly, the technicians, who should effect the work, could work in an efficient way even under harsh weather conditions.

Description of the Drawing

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. 1 shows a perspective view of a wind turbine,

Fig. 2 shows a perspective view of an operating a platform system not being a part of the present invention,

Fig. 3 shows a perspective view corresponding to fig. 2 to illustrate an embodiment for a working platform system according to the present invention,

Fig. 4 shows a partial perspective view of a detail of the working platform illustrated in figs. 2 and 3,

Fig. 5 shows a partial view of another detail of the working platform illustrated in figs. 2 and 3,

Fig. 6 shows a partial view of a nacelle provided with main beams for use in the second embodiment illustrated in fig. 3,

Fig. 7 shows a partial side view seen from the outside of the nacelle illustrating the main beams extending out from the nacelle,

Fig. 8 shows a partial perspective view seen from the front side with a working platform system mounted on a nacelle,

Fig. 9 shows a partial view seen from the front side of the nacelle illustrating a roof section to be used over the working platform, and Fig. 10 shows a schematic view illustrating the hoisting of a working platform from ground level to the nacelle.

Detailed Description of the Invention

In the following text the figures will be described one by one, and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure. Position number list

1 Wind turbine

2 Wind turbine tower

3 Foundation

4 Nacelle

5 Rotor hub

6 Wind turbine rotor blade

7 First end of blade (root end)

8 Second end of blade (tip end)

9 Working platform system

10 Working platform

11 Platform base

12 Platform floor

13 Railing

14 First fastening means

15 Hook member

16 Rod

17 Rod member

18 First counterpart fastening means

19 Basis portion

20 Hole

21 Upper portion

22 Open space

23 Outer floor portions

24 Central floor portion 25 First Tube profiles

26 Second tube profiles

27 Horizontal tube profiles

28 Main beams

29 First part of main beam

30 Second part of main beam

31 First connection means/feet

32 Bolt

33 Opening

34 Hole

35 Main structure

36 Surface/floor

37 Bracket

38 Bolt

39 Hole

40 Moment bearing

41 Roof section

42 Frame

43 Legs

44 Feet

45 Leg

46 Opening

47 Hatch

48 Covering

49 Ground level

50 Crane

51 Hook

52 Strap

53 Hole

Detailed Description of the Invention

In fig. 1, a typical wind turbine 1 is seen comprising a tower 2 installed at a foundation 3. At the top of the tower 2, a nacelle 4 comprising e.g. a gearbox, a generator, and other components is seen. At the nacelle 4, a shaft for carrying a rotor comprising a hub 5 and three wind turbine rotor blades 6 is also installed. The rotor blades 6 are arranged at the hub 5 at a first end 7 called the root end of the rotor blade 6. The second end 8 of the rotor blades 6 constitutes a tip end.

Fig. 2 shows a working platform system 9 not being apart of the present invention. The working platform system comprises a working platform 10. The working platform 10 comprises a platform base 11, a platform floor 12 and a railing 13 attached to the platform base 11.

The working platform system furthermore comprises first fastening means 14 arranged at the platform base 1 1. The first fastening means 14 comprise a hook member 15 consisting of a rod 16 which is attached in the platform base 11 and connected therewith with connection means (not illustrated).

At the free end of the rod 16 extending from the platform base, a downwardly orientated rod member 17 is arranged in order to establish the hook 15.

The hook 15 cooperates with first counterpart fastening means 18 which are arranged to be attached to the main structure of the nacelle. The first counterpart fastening means comprise a basis portion 19 provided with holes 20 which are intended for the passage of a bolt through which the first counterpart fastening means are attached to the nacelle. Furthermore, the first counterpart fastening means comprise an upper portion 21 being thinner than the basis portion 19. Hereby, an open space 22 is provided between the upper portion 21 and a surface of the main part of the nacelle to which the first counterpart fastening means 18 is attached.

This open space 22 constitutes an eye part in which the rod 19 could be arranged. In this way, the working platform 9 will be hooked to the main structure of a nacelle.

The working platform 9 comprises a double floor having a first outer floor portions 23 and a central floor portion 24. The central floor portion 24 is arranged in a way that it can be raised and lowered by height adjusting means (not shown). The platform base 11 comprises first tube profiles 25 which are intended to hold a second tube profiles 26 constituting a part of the railing 13. The tube parts could be telescopically entered into each other and they are provided with holes 35 (see fig. 5) in which thread and bolts are used to secure the railing 13 to the platform base 11.

The second tube profile 26 would be substantial vertical in use and is interconnected with substantially horizontal tube profiles 27 in order to create a secure railing. The railing is provided with three sides leaving one side open which would face the nacelle.

The working platform in fig. 3 corresponds to the working platform in fig. 2 and explanation for the parts of the working platform which is similar will not be explained in connection with fig. 3. The embodiment of the working platform system illustrated in fig. 3 comprises fastening means which differs from the fastening means illustrated in fig. 2.

Fig. 3 discloses first fastening means 14 in the form of two main beams 28. The main beams 28 have a first part 29 and a second part 30. In the first part 29, first connection means 31 are arranged. The first connection means are arranged in the form of feet at the lower side of the main beams 28. These first connection means are intended for cooperation with first counterpart connection means in the main structure of the nacelle (explained in connection with fig. 6) whereby the main beams could be releasa- ble fastened to the main structure in the nacelle.

The first counterpart connection means would be provided in form of holes 53 cooperating with bolts 32 which are screwed through the main beam and the feet as illustrated in fig. 3. When the first part 29 of the main beam 28 is mounted in the nacelle the second part 30 would extend outside an opening 33 in the nacelle 4. The two sec- ond parts 30 are arranged with a parallel extension as illustrated in Fig. 6.

In the second part 30 of each main beam second connection means in form of holes 34 are arranged. The holes 34 are intended for receiving bolts (not shown) which are used for connecting the second part 30 to the platform base 11. In the end of the main beams, the opening 53 is provided. A corresponding hole is arranged in the other end of the main beam (not visible) in the figure. The holes 53 will, during the lifting and mounting of the main beam from ground level to the na- celle, be used as eyes to which a strap is attached to each end of the main beam. The use of these straps and the holes is explained in the introductory part of the description. Separate eyes may alternatively be provided.

Figs. 6 and 7 illustrate the main beams 28 attached in the nacelle. Here, it is illustrated that the main structure 35 comprises a surface or a floor 36 and to this surface the first parts 29 of the main beams are attached by means of the screws 32. Fig. 6 illustrates the situation seen from above with a part of the nacelle removed for clarity reasons.

Fig. 7 illustrates the situation seen from outside and in a side view. It occurs that the second part 30 of the main beam 28 is arranged in a substantial horizontal orientation. Accordingly, this orientation would be adapted with the use of the feet 31 in order to accommodate the tilt of the nacelle.

Fig. 4 illustrates a partial view of the railing 13. Here, it is seen that the horizontal tube profiles 27 are connected with the vertical tube profile 26. Brackets 37 (only one illustrated) is attached to the vertical tube profile 26 and is used to support the ends of the horizontal tube profiles 27. The parts are connected with each other by means of bolts 38. Fig. 5 illustrates a partial view of the interconnection of a vertical tube profile 26 and a first tube profile 25 being a part of the platform base 1 1. The tube profiles 25,26 are telescopically entered into each other. Holes 39 (only one illustrated) are provided through the tube profiles in order to interconnect the tube profiles by means of thread and bolt connections.

Fig. 8 illustrates a partial view as seen from the front side illustrating the nacelle 4 on top of the tower 2 with a working platform 10 attached to the front side of the nacelle. Through the opening 33, a moment bearing 40 is seen which may be serviced by technicians being positioned on the platform floor 12. The railing is shown without any covering. However, a covering can be provided to cover the three side walls comprising the tube sections 27. Such covering may be attached to the horizontal tube section 27. Hereby, the technicians being positioned on the working platform 10 will be secured against harsh weather.

Fig. 9 illustrates a further embodiment with a roof section 41 for the working platform. The roof section can also be provided with a cover (not illustrated). The roof section 41 comprises a frame 42 which is provided with legs 43 having feet 44 for connection to the main structure 35 of the nacelle. Furthermore, legs 45 extend through openings 46 into the nacelle in order to provide attachment to other part of the main structure of the nacelle. In the nacelle 4, a hatch 47 is provided in the covering 48. Persons who should work on the working platform can go out through the hatch 47 and easily enter the working platform.

Fig. 10 illustrates a situation where a working platform 9 is being hoisted from ground level 49 to the nacelle. In this figure no taglines are arranged even though such tag- lines would be used in order to control the movement of the working platform during the hoisting and the positioning in front of the nacelle 4.

A crane 50 is used having a hook 51 which is attached to straps 52 connected with the working platform 9. The different steps for mounting the working platform 9 are explained in the introductory part of the description.

It is noted that the embodiment illustrated above is an example, and that modifications are possible. It is also possible to combine the features from different embodiments.