The present invention relates to a lifting harness for lifting a blade tip extension for a wind turbine blade. It relates further to a method using a lifting harness.

The lifting harness is disclosed and explained in relation to a lifting of a blade tip extension. The lifting harness could as well be used for lifting of other objects, which need to be aligned to the inclination of the element to which it is lifted up to or down to.

Wind turbine blades often need inspection, service, and maintenance.

Furthermore, they may be upgraded, for example with a tip protection and/or a tip extension. A tip segment of the rotor blade is the part of the blade which is exposed to maximum speed and therefore has a particular need to be repaired or replaced.

Mounting additional tip extensions to turbine blades is a way to increase the performance of existing wind turbines.

Devices have been proposed in order to lift up a blade tip extension to a turbine blade of a wind turbine to which the blade tip extension shall be installed.

For example, a blade sling apparatus for moving a blade tip has been proposed in US 9,488,156 B2.

In recent years, wind turbines have grown significantly in size and the outer shape of the rotor blades has changed to a complex structure. Not only the thickness and the width change from the hub end to the tip end and from the leading edge to the trailing edge. The blade may also be pre-bent, angled, and/or twisted. ln particular, a blade of a wind turbine is in many cases inclined with respect to the direction of gravity. This is considered to be necessary to avoid a contact between the blade and the tower of the wind turbine during operation. This makes it difficult to mount or dismount a blade tip extension on a tip of the turbine blade. In particular, the blade tip extension must be aligned to the inclination of the turbine blade during mounting. This complicates the mounting, requires additional working steps and even increases a risk that workers are injured during the procedure and a risk that the blade tip extension or the turbine blade are damaged due to misalignment

therebetween.

The object underlying the invention is to provide a lifting harness which facilitates the lifting and mounting for a blade tip extension.

This object is solved by a lifting harness for lifting a blade tip extension for a wind turbine blade according to claim 1.

In particular, the lifting harness comprises: a circumferential top harness band defining an opening for introducing the blade tip extension; a front anchor point and a back anchor point disposed spaced apart from each other on the top harness band; a circumferential bottom harness band; two front harness straps connecting the bottom harness band with a front anchor point portion of the top harness band at which the front anchor point is disposed, wherein the two front harness straps are connected to the bottom harness band at front junction sites spaced apart from each other; two back harness straps connecting the bottom harness band with a back anchor point portion of the top harness band at which the back anchor point is disposed, wherein the two back harness straps are connected to the bottom harness band at back junction sites spaced apart from each other; wherein a rear edge portion of the top harness band extending between the front anchor point portion and the back anchor point portion is shorter or longer than a front edge portion of the top harness band extending between the front anchor point portion and the back anchor point portion opposite to the rear edge portion.

The structure of the lifting harness is configured to at least substantially fittingly adapt to an outer shape of the tip extension blade. In other word, if the tip extension blade is correctly placed in the lifting harness, the above specified structure ensures that the tip extension blade is fittingly

accommodated in the lifting harness.

A part of the blade tip extension to be accommodated in the lifting harness basically comprises a tip, a front edge, a rear edge and two side surfaces (a front side and an opposite backside) extending between the front edge and the rear edge, respectively. The blade tip extension substantially extends along a longitudinal direction thereof, whereas the front edge, the rear edge, the front side, and the backside substantially extend parallel to the

longitudinal direction.

The rear edge of the blade tip extension is the edge, which faces the tower of a wind turbine when the tip extension is installed on the wind turbine. The front edge of the blade top extension is the opposite edge, which faces away from the tower in this situation. However, a pitch of mounted turbine blades may be variable. Usually, the rear edge is more tapered than the front edge, whereas the front edge comprises a more bulge-like shape.

With respect to the wording used in this application, the tip of the blade tip extension constitutes a bottom end of the blade tip extension in the longitudinal direction. This does not imply any technical features or characteristics.

Corresponding spatial denotations - as front edge, rear edge, front side, backside, bottom, top - are used with respect to the lifting harness as well, especially with respect to a spread-out configuration.

The tip of the blade tip extension is located near to the bottom harness band if the blade tip extension is suspended and/or lifted in the lifting harness. In particular, the tip may reside in a tip accommodating portion below the bottom harness band.

The lifting harness may be held for suspending and/or lifting at the two anchor points.

In terms of the present invention, lifting the blade tip extension encompasses lifting up and/or lifting down. For example, the blade tip extension may be already installed on the turbine blade but is demounted and lifted down in order to be repaired or to be replaced by another one.

As the two front harness straps are connected to the bottom harness point at two front junction sites spaced apart from each other, the two front harness straps and a part of the bottom harness band extending between the two front junction sites constitute a triangular strap structure. The same applies with regard to the back harness straps and the back junction sites. Hence, when the tip blade extension is suspended and/or lifted in the lifting harness, a force exerted from the blade tip extension to the bottom harness band can be reliably and evenly transferred from the bottom harness band to the top harness band and the two anchor points.

In a preferred embodiment a front edge portion and a back edge portion of the bottom harness band, which respectively extend between the back junction sites and the adjacent front junction sites, are shorter than a front surface portion of the bottom harness band extending between the front junction sites and than a back surface portion of the bottom harness band extending between the back junction sites, respectively;

In another preferred embodiment of the present invention, a first front junction site is provided at or near a front edge end of the bottom harness band, which is adapted to abut on a front edge of the blade tip extension, and a first back junction site is provided at or near the front edge end of the bottom harness band. Additionally or alternatively, a second front junction site is provided at or near a rear edge end of the bottom harness band, which is adapted to abut on a rear edge of the blade tip extension, and a second back junction site is provided at or near the rear edge end of the bottom harness band. This improves proper load transfer to the front and/or back harness straps.

More preferably, the first front junction site and the first back junction site can coincide in a single front edge junction site. In this case, the front edge portion of the bottom harness band consists only of the front edge junction site.

Additionally or alternatively, the second first front junction site and the second back junction site can coincide in a single rear edge junction site. In this case, the back edge portion of the bottom harness band consists only of the rear edge junction site. In a preferred embodiment the bottom harness band has a positive angle of inclination with regard to the top harness band when the lifting harness is spread out;

As noted above, the bottom harness band has a positive angle of inclination with regard to the top harness band when the lifting harness is spread out. In other words, the bottom harness band is not parallel to the top harness band then. Especially if the blade tip extension is placed in the lifting harness, the lifting harness is in the spread-out configuring.

An angle of inclination may be defined as positive if a smallest distance between the rear edge end of the bottom harness band to the top harness band is larger than a smallest distance between the front edge end of the bottom harness band to the top harness band if the lifting harness is spread out. In other words, in this case, an upper side of the bottom harness band, which primarily faces to the top harness band, rather faces the rear edge portion of the top harness band than the front edge portion of the top harness band.

Preferably, the positive angle of inclination between the bottom harness band and the top harness band is within a range from 5° to 25° when the lifting harness is stretched out, more preferably within a range from 6° to 16°, and most preferably between 9° and 15°.

Due said angle of inclination, lengths of the two front harness straps and/or the two back harness straps may be at least substantially the same.

Preferably, the lengths of the two front harness straps and/or the two back harness straps differ by less than 20 % with regard to the shortest of said lengths, more preferably by less than 5 %. This contributes to an even load distribution if the blade tip extension is suspended and/or lifted in the lifting harness.

With the rear edge portion of the top harness portion being shorter or longer than the front edge portion, at least one or preferably both anchor points are located nearer to or father away from a rear edge of the blade tip extension than to the front edge of the blade tip extension opposite to its rear edge.

In other words, due to the rear edge portion of the top harness band being shorter or longer than the front edge portion of the top harness band, at least one the anchor points is - or preferably both of are - laterally offset from a center of the top harness band towards its rear edge end or away from its rear edge end (seen in a lateral direction perpendicular to the longitudinal direction of the blade tip extension if the blade tip extension is

accommodated in the lifting harness). Due to the lateral offset of one or both anchor points, a predetermined spatial tilt of the longitudinal axis of the blade tip extension being suspended and/or lifted with respect to a vertical direction is ensured. By providing a different lateral offset for the both anchor points, the predetermined spatial tilt cannot only adjusted in a horizontal direction between the front edge and the rear edge but also in the horizontal direction between the front side and the backside.

In particular, the rear edge portion of the top harness band may be longer than the front edge portion of the top harness band. This structure is, for example, suitable for adjusting the predetermined spatial tilt if the anchor points are directly held by corresponding ropes or cables without using any part of the suspended and/or lifted blade tip extension above the top harness band as support area.

Alternatively, the rear edge portion of the top harness band may be shorter than the front edge portion of the top harness band. This structure is especially suitable for adjusting the predetermined spatial tilt if the anchor points are held by corresponding ropes or cables and using any part of the suspended and/or lifted blade tip extension above the top harness band as support area.

Preferably, the rear edge portion constitutes less than 40% of a

circumferential length of the top harness band, more preferably less than 35 %, most preferably less than 30 %.

Preferably, the rear edge portion constitutes more than 10 % of the circumferential length of the top harness band, more preferably more than 15 %, most preferably more than 20 %.

In a further, preferred embodiment of the present invention, a circumferential length of the bottom harness band is in a range from 15 % to 50 % of a circumferential length of the top harness band, more preferably from 25 % to 45 %, and most preferably from 30 % to 40 %.

Preferably, lengths of the two front harness straps and the two back harness straps are in a range from 90 % to 200 % of the circumferential length of the top harness band, respectively, more preferably from 105 % to 135 %, most preferably from 110 % to 130 %.

According to a preferred embodiment of the present invention, the lifting harness further comprises a front connecting means and a back connecting means, the front connecting means being configured for connecting the front anchor point to a common suspension point and the back connecting means being configured for connecting the back anchor point to the same common suspension point. The common suspension point may be, for example, a hook. Said hook may be a hook of a winch, which is installed on a working platform mounted on the turbine blade to which the blade tip extension shall be mounted or from which the blade tip extension shall be dismounted. More preferably, the front connecting means and the back connecting means comprise a sling, respectively. For example, the sling may comprise a rope and/or a cable. In particular, it may consist of a cope or a cable.

In particular, shackles may be used to attach the front connection means and the back connection means to the front anchor point and the back anchor point, respectively. In a more preferred embodiment of the present invention, the front

connecting means and the back connection means are configured such that at least one portion of the blade tip extension suspended and/or lifted in the lifting harness above the top harness band is used for constituting an additional support area and/or bearing area. For example, the above- mentioned slings may be configured to abut on respective portions at of the front side and the backside of the blade tip extension above the top harness band. Most preferably, the slings are sufficiently flexible such that the common suspension point is arranged at or near to the front edge of the blade tip extension above the top harness band and constitutes a deflection point regarding a load transfer direction.

In other words, one of the anchor points or both anchor points are laterally offset towards the rear edge in order to adjust the predetermined spatial tilt of the blade tip extension due to a gravitational force of the blade tip extension, if the latter is suspended and/or lifted in the lifting harness.

This is very advantageous because wind turbine blades are, as mentioned below, usually mounted with a predetermined angle of inclination with respect to the vertical direction such that their outer tip is located further away from the turbine tower in the horizontal direction than their inner end mounted in a hub. Flence, a distance between the tip and the tower in the horizontal direction is big enough that the tip does not collide to the latter even if the turbine blade is considerably bent towards the tower due to strong wind.

Preferably, the lifting harness is configured to ensure that the predetermined spatial tilt of the blade tip extension with respect to the vertical direction is within a range from 3° to 20°, more preferably from 5° to 10°, most preferably between 6° and 8°, by using the gravitational force of the blade tip extension, if the latter is suspended and/or lifted in the lifting harness. The vertical direction is defined by a direction of gravity. In particular, the predetermined spatial tilt may refer to the longitudinal axis of the blade tip extension.

With the lifting harness according to the present invention, the spatial tilt of the blade tip extension that shall be installed on an outer end of turbine blade is already adapted to a spatial tilt of a tip portion of the turbine blade to which the blade tip extension shall be attached.

Therefore, the blade tip extension can be correctly mounted on the tip portion (of the mounted turbine blade) by only lifting it up in the vertical direction at the right place. Additional adjustment, in particular additional adaption of the spatial tilt in one or more direction, is not necessary. Furthermore, the predetermined spatial tilt of the blade tip extension prevents jamming when the blade tip extension is mounted to or dismounted from the turbine blade.

Consequently, the lifting harness according to the present invention considerably facilitates the mounting and demounting of the blade tip extension and reduces a risk of damages and a risk of injuries of technicians during mounting and demounting.

Due to the above specified structure, the front edge of the tip extension blade abuts at least the front edge portion of the top harness band and the front edge portion of the bottom harness band. The rear edge of the tip extension abuts at least the rear edge portion of the top harness band and the rear edge portion of the bottom harness band.

Furthermore, in this situation, the front side the blade tip extension faces and/or abuts at least:

• The front harness straps,

• the front surface portion of the bottom harness band, and

• a part of the front edge portion of the top harness band and a part of the rear edge portion of the top harness band, respectively.

Correspondingly, in this situation, the backside of the tip blade extension faces and/or abuts at least:

• The back harness straps,

• the back surface portion of the bottom harness band, and

• another part of the front edge portion of the top harness band and

another part of the rear edge portion of the top harness band, respectively.

Preferably, the lifting harness comprises a front edge harness strap, which connects the front edge portion of top harness band and the front edge portion of the bottom harness band and is configured to face the front edge of the blade tip extension if the blade tip extension is placed in the lifting harness.

Additionally or alternatively, the lifting harness comprises a rear edge harness strap, which connects the rear edge portion of top harness band and the rear edge portion of the bottom harness band and is configured to face the rear edge of the blade tip extension if the blade tip extension is placed in the lifting harness. With the additional front and/or rear edge harness strap, a strength of the lifting harness is improved. Further, the load applied by the blade extension tip during suspending and/or lifting the latter is better distributed, the structural integrity of the lifting harness is improved, and higher loads can be carried by the lifting harness.

Most preferably, the lifting harness comprises a front support harness strap, which connects the front anchor point portion of the top harness band and the rear edge band. The front support harness strap may be connected to the rear edge band in a second upper quarter thereof. It may extend at least substantially along the vertical direction if the blade tip extension is suspended and/or lifted in the lifting harness. Most preferably, the lifting harness additionally or alternatively comprises a back support harness strap, which connects the back anchor point portion of the top harness band and the rear edge band. The back support harness strap may be connected to the rear edge band in a second upper quarter thereof. It may extend at least substantially along the vertical direction if the blade tip extension is suspended and/or lifted in the lifting harness.

Hereinafter, the top harness band, the bottom harness band, the front harness straps, the back harness straps, the front edge harness strap (if provided), the rear edge harness strap (if provided), the front support harness strap (if provided), and the back support harness strap (if provided) may be commonly denoted with the term "bearing structure".

According to a preferred embodiment of the present invention, the lifting harness further comprises a sack which is configured to receive at least a bottom portion of the blade tip extension, wherein a shape of the sack corresponds to an outer shape of the blade tip extension in the bottom portion.

More preferably, the bearing structure is formed integrally with the sack.

The sack ensures an additional protection of the bottom portion of the blade tip extension against environmental influences and damages. Furthermore, the sack can improve the structural integrity of the lifting harness.

In general, the bearing structure and the sack do not have to be made of the same material. However, the bearing structure and/or the sack are made of the same material in a preferred embodiment of the present invention.

The top harness band can constitute a top end of the sack. Vice versa, a top end of the sack may be regarded as the top harness band even if it is not additionally reinforced.

More preferably, the sack comprises a layered structure with at least two layers. Hence, the mechanical and/or environmental characteristics of the sack can be improved.

For example, an innermost layer of the sack can be made of a softer material than the other layer or the other layers of the sack. Therefore, the surface of the blade tip extension is better protected from damages.

Additionally or alternatively, the innermost layer is a low-friction layer. Hence, a friction between the sack and the surface of the blade tip extension is reduced. This facilitates removing the sack from the blade tip extension when the latter has been mounted on the turbine blade. For example, the

innermost layer can comprise or consist of felt. Most preferably, at least the innermost layer may separate the bearing structure from the surface of the blade tip extension.

Further, in a more preferred embodiment of the present invention, the sack comprises a waterproof layer and/or coating.

In a further, more preferred embodiment of the present invention, the sack comprises at least one drain opening in the tip accommodating portion. In particular, at least three drain holes may be provided in the tip

accommodating portion both at the back side of the and the front side of the sack, respectively.

The tip accommodating portion of the sack is a bottom end of the sack configured to accommodate the tip of the blade tip extension. For example, the tip accommodating portion of the sack may extend between a tip end of the sack and the bottom harness band in the longitudinal direction.

In a preferred embodiment of the present invention, a front surface protection sheet is disposed on an inner side of the front anchor point portion, the surface protection sheet protruding (in the longitudinal direction) away from the tip accommodating portion, wherein the surface protection sheet is configured to be interposed between the front anchor point and the surface of the blade tip extension if the blade tip extension is suspended and/or lifted in the lifting harness. The surface protection sheet protects said surface from damages due to the suspension at the front anchor point, for example by the shackles mentioned above.

Additionally or alternatively, preferably a back surface protection sheet is disposed on an inner side of the back anchor point portion, the surface protection sheet protruding (in the longitudinal direction) away from the tip accommodating portion, wherein the surface protection sheet is configured to be interposed between the back anchor point and the surface of the blade tip extension if the blade tip extension is suspended and/or lifted in the lifting harness.

Preferably, the lifting harness comprises at least one tagline loop. A tagline can be connected to the tagline loop and used for maintaining or further adjusting the spatial alignment of the blade tip extension during

suspending/lifting. This is advantageous, for example, in the case strong wind and/or wind gusts.

For example, the tagline loop(s) may be disposed on

• the front edge end of the top harness band,

• the rear edge end of the top harness band,

• the front edge end of the bottom harness band, and/or

• the rear edge end of the bottom harness band.

Specifically, a tagline connected to the tagline loop at the top harness band may be used from the working platform, if the blade extension tip is suspended and/or lifted from or to the working platform. At the other hand, a tagline connected to the tagline loop at the bottom harness band may be used for guiding the lifting harness from the ground.

More preferably, the lifting harness comprises at least four tagline loops. This further facilitates the handling as force can be exerted by taglines attached to the tagline loops in different directions.

In a further preferred embodiment according to the present invention, the lifting harness comprises at least one handle disposed on an outside of thereof.

For example, the handle(s) may be disposed on the outside thereof • at the top harness band, for example, in an at least substantially central position at the front side,

• at the top harness band, for example, in an at least substantially

central position at the backside,

• at the bottom harness band for example, in an at least substantially central position at the front side, and/or

• at the bottom harness band, for example, in an at least substantially central position at the backside.

More preferably, the lifting device comprises at least two handles, one at the front side of its outside and one at its backside.

Most preferably, the lifting device comprises at least four handles, wherein at least two handles are disposed on the front side and on the backside of the outside, respectively. The at least four handles considerably ease the handling of the tip extension during transport and movement, especially on the ground. If four handles are provided, the lifting harness can be handled by at least four persons. Disposing at least two handles both at the front side and on the backside makes it possible to distribute a weight to be carried by the operators evenly.

Preferably, the lifting harness has a working load limit in a range from 75 kg to 300 kg, more preferably from 100 kg to 200 kg. This is enough to safely suspend and/or lift typical blade tip extensions.

In a preferred embodiment of the present invention, the lifting harness has a weight of less than 15 kg, more preferably less than 10 kg, most preferably less than 5 kg.

The proposed lifting harness is a safe and easy solution for lifting a blade tip extension for a wind turbine blade. In addition, the lifting harness may serve as a protection harness for the tip extension during transporting and storage. The present invention further also relates to a method of using a lifting harness according to any one of the embodiments described above, comprising the step of suspending and/or lifting the lifting harness from a working platform, which is mounted on a turbine blade of a wind turbine. Any one of the embodiments of the lifting harness described above may be used. Features, embodiments and advantages described above with regard to the lifting harness correspondingly apply to the method using the lifting harness and vice versa. Preferably, the method comprises the step of suspending the lifting harness from the working platform by means of the front anchor point and the back anchor point.

In a preferred embodiment of the method according the present invention, the method further comprises the step of placing the blade tip extension in the proposed lifting harness and the step of using the lifting harness for suspending and/or lifting the blade tip extension.

In particular, both anchor points may be used simultaneously for suspending and/or lifting the blade tip extension. Hence, the blade tip extension carried is adjusted to the predetermined spatial alignment of with the aid of gravity. Further, this ensures an equally distributed load on the lifting harness.

In another, more preferred embodiment of the method according to the present invention, the method further comprises the step of using at least one tagline loop for maintaining and/or adjusting a predetermined spatial alignment of the tip extension during suspending and/or lifting. In particular, a tagline may be detachably connected to the at least one tagline loop.

Additionally or alternatively, the at least one tagline loop does not bear a substantial portion of a weight force of the tip extension during suspending and/or lifting of the tip extension. In particular, the at least one tagline loop may bear less than 10 % of the weight force, most preferably less than 3 %. Extraordinarily preferably, the at least one tagline loop is not used for bearing any portion of a weight force of the tip extension during suspending and/or lifting the tip extension.

If several (at least two) tagline loops are provided, the limits mentioned in the above paragraph may apply to each single one of the tagline loops.

Alternatively, the limits may refer to all tagline loops together.

Additional features, advantages and possible applications of the invention result from the following description of exemplary embodiments and the drawings. All the features described and/or illustrated graphically here form the subject matter of the invention, either alone or in any desired

combination, regardless of how they are combined in the claims or in their references back to preceding claims.

Fig. 1 shows a view on the front side of an embodiment of an lifting harness according to the present invention in a spread-out configuration, wherein no blade tip extension is placed in the lifting harness;

Fig. 2 shows a view on the front side of the lifting harness of Fig. 1 , wherein a blade tip extension is placed in the lifting harness, wherein the lifting harness is suspended from an above working platform, which is mounted on a turbine blade of a wind turbine; Fig. 3 shows the same configuration as Fig. 2, wherein the lifting harness has been lifted further up. The lifting harness 1 shown in Fig. 1 is spread-out and ready to take up a bottom portion of a blade tip extension 100 (see Fig. 2). Fig. 1 is a side view upon a front side of the lifting harness 1.

Therefore, in the following, the element visible on the front side are described. Flowever, as a backside (not shown) of the lifting harness 1 is substantially mirror-symmetric to its front-side, the description also applies to the backside in a corresponding manner. Flowever, as the shape of the lifting harness 1 is adapted to the complex shape of the bottom portion of the blade tip extension 100, it is not exactly mirror-symmetrical.

The lifting harness 1 comprises a bearing structure including a top harness band 11 , a bottom harness band 13, two front harness straps 14, 15 and a front support harness strap 18 on the front side, two corresponding back harness straps and a corresponding back support harness strap on the backside (not shown), a front edge harness strap 16, and a back end harness strap 17.

All parts of the bearing structure may be made of the same material. A front anchor point 12 is fixed to a front anchor point portion 11 c of the top harness band 11. A corresponding back anchor point is fixed to a

corresponding back anchor point portion of the top harness band 11 at the backside of the lifting harness (not schown). A rear edge portion 11 b of the top harness band 11 extends between the front anchor portion 11 c and the back anchor portion. I addition, a front edge portion 1 1 a of the top harness band 1 1 extends between the front anchor portion 1 1 c and the back anchor portion opposite to the rear edge

portion 1 1 b. The rear edge portion 1 1 b (in more detail: a rear edge end of the top harness band 1 1 located in the rear edge portion 1 1 b) is adapted to abut on a rear edge 104 of the blade tip extension 100 and the rear edge portion 1 1 a (in more detail: a front edge end of the top harness band 1 1 located in the front edge portion 1 1 a) is adapted to abut on a front edge 103 of the blade tip extension if the latter is accommodated in the lifting harness 1 . Regarding both the front edge portion 1 1 a and the rear edge portion 1 1 b, only a half of them on the front side is shown. The other halves

correspondingly extend on the substantially mirror-symmetric backside in the same manner.

In order to ensure a predetermined spatial tilt of the blade tip extension with respect to a vertical direction V by using a gravitational force of the blade tip extension if the blade tip extension 100 is suspended and/or lifted in the lifting harness 1 , both the front anchor point 12 and the back anchor point are offset from a center of the top harness band 1 1 towards the rear edge end of the top harness band 1 1 .

Accordingly, the rear edge portion 1 1 b of the harness band 1 1 is shorter than the front edge portion 1 1 a.

The two front harness straps 14, 15 connect the front anchor point portion 1 1 c with the bottom harness band 13. In particular, the front harness strap 14 connects the front anchor point 1 1 c with a first front junction site 13a of the bottom harness band 13 and the front harness band 15 connects the front anchor point 1 1 c with a second front junction site 13b of the bottom harness band 13. The two front harness straps 14, 15, the front anchor point 12, and a front surface portion of the bottom harness band 13, which extends between the first front junction site 13a and the second front junction site 13b, form a triangular-shaped bearing structure in order to transfer a load on the bottom band 13 evenly to the anchor point 12. A front edge portion and a back edge portion of the bottom harness band 13, which respectively extend between the back junction sites and the adjacent front junction sites 13a, 13b, are shorter than the front surface portion of the bottom harness band 13. A corresponding substantially mirror-symmetric structure is found on the backside of the lifting harness 1 (not shown).

The front edge harness strap 16 connects the front edge end of the top harness band 11 with a front edge end of the bottom harness band 13. From there, it further extends around half a tip accommodating portion to a bottom end of the lifting harness 1 , the bottom end or tip end of the harness 1 being the end opposite to an top end defined by the top harness band 11.

Correspondingly, the rear edge harness strap 17 connects the rear edge end of the top harness band 11 with a rear edge end of the bottom harness band 13. From there, it further extends around half the tip accommodating portion to the bottom end of the lifting harness 1.

In the present embodiment, the front edge harness strap 16 and the rear edge harness strap 17 seamlessly merge into each other at said bottom end.

In the present embodiment, the front edge portion and the back edge portion of the bottom harness band 13 (only the half on the front side is shown) are very short. It is also possible that the first front junction site and the corresponding first back junction side coincide and are located on the front edge harness strap 16, for example (not shown). In this case, only this common first junction site constitutes the front edge portion of the bottom harness band 13. The same is true regarding the second front junction side, the corresponding second back junction side, and the rear edge harness strap 17. The front support harness strap 18 connects the front anchor portion 11 c with the rear edge harness strap 17 in order to improve the strength of the bearing structure. In more detail, the front support harness strap 18 extends between a junction site in a second upper quarter of the rear edge harness strap 17 to the front anchor point 11 c. A corresponding back support harness strap is provided on the backside (not shown).

In the depicted spread-out configuration and, accordingly, if the blade extension tip 100 is accommodated in the lifting harness, the bottom harness band 13 has a positive angle of inclination 13c with regard to the top harness band 11. For example, the angle of inclination is 11 ,5° in the present embodiment. Due to this positive angle of inclination, the load applied by the blade tip extension in the case of suspending and/or lifting can be better transferred from the bottom band 13 to the anchor points (front anchor point 12 and back anchor point).

A handle 41 is disposed at a center of a front side surface of the top harness band 11. A further handle 42 is disposed at a center of a front side surface of the bottom harness band 13. In addition, corresponding handles are provided on the backsides of the top harness band 11 and the bottom harness band 13.

The bearing structure is integrally provided on an outside of a sack 20. Both a shape of the sack 20 and the shape of the bearing structure are adapted to the outer shape of the bottom portion of the blade tip extension 100 such that the lifting harness 1 is adapted to fittingly accommodate said bottom portion (see Fig. 2). In the present embodiment, the sack 20 is disposed integrally on an inside of the bearing structure in order to be interposed between the bearing structure and an surface of the blade tip extension 100 if the latter is placed into the lifting harness 1. Hence, the sack 20 protects the blade tip extension 100 from damages from the bearing structure.

The sack 20 comprises a waterproof layer and an innermost low-friction layer made of felt (not shown). Therefore, at the one hand, the sack 20 protects the blade tip extension 100 (obviously, more precisely, its bottom portion) from mechanical damage and environmental influences, if the blade tip extension 100 is accommodated in the lifting harness 1. At the other hand, the innermost low-friction layer makes it possible to put the lifting harness 1 on and off easily.

In the tip accommodating portion of the sack 20, three drain holes 21 are disposed on the front side. An additional drain hole 21 is located above the bottom harness band 13. Corresponding drain holes are provided on the backside as well (not shown).

Four tagline loops 31 , 32, 33, 34 are fixed to the lifting harness 1. In particular, one tagline loop 31 is fixed to the front edge end of the top harness band 13 and a further tagline loop 32 is fixed to the rear edge end of the top harness band 13. In addition, a tagline loop 33 is attached to the front edge end of the bottom harness band 13 and a further tagline loop 34 is fixed to the rear edge end of the bottom harness band 13.

Taglines can be detachably connected to the tagline loops 31 , 32, 33, 34 in order to support and correct the spatial alignment of the lifting harness 1 , especially if the blade extension tip 100 is suspended and/or lifted therein.

In particular, taglines from an above working platform 300 may be connected to the upper tagline loops 31 , 32 and/or taglines attached to the lower tagline loops 33, 34 may extend down towards a ground. For example, the lifting harness 1 according to the present embodiment has a weight load limit of 150 kg and a net weight of 3,3 kg.

Fig. 2 shows an intended use of the lifting harness 1. The bottom portion of the blade tip extension 100 is fittingly accommodated in the lifting harness 1 . In particular, the front edge 103 of the blade tip extension 100 faces towards the front edge harness strap 16 and the rear edge 104 of the blade tip extension 100 faces towards the rear edge harness strap 17. A tip (not shown) of the blade tip extension 100 is accommodated in the tip

accommodating portion of the lifting harness 1. As the shape of the lifting harness 1 is adapted to the shape of the bottom portion of the blade tip extension 100, the latter is safely guided in the lifting harness 1 and cannot drop out.

In Fig. 2, the working platform 300 is mounted to a turbine blade 200 of a wind turbine. A longitudinal axis 201 of the turbine blade 200 has an angle 202 with regard to the horizontal direction FI of only 82° but not 90° such that a tip of the turbine blade 200 slightly protrudes away from a tower of the wind turbine. In other words, the longitudinal axis 201 is inclined with respect to a vertical axis V perpendicular to the horizontal direction FI and being defined by a direction of gravity by a predetermined spatial tilt with an angle 203 of 8°.

The lifting harness 1 lifting the blade tip extension 100 is suspended on a cable 302, which is let down from a winch 301 mounted on the working platform 300. In other word, the lifting harness is directly suspended from the working platform 300 and no additional crane or lifting device is needed.

In more detail, a front sling 50 is detachably fixed to the front anchor point 12 by means of a shackle. The front sling 50 connects the front anchor point 12 with a hook 51 fixed to the cable 302. In a corresponding manner, the back anchor point is connected to the hook 51 by means of a shackle and a back sling (not shown).

Hence, both the front sling 50 and the back sling are attached to the common hook 51. Above from the top harness band 11 , the front sling 50 abuts on a front side of the blade tip extension 100 and the back sling abuts on a backside of the blade tip extension 100.

The blade tip extension 100 extends substantially along a longitudinal direction 101 thereof. Due to the weight of the blade tip extension 100 carried therein, the lifting harness 1 rotates around the front anchor point 12 and the back anchor point in a clockwise manner until the blade tip extension 100 abuts the front sling 50 and the back sling and/or the hook 51.

In this situation, an inclination angle 102 of the lifted blade tip extension 100 with respect to the horizontal direction H is determined by the lateral offset of the front anchor point 12 and the back anchor point.

Correspondingly, a predetermined spatial tilt 105 of the blade tip extension 100 with respect to the vertical direction V is adjusted to be exactly the same as the predetermined spatial tilt 203 of the turbine blade 200, to which the blade tip extension 100 shall be mounted. In particular, with respect to the present embodiment, the following relationship applies: The bigger the lateral offset of the front anchor point 12 and the back anchor point towards the rear edge end of the top harness band 11 , the smaller the angle 102 and the bigger the predetermined spatial tilt 105 - at least, as long as a length of the front sling 50 and the back sling is not changed.

Consequently, the blade tip extension 100 can be lifted up to the turbine blade 200 with the corresponding predetermined spatial tilt 105. Therefore, the mounting of the blade tip extension 100 is considerably facilitated. In a similar manner, dismounting of a blade tip extension to be maintained or to be replaced is facilitated as well (not shown) because the risk of jamming during dismounting is considerably reduced if using the lifting harness 1. In Fig. 3, a situation is shown where the blade tip extension 100 has been lifted up further with respect to Fig. 2. Now, the tip of the turbine blade 200 mounted on the wind turbine is on the brink on entering an opening of the blade tip extension 100. As in Fig. 2, the angle 102 of the longitudinal axis 101 of the blade tip extension 100 with respect to the longitudinal direction FI is still exactly the same as the angle 202 of the longitudinal axis 201 of the turbine blade 200 with respect to the horizontal direction FI.

More exactly, the lifting harness 1 ensures that the longitudinal axis 101 of the blade tip extension 100 is exactly parallel to the longitudinal axis 201 of the turbine blade 200. Flence, the blade tip extension can be lifted up and fittingly mounted to the turbine blade 200 without further alignment procedures.

The proposed lifting harness 1 is light, reliable, rugged, easy to handle and ensures a proper predetermined alignment of the blade tip extension 100 if the latter is suspended and/or lifted in the lifting harness 1. In particular, with the lifting harness 1 , the blade tip extension 100 can be lifted up suspend from the working platform 300 without the need for an additional crane or lifting device. Thus, the lifting harness 1 provides easy and cost-efficient lifting. List of reference signs:

1 lifting harness

1 1 top harness band

11 a front edge portion

11 b rear edge portion

11 c front anchor point portion

12 front anchor point

13 bottom harness band

13a first front junction site

13b second front junction site

13 angle of inclination

14, 15 front harness strap

16 front edge harness strap

17 rear edge harness strap

18 front support harness strap 20 sack

21 drain hole

31 , 32, 33, 34 tagline loop

41 , 42 handle

50 front sling

100 blade tip extension

101 longitudinal axis

102 angle

103 front edge

104 rear edge

105 predetermined spatial tilt 200 turbine blade

201 longitudinal axis

202 angle

203 predetermined spatial tilt 300 working platform

301 winch

302 cable

H horizontal direction V vertical direction