WO2014206482A1

WO2014206482A1 - Tool for temporarily connecting a hub element and a blade of a wind turbine

Info

Publication number: WO2014206482A1
Application number: PCT/EP2013/063612
Authority: WO
Inventors: Jascha Van Pommeren; Koos WELLING
Original assignee: Aktiebolaget Skf
Priority date: 2013-06-28
Filing date: 2013-06-28
Publication date: 2014-12-31

Abstract

The invention relates to a tool (1) for temporarily connecting a hub element (2) and a blade (3) of a wind turbine for establishing a firm connection between the hub element (2) and the blade (3) when a slewing bearing (4), which is effectively arranged between the hub element (2) and the blade (3), is not activated. To obtain a stable but quick mountable and releasable connection between the hub element and the blade the invention suggests that the tool comprises: a plurality of clamping elements (5) which are arrangeable between an inner circumference of the hub element (2) and the blade (3) in the region of the slewing bearing (4), wherein each clamping elements (5) is designed to be connected with a part of the hub element (2) and a part of the blade (3) at a defined circumferential position; and a holding device (6) which holds the clamping elements (5) and which is designed to exert a radial pressure to the clamping elements (5) which is directed in an outward direction (R).

Description

Tool for temporarily connecting a Hub element and a

Blade of a Wind Turbine

Technical Field

The invention relates to a tool for temporarily connecting a hub element and a blade of a wind turbine for establishing a firm connection between the hub element and the blade when a slewing bearing, which is effectively arranged between the hub element and the blade, is not in operation, i.e. is not activated.

Background

In a wind turbine a number of blades is arranged at a hub element; the hub element rotates during normal operation of the wind turbine around an axis. Each blade is arranged by means of a slewing bearing (pitch bearing) in such a manner that the blade can be rotated around the longitudinal axis of the blade relatively to the hub element to adjust the pitch of the blade. Thus, the blade can be positioned at the hub element such that the wind turbine can be operated in an optimal way.

So, the blade is rotated around its longitudinal axis around a quite small swivel angle, e.g. between 0° and 35°, which is the working range of the blade during power production. For adjusting the blade a pitch drive is employed.

Over time, fatigue effects and wear occur in the slewing bearing in the working range, i.e. during operation of the wind turbine, the slewing bearings will slowly be worn out and fatigue takes place.

It is a possibility to avoid this problem by using an oversized slewing bearing. But this causes not only respective high costs, also the weight of the whole system rises detrimentally.

Also, the replacement of the slewing bearings is very costly, because normally it is necessary to use a crane for doing so.

The life of the slewing bearing is mostly consumed locally as a result of beinding loads which are dominant and which mostly act in the same region of the circumference of the bearing rings. A beneficial way to avoid the substitution of the slewing bearing is thus to bring a section of the slewing bearing (which extends around 360° of the hub and blade respectively) into operation which has not yet been used. Thus, if the slewing bearing could be temporary detached from the wind turbine, the bearing could be rotated (around a certain angle, e.g. 90° or 180°) so that an almost "fresh" or "unused" part of the bearing is brought into operational contact. So, the life time of the bearing can be be increased without replacing it.

US 2012/0141280 Al describes a method for bringing the slewing bearing in an unused working section which employs a hoisting device. By this the blade is moved in a vertical direction relatively to the hub after the blade is oriented in vertical direction. While a crane is not necessary here to do the mentioned process it is a drawback of this pre-known solution that the required hoisting means are necessary which causes respective costs.

Thus, it is an o b j e c t of the present invention to propose a tool for temporarily connecting a hub element and a blade of a wind turbine which is cost saving and which allows an easier movement of the slewing bearing to bring the bearing relative to the hub element and blade respectively in a not yet used position. Also, the substitution of the slewing bearing - especially when designed as a segmented bearing - should be possible in an easy and cost efficient manner. Thus, a stable but quick mountable and releasable connection between the hub element and the blade should be obtained.

Summary of the invention

A s o l u t i o n according to the invention is characterized in that the tool comprises: a plurality of clamping elements which are arrangable between an inner circumference of the hub element and of the blade in the region of the slewing bearing, wherein each clamping elements is designed to be connected with a part of the hub element and a part of the blade at a defined circumferential position; and a holding device which holds the clamping elements and which is designed to exert a radial pressure to the clamping elements which is directed in an outward direction.

Preferably, the clamping elements are designed to be connected with the part of the hub element and the part of the blade at a defined circumferential position by a form- fit connection. More specifically, a preferred embodiment suggests that the clamping elements have a first radial projection for engagement with a recess in the hub element and have a second radial projection for engagement with a recess in the blade. The first radial projection is preferably- designed for engagement with a circumferential groove in the hub element, while the second radial projection is designed for engagement with a circumferential groove in the blade.

As an alternative no form-fit connection can be used for the fixation of the clamping elements but a connection by factional engagement. In this case it is provided that the clamping elements are designed to be connected with the part of the hub element and the part of the blade at a defined circumferential position by a factional engagement.

The clamping element has preferably a substantially U-shaped form seen in circumferential direction of the hub element and the blade. Then, the first radial projection can be arranged at one of the legs of the U-shaped form of the clamping element and the second radial projection can be arranged at the other leg of the U-shaped form of the clamping element.

The clamping element can comprise a bearing element for supporting one of the bearings rings or a part of a bearing ring of the slewing bearing. That is, after dismounting of connection screws for the inner bearing ring of the slewing bearing (see explanations below) the bearing element can support the bearing ring of the slewing bearing. The bearing element can comprise a sliding surface for one of the bearings rings or a part of a bearing ring of the slewing bearing. A preferred embodiment proposes that the bearing element comprises a roll (supported by a rolling bearing in the clamping element) for supporting one of the bearings rings or a part of a bearing ring of the slewing bearing. The holding device comprises preferably at least three upper rods which connect an upper part of a centre element with the clamping elements and comprise at least three lower rods which connect a bottom part of the centre element with the clamping elements. Also a higher number of upper and lower rods is beneficial, e. g. six rods of both kinds. Normally, all upper and lower rods are arranged around the centre element equidistantly along the circumference. The rods are preferably at least partially removable. The rods can be adjustable in their effective length, specifically by means of a left-right threaded element. This allows also the adjustment of the tool for different wind turbine systems.

The clamping element is preferably connected with an upper rod and a lower rod by means of a single hinge.

An actuator can be effectively arranged between the upper part and the lower part of the centre element. This actuator can be a piston-cylinder element, specifically a pneumatically or hydraulically operated piston-cylinder element.

By using such a tool the following process can be carried out to turn the slewing bearing around a certain angle to bring a "fresh" part of the bearing rings into engagement: a) Mounting the tool between the hub element and a blade of the wind turbine, wherein the blade is arranged preferably in a vertical position. So, a firm connection is established between the hub element and the blade; b) Dismounting connection means between the blade and the first ring (inner ring) of the slewing bearing, so that the first ring can rotate relatively to the blade and/or dismounting connection means between the hub element and the second ring (outer ring) of the slewing bearing, so that the second ring can rotate relative to the hub element; c) Turning the first ring and the second ring of the slewing bearing around a predetermined angle by means of the pitch drive, relative to the blade and/or relative to the hub element; d) Mounting the connection means between the blade and the first ring of the slewing bearing and/or mounting the connection means between the hub element and the second ring of the slewing bearing; e) Dismounting the tool, that is the connection means between the hub element and the blade.

Thus, as a general concept at least one bearing ring of the slewing bearing is rotated around a predetermined angle to bring the bearing ring in a fresh or unused section of its circumference. For doing so, neither a crane nor a complex device - like in the state of the art - is required but the pitch drive is used. The only required device is the mentioned tool according to the invention.

It is also possible to carry out the following step between the above mentioned step b) and step c): Mounting connection means for establishing a firm connection between the first ring and the second ring of the slewing bearing. The predetermined angle can be between 60° and 180°, preferably it is 120°. So, in total 2 to 6 different circumferential sections of the bearing ring of the slewing bearing can be used until the slewing bearing has reached the end of its life time.

The mentioned connection means are mostly screw connections.

The hub element can comprise two, three or four blade receptions, wherein the mentioned method is carried out sequentially for all blades. The mentioned method is preferably carried out repeatedly after a predetermined operation time of the wind turbine.

Thus, the present invention proposes a tool which can be produced in a cost efficient way. It allows to establish a temporary firm connection between the hub element and the blade. This is not only used to turn the slewing bearing around a certain angle but also to substitute used bearing rings or parts of it (in the case of a segmented bearing ring) in an easy manner.

Thus, the blade is temporarily firmly attached to the hub element by means of the tool according to the invention. The bearing rings of the slewing bearing are released from their connection to the hub element and blade respectively. The pitch drive is then used to turn the bearing rings in a "fresh" or "unused" position in which the slewing bearing (i.e. a part of the same) can operate again properly. So, the life time of the slewing bearing will be increased significantly, especially if the mentioned process is repeated from time to time. In other words: Sections of the bearing rings which have been in the loaded zone of the slewing bearing are shifted in the described manner from time to time, unless the whole circumference of the bearing rings of the slewing bearing has reached the end of the lifetime. Beneficially, the proposed procedure allows an "in situ" rotation of the bearing rings relative to the hub and blade.

Thus, the cost for replacing the slewing bearing specifically in the case of a segmented bearing ring will be significantly reduced.

The mentioned re-adjustment of the rings of the slewing bearing can beneficially be done without removing the blade from the hub element. The readjustment of the inner ring and the outer ring of the slewing bearing can be done without removing or rotating the hub or the blade.

Additional devices - beside the proposed tool - for the mentioned shifting can be avoided by the fact that the regular pitch drive is used for repositioning the bearing rings. Advantageously, no extra actuator is needed. The shifting is done only with the regular pitch drive.

With regard to the mentioned slewing bearing all possible kinds of pitch bearing are to be understood which allow a rotation of the blade around its longitudinal axis relatively to the hub element.

Furthermore, it is possible to equip the tool with measurement devices, especially with strain gauges, to measure the clamping force which is applied to the clamping element. Those strain gauges can for example be arranged in the rods. By doing so it can be made sure that the clamping load is high enough for securely hold the blade and that the load is well balanced.

The proposed tool can be disassembled for the purpose of transportation, especially into and out of the turbine. Brief description of the drawings

The drawings show an embodiment of the invention.

Fig. 1 shows a partial perspective and partial sectional view of a hub element of a wind turbine which has three blades, wherein a tool according to the invention is mounted between the hub element and the blade, which reaches vertically downwards,

Fig. 2 shows an enlarged part of the perspective and partial sectional view according to Fig. 1 and

Fig. 3 shows a perspective view of a clamping element of the tool according to the invention.

Detailed description of the invention

In Fig. 1 a hub element 2 of a wind turbine is shown. It is designed to take three blades 3. Each blade 3 must be adjusted with respect to the pitch angle. Thus, a respective pitch drive 21, 22 (see Fig. 2; a motor 21 is not depicted but only schematically denoted) is arranged at the transition zone between the hub element 2 and the blade 3. The pitch drive comprises a motor 21 with a gearbox and with a pinion (also not shown) which meshes with a gear 22. In general the pitch drive is designed according to the state of the art so that additional explanations are redundant. In Fig. 2 details become apparent concerning the design of the transition zone between the hub element 2 and the blade 3. To allow the adjustment of the pitch angle, i.e. the rotation of the blade 3 relative to the hub element 2 around the longitudinal axis of the blade 3, a slewing bearing 4 is employed. The slewing bearing 4 has a first ring 14 (inner ring) and a second ring 23 (outer ring), between which roller elements (balls) 24 are arranged.

The first ring 14 of the slewing bearing 4 is firmly connected to the blade 3 by first connection means (screws). Similarly, the second ring 23 of the slewing bearing 4 is connected to the hub element 2 by connection means (screws).

After a certain operation time, wear and/or fatigue has taken place in the slewing bearing 4 but - due to the small swivel angle of the slewing bearing - this wear extends along a small part of the circumference of the bearing rings 14, 23 only. Thus, a used part of the bearing ring circumference adjoins to parts of the circumference which are almost un-used or fresh. Now it is aimed to readjust the slewing bearing 4 to bring parts of it into operation which are not yet used. So, the cost-intensive substitution of the slewing bearing 4 should be avoided.

For doing so, the following process is carried out:

The blade 3 in which the slewing bearing 4 has to be swivelled (or which slewing bearing 4 and the segments of the bearing rings in the case of a segmented bearing ring has to be substituted respectively) is brought into a vertical position, i.e. the blade is pointing downwards, as shown in Fig. 1 and Fig. 2 In a first step, at several locations along the circumference, a number of screws are dismounted to provide the space for mounting a tool 1 as shown in Fig. 1 and Fig. 2. More specifically, a number of clamping elements 5, e.g. three clamping elements 5, are arranged at three circumferential positions which are equidistantly chosen. A clamping element 5 of this kind is shown in Fig. 3.

Each clamping element 5 has a first, upper radial projection 7 and a second, lower projection 9. The projections 7, 9 are arranged at the face side of two legs 11, 12 of a general U-shaped structure of the clamping element 5.

On the other side, the hub element 2 has a recess 8 being a circumferential groove; also the blade 3 has a recess 10 being a circumferential groove. The grooves 8, 10 and the projections 7, 9 of the clamping element 5 respectively are arranged for a form-fit connection when the clamping element 5 is brought into interference with the hub element 2 and blade 3 respectively.

Thus, after arrangement of the clamping elements 5 a form-fit connection is established between the hub element 2 and the blade 3.

To hold the clamping elements 5 in position and to press them firmly in a radial outward direction R against the hub element 2 and blade 3 and thus into the grooves 8, 10 a holding device 6 is provided. In general, the holding device 6 has a centre element 17 (see Fig. 1) from which a number of rods 16, 18 extend. The rods 16, 18 are detachably arranged. Their length can be adjusted by means of left-right-threads.

A group of upper rods 16 run from an upper part of the centre element 17 to the clamping elements 5, a group of lower rods 18 run from a lower part of the centre element 17 to the clamping elements 5. Both rods 16, 18 meet at a hinge point 19 in each clamping element 5.

While the clamping elements 5 are located in the grooves 8, 10 only the upper rods 16 are mounted. Then, the lower rods 18 can be mounted. Of course, also all rods can be brought into place at the same time.

Now (and optionally) additional clamping elements 5 - e. g. up to a total of 6 clamping elements 5 - are mounted together with the respective upper and lower rods 16, 18.

Then an actuator 20 is activated which is effectively arranged between the upper and the lower part of the centre element 17. The upper and the lower part of the centre element 17 are thus pulled together. This causes a radial force to be generated by the rods 16, 18, which force is transmitted to the clamping elements 5 in a radially outward manner (see direction R). So, the clamping elements 5 are firmly pressed with their projections 7, 9 into the grooves 8, 10.

Thus, a firm connection is established by means of the tool 1 between the hub element 2 and the blade 3 which bypasses the slewing bearing 4.

Now the screws which connect the slewing bearing rings 14, 23 with the blade 3 and hub element 2 can be dismounted to swivel the bearing rings or to substitute them. To facilitate the handling of the inner bearing ring 14 of the slewing bearing 4 the clamping elements 5 have a bearing element 13 which supports the inner bearing ring 14 of the slewing bearing 4. In the depicted embodiment the bearing element 13 comprises a roll 15 which is arranged under an angel (of about 45°) to the horizontal direction as can be seen in Fig. 2. By doing so, the bearing ring 14 is supported radially and axially during its handling; thus, the bearing ring 14 remains centred.

When the screws are dismounted from the bearing rings 14, 23 the blade 3 is shifted a little in vertical direction due to the gravity and due to the fact that the axial extension of the grooves 8, 10 in vertical direction is a bit longer than the axial extension of the projections 7, 9. This enables that the bearing ring 14 will be released and well supported by the roll 15. Then, the bearing rings are connected relatively to another with suitable elements.

Now the bearing rings 14, 23 can be rotated by means of the pitch drive motor 21 around a defined angle.

Afterward, the screws are again mounted and thus the bearing rings 14, 23 are again fixed with the hub element 2 and blade 3 respectively.

Finally, the tool 1 is removed by activating the actuator and pulling back the clamping elements 5 into the direction to the centre of the tool 1.

Now, the next blade 3 can be treated in the same manner.

So, a new un-used part of the slewing bearing is brought into engagement. The substitution of the slewing bearing 3 was avoided or at least postponed.

This process can be repeated after a certain operation time again to bring further fresh parts of the bearing into engagement.

Replacement of the slewing bearing only becomes necessary when all sections of the bearing rings have experienced wear due to tribological contacts. The clamping elements can be exchangeable to make the tool suitable for different types and sized of wind turbines. The tool can be provided with eye bolts. By doing so it can be made sure that the tool can be arranged at the hub or at the blade via a cable to prevent that the tool accidentally falls down into the blade.

Reference Numerals:

1 Tool

2 Hub element

3 Blade

4 Slewing bearing

5 Clamping element

6 Holding device

7 First radial projection

8 Recess (groove)

9 Second radial projection

10 Recess (groove)

11 Leg

12 Leg

13 Bearing element

14 Bearings ring of the slewing bearing

15 Roll

16 Upper rod

17 Centre element

18 Lower rod

19 Hinge

20 Actuator

21, 22 Pitch Drive

21 Motor Gear

Bearing ring of the slewing bearing Ball

Radial outward direction

Claims

Patent Claims:

1. Tool (1) for temporarily connecting a hub element (2) and a blade (3) of a wind turbine for establishing a firm connection between the hub element (2) and the blade (3) when a slewing bearing (4), which is effectively arranged between the hub element (2) and the blade (3), is not in operation, characterized in that the tool comprises: a plurality of clamping elements (5) which are arrangable between an inner circumference of the hub element (2) and the blade (3) in the region of the slewing bearing (4), wherein each clamping elements (5) is designed to be connected with a part of the hub element (2) and a part of the blade (3) at a defined circumferential position; and a holding device (6) which holds the clamping elements (5) and which is designed to exert a radial pressure on the clamping elements (5) which is directed in an outward direction (R).

2. Tool according to claim 1 , characterized in that the clamping elements (5) are designed to be connected with the part of the hub element (2) and the part of the blade (3) at a defined circumferential position by a form- fit connection.

3. Tool according to claim 2, characterized in that the clamping elements (5) have a first radial projection (7) for engagement with a recess (8) in the hub element (2) and have a second radial projection (9) for engagement with a recess (10) in the blade (3).

4. Tool according to claim 3, characterized in that the first radial projection (7) is designed for engagement with a circumferential groove (8) in the hub element (2) and the second radial projection (9) is designed for engagement with a circumferential groove (10) in the blade (3).

5. Tool according to claim 1 , characterized in that the clamping elements (5) are designed to be connected with the part of the hub element (2) and the part of the blade (3) at a defined circumferential position by a firic- tional engagement.

6. Tool according to one of claims 1 to 5, characterized in that the clamping element (5) has a substantially U-shaped form seen in circumferential direction of the hub element (2) and the blade (3).

7. Tool according to claims 3 and 6, characterized in that the first radial projection (7) is arranged at one of the legs (1 1) of the U-shaped form of the clamping element (5) and that the second radial projection (9) is arranged at the other leg (12) of the U-shaped form of the clamping element (5).

8. Tool according to one of claims 1 to 7, characterized in that the clamping element (5) comprises a bearing element (13) for supporting one of the bearings rings (14) or a part of a bearing ring of the slewing bearing (4).

9. Tool according to claim 8, characterized in that the bearing element (13) comprises a sliding surface for one of the bearings rings (14) or a part of a bearing ring of the slewing bearing (4).

10. Tool according to claim 8, characterized in that the bearing element (13) comprises a roll (15) for supporting one of the bearings rings (14) or a part of a bearing ring of the slewing bearing (4).

11. Tool according to one of claims 1 to 10, characterized in that the holding device (6) comprises at least three upper rods (16) which connect an upper part of a centre element (17) with the clamping elements (5) and comprise at least three lower rods (18) which connect a bottom part of the centre element (17) with the clamping elements (5).

12. Tool according to claim 11, characterized in that the rods (16, 18) are at least partially removable.

13. Tool according to claim 11 or 12, characterized in that the rods (16, 18) are adjustable in their effective length, specifically by means of a left- right threaded element.

14. Tool according to one of claims 11 to 13, characterized in that the clamping element (5) is connected with an upper rod (16) and a lower rod (18) by means of a single hinge (19).

15. Tool according to one of claims 11 to 14, characterized in that an actuator (20) is arranged between the upper part and the lower part of the centre element (17), whereby actuation of said actuator (20) causes the upper and lower parts of the centre element (17) to be pulled together.