DESC:3. PREAMBLE TO THE DESCRIPTION:

The following specification describes the invention.

WASHER ELEMENT, FIXING ARRANGEMENT AND WIND TURBINE

TECHNICAL FIELD
The invention relates to the attachment of components, for example within a nacelle of a wind turbine, and more particularly to a washer element, a fixing arrangement and the wind turbine incorporating same.

BACKGROUND
In equipment such as wind turbines, components such as those attached to or making up a main frame within a nacelle are subject to large forces, for example, due to winds. It is typically necessary to attach one component to another, e.g. to (part of) a mainframe, that is, using multiple bolts. In doing so, it is known in the art to use washers or fixing arrangements incorporating them.

Figure 1 (PRIOR ART) shows a known wind turbine 1 with multiple blades. The wind turbine 1 includes a tower 3 and a nacelle 2 rotatably mounted on the tower 3. The nacelle 2 comprises a nacelle cover 4 mounted on a main frame (not shown), which is described in more detail further below. On a rotor shaft (not shown) inside the nacelle 2, a rotor 7 is arranged, which in turn comprises a hub 5 and at least one rotor blade 6 (For illustrative purposes, three blades are shown in the Figure 1).

The securing of screw connections/bolted connections against loosening is often done by means of bolts with ribs under the head thereof, nuts with ribs on their contact surface, and more particularly by means of washers having a serrated/ribbed surface on both sides. Various washer designs are known in the art. One such conventional washer is formed by two rings separated by a gap as illustrated in the example of Figure 2(a) (PRIOR ART), discussed in further detail hereinbelow. A disadvantage is the additional manufacturing complexity in order to form dual ring washers with gaps with multiple serrated surfaces. Another type of conventional washer is in the form of a single ring having on opposing surfaces, a dimpled pattern for grippingly engaging bolt head surfaces and component surfaces as illustrated in the example of Figure 2(b) (PRIOR ART), discussed in further detail hereinbelow.

In each case, the interlocking aspect – patterned (serrated/ribbed) surfaces – leads to a damage of the component surface in the area of the washer, which, depending on the thickness of the component, can lead at least to corrosion problems. That is, even notch creation through the deformed component surface can occur.

Further, in the case of dual-ring washers, increased preload force losses result from the additional gap defined between the rings compared to a standard screw connection. Finally, two interlocked (opposing) surfaces of the washer result in additional preload force losses compared to a standard screw connection. More specifically, such dual-ring arrangements introduce additional interfaces which lead to increased loss of pretension by embedding; and interfaces are also serrated, further increasing such loss of pretension by embedding, due to the surface design itself.

In a wind turbine field, washer-type elements including extending/projecting portions are known in the art. In one example, for the assembly, anti-rotation nut tabs are placed over flange nuts on the exterior side of a panel. The anti-rotation nut tabs prevent the tightened flange nuts from turning during assembly as an extending end of the anti-rotation nut tab contacts the adjacent flange nut. The flange nut may be provided with a groove that receives a snap ring that comprises a plastic washer that urges or holds the anti-rotation nut tab onto the flange nut.

In another known example, for a modular tower structure for a wind turbine, during assembly a fastener pack is used that generally includes a fastener tray, anti-rotation nut tabs, and a position cover. The fastener pack attaches or connects to threaded studs that are connecting the vertical edges of panels or the horizontal edges of sections. The anti-rotation nut tab prevents a flange nut from rotating when the flange nut on an opposite end of a threaded stud is tightened. A position cover holds the anti-rotation nut tabs and the flange nuts in position in the fastener tray, such that the flange nuts are aligned to receive the threaded studs. However, this provides a complex arrangement involving multiple components and complicated manufacturing techniques. All known solutions only secure one of the nuts during tightening. After tightening a threaded nut (in the example of this tower, the interior one) is still not secured against loosening.

The present invention seeks to overcome the aforementioned problems and to provide an improved washer element, fixing arrangement and wind turbine incorporating same.

SUMMARY
According to one aspect of the invention, a washer element is provided for use in the attachment of one or more bolts to a first component. The washer element comprises a first washer portion, the first washer portion having a first aperture through which, in use, a first bolt passes, a first surface and, opposite the first surface, a second surface. The washer element further comprises a projection, integrally formed with the first portion. The washer element is characterized in that one of the first surface and the second surface is patterned or roughened, so as to grippingly engage a head of the first bolt.

Preferably, the other of the first surface and the second surface is smooth.

Preferably, the projection includes a second washer portion, the second washer portion having a second aperture through which, in use, a second bolt passes.

Preferably, the second washer portion has a third surface and, opposite the third surface, a fourth surface.

Preferably, one of the third surface and the fourth surface is patterned or roughened, so as to grippingly engage a head of the second bolt.

Preferably, the other of the third surface and the fourth surface is smooth.

Preferably, (i) the one of the first surface and the second surface that is patterned or roughened, and (ii) the one of the third surface and the fourth surface that is patterned or roughened, is on the same side of the washer element.

Preferably, the projection includes a torque arm integral with and extending from the first washer portion.

Preferably, the torque arm has a length c. 0.25-2x, 0.5-1x or 0.5 to 0.75x the transverse dimension of the first washer portion.

Preferably, the torque arm has a thickness less than that of the first washer portion and/or the second washer portion.

Preferably, the first washer portion and the second washer portion have the same size and/or shape.

Preferably, the first washer portion and/or the second washer portion is ring-shaped.
According to another aspect of the invention, a fixing arrangement comprises a first component; one or more bolts attached to the first component; and a second component fixedly attached to the first component by means of the bolt(s); characterized in that a washer element according to any of the preceding claims is disposed between the or each bolt and the first component.

In one embodiment, the first component comprises a component in or on a main frame of a wind turbine, the second component comprising a further wind turbine component fixedly attached the main frame.

According to another aspect of the invention, a wind turbine comprises a main frame, the main frame having therein or thereon a first component and a second component. The wind turbine is characterized in that a washer element according to any of claims 1 to 12 of the appended claims, or as described and/or illustrated herein, is disposed between the or each bolt and the first component. Alternatively, the wind turbine is characterized in that a fixing arrangement according to claims 13 of the appended claims, or as described and/or illustrated herein, is disposed on the main frame.

In the present invention, where a “bolt” is specified, this may alternatively be replaced by a nut, with a shaft with an external screw tread (to be engaged by the nut) being provided on or integral with another component, such as a main frame component, strut, plate, connecting piece, etc. Further, while bolts and nuts are referred to, “bolts” can be interpreted as any fixing element adapted to apply a force or (pre)load, whether manually or otherwise applied or mounted, for example by means of screw thread or other retaining element or means. The term “nut” should be interpreted similarly.

An advantage of the invention is secure positioning of the washer by means of the “torque arm”/ “second screw”.

In addition, no anchoring is required in the component surface and no special coating measures are required. An even/flat underside surface is provided: as there is therefore less or no damaging of the surface, risk of (crevice) corrosion at the component is reduced.

A further advantage is that there are fewer gaps/parting lines and thus less preload force loss in the connection compared to conventional solutions.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will become apparent from the drawings according to the description. In the drawings:

Figure 1 (PRIOR ART) shows a known wind turbine;

Figure 2(a) (PRIOR ART) shows a known washer 10 formed by two rings, and Figure 2(b) (PRIOR ART) shows another type of known washer 10’ in the form of a single ring 11’ having dimpled surfaces;

Figure 3(a) shows a washer element according to an embodiment of the invention in perspective view from above, and Figure 3(b) shows the same in perspective view from below;

Figure 4 is a perspective view of a portion of a main frame of a wind turbine, showing the joining of components;

Figure 5 is a close up view of a fixing arrangement of Figure 4; and

Figures 6(a) and 6(b) show in even further close up the fixing arrangement of Figure 5, from slightly above and from slightly below, respectively.

DETAILED DESCRIPTION

Figure 1 (PRIOR ART) shows a known wind turbine 1 with multiple blades. The wind turbine 1 includes a tower 3 and a nacelle 2 rotatably mounted on the tower 3. The nacelle 2 comprises a nacelle cover 4 mounted on a main frame (not shown), which is described in further detail below. On a rotor shaft (not shown) inside the nacelle 2, a rotor 7 is arranged, which in turn comprises a hub 5 and at least one rotor blade 6 (For illustrative purposes, three blades are shown in the Figure 1).

Near the axis of the hub 5, an end portion or blade root 8 of blade 6 is retained in place, e.g. within jacket 9. In use, the hub 5 is rotatable about the z-axis, and during installation, maintenance and/or calibration, blade 6 is rotatable about the x-axis. In this embodiment, the blade 6 is made of glass fibre. However, it will be appreciated that the blade 6 may be made of other materials, such as carbon or carbon composites.

Various washer designs are known in the art. The securing of screw connections/bolted connections is often done by means of washers having a serrated/ribbed surface on both sides. Figure 2(a) (PRIOR ART) shown one such type of known washer 10 formed by two rings 11, 12 separated by a gap 13 defined by opposing toothed internal surfaces of the rings 11, 12. By pressing the interlocking rings 11, 12, loosening of the screw is prevented. Moreover, patterned (serrated/ribbed) surfaces 14, 15 on both sides of the washer 10 grippingly engage bolt head surfaces and components surfaces during tightening. A disadvantage is the additional manufacturing complexity in order to form dual ring washers with gaps.

Further, Figure 2(b) (PRIOR ART) shows another type of conventional washer 10’ in the form of a single ring 11’ having opposing surfaces 14’, 15’, a dimpled pattern for grippingly engaging bolt head surfaces and components surfaces.

Figure 3(a) shows a washer element 16 according to an embodiment of the invention in perspective view from above. The washer element 16 comprises a first washer portion 17. The first washer portion 17has a first surface 18, and a second surface 19 on the side of the first washer portion 17 opposite the first surface 18. In this embodiment, the first surface 18 has serrated formations 20. However, in other embodiments, a roughened surface or other pattern adapted to have a gripping effect upon bolts or other fixing elements in contact therewith, may be used.

The washer element 16 further comprises a projection 21 extending from the first washer portion 17 and formed integrally therewith (during manufacture) for preventing, in use, rotation of the first washer portion 17 (e.g. with a bolt head (not shown) during tightening). In this embodiment, the projection 21 comprises a torque arm 22 coupling a second washer portion 23 to the first washer portion 17. However, in other embodiments, the second washer portion 23 may be omitted, or the second washer portion 23 may be formed integrally with the first washer portion 17 and the torque arm 22 omitted.

The second washer portion 23 includes a third surface 24, and a fourth surface 25 on the side of the second washer portion 23 opposite the third surface 24. In this embodiment, the third surface 24 has serrated formations 20. However, in other embodiments, a roughened surface or other pattern adapted to have a gripping effect upon bolts or other fixing elements in contact therewith, may be used. In any event, preferably the third surface 24 and the first surface 18 are provided with serrated formations 20, or a roughened surface or other similar pattern, while the second surface 19 and the fourth surface 25 are smooth.

Figure 3(b) shows the washer element 16 in perspective view from below, that shows the second surface 19 and the fourth surface 25 are smooth.

Figure 4 is a perspective view of a portion 26 of a main frame of a wind turbine 1, illustrating the joining of components using a fixing arrangement 27 in accordance with an embodiment of the invention. More particularly, a girder 28 is fixedly attached to an upright 29 using bolt heads 30, assisted by one or more of the washer elements 16 of Figures 3(a) and 3(b).

Figure 5 is a close up view of a fixing arrangement 27 of Figure 4. More specifically, a plurality of bolt heads 30 are used to strongly attach a first component referred as a girder 28 to a second component referred as an upright 29 of the main frame. A washer element 16 is used for one or more pairs of bolt heads 30, as illustrated with respect to one pair of bolt heads 30’, 30’’. With this arrangement, torques are resisted, and rotation of one bolt head 30’ relative to a first washer portion 17 prevented due to the insertion of another bolt head 30’’ in the second washer portion 23 of the washer element 16. At the same time, the smooth second surface 19 and the fourth surface 25 are in contact with surface 31 of the girder 28, thereby preventing or reducing the abovementioned damage and corrosion effects. As used herein, for the purposes of describing the invention the bolts 30, 30’, 30’’ have been interchangeably referred to as bolt heads 30, 30’, 30’’, without deviating from the structure and functioning of bolts.

Figures 6(a) and 6(b) show in even further close up the fixing arrangement of Figure 5, from slightly above and from slightly below, respectively. Bolt heads 30’, 30’’ engage a washer element 16 on surface 31. At the opposite end of bolt heads 30’, 30’’ are end of shafts 33’, 33’’, onto which, nuts 32’, 32’’ are screwed for fixing a girder 28 to an upright 29 with increased security against loosening. A corresponding second washer element 16’ is disposed between contacting surfaces (not shown) of nuts 32’, 32’’ and lower surface of the upright 29.

Advantages of the invention include the following:

• Secure positioning of the washer by means of the “torque arm”/second screw.
• No anchoring in the component surface is required. No special coating measures are required.
• No damaging of the surface. Risk of (crevice) corrosion at the component is reduced.
• Fewer gaps/parting lines and thus less preload force loss in the connection compared to conventional solutions.
• Defined friction surfaces when rotationally tightening. Rotating/turning is prevented.
• No loosening/unscrewing of the screw – affording reduced maintenance.
List of reference signs

1 wind turbine
2 nacelle
3 tower
4 nacelle cover
5 hub
6 rotor blade
7 rotor
8 blade root
9 jacket
10 washer
11, 12 ring
13 gap
14, 15 patterned surface
16 washer element
17 first washer portion
18 first surface
19 second surface
20 serrated formations
21 projection
22 torque arm
23 second washer portion
24 third surface
25 fourth surface
26 portion of a main frame
27 fixing arrangement
28 girder
29 upright
30 bolt heads
31 surface
32 nuts
33 shafts
,CLAIMS:Claims:

1. A washer element (16) for use in the attachment of one or more bolts (30, 30’, 30’’) to a first component, the washer element (16) comprising:
a first washer portion (17), the first washer portion (17) having a first aperture through which, in use, a first bolt (30’) passes, a first surface (18) and, a second surface (19) opposite the first surface (18);
a projection (21), integrally formed with the first washer portion (17); characterized in that one of the first surface (18) and the second surface (19) is patterned or roughened, so as to grippingly engage a head of the first bolt (30’).

2. A washer element (16) according to claim 1, characterized in that the other of the first surface (18) and the second surface (19) is smooth.

3. A washer element (16) according to claim 1 or 2, characterized in that the projection (21) includes a second washer portion (23), the second washer portion (23) having a second aperture through which, in use, a second bolt (30’’) passes.

4. A washer element (16) according to claim 3, characterized in that the second washer portion (23) has a third surface (24) and, opposite the third surface (24), a fourth surface (25).

5. A washer element (16) according to claim 4, characterized in that one of the third surface (24) and the fourth surface (25) is patterned or roughened, so as to grippingly engage a head of the second bolt (30”).

6. A washer element (16) according to claim 5, characterized in that the other of the third surface (24) and the fourth surface (25) is smooth.

7. A washer element (16) according to claim 6, characterized in that (i) the one of the first surface (18) and the second surface (19) that is patterned or roughened, and (ii) the one of the third surface (24) and the fourth surface (25) that is patterned or roughened, is on the same side of the washer element (16).

8. A washer element (16) according to any of the preceding claims, characterized in that the projection (21) includes a torque arm (22) integral with and extending from the first washer portion (17).

9. A washer element (16) according to claim 8, characterized in that the torque arm (22) has a length c. 0.25-2x, 0.5-1x or 0.5 to 0.75x the transverse dimension of the first washer portion (17).

10. A washer element (16) according to claim 8 or 9, characterized in that the torque arm (22) has a thickness less than that of the first washer portion (17) and/or the second washer portion (23).

11. A washer element (16) according to claim 3, or any claim dependent thereon, characterized in that the first washer portion (17) and the second washer portion (23) have the same size and/or shape.

12. A washer element (16) according to any of the preceding claims, characterized in that the first washer portion (17) and/or the second washer portion (23) is ring-shaped.

13. A fixing arrangement (27) comprising:
a first component (28);
one or more bolts (30, 30’, 30’’) attached to the first component (28);
a second component (29) fixedly attached to the first component (28) by means of the bolt(s) (30, 30’, 30’’);
characterized in that a washer element (16) according to any of the preceding claims is disposed between the or each bolt (30, 30’, 30’’) and the first component (28).

14. A fixing arrangement (27) according to claim 13, wherein the first component (28) comprises a main frame of a wind turbine (1), the second component (29) comprising further a wind turbine component fixedly attached the main frame.

15. A wind turbine (1), comprising:
a main frame, the main frame having therein or thereon a first component (28) and a second component (29);
characterized in that a washer element (16) according to any of claims 1 to 12 is disposed between the or each bolt (30, 30’, 30’’) and the first component (28); or
a fixing arrangement (27) according to claims 13 is disposed on the main frame.