U.S. patent application number 12/856024 was filed with the patent office on 2011-06-16 for wind turbine anchor element.
Invention is credited to Ingo Paura, Stefan Schwede, Stefan Voss.
Application Number | 20110138706 12/856024 |
Document ID | / |
Family ID | 44141351 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110138706 |
Kind Code |
A1 |
Voss; Stefan ; et
al. |
June 16, 2011 |
WIND TURBINE ANCHOR ELEMENT
Abstract
An anchor element for a tower includes an anchor plate element
including an upper surface, a lower surface, and at least one first
through-hole extending between the upper surface and the lower
surface; and at least one first nut having a female thread, the at
least one first nut being provided at the at least one first
through-hole at the lower surface of the anchor plate element so as
to cover the at least one first through-hole, wherein the at least
one first nut is non-releasably connected to the lower surface of
the anchor plate element.
Inventors: |
Voss; Stefan; (Salzbergen,
DE) ; Schwede; Stefan; (Munster, DE) ; Paura;
Ingo; (Meppen, DE) |
Family ID: |
44141351 |
Appl. No.: |
12/856024 |
Filed: |
August 13, 2010 |
Current U.S.
Class: |
52/173.1 ;
52/705; 52/745.21 |
Current CPC
Class: |
F05B 2260/301 20130101;
E04B 1/4157 20130101; E02D 27/42 20130101; Y02E 10/728 20130101;
F03D 13/10 20160501; Y02E 10/72 20130101; F03D 13/22 20160501 |
Class at
Publication: |
52/173.1 ;
52/705; 52/745.21 |
International
Class: |
E04H 12/00 20060101
E04H012/00; E04B 1/38 20060101 E04B001/38; E04H 14/00 20060101
E04H014/00 |
Claims
1. An anchor element for a tower, comprising: an anchor plate
element comprising an upper surface, a lower surface, and at least
one first through-hole extending between the upper surface and the
lower surface; and at least one first nut having a female thread,
said at least one first nut being provided at the at least one
first through-hole at the lower surface of the anchor plate element
so as to cover the at least one first through-hole, wherein said at
least one first nut is non-releasably connected to the lower
surface of the anchor plate element.
2. The anchor element according to claim 1, wherein the at least
one first nut is connected to the lower surface of the anchor plate
element such that a lower portion of the at least one first
through-hole is sealed from the space below the lower surface of
the anchor plate element.
3. The anchor element according to claim 1, wherein a shape of the
anchor plate element is an ring sector.
4. The anchor element according to claim 1, wherein a shape of the
anchor plate element is a closed ring.
5. The anchor element according to claim 1, wherein the at least
one first nut is closed at the end distal from the anchor plate
element.
6. The anchor element according to claim 1, wherein the at least
one first nut is a cap nut.
7. The anchor element according to claim 6, wherein the cap nut
further comprises a torque member adapted for anchoring the cap nut
in concrete when the anchor element is embedded within a tower
foundation.
8. The anchor element according to claim 7, wherein a cap of the
cap nut has a convex shape and the torque member comprises a plate
which is tangent to the cap of the cap nut.
9. The anchor element according to claim 7, wherein the torque
member comprises a plate attached to an outer surface of the cap
nut and extending at least partially in an axial direction of the
cap nut.
10. The anchor element according to claim 1, wherein the at least
one first nut is integrally formed with the lower surface of the
anchor plate element.
11. The anchor element according to claim 1, wherein at least one
first washer is provided between the lower surface of the anchor
plate element and the at least one first nut, the at least one
first washer being non-releasably connected to both the lower
surface of the anchor plate element and the at least one first
nut.
12. The anchor element according to claim 1, wherein the at least
one first nut is integrally formed with a washer.
13. The anchor element according to claim 1, further comprising: a
tower base plate provided above the anchor element, the tower base
plate having an upper surface, a lower surface, and at least one
second through-hole extending between the upper surface of the
tower base plate and the lower surface of the tower base plate; at
least one conduit extending between the lower surface of the tower
base plate and the upper surface of the anchor plate element and
connecting said at least one first and at least one second through
holes; and at least one anchor bolt accommodated within the at
least one conduit, a lower portion of the anchor bolt being
screwedly fixed to the female thread of the at least one first nut
and an upper portion of the at least one anchor bolt protruding
from the upper surface of the tower base plate and being fixed to a
second nut provided at the upper surface of the tower base
plate.
14. A wind turbine comprising: a tower having a lower portion; a
foundation having an upper surface; an anchor comprising: a lower
anchor member within the foundation and comprising an upper
surface, a lower surface, and a plurality of first through-holes
connecting the upper and the lower surface of the lower anchor
member, a plurality of lower nuts, each lower nut being provided at
a respective first through-hole at the lower surface of the lower
anchor member so as to cover said first through-hole and being
non-releasably connected to the lower surface of the lower anchor
member; an upper anchor member comprising an upper surface, a lower
surface, and a plurality of second through-holes connecting the
upper and the lower surface of the upper anchor member, each second
through-hole being substantially vertically aligned with one of the
first through-holes; a plurality of guide tubes, each guide tube
connecting a pair of first and second through-holes; a plurality of
anchor bolts, each anchor bolt being accommodated within one of the
guide tubes, a lower portion of said anchor bolt being screwedly
engaged with an inner thread of a corresponding lower nut and an
upper portion of said anchor bolt protruding from the upper surface
of the upper anchor member; and a plurality of upper nuts, each
upper nut fixing an upper portion a corresponding anchor bolt;
wherein the lower portion of the tower is rigidly connected to the
upper surface of the upper anchor member.
15. The wind turbine according to claim 14, further comprising: a
plurality of first washers, each first washer being provided
between the lower surface of the lower anchor member and one of the
lower nuts and being non-releasably connected to both the lower
surface of the lower anchor member and said lower nut.
16. The wind turbine according to claim 14, wherein at least one of
the lower anchor member and the upper anchor member is a plate
having a ring shape.
17. The wind turbine according to claim 14, wherein said lower nuts
are cap nuts.
18. A method for replacing an anchor bolt of a wind turbine,
comprising: (a) loosening and removing an upper nut at an upper
anchor member, (b) removing said anchor bolt by unscrewing a lower
portion of said anchor bolt from a lower nut which is
non-releasably connected to a lower anchor member and pulling said
anchor bolt out of a conduit extending between the lower anchor
member and the upper anchor member, (c) inserting an exchange
anchor bolt into said conduit and screwing together a lower portion
of said exchange anchor bolt and said lower nut, (d) forming a
rigid connection between the upper and lower anchor members by
fastening said upper nut at an upper portion of said exchange
anchor bolt.
19. The method according to claim 18, wherein the rigid connection
is formed by prestressing the anchor bolt.
20. The method according to claim 19, wherein prestressing the bolt
includes pulling said exchange anchor bolt into an axial direction
thereof such that a gap is formed between the upper nut and the
upper anchor member; tightening the upper nut; and releasing the
pulling force.
Description
BACKGROUND OF THE INVENTION
[0001] The subject matter described herein relates generally to
methods and systems for anchoring a wind turbine tower, and more
particularly, to methods and systems for anchoring a wind turbine
tower to a tower foundation.
[0002] At least some known wind turbines include a tower and a
nacelle mounted on the tower. A rotor is rotatably mounted to the
nacelle and is coupled to a generator by a shaft. A plurality of
blades extend from the rotor. The blades are oriented such that
wind passing over the blades turns the rotor and rotates the shaft,
thereby driving the generator to generate electricity.
[0003] As several other technical installations, a wind turbine
requires a tower or a mast to which the machine nacelle and the
wind rotor are mounted. Typically, the tower is made of steel and
is connected to a foundation made of reinforced concrete.
Typically, the connection is established by means of a flange with
through-holes at the bottom of the tower. Anchor bolts are inserted
into the through-holes and are fastened with nuts. Typically, the
anchor bolts are connected to an anchor ring embedded in the
foundation. Typically, the concrete surface of the foundation is
relatively rough so that a grout joint is formed on which the
flange is placed.
[0004] During operation of the wind turbine, varying wind loads are
applied to the wind rotor and nacelle and are transferred to the
foundation via the anchor bolts. Thus, it is desirable that damaged
or broken bolts can be exchanged. Furthermore, it is desirable to
inspect the anchor bolts so that damages can be detected at an
early stage.
BRIEF DESCRIPTION OF THE INVENTION
[0005] In one aspect, an anchor element for a tower includes an
anchor plate element comprising an upper surface, a lower surface,
and at least one first through-hole extending between the upper
surface and the lower surface; and at least one first nut having a
female thread, said at least one first nut being provided at the at
least one first through-hole at the lower surface of the anchor
plate element so as to cover the at least one first through-hole,
wherein said at least one first nut is non-releasably connected to
the lower surface of the anchor plate element.
[0006] In another aspect, a wind turbine includes a tower having a
lower portion; a foundation having an upper surface; an anchor
including a lower anchor member within the foundation and
comprising an upper surface, a lower surface, and a plurality of
first through-holes connecting the upper and the lower surface of
the lower anchor member, a plurality of lower nuts, each lower nut
being provided at a respective first through-hole at the lower
surface of the lower anchor member so as to cover said first
through-hole and being non-releasably connected to the lower
surface of the lower anchor member; an upper anchor member
comprising an upper surface, a lower surface, and a plurality of
second through-holes connecting the upper and the lower surface of
the upper anchor member, each second through-hole being
substantially vertically aligned with one of the first
through-holes; a plurality of guide tubes, each guide tube
connecting a pair of first and second through-holes; a plurality of
anchor bolts, each anchor bolt being accommodated within one of the
guide tubes, a lower portion of said anchor bolt being screwedly
engaged with an inner thread of a corresponding lower nut and an
upper portion of said anchor bolt protruding from the upper surface
of the upper anchor member; and a plurality of upper nuts, each
upper nut fixing an upper portion a corresponding anchor bolt;
wherein the lower portion of the tower is rigidly connected to the
upper surface of the upper anchor member.
[0007] In yet another aspect, a method for replacing an anchor bolt
of a wind turbine includes loosening and removing an upper nut at
an upper anchor member, removing the anchor bolt by unscrewing a
lower portion of the anchor bolt from a lower nut which is
non-releasably connected to a lower anchor member and pulling the
anchor bolt out of a conduit extending between the lower anchor
member and the upper anchor member, inserting an exchange anchor
bolt into the conduit and screwing together a lower portion of the
exchange anchor bolt and the lower nut, forming a rigid connection
between the upper and lower anchor members by fastening the upper
nut at an upper portion of the exchange anchor bolt.
[0008] Further aspects, advantages and features of the present
invention are apparent from the dependent claims, the description
and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A full and enabling disclosure including the best mode
thereof, to one of ordinary skill in the art, is set forth more
particularly in the remainder of the specification, including
reference to the accompanying figures wherein:
[0010] FIG. 1 is a perspective view of an exemplary wind
turbine.
[0011] FIG. 2 is a view of an anchor comprising anchor elements
according to embodiments described herein.
[0012] FIG. 3 is a cross-sectional detail view of an anchor element
according to embodiments described herein.
[0013] FIGS. 4 and 5 show top views of anchor plate elements
according to embodiments described herein.
[0014] FIGS. 6 and 7 show an anchoring device according to
embodiments described herein.
[0015] FIGS. 8 to 10 illustrate different embodiments of a cap nut
according to embodiments described herein.
[0016] FIG. 11 illustrates a method for replacing an anchor bolt
according to embodiments described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Reference will now be made in detail to the various
embodiments, one or more examples of which are illustrated in each
figure. Each example is provided by way of explanation and is not
meant as a limitation. For example, features illustrated or
described as part of one embodiment can be used on or in
conjunction with other embodiments to yield yet further
embodiments. It is intended that the present disclosure includes
such modifications and variations.
[0018] The embodiments described herein include a wind turbine
system in which the anchor bolts can be easily exchanged and
replaced. More specifically, damaged anchor bolts can be easily
replaced. In addition, an inspection of the anchor bolts is
enabled.
[0019] As modern wind turbines produce more and more power, they
also have to bear higher loads. These loads are transferred to the
foundation via the means for fastening the tower to the foundation
including anchor bolts. High fatigue loads that are transferred via
the anchor bolts may lead to an initial crack in the material and
cause further propagation of this crack. Before or after breakage
of the bolt, the bolt should be exchanged in order to maintain the
structural integrity of the bolt connection. As anchor bolts are
normally fixed inside a concrete foundation, it is typically an
elaborate and costly task to exchange such an anchor bolt.
[0020] However, problems may occur when there forms a bond between
the anchor bolt and the concrete. In other cases, a connection
between a nut and the anchor bolt is stronger than the connection
between the nut and the surrounding concrete. When trying to
unscrew the anchor bolt from the nut, it may therefore occur that
the connection between the fixing nut and the surrounding concrete
loosens and breaks leaving the nut and the anchor bolt inseparably
connected. Accordingly, the nut and anchor bolt turn loose below a
lower anchor plate, thus rendering it impossible to unscrew the
anchor bolt from the nut.
[0021] In view of the above, the present disclosure proposes to fix
the position of the nut such that after an initial installation the
nut is no longer able to move or turn. Also, it is suggested to
cover or protect the anchor bolt from concrete or other materials.
By these measures, the anchor bolt may be unscrewed from the nut
and exchanged.
[0022] It is an advantage of the embodiments disclosed herein that,
upon exchange of a damaged or broken anchor bolt, the nut fixing a
lower portion of the damaged anchor bolt will not turn which allows
removing the damaged anchor bolt without damaging the foundation.
This avoids a partial or total rebuilding of the foundation.
[0023] It is another advantage of the embodiments disclosed herein
that it is not necessary to leave damaged anchor bolts within the
foundation as it was done in the past. This will improve tower
stability and structural integrity.
[0024] It is yet another advantage of the embodiments disclosed
herein that the disclosed methods of exchanging a damaged anchor
bolt are cheaper than alternative solutions for fixing broken
anchor bolts.
[0025] As used herein, the term "anchor element" is intended to be
representative of a structure embedded or attached to a foundation,
wherein the structure is designed and adapted so that a bottom part
of wind turbine tower can be connected to it. As used herein, the
term "blade" is intended to be representative of any device that
provides a reactive force when in motion relative to a surrounding
fluid. As used herein, the term "wind turbine" is intended to be
representative of any device that generates rotational energy from
wind energy, and more specifically, converts kinetic energy of wind
into mechanical energy. As used herein, the term "wind generator"
is intended to be representative of any wind turbine that generates
electrical power from rotational energy generated from wind energy,
and more specifically, converts mechanical energy converted from
kinetic energy of wind to electrical power.
[0026] FIG. 1 is a perspective view of an exemplary wind turbine
10. In the exemplary embodiment, wind turbine 10 is a
horizontal-axis wind turbine. Alternatively, wind turbine 10 may be
a vertical-axis wind turbine. In the exemplary embodiment, wind
turbine 10 includes a tower 12 that extends from a tower foundation
150, a nacelle 16 mounted on tower 12, and a rotor 18 that is
coupled to nacelle 16. Rotor 18 includes a rotatable hub 20 and at
least one rotor blade 22 coupled to and extending outward from hub
20. In the exemplary embodiment, rotor 18 has three rotor blades
22. In an alternative embodiment, rotor 18 includes more or less
than three rotor blades 22. In the exemplary embodiment, tower 12
is fabricated from tubular steel to define a cavity (not shown in
FIG. 1) between support system 14 and nacelle 16. In an alternative
embodiment, tower 12 is any suitable type of tower having any
suitable height.
[0027] Rotor blades 22 are spaced about hub 20 to facilitate
rotating rotor 18 to enable kinetic energy to be transferred from
the wind into usable mechanical energy, and subsequently,
electrical energy. Rotor blades 22 are mated to hub 20 by coupling
a blade root portion 24 to hub 20 at a plurality of load transfer
regions 26. Load transfer regions 26 have a hub load transfer
region and a blade load transfer region (both not shown in FIG. 1).
Loads induced to rotor blades 22 are transferred to hub 20 via load
transfer regions 26 and then down into tower foundation 150 via
tower 12.
[0028] In one embodiment, rotor blades 22 have a length ranging
from about 15 meters (m) to about 91 m. Alternatively, rotor blades
22 may have any suitable length that enables wind turbine 10 to
function as described herein. For example, other non-limiting
examples of blade lengths include 10 m or less, 20 m, 37 m, or a
length that is greater than 91 m. As wind strikes rotor blades 22
from a direction 28, rotor 18 is rotated about an axis of rotation
30. As rotor blades 22 are rotated and subjected to centrifugal
forces, rotor blades 22 are also subjected to various forces and
moments. As such, rotor blades 22 may deflect and/or rotate from a
neutral, or non-deflected, position to a deflected position.
[0029] FIG. 2 is a view of an anchor 200 which is placed within a
tower foundation 150 which, e.g., may be a foundation of a wind
turbine 100. The anchor includes a lower anchor member 217 and an
upper anchor member 315, the latter being a part of a tower base
member 300. The lower anchor member 217 and the upper anchor member
315 are connected to each other by anchor bolts 340. The anchor
bolts 220 are screwed together with lower nuts 225 which are
mechanically fixed at a lower surface of a lower anchor plate. At
the upper end, the anchor bolts 340 are fixed to the upper anchor
member 315 by upper nuts 325. The anchor bolts 340 are accommodated
in guide tubes (not shown in FIG. 2) extending between the lower
surface of the upper anchor member and the upper surface of the
lower anchor member. The guide tubes protect the anchor bolts 340
from concrete of the foundation which may harm the connection
between the lower nuts 325 and the anchor bolts 340.
[0030] The tower base member 300 and the upper anchor member 315
both have a cylindrically symmetric shape and are machined as one
piece. According to some embodiments, both the lower anchor member
217 and the upper anchor member 315 are plates and have a shape of
a closed ring. According to some embodiments, the ring-shaped
members are formed from a plurality of sectoral pieces, in a
non-limiting example eight to twelve sectoral pieces. The pieces
may then be fixed to each other, for example by welding, at the
construction site. Alternatively, the plate members may be formed
in one piece.
[0031] FIG. 2 shows that the lower anchor member 217 is placed in a
lower part of the foundation 150. The upper ends of anchor bolts
340 protrude from foundation 150 at a point where a recess is
formed. The upper anchor member 315 is placed over the upper ends
of anchor bolts 340 such that anchor bolts 340 protrude through
second through-holes formed within upper anchor member 315. Here,
the tower base member 300 is aligned such that the side walls of
the tower base member 300 are vertical. Then, a grout joint 360 is
produced within a gap between foundation 150 and the lower end of
upper anchor member 315. After the grout joint 360 has cured, tower
foundation 150 is finished including tightening anchor bolts 340 to
upper anchor member 315 by means of upper nuts 325. Thereafter, the
tower can be built further to the top.
[0032] According to another embodiment, upper anchor member 315 may
be a part which is separate from tower base member 300. In that
case, upper anchor member 315 may be connected to a lower tower
portion by other means, for example by welding, screwing, riveting
or using further anchor bolts.
[0033] FIG. 3 shows a detailed cross-sectional view of an anchor
element 200 according to an embodiment. The anchor element 200
includes an anchor plate element 215, a tower base member 300, a
conduit 350, an anchor bolt 340, a first nut 220, a second nut 320,
a first washer 230, and a second washer 330. The tower base member
300 includes a tower base plate 310 and a T-flange 316 for
connecting the anchor element 200 to a lower portion of tower 12.
In a typical embodiment, anchor plate element 215 is a ring sector
as shown in FIG. 4. In the embodiment shown in FIG. 4, the ring
sector spans 40.degree. degrees so that nine ring sector element
make a full 360.degree. ring. However, the 360.degree. degree
ring-shaped lower anchor member 217 may be formed from less or more
than nine anchor elements. Accordingly, the ring sectors may span
more or less than 40.degree. degrees. Typically, the ring sectors
are welded to each other before foundation 150 is filled with
concrete.
[0034] The anchor element 200 shown in FIG. 3 includes an anchor
plate element 215 having an upper surface 211, a lower surface 212
and a first through-hole 213 which extends between the upper
surface 211 and the lower surface 212. The anchor plate element 215
may be assembled with other anchor plate elements to form a
ring-shaped anchor plate 210. Typically, the upper 211 and lower
surfaces 212 are flat surfaces and parallel to each other.
Typically, the first through-hole 213 is a cylindrical aperture
having a constant diameter over its length and is formed
perpendicular to surfaces 211 and 212.
[0035] The anchor element 200 further includes a tower base plate
310 provided above the anchor plate element 215 or the anchor plate
210. The tower base plate 310 has an upper surface 311, a lower
surface 312, and a second through-hole 313 which extends between
the upper surface 311 and the lower surface 312. Typically, tower
base plate 310 has a cylindrically symmetric shape and is machined
as one piece. However, it may be formed from several pieces in a
similar way as anchor plate 210. Tower base plate 310 forms a part
of tower base member 300 which is the lowest part of the tower 12.
The tower base plate 310 further includes a T-flange 316 which is
used to connect tower 12 to the tower base member 300.
[0036] The upper 311 and lower surfaces 312 are flat surfaces and
parallel to each other. Each second through-hole 313 is a
cylindrical tube having a constant diameter over its length and is
perpendicular to surfaces 311 and 312. The diameter of the second
through-hole 313 may be equal or different than the diameter of the
first through-hole 213. Furthermore, the second through-hole 313 is
vertically aligned with the first through-hole 213.
[0037] Tower base plate 310 and anchor plate 210 are connected to
each other by anchor bolt 340, a first washer 230, a second washer
330, first nut 220, and second nut 320. Within the completed
foundation 150, the anchor is surrounded by concrete. However, the
concrete does not come into contact with anchor bolt 340 since the
conduit 350 and the first nut 220 shield anchor bolt 340 from the
concrete.
[0038] In one embodiment, conduit 350 is a cylindrical tube which
has a diameter slightly smaller than first through-hole 213 and
second through-hole 313. Conduit 350 has a length so that it may be
disposed between the upper surface 311 of the tower base plate 310
and the lower surface 212 of the anchor plate element 215 within
first through-hole 213 and second through-hole 313. According to an
alternative embodiment, conduit 350 may have a slightly larger
diameter than the first 213 or second through-hole 313 and may be
attached to upper surface 211 or lower surface 312 around a
respective through-hole 213, 313.
[0039] According to the embodiment of FIG. 3, the anchor element
200 further includes anchor bolt 340 which is accommodated within
conduit 350 and fixed below a lower surface 212 of the anchor plate
210 and above an upper surface 311 of the tower base plate 310.
Anchor bolt 340 includes a lower anchor bolt external thread 341 at
a lower portion of the anchor bolt 340 and an upper anchor bolt
external thread 342 at an upper portion of the anchor bolt 340.
[0040] The lower anchor bolt external thread 341 is screwed
together with the internal thread of first nut 220. The upper
portion of anchor bolt 340 protrudes from the upper surface 311 of
the tower base plate 310 where upper anchor bolt external thread
342 is screwed together with the internal thread of second nut 320.
The second washer 330 is disposed between second nut 320 and upper
surface 311 of the tower base plate 310.
[0041] The first nut 220 is provided around the rim of first
through-hole 213 at the lower surface 212 of the anchor plate
element 215. First nut 220 is connected in a non-releasable manner
to the lower surface 212 of anchor plate 210. For example, first
nut 220 may be welded to lower surface 212 or be integrally formed
with lower surface 212 in a different way. Typically, first nut 220
is a closed cap nut but may also be an open cap nut according to
another embodiment.
[0042] According to the embodiment of FIG. 3, a first washer 230 is
provided between lower surface 212 of anchor plate element 215 and
first nut 220. According to this embodiment, first washer 230 is
spot-welded to lower surface 212 and first nut 220 is spot-welded
to first washer 230. According to another embodiment, a stiff
connection between anchor plate element 215 and first nut 220 is
established mechanically.
[0043] According to yet another embodiment, first nut 220 is closed
at an end distal from anchor plate element 215. Thus, it may be
avoided that concrete flows inside first nut 220 and does harm to
the connection between anchor bolt 340 and first nut 220.
[0044] To provide a better grip of first nut 220 to the concrete
and, thus, to avoid turning loose of first nut 220 and anchor bolt
340, a torque member 221 is provided at nut 220. Torque member 221
is adapted for supporting the cap nut in the concrete. If the screw
joint between bolt 340 and nut 220 is loosened, torque member 221
absorbs the applied torque and provides sufficient counter torque
so that cap nut 220 is held in place. Thus, unscrewing bolt 340
from cap nut 220 is enabled even if the connection between cap nut
220 and lower surface 212 breaks.
[0045] In one embodiment, torque member 221 is a metal plate having
essentially the same thickness as the wall of the cap nut. A
central area of the torque member 221 is fixed to the cap nut at a
portion of the convex cap of the cap nut, typically at the apex
thereof. According to another embodiment, the torque member is a
plate provided at a cylindrical outer surface of the cap nut and
substantially extending along an axial direction of the nut. Yet
further embodiments for the torque member 221 are described below
with reference to with FIGS. 6 and 7.
[0046] FIGS. 4 and 5 show top views of an anchor plate element 215.
FIG. 4 illustrates an anchor plate element 215 in the shape of a
ring sector spanning 40.degree. degrees or one-ninth of a full
circle. Accordingly, nine anchor plate elements 215 like the one
depicted in FIG. 4 may be used to form a full ring, i.e. to form
anchor plate 210. Typically, the nine anchor plate elements 215 are
assembled by spot-welding the anchor plate elements 215 to each
other.
[0047] Anchor plate element 215 of FIG. 4 has two rows of
through-holes 213. According to a typical embodiment, the number of
through-holes 213 in a full ring is 54 or 62 for a single row.
Therefore, the anchor plate element 215 of FIG. 4 includes only
one-ninth, i.e. six through-holes in each row. It will be
understood that these numbers are merely examples and may be higher
or lower in actual embodiments of the present invention.
[0048] FIG. 5 illustrates an anchor plate element 215 having the
shape of a full ring, i.e. spanning 360.degree. degrees. As
explained with reference to FIG. 4, each row of the anchor plate
according to this embodiment includes 54 through-holes, resulting
in a total of 108 through-holes for the whole anchor plate
element.
[0049] FIGS. 6 and 7 show different views of an embodiment of a
torque member 221. FIG. 6 shows a cross sectional side view of the
first nut 220 with torque member 221. FIG. 7 shows a top view of
the same first nut 220 depicted in FIG. 6. Torque member 221 is a
wing shaped metal plate extending in a direction substantially
parallel to the longitudinal axis of cap nut 220. Thus, the
wing-shaped torque member 221 will resist any torque applied to cap
nut 220 when anchor bolt 340 is screwed together or unscrewed
therefrom.
[0050] FIGS. 8 to 10 illustrate different realizations of cap nut
220. In the embodiments shown in FIGS. 8 to 10, a lower anchor bolt
external thread 341 of anchor bolt 340 forms a screw joint with an
internal thread (not shown in FIGS. 8 to 10) of cap nut 220.
Furthermore, first nut 220 is non-releasably connected to a lower
surface 212 of an anchor plate 215 element in the embodiments shown
in FIGS. 8 to 10.
[0051] FIG. 8 shows the lower part of anchor element 200 in which
first nut 220 is spot-welded to lower surface 212 of anchor plate
member 215 around the rim of first through-hole 213.
[0052] FIG. 9 shows a different embodiment of first nut 220 in
which first nut 220 includes a washer which is integrally formed
with first nut 220. According to this embodiment, first nut 220 is
spot-welded to lower surface 212 of anchor plate member 215 around
the rim of first through-hole 213.
[0053] FIG. 10 shows yet another embodiment of anchor plate member
215 in which first nut 220 is integrally formed with the lower
surface 212 of anchor plate element 215. Due to the omission of
welding, the long-term stability of the connection of first nut 220
to anchor plate member 215 is improved.
[0054] FIG. 11 illustrates a method 400 for replacing an anchor
bolt. After the start of the method, it is decided in a first block
405 whether there is a broken or damaged anchor bolt. In case there
is no broken or damaged anchor bolt, the method terminates. In case
there is at least one broken or damaged anchor bolt 340, the method
continues to block 410.
[0055] In the next block 410, a second nut 320 securing a
connection between an anchor bolt 340 and an upper surface 311 of a
tower base plate 310 is loosened and removed. In this context, the
tower base plate 310 is considered a part of a wind turbine tower
base member 300.
[0056] In a next block 415, the anchor bolt 340 is removed by
unscrewing the anchor bolt 340 from of a first nut 220 which is
connected to an anchor plate element 215, and guided out of a
conduit 350 extending between the anchor plate element 215 and the
tower base plate 310.
[0057] In the next block 420, an exchange anchor bolt is inserted
into the conduit 350 and screwedly fixed to the first nut 220.
[0058] In the following blocks 425, 430 and 435 the second nut 320
is fastened onto the exchange anchor bolt 340 on an upper surface
311 of the tower base plate 310.
[0059] To this end, in block 425 the exchange anchor bolt 340 is
pulled into a direction orthogonal to the surface of the tower base
plate 310 such that a gap is formed between said second nut 320 and
the tower base plate 310, thus prestressing the anchor bolt.
[0060] In the next block 435, the second nut 320 is fastened such
that the gap vanishes. In the following block 440 the pulling force
is released such that the anchor bolt 340 is pressed towards the
tower base plate 310. This fastens the second nut 320 onto the
exchange anchor bolt 340 and leaves bolt 340 prestressed. According
to some embodiments, the second nut 320 may be tightened on the
exchange anchor bolt 340 with a predetermined torque.
[0061] In the next block 440 it is decided whether there still is a
broken or damaged anchor bolt 340. In case there is still at least
one broken or damaged anchor bolt 340, the method goes back to step
410. In case there is no broken or damaged anchor bolt 340, the
method terminates. Alternatively, the method may terminate after
block 435, i.e. after exchanging a single anchor bolt.
[0062] Exemplary embodiments of anchor elements and methods for
exchanging anchor bolts are described above in detail. The anchor
elements and methods for exchanging anchor bolts are not limited to
the specific embodiments described herein, but rather, components
of the elements and/or steps of the methods may be utilized
independently and separately from other components and/or steps
described herein. For example, the anchor elements may also be used
for antenna towers or bridge pylons, and are not limited to
practice with only the wind turbine systems as described herein.
Rather, the exemplary embodiment can be implemented and utilized in
connection with many other applications.
[0063] Although specific features of various embodiments of the
invention may be shown in some drawings and not in others, this is
for convenience only. In accordance with the principles of the
invention, any feature of a drawing may be referenced and/or
claimed in combination with any feature of any other drawing.
[0064] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. While various specific embodiments have been disclosed in
the foregoing, those skilled in the art will recognize that the
spirit and scope of the claims allows for equally effective
modifications. Especially, mutually non-exclusive features of the
embodiments described above may be combined with each other. The
patentable scope of the invention is defined by the claims, and may
include other examples that occur to those skilled in the art. Such
other examples are intended to be within the scope of the claims if
they have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal language
of the claims.
* * * * *