FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ADAPTER FOR A HYBRID TOWER OF A WIND TURBINE;
SUZLON ENERGY LIMITED, A REGISTERED
COMPANY UNDER THE LAWS OF INDIA WHOSE
ADDRESS IS ONE EARTH, OPPOSITE
MAGARPATTA CITY, HADAPSAR PUNE – 411028, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Adapter for a hybrid tower of a wind turbine
Field of the Invention
The present invention relates to an adapter for connecting a steel tubular tower to a lattice tower of a wind turbine.
Background of the Invention
Very high steel tubular towers need certain stiffness due to arising vibration and the natural frequency. That is why a large tower diameter or a large wall thickness is required. The anchorage of steel tubular towers is often realized by means of a flange, particularly by means of a T-flange, which is mostly braced with a foundation by two ring-circularly arranged rows of anchor screws.
A maximum travelling height of 4.5 meters results due to the height of bridges as the transport of steel tubular towers from the manufacturing sites of the manufacturers to the installation sites has to be mostly realized by heavy goods transports onshore. The tower segments are mostly horizontally transported during transport which is why the maximum diameter of the tower segments in the area of the flange should not exceed the travelling height. The distance between the road and the transported tower segments corresponds at most of the heavy goods vehicles to approximately 0.1 to 0.2 meters. For this reason the maximum diameter of the tower segments including the flange should not exceed approximately 4.3 or rather 4.4 meters. In order to provide a sufficient platform and enough space for the positioning of the anchor screws, the outer width of the flange – that is the part of the T-flange which exceeds the diameter of the lateral area – should be greater than 0.25, mostly greater than 0.3 meters. This applies especially for towers with a height of more than 80 meters. For this reason the maximum tower diameter in the panel of the lateral area without the flange at the usage of conventional anchorage systems should not exceed a certain size, approximately 4.0 meters.
Because of the limitation in cross section of the tower segments due to the transport, 25 different measures have to be taken for wind turbines with higher towers in order to guarantee a sufficient stiffness of the tower. One possibility is

the development of the tower as lattice-tubular-hybrid tower. This hybrid tower combines a lattice tower with a tubular tower. Thus, the advantage arises that the upper tower segment formed as tubular tower is very torsional stiff and the lower tower segment formed as lattice tower can be transported in individual parts to the installation site. Therefore a very large platform can be achieved which leads to a high bending stiffness without exceeding the maximum travelling height of the tower segments. The lattice tower comprises at least three corner bars which are connected by means of several stabilizers and horizontal cross girders. The corner bars are designed for dissipating the bending moments which operate perpendicularly to the tower axis as well as for dissipating forces which operate in the tower axis. The stabilizers and the cross girders of the lattice tower are designed for dissipating torsional moments which operate around the tower axis as well as for dissipating forces which operate perpendicularly to the tower axis. At the tubular tower all forces and moments are dissipated via the cylindrical shell of the tube. Hence a problem occurs to combine the round tubular tower with the square lattice tower.
Summary of the Invention
It is an object of the invention to realize a transition between tubular and lattice tower without affecting the stability of the tower. According to the invention the object is solved with the features of claim 1 by means of an adapter for a hybrid tower of a wind turbine. The adapter according to the invention comprises an adapter shell and a number of adapter plates. The adapter shell is of tubular shape and has at least one flange with the same diameter as the lowermost section of the tubular tower so that the adapter shell may be connected with the tubular tower. Several elongated adapter plates are detachably arranged on the adapter shell in such a way that the adapter plate and adapter shell are overlapping in longitudinal direction of the tower. The adapter plate is designed in such a way that it may be connected with a corner bar of the used lattice tower. Due to the combination of the tubular adapter shell and adapter plates a transition from the round tubular tower to the square lattice tower is thus created. According to an embodiment of the invention, the adapter plates are designed double Y-shaped so that the vertical part of the Y forms a first central restiform or

longitudinal area for fastening of the adapter plate on the corner bar of the lattice tower and the expanded part of the Y forms a second area, quasi wings, for fastening the adapter plate on the adapter shell. Due to the Y-shaped design of 5 the adapter plate essentially four racks sticking out of the central area of the adapter plate are formed which are designed for incorporating fastening devices for fastening on the adapter shell.
The fastening devices arranged on the racks are also responsible for the transmission of loads from the adapter shell onto the adapter plate. The adapter plate is prepared with bore holes which are mostly arranged on the racks for accommodating the fastening devices. Thus essentially two upper and two lower areas with fastening devices are formed on each adapter plate according to this embodiment.
Due to intensive investigations it showed that the racks and the bore holes, which are arranged in the racks, for accommodating the fastening devices are advantageously aligned in an angle of 20-45° to the longitudinal axis of the adapter plate. It showed that hereby the vertical loads are possible evenly introduced without large changes in stiffness from the adapter plate via the adapter shell into the corner bar of the lattice tower and hence stress concentration can be avoided in the adapter shell and the corner bar.
In order to avoid an overload of individual fastening devices, the lower areas of the adapter plate are advantageously designed in a way that the fastening devices are located perpendicularly to the expected bending direction of the adapter plate. The upper areas with fastening devices are advantageously arranged in a way that the bending directions of the adapter shell are located perpendicularly to the outer fastening devices of the area. This arrangement of the areas shall achieve that no fastening device stands exposed and that therefore it comes to an overload of an individual fastening device and stress peaks in the area of the fastening device in the adapter plate and the adapter shell can be avoided.

According to the invention, the fastening devices can be for instance bolts, rivets or latches, advantageously bolts are used as these are detachable during the maintenance of the adapter piece and/or the tower. All bolted assemblies should be designed as high-strength pre-stressed bolted assemblies (GV-connections).
According to the invention, the central restiform or longitudinal area of the adapter plate is adapted to the form of the corner bar so that the adapter plate can be introduced into the corner bar and fastened. Preferably, the corner bar has a cruciform cross section, then the central longitudinal area preferably has a kind of V shape which fits between two flanks of the cross. The shape of the central longitudinal area can be achieved for example by bending of the adapter plate along the longitudinal axis or by division of the adapter plate along the longitudinal axis. By dividing the adapter plate the work effort is reduced as the step of the bending along the longitudinal axis is not applicable. Advantageously the central restiform area of the adapter plate shall be introduced until the connection of the next crossbrace of the lattice tower and should not end between two crossbraces, thus a secure transmission of forces and moments from the tubular tower section onto the lattice tower section is ensured.
At the lattice tower the corner bars define the bending stiffness and the crossbraces define the torsional stiffness, whereas at the tubular tower both are defined by the tower shell. The design of an adapter plate according to the invention for the first time ensures that the occurring vertical forces and bending moments of the tubular tower can be cleanly transmitted to the corner bars of the lattice tower whereas the torsional moments and shearing forces from the adapter plate are transmitted directly into the crossbraces of the lattice tower which is located under the adapter.
According to an embodiment, the adapter shell can be designed cylindrically. In a further preferred embodiment the adapter plate is designed so as to compensate for the difference between the vertical surface of the cylindrical adapter shell and the inclination of the corner bar. According to an alternative embodiment, the adapter plate has an angle, kink or bend, underneath the areas of the adapter plate which are connected to the adapter shell in order to guarantee a transition

from the inclination angle of the corner bars to the cylindrical adapter shell running parallel to the tower axis.
According to another embodiment, the adapter shell is designed conically. In this case it is preferred, that the cone angle of the adapter shell, i.e. the inclination angle of the adapter shell, corresponds to the inclination angle of the corner bars. This is not implicitly necessary, but makes sure that the adapter plate is designed compactly and the vertical forces and bending moments are transferred mainly by shear. The offset moments, which occur due to the offset between the adapter shell and the corner bars, stay small. The adapter shell can be produced from a formed steel sheet. Advantageously the adapter is made out of steel.
According to a further embodiment, only a lower part of the adapter shell is designed conically. In this case, the cone angle of the adapter shell should correspond to the inclination angle of the corner bars, too. The upper part of the adapter shell is designed cylindrically as this facilitates the assembly of the tubular tower to the adapter shell. Preferably, the adapter shell is designed such that the segments of an already existing tubular tower can be mounted onto the adapter.
Additionally, the conical adapter shell may be designed divisibly. Hence the diameter of the adapter shell can be larger than the diameter limited by the transport restrictions and the diameter possible for the transport can be fully used for the tubular tower. Advantageously the parts of the adapter shell are jointly connected with fish plating.
As the adapter plate transmits the vertical forces and the bending moments via shear force from the adapter plate into the corner bar, an offset moment is also generated by the eccentricity between adapter plate and corner bar which has to be carried by the corner bars and the adapter plate. The adapter plate has only a limited ability to carry forces perpendicular to the shell level; thus in a further preferred embodiment the adapter shell is advantageously stiffened with reinforcing ribs above and/or below the adapter plate.

Especially advantageously is an arrangement of a reinforcing rib at the upper end of the connection of the adapter plate and a reinforcing rib below the connection of the adapter plate. When a conical adapter shell is used, it is advisable to arrange an additional reinforcing rib between the cylindrical and conical shell area. This additional reinforcing rip inhibits a local buckling at this point of the adapter shell under pressure load and inhibits a straightening of the kink between the conical and cylindrical area under tensile load. The lowermost reinforcing rib is also used to transmit the torsional moments and shearing forces (forces acting perpendicularly to the tower axis) into the subjacent cross girder and to pass them onto the framework of the lattice tower. When connecting the lower reinforcing rib to the cross girder it should be prevented that the adapter shell rests on the cross girder or induces noteworthy vertical loads. This can be achieved for instance by means of a distance piece between the adapter shell and the cross girder. The gap should be defined in a way that it does not close, not even under extreme loads. The lowermost reinforcing rib now acts as a feather that can transmit horizontal loads, but has a limited ability to transmit vertical loads. The reinforcing ribs should be designed as T-profile or L-profile in order to prevent a buckling of the reinforcing rib as such.
The described combination of corner bar, adapter plates, adapter shell, stiffeners and cross girders allows to cleanly transfer the occurring forces and moments of the tubular section to the particularly responsible components of the lattice tower.
Advantageously, the adapter is arranged at the level of the blade tip of the erected wind turbine. Thus the very slim and torsional stiff tubular tower goes up to the blade tip, which creates a lot of clearance for the blades. This allows to design very flexible and therefore economically blades.
The adapter and the tubular tower may be connected conventionally, i.e. for example with ring flange connections or fish platings. If a division of the adapter should be necessary, this should be realized with fish platings, too. Advantageously the connections are screwed because this allows to replace damaged components quickly and economically, and unfavorable notches can be avoided.

Another aspect of the invention applies to a hybrid tower which is equipped with an upper part, designed as a tubular tower, a lower part, designed as a lattice tower, and the adapter according to the invention. Furthermore, the invention applies to a wind turbine with the hybrid tower as described above.
Brief Description of Drawings
Further details of the invention become apparent from the drawings description
with the help of the description.
Fig. 1 a wind turbine with a tubular tower known from the state of the art;
Fig. 2 a hybrid tower according to the invention;
Fig. 3 an exterior view of an adapter according to an embodiment of the
invention;
20 Fig. 4 an interior view of the adapter according to Fig. 3;
Fig. 5 a first top view of a first embodiment of an adapter plate according to the
Invention;
Fig. 6 a second top view of the adapter plate according to Fig. 5;
Fig. 7 a detailed view of a distance piece between the adapter and the cross
girder according to the invention; and
Fig. 8 to Fig. 12 show alternative embodiments of adapter plates according to the
invention.
Detailed Description of the Invention
Figure 1 shows a wind turbine 2 with a tubular tower 3 known from the state of the art, with a nacelle 4 mounted on the tower 3 and a rotor 5 with a hub 8 and three rotor blades 6 each being pivotable around a blade axis. The hub 8 is mounted on a rotor shaft, which is pivot-mounted in the nacelle 4. According to this embodiment the 10 tubular tower 3 is designed out of several tubular segments 16.
The specifications used in the following about an axial direction 9, radial direction 10 and specifications about “above”, “on top”, “upper”, “uppermost”, “below”, “lower”, “lowermost” etc. apply with respect to a longitudinal axis 7 of the erected tower 3 of the wind turbine 2.

Figure 2 shows a hybrid tower 11 according to the invention wherein an upper section of the hybrid tower 11 is designed as a tubular tower 3 and a lower section of the hybrid tower 11 is designed as a lattice tower 12. The tubular tower 3 and the lattice tower 12 are connected with each other by means of an adapter 1. The lattice tower 12 comprises at least three, in this embodiment four, corner bars 13 which are connected to each other by a number of cross girders 14 and cross braces 15. The corner bars 13 are designed for dissipating the bending moments acting perpendicularly to the tower axis 7 as well as for dissipating forces acting in the tower axis 7. The cross braces 15 of the lattice tower 12 are designed for dissipating torsional moments acting around the tower axis as well as for dissipating forces acting perpendicularly to the tower axis 7. The corner bars 13 are arranged with an inclination angle to the tower axis 7. The tubular tower 3 is connected to the lattice tower 12 via the adapter 1. For the tubular tower 3 already existing tubular segments 16 from the known tubular tower 3 can be used; here, for instance, the two uppermost segments 16 of the known tubular tower 3 are used. The adapter 1 is arranged on the level of the tip of the one rotor blade 6 located in the lowermost position. Hence the hybrid tower 11 is designed very slimly in the section of the rotor 5 so that it is ensured that the rotor blades 6 can freely move in relation to the hybrid 5 tower 11 even at high deflection of the rotor blades 6. Below the rotor 5 the width of the lattice tower 12 can be freely increased so that a large platform and thus a stable standing of the hybrid tower 11 can be guaranteed.
Figure 3 shows an adapter 1 mounted on top of the lattice tower 12. The adapter 1 comprises an adapter shell 17 and several adapter plates 18. The number of adapter plates 18 corresponds to the number of corner bars 13 of the lattice tower 12, hier four corner bars 13 and four adapter plates 18. In this embodiment, the adapter shell 17 is designed partly conically, here conical in a lower area and cylindrical in an upper area, with the cone angle αshell of the adapter shell 17 corresponding to the inclination angle αbar of the corner bars 13. Due to the conical design of the adapter shell 17 the adapter plate 18 can be designed compactly, and vertical forces and bending moments are mainly transmitted via shearing forces from the adapter shell 17 to the corner bars 13 of the lattice tower

12. The offset moments occurring due to the offset δ between adapter shell 17 and corner bar 13 remain low. In this embodiment, the production of the adapter plate 18 also proves to be easier for a (at least partially) conical adapter shell 17 as the adapter plate 18 does not have to compensate the inclination difference between adapter shell 17 and corner bar 13. An upper section of the adapter shell 17 in the area of the connection to the tubular tower 3 is here designed cylindrically, thus an easier installation and a better transfer of forces and moments from the tubular tower 3 are ensured. In order to fully utilize the maximum transport diameter for the tubular tower 3, the adapter shell 17 is of a divided design, here. Hence, the diameter of the lower section of the adapter shell 17 can exceed the maximum transport diameter in assembled state. During transport, the parts of the adapter shell 17 are dismantled so that the width to be transported is reduced. The parts of the adapter shell 17 are connected to each other via a screwed fish plating 20, here. The adapter plates 17 are detachably linked with the adapter shell 17 via fastening devices 19. Here the fastening devices 19 are designed as screwed connections.
Figure 4 shows an interior view of the adapter shell 17 with a 5 ring flange 21 for fastening the tubular tower 3 onto the adapter shell 17 of the adapter 1. In order to avoid deformation of the adapter shell 17 by forces acting perpendicularly to the shell level, the adapter shell 17 is stiffened with at least one reinforcing rib 22. In this embodiment, the adapter shell 17 is designed with a total of three reinforcing ribs 22. A first reinforcing rib 22a is arranged above the adapter plate 18 and a second reinforcing rib 22b is arranged below the adapter plate 18. The lower reinforcing rib 22b is additionally used to transmit the torsional moments and shearing forces (forces acting perpendicularly to the tower axis) to the subjacent horizontal cross girder 14 of the lattice tower 12, and onto the framework of the lattice tower 12 defined by the cross braces 15 and the cross girders 14. When connecting the lower reinforcing rib 22b to the cross girder 14 it should be preferably prevented that the adapter shell 17 rests on the cross girder 14 or induces noteworthy vertical loads.
The gap should be defined in a way that it does not even close under extreme loads. The lowermost reinforcing rib 22a now acts as a feather that can transmit

horizontal loads, but has only a limited ability to transmit vertical loads. If the adapter shell 17 is designed at least partially conically, additionally a reinforcing rib 22c should be arranged in the transition area from the conical to the cylindrical section. This reinforcing rib 22c prevents a local buckling at this point of the adapter shell 17 under pressure load and a straightening of the kink between the conical and cylindrical area under tensile load. The reinforcing ribs 22 should be advantageously designed as T profile or L-profile in order to prevent a buckling of the reinforcing rib 22 as such.
Figure 5 shows a first embodiment of an adapter plate 18 according to the invention in a top view orthogonally to a longitudinal axis 23 of the adapter plate 18. The adapter plate 18 is designed double Y-shaped and has a first central longitudinal area 31 for fastening the adapter plate 18 onto the corner bar 13 of the lattice tower 12. The central longitudinal area 31 is designed with bore holes 26 for accommodating the fastening devices 19.
The adapter plate 18 according to Fig. 5 further comprises a kind of wings 35 which extend laterally from the central longitudinal area 31. The wings 35 comprise four racks 27. Thus, in an upper section of the adapter plate 18 the double Y-shape forms four racks 27 which protrude from the central longitudinal area 31 of the adapter plate 18. The racks 27 are designed to accommodate the fastening devices 19 for fastening the adapter plate 18 onto the adapter shell 17. The fastening devices 19 arranged on the racks 27 are also responsible for the transmission of loads from the adapter shell 17 into the adapter plate 18. In order to accommodate the fastening devices 19, the adapter plate 18 comprises bore holes 26 which are mainly arranged on the racks 27. Thus on each adapter plate
18 basically two upper areas 29 and two lower areas 28 with fastening devices
19 are formed to fasten the adapter shell 17. The adapter shell 17 is provided with corresponding bore holes 26 to accommodate the fastening devices 19.
In this embodiment, the central longitudinal area 31 extends restiform between the wings 35 and below the wings 35. While in assembled status the wings 35 overlap the adapter shell 17, the part of the central longitudinal area 31 below the wings 35 does longitudinally protrude from the adapter shell 17, while on the

other hand, preferably, the central longitudinal area 31 is covered by the corner bar 13 both in the part between the wings 35 and in the part below the wings 35.
In order to avoid stress concentrations in the adapter plate 18, the transition areas from the racks 27 to the central longitudinal area 31 of the adapter shell 18 are designed with a radius R1, R2, R3. The radius R1, R2, R3 should be at least 150 mm, advantageously the radius R1, R2, R3 is at least 500 millimeters. The radii R1, R2, R3 can be equal; advantageously the radii R1, R2, R3 should be of different values and should be adapted to the loads in the respective area of the adapter plate 18.
Advantageously the racks 27 and the bore holes 26 arranged on the racks 27 for accommodating the fastening devices 19 are aligned in an angle ß of 20-45° to the longitudinal axis 23 of the adapter plate 18. Thus, it showed, that 5 the vertical loads are introduced from the adapter shell 17 via the adapter plate 18 into the corner bar 13 of the lattice tower 12 preferably constantly without large changes in stiffness, and thus stress concentrations in the adapter shell 17 and the corner bar 13 can be avoided.
In order to avoid an overload of individual fastening devices 19, the two lower areas 28 with fastening devices 19 are advantageously designed in a way that the fastening devices 19 are arranged perpendicularly to the expected bending direction of the adapter plate 18. The upper areas 29 with fastening devices 19 are advantageously designed in a way that the bending directions of the adapter shell 17 are arranged perpendicularly to the outermost fastening devices 19 of the area 29. By this arrangement of the areas 28 and 29 it is to be achieved that no fastening device 19 is exposed and an overload of an individual fastening device 19 can occur; thus, stress peaks in the area of the fastening device 19 in the adapter plates 18 and the adapter shell 17 shall be avoided.
When the adapter shell 17 is of a complete cylindrical design, the adapter plate 18 according to Fig. 5 would have to be adapted by bending along the bending line 33, so that a difference in angle between the adapter shell 17 and the corner bar 13 is compensated from the bending of the adapter plate 17.

Figure 6 shows the adapter plate 18 according to Fig. 5 in direction of the longitudinal axis 23. The adapter plate 18 is bended around the longitudinal axis 23, so that the central longitudinal area 31 of the adapter plate 18 has a V-form with two flanks. The spread of both flanks is defined by the used corner bar 13 of the lattice tower 12, so that contact surfaces 30 of the central longitudinal area 31 of the adapter plate 18 are aligned parallel to a respective contact surface of the corner bar 13 of the lattice tower 12. The racks 27 also have an angle to the contact surfaces 30, so that the racks 27 are aligned parallel to the contact surface of the adapter shell 17 and the bore holes 26 in the adapter plate 18 are aligned with the bore holes 26 in the 5 adapter shell 17.
In another embodiment the adapter plate 18 can be divided along the longitudinal axis 23 instead of being bended around the longitudinal axis 23. In this case, the adapter plate 18 is being cut along the longitudinal axis 23. Thus, both parts of the adapter plate 18 can be arranged to each other with the desired spread.
Figure 7 shows the connection of the reinforcing rib 22b with the cross girder 14 via a distance piece 32. The distance piece 32 should be defined in a way that the gap between the reinforcing rib 22b and the cross girder 14 does not even close in case of extreme loads. The gap between reinforcing rib 22b and cross girder 14 should be at least 20 mm. The lowermost reinforcing rib 22b now acts as a feather which transmits horizontal loads, but has only a limited ability to transmit vertical loads.
Fig. 8 to 12 show alternative embodiments of adapter plates according to the invention.
All embodiments of adapter plates 18, 118, 218, 318, 418, 518 according to the invention have in common a first, central longitudinal area 31, 131, 231, 331, 431, 531 and a second area comprising at least one wing 35, 135, 235, 335, 435, 535 which extends laterally from the central longitudinal area 31, 131, 231, 331, 431, 531 in circumferential direction of the adapter shell (e.g. 17). The embodiments of adapter plates presented in the figures each comprise two wings 35, 135, 235, 335, 435, 535 extending to both sides of the central longitudinal area 31, 131,

231, 331, 431, 531. But there could be embodiments (not shown) with only one wing extending to only one side of the central longitudinal area.
Further, all embodiments of adapter plates 18, 118, 218, 318, 418, 518 according to the invention have in common that the central longitudinal area 31, 131, 231, 331, 431, 531 is destined for the fastening of the adapter plate 18, 118, 218, 318, 418, 518 to the corner bar 13 of the lattice tower 12. Therefore the central longitudinal area 31, 131, 231, 331, 431, 531 has a restiform profile, which is conform to 5 the profile of the corner bar 13 in its area facing the adapter shell (e.g. 17, Fig. 4, but the adapter shell may not only be of partially conical shape, wherein a lower part of the adapter shell 17 is conical and an upper part of the adapter shell 17 is cylindrical, as shown in Fig. 4, but the adapter shell may alternatively be of full conical shape or cylindrical shape or partially conical shape with the lower part to be cylindrical and the upper part to be conical (not shown in the figures); usually, the cross-section dimension of the tubular tower in the area facing the adapter shell is not larger than the cross-section dimension of the lattice tower in the area facing the adapter shell). According to the invention the corner bars face the adapter shell from outside the adapter shell (e.g. 15 Fig. 3, 4).
The corner bars 13 according to the invention have a cruciform cross section, as can be seen in Fig. 4. Two of the four flanks of the cross surround the central longitudinal area 31, 131, 231, 331, 431, 531 of the adapter plate 18, 118, 218, 318, 418, 518. In alternative embodiments (not shown) the corner bars may have a V-shaped cross section, wherein the flanks of the V surround the central longitudinal area of the adapter plate. Preferably, the corner bars overlap with the adapter shell with respect to the longitudinal axis of the hybrid tower.
Further, all embodiments of adapter plates 18, 118, 218, 318, 418, 518 according to the invention have in common that the wings 35, 135, 235, 335, 435, 535 are destined for the fastening of the adapter plate 18, 118, 218, 318, 418, 518 to the adapter shell (e.g. 17). Therefore the wings 35, 135, 235, 335, 435, 535 have a profile, which is partially conform to the circumferential profile of the adapter shell (e.g. 17) on its outside facing the corner bar 13. Thus the adapter plate 18, 118,

218, 318, 418, 518 is arranged between the adapter shell (e.g. 17) and the corner bar 13.
The adapter plate 18 according to the embodiment of Fig. 5 is preferably used with an adapter shell 17, which is conical at least in the area where the adapter plate 18 is in contact with the adapter shell 17, i.e. the inclination angle αshell of the 5 adapter shell 17 is virtually identical with the inclination angle αbar of the corner bar 13 (e.g. Fig. 3, 4).
The adapter plates 118, 218, 318, 418, 518 according to the embodiments of Fig. 8 to 13 are preferably used with an adapter shell, which is cylindrical in the area where the adapter plate 118, 218, 318, 418, 518 is in contact with the adapter shell (not shown). Therefore the adapter plates 118, 218, 318, 418, 518 compensate for the difference between the inclination angle αshell of the adapter shell and the inclination angle αbar of the corner bar, i.e. while the wings 135, 235, 335, 435, 535 are in contact with the cylindrical surface of the adapter shell the central longitudinal area 131, 231, 331, 431, 531 is inclined with the inclination angle αbar of the corner bar. The wings 135, 15 235, 335, 435, 535 virtually taper along the longitudinal axis of the adapter plate 118, 218, 318, 418, 518.
The adapter plates according to the invention may comprise reinforcement elements 334, 434, which extend substantially orthogonally with respect to the longitudinal axis of the adapter plate 18, 118, 218, 318, 418, 518 within the central longitudinal area 20 31, 131, 231, 331, 431, 531, i.e. the reinforcement elements 334, 434 face the adapter shell. The reinforcement elements may be optionally comprised in all embodiments of the adapter plates. The reinforcement elements 334, 434 are shown for example in Fig. 10 and 11. But the reinforcement elements may be comprised in any embodiment of the adapter plates 18, 118, 218, 318, 418, 518.
The adapter plates 18, 118, 218, 318, 418, 518 may be casted or welded. They may be connected to the adapter shell by welding and/or by fastening devices, such as bolts, rivets, latches or screws. For example, it is intended, that the adapter plate 18 according to Fig. 5, 6, as well as Fig. 9, 10, 11, is connected

with both the adapter shell 17 and the corner bar 13 via fastening devices 19, which are inserted through bore holes 26, 226, 326, 426 in the adapter plate 18, 218, 318, 418, in the adapter shell 17 and in the corner bar 13. According to the embodiment of the adapter plate 118 of Fig. 8 it is intended, that the wings 135 of the adapter plate 5 118 are welded to the adapter shell, while the central longitudinal area 131 of the adapter plate 118 is connected with the corner bar via fastening devices, which are inserted through bore holes 126 in the adapter plate 118 and in the corner bar 13. Various combinations are possible.

We Claim :
1. Adapter (1) for a hybrid tower (11) of a wind turbine (2),
- wherein a lower section of the hybrid tower (11) is designed as lattice tower (12)
and an upper tower section of the hybrid tower (11) is designed as tubular tower
(3),
- the lattice tower (12) comprises at least three corner bars (13) connected with each other by cross girders (15) and cross braces (14), and the corner bars (13) are arranged in an angle (αbar) to a longitudinal axis (7) of the hybrid tower (11),
- the tubular tower (3) comprises at least one tubular section (16), and
- the lattice tower (12) and the tubular tower (3) are connected detachably by means of the adapter (1),
- wherein the adapter (1) comprises a tubular adapter shell (17) and a number of adapter plates (18) corresponding with the number of corner bars (13),
- wherein the adapter shell (17) and the adapter plates (18) are connected
detachably in a way that the adapter plates (18) at least partially overlap the
adapter shell (17) in longitudinal direction of the hybrid tower (11) and the adapter
plates (18), in assembled state of the adapter (1), are connected with the corner
bars (13) of the lattice tower (12), and wherein the adapter shell (17), in
assembled state of the adapter (1), is connected with the tubular tower (3).
2. Adapter (1) according to claim 1, wherein the adapter plate (18) comprises a first central area (31) for fastening of the corner bars (13) and a second area (35) for fastening the adapter shell (17), wherein the second area of the adapter plate (18), from an orthogonal view to a longitudinal axis (23) of the adapter plate (18), is designed as racks (27) sticking out from the upper part of the central area of the adapter plate, so that the adapter plate (18) basically forms a double Y-form and the racks (27) are designed for accommodating the fastening devices (19) for fastening the adapter shell (17) and to transfer loads from the adapter shell (17) into the corner bar (13).
3. Adapter (1) according to claim 2, wherein the racks (27) of the adapter plate (18) are basically arranged in an angle (β) of 20-45° to the longitudinal axis (23) of the adapter plate (18).

4. Adapter (1) according to claims 2 to 3, wherein the first part of the adapter plate (18) is designed in such a restiform way that the first part of the adapter plate (18) is insertable into the corner bar (13) of a lattice tower (12) and connectable with the corner bar (13) by means of fastening devices (19).
5. Adapter (1) according to claim 4, wherein the second restiform area of the adapter plate
(18) has a length so that the adapter plate (18), in a mounted condition within the corner bar (13) of a lattice tower (12), extends to a connection of the first cross brace (15) of the lattice tower (12).
6. Adapter (1) according to any of the preceding claims, wherein the adapter shell (17) is designed conically so that the adapter shell (17) has the same angle (αshell) to the longitudinal axis (7) of the tower (11) as the corner bars (13) of a lattice tower (12) connectable with the adapter (1).
7. Adapter (1) according to any of the preceding claims, wherein the adapter shell (17) has bore holes (26) for accommodating fastening devices (19) in order to fasten the adapter plate (18) onto the adapter shell (17).
8. Adapter (1) according to any of the preceding claims, wherein the adapter shell (17) has at least one reinforcing rib (22) pointing radially inwards.
9. Adapter (1) according to claim 7 and 8, wherein the adapter shell (17) has at least two reinforcing ribs (22) pointing inwards, wherein a first reinforcing rib (22a) is arranged above and a second reinforcing rib (22b) below the bore holes (26).

10. Adapter (1) according to claim 9, wherein the second reinforcing rib (22b) is detachably connected with the cross girder (14) by means of at least one distance piece (32).
11. Adapter (1) according to one of the preceding claims, wherein the adapter shell (17) is designed divisibly along the longitudinal axis (7) in such way that the

single parts of the adapter shell (17) do not exceed a width of approximately 4.3 meters in at least one direction.
12. Adapter (1) according to claim 11, wherein the parts of the adapter shell (17) are detachably connected to each other by means of a screwed connection.
13. Hybrid tower (11) for a wind turbine (2),

- wherein a lower section of the hybrid tower (11) is designed as lattice tower (12) and an upper section of the hybrid tower (11) is designed as tubular tower (3),
- the lattice tower (12) has at least three corner bars (13) connected with each other by means of cross girders (14) and cross braces (15) and the corner bars (13) are arranged in an angle (αbar) to the longitudinal axis (7) of the hybrid tower (12),
- the tubular tower (3) comprises at least one tubular section (16),
- wherein the lattice tower (12) and the tubular tower (3) are connected with each other by means of an adapter (1) according to one of the preceding claims.
14. Wind turbine (2), comprising a hybrid tower (11), a nacelle (4) rotatably
supported on the tower, a rotor shaft rotatably supported in the nacelle (4), and a
rotor (5) arranged on the rotor shaft with rotor blades (6) arranged on the rotor
(5), wherein the tower is designed as hybrid tower (11) according to claim 12.