Device and method for connecting a wind turbine tower to a base

Abstract

The present invention relates to a metal ring for connecting a metal wind turbine tower to a concrete base, the ring being annular in shape, centred about an axis, and comprising: a first disc comprising a plurality of anchoring holes, each anchoring hole allowing the passage of a preloaded cable in order to anchor the first disc to the concrete base, and a second disc, spaced apart from the first disc, and comprising a plurality of clamping holes, each of the clamping holes being situated facing a corresponding anchoring hole in the first disc to allow a clamping tool to engage in the clamping hole, in order to apply tension to the preloaded cable passed through the anchoring hole that faces the clamping hole. The first and second discs are interconnected by a first generally annular metal spacer and form a single piece.

Description

[0001] DESCRIPTION

[0002] TITLE Device and method for connecting a wind turbine mast to a base

[0003] FIELD OF INVENTION

[0004] The present invention relates to a device and a method for connecting a metal structure to a concrete structure. More specifically, it relates to the connection of a metal wind turbine mast to a concrete base, gravity-based or floating.

[0005] STATE OF THE ART

[0006] An offshore wind turbine consists of a wind turbine with a rotor and a generator, which is placed at the top of a mast. The mast itself is attached to a structure (or base), fixed to the seabed or floating on the water. The bases are generally made of concrete.

[0007] Attaching a metal wind turbine mast to a concrete base generally involves a device for connecting the mast to the base. The connection device, which is fixed between the mast and the base, must be able to withstand significant stresses. These stresses can be mechanical (significant moments, horizontal and vertical forces during assembly of the mast on the base and during operation). Stresses are also induced by the marine environment.

[0008] Document NO345416B1 proposes a device for connecting a metal mast to a concrete base comprising several metal rings separated by concrete-filled formwork. This connection device comprises two rings, each of which must be successively positioned and fixed, which requires several operations during the connection of the mast to the base and makes the installation of the connection relatively long and complex. Furthermore, this connection device does not allow the cables to be tensioned after the positioning of the connection device.

[0009] Document CN 105673354A proposes a connection device which also uses two metal rings separated by one or more concrete-filled formworks. The connection device in this document is subject to the same limitations as the device in NO345416B1.

[0010] WO 2017 / 108043A1 proposes a device for connecting a metal mast, the mast resting on a metal ring, to a concrete base by means of two rows of bolts. To fix the connection device, the bolts pass through this base and are fixed on the one hand to the mast and on the other hand to another metal ring. Pre-stressing of the cables is then not possible after the installation of the connection device. Furthermore, the same bolts fix both the mast to the metal ring, and the metal ring to the concrete base, which requires in particular a large dimensioning of these bolts.

[0011] It would be advantageous to address some or all of the limitations outlined above.

[0012] STATEMENT OF THE INVENTION

[0013] One aim of the invention is to solve at least one of the problems mentioned above.

[0014] To this end, according to one aspect of the present invention, a metal crown is proposed for connecting the T-shaped flange of the foot of a metal wind turbine mast to a concrete base, the crown being generally annular in shape, centered around an axis of the mast, and comprising:

[0015] - an anchor disc comprising several anchor holes, each anchor hole being adapted to allow the passage of a prestressing cable in order to anchor said anchor disc in the concrete base, and

[0016] - a fixing disc, spaced from the anchoring disc by a first spacer, and comprising several clamping holes, each of said clamping holes being located opposite a respective anchoring hole of the anchoring disc to allow the engagement of a clamping tool in said clamping hole, in order to apply tension to the prestressing cable passed through said anchoring hole which is opposite said clamping hole; the anchoring disc and the fixing disc being connected to each other by the first generally annular metal spacer; the anchoring disc, the fixing disc and the spacer being centered on the axis and forming a single part; the fixing disc further comprising through fixing holes, adapted to allow the mast to be fixed to the fixing disc.

[0017] This connecting crown is thus made up of a single metal element whose geometry allows it to adapt to the shape of the base. Such a crown is also very easy to produce in the factory.

[0018] Furthermore, such a crown can be installed easily and in a single step. Indeed, it can be entirely produced prior to its positioning on the base. Advantageously, but optionally, the exposed crown includes at least one of the following characteristics:

[0019] - the anchoring disc and the fixing disc are connected to each other by a second generally annular metal spacer, centered on the axis and forming a single piece with the anchoring disc, the fixing disc and the first spacer;

[0020] - the first and second spacers are hollow cylinder-shaped, one of the first and second spacers forming a first hollow cylinder, and being positioned radially internally with respect to the anchoring and clamping holes, and the other forming a second hollow cylinder, and being positioned radially externally with respect to the anchoring and clamping holes; the first and second spacers are welded to the anchoring disc and to the fixing disc;

[0021] - the anchor disc and the fixing disc are connected to each other by several additional metal spacers, each of the neighboring anchor holes being separated from each other by an additional spacer, the additional spacers are welded onto the anchor disc and onto the fixing disc;

[0022] - the fixing disc comprises a plurality of groups of fixing holes, each group being located near each respective clamping hole and framing said clamping hole, two intrados fixing holes being positioned radially internally relative to the clamping hole and two extrados fixing holes being positioned radially externally relative to the clamping hole;

[0023] - the crown comprises several angular portions of adjoining crowns, around the axis.

[0024] According to another aspect, there is provided a connection device, comprising a crown according to one of the above aspects, and anchoring means for fixing the crown to a concrete base, the anchoring means each comprising several prestressing cables, intended to be fixed in the concrete base, and an anchoring head for fixing the crown to the prestressing cables.

[0025] According to another aspect, there is provided a wind turbine comprising a rotor, a generator, a mast, a base and such a connection device.

[0026] According to another aspect, there is provided a method of connecting a metal wind turbine mast to a concrete base by means of such a connection device, the method comprising the following steps of: - casting the concrete base, the casting providing sheaths, by means of metal trumpets, for the placement of the prestressing cables;

[0027] - adjustment of several leveling devices on an upper end of the concrete base;

[0028] - positioning of a circular seal around each respective sheath at the upper end of the concrete base;

[0029] - placing the crown on the leveling devices, the anchor disc facing the concrete base and each anchor hole being coaxial with each respective sheath;

[0030] - injection of a layer of setting mortar between the concrete base and the crown

[0031] - insertion of prestressing cables into the sheaths;

[0032] - positioning an anchor plate and the anchor head at each respective anchor hole, to tighten the prestressing cables in each anchor hole;

[0033] - fixing the crown on the concrete base by means of the tightening tool, introduced through each respective tightening hole, and tensioning the prestressing cables on the anchor heads;

[0034] - injection of cement grout into the sheaths around the prestressing cables and around the anchor heads; and

[0035] - fixing the mast on the crown by tightening fixing means in each fixing hole of the fixing disc.

[0036] Advantageously, but optionally, the method may comprise the following characteristic:

[0037] - the step of fixing the crown on the concrete base is carried out using a tensioning jack.

[0038] DESCRIPTION OF THE FIGURES Other characteristics, aims and advantages of the invention will emerge from the following description, which is illustrative and not limiting, and which must be read in conjunction with the appended drawings in which:

[0039] Figure 1 is a perspective view of a wind turbine, fixed to a base by a connection device, according to an embodiment of the present invention;

[0040] Figures 2a and 2b are top views of a connecting crown according to an embodiment of the present invention;

[0041] Figure 3 is a top and perspective view of an angular portion of the crown, according to another embodiment of the present invention;

[0042] Figure 4 is a partial sectional view in a radial plane - that is to say a plane comprising the central longitudinal axis of the mast (this axis being the axis of symmetry of the mast in the case of a cylindrical mast) - of a device for connecting a wind turbine mast to a concrete base, according to an embodiment of the present invention, with a partial view of the mast and the base;

[0043] Figures 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j represent steps of a method of connecting a wind turbine mast to a concrete base by means of a connecting device, according to a particular implementation of the present invention; and

[0044] Figure 6 is a flowchart of a method of connecting a metal wind turbine mast to a concrete base, according to a particular implementation of the present invention.

[0045] Throughout the figures, identical elements have identical references.

[0046] DETAILED DESCRIPTION OF THE INVENTION

[0047] General presentation of a wind turbine

[0048] In the remainder of the description, we will call "radial" that which is oriented primarily by a vector collinear with a radius and "axial" that which is oriented primarily by a vector collinear with an axis of symmetry. And we will call internal that which is radially closer to the axis of symmetry and external that which is radially less close to the axis of symmetry. A wind turbine E as illustrated in Figure 1 can be a fixed, gravity or floating wind turbine.

[0049] The wind turbine E comprises a base 1, otherwise called a base, a mast 2, or pylon, a means 3 for fixing the mast 2 to the base 1, otherwise called a connection device, and a means of producing energy 4.

[0050] The energy production means 4 comprises a generator 41 and a rotor 42. The generator 41 is fixed to an upper end 22 of the mast 2 and is connected to the rotor 42.

[0051] The rotor 42 comprises several blades 421. The rotor 42 is driven in rotation along an axis Y of rotation perpendicular to the axis X of the mast 2. The generator 41 produces electricity under the action of the rotation of the blades 421 driving the rotor 42 in rotation relative to the generator 41.

[0052] The base 1 may have various shapes depending on whether the wind turbine E is a land-based or marine wind turbine, and depending on the environmental conditions in which it is positioned. The base 1 ensures the stability of the wind turbine E. The base 1 is advantageously made of concrete. The concrete may be of various types depending on the type of wind turbine E and the environment in which it is positioned. The base 1 may include ballasts (not shown) in order to stabilize the wind turbine E.

[0053] Advantageously, the base 1 comprises a central tower 11 supporting at least one wind turbine E, a lower pontoon structure 12 having at least three arms 121 arranged in a stellar configuration and pads 13 rigidly connected to the pontoon structure 12. The pontoon structure 12 projects from a lower portion 111 of the central tower 11. The pads 13 are rigidly connected to the pontoon structure 12 at the distal sections 1221 of each arm 121. The central tower 11 is preferably cylindrical in shape and may be hollow or partially hollow. This configuration ensures good stability for the base 1 and therefore for the wind turbine E.

[0054] The mast 2 extends along its axis X. The mast 2 is advantageously cylindrical or conical in shape. Preferably, the mast 2 has a circular or polygonal section. The mast 2 is preferably made of a metallic material because it must withstand significant mechanical bending and torsional stresses. The choice of metal also makes it possible to reduce the weight of the mast, which facilitates its transport and installation. Still with reference to Figure 1, and also to Figure 4, a lower end 21 of the mast 2 is fixed to the base 1 by means of the connection device 3. For this, the lower end 21 of the mast 2, in other words the foot of the mast 2, comprises a flange 211 in the shape of an inverted T. More precisely, the flange 211 has a radial section which forms an inverted T.The flange 211 comprises a central branch 2111, merged with the wall of the mast 2, and two transverse branches 2112 which extend on either side of this central branch 2111, at the lower end of the flange 211 foot 21 of the mast 2. The elements 211, 2111, 2112, 2113, 2114 are not visible in figure 1 but they are visible in figure 4.

[0055] Thus, the transverse branches 2112 forming the flange 211 of the foot 21 of the mast 2 allow, as illustrated more particularly in FIG. 4, a fixing of the latter to the connection device 3. The two transverse branches 2112 which extend on either side of the central branch 2111 of the flange 211 make it easier to fix the mast 2 to the crown 31 and therefore the connection of the mast 2 to the base 1. Thus, the flange 211 can be fixed to the crown 31 by each of the two transverse branches 2112 on either side of the central branch 2111, and distribute the forces uniformly on the crown 31.

[0056] As illustrated in Figure 4, the flange 211 comprises a plurality of fixing holes 2113, 2114 for fixing the flange 211. The fixing holes 2113, 2114 of the flange 211 are positioned at regular intervals and at a constant radius around the axis X of the mast 2. Preferably, the fixing holes 2113, 2114 are distributed in an alignment of holes, called intrados fixing holes 2113, positioned radially internally with respect to the central branch 2111, and in an alignment of holes, called extrados fixing holes 2114, positioned radially externally with respect to the central branch 2111. The intrados fixing holes 2113 and the extrados fixing holes 2114 are equidistant from the central branch 2111. The central branch 2111 of the flange 211 forms thus a circular symmetry between the alignment of the intrados fixing holes 2113 and the alignment of the extrados fixing holes 2114.This allows the flange 211 to be uniformly fixed to the crown 31 without inducing moments in the flange 211.

[0057] Connection device

[0058] The connecting device 3 makes it possible to connect the metal mast 2 of the wind turbine E to the concrete base 1 of the wind turbine E. The connecting device 3 comprises a connecting ring 31. Figure 2a illustrates an axial view of the connecting ring 31. In other words, Figure 2a illustrates a view of the connecting ring 31 along the axis X of the mast 2.

[0059] Advantageously, the connecting crown 31, called crown for simplicity hereinafter, is annular in shape, centered around the axis X of the mast 2. Thus, the crown 31 comprises a circular internal edge 34 and a circular external edge 35. The circular internal edge 34 and circular external edge 35 are coaxial with the axis X of the mast 2. The crown 31 is preferably metallic.

[0060] According to one embodiment, the crown 31 comprises a single annular portion extending all around the axis X of the mast 2.

[0061] According to another embodiment, illustrated by figure 2b, the crown 31 comprises several adjoining angular portions 36. In other words, the crown 31 is formed around the axis X of the mast 2 of several portions 36, which can be assembled together to form the crown, in order to facilitate its transport and placement on the base 1.

[0062] As illustrated in Figure 2a and Figure 3, the crown 31 comprises anchoring holes 3113 and fixing holes 3124. The anchoring holes 3113 are configured to allow the crown 31 to be fixed to the base 1 and the fixing holes 3123 are configured to allow the mast 2 to be fixed to the crown 31.

[0063] The anchoring holes 3113 and the fixing holes 3124 are positioned on the crown 31 at regular intervals and respectively at constant radius around the axis X of the mast 2. The anchoring holes 3113 and the fixing holes 3124 are therefore distributed on the crown 31, respectively forming circular alignments.

[0064] Advantageously, the fixing holes 3124 are grouped into as many groups 3125 as there are anchoring holes 3113, as visible in FIG. 2a. Each group 3125 of fixing holes 3124 is positioned so that each anchoring hole 3113 is framed, axially, by several fixing holes 3124. And, at least one fixing hole 3124a, called intrados, of each group 3125 of fixing holes 3124 is positioned radially internally relative to the respective anchoring hole 3113 and at least one fixing hole 3124b, called extrados, of each group 3125 of fixing holes 3124 is positioned radially externally relative to the anchoring hole 3113.Preferably, each group 3125 of fixing holes 3124 is positioned close to a respective anchoring hole 3113 so that two fixing holes 3124a, called intrados, of each group 3125 of fixing holes 3124, are positioned radially internally relative to the respective anchoring hole 3113 and two fixing holes 3124b, called extrados, of each group 3125 of fixing holes 3124, are positioned radially externally relative to the anchoring hole 3113.

[0065] Each intrados fixing hole 3124a and each extrados fixing hole 3124b are radially equidistant from their anchoring hole 3113. In other words, the alignment formed by the anchoring holes 3113 forms a circular symmetry between the alignment of the intrados fixing holes 3124a and the alignment of the extrados fixing holes 3124b. This makes it possible to reduce the moments induced by the fixing of the mast on the crown 31.

[0066] Thus, the fixing holes 3124 allow uniform and efficient fixing of the metal mast 2 on the crown 31.

[0067] Furthermore, the forces exerted by the base 1 and by the mast 2 are uniformly distributed on the connection device 3 and do not generate any moment in the crown 31, the central branch 2111 of the flange 21 and the alignment of the anchoring holes 3113 being coaxial and of the same radius.

[0068] The anchoring holes 3113 are configured to receive anchoring means 32 and the fixing holes 3123 are configured to receive fixing means 33, as seen in FIG. 4.

[0069] Figure 4 illustrates a radial section of the connection device 3, along a plane AA comprising the axis X of symmetry of the mast 2. The view illustrated by Figure 4 represents a view of the connection device 3 along an axis X1, parallel to the axis X, at the level of each respective anchoring means 32.

[0070] The connection device 3 thus comprises, and all around the axis X of the mast 2, the crown 31, anchoring means 32, for fixing the crown 31 to the concrete base 1 and fixing means 33, such as for example bolts, for fixing the mast 2 to the crown 31.

[0071] The anchoring means 32 and the fixing means 33 are thus respectively configured to be positioned on the crown 31, at regular intervals and with a constant radius, respectively in the anchoring holes 3113 and the fixing holes 3124. In other words, the anchoring means 32 and the fixing means 33 are distributed over the crown 31, respectively forming circular alignments.

[0072] Advantageously, each anchoring means 32 is therefore framed by several fixing means 33. Optionally, for each anchoring means 32, one, or even two, fixing means 33 are positioned on the crown 31 radially internally relative to the anchoring means 32 and one, or even two, fixing means 33 are positioned radially externally relative to the anchoring means 32.

[0073] As visible in Figure 4, each anchoring means 32 comprises at least one prestressing cable 321, and an anchoring head 322. Advantageously, each anchoring means 32 comprises several strands braided together and forming one or more prestressing cables 321 braided together. The anchoring head 322 of each anchoring means 32 makes it possible to fix the crown 31 to the prestressing cables 321 of each respective anchoring means 32.

[0074] According to one embodiment, each anchoring means 32 further comprises an anchoring plate 323. The anchoring plate 323 is in the form of a washer and supports the anchoring head 322 on the crown 31. The plate 323 makes it possible to distribute the forces of the anchoring head 322 on the crown 31.

[0075] As seen in Figure 4, the crown 31 comprises a first disc 311, a second disc 312 and at least one spacer 313, 314, configured to rigidly connect the first disc 311 and the second disc 312, and provide a space between them. The crown 31 is in one piece in that the first disc 311, the second disc 312 and the spacer 313, 314 are welded together.

[0076] In Figure 4, the crown 31 comprises a first spacer 313 and a second spacer 314. It is however possible that the crown 31 comprises only one of the first spacer 313 or the second spacer 314.

[0077] The first disc 311 and the second disc 312 are preferably hollow, in other words, they each form a plate comprising a respective inner edge 3111, 3121, and a respective outer edge 3112, 3122, circular and coaxial with the axis X of the crown 31. The first disc 311 and the second disc 312 are also coaxial with the axis X of the crown 31. The first disc 311 is called the anchoring disc 311 because it is positioned on one side of the crown 31 configured to be in contact with the base 1 and connected to the latter by the anchoring means 32.

[0078] The anchoring disc 311 comprises the anchoring holes 3113, visible in Figure 2a. The anchoring holes 3113 of the anchoring disc 311 are distributed on the anchoring disc 311 at an equal distance from the axis X of symmetry of the mast 2, as visible in Figure 2a. The anchoring holes 3113 are advantageously positioned at an equal distance from the inner edge 3111 and the outer edge 3112 of the anchoring disc 311. The crown 3 is thus configured to be fixed to the base 1 in a balanced manner and so that the stresses are uniformly distributed on the anchoring disc 311.

[0079] As illustrated in particular in Figure 4, the anchoring hole 3113 of the anchoring disc 311 is adapted to allow the passage of one or more prestressing cables 321 in order to fix the first anchoring disc 311 to the concrete base 1. The same is of course true for all the anchoring holes 3113 of the anchoring disc 311. In other words, the anchoring head 322 of each anchoring means 32 fixes the anchoring disc 311 to the prestressing cables 321 of each respective anchoring means 32. The crown 3 is therefore fixed to the base 1 by the anchoring head 322 which rests on the anchoring disc 311.

[0080] The second disc 312, as illustrated in Figure 4, is spaced from the first disc 311 by the first spacer 313 and the second spacer 314. The second disc 312 is called the fixing disc 312 because it is positioned on the side of the crown 3 configured to be in contact with the mast 2 and connected to it by the fixing means 33. The fixing disc 312 comprises several clamping holes 3123 and the fixing holes 3124, visible in Figure 2a.

[0081] As visible in Figure 4, each clamping hole 3123 of the fixing disc 312 is positioned on the fixing disc 312 respectively opposite one of the anchoring holes 3113 of the anchoring disc 311, in other words, each clamping hole 3123 of the fixing disc 312 is coaxial with an anchoring hole 3113 of the anchoring disc 311. The clamping holes 3123 are advantageously through holes. The clamping holes 3123 allow the engagement of a clamping tool 5 configured to apply tension to the prestressing cables 321 passed through the anchoring hole 3113 which is opposite the respective clamping hole 3123, to fix the prestressing cables 321 in the anchoring hole 3113. Thus, the clamping holes 3123 have a diameter greater than the diameter of the anchoring holes 3113 because the clamping tool 5 is necessarily of a larger diameter than the diameter of the prestressing cable 321 passed through the anchoring hole 3113.

[0082] The fixing holes 3124 are adapted to allow the mast 2 to be fixed to the fixing disc 312 using the fixing means 32. The fixing holes 3124 are advantageously through holes.

[0083] As seen in Figure 4, the intrados fixing holes 3124a and the extrados fixing holes 3124b are configured to cooperate respectively with the intrados fixing holes 2113 and the extrados fixing holes 2114, of the flange 211 in order to fix the mast 2 to the connection device 3.

[0084] Thus, such an arrangement makes it possible to use, for fixing the mast 2 of the wind turbine E to the crown 31, fixing means 33, such as for example bolts, which only pass through the fixing disc 312 and not the entire thickness of the crown 31. This makes it possible to avoid oversizing these fixing means 33 while supporting the significant loads imposed.

[0085] The first spacer 313 and the second spacer 314 are annular and preferably cylindrical in shape. The first spacer 313 and the second spacer 314 are centered on the X axis of the mast 2. The first spacer 313 and the second spacer 314 are hollow cylinders. The first spacer 313 is positioned radially internally relative to the second spacer 314. The first spacer 313 and the second spacer 314 are both welded by their respective ends in the direction of the X axis of symmetry of the mast 2, to the anchoring disc 311 and to the fixing disc 312.

[0086] Advantageously, the first spacer 313 is welded to the anchoring disc 311 and to the fixing disc 312 radially internally relative to the anchoring holes 3113 and to the clamping holes 3123 respectively of the anchoring disc 311 and of the fixing disc 312. And the second spacer 314 is welded to the anchoring disc 311 and to the fixing disc 312 radially externally relative to the anchoring holes 3113 and to the clamping holes 3123 respectively of the anchoring disc 311 and of the fixing disc 312. In addition, the first spacer 313 is welded to the fixing disc 312 radially externally relative to the intrados fixing holes 3114a of the fixing disc 312. And the second spacer 314 is welded to the fixing disc 312 radially internally relative to the fixing holes 3124b extrados of the fixing disc 312. This makes it possible to distribute the stresses evenly on the crown 31.Thus, and thanks to the fixing of the anchoring head 322 on the anchoring disc 311, the anchoring head 322 is protected from the environment by the crown 31. In other words, the anchoring head 322 is protected from the environment by the second disc 312, the first spacer 313 and the second spacer 314.

[0087] Furthermore, by such positioning of the anchoring head 322, the flange 21 of the mast 2 can be fixed to the connection device 3 without generating a moment likely to deform the crown 31. Indeed, the fixing of the flange 21 centered on the crown 31 and the centering of the anchoring holes 3113 makes it possible to distribute the stresses uniformly over the entire crown 31 and to align the central branch 2111 of the flange 21 and the anchoring holes 3113.

[0088] Furthermore, the fixing holes 3124 are on a part of the crown which is accessible even once the crown 3 is formed from a single piece, that is to say even after the welding of the first spacer 313 and the second spacer 314 to the anchoring disc 311 and to the fixing disc 312. It is thus possible to put in place, or replace, a fixing means 3124, of the connection device 3, during the positioning of the crown 31 and / or after the positioning of the mast 2 on the crown 31.

[0089] Such a crown 31 therefore makes it possible to connect the T-shaped flange 211 of the foot 21 of the metal wind turbine mast 2 to the concrete base 1: by protecting the prestressing cables from the environment and from corrosion by their direct fixing to the anchoring disc 311, without generating a moment between the foot 21 of the mast 2 and the anchoring holes 3113, and by distributing the forces uniformly over the crown 31.

[0090] Preferably, the crown 31 further comprises a plurality of additional spacers 315. The additional spacers 315 may in particular be radial spacers. The additional spacers 315 are each welded to the anchoring disc 311 and to the fixing disc 312. The additional spacers 315 are also welded to the first spacer 313 and the second spacer 314. The additional spacers 315 are positioned in the crown 31 between each neighboring anchoring hole 3113 and are configured to improve the rigidity of the crown 31.The additional spacers 315 may be plate-shaped spacers orthogonal to the planes tangent to the anchoring disc 311 and the fixing disc 312 or be spacers of a different shape but always positioned on the anchoring disc 311 and the fixing disc 312 so as not to obstruct an anchoring hole 3113, a clamping hole 3123 or a fixing hole 3124.

[0091] Method of connecting the mast to the base

[0092] The crown 31 is preferably manufactured prior to the assembly of the wind turbine E. In the case of a marine wind turbine E for example, the crown 31 is directly supplied in a single piece, or in several joined angular portions 36 each being in one piece as illustrated in figure 2b, at the time of connection of the mast 2 to the base 1.

[0093] The method of connecting the mast 2 to the base 1 may comprise several steps as visible in Figure 6 and involving the different elements making up the wind turbine E previously described. The method is illustrated by Figures 5a-5j on a radial section of the wind turbine E relative to the view illustrated by Figure 4.

[0094] First, the method comprises a step of providing the base 1 whose central tower 11 has been cast (step E1), by means of a formwork 6, by providing a sheath 14 for the placement of the prestressing cables 321. The sheaths 14 have been provided by placing metal trumpets 15 in the formwork 6 before the concrete is poured into the formwork 6. The trumpets 15 allow the sheaths 14 to remain empty of concrete, thus allowing the subsequent placement of the prestressing cables 321. Each trumpet 15 is a continuation of a sheath 14. The trumpet 15 makes it possible to absorb implantation defects between the sheath 14 and the crown 31. Figure 5a illustrates a radial section of a portion of a central tower 11 cast in the shape of a hollow cylinder.

[0095] Once the base 1 has been cast, the formwork 6 is removed and leveling devices 7 can be positioned and adjusted (step E2) on an upper end 112 of the central tower 11 of the base 1, as seen in Figure 5b.

[0096] A circular seal 8 is positioned (step E3) on the upper end 112 of the central tower 11 and around each metal trumpet 15, in other words, around each sheath 14 provided for the placement of the prestressing cables 321, as illustrated in FIG. 5c. The circular seal 8 around each sheath 14 makes it possible to protect the sheath 14 from unwanted injections, as explained below.

[0097] The crown 31 is then positioned (step E4) on the central tower 11 of the base 1, in other words on the base 1, as visible in Figure 5d. In this way the anchoring disc 311 of the crown 31 rests on the leveling devices 7 previously positioned on the base 1. The position of the crown 31 is adjusted using the leveling devices 7. The crown 31 is positioned in such a way that each anchoring hole 3113 of the anchoring disc 311 of the crown 31 is facing a sheath 14 provided for the placement of the respective prestressing cables 321.

[0098] Once the crown 31 is positioned and its position adjusted, a layer of wedging mortar 9 is injected (step E5) between the concrete base 1 and the crown 31, that is to say between the upper end 112 of the central tower 11 of the base 1 and the anchoring disc 311 of the crown 31. The layer of wedging mortar 9 as illustrated in FIG. 5e makes it possible to improve the positioning of the crown 31 on the base 1. The wedging mortar 9 does not enter the sheaths 14 provided for the placement of the prestressing cables 321 thanks to the presence of the circular seal 8 around each of these sheaths 14.

[0099] Then, the prestressing cables, or cable braids, 321 are inserted (step E6) into each of the sheaths 14 provided in the base 1, as visible in FIG. 5f. Then the anchoring plate 323 and the anchoring head 322 of each anchoring means 32 are positioned on the respective prestressing cables 321 (step E7) to tighten the prestressing cables 321 in each anchoring hole 3113 and thus fix the crown 31 to the base 1, as visible in FIG. 5g.

[0100] Optionally, it is possible not to position an anchor plate 323 in order to simplify the process. The anchor head 322 then rests directly on the anchor disc 311 to fix the crown 31 to the base 1.

[0101] As illustrated in Figure 5h, a tightening tool 5 is then inserted into each tightening hole 3123 and fixes the crown 31 to the base 1 (step E8) by tensioning the prestressing cables 321 in each anchor head 322. The tightening tool 5 may be a tensioning jack.

[0102] Once the crown 31 is fixed to the base 1 by each anchoring means 32, a cement grout 10 is injected (step E9) into each sheath 14 around the prestressing cables 321 which have been inserted therein, as illustrated in FIG. 5i. The cement grout 10 is injected through each clamping hole 3123 and anchoring hole 3113. In addition, the cement grout 10 is also injected around each anchor head 322. Such an injection makes it possible to protect the prestressing cables 321 and to make them adhere to the concrete, the purpose of which is to improve the fixing of the crown 31 to the base 1.

[0103] Finally, the mast 2 of the wind turbine E is positioned (step E10) on the crown 31, as illustrated in FIG. 5j. In other words, the flange 211 of the foot 21 of the mast 2 of the wind turbine E is positioned on the fixing disc 312 of the crown 31. The mast 2 is positioned, as illustrated in FIG. 4, such that the fixing holes 2113, 2114 of the flange 211 face the respective fixing holes 3124a, 3124b of the fixing disc 312. The fixing means 33 are then inserted into the fixing holes 2113, 2114 of the flange 21 and the mast 2 is fixed to the crown 31. Thus, the mast 2 of the wind turbine E is fixed to the crown 31 by means of the fixing means 33 and the crown 31 is itself directly fixed to the base 1 by means of the anchoring means 32. The mast 2 is therefore connected to the base 1 by a single intermediate part, the crown 31, and the respective fixings of the mast 2 and the base 1 to the crown 31 are independent of each other.

Claims

CLAIMS 1. Metal ring (31) for connecting the T-shaped flange (211) of the foot (21) of a metal wind turbine mast (2) to a concrete base (1), the ring (31) being of generally annular shape, centered around an axis (X) of the mast (2), and comprising: an anchoring disc (311) comprising several anchoring holes (3113), each anchoring hole (3113) being adapted to allow the passage of a prestressing cable (321) in order to anchor said anchoring disc (311) in the concrete base (1), and a fixing disc (312), spaced from the anchoring disc (311) by a first spacer (313, 314), and comprising several clamping holes (3123), each of said clamping holes (3213) being located opposite a hole anchoring hole (3113) respective of the anchoring disc (311) to allow the engagement of a clamping tool (5) in said clamping hole (3123),in order to apply tension to the prestressing cable (321) passed through said anchoring hole (3113) which is opposite said clamping hole (3123); the anchoring disc (311) and the fixing disc (312) being connected to each other by the first generally annular metal spacer (313, 314); the anchoring disc (311), the fixing disc (312) and the spacer (313, 314) being centered on the axis (X) and forming a single piece; the fixing disc (312) further comprising through fixing holes (3124a, 3124b), adapted to allow the mast (2) to be fixed to the fixing disc (312)., 2. Crown (31) according to claim 1, in which the anchoring disc (311) and the fixing disc (312) are connected to each other by a second generally annular metal spacer (313, 314), centered on the axis (X) and forming a single piece with the anchoring disc (311), the fixing disc (312) and the first spacer (313, 314).

3. Crown (31) according to claim 2, wherein the first and second spacers (313, 314) are in the form of a hollow cylinder, one of the first and second spacers (313, 314) forming a first hollow cylinder, and being positioned radially internally relative to the anchoring holes (3113) and the clamping holes (3123), and the other forming a second hollow cylinder, and being positioned radially externally relative to the anchoring holes (3113) and the clamping holes (3123); the first and second spacers (313, 314) are welded to the anchoring disc (311) and to the fixing disc (312).

4. Crown (31) according to any one of claims 1 to 3, in which the anchoring disc (311) and the fixing disc (312) are connected to each other by several additional metal spacers (315), each of the neighboring anchoring holes (3113) being separated from each other by an additional spacer (315), the additional spacers (315) are welded onto the anchoring disc (311) and onto the fixing disc (312).

5. Crown (31) according to any one of claims 1 to 4, wherein the fixing disc (312) comprises a plurality of groups (3125) of fixing holes (3124a, 3124b), each group (3125) being located close to each respective clamping hole (3123) and framing said clamping hole (3123), two intrados fixing holes (3124a) being positioned radially internally relative to the clamping hole (3123) and two extrados fixing holes (3124b) being positioned radially externally relative to the clamping hole (3123).

6. Crown (31) according to one of claims 1 to 5, comprising several angular portions of crowns (36) adjoining, around the axis (X).

7. Connection device (3), comprising a crown (31) according to one of claims 1 to 6, and anchoring means (32) for fixing the crown (31) to a concrete base (1), the anchoring means (32) each comprising several prestressing cables (321), intended to be fixed in the concrete base (1), and an anchoring head (322) for fixing the crown (31) to the prestressing cables (321).

8. Wind turbine (E) comprising a rotor (42), a generator (41), a mast (2), a base (1) and a connection device (3) according to claim 7.

9. Method for connecting a metal wind turbine mast (2) to a concrete base (1) by means of a connection device (3) according to claim 7, the method comprising the following steps of: casting (E1) of the concrete base (1), casting in a manner suitable for sheaths (14), by means of metal trumpets (15), for the placement of the prestressing cables (321); adjusting (E2) several leveling devices (7) on an upper end (112) of the concrete base (1); positioning (E3) a circular seal (8) around each respective sheath (14) at the upper end (112) of the concrete base (1); placing (E4) the crown (31) on the leveling devices (7), the anchoring disc (311) facing the concrete base (1) and each anchoring hole (3113) being coaxial with each respective sheath (14); injecting (E5) a layer of wedging mortar (9) between the concrete base (1) and the crown (31);inserting (E6) the prestressing cables (321) into the sheaths (14); positioning (E7) an anchor plate (323) and the anchor head (322) at each respective anchor hole (3113), to tighten the prestressing cables (321) in each anchor hole (3113); fixing (E8) the crown (31) on the concrete base (1) by means of the tightening tool (5), introduced through each respective tightening hole (3123), and tensioning the prestressing cables (321) on the anchor heads (322); injecting (E9) a cement grout (10) into the sheaths (14) around the prestressing cables (321) and around the anchor heads (322); and fixing (E10) the mast (2) on the crown (31) by tightening fixing means (33) in each fixing hole (3124a, 3124b) of the fixing disc (312).; 10. Method according to claim 9, in which the step of fixing (E8) the crown (31) on the concrete base (1) is carried out by means of a tensioning jack (5).

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