Patent Description:
A tall wind turbine tower is generally constructed to include a gradually tapering tower section, so that the diameter at the upper tower level (at the yaw interface) is significantly smaller than the diameter at a lower tower level.

Access to different levels inside a tower is required for various reasons, for example to carry out maintenance procedures in the tower, or to provide access to the nacelle. To fulfil safety requirements, a platform should extend to essentially completely seal the circular area at the platform level. Since there are many wind turbine tower designs with widely varying geometries, it is usual practice to design interior platforms to match the requirements of a specific tower design. Platforms designed for use with one tower type generally cannot be used for a different tower type. The access platforms therefore add significantly to the overall cost of a wind turbine.

In one approach to avoiding such costs, a basic platform design may be considered for installation at a higher (narrower) tower level, and an added perimeter of a flexible material can be arranged about this basic platform when installed at a lower (wider) tower level. A drawback of this approach is that the added perimeter may not be effective in preventing objects or people from falling off the platform. In another approach, a basic platform may be augmented by a rigid railing or kickplate which is more effective at preventing objects from falling off the platform. However, such adaptations are expensive and may not always comply with strict safety requirements.

An example of a prior art adaptable tower platform arrangement is disclosed in <CIT>.

It is therefore an object of the invention to provide an improved way of providing access to various levels in a tower interior.

This object is achieved by the adaptable tower platform arrangement of claim <NUM>; by the tower of claim <NUM>; and by the method of claim <NUM> of providing access to a tower interior level.

The inventive adaptable tower platform arrangement is intended for use in the interior of a tower that has at least one frustoconical section, i.e. the tower tapers from a wider diameter at the base of the frustoconical section to a narrower diameter at the top of the frustoconical section.

According to the invention, the adaptable tower platform arrangement is constituted as stipulated by appended claim <NUM>.

The inventive adaptable tower platform arrangement can comprise a set of components, i.e. at least one platform and several adapter rings. An advantage of the inventive adaptable tower platform arrangement is that only a single type of platform is needed, i.e. the platform can be mounted to any one of the adapter rings. Because the adapter rings can all have different outer diameters, each adapter ring will fit at a specific level inside a frustoconical tower section. According to the invention multiple platforms are part of a set, and the platforms are essentially identical (having at least the same diameter) i.e. any platform can be mounted to any one of the adapter rings. Of course, any adapter ring can be used inside a right cylindrical tower section with the corresponding interior diameter.

The inventive adaptable tower platform arrangement can therefore be significantly more economical than a solution requiring custom-made platforms for installing at various levels in one or more towers with different interior diameters. The installation time of a tower can also be shortened, since mounting of the platform assemblies at various tower levels is favourably straightforward.

According to the invention, the tower - for example a hollow wind turbine tower - comprises a plurality of platform assemblies installed at different levels in the tower interior. Each platform assembly comprises an instance of the circular platform, mounted to an adapter ring with an outer diameter corresponding to the tower interior diameter at that level.

According to the invention, the method of providing access to a tower interior level using an embodiment of the inventive adaptable tower platform arrangement comprises the steps of determining the diameter at a tower interior level; preparing a platform assembly by selecting an adapter ring with an outer diameter that corresponds to the tower interior diameter at that level and mounting an instance of the platform to the selected adapter ring; and arranging the platform assembly at that tower interior level.

In the following, it may be assumed that the tower is a tall structure such as a wind turbine tower. It may also be assumed that the tower has at least one frustoconical tower section, i.e. the tower is frustoconical in shape over at least part of its height. The tower may also comprise one or more right cylindrical sections, i.e. tower sections with essentially constant diameter. Tower sections may be connected using flanges as will be known to the skilled person.

A platform can be constructed in any suitable manner. For example, a platform can be made a circular disc of a strong material such as steel. However, the interior diameter of a tower such as a wind turbine tower can comprise several metres, and a circular platform with such a diameter would be expensive and may lack structural stability. Therefore, in a preferred embodiment of the invention, a platform is constructed from a plurality of platform sections. Preferably, each section is essentially rectangular and has at least two straight edges. A platform section that extends to the perimeter will have a curved edge corresponding to an arc of the perimeter.

Adjacent platform sections are preferably joined in a robust manner, for example by welding and/or by means of fasteners. In a particularly preferred embodiment of the invention, any two platform sections are shaped so that their common edges have lateral extensions which are folded at right angles and joined together. Preferably, the edges are folded vertically downward, so that the upper platform surface remains flat. The joints formed by connecting these downwardly-folded edges act as stiffening structures for the platform. In this way, a robust and economical platform can be provided in a straightforward manner.

A platform of a platform assembly can be connected in any suitable manner to an adapter ring. In a preferred embodiment of the invention, an assembly interface comprises an annular overlap between an adapter ring inner diameter and the platform diameter. Preferably, the overlap between platform and adapter ring comprises at least <NUM>.

A platform assembly is preferably secured to the tower wall by means of a suitable installation interface. In a preferred embodiment of the invention, a platform can be adapted for connection to an installation interface provided as a set of brackets extending outward from the tower wall. For example, a platform assembly with an outer diameter in the order of <NUM> may be supported by <NUM> brackets evenly distributed in an annular arrangement about the tower interior at that mounting level. The platform can be secured to the tower wall by brackets, magnets, direct fasteners or other similar solutions. For example, several brackets can be attached to the tower wall, or can be secured to a flange at the junction of two tower sections. The brackets can be fastened to the platform assembly, for example the brackets can be screwed or welded to the joints between platform sections. In such an embodiment, the positions of the brackets are determined by the platform section design.

Alternatively or in addition, a platform assembly may be suspended from points on the tower wall. For example, an installation interface can comprise an annular arrangement of appropriate wall fittings may be secured to the tower wall, and a corresponding number of cables, stays or rods that each extends between a wall fitting and an attachment fitting provided near the perimeter of the platform. For example, a platform assembly with an outer diameter in the order of <NUM> may be suspended from eight, ten or more wall fittings evenly distributed in an annular arrangement about the tower interior.

In a preferred embodiment of the invention, the outer diameters of the adapter rings are chosen on the basis of a tower with interior diameters in the range of <NUM> - <NUM>. Of course, the invention can be used with smaller and/or larger tower diameters, and these values are only mentioned to give an indication of the dimensions of the tower type that may be equipped with the invention. To ensure a desired structural stability, the width of an adapter ring is preferably at least <NUM>. Since the platform diameter preferably exceeds the adapter ring inner diameter by the desired overlap amount, the platform diameter is essentially also derived from the smallest interior diameter of the tower, and is preferably at most <NUM>% of the smallest tower interior diameter. The inner diameter of each adapter ring is determined by subtracting the preferred overlap width from the platform diameter.

As indicated above, the difference between the smallest and largest diameters of a hollow tower can vary widely, particularly in the case of towers that are assembled by stacking sections one on the other. In such realisations, the largest diameter of a lower tower section can be significantly greater that the largest diameter of another tower section. Therefore, in a preferred embodiment of the invention, access to various levels inside the tower is provided by using two or more instances of the inventive adaptable tower platform arrangement. Each adaptable platform arrangement covers a range of tower interior diameters. For example, a first adaptable platform arrangement is used in a lower region with the largest diameters; and a second adaptable platform arrangement is used in an upper tower region with a range of smaller diameters. The circular platform of the first instance can be larger than the outer diameter of the adapter ring of the largest platform assembly of the second instance. The interior of a wind turbine tower is usually utilized for various purposes. Power cables from the generator usually pass from the nacelle to the base of the tower, and enter the tower at the level of the yaw ring. Therefore, in a preferred embodiment of the invention, any platform assembly in the tower interior comprises an opening to permit the passage of power cables. Such an opening can be provided in the platform, for example by the omission of a rectangular platform section. Alternatively, an opening can be provided as a cut-out at the edge of the platform assembly, e.g. by omitting a section of the adapter ring.

It is generally also required to provide personnel access to various levels in the tower, for example to perform maintenance procedures on aviation lights on the tower, to perform maintenance procedures on the yaw system, etc. To this end, in a further preferred embodiment of the invention, any platform assembly in the tower interior comprises an access opening to accommodate a ladder and/or to accommodate an elevator.

Preferably, a platform assembly is constructed so that there are essentially no significant gaps in the surface comprising platform and adapter ring, to avoid the risk of tools or other objects from falling off the platform assembly. To this end, a hatch may be used to close off an access opening when not in use.

<FIG> illustrates the principle of the inventive adaptable platform arrangement <NUM>. For a tower <NUM> with gradually decreasing diameter and multiple desired access levels 2L_1,. , 2L_n, the adaptable platform arrangement <NUM> comprises a single type of platform <NUM> and multiple adapter rings 11_1,. , 11_n, each having an outer diameter Do_1,. , Do_n that corresponds to the tower inner diameter D1,. , Dn at that access level 2L_1,. A platform assembly 12_1,. , 12_n is constructed by attaching an instance of the platform <NUM> to an adapter ring 11_1,. The adapter ring 11_1,. , 11_n is selected according to tower diameter at the level at which the platform assembly is to be installed.

The cost of equipping the tower <NUM> with multiple platform assemblies 12_1,. , 12_n is favourably low, since the platform <NUM> is the same in each assembly 12_1,. , 12_n, and only the adapter rings 11_1,. , 11_n differ in dimension.

<FIG> shows an exemplary embodiment of the platform <NUM>. Here, the platform <NUM> is made by joining multiple platform sections <NUM>. Some sections <NUM> are rectangular, with adjacent sections <NUM> along their straight sides. Other sections <NUM> are based on a rectangular shape, with three straight sides and one curved edge at the perimeter of the platform <NUM>. The overall shape of the platform <NUM> is circular with diameter D10.

The diagram also indicates the manner in which the platform sections <NUM> are joined. The surface of a section <NUM> extends beyond its straight sides, and these additional areas are bent downwards at right angles to form vertical planar extensions that serve as connecting faces 10e. Adjacent platform sections <NUM> are joined by welding or otherwise connecting their vertical planar connecting faces 10e. The resulting joint provides structural stiffness to the platform <NUM>.

By omitting one or more platform sections, access openings 10a can be provided in the platform <NUM>, for example to afford passage to a cable arrangement, to allow personnel access, to accommodate a ladder, to accommodate an elevator, etc. The downward-bent planar extensions 10e of the platform sections <NUM> enclosing the access opening 10a serve are shown in the diagram.

<FIG> shows a number of adapter rings 11_1,. The inner diameter Di is essentially the same for all adapter rings 11_1,. The outer diameter Do_1,. , Do_n is different for each adapter ring 11_1,. , 11_n so that each adapter ring 11_1,. , 11_n will fit at a different level in the interior of a frustoconical tower. The width 11w of an adapter ring 11_1,. , 11_n can be in the order of <NUM> - <NUM>. The inner diameter Di is preferably at most <NUM>% of the platform diameter D10, so that there is sufficient overlap when an instance of the platform <NUM> rests on an adapter ring 11_1,. The diagram indicates that an adapter ring can be made of multiple segments, which can be connected by welding and/or by appropriate fasteners. Cut-outs 11c are provided at specific positions that correspond to the positions of the downward-bent extensions 10e of platform sections <NUM> shown in <FIG>.

<FIG> shows a cross-section through a platform assembly 12_1 installed in a tower <NUM>. The diagram illustrates how the outer rim of the platform <NUM> rests on the upper surface of the adapter ring 11_1, which in turn can rest on or be bolted to a flange (not shown) between tower sections. A vertical downward-extending edge 10e of a platform section <NUM> is secured to a bracket <NUM> that is mounted to the tower wall. The adapter ring 11_1 is provided with a cut-out 11c as shown in <FIG>, which is shaped and positioned to fit about the vertical downward-extending edge 10e.

<FIG> shows a schematic cross-section through a wind turbine tower <NUM>. The tower <NUM> is equipped with an embodiment of the inventive adaptable platform arrangement <NUM>, with a platform assembly 12_1,. , 12_5 at each of multiple access levels 2L_1,. The tower <NUM> is constructed from two right cylindrical sections <NUM>, <NUM> and two frustoconical sections <NUM>, <NUM>.

For the sake of clarity, the platform assemblies are shown in a very simplified manner, but it shall be understood that each platform assembly comprises a platform and an adapter ring as explained above.

Three essentially identical platform assemblies 12_1 are installed in the two lower tower sections <NUM>, <NUM> at access levels 2L_1 - 21_3, i.e. each of these platform assemblies 12_1 uses an adapter ring with the same outer diameter. The lowest platform assembly 12_1 rests on a supporting structure <NUM> installed on the tower foundation and serves as a floor for personnel entering the tower <NUM>; the next platform assembly 12_1 rests on support brackets <NUM> connected to a tower section flange <NUM>; the next platform assembly 12_1 is suspended by stays <NUM> secured to suspension fittings <NUM> mounted to the tower wall.

In the next tower section <NUM>, platform assemblies 12_2, 12_3 are installed at the next two access levels 2L_4, 2L_5, whereby the outer diameter of the adapter ring of the platform assembly 12_2 at access level 2L_4 is wider than the outer diameter of the adapter ring of the platform assembly 12_3 at access level 2L_5.

These platform assemblies 12_4, 12_5 can be installed as described above, for example suspended by stays <NUM> secured to suspension fittings <NUM> mounted to the tower wall, or resting on support brackets <NUM>.

In the next tower section <NUM>, platform assemblies 12_4, 12_5 are installed at the next two access levels 2L_6, 2L_7, whereby the outer diameter of the adapter ring 11_4 of the platform assembly 12_4 at access level 2L_6 is wider than the outer diameter of the adapter ring 11_5 of the platform assembly 12_5 at access level 2L_7.

These platform assemblies 12_6, 12_7 can be installed as described above, for example suspended by stays <NUM> secured to suspension fittings <NUM> mounted to the tower wall, or resting on support brackets <NUM>.

The diagram also indicates a cable suspension arrangement <NUM>, with power cables extending from the upper level of the tower <NUM> (from a generator in a nacelle) through openings in the platforms <NUM>, so that the cables can reach the base of the tower <NUM>. The tower <NUM> can also be equipped with an elevator that can pass through openings in the platforms <NUM>, or various ladders that extend from one platform to the next.

<FIG> shows a further schematic cross-section through a wind turbine tower <NUM>. The tower <NUM> is equipped with two instances of the inventive adaptable platform arrangement 1A, 1B.

With the upper platform arrangement 1A, four access levels are installed. The uppermost level uses simply the platform 10A of the adaptable arrangement 1A, and the other three levels use adapter rings 11_1A, 11_2A, 11_3A.

With the lower platform arrangement 1B, further access levels are provided. The uppermost level in this wider tower region uses a platform 10B of the adaptable arrangement 1B with an adapter rings 11_1B. The other two levels near the cylindrical base of the tower <NUM> simply use the platform 10B in each case.

<FIG> shows a further schematic cross-section through a wind turbine tower <NUM>. In this case also, the tower <NUM> is equipped with two instances of the inventive adaptable platform arrangement 1A, 1B.

With the lower platform arrangement 1B, further access levels are provided. The uppermost level in this wider tower region is provided by only the platform 10B of the adaptable arrangement 1B, and the other two levels use adapter rings 11_1B, 11_2B.

Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

Claim 1:
An adaptable tower platform arrangement (<NUM>) for use in a tower interior (<NUM>), comprising
- circular platforms (<NUM>), each with an essentially identical platform diameter (D10);
- a plurality of annular adapter rings (11_1, ..., 11_n) each with essentially the same inner diameter (Di) and an outer diameter (Do_1, ..., Do_n), wherein
each outer diameter (Do_1, ..., Do_n) exceeds the platform diameter (D10) and corresponds to a different tower interior diameter (D1, ..., Dn); and
- an assembly interface configured to facilitate connection of a platform (<NUM>) to an adapter ring (11_1, ..., 11_n) to obtain a platform assembly (12_1, ..., 12_n) having the outer diameter of that adapter ring (11_1, ..., 11_n).