Patent Description:
Such a wind turbine blade maintenance platform is known, for example, from <CIT>.

<CIT> describes a sealing arrangement with a gap within a transverse direction of the gap and a gap length in longitudinal direction of the gap between a first and a second surface, wherein a strip-shaped sealing element is arranged in the first surface over the gap length in the longitudinal direction of the gap and is pressed by means of at least one fastening element onto the first surface for sealing processes, and wherein a flat sealing element for bridging the gap within the transverse direction of the gap is connected on one end of the stripe-shaped sealing element and on the other end of the second surface.

<CIT> describes an apparatus and method for repairing fibre-composite structures, wherein an enclosure is provided which can be sealed to the structure so that repair can be conducted at any desired time. The enclosure is large enough to enclose a desired work area with the apparatus hand and arms entering to carry out the work through hands and arm seals.

<CIT> describes a temporary maintenance enclosure for maintenance of at least part of a turbine blade. The enclosure comprises a platform arranged to border at least of the circumference of a blade. At least one wall and a roof are carried by the platform. The roof extends from the wall towards the blade, wherein the wall extends from the platform. Further, the enclosure comprises a flexible sheath which seals onto the blade to provide the sealed volume for maintenance of said blade.

The blades of a wind turbine need from time to time an inspection and, if necessary, also a maintenance or repair. To this end a maintenance platform is used which is usually hoisted from the bottom up to a height in which it encloses the wind turbine blade. The platform comprises a tower end which is directed to the tower of the wind turbine and a front end which is directed in the opposite direction. In some embodiments of a maintenance platform the front end can be open to allow the insertion of the blade into the blade access area.

Once the blade is accommodated in the blade access area, the maintenance people can inspect the blade over the whole circumference. The inspection over the length of the blade is possible by raising or lowering the platform.

Inspection and maintenance of the blade of the wind turbine must be possible under nearly all-weather conditions, in particular even when it is raining. However, rainwater running down the rotor blade makes inspection difficult and maintenance almost impossible. If a defect is to be repaired, this usually requires a dry surface of the rotor blade.

The object underlying the invention is to provide a platform which allows working at the rotor blade even under bad weather conditions.

This object is achieved with a wind turbine blade maintenance platform as described at the outset with the additional features according to claim <NUM>.

The sealing means comprise a drain path, wherein the drain path opens into the blade access area.

The region of the rotor blade below the sealing means can be kept dry. However, since the sealing means comprise a drain path opening into the blade access area, the rainwater needs not to flow over a cover of the platform, but can be drained directly through the blade access area. The rainwater flowing down the blade is separated from the blade by means of the sealing means. It is then directly guided over the sealing means to the blade access area without flowing over the cover of the platform. The load of the rainwater on the platform can be kept small, since the time in which the water remains on the platform is short due to the short distance between the sealing means and the end of the drain path where the water flows into the blade access area. The area of the blade to be repaired can be held in a condition of the right humidity.

In an embodiment of the invention the sealing means comprise a sealing area between a leading edge and a trailing edge of the sealing means, wherein the trailing edge is arranged facing the tower end of the platform and the drain path is arranged at the trailing edge. When a rotor blade has to be inspected or to be repaired, it is usually moved in a position in which it points downwardly in the direction of gravity. Many wind turbines have three blades, so that the remaining two blades point upwardly in the direction of gravity. In this position, rain is equally distributed over the area above the blades. Rain falls onto the blades and starts its flow along the blade. More and more water is collected as the flow moves towards the hub. Water from the two upper blades will pass the hub and flow along the downwards facing blade which is to be inspected or to be repaired. Due to the geometric designs and angle of hub and blade, a large portion of the water will start to flow on the trailing edge of the downwards facing blade. Thus, when the drain path is arranged at the trailing edge of the sealing means, the drain path is arranged in a position in which the most water is to be expected. When the blade is in position for maintenance, the trailing edge of the blade is usually directed to the tower of the wind turbine. The trailing edge of the sealing means and the trailing edge of the blade are in this case both arranged facing the tower of the wind turbine.

In an embodiment of the invention the sealing means form an upper border of a working space, the working space being laterally closed in the blade access area by means of wall elements, in particular wall elements which can be placed in different positions. Thus, the working conditions within the working space can be made to meet the requirements, for example for repairing a glass fiber damage of the blade. In this case a certain humidity range and a certain temperature range is required. The working space is thus limited by the blade, a wall of the working space at the side opposite the blade and some wall elements between the blade and the wall at the side opposite the blade. The wall elements can be, for example, in form of a canvas. They can be shifted, moved or repositioned to adjust a size of the working space to requirements of a repair.

In an embodiment of the invention the wall elements extend over a floor of the platform. In this case a rather small working space can be formed, wherein it is easier to maintain the desired conditions of humidity and temperature. Such a working space is in form of a "chamber" which needs not to be larger than necessary for the repair. The wall elements can be movable to adjust the size of the chamber according to the requirements.

In an embodiment of the invention the sealing means comprise a sealing element structured and arranged to contact the blade and a roof element, wherein the roof element forms at least part of the drain path. The water running down the blade is separated from the surface of the blade by means of the sealing element and directed to the roof element. The water then can flow over the roof element to the drain path. The roof element covers a part of the blade access area and keeps it dry.

In an embodiment of the invention the platform comprises a floor and a cover, wherein the roof element is arranged at a lower height in the direction of gravity than the cover. The floor is the element on which the operator can stand or walk. The cover is the upper limit of the working space in the direction of gravity, however, only in the area of the platform. In the blade access area, the upper limit of the working space is formed by the roof element, which can also be termed "temporary roof element". Thus, the water running down the blade is not directed over the cover but can flow directly over the roof element to the drain path. Thus, the risk of an untight cover through which water flowing down the blade can enter the working space between the bottom and the cover, can be kept small or even eliminated.

In an embodiment of the invention a size of the roof element can be changed from a working state to a stowing state. Thus, when the roof element is not needed, it can be stowed in a position of the working platform in which it does not disturb the inspection or maintenance of the blade.

In an embodiment of the invention the roof element can be folded or rolled. The roof element can in particular have a pleat or wave form which is positive for a good water control.

In an embodiment of the invention the roof element is connected to a support element. The roof element itself can then have a low mass. The mechanical stability is achieved by the support element.

In an embodiment of the invention the support element is connected to the sealing element. The support element is used to move the sealing element towards the blade. When the sealing element contacts the blade, it can be held in contact with the plate by, for example, suction cups, so that the support element is also held in a stable position and the roof element can form a flow basis for the rainwater.

In an embodiment of the invention the sealing means comprise at least one sealing segment. If the sealing segment is long enough to cover the desired working area, one segment is sufficient. If one segment is not sufficient to achieve the required rain protection, more segments can be used. The sealing segment can be fixed to a section of the platform. It is, however, also possible to move a sealing segment from one section to another section of the platform.

In an embodiment of the invention the sealing means comprise at least two sealing segments, wherein one sealing segment overlaps another sealing segment. Thus, water flowing over the first segment falls down to the next segment, so that there is no risk of water flowing into the desired working area.

In an embodiment of the invention the sealing segments are arranged in a staircase and rise away from the trailing edge. Thus, water flowing over the segment flows over the staircase down to the drain path.

In an embodiment of the invention the sealing segment is shorter than an average width of the blade. In many cases a repair or maintenance of the whole width of the blade is not necessary. Thus, the sealing segment needs to cover only a part of the width of the blade. This allows for a time and cost saving construction.

In an embodiment of the invention the platform comprises a number of platform sections and at least two platform sections are each provided with sealing means. Thus, the sealing means can be used in sections of the platform in which the workers are working. The area of the blade in which repairing can be performed, can be extended by connection of two or more sealing means or working spaces, wherein the connection of the sealing means produce a larger chamber. However, as long as a repair area is smaller than one chamber or working space, one sealing means, i.e., one chamber, is sufficient independently of where on the blade the repair area is positioned.

In an embodiment of the invention at least one of the sealing means has an extension along the platform which is larger than the extension of the platform section in the same direction. Thus, it is possible that the sealing means of adjacent platform sections can overlap each other.

In an embodiment of the invention the sealing means are inclined and descend in a direction to the tower end of the platform. Thus, water can run down an inclined surface so that the risk that water enters a working space is kept in a minimum.

A preferred embodiment of the invention will now be described with reference to the drawing, in which:.

In all Figures the same elements are denoted with the same reference numerals.

<FIG> shows schematically a wind turbine <NUM> having a tower <NUM> and a nacelle <NUM>. A rotor <NUM> of the wind turbine <NUM> is rotatably supported at the nacelle <NUM> by means of a hub <NUM>. The rotor <NUM> comprises a number of rotor blades <NUM>. In many cases the number of rotor blades <NUM> is three.

When a rotor blade <NUM> is to be inspected or repaired, it is usually moved into a safe position, for example in which it points downwardly in the direction of gravity. The edge of the rotor blade <NUM> is adjusted so that the wind cannot produce forces onto the rotor blade. When a wind turbine having three rotor blades <NUM> is used, the other two rotor blades point diagonally upwards.

Under bad weather condition, rain is equally distributed over an area above the blades. Rain falling onto the blade starts to flow along the blade. More and more water is collected as the flow moves toward the hub <NUM>. Water from the two upper blades will pass the hub <NUM> and follow along the downwards facing blade <NUM>. Due to the geometric design and angle of hub <NUM> and blade <NUM>, a large portion of the water will start its flow on the trailing edge <NUM> of the rotor blade <NUM>. This is schematically shown in <FIG> in which the flow path of the rainwater is shown with dashed lines. Flowing further down the blade <NUM>, the water flow will increase and continue to collect at the trailing edge <NUM>.

From time to time, it is necessary to inspect the blade <NUM> and, if a defect is detected, the blade <NUM> must be repaired. To this end a maintenance platform <NUM> is used which is shown in a top view in <FIG>.

The blade maintenance platform <NUM> comprises a frame which is built by a number of platform sections <NUM>-<NUM>, at least some of which are hinged together. The platform <NUM> comprises a tower end <NUM> which during operation faces the tower <NUM> and a front end <NUM> which is in operation farther away from the tower <NUM>. Furthermore, the maintenance platform <NUM> comprises a blade access area <NUM> which is structured and arranged to accommodate the blade <NUM> of the wind turbine <NUM>.

At least the platform sections <NUM>, <NUM> at the front end <NUM> can be moved away from each other, so that the blade access area <NUM> is opened. In many cases the platform sections <NUM>, <NUM>, <NUM>, <NUM> can be moved as well. However, this depends on the specific construction of the platform <NUM>. The maintenance platform <NUM> is usually hoisted along the tower <NUM>. When the necessary height is reached and the blade access area <NUM> is opened by moving the platform sections <NUM>, <NUM> away from each other, the maintenance platform <NUM> can be moved away from the tower, so that the blade <NUM> can enter the blade access area <NUM>. The platform sections <NUM>, <NUM> can then be closed again.

In order to produce a dry area on the surface of the blade <NUM> in which a defect can be repaired, sealing means <NUM> are provided which are structured and arranged to contact the blade <NUM>. To this end, the sealing means <NUM> comprise a number of suction cups <NUM> with which the sealing means <NUM> can be fixed to the blade <NUM> by suction, i.e., by a pressure below atmospheric pressure. The suction cups <NUM> are positioned below the sealing means <NUM>.

In <FIG>, the sealing means <NUM> are provided at the platform segment <NUM>. However, it is clear that other platform sections, in particular platform sections <NUM>-<NUM> and <NUM>-<NUM> can be provided with sealing means <NUM> as well. As it is shown in <FIG>, the sealing means <NUM> have a width which may be larger than the corresponding width of the platform section <NUM>.

The sealing means <NUM> comprise a leading edge <NUM> and a trailing edge <NUM>. The trailing edge <NUM> is arranged towards the tower end <NUM> of the maintenance platform <NUM>. The sealing means <NUM> are slightly inclined downwardly from the leading edge <NUM> to the trailing edge <NUM>, so that rainwater or other water running down the blade <NUM> flows over the sealing means <NUM> towards the trailing edge <NUM> and from there through the blade access area <NUM> to the ground.

In other words, the sealing means <NUM> comprise a drain path <NUM> (illustrated as an arrow) opening into the blade access area <NUM>. Thus, there is no water load on the covers of the platform section <NUM>-<NUM> stemming from water from the blade <NUM>. The drain path <NUM> is the area on the sealing means <NUM> in which rainwater flows from the blade <NUM> to the blade access area <NUM>.

<FIG> shows a view similar to <FIG>. However, the sealing means <NUM> and covers of the platform sections <NUM>-<NUM> have been removed, so that some safety means <NUM> can be seen. The safety means <NUM> (only the corresponding enclosure wall <NUM> is labelled in platform section <NUM>) form a kind of protection protecting an operator.

On the side facing away from the blade access area <NUM> the platform <NUM> comprises walls, for example in form of a canvas or the like. Together with a floor <NUM> (<FIG>) and a cover <NUM> (<FIG>) they form a protection against bad weather conditions. The space enclosed by the walls, the floor <NUM> and the cover <NUM> is still open to the blade access area.

In order to form a working space in which defined conditions of humidity and temperature can be maintained, lateral wall elements <NUM>, <NUM> (<FIG>) are provided between the sealing means <NUM> and the platform <NUM>. These lateral wall elements <NUM>, <NUM> can extend over the floor <NUM> of the platform. They can be movable and, for example, can be folded or deformed in another way to be adapted to different distances between the blade <NUM> and the platform <NUM>. They are arranged below the sealing means <NUM> in the direction of gravity, so that no rainwater can enter the working space. The lateral wall elements can have a distance to each other (in a direction from the trailing edge <NUM> to the leading edge <NUM> of the platform <NUM>) which is smaller than the extension of the sealing means <NUM> in the same direction. This distance can be adapted to the size of the working space required or wanted, so that there is a great flexibility in the size of the working space.

Platform section <NUM> is provided with an extendable bottom cover <NUM> which can be moved towards the blade <NUM>, for example in form of a canvas so that the working space is also closed from the bottom.

<FIG> shows the working platform <NUM> in a condition in which another area on the surface of the blade <NUM> is to be inspected or to be repaired. To this end other sealing means <NUM> are provided at the platform sections <NUM> and further sealing means <NUM> are provided at platform section <NUM>. In addition, a cover <NUM> is used at the leading edge <NUM> of the blade <NUM> to cover a triangular gap which may occur between the sealing means <NUM>, <NUM>. It is also possible to move sealing means <NUM> in the position shown for sealing means <NUM>.

Again, the sealing means <NUM>, <NUM> are inclined towards the respective trailing edges <NUM>, <NUM> which are closer to the tower end <NUM>, so that water running down the blade <NUM> can directly flow into the blade access area <NUM>.

<FIG> shows a situation, in which nearly the whole blade access area <NUM> is covered by sealing means <NUM>, <NUM>, <NUM>, 29a, 29b, 29c with exception of a small area <NUM> through which rainwater can directly flow to the ground. The drain path is again shown by arrows <NUM>. At the end of the platform <NUM> opposite the trailing edge <NUM> the small cover <NUM> is again provided.

<FIG> shows more details of the sealing means <NUM>. The other sealing means <NUM>, <NUM> are of a similar construction. It should be noted that each platform section can be provided with its own sealing means <NUM>. However, it is also possible, that at least one sealing means <NUM> is movable from one platform section to another one.

The sealing means <NUM> comprises a carrier <NUM> carrying the suction cups <NUM>. Furthermore, the carrier <NUM> carries a sealing element <NUM>, for example in form of an inflatable tube or another flexible element. Furthermore, the carrier <NUM> is connected to a support element <NUM>. The support element <NUM> is connected to the platform section <NUM>. A roof element <NUM> is connected to the support element <NUM>. The roof element <NUM> can be folded or rolled, as it is shown in <FIG>. The roof element <NUM> can be changed from a working stage (on the right-hand side of the blade <NUM> in <FIG>) to a stowing stage as shown on the left-hand side of the blade <NUM> in <FIG>).

The working platform sections <NUM>-<NUM> have the floor <NUM> which is shown in <FIG> and the cover <NUM> which is shown in <FIG>. The roof element <NUM> covers a distance between the cover <NUM> and the blade <NUM>. As can be seen in <FIG>, the roof element <NUM> is arranged at a lower height in the direction of gravity than the cover <NUM>. The roof element <NUM> forms at least part of the drain path, so that water running down the surface of the blade <NUM> flows only over the roof element <NUM> and cannot flow over the cover <NUM>, so that the water load onto the cover <NUM> is kept at a minimum.

As can be seen in <FIG>, the sealing means <NUM> are inclined, i.e., a height in the direction of gravity at the trailing edge <NUM> of the blade <NUM> is lower than an end of the sealing means <NUM> at the leading edge <NUM> of the blade <NUM>. The angle of inclination is in a range from <NUM>° to <NUM>°, for example, <NUM>°.

When the sealing element <NUM> is made from more than one sealing segment <NUM>-<NUM>, as shown in <FIG>, the sealing segments <NUM>-<NUM> are arranged in a staircase and overlap each other, so that water is directed to the trailing edge of the blade <NUM>.

<FIG> shows platform section <NUM> and the blade <NUM> in a schematic side view. The platform section <NUM> is provided with an outer wall <NUM>. Such outer walls <NUM> and covers <NUM> are provided on all platform sections <NUM> - <NUM>, so that an operator working on the platform <NUM> is already protected from bad weather conditions. The support element <NUM> is fixed to the blade <NUM> by means of the carrier <NUM>. The roof <NUM> fixed to the support element <NUM> has been unfolded or unrolled to cover the distance between the blade <NUM> and the cover <NUM> of the platform section <NUM> thus forming a working chamber <NUM>. The working chamber <NUM> is laterally closed by the wall elements <NUM> (and <NUM> on the opposite side, <FIG>). The bottom of the working chamber <NUM> is closed by means of the bottom cover <NUM>, so that the working chamber is even more protected than the rest of interior of the platform <NUM>. In this working chamber <NUM> it is possible to produce an atmosphere having the desired temperature and humidity.

Claim 1:
Wind turbine blade maintenance platform (<NUM>) comprising a frame having a blade access area (<NUM>) structured and arranged to accommodate a blade (<NUM>) of a wind turbine (<NUM>), a tower end (<NUM>), and a front end (<NUM>), a cover (<NUM>), and sealing means (<NUM>, <NUM>, <NUM>) structured and arranged to contact the blade (<NUM>), and the sealing means (<NUM>, <NUM>, <NUM>) comprise a drain path (<NUM>), characterized in that
the drain path (<NUM>) opens into the blade access area (<NUM>) such that rainwater flowing down the blade (<NUM>) is separated from the blade (<NUM>) by means of the sealing means (<NUM>, <NUM>, <NUM>) and is then directly guided over the sealing means (<NUM>, <NUM>, <NUM>) to the blade access area (<NUM>) without flowing over the cover (<NUM>) of the platform (<NUM>).