Patent Description:
Such a blade access arrangement is known from <CIT>.

<CIT> shows a frame of a blade access arrangement the length of which can be extended and which comprises tower guide means for guiding the frame against the tower.

<CIT> shows a maintenance platform for wind turbines which is slidably arranged on a frame having tower guide means for guiding the frame against the tower. The frame comprises a suspension point at the end near the tower.

A further blade access arrangement is known, for example, from <CIT>. A platform comprising three sub-platforms connected and with a hoisting arrangement comprising three lifting devices placed at the platform one at each of the sub platforms. It is challenging to control the platform in a horizontal plan in all positions of the platform. Especially in the situation where the platform is moving from the tower towards the blade and even more challenging when platform is moved closer to the blade tip where the distance between tower and blade is at its maximum.

The object underlying the invention is to have a blade access arrangement where the platform in all positions moves horizontal and controlled.

This object is solved with a blade access arrangement as described at the outset in that where the bar suspension point is placed in an area a third part from tower guiding means and a third part from the platform.

In most wind power plants, the tip of a downwardly pointing blade has a larger distance to the tower than the root of the blade. Blade access arrangement therefor have a tower guiding means for guiding the platform against the tower and a bar arrangement connecting the platform with the tower guiding means. Platforms may carry persons and or expensive and sensitive equipment's for servicing and/or repairing the blade. A stable and horizontal movement of the platform is essential, both when the platform moves along the tower and when the platform move from the tower towards the blade. A suspension point at the bar arrangement secure that the suspension point can be used for both supporting and carrying the tower guiding means, the bar arrangement and parts of the platform depending on how far the platform are from the tower guiding means.

In an embodiment of the invention the bar suspension point is placed at the bar arrangement between the tower guiding means and the platform.

One could imagine a solution where instead of having one suspension point placed at the bar arrangement between the tower guiding means and the platform two suspension points are used one placed at a sub platform closes to the tower and one at the tower guiding arrangement. These two-suspension points could be connected with one wire and the wire running over a pully placed above the blade access arrangement for example at the nacelle. Such a solution is not giving the same freedom of movement of the forces and weight as the present solution where the suspension point is placed at the bar arrangement. A solution where the bar suspension point is placed in an area a third part from tower guiding means and a third part from the platform gives a good position for a suspension point which in all situation can share forces and weight with further suspension points placed at the platform. A suspension point placed in an area a third part from tower guiding means and a third part from the platform, should be understood as, dividing the distance between tower guiding means and platform in three equal distances the suspension point is placed in the middle third part.

In an embodiment of the invention the bar suspension is placed at the bar arrangement halfway between the tower guiding means and the platform. This position of the suspension point gives in all location of the platform a good suspension point both when platform is close to tower, at distance max away from tower and when platform is at the blade tip or root.

In an embodiment of the invention the tower guide means comprise a bar arrangement having a variable length. When the length of the bar arrangement can be varied, it is possible to move the platform away from the tower towards the blade.

In an embodiment of the invention the bar arrangement comprises at least one telescopic bar. A telescopic bar can change the length by shifting one element into another element. This saves space.

In an embodiment of the invention the platform is arranged above the bar arrangement in direction of gravity. This minimizes the risk of an unwanted tilting of the platform.

In an embodiment of the invention the bar arrangement is retractable into a platform space. A platform space is a space extending from the platform in the direction of gravity and having a section corresponding to the form of the platform. When the bar arrangement can be retracted into this platform space, the platform can simply be balanced without having masses which are positioned in a disadvantageous position. The bar arrangement can be retracted into a space below the platform, into a space inside the platform or even into a space above the platform.

In an embodiment of the invention the bar arrangement comprises two bars. An arrangement of two bars has the advantage that the platform can be supported at the tower at two points. Thus, a lateral movement of the platform can be avoided or at least controlled.

In an embodiment of the invention an angle between the two bars is adjustable. This is of advantage when the bars are connected to sub-platforms which are moved relatively to each other to adjust an open configuration of the platform. Such an adjustment is not blocked by the bars.

In an embodiment of the invention the hoisting arrangement comprising a hoisting beam connecting the two bars and the bar suspension point is arranged at the hoisting beam. A suspension point arranged at the beam connecting the two bars gives a good suspension point for covering weight and forces from both bars.

In an embodiment of the invention the bar suspension point is arranged at the hoisting beam in a position approximately half way between the two bars. This is an advantage when the platform has two approximately parallel sides facing each other with approximately similar weight and forces acting on the blade access arrangement.

In an embodiment of the invention the bar suspension point can be moved along the hoisting beam such a movement can compensate for change in weight and forces between sub platforms.

In an embodiment of the invention the hoisting beam is connected with wire ropes to the two bars this allows the distance between the bars to be changed without changing the picture of the forces and weight for the blade access arrangement.

In an embodiment of the invention the hoisting beam has form as a triangle, the wording triangle is referring to the form of the music instrument with the same name. Such a form can give basis for support not only for the bar suspension point but also support for a lifting device, winding gear or an electric powered wire rope hoist.

The blade access arrangement can be hoisted from a lifting apparatus such as a crane. A crane placed in connection with the nacelle or a standalone crane solution. But the hoisting could as well be the situation that the bar suspension point and further suspension points are connected to the upper part of the wind power plan like the nacelle or rotor or other arrangement located in connection with the nacelle or rotor. For such a solution a lifting arrangement can be connection with the bar suspension point. A lifting device could for example be winding gear or an electric powered wire rope hoist.

In an embodiment of the invention the hoisting arrangement comprising further suspension points placed at the platform preferably at least three suspension points, one at the bar arrangement and two at the platform. The two platform suspensions are typically placed opposite each other on two sub- platforms. The suspension points from the platform can in relation to the sub-platform be stationary suspension points or suspension points movable along the sides of the sub-platforms.

The invention will now be described in more detail with reference to the drawing, in which:.

<FIG> is split into two figures a <FIG> showing a wind power plan and a blade access arrangement where <FIG> shows a detail A of <FIG>. In the following <FIG> in combination referred to as <FIG>.

<FIG> shows a blade access arrangement <NUM> for a rotor blade <NUM> of a wind power plant <NUM>. The wind power plant <NUM> has a tower <NUM>. A nacelle <NUM> is arranged on top of the tower. The blade <NUM> is fixed to a hub <NUM> of a rotor <NUM> which is rotatably supported in the nacelle <NUM>.

It can be seen in <FIG>, that a tip <NUM> of the blade <NUM> has a larger distance to the tower than a root <NUM> of the blade. This makes access of the blade <NUM> difficult. However, access is necessary, for example for inspection, maintenance and repair of the blade <NUM>.

The blade access arrangement <NUM> comprises a platform <NUM>, The platform <NUM> is connected to tower guide means <NUM> which rest against the tower <NUM>. The tower guide means <NUM> can be provided with rollers so that the tower guide means can guide the platform <NUM> along the tower <NUM>. The tower guide means <NUM> are connected to the platform <NUM> by means of a bar arrangement which is difficult to see at <FIG> but will be described in detail with reference to the following figures.

<FIG> shows the blade access arrangement <NUM> in a starting position, in which the platform <NUM> is near ground. The blade access arrangement <NUM> is suspended by three wire ropes <NUM>, <NUM> from the nacelle <NUM>. Only two of the wire ropes are visible, because one of the wire ropes is located behind the wire rope <NUM>. The blade access arrangement disclosed has three suspension points, each represented by an electric powered wire rope hoist where two of them <NUM> are attached to the platform <NUM>. The third wire rope <NUM> is attached to the bar arrangement this arrangement will be described further with reference to <FIG>.

<FIG> is disclosing a blade access arrangement <NUM> comprises a platform <NUM> having blade guide means <NUM>, <NUM>. These guiding elements <NUM>, <NUM> can comprise rollers which can be pivoted with respect to the platform <NUM>. The platform <NUM> disclosed at the <FIG> is a blade guided platform which as well can be tower guided. The invention function as well for platforms which alone is tower guided.

The tower guide means <NUM> are connected to the platform <NUM> by means of a bar arrangement which has, in the embodiment shown in <FIG>, two bars <NUM>, <NUM> which have a variable length. This is realized by the fact that the bars <NUM>, <NUM> are telescopic bars. The bars <NUM>, <NUM> can be retracted in a space below the platform <NUM> or into the platform <NUM>. This makes it easier to balance out the platform <NUM> in a working position.

<FIG> discloses the blade access arrangement <NUM> in three different working position for the platform in relation to the tower. The tower and the blade are not disclosed in the figures. All three working positions are disclosed in a sectional view and in addition the blade access arrangement <NUM> from above.

Shows the blade access arrangement <NUM> in a starting position, in which the platform <NUM> is near ground and the two bars <NUM>, <NUM> is not extended. The blade access arrangement <NUM> has the same configuration for the bars <NUM>, <NUM> in the situation where the platform <NUM> has been lifted up to the nacelle <NUM>. This means that the platform <NUM> is lifted near to the root <NUM> of the blade <NUM>, where the distance between tower and blade is at I shortest distance.

<FIG> shows the blade access arrangement <NUM> in a situation in which the distance between the tower and blade is longer. In this situation, the bars <NUM>, <NUM> are extended. Upon this extension the platform <NUM> is pushed away from the tower and can approaches the blade.

<FIG> shows the blade access arrangement <NUM> in a situation in which the distance between the tower and blade is longer in this situation, the bars <NUM>, <NUM> are extended even further compared to the situation disclosed in <FIG>.

<FIG> shows a hoisting arrangement <NUM> with a hoisting beam <NUM> connecting the two bars <NUM>, <NUM> and with the bar suspension point <NUM> arranged at the hoisting beam <NUM>.

It can be seen from the figures that in all situation is the bar suspension point <NUM> situated in a position at the bar arrangement <NUM>, <NUM> halfway between the tower guiding means <NUM> and the platform <NUM>.

The typical use of a tower guided platform with blade guiding elements <NUM>, <NUM> is that the Blade access arrangement is placed closed to the tower <NUM>, wires <NUM>, <NUM> from the hoisting arrangement is connected to the wind power plan typical in connection with the nacelle <NUM>. The tower guide means <NUM> rest against the tower <NUM>. The tower guide means <NUM> can be provided with rollers so that the tower guide means can guide the platform <NUM> along the tower <NUM>. The bar arrangement <NUM>, <NUM> is in this situation in a not extended position, this is the situation as disclosed in <FIG>. The blade access arrangement is lifted with the wires <NUM>, <NUM>. When the platform <NUM> is lifted to a position in which the platform <NUM> is close to the blade <NUM>. This means that the platform is lifted near to the root <NUM> of the blade <NUM>. In this position the bars <NUM>, <NUM> are extended. Upon this extension the platform <NUM> is pushed away from the tower <NUM> and approaches the blade <NUM>. During this movement (or before the movement) the platform <NUM> has been changed from a closed configuration as disclosed into an open configuration (not disclosed) so that an opening <NUM> of the platform <NUM> is open to the blade <NUM>. To this end, two sub-platform parts have been moved away from each other. As soon as the open configuration has been adjusted, the platform <NUM> can be shifted to catch the blade <NUM> and then be adjusted again in closed configuration wherein the blade <NUM> is accommodated within the opening <NUM> and the guiding elements <NUM>, <NUM> rest against the leading edge of the blade <NUM>. In this situation the platform <NUM> is guided at the tower <NUM> and at the blade <NUM>. Such a double guiding is in principle not necessary, so that in a further step the bar arrangement <NUM>, <NUM> are retracted by shortening the bars <NUM>, <NUM> so that finally a situation as shown in <FIG> is reached. Once the blade <NUM> guides the platform <NUM>, the platform <NUM> can be lowered in a direction to the tip <NUM> of the blade or raised in the opposite direction, so that the whole blade <NUM> can be inspected, maintained, or repaired. Thus, the blade access arrangement <NUM> combines the advantages of a tower guided system with the advantages of a blade guided system. However, the access to the blade <NUM> is made simpler and the platform <NUM> or working plane can be kept stable in all positions.

It should be noted that the bars <NUM>, <NUM> can be retracted into or below the platform <NUM> once the desired position is achieved and the platform <NUM> is guided by the blade <NUM> This makes it easier to balance out the platform <NUM> in a working position. The bars <NUM>, <NUM> can furthermore be retracted into or below the platform <NUM> when the platform is in a position close to the tower <NUM> or when the blade access arrangement is in a transportation situation.

An angle between the two bars <NUM>, <NUM> is variable. It can be adjusted, wherein the adjustment is made by varying the distance of the platform <NUM> from the tower <NUM>.

<FIG> disclose the blade access arrangement <NUM> in a situation where the bar arrangement <NUM>, <NUM> connecting the platform <NUM> with the tower guiding means <NUM> is extended. Three suspension points are disclosed two at the platform and one at the bar arrangement <NUM>, <NUM>. The bar suspension point <NUM> is place on a hoisting beam <NUM> connecting the two bars. A suspension point arranged at the beam connecting the two bars gives a good suspension point for covering weight and forces from both bars.

<FIG> shows a blade access arrangement from the side, <FIG> shows the section cut A-A from <FIG>.

The bar suspension point <NUM> is arranged at the hoisting beam <NUM> in a position approximately half way between the two bars. This is an advantage when the platform has two approximately parallel sides facing each other with approximately similar weight and forces acting on the blade access arrangement. The bar suspension point <NUM> can be moved along the hoisting beam <NUM> such an movement can compensate for change in weight and forces between sub platforms. The hoisting beam <NUM> is connected with wire ropes to the two bars this allows the distance between the bars to be changed without changing the picture of the forces and weight for the blade access arrangement. The hoisting beam <NUM> has form as a triangle, the wording triangle is referring to the form of the music instrument with the same name. Such a form can give basis for support not only for the bar suspension point but also support for a lifting device, winding gear or an electric powered wire rope hoist.

Claim 1:
Blade access arrangement (<NUM>) for a rotor blade (<NUM>) of a wind power plant (<NUM>) having a tower (<NUM>), the arrangement (<NUM>) comprising a platform (<NUM>), tower guide means (<NUM>) for guiding the platform (<NUM>) against the tower (<NUM>), bar arrangement (<NUM>, <NUM>) connecting the platform (<NUM>) with the tower guiding means (<NUM>) and a hoisting arrangement (<NUM>) for hoisting the blade access arrangement (<NUM>) up and down, the hoisting arrangement (<NUM>) comprising two suspension points at the platform (<NUM>) and a bar suspension point (<NUM>) placed at the bar arrangement (<NUM>, <NUM>), characterized in that the bar suspension point (<NUM>) is placed in an area a third part from tower guiding means (<NUM>) and a third part from the platform (<NUM>), meaning that the distance between the tower guiding means and the platform is divided in three equal distances and the suspension point is placed in the middle third part.