Patent Description:
Wind turbine rotor blades are large, heavy and fragile parts. Handling wind turbine rotor blades at the manufacturing site, during transportation or at an erection site therefore is difficult and requires specific tools and expertise. A particularly fragile portion of a wind turbine rotor blade is the trailing edge, which is often very thin for aerodynamic reasons. When moving a wind turbine rotor blade from one place to another, it needs to be supported at at least two different positions, namely at the blade root, which is typically circular and has a large wall thickness providing a high strength, and at a midsection where the wind turbine rotor blade typically has an aerodynamic profile and a relatively thin trailing edge. When supporting the midsection with a belt, for example, it is almost impossible not to damage the trailing edge. This is true in particular when the wind turbine rotor blade during the handling process at the rotor blade manufacturing site needs to be rotated about its longitudinal axis, for example from a first position where the profile chord is arranged horizontally into a second position, where the profile chord is arranged vertically with a trailing edge pointing upwardly. Such a rotation of the wind turbine rotor blade about its longitudinal axis is required for example when the wind turbine rotor blade has to be equipped with an anti-icing system at the leading edge. Then horizontally transported rotor blade has to be positioned with the trailing edge pointing downwards and the leading edge pointing upwards. In this turning position a force resulting from the weight of the rotor blade pushes the trailing edge into the protector.

It is known to place a trailing edge protector at the wind turbine rotor blade's trailing edge during the installation of the rotor blade to a rotor hub, so that the fragile trailing edge will not be damaged when handling the wind turbine rotor blade.

The document <CIT> discloses an edge cutting tool for a trailing edge of a wind turbine blade. The tool includes two plates which are arranged on the pressure and suction sides of the wind turbine rotor blade and held in place by holders <NUM>. Once the plates <NUM> are fixed to the rotor blade, the trailing edge is cut along the rear ends of the plates <NUM>.

The document <CIT> discloses a trailing edge protector for a wind turbine rotor blade. The protector includes two legs for contacting outer surfaces of the wind turbine rotor blade. The legs are connected to each other by a flexural element. The protector is fastened to the rotor blade by means of a belt guided around the flexural element, so that under tension, the belt presses both legs towards each other and against the outer surfaces of the wind turbine rotor blade.

The document <CIT> discloses a trailing edge protector for a wind turbine rotor blade. The protector includes a first leg with a cushion pad and a second leg with a cushion pad, the legs engaging a pressure side and a suction side of the rotor blade. The protector acts like a spring and effectively holds itself on the rotor blade when installed.

The disclosed trailing edge protectors are used for the protection of the trailing edge during the transportation and/or lifting of a rotor blade having a position with an upwardly pointing trailing edge.

It is an object of the invention to provide a trailing edge protector for a wind turbine rotor blade that provides optimal protection and is easy to use.

This object is solved by the trailing edge protector for a wind turbine rotor blade with the features of claim <NUM>. Aspects of the invention are given in the dependent claims.

The trailing edge protector for a wind turbine rotor blade has the following features:.

In use, the trailing edge protector is placed at the trailing edge of the wind turbine rotor blade and may be held in this position for example by a belt of a hoisting means used for moving the wind turbine rotor blade. If desired, the trailing edge protector may be fastened to the wind turbine rotor blade by any other suitable means.

The invention is based on the insight that conventional trailing edge protectors, which are used e.g. for transporting or lifting a rotor blade, due to their inherent deformability on the one hand do not provide optimal protection. They may apply concentrated loads on the wind turbine rotor blade surface when being deformed, which has been observed in particular after extended use and large number of load cycles. On the other hand, it was found that under load, the trailing edge protectors can be pressed onto the trailing edge in a manner that makes it difficult or even impossible to remove them from the rotor blade without damaging of the trailing edge.

The inventors realized that these difficulties can be overcome by forming the trailing edge protector body as a stiff metal assembly. In particular, the at least one stiffening rib mounted to both legs imparts sufficient stiffness to the protector body such that both legs will always remain essentially at the desired relative angle, even when under load. This helps to avoid damaging of a trailing edge as long as the trailing edge protector is in place, and also avoids that, once the load is released, excessive clamping forces will be exerted by the legs' contact surfaces on the wind turbine rotor blade.

In addition, at least one leg is equipped with a release means adapted to exert a force moving the body in a direction away from the rotor blade. Preferred each leg is equipped with a release means. As these forces can be applied to each leg, it can be avoided that the trailing edge protector and the wind turbine rotor blade become wedged together when removing the trailing edge protector. This makes removing the trailing edge protector easy and safe.

In an aspect, the first leg comprises a first metal plate having an inner side forming the first contact surface and an outer side, and the second leg comprises a second metal plate having an inner side forming the second contact surface and an outer side, wherein the at least one stiffening rib is mounted to the outer side of the first metal plate and to the outer side of the second metal plate. The first metal plate may be shaped to complement the suction side surface of the rotor blade, and/or the second metal plate may be shaped to complement the pressure side surface of the rotor blade. It was found that forming the legs and in particular the contact surfaces of the legs from metal plates provides stiff contact surfaces with excellent long-term stability. Manufacturing of these contact surfaces is particularly easy, because an appropriate shape corresponding to the outer surfaces of the wind turbine rotor blade can be obtained by bending the metal plates in one direction only. The desired bends of the metal plates can be maintained by means of the at least one stiffening rib mounted e.g. directly to the outer sides of the metal plates. Preferably, the mounting can be exercised by welding, so that a stable structure is obtained.

In an aspect, the metal assembly comprises a metal tube arranged at the central portion and having a longitudinal slit with a first longitudinal edge mounted to the first leg and a second longitudinal edge mounted to the second leg. The metal tube may have an inner diameter for example in the range of <NUM> to <NUM>. The longitudinal slit may have a width in the range of for example <NUM> to <NUM>. The metal tube provides a protected free inner space for receiving the trailing edge of the wind turbine rotor blade.

In an aspect, the stiffening rib extends from the central portion along each of the legs for at least <NUM>% of the total length of the respective leg. The stiffening rib may also extend along each of the legs for at least <NUM>% of the total length or even over the entire length or almost the entire length of the respective leg. In this manner, the stiffening rib provides sufficient stability to the legs up to a position close to their free ends.

In an aspect, the stiffening rib at the central portion has a height of at least <NUM>% of the total length of one of the legs, wherein the height is measured in a plane perpendicular to a trailing edge of a wind turbine rotor blade at which the trailing edge protector is placed. This ensures the stiffening rib has a sufficient static height providing a high level of stiffness to the legs. The mentioned rib height may be present at the central portion and optionally also at those portions of the stiffening rib mounted to the legs.

In an aspect, the body comprises two stiffening ribs arranged in a lateral distance from each other. Of course, the body may comprise any number of stiffening ribs, for example <NUM>, <NUM>, <NUM>, <NUM> or more. Two stiffening ribs in a lateral distance sufficient to receive a belt of a hoisting means in between is particularly advantageous, because then these ribs secure the belt against slipping off from the body.

In an aspect, each of the release means comprises a solid metal block mounted to an outer side of the respective leg. This design of the release means allows to apply the force directly onto the solid metal block, for example with a hammer. When both legs are equipped with such solid metal blocks, the protector can be removed from the wind turbine rotor blade carefully with successive hammer strokes on both metal blocks. If only one solid metal block is mounted to each leg, it is preferably arranged at a central portion of the leg with reference to the longitudinal direction of the body, corresponding to the trailing edge direction. It is also possible to provide each leg with two or more solid metal blocks, for example in a lateral distance, and/or close to the lateral edges of the legs. Then, the hammer strokes can be applied even more carefully at selected sides.

In an aspect, the inlay is separate from the body and each of the inlay sections comprises a mechanical stop, wherein each of the release means is adapted to exert a force on one of the mechanical stops. This means the stiff body can be removed from the trailing edge basically by pushing away the body from the inlay. Applying forces on the rotor blade itself, for example for holding the rotor blade in position when pulling the trailing edge protector away from the rotor blade, is not necessary. Moreover, a relative motion of the inlay with reference to the rotor blade is not required when moving the body away from the rotor blade.

In an aspect, the contact surfaces of the legs and outer surfaces of the inlay sections abutting these contact surfaces when the trailing edge protector is placed at a trailing edge exhibit a low friction coefficient. To this end, the contact surfaces and/or the outer surfaces of the inlays may be smooth and even, coated with a low friction material and/or provided with a lubricating film. No matter how the low friction coefficient is obtained, it is desired to make this friction coefficient lower than a friction coefficient between the wind turbine rotor blades' outer surface and the inlay sections, so that when applying a force onto the body, the body will move relative to the inlay, not the inlay relative to the wind turbine rotor blade. This is helpful in particular when applying an external force to the body. In combination with a release means exerting a force on the inlay (for example on one of the mentioned mechanical stops thereof), the low friction coefficient helps to remove the body from the inlay with lower forces.

In an aspect, the inlay sections are formed by a flexible plate made of fibre reinforced polymer. Both inlay sections may be formed by the same flexible plate which is folded to form both sections, or by two or more separate flexible plates. Using a flexible plate made of fibre-reinforced polymer ensures sufficient stability of the inlay, so that the inlay can be used many times, while at the same time provides a material contacting the wind turbine rotor blade compatible with the rotor blade structure, so that the inlay sections will not damage the wind turbine rotor blade surfaces.

In an aspect, the mechanical stops are each formed by a metal profile having a flat fastening section embedded in the fibre-reinforced polymer of the respective flexible plate. This ensures a durable connection between the highly loaded mechanical stops and the inlay sections.

In an aspect, the inlay sections are formed by sandwich plates having metal top layers and an elastic core. The elastic core may be formed of an elastomeric material, for example. The metal top layers may be formed by an aluminium or steel sheet each, for example. The sandwich plate has a strong and durable surface while it is elastically deformable to some extent in a thickness direction of the plate, making it possible to accept tolerances between the wind turbine rotor blades' outer surfaces and the contact surfaces of the body.

In an aspect, the release means comprises a threaded bolt adapted to be screwed against one of the mechanical stops embedded in the flexible plate. In particular, the threaded bolt may be received in a threaded hole formed at the respective leg and/or at the at least one stiffening rib. A longitudinal axis of the threaded bolt may be arranged perpendicular to the wind turbine rotor blades' trailing edge and approximately parallel to the contact surface of the respective leg, so that when screwing the threaded bolt against the mechanical stop, a force in the desired direction for moving the body away from the inlay is obtained.

In an aspect, the release means comprises a hand-lever. The hand-lever may be arranged at the respective leg in a pivotable manner, for example on a pin welded to the leg. By turning the hand-lever, strong forces can easily be applied.

In an aspect, the hand-lever comprises a radial cam. The radial cam may have a helical shape, so that an effective diameter of the cam increases when the hand-lever is rotated. In this manner, very strong forces can be applied.

In the following, the invention is explained in greater detail based on embodiments shown in drawings. The figures show:.

The wind turbine rotor blade <NUM> shown in <FIG> has a blade root <NUM>, a blade tip <NUM>, a leading edge <NUM>, a trailing edge <NUM>, a suction side surface <NUM> and a pressure side surface <NUM>. In the position shown in <FIG> the trailing edge <NUM> is pointing downwards.

The blade root <NUM> is circular and has a large wall section, so that a first belt <NUM> supporting the blade root <NUM> can be wound about the blade root <NUM> without running a risk to cause any damages to the blade root <NUM>. To further support the turbine rotor blade <NUM> in a midsection, a second belt <NUM> is guided around the wind turbine rotor blade's profile. A trailing edge protector <NUM> is placed at the trailing edge <NUM>, between the turbine rotor blade <NUM> and the second belt <NUM>. The trailing edge protector <NUM> is shown in greater detail in <FIG>.

The exploded view of <FIG> shows the trailing edge protector <NUM> having a body <NUM> which is a welded metal assembly a metal tube <NUM>, a first metal plate <NUM>, a second metal plate <NUM> and two stiffening ribs <NUM> arranged in a lateral distance from each other for receiving the second belt <NUM> in between. The first metal plate <NUM> has an inner side forming a first contact surface <NUM> and an outer side <NUM>. The second metal plate <NUM> has an inner side forming a contact surface <NUM> and an outer side <NUM>. Both stiffening ribs <NUM> are welded to the outer side <NUM> of the first metal plate <NUM> as well as to the outer side <NUM> of the second metal plate <NUM>.

The stiffening ribs <NUM> are formed from a thick metal sheet cut into a pincer-like shape, with two arms <NUM> extending along the outer sides <NUM>, <NUM> of the metal plates and a central section <NUM> running around the metal tube <NUM>. At least at the central section <NUM>, the stiffening ribs <NUM> have a height of at least <NUM>% of a length of their arms <NUM> of the metal plates <NUM>, <NUM>, and of about the same size as the diameter of the metal tube <NUM>.

The trailing edge protector <NUM> further comprises an inlay <NUM> having a first inlay section <NUM> and the second inlay section <NUM>.

The first metal plate <NUM> forms a first leg <NUM>, the second metal plate <NUM> forms a second leg <NUM> of the body <NUM>. A central portion <NUM> of the body is formed by the metal tube <NUM> and by the central sections <NUM> of the stiffening ribs <NUM>.

The trailing edge protector <NUM> of <FIG> further includes two thickening elements, each comprising a core <NUM> and a cover <NUM>, to be placed between the stiffening ribs <NUM> in order to provide a smooth, rounded outer surface for the belt <NUM>.

<FIG> shows the trailing edge protector <NUM> of <FIG> in another perspective view with the inlay <NUM> placed at the respective metal plates <NUM>, <NUM>, so that when the trailing edge protector <NUM> is placed at the trailing edge <NUM> of a wind turbine rotor blade <NUM> as shown in <FIG>, the first inlay section <NUM> is arranged between the contact surface <NUM> and the suction side surface <NUM> of the wind turbine rotor blade <NUM>, and the second inlay section <NUM> is placed between the contact surface <NUM> of the second metal plate <NUM> and the pressure side surface <NUM> of the wind turbine rotor blade <NUM>. The figure also shows that the tube <NUM> has a longitudinal slit <NUM> with a first longitudinal edge to which the first metal plate <NUM> is welded, and with a second longitudinal edge to which the second metal plate <NUM> is welded. The inlay sections <NUM>, <NUM> cover the contact surfaces <NUM>, <NUM> of the metal plates <NUM>, <NUM> in their entirety and further extend into the longitudinal slit <NUM>.

<FIG>show a trailing edge protector <NUM> similar to the one shown in <FIG>, <FIG> with a release means including four solid metal blocks <NUM>. Two of the solid metal blocks <NUM> are welded to the outer surface <NUM> of the first metal plate <NUM> and two of these solid metal blocks <NUM> are welded to the outer surface <NUM> of the second metal plate <NUM>. Each of the <FIG>illustrates how a force can be applied to one of the metal blocks <NUM> by means of a hammer <NUM>. In the <FIG>, the body <NUM> and the inlay <NUM> with inlay sections <NUM>, <NUM> are in the relative position in which they are when the trailing edge protector <NUM> is placed at a trailing edge <NUM> of a wind turbine rotor blade <NUM>. In <FIG> the body <NUM> forced by the hammer strokes moves away from the inlay <NUM> and thus from the wind turbine rotor blade <NUM>.

<FIG> show three views of another trailing edge protector <NUM> similar to the one shown in <FIG> but with another release means comprising four threaded bolts <NUM> guided in metal blocks <NUM> each including a threaded bolt and welded to the outer sides <NUM>, <NUM> of the metal plates <NUM>, <NUM>. The arrows illustrate the direction of a force exerted by the threaded bolts <NUM> when these are screwed into the threaded holes of the metal blocks <NUM>. To accept these forces, each of the inlay sections <NUM>, <NUM> is provided with a mechanical stop <NUM> positioned close to a free end of the respective leg of the body <NUM>. The threaded bolts <NUM> can be screwed against these mechanical stops <NUM>, thereby forcing the body <NUM> away from the respective inlay sections <NUM>, <NUM>, as illustrated in <FIG>.

<FIG>show still another release means on a trailing edge protector <NUM>, otherwise being similar to the trailing edge protector <NUM> shown in <FIG>. This release means includes a hand lever <NUM> guided on a metal pin <NUM> welded to one of the outer surfaces <NUM>, <NUM> of the respective metal plate <NUM>, <NUM>. The hand lever <NUM> can be pivoted about the pin <NUM> as illustrated by the arrow <NUM> in <FIG>. The hand lever <NUM> has a radial cam <NUM> with a surface contour arranged in a helical manner with reference to the pivoting axis defined by the pin <NUM>. When turning the hand lever <NUM> as illustrated by the arrow <NUM>, the radial cam <NUM> will exert a force onto the mechanical stop <NUM> of the respective inlay section <NUM>, <NUM>. The effect is shown to the right, the body <NUM> is forced away from the respective inlay section <NUM>, <NUM>.

Claim 1:
A trailing edge protector (<NUM>) for a wind turbine rotor blade (<NUM>), the trailing edge protector (<NUM>) comprising:
• a body (<NUM>) having a central portion (<NUM>), a first leg (<NUM>) with a first contact surface (<NUM>) and a second leg (<NUM>) with a second contact surface (<NUM>), wherein the first leg (<NUM>) and the second leg (<NUM>) extend from the central portion (<NUM>) at a fixed angle and the first contact surface (<NUM>) is facing the second contact surface (<NUM>),
• an inlay (<NUM>) having a first inlay section (<NUM>) and a second inlay section (<NUM>),
• wherein the trailing edge protector (<NUM>) is designed to be placed at a trailing edge (<NUM>) of a wind turbine rotor blade (<NUM>) such that the central portion (<NUM>) is arranged near the trailing edge (<NUM>), the first inlay section (<NUM>) is arranged between the first contact surface (<NUM>) and a suction side surface (<NUM>) of the wind turbine rotor blade (<NUM>) and the second inlay section (<NUM>) is arranged between the second contact surface (<NUM>) and a pressure side surface (<NUM>) of the wind turbine rotor blade (<NUM>), characterised in that
• the body (<NUM>) is a metal assembly comprising at least one stiffening rib (<NUM>) arranged at the central portion (<NUM>) and mounted to both legs (<NUM>, <NUM>), and further in that
• at least one leg comprises a release means adapted to exert a force moving the body (<NUM>) in a direction away from the wind turbine rotor blade (<NUM>).