Patent Description:
A wind turbine comprises a rotor connected to a generator arranged inside a nacelle. The nacelle is arranged at an upper end of a tower of the wind turbine. The tower has a plurality of tower sections that are arranged on top of each other. The tower sections comprise flanges that are connected to each other by means of bolts to form the tower. The bolts can have a length of <NUM> to <NUM> and a weight of up to <NUM> or even more. Due to these dimensions of the bolts, it is difficult to handle the bolts manually on a construction site where the tower must be assembled or disassembled.

<CIT> discloses a lifting device for mounting a rotor on a drive train of a wind turbine. The end sections of the gripping levers are designed to engage the receiving means of the hub. However, it does not disclose a lifting device for gripping bolts of a wind turbine.

It is one object of the present invention to provide an improved bolt gripper.

Accordingly, an adjustable bolt gripper for gripping bolts of a wind turbine is provided. The adjustable bolt gripper comprises a frame, a first shovel mechanism to engage with a first bolt, a second shovel mechanism to engage with a second bolt, wherein the first shovel mechanism and the second shovel mechanism are both slidably supported at the frame for bringing the bolt gripper from a folded status into an unfolded status and vice versa, and wherein the first shovel mechanism and the second shovel mechanism are positioned further away from each other in the unfolded status than compared to the folded status.

Since the bolt gripper can be brought from the folded status into the unfolded status and vice versa, it is possible to adjust the bolt gripper to a specific distance between two axes of symmetry of two bolts that are received in a magazine. Thus, one bolt gripper can be used for different distances between the axes of symmetry.

"Adjustable" in this context means that the shovel mechanisms can be moved along the frame to bring the bolt gripper from the folded status or folded position into the unfolded status or unfolded position. "Gripping" in this context means that the bolt gripper receives the bolts for transportation purposes. In particular, the bolt gripper is designed to grip two bolts at the same time. The bolt gripper can be used to receive the bolts from a magazine and to transport it to an assembly site for assembling a tower of the wind turbine or the like.

When bringing the bolt gripper from the folded status into the unfolded status, the first shovel mechanism and the second shovel mechanism move away from each other along the frame. When bringing the bolt gripper from the unfolded status into the folded status, the first shovel mechanism and the second shovel mechanism move toward each other along the frame.

Hence, "folded" in this context means that the shovel mechanisms are arranged close to each other or adjacent to each other. In contrast to that, "unfolded" in this context means that the shovel mechanisms are arranged spaced apart from each other. Thus, the bolt gripper can be telescoped. "Telescoped" in this context means that the size, in particular the width, of the bolt gripper along a width direction or x-direction can be adjusted or changed.

The shovel mechanisms are movably or slidably supported by the frame. "Slidable" or "movable" in this context means a transversal or linear movement along the frame. "Engaging" the bolt means that the shovel mechanisms are designed to encompass the bolts in such a way that the bolts can be lifted and/or transported by means of the bolt gripper without falling out of the bolt gripper. The shovel mechanisms can be named engaging mechanisms. Thus, the formulation "shovel mechanism" can be replaced by the formulation "engaging mechanism" and vice versa.

The bolt gripper has a coordinate system comprising the width direction or x-direction, a height direction or y-direction and a depth direction or z-direction. The directions are arranged perpendicular to each other. The shovel mechanisms can be moved along the x-direction. Preferably, the frame comprises a vertical profile and two horizontal profiles. The shovel mechanisms are guided along the horizontal profiles. The horizontal profiles preferably run along the x-direction.

Preferably, the bolt gripper comprises an eyelet. A hook of a winch or crane can be hooked into the eyelet for lifting the bolt gripper. The eyelet can be attached to the frame. Furthermore, the bolt gripper preferably comprises two handles that can be gripped by an operator. The handles can also be attached to the frame. A holder for holding a remote control of the winch or crane can be provided. The holder can also be attached to the frame.

According to an embodiment, the frame comprises a vertical profile, a first horizontal profile and a second horizontal profile, wherein the vertical profile is sandwiched between the first horizontal profile and the second horizontal profile, wherein the first shovel mechanism is slidably supported at the first horizontal profile, and wherein the second shovel mechanism is slidably supported at the second horizontal profile.

The vertical profile preferably runs along the y-direction. The horizontal profiles preferably run along the x-direction. Thus, the frame has an inverted T-shape. The profiles can be bolted or welded together. The profiles are preferably hollow profiles and comprise a rectangular cross section. The profiles can be made of steel or aluminum.

According to a further embodiment, the first shovel mechanism comprises a slide profile that is slidably supported at the first horizontal profile, wherein the second shovel mechanism comprises a slide profile that is slidably supported at the second horizontal profile.

Each shovel mechanism has a slide profile of its own. The slide profiles are hollow profiles. The slide profiles preferably have a rectangular cross-section. The slide profiles can be made of steel or aluminum.

According to a further embodiment, the slide profile of the first shovel mechanism receives the first horizontal profile, wherein the slide profile of the second shovel mechanism receives the second horizontal profile.

"Receiving" in this context means that horizontal profiles are arranged within the slide profiles.

According to a further embodiment, the first horizontal profile comprises a first bolt against which the slide profile of the first shovel mechanism lies in the unfolded status, wherein the second horizontal profile comprises a second bolt against which the slide profile of the second shovel mechanism lies in the unfolded status.

This prevents the shovel mechanisms from falling off the frame. Thus, the shovel mechanisms cannot be lost. The bolts can be screws or the like that are screwed into bores being provided in the horizontal profiles.

According to a further embodiment, the first shovel mechanism comprises a shovel element that is attached to the slide profile of the first shovel mechanism, wherein the second shovel mechanism comprises a shovel element that is attached to the slide profile of the second shovel mechanism.

Preferably, the shovel elements are identical. However, the shovel elements are mirror-inverted. The shovel elements can be C-shaped. The shovel elements can be named receiving elements. Hence, the formulation "shovel element" can be replaced by the formulation "receiving element" and vice versa.

According to a further embodiment, the frame comprises a support plate that is sandwiched between the shovel element of the first shovel mechanism and the shovel element of the second shovel mechanism.

The support plate preferably runs along the z-direction. The support plate can be welded or bolted to the vertical profile.

According to a further embodiment, the shovel element of the first shovel mechanism and the shovel element of the second shovel mechanism are attached to the support plate by means of at least one bolt.

Preferably, there are provided two bolts. The support plate has at least one bore or breakthrough through which the at least one bolt is guided. Preferably, there are provided two breakthroughs in the support plate. The shovel elements have corresponding bores or breakthroughs through which the bolt or the bolts are guided. The bolt can be a screw.

According to a further embodiment, each shovel element comprises an outer arm section and an inner arm section, wherein the support plate is sandwiched between the inner arm sections.

Each shovel element has a base section. The arm sections are bent in relation to the base section. At each end of the base section, one of the arm sections is provided. This results in the afore-mentioned C-shape of the shovel elements. The shovel elements can be made of bent metal sheets.

According to a further embodiment, the at least one bolt is guided through the inner arm sections and the support plate.

The inner arm sections have bores or breakthroughs for receiving the at least one bolt. For example, each inner arm section has two breakthroughs.

According to a further embodiment, the bolt gripper further comprises several distance elements, wherein at least one distance element is sandwiched between the support plate and the shovel element of the first shovel mechanism, and wherein at least one distance element is sandwiched between the support plate and the shovel element of the second shovel mechanism for bringing the bolt gripper from the folded status into the unfolded status.

The distance elements can be washers or the like. By means of the distance elements, a distance or space between the shovel elements can be adjusted. The distance elements are arranged between the inner arm sections and the support plate.

According to a further embodiment, each shovel element comprises a first support section, which is bent toward the outer arm section, and a second support section, which is bent toward the inner arm section, wherein the first support section carries a first pad, and wherein the second support section carries a second pad.

Preferably, the support sections are arranged perpendicular toward the arm sections. The pads can be bolted to the support sections. The pads can be replaced. For example, replacing the pads can be necessary for maintenance reasons.

According to a further embodiment, the first pad and/or the second pad is made of a plastic material.

For example, the pads are made of polyoxymethylene (POM), polytetrafluoroethylene (PTFE), or the like. This improves the sliding properties. The bolts rest on the pads when being received in the bolt gripper.

According to a further embodiment, the bolt gripper further comprises a lock mechanism for locking the first bolt in the first shovel mechanism and for locking the second bolt in the second shovel mechanism.

The lock mechanism prevents the bolts from falling out of the shovel mechanism. Preferably, the lock mechanism comprises a notch that is provided in the support plate and runs along the y-direction. The lock mechanism further comprises a lock plate that is guided in the notch and a lock wire for moving the lock plate along the notch. The lock plate can engage with an undercut that is provided at an upper end of the notch. The lock plate can be exchanged.

According to a further embodiment, the bolt gripper can be steplessly adjusted between the folded status and the unfolded status.

In other words, there is provided an arbitrary number of intermediate statuses or positions between the folded status and the unfolded status. Adjustment can be done by the distance elements as explained before. Distance elements of varying thicknesses can be provided for this purpose.

<FIG> shows a wind turbine <NUM> according to one embodiment.

The wind turbine <NUM> is an offshore wind turbine. The wind turbine <NUM> comprises a rotor <NUM> connected to a generator (not shown) arranged inside a nacelle <NUM>. The nacelle <NUM> is arranged at the upper end of a tower <NUM> of the wind turbine <NUM>. The tower <NUM> can be named wind turbine tower.

The tower <NUM> has a plurality of tower sections <NUM> to <NUM> that are arranged on top of each other. The tower sections <NUM> to <NUM> comprise flanges that are connected to each other by means of bolts to form the tower <NUM>. The tower sections <NUM> to <NUM> can be identical. However, the tower sections <NUM> to <NUM> can also be different from each other.

The rotor <NUM> comprises three rotor blades <NUM>. The rotor blades <NUM> are connected to a hub <NUM> of the wind turbine <NUM>. Rotors <NUM> of this kind may have diameters ranging from, for example, <NUM> to <NUM> meters or even more. The rotor blades <NUM> are subjected to high wind loads. At the same time, the rotor blades <NUM> need to be lightweight. For these reasons, rotor blades <NUM> in modern wind turbines <NUM> are manufactured from fiber-reinforced composite materials. Therein, glass fibers are generally preferred over carbon fibers for cost reasons. Oftentimes, glass fibers in the form of unidirectional fiber mats are used.

<FIG> shows a rotor blade <NUM> according to one embodiment.

The rotor blade <NUM> comprises an aerodynamically designed portion <NUM>, which is shaped for optimum exploitation of the wind energy and a blade root <NUM> for connecting the rotor blade <NUM> to the hub <NUM>.

<FIG> shows a bolt <NUM> according to one embodiment.

A plurality of bolts <NUM> is used to connect the tower sections <NUM> to <NUM> together to form the tower <NUM>. In the following, only one bolt <NUM> will be referred to. The bolt <NUM> comprises a bolt element <NUM>. The bolt element <NUM> can be a screw or the like. The bolt element <NUM> comprises a bolt head <NUM>. The bolt head <NUM> can have a hexagonal shape.

A bolt shaft <NUM> protrudes from the bolt head <NUM>. The bolt shaft <NUM> is designed to be rotation symmetric toward an axis of symmetry <NUM> of the bolt <NUM>. A thread <NUM> is provided at an end of the bolt shaft <NUM> that faces away from the bolt head <NUM>. The bolt shaft <NUM> is guided through a washer <NUM> that abuts the bolt head <NUM>.

The bolt <NUM> can have a length <NUM> of <NUM> to <NUM> and a weight of up to <NUM> or even more. Due to these dimensions of the bolt <NUM>, it is difficult to handle the bolt <NUM> manually on a construction site where the tower <NUM> has to be assembled or disassembled.

<FIG> shows a perspective view of an adjustable bolt gripper <NUM> according to one embodiment. <FIG> and <FIG> both show top views of the bolt gripper <NUM>. In the following, <FIG> will be referred to at the same time.

The bolt gripper <NUM> is designed to handle at least one bolt <NUM> as describes before. Preferably, the bolt gripper <NUM> is designed to carry or handle two bolts <NUM> at the same time. The handling of the bolt <NUM> or the bolts <NUM> is done winch-assisted or crane-assisted as will be explained in detail later.

The bolt gripper <NUM> has a coordinate system comprising a width direction or x-direction x, a height direction or y-direction y and a depth direction or z-direction z. The directions x, y, z are arranged perpendicular to each other.

The bolt gripper <NUM> comprises a T-shaped frame <NUM>. The frame <NUM> has a vertical profile <NUM> that runs along the y-direction y. The vertical profile <NUM> can be a hollow steel or aluminum profile with a rectangular cross-section.

Two horizontal profiles <NUM>, <NUM> are attached to the vertical profile <NUM> to form a reversed T-shaped geometry of the frame <NUM>. There are provided a first horizontal profile <NUM> and a second horizontal profile <NUM>. The horizontal profiles <NUM>, <NUM> run along the x-direction x. The vertical profile <NUM> is sandwiched between the two horizontal profiles <NUM>, <NUM>. The horizontal profiles <NUM>, <NUM> are firmly attached to the vertical profile <NUM>. The horizontal profiles <NUM>, <NUM> are bolted or welded to the vertical profile <NUM>. The horizontal profiles <NUM>, <NUM> can both be a hollow steel or aluminum profile with a rectangular cross-section.

In the orientation of <FIG> at a back side of the vertical profile <NUM>, a holder <NUM> for holding a winch remote control (not shown) is attached to the vertical profile <NUM>. The holder <NUM> can be welded to the vertical profile <NUM>. Alternatively, the holder <NUM> can be bolted to the vertical profile <NUM> by means of bolts <NUM> of which only one is shown in <FIG> and <FIG>.

The holder <NUM> is sandwiched between two handles <NUM>, <NUM> that can be gripped by an operator for operating the bolt gripper <NUM>. The handles <NUM>, <NUM> can be firmly attached to the horizontal profiles <NUM>, <NUM>. The handles <NUM>, <NUM> can be bolted or welded to the horizontal profiles <NUM>, <NUM>. The handle <NUM> can be attached to the first horizontal profile <NUM>. The handle <NUM> can be attached to the second horizontal profile <NUM>. The handles <NUM>, <NUM> have a circular cross-section. The handles <NUM>, <NUM> can be made of a steel or aluminum tube.

Facing away from the holder <NUM>, a support plate <NUM> is attached to the vertical profile <NUM>. The support plate <NUM> is part of the frame <NUM>. The support plate <NUM> protrudes from the vertical profile <NUM> along the z-direction z. The support plate <NUM> can be bolted or welded to the vertical profile <NUM>.

<FIG> shows the support plate <NUM> according to one embodiment.

The support plate <NUM> has a base section <NUM> that carries an eyelet <NUM> that can receive a hook from a winch or crane (not shown). The base section <NUM> is plate-shaped and comprises a face <NUM> that is attached to the vertical profile <NUM>. Two breakthroughs <NUM>, <NUM> in the form of bores are provided at the base section <NUM>. The base section <NUM> runs along the z-direction z.

The support plate <NUM> has a L-shaped geometry and comprises the afore-mentioned base section <NUM> that runs along the z-direction z and a lock section <NUM> that runs along the y-direction y. On top of the lock section <NUM>, an end plate <NUM> (<FIG>) is attached to the lock section <NUM>. The end plate <NUM> can be welded to the lock section <NUM>. The end plate <NUM> has two breakthroughs <NUM>, <NUM>. The lock section <NUM> of the support plate <NUM> comprises a notch <NUM> that runs along the y-direction y. At an upper end of the notch <NUM>, an undercut <NUM> is provided. The undercut <NUM> is part of the notch <NUM>.

A lock plate <NUM> is guided in the notch <NUM> along the y-direction y. The lock plate <NUM> is exchangeable. A lock wire <NUM> is connected to the lock plate <NUM> and guided through the breakthroughs <NUM>, <NUM> of the end plate <NUM>. The notch <NUM>, the lock plate <NUM> and the lock wire <NUM> together form a lock mechanism <NUM> of the bolt gripper <NUM>.

The function of the lock mechanism <NUM> will be explained in the following. <FIG> shows the lock mechanism <NUM> in a locked position or status. In the locked status, the lock plate <NUM> is positioned at a lower end of the notch <NUM> of the support plate <NUM>. To unlock the lock mechanism <NUM>, the lock wire <NUM> is pulled upwards along the y-direction y. The lock plate <NUM> is thus moved upwards along the notch <NUM> until the lock plate <NUM> or a part of the lock plate <NUM> engages with the undercut <NUM>. The lock plate <NUM> is now held in position by means of the undercut <NUM>. The lock mechanism <NUM> is now in an unlocked status.

To lock the lock mechanism <NUM> again, the lock plate <NUM> is disengaged with the undercut <NUM> by means of the lock wire <NUM>. As soon as the lock plate <NUM> is disengaged with the undercut <NUM>, the lock plate <NUM> moves downwards along the notch <NUM> until the lock plate <NUM> reaches a lower end of the notch. Moving down the lock plate <NUM> is done by gravity. The lock mechanism <NUM> is now back in the locked status thereof.

Now turning back to <FIG>, the bolt gripper <NUM> comprises two shovel mechanisms <NUM>, <NUM>. There are provided a first shovel mechanism <NUM> and a second shovel mechanism <NUM>. The shovel mechanisms <NUM>, <NUM> are identical, but mirror-inverted in design. Thus, in the following only the first shovel mechanism <NUM> will be referred to.

The first shovel mechanism <NUM> comprises a slide profile <NUM> that is guided along the first horizontal profile <NUM>. The slide profile <NUM> can be a hollow and rectangular steel or aluminum profile. The first horizontal profile <NUM> is arranged inside the slide profile <NUM>. The slide profile <NUM> can be moved along the x-direction x in relation to the first horizonal profile <NUM>. A bolt <NUM>, <NUM> can be provided on each horizontal profile <NUM>, <NUM> to limit the movement of the shovel mechanisms <NUM>, <NUM> along the horizontal profiles <NUM>, <NUM>. There are provided a first bolt <NUM> and a second bolt <NUM>. Each slide profile <NUM> can have a cutout for one of the handles <NUM>, <NUM>.

A shovel element <NUM> is attached to a front side of the slide profile <NUM>. The shovel element <NUM> can be a bent steel or aluminum sheet. The shovel element <NUM> comprises a plate-like base section <NUM> that is firmly attached to the slide profile <NUM>. The base section <NUM> can be bolted or welded to the slide profile <NUM>. An outer arm section <NUM> and an inner arm section <NUM> protrude from the base section <NUM>. Thus, the shovel element <NUM> has a C-shaped geometry.

The inner arm section <NUM> is attached to the support plate <NUM> by means of two bolts <NUM>, <NUM>. The bolts <NUM>, <NUM> are guided through the breakthroughs <NUM>, <NUM> of the support plate <NUM>. The inner arm section <NUM> has breakthroughs that receive the bolts <NUM>, <NUM>. The second shovel mechanism <NUM> is also attached to the support plate <NUM> by means of the bolts <NUM>, <NUM>.

A support section <NUM>, <NUM> protrudes from each arm section <NUM>, <NUM>. A first support section <NUM> protrudes from the outer arm section <NUM>. A second support section <NUM> protrudes from the inner arm section <NUM>. The support sections <NUM>, <NUM> are arranged perpendicular to the arm sections <NUM>, <NUM>. Each support section <NUM>, <NUM> carries a pad <NUM>, <NUM>. There are provided a first pad <NUM> and a second pad <NUM>. The pads <NUM>, <NUM> can be bolted to the support sections <NUM>, <NUM>. The pads <NUM>, <NUM> can be made of a plastic material. For example, the pads <NUM>, <NUM> are made of polyoxymethylene (POM), polytetrafluoroethylene (PTFE), or the like.

<FIG> shows a distance element <NUM> according to one embodiment.

The distance element <NUM> is part of the bolt gripper <NUM>. The distance element <NUM> can be a washer or the like. In this case, the distance element <NUM> can have a circular outer contour <NUM>. However, the contour <NUM> can have any arbitrary geometry. For example, the contour <NUM> can be rectangular. The distance element <NUM> has a breakthrough <NUM>. One of the bolts <NUM>, <NUM> can be guided through the breakthrough <NUM>.

A plurality of distance elements <NUM> can be assigned to each bolt <NUM>, <NUM>. These distance elements <NUM> can have different thicknesses. The distance element <NUM> can have two breakthroughs <NUM>, namely one breakthrough <NUM> for each bolt <NUM>, <NUM>. In this case, the distance element <NUM> can have a rectangular shape.

The functionality of the shovel mechanisms <NUM>, <NUM> is explained in the following with reference to <FIG> and <FIG>. <FIG> shows the bolt gripper <NUM> in an initial or folded status Z1. In the folded status Z1, the inner arm sections <NUM> of the shovel elements <NUM> of the two shovel mechanisms <NUM>, <NUM> directly lie against the support plate <NUM> so that the support plate <NUM> is sandwiched between the inner arm sections <NUM>. The bolts <NUM>, <NUM> clamp the inner arm sections <NUM> and the support plate <NUM> together.

<FIG> shows the bolt gripper <NUM> in an extended or unfolded status Z2. The unfolded status Z2 differs from the folded status Z1 in that the shovel mechanisms <NUM>, <NUM> are slid outwards away from the support plate <NUM>. In other words, the shovel mechanisms <NUM>, <NUM> are spaced further apart from each other in the unfolded status Z2 than compared to the folded status Z1. To bring the bolt gripper <NUM> from the folded status Z1 into the unfolded status Z2, the bolts <NUM>, <NUM> are removed.

Then the slide profiles <NUM> of the shovel mechanisms <NUM>, <NUM> are moved along the horizontal profiles <NUM>, <NUM> until the slide profiles <NUM> abut the bolts <NUM>, <NUM>. However, the sliding movement can be stopped before contacting the bolts <NUM>, <NUM>.

One or more distance elements <NUM> are placed between the support plate <NUM> and the two inner arm sections <NUM> of the shovel mechanisms <NUM>, <NUM>. A thickness of the distance elements <NUM> defines a distance between the two inner arm sections <NUM> of the shovel mechanisms <NUM>, <NUM>. After placing the distance elements <NUM>, the bolts <NUM>, <NUM> are tightened again to lock the shovel mechanisms <NUM>, <NUM> again.

By using a plurality of distance elements <NUM> and/or using distance elements <NUM> of different thicknesses, it is possible to position the shovel mechanisms <NUM>, <NUM> in any arbitrary position between the folded status Z1 and the unfolded status Z2. The bolt gripper <NUM> can thus be adjusted in a stepless way.

<FIG> shows the use of the bolt gripper <NUM>. In the following, <FIG> will be referred to at the same time.

A plurality of bolts <NUM> is stored in a magazine <NUM>. As can be seen in <FIG>, the axes of symmetry <NUM> of two neighbored bolts <NUM> are spaced apart from each other in a distance <NUM>. The distance <NUM> is preferably the same distance the axes of symmetry <NUM> have when the bolts <NUM> are used to bolt the tower sections <NUM> to <NUM> together. The distance <NUM> can be <NUM> to <NUM> or the like.

The bolt gripper <NUM> is adjusted to the distance <NUM> by sliding the shovel mechanisms <NUM>, <NUM> sideways as explained before. The bolt gripper <NUM> is attached to a crane or winch <NUM> (<FIG>) by means of a chain <NUM> and a hook <NUM> that is hooked into the eyelet <NUM>. A remote control <NUM> is placed in the holder <NUM>. Preparation of the lifting procedure is now finished.

An operator <NUM> moves the bolt gripper <NUM> toward the magazine <NUM> as indicated by an arrow <NUM> in <FIG>. The remote control <NUM> is used to position the bolt gripper <NUM> at the right height level to grip two of the bolts <NUM>.

The lock mechanism <NUM> is unlocked by pulling the lock wire <NUM> as explained before. Then, the shovel elements <NUM>, in particular the pads <NUM>, <NUM>, are pushed under the bolt heads <NUM> or the washers <NUM> of the bolts <NUM> as indicated by arrows <NUM>, <NUM> in <FIG> and <FIG>. A distance or space is provided between the magazine <NUM> and the bolt heads <NUM> or the washers <NUM> so that the pads <NUM>, <NUM> can be placed between the magazine <NUM> and the bolt heads <NUM> or the washers <NUM>.

As soon as the shovel elements <NUM> are fully engaged with two bolts <NUM>, as can be seen in <FIG>, the lock mechanism <NUM> is locked again by pulling the lock wire <NUM> that disengages the undercut <NUM> and the lock plate <NUM> so that the lock plate <NUM> moves down and locks the bolts <NUM> in the shovel mechanisms <NUM>, <NUM>. The bolts <NUM> are now securely fixed to the bolt gripper <NUM>.

Then the bolts <NUM> can be lifted from the magazine <NUM> as indicated by an arrow <NUM> in <FIG>. The bolts <NUM> can now be safely transported to an assembly area. Returning the bolts <NUM> to the magazine <NUM> can be done in an inverted procedure as explained before.

Claim 1:
An adjustable bolt gripper (<NUM>) for gripping bolts (<NUM>) of a wind turbine (<NUM>), comprising a frame (<NUM>), a first shovel mechanism (<NUM>) to engage with a first bolt (<NUM>), a second shovel mechanism (<NUM>) to engage with a second bolt (<NUM>), characterized in that the first shovel mechanism (<NUM>) and the second shovel mechanism (<NUM>) are both slidably supported at the frame (<NUM>) for bringing the bolt gripper (<NUM>) from a folded status (Z1) into an unfolded status (Z2) and vice versa, and wherein the first shovel mechanism (<NUM>) and the second shovel mechanism (<NUM>) are positioned further away from each other in the unfolded status (Z2) than compared to the folded status (Z1).