Patent Publication Number: US-8534421-B2

Title: Device for enabling access to a structure above ground level

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 10/585,005, filed on Sep. 26, 2007, and published as U.S. Patent Application Publication No. 2009/0020361, which is the National Stage of International Application No. PCT/DK2004/000930, filed Dec. 30, 2004, which claims priority to Danish Patent Application No. PA 2003 01955, filed on Dec. 20, 2003, and Danish Patent Application No. PA 2004 00737, filed on May 8, 2004. U.S. patent application Ser. No. 10/585,005 and International Application No. PCT/DK2004/000930 are herein incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a device for enabling access to a structure above ground level, e.g. of considerable height such as a wind turbine, a rotor blade or a tower of such a wind turbine, the device comprising a part that may be lowered and/or lifted in relation to the structure. 
     BACKGROUND OF THE INVENTION 
     Within the field of wind turbines it is necessary to perform work on parts that is situated at a considerable height above ground level (or sea level, when sea wind turbines are concerned) such as e.g. repair of rotor blades, the surface of these, surface treatment of rotor blades and the tower etc. Further, it has been recognized that it is advantageous or even necessary to clean such parts and in particular the rotor blades in order to maintain good results as regards the power efficiency. Further, it may be advantageous to perform other forms of maintenance in order to achieve good power production results and optimal economic results, such as e.g. surface treatments, inspection etc. 
     In order to perform such work a number of hoisting arrangements have been proposed in the prior art. 
     Such a hoisting arrangement is known from German utility model DE 296 03 278 U in which suspension means are fastened to each of the two rotor blades near the hub of the rotor once the windmill has been brought to a stop and with one rotor blade pointing straight downwards. A special work platform with a through-going slit at the bottom has been fixed to these suspension means so that the rotor blade pointing downwards could be inserted into this slit. The work platform has subsequently been hoisted upwards in a stepwise manner, while the crew has rinsed the surface of the rotor blade manually, e.g. with one person located on each side of the rotor blade. 
     Even with such an arrangement, it is a time-consuming process to carry out a cleaning of the rotor blades of a windmill, just as such a known arrangement would probably require the use of machinery, such as a crane, for fixation of the suspension means. Further, the platform itself will have a considerable weight and size, thereby leading to further costs and use of heavy machinery for lifting and lowering the platform. 
     Devices of corresponding kind are known from DE 199 09 698 A1 and DE 43 39 638 A1, which are encumbered with the same disadvantages as those mentioned above, including that extensive use must be made of special material such as cranes, for example mobile cranes, or relatively comprehensive materials which, for example, are mounted on the turbine tower beforehand. 
     Further, these prior art systems are generally not configured in a manner facilitating user-friendliness and do not provide the personnel with an optimal safety environment. 
     Thus, it is an objective of the invention to provide an improved device for performing such work at a structure such as a wind turbine, e.g. on a rotor blade or on a wind turbine tower. 
     It is a further objective to provide such a device whereby improved user-friendliness and safety may be achieved. 
     A further objective is to provide such a device that allows access to virtually all parts of e.g. a rotor blade with relatively simple and few means. 
     It is also an objective to provide such a device that may be designed as a relatively light structure and in relatively light materials while maintaining safety standards and even provide improvements in safety aspects. 
     These and other objectives are achieved by the invention as explained in detail in the following. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the invention relates to a device for enabling access to a structure above ground level, e.g. of considerable height such as a wind turbine, a rotor blade or a tower of such a wind turbine, the device comprising a part that may be lowered and/or lifted in relation to the structure, wherein the device comprises a first main part that is suspended by the structure, and a second main part that comprises means for carrying an object such as a tool device or means for carrying a person, and that is movably connected to the first main part. 
     Hereby an arrangement is achieved by means of which the user may be able to reach or access all parts of the surface of e.g. a rotor blade of a wind turbine, since the second part is moved, e.g. rotated in relation to the first part in order to reach a desired location. 
     The device according to the invention, e.g. carrying a tool device or one or more persons may be located in any vertical position along e.g. a wind turbine rotor blade or tower, preferably controlled by a person at the device or at ground level, e.g. by controlling the length of the means, e.g. wires suspending the first main part or by climbing up or down such suspending means. Further, the means for carrying a tool or a person may be controlled to rotate preferably within a full revolution, i.e. 360.degree. or even more around the structure, e.g. the wind turbine rotor blade or tower and to be stopped at any position, preferably also controlled by a person at the device. 
     Thus, a large and heavy platform is avoided, since a person using the device according to the invention may be located at virtually any desired position in relation to the structure, e.g. a wind turbine rotor blade or tower. Hereby the necessary work may be performed using a relatively light construction. Further the safety standard is enhanced since a person using the device according to the invention may be secured in a reliable and dependable manner and since such a person need not move around on a platform that may e.g. be swerving under the influence of the wind and which may be slippery in moist conditions. 
     Further, it is noted that such a device may be configured to be lowered and lifted by means of hoisting apparatus placed outside the device, e.g. on the wind turbine, on anchoring means and/or at the ground, e.g. on a vessel or at a vehicle, whereby a pull is exerted by means of wires, lines, etc., possibly over pulleys etc. placed on the wind turbine. Instead, the device may be configured to be lowered and lifted by means of hoisting apparatus placed at the device, whereby the device will be able to operate independent of e.g. a support vessel or a vehicle on the ground. 
     The device may comprise a counterweight located essentially opposite the means for carrying an object. Hereby it is achieved that a state of balance will be inherent in the system, adding to the safety and user friendliness of the device according to the invention. 
     The second main part may comprise a counterweight located essentially opposite the means for carrying an object, e.g. a person. Hereby it is achieved that the balance of the system is maintained in a simple manner as the counterweight moves with the person or persons using the device. 
     The means for carrying an object, e.g. a person may be adjustable in relation to the second main part. Hereby it will be possible for the user(s) not only to rotate the two parts in order to reach a desired position, but also to displace the platform, the seat etc. in relation to the second main part. Hereby the flexibility is enhanced. The means for carrying an object, e.g. a person may be displaced linearly and/or rotatably in relation to the second main part. Hereby the user will in an effortless manner be able to reach any part of the surface without regard to the distance from the second part to the surface in question. 
     The means for carrying an object, e.g. a person may be connected to the second main part by means of at least one linkage or connection that provides a rotatable connection. Hereby the displacement in relation to the second part may be achieved in a particular simple and efficient manner. Advantageously, the device, e.g. the first main part may be suspended by wires, lines or the like from anchoring means. 
     The counterweight may be designed to be controlled in dependence on the position of the means for carrying an object, e.g. a person. Hereby the balance of the system will be maintained even when the means for carrying a person is displaced in relation to the second part, e.g. towards the centre of the circular parts. The counterweight may be mechanically connected to the object, possibly via intermediate means, by means of cables, wires etc, or the connection may be performed by having a electronic or electric link, e.g. by having two in principle independent objects moving in synchronicity, for example by moving the two objects by means of servo motors and having a control system controlling the relation between these, etc. 
     The means for carrying an object, e.g. a person may comprise a work platform for one or more persons. Furthermore, the means for carrying an object, e.g. a person may comprise seating for one or possibly more persons. Hereby the device may be designed in a particular straightforward manner using a minimum of material and the person using it may enjoin an effortless use of the device while still being subjected to an optimal safety standard since the person will be fastened to the seat using belts, safety harness etc. 
     The device and in particular the means for carrying an object, e.g. a person may comprise control means for controlling the position of the means, e.g. the height, the angular position, the position in relation to an axis etc. Hereby, the person or the persons using the device may control the device and in particular their own position, e.g. work position in relation to e.g. the surface of a rotor blade, in an optimal manner. 
     The first main part and/or second main part may comprise a frame that may be essentially circular in shape. Alternatively, the first main part and/or second main part may comprise a frame having an essentially elongated shape, whereby the device may be particularly suitable for use in connection with a structure having an elongated section such as e.g. a rotor blade of a wind turbine. 
     The first main part may comprise a number of parts that may be assembled to form different sizes and/or forms. Hereby it is achieved that the device may be dismantled and easily transported and further it may be assembled to suit a range of differently sized structures. 
     The first main part and second main part may comprise a roller or a movable suspension for providing the movable, e.g. rotatable connection. Hereby the e.g. rotational movement between the two main parts may be achieved in a particular advantageous and reliable manner. Obviously, the roller suspensions may be configured in numerous manners and in suitable numbers, e.g. two, three four or more. 
     The device may comprise anchoring means for fastening to the structure. Such anchoring means may be pre-established or may be established particularly for the purpose of supporting the device. 
     The device may comprise elevation means for lifting and lowering of the device, the elevation means comprising wires or the like connected to the structure, e.g. to anchoring means on the structure. 
     The elevation means may comprise two or more such wires or the like, e.g. three, four, five etc., whereby also safety aspects are improved as well as stability etc. 
     Further, it is noted that elevation means in the form or wires or the like may be used for lifting and/or lowering the device according to the invention by pulling the device by means located at the wind turbine or at the ground, e.g. located at a vehicle or at a vessel. 
     The device may comprise a securing arrangement for stabilizing the device to the structure, whereby the effect of the wind may be neutralized, e.g. the service device will be stable in relation to the e.g. rotor blade. 
     The securing arrangement may comprise two securing elements for releasable pressing against the structure, e.g. a rotor blade. In this manner the stabilizing effect will be achieved in a surprisingly effective manner. 
     The securing elements may be inflatable, whereby the elements may press essentially evenly over the surface of the structure, and further the structure will not be treated to any harmful contact. 
     The securing elements may contract in length when inflated. Further, the securing elements may expand in width when inflated. 
     The securing elements may be located by means of adjustable fixation means, whereby the device may readily be adapted to structures, e.g. rotor blades of different sizes. 
     The securing elements may be rotatably mounted. Hereby it is achieved that the device may be lifted and/or lowered while the securing elements are activated, for example when performing work on a rotor blade and shifting from one level to the next. In this manner the device and the carried object will be held securely in relation to the structure, also when shifting position. Further, the securing elements may be individually inflatable. Hereby it is achieved that the position of the device and the object being carried may be adjusted in relation to the structure, for example by adding air to one element and releasing air from the other. In this manner the device will be shifted sidewards. 
     The securing elements may comprise means for supporting when they are not inflated. When not inflated, the securing elements may sag downwards, whereby it may prove difficult to enter e.g. a tip of a rotor blade in the space between these. To alleviate this problem, supports may be placed at an intermediate part of each, connected to frame parts, or flexible telescopic rod elements may be placed inside the securing elements from one end to the other. 
     The device may comprise power means, e.g. electric motors, hydraulic and pneumatic means for lifting, lowering and displacing the parts. 
     Hereby the device will be able to lift and lower itself without power assistance from e.g. a hoist located at a vehicle or a vessel. Thus, the device will be able to operate independently, e.g. without concern for power assistance from other devices. This further enhances safe operation since accidents caused by a power failure at a ground vehicle or a vessel are prohibited. Particularly when operation at sea is concerned, e.g. at sea wind turbines, such an independent configuration is preferable since a support vessel may be unstable, e.g. subjected to waves, current, wind etc. Thus, an arrangement at sea where a vessel provides the elevation by e.g. hoist(s) located on the vessel is prone to accidents and malfunction, and therefore a device comprising power means as mentioned above is advantageous not only in general but especially at sea. 
     Further, it is noted that even when power supply to such a device is subjected to failure, e.g. when electric power is cut off, a device according to the invention will be able to be manually operated, e.g. to be hoisted to the ground and will in general present a safe work tool for all involved, in particular persons occupying the device. 
     The device may comprise means for lifting and/or lowering anchoring means in relation to the structure. Hereby it will be possible to establish suitable anchoring using the device according to this embodiment, since e.g. the means for lifting and/or lowering anchoring means may be used for climbing up the structure using e.g. a relatively thin wire hanging from or lowered from the structure, until the means reaches a desired and suitable level where it establishes an anchoring location which is secure for suspending the first and the second main part of the device including e.g. the person or persons carried by the second main part. 
     The means for lifting and/or lowering anchoring means in relation to the structure may comprise means for elevating using a wire or the like connected to a part of the structure, e.g. the wind turbine. 
     The means for lifting and/or lowering anchoring means in relation to the structure may comprise an uplift device. 
     Still further, the device may be adapted for performing inspection, work, repair, surface treatment, etc on a rotor blade of a wind turbine. 
     Also, the device may be adapted for performing inspection, work, repair, surface treatment etc on a tower structure of a wind turbine. 
     The device may comprise a work platform for carrying at least one person, the work platform being provided with an indentation. The indentation may thus serve to accommodate the edge of a rotor blade, when the device or the platform is being lifted or lowered, whereby a stabilization has been achieved. 
     Further, the work platform may comprise protection means in the form of a roller or the like placed in the indentation. Hereby it is achieved that the edge of e.g. a rotor blade will not be subjected to potentially damaging contact when the device is lowered or lifted. 
     In addition, the work platform may comprise protection means in the form of a protection strip placed on the circumference of the platform, whereby the surface of the structure will not suffer from contact with the platform, e.g. the tubing of the railing etc. 
     Further, the work platform may comprise control means for controlling the lifting/lowering and the positioning in relation to the structure, which control means may be in the form of a joystick or the like and by means of which any controllable part may be individually controlled and/or controlled simultaneously with other parts. For example, if four hoisting arrangement are provided, these may naturally be controlled simultaneously, whereby an evenly lifting or lowering will be performed, but also one or more of these hoisting arrangements may be controlled separately, whereby a tilting may be performed, e.g. in order to adapt to an inclination of a rotor blade. Further, it is noted that a gyroscopic arrangement may be included in the control system. 
     The work platform may comprise hoisting means, whereby small parts, tools etc. may quickly be provided to a person in the platform. 
     The work platform and the device may comprise illumination means, whereby the device may be utilized also when daylight is not present, at least not in a sufficient amount, thereby enhancing the utilization rate of the device and lowering the costs. 
     The work platform may comprise shielding means, whereby the platform may be used in virtually any weather conditions apart from stormy conditions. The shielding means may be in the form of a transparent cover at the top, allowing the person to observe the structure above, and adjustable and/or removable shielding to the side, e.g. in the form of roller coverings or the like. 
     In a second aspect, the present invention relates to a device for lifting and/or lowering of objects in connection with a wind turbine or a similar construction, wherein the device comprises an uplift device and means for carrying at least one object supported directly or indirectly by the uplift device. 
     By means of this device, access can be gained to places on for example a wind turbine which are otherwise accessible only with difficulty, for example on a rotor blade, without the necessity of having to arrange hoists, cranes, scaffolding or the like for use for this purpose. 
     The uplift device will be of a relatively light construction, which by means of a relatively light vehicle or vessel can be transported to the wind turbine, where it is filled with a suitable air or gas which is lighter than the atmospheric air. When the uplift device is filled with this air or gas, with suitable dimensioning it will have such a buoyancy that it can lift itself and the object or objects which are supported by the device. The uplift device will have means for at least partial control so that it can be moved to the desired position in relation to the wind turbine, or such that it can be moved in or along a desired path, for example along a rotor blade. 
     The at least one object may comprise a device for inspection, treatment or the like of at least a part of the wind turbine or the similar construction. 
     In an advantageous embodiment relating to a device for the establishing of an anchoring on or at a wind turbine, the device may comprise an uplift device and a locking device, the locking device comprising means for gripping in or around a part of a wind turbine, preferably in a releasable manner. 
     It is hereby achieved with the device that a fastening can be established on or at a wind turbine, without the necessity of having to arrange cranes, including mobile cranes, hoists, scaffolding or the like for this purpose. 
     This is achieved by transporting the uplift device, which will be of a relatively light construction, to the wind turbine by means of a relatively light vehicle or vessel, where it is filled with a suitable air or gas, for example helium, which is lighter than the atmospheric air. 
     When the uplift device is filled with this air or gas, with suitable dimensioning it will have such a buoyancy that it can lift itself and the locking device connected herewith. The uplift device will be at least partly controlled so that it moves to the desired position in relation to the wind turbine, where an activation of the locking device is effected so that this grips around or in a part of the wind turbine. It will be understood that the locking device is configured in such a way that it can serve as an anchor for lifting and/or lowering of various parts. 
     Such an anchoring can thus be used for lifting and/or lowering work platforms, cleaning apparatus, various work equipment and personnel, and there is thus also established the possibility of being able to lift and/or lower various parts such as spare parts or parts which are required for replacement. With the device, the basis will thus be established for being able, for example, to replace a wind turbine blade in a relatively simple manner. 
     It shall be noted that the work operations shall be understood to be a wide range of operations or actions, which can be effected in connection with a rotor blade or a wind turbine as a whole. Thus, it can include washing, other cleaning, drying, for example with air, heated air, radiation heating etc., painting, pre-treatment, after-treatment, sealing of the surface etc. Moreover, it can include inspection of the surface, examination of the surface of the rotor blade as such, for example by means of known inspection methods such as radiation examinations etc. 
     The device may comprise means for fastening of elements for use in positioning, lifting, lowering or the like of an object. 
     The uplift device may comprise at least one element, which can be filled with an air or gas, for example helium, and which are connectable directly or indirectly to the locking device. 
     The device may comprise a control part, possibly in the form of a wind vane, which, under influence of the wind, can at least partly control the position of the device in relation to the wind direction. 
     With the use of, for example, such a wind vane, a greater stability can be achieved during ascent and descent, so that even under windy conditions the use of the device will not be problematic. 
     The locking device may comprise a frame having two parts that are pivotally connected at one location and connected by means of an adjustable element essentially opposite the one location. Hereby an initial grip on the structure may easily be achieved, e.g. by having the two parts performing a clamping operation. Further, the frame may possibly be opened in full, allowing the gripped structure, e.g. a rotor blade, to move out of the locking device, and another rotor blade to enter the locking device. 
     The two frame parts may comprise elongated support parts for legs of the uplift device, whereby a stable and reliable construction is achieved. 
     Preferably, the locking device may be configured in such a manner that a loading of the device will result in the transfer of a force to the means for gripping in or around a part of the wind turbine. 
     Hereby, it will be achieved that the anchoring of the device which has been effected will be strengthened further when lifting or lowering is carried out, or when the device merely supports an object such as a washing robot, a machine, an instrument etc. Hereby, an increased lifting capacity for the device can be obtained as well as the security is improved. 
     The means for gripping in or around a part of the wind turbine may comprise a plurality of strips that comprise a surface having friction-enhancing means, whereby a flexible gripping arrangement as well as a gripping arrangement having enhanced strength is achieved. 
     In a second aspect, the present invention relates to a unit for transport and/or storage of means for performing work at a wind turbine, wherein the unit comprises a container or the like having a top part comprising lids or flaps that may be opened and fixed in an essentially horizontal position. 
     Hereby a construction is provided that allows the necessary parts to be transported etc. in an expedient manner and simultaneously provides a readily available work space since the opened flaps may be used as a stable platform for e.g. assembling the parts, filling the uplift device, controlling the operation etc. 
     The container may comprise two lids or flaps that in total cover an area larger than the area of the top of the container. Hereby an enlarged work platform is provided. 
     The container may comprise two lids or flaps, each one having an area substantially larger than half the area of the top of the container. 
     The container may comprise two lids or flaps, each one having an area substantially corresponding to the area of the top of the container. Hereby a platform having an optimal size is provided in en expedient manner. 
     The container may comprise an opening arrangement that in an open state may support the lids or flaps in an essentially horizontal position. In this manner the unit may relatively quickly provide a suitable work platform for the preparatory work, when a device, e.g. a service device, according to the invention is put into use. 
     Further it is noted that the unit in accordance with the invention may comprise such means as compressor means, an electric generator, tanks for helium, control equipment etc. 
     Further, it is noted that such a unit may also be utilized in connection with a device according to the invention when this is used for operating a washing robot as disclosed in WO 03/048569. 
     It will be understood that numerous tasks may be performed using the devices according to the invention. 
     In a third aspect, the present invention relates to a device for enabling access to a structure above ground level by lowering and/or lifting the device in relation to the structure, the device comprising a first endless frame structure defining an opening, wherein at least part of the first endless frame structure forms a track portion, the track portion being adapted to guide an, in relation to the track portion, movable object along the track portion. 
     The device may further comprise a second endless frame structure aligned with the first endless frame structure. Normally, the second endless frame structure is arranged above the first endless frame structure so that the first endless frame structure is the frame structure closest to ground. 
     Preferably, the first endless frame structure forms an endless track. The object may comprise a work platform adapted to carry one or more individuals. Alternatively, the object may comprise seating for one or more individuals. 
     The object may comprise control means for controlling the position of the object in relation to the track portion. The endless structures may form an essentially circular structure. 
     Alternatively, and more preferably, the endless structures may form an essentially elongated structure. 
     The device according to the third aspect of the present invention may further comprise means for lifting and/or lowering the device in relation to the structure, the lifting and/or lowering means comprising power means such as electric motors, hydraulic and/or pneumatic means for lifting, lowering and/or displacing the device in relation to the structure. The device may further comprise control means for controlling the lifting and/or lowering means. 
     The device may be adapted to perform inspection, work, repair, surface treatment etc on a rotor blade of a wind turbine. 
     The device may further comprise an arrangement for aligning the structure with the opening defined by the endless structures. The alignment arrangement may comprise a first displaceable arm having guiding means, the first displaceable arm being adapted to be brought from a first to a second position when the device is to be aligned with the structure, the first displaceable arm being, in its second position, capable of bringing a catch element into contact with the structure via its guiding means, and bringing the device in approximate or complete alignment with the structure by withdrawing by displacement the catch member along the guiding means while the catch member is in contact with the structure. Thus, the catch member is brought to the structure by pushing it in a forward direction, whereas the step of bringing the structure in approximate or complete alignment with the device is achieved by withdrawing the catch member along the guiding means of the arm. By approximate or complete alignment is meant that the device may be brought into complete alignment with the device using only the displacement of the catch member along the guiding means. Alternatively, the structure may be brought only into approximate alignment with the device. In order to bring it into full or complete alignment an addition step may be taken—such as for example a displacement or a movement of the arm relative to the device. 
     By displaceable arm is meant any kind of elongated element, such as a rod, bar or stick, capable of bringing the catch member from a position at or near the frame to a position where it is in contact with the structure to be serviced, inspected or repaired. The elongated element may have a linear, a substantially linear, or a curved shaped. The shape of the elongated element may also be a combination of these shapes. 
     The device may further comprise a second displaceable arm having guiding means, the second displaceable arm being adapted to be brought from a first to a second position when the device is to be aligned with the structure, the first and second displaceable arms being, in their second position, capable of bringing a catch element into contact with the structure via their guiding means, and bringing the device in approximate or complete alignment with the structure by withdrawing the catch member along their guiding means while the catch member is in contact with the structure. 
     The first and second arms may be pivotably mounted on a first and a second support element, respectively. Similarly, the first and second support elements may be pivotably mounted on the first or second endless frame structure. The pivotably mounting of the arms to the support elements, and of the support elements to one of the endless frame structures may be provided with hinges. 
     The device may further comprise rotatably mounted docking means preferably arranged in the opening defined by the second endless frame structure, the rotatably mounted ducking means being adapted to fixate the structure in relation to the device when the structure has been brought into the opening defined by the second endless frame structure. Depending on the configuration of the docking means, one or several rotatably mounted docking means may be arranged in the opening defined by the second endless frame structure. Thus, the number of docking means may be 1, 2, 3, 5, 10 or even higher. 
     The device may further comprise a docking arrangement adapted to fixate the structure in relation to the device when the structure has been brought into the opening defined by the second endless frame structure, the docking arrangement comprising a pair of flexible belts, each belt being arranged between a rigid end point and a belt tightener, the belt tighteners and the end points being arranged on the second endless frame structure, the belt tighteners being adapted to tighten the belts by bringing them from a relaxed state to a tightened state in order to fixate the structure in relation to the device. 
     In a fourth aspect, the present invention relates to a device for enabling access to a structure above ground level by lowering and/or lifting the device in relation to the structure, the device comprising an endless path for individuals, the endless path defining an opening, the device further comprising an arrangement for aligning the structure with the opening defined by the endless path. 
     The alignment arrangement may comprise a first displaceable arm having guiding means, the first displaceable arm being adapted to be brought from a first to a second position when the device is to be aligned with the structure, the first displaceable arm being, in its second position, capable of bringing a catch element into contact with the structure via its guiding means, and bringing the device in approximate or complete alignment with the structure by withdrawing the catch member along the guiding means while the catch member is in contact with the structure. 
     The device may further comprise a second displaceable arm having guiding means, the second displaceable arm being adapted to be brought from a first to a second position when the device is to be aligned with the structure, the first and second displaceable arms being, in their second position, capable of bringing a catch element into contact with the structure via their guiding means, and bringing the device in approximate or complete alignment with the structure by withdrawing the catch member along their guiding means while the catch member is in contact with the structure. 
     The device may further comprise rotatably mounted docking means arranged in the opening defined by the endless path, the rotatably mounted ducking means being adapted to fixate the structure in relation to the device when the structure has been brought into the opening defined by the endless path. Depending on the configuration of the docking means, one or several rotatably mounted docking means may be arranged in the opening defined by the second endless frame structure. Thus, the number of docking means may be 1, 2, 3, 5, 10 or even higher. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail in the following with reference to the drawings, in which 
         FIG. 1  illustrates a wind turbine with a device according to an embodiment of the invention, 
         FIG. 2   a  shows in a larger scale part of  FIG. 1  showing the device in a detailed view, 
         FIG. 2   b  shows corresponding to  FIG. 2   a  another embodiment according to the invention, 
         FIG. 2   c  illustrates corresponding to  FIG. 1  a wind turbine with a device according to an embodiment of the invention seen from another angle, 
         FIG. 2   d  shows corresponding to  FIGS. 2   a  and  2   b  an embodiment of the device according to the invention, 
         FIG. 3  is a device according to an embodiment of the invention in further detail, 
         FIG. 4  shows another embodiment of the device according to the invention, 
         FIG. 5  shows a wind turbine from the side with anchoring means in accordance with a further embodiment of the invention, 
         FIG. 6  shows in a larger scale part of  FIG. 5  showing the anchoring means in a detailed view, 
         FIG. 7  shows corresponding to  FIG. 5  anchoring means for anchoring at the tower, 
         FIG. 8  shows in a larger scale part of  FIG. 7  showing the anchoring means in a detailed view, 
         FIG. 9  shows a still further embodiment of a service device in accordance with the invention in a perspective view, 
         FIG. 10  shows a service device as illustrated in  FIG. 9 , but seen from another angle, 
         FIG. 11  shows a work platform for use in connection with for example a service device as shown in  FIGS. 9 and 10 , 
         FIG. 12  shows a device for establishing an anchoring at a wind turbine, 
         FIG. 13  shows a locking device in accordance with a further embodiment of the invention, 
         FIG. 14  shows a clamping element for use in connection with the locking element shown in  FIG. 13 , 
         FIG. 15  shows a unit for transport and/or storage of means for performing work at for example a wind turbine, 
         FIG. 16  shows a third embodiment of the present invention, 
         FIG. 17  shows the third embodiment of the present invention catching a blade of a windmill, 
         FIG. 18  shows the third embodiment of the present invention in almost complete alignment with a blade of a windmill, 
         FIG. 19  shows the third embodiment of the present invention in alignment with a blade of a windmill, 
         FIG. 20  shows the third embodiment of the present invention fixed to the blade of a windmill, 
         FIG. 21  shows the third embodiment of the present invention fixed to the blade of a windmill by alternative docking means, 
         FIG. 22  shows the third embodiment of the present invention fixed to the blade of a windmill by alternative docking means, 
         FIG. 23  shows the gondola according to the third embodiment of the present invention, and 
         FIG. 24  shows the third embodiment of the present invention configured as a platform. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a wind turbine  1  having a tower  2 , a nacelle  3  and three rotor blades  4 . The wind turbine has been stopped with one of the rotor blades pointing essentially downwards and a service device  10  according to an embodiment of the invention has been hoisted up along the rotor blade  4 . As it will be explained in further detail later on, the service device  10  is connected to anchoring means generally designated  20  by means of lines, wires etc. The anchoring means may be in the form of a locking device that grips a part of the wind turbine, e.g. the root of the rotor blade  4  or the tower  2 . Further, such a locking device may be an integral part of and/or may be lifted to the desired level by means of an uplift device, e.g. comprising a part lighter than air. Such lifting and/or locking devices may be of the kind described in PCT/DK03/00577 (WO 2004/022970 A1). It will be understood that such a lighter-than-air device may be guided by means of wires  21  connected to the ground, to a vehicle or to a vessel. However, other means of anchoring and/or establishing and/or placing anchoring means may be used as well. In particular, further examples of such lifting and/or locking devices will be described further on. 
     The service device  10  will be explained in further detail with reference to  FIG. 2   a  that shows an enlarged detailed view corresponding to  FIG. 1 . Thus, the anchoring/lifting device  20  is as indicated locked to the rotor blade  4  and carrying the service device  10  by means of wires or the like  18 , for example three, four etc. such wires uniformly distributed around the circumference of the service device  10 . The service device comprises essentially two main parts, e.g. a first main part  12  and a second main part  14 . 
     The first main part  12  may as shown be in the form of a generally circular part that is suspended by the abovementioned wires  18  that may be attached to brackets  19 . The first main part  12  may be constructed using tubes, rods etc. of aluminium, composite materials, plastic material, fibre reinforced materials etc. It will be understood that the first main part  12  can be lifted and/or lowered in relation to the anchoring means  20  and the rotor blade  4  by means of the wires or lines  18 , e.g. by hoisting means (not shown). Such hoisting means may be placed at the device itself, e.g. at the first main part, whereby the device may hoist itself, e.g. climb up and down the wires, at the anchoring means or at the ground, e.g. at a vehicle or at a vessel, whereby the hoisting means will elevate the device by e.g. pulling the lines or wires. 
     The second main part  14  may have a form similar to the form of the first main part and may also be constructed using tubes, rods etc. The second mains part is connected to the first main part  12  in such a manner that the second main part  14  may be rotated in relation to the first main part  12 . The two main parts may be connected to each other at suitable locations along the circumference, e.g. at locations corresponding to the locations of the brackets  19 . Here, bearings may be arranged and further means of performing a rotational action, e.g. electric motors etc. may be arranged (not shown). The two main parts may thus be mutually rotated, preferably up to a full revolution. i.e. 360.degree. or even more, possibly only limited by electric wires, cables etc. connecting the two parts. 
     Further, the second main part  14  suspends or carries an object such as a work tool for performing work operations, inspection etc. at a rotor blade or tower, a work platform  16 , e.g. a basket, a cage, a stand etc. for carrying one or more persons that have to perform some sort of work at the wind turbine, e.g. inspection, cleaning, repair, surface treatment etc. This work platform  16  is suspended by means of an arrangement  15  allowing e.g. multidirectional displacement in relation to the second main part  14 , as will be explained in further detail later on and whereby virtually any desired position may be taken by the platform  16 , e.g. in relation to the rotor blade or another part of the wind turbine. Instead of a work platform  16 , a work tool or another object may be carried by the second main part controlled to take any desired position in relation to the structure. 
     Further on, the second main part  14  suspends a counterweight body by means of a suspension arrangement  17 , which will also be explained in further detail later on. However, the counterweight body is suspended and controlled in such a manner that it is moved in correspondence with the movements of the work platform, whereby a perfect balance is achieved. 
       FIG. 2   b  shows an enlarged detailed view corresponding to a further embodiment of the invention. This embodiment corresponds to the one described with reference to  FIG. 2   a , but instead of a work platform this embodiment comprises a seating or a chair  16 ′ for one person only or possibly two or even more persons. It will be understood that such seating will comprise means for securing a person, e.g. seat belt(s) etc. and further means for controlling the position of the chair  16 ′, e.g. a joy stick or similar means for controlling the vertical position, the position in relation to the rotor blade (the rotational position) and the distance to the rotor blade. As explained above, the device comprises a counterweight body suspended by means of an arrangement  17  that provides a balancing of the device. 
       FIG. 2   c  shows a wind turbine with a service device according to the invention corresponding to  FIG. 1 , but seen from another side.  FIG. 2   d  shows similarly an enlarged detailed view seen from this angle, showing the abovementioned counterweight body  13  suspended by the arrangement  17  from the second main part  14 . 
       FIGS. 3 and 4  show in more detail and in schematic manner service devices according to further embodiments of the invention, the device shown in  FIG. 3  comprising a work platform as described above with reference to  FIG. 2   a  and the device shown in  FIG. 4  comprising a seating arrangement as described above with reference to  FIG. 2   b . Apart from this the two illustrated devices are similar. 
     The first  12  and the second  14  main parts are illustrated as similar essentially circular parts, but it will be understood that other forms may be utilized. The first main part  12  is situated below the second main part  14  and is designed with a number, e.g. four, of brackets  19  for suspending the device from an anchoring means placed on a wind turbine. The brackets  19  may be means for attaching wires (not shown) etc. 
     The second main part  14  comprises a number of means for suspending this part in relation to the first part  12 . Four of these means are utilized in  FIGS. 3  and  4 , but it will be understood that other numbers may be utilized, e.g. two, three, five, etc. These means may as illustrated comprise e.g. a number of bolts  32  connected to the second main part, each one carrying wheels or similar means  34  having an outer shape corresponding to the shape of (a part of) the first main part  12 . In this manner the two main parts will be connected to each other in a secure manner while still allowing mutual rotational movement that may be up to 360.degree. or more. It will be understood that driving means (not shown) may be connected to one or more of the wheels whereby the rotational action can be made available. Further, it will be understood that the two main parts  12  and  14  may be located differently in relation to each other, e.g. located in the same vertical level or the second part below the first part. 
     The work platform  16  is as described above suspended by a suspension arrangement  15  that is connected to the second main part, e.g. at the same location as one of the set of wheels  34  or at another location. This suspension arrangement  15  is able to adjust the location of the platform, e.g. by providing rotational movement at a link  36  and/or at a link  38 , controlled by suitable control means such as e.g. handles, levers, switches, a joystick or the like (not shown) placed at the work platform  16 . Further it will be understood that the suspension arrangement  17  for the counterweight  13  may be configured in a similar manner and/or with a less degree of manoeuvrability as illustrated. 
     It will also be understood that the suspension arrangements  15  and  17  may be configured in numerous manners which will be obvious to a person skilled in the art, e.g. using rotational joints, telescopic joints etc. 
       FIGS. 5 to 8  illustrate further uses of a service device according to the invention and in particular different manners of providing anchoring for a device according to the invention. 
       FIG. 5  shows a wind turbine  1  with tower  2 , nacelle  3  and rotor blades  4 . A wire or the like  42  is attached to a part of the wind turbine at the top, e.g. extending from the rotor hub, the nacelle  3  or from another part in this area as it is shown in an enlarged view in  FIG. 6 . This wire that may be lowered from the e.g. nacelle or that is hoisted and connected to the e.g. nacelle, serves to bring an anchoring means  44  to the top of the wind turbine  1 . This may for example take place by having a carrier device  40  that carries the anchoring means  44  climb the wire  42  or by having the carrier device being hoisted by the wire  42 . When the carrier device  40  is at a desired level, the anchoring means is brought to grip and establish an anchoring at the wind turbine. As shown in  FIGS. 5 and 6  the anchoring means  44  may establish anchoring at a rotor blade  4 , or as shown in  FIGS. 7 and 8  the anchoring means  44  may establish anchoring at the tower of the wind turbine  1 . In both cases the anchoring means  44  may serve as anchoring for a service device or the like as described above, e.g. for allowing access to any part of a wind turbine e.g. a rotor blade or the tower, at any place, e.g. at any level and at any circumferential spot. 
     A still further embodiment of a service device  50  in accordance with the invention will be described with reference to  FIG. 9 , wherein such a device is shown in a perspective view. Here, the first main part is generally designated  62  and comprises end parts  71  and  72  and side parts  73  and  74 , which parts are connected to each other at connection points, e.g.  75 . These connections  75  are releasable and possibly also adjustable. The connections may be in the form of screw-connections or the like or in the form of snap-action connections or other forms of quickly releasable connections. The end parts  71  and  72  may be essentially semicircular in shape and the side parts  73  and  74  may be essentially linear elements. In this manner the first main part  62  may take an elongated shape, e.g. an oval-shape or the like, e.g. suitable for work on a rotor blade of a wind turbine. The size may be adjusted, e.g. by using side parts of different lengths and end parts of different widths. As shown, these parts may comprise tubular elements, e.g. one at the bottom and one at the top, and reinforcing plate material between these tubular elements. 
     As explained above, the first main part may comprise hoisting means which in  FIG. 9  are shown as four hoisting means  69 , two located at each side of each of the end parts  71  and  72 . These hoisting means  69 , which may be driven by electric motors or other suitable means, are connected to wires or the like (not shown in  FIG. 9 ) that are connected to anchoring means  20  e.g. near the hub of the wind turbine as explained above, whereby the service device  50  may be lowered or lifted. 
     In correspondence with what has been described in connection with other embodiments of the invention the service device  50  comprises a second main part  64  comprising an object such as a tool or a work platform  66  that is suspended by a suspension arrangement  65  that is connected to movable suspension means  68 . These movable suspension means  68  can travel along the first main part  62 , e.g. riding on the rail shaped or tubular elements of the parts  71 ,  72 ,  73  and  74 , preferably driven by electric motors or the like. As also explained above, the service device  50  may comprise a counterweight part (not shown in  FIG. 9 ) that may be designed with parts corresponding to the parts  65  and  68 . It will be understood that the counterweight part and the work platform need not be mechanically connected but may be controlled in such a manner that they will be located opposite each other when the device  50  is used. The counterweight part may serve to carry necessary equipment such as batteries or other power supply means, compressors, etc. 
     Further, the service device  50  shown in  FIG. 9  comprises a securing and/or stabilizing arrangement  80  which may serve to stabilize and possibly also secure the device  50  when it is located at a specific height where work is to be done. For this purpose the arrangement  80  comprises two flexible securing elements  81  and  82  that may be elements known in the art as flexible muscles, e.g. tubular elements that may be inflated by compressed air in which case they expand and simultaneously reduce their length. As shown these elements  81  and  82  are connected to securing beams  83  and  84  that are located on each of the end parts  71  and  72 . The securing elements  81  and  82  are located at the beams  83  and  84  by means of fixation means  85  in such a manner that the position may be adjusted, e.g. transversely, and fixed. In a non-activated state these elements  81  and  82  may cross each other as shown in  FIG. 9 , thereby allowing a structure such as e.g. a rotor blade to pass between the elements. The securing elements  81  and  82  are as described above connected to fixation means  85  that may also serve as means for leading compressed air to and/or from the securing elements. Further, the securing elements  81  and  82  may be connected to the fixation means  85  in such a manner that the securing elements  81  and  82  may rotate while maintaining airtightness. The securing elements  81  and  82  may be filled with air by means of e.g. one or more electrically driven compressors. Air may be pumped to and/or released from the securing elements separately, e.g. the pressure in each of the securing elements may be controlled. It will be understood that these securing elements  81  and  82  may be provided in different lengths, corresponding to e.g. the different lengths of the side parts  73  and  74 . 
     When using this service device  50 , e.g. in connection with a rotor blade of a wind turbine, the hoisting means  69  are connected to anchoring means located near or at the rotor of the rotor blade by means of wires or the like (not shown), and the height of the device  50  is adjusted by means of the hoisting means  69 , e.g. controlled by a person situated e.g. at the ground, in the work platform  66  etc. and by means of suitable control means (not shown) such as a joystick etc. When the desired height is reached, the hoisting means  69  are stopped. As it is commonly known, brakes may be activated for holding the device e.g. brakes integrated with the electric motors, or the hoisting means may be equipped with self-locking gear means, worm gear wheels etc. 
     For stabilizing the device in relation to e.g. a rotor blade, and possibly for further securing the device, the securing arrangement  80  may now be activated, which is done by means of compressed air led to the securing elements  81  and  82  via the fixation means  85 . These means may as described above be connected to compressor means that fill the securing elements, e.g. flexible muscles with air, whereby they will contract in length and expand in width. Thus, the securing elements  81  and  82  will press against and clamp the e.g. rotor blade. The service device  50  will in this manner be positioned firmly in relation to the e.g. rotor blade and will not tend to move under the influence of the wind etc. Further, since the air pressure and/or the volume of air contained in each securing element can be controlled individually, the position of the service device and thus also the position of e.g. the work platform can be adjusted in this manner. For example, if an additional amount of air is led to the securing element  81  shown in  FIG. 9  and/or air is released from the securing element  82 , the service device will be moved to the right in relation to e.g. a rotor blade gripped by the securing elements, and vice versa. 
       FIG. 10  shows a service device as illustrated in  FIG. 9 , but seen from another angle. Thus, the same reference signs are used for the same elements and features and will not be described again here. However, here it is more clearly shown that an object such as a work platform  66  is suspended from movable suspension means  68 , and that these means comprises a frame  90  having a lover set of guiding wheels  91  and an upper set of guiding wheels  92  located at each end. The frame  90  is located on the inside of the first main part in the illustrated example in order to be able to pass the fastening means for the securing beams  83  and  84  and the mounting means for the hoisting means  69 . The guiding wheels  91  and  92  are designed for riding on the edges, e.g. the tubes of the first main part, and it will be understood that these wheels are located in such a manner that they may be turned at least a small angle in relation to the frame  90  in order to be able to pass the curved parts of the first main part, e.g. the end parts  71  and  72 . Further, this frame  90  is equipped with a drive motor  93  for moving the frame  90  along the first main part. The features relating to this drive motor will be further explained in connection with a similar movable suspension means located opposite the first one. This comprises a similar frame  94  for carrying a counterweight (not shown), e.g. by means of attachment means such as a hook, a ring or the like  98 , which counterweight may comprise a battery power source etc. This frame  94  comprises similar wheels etc as described in connection with the frame  90  and a drive motor  95 . This has driving means in the form of e.g. a toothed wheel for interaction with e.g. a toothed rack  97  located on the inside of the first main part. In  FIG. 10  this is only shown on the part  73 , but it is clear that it will be located all along the first main part. An engagement link  96  serves to bring the drive engine  95  into contact with the e.g. toothed rack  97  on the first main part. The frame  90  may naturally be provided with a similar arrangement. 
     As previously described, the two parts, e.g. the frame  90  and the frame  94 , of the second main part will be located diametrically opposite each other and will thus also be moved synchronously. They may be connected mechanically as previously described, e.g. where they were placed on a common frame. In the embodiment shown in  FIG. 10 , they may also be mechanically coupled, for example by means of cables, wires etc. They may especially be coupled via one or more additional movable means (not shown) located on the first main part, e.g. movable means comprising upper and lower guiding wheels, in which case a connection between the two frames  90  and  94  may be established by having a rod or the like connecting the frame  90  with a first additional movable means, by having a similar rod connecting the first additional movable means with a second additional movable means, that again is connected to the frame  94  by means of a rod or the like. It will be understood that one, two three or more of such additional movable means may be utilized, and that in this manner the two parts, e.g. the frames  90  and  94 , will be moved along the first main part in synchronicity. It will also be understood that when a mechanical connection is involved, one drive motor will suffice. However, instead of using a mechanical arrangement, the two parts may be controlled e.g. electronically to move in synchronicity, which will be evident to the skilled person. For example, the drive motors may be step motors and/or servo motors, a wireless communication may be established between the two parts etc. 
     In connection with  FIG. 10  it is also noted that the two securing elements  81  and  82 , when not activated, e.g. filled with air, may tend to fall downwards, meaning that it may be difficult to introduce a rotor blade in the device and in between the to elements  81  and  82 , e.g. to lift the device  50  up on the rotor blade. In order to relieve this, support means may be located on the first main part, e.g. at the part  74  for the securing element  82  and on the part  73  for the securing element  81 . Instead special means may be located in the securing elements  81  and  82  for maintaining a proper location. Such means may for example be telescopic flexible rods that stretch from one fixation element  85  on the securing beam  84  and to a fixation element  85  on the securing beam  83  inside the tubular elements  81  and  82 . 
     As it has been described previously, the securing elements  81  and  82  are rotatably mounted at the fixation means  85 . Thus, when the securing means have been activated and press against the surface of e.g. a rotor blade, the service device may be lifted and/or lowered without deactivating the securing elements, since these will roll along the surface. 
     Further, it is noted that the service device  50  may be equipped with wheels or similar elements for supporting against the surface of e.g. a rotor blade. These may also serve to support the device  50  against e.g. a rotor blade or a wind turbine tower when it is lifted and lowered. 
     In  FIG. 11  a work platform  66  is shown in an enlarged view. This may be designed in lightweight material such as aluminium tubing and may have a size suitable for one person or two persons. Larger platforms may be available. As shown the platform is designed with a central vertical indentation or notch  101  in the guardrail which may serve to accommodate the edge of a rotor blade when the service device with the platform  66  is being lifted or lowered. For this purpose the platform  66  is provided with protection means, e.g. in the form of a roller or the like  102  situated in the indentation  101  as schematically indicated in  FIG. 11 . This roller  102  will contact the edge of the rotor blade and roll along this during lifting and lowering and will thus prevent harmful contact. More than one roller may be provided. Further, the platform  66  is equipped with further protection means for protection against harmful contact between the platform and e.g. a rotor blade when working on a rotor blade. Such protection means may for example be in the form of a protection strip as indicated at  103 . Such a strip may for example comprise foam material, rubber material or any other suitable materials. Further, air-filled tubing may be utilized. Even though only one strip  103  has been indicated, more than one may be provided. Preferably, such a strip will be placed near the bottom and on all sides of the platform  66 . 
     The platform may be suspended by a hook, a ring  104  or the like from e.g. a device as shown in  FIG. 10  in such a manner that it may be freely rotated, e.g. by hand. Also, it may be rotated by power means, for example controlled by a person in the platform. The platform will be equipped with control means (not shown) comprising means for lifting and lowering the device, e.g. for controlling the hoisting means  69  ( FIGS. 9 and 10 ), and for controlling the position along the circumference of the rotor blade e.g. by controlling the drive motor  93  or  95  (FIG.  10 ). Further, means for controlling the securing elements  81  and  82  are also present. The control means may comprise a joystick and/or other suitable control input means and may be used for controlling the service device as well as the platform itself, e.g. the positions of these. Further, it is noted that individual means may be controlled, if necessary, for example may the hoisting means  69  be controlled individually, e.g. in order to control the inclination of the device, which may be necessary since the edge of a rotor blade of a wind turbine in many cases may incline in relation to the vertical direction when parked for service. It is also noted that the device or the platform may be equipped with a gyro arrangement e.g. in order to maintain a predetermined inclination, angular position etc. 
     Finally it should be mentioned in relation to the platform shown in  FIG. 11  that it may be designed in order to protect a person against the wind, rain etc. e.g. by having a covering of the top, which will preferably be a transparent material such as Plexiglas or a similar material, and by having coverings or shielding for the sides which may be in the form of roller curtains or the like. Also it is noted that the platform and/or the service devise is equipped with illumination means, lighting means etc. in order to allow the platform and/or the service device to be used also when daylight is not present. The platform may be provided with a small winch or the like lifting and/or lowering necessary items, tools, spare parts, etc. It will thus not be necessary to bring the platform and the service device down to the ground when such parts are needed. 
     A device  110  for establishing an anchoring at a wind turbine, e.g. at a rotor blade, at a tower etc., for example for use in connection with a service device as described above or in connection with other devices, is shown in  FIG. 12 . This device  110  is designed in analogy with the devices disclosed in PCT/DK2003/000577 (WO 2004/022970 A1), and reference is made to this publication for further details and information. However, the device  110  shown in  FIG. 12  involves a number of particular important features which will be described in further detail in the following. 
     The device  110  comprises an uplift device  112  and a locking device generally designated  120 . The uplift device  112  is substantially U-shaped or shaped like a horseshoe. It thus comprises a pair of legs  116  and may comprise a number of separate uplift elements or may be formed as a single element. These elements can be flexible chambers filled with a gas, for example helium, which is lighter than the atmospheric air. These elements can be separated, but can also form a continuous chamber. Further, the uplift device  112  may as indicated comprise a number of vanes  114  placed at the legs  116  for adding e.g. stability and directional control and for using the wind as a supporting factor. As also described in the above-mentioned WO 2004/022970 A1 the device  110  may be located at a wind turbine, the uplift device can be filled with e.g. helium in a sufficient amount to allow the device to lift itself up to the tip of a rotor blade and further up along this or up along a tower. At a suitable position, for example at the root of the rotor blade or at the top of the tower, the locking device  120  will be activated to grip around the respective part of the wind turbine. Hereafter an object such as e.g. a service device as described above may be hoisted up, e.g. by means of wires etc. and the hoisting means  69 , or another object may be lifted and put to use while being suspended by the locking device  120 . 
     The locking device according to this embodiment will be further described with reference to  FIG. 13 , wherein the frame and other particular components of the locking device  120  is shown in an enlarged view, and with reference to  FIG. 14 , wherein a clamping element  140  is shown in an enlarged view. 
     The locking device  120  comprises two frame parts  122  and  124  that are made for example of tubing or rods of lightweight material such as e.g. aluminium. These frame parts are joined at one end by means of a hinge joint  126  that allows the frame to be opened up. At the other end the frame parts  122  and  124  comprise extension parts  127  and  128 , respectively, for cooperation with the clamping element  140 . Further, the frame parts  122  and  124  comprise support parts  123  and  125 , respectively, for the legs  116  of the uplift device  112 . As described in the above-mentioned WO 2004/022970 A1 the locking element is designed to grip an object located in the interior space  130 , e.g. rotor blade or a tower of a wind turbine. This is done by means of at least two clamping parts. These clamping parts are constituted by a number of flexible clamping means  132  and  134 , e.g. three at each side as shown, although it will be understood that more or less than three may be used. The clamping means  134  are supported by arms  135  and the clamping means  132  are similarly supported by arms  133 . 
     The clamping means  132  and  134  can be configured from a flexible material so that these adapt themselves to the surface of the rotor blade, e.g. the root of the rotor blade or a tower. Thus they may also adapt themselves to other shapes than circular shapes, e.g. elliptical shapes, elongated shapes, shapes comprising linear parts joined at angles etc. That side of the clamping means  132  and  134  which faces towards the e.g. rotor blade or the tower can be configured with a surface which in structure and/or material ensures a good friction to the rotor blade. It can thus be a surface coating of a rubber material or similar materials known within the art, which, for example, can also have a pattern, grooves, projections or the like on the surface to provide a good grip without harming the surface. 
     The clamping element  140  shown in  FIG. 14  comprises two end parts  142  and  144 , which can be connected to the extension parts  127  and  128 , respectively, and an activating rod  146 , e.g. a threaded rod, which is rotatably fixed at the end part  142  and is connected to a gear motor  148  located at the end part  144 . It will thus be understood that when the gear motor, which preferably is wirelessly controlled, is activated, the two frame parts  122  and  124  may be opened up or brought closer together. 
     Further, it is noted that at each end of the clamping means  132  and  134 , e.g. at the arms  133  and  135 , means  138  for enhancing the clamping function is provided, e.g. in the form of tackles etc. that is connected by means of wires, lines etc. (not shown in  FIG. 13 ) similarly to what is described in the above-mentioned WO 2004/022970 A1. 
     The functioning of the locking device  120  will now be explained. It will be understood that the locking device may initially be dismantled e.g. for transport, but may quickly be assembled. The uplift element is connected to the frame parts, e.g. with the leg parts  116  to the support parts  123  and  125  and the other interior parts connected to the frame parts  122  and  124  as shown in  FIG. 12 . This may be done using means connected to the material of the uplift device, e.g. reinforcing material, string means, zipper means etc. Lines, wires etc. may be placed on the means  138  for enhancing the clamping function, whereby a number of lines, e.g. four, will remain and extend downwards. Further, the clamping element  140  may be placed at the locking device, preferably in a state where the two frame parts  122  and  124  are opened up, removed a suitable distance from each other. 
     The uplift device may now be filled with e.g. helium, whereby the device  110  comprising the uplift device  112  and the locking device  120  will be lifted up along the e.g. rotor blade or the tower, possibly additionally controlled by one or more lines or wires extending down to the ground. When the desired height is reached, the clamping element  140  is activated, whereby the two frame parts  122  and  124  will be brought closer together, and whereby the locking device will be closed around the relevant part, until the clamping means  133  and  134  is in close proximity of the surface and possibly contacting this. It will be understood that the clamping element  140  does not provide the clamping effect for securing the anchoring. This will be provided by the means  138  for enhancing the clamping function in analogy with what has been disclosed in the above-mentioned WO 2004/022970 A1. It will thus be understood that the above-mentioned lines, e.g. four lines, extending down from the means  138  may be connected to an object that is to be lifted up, e.g. the service device  50 . When for example the hoisting means  69  lift the service device upwards the pull in the lines provided by the weight of the service device will force the clamping means  133  and  134  closer together, thereby enhancing the grip around the e.g. rotor blade or the tower. 
     It will similarly be understood that when an object has been lowered completely to the ground, the grip on the wind turbine or rotor blade will be loosened, and the clamping element  140  can be controlled to open the frame again, whereafter the device may be brought downwards. 
     In connection with  FIGS. 12 and 13  the locking device has been illustrated in combination with an uplift device, e.g. a device lighter than air for lifting the locking device. However, the locking device shown in  FIG. 13  may also be used as described in connection with  FIGS. 5 to 8 , where a carrier device  40  is used for lifting and lowering the anchoring means  44 . The locking device  120  shown in  FIG. 13  may be such anchoring means that may be lowered and lifted by means of a line or wire extending down from the wind turbine. 
     In  FIG. 15  is shown a unit  200  for transport and/or storage of means for performing work at e.g. a wind turbine, e.g. an uplift device and a locking device. Such a unit  200  comprises a container  202 , which may serve to accommodate the respective devices, tools etc. and the necessary equipment such as for example an electrical generator, a compressor, communication and control means, tanks for e.g. helium etc. (not shown in  FIG. 15 ). Such a container  202  may be placed and transported on a vehicle, on a lorry, on a vessel such as a small ship or a barge and may be brought directly to a wind turbine and placed e.g. near the tower when work, e.g. service work has to be performed. The unit is as shown provided with two lids or flaps  204  and  206  at the top, by means of which the top of the container may be opened completely. Each of these flaps  204  and  206  corresponds essentially to the size of the top of the container and it will thus be understood that when the top is closed, the two flaps or lids will be placed one above the other. 
     The flaps or lids  204  and  206  are as shown connected to the sides of the container  202  by means of hinges and the unit is opened by means of an arrangement that will be described in the following. The flaps  204  and  206  are opened by means of arms  208  and  222 , respectively, that are hinged at one end  210  and  224 , respectively, to the container, and at the other end  212  and  226 , respectively, are slidingly connected to rectilinear guiding means  214  and  228 , respectively, at the edges of the flaps. The arms  208  and  222  are moved by means of actuators  216  and  230 , respectively, e.g. pneumatic or hydraulic actuators, which are connected to the container at a common fixing point  218  and at their other ends are connected to intermediate points, e.g. bends  220  and  232 , respectively, of the arms  208  and  222 . It will be seen that by this arrangement the lids or flaps may be opened and closed by activating the actuators  216  and  230 , although they must be activated sequentially. When the flaps are opened, they will extend from the container  202  in a horizontal direction. The advantage of this will be explained in the following. 
     As described above, the unit  200  may be brought directly to a wind turbine, e.g. by a vessel or a vehicle, and may be placed here, e.g. directly underneath a rotor blade. The container may be opened as explained above (it will be understood, though, that doors will normally also be present in the side and/or in the end of the container), and the flaps  204  and  206  may now be used as workspace and support for the devices used. For example, when an uplift device is used, this may be taken up and unfolded on the flaps, e.g. with the legs placed extending in the longitudinal direction of the flaps. The locking device may now be taken up and assembled, if necessary, and it may be connected to the uplift device. The uplift device may now be filled with air e.g. helium, from tanks placed in the container and by means of a compressor placed in the container. When filled, the uplift device may be allowed to lift itself and a locking device and/or other means, up along the tower or the rotor blade, possibly additionally controlled by means of lines or wires anchored on the ground, on the container, on a vessel etc. 
     Further, if a service device or another tool device has to be lifted up, e.g. by using the locking device as anchoring means, such a device, that may also be stored in the unit, may also be assembled on the top of the container and lifted from here. 
     When the work has been completed, the devices used and in particular the uplift device may be brought down, the helium may be pumped back into tanks, the devices may be disassembled and/or folded and stored in the unit  200 . 
     During the operations the necessary electric energy may preferably be supplied by the generator located in the unit, and the devices may be controlled in wireless manner from the unit, although, if a work platform is used, this is primarily controlled (also using wireless control) from the control means in the platform. 
     It will be understood that the invention is not limited to the particular examples described above but may be used in connection with a wide variety of applications. Further, it will be understood that the system according to the invention may be designed in a multitude of varieties within the scope of the invention as specified in the claims. Thus, it will also be understood that the elements forming part of the device may be designed in numerous manners, as it will be evident to a person skilled in the art. Further, it is also noted that the device according to the invention may be equipped with means not illustrated in the drawings, such as e.g. cables and electric wires for power supply, communication etc. and means for providing mechanical operation, e.g. hoists, pneumatics, hydraulics etc. which will also be obvious to the skilled person. 
     In  FIG. 16  a device according to the third aspect of the present invention is shown. The device is constituted by a pair of aligned frames  250  and  251  interconnected by a number of rigid interconnections  252 . In  FIG. 16  the device is illustrated as being lifted up along the tower  253  of a windmill. The tip of a windmill blade  254  is shown to the right of the device. The device is lifted in three wires  255  which are anchored at the top of the windmill. The lifting force is provided by a number of electronic motors  256  arranged on the outside of the frames  250  and  251 . A gondola  257  is movably arranged relative to the frame  251  which forms an endless track so that the gondola  257  can be moved 360 degrees around an object, such as a windmill blade, positioned in the opening defined by the frames  250  and  251 . One or more wheels or rollers  258  are mounted on the backside of the gondola  257  for guiding the device during lifting/lowering of the device along the windmill tower  253 . The gondola itself will be explained in further details in connection with  FIG. 23 . A number of rollers  259  for docking and fixating the windmill blade to the device are positioned within the opening of the frames. These docking rollers, and an alternative arrangement, will be described in further details in connection with  FIGS. 20 and 21 . 
       FIG. 17  shows the device of  FIG. 16  elevated to a higher position on the windmill tower.  FIG. 17  further shows an alignment arrangement  260  attached to the upper frame  250 . The alignment arrangement  260  is adapted to bring the device from a position near the windmill tower to the windmill blade to be serviced, inspected or repaired. Thus, the alignment arrangement brings the device from the windmill tower to a position immediately below a substantially vertical oriented windmill blade in an easy, reliable and comfortable manner. 
     The alignment arrangement shown in  FIG. 17  comprises two arms  261  and  262  each being pivotably mounted on a support arm  263  and  264 . The arms  261  and  262  are interconnected by a connection element  265 . Each of the arms  261  and  262  has some sort of guiding arrangement for guiding a catch element  266  to the ends of the arms. The catch element  266  is in  FIG. 17  shown in two states—the dashed line illustrates the catch element in a relaxed state, whereas the solid line illustrates the catch element in a less relaxed state. The catch element itself can be a flexible wire or a flexible belt. 
     The guiding arrangement for guiding and thereby bringing the catch element to the windmill blade and afterwards pulling the device to the windmill blade (or vice versa) can be implemented in various ways. For example, the guiding arrangement can involve a wire arranged in a track formed in each of the arms  261  and  262 . Thus, one wire is guided in a track formed in arm  261 , whereas another and similar wire is guided in a track formed in arm  262 . At the ends of wires pointing towards the ends of the arms an eye or a loop may be formed. These eyes or loop can independently be moved along the axial directions of the arms  261  and  262 . The catch element  266  is, at one of its ends, connected to the eye or loop of the arm  261 . The other end of the catch element  266  is connected to the eye or loop of the arm  262 . 
       FIG. 18  shows the situation where the device is free from the windmill tower and has been pulled towards the windmill blade using the alignment arrangement. It is seen that the device is not yet in complete alignment with the blade. In order to achieve this, the catch element needs to be withdrawn a little further which will bring the device further to the left and thereby into alignment with the windmill blade. 
     Complete alignment between the device and the blade has been established in  FIG. 19 . Compared to  FIG. 18 , the supports arms  263  and  264  have been angled which brings the blade into complete alignment with the device. The angling of the support arms  263  and  264  has been provided by shortening the adjustment wire or belt  267 . Compared to  FIG. 18  the device has also been slightly lifted by shortening the wires  255 , and the tip of the blade has now entered the opening of the frame. As soon as the top docking roller  268  and the side docking rollers  269  are able to obtain contact with the blade, the alignment arrangement can be fully withdrawn, and the blade and the device are then kept in a fixed horizontal relationship by the top and side rollers  268  and  269 . The vertical alignment of the device is adjusted by shortening or extending the length of the wires  255 . 
     The positioning of the device relative to the blade is illustrated in  FIGS. 20   a  and  20   b , where  FIG. 20   b  is a top view of the device with a windmill blade  270  fixated by rollers  268  and  269 . The gondola is now allowed to move freely around the blade, and in principle any kind of service, inspection or repair may be performed at any vertical position of the blade. In  FIGS. 20   a  and  20   b  the number of side rollers  269  is four. However, this number can in principle be arbitrary and it may vary with the size and shape of the blade. Thus, the number of side roller can be lower as well as higher than four. Similar arguments apply for the top roller  268 . Also, the number of lifting arrangements  256  may vary from one device to another device. 
     In  FIGS. 21   a  and  21   b , an alternative arrangement to the top and side rollers is illustrated. Here, the blade is fixated to the device using two flexible belts  271  and  272 . Each belt is arranged between a rigid end point  273  and  274  and a belt tightener  275  and  276 , As seen, the belt tighteners  275  and  276  and the end points  273  and  274  are mounted on the frame. The belt tighteners  275  and  276  are used to tighten the belts by bringing them from a relaxed state to a tightened state in order to fixate the windmill blade to the device.  FIGS. 21   a  and  21   b  only show the tightened state of the belts, whereas  FIGS. 22   a  and  22   b  illustrate the belts in the relaxed state. In the relaxed state, belt  277  is fixed to end point  278  and a belt tightner (not shown), and biased towards end point  279  and point  280 . Similarly, in the relaxed state, belt  281  is fixed to end point  279  and belt tightener  282 , and biased towards end point  278  and point  283 . 
     The biasing of the belts can be provided by spring loading the belts via wires connecting the belts with points  278 ,  279 ,  280  and  281 . Such wire connections are illustrated in  FIG. 21   b —see wires  284 ,  285 ,  286  and  287 . 
     The gondola is shown in  FIGS. 23   a  and  23   b . As seen, the gondola is formed as an open cage of aluminium tubes  288  with fenders  290  arranged on the front of the cage. The fenders prevent that the gondola damages the windmill blade being inspected, serviced or repaired. The cage can accommodate one, two or even more individuals. The gondola also comprises a control panel  291  which allows the individual(s) using the gondola to move the gondola around the windmill blade and lift and/or lower the gondola relative to the blade. The up and down movements of the gondola can for example be provided by use of a Joystick. Further facilities such as rooms  292  for repair equipment can also be provided. 
     A final embodiment of the present invention is shown in  FIG. 24 . Here the gondola has been omitted and replaced by a 360 degrees working platform. The previously described alignment arrangement and the docking roller arrangement for fixating the device/platform to the blade also apply to this embodiment. 
     Finally it should be mentioned that the alignment arrangement used for bringing the device from the windmill tower to the blade is also applicable when service, inspection or repair of the blade is completed and the device is to be moved from the blade to the windmill tower and further down to ground level. 
     While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present.