GRINDING DEVICE FOR MACHINE BASED GRINDING OF ROTOR BLADES FOR WIND ENERGY SYSTEMS

Abstract

Grinding device 1 for machine-based grinding of rotor blades 100 for wind energy systems, comprising at least one industrial robot 30 and a grinding unit 10, 50, 70 that is guided by the industrial robot 30, wherein the grinding unit 10, 50, 70 comprises a grinding means, 12, 52 and a cleaning device 20, that cleans the grinding means 12, 52 at its grinding surface 64, 53.

Description

1. FIELD OF THE INVENTION

The present invention relates to a grinding device for a machine based grinding of rotor blades for wind energy systems. By the use of the grinding device, grinding tasks can be automated during the manufacturing and during the maintenance of rotor blades.

2. PRIOR ART

The use of wind force for the energy generation is seen as one of the most environmentally compatible forms of winning energy. Therefore, wind energy systems are used, that comprise a rotor that drives a generator and that is supported rotatably at a mast. The loads, that effect on the parts in particular the rotor blades of a wind energy system is however very high.

Atmospheric influences, like for instance wind, water, hail, UV-radiation, erosion- and bending-loads lead to highest requirements for the material of the rotor blades. The correct operation and the surface quality are relevant for the effectivity and economic efficiency of wind energy systems. Thus, rotor blades comprise a specific coating, wherein its application is very time-consuming, since as a rule every single layer of the coating has to be ground.

The extremely loaded polymer surfaces of rotor blades are coated by a plurality of layers. The layer systems for the protection of the surfaces consist of a so called gel coat, spatling compound, etch protection and cover lacquers. The products that are used therefore consist as a rule of solvent-free, two-component polyurethane compounds. After the application of the single layers, each one has to be ground.

These grinding tasks are a very human resource-intensive process, since they are carried out manually by hand grinding machines. The rotor blades to be ground comprise for instance a length of up to about 80 m and a surface to be ground of up to about 300 m². According to this, the surface that has to be manually ground is very large.

A further reason for the fact that grinding tasks at rotor blades are still carried out manually by means of hand grinding machines, for instance by means of eccentric grinders with dust suctions lies in the fact that the coatings of the rotor blades to be ground are designed very viscoplastic and thus the grinding discs clog very fast.

With one grinding disc only a little surface can be ground and then this grinding disc has to be exchanged by a new grinding disc. This can be done very fast by hand for hand grinding machines. Up to now there are high changing rates so that grinding robots could not be used economically. With a grinding disc—instead of a suction device—only about 0.5 m²-1.5 m² of the viscoplastic coating of a rotor blade can be usually ground. But the surface of a wind energy wing of about 60 m to about 80 m wing length is 160 m² to 300 m², so that per rotor blade and per grinding iteration about 300-600 grinding discs have to be used. Usually, there are 3-4 grinding iterations per rotor blade.

The viscoplastic coatings of the rotor blades are used, because rotor blades move with speeds of up to 300 km/h and they are not allowed to be damaged, when for instance hail stones dash against them. In the documents DE 298 05 833 U1, DE 199 29 386 A and DE 297 09 342 U1 coating systems for rotor blades are described.

The enormous dimensions of rotor blades and the problems that come up during the grinding of the viscoplastic coating did not allow an automization of the grinding tasks up to now. The cost for the grinding tasks may be 30% and more of the manufacturing costs of a rotor blade.

Thus, it is the problem of the present invention to solve the above mentioned problems and to optimize the grinding process for rotor blades of wind energy systems and to design it more cost effective.

3. SUMMARY OF THE INVENTION

The above mentioned problem is solved by a grinding device for machine-based grinding of rotor blades for wind energy systems according to patent claim 1.

In particular the above mentioned problems are solved by a grinding device for machine-based grinding of rotor blades for wind energy systems, comprising at least one industrial robot and a grinding unit that is guided by the industrial robot, wherein the grinding unit comprises a grinding means and a cleaning device that cleans the grinding means at its grinding surface.

By using a grinding unit that comprises a grinding means that is cleaned at the grinding surface, an industrial robot that guids a grinding unit can be used in a grinding device in an advantageous manner. This was not possible for conventional grinding means, since a use of a robot was uneconomical because of the fast clogging of the grinding means and the high exchange rates of the grinding means. Now, the lifetime of the grinding means is raised 10-100 times by the cleaning device, so that none or only very few tool exchanges are necessary for the grinding of the surface of a rotor blade and an industrial robot can be now used economically for the grinding of rotor blades.

Preferably, the cleaning device cleans the grinding surface of the grinding means either from time to time or continuously during the grinding. The grinding surface can—if necessary—be cleaned from time to time, for example depending on the degree of clogging of the grinding surface, by bringing the grinding surface after a specific grinding time into contact with a cleaning device. Alternatively, the cleaning device is in contact with a part of the grinding surface during the grinding and cleans it continuously during the grinding.

Preferably, the cleaning device cleans the grinding surface by means of a nozzle for blowing on of pressurized air and/or a device for the suchtion of grinding dust and/or a brush for brushing the grinding surface. These three measures, lead either on their own or in any combination with each other to the fact that also the abrasion of viscoplastic coatings is removed nearly completely from the grinding surface of the grinding means and cannot adhere there and cannot clog the grinding surface. By the active cleaning of the cleaning surface, the life time of the grinding means is increased but also the quality of the grinding task.

During the blowing of pressurized air by means of a nozzle, adhering grinding particles are loosened, these particles are removed actively from the grinding surface by the suction of grinding dust and it is possible by means of a brush to remove even strongly adhering grinding dust on the grinding surface or larger sticky adhesions safely. Such a grinding device can be used for a discontinuous as well as for continuous cleaning of the grinding surface of the grinding means.

In a preferred embodiment, the grinding device comprises furthermore a drive unit for moving the industrial robot in the direction of the longitudinal axis L of a rotor blade. By doing so, the industrial robot can move along the rotor blade and grind the entire surface of the rotor blade.

In a preferred embodiment the grinding unit comprises a cylinder grinding unit with a grinding sleeve. A grinding sleeve comprises a comparatively large grinding surface that can be cleaned in its region that is currently not in contact with the rotor blade. The cylinder grinding units are furthermore very compact and can be moved very well with an industrial robot in order to grind the surface of the rotor blade as desired.

In a preferred embodiment the cylinder grinding unit comprises a rigid suction drum and elastic, pneumatically expandable clamping elements that are arranged at the barrel of the suction drum wherein the grinding sleeve is fixed to the clamping elements at the suction drum by the application of pressure. It is possible by such an arrangement of the drum grinding unit, to fix the grinding sleeve very simple and fast at the suction drum so that a tool exchange—that means the exchange of the grinding sleeve—can be carried out very easy and fast.

Furthermore the elastic, pneumatically expandable clamping elements have the advantage that the grinding sleeve can adapt itself in some degree to the surface of the rotor blade and compensates smaller inconsistencies of the positioning of the grinding device.

Preferably, the suction drum comprises suction openings at the barrel and air permitting spaces are present between the clamping elements and the grinding sleeve comprises perforation openings arranged essentially over its entire surface in order to be able to suck grinding dust from the grinding surface through the perforation openings and through the air permitting spaces and through the suction openings. With such a construction of the drum grinding unit it is possible on the one hand to carry out the above mentioned simple pneumatic clamping of the grinding sleeve to a rigid suction drum and on the other hand to suck grinding dust from the grinding surface through the clamping elements, the suction drum and through the grinding sleeve. By doing so, the dust removal can be carried out from the grinding surface over the entire surface, whereby a clogging of the grinding surface is furthermore minimized and a nearly dustless grinding becomes possible.

In a preferred embodiment, the grinding sleeve comprises an air- and particle-flow-permitting layer, in particular a fleece layer, through which suction air and grinding dust are able to flow transversely behind the grinding surface from the perforation openings to the air permitting spaces. By the fleece layer, through which the suction air and the grinding dust can flow transversely behind the surface, perforation openings can be arranged over the entire surface of the grinding surface of the grinding sleeve, so that the way of the grinding dust from its generation at the grinding surface to the perforation opening at which it is sucked away is very short. According to this the air- and particle-flow-permitting layer behind the grinding surface allows a dust suction over the entire surface and permits a clogging of the grinding sleeve. Thus, this dust transport is carried out over the entire surface and independently from the arrangement of the air permitting spaces that are formed by the elastic, pneumatically expandable elements.

Preferably, the grinding unit comprises several drum grinding units, that each can be individually brought into contact with the surface of the rotor blade. By such an arrangement, for instance in form of a drum grinding unit revolver, grinding sleeves that are presently not in contact with the rotor blade can be replaced or cleaned without significantly enlarging the overall grinding time for the rotor blade. It is also possible to use on the single drum units grinding sleeves with different graining or dust drums and to use them very fast.

Preferably, a cleaning unit cleans one of the drum grinding units which is not in contact with the surface of the rotor blade.

In a further preferred embodiment, the grinding unit comprises a belt grinding unit with a circulating grinding belt. A circulating grinding belt is only in contact with the rotor blade with a part of its grinding surface and the part of the circulating grinding belt that is not in contact with the rotor blade can move along a cleaning device, which carries out a cleaning of the grinding surface. According to this, this embodiment is also appropriate very well for a continuous cleaning of the grinding surface during the operation.

Preferably, the grinding belt is a perforated grinding belt that comprises perforation openings arranged essentially over its entire surface. The generated grinding dust can be sucked though this perforation openings on the shortest-possible way behind the grinding surface so that a clogging of the grinding belt is avoided and a nearly dustless grinding is possible.

In a further preferred embodiment, the grinding device further comprises a dust removing unit with a circulating dust belt or a dust sleeve that can be guided by the industrial robot along at least one surface of the rotor blade, in order to remove dust mechanically from the surface of the rotor blade. By the use of the device according to the invention it is not only possible to grind the surface of a rotor blade automatically but it is also possible to remove dust from the ground surface completely by means of a circulating dust belt or a dust sleeve. So it is possible to carry out the application of a further lacquer layer directly afterwards. In an advantageous manner, therefore the already present grinding unit can be used as dust removing unit so that herein only a little additional effort has to be spent. An automized dedusting of the grinding surface is significantly faster executable than manual dedusting by means of towels or similar means.

In a preferred embodiment, the industrial robot comprises pressure sensors at at least one robot arm or at the head for controlling the contact pressure of the grinding unit onto the rotor blade. By means of these pressure sensors it is ensured, that the robot arm applies the necessary grinding pressure and the necessary and precisely defined pressure for cleaning the surface of the rotor blade respectively. Therefore a very homogenous grinding- and cleaning-result is achieved.

Preferably, the industrial robot is also used for lacquering the rotor blades. By doing so the investment costs of the entire system is reduced to a minimum, wherein in one system lacquering of a rotor blade as well as the grinding and the dedusting of the rotor blade respectively is carried out with the same industrial robot that has only to exchange the necessary tools between the single process steps. Also such an exchange can be carried out automatically. According to this the entire coating processes, including grinding and dedusting of a rotor blade is reduced to a fraction of time, compared with conventional systems in which it has to be ground manually and often also to be lacquered manually. According to this the manufacturing times as well as the manufacturing costs are reduced by the grinding device according to the invention.

Further preferred embodiments of the invention result from the sub claims.

4. BRIEF DESCRIPTION OF THE FIGURES

In the following, preferred embodiments of the invention are described with reference to the accompanying figures. In which shows:

FIG. 1: A first preferred embodiment of a grinding device for machine-based grinding of rotor blades for wind energy systems in a front view;

FIG. 2: The grinding device of FIG. 1 in a top view;

FIG. 3: A drum grinding unit of the grinding device according to FIG. 1 in a cross sectional view from the side;

FIG. 4: A detail of a drum grinding device of FIG. 3 in a cross sectional view from the side;

FIG. 5: The drum grinding device of FIG. 3 in an cross sectional view from the from;

FIG. 6: A second embodiment of a grinding device for machine based grinding of rotor blades for wind energy systems in a front view;

FIG. 7: A grinding device according to FIG. 6 with an alternative guiding of the industrial robot at a wall in a top view; and

FIG. 8: A front view of a further preferred embodiment of a grinding device for a machine based grinding of rotor blades for wind energy systems with a belt grinding unit in a front view;

5. DESCRIPTION OF PREFERRED EMBODIMENTS

In the following preferred embodiments of the invention are described with reference to the figures. Single features of the herein described embodiments can be combined with other embodiments of the invention.

FIGS. 1 and 2 show a front view and a top view of a grinding device 1 for machine-based grinding of rotor blades 100. In FIG. 1 an industrial robot 30 is arranged on the right hand side of the rotor blade 100 at the wall 60 of a building, wherein it is possible to move the industrial robot 30 in the longitudinal direction. The industrial robot 30 can move by means of an undercarriage 32 at the wall 60 along a longitudinal axis L of the rotor blade 100 at wall tracks 42. The industrial robot 30 is only shown in a symbolic manner and can be every industrial robot that is appropriate for the task that is described in the following. As shown, the industrial robot 30 comprises an undercarriage 32, a drive motor 40, a first arm 34, that is attached to the undercarriage 32 in a hinged manner, a second arm 36 that is attached to the first arm 34 in a hinged manner as well as a head 38, that is attached to the second arm in a hinged manner Depending on the construction type of the industrial robot 30 further swiveling- or rotating-axes can be foreseen. All axes of the industrial robot 30 are driven in a common manner by a motor and are controlled by means of a NC-control by means of a program.

At the head 38 of the industrial robot 30 a grinding unit in form of a drum grinding unit 10 is attached, that can be guided NC-controlled by the industrial robot 30 along the surface 102 of the rotor blade 100, in order to grind the surface. By means of the industrial robot 30 it is thus possible to grind at least one side of the surface 102 of the rotor blade 100 in a machine-based manner For the other side of the rotor blade 100 a second industrial robot 30 with a grinding unit 10, 50, 70 can be provided.

Alternatively, the rotor blade 100 can be also supported rotatably around its longitudinal axis, so that the side to be ground can be rotated in the direction of the industrial robot 30.

The drum grinding unit 10 is shown in the following in the FIGS. 3, 4 and 5 in detail. FIG. 3 shows a cross section through a preferred drum grinding unit 10. The drum grinding unit 10 comprises a rigid suction drum 15 that is equipped with suction openings 16 around its circumference. Elastic and pneumatically extendable clamping elements 17 are arranged around the barrel of the rigid drum 15 that consists preferably of a light metal. The elastic clamping elements 17 consist preferably of a polymer material and are supported by an inlet for pressurized air 18 with clamping air. The clamping elements 17 are connected amongst each other pneumatically via ducts 19, so that they generate between themselves air permitting spaces 11, through which the dust can be sucked into the suction drum 15. The clamping elements 17 are preferably realized in form of shallow torus-shaped rings or as single pillows that are arbitrarily shaped.

A grinding means in form of a grinding sleeve 12 is slided onto to the suction drum 15 with the clamping elements 17 that are arranged at the barrel and is fixed to the suction drum 15 by an application of pressure onto the clamping element 17. Herein the clamping element 17 expand by inducing of clamping air 18 and fix the grinding sleeve 12 from inside onto the suction drum 15. It is especially simple by this pneumatic way of fixation to clamp the grinding sleeve 12 onto the suction drum 15 and to exchange the grinding sleeve 12 after the expiration of its lifetime. The grinding sleeve 12 consists preferably of a wide grinding belt 66 that is coated with grinding particles and is made of a tissue that is glued together to a cylinder-shaped sleeve.

The drum grinding unit 10 is preferably equipped with a dust suction device 14 that allows sucking the generated grinding dust through the grinding sleeve 12 during the grinding. Therefore, the grinding sleeve 12 preferably comprises over its entire surface peroration openings 62 that expand at least through the grinding belt layer 66 so that grinding dust can be sucked from the grinding surface 64 through the perforation openings 62 and through the air-permitting spaces 11 between the clamping elements 17 and through the suction openings 16 into the suction drum 15. From the suction drum 15 the suction air is sucked together with grinding particles through a suction air connection 14 into a suction system (similar to a vacuum cleaner).

A particular effective dust suction is achieved when the grinding sleeve 12 comprises in addition on its inner side an air- and particle-flow-permitting layer 13, in particular a fleece layer, through which the sucked air and the grinding dust is able to flow transversally behind the grinding surface 64 from the perforation openings 62 to the air-permitting spaces 11. This is exemplarily shown by the arrow 68 in FIG. 4. Thus, the size and the arrangement of the perforation openings 62 of the grinding sleeve 12 can be chosen according to the generated grinding dust and has not to be adapted to the arrangement of the air-permitting space 11 between the clamping elements 17. Preferably, the perforation openings 62 comprise a diameter of about 1 mm-6 mm and are spaced apart from each other in a distance of about 10 mm-50 mm and are distributes essentially homogenously over the entire surface of the grinding sleeve 12. According to this, a nearly complete suction off of the grinding dust can be carried out so that also for this reason a clogging of the grinding surface 64 of the grinding sleeve 12 is avoided and only little dust is dispensed to the environment.

The drum grinding unit 10 comprises furthermore a drive motor (not shown) that rotatably drives the suction drum 15 with the grinding sleeve 12 around its rotation axis in order to grind the surface 102 by that.

The industrial robot 30 comprises preferably in its head 38 or in its arms 34, 36 a pressure sensor (not shown) in order to control the contact pressure of the grinding unit 10 onto the rotor blade 100.

As shown in FIG. 5, the drum grinding unit 10 comprises furthermore a cleaning device 20. The cleaning device 20 comprises a brush 22 for brushing the grinding surface 64 of the grinding sleeve 12. Furthermore, the cleaning device 20 comprises a nozzle 24 that can be used for blowing pressurized air onto the surface 64 of the grinding sleeve 12. In addition the cleaning device 20 comprises a surrounding hood 28 that is connected to a suction element 26, in order to suck grinding dust that was detached by the brush 22 and the nozzle 24. The suction element 26 can be connected to the suction element of the suction drum 15.

The cleaning device 20 detaches in an effective manner at the grinding surface 64 of the grinding sleeve 12 adhering grinding dust that cannot be removed by the common suction element. This is in particular decisive for an effective use of the grinding device 1 according to the invention, since an industrial robot 30 can be only used in a reasonable manner for grinding of rotor blade 100, when the life time of the grinding means 12, 52 is so high, that a significant surface of the rotor blades 100 can be ground without having to exchange the grinding means 12, 52. By means of the cleaning device 20 it is possible, also to remove firmly adhering or sticky grinding dust of viscoplastic coatings of a rotor blade 100 from the grinding surface 64 of a grinding sleeve 12 or the later described grinding belt 52.

The FIGS. 6 and 7 show a further embodiment of a grinding device 1 with an industrial robot 30. In FIG. 6 the industrial robot is guided via an undercarriage 32 at floor tracks 44 on the floor 61 of a system in a longitudinally moveable manner FIG. 7 shows an alternative embodiment, wherein the industrial robot 30 is guided via a undercarriage 32 at wall tracks 42 at the wall 60 of a building. The grinding device 1 of the FIGS. 5 and 6 differs from the embodiment according to FIGS. 1 and 2 therein, that at the head 38 of the industrial robot 30 a 4-fold grinding unit 70 is attached, that comprises three drum grinding units 10 like these of FIGS. 3-5, as well as one dust removing unit in form of a cleaning drum 72. The 4-fold grinding unit 70 can—similar to a tool revolver—be moved around an angle of 90° each so that either a new drum grinding unit 10 or the cleaning drum 72 can be used at the rotor blade 100.

The cleaning drum 72 is similar to the drum grinding unit 10 in its construction, but comprises instead of a grinding sleeve 12, a cleaning sleeve made of a soft, dust attracting and air-permitting tissue- or fleece-material. By means of the dust removing unit in form of a cleaning drum 72 the surface 102 of the rotor blade 100 can be cleaned mechanically after the grinding process of remaining dust, so that it can be coated again directly afterwards.

In the embodiment that is shown in FIGS. 6 and 7 the grinding devices 10 and the cleaning drum 72 respectively are not provided each with an own cleaning device 20, but there is one common cleaning device 20 for all four units 10, 72. The cleaning device 20 is fixed to the head 38 at a fixed position, for instance in the position of FIG. 6. For the discontinuous cleaning, the drum grinding unit 10 and the cleaning drum 72 each are pivoted to the cleaning device 20 and is cleaned there. Thus, a cleaning of one of the drum grinding units 10 and the cleaning drum 72 respectively is possible when at the same time another unit 10, 72 is in contact with the rotor blade 100.

FIG. 8 shows a further embodiment of the grinding device 1 for machine-based grinding of rotor blades 100 for wind energy systems. In this embodiment of the grinding device 1, the industrial robot 30 guides a belt grinding unit 50 along the surface 102 of the rotor blade in order to grind it. The belt grinding unit 50 comprises a frame 51, at which guide rolls 54 are rotatably supported, which guide a grinding belt 52 continuously. A tension roll 56 tightens the grinding belt 52. One of the guide rolls 54 is preferably driven by an electric motor, in order to circulate the grinding belt 52. The grinding belt 52 is pressed by means of pressure elements 58 homogenously onto the surface 102 of the rotor blade 100 so that a homogenous grinding pressure is ensured. The pressure elements 58 comprise furthermore a suction element 59, so that the grinding dust can be sucked directly during grinding. Therefore the grinding belt 52 is preferably perforated at its entire surface like the above described grinding sleeve 12, so that the grinding dust can be removed on the shortest possible way from the grinding surface 53 and a nearly dust-free grinding becomes possible. A significant advantage of the belt grinding unit 50 lies in the fact that during the grinding only a part of the grinding belt 52 is in grinding contact with the surface 102 of the rotor blade 100. Thus it is possible, to execute a cleaning of the areas, that are currently not in contact with the surface 102 by the cleaning device 20. The cleaning device 20 comprises like in the above described embodiments a nozzle 24 for blowing of pressurized air onto the grinding surface in order to remove adhering grinding dust. Furthermore, the cleaning device 20 comprises a brush 22, in order to remove stronger adhering grinding dust from the grinding surface of the grinding belt 52. The removed grinding dust is sucked off by a suction element 26. The grinding device 20 is surrounded by a hood 28, so that no dust can be dispersed to the environment. By means of the cleaning device 20 it is possible to clean the grinding belt 52 continuously during the operation at its grinding surface, so that grinding dust cannot adhere and it cannot come to a clogging of the grinding belt 52. This significantly increases the lifetime of the grinding belt 52, so that it is possible, to grind the complete rotor blade 100 with only one grinding belt completely.

Another advantage of the belt grinding unit 50 also compared to drum grinding units lies in the fact that its grinding performance is adaptable by a corresponding dimensioning of the grinding means surface. By the choice of the grinding means surface that is determined by the length and the width of the grinding belt 52 the grinding performance can be adjusted according to the rotor blade to be ground so that none or at the most only few exchanges of the grinding belt 52 are necessary per grinding iteration.

Like in the above mentioned embodiments, the industrial robot 30 can be guided by means of a drive unit 32, 32′ either at the wall 60 or also at the floor 61 and can move all in all along the longitudinal direction L at the rotor blade 100. In FIG. 9 both alternatives of the drive unit 32 and 32′ are shown. Furthermore, the industrial robot 30 can be equipped at one of its arms 34, 36 or at its head 38 with pressure sensors in order to adjust the contact pressure of the belt grinding unit 50 onto the surface 102 exactly.

By means of the above described embodiments it is possible for the first time to use industrial robots 30 economically for the grinding of rotor blades 100 of wind energy systems. Preferably, these industrial robots 30 can also execute further functions like for instance the dedusting of the rotor blade 100 and the lacquering and coating of the rotor blade 100 respectively.

When a belt grinding unit 50 is used for dedusting of the rotor blades 100 the belt grinding unit 50 can be equipped with a dust belt instead of the grinding belt 52, wherein the dust belt consists of an air-permitting tissue- or fleece-material. This is guided similarly to the grinding belt 52 along the surface 102 of the rotor blade 100 and picks up there the adhering grinding dust mechanically and cleans the surface 102 so that it can be lacquered and coated respectively directly afterwards.

For this lacquer process the industrial robot 30 that is used for grinding and dedusting respectively can be also used. Thus, it is possible to carry out in one single system with the same industrial robot 30 the entire coating process, which consists of several lacquer-, grinding- and cleaning-processes. Manual work like for instance the manual grinding or a manual cleaning is omitted completely. Thus the manufacturing time for the rotor blade of wind energy systems and according to this also the manufacturing costs are reduced. Furthermore, by the cleaning of the grinding means high savings concerning grinding means are achieved, that also reduce the manufacturing costs.

Claims

1. Grinding device (1) for machine-based grinding of rotor blades (100) for wind energy systems, comprising:

a. at least one industrial robot (30); and

b. a grinding unit (10, 50, 70) that is guided by the industrial robot (30); wherein

c. the grinding unit (10, 50, 70) comprises a grinding means (12, 52) and a cleaning device (20) that cleans the grinding means (12, 52) at its grinding surface (64, 53).

2. Grinding device according to claim 1, wherein the cleaning device (20) cleans the grinding surface (64, 53) of the grinding means (12, 52) either

a. from time to time in a cleaning process; or

b. continuously during the grinding.

3. Grinding device according to claim 1, wherein the cleaning device (20) cleans the grinding surface (64, 53) by means of:

a. a nozzle (24) for blowing on of pressurized air; and/or

b. a device (26) for the suction of grinding dust; and/or

c. a brush (22) for brushing the grinding surface (64, 53).

4. Grinding device according to claim 1, further comprising a drive unit (32, 32′) for moving the industrial robot (30) in a direction (L) of the longitudinal axis of a rotor blade (100).

5. Grinding device according to claim 1, wherein the grinding device (10, 70) comprises a drum grinding unit (10) with a grinding sleeve (12).

6. Grinding device according to claim 5, wherein the drum grinding unit (10) comprises:

a. a rigid suction drum (15); and

b. elastic, pneumatically extendable clamping elements (17), that are arranged at the barrel of the suction drum (15), wherein

c. the grinding sleeve (12) is fixed at the suction drum (15) by the application of pressure onto the clamping elements (17).

7. Grinding device according to claim 6, wherein

a. the suction drum (15) comprises suction openings (16) at the barrel;

b. air-permitting spaces (11) are present between the clamping elements (17); and

c. the grinding sleeve (12) comprises perforation openings (62) arranged essentially over its entire surface;

so that grinding dust can be sucked from the grinding surface (64) through the perforation openings (62), the air-permitting spaces (11) and through the suction openings (16).

8. Grinding device according to claim 7, wherein the grinding sleeve (12) comprises an air- and particle-flow-permitting-layer (13), preferably a fleece-layer (13), through which suction air and grinding dust can flow transversally behind the grinding surface (64) from the perforation openings (62) to the air-permitting spaces (11).

9. Grinding device according to claim 5, wherein the grinding unit (70) comprises several drum grinding units (10) that each can be individually brought into contact with the surface (102) of the rotor blade (100).

10. Grinding device according to claim 9, wherein the grinding unit (20) can clean one of the drum grinding units (10) that is not in contact with the surface of the rotor blade (100).

11. Grinding device according to claim 1, wherein the grinding unit (50) comprises a belt grinding unit (50) with a circulating grinding belt (52).

12. Grinding device according to claim 11, wherein the grinding belt (52) is a perforated grinding belt, that comprises perforation openings arranged essentially over its entire surface in order to suck dust through the grinding belt (52).

13. Grinding device according to claim 12, further comprising a dust removal unit (72) with

a. a circulating dust belt; or

b. a dust sleeve (74);

that can be guided by the industrial robot (30) at at least one surface (102) of a rotor blade (100) in order to clean the surface (102) of the rotor blade (100) from dust mechanically.

14. Grinding device according to claim 1, wherein the industrial robot (30) comprises pressure sensors at at least one robot arm (34, 36) or at the head (38), for controlling the contact pressure of the grinding unit (10, 50, 70) or the dust removal unit (72) onto the rotor blade (100).

15. Grinding device according to claim 1, wherein the industrial robot (30) is also used for coating or lacquering the rotor blade (100).