EP2422929B1 - Grinding device for mechanical grinding of rotor blades for wind power systems - Google Patents

Description

1. Field of the invention

The present invention relates to a grinding apparatus for machine grinding rotor blades for wind turbines. The grinding device can be used to automate grinding operations during the manufacture and maintenance of rotor blades.

2. State of the art

As one of the most environmentally friendly forms of energy production, the use of wind power for power generation is considered. For this purpose, wind turbines are used which have a rotor which drives a generator and which is rotatably mounted on a mast. However, the stresses to which the components, in particular the rotor blades of the wind turbine are exposed, are enormous.

Weather influences, such as wind, water, hail, UV radiation, erosion and bending loads place the highest demands on the material of the rotor blades. The functionality and the surface quality are essential for the effectiveness and efficiency of wind turbines. Therefore, the rotor blades have a special coating, the application of which is very time-consuming, since each individual layer of the coating usually has to be ground.

The extremely contaminated plastic surfaces of rotor blades are coated several times. The coating systems for protecting the surfaces consist of a so-called gelcoat, spatula, edge protection and topcoats. The dafiir used products generally consist of solvent-free, two-component polyurethane compounds. After the application of the individual layers, these must be ground in each case.

These sanding operations are a very labor intensive process as they are done manually with hand grinders. For example, the rotor blades to be ground have a length of up to about 80 m and a surface to be ground of up to about 300 m 2. Accordingly, the area to be ground manually is very large.

Another reason for the fact that grinding work on rotor blades is still carried out manually using hand grinders, for example with eccentric grinders with dust extraction, is that the rotor blade coatings to be ground are set very viscous and therefore the grinding wheels clog very quickly. With a grinding wheel, only a small area can be ground and then this grinding wheel has to be replaced with a new grinding wheel, which is possible very quickly with hand grinding machines by hand. Due to the frequent change rates, grinding robots could not be used economically. With a grinding wheel, only approx. 0.5 m² - 1.5 m² of the viscoelastic coating of a rotor blade can be sanded despite extraction. However, the area of a wind turbine blade of approx. 60 m to approx. 80 m wing length is 160 m² to 300 m², so that approx. 300 - 600 grinding wheels have to be used per rotor blade and grinding cycle. There are usually 3-4 sanding passes per rotor blade.

From the WO-A-2008/077398 a grinding apparatus according to the preamble of claim 1 is known. It has a cylindrical rotatable grinding element, are attached to the radially projecting abrasive sheets.

To increase the life of abrasive belts, slip belt cleaning systems are sometimes used. The Where 2006/006843 A1 shows such a sanding belt cleaning system for a portable belt sander, wherein the portable belt sander has a revolving sanding belt.

The viscoelastic coatings of the rotor blades are used because rotor blades move at speeds of up to 300 km / h and they must not be damaged when, for example, hailstones hit them. In the pamphlets DE 298 05 833 U1 . DE 199 29 386 A and DE 297 09 342 U1 describes coating systems for rotor blades.

The enormous dimensions of the rotor blades and the problems that occur when grinding the viscoelastic coating, have not yet allowed automation of the grinding work. The cost of the grinding work can be 30% and more of the manufacturing cost of a rotor blade.

It is therefore the object of the present invention to solve the above-mentioned problems and to improve the grinding process in rotor blades for wind turbines and to make them cheaper.

3. Summary of the invention

The above-mentioned object is achieved by a grinding device for the mechanical grinding of rotor blades for wind power plants according to claim 1.

By using a grinder to mechanically grind rotor blades, the grinding process can be automated, eliminating the need for manual grinding. Grinding work, which is currently carried out with hand grinders, can be omitted and carried out by means of the grinding device according to the invention. This is made possible by the use of a belt grinding unit with a revolving sanding belt, which makes it possible to mechanically grind several 100 square meters of tough-elastic coating of a rotor blade for wind turbines.

The use of revolving abrasive belts has the advantage that only one part of the abrasive belt is engaged with the rotor blade while another part of the abrasive belt is freely accessible and in this area of the tough-elastic sanding dust can be cleaned. This prevents a rapid clogging of the sanding belt with the likewise viscoelastic sanding dust.

Furthermore, the effective usable surface of an abrasive belt is much larger than in grinding wheels for hand-held grinding machines. Thus, the grinding surface of the grinding belt can be designed according to the size of the surface of a rotor blade, so that a grinding belt change is necessary only after grinding at least one side of a rotor blade or the entire rotor blade. Furthermore, an abrasive belt has the advantage that the grinding speed is infinitely variable and can be exactly adapted to the coating of the rotor blades. With rotating or oscillating grinding wheels, there is always the problem that in principle lower speeds prevail inside the grinding wheel than in the outer areas, which leads to a poorer grinding result and to a rapid clogging of the grinding wheels used.

Preferably, the grinding device further comprises a drive unit for moving the belt grinding unit in the direction of the longitudinal axis of a rotor blade. The belt grinding unit with the preferably transverse to the rotor blade rotating belt is moved by a drive unit in the direction of the longitudinal axis of the rotor blade. This makes it possible to continuously grind one side of a rotor blade in a grinding pass. The continuous grinding process also gives a smoother grinding result than a batch hand grinding. By rotating the rotor blade about its longitudinal axis, the entire surface of the rotor blade can be mechanically ground in further passages.

Preferably, the grinding device further comprises a dust belt unit with a circumferential dust belt, which is guided along at least one surface of a rotor blade in order to free the surface of the rotor blade from dust. With the aid of the dust band, after sanding, the surface of the Rotor blades are cleaned of Straub so that it is suitable for direct recoating. By using the dust-tape unit, a quasi-dust-free surface of the rotor blade is obtained.

Preferably, the grinding device further comprises at least one belt cleaning device. By means of the belt cleaning device, the abrasive belt and / or the dust belt are cleaned continuously during the respective use of the belt. This increases in particular the service life of the grinding belt many times over a sanding belt without suction or even a sanding belt, is sucked in the dust.

Preferably, the belt cleaning device cleans the abrasive belt and / or the dust belt by means of a nozzle for inflating compressed air and / or a device for extracting sanding dust and / or a brush for brushing the abrasive belt and / or the dust belt. These three measures, which can be used singly or in combination, allow almost complete cleaning of the sanding belt and the dust belt so that the service life of both belts is limited only by mechanical wear. Clogging of the tapes is thus effectively delayed and the grinding dust is effectively removed without getting into the environment.

The belt grinding unit preferably has pressure elements which press the sanding belt and / or the dust belt against a surface of a rotor blade and which are mounted on the drive unit. By the pressure elements of the grinding pressure of the abrasive belt or the cleaning pressure of the dust belt can be precisely determined and varied, and thus the grinding and cleaning conditions are precisely determined on the surface of the rotor blade.

Preferably, the pressure elements in the direction of the transverse axis of a rotor blade on the drive unit movable link pressure bar or pressure rollers. Sectional pressure bars or pressure rollers can adhere to the curved surface adjust the rotor blade and thus results in a uniform contact pressure for the abrasive belt or the dust belt. By moving the printing elements, it is ensured that each surface area is ground or cleaned for a sufficiently long time and with the required contact pressure.

Preferably, the pressure elements can be pneumatically driven against the surface of a rotor blade to set the grinding pressure of the abrasive belt and / or the cleaning pressure of the dust belt on the surface. Due to the pneumatic control, the grinding pressure of the grinding belt can be precisely determined by the air pressure used. In this case, the pressure element adapt automatically to the curved surface of the rotor blade, without the need for a complex control is necessary. The individual members of the sectional pressure bar or the pressure rollers are each subjected to the same air pressure, so that their pressure on the surface is always constant even with variable geometries of the surface of the rotor blade. Of course, the same principle can also be realized via a hydraulic control.

The pressure elements preferably have a suction hood in order to suck off grinding dust through the abrasive belt and / or the dust belt and through the pressure element. Thus, the sanding dust, already partially sucked out where it is created or absorbed, thus avoiding clogging of the sanding belt and the dust band.

Preferably, the dust belt unit is attached to the drive unit and can therefore also be moved along the rotor blade in the longitudinal direction.

The drive unit preferably has a drive carriage which can be moved in the longitudinal direction, on which the belt grinding unit and / or the dust belt unit are mounted so as to be movable perpendicular thereto. The drive unit serves the belt grinding unit and / or the dust belt unit during the respective processing along the rotor blade and onto the rotor blade to and from it.

The grinding device preferably also has a control unit which numerically controls at least the movements of the drive unit and / or the movements of the pressure elements in the direction of a rotor blade. The movement of the drive unit and / or the movements of the pressure elements in the direction of the rotor blade are preferably numerically controlled (NC) in order to grind the entire surface of the rotor blade with a uniform contact pressure and to the desired degree. The control unit causes the contours of the respective rotor blade to be traced by the drive unit.

Preferably, the grinding device further comprises a belt tensioner which holds the abrasive belt in a tension necessary for grinding.

Preferably, the abrasive belt is a perforated abrasive belt which is provided with perforations substantially over its entire surface. By using a perforated abrasive belt which, in contrast to ordinary abrasive belts, has many small, closely spaced perforations, the sanding dust on the abrasive surface has only a very short distance to travel through the sanding belt to be sucked backwards. Accordingly, the use of perforated abrasive belts reduces the risk of the abrasive belt clogging.

In a preferred embodiment, the grinding apparatus further comprises a coating unit for automatically coating the surface of a rotor blade, which is attached to the drive unit. Using a coating unit, the rotor blade can be recoated or repainted after grinding with the same device. This has the advantage that the rotor blade can remain on the system and not to a Painting plant must be moved. Furthermore, an automated coating is much more uniform than a manual job and without dangers for a painter.

Preferably, the coating unit has at least one automatically movable coating roller and / or at least one automatically movable spray unit and / or at least one radiant heater. The coating of the rotor blade can be carried out by rolling or by spraying, wherein the respective type of coating depends on the material used for the coating. After coating, or even parallel to this, the newly coated surfaces can be dried by means of a radiant heater accelerated. This reduces the total machining time of the rotor blade.

In a further embodiment of the invention, this relates to a ship for processing rotor blades of wind turbines with a grinding device as described above. Such a ship with a grinding device for mechanical grinding of rotor blades for wind turbines could be used in particular for the revision of rotor blades in offshore wind turbines. The possibility of grinding and re-coating the rotor blades directly on the sea reduces the transport times of the rotor blades during the overhaul and the wind turbine can be reused in a very short time.

4. Brief description of the drawings

Fig. 1:

eine Querschnittsansicht durch eine erste Ausführungsform einer erfindungsgemäßen Schleifvorrichtung zum maschinellen Schleifen von Rotorblättern für Windkraftanlagen;

Fig. 2:

eine Seitenansicht der Schleifvorrichtung gemäß Fig. 1;

Fig. 3:

eine Ansicht von oben einer weiteren Ausführungsform einer Schleifvorrichtung zum maschinellen Schleifen von Rotorblättern für Windkraftanlagen;

Fig. 4:

eine Querschnittsansicht einer Bandschleifeinheit im Eingriff mit einem Rotorblatt; und

Fig. 5:

eine Querschnittsansicht einer Bandreinigungsvorrichtung beim Reinigen eines Schleifbandes.

Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. In which shows:

Fig. 1:

a cross-sectional view through a first embodiment of a grinding device according to the invention for machine grinding rotor blades for wind turbines;

Fig. 2:

a side view of the grinding device according to Fig. 1 ;

3:

a top view of another embodiment of a grinding device for machine grinding rotor blades for wind turbines;

4:

a cross-sectional view of a belt grinding unit in engagement with a rotor blade; and

Fig. 5:

a cross-sectional view of a belt cleaning device when cleaning a sanding belt.

5. Description of preferred embodiments

Hereinafter, preferred embodiments of the invention will be described with reference to the figures. Individual features of the embodiments described herein may be combined with other embodiments of the invention.

Fig. 1 shows a side view of a grinding apparatus 1 for machine grinding of rotor blades 100. In Fig. 1 To the right of the rotor blade 100, a belt grinding unit 10 is arranged, which can grind a surface 110 of a rotor blade 100 of a wind turbine with a revolving grinding belt 12. As shown, the rotating abrasive belt 12 by means of guide rollers 22 out, which are attached to a main body 21 of the belt grinding unit 10. The drive of the sanding belt 12 via a controllable electric drive motor 20, which sets the grinding speed. So that the grinding belt 12 is always under the required tension, the belt grinding unit 10 is equipped with a belt tensioner 18, which acts on the belt 12 via a guide roller 22.

The belt grinding unit 10 has pressure elements 14, 15, which can be driven in the transverse direction Q to the main body 21 numerically controlled up and down and which press in the direction Z pneumatically against the back of the grinding belt 12. The pressure elements 14, 15 serve to press the sanding belt 12 with the required sanding pressure to the surface 110 of the rotor blade 100 and to apply this sanding pressure to any desired location of the surface 110 in a targeted manner. As a result of the mobility of the printing elements 14, 15 on the base body 21, it is possible to sand each surface area of the surface 110 with the desired pressure and the desired duration in a targeted manner.

The pressure elements 14, 15 can be moved pneumatically by means of one or more pneumatic cylinders 26 in the direction Z against the surface of the rotor blade in order to apply the necessary grinding pressure. The required grinding pressure can then be adjusted very easily via the pressure in the respective pneumatic cylinders 26. This has the advantage that even with changing geometries of the surface 110, the same defined grinding pressure can always be set for grinding. This happens purely by mechanical means, without the need for elaborate control devices are necessary.

The printing elements can be designed as movable segmental pressure bars 14 or pressure rollers 15, as described in detail in FIG Fig. 4 are shown. Exemplary is in Fig. 4 shown on the left side of a pressure element 15 with three pressure rollers 23 which press against the back of the grinding belt 12. Both the pressure element 15 as a whole, as well as the individual pressure rollers 23 are with corresponding Pneumatic cylinders 26 provided that are individually adjustable. For a precise and individually adjustable grinding of the surface 110 is possible. The pressure rollers 23 are surrounded by a suction hood 17, to which a negative pressure is applied in order to suck the grinding dust through the grinding belt 12 therethrough. As in Fig. 1 and Fig. 4 illustrated, the pressure elements 14, 15 may be further provided with guide rollers 22, which ensure a low-friction transition of the abrasive belt 12 to the pressure element 14, 15.

On the right side of the Fig. 4 a pressure element 14 in the form of a sectional pressure bar 14 is shown. The segmental pressure beam 14 as a whole is also pressed by a pneumatic cylinder 26 against the back of the abrasive belt 12, wherein the members 25 of the link pressure beam 14 are individually controllably pressed against the grinding belt 12 also via their own pneumatic cylinder 26. Again, an individually adjustable and pinpoint grinding of the surface 110 of the rotor blade 100 is possible. The segmented pressure bar 14 is provided with an exhaust (not shown) which acts on a suction hood 16. For effective extraction, the segmented pressure beam 14 is provided with openings that allow extraction of grinding dust through the abrasive belt 12.

The sanding belt 12 is preferably a perforated sanding belt which is provided with comparatively small perforation openings which have a diameter of preferably 1 mm to 4 mm and a spacing of the perforation openings from one another of preferably 10 mm to 20 mm. Through this perforation, it is possible to virtually dissipate the sanding dust from the grinding surface and suck it out through the sanding belt 12. Accordingly, a clogging of the abrasive belt is already reduced by this type of suction. The abrasive belt may otherwise be constructed of a base fabric having abrasive grains coated thereon and having a width of preferably 100-300 mm.

However, since the coatings to be ground in the manufacture and overhaul of rotor blades 100, namely gelcoat, filler, filler and cover layers are rather tough elastic, only a suction of the abrasive belt 12 can not be prevented by a mere suction alone. Therefore, the belt grinding unit 10 is further equipped with a belt cleaner 16 for the abrasive belt 12. The belt cleaning device 16 preferably comprises, as in Fig. 5 As a result, easily adhering dust particles detach from the grinding surface of the grinding belt 12, which can then be sucked off by a suction unit (not shown) connected to a suction hood 29. Furthermore, the belt cleaning device 16 comprises a brush 27, which are pressed by means of pressure cylinder 26 against the grinding surface of the sanding belt 12. The brush 27 also dissolves stuck, tough grinding dust, which is not yet removed by blowing off with the nozzle 28. The thus dissolved grinding dust is then sucked by means of the suction hood 29 and an additional suction 24, which is directed to the grinding side of the grinding belt 12.

With the belt cleaning device 16, it is possible to virtually completely clean the sanding belt 12 of adhering sanding dust of the viscoelastic coatings of the rotor blade 100. In this case, the fact is exploited that only a part of the grinding belt 12 is always in engagement with the surface 110 of the rotor blade 100 and a large part of the grinding belt 10 is freely accessible, in particular for belt cleaning.

As in the Fig. 1 . 2 and 3 shown, the belt grinding unit 10 by a drive unit 30 along the rotor blade 100 is movable. This is preferably done by an electrically driven drive carriage 32, which is guided on rails 33, numerically controlled (NC) along the longitudinal axis L of the rotor blade can be moved. On the drive carriage 32, in turn, with an electrically driven carriage 34, the belt grinding unit 10 is numerically total controlled (NC) in the direction Z on the rotor blade 100 to or from the rotor blade 100 movable away.

Together with the individual mobility of the printing elements 14, 15 within the belt grinding unit 10 in the transverse direction Q and direction Z and the mobility of the belt grinding unit 10 overall in the longitudinal direction L, the surface 110 of the rotor blade 100 can thus be ground precisely at any point.

As in Fig. 1 In order to grind the profile nose or the lower shell of the rotor blade, it is also possible to rotate the rotor blade 100 about the longitudinal axis L and for machining the rotor blade in determine the desired positions 100. However, it is also possible to equip the grinding devices with a plurality of belt grinding units 10 so that the rotor blade 11 can be machined on both sides or on all sides at the same time. It is further advantageous that opposite belt grinding units 10 each exert a counter-pressure on the rotor blade 100, so that a bending of the rotor blade 100 is largely avoided during grinding.

In a similar manner as the belt grinding unit 10 is in Fig. 1 mounted on the left side of a dust belt unit 40 with a rotating dust belt 42 on the grinding device 1. A base body 41 carries guide rollers 49, which ensure the circulation of a dust belt 42. The dust band 42 is guided along the surface 110 of a rotor blade 100 in order to pick up the resulting grinding dust there and to almost completely clear the surface 110 of dust. This can be done with a dust belt unit 40 automatic wiping or dedusting of the rotor blade 100. The dust belt unit 40 has a belt tensioner 48 which holds the dust belt 40, which preferably consists of a nonwoven material, in the required tension.

The dust belt unit preferably has pneumatically controlled pressure elements 44 which press the dust belt 42 against the surface 110. The printing elements 44 can be moved up and down on the main body 41 in the transverse direction Q to selectively press the dust belt 42 to the desired location of the surface 110 of the rotor blade 100. The pressure elements 44 are constructed similarly to the pressure elements 14, 15 for the abrasive belt 12, which in Fig. 4 are shown.

The pressure elements 44 furthermore have a suction hood 47 in order to suck the dust absorbed by the dust band 42 out of the dust band 42. In addition, the dust belt unit 40 is also provided with a belt cleaning device 46, which essentially corresponds to the belt cleaning device 16 of the abrasive belt 12, which in FIG Fig. 5 is shown. By this belt cleaning device 46, the dust belt 42 is continuously cleaned by the recorded grinding dust, so that clogging of the dust belt 42 is avoided.

The dust belt unit 40 as a whole is similar to the belt grinding unit 10 on the movable drive carriage 32 by means of another in the Z direction numerically controlled (NC) movable and electrically driven carriage 35 stored so that the entire surface 110 of the rotor blade 100 can be cleaned.

As in Fig. 2 As shown, the grinding apparatus 1 further comprises a coating unit 50 which serves to automatically coat the surface 110 of a rotor blade 100. The coating unit 50 may comprise at least one automatically displaceable coating roller 52 and / or at least one automatically movable spray unit and / or at least one radiant heater 54 (cf. Fig. 3 ) exhibit. By means of such a coating unit 50, the ground and cleaned rotor blade 100 can be coated with the next layer of the layer system to be applied. Depending on the viscosity of the coating to be applied, a spray unit (not shown) or an automatically movable coating roller 52 is used.

So that the newly applied coating dries faster and the rotor blade 100 can be further processed faster, the grinding apparatus 1 can also be equipped with at least one electric radiant heater 54, which can likewise be positioned at any point on the surface 110 of the rotor blade 100.

Rotor blades 100 for wind turbines must be serviced at regular intervals and, if required by damage and stress, also be recoated. For this purpose, the surface 110 of the rotor blade 100 is abraded and provided with a new coating. Since many of the wind turbines are installed in the sea (so-called offshore wind turbines) is provided to provide a ship for processing rotor blades of wind turbines, on which an automatic grinder 1, as described above, is installed. Thus, a revision of the rotor blades 100 is possible on site and it reduces the transport routes. Due to the complete automation of grinding, cleaning and recoating, these processes can also be carried out on a constantly moving ship.

LIST OF REFERENCE NUMBERS

1

grinder

10

Belt grinding unit

12

sanding belt

14

Pressure element as a sectional pressure bar

15

Pressure element with pressure rollers

16

Belt cleaning device

17

exhaust hood

18

belt tensioner

20

drive motor

21

body

22

guide rollers

23

pressure rollers

24

suction

25

Limbs of the limb pressure bar

26

pressure cylinder

27

brush

28

jet

29

exhaust hood

30

drive unit

32

drive car

33

rails

34

dare

35

dare

40

Dust belt unit

41

body

42

dust lane

44

print elements

46

Belt cleaning device

47

exhaust hood

48

belt tensioner

49

guide rollers

50

coating unit

52

coating roll

54

heater

100

rotor blade

110

Surface of the rotor blade

Claims (15)

1. Grinding device (1) for machine-based, automated grinding of rotor blades (100) for wind energy systems,
   characterized in that
   the grinding device (1) comprises a belt grinding unit (10) with a circulating grinding belt (12).
2. Grinding device according to claim 1, further comprising a drive unit (30) for moving the belt grinding unit (10) in the direction (L) of the longitudinal axis of a rotor blade (100).
3. Grinding device according to one of the claims 1 or 2, further comprising a dust belt unit (40) with a circulating dust belt (42) that is guided along at at least one surface (110) of a rotor blade (100), in order to remove dust from the surface (110) of the rotor blade (100).
4. Grinding device according to one of the claims 1 - 3, further comprising at least one belt cleaning device (16, 46).
5. Grinding device according to claim 4, wherein the belt cleaning device (16, 46) cleans the grinding belt (12) and/or the dust belt (42) by means of:

   a) a nozzle (28) for blowing on of pressurized air; and/or

   b) a device (24) for suctioning grinding dust; and/or

   c) a brush (27) for brushing the grinding belt (12) and/or the dust belt (42).
6. Grinding device according to claim 2, wherein the belt grinding unit (10) comprises pressure members (14, 15, 44) that press the grinding belt (12) and/or the dust belt (42) against a surface (110) of a rotor blade (100) and that are supported at the drive unit (30).
7. Grinding device according to claim 6, wherein the pressure members (14, 15, 44) comprise in direction (Q) of the transverse axis of a rotor blade (100) moveable element pressure bars (14) or pressure rollers (15) at the drive unit (30) that can be moved preferably pneumatically to the surface (110) of a rotor blade (100) in order to define the grinding pressure of the grinding belt (12) and/or the cleaning pressure of the dust belt (42) onto the surface (110).
8. Grinding device according to one of the claims 6 or 7, wherein the pressure members (14, 15, 44) comprise a suction hood (17, 47), in order to suck grinding dust through the grinding belt (12) and/or the dust belt (42) and through the pressure member (14, 15, 44).
9. Grinding device according to one of the claims 3 - 8, wherein the dust belt unit (40) is mounted at the drive unit (30).
10. Grinding device according to one of the claims 2 - 9, wherein the drive unit (30) comprises a drive wagon (32) moveable in longitudinal direction (L) on which perpendicular thereto (Z) the belt grinding unit (10) and/or the dust belt unit (40) are moveably supported.
11. Grinding device according to one of the claims 2- 10, further comprising a control unit that controls numerically at least the movements of the drive unit (30) and/or the movements of the pressure members (14, 15) in direction (Z) of the rotor blade (100).
12. Grinding device according to one of the claims 1 - 11, further comprising a belt tensioner (18) that provides the grinding belt (12) with the tension that is necessary for grinding.
13. Grinding device according to one of the claims 1 - 12, wherein the grinding belt (12) is a perforated grinding belt, which is provided essentially over its entire surface with perforation openings.
14. Grinding device according to one of the claims 1 - 13, further comprising a coating unit (50) for automated coating of the surface (110) of a rotor blade (100), wherein the coating unit (50) is mounted to the drive unit (30).
15. Grinding device (1) according to claim 14, wherein the coating unit (50) comprises:

    a) at least one automatically moveable coating roller (52); and/or

    b) at least one automatically moveable spray unit; and/or

    c) at least one radiant heater (54).

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