WO2016111625A1

WO2016111625A1 - Vehicle urged against a magnetizable wall by magnetic forces

Info

Publication number: WO2016111625A1
Application number: PCT/NL2016/050010
Authority: WO
Inventors: Andries Van Berkum; Kamiel Reinier Zale Geenen; Pim Johan Hans GIJSBERS; Johannes Andreas RANSDORP; Simon Alexander Verheul
Original assignee: Stichting Quick Docking
Priority date: 2015-01-09
Filing date: 2016-01-08
Publication date: 2016-07-14
Also published as: NL2014104B1; NL2014104A

Abstract

The invention relates to a vehicle for transporting a load along a magnetizable wall, which vehicle is configured to be urged against the wall by magnetic forces, comprising a frame, at least four wheels bearing-mounted in the frame, a motor for driving at least one of the wheels, at least one magnet connected to the frame and load-bearing means for supporting the load, wherein at least four of the wheels are bearing-mounted in the frame at the corners of a rectangular structure and the magnet is placed inside the rectangular structure. Due to the placing of the magnet inside the rectangular structure the attractive force generated by the magnet is applied within the reactive forces generated by the at least four wheels, so that an inherent stability is obtained. The invention further relates to a device provided with such a vehicle and to a method to be performed with such a vehicle.

Description

Vehicle urged against a magnetizable wall by magnetic forces

The invention relates to a vehicle for transporting a load along a magnetizable wall, wherein the vehicle is configured to be urged against the wall by magnetic forces, wherein the vehicle is provided with a frame with at least four wheels which are each bearing-mounted in the frame by means of a shaft, a motor for driving at least one of the wheels, at least one magnet connected to the frame and load-bearing means for supporting the load. Such a vehicle finds application for instance in the treatment of hulls of ships in dock, such as cleaning or applying a paint layer to the ship's hull by means of spraying. The load comprises here a tool for carrying out work. This is because this is work which is difficult to carry out manually, due in part to the usually great height of a ship's hull and the climbing equipment required therefor, and which are preferably carried out by machines in order to ensure the quality of the work carried out. Ships' hulls are usually manufactured from magnetizable material such as steel, which provides the option in principle of making use of magnetic forces for the attachment between the vehicle and the ship's hull. The invention further relates to a method for transporting a load over a magnetizable wall by means of a vehicle, which is urged against the wall by magnetic forces.

Both the device and the method are known from US-A-2013/0140801. In this prior art device magnets are received in the running gear of a caterpillar track or are placed between the wheels in the direction of travel of the wheels. This has the result that the forces generated by the magnet lie in the same plane as the reactive forces generated by the wheels, such that such devices of themselves have insufficient stability. Stability can be obtained by combining such a device with a second device which is placed in a different plane, which necessitates more magnets, makes the construction more complex and increases costs. The distance between the magnet and the surface of the wall moreover has to be great in order to prevent the magnet being scraped along the wall. Such a great distance requires powerful and expensive magnets.

The invention has for its object to avoid these drawbacks. The invention provides for this purpose a vehicle of the above stated type, wherein at least four of the wheels are bearing-mounted in the frame at the corners of a rectangular structure and the at least one magnet is placed inside the rectangular structure.

Due to the placing of the magnet inside the rectangular structure the attractive force generated by the magnet is applied within the reactive forces generated by the at least four wheels, so that an inherent stability is obtained. It is also possible in principle to make use of a magnet with a changeable distance between the wall and the magnet, although this requires a complicated construction.

The invention further provides a method of the above stated type, wherein the magnetic forces are generated by at least one magnet which is enclosed between at least four wheels with which the vehicle travels over the wall and at least one of which is driven.

A structurally attractive embodiment provides the measure that the vehicle comprises two shafts bearing-mounted in the frame, two wheels are placed on each shaft and that a caterpillar track is arranged around each pair of wheels lying in the same plane.

Applying caterpillar tracks increases the contact surface area between the wall and the vehicle, so that the normal pressure on the wall can be limited to a low value, which enables travelling over vulnerable layers, such as paint layers, on the wall.

This embodiment also prevents a method wherein the magnet is placed between two caterpillar tracks which are each arranged around two wheels.

In order to distribute the forces over the whole part of the caterpillar track which rests on the wall it is recommended for the frame to be provided with frame parts lying between the wheels and at the position of the two caterpillar tracks, and for slide plates to be placed between these frame parts and the sections of caterpillar track lying thereunder. The force exerted on the caterpillar tracks in the part between the wheels is hereby transmitted to the frame. It is otherwise also possible to place slide plates between the frame parts and the part of the caterpillar track situated thereabove; sagging of the caterpillar tracks is hereby prevented. In order to keep the normal pressure on the wall as uniform as possible, so that extreme values which could result in damage to layers applied to the wall, it is recommended for the caterpillar track to comprise blocks manufactured from resilient material, these blocks each being pivotally connected to each other at their inward directed ribs. The extent to which the resilient material can be compressed preferably differs greatly at moderately varying pressures. It is otherwise also possible to make use of caterpillar tracks manufactured as a whole from flexible material and embodied without hinges.

According to a structurally simple embodiment, the caterpillar track comprises a plastic belt, on the outer side of which the blocks of resilient material are arranged.

The belt is preferably a belt toothed on the inner side, the teeth of which extend over only a part of the width of the blocks and connecting to the edges, wherein a strip in the centre of the belt is left clear, a string is placed in this strip and the wheels are provided with guide grooves configured to receive the string. If guide plates are present these are preferably also provided with guide grooves for receiving the string.

In order to make effective use of the magnets it is recommended that two magnets are mounted on the auxiliary frame, that the magnetizing direction of the magnets extends transversely of the plane of the two shafts but in opposite direction, and that the side of the magnets remote from the wall is connected by a piece of magnetizable material. It is otherwise not precluded that larger numbers of permanent magnets are applied, wherein they are directed for the purpose of enhancing each other's action. Nor is it precluded to apply electromagnets, optionally to support the permanent magnets.

In order to enable heavy loads to be transported over the wall it is recommended that the frame is provided with a main frame and with at least two auxiliary frames, that the load-bearing means are connected to the main frame, that each of the auxiliary frames comprise two shafts bearing-mounted in the frame, that two wheels are placed on each shaft, that a caterpillar track is arranged around each pair of wheels with a common plane of rotation and that at least one magnet is placed in each auxiliary frame. This is because the load is hereby distributed over two auxiliary frames, the magnets associated therewith and the caterpillar tracks. In order to enable heavier loads to be transported another embodiment provides the measure that the frame is provided with four auxiliary frames, that each of the auxiliary frames comprises two shafts bearing-mounted in the frame, that two wheels are placed on each shaft and that a caterpillar track is arranged around each pair of wheels with a common plane of rotation, and that at least one magnet is placed in each auxiliary frame.

According to a structurally attractive embodiment, the main frame has an H-shaped structure, an auxiliary frame is connected to the main frame at each end of a leg of the H-shaped structure by means of a cardan joint, and the transverse part of the H-shaped structure is connected to the load-bearing means. This embodiment also enables the caterpillar tracks to remain in constant contact with the wall so that the stability is increased. According to a structurally attractive embodiment, the main frame is provided with rods extending downward from the ends of the legs of the H-shaped structure and each connected to the associated auxiliary frame by the cardan joint, and the piece of magnetizable material extends on either side of the cardan joint. Since the auxiliary frames usually provide little space, according to a further embodiment each auxiliary frame is provided with a motor and each motor is placed above a shaft of the auxiliary frame. This placing enables the motor shaft to be connected to the associated shaft by means of a toothed belt. In order to make the position of the load as stable as possible, i.e. as insensitive to unevenness in the wall as possible, the transverse part of the H-shaped structure is further preferably rotatably connected on either side to a combination, which is embodied as a single rod, of two horizontal legs of the H-shaped structure lying mutually in line, and the two rods are connected to an equalizing member configured to make the load-bearing means connected to the transverse part take up an angular position which is the average of the angular position of the two rods. Another embodiment provides the measure that the load-bearing means are configured to be connected to a tool which is configured to treat the wall over which the vehicle is moved. This embodiment further provides a method wherein the load comprises a tool which performs a treatment on the wall while the vehicle travels.

Performing a treatment on a wall usually entails the whole surface area of the wall having to be treated. It is recommended for this purpose that the load-bearing means comprise a manipulator connected to a part of the load-bearing means which is connected to the transverse part of the main frame, and that the manipulator is configured to bring about a reciprocal swinging movement extending substantially transversely of the direction of movement of the vehicle. The tool mounted on an end of the manipulator can hereby reach the whole surface area of the wall.

This embodiment further provides a method wherein the tool performs a reciprocal movement transversely of the direction of travel of the vehicle while the treatment is being performed. In order to achieve a uniform coverage of the surface of the wall the vehicle is preferably provided with a control unit for controlling the drive unit of the motors and of the manipulator, and the drive units of the pivot arm and manipulator are controlled in mutual dependency. The control unit is preferably provided with a camera for detecting the wall and for controlling the motors and the drive unit of the pivot arm on the basis of the detected image.

The coverage of the treatment of the surface of the wall is optimal when the control unit is configured to make the tool perform a movement extending substantially according to an intersecting line between a flat plane and the surface of the wall during travel of the vehicle. This embodiment also provides a method wherein the tool performs a movement extending substantially according to an intersecting line between a flat plane and the surface of the wall during travel of the vehicle. Although treatments on the wall such as cleaning or blasting are not precluded, the advantages of the invention become particularly manifest when the load-bearing device is configured to be connected to a paint spraying device.

This embodiment moreover provides a method wherein the treatment is the spraying of a paint layer.

The invention further relates to a device for performing a treatment on a magnetizable wall, comprising a vehicle of the above stated type which is provided with a holding station configured to receive the vehicle, wherein the holding station is connected to the movable end of a macromanipulator. This provides the option of delivering the vehicle to the wall to be treated, of temporarily storing the vehicle when no work is being carried out, and of removing the vehicle from the treated wall.

This embodiment further provides a method wherein the vehicle is initially placed in a holding station, leaves the holding station and carries out the treatment, and travels to the holding station and is received in the holding station after carrying out the treatment.

It is attractive if before placing the vehicle on the wall the holding station is initially placed onto the wall, the vehicle is then moved from the holding station, wherein the distance between the vehicle and the wall is gradually reduced, and the vehicle is moved into the holding station placed on the wall when the vehicle is removed from the wall, wherein the distance between the vehicle and the wall is gradually increased and the holding station is then moved away from the wall. The magnetic forces which prevail between the vehicle and the wall when permanent magnets are applied in the vehicle and which can hardly be influenced in other manner can hereby be gradually reduced when the vehicle moves in the direction having a small component in the direction of the force, and can be gradually increased when the vehicle travels from the holding station and onto the wall. It must of course be ensured that the vehicle is retained in the holding station in the case of small magnetic forces. In order to supply electrical energy and materials to be used in the treatment, such as (optionally pressurized) paint, cleaning fluid or blasting grit, the vehicle is also coupled to the macromanipulator by means of a cable when it is located outside the holding station.

The invention will be elucidated hereinbelow with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a ship in dock, with a wall which is treated with a vehicle according to the invention;

Figure 2 is a detail view of a vehicle according to the invention;

Figure 3 is an exploded view of an auxiliary frame of the vehicle shown in figure 2 with the parts connected thereto; and

Figure 4 is a cross-sectional perspective view of the auxiliary frame shown in figure 3.

Figure 1 shows a wall 1 of a ship 2 placed in a dock. A paint layer has to be arranged on wall 1, for which purpose use is made of a device provided with a macromanipulator 3, which is placed on floor 4 of the dock. Arranged on the free end of the arm of the macromanipulator is a coupling station 5 which can be moved against wall 1 by macromanipulator 3.

The device further comprises a base station 6 placed on floor 4 of the dock and configured to supply electrical energy to the treatment device as discussed below. Base station 6 is provided with supply means for supplying to the treatment device substances which are used in the treatment, such as paint, which is optionally supplied pressurized and for which purpose base station 6 can be provided with a compressor 7, or water or compressed air, for which purpose base station 6 can be provided with a pump.

Finally, the device comprises a treatment device 10. This treatment device can be placed into the coupling station on floor 4 and, once placed therein, be moved to the wall by means of macromanipulator 3. Treatment device 10 can then advance from coupling station 5 and over wall 1, wherein it attaches to steel wall 1 owing to magnetic forces. After the required work has been carried out, treatment device 10 moves back to coupling station 5, which is moved to floor 4 by means of the macromanipulator. For supply of electrical energy and agents necessary in the treatment, such as paint, compressed air or cleaning fluid, treatment device 10 is connected by means of a cable 11 to base station 6. This cable can be guided via coupling station 5.

The construction of treatment device 10 will be discussed below with reference to figure 2, which shows a perspective view of this treatment device. This treatment device 10 comprises a vehicle 12 and a tool 13. The vehicle comprises a substantially H-shaped frame 14 comprising two beams 15 extending in the direction of travel and transverse part 16 connecting these beams. Legs 17 extending toward wall 1 are arranged on the four ends of the beams, and placed at the end of each of these legs 17 is a cardan coupling 18, each of these couplings being connected to an auxiliary frame 20. The construction of auxiliary frame 20 is elucidated with reference to figures 3 and 4. Auxiliary frame 20 takes the form of a sleeve 20a, at each end of which are arranged two bearings 21, through each of which a shaft 22 extends. Shafts 22 are provided on either side of frame 20 with a wheel 23, and placed on each pair of wheels 23 on a side of the frame is a caterpillar track 24.

Caterpillar tracks 24 each comprise a series of blocks 25 of resilient soft material, the surface of which has a high coefficient of friction. Blocks 25 are each mounted on a wide belt 26. This placing enables blocks 25 to move apart on their outer side to be able to pass through the bend formed by wheels 23. Belt 26 is provided on its inner side with two sets of teeth 26a, each extending over only a part of the width and connecting to the edges of the belts, wherein a strip has been left clear in the centre, on which strip a string 26b is placed.

Placed on one side above auxiliary frame 20 is a motor 27 with output shaft 27a which is coupled to one of the two shafts 22 by means of a toothed belt 27b for the purpose of driving shaft 22, and thereby wheels 23 and the caterpillar tracks 24 arranged therearound. The motor can be formed by an electric motor or by a hydromotor.

Arranged between the lower part of caterpillar track 24 and the associated ear 20b is a slide plate 28 which absorbs a significant part of the forces to be transmitted to the auxiliary frame by wall 1. A slide plate 29 which prevents sagging of the caterpillar track is arranged between the upper part of caterpillar track 24 and the associated ear 20b. Arranged in the running surface of wheels 23 and in slide plates 28 and 29 are guide grooves 30, in which strings 26b of belt 26 fit. These guide grooves 30 guide the caterpillar tracks, particularly when passing through bends and when wall 1 is not flat.

Arranged in the centre of sleeve-like part 20a of auxiliary frame 20 is an opening 31, into which the end of the associated leg 17 extends and in which cardan coupling 18 is placed. Cardan coupling 18 is connected to sleeve-like part 20a of frame 20 by means of plates 32 and bolts 33. Cardan coupling 18 is placed as low as possible in auxiliary frame 20 in order to keep the reactive forces as small as possible.

A soft-iron plate 34 is arranged under sleeve-like part 20a of frame 20 by means of bolts, which plate 34 is provided with an opening 35 which corresponds to the opening 31 arranged in frame 20. Arranged under each of the ends of plate 34 is a respective permanent magnet 35a, 35b, these with the magnetizing direction in the direction transversely of the plane of the wall over which the vehicle can travel and with the magnetizing direction in opposite direction. A magnetic circuit is thus obtained which extends from the wall to the magnetizable wall via a first air gap between the wall and magnet 35a, via first magnet 35a, via soft-iron plate 34, via second magnet 35b and via the second air gap between second magnet 35b and the wall. This placing of the magnets between caterpillar tracks 24 enables the gaps to be made as small as possible, so that smaller and lighter magnets can suffice in generating the required attractive force.

A support beam 40, which serves as support for the tool, is arranged on transverse part 16 of the H- shaped frame of the vehicle for rotation about transverse part 16. The position of support beam 40 relative to the position of beams 15 is determined by a rod mechanism 41 which is configured to make support beam 40 take up a position which is the average of the positions of the two beams 15. A manipulator 42 in the form of a multi-way pivot arm is arranged on the free end of the support beam together with the drive unit 43 associated with the pivot arm. The drive unit is configured to make the tool perform a desired movement by controlling linear drive members at the position of hinges between support beam 40 and first pivot arm 42a, between the two pivot arms 42a and 42b, and between second pivot arm 42b and tool 13. Drive unit 43 is configured to control the pivot arm consisting of parts 42a and 42b such that it performs the desired reciprocal movement. This is substantially a linear movement, although it is likewise possible to perform a movement which takes the form of a lemniscate. In combination with a uniform movement of the vehicle, this form produces the best possible coverage of the surface of the wall. Such manipulators are per se known from the field of robotics.

Mounted on the free end of manipulator 42 is tool 13, which in the shown embodiment is formed by a spraying device for applying a paint layer to the wall by means of spraying. It is of course possible to apply other types of tool, such as cleaning or blasting devices.

The operation of the device will now be elucidated. Starting from a position in which treatment device 10 is on the floor of the dock, wherein treatment device 10 is situated in coupling station 5, boom lift 3 moves coupling station 5 with treatment device 10 placed therein to wall 1. The treatment device then leaves coupling station 5, wherein the distance between the treatment device and the wall is reduced and the air gap between the magnets and the wall becomes so small that the magnetic force is sufficiently great to hold the treatment device against the wall, and the treatment device travels to the desired starting position.

Control unit 43 of manipulator 42 is then switched on so that the spraying device begins to perform its reciprocal movement, and pump 6 in the base station is then switched on and paint is supplied via cable 11. The tool thus applies a paint layer to the surface of wall 1 by means of spraying, wherein the spraying device performs a reciprocal movement and the vehicle performs a linear movement, wherein the two movements are adapted to each other so as to obtain a good coverage of the wall. The spraying is temporarily stopped when the vehicle changes track and resumes when the vehicle has reached a new track.

When the spraying operations have been completed, the vehicle travels to coupling station 5 and then enters the coupling station, wherein the distance between the vehicle and the wall is gradually increased and the magnetic force decreases as the distance increases. When the vehicle has been wholly received in the coupling station the boom lift returns the coupling station to the floor of the dock together with the treatment device. It will be apparent that numerous variations of the embodiment shown here can be applied within the context of the invention as defined by the appended claims.

Claims

1. Vehicle for transporting a load along a magnetizable wall, wherein the vehicle is configured to be urged against the wall by magnetic forces, comprising:

- a frame;

- at least four wheels bearing-mounted in the frame by means of a shaft;

- a motor for driving at least one of the wheels;

- at least one magnet connected to the frame; and

- load-bearing means for supporting the load,

characterized in that at least four of the wheels are bearing-mounted in the frame at the corners of a rectangular structure and that the at least one magnet is placed inside the rectangular structure.

2. Vehicle as claimed in claim 1, characterized in that the vehicle comprises two shafts bearing-mounted in the frame, that two wheels are placed on each shaft and that a caterpillar track is arranged around each pair of wheels lying in the same plane.

3. Vehicle as claimed in claim 2, characterized in that the frame is provided with frame parts lying between the wheels and at the position of the two caterpillar tracks, and that slide plates are placed between these frame parts and the sections of caterpillar track lying thereunder.

4. Vehicle as claimed in claim 2 or 3, characterized in that the caterpillar track comprises blocks manufactured from resilient material, these blocks being pivotally connected to each other at their inward directed ribs.

5. Vehicle as claimed in claim 4, characterized in that the caterpillar track comprises a plastic belt, on the outer side of which the blocks are attached.

6. Vehicle as claimed in claim 5, characterized in that the belt is a belt toothed on the inner side, the teeth of which extend over only a part of the width of the belt and adjacent to the edges of the belt, a strip in the centre of the belt is left clear, a string is placed in this strip and the wheels are provided with guide grooves configured to receive the string.

7. Vehicle as claimed in any of the foregoing claims, characterized in that two magnets are mounted on the frame, that the magnetizing direction of the magnets extends transversely of the plane of the two shafts but in opposite direction, and that the side of the magnets remote from the wall is connected by a piece of magnetizable material.

8. Vehicle as claimed in any of the foregoing claims, characterized in that the frame is provided with a main frame and with at least two auxiliary frames, that the load-bearing means are connected to the main frame, that each of the auxiliary frames comprise two shafts bearing-mounted in the frame, that two wheels are placed on each shaft, that a caterpillar track is arranged around each pair of wheels with a common plane of rotation and that at least one magnet is placed in each auxiliary frame.

9. Vehicle as claimed in claim 8, characterized in that the frame is provided with four auxiliary frames, that each of the auxiliary frames comprises two shafts bearing- mounted in the frame, that two wheels are placed on each shaft and that a caterpillar track is arranged around each pair of wheels with a common plane of rotation, and that at least one magnet is placed in each auxiliary frame.

10. Vehicle as claimed in claim 9, characterized in that the main frame has an Pi- shaped structure, that an auxiliary frame is connected to the main frame at each end of a leg of the H- shaped structure by means of a cardan joint, and that the transverse part of the H-shaped structure is connected to the load-bearing means.

11. Vehicle as claimed in claim 10, characterized in that the main frame is provided with rods extending downward from the ends of the legs of the H-shaped structure and each connected to the associated auxiliary frame by the cardan joint, and that the piece of magnetizable material extends on either side of the cardan joint.

12. Vehicle as claimed in claim 9, 10 or 11, characterized in that each auxiliary frame is provided with a motor and that each motor is placed above a shaft of the auxiliary frame.

13. Vehicle as claimed in claim 11 or 12, characterized in that the transverse part of the H-shaped structure is rotatably connected on either side to a combination, which is embodied as a single rod, of two horizontal legs of the H-shaped structure lying mutually in line, and that the two rods are connected to an equalizing member configured to make the load-bearing means connected to the transverse part take up an angular position which is the average of the angular position of the two rods.

14. Vehicle as claimed in any of the foregoing claims, characterized in that the load-bearing means are configured to be connected to a tool which is configured to treat the wall over which the vehicle is moved.

15. Vehicle as claimed in claim 14, characterized in that the load-bearing means comprise a pivot arm which is pivotally connected to a part of the load-bearing means which is connected to the transverse part of the main frame, and that the pivot arm is coupled to a drive unit so as to bring about a reciprocal swinging movement extending substantially transversely of the direction of movement of the vehicle.

16. Vehicle as claimed in claim 15, characterized by a control unit for controlling the drive unit of the pivot arm and for controlling the motors and the drive unit of the pivot arm in mutual dependency.

17. Vehicle as claimed in claim 16, characterized in that the control unit is provided with a camera for detecting the wall and for controlling the motors and the drive unit of the pivot arm on the basis of the detected image.

18. Vehicle as claimed in claim 16 or 17, characterized in that the control unit is configured to make the tool perform a movement extending substantially according to an intersecting line between a flat plane and the surface of the wall during travel of the vehicle.

19. Vehicle as claimed in claim 18, characterized in that the load-bearing means are configured to be connected to a paint spraying device.

20. Device for performing a treatment on a magnetizable wall, comprising a vehicle as claimed in any of the claims 14-19, characterized in that the device is provided with a holding station configured to receive the vehicle and that the holding station is connected to the movable part of a macromanipulator.

21. Device as claimed in claim 20, characterized in that the holding station is provided with a support surface configured to support the vehicle, wherein the support surface encloses a small angle with the wall when the holding station is placed against the wall.

22. Device as claimed in claim 20 or 21, characterized in that the device is configured to apply a paint layer to the magnetizable wall by means of spraying.

23. Method for transporting a load over a magnetizable wall by means of a vehicle which is urged against the wall by magnetic forces, characterized in that the magnetic forces are generated by at least one magnet which is enclosed between at least four wheels with which the vehicle travels over the wall and at least one of which is driven.

24. Method as claimed in claim 23, characterized in that the magnet is placed between two caterpillar tracks which are each arranged around two wheels.

25. Method as claimed in claim 24, characterized in that the vehicle is urged against the wall by four magnet units, each enclosed between two caterpillar tracks.

26. Method as claimed in any of the claim 22-25, characterized in that the load comprises a tool which treats the wall during travel of the vehicle.

27. Method as claimed in claim 26, characterized in that the tool performs a reciprocal movement transversely of the direction of travel of the vehicle while the treatment is being performed.

28. Method as claimed in claim 27, characterized in that the tool performs a movement extending substantially according to an intersecting line between a flat plane and the surface of the wall during travel of the vehicle.

29. Method as claimed in claim 26, 27 or 28, characterized in that the treatment is the spraying of a paint layer.

30. Method as claimed in any of the claims 26-29, characterized in that the vehicle is initially placed in a holding station, leaves the holding station and carries out the treatment, and travels to the holding station and is received in the holding station after carrying out the treatment.

31. Method as claimed in claim 30, characterized in that before placing the vehicle on the wall the holding station is initially placed onto the wall, the vehicle is then moved from the holding station, wherein the distance between the vehicle and the wall is gradually reduced, and the vehicle is moved into the holding station placed on the wall when the vehicle is removed from the wall, wherein the distance between the vehicle and the wall is gradually increased and the holding station is then moved away from the wall.