A suction cup device

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a suction cup device intended to be attached to a wall surface in a liquid filled space, wherein the suction cup device comprises at least a suction cup, which comprises a cup-shaped recess and a front surface which defines an opening to the cup-shaped space, and vacuum generating means, which is adapted to provide a negative pressure in the cup-shaped recess of the suction cup for attaching the suction cup to the wall surface.

It is known to equip such a suction cup device with measuring equipment which uses ultrasonic technique, eddy current technique, visual technique or other testing technique for indicating defects in spaces difficult of access. The suction cup device may also carry with itself equipment for performing repair works. When the suction cup device is attached to a wall surface by means of its suction cups, the equipment carried with it is activated. Reactor tanks in nuclear plants have areas which have to be checked regularly for security reasons. The reactor tank is the pressure vessel in which the power production process occurs during operation. During shutdown and services, the internal parts of the reactor are picked out of the reactor tank and are placed on determined putting up places in surrounding basins. This occurs when the basins are filled with reactor water. The suction cup device shall be able to be attached on substantially all wall surfaces of the reactor tank and on the internal

parts. Thereby, the suction cup device shall, inter alia, be able to be moved down and be attached to wall surfaces which define the narrow gap between the reactor tank and an internally located moderator tank.

A problem with conventional suction cup devices is that it is difficult to get the suction cups to attach to a wall surface. All suction cups of the suction cup device have to be in a position very close to a wall surface in order it to be possible to create a suf- ficient negative pressure in the suction cups in relation to surround pressure in order for them to be able to get caught to the wall surface. To move the suction cups to such a position is particularly difficult in narrow and liquid filled spaces such as in the above-described gap-shaped space between the moderator tank and the reactor tank. It is known to from a bridge extending over a reactor basin by means of elongated lifting rods exert a force which moves the suction cup device towards the reactor wall. However, this force is very difficult to accomplish since it is perpendicular to the longitudinal direction of the lifting rods. Fur- thermore, the suction cups thus have to be moved to a position where they nearly abut against the wall surface in order for it to be possible to establish a negative pressure in the suction cups. The above-described work to move the suction cups to such an attachment position requires a very high precision and this work can therefore be very time consuming.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a suction cup device which has a construction such that it relatively quickly and with a good precision can be steered to a position in relation to a wall surface such that a negative pressure can be created in its suction cup such that it attaches to the wall surface. Another object is to provide a suction cup device having few in- eluded components and substantially no movable parts.

The first object is achieved with a suction cup device which comprises force-generating means, which are adapted to provide a flow of a first medium in the liquid filled space in such a direction in relation to the suction cup device such that a reac- tion force is created which moves the front surface of the suction cup towards the wall surface. Before said force-generating means is activated, the suction cup device is preferable set in a turning position such that the opening of the suction cup substantially is directed towards the wall surface. Thereafter, said force-generating means is activated such that a medium flow is created in a direction in the liquid filled space such that the reaction force moves the suction cup device towards the wall surface. Consequently, said force-generating means provides a fine positioning of the suction cup device in relation to the wall sur- face to a position from which it is possible to attach the suction cup to the wall surface. Said force-generating means is at least activated until the suction cup is in such an attachment position in relation to the wall surface. In the attachment position of the suction cup, the gap between the front surface of the suction cup and the wall surface has become so small that said vacuum generating means can suck out a larger quantity of the liquid medium from the cup-shaped space of the suction cup than that which flows into the space. Thereby, the pressure inside the cup-shaped space decreases in relation to the surrounding pressure. Thereby, the wall surface closes the opening of the suction cup and a negative pressure is created in the cup- shaped space of the suction cup of a magnitude which leads to the fact that the suction cup is safely retained against the wall surface.

According to a preferred embodiment of the present invention, said first medium, which is used by said force-generating means, is the same liquid, which is used in the liquid filled space. Thus, no problems arise with mixtures of different mediums in the liquid filled space. Advantageously, said liquid is water. According to an embodiment, said force-generating means may

comprise a propeller or any other liquid driving member which is attached to the suction cup device. Preferably, said force- generating means is adapted to provide a flow of the first medium in such a direction in relation to suction cup device such that a reaction force is created which acts in a substantially perpendicular direction to a plane extending through the front surface of the suction cup. Thereby, the suction cup device under most circumstances can achieve a substantially optimally directed motion in the liquid medium towards said attachment po- sition.

According to another preferred embodiment of the present invention, the suction cup device comprises at least one suction cup unit, wherein the suction cup unit comprises a suction cup, which comprises a cup-shaped recess and a front surface which defines an opening to the cup-shaped space, vacuum generating means, which is adapted to provide a negative pressure in the cup-shaped recess of the suction cup for attaching the suction cup to the wall surface, and force-generating means, which are adapted to provide a flow of a first medium in the liquid filled space in such a direction in relation to the suction cup device such that a reaction force is created which moves the front surface of the suction cup towards the wall surface. Consequently, the suction cup device may comprise one or several such suc- tion cup units. Each one of the suction cup units comprises vacuum generating means which enables an individual activation of the suction cup. Each one of the suction cup units also comprises force-generating means which enables the creation of an individual reaction force which moves the suction cup of the suc- tion cup unit in direction towards a wall surface.

According to another preferred embodiment of the present invention, said force-generating means comprises a medium source which contains the first medium in a compressed state, at least one channel for transportation of the medium and an opening in the suction cup device from which the medium flows

out into the liquid filled space. Such a medium source may comprise a conduit which supplies the suction cup device with the compressed medium. The compressed medium must have a pressure of a value exceeding the pressure in the liquid filled space in order for it to be able to flow out into the liquid filled space. With pressure is here meant the total pressure which thus is the sum of the static pressure and the dynamic pressure. Said force-generating means may comprise a valve member for controlling the flow of the first medium out from said opening in the suction cup device. By means of a valve member which is adjustable to a closed position and an open position, it is easy to start and close the flow of the medium from the suction cup device. Such a valve member may be arranged in the suction cup device. Alternatively, the medium source and/or the valve member may be arranged at a position externally of the liquid filled space.

According to another preferred embodiment of the present invention, said force-generating means comprises a second valve member which is adapted to stop the flow of the medium from the suction cup device when a determined negative pressure has been created in the cup-shaped space of the suction cup. Consequently, such a valve member automatically shuts off the flow of the medium from the suction cup device when a negative pressure has been created in the suction cup which is sufficient for the suction cup device to be retained against the wall surface. Thus, the flow of the medium from the suction cup device does not need to be manually shut off since this function no longer is necessary. Alternatively, the operator may obtain in- formation from a sensor or the like when a load holding negative pressure has been created whereupon the operator shuts off the flow of the medium from the suction cup device. Advantageously, said force-generating means comprises a nozzle which comprises said opening in the suction cup device. A nozzle con- sists in its most simple design of a flow channel having a decreased cross section area in the flow direction of a medium.

Consequently, it is with a nozzle possible to accelerate the medium such that it in the form of a jet flows out in a desired direction with a good precision. Thus, also a reaction force may be created which with a good precision moves the suction cup de- vice towards a wall surface. Said force-generating means may comprise an articulated attachment of the nozzle. Thus, an adjustment of the flow direction of the medium out from the suction cup device in the liquid filled space is made possible. During certain circumstances, it can be desirable to vary the flow direc- tion of the medium into the liquid filled space for, for example, fine adjustment of the motion direction of the suction cup devices in towards a wall surface. Such a fine adjustment of the motion of the suction cup device in towards a wall surface may be performed in three dimensions.

According to another preferred embodiment of the present invention, said vacuum generating means comprises a pump device which is arranged in the suction cup device and a vacuum channel extending between the pump device and the cup- shaped space of the suction cup. By arranging the pump device in the suction cup device, a very short vacuum channel may be used for sucking liquid from the cup-shaped space of the suction cup. With such a short vacuum channel, low flow losses and a very effective sucking out of liquid from the cup-shaped space of the suction cup is obtained. When a suction cup device with such a pump device and vacuum channel is used in a basin for a reactor tank, a very small surface is subjected to contaminated water. Furthermore, it is avoided that water with contaminated particles is moved up to the water surface in the reactor basin or even to a level above the water surface. Such a pump device may be a pump of a substantially conventional kind. Advantageously, the pump device is an ejector which is adapted to be flowed through by a second medium with a velocity such that a negative pressure is created in the vacuum channel. An ejector has no movable parts for what reason it has a very safe function. It also does not require a lot of space and it can therefore

be installed in a suction cup device in a relatively simple manner. The suction cup device may comprise a medium source which contains the second medium in a compressed state, at least one channel for transportation of the second medium to the ejector and a valve member for controlling the flow of the second medium through the ejector. By means of, for example, a valve member, which is adjustable to at least an open position and to a closed position, start and stop of the vacuum suction of the cup-shaped space of the suction cup can be obtained in an uncomplicated manner. Advantageously, the second medium, which is used by said vacuum generating means, is of the same kind as the first medium, which is used by said force-generating means. Suitably, said force-generating means and vacuum generating means use the same liquid as is used in the liquid filled space. Thereby, said force-generating means and vacuum generating means can also use the same medium source and the same valve member for controlling the supply of the medium. The number of components in the suction cup device can thus be reduced.

According to another preferred embodiment of the present invention, the suction cup device comprises a displacement mechanism which is adapted to position the suction cup in a pushed-out position and in a pushed-in position. Thus, it is pos- sible to position the suction cup in a pushed-in position during displacements of the suction cup device in narrow spaces and in a pushed-out position when the suction cup device shall be attached to a wall surface. The displacement mechanism may comprise the same medium source and the same valve member as said vacuum generating means and said force-generating means for controlling the displacement motions of the suction cup between said positions. Thus, the number of components in the suction cup device can be further reduced. The suction cup may comprise an articulated attachment in the suction cup de- vice. Thereby, the suction cup can provide at least some angular motion when it gets in contact with a wall surface. If the suction

cup comes in somewhat inclined towards the wall surface, the suction cup can be angled such that the whole front surface of the suction cup comes into abutment against the wall surface.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, preferred embodiments of the invention are described as examples with reference to the attached drawings, in which:

Fig. 1 shows examples of apparatus with suction cup devices for indicating defects in a reactor, Fig. 2 shows schematically included parts of an apparatus with a suction cup device, Fig. 3 shows a suction cup unit during an attachment phase to a wall surface,

Fig. 4 shows a control system for a suction cup unit and Fig. 5 shows an alternative suction cup device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 shows selected parts of a nuclear plant which comprises a reactor tank 1 . The reactor tank 1 is arranged at a bottom sur- face of a reactor basin 2. The reactor tank 1 and the reactor basin 2 are filled with water. A bridge 3 extends over the reactor basin 2. The bridge 3 is provided with a moveably arranged lifting device 4. The reactor tank 1 has here been opened and partly emptied of internal parts for making an inspection of the reactor tank 1 possible. However, the reactor tank 1 contains some remaining internal parts such as a moderator tank 5 which contains the reactor core. The moderator tank 5 can in this state contain fuel rods which are not unloaded, the core grid, remaining control rods etc. Operators 6 which are intended to perform the inspection of the reactor tank 1 are located near the reactor basin 2. Fig. 1 shows two apparatus which each comprises a

suction cup device 7a, b which are provided with at least one suction cup such that they are attachable to substantially all existing wall surfaces in a reactor tank environment. With a reactor tank environment is meant the reactor tank 1 and all its sur- rounding basins. The suction cup devices 7a, b can be equipped with ultrasonic probes or other testing equipment for indicating the presence of possible defects in the reactor tank 1 . The suction cup devices 7a, b can also be provided with equipment for performing repairs.

The first suction cup device 7a is movably arranged between different areas in the reactor tank 1 by means of swingable lifting rods 8. Alternatively, the first suction cup device 7a can be suspended in cables or in some form of wires. An operator 6a is provided with a remote control device 9a for controlling the first suction cup device 7a. The remote control device 9a may consist of a computer device, which is provided with software for controlling the first suction cup device 7a. The remote control device 9a can be provided with an auxiliary system for transmit- ting control signals between the remote control device 9a and individual components in the first suction cup device 7a. One or several control lines 10 therefore extend between the remote control device 9a and the suction cup device 7a. The control lines 10 can be electric, hydraulic, pneumatic or constitute com- binations of these. The control lines 10 can also be intended to transmit signals from, for example, sensors in the first suction cup device 7a to the remote control device 9a. A pump aggregate 1 1 a is arranged at the edge of the basin. The pump aggregate 1 1 a has the purpose of maintaining a substantially constant pressure level and a flow in a flexible conduit, in the form of a hose 12a, which has an extension between the pump aggregate 1 1 a and the first suction cup device 7a. For attaching the first suction cup device 7a to the internal wall surface of the reactor tank 1 , a force F _v has to be supplied which is substantially per- pendicular to the wall surface. The force F _v has to be supplied with a very good precision in order for the suction cup device 7a

to be able to be moved to a position from where it is possible to create a negative pressure in the suction cup of the suction cup device 7a such that it attaches to the wall surface.

The second suction cup device 7b comprises drive members such that it itself can move "swim" in the reactor basin 2 between different places in the reactor tank 1 . Such drive members can consist of propellers or water jet nozzles. An operator 6b is provided with a remote control device 9b for controlling the sec- ond suction cup device 7b. The remote control device 9b can consist of a computer device, which is provided with suitable software. In this case, the remote control device 9b comprises a transmitter and the suction cup device 7b a receiver such that a wireless transmission of control signals is made possible. Thereby, no control lines need to be arranged between the remote control device 9b and the second suction cup device 7b. A pump aggregate 1 1 b is arranged at the edge of the basin. The pump aggregate 1 1 b has the purpose of maintaining a substantially constant pressure level in a hose 12b which has an exten- sion between the pump aggregate 1 1 b and the second suction cup device 7b.

Fig. 2 shows a remote control device which is exemplified as a portable computer device 9. However, the remote control device 9 can be of another kind. However, it ought to be provided with button members or the like with which an operator 6 can control the suction cup device 7. It also ought to have a display or viewing screen which shows relevant data, for example, related to the actual position of the suction cup device 7 in the reactor tank 1. The computer device 9 is, via a line 13, connected to the pump aggregate 1 1. Thus, it is possible to at least initiate start/stop of the pump aggregate 1 1 by means of the computer device 9. The computer device 9 is also, via said line 13, connected to a pressure limiting valve 14. Thus, it is possible to by means of the computer device 9 set a desired constant positive pressure which the water shall maintain in the hose 12 during

operation of the pump aggregate 1 1 . Alternatively, the pressure limiting valve 14 can be freestanding and be adjusted to work with a predetermined pressure. The positive pressure is at least of a magnitude such that it exceeds the pressure of the water down in the reactor tank 1 . The pump aggregate 1 1 is connected to a water source 15. The water source 15 can be pure de- ionized water which is accessible at different taping points in a reactor hall. Alternatively, it can be contaminated water which is sucked up from some basin in the reactor tank environment.

During operation, the pump aggregate 1 1 pumps water from the water source 15 to the hose 12, via the pressure limiting valve 14, such that an intended water pressure is maintained in the flexible line 12. The surplus water is conducted away via a con- duit 16. In this case, the apparatus comprises a suction cup device 7 which is provided with two substantially identical suction cup units 17, 17'. Each of the suction cup units 17, 17' is provided with a suction cup 18, 18'. The hose 12 is branched in connection with the device 7 into two end portions 12, 12' such that each one of the suction cup units 17, 17' provides access to water with said positive pressure. The suction cup units 17, 17' are, via signal lines 10, 10', connected to the computer device 9. Thus, it is possible to provide an individual control of the suction cup units 17, 17'.

Fig. 3 shows a side view of a suction cup unit 17. The suction cup unit 17 comprises a suction cup 18 which is designed with a flexible element 19 extending peripherally around a bottom plate 20. The flexible element 19 and the bottom plate 20 form a cup- shaped recess 21 of the suction cup 18. The flexible element 19 comprises a front surface 22 which defines an opening to the cup-shaped space 21 . The bottom plate 20 is, via an articulated and turnable connection 23, connected to a displaceably arranged piston 24. The piston 24 divides a first space 25 and a second space 26. The second space 26 has en larger contact surface with the piston 24 than the first space 25. The hose 12

is connected to a main valve 27 in the suction cup unit 17. The main valve 27 is adjustable to an open position and to a closed position by means of control signals, which are transmitted through the line 10, from the computer device 9. In the open po- sition of the main valve 27, water with said positive pressure is conducted from the hose 12 to, inter alia, an ejector 28. Thereby, the water flows with a high velocity through the ejector

28 such that a negative pressure is created in a vacuum channel

29 extending between the ejector 28 and the cup-shaped space 21 of the suction cup.

The suction cup unit 17 also comprises a second valve 30 which is adjustable to an open position and to a closed position. The second valve 30 is controlled by the pressure in the cup-shaped space of the suction cup 21 via a control channel 31. When the main valve 27 and the second valve 30 are open, water with said positive pressure is supplied from the hose 12 to a nozzle 32 which has an opening 33 through which the water flows out in the form of a jet. The nozzle 32 is attached to the suction cup unit 17 by means of an articulated connection 34. Thereby, it is possible to adjust the direction of the water jet which flows out from the suction cup unit 17. However, the flow direction of the water jet ought mainly to be substantially perpendicular to a plane A extending through the front surface 22 of the suction cup. The suction cup 18 can thereby be moved in towards a wall surface 35 in the liquid filled space to an attached position from which it is possible to attach the suction cup 18 to the wall surface 35. In said attachment position, the gap between the front surface 22 of the suction cup and the wall surface 35 is so small such that a negative pressure can be created in the cup-shaped space 21 of the suction cup such that the suction cup 18 safely is maintained against the wall surface 35.

Fig. 4 shows more in detail how the suction cup unit 17 is con- trolled. During operation, the pump aggregate 1 1 and the pressure-limiting valve 14 maintain a positive pressure of the water

in the hose 12 with an adjustable value. When the main valve 27 is closed, water is supplied from the hose 12 to the space 25, which thus is located on one of the sides of the piston 24, via a water channel 36. When no corresponding pressure prevails in the space 26 on the opposite side of the piston 24, the piston 24 provides a motion to the left in Fig. 3 such that the suction cup 18 is displaced to a pushed-in position on the suction cup unit 17. This motion guarantees that the suction cup 18 is quickly released from a wall surface 35. With the suction cup 18 in a pushed-in position, the suction cup unit 17 is relatively flat which facilitates motions of the suction cup unit 17 in narrow passages. In this position, the front surface 22 of the suction cup, which comprises sensitive sealing surfaces, also is protected against wear. In the pushed-in position, it is guaranteed that the front surface 22 of the suction cup is the surface of the suction cup device 7 which first reaches the wall surface 35.

When the suction cup unit 17 reaches a position where it shall be attached to a wall surface 35, it is initially placed in a turning position such that the opening of the suction cup 18 is directed towards the wall surface 35. Thereafter, a control signal is transmitted from the computer device 9, via the signal line 10a, to the main valve 27 such that it opens. Thereby, water flows from the hose 12 with said positive pressure through a water channel 37 to the second valve 30. This second valve 30 is controlled by the pressure in the cup-shaped space 21 via the control channel 31 . The second valve 30 is adapted to be open until a sufficient negative pressure has been created in the cup- shaped space 21 . When no such negative pressure has yet been created in the cup-shaped space 21 , the second valve 30 is open. Thereby, the water flows further into a water channel 38 to the nozzle 32 and out via the opening 33 of the nozzle. A water jet thereby flows out into the water filled space of the reactor tank 1 . The nozzle 32 is here directed such that the water jet provides a substantially perpendicular direction to the plane A which thus extends through the front surface 22 of the suction

cup. The outwardly flowing water thereby creates a reaction force which moves the suction cup unit 17 in towards the wall surface 35. The magnitude of the reaction force is related to the mass flow of the ejecting water and flow velocity.

When the main valve 27 is open, water is at the same time conducted from the hose 12, via a water channel 39, towards the ejector 28. The vacuum channel 29 has an outlet at a central part of the ejector 28. Since the ejector 28 has a relatively small cross section area at the central part, the water here provides a very high velocity. Thereby, a negative pressure is created in the vacuum channel 29, which sucks out water from the cup- shaped space of the suction cup 21 . The water in the water channel 39 also flows into a water channel 40 which is con- nected to the space 26. Water with the same pressure thereby fills both the space 26 and the space 25 which is located on the opposite side of the piston 24. When the water in the space 26 has a larger contact surface with the piston 24 than the water in the space 25, the piston 24 is displaced to the right to a push- out position which is shown in Fig. 3.

The water from the nozzle 32 which flows out into the water in the reactor tank 1 thus provides a reaction force which moves the suction cup unit 17 in towards the wall surface 35. When the suction cup 18 reaches an attachment position, the gap between the front surface 22 of the suction cup and the wall surface 35 is so small that a larger quantity of water is sucked out from the cup-shaped space 21 of the suction cup than the quantity of water which flows in via said gap. Thereby, a negative pressure is created in the suction cup 18 such that the whole front surface 22 of the suction cup is pressed against the wall surface 35. The negative pressure in the vacuum channel 29, which is created by the water flowing through the ejector 28 with a high velocity, results in that the remaining water in the cup-shaped space 21 relatively quickly is sucked out. Thereby, a negative pressure is created in the cup-shaped space 21 of the suction cup of a

magnitude which makes the suction cup 18 safely maintained against the wall surface 35. When a sufficient negative pressure has been created in the cup-shaped space 21 of the suction cup, this is sensed by the second valve 30, via the control chan- nel 31 , whereupon the valve 30 is closed. Thus, water stops flowing out through the nozzle 32 when this function no longer is necessary since the suction cup 18 now is attached to the wall surface 35 as a result of the prevailing negative pressure in the suction cup 18. A first pressure sensor 41 is arranged in con- nection with the cup-shaped space of the suction cup 21 for sensing the here prevailing pressure. The first pressure sensor 41 is intended to, via a signal line 10b, inform the computer device 9 about this pressure value. Thus, an operator 6 can obtain information about the magnitude of the prevailing negative pres- sure in the suction cup 18 and the force with which the suction cup 18 is attached to the wall surface 35. A second pressure sensor 42 is arranged in the water channel 38 for sensing the here prevailing pressure. The second pressure sensor 42 is intended to, via a line 10c, inform the computer device 9 about the value of this pressure. The computer device 9 is, via a line 10d, arranged to control a schematically shown power member 43 which makes an angle adjustment of the nozzle 32 possible. By varying the angle adjustment of the nozzles 32 in a suitable manner and thereby the direction of the reaction force, the suc- tion cup device 7 can be precision positioned to the attachment position, in which the suction cup 18 is attachable to the wall surface 35.

When the suction cup 18 is to loose its grip to the wall surface 35, the computer device 9 closes the main valve 27. Thereby, the water flow through the ejector 28 ceases. The negative pressure in the vacuum conduit 29 is ceased and surrounding water can flow in the back way through the ejector 28 and vacuum conduit 29 to the cup-shaped space 21. Since the flow path of the water is very short, the pressure in the cup-shaped space 21 increases quickly to the same level as the pressure of the

surrounding water. At the same time, the pressure in the space 26 is decreases while the negative pressure in the space 25 on the opposite side remains. Thus, the suction cup 18 is displaced by the piston 24 to its pushed-in position. This motion speeds up the releasing process of the suction cup from the wall surface 35. The flow resistance through the ejector 28 and the nozzle 32 is adapted such that a desired distribution of the water from the hose 12 is obtained between the parallel channels 37, 39 which supply the ejector 28 and the nozzle 32 with water.

The suction cup device 7, which is shown in Fig. 2, comprises two suction cup units 17 which are fixedly arranged in relation to each other. The motion of such a suction cup device 7 between different areas on a wall surface 35 where indications of defects is to be detected can thus be performed by means of swingable lifting rods 8. Fig. 5 shows a more advanced suction cup device 7 which after that it has been positioned near a starting position on a test object can be moved by itself to desired positions. The suction cup device 7 comprises a base portion 44 which is con- nected to a first movable portion 45 and a second movable portion 46. The base portion 44 has a side 44a which, via a rail or the like, is displaceably connected to a side 45a of the first moveable portion 45. The base portion 44 has a second side 44b which, via a rail or the like, is displaceably connected to a side 46b of the second movable portion 46. The sides 44a, b of the base portion have extensions which form a substantially right angle to each other. The first movable portion 45 and the second movable portion 46 are thus movably arranged in perpendicular directions in relation to each other. The first movable portion 45 can have a curved shape which corresponds to the curve of an existing wall surface 35 in a reactor tank environment. Both the first movable portion 45 and the second movable portion 46 are each equipped with two suction cup units 17. Each suction cup unit 17 is equipped with a suction cup 18. The second movable portion 46 is also provided with equipment 47 for making indications of defects possible.

When the suction cup device 7 is to be positioned in a starting position, it is initially positioned in a turning position such that the suction cups 18 are directed towards a wall surface 35 where it is desired to attach the suction cup device 7. Thereafter, the main valves 27 are opened in an optional number of the suction cup units 17 such that water flows out from the respective nozzles 32 wherein the device is moved in towards the wall surface 35 to an attachment position from where it attaches, in the above mentioned manner by means of the suction cups 18, to the wall surface 35. If the suction cup device 7 is to be moved from the shown position in, for example, a horizontal direction to the right on a wall surface 35, the main valves 27 of the suction cup units 17 of the second movable portions 46 are closed. The suction cups 18 of the second movable portion 46 are thus no longer attached to the wall surface. The second movable portion 46 is thereafter displaced together with the base portion 44 as a device in relation to the first movable portion 45 until the base portion 44 reaches a right end position in relation to the first movable portion 45. However, this motion can be stopped in an optional position. In this right end position, the main valves 27 of the second movable portion 46 are opened such that its suction cups 18 are attached to the wall surface 35. Thereafter, the main valves 27 of the suction cup units 17 of the first movable portion 45 are closed such that its suction cups 18 are released from the wall surface 35. Thereafter, the first movable portion 45 is displaced to the right in relation to the base portion 1 and the second movable portion 46. The motion to the right proceeds alternately in the above-mentioned manner with the first mov- able portion 45 or the second movable portion 46 in altering fixed states on the wall surface 35. When the suction cup device 7 has reached a desired position, the motion can be stopped very exactly. The motion is performed with the helps of linear units which make motions with a very high precision possible. The motion to the left of the suction cup device 7 proceeds in a substantially corresponding manner. The base portion 44 and

the second movable portion 46 here also constitute a unit which alternately with the first movable portion 45 provides the motion and the fixing of the device. The motion of the suction cup devices 7 in a vertical direction motion proceeds in a substantially corresponding manner with the difference that the base portion 44 and the first movable portion 45 instead constitute a unit which alternately with the second movable portion 46 provides the motion and fixing of the device.

By combining the above desired motions in the vertical direction and in the horizontal direction, the suction cup device can be moved to a substantially arbitrary position on a wall surface 35. The suction cup device 7 can, for example, perform horizontal, vertical, diagonal and circular motions along a wall surface 35. Since the suction cup device 7 continuously has at least one portion 45, 46 in a fixed position to the wall surface 35, the suction cup device 7 can be moved to a desired position on the wall surface 35 with a very good precision. When the suction cup device 7 reaches a desired position, the first movable portion 45 is fixed to the wall surface by means of the suction cups 18. Thereafter, the equipment 47 of the second movable portion 46 can be moved along a path over the wall surface 35 for indicating possible defects. The path is defined by a horizontal component which is determined by displacement motions between the base portion 44 and the fixed first movable portion 45 and a vertical component which is determined by displacement motions between the base portion and 44 the second movable portion 46. With such displacement motions the path can be given a substantially arbitrary shape and extension.

The suction cup device 7 has the function that it can correct its position if it would differ from an imagined path along a curved wall surface. By fixing one of the suction cups 18 of the first portion 45 and one of the suction cups 17 of the second portion 45 some correcting motions can be provided by means of a combination of vertical and horizontal motions and the turnable at-

tachment of the suction cups 17, 18. By means of such correcting motions, the suction cup device 7 can again be given a desired angle position. The sensing of an incorrect angle position of the suction cup device 7 can be detected by an inclinometer. From a detected incorrect angle position of the suction cup device 7 appropriate correcting motions can be calculated and performed for correcting the incorrect angle position.

The present invention is not in any way restricted to the above- described embodiments on the drawings but may be modified freely within the scope of the claims. A suction cup device does not need to comprise one suction cup unit but it may consist of an arbitrary number of suction cups and at least one force generating medium jet which provides a reaction force which moves the suction cup device as a unit towards a wall surface. The suction cup device can in its simplest form be identical with the above described suction cup unit.