Arrangement for spraying fluid, cleaning machine and method

Abstract

An arrangement for spraying fluid, a cleaning machine, and a method. The arrangement (7) comprises a spraying system (8) provided with a spray arm (9) rotated by means of a rotation system (11). Pressurized fluid is delivered the spray arm comprising nozzles (10). The spray arm is moved along a movement path (14) comprising two or more linear sides (19a - 19d).

Description

Background of the invention

[0001] The invention relates to an arrangement for spraying fluid.

[0002] The invention further relates to a cleaning machine and to a method for spraying fluid.

[0003] The field of the invention is defined more specifically in the preambles of the independent claims.

[0004] At different production plants and workshops there is a need to clean mechanical objects in cleaning machines wherein fluid material is sprayed inside a workspace on the objects to be treated. The known cleaning machines comprise rotating spray arms which comprise nozzles for spraying the fluid. However, the known solutions have shown to include some problems.Brief description of the invention

[0005] An object of the invention is to provide a novel and improved arrangement, cleaning machine and method for spraying fluids.

[0006] The arrangement according to the invention is characterized by the characterizing features of the first independent apparatus claim.

[0007] The cleaning machine according to the invention is characterized by the characterizing features of the second independent apparatus claim.

[0008] The method according to the invention is characterized by the characterizing features and steps of an independent method claim.

[0009] An idea of the disclosed solution is that an arrangement for spraying fluid comprises a spraying system provided with one or more spray arms provided with nozzles for spraying the fluid. The spray arm is rotated around a rotation centre by means of a rotation system comprising a rotation motor. The spray arm is moved along a movement path which limits inside the movement path a workspace for receiving objects to be subjected to the spraying of fluid. The pressurized fluid is sprayed from the nozzles towards the workspace. Further, the movement path of the spray arm comprises two or more linear sides.

[0010] In other words, the movement path of the rotating spray arm has several linear sections instead of just rotating around a circle.

[0011] An advantage of the disclosed solution is that the movement of the spray arm can be designed to follow a shape of an allowable work area whereby the workspace may be greater. This improves efficiency and saves floor space since outer dimensions of the spraying arrangement can be minor due to the effective utilization of space.

[0012] Further, the disclosed solution can be utilized in a versatile manner in different spraying solutions, and it is even possible to retrofit the new design to the existing apparatuses.

[0013] According to an embodiment, the spraying system comprises a plurality of nozzles in each of the one or more spray arms. The nozzles may be arranged in desired nozzle patterns, and they may have different orientations and height positions. However, in some cases there may be only one nozzle in the spray arm.

[0014] According to an embodiment, the spraying system comprises one spray arm. In some cases only one spray arm is enough to provide desired spraying effect.

[0015] According to an embodiment, the spraying system comprises 2 - 4 spray arms. In some situations it is beneficial to enhance the spraying by using a plurality of spray arms.

[0016] According to an embodiment, each of the spray arms is a tube-like element comprising one or more nozzles through which the pressurized fluid conveyed from the fluid housing to a hollow inner space of the spray arm is sprayed towards the workspace.

[0017] According to an embodiment, axis of rotation of the rotation centre is vertical and the spray arm is rotated on a horizontal plane.

[0018] According to an alternative embodiment, axis of rotation of the rotation centre is horizontal and the spray arm is rotated on a vertical plane.

[0019] According to a further alternative embodiment, axis of rotation of the rotation centre is inclined and the spray arm is rotated on a slanted plane. Basically, the axis of rotation may have any orientation. In some cases the orientation may even be adjustable.

[0020] According to an embodiment, the fluid is sprayed at 3 - 5 bar pressure.

[0021] According to an embodiment, the fluid is sprayed at 60 - 80°C temperature.

[0022] According to an embodiment, the fluid to be sprayed is a mixture of water and at least one cleaning chemical or detergent. The cleaning chemical may be alkaline washing agent.

[0023] According to an embodiment, fluid to be sprayed is alternatively any other liquid than water, such as solvent, paint, coating substance, or protective agent.

[0024] According to an embodiment, fluid to be sprayed is alternatively a gaseous substance or gaseous compound. It is also possible to use the arrangement for spraying steam.

[0025] According to an embodiment, the spraying system is provided with a suction feature. When the spraying of fluid is stopped, it is possible to implement the suction feature wherein the spray arm is provided with suction whereby air, gas or steam is conveyed through the spray arm away. Then the arrangement can be used for drying measures.

[0026] According to an embodiment, the spray nozzles are simple holes with relatively small diameter. Alternatively, the spray nozzles may be separate nozzle elements mounted to the spray arm. The nozzle elements may be adjustable and changeable.

[0027] According to an embodiment, the spray arm is rotatable an unlimited number of rotations at least in one direction of rotation. This is possible since the fluid feed system is without separate feed hoses or tubes which would limit the amount of rotation.

[0028] According to an embodiment, the spray arm is rotatable in both directions of rotation.

[0029] According to an embodiment, the nozzles of the spray arm are directed to, or at least nearly to, the centre of rotation during the entire rotation movement along the movement path.

[0030] According to an embodiment, the spray arm is rotated along a quadrilateral movement path comprising four linear sides connected to each other by means of four corners. In other words, the spray arm is moved along a substantially rectangular movement path.

[0031] An advantage of this embodiment is that the spray arm can be arranged to move close to limiting surfaces around the spraying arrangement.

[0032] According to an embodiment, the four linear sides have equal lengths. In other words, the four-cornered movement path resembles a shape of a square.

[0033] An advantage of the disclosed embodiment is that the spray arm can move in accordance with side surfaces of the cube-like surrounding structure with square-like cross-section. Typically, the spraying arrangement is arranged inside a casing having a shape of a cube. Then the inner space of the casing can be well utilized and there can be more of sprayed objects inside the workspace which is significantly bigger compared to an arrangement wherein the spray arm is rotated around a circle inside the casing.

[0034] According to an embodiment, the quadrilateral movement path comprises two opposite longer sides and two opposite shorter sides. In other words, the four-cornered movement path has an oblong shape. An advantage of this embodiment is that the arrangement can be implemented for spraying longitudinal objects.

[0035] According to an alternative embodiment, the movement path may have pentagonal, hexagonal or octagonal shape with several corners and several linear sides. Thus, the shape of the movement path can be designed relatively freely.

[0036] According to an embodiment, the corners of the movement path are rounded. In other words, the rounded corners facilitate the rotation movement of the spray arm and may also allow faster rotation movement.

[0037] According to an embodiment, the arrangement is provided with a body comprising a casing surrounding a workspace inside which the spray system is arranged. In other words, the arrangement is an independent apparatus provided with the own body structure.

[0038] According to an embodiment, the arrangement may comprise an independent single machine which may be a batch-type loaded machine or it may be a flow-through loaded machine.

[0039] According to an embodiment, the arrangement may comprise one or more spraying machine configurations arranged on a production line, or on treatment line.

[0040] According to an embodiment, the disclosed arrangement with the spraying system is arranged in connection with a production line, or it is part of a larger configuration or machine. Then the arrangement is not necessarily provided with any own body structure with the casing, basin and door. Thus, the disclosed arrangement may be an accessory mountable to another apparatus.

[0041] According to an embodiment, the spray arm comprises a radial portion extending away from the rotation centre and a spraying portion comprising the nozzles and being located at a distal end of the radial portion and being transverse orientated in relation to the radial portion. In other words, shape of the spray arm resembles upside down turned letter L. The radial portion provides desired reach for the spray arm and the spraying portion provides sufficient transverse dimensions for providing the spray arm with a plurality of nozzles for providing proper spraying coverage.

[0042] According to an embodiment, length of the radial portion of the spray arm is fixed.

[0043] According to an embodiment, length of the radial portion of the spray arm is adjustable by means of one or more actuators in response to the rotation movement of the spraying system. Then the arrangement may comprise an automatically controlled length adjustment feature so that the desired movement path is achieved by controlling the length of the radial portion. There is at least one control unit for controlling the rotation movement and the length adjustment in relation to each other to thereby provide desired movement path for the spray arm.

[0044] According to an embodiment, length of the radial portion of the spray arm is adjustable telescopically and the fluid is conveyed inside the telescopic structure. Then there is no need for separate fluid paths and the structure may be compact. The telescopic structure comprises sealing elements for sealing fluid tightly tubular elements arranged to be moved relatively to each other during the length adjustment.

[0045] According to an embodiment, length of the radial portion of the spray arm is adjustable either telescopically or by implementing any other suitable mechanical structure. Then there is fluid hose for conveying the fluid to the one or more nozzles. The fluid hose is provided with a bow section allowing the length adjustment of the radial portion. It can be considered that the bow section provides additional hose length for the length adjustment of the spraying system.

[0046] According to an embodiment, the rotation centre of the rotation system is arranged linearly movably. This way range of the spraying system can be increased. The linear movement is easy to control.

[0047] According to an embodiment, the arrangement is provided with a mechanical rotation system comprising an outer disc mounted immovably and provided with an inner toothing on an inner circumference of the outer disc, and an inner disc mounted rotationally inside the inner circumference of the outer disc and comprising an outer toothing on an outer circumference of the inner disc. A first diameter of the inner circumference of the outer disc is greater than a second diameter of the outer toothing of the inner disc. The outer toothing is in tooth contact with the inner toothing only at a limited section of the inner circumference. The spray arm is rotating together with the inner disc. Further, the inner disc is rotating eccentrically inside the outer disc. In other words, the arrangement comprises a mechanical system for providing substantially square-like rotation movement for the one or more spray arms.

[0048] The disclosed mechanical square rotation system is operationally reliable and easy to control. The operation does not require complicated control systems, control actuators and sensing devices since the mechanism takes care of the designed movement control.

[0049] The inner and outer teeth being in tooth contact have a constant ratio whereby the rotation movement of the inner disc and the spray arms is synchronized to perform the disclosed movement path.

[0050] According to an embodiment, there is a constant ratio between the inner and outer teeth and the ratio is 3:4.

[0051] According to an embodiment, a rotation motor is rotating a hub around central axis. A center of the inner disc is connected to the hub being rotated at the center. The inner disc is coupled to the bub by means of a free rotation joint allowing the inner disc to rotate freely under guidance of the rotation movement of the hub and the tooth contact between the toothing of the inner and outer discs.

[0052] According to an embodiment, the fluid is conveyed through the rotating hub wherefore the hub comprises fluid tight rotating joints. The hub is connected to a centre part by means of at least one fluid connector element. The centre part is in fluid connection to the one or more spray arms. The fluid connector element may serve also as a mechanical connecting element between the hub and the centre part. Length of the fluid connector element, or intermediate element, is needed for providing the required eccentrical rotation movement for the inner disc and the one or more spray arms connected to the inner disc.

[0053] According to an embodiment, the spray system comprises three spray arms which are evenly spaced and are arranged be rotated eccentrically together with the inner disc.

[0054] According to an embodiment, the mechanical rotation system is linearly movable whereby the spray arm may move along an oblong quadrilateral movement path having two opposite longer sides and two opposite shorter sides. Thus, the linear movement of the rotations systems increases possibilities to form differently dimensioned and shaped movement paths for the mechanical system.

[0055] According to an alternative solution, the spray arm is moved along a coulisse configured to guide the spray arm along the movement path comprising the linear sides. The coulisse may be a structure provided with a groove or other guide structure comprising mechanical surfaces between which the spray arm is guided along the pre-determined movement path.

[0056] According to a further alternative solution, the spray arm is moved under guidance of a chain or belt so that the spray arm is guided to move along the movement path comprising the linear sides. The chain or belt is arranged to be moved along the desired movement path under control of support and guidance rolls and other guide elements.

[0057] According to an embodiment, the disclosed solution relates also to a cleaning machine for cleaning mechanical objects. The cleaning machine comprises: a body comprising a casing surrounding the workspace from sides and a top; a basin below the workspace for collecting the spayed fluid; at least one openable and closable door on at least one side of the casing; and an arrangement for spraying fluid from at least one spray arm rotatable around the workspace configured to receive the mechanical objects. The arrangement for spraying fluid is in accordance with the features and embodiments disclosed in this document. Further, the spray arm is configured to be moved along a movement path comprising two or more linear sides.

[0058] According to an embodiment, the cleaning machine comprises at least two parallel rails on which a cradle is arranged movably and on which objects being sprayed can be arranged.

[0059] According to an embodiment, the disclosed solution relates also to a method for spraying fluid. The method comprises: spraying pressurized fluid through a plurality of nozzles arranged on at least rotating spray arm; providing the spray arm with a movement path limiting a workspace; and arranging objects to be sprayed inside the workspace. The method further comprises moving the at least one spray arm along a movement comprising at least two linear sides.

[0060] The above disclosed embodiments may be combined to form suitable solutions having those of the above features that are needed.Brief description of the figures

[0061] Some embodiments are described in more detail in the accompanying drawings, in which Figure 1 is a schematic diagram showing some fluids sprayable by means of the disclosed solution, Figure 2 is a schematic diagram of some features of a disclosed arrangement, Figure 3 is a schematic top view of a prior art solution with a circular movement path, Figures 4 and 5 are a schematic top views of square shaped movement paths and two different movement directions, Figure 6 is a schematic top view of an oblong rectangularly shaped movement path and linear movement of a rotation center; Figure 7 is a schematic top view of an oblong movement path comprising two opposite linear sides and two opposite curved ends, Figure 8 is a schematic top view of a hexagonal movement path, Figure 9 is a schematic view of an extendable spray arm configuration and its controllable three movement axis, Figure 10 is a schematic view of a telescopically extendable spray arm configuration provided with internal fluid conveying paths, Figure 11 is a schematic view of a telescopically extendable spray arm configuration provided with a separate external fluid conveying hose, Figure 12 is a schematic top view showing a basic principle of a mechanical square rotating system, Figures 13 and 14 are schematic top views showing basic components of a mechanical square rotating system in two different rotation position, Figures 15 - 17 are schematic views in different view angles showing a spraying system with sprays arms and a mechanical rotating arrangement with an outer disc and an inner disc, Figure 18 is a schematic and simplified view showing support of a rotating inner disc to inner edges of an outer disc, and Figure 19 is a schematic side view of a cleaning machine provided with a spraying arrangement.

[0062] For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.Detailed description of some embodiments

[0063] Figure 1 discloses that different fluid materials can be used in a versatile manner as sprayed fluids 1 in the disclosed solution. Thus, it is possible to spray liquid or liquid mixtures 2, liquid and different additives or chemicals 3, gas or gas mixtures 4, coating materials such as paints 5, and sprayable granular materials 6 such as abrasive materials used in abrasive blasting.

[0064] Figure 2 discloses some basic features of an arrangement 7 for spraying fluid. The arrangement comprises a spraying system 8 provided with at least one spray arm 9. The spray arm 9 comprises one or more nozzles 10 through which the pressurized fluid is sprayed. The spray arm 9 is rotated by means of a rotation system 11 comprising a rotation motor 12. Pressurized fluid is delivered to the spray arm 9 via a fluid housing 13. The spray arm 9 is moved along a movement path 14 comprising linear sides.

[0065] Figure 3 discloses a prior art solution with a circular movement path 15. In this solution a spray arm 9 is rotated around central axis 16 wherefore effective workspace 17 is also circular. As can be noted, relatively large corner areas 18 remain outside the effective workspace and full capacity of the space cannot be utilized.

[0066] Figures 4 and 5 disclose solutions with a square-rotation principle wherein movement paths 14 comprise four linear sides 19a - 19d. Spray arms 9 are rotated around rotation centers 20. The movement path 14 limits a workspace 14 which is in Figures 4 and 5 square-shaped and is capable to receive effectively inside it objects, which are to be sprayed with fluid. The nozzles 10 are arranged to provide sprays towards the workspace 21. The nozzles 10 are arranged to keep their orientation towards the rotation center 20 despite of their movement along the movement path 14.

[0067] Figure 6 discloses a rectangular shaped movement path 14 provided with two opposing shorter linear sides 19a' and 19b' and two opposing longer linear sides 19c' and 19d'. A rotation center 20 is linearly movable along a center line, as it is indicated by means of an arrow L.

[0068] Figures 4 - 6 further show that corners 24 of quadrilateral movement paths 14 may be rounded for improving movement of spray arms at the corners.

[0069] Figure 7 discloses an oblong shaped movement path 14 provided with two opposing linear sides 19a' and 19b' and two opposing curved ends 25a and 25b. A rotation center 20 is linearly movable along a center line, as it is indicated by means of an arrow 23. At the curved ends 25a, 25b a spray arm can turn and provide the shown curved section for the movement path 14.

[0070] Figure 8 discloses a movement path 14 with a hexagonal shape. Then there are six linear sides 19 connected to each other by means of six corners 24. The disclosed solution is capable of forming also other movement paths 14 with polygonal shapes.

[0071] Figures 4 - 8 demonstrate that when the movement path 14 is controlled in accordance with the solution disclosed in this document, the differently shaped workspaces 21 can be provided. This improves better utilization of space and allows higher spraying capacity.

[0072] Figure 9 discloses one possibility to control a spray arm 9 for providing linear movements for desired movement paths. The spray arm 9 comprises an extendable configuration. Structure of the extendable spray arm 9 may be telescopic and its length can be adjusted by means of an extension movement actuator 26 controlled by means of a control unit CU for providing desired extension E. The spray arm 9 can be turned R around a rotation center 20 by means of a rotation actuator 27. Further, the rotation center 20 can be moved linearly L by means of a linear movement actuator 28. Thus, there are three controllable movement axis extension E, rotation R and linear movement L which are controlled under control of the control unit CU so that movements paths with linear sides and curved sections can be provided.

[0073] Figure 10 discloses a telescopically extendable spray arm 9 comprising channels 29 inside its extendable parts for conveying fluid through the structure.

[0074] Figure 11 discloses a telescopically extendable spray arm 9 differing from the one shown in Figure 10 in that there is a separate fluid path 30 for conveying fluid. The fluid path 30 may be a hose, for example. The fluid path 30 is provided with a bow 31 for allowing length changes of the spray arm 9. Alternatively, or in addition to, there may be an extendable section in the hose.

[0075] Figure 12 discloses in a simplified top view a spraying arrangement comprising a mechanical rotation system for providing square like movement path 14 with four linear sides 19a - 19d and four corners 24. The movement path 14 limits a workspace 21 which almost fully covers an area inside a casing 32 surrounding the workspace 21. The mechanical structure of a rotation system 11 comprises an outer disc 33 mounted immovably and provided with an inner toothing 34 on an inner circumference of the outer disc 33. An inner disc 35 is mounted rotationally inside the inner circumference of the outer disc 33 and comprises an outer toothing 36 on an outer circumference of the inner disc 35. A first diameter D1 of the inner circumference of the outer disc 33 is greater than a second diameter D2 of the outer toothing of the inner disc 35. The outer toothing 36 is in tooth contact with the inner toothing 34 only at a limited section of the inner circumference of the inner disc 35. A spray arm 9 is rotated together with the inner disc 35 which is rotated eccentrically inside the outer disc 34. A rotation motor 12 generates rotation movement which is transmitted to a rotation center 20 which is located at central point of the workspace 21. Fluid to be sprayed may also be conveyed through the rotation center 20. In connection with the rotation center 20 may be a fluid hub provided with fluid passages, a through passing rotating axle, and rotating sealing assemblies. The fluid hub is in fluid connection to a fluid feed system 37. The rotation center 20 provided with the fluid hub is connected with one or more intermediate parts 38 connecting the fluid hub to a center part 39 of the inner disc 35. The center part 39 is located at a distance from the rotation center 20 due to the intermediate part 38 and thereby inner disc 35 is rotated eccentrically in relation to the rotation center 20. The center part 39 comprises a free rotation joint 40 so that the inner disc can freely rotate when forces are transmitted from the rotation center 20 via the intermediate part 38. Arrows in Figure 12 demonstrate the rotation movements occurring in the rotation system 11. The spray arm 9 comprises a radial part 9a and a vertical part 9b and is connected to the center part 39 and is fluid connection through the intermediate part 38 to the hub being in connection with the rotation center 20. The eccentric rotation and tooth contact between the inner and outer toothing 34, 36 cause the vertical part 9b to move along the shown movement path 14. The inner toothing 34 and the outer toothing 36 have a fixed ratio 3:4 so that rotation movement is synchronized to provide the shown movement path 14. Then the inner toothing 34 may comprise 30 teeth and the outer toothing 36 may comprise 40 teeth.

[0076] Figures 13 and 14 disclose the mechanical rotation system 11 in different positions. The disclosed structure differs from the one shown in Figure 12 in that there are three spray arms 9 connected to the center part 39 of the inner disc 35. Further, the center part 39 is coupled to the rotation center 20 by means of two intermediate parts 38, which are curved tubular pieces comprising fluid channels inside them. Figures 13 and 14 also disclose that the outer disc 33 may comprise fastening elements of flanges 41 for mounting the outer disc 33 immovably to the structure of a cleaning machine or other surrounding structure.

[0077] Figure 15 discloses the rotation system 11 of previous Figures 13 and 14 seen from a side. It can be seen that vertical parts 9b of the spray arms 9 comprise a plurality of openings serving as spray nozzles 10.

[0078] Figure 16 shows the rotation system 11 of Figures 13 - 15 seen in one more additional angle of view.

[0079] Figure 17 shows the rotation system 11 may also comprise a protective element 42 such as a plate for preventing the rotation system 11 to be contaminated. Lines 43 demonstrate an inner space of a cleaning machine or corresponding structure inside which spray arms 9 are arranged to move.

[0080] Figure 18 discloses that an outer disc 33 is supported immovably and comprises at an inner edge portion a support element 44, such as a plate-like ring, which supports an inner disc 35 at its edges in vertical direction. This way the inner disc 35 and connecter one or more spray arms and related components can be supported in a conveniently manner without separate supporting arrangements. The support element 44 surrounds an inner surface of the outer disc 33 on a lower surface of the outer disc 33 and protrudes partly from the inner surface so that supporting surfaces are formed.

[0081] Figure 19 discloses a cleaning machine 45 for cleaning mechanical objects. The cleaning machine 45 comprises a body 46 comprising a casing 32 surrounding a workspace 21 from sides and a top. Below the workspace 21 is a basin 47 for collecting sprayed fluid. The body 46 comprises also an openable and closable door 48 on at least one side of the casing 32. In Figure 19 the doors 48 is shown as sliding door capable to move to one side of the cleaning machine 45. However, any door structures and movement directions can be implemented. It can be noted that a spray arm 9 of a spraying system 8 moves close to an inner surface of the casing 32 and thereby utilizes the available space well. In Figure 19 a mechanical rotation system 11 is shown. However, the rotation system 11 may alternatively be another type of the rotation system disclosed in this document. The cleaning machine 45 further comprises a fluid pump 49 for providing pressurized fluid to the spraying system 8. The fluid can be conveyed through a rotating joint 50 to the spraying system 8. Operation of the cleaning machine 45 and its operating actuators can be controlled by one or more control units CU.

[0082] Figure 19 further discloses two or more parallel rails 51 on which a cradle 52 is arranged movably so that objects being sprayed can be arranged on the cradle and can be moved in and out of the workspace 21.

[0083] The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.

Claims

1. An arrangement (7) for spraying fluid, wherein the arrangement (7) comprises: a spraying system (8) provided with at least one spray arm (9); a rotation system (11) configured to rotate the spray arm (9) around a rotation centre (20) and comprising at least a rotation motor (12); a fluid housing (13) for delivering pressurized fluid to the spray arm (9); the spray arm (9) is configured to be moved along a movement path (14) limiting inside the movement path (14) a workspace (21) for receiving objects to be subjected to the spraying of fluid; and the spray arm (9) comprises at least one nozzle (10) through which the pressurized fluid conveyed from the fluid housing is sprayed towards the workspace (21); characterized in that the spray arm (9) is configured to be moved along a movement path (14) comprising at least two linear sides (19a - 19d).

2. The arrangement as claimed in claim 1, characterized in that the spray arm (9) is configured to be rotated along a quadrilateral movement path (14) comprising four linear sides (19a - 19d) connected to each other by means of four corners (24).

3. The arrangement as claimed in claim 2, characterized in that the four linear sides (19a - 19d) have equal lengths.

4. The arrangement as claimed claim 2, characterized in that the quadrilateral movement path (14) comprises two opposite longer sides (19a', 19b') and two opposite shorter sides (19c', 19d').

5. The arrangement as claimed in any one of the preceding claims 1 - 4, characterized in that the corners (24) of the movement path (14) are rounded.

6. The arrangement as claimed in any one of the preceding claims 1 - 5, characterized in that the arrangement (7) is provided with a body comprising a casing (32) surrounding the workspace (21) inside which the spray system (8) is arranged.

7. The arrangement as claimed in any one of the preceding claims 1 - 6, characterized in that the spray arm (9) comprises a radial portion (9a) extending away from the rotation centre (20) and a spraying portion (9b) comprising the nozzles (10) and being located at a distal end of the radial portion (9a) and being transverse orientated in relation to the radial portion (9a).

8. The arrangement as claimed in claim any one of the preceding claims 1 - 7, characterized in that the rotation centre (20) is arranged linearly movably.

9. The arrangement as claimed in claim any one of the preceding claims 1 - 6, characterized in that the arrangement (7) is provided with a mechanical rotation system comprising: an outer disc (33) mounted immovably and provided with an inner toothing (34) on an inner circumference of the outer disc (33); an inner disc (35) mounted rotationally inside the inner circumference of the outer disc (33) and comprising an outer toothing (36) on an outer circumference of the inner disc (35); a first diameter (D1) of the inner circumference of the outer disc (33) is greater than a second diameter (D2) of the outer toothing (36) of the inner disc (35) and the outer toothing (36) is in tooth contact with the inner toothing (34) only at a limited section of the inner circumference; the spray arm (9) is arranged to be rotated together with the inner disc (35); and wherein the inner disc (35) is rotatable eccentrically inside the outer disc (33).

10. A cleaning machine (45) for cleaning mechanical objects, wherein the cleaning machine (45) comprises: a body (46) comprising a casing (32) surrounding a workspace (21) from sides and a top; a basin (47) below the workspace (21) for collecting sprayed fluid; at least one openable and closable door (48) on at least one side of the casing (32); and an arrangement (7) for spraying fluid from at least one spray arm (9) rotatable around the workspace (21) configured to receive the mechanical objects; characterized in that the arrangement (7) for spraying fluid is in accordance with any one of the claims 1 - 9 and the spray arm (9) is configured to be moved along a movement path (14) comprising at least two linear sides (19a - 19d).

11. A method for spraying fluid, the method comprises: spraying pressurized fluid through a plurality of nozzles (10) arranged on at least rotating spray arm (9); providing the spray arm (9) with a movement path (14) limiting a workspace (21); and arranging objects to be sprayed inside the workspace (21); characterized by moving the at least one spray arm (9) along a movement path (14) comprising at least two linear sides (19a - 19d).

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