System for forming an artificial wave

Abstract

The invention discloses a system for forming an artificial wave (W) in a water environment, which comprises a pulling apparatus (6), a pulled apparatus (10, 10a, 10b, 10c, 10d) and a pulling arrangement (11), wherein the pulling apparatus (6) comprises a power pack (12) and the pulled apparatus (10) comprises a wave-forming profile (13), wherein the pulling arrangement (11) comprises at least two pulleys (14, 15) and at least one rope or line (16) provided at or via both ends of the pulled apparatus (10) and further via the pulleys (14, 15) for providing the movement of the pulled apparatus (10) between a first pulley (14) and a second pulley (15). According to the invention, the wave-forming profile (13) comprises at least two wings (1, 2), of which at least one wing (1, 2) is mainly transverse relative to the direction of advancement (A) of the pulled apparatus (10, 10a, 10b, 10c, 10d).

Claims

1. A system for forming an artificial wave (W) in a water environment, which comprises a pulling apparatus (6), a pulled apparatus (10, 10a, 10b, 10c, 10d) and a pulling arrangement (11), wherein the pulling apparatus (6) comprises a power pack (12) and the pulled apparatus (10, 10a, 10b, 10c, 10d) comprises a wave-forming profile (13), wherein the pulling arrangement (11) comprises at least two pulleys (14, 15) and at least one rope or line (16) provided substantially at or via both ends of the pulled apparatus (10, 10a, 10b, 10c, 10d) and further via the pulleys (14, 15) for providing the movement of the pulled apparatus (10, 10a, 10b, 10c, 10d) between a first pulley (14) and a second pulley (15), characterized in that the wave-forming profile (13) comprises at least two wings (1, 2), of which at least one wing (1, 2) is mainly transverse relative to the direction of advancement (A) of the pulled apparatus (10, 10a, 10b, 10c, 10d).

2. The system according to claim 1, characterized in that the rope or line (16) is endless and/or forms a loop via the first pulley (14) and the second pulley (15).

3. The system according to claim 1 or 2, characterized in that the pulling apparatus (6) is provided on a shore.

4. The system according to claim 1 or 2, characterized in that the pulling apparatus (6) is provided on a ship, a vessel, a barge or other watercraft.

5. The system according to claim 1 or 2, characterized in that the system comprises a structure (27) that floats or that is disposed in and/or on water and anchored in place for providing the pulling apparatus (6) thereon.

6. The system according to claim 3, characterized in that the system comprises an anchoring arrangement (17) for holding the pulling apparatus (6) in place on the shore, which comprises a tank (18) which is to be filled with water.

7. The system according to claim 6, characterized in that the tank (18) is a transportation container in which the components of the system are adapted to be moved and/or transported.

8. The system according to claim 6 or 7, characterized in that the pulling apparatus (6) comprises a water pump (19) by which the tank (18) is filled and/or emptied.

9. The system according to any preceding claim 1-8, characterized in that the wings (1, 2) are positionable relative to each other and to the direction of advancement (A) of the pulled apparatus (10, 10a, 10b, 10c, 10d) for adjusting the movement and/or floating characteristics of the pulled apparatus (10, 10a, 10b, 10c, 10d).

10. The system according to any preceding claim 1-9, characterized in that the wings (1, 2) are positionable relative to each other in terms of distances (d) and angles (α, β) as well as in terms of the transverse direction relative to the distance between the wings and of the water surface (S).

11. The system according to any preceding claim 1-10, characterized in that a floating apparatus (20) is provided in connection with the second pulley (15) for holding the second pulley (15) at a correct depth.

12. The system according to claim 11, characterized in that a first anchor (21a) is provided in connection with the second pulley (15) and/or the floating apparatus (20) for anchoring the second pulley (15) and/or the floating apparatus (20) in place.

13. The system according to any preceding claim 1-12, characterized in that the pulling apparatus (6) comprises a third pulley (22), wherein the space between the first pulley (14) and the third pulley (22) is provided with drive elements (23) for providing the drive between the power pack (12) and the pulling arrangement (11).

14. The system according to claim 13, characterized in that the drive element (23) is one or more endless ropes, wires, cables, belts or chains provided via the third pulley (22) and the first pulley (14).

15. The system according to any preceding claim 1-14, characterized in that the rope or line (16) comprises floating material.

16. The system according to any preceding claim 1-15, characterized in that the system comprises a pushing apparatus (24) provided between the pulling apparatus (6) and the first pulley (14) for pushing the first pulley (14) into water to a suitable depth.

17. The system according to any preceding claim 1-16, characterized in that the wave (W) is formed by a combined effect of the wings (1, 2), whereby at least one of the wings (1, 2) of the pulled apparatus is provided in such a way that, as the pulled apparatus (10, 10a, 10b, 10c, 10d) moves, it guides the flow of water in a downward direction to form a trough (W.sub.1) for the wave, and whereby at least one other second wing (1, 2) of the pulled apparatus (10, 10a, 10b, 10c, 10d) following the wing (1, 2) that guides the flow in a downward direction is arranged to guide the water flow in an upward direction to enhance the movement of water that flows back up to form (W) a crest (W.sub.2) for the wave.

18. The system according to any preceding claim 1-17, characterized in that the pulled apparatus (10d) comprises actively adjustable (30) and/or fixed aerofoils (36) that guide the travel of the pulled apparatus.

19. The system according to any preceding claim 1-18, characterized in that the pulled apparatus (10b) comprises weights and/or floats (28a, 28b) that contribute to the balance of the pulled apparatus (10b).

20. The system according to any preceding claim 1-19, characterized in that the pulled apparatus (10c) comprises a keel (29) installed below the pulled apparatus (10c) for balancing the pulled apparatus (10c).

21. The system according to any preceding claim 1-20, characterized in that the position and/or traveling depth of the pulled apparatus (10, 10a, 10b, 10c, 10d) are controlled by adjusting the pulling speed of the pulled apparatus (10, 10a, 10b, 10c, 10d).

22. The system according to any preceding claim 1-21, characterized in that the system comprises at least two pulling apparatuses (6, 6a) positioned at each end of the pulling arrangement (11).

23. A system for forming an artificial wave (W) in a water environment, characterized in that the system for forming an artificial wave (W) comprises a pulled apparatus (10, 10a, 10b, 10c, 10d), at least a first pulling apparatus (6b) and a second pulling apparatus (6c), each pulling apparatus (6b, 6c) comprising a power pack (12) and the pulled apparatus (10, 10a, 10b, 10c, 10d) comprising a wave-forming profile (13), wherein at least one rope or line (16) coupled to the first pulling apparatus (6b) and to the second pulling apparatus (6c) is provided substantially at or via both ends of the pulled apparatus (10, 10a, 10b, 10c, 10d) for providing the movement of the pulled apparatus (10, 10a, 10b, 10c, 10d) between the first pulling apparatus (6b) and the second pulling apparatus (6c), wherein the wave-forming profile (13) comprises at least two wings (1, 2), of which at least one wing (1, 2) is mainly transverse relative to the direction of advancement (A, B) of the pulled apparatus (10, 10a, 10b, 10c, 10d).

Description

LIST OF FIGURES

[0034] The accompanying figures, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the figures:

[0035] FIG. 1 is a fully schematical illustration produced by simulation software of a cross section of a pulled apparatus in the system according to the invention and of a wave produced thereby;

[0036] FIG. 2 is an illustration produced by simulation software of a flow pattern in wave formation;

[0037] FIG. 3 illustrates one example of an apparatus pulled in water for use in the system;

[0038] FIG. 4 illustrates one possible solution of an apparatus pulled in water;

[0039] FIG. 5 schematically illustrates one example of the system;

[0040] FIG. 6 schematically illustrates one example of the system;

[0041] FIG. 7 illustrates one possible solution of an apparatus pulled in water;

[0042] FIG. 8 illustrates one possible solution of an apparatus pulled in water;

[0043] FIG. 9 illustrates one possible solution of an apparatus pulled in water;

[0044] FIG. 10 schematically illustrates one example of the system; and

[0045] FIG. 11 schematically illustrates one example of the system.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying figures. In the accompanying figures, similar components are referred to by the same numbers.

[0047] The wave-forming profile 13 of a pulled apparatus 10 is not intended to be limited merely to a wing-like structure; it can be any wave-forming profile such as a plow-like V-shaped profile or the like, by which an artificial wave W is provided. As an example, one solution of a wave-forming profile 13 and two preferred embodiments of a pulled apparatus 10 will be disclosed below.

[0048] In FIG. 1, a wave W is formed on or in immediate proximity to a trailing wing, i.e. a second wing 2. The effect is shown in accompanying FIG. 1. The mechanism of the formation of the wave W is better illustrated in accompanying FIG. 2, which shows the flow pattern of the flow effect shown in FIG. 1. In both figures, the direction of advancement of the pulled apparatus is indicated with reference letter A.

[0049] In contrast to single-wing wave machines, the wave W is thus formed through a combined effect of two wings 1, 2. A first wing 1 of the pulled apparatus guides the flow in a downward direction towards the bottom of the water environment, forming a trough W.sub.1 for the wave W. The trailing second wing 2 enhances the movement of water that flows back up and thus raises the crest W.sub.2 of the wave. The wings 1, 2 are sized and positioned in a precise configuration relative to each other and the water surface S to create said interaction. The wave W is to be made as much as a natural wave as possible. The operating parameters for the formation of the wave W are determined e.g. as a function of the angles of attack, distance between the wings and pulling speed.

[0050] FIGS. 3 and 4 are schematical illustrations of two different implementations of the apparatus 10 pulled in water. In FIGS. 3 and 5, the pulled apparatus is generally indicated as reference number 10 and, respectively, in FIG. 4 as 10a. In the case of FIG. 3, the front and rear wing 1, 2 of the pulled apparatus 10 are fixed at their ends to frame beams 3 at a specific distance d from each other. The wings 1, 2 are further fixed to the frame beams 3 at specific angles α, β, in such a way that the angle of attack of the wings 1, 2 relative to water or to the direction of advancement A is as desired. In this case, the wings 1, 2 are also disposed at a desired angle relative to each other. The distance d between the wings 1, 2 from each other and their angle relative to each other are interdependent and essential in terms of wave formation and the depth at which the pulled apparatus 10 travels when it is pulled. The point of pulling the pulled apparatus 10 is indicated in FIGS. 3 and 4 as 4, 4a. In some cases it is preferred that at least one of the wings 1, 2 of the pulled apparatus 10 is fixed to the frame beams 3 in an adjustable manner in such a way that the angle between the wings 1, 2 can be adjusted if necessary. The pulled apparatus 10a according to FIG. 4 differs from the one illustrated in FIG. 3 in that the apparatus 10a comprises one central frame beam 5 to which the front and rear wing 1, 2 are fixed at a distance d from each other. It is also preferred in the case of FIG. 4 that the angle of attack of the wings 1, 2 relative to water may be adjusted. The wings 1, 2 of FIG. 3, 4 may be hollow.

[0051] The material of the surface of the wings 1, 2 and of the frame 3, 5 of the pulled apparatus 10 may vary. Furthermore, the structure of the pulled apparatus 10 may vary in terms of support, fixing of the pulling point and stabilizers (not illustrated). One possible material of the wings 1, 2 and/or the frame 3, 5 is aluminum. The wings 1, 2 can be attached together with frame beams 3 disposed on the sides as shown in FIG. 3. The wings 1, 2 can also be attached together with only one frame beam 5 disposed in the center of the wings 1, 2 as in FIG. 4.

[0052] For the wave W to be surfable, it may not advance so as to be perpendicular all over relative to the direction of advancement A. In practice, this requires that the ends of the wave W must have a section that breaks in a specific manner. This can be provided by suitably shaping the wings 1, 2 or at least one wing of the pulled apparatus 10 in the width direction. One possibility is to make at least one wing 1, 2 of the pulled apparatus 10 V-shaped. A similar effect may be reached by installing at least one of straight wings 1, 2 of the pulled apparatus 10 obliquely relative to the direction of advancement A.

[0053] Below, with reference to FIG. 5, one example of the system of the invention will be described. FIG. 5 shows that the pulled apparatus 10 of the system is provided with a wave-forming profile 13 which comprises two wings 1, 2. However, it is possible to enhance the formation of the artificial wave W and/or shape the resulting wave W by using more than two wings in the pulled apparatus 10. As stated above, the actual shape of the wings may vary. The wings or at least one of them can be e.g. straight, V-shaped, curved etc. The wing may be V-shaped in a plane extending parallel to the surface of water as well as in a plane extending perpendicular to the direction of advancement. Other shapes are also possible. Furthermore, the cross section of the wing 1, 2 may vary even within one wing, and it may be e.g. curved in several directions, and the wings 1, 2 may be hollow.

[0054] FIG. 5 shows one example of a system for forming an artificial wave W in a water environment, comprising a pulling apparatus 6, a pulled apparatus 10 and a pulling arrangement 11, wherein the pulling apparatus 6 comprises a power pack 12 and the pulled apparatus 10 comprises a wave-forming profile 13. The pulling arrangement 11 comprises at least two pulleys 14, 15 and at least one rope or line 16 provided at or via both ends of the pulled apparatus 10 and further via the pulleys 14, 15 for providing the movement of the pulled apparatus 10 between a first pulley 14 and a second pulley 15. Substantially at both ends of the pulled apparatus 10 means that the rope or line 16 can be fixed right to the end of the pulled apparatus 10 or for example at less than one meter from the end of the pulled apparatus 10. The wave-forming profile 13 is preferably floating.

[0055] The rope or line 16 can be provided so as to be fixed to the pulled apparatus 10 in many different ways. In one solution, the rope or line 16 can also be fixed in connection with the end of the pulled apparatus 10, in which case the pulled apparatus 10 is provided with hangers which for example protrude from the pulled apparatus 10 at the end of the pulled apparatus 10. In this case, the rope or line 16 is fixed to the hangers disposed at both ends of the pulled apparatus 10.

[0056] The rope or line 16 is preferably endless and/or forms a loop via the first pulley 14 and the second pulley 15. The rope or line 16 can alternatively be provided in such a way that it is fixed to the pulled apparatus 10 at one point only, e.g. at the center or near the center of the pulled apparatus 10. However, this requires that the rope or line 16 is to be guided to the pulleys 14, 15 via both ends of the pulled apparatus 10 in order that rotation of the pulled apparatus 10 by the effect of water can be prevented. In this case, the rope or line 16 is not fixed to both ends of the pulled apparatus 10. The rope or line 16 can alternatively be provided in such a way that the rope or line 16 extends through the pulled apparatus 10 in a continuous configuration or with the ends of the rope or line 16 attached together, in which case the rope or line 16 is a loop and may can be fixed to one or more points of the pulled apparatus 10. If the rope or line 16 is only fixed to the pulled apparatus 10 at one point, the pulled apparatus 10 must be prevented from rotating by guiding the rope or line 16 as described above.

[0057] The location of the pulling apparatus 6 may can be selected according to the operating site selected by the user of the system. A simple way is to place the pulling apparatus 6 on the shore. If the pulling apparatus 6 is placed on the shore, it means herein that the pulling apparatus 6 is placed on the shore right at the water's edge, in shallow water or farther away from the water's edge in the shore area. Alternatively, however, the pulling apparatus 6 may be provided on a ship, a vessel, a barge or other watercraft (not illustrated). In this case, the pulling apparatus 6 may can be placed for example on the deck of a ship and/or at the stern of a ship (not illustrated). The driving force for the pulling apparatus 6 and for the power pack 12 is most preferably electricity. A third example of the location of the pulling apparatus 6 is to provide the pulling apparatus 6 on a structure 27 that is included in the system so as to float or be disposed in and/or on water and anchored in place. One example of a suchlike structure 27 is shown and described below with reference to FIG. 6.

[0058] The pulled apparatus 10 is pulled for example at a depth of 1-3 meters from the water surface S. The pulling distance may be hundreds of meters. Preferably, the suitable water area is several meters deep.

[0059] The wave-forming profile 13 comprises at least two wings 1, 2, of which at least a first wing 1 is mainly transverse relative to the direction of advancement A of the pulled apparatus 10. As the wings 1, 2 are positionable relative to each other and to the direction of advancement A of the pulled apparatus 10, the movement and/or floating characteristics of the pulled apparatus 10 may be adjusted. As described above with reference to FIGS. 3 and 4, also in FIG. 5 the wings 1, 2 are positionable relative to each other in terms of distances d and angles α, β, as well as in terms of the transverse direction relative to the distance between the wings 1, 2 and of the water surface S. The height of the resulting wave W may thus be adjusted by adjusting the wings 1, 2 relative to each other. The wings 1, 2 are preferably hollow and/or floating.

[0060] The system comprises an anchoring arrangement 17 for holding the pulling apparatus 6 in place on the shore, which comprises a tank 18 which is to be filled with water. The tank 18 is a transportation container, the components of the system being adapted to be moved and/or transported therein. The pulling apparatus 6 comprises a water pump 19 by which the tank 19 is filled and/or emptied. The suction and discharge lines (not illustrated) of the water pump 19 for the pulling apparatus 6 are provided in connection with the body of water used as the surfing area for filling and emptying the tank 18 with the water pump 19. The tank 18 functions as a counterweight for the pulling apparatus 6, supporting the holding in place of the pulling apparatus 6. When the system is to be disassembled, all the components required for the system are moved into the emptied tank 18 and the tank 18 is used as a transportation container, so that the entire system can be moved to another place and/or for example stored for winter. This also facilitates the delivery of the system from manufacture to the buyer, as the components are already packed within a transportationproof structure. If a ship or other watercraft (not illustrated) is the fixed place of the pulling apparatus 6, the system may be used as if it was disposed on the shore. The difference is that the weighty ship does not necessarily require the further weight of a water-filled tank 18. From a ship or other such watercarft, the system may be operated and used as from the shore.

[0061] A floating apparatus 20 is provided in connection with the second pulley 15 for holding the second pulley 15 at the right depth. A first anchor 21a is provided in connection with the second pulley 15 and/or the floating apparatus 20 for anchoring the second pulley 15 and/or the floating apparatus 20 in place. Most preferably, the floating apparatus 20 is provided with a pontoon-like structure or other similar solution, by which the floating is provided. If a ship or other watercraft is used as the fixed place for the pulling apparatus 6, the ship may be steered to an island or other similar fixed place (not illustrated) within the water area. In this case, the second pulley may be taken from the ship for example to the island and fixed thereto, whereby the first anchor 21a and the floating apparatus 20 are not necessary.

[0062] The pulling apparatus 6 comprises a third pulley 22, wherein the space between the first pulley 14 and the third pulley 22 is provided with drive elements 23 for obtaining the drive between the power pack 12 and the pulling arrangement 11. A number of alternative solutions may be used as the drive element 23. The drive element 23 is for example one or more endless ropes, wires, cables or belts provided via the third pulley and the first pulley 14. The first pulley 14 and the third pulley 22 can alternatively be provided with teeth (not illustrated) for providing a chain drive between the pulleys 14, 22, in which case a chain is used as the drive element 23. In the above-described cases, the drive element 23 forms a loop via the third pulley and the first pulley. Further, the drive element 23 may alternatively be a Cardan joint for providing the drive between the first pulley 14 and the third pulley 22. By adjusting the rotation of the drive element 23, the height of the wave W can be varied.

[0063] The system comprises a pushing apparatus 24 provided between the pulling apparatus 6 and the first pulley for pushing the first pulley 14 into water to a suitable depth. The pushing apparatus 24 is a device operated from the shore and having a rigid beam-type or pole-type structure for controlling the position of the first pulley 14 in water or alternatively for holding it in place. The pushing apparatus 24 is used for adjusting the tightness of the rope or line 16. The pushing apparatus 24 adjusts the position of the first pulley 14 and the second pulley 15 relative to each other. The pushing apparatus is used to provide the first pulley 14 flush with the second pulley 15. Alternatively, the first pulley 14 may be provided on the bottom of the water area in a fixed or detachable manner so that no pushing apparatus is required.

[0064] The rope or line 16 of FIG. 5 is made from floating material, whereby the rope or line 16 floats. For example, the rope 16 may be made from polyethylene. Basically, the pulling direction is to be kept constant, and thus the rope or line 16 is most preferably floating. The pulling arrangement 11 is used for moving the pulled apparatus 10 in the direction of advancement A and in the opposite direction B. Since in order to form an artificial wave the pulled apparatus 10 comprising the wave-forming profile 13 is pulled in water in only one direction, after each pulling maneuver the pulled apparatus 10 must be returned to the initial position. The pulling arrangement 11 forms a rope drive for moving the pulled apparatus 10 also in the opposite direction B relative to the direction of advancement A for returning the pulled apparatus 10 to the initial position.

[0065] Stabilizing, i.e. balancing, the wings may be appropriate and even necessary in some cases. Examples of stabilization methods are shown in FIG. 7-9. Stabilization can be provided e.g. by a keel installed below the pulled apparatus 10 comprising the wings 1, 2. It may also be necessary to use pontoons disposed at the edges of the wings 1, 2 or, more precisely, of the pulled apparatus 10 itself. In an optimal situation, these structures are sufficient to secure the stability of the pulled apparatus 10 as it moves in water. In addition to the methods described, the stability may be improved, if necessary, for example with a rudder or other guide aerofoils (not illustrated in FIG. 5). Such stabilizing structures may be passive or active, adjustable according to the location of swimming of the pulled apparatus 10. The pulled apparatus 10 may comprise a third wing (not illustrated in FIG. 5) and/or one or more weights (not illustrated in FIG. 5) for stabilizing the movement of the pulled apparatus 10 in water. With a suitable angular position of the wings 1, 2 and possible stabilizing structures, the wave W forming pulled apparatus 10 may be moved in a correct position and at a correct depth from the surface S of flowing water so as to provide the desired wave formation.

[0066] The system comprises an automation and control system for automatizing the operation of the system. A control center 26 is necessary for adjusting and controlling the system. The pulling apparatus 6 is connected under control of the automation and control system 25.

[0067] As stated above, the system is provided with a suitable automation and control system 25. The automation and control system 25 is used for starting the wave-forming pulling movement and, if necessary, for stopping the operation of the system. The control system may be manually operated and optionally provided with remote control. The operating system must also include automation by which the pulling duration and speed are adjusted. Also, the pulling direction may need to be adjusted.

[0068] FIG. 6 shows another example of a system for forming an artificial wave W in a water environment. FIG. 6 corresponds in other respects to the system shown in FIG. 5 except that the pulling apparatus 6 and the anchoring arrangement 17 comprising a tank 18 are disposed on a structure 27 included in the system so as to float or be provided in and/or on water and anchored in place. FIG. 6 shows the above-mentioned structure 27 as a pontoon-like structure. The place 27 can also be a pier that is fixed in place in or on water or other similar structure bearing the load of the pulling apparatus 6 that is disposed in or on water so as to float or be fixed to the bottom of the water area. The structure 27 is arranged to be held in place for example by means of a second anchor 21b. This allows the entire system to be disposed in the water area in a floating manner. If, in addition, the pulling apparatus 6 and the anchoring arrangement 17 comprising a tank 18 are provided on a floating structure 27 that is anchored in place and the first pulley 14 is provided in connection with the pulling apparatus 6, the entire system is floating and can be easily taken to a suitable place within the water area and anchored in place for surfing.

[0069] If the structure 27 is a pier (not illustrated in FIG. 6), it can be fixed in place for example with pillars (not illustrated in FIG. 6) disposed on the bottom of the water area or, correspondingly, by anchoring the pier by means of a second anchor 21b.

[0070] In one solution, the first pulley 14 is also arranged to float in addition to the second pulley 15, whereby the first pulley 14 is anchored to be held in place in water for example with a third anchor (not illustrated in FIG. 6) fixed to the first pulley 14 and dropped to the bottom of the water area. In FIG. 6, the first pulley is fixed to the floating structure 27 that is anchored in place with a pushing apparatus 24 provided between the pulling apparatus 6 and the first pulley.

[0071] FIG. 7 shows one possible solution of an apparatus 10b pulled in water. As described above, the pulled apparatus 10b may comprise stabilizing structures to secure the stability of the pulled apparatus 10b as it moves in water. The pulled apparatus 10b of FIG. 7 comprises weights and/or floats 28a, 28b that contribute to the balance of the pulled apparatus 10b. If floats 28a, 28b are used, they can be arranged for example to float near surface. In this case, it must be secured that the floats 28a, 28b do not disturb surfing too much. Alternatively, the pulled apparatus 10b may comprise for example sand-filled weights (not illustrated in FIG. 7) fixed to or hanging from the sides of the pulled apparatus for stabilizing the movement of the pulled apparatus 10b in water. The stabilizing structure may be a passive structure such as an aerofoil 36. One example of an aerofoil 36 is illustrated in FIG. 7. The aerofoil 36 can be installed for example behind the second wing 2 of the pulled apparatus 10b to guide the travel of the apparatus 10b. The aerofoil 36 may alternatively be adjustable with a separate adjusting element (not illustrated in FIG. 7) or its position may be manually adjusted by changing the fixing points.

[0072] FIG. 8 shows one possible solution of an apparatus 10c pulled in water. Stabilization may be provided for example with a keel 29 installed below the pulled apparatus 10c comprising the wings 1, 2. The keel may be shaped for example to be spindle-like or alternatively as a fin or their combination.

[0073] FIG. 9 shows one possible solution of an apparatus 10d pulled in water. In addition to the methods described above, such as weights, wings and a keel, the stability may be improved, if necessary, for example by means of a rudder 30 or other guide aerofoils. Such stabilizing structures may be passive or active, adjustable according to the location of swimming of the pulled apparatus 10d. Passive wings may be fixed or manually adjustable as shown in FIG. 7. The rudder 30 may be controlled from example by means of an actuator 32. The rudder 30 is coupled to the pivoting points 31a, 31b of the pulling apparatus 10d in a hinged manner. As the rudder 30 is moved by the actuator 32 in the directions of a first arrow 34, the rudder 30 can be turned according to a second arrow 33. The control of the actuator can be provided for example with remote control 35. One possible way of remote control may be radio control. In this case, for example an antenna that extends near the water surface may be used.

[0074] FIG. 10 schematically shows one example of the system. In the example of FIG. 10, the system comprises two pulling apparatuses 6, 6a which are positioned at each end of the pulling arrangement 11. One pulling apparatus 6b can be used for example to control the tightness of the rope or line 16 and to hold it at a suitable depth, whereby for example floating apparatuses and/or weights are not required for fixing the pulling arrangement 11. Said system may be placed in a suitable water environment such as a small lake, a deep pond or even in a man-made place such as a harbor basin.

[0075] FIG. 11 schematically shows one example of the system. The system shown in FIG. 11 differs from the system according to FIG. 5 in that pulleys as such are not necessarily required in the system of FIG. 11. The pulling apparatuses 6b, 6c are provided on each side of a suitably sized water area. The pulling apparatuses 6b, 6c are disposed on a level below the water surface at a suitable depth, whereby wave formation is possible without pulleys. As a first pulling apparatus 6b feeds the rope or line 16, a second pulling apparatus 6c receives it, whereby the rope or line 16 provides the movement of the pulled apparatus 10 between the first pulling apparatus 6b and the second pulling apparatus 6c. The wave-forming profile 13 comprises at least two wings 1, 2, of which at least one wing 1 is mainly transverse relative to the direction of advancement A, B of the pulled apparatus 10.

[0076] In all of the examples described above, the position and/or traveling depth of the pulled apparatus 10, 10a, 10b, 10c, 10d may also be controlled by adjusting the pulling speed of the pulled apparatus 10, 10a, 10b, 10c, 10d.

[0077] The pulled apparatus may contain structures from a number of examples of the pulled apparatus 10, 10a, 10b, 10c, 10d as described. The pulled apparatus 10, 10a, 10b, 10c, 10d may for example comprise a number of different stabilizing structures. With a suitable angular position of the wings 1, 2 and possible stabilizing structures, the wave W forming pulled apparatus 10, 10a, 10b, 10c, 10d can be moved in a right position and at a right depth from the surface S of flowing water so as to provide a desired height of the wave W.

[0078] The functions described above are not exclusively limited to surfing; the applications may also include other cases where a controllable artificial wave W is to be provided. Other forms of physical activity which are not specifically surfing but are closely related to it, such as bodyboarding, can also be performed on top of a wave W. Furthermore, it may be possible to use the system for surfing with equipment which is not necessarily actual surfing equipment.

[0079] FIGS. 3 and 4 show two different ways of attaching and securing the wings to the frame structure. However, these are only examples which can be deviated from. The essential feature is that the wings can be positioned in a desired and specific way relative to each other e.g. in terms of distances and angles. The positioning of the wings may be static or adjustable.

[0080] The invention has been described above mainly with the formation of a wave being based on an idea of pulling the pulled apparatus 10 from a fixed place that carries the pulling apparatus 6, such as a shore, a watercraft or a floating structure 27 that has been anchored in place. When placing the pulling apparatus 6 near shoreline, it can be disposed for example right at the water's edge. However, suitable distances from the water's edge may vary according to the operating area.

[0081] The system has been exemplified above with reference to the accompanying figures. However, the scope of protection of the invention is not limited merely to the examples illustrated in the figures; instead, the embodiments of the invention may vary within the scope of the inventive idea defined in the accompanying claims.