EP2839174A1

EP2839174A1 - A submerged unit for pivotally securing an elongated portion to a foundation

Info

Publication number: EP2839174A1
Application number: EP13778737.0A
Authority: EP
Inventors: Hans Lindén
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2012-04-16
Filing date: 2013-04-04
Publication date: 2015-02-25
Also published as: EP2839174A4; WO2013158006A1

Abstract

The invention concerns a submerged unit (1 ) for securing an elongated portion (100) such as a wire to a foundation (1 10). The unit comprises a first hollow part (2) presenting an inner spherical surface (21 ), a second part (3) presenting an outer spherical surface (31 ), wherein the spherical surface (31 ) of the second part (3) essentially matches the spherical surface (21) of the first part (1 ). The second part (3) is received in the first hollow part (2) such that a relative rotation between the first and second part (2, 3) around a pivot point (4) can be accomplished. The first or second part (2, 3) further presents a connecting means (5) meant to connect to the elongated portion (100). A housing (6) at least partly surrounds the first part (2) to seal off the first and second part (2, 3) from the surrounding environment. Furthermore, the invention concerns a device (200) for locking a submerged unit (1) to a foundation (110).

Description

A submerged unit for pivotally securing an elongated portion to a foundation.

TECHNICAL FIELD

The invention relates to sub sea applications, such as sub sea arrangements for generating electrical energy from tidal water, water streams or waves.

According to a first aspect, the invention regards a submerged unit for securing an elongated portion, such as a wire, to a foundation on the bottom of the sea.

According to a second aspect, the invention regards a device for locking a submerged unit to a foundation on the bottom of the sea.

BACKGROUND

Sub sea applications can be very demanding in many aspects. For instance, it is often difficult and also expensive to perform maintenance and repair work on such applications. Furthermore, installation of sub sea applications is often difficult. Especially if the application is located on the bottom of the sea it will be hard to perform e.g. repair and maintenance work on the device due to the harsh environment on the bottom, i.e. low visibility, high pressures etc.

One application that needs to be secured to the bottom of the sea is a tidal water power plant, such as for instance described in patent application EP2295792A2. This application is secured to the bottom via e.g. a wire. The kite that moves in the water and thereby generates electrical energy via a turbine also generates very high forces at the securing location of the wire at the bottom of the sea.

Other applications that may need to be secured to the bottom can be wave energy power plants, buoys etc. There is a need to develop an arrangement that is very robust and reliable and that can handle the high forces generated from e.g. a wire. SUMMARY OF THE INVENTION

An object of the invention is thus to provide an arrangement that is very robust and reliable and that can handle the high forces generated from e.g. a wire.

According to the first aspect of the invention, this object has been achieved by a submerged unit for securing an elongated portion such as a wire to a foundation. The unit comprises a first hollow part presenting an inner spherical surface and a second part presenting an outer spherical surface,. The second part is received in the first hollow part such that a relative rotation between the first and second part around a pivot point can be accomplished. Furthermore, the first or second part further presents a connecting means, which connects the elongated portion to the unit, and a housing which at least partly surrounds the first part to seal off the first and second part from the surrounding environment.

This design has the advantage of being very robust and reliable and also in that it can perform a three axis rotational movement to secure a wire that moves in the water, for instance a wire connected to a submerged tidal water power plant.

In an embodiment, the spherical surface of the second part essentially matches the spherical surface of the first part. The two matching surfaces of the first and second part may be sliding against each other with a lubrication film in-between and thereby function as a sliding bearing (also known as plain bearing). The surfaces may be made of a material that is good for enabling a relative sliding, such as a steel or a polymer. A polymer may for instance be a polymer surface that can accommodate a lubricant, such as oil.

In an embodiment, rolling elements are interposed between the two spherical surfaces. The spherical surfaces and the rolling elements are arranged such that a relative rotation between the two parts can be accomplished. The rolling elements may e.g. be in the form of rollers or balls.

In an embodiment, the submerged unit further comprises a through-hole from the region of the connecting means via the pivot point. The through hole may be used to accommodate different types of devices etc and to integrate sensitive devices into the submerged unit. In an embodiment, the submerged unit further comprises a retractable elastic means, such as a coil spring, in the through-hole, the retractable means being configured to strive to retain the first and second part in a specific relative rotational position to each other. If for instance, in the case of a tidal power plant, the movement of the kite is stopped, there is a risk that the kite will start to move in the water in an uncontrolled manner. An integrated spring in the device would ascertain that the kite will remain in an essentially upward position in the water. The retractable elastic means may be any type of means that is able to strive to retain the first and second part in a specific position. In another embodiment, at least one cable is present in the through-hole. The cable may be configured to transfer electrical energy and/or electrical signals. It is advantageous to be able to integrate cables etc. into the submerged unit instead of leading cables etc. outside the unit. This will increase robustness and the reliability of the unit. In an embodiment, the submerged unit further comprises a sensor for sensing a relative rotation between the first and second part around at least one axial direction. There may be a need to be able to determine an angular position of the elongated means which is connected to the submerged unit. A sensor in the unit would be able to determine this angular position. In another embodiment, the sensor is integrated in a bearing. The bearing may be located such that it can measure angular displacement around one axis. There may also be more bearings with integrated sensors for measuring angular displacements around other orthogonal axial directions. In an embodiment, the sensor is located within the housing. In another embodiment, the sensor is also integrated in any of the first part or the second part. The robustness and reliability of the unit, and also the sensing function, will be maintained by integrating the sensor into the housing and also into one of the first and second parts.

In an embodiment, a moisture sensing means is integrated in the unit. By measuring moisture in the unit it will be possible to get an indication of the condition of the unit. If the moisture level would exceed a certain value it could be an indication of that the unit needs to be reconditioned or replaced. The signal from the sensing means may be sent to a computer means that calculates a value indicative of the condition of the unit.

In an embodiment, the unit further comprises a load sensing means for measuring a load originating from the elongated portion. The load sensing means is preferably integrated into the unit. If for instance the elongated member is holding a kite of a tidal water power plant, it may be good to get an indication of the loads emanating from the kite. If the loads are too high or even too low that may be an indication of that something is not correct with the kite.

In another embodiment, a temperature sensing means is integrated into the unit. Temperature may for instance be measured to get an indication of the condition of the unit. The temperature value may be sent to a computer means that calculates a value indicative of the condition of the unit.

In an embodiment, the submerged unit further comprises a bellow surrounding at least parts of the housing. This will even further increase robustness and reliability of the unit. The bellow may be made by e.g. rubber or any other flexible material.

In an embodiment, the elongated portion is rotatably connected to the connecting means. The elongated portion, such as a wire, may need to rotate. For instance, if a tidal water plant with a kite would move in a circular path in the water, the wire securing the kite to the bottom may need to rotate. In an embodiment, a motor is configured to be able to rotate the elongated portion. The motor is preferably integrated into the submerged unit and sealed off from the surrounding environment.

In an embodiment, the housing presents an elongated crevice along a part of the circumference of the housing for permitting a rotational relative movement between the first and second part.

According to the second aspect of the invention, the object is achieved by a device for locking a submerged unit to a foundation, wherein the submerged unit is meant to secure an elongated portion such as a wire to the foundation. The device comprises a locking means meant to be able to be inserted into the foundation, wherein the locking means presents elongated locking portions.

Furthermore, the device comprises an actuator which comprises a screw and nut arrangement and a motor for enabling a relative rotational motion of the screw and nut such that a translational movement is accomplished. Furthermore, the device comprises a chamber for accommodating a fluid, wherein the translational movement is arranged to increase and decrease the volume of the chamber to thereby transfer a hydraulic force, wherein the hydraulic force is meant to lock and unlock the locking means to/from the foundation. This design is very robust and reliable for securing the submerged unit. The submerged unit may for instance be a submerged unit as presented in the first aspect of the invention.

It shall be noted that all embodiments of the first aspect are applicable to the second aspect and vice versa.

The actuation of the nut and screw may for instance be accomplished by providing electrical energy generated from the tidal water plant. The energy may for instance be stored in a battery.

BRIEF DESCRIPTION OF DRAWINGS

Below, a more detailed description of a number of preferred embodiments will be described. It should be noted that the accompanying drawings are not drawn to scale, and in some cases specific details may have been exaggerated in order to better explain the invention. Furthermore, the invention as claimed is not limited to the embodiments described and shown, but modifications are possible for a skilled person within the scope of the claims.

Figure 1 is a cross sectional schematic view of an embodiment of the invention.

Figure 2 is showing an embodiment of a submerged unit according to the invention.

Figure 3 discloses a submerged unit according to the invention which is anchoring a tidal water power plant kite. Figure 4 discloses a submerged unit according to the invention which is anchoring a tidal water power plant kite and which further presents a bellow.

Figure 5 shows a schematic cross sectional view of a device according to the second aspect of the invention.

Figure 6 shows a part of an embodiment of a device according to the second aspect of the invention.

Reference numerals:

1 : Submerged unit 2: First hollow part

3: Second part

4: Pivot point

5: Connecting means

6: Housing 7: Through-hole

8: Retractable elastic means

9: Bellow

10: Crevice on housing

21 : Inner spherical surface on first part 31 : Outer spherical surface on second part

100: Elongated portion

1 10: Foundation

120: Kite

200: Device 201 : Locking means 202: Elongated locking portions 203: Screw

204: Nut 205: Motor

206: Chamber

207: Spring

208: Elongated mounting and dismounting portions

209: Positioning portions

DETAILED DESCRIPTION OF DRAWINGS

Figure 1 discloses a cross sectional schematic view of a submerged unit 1 according to the invention. The unit 1 comprises a first hollow part 1 and a second part 2. The first part presents an inner spherical surface 21 and the second part presents an outer spherical surface 31. The two surfaces 21 and 31 essentially match each other so that a relative rotational movement can be accomplished around a pivot point 4. The space between the two surfaces 21 and 31 is exaggerated in this figure. The space may for instance contain a lubricant such as oil for facilitating the sliding motion between the first and second part 21 and 31. The surfaces 21 and 31 may also be made of a material that is suitable for sliding motion. Such material could for instance be steel or a polymer. A preferable material would be a material that is able to accommodate a lubricant, such as a polymer that presents lubricant holes or pores. In another embodiment, rolling elements (not shown) may be interposed between the two surfaces 21 and 31 for accomplishing the relative rotation. Furthermore, the unit comprises a through hole 7 that starts close to a connecting means 5 in the top of the unit 1. The connecting means 5 is configured to connect to an elongated portion 100, such as a wire. The connecting means 5 is located on the first part 2 and will rotate with the first part 2. However, the connecting means 5 could likewise be connected to the second part 3 and rotate with the second part 3. Furthermore, the top of the connecting means 5 is rotatable with the wire 100. An electrical cable (not shown) may be located in the through hole 7. The electrical cable may for instance transfer electrical energy that has been generated in a turbine and generator arrangement in tidal water power plant kite. At the bottom of the unit 1 there may be located a slip ring (not shown) for transferring electrical energy. Furthermore, the unit 1 presents a retractable elastic means 8, which in this illustration is a coil spring. The spring 8 is meant to strive to hold the elongated portion 100 in an upright position. In the case when the wire 100 is connected to a tidal water power plant kite, there may be a need to hold the kite in an upright position when the kite is not in operation. For instance, if repair or service work is to be done on the kite it is preferable if the kite is in an upright position close to the surface of the sea. The unit 1 may further comprise sensors for sensing an angular position of the unit 1 . The sensors may for instance be integrated in bearings (not shown) in the unit 1 . The design of the unit 1 leads to a very robust and reliable construction, which is of high importance for sub sea applications.

Figure 2 shows a submerged unit 1 according to the invention. In this illustration, a housing 6 is seen, which encloses the first and second part 2 and 3 from the surrounding environment, i.e. the sea. The housing 6 is divided in two parts which are joined together. A wire 100 is also seen which is connected to the unit 1 via a connecting means. The connecting means 5 may be able to rotate.

Furthermore, the connecting means may contain an electrical motor for rotating the wire 100. Furthermore, a crevice 10 on the housing 6 is seen. The crevice 10 allows the unit 1 to rotate around the horizontal axis in the figure.

Figure 3 discloses a submerged unit 1 according to the invention which is anchoring a tidal water power plant kite 120. The kite 120 is connected to the submerged unit 1 via an elongated portion 100, such as a wire. The submerged unit 1 is in turn connected to the ground via a foundation 1 10. The foundation may for instance be of concrete. Figure 4 discloses a submerged unit 1 according to the invention which is anchoring a tidal water power plant kite 120. The kite 120 is connected to the submerged unit 1 via an elongated portion 100, such as a wire. The submerged unit 1 is in turn connected to the ground via a foundation 110. The foundation may for instance be of concrete. Furthermore, the unit comprises a bellow 9 enclosing at least parts of the unit 1 . The bellow 9 increases the robustness and reliability of the unit 1 .

Figure 5 shows an embodiment of a device 200 according to the second aspect of the invention. The device 200 is meant to for lock a submerged unit 1 to a foundation 1 10, wherein the submerged unit 1 is meant to secure an elongated portion (not shown) such as a wire to the foundation 110. The submerged unit 1 does not necessarily need to be a unit 1 as disclosed in the first aspect of the invention. The device 200 comprises a locking means 201 meant to be able to be inserted into the foundation 1 10. The foundation 1 10 is in a cross sectional view in this figure. The locking means 201 presents elongated locking portions 202. The locking portions 202 can move in and out from the locking means 201 .

Furthermore, the device 200 comprises an actuator which comprises a screw 203 and nut 204 arrangement and a motor 205 for enabling a relative rotational motion of the screw 203 and nut 204 such that a translational movement is accomplished. Furthermore, the device 200 comprises a chamber 206 for accommodating a fluid, wherein the translational movement is arranged to increase and decrease the volume of the chamber 206 to thereby transfer a hydraulic force, wherein the hydraulic force is meant to lock and unlock the locking means 201 to/from the foundation. The nut 204 will thus function as a piston in a hydraulic system. It will be an electromechanical system combined with a hydraulic system. This configuration is very robust and reliable. The locking portions 202 are meant to be inserted into holes in the foundation 10. This design is very robust and reliable for securing the submerged unit 1. The actuator may be integrated into the locking means 201. It may also be located outside the locking means 201. Furthermore, the foundation 1 10 may present a recess (not shown) on the top of the foundation 1 10 where the actuator can be located. The motor 205 may be driven by electrical energy created in the tidal power plant. A battery may also be connected to the device 200 to power the motor 205. Furthermore, a spring 207 is located in the actuator. The spring 207 is a safety spring that will assure that the locking means 201 will not be

unintentionally released from the foundation 1 10, for instance if the screw 203 and nut 304 arrangement would brake. The motor 205 may be able to measure a position of the nut in the chamber 206 to thereby get an indication of the position of the locking portions 202. In another embodiment, sensing means may be located in other locations to measure the position of the locking portions 202. For instance, the sensing means may be located close to the locking portions 202 or it may be located in or close to the chamber 206.

Figure 6 shows a part of an embodiment of a device 200 according to the invention. The device 200 further comprises elongated mounting and

dismounting portions 208. The portions 208 may be pipes made of a polymer, such as rubber. The pipes 208 are connected to the unit 1 by positioning portions 209, which in this illustration are ring-formed members into which the pipes 208 are located. Further, the pipes 208 are connected to the foundation 1 10 in a position such that the locking means 201 of the unit 1 will fit correctly into the foundation 1 10. When installing or dismounting the unit 1 from the foundation 1 10 by releasing the locking means 201 by retracting the locking portions 202, the pipes 208 are used to locate and correctly position the unit 1 to the foundation 110. When the unit 1 has been correctly positioned and locked to the foundation 1 10, the pipes 208 may fall down to the bottom of the sea. Due to the fact that the portions 208 may be made of a polymeric material, such as rubber, the weakness of the pipes 208 will lead to that the pipes 208 may fall down. In an embodiment, the pipes 208 comprise weights (not shown) in the top region of the pipes 208 to thereby facilitate that the pipes 208 descend to the bottom. In an embodiment, the pipes 208 can be hollow and be able to lead a pressurized fluid to the foundation 1 10. This can for instance be advantageous if there is a need to clean the part of the foundation 1 10 where the unit 1 is meant to be installed. This will thus facilitate mounting of the unit 1 . In this illustration, two elongated mounting and dismounting portions 208 are shown, but it can of course be more than two if considered needed.

Claims

1. Submerged unit (1) for securing an elongated portion (100) such as a wire to a foundation (110), the unit comprising,

- a first hollow part (2) presenting an inner spherical surface (21),

- a second part (3) presenting an outer spherical surface (31),

- wherein the second part (3) is received in the first hollow part (2) such that a relative rotation between the first and second part (2, 3) around a pivot point (4) can be accomplished,

- the first or second part (2, 3) further presents a connecting means (5) connecting the elongated portion (100) to the unit, and

- wherein a housing (6) at least partly surrounds the first part (2) to seal off the first and second part (2, 3) from the surrounding environment.

2. Submerged unit (1) according to claim 1 , further comprising,

- a through-hole (7) from the region of the connecting means (5) via the pivot point (4).

3. Submerged unit (1) according to claim 2,

- further comprising a retractable elastic means (8) in the through-hole (7), the retractable means (8) being configured to strive to retain the first and second part (2, 3) in a specific relative rotational position to each other.

4. Submerged unit (1 ) according to claim 2,

- wherein at least one cable is present in the through-hole.

5. Submerged unit (1) according to claim 4,

- wherein the at least one cable is meant to transfer any of electrical energy or electrical signals.

6. Submerged unit (1 ) according to any of the preceding claims,

- further comprising a sensor for sensing a relative rotation between the first and second part around at least one axial direction.

7. Submerged unit (1) according to claim 6,

- wherein the sensor is integrated in a bearing.

8. Submerged unit (1) according to claim 6 or 7,

- wherein the sensor is located within the housing (6).

9. Submerged unit according to claim 8,

- wherein the sensor further is integrated in any of the first part (2) or the second part (3).

10. Submerged unit (1) according to any of the preceding claims,

- wherein the unit (1) further comprises a bellow (9) surrounding at least parts of the housing (6).

11. Submerged unit (1) according to any of the preceding claims,

- wherein the elongated portion (100) is rotatably connected to the connecting means (5).

12. Submerged unit (1) according to claim 11 ,

- wherein a motor is configured to be able to rotate the elongated portion (100).

13. Device (200) for locking a submerged unit (1) to a foundation (1 10), wherein the submerged unit (1) is meant to secure an elongated portion (100) such as a wire to the foundation (110), the device comprising,

- a locking means (201) meant to be able to be inserted into the foundation (110), the locking means presenting a number of elongated locking portions (202)

- an actuator comprising a screw (203) and nut (204) arrangement and a motor (205) for enabling a relative rotational motion of the screw (203) and nut (204) such that a translational movement is accomplished,

- a chamber (206) for accommodating a fluid,

- wherein the translational movement is arranged to increase and decrease the volume of the chamber (206) to thereby transfer a hydraulic force, wherein the hydraulic force is meant to move the locking portions (202) to thereby lock and unlock the locking means (201) to/from the foundation.