NL2020968B1

NL2020968B1 - Assembly comprising a first and a second section and a fixation

Info

Publication number: NL2020968B1
Application number: NL2020968A
Authority: NL
Inventors: Winkes Jasper
Original assignee: Fistuca B V
Priority date: 2018-05-22
Filing date: 2018-05-22
Publication date: 2019-11-28

Abstract

The present invention relates to an assembly, comprising a first and a second section, each section comprising a longitudinal axis, and a fixation configured to fix the first and the second section, wherein at least one of the first and the second section comprises a body that is configured to be engaged by the fixation, and wherein the fixation comprises an abutment and a displaceable actuator, wherein the actuator is radially displaceable relative to the longitudinal axis of the section that comprises the actuator, and further comprising an insert that is arranged between the abutment and the displaceable actuator.

Description

Θ 2020968 ©B1 OCTROOI (2?) Aanvraagnummer: 2020968 (51) Int. Cl.:

F03D 13/25 (2018.01) F16L 25/06 (2019.01) (22) Aanvraag ingediend: 22 mei 2018 (30) Voorrang:

(4^) Aanvraag ingeschreven: 28 november 2019 (43) Aanvraag gepubliceerd:

(73) Octrooihouder(s):

Fistuca B.V. te DELFT (72) Uitvinder(s):

Jasper Winkes te Den Haag (74) Gemachtigde:

ir. P.J. Hylarides c.s. te Den Haag

47) Octrooi verleend:

november 2019 (45) Octrooischrift uitgegeven:

november 2019 (54) ASSEMBLY COMPRISING A FIRST AND A SECOND SECTION AND A FIXATION (57) The present invention relates to an assembly, comprising a first and a second section, each section comprising a longitudinal axis, and a fixation configured to fix the first and the second section, wherein at least one of the first and the second section comprises a body that is configured to be engaged by the fixation, and wherein the fixation comprises an abutment and a displaceable actuator, wherein the actuator is radially displaceable relative to the longitudinal axis of the section that comprises the actuator, and further comprising an insert that is arranged between the abutment and the displaceable actuator.

B1 2020968

Dit octrooi is verleend ongeacht het bijgevoegde resultaat van het onderzoek naar de stand van de techniek en schriftelijke opinie. Het octrooischrift komt overeen met de oorspronkelijk ingediende stukken.

Assembly comprising a first and a second section and a fixation

The present invention relates to an assembly, comprising a first and a second section, and a fixation configured to fix the first and the second section.

The present invention is particularly suitable for offshore applications, e.g. for connecting a wind turbine to a monopile, a wind turbine to a transition piece, a transition piece to a monopile, as well as between sections of a monopile or wind turbine, and jacket connections.

According to prior art applications in offshore, the sections of such assemblies are provided with flanges which are connected using bolts of significant size. Currently M72 bolts are used for connecting a wind turbine tower to a monopile or transition piece. In a first step, these bolts are electrically tightened with 8.000 Nm. In a second step, the preload is increased with hydraulic tools to 22.000 Nm. The bolts itself are heavy and the tools for tightening the bolts are also heavy and hard to handle.

It appears that the actual preload on the bolts after some settling time is hard to predict and control, and may vary significantly. Although it is not exactly clear which factors influence the torque-tension relationship of the bolts, it may be concluded that installing the bolts using a “constant torque” method does not achieve satisfying results. The preload on the bolts must be regularly checked and adjusted, periodically requiring significant maintenance work.

Furthermore, the bolts are arranged all around the circumference of the flanges, leaving only a very limited gap between adjacent bolts. A connection using flanges with bolts is insufficiently scalable to meet the ever increasing demands resulting from even larger wind turbines and greater depths at sea where they are installed.

Applicant proposed an alternative solution that is the subject of the non prepublished international application WO/NL2018/050059. The embodiments described in this prior right publication required specifically machined recesses that comprised a slanted engagement surface that was configured to engage a contact surface of a displaceable actuator. This machining is laborious and the required milling resulted in a geometrical configuration with a sub-optimal shape resulting in high stress concentrations.

An object of the present invention is to provide an assembly, that is improved relative to the prior art and wherein at least one of the above stated problems is obviated.

Said object is achieved with the assembly according to claim 1 of the present invention, comprising a first and a second section, each section comprising a longitudinal axis, a fixation configured to fix the first and the second section, wherein at least one of the first and the second section comprises a body that is configured to be engaged by the fixation, and wherein the fixation comprises an abutment and a displaceable actuator, wherein the actuator is radially displaceable relative to the longitudinal axis of the section that comprises the actuator, and further comprising an insert that is arranged between the abutment and the displaceable actuator.

The actuator is radially displaceable with respect to the longitudinal axis of the section that comprises the actuator. This allows the actuator itself to be employed as part of a clamp. In a preferred embodiment, the actuator may also be an integral part of the clamp.

Relative to the prior right application WO/NL2018/050059, it is novel to apply an insert. The insert prevents the need for machining a slanted engagement surface for engagement with the actuator in the first section or in the second section.

An insert has many benefits and advantageous technical effects.

Firstly, an insert allows the application of round holes, which tire easy to machine and which are - due to there continuous shape -will result in low stress concentrations. Lower stress concentrations allow for a smaller wall thickness of the sections, thereby reducing material and possibly even allowing that the first section may be a can section of a monopile. I.e., the first section may - in contrast to the prior art - not be a flange that is w'elded to a can section of a monopile, but may instead be the can section of the monopile as such. Thus, a laborious and time consuming step of forging a flange and welding said flange to the can section of the monopile may become obsolete as a result of an insert allowing round holes.

Secondly, an insert provides added flexibility, and may be easily machined as a relative small element. The insert may be made of a material that differs from the material of the first and/or second section, providing the opportunity to choose a material with characteristics that are optimal for the specific type of engagement. It is also conceivable that the insert comprises a specifically machined contact surface that has undergone a specific surface treatment. In this way, a locking interface may be provided between the insert and the actuator. Such a locking interface may be of a mechanical and/or a chemical nature.

The body that is engaged by the fixation is clamped between the abutment and the radially displaceable actuator, wherein the insert is configured to be arranged between the radially displaceable actuator and the body. More in particular, the insert is configured to be arranged in between a contact surface of the actuator and an engagement surface of the body.

Further preferred embodiments are the subject of the dependent claims.

In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which:

Figure 1 is a schematic view of an offshore wind turbine tower supported by a monopile;

Figures 2A and 2B are a cross sectional views of an assembly that is subject of the non pre-published international application WO/NL2018/050059;

Figures 3A and 3B are a cross sectional views in line with Figures 2A and 2B, wherein an assembly with an insert according to the invention is shown;

Figures 4A and 4B are perspective views of a preferred and alternative embodiment according to the invention; and

Figure 5-8 show cross sectional schematic view's according to further preferred embodiments.

An example of an offshore construction comprising multiple connections C where an assembly according to the invention may be applied is shown in Figure 1. An offshore wind turbine tower 1 is supported by a supporting base structure 2 which is in Figure 1 embodied as a monopile 3 with a transition piece 4. The skilled person will understand that similar connections are present for alternative supporting base structures 2, such as (not shown) jackets.

The connections C may be applied between separate sections 8 of the monopile 3, between the monopile 3 and the transition piece 4, between the transition piece 4 and the turbine tower 1, between sections 9 of the turbine tower 1, and between a rotor blade 6 and a hub of a rotor.

During use, a wind turbine 5 will be oriented such that the rotor blades 6 are optimally driven by the available wind power. The rotor blades 6 drive a (not shown) generator in the nacelle 7, wherein the generator generates electricity. The wind turbine 5 causes alternating loads on any connection C in the construction, and dependent on the wind direction, specific parts of the connection C have to absorb most of the loads.

The assembly as shown in Figures 2A, 2B and Figures 3A, 3B comprises a first section 18 and a second section 19. Each section 18, 19 may be longitudinal, and may comprise a longitudinal axis. The assemblies further comprise a fixation 20 configured to fix the first 18 and the second section 19. The fixation 20 is embodied as an abutment 23 and a radially, i.e. transverse relative to the longitudinal axis, displaceable actuator 24 that itself may be employed as part of a clamp 41. At least one of the first 18 and the second section 19 comprises a body 25 that is configured to be engaged by the fixation 20.

By using a fixation 20 that renders conventional bolts abundant, there is no need for through holes anymore. Consequently, the body 25 according to the invention can be less bulky than a conventional flange in a bolted connection. This results in a more elegant design, requiring less material and possibly also allowing alternative manufacturing methods. Whereas thick parts need to be forged, smaller parts may also be rolled.

In the shown embodiments, the longitudinal axes of the first 18 and the second section 19 are at least parallel. In a more preferred situation, the axes coincide.

The abutment 23 is preferably part of the other of the first 18 and the second section 19. In the shown embodiments, the body 25 is part of the first section 18, and the abutment 23 is part of the second section 19.

The abutment 23 abuts against a support surface 26 of the body 25. This support surface 26 is oriented in radial direction relative to the longitudinal axis of the first longitudinal section 18.

The actuator 24 is preferably part of the other of the first 18 and the second section 19. In the shown embodiments, the body 25 is part of the first section 18, and the actuator 24 is part of the second section 19.

Preferably, both the abutment 23 and the actuator 24 are part of the other of the first 18 and the second section 19. In the shown embodiments, the body 25 is part of the first section 18, and the abutment 23 and the actuator 24 are both part of the second section 19. In this way, the second section 19 partly encloses the body 25 of the first section 18. Thus, abutment 23 and radially displaceable actuator 24 together define a clamp 41 configured for clamping the body 25 in between. The clamping action of this clamp 41 is directed in the axial direction of the assembly. Using actuator 24, the body 25 is clamped between the abutment 23 and the actuator 24, thereby providing a reliable fixation between the first 18 and second section 19. Furthermore, additional fixation means, such as bolts according to the prior art, are redundant. Also, the body 25 may be less bulky than a flange comprising through holes to accommodate a bolt.

In the prior right WO/NL2018/050059, the actuator 24 has a contact surface 29 that is configured to directly engage a mating engagement surface 28 of the body 25. The contact surface 29 and the engagement surface 28 correspond to each other in order to form a mating interface, thereby putting high demands on the quality and processing of these surfaces 28, 29. Especially for the engagement surface 28 of the body 25, processing may be laborious and inconvenient, because body 25 is part of a relatively large first section 18.

According to the present invention, an insert 11 is arranged between the abutment 23 and the displaceable actuator 24. More in particular, the insert 11 is configured to be arranged between the radially displaceable actuator 24 and the body 25 that is configured to be engaged by the fixation 20.

Thus, the actuator 24 now indirectly engages the engagement surface 28 of the body 25 via the insert 11. The insert 11 is arranged in between the contact surface 29 of the actuator 24 and the engagement surface 28 of the body 25. As a result the engagement surface 28 of the body 25 is less critical, and the high demands previously posed on the quality and processing of the engagement surface 28 of the body 25 is now transferred to the insert 11. However, as the insert 11 is a small and separate part, it is relatively easy to process and obtain desired specifications. It is even possible to manufacture the insert 11 from a material that is different from the material of the first section 18 that comprises the body 25.

The support surface 26 and the engagement surface 28 are arranged on opposite sides of the body 25, and are clamped by clamp 41. In the embodiments described in the prior right WO/NL2018/050059, the body 25 is a tolerance critical part of the first section 18. The body 25, and the support surface 26 and engagement surface 28 thereof, need to correspond to the dimensions of the fixation 20. For example, the contact surface 29 of the actuator 24 and the engagement surface 28 of the body 25 comprise a corresponding chamfer. When the chamfer of the contact surface 29 and the chamfer of the engagement surface 28 are substantially equal, a reliable mating interface is obtained. Due to the chamfer, a radial displacement of the actuator 24 is converted to a clamping action of clamp 41, wherein the body 25 is clamped between the abutment 23 and the contact surface 29 of the actuator 24. The axial clamping force of the clamping action may be gradually increased or decreased by radial displacement of the actuator 24.

Due to the insert 11 of the present invention, the body 25 has become a less critical part. The insert 11 has an engagement surface 12 that is configured to engage the mating engagement surface 28 of the body. Engagement surface 28 of body 25 now only serves to engage with a mating engagement surface 12 of insert 11.

The insert has a contact surface 13 that is configured to engage a mating contact surface 29 of the actuator.

The insert 11 may comprise a tapering portion 14 over at least a part of an axial length thereof. The distance between the engagement surface 12 and the contact surface 13 of the insert 11 decreases along the tapering portion 14. The chamfer may now be provided by the insert 11, and engagement surface 28 does not need to be chamfered anymore.

The tapering portion of the insert may define a chamfer that has an angle of less than 25°, preferably less than 20°, more preferably less than 15°, and most preferably equal to or less than 10°. This provides the opportunity to e.g. drill straight holes as recesses 42 in the first section 18, while the actuator 24 may still have a chamfered surface. By providing a chamfer with a relatively flat angle, it is possible to apply a relatively high axial clamping force F_c with a relatively small radial actuation force F_a. The angle of the chamfer functions as a lever.

A high axial clamping force of clamp 41 provides the advantage that the assembly is less susceptible for load variations. This is best understood when compared to how a bolted joint carries a direct load. An adequately pretensioned bolt can survive in an application that an untightened, or loose bolt, would fail in little time. In short, the effect of an applied load first decreases a clamp force of the bolt, before the bolt starts to actually ‘feel’ any of the applied force.

A further advantage of a chamfer with a relatively flat angle follows from a force decomposition (Figures 2B and 3B). When the fixation 20 clamps the body 25, and according to the invention also the insert 11, between the abutment 23 and the actuator 24 of the fixation 20, the clamping force F_c will try to pivot the actuator 24 around the pivot points 30 and 31 and clamping interface 41. This results in friction in the interface between the contact surface 29 of the actuator 24 and the engagement surface 28 of the body 25, wherein:

Ffriction ~ A * ^pressure and μ is the friction coefficient. If the chamfer has a relatively flat angle, the force F_d will remain smaller than the friction forces in points 30 and 31. As a result, the clamping action will not be able to displace the actuator 24 away from the body 25. In this way, a secure fixation is guaranteed.

The radially displaceable actuator 24 is arranged in a radial bore 32 of the other of the first 18 and the second section 19. The actuator 24 is preferably arranged in said bore 32 with a sliding fit or press-fit. In the embodiment shown in Figures 2 and 3, two seals 33, e.g. o-rings, seal the actuator 24 in the bore 32.

Multiple radially displaceable actuators 24 may be arranged along the circumference of the other of the first 18 and the second section 19, e.g. one actuator 24 for every hole 42 in Figure 4A. Using multiple radially displaceable actuators 24, the clamping force for fixing the first 18 and the second section 19 is distributed. This on the one hand increases the reliability of the assembly by distributing the force over multiple surfaces. On the other hand, it also distributes the positon of the clamping surfaces over the circumference. This is especially advantageous for wind turbines, which are exposed to forces which have an orientation that is dependent on the wind direction.

Although the skilled person could envisage alternative ways of radially displacing the actuator 24, the one or more than one actuator 24 is preferably hydraulically displaced.

A robust clamping action may be obtained with a symmetrical clamping action that is provided by the embodiment shown in Figures 4A and 4B. This embodiment obtains symmetrical load transfer from one side. This one side is preferably an inner side of a section 18, 19, as further explained below. The symmetrical clamping action is beneficial, because it allows a load to be distributed over two sides, i.e. distributed over an inner flange 69 and an outer flange 70, and preferably in line with the load bearing walls of connected sections. The second section 19 comprises near its end an inner flange 69 and an outer flange 70 which are spaced apart and configured to receive the first section 18 there between.

The radially displaceable actuator 24 is arranged on one of the inner flange 69 and the outer flange 70 and is configured to extend from the one of the inner flange 69 and the outer flange 70 through the first section 18 towards the other of the inner flange 69 and the outer flange

70, wherein the radially displaceable actuator 24 is suspended by both the inner flange 69 and the outer flange 70 when the fixation fixes the first 18 and the second section 19. In the shown embodiment, the radially displaceable actuator 24 is arranged on the inner flange 69, causing the radially displaceable actuator 24 to be arranged inside the monopile tower, where it is readily available for servicing and protected against outside influences such as salt sea water. The symmetrical clamping action provided by this embodiment is beneficial, because the actuator 24 is suspended on opposite sides, and will thus distribute a load over both suspended sides without tilting. An actuator 24 that is suspended on opposite sides will be exposed to a bending force that is distributed. Contrary to embodiments with an actuator 24 that is suspended on one side, e.g. the Figure 3 embodiment, tilting of the actuator 24 is prevented when it is suspended on opposite sides conform the embodiment of Figures 4A, 4B.

A further advantage of the embodiment in Figures 4A, 4B is that actuators 24 need to be arranged on one side only. Moreover, if the actuators 24 are arranged on the inner flange, they can be easily reached for service, and they can be arranged below the water line without being exposed to sea water. After all, the inner flange 69 comprises a through hole and the outer flange 70 a recess with a wall shielding the displaceable actuator 24 from sea water. An inflatable seal 51 arranged in a recess 50 in the outer flange 70 of the second section 19 may be provided.

Multiple embodiments of an assembly according to the present invention are shown in Figures 5-8. These Figures show simplified and schematic cross sectional views in line with an embodiment of Figure 4A and 4B. It is noted that one of the simplification of Figures 5-8 comprises an open end of the outer flange 70 on the left side in the Figures.

In Figure 5, the insert 11 is glued to the body 25. More in particular, there is a glue connection between the engagement surface 28 of the body 25 and the mating engagement surface 12 of the insert 11.

In Figure 6, the insert 11 comprises a protruding stop 15 that is configured to engage a corresponding shoulder portion 16 of the body 25.

In Figure 7, the insert 11 comprises a shoulder portion 21 configured to engage a corresponding stop portion 22 of the body 25. Although shown in conjunction with the insert 11 comprising a protruding stop 15 that is configured to engage a corresponding shoulder portion 16 of the body 25 in line with Figure 6, the skilled person will understand that the shoulder portion 21 and stop portion 22 may also be used independently.

Relative to the embodiment shown in Figure 6, the insert 11 of the embodiment of Figure 8 comprises a further shoulder portion 15 configured to engage a further corresponding stop portion 16 of the body 25. Because both shoulder portions of the insert 11 are arranged on opposite sides of the insert 11, the insert 11 needs to be brought into engagement with the body 25 before the actuator 24 is brought into clamping engagement with the insert 11.

Whereas the embodiments shown in Figures 5 and 8 require that the insert 11 is arranged in advance in engagement with body 25, the embodiments of Figures 6 and 7 have the additional option that the insert 11 may be inserted into the recess 42 together with the displaceable actuator 24. Thus, in the embodiments of Figures 6 and 7, the insert 11 may be arranged on the displaceable actuator 24. When the actuator 24 is displaced, the insert 11 moves together with the actuator 24 until it abuts shoulder 16 (Figure 6 and 7) and/or stop 22 (Figure 7). The insert 11 is than prevented from further movement. If the actuator 24 is displaced further, it moves relative to the insert 11 to provide a clamping action.

In all embodiments of Figures 5-8, optional but preferred bushings 27 are shown. These bushings 27 may be made of a material that is different from the material of the respective second section 19. If a material w'ith a low'er Young’s modulus is applied, the deformation of said bushings 27 thereof during clamping may improve the clamping effect. Furthermore, it will reduce the stiffness of the clamping mechanism, which will analogous to a pre-stressed bolted connection, reduce the stress fluctuations in the wedge when the connection is properly pre-stressed.

As mentioned before in relation to Figure 1, the connections C for which the assembly according to the invention may be used are multiple. For example, each of the first 18 and the second section 19 may be tin upright section of a monopile tower. Also, one of the first 19 and the second section 19 may be a rotor blade of a wind turbine. The other of the first 18 and the second section 19 may be arranged on a hub, or - alternatively - be either a (not shown) fastening tool fixed to a structural part of a ship for sea fastening, or be a (not shown) lifting tool. Such a fastening tool for sea fastening may also be used for fixing e.g. an upright section 19 of a monopile tower to a ship. Likewise, such a lifting tool may be used for coupling to a section of a monopile tow'er for successive lifting and handling thereof.

Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Figure 1 shows an offshore wind turbine tower construction, but the assembly according to the invention is not limited to offshore use, nor to wind turbine applications alone.

It is remarked that in the following description of the shown embodiments, the lower section is denoted as the first section 18, and that the upper section is denoted as the second section 19. The skilled person will understand that the lower section could be interpreted as a second section 19 and the upper section could be interpreted as a first section 18 within the scope of the invention.

It should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments. For example, in the embodiments of Figures 6-8, the insert 11 may additionally be glued to the body 25.

The scope of the invention is defined solely by the following claims.

Claims

Conclusions

An assembly comprising:

- a first and a second section, each comprising a longitudinal axis;

- a fixation which is adapted to fix the first and the second section;

- wherein at least one of the first and the second section comprises a body which is adapted to be engaged by the fixation; and

- the fixation comprises:

- an attack; and

- a movable actuator, which is movable radially with respect to the longitudinal axis of the section comprising the actuator, characterized by an insert arranged between the stop and the movable actuator.

An assembly according to claim 1, wherein the insert is arranged to be arranged between the radially displaceable actuator and the body which is arranged to be engaged by the fixation.

Assembly according to claim 1 or 2, wherein the insert is arranged to be arranged between a contact surface of the actuator and an engagement surface of the body.

Assembly as claimed in any of the foregoing claims, wherein the stop and the radially displaceable actuator together define a clamp which is adapted to clamp the insert between them.

Assembly according to claim 4, wherein a clamping action of the clamp is directed in the axial direction of the assembly.

Assembly according to any of the preceding claims, wherein the insert comprises an engagement surface which is adapted to engage with a cooperating engagement surface of the body.

An assembly according to any one of the preceding claims, wherein the insert comprises a contact surface adapted to engage with a cooperating contact surface of the actuator.

An assembly according to claim 7, wherein the contact surface of the insert has undergone a surface treatment.

Assembly as claimed in any of the foregoing claims, wherein the insert comprises a tapered part over at least a part of an axial length thereof.

An assembly according to any of the preceding claims and at least claims 6 and 7, wherein the distance between the engagement surface and the contact surface of the insert decreases along the tapered part.

Assembly according to claim 9 or 10, wherein the tapered part of the insert comprises a chamfer, which comprises an angle of less than 25 °, preferably less than 20 °, more preferably less than 15 °, and with most preferably equal to or less than 10 °.

An assembly according to any one of the preceding claims, wherein the insert is glued to the body.

An assembly according to any of the preceding claims, wherein the insert comprises a protruding stop, which is adapted to engage with a corresponding shoulder part of the body.

Assembly as claimed in claim 13, wherein the insert comprises an additional shoulder part which is adapted to engage with an additional corresponding stop part of the body.

Assembly according to any of the preceding claims, wherein the insert comprises a shoulder part which is adapted to engage with a corresponding stop part of the body.

An assembly according to any of the preceding claims, wherein the insert is made of a material different from the material of the first or the second section, which comprises the body adapted to be engaged by the fixation.

Assembly according to any of the preceding claims, wherein the radially displaceable actuator is arranged in a radial borehole of the other of the first and the second section.

18. An assembly according to any one of the preceding claims, wherein a plurality of radially displaceable actuators are arranged along the periphery of the other of the first and the second section.

Assembly according to any of the preceding claims, wherein the first and the second sections are tubular sections, and preferably sections of an offshore structure, and more preferably of an offshore wind turbine construction.

Assembly according to any of the preceding claims, wherein the second section comprises near its end an inner flange and an outer flange, which are arranged at a distance from each other and are adapted to receive the first section between them.

An assembly according to claim 20, wherein the radially displaceable actuator is mounted on one of the inner flange and the outer flange and is adapted to extend from one of the inner flange and the outer flange through the first section to the other from the inner flange and the outer flange, wherein the radially movable actuator is suspended from both the inner flange and the outer flange when the fixation fixes the first and the second section.

An assembly according to any of the preceding claims, wherein each of the first and the second section is a post section of a monopile tower.

An assembly according to claims 21 and 22, wherein the radially displaceable actuator is mounted on the inner flange and within the monopile tower.

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