Assembly and method of assembling an assembly

Abstract

Actuator for use in an expansion connector in an assembly, the actuator comprising: - a longitudinal member extending along a longitudinal axis; - a wedge-shaped member extending from a first section of the longitudinal member in at least a secondary direction, wherein said secondary direction is substantially perpendicular to the longitudinal axis; - wherein a cross-section of at least the first section of the longitudinal member has a non-round cross section.

Description

[0001]ASSEMBLY AND METHOD ASSEMBLING AN ASSEMBLY The present invention relates to an assembly, comprising a first and a second member, and an expansion connector to connect the first and second member relative to each other and an actuator for use in the expansion connector. The invention further relates to a method of assembling such an assembly of a first and a second member that each comprise at least one passage. 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 members, i.e. tower segments, of a monopile or wind turbine, and jacket connections. It may also be used for a connection between the tower of a monopile and a nacelle, and possibly also for connecting rotor blades to the nacelle. According to prior art applications in offshore, the members of such assemblies are traditionally 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 is 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. Similar issues occur with tensioning systems for bolting. 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 as sea where they are installed. International patent application WO A1 of the same inventor proposes an assembly that is improved relative to a connection using flanges connected by bolts. This improved prior art assembly comprises: - a first and a second section, each 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 radially 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. During radial displacement of the actuator, an inclined surface of the actuator engages a specially machined surface of the first section and gradually increases the clamping force that connects the first and the second section. Although the assembly of WO 2018 / 139929 A1 already provided a significant improvement relative to the above-described traditional prior art connections using flanges connected by bolts, the inventor proposed further improvements, especially in order to overcome the disadvantage of the assembly of WO 2018 / 139929 A1 that a radial displacement of the actuator required a significant force due to the clamping action. Moreover, sections with a specially designed contact surface were required. International patent application WO 2020 / 035770 A1 of the same inventor, which is considered the closest prior art for the present invention, proposed an improved assembly. At least the features of the characterizing portion of claim 1 are novel relative to WO 2020 / 035770 A1. Relative to the assembly of WO 2018 / 139929 A1, a user may insert the connector of WO 2020 / 035770 A1 into the channel to an end position in a first step, followed by a further step of consecutively expanding said connector radially relative to said channel, to thereby connect the first and second member relative to each other. In this way, the connector may be accurately and easily placed in the channel by a user with very limited hassle or force. Only when the connector is placed in its desired end position, it is expanded in the channel to connect the first and second member relative to each other. Use of a connector as described in WO 2018 / 139929 A1 also makes specially machined contact surfaces with an inclination corresponding to an inclination of the radially displaceable actuator redundant. Relative to the older prior art of bolted flanges, large scale (e.g. M72 as used nowadays in the year 2021, and future wind parks even considering bolts up to M90) bolts are redundant. Also, the body may be less bulky than a flange comprising to accommodate a bolt. As a result, the assembly according to the invention, requires less material, is therefore more compact and lighter, and also more elegant. Whereas thick parts need to be forged, smaller parts may also be rolled, possibly allowing the members to be formed with alternative and more attractive manufacturing methods. Also, the assembly as described in WO 2018 / 139929 A1 is scalable, providing the opportunity to arrange multiple connectors in an axial direction of the members. A further advantage of the assembly of WO 2020 / 035770 A1 relative to traditional bolted flanges, is the absence of these flanges, that would provide a significant mass outside the path where forces travel during driving the assembly into a ground using a hammer. The mass of conventional flanges may result in bending of the neck of the flanges. These bending stresses currently result in significantly reduced life time of the welds of these flanges when installed with a conventional impact hammer. An even further advantage of the assembly of WO 2020 / 035770 A1 relative to bolted flanges, is that it may be applied for connecting members under the waterline. On the one hand, longitudinal members of a limited length may be used, allowing smaller ships to transport them to a desired location for an offshore construction. The successively tightening the bolts of a bolted flange – which are typically tightened in multiple steps, as mentioned above – is very time consuming and labour-intensive. The assembly proposed in WO 2020 / 035770 A1 is less labour-intensive and time consuming than a connection having bolted flanges. Compared to the older prior art of bolted flanges as described above, the connection provided by WO 2020 / 035770 A1 will show a superior fatigue resistance which is less sensitive to preload loss than typical bolted L-flanges, even under reduced preload levels relative to the initial torque, or initial tension, upon instalment. In bolted L-flanges the pre-tension is vital to prevent significant load fluctuations from occurring in the bolts or studs which have a poor fatigue resistance due to the presence of the threads. The connection provided by the proposed assembly proposed in WO 2020 / 035770 A1 does not experience these issues since the bolt only keeps the wedges in place but is, due to its orientation, not subjected to large load fluctuations. The main / dominant load fluctuations are experienced in the first member. As discussed above, the previous international patent applications WO 2018 / 139929 A1 and WO 2020 / 035770 A1 of the same inventor already proposed a large number of significant improvements relative to the older prior art of flanges. Nevertheless, there is an ongoing need to further improve such assemblies. In particular, with further increasing turbine, and rotor sizes of said turbines, the connections between respective assembled tower segments and / or the connections between the root of a blade and the rotor hub need to be able to cope with even larger overturning moments. The maximum overturning moments the assembly according to the closest prior art is able to cope with is typically limited by the amount of connectors that can be arranged around the circumference and by the load that a single connector can cope with. Increasing the size of the connector to be able to increase the load a single connector can handle, results in the negative side effect, that less connectors may be arranged around the circumference. The current invention therefore seeks to address this issue, in particular seeks to provide a solution that enables to increase the maximum overturning moments beyond the capabilities that the connectors according to the prior art provide. The present disclosure relates to an assembly and a method of assembling an assembly according to the independent claims. In an aspect, the invention relates to an actuator for use in an expansion connector, in particular an expansion connector as described further below comprising a first and a second expansion block, wherein, in an assembled state of the expansion connector, the actuator is received in between the first and second expansion block and is arranged to abut respective contact surfaces of the first and second expansion block, and wherein, when moving the actuator along the longitudinal axis in the assembled state of the expansion connector, a height of the expansion connector, as seen in a direction perpendicular to the longitudinal axis, is adjusted, wherein, the actuator comprises: - a longitudinal member extending along a longitudinal axis; - a wedge-shaped member extending from a first section of the longitudinal member in at least a secondary direction, wherein said secondary direction is substantially perpendicular to the longitudinal axis; - wherein a cross-section of at least the first section of the longitudinal member has a non-round cross section. The connectors according to the prior art comprise an actuator comprising a threaded longitudinal member having a circular cross-section that is employed for moving the wedges of said connector from an unexpanded state to an expanded state, wherein, as is described in more details below, it is able to connect two members. In order to increase the capacity of a single connector, the diameter of the longitudinal member is typically which in turn leads to an increased overall size of the connector, in particular an increased width of the actuator in order to accommodate the longitudinal member therein, thereby reducing the amount of connecters that can be arranged in the circumference of, for instance, a wind turbine tower segment, which has a negative effect on the overall overturning moment the connection can transfer. By providing a longitudinal member that has a first section having a non-round cross-section, the surface area of the cross-section of the first section can be increased, without increasing the width, as seen in an assembled state of the expansion connector, of the first section of the longitudinal member. The increased surface area leads, when assuming a maximum allowable tensile stress in the longitudinal member, to an increased tensile force that the longitudinal member can cope with. The increased tensile force thereby allows, when used in an assembly according to any of the embodiments given below, to apply a large pre-stress for expanding the expansion connector to the expanded state. The increase pre-stress thereby enables the expansion connecter to apply a larger clamping force in the assembly, such that, for the example of the wind turbine tower, an increased bending moment can be transferred over the connection between the tower segments. At the same time, as the surface area of the cross-section of the first section of the longitudinal member can be increased, without increasing the width of the longitudinal member, the width of the expansion connector can remain constant, or even decrease, such that at least the same number of expansion connectors can be arranged over the circumference of the connection. Preferably, the non-round cross-section of the first section has a major axis and a minor axis, wherein a width of the non-round cross section is larger, in particular largest, along the major axis, than along the minor axis and wherein the secondary direction is parallel to the minor axis or comprises a first component that is parallel to the minor axis and a second component that is parallel to the major axis, wherein said first component is larger than said second component. Additionally, or alternatively, a width of the contact surfaces of the respective expansion blocks, as seen in the assembled state of the expansion connector (as is described in more detail below), may be increased without increasing the overall width of the expansion connector. The surface area of contact between the contacts surfaces, that are arranged to abut corresponding contact and / or inclined surfaces on the wedge-shaped member is increased, thereby allowing the clamping force of the expansion connector, that is transferred through the respective surface area of contact, to also increase. These effects thus allow to increase the capacity of the connection. In a preferred embodiment said non-round cross-section is formed from opposing circular arc sections around a shared center having a single predefined radius whose outer ends are interconnected by secondary line segments for a closed circumference of the non-round cross section, wherein said secondary line segments are substantially straight and / or curved having a larger radius than the single predefined radius. By flattening the side of the circular cross-section, a significant decrease in the width of said cross-section is obtained, while only slightly decreasing the surface area of said cross-section (when compared to a full circular cross section having the single predefined radius). Hereby, the above described advantages can be efficiently obtained. In addition, the actuator having flattened sides improves the guidance of the actuator within the expansion connector, thereby improving the precision at which the pre-tensioned connection can be established. Preferably, said wedge-shaped member comprises at least a first inclined surface, wherein said inclined surface is arranged at an acute angle with respect to the longitudinal axis. The inclined surface can thereby contact a corresponding contact surface on the first or second expansion block to enable expanding the expansion connector. It is then preferred that the first inclined surface is arranged such that, at a first location, a tangential of the first inclined surface has a first acute angle with respect to the longitudinal axis and that, at a second location different from the first location, a tangential of the first inclined surface has a second acute angle with respect to the longitudinal axis, wherein said first acute angle is different from said second acute angle, preferably due to one or more gradual curvatures of the first inclined surface, further preferably wherein at least one of the one or more gradual curvatures has a constant radius of curvature. Preferably, wherein as seen in a radial direction of increasing height of said wedge-shaped member, that is parallel to the longitudinal axis, wherein the height is determined along a radial direction that is substantially perpendicular to the longitudinal axis and substantially perpendicular to the second direction, the second angle, associated to the second location that is closer to the maximum height of the wedge-shaped member than the first location, is smaller than the first angle, associated to the first location that is further from the maximum height of the wedge-shaped member than the second location. The expansion block of the expansion that presses against the face of the first member in the assembly as described in more detail below, will experience some downward bending. By arranging the wedge-shaped body, in particular the first inclined surface, as described above, a gap between the frontal section of the wedge (i.e. closer to the end of the wedge having the minimum thickness) and the contact surface of the respective expansion block exist in the unloaded (i.e. non- expanded) state of the expansion connecter When expanding the expansion connector, a clamping force is induced on the face of the first member, whereby, due to the reaction force, bending in induced in the respective expansion block. The expansion block thereby conforms to the shape of the first inclined surface, such that a more even distribution of the surface pressure between the respective contact surface and inclined surface is obtained. Plastic deformations in the expansion block and / or wedge-shaped member are thereby reduced, or even avoided, allowing an even further increased (average) surface pressure and thereby an even further increased clamping actions of the respective expansion connector. It is noted that this aspect may also be applied without the feature of the non-round cross-section of the longitudinal member, but may also lead to an increased capacity for expansion connectors having a longitudinal member having a circular (i.e. round) cross-section. Preferably, a maximum height of said wedge-shaped member, as determined along a radial direction that is substantially perpendicular to the longitudinal axis and substantially perpendicular to the second direction, is smaller than the width of the non-round cross-section of the first section along the major axis. The wedge-shaped member may thereby have in improved guidance in the assembled state of the connector, when moving said actuator in the longitudinal direction for moving the expansion connector to the expanded state. It is preferred that said wedge-shaped member comprises at least a second contact surface that is at an opposite side of the first inclined surface, wherein said second contact surface is arranged parallel to, or at an acute angle with respect to, the longitudinal axis. Preferably, the second contact surface is arranged as a second inclined surface that is arranged such that, at a first location, a tangential of the second inclined surface has a first acute angle with respect to the longitudinal axis and that, at a second location different from the first location, a tangential of the second inclined surface has a second acute angle with respect to the longitudinal axis, wherein said first acute angle is different from said second acute angle, preferably due to one or more gradual curvatures of the first inclined surface, further preferably wherein at least one of the one or more gradual curvatures has a constant radius of curvature. Preferably, wherein the second location on the second inclined surface is closer to a location of the maximum height of the wedge-shaped member and the first location is farther from the location of the maximum height of the wedge-shaped member than the second location and wherein the second angle is smaller than the first angle. In other words, preferably, wherein as seen in of increasing height of said wedge- shaped member, that is parallel to the longitudinal axis, wherein the height is determined along a direction that is substantially perpendicular to the longitudinal axis and substantially perpendicular to the second direction, the second angle, associated to the second location on the second inclined surface that is closer to the location of the maximum height of the wedge-shaped member than the first location on the second inclined surface, is smaller than the first angle, associated to the first location that is farther from the location of the maximum height of the wedge-shaped member than the second location. An inclined surface on the opposite side of the wedge-shaped member allows to radially displace both the expansion blocks when moving the actuator in the longitudinal direction, when in the assembled state of the expansion connector. Furthermore, the above described effect of accommodating for (elastic) deformations, e.g. bending, of the expansion blocks can hereby also be accommodated on the opposite side of the wedge-shaped member. In a preferred embodiment, the actuator comprises a second wedge-shaped member extending from the first section of the longitudinal member in at least a tertiary direction, wherein said tertiary direction is substantially perpendicular to the longitudinal axis and substantially parallel and opposite the secondary direction. The second wedge-shaped member allows to increase the surface area of contact, while also obtaining a balanced expansion connector. In a preferred embodiment, the actuator is formed monolithically, preferably by forging said actuator from a single piece of steel. The actuator is able to cope with higher material stresses if it is formed, preferably by forging, from a single piece of steel. Preferably, a length of the first section is at least two times a length of the wedge-shaped member, as determined parallel to the longitudinal axis. Thereby, the reduced width of the first section can extend over substantially the full length of the expansion blocks that, in the assembled state of the expansion connector, surround the actuator, which aids in obtaining the above noted technical benefits. It is preferred that the first section is arranged at an outer end of the longitudinal member and wherein at the opposite outer end of the longitudinal member an engaging section is arranged, in particular comprising threading, for engaging with an adjustment member, in particular a nut, whose position can be adjusted along the engaging section, and preferably wherein said engaging has a circular cross section, in particular having the same radius as the single predefined radius and / or wherein the said engaging section has a non- round cross section, preferably the same non-round cross-section as the first section. The engaging section, in particular the threaded section, thereby cooperates with the adjustment member for applying a pre-stress to the longitudinal member, when in the assembly according to the below described embodiments. Preferably, the engaging section comprises external threading, and the adjustment member, in particular the nut, comprises internal threading. Further preferably, a first pitch of the external threading differs from a second pitch of the internal threading. Accordingly, the load on the external threading of the engaging section is more evenly distributed. Preferably, the first pitch is smaller than the second pitch. In addition, the load can more evenly be distributed along the length of the internal threading of the adjustment member. Preferably, the external threading of the engaging section and / or the internal threading of the adjustment member have a relatively large pitch and / or a relatively large thread angle. Particularly, the pitch and / or the thread angle are greater than standard values used in metric screw thread. Accordingly, the load on the engaging section and adjustment member is more evenly distributed. Preferably, an outer diameter of the adjustment member, particularly the nut, is larger than a standard size used with metric screw thread. Providing such relatively large outer diameter of the nut further improves the load distribution between the engaging section and adjustment member. Preferably, wherein an elastic modulus of the material of the adjustment member is lower than an elastic modulus of the material of the engaging section. This leads to a more even distribution of the load along the length of the adjustment member. Preferably, the adjustment member and / or the engaging section have a friction coefficient of between 0.04 and 0.16. Lower frictional forces between the adjustment member and engaging section improves the load distribution between both. The surface structure and / or material can be chosen accordingly. The load distribution between the adjustment member and / or the engaging section may further be improved by using threading other than metric threading, such as for instance threading having a pitch difference, larger pitch, larger thread angle, and / or larger nut diameter than standard values used in metric thread. In a further aspect, the invention relates to a method of manufacturing an actuator according to any of the preceding embodiments, wherein the method comprises the step of forming the actuator from a single piece of steel, wherein the forming step preferably comprises a forging step. Hereby, an actuator having the above noted advantages can be obtained. In a further aspect, the invention relates to an expansion connector for interconnection two members in an assembly, in particular an assembly as described below comprising a first member and a second member, wherein the second member has a fork-shaped cross section with a main body arranged between two substantially parallel walls that each comprise at least one passage, the first member is arranged between the two walls of the second member in abutting contact with a face of the main body of the second member, the first member comprising a passage, said passage of the first member and the passages of the second member define a channel wherein the expansion actuator is axially insertable into said channel to an end position and consecutively expandable radially relative to said channel, to connect the first and second member relative to each other by pushing, in an expanded state of the connector, the first member in a radial direction relative to said channel against the face of the main body of the second member, the expansion connector comprising: - an actuator according to any of the preceding embodiments; - a first and a second expansion block; wherein, in an assembled state of the expansion connector, the actuator is received in between the first and second expansion block and the wedge-shaped body is arranged to abut respective contact surfaces of the first and second expansion block; and wherein, when moving the actuator along the longitudinal axis in the assembled state of the expansion connector, a height of the expansion connector, as seen in a radial direction perpendicular to the longitudinal axis, is adjusted. By arranging the non-round section of the longitudinal member in such a manner in the expansion connector that the smaller dimension of the respective non-round cross-section is arranged in the width of the expansion connector, the expansion connector can be made less wide, or given a greater contact surface with the respective wedge-shaped member. In the former case, the width of the connector can be limited thereby allowing for a greater number of expansion connectors in the connection, and in the latter case, the capacity of a connector can be increased, without increasing its width. In a preferred embodiment of the expansion at least one of said first and a second expansion block comprise an open channel extending in longitudinal direction through the respective expansion block, wherein the open channel is arranged for receiving the longitudinal member of the actuator therein. Preferably, the first and a second expansion blocks comprises contact surfaces for abutting the wedge-shaped member, in particular the inclined surfaces thereof, in particular wherein the contact surfaces are arranged on opposites side of the open channel for abutting the wedge-shaped member, in particular the inclined surfaces thereof. The non-round cross section of the longitudinal member allows for a relatively narrow open channel, such that the width of the connector can be limited and / or the contact surface can be increased, as was described above. It is then further preferred that, in the assembled state, the respective inclined surface of the wedge- shaped member is substantially parallel to the respective contact surface of the respective first or second expansion block it abuts at a rear section of wedge-shaped member that is closer to the maximum thickness of the wedge-shaped member than that of a frontal section of the wedge shaped body and / or wherein at the frontal section of the wedge shaped body, the inclined surface of the wedge-shaped member is at a non-zero acute angle (of e.g. less than 10 degrees, preferably, less than 5 degrees, most preferably, less than 2 degrees) with respect to the respective contact surface of the respective first or second expansion block it faces, such that, in at least un unloaded state of the connector, a gap exists at the frontal section between the respective inclined surface of the wedge-shaped member and the respective contact surface of the respective first or second expansion block it faces. This allows to accommodate the bending of the expansion block, as was described above. Preferably, the expansion connector comprises a second wedge-shaped member arranged at the opposite side relative to a cross section halfway the length of the expansion connector, wherein, preferably, the wedge-shaped members are arranged in a mirrored arrangement relative to the cross section halfway the length of the expansion connector, meaning that the apexes of the wedge- shaped members face each other. The apex can be defined as the location where the wedge-shaped member has its smallest thickness as seen in the direction of the major axis of the non-round cross- section of the first section of the actuator. The apex may also be referred to as a tip or point of the wedge-shaped member. The second wedge-shaped member allows to increase the contact surface area, such that an increased clamping force is obtainable in the expanded state, when installed in the assembly, as described below. It is further preferable that the second wedge- member is provided with a distal section that, in the assembled state of the expansion connector, extends along the longitudinal direction beyond the length of first and second expansion blocks, wherein the longitudinal member, in particular the engaging section thereof, extends through the distal section that further comprises an abutment section for contacting an adjustment member that is arranged, upon moving the adjustment member along the engaging section, for moving the actuator along the longitudinal axis. The longitudinal member can thereby be arranged such that the first section extends over a length corresponding the open channel, whereas the engaging section extends beyond the open channel, such that it can have the circular cross section, as was described above. The distal section is therefore arranged to receive the engaging section therein, and through, such that the position of an adjustment member, e.g. a nut, can be adjusted on the engaging section to abut the abutment section for longitudinally moving the actuator and applying the pre-stress in the actuator that enables to provide the clamping force in the expanded state of the expansion connector, when installed in the assembly. In a preferred embodiment, the expansion connector comprises alignment means for mutually aligning the first and second expansion block, in particular wherein the alignment means comprise an alignment pin and in each of the first and second expansion block an alignment pin opening that is arranged for receiving the alignment pin therein, wherein the alignment holes are arranged in respective surfaces of the respective expansion blocks that face each other, at the outer longitudinal ends of the respective expansion blocks. By positioning the alignment pin at the outer longitudinal ends of the respective expansion blocks, the wedge-shaped members have a longer longitudinal path of travel, thereby enabling longer wedge-shaped members having an increase surface area of contact with the expansion blocks and / or an increased stroke of the expansion blocks in the radial direction. Additionally, the alignment pin openings are arranged at the ends of the respective expansion blocks, which do not experience significant bending stresses. The alignment openings thereby do not negatively affect the maximum bending that expansion blocks may experience. It is noted that this aspect may also be applied without the feature of the non-round cross-section of the longitudinal member, but is also advantageous for expansion connectors having a longitudinal member having a circular (i.e. round) cross-section. In a further aspect, the invention relates to an assembly, comprising: - a first member and a second member, wherein; - the second member has a fork-shaped cross section with a main body arranged between two substantially parallel walls that each comprise at least one passage; - the first member is between the two walls of the second member in abutting contact with a face of the main body of the second member, the first member comprising a passage; - said passage of the first member and the passages of the second member define a channel, wherein, preferably, said channel has an elongate cross section extending in a longitudinal direction of at least one of said first and said second member; - an expansion connector according to any of the preceding embodiments according to the third aspect that is axially insertable into said channel to an end position and consecutively expandable radially relative to said channel, to connect the first and second member relative to each other by pushing, in an expanded state of the connector, the first member in a radial direction relative to said channel against the face of the main body of the second member to define a clamping contact and thereby a pre-tensioned connection in said radial direction relative to said channel between the face of the main body of the second member and faces defined by the passages in the substantially parallel walls of the second member; - wherein said expansion connector exhibits a length extending in a longitudinal direction of the channel and wherein: - the first expansion block is configured to push the first member against the face of the main body of the second member; - the second expansion block that is configured to contact the faces defined by the passages in the substantially parallel walls of the second member; and - the actuator according to any of the preceding embodiments according to the first aspect that is arranged in between the first expansion block and the second expansion block, and that is configured to be displaced longitudinally relative to the channel to thereby radially expand the expansion connector relative to the channel. Such an assembly is able to transfer larger forces and / or moments, as is described above. Preferably, a bearing surface of an upper one of the first and second expansion blocks, which bearing surface contacts the first member of the assembly in an expanded state of the expansion connector, is shorter than a wall thickness of the first member in the longitudinal direction of the channel (or the longitudinal directions of the actuator and / or expansion connector), or in direction of the wall thickness of the first member. Additionally or alternatively, the bearing surface is shaped such that high contact pressures are mitigated. Accordingly, there is no edge contact between the upper expansion block and the first member, thereby reducing contact pressure at the edges of the hole through the first member which in turn reduces plasticity. Preferably, at least one of the contact surfaces the first and / or second expansion blocks, for abutting the wedge-shaped member (and / or second wedge-shaped member), has a lateral inclination in a lateral direction of the channel (or the lateral directions of the actuator and / or expansion connector). Through this lateral inclination, the load exerted on the upper expansion block can be directed through a desired part of the wedge-shaped member, second wedge-shaped member, and / or lower expansion block. Preferably, the desired part is further away from the centre of the actuator as compared to a situation without said lateral inclination. Preferably, the shape of the bearing surface differs from the shape of the contact surface(s), for the first expansion block and / or the second expansion block. The benefits are furthermore obtainable through a further aspect of the invention that relates to a method of assembling a first and a second member that each comprise at least one passage, wherein the second member has a fork-shaped cross section with a main body arranged between two substantially parallel walls that each comprise at least one passage, said method comprising the steps of: - arranging the first member between the two walls of the second member; - positioning the passages of the first and the second member to define a channel, wherein, preferably, said channel has an elongate cross section extending in a longitudinal direction of at least one of said first and said second member; - providing a expansion connector according to any of the preceding embodiments according to the third aspect, wherein: - the first expansion block is configured to push the first member against the face of the main body of the second member; - the second expansion block is configured to contact faces defined by the passages in the substantially parallel walls of the second member; and - the actuator according to any of the preceding embodiments according to the first aspect that is arranged in between the first expansion block and the second expansion block, and that is configured to be displaced longitudinally relative to the channel to thereby radially expand the expansion connector relative to the channel; - inserting the expansion connector into the channel to an end position; - consecutively expanding said connector radially relative to said channel, to thereby connect the first and second member relative to each other; and - the expanded expansion connector pushing the first member in a radial direction relative to said channel against a face of the main body of the second member to define a clamping contact and thereby a pre-tensioned connection in a radial direction relative to said channel between the face of the main body of the member and faces defined by the passages in the substantially parallel walls of the second member. The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, and in particular the aspects and features described in the attached dependent claims, may be an invention in its own right that is related to a different problem relative to the prior art and that may be made the subject of a divisional patent application. 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; - Figure 2 is a perspective view of an assembly according to the fourth aspect; - Figure 3 is a cross sectional perspective view of the expansion connector according to the third aspect. - Figure 4 is an exploded perspective view of the expansion connector of Figure 3. - Figure 5 is a cross sectional perspective view of the expansion connector of Figure 3, wherein the first expansion block is removed. - Figure 6 is a perspective view of an actuator according to a first embodiment, wherein said actuator is mounted in the second wedge-shaped member. - Figure 7A is a perspective view of an actuator according to a second embodiment. - Figure 7B is a frontal view of the actuator according to the second embodiment. - Figures 8-10 are cross sectional views of successive steps of assembling an assembly according to the invention; - Figure 11A shows a side view of the expansion connector of figure 2. - Figure 11B is a detailed view of figure 11A. 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 members 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 members 9 of the turbine tower 1, segments of a rotor blade 6 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 according to the present invention comprises a first member 10 and a second member 11. The second member 11 has a fork-shaped cross section with a main body 12 arranged between two substantially parallel walls 13 that each comprise at least one passage 14 (Figure 8). The first member 10 is arranged between the two walls 13 of the second member 11 in abutting contact with a face 15 of the main body 12 of the second member 11. The first member 10 also comprises a passage 16. The passage 16 of the first member 10 and the passages 14 of the second member 11 define a channel 17 (Figure 9). The term “substantially” in relation to the substantially parallel walls 13 of the second member 11 is to be interpreted as said walls 13 enclosing an angle of less than 10º. An expansion connector 18 (Figures 3 – 5, 11A) is axially insertable into said channel 17 to an end position and consecutively expandable radially relative to said channel 17, to connect the first member 10 and the second member 11 relative to each other by pushing, in an expanded state of the connector 18, the first member 10 in a radial direction relative to said channel 17 against the face 15 of the main body 12 of the second member 11. Due to this pushing action, a clamping contact is defined, which results in a pre-tensioned connection in said radial direction relative to said channel 17 between the face 15 of the main body 12 of the second member 11 and faces 19 (Figure 8) that are defined by the passages 14 in the substantially parallel walls 13 of the second member 11. The expansion connector 18, in particular defined by the lengths of the first and second expansion blocks 20, 21, exhibits a length L extending in a longitudinal direction of the channel 17 and comprises a first expansion block 20 that is configured to push the first member 10 against the face 15 of the main body 12 of the second member 11, and a second expansion block 21 that is configured to contact the faces defined 19 by the passages 14 in the substantially parallel walls 13 of the second member 11. The expansion connector 18 furthermore comprises one or more than one wedge 22, 23 that is arranged in between the first expansion block 20 and the second expansion block 21, and that is configured to longitudinally relative to the channel 17 to thereby radially expand the connector 18 relative to the channel 17. At a cross section CS halfway the length L of the expansion connector 18, the cross sectional area and the height h1 of the first expansion block 20 in the radial direction relative to said channel 17 is smaller than the cross sectional area and the height h2 of the second expansion block 21 in said radial direction relative to said channel 17. In the expanded state of the expansion connector 18, it pushes against faces 19 of the passages 14 of the second member 11 that are directed away from the main body 12 thereof to define the pre- tensioned connection between the first member 10 and the second member 11. In the expanded state of the expansion connector 18, wherein the connection between the first member 10 and the second member 11 is pre-tensioned, the passage 16 of the first member 10 is arranged at an offset relative to the passages 14 in the second member 11. This offset is arranged in the radial direction relative to the channel 17. The expansion connector 18 comprises a compacted state, wherein the expansion connector 18 has a size that is freely insertable into and out of the channel 17 (Figure 9), and a connecting state, wherein the expansion connector 18 is radially expanded in the channel 17 to connect the first 10 and second member 11 relative to each other. In the shown preferred embodiment, the second expansion block 21 is configured to abut the faces 19 defined by the passages 14 in the substantially parallel walls 13 of the second member 11 only at or near longitudinal ends 37 of said second expansion block 21 when the expansion connector 18 is in an unloaded state, i.e. the compacted state, prior to the expansion connector 18 being expanded to the expanded state thereof. Thus, for the method, the step of inserting the connector 18 into the channel 17 to an end position comprises an end position wherein the second expansion block 21 abuts the faces 19 defined by the passages 14 in the substantially parallel walls 13 of the second member 11. In the shown preferred embodiment, the second expansion block 21 is configured to abut the faces 19 defined by the passages 14 in the substantially parallel walls 13 of the second member 21 over at least half of the length of said faces 19 when the expansion connector 18 is radially expanded to the expanded state to define the pre-tensioned connection. Thus, for the method, the step of the expanded connector 18 pushing the first member 10 in a radial direction relative to said channel 17 comprises deforming the second expansion 21 of the expansion connector 18 until the second expansion block 21 abuts the faces 19 defined by the passages 14 in the substantially parallel walls 13 of the second member 11 over at least half of the length of said faces 19 when the expansion connector 18 is radially expanded to the expanded state to define the pre-tensioned connection. The expansion connector 18 is shown in great detail in Figures 4-5 and 11A. The one or more than one wedge 22, 23 comprises a first sliding surface 27, 28 in contact with the first expansion block 20 and a second sliding surface 29, 30 that is in contact with the second expansion block 21. The shown connector 18 comprises a wedge 22, 23 on either side relative to the cross section CS halfway the length L of the expansion connector 18. These wedges 22, 23 are arranged in a mirrored arrangement relative to the cross section CS halfway the length L of the connector 18, such that their apexes face each other. The first sliding surfaces 27, 28 of the wedges 22, 23 slide along sliding surfaces 34 of the first expansion block 20. Likewise, the second sliding surface 29, 30 of the wedges 22, 23 slide along sliding surfaces 35 of the second expansion block 21. Although both wedges 22, 23 may be identical in size, this is not the case in the shown embodiment. The wedge 22 exhibits a greater length to make it easily accessible and actuated by an actuator 31, which is embodied as a nut 32 that may be driven along a threaded outer section 331 of the longitudinal member 33. However, the opposite wedge 23, that doesn’t need to be readily accessible, may deliberately be designed smaller to save weight and design the connector 18 as lightweight as possible. In the current embodiment (see figure 6), the opposite wedge (or wedge-shaped member) 23 is formed integrally with the actuator 31. The wedge 23 extends, in both opposite directions along the secondary axis II, from the first section 332 of the longitudinal member 33. Said secondary axis II is seen to be substantially perpendicular to the longitudinal axis I of the longitudinal member 33. A cross-section of at least the first section 332 of the longitudinal member 33 has a non-round cross section. As is best seen from the frontal view of an actuator 131 according to an alternative embodiment (figures 7A, 7B), the non-round cross-section of the first section 332, 1332 has a major axis III and a minor axis IV, wherein a width wIII of the non-round cross section is larger, in particular largest, along the major axis, than a width wIValong the minor axis. The secondary direction II is parallel to the minor axis IV. The non-round cross-section is formed from opposing circular arc sections 1334 around a shared center having a single predefined radius r1 whose outer ends are interconnected by secondary line segments 1335 for forming a closed circumference of the non-round cross section, wherein said secondary line segments are substantially straight. The actuators 31, 131 are provided with respective threaded engaging sections 331, 1331, that are provided at the opposite end of the longitudinal member 33 with respect to the wedge 23, for receiving a nut 32 thereon. Actuator 31 is seen to have a threaded engaging sections 331 with a round cross section having a the predefined radius r1. The longitudinal member thereby has a non- constant cross section, whereas the threaded engaging sections 1331 of actuator 131 is provided with the non-round cross-section as described above. The first section 333, 1333 is seen to have flattened sides extending for at least such a length that, in the assembled state of the connector, the first section 333, 1333 is received in an open channel 36 extending through the second expansion block 21. The first section 333, 1333 thereby has a length that is substantially equal to, or larger than, the length L of the respective expansion blocks 20, 21. The non-round cross section of the longitudinal member 33 thereby allows for a relatively narrow open channel, such that the width w3 of the expansion connector 18 can be limited and / or the contact surface can be increased, as was described above. Alternatively, the threaded engaging section may already start in an end section of the open channel, such that the open channel has an expanded with in the respective end section to accommodate the threaded engaging section therein. The wedge 22 is seen to be connected to an abutment section 40 that extends from the wedge 22 and, in the assembled state of the expansion connector 18, extends beyond the outer ends 36, 37 of the expansion blocks 20, 21, to at least partly facilitate the excess length L2 of the actuator 31, in particular the threaded engaging sections 331 thereof. By screwing nut 32 onto the threaded engaging sections 331, the nut 32 abuts abutment surface 41 of the abutment section, such that the wedge 23 is moved in longitudinal direction V and the wedge 22 is moved into opposite longitudinal direction VI, thereby forcing the expansion blocks 20, 21 to move in respective radial directions R1, R2 (see fig.11A). In order to introduce the threaded engaging sections 331 through a hole 42 in the abutment surface, the longitudinal member 33 and the wedge 22, including the abutment section 40, are first rotated relative with respect to each other. After a certain length of penetration, the wedge 22 is rotated back to be in line with the wedge 23. As is shown in figures 11A and 11B, the first sliding surface 27, 28, i.e. the first inclined surface, is arranged such that, at a first location, a tangential T1 of the first inclined surface has a first acute angle ^1with respect to the sliding surfaces 34 of the first expansion block 20, which is in the current embedment parallel to longitudinal axis I, and that, at a second location different from the first location, a tangential T2 of the first sliding surface 27,28 has a second acute angle ^2 with respect to the longitudinal axis, wherein said first acute angle ^1 is larger than the second acute angle ^2. The second acute angle ^2 is in the current embodiment 0 degrees, or at least <1 degree. As seen, the first location is closer to the part of the wedge 23 and the second location is closer to the thickest part of the wedge 23. In the unloaded state, a gap between the sliding surfaces 34 and the front side of the sliding surface 27, 28 thereby exists, Hereby, a bending of the first expansion block 20 is accommodated, as was explained above. An alignment mechanism 50, comprising alignment pin 51, is arranged near the respective outer ends 38, 39 of the expansion blocks 20, 21. Outer ends 38, 39 are opposite to outer ends 36, 37. The expansion blocks 20, 21 are provided with alignment holes () for receiving the alignment pin 51 therein. By arranging the alignment pin 51 at the outer ends 38, 39, the alignment pin does not limit the movement of the wedges 22, 23 towards the center of the expansion blocks 20, 21 (i.e. cross section CS halfway the length L), such that the wedges 22, 23 may made large to increase the surface area of contact and / or may be given a larger length of stroke. The above described embodiment is intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, 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. The scope of protection is defined solely by the following claims.

Claims

- the second member has a fork-shaped cross section with a main body arranged between two substantially parallel walls that each comprise at least one passage; - the first member is arranged between the two walls of the second member in abutting contact with a face of the main body of the second member, the first member comprising a passage; and - said passage of the first member and the passages of the second member define a channel, wherein, preferably, said channel has an elongate cross section extending in a longitudinal direction of at least one of said first and said second member; - an expansion connector that is axially insertable into said channel to an end position and consecutively expandable radially relative to said channel, to connect the first and second member relative to each other by pushing, in an expanded state of the connector, the first member in a radial direction relative to said channel against the face of the main body of the second member to define a clamping contact and thereby a pre-tensioned connection in said radial direction relative to said channel between the face of the main body of the second member and faces defined by the passages in the substantially parallel walls of the second member, the expansion connector comprising: - an actuator, comprising a longitudinal member extending along a longitudinal axis, and a wedge-shaped member extending from a first section of the longitudinal member in at least a secondary direction, wherein said secondary direction is substantially perpendicular to the longitudinal axis, and wherein a cross-section of at least the first section of the longitudinal member has a non-round cross section; and - a first and a second expansion block, wherein in an assembled state of the expansion connector, the actuator is received in between the first and second expansion blocks and the wedge-shaped body is arranged to abut respective contact surfaces of the first and second expansion blocks, and wherein, when moving the actuator along the longitudinal axis in the assembled state of the expansion connector, a height of the expansion connector, as seen in a direction perpendicular to the longitudinal axis, is adjusted; wherein said expansion connector exhibits a length extending in a longitudinal direction of the channel and wherein: the first expansion block is configured to push the first member against the face of the main body of the second member,the second expansion block configured to contact the faces defined by the passages in the substantially parallel walls of the second member; and the actuator is arranged in between the first expansion block and the second expansion block, and configured to be displaced longitudinally relative to the channel to thereby radially expand the expansion connector relative to the channel.

2. Assembly according to claim 1, wherein the non-round cross-section of the first section of the actuator has a major axis and a minor axis, wherein a width of the non-round cross section is larger, in particular largest, along the major axis, than along the minor axis and wherein the secondary direction is parallel to the minor axis or comprises a first component that is parallel to the minor axis and a second component that is parallel to the major axis, wherein said first component is larger than said second component.

3. Assembly according to claim 1 or 2, wherein said non-round cross-section of the actuator is formed from opposing circular arc sections around a shared center having a single predefined radius whose outer ends are interconnected by secondary line segments for forming a closed circumference of the non-round cross section, wherein said secondary line segments are substantially straight and / or curved having a larger radius than the single predefined radius.

4. Assembly according to any of the preceding claims, wherein said wedge-shaped member of the actuator comprises at least a first inclined surface, wherein said inclined surface is arranged at an acute angle with respect to the longitudinal axis.

5. Assembly according to claim 4, wherein the first inclined surface is arranged such that, at a first location, a tangential of the first inclined surface has a first acute angle with respect to the longitudinal axis and that, at a second location different from the first location, a tangential of the first inclined surface has a second acute angle with respect to the longitudinal axis, wherein said first acute angle is different from said second acute angle.

6. Assembly according to claim 5, wherein as seen in a direction of increasing height of said wedge-shaped member, that is parallel to the longitudinal axis, wherein the height is determined along a direction that is substantially perpendicular to the longitudinal axis and substantially perpendicular to the second direction, the second angle, associated to the second location that is closer to the maximum height of the wedge- shaped member than the first location, is smaller than the first angle, associated to the first location that is further from the maximum height of the wedge-shaped member than the second location.

7. Assembly according to any of the preceding claims, wherein a maximum height of said wedge-shaped member of the actuator, as determined along a direction that is substantially perpendicular to the longitudinal axis and substantially perpendicular to the second direction, is smaller than the width of the non-round cross-section of the first section along the major axis.

8. Assembly according to any of the preceding claims, wherein said wedge-shaped member of the actuator comprises at least a second contact surface that is at an opposite side of the first inclined surface, wherein said second contact surface is arranged parallel to, or at an acute angle with respect to, the longitudinal axis.

9. Assembly according to claim 8, wherein the second contact surface is arranged as a second inclined surface that is arranged such that, at a first location, a tangential of the second inclined surface has a first acute angle with respect to the longitudinal axis and that, at a second location different from the first location, a tangential of the second inclined surface has a second acute angle with respect to the longitudinal axis, wherein said first acute angle is different from said second acute angle.

10. Assembly according to claim 9, wherein the second location on the second inclined surface is closer to a location of the maximum height of the wedge-shaped member and the first location is farther from the location of the maximum height of the wedge-shaped member than the second location and wherein the second angle is smaller than the first angle.

11. Assembly according to any of the preceding claims, wherein the actuator comprises a second wedge-shaped member extending from the first section of the longitudinal member in at least a tertiary direction, wherein said tertiary direction is substantially perpendicular to the longitudinal axis and substantially parallel and opposite the secondary direction.

12. Assembly according to any of the preceding claims, wherein the actuator is formed monolithically, preferably by forging said actuator from a single piece of steel.

13. Assembly according to any of the preceding claims, wherein a length of the first section is at least 2 times a length of the wedge-shaped member, as determined parallel to the longitudinal axis.

14. Assembly according to any of the claims, wherein the first section of the actuator is arranged at an outer end of the longitudinal member and wherein at the opposite outer end of the longitudinal member an engaging section is arranged, in particular comprising threading, for engaging with an adjustment member, in particular a nut, whose position can be adjusted along the engaging section, and preferably wherein said engaging section has a circular cross section, in particular having the same radius as the single predefined radius.

15. Assembly according to any of the preceding claims, wherein at least one of said first and a second expansion block comprise an open channel extending in longitudinal direction through the respective expansion block, wherein the open channel is arranged for receiving the longitudinal member of the actuator therein.

16. Assembly according to any of the preceding claims, wherein the first and a second expansion blocks comprises contact surfaces for abutting the wedge-shaped member, in particular the inclined surfaces thereof, in particular wherein the contact surfaces are arranged on opposites side of the open channel for abutting the wedge-shaped member, in particular the inclined surfaces thereof.

17. Assembly according to claim 16, wherein, in the assembled state, the respective inclined surface of the wedge-shaped member is substantially parallel to the respective contact surface of the respective first or second expansion block it abuts at a rear section of wedge-shaped member that is closer to the maximum thickness of the wedge-shaped member than that of a frontal section of the wedge shaped body, and / or wherein at the frontal section of the wedge shaped body, the inclined surface of the wedge- shaped member is at a non-zero acute angle with the respective contact surface of the respective first or second expansion block it faces, such that, in at least un unloaded state of the connector, a gap exists at the frontal section between the respective inclined surface of the wedge-shaped member and the respective contact surface of the respective first or second expansion block it faces.

18. Assembly according to any of the preceding claims, wherein the expansion connector comprises a second wedge-shaped member arranged at the opposite side relative to a cross section halfway the length of the expansion connector, wherein, preferably, the wedge-shaped members are arranged such that the apexes of the wedge-shaped members face each other.

19. Assembly according to claim 18, the second wedge-shaped member is provided with a distal section that, in the assembled state of the expansion connector, extends along the longitudinal direction beyond the length of first and second expansion blocks, wherein the longitudinal member, in particular the engaging section thereof, extends through the distal section that further comprises an abutment section for contacting an adjustment member that is arranged, upon moving the adjustment member along the engaging section, for moving the actuator along the longitudinal axis.

20. Assembly according to any of the preceding claims, wherein the expansion connector comprising alignment means for mutually aligning the first and second expansion block, in particular wherein the alignment means comprise an alignment pin and in each of the first and second expansion block an alignment pin opening that is arranged for receiving the alignment pin therein, wherein the alignment holes are arranged in respective surfaces of the respective expansion blocks that face each other, at the outer longitudinal ends of the respective expansion blocks.

21. Method of assembling an assembly according to any of the preceding claims, the method comprising the steps of: - arranging the first member between the two walls of the second member; - positioning the passages of the first and the second member to define the channel, wherein, preferably, said channel has an elongate cross section extending in a longitudinal direction of at least one of said first and said second member; - providing the expansion connector, wherein: - the first expansion block is configured to push the first member against the face of the main body of the second member; - the second expansion block is configured to contact faces defined by the passages in the substantially parallel walls of the second member; and - the actuator is arranged in between the first expansion block and the second expansion block, and configured to be displaced longitudinally relative to the channel to thereby radially expand the expansion connector relative to the channel; - inserting the expansion connector into the channel to the end position; - consecutively expanding said connector radially relative to said channel, to thereby connect the first and second member relative to each other; and - the expanded expansion connector pushing the first member in the radial direction relative to said channel against the face of the main body of the second member to define the clamping contact and thereby the pre-tensioned connection in the radial direction relative tosaid channel between the face of the main the second member and faces defined by the passages in the substantially parallel walls of the second member.

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