WO2014185778A1

WO2014185778A1 - Flexible coupling having a torque transmission structure comprising an arrangement of fiber strands

Info

Publication number: WO2014185778A1
Application number: PCT/NL2014/050303
Authority: WO
Inventors: Marco Wilmsen
Original assignee: Humen, Technology And Business B.V.
Priority date: 2013-05-15
Filing date: 2014-05-14
Publication date: 2014-11-20
Also published as: NL2010806C2

Abstract

The invention relates to a flexible coupling (4) for coupling a drive shaft and a driven shaft, comprising: an axial coupling structure (7) having a central longitudinal axis (ZC) that during use can be substantially aligned with the rotational axes of the drive shaft (3) and the driven shaft (6,52), the axial coupling structure extending along the central axis and comprising two axially opposing ends (8a, 8b), wherein one axial end can be connected to the drive shaft and the opposing axial end can be connected to the driven shaft, wherein at least one of the axial ends is provided with a torque transmission structure (10,30) for, during use, transmitting torque from the drive shaft to the axial coupling structure, or for transmitting torque from the axial coupling structure to the driven shaft, respectively, whereby the torque transmission structure (10,30) comprises an arrangement of fiber strands (20) configured in such a way that at least part of the torque is transmitted via that arrangement of fiber strands. Another aspect of the invention relates to an assembly of a flexible coupling (4), comprising a drive shaft (3) and a driven shaft (6,52), wherein the coupling is connected to one end of the drive shaft and one end of the driven shaft, the central axis of the axial coupling structure being substantially aligned with the rotational axes of the drive shaft and the driven shaft, as to transmit torque from the drive shaft to the driven shaft.

Description

FLEXIBLE COUPLING HAVING A TORQUE TRANSMISSION STRUCTURE COMPRISING AN ARRANGEMENT OF FIBER STRANDS

Field of the invention

The present invention relates to a flexible coupling for coupling a drive shaft and a driven shaft, comprising: an axial coupling structure having a central longitudinal axis that during use can be substantially aligned with the rotational axes of the drive shaft and the driven shaft, the axial coupling structure extending along the central axis and comprising two axially opposing ends, wherein one axial end can be connected to the drive shaft and the opposing axial end can be connected to the driven shaft,

- wherein at least one of the axial ends is provided with a torque transmission structure for, during use, transmitting torque from the drive shaft to the axial coupling structure, or for transmitting torque from the axial coupling structure to the driven shaft, respectively. Background of the invention

It is known to use flexible disc couplings for connecting elements and for transferring an input force or displacement from one point to another point and in particular from a drive shaft to a driven shaft. Therein the flexible coupling is used for compensating possible axial and angular misalignments due to for instance bending of the connected elements or manufacturing tolerances.

During use, couplings of this nature are subjected to repeated alternating loads which seriously impairs their service life.

A disc coupling of this type that seeks to deal with the abovementioned problem is disclosed in L 2003735 wherein a flexible coupling for coupling a drive shaft and a driven shaft is disclosed. The coupling has a couple of disc ends enclosing a tubular part. The flexible coupling comprises several flexible wires whose first end is connected to one of the disc ends, while the other end is connected to the tubular part at a place close to its nearest edge, next to the disc end. This allows the disc ends to have radial and axial movement relative to each other allowing compensation of possible axial and angular misalignments.

A disadvantage of the known structure is that it requires relatively high maintenance due to the fact that the flexible wires may break relatively easily during operation due to excessive wear, therefore leading to relatively high maintenance costs. Furthermore, the torque transmission of the known flexible coupling can be compromised due to the fact that the known coupling is relatively sensitive to excessive deviations between the end discs and the tubular element, causing the coupling to have decreased performance.

It is therefore an object of the present invention to provide a flexible coupling for coupling a drive shaft and a driven shaft that overcomes at least one of the disadvantages of the prior art.

Summary of the invention An object of the invention is achieved by a flexible coupling that is characterized in that the torque transmission structure comprises an arrangement of fiber strands configured in such a way that at least part of the torque is transmitted via that arrangement of fiber strands. Thus, a flexible connection between the drive shaft and the driven shaft is achieved that remains relatively torsionally strong under high torque loads, and high RPM, e.g. at 12000 rpm. Moreover, the flexible coupling according to the invention remains corrosion-free, while also being water-resistant and resistant to UV-radiation. The expression "at least part of the torque" means: at least 10%, preferably more than 30%, more preferably more than 50%, most preferably more than 80%, or even 100%, of the torque is transmitted via the arrangement of fiber strands. The skilled person will understand that the abovementioned advantageous effects are more pronounced when more torque is transmitted via the arrangement of fiber strands.

The coupling may further comprise an end part arranged near the axial end provided with the torque transmission structure, extending substantially transversely with respect to the central axis, wherein the fiber strands of the torque transmission structure are connected to the end part and the end part can be rigidly connected to the respective drive shaft or driven shaft. As a result, the coupling can be more easily connected to either the drive shaft or driven shaft, as the latter two are often provided with similar transversal end parts. Preferably, the end part has the shape of a circular disc, and the fiber strands connect to the circular disc near the circumference thereof, preferably by forming an essentially circular web-like structure, allowing more even distribution of torque. Preferably, the arrangement of fiber strands is used to transmit all of the torque from the axial end to the end part, allowing the advantageous mechanical properties of the fiber strands, i.e. high stiffness in length direction and high flexibility in transversal direction, to be fully utilized. To electrically isolate the circular disc, the circular disc can also advantageously be made of a structure comprising fiber strands.

In a preferred embodiment, the circumference of the circular disc is provided with grooves and the fiber strands are securely received in the grooves. In this manner, the fiber strands are rigidly connected to the circular disc. Moreover, the arrangement of fiber strands allows relatively optimal use of elastic properties of the fiber strands. Additionally, the end part can be advantageously used during the weaving process for taking up the fiber strands.

In an embodiment, the axial coupling structure has the form of a cylinder, the longitudinal axis of which can be substantially aligned with the rotational axes of the drive shaft and the driven shaft during use. Moreover, the cylinder may have a circumferential wall that is substantially formed by an arrangement of fiber strands. As a result, an extremely strong and light coupling structure is provided. Additionally, when the circumferential wall is formed by an arrangement of fiber strands, flexibility will be provided to the coupling. The arrangement of fiber strands forming the circumferential wall and the arrangement of fiber strands comprised by the torque transmission structure can be formed of a single continuous arrangement of fiber strands allowing the coupling to be woven during a single manufacturing process. Thus, the process of producing the coupling can become cheaper and at the same time the structure will have improved fatigue failure properties, relative to other structures or parts. In addition, the length of the coupling can go up to for instance about 50 m.

In a preferred embodiment of the present invention the end part is displaceable along the central axis. This provides the coupling with axial shock absorption capabilities without the need of extra parts. Especially the use of carbon fiber strands in the torque transmission structure should be mentioned in this respect, as such fiber strands allow bending in a direction perpendicular to their length direction. The end part can comprise a telescopic element protruding along the central axis inside the cylinder, having an outer diameter that is equal to or smaller than the inner diameter of the circumferential wall of the cylinder. It should be noted that by having the telescopic element being received in the cylinder, the fiber strands are allowed to act as a shock absorber, while preventing direct transmission of axial shocks to the cylinder wall by the end part.

An embodiment relates to a coupling, wherein the fiber strands of the torque transmission structure extend from the respective axial end of the axial coupling structure away from the central axis, in a plane transversal to the central axis, wherein the longitudinal fiber axes of each fiber strand do not intersect the central axis. Thus, optimal torque transfer can be achieved. It should be noted that the prior art may teach that the fiber strands are to intersect the central axis, thereby being highly disadvantageous for transferring torque. An embodiment relates to a coupling, wherein the fiber strands of the torque transmission structure are substantially straight. The fiber strands may even be pre- tensioned. An embodiment relates to a coupling, wherein, in the plane transversal to the central axis, the fiber strands of a first group of adjacent fiber strands have a same angular spacing with respect to each other. Thus, an even transmission of torque is achieved from the axial end to for instance the circular disc.

An embodiment relates to a coupling, wherein, in the plane transversal to the central axis, the fiber strands of a second group of adjacent fiber strands have a same angular spacing with respect to each other. An embodiment relates to a coupling, wherein the first and second groups of adjacent fiber strands have an opposing rotational angle with respect to the central axis, wherein the fibers of the first and second groups intersect, thereby forming a hub-and-spoke like structure. Thus, optimal stiffness is achieved for transmitting torque, while still allowing the groups of fiber strands to bend at an angle, such as 5°, out of the plane perpendicular to the central axis. At the same time the circular disc, for instance, may be allowed to translate along the central axis. Thus, the coupling is allowed to deal with all sorts of misalignment.

An embodiment relates to a coupling, wherein the first group of fiber strands comprises 5-15, such as 10, separate fiber strands.

In another embodiment, the axial coupling structure can be formed by one or more coupling rods extending in a direction parallel to the central axis, the rods being distributed at substantially the same mutual angles with respect to the central axis, the axial ends of the coupling rods forming the opposing axial ends of the axial coupling structure. By having one or more coupling rods forming the axial coupling structure, a relatively lighter structure is provided, compared to a single relatively bulky part. The skilled person will understand that instead of coupling rods, any elongated structure with appropriate stiffness/rigidity properties can be used.

Furthermore, the fiber strands of the torque transmission structure can be arranged in such a way as to transversally connect connection points situated at the axial ends of the coupling rods, at one end of the axial coupling structure, to form a ring-like structure capable of transmitting torque. Advantageously, the ring-like structure provides a relatively thin and strong structure capable of transmitting torque in an optimal way, while providing relatively good misalignment compensation due to the ring-like structure being capable of bending in an axial direction. Again, the use of carbon fiber strands are worth mentioning, as such fiber strands advantageously allow bending in a direction perpendicular to their length direction. In addition, this also provides relatively smaller reactionary forces on other parts of the coupling compared to conventional disc couplings, which allows for longer coupling life. The fiber strands connecting two adjacent connection points can be routed via an intermediate connection point situated between the two adjacent connection points. Said intermediate connection points are connectable to an end of the drive shaft or the driven shaft in any way desired by the user. It is for instance possible to connect the intermediate connection points to a spacer element and then connect the spacer element to the drive shaft or driven shaft, allowing axial displacement of the ring-like structure at the (primary) connection points.

Preferably, for all embodiments of the coupling, the fiber strands have a substantially circular cross-section. Thus, a single, evenly shaped fiber strand can be formed capable of transmitting force in an even manner. From the prior art it is known to form fiber strands having a strip-like cross-section. However, these strip-like fiber strands have the disadvantage that one part may be heavily loaded while another part may be hardly loaded at all. The fiber strands may advantageously have an outer diameter of 0.5 - 5 mm, more preferably 1 - 3 mm, for instance approximately 2 mm.

An embodiment relates to a coupling, wherein the arrangement of fiber strands is embedded in a thermoplastic body or layer, such as a body or layer of polyurethane. The inventor has surprisingly found that the generation of noise (in particular due to vibrations) substantially decreases during use by embedding the fiber strands in such a thermoplastic body. Another surprising advantage is that the amount of damping (i.e. of movements) achieved can be fine-tuned by changing e.g. the dimensions of the body or layer, or the type of plastic used (or the composition thereof). Furthermore, wear of the fiber strands substantially decreases due to the separate fiber strands being isolated from each other by the body. Preferably, the body is axi symmetrically (e.g. rotationally symmetric) arranged around the central axis (ZC). More preferably, the body is a solid body or layer. The thermoplastic body or layer can also be used advantageously when the coupling is operated underwater, such as in sea water. The thermoplastic body or layer then protects the fiber strands against the water surrounding it.

Another embodiment relates to a coupling, wherein the thermoplastic body has the shape of a circular disc. Preferably, the disc-shaped body is paired with the end part, in particular the disc-shaped end part. Thus, a more or less integral body is conveniently formed.

The thickness of the body or layer can for instance be 3-30 mm, such as 4-20 mm, for instance 5-10 mm, in the direction parallel to the central axis.

Another aspect of the invention concerns an assembly comprising a drive shaft and a driven shaft, wherein the flexible coupling is connected to one end of the drive shaft and one end of the driven shaft, the central axis of the axial coupling structure being substantially aligned with the rotational axes of the drive shaft and the driven shaft, as to transmit torque from the drive shaft to the driven shaft.

Preferably, when using the aforementioned embodiment with one or more coupling rods and a ring-like structure, the flexible coupling is connected to an end of the drive shaft or driven shaft by suitable connection means provided at the intermediate connection points in such a way as to distance the intermediate connection points from the respective end of the drive shaft or driven shaft, allowing the connection points to be displaceable along the central axis. Brief description of the drawings Other aspects, features and details of the present invention will be readily understood by reference to the following detailed description of preferred embodiments, taken in conjunction with the drawings and the appended claims. In the appended drawings: Fig. 1 shows a schematic side view of a drive arrangement comprising the assembly according to the invention, with the flexible coupling according to the invention;

Fig. 2 shows a perspective longitudinal cross-section view of the flexible coupling according to an embodiment of the present invention;

Fig. 3 shows a perspective view of the flexible coupling according to an embodiment of the present invention;

Fig. 4 shows a perspective view of a flexible coupling according to another embodiment of the present invention; and

Fig. 5 shows a side view of the flexible coupling of figure 4 with a partial cross-section along the lines IV-IV.

Detailed description of the embodiments

Figure 1 shows a schematic view of a drive train comprising the assembly with the flexible coupling according to the invention having a drive motor 2 connected directly to a drive shaft 3 which is coupled to one end of a flexible coupling 4 along the central axis of the assembly, while at the other end of the flexible coupling 4, a driven shaft 6 is connected to the flexible coupling 4 along with a part that is to be driven, ultimately.

In figure 2 a perspective cross-section view of the flexible coupling 4 according to the first embodiment of the invention can be seen, wherein the flexible coupling 4 comprises an axial coupling structure in the form of a hollow tube 7, having a central axis ZC. The hollow tube 7 extends along the central axis ZC of the flexible coupling 4.

The flexible coupling 4 further comprises a couple of axially opposing ends 8a, 8b provided with a torque transmission structure 10. Said torque transmission structure 10 comprises an arrangement of fiber strands 20 which are securely attached to the axial ends 8a, 8b on the one hand, and to at an outer circumference of an end part 12 on the other hand. Preferably, the hollow tube 7 comprises a substantially cylindrical hollow tube or a solid rod or tube.

As can be seen in figure 2, the edge parts 12, are in the form of a circular discs, but are not limited thereto, because these ends parts 12 can also have a triangular, squared, oval, pentagonal or any other geometrical shape.

Moreover, the discs 12 further comprise partly a plurality of radial grooves 18 arranged in the outer circumference of the discs 12 wherein the fiber strands 20 are received to be securely connected there, while preferably being kept under certain pretension. Said grooves 18, can have any form as long as they are capable of receiving the ends of the fiber strands 20 and withstand the occurring forces as to keep the fiber strands 20 from being released from the grooves 18. It should be noted that a retention member 22 can also be provided around the outer circumference of the discs 12, as shown in figure 2, to securely retain the fiber strands 20 in the plurality of grooves 18.

The discs 12 furthermore comprise a protruding cylindrical tube 24. The tube 24 can be open at one axial end forming a hollow tube, or can also comprise an internal wall 26 at the axial end of said tube 24 for closing the tube 24. Moreover, the internal wall 26 can be configured for comprising a shaft (not illustrated) or for other purposes. The drive shaft 3 of the motor 2 as shown in figure 1, can be inserted and secured by any kind of securing means in the tube 24, while at the axially opposing end, the driven shaft 6 can be inserted and secured by any kind of securing means, which can be the same or a different kind of securing means as the ones used with the drive shaft 3.

It will be appreciated that the fiber strands 20 connect the discs 12 to the axial ends 8a, 8b of the hollow tube 7 in such a way that essentially a radial, circumferential web is formed between them, in such a way, that when the discs 12 rotate, the hollow tube 7 rotates along with the discs 12, and vice versa. As illustrated in figure 2, the fiber strands 12 of the torque transmission structure 10 may form a single continuous arrangement of fiber strands 20 with fiber strands forming the circumferential wall of the hollow tube 7.

Preferably, the fiber strands 20 material will be selected from, but not limited to, carbon fiber, glass fiber, and mixed with a plastic resin as to form carbon fiber reinforced plastic or the like. As mentioned before, the use of carbon fiber is especially advantageous since it allows bending in a direction perpendicular to the length direction of the fiber strand, breaking only at relatively high perpendicular loads. Figure 3 shows the flexible coupling 4 according to the present invention wherein the discs 12 comprise through-holes 29 being distributed at substantially the same mutual angles with respect to the central axis ZC of the flexible coupling 4 and from each other. The through-holes 29 are embodied in such a way as to receive connection means (not illustrated), such as a bolted connection, for connecting each of the discs 12 to the drive shaft 3 or to the driven shaft 6.

In figure 3 it can be appreciated that the fiber strands 20 located on top of the hollow tube 7, and comprise a very compact density when compared with the fiber strands 20 forming the circumferential wall around the inner part 14 of the discs 8a, 8b.

As illustrated, a couple of fiber strands 20 ends are received in the grooves 18 in pairs, but the amount of fiber strands to be received in the grooves may vary, e.g. depending on requirements with respect to the torque to be transmitted by the coupling. The retention member 22 as here illustrated extends along the whole periphery of the discs 12 and has a strip-like shape.

Figure 4 shows another embodiment of the flexible coupling 4 wherein one or more coupling rods 32 extend in a direction parallel to the central axis. The coupling rods 32 are distributed at substantially the same distance from each other and from the central axis ZC. Moreover, the flexible coupling 4 comprises a torque transmission structure 30 having fiber strands 40 forming a ring-like structure 38 capable of transmitting torque from the drive shaft 50 to the driven shaft 52. As it can be appreciated, the ring-like structure 38 comprises a cross-linked or trusslike configuration arranged in such a way that two adjacent cross-linked configurations are connected together at a central point formed by an annular ring 42. In this respect "cross-linked" means the respective fiber strands intersect each other to form an X- shaped configuration. The annular ring 42 can be used during the weaving process for routing or taking up the fiber strands. The ring-like structure 38 extends transversally with respect the coupling rods 32 as form a "closed circuit" torque transmission structure 30. It should be noted that the ring-like structure 38 comprises a configuration wherein the rods 32 are connected to the ring-like structure 38 via an intermediate annular ring 42 of the ring like structure 38. It should be noted that the configuration of the ring like structure 38 will be determined by the number of joint points, in other words, by the number of annular rings 42 provided.

The drive shaft 50 and the driven shaft 52 are connected to the torque transmission structure 30 at each of its ends via circular end plates bolted to the intermediate annular rings 42 of the ring-like structure 38 (i.e. the annular rings 42 in which the coupling rods 32 are not connected). This creates a strong structure capable of transmitting maximum torque. The drive shaft 50 and driven shaft 52 as here illustrated comprise the same disc shape configuration, although it should be noted that the drive shaft and driven shaft can have different shapes individually from each other.

Moreover, the torque transmission structure 30 comprises a configuration of cross- linked fiber strands 44 being routed in a transversal direction with respect to the coupling rods 32 and therefore to the central axis ZC, as to provide extra strength to the torque transmission structure 30. This provides a strong structure for avoiding radial misalignment of the ring-like structure 38, and as a consequence, of the drive shaft 50 and driven shaft 52.

The drive shaft 50 and driven shaft 52 are securely connected to the torque transmission structure 30 by attachment means in a form of bolts 54 and locknuts 56, but the skilled person will notice that other attachment means could be also suitable for this type of structure. In figure 5 a side view of the embodiment illustrated in figure 4 is shown wherein, in the top left part of the drawing, a cross-section of the connection between the drive shaft 50 and the torque transmission structure 30 via one of the annular rings 42 of the of the ring like structure 38 is illustrated. The bolt 54 goes though a through hole 58 located in the outer periphery on the disc wall of the drive shaft 50, and extends in a direction axially parallel to the central axis. At the end of said bolt 54, the locknut 56 tightens the torque transmission structure 30 as to keep it firmly connected to the drive shaft 50. As illustrated, in between the annular ring 42 and the inner wall of the drive shaft 50 there is a spacer element or shock absorber element 60 which provides axial shock dampening when the torque transmission structure 30 is in use. It can be appreciated that by having the shock absorber element 60 in between the torque transmission structure 30 and the drive shaft 50, a gap 62 is created between these two parts as to allow axial movement between them, i.e. allowing the ring-like structure 38 to bend in axial direction.

It should be noted that the shock absorber element 60 can be found in all the points where the torque transmission structure 30 is connected to the drive shaft 50 and/or the driven shaft 60. In light of the above, variants will be immediately apparent to those skilled in the art that are obvious in the light of the above description and fall within the scope of the appended claims.

List of reference numerals

2 Drive motor

3 Drive shaft

4 Flexible coupling

6 Driven shaft

7 Axial coupling structure / hollow tube

8a, 8b Axially opposing ends

10 Torque transmission structure

12 Disc

14 Protruding tube

18 Radial grooves

19 Fiber strands

20 Arrangement of fiber strands

22 Retention member

24 Cylindrical tube

26 Inner wall of the central hub

28 Opening of the inner wall

29 Through-holes of the discs

30 Torque transmission structure

32 Coupling rods

38 Ring-like structure

40 Fiber strands

42 Annular ring

43 -

44 Cross-linked fiber strands

50 Drive shaft

52 Driven shaft

54 Bolt

56 Locknuts

58 Through-hole of the drive shaft

60 Shock absorber element / spacer element

62 Gap

Claims

Flexible coupling (4) for coupling a drive shaft (3,50) and a driven shaft (6,52), comprising: an axial coupling structure (7) having a central longitudinal axis (ZC) that during use can be substantially aligned with the rotational axes of the drive shaft (3) and the driven shaft (6,52), the axial coupling (7) structure extending along the central axis (ZC) and comprising two axially opposing ends (8a,8b), wherein one axial end (8a,8b) can be connected to the drive shaft (3,50) and the opposing axial end (8a,8b) can be connected to the driven shaft (6,52), wherein at least one of the axial ends (8a, 8b) is provided with a torque transmission structure (10,30) for, during use, transmitting torque from the drive shaft (3,50) to the axial coupling structure (7), or for transmitting torque from the axial coupling structure (7) to the driven shaft (6,52), respectively, characterized in that the torque transmission structure (10,30) comprises an arrangement of fiber strands (20) configured in such a way that at least part of the torque is transmitted via that arrangement of fiber strands (20).

Coupling (4) according to claim 1, wherein the fiber strands (19,40) of the torque transmission structure (10,30) extend from the respective axial end (8a,8b) of the axial coupling structure (7) in a radial manner, away from the central axis (ZC).

3. Coupling (4) according to claim 2, further comprising an end part (12) arranged near the axial end provided with the torque transmission structure (10,30), extending substantially transversely with respect to the central axis ZC, wherein the fiber strands (19,40) of the torque transmission structure (10,30) are connected to the end part (12) and the end part (12) can be connected to the respective drive shaft (3,50) or driven shaft (6,52).

4. Coupling (4) according to claim 3, wherein the end part (12) has the shape of a circular disc (12).

5. Coupling (4) according to claim 4, wherein the fiber strands (19,40) connect to the circular disc (12) near the circumference thereof.

6. Coupling (4) according to claim 5, wherein the circumference of the circular disc (12) is provided with grooves (18) and the fiber strands (19,40) are securely received in the grooves (18).

7. Coupling (4) according to any one of the preceding claims, wherein the axial coupling structure (7) has the form of a cylinder, the longitudinal axis (ZC) of which can be substantially aligned with the rotational axes of the drive shaft (3,50) and the driven shaft (6,52) during use.

8. Coupling (4) according to claim 7, the cylinder having a circumferential wall that is substantially formed by an arrangement of fiber strands (20).

9. Coupling (4) according to claim 8, wherein the arrangement of fiber strands (20) forming the circumferential wall and the arrangement of fiber strands (2) comprised by the torque transmission structure (10) form a single continuous arrangement of fiber strands (19,40).

10. Coupling (4) according to any one of the claims 3-9, wherein the end part (12) is displaceable along the central axis (ZC).

11. Coupling (4) according to claim 10, when dependent on claim 7, wherein the end part (12) comprises a telescopic element (24) protruding along the central axis (ZC) into the cylinder (7), having an outer diameter that is equal to or smaller than the inner diameter of the circumferential wall of the cylinder (7).

12. Coupling (4) according to any one of the preceding claims, wherein the fiber strands (19) of the torque transmission structure (10) extend from the respective axial end (8a,8b) of the axial coupling structure (7) away from the central axis (ZC), in a plane transversal to the central axis (ZC), wherein the longitudinal fiber axes of each fiber strand do not intersect the central axis (ZC).

13. Coupling (4) according to any one of the preceding claims, wherein the fiber strands (19, 40) of the torque transmission structure (10) are substantially straight.

14. Coupling (4) according to claim 13, wherein, in the plane transversal to the central axis (ZC), the fiber strands (19) of a first group of adjacent fiber strands (19) have a same angular spacing with respect to each other.

15. Coupling (4) according to claim 14, wherein, in the plane transversal to the central axis (ZC), the fiber strands (19) of a second group of adjacent fiber strands (19) have a same angular spacing with respect to each other.

16. Coupling (4) according to claim 15, wherein the first and second groups of adjacent fiber strands (19) have an opposing rotational angle with respect to the central axis (ZC), wherein the fibers of the first and second groups intersect, thereby forming a hub-and-spoke like structure.

17. Coupling (4) according to claim 14, wherein the first group of fiber strands comprises 5-15, such as 10, separate fiber strands (19).

18. Coupling (4) according to claim 1, wherein the axial coupling structure (7) is formed by one or more coupling rods (32) extending in a direction parallel to the central axis (ZC), the rods (32) being distributed at substantially the same mutual angles with respect to the central axis (ZC), the axial ends of the coupling rods (32) forming the opposing axial ends of the axial coupling structure (30).

19. Coupling (4) according to claim 18, wherein the fiber strands (19,40) of the torque transmission structure (30) are arranged in such a way as to transversally connect connection points situated at the axial ends of the coupling rods (32), at one end of the axial coupling structure (7), to form a ring-like structure (38) capable of transmitting torque.

20. Coupling (4) according claim 19, wherein the fiber strands (19,40) connecting two adjacent connection points are routed via an intermediate connection point (42) situated between the two adjacent connection points.

21. Coupling (4) according to claim 20, wherein the intermediate connection points (42) are connectable to an end of the drive shaft (3,50) or the driven shaft (6, 52).

22. Coupling (4) according to any one of the preceding claims, wherein the fiber strands (19) have a substantially circular cross-section.

23. Coupling (4) according to claim 22, wherein the fiber strands (19) have an outer diameter of 0.5 - 5 mm, more preferably 1 - 3 mm, for instance approximately 2 mm.

24. Coupling (4) according to any one of the preceding claims, wherein the arrangement of fiber strands is embedded in a thermoplastic body, such as a body or layer of polyurethane.

25. Coupling (4) according to claim 24, when dependent on any one of claims 1-17, wherein the thermoplastic body has the shape of a circular disc.

26. Assembly of a coupling (4) according to any one of the preceding claims, comprising a drive shaft (3,50) and a driven shaft (6,52), wherein the coupling is connected to one end of the drive shaft (3,50) and one end of the driven shaft (6,52), the central axis (ZC) of the axial coupling structure (7) being substantially aligned with the rotational axes of the drive shaft (3,50) and the driven shaft (6,52), as to transmit torque from the drive shaft (3,50) to the driven shaft (6,52).

27. Assembly according to claim 26, when dependent on claim 21, wherein the coupling (4) is connected to an end of the drive shaft (3,50) or driven shaft (6, 52) by suitable connection means (54,56) provided at the intermediate connection points in such a way as to distance (62) the intermediate connection points from the respective end of the drive shaft (3,50) or driven shaft (6,52), allowing the intermediate connection points to be displaceable along the central axis (ZC).