The invention relates to a modular bicycle hub, more particularly to a modular bicycle hub containing a sprocket wheel unit and a separately removable wheel unit.

Such a modular bicycle hub is known, for example, from EP1213158. This modular bicycle hub is configured to be rotatably fastened between a first blade and a second blade of a fork of a bicycle for rotation about a rotation axis. In order to provide greater flexibility regarding variation in the combination of wheels and sprocket wheel units and to render replacement of a defect wheel quicker and easier, the modular bicycle hub from EP1213158 contains a sprocket wheel unit and a separately removable wheel unit. The sprocket wheel unit contains a stationary sprocket wheel axle and a sprocket wheel hub mounted thereon. In the fitted state, the stationary sprocket wheel axle is fastened to a first blade and extends axially along the rotation axis in the direction of the second blade. Furthermore, the modular bicycle hub also contains a separately removable wheel unit which contains a stationary wheel axle and a wheel hub mounted thereon. In the mounted state, the stationary wheel axle is removably fastened to the second blade and extends axially along the rotation axis in the direction of the first blade up to a certain axial intermediate distance between the stationary sprocket wheel axle and the sprocket wheel unit. The stationary sprocket wheel axle contains a stationary, internal axial coupling part in the form of an internal screw thread 48a arranged on the inside, as is illustrated in Figures 5 and 6 of EP1213158. The stationary wheel axle contains an axially movable, internal coupling part 30 in the form of an axle 30 arranged on the inside, with an external screw thread 37a at its end near the sprocket wheel unit, as is illustrated, for example, in Figures 5 to 7 of EP1213158. As is clearly illustrated in Figures 5 and 6 of EP1213158, this makes it possible to selectively couple the axially movable, internal coupling part of the wheel unit to the axially stationary, internal coupling part of the sprocket wheel unit by means of a screw connection.

The sprocket wheel hub contains an axially stationary, rotatable coupling part which is arranged thereon. This axially stationary coupling part contains internal axial teeth or splines 95 as is illustrated in Figure 4 of EP1213158. The wheel hub contains an axially movable, rotatable coupling part 26 which is arranged thereon. On the side opposite the axially stationary coupling part, this axially movable, rotatable coupling part 26 contains external teeth or splines 60 which can be introduced selectively in the corresponding internal axial teeth or splines 95 of the axially stationary rotatable coupling part by means of an axial movement, in order to thus selectively couple the axially movable, rotatable coupling part to the axially stationary, rotatable coupling part. It is clear that the axially movable, rotatable coupling part can be moved axially with respect to the wheel hub, since this axial movement is allowed by external axial teeth or splines 62 which cooperate with corresponding internal axial teeth or splines 59 of the wheel hub. The axially movable, rotatable coupling part 26 is fastened to the axially movable internal coupling part 30, as is illustrated in Figure 7 of EP1213158, at the location of a zone A between a first axial stop, formed by a radial support surface 39 on the side facing away from the sprocket wheel part and a radial ring 45 on the side opposite the sprocket wheel part. This makes it possible to transmit the axial movement of the axially movable, internal coupling part to the axially movable, rotatable coupling part. This means that, in the mounted state, as illustrated in Figure 5 or 21 of EP1213158, the radial support surface 39 pushes the axially movable, rotatable coupling part in the direction of the sprocket wheel unit in order to thus keep it in a coupled state, introduced in the axially stationary, rotatable coupling part. It is clear that, in this coupled position in the mounted state of the modular bicycle hub, a drive torque of the sprocket hub can be transmitted to the wheel hub via the axially stationary rotatable coupling part and the axially movable rotatable coupling part. As is generally known, the axially stationary rotatable coupling part is connected to the sprocket wheel hub, preferably by means of a freewheeling coupling. In the uncoupled position, as illustrated in Figure 6 or 22 of EP1213158, the radial ring 45 pushes the axially movable, rotatable coupling part in the direction away from the sprocket wheel unit in order to thus keep it in an uncoupled state, detached from the axially stationary, rotatable coupling part. In this case, the axial intermediate distance between the stationary wheel axle and the stationary sprocket wheel axle is necessary to make the axial movement of the axially movable, rotatable coupling part by means of the axially movable internal coupling part possible.

However, the modular bicycle hub from EP1213158 has several drawbacks. The axial intermediate distance between the stationary wheel axle and the stationary sprocket wheel axle causes a reduction in the axial bending stiffness of the hub. Furthermore, it is clear that, in the mounted state, an axial force has to be exerted on the axially movable, rotatable coupling part 26 by the stationary radial support surface 39 in order to keep the axially movable rotatable coupling part in a coupled state with the axially stationary rotatable coupling part, thus leading to friction and an increase in resistance. The latter also implies that an axial force component is acting on the various bearings, in particular on the bearings of the sprocket wheel unit, which also leads to an increase in resistance.

Furthermore, a modular bicycle hub is known from US201 1/0133543 which also contains a sprocket wheel unit and a separately removable wheel unit. This modular bicycle hub contains a wheel unit with an axial coupling in the form of a pin 240 which extends through the stationary wheel axle and is configured to transmit the axial movement of the axially movable, internal coupling part to the axially movable, rotatable coupling part. Here, the stationary wheel axle is removably fastened to the second blade and extends axially along the rotation axis in the direction of the first blade up to the stationary sprocket wheel axle of the sprocket wheel unit and this makes it possible to produce a modular bicycle hub having a relatively high axial bending stiffness. However, due to the direct axial coupling to the pin 240, the axially movable rotatable coupling part and the axially movable internal coupling part, in the coupled state, this axially movable rotatable coupling part exerts an axial load on the wheel hub which consequently results in an axial load on the bearings of the modular bicycle hub, in particular the bearing of the wheel hub on the side of the second blade, as well as the bearings of the sprocket hub, as is illustrated in Figure 3A of US201 1/0133543. Yet another modular bicycle hub is known from EP1213217, but due to the lack of an axially movable rotatable coupling part in the wheel unit, the wheel unit is more difficult to remove from the sprocket wheel unit in the mounted state in the fork of a bicycle. Although in this case as well, the adjoining wheel axle and sprocket wheel axle make a higher axial bending stiffness possible, the axially stationary rotatable coupling part of the wheel hub will cause an axial force component in the coupled state which will act on the bearings of the wheel hub and the sprocket wheel hub, as a result of which the resistance will increase.

Thus, there is still a need for a modular bicycle hub, the wheel unit of which can easily be uncoupled from the sprocket wheel unit, even in the mounted state between a fork of a bicycle, which can produce a high axial bending stiffness and can simultaneously guarantee low resistance.

In order to achieve this object, according to a first aspect of the invention, a modular bicycle hub is provided which is configured to be rotatably fastened between a first blade and a second blade of a fork of a bicycle for rotation about a rotation axis, the modular bicycle hub containing:

- a sprocket wheel unit which contains a stationary sprocket wheel axle and a sprocket wheel hub mounted thereon, in which, in the mounted state, the stationary sprocket wheel axle is fastened to the first blade and extends axially along the rotation axis in the direction of the second blade, the stationary sprocket wheel axle containing an axially stationary, internal coupling part arranged therein, and the sprocket wheel hub containing an axially stationary, rotatable coupling part arranged thereon; and

- a separately removable wheel unit which contains a stationary wheel axle and a wheel hub mounted thereon, in which, in the mounted state, the stationary wheel axle is removably fastened to the second blade and extends axially along the rotation axis in the direction of the first blade up to the stationary sprocket wheel axle of the sprocket wheel unit, the stationary wheel axle containing an axially movable, internal coupling part arranged therein for selective coupling to the stationary, internal coupling part, and the wheel hub containing an axially movable, rotatable coupling part arranged thereon for selective coupling to the axially stationary, rotatable coupling part,

CHARACTERIZED IN THAT

the wheel unit is configured such that, during a coupling and/or uncoupling operation, the axial movement of the axially movable, internal coupling part is greater than the axial movement of the axially movable, rotatable coupling part.

As a result thereof, a high axial bending stiffness is achieved without this resulting in an increase of the resistance due to resulting axial forces which act on the bearings. Furthermore, this makes a simple construction possible, which allows the axially movable, rotatable coupling part to move axially in order thus to remove the wheel unit separately, even in the mounted state, in a simple manner.

According to an embodiment, the wheel unit furthermore contains an axial coupling which extends through the stationary wheel axle and is configured to selectively transmit the axial movement of the axially movable, internal coupling part to the axially movable, rotatable coupling part. Selectively transmitting the axial movement of the axially movable, internal coupling part to the axially movable, rotatable coupling part by the axial coupling makes it possible to generate a great axial retaining force in the coupled state using the axially movable internal coupling part, so that the wheel axle and the sprocket wheel axle are coupled axially and thus result in a high axial bending stiffness without the axially movable rotatable coupling part transmitting a similar axial force to the wheel hub and/or the sprocket wheel hub and the respective bearings. As a result thereof, a high axial bending stiffness is achieved without this resulting in an increase in the resistance due to resulting axial forces which act on the bearings. Because the coupling part extends through the stationary wheel axle, a simple construction is possible, which allows the axially movable, rotatable coupling part to move axially in order thus to remove the wheel unit separately, even in the mounted state, in a simple manner.

According to an embodiment, the axial coupling is configured such that the axial movement trajectory of the axially movable, internal coupling part from an uncoupled position in the direction of the first blade to a coupled position, in which the axially movable, internal coupling part is completely coupled to the stationary, internal coupling part, is not transmitted entirely to the axially movable, rotatable coupling part.

As a result thereof, the axially movable, internal coupling part can move axially to a sufficient degree in the direction of the coupled position to generate a sufficiently high axial retaining force without this resulting in a similar axial movement of the axially movable rotatable coupling part and the associated risk of resulting axial forces on the bearings and an associated increase in the resistance of the modular bicycle hub. According to an embodiment, in the coupled position:

- the axially movable internal coupling part and the stationary, internal coupling part are configured such that they exert a resulting axial force on the stationary wheel axle and the stationary sprocket wheel axle which exceeds a retaining force threshold value, and

- the axially movable rotatable coupling part and the rotatable coupling part are configured such that they do not exert an axial force on the wheel hub and the sprocket wheel hub which exceeds a coupling force threshold value, in which case the coupling force threshold value is lower than the retaining force- threshold value.

In this way, it is possible to achieve a high axial bending stiffness without this resulting in an increase in the resistance.

According to a further embodiment, the axial coupling is configured such that the axial movement trajectory of the axially movable, internal coupling part from the coupled position in the direction of the second blade to an uncoupled position, in which the axially movable, internal coupling part is completely uncoupled from the stationary, internal coupling part, is at least partly transmitted to the axially movable, rotatable coupling part, so that the axially movable, rotatable coupling part is also moved to an uncoupled position, in which the axially movable, rotatable coupling part is uncoupled from the axially stationary, rotatable coupling part. In this way, the wheel unit can be removed separately from the sprocket wheel unit, even in the mounted state in a fork of a bicycle.

According to a further embodiment:

- the stationary wheel axle contains at least one axial slot; and

- the axial coupling contains at least one corresponding ball which extends radially through the respective axial slot between the axially movable, internal coupling part and the axially movable, rotatable coupling part, and is configured to axially couple the axially movable, rotatable coupling part selectively to the axially movable, internal coupling part during a part of its axial movement trajectory between the coupled and the uncoupled position.

In this way, the axial coupling is produced in a particularly simple and sturdy way, in which case an optimum contact surface can be produced by means of the balls so that friction between the axially movable internal coupling part and the axially movable, rotatable coupling part rotating about the rotation axis can be reduced.

According to a further embodiment, the at least one axial slot extends axially up to an end point near the internal axle of the sprocket wheel unit, and the wheel unit furthermore contains an axial pretensioner which is configured to pretension the at least one ball axially to this end point via the axially movable, rotatable coupling part, in which case the axially movable, rotatable coupling part is in the coupled position with the axially stationary, rotatable coupling part.

In this way, the axially movable, rotatable coupling part may be held in the coupled position by the axial pretensioner and the end point of the slot while the axial movement trajectory of the axially movable, internal coupling part can be continued to its coupled position. In this case, the axial coupling force is determined by the axial force generated by the axial pretensioner, absorbed by the end point of the slot and not transmitted to the sprocket wheel hub and/or the wheel hub and their bearings.

According to a further embodiment, the axially movable, internal coupling part contains a radial stop which, in the coupled state, is situated axially between the end point and the first blade and which is configured such that, when following the axial movement trajectory of the coupling part from the coupled position to the uncoupled position in the direction of the second blade, it moves axially beyond this end point, in which case:

- the axially movable, internal coupling part, during the part of the axial movement trajectory between the coupled position and this end point, can move freely with respect to the axially movable, rotatable coupling part via the at least one ball, and is thus not axially coupled; and - the axially movable, internal coupling part, during the part of the axial movement trajectory from this end point to the uncoupled position, with the stop, carries along the axially movable rotatable coupling part in the direction of its uncoupled position via the at least one ball, and is thus axially coupled. In this way, the selective axial coupling can be achieved in a simple manner.

According to a further embodiment, the wheel unit or the sprocket wheel unit contains at least partly a freewheeling coupling, in which case the freewheeling coupling is configured to radially couple the axially movable, rotatable coupling part or the axially stationary, rotatable coupling part, respectively, to the wheel hub or the sprocket wheel hub.

In this way, it is possible to form a freewheeling function in the modular bicycle hub in a simple manner.

According to a further embodiment, the axially movable, rotatable coupling part and the axially stationary, rotatable coupling part on the opposite side respectively contain a corresponding toothing with at least one axial component, configured to mesh with each other in the coupled position.

In this way, a radial coupling can be achieved which makes it possible to transmit the drive torque of the sprocket wheel unit to the wheel unit in the coupled position.

According to a further embodiment, the corresponding toothing may in addition be arranged at a certain angle with respect to the axial direction, for example, in the range from 3° to 30°, so that, when transmitting a drive torque from the sprocket wheel unit to the wheel unit in the coupled position, an axial force component is produced which forces the axially movable, rotatable coupling part in the direction of the axially stationary, rotatable coupling part.

According to a second aspect of the invention, a bicycle containing a modular bicycle hub according to the first aspect of the invention is provided. According to a third aspect of the invention, a wheel unit for use in a modular bicycle hub according to the first aspect of the invention is provided.

According to a fourth aspect of the invention, a method for removably coupling a wheel unit to a sprocket wheel unit of a modular bicycle hub according to the first aspect of the invention is provided, characterized in that the axial movement of the axially movable, internal coupling part is selectively transmitted to the axially movable, rotatable coupling part.

In this way, the wheel unit can be removed and uncoupled from the sprocket wheel unit in a simple manner, even in the mounted state between a fork of a bicycle. In this case, a high axial bending stiffness can be achieved and a low resistance be guaranteed. According to an embodiment, the axial coupling does not completely transmit the axial movement trajectory of the axially movable, internal coupling part from the uncoupled position in the direction of the first blade to the coupled position, to the axially movable, rotatable coupling part.

As a result thereof, the axially movable, internal coupling part can move axially in the direction of the coupled position to a sufficient degree to generate a sufficiently high axial retaining force without this resulting in a similar axial movement of the axially movable rotatable coupling part and the associated risk of resulting axial forces on the bearings and an associated increase in the resistance of the modular bicycle hub.

According to a further embodiment, the axial coupling transmits the axial movement trajectory of the axially movable, internal coupling part from the coupled position in the direction of the second blade to an uncoupled position, at least partly to the axially movable, rotatable coupling part, so that the axially movable, rotatable coupling part is also moved to the uncoupled position.

In this way, the wheel unit can be removed separately from the sprocket wheel unit, even in the mounted state in a fork of a bicycle. By way of example, the invention will be described below by means of exemplary embodiments illustrated in the figures, in which:

- Figure 1 shows a partial cross section of an embodiment of a modular bicycle hub according to the invention in the coupled state, mounted in a fork of a bicycle;

- Figure 2 shows the embodiment from Figure 1 in an uncoupled state;

- Figure 3 shows the embodiment from Figure 1 during the separate removal of the bicycle unit;

- Figure 4 diagrammatically shows a perspective view of a modular bicycle hub similar to the embodiment from Figures 1 to 3;

- Figure 5 diagrammatically shows the positioning of the modular bicycle hub in a bicycle;

- Figure 6 shows an embodiment of the stationary wheel axle;

- Figures 8 to 1 1 respectively show a side view, a cross section and two perspective views of an embodiment of the axially movable rotatable coupling part;

- Figures 12 and 13 show an alternative embodiment of the modular bicycle hub;

- Figure 14 shows an alternative embodiment of the rotatable coupling parts;

- Figure 15 shows an embodiment of a rear fork of a bicycle which uses dropouts suitable for fitting the modular bicycle hub;

- Figures 16A, 16B, and 16C show different views of a variant embodiment of the axially movable, rotatable coupling part;

- Figures 17A and 17B show a variant embodiment of a wheel unit;

- Figure 18 shows a variant embodiment of the axially movable, rotatable coupling part; - Figure 19 shows a view of the embodiment of the axially movable, rotatable coupling part from Figure 18, in a coupled position with the corresponding rotatable coupling part;

- Figure 20 shows a perspective view of a variant embodiment of the rotatable coupling parts;

- Figures 21 to 23 show similar views as Figures 1 to 3 of a variant embodiment of a modular bicycle hub which uses the embodiment of the rotatable coupling parts from Figure 20; and

- Figure 24 shows an exploded drawing of a number of parts of a modular bicycle hub similar to the embodiment from Figures 21 to 23.

Figure 1 diagrammatically shows a partial cross section along line l-l in Figure 4 of an embodiment of a modular bicycle hub 100. In the mounted state, the bicycle hub 100 is fastened between a first blade 14 and a second blade 12 of a fork 10 of a bicycle 1 , as can also be seen in Figure 4. As is generally known, the modular bicycle hub 100 is fastened in this fork 10 for rotating about a rotation axis 20. As can be seen in Figures 1 to 4, the modular bicycle hub 100 contains two units which are axially arranged next to one another according to the rotation axis 20, namely a wheel unit 200 and a sprocket wheel unit 300. Figure 5 diagrammatically shows a bicycle 1 with a bicycle frame 2 to which a handlebar is fastened at the front for steering a front fork 4 in which a front wheel 5 is arranged so as to be able to rotate by means of a bicycle hub 6. Furthermore, this bicycle 1 also contains a rear wheel 7 which is driven by means of sprocket wheels 8 of a chain-drive system comprising a chain, a drive sprocket wheel and pedals. As illustrated in Figure 5, the rear wheel 7 is fitted in the fork 10 by means of the modular hub 100 for rotating around the rotation axis 20. As is known to someone skilled in the art, the spokes of the wheel are arranged on the outer circumference of the wheel unit 200 in a conventional manner and one or more sprocket wheels are arranged on the outer circumference of the sprocket wheel unit 300 in order to drive the rear wheel. As can be seen in Figure 4, in the mounted state, the sprocket wheel unit 300 extends axially along the rotation axis 20 from the first blade 14 in the direction of the second blade 12. Subsequently, the modular bicycle hub 100 contains a wheel unit 200 which also extends axially along the rotation axis from the sprocket wheel unit 300 in the direction of the second blade 12. As can be seen, the modular bicycle hub 100 extends axially between the first blade 14 and the second blade of the fork 10 according to the rotation axis 20, by means of the axially aligned and axially sequential wheel unit 200 and sprocket wheel unit 300 which together form the modular bicycle hub 100. As can be seen in Figure 4, the modular bicycle hub 100 is fastened on the side of the first blade 14 by means of a screw connection based on a bolt or nut 31 and on the other side by means of a known quick- release system 210. Such a quick-release system 210 makes it possible to perform a screwing movement about the rotation axis, but also contains a lug which is configured to cause an axial movement along the rotation axis, so that a certain retaining force for fastening of the modular bicycle hub can be achieved.

As can be seen in Figure 1 , the sprocket wheel unit 300 contains a stationary sprocket wheel axle 304 and a sprocket wheel hub 302 mounted thereon. The exemplary embodiment shows two ball bearings 306 which are coaxially arranged with the rotatable sprocket wheel hub 302 and the stationary sprocket wheel axle 304, at different axial positions in the sprocket wheel unit 300, and thus rotatably arrange the sprocket wheel hub 302 on the stationary sprocket wheel axle 304. It is obvious that an alternative embodiment of the bearing is possible as long as the rotatable sprocket wheel hub 302 is coaxially fastened to the sprocket wheel axle 304 so as to be able to rotate, so that, in the mounted state, it rotates about the rotation axis 312 of the modular bicycle hub 100. In the illustrated mounted state, this stationary sprocket wheel axle 304 is fastened to the first blade 14. According to this exemplary embodiment, the sprocket wheel axle 304 which is formed as a hollow axle is fastened, by means of a bolt 310, to the outer side of the first blade 14 of the fork 10 which cooperates with a screw thread element 320 which is fastened in the hole of the hollow sprocket wheel axle 304. The bolt 310 extends axially with its external threaded male axle 31 1 along the rotation axis 20 through an opening or hole 15 in the first blade 14 of the fork 10 and into the axial hole of the hollow stationary sprocket wheel axle 304. There, the male part 31 1 of the bolt 310 which is provided with external screw thread is screwed into a corresponding female part 320 provided with a corresponding internal screw thread. This female part 320 is secured in the hole of stationary sprocket wheel axle 304 in a suitable manner, but may, for example, also be achieved by providing a suitable internal screw thread in the hole of the sprocket wheel axle 304. In this way, the sprocket wheel axle 304 can be fastened to the first blade 14 by tensioning the screw connection formed by the bolt 310 with its bolt head and the male axle 31 1 and the female part 320 in the stationary sprocket wheel axle 304, respectively on either side of the hole 15 of the first blade 14. It will be clear that alternative connecting elements are possible to fasten the sprocket wheel axle 304 to the first blade 14 in this way, it is, for example, possible to fasten a male screw element instead of a bolt 310 in a suitable manner to the stationary sprocket wheel axle 304 which then extends through the hole 15 of the first blade where a nut or another female screw element is fastened on the opposite side. As is illustrated, the stationary sprocket wheel axle extends axially along the rotation axis 20 from this first blade 14 in the direction of the second blade 12. As can furthermore be seen in Figure 1 , in the mounted state, the male part 31 1 of the bolt 310 extends axially along the rotation axis 20 through and beyond the female part 320, up to an end which is directed to the wheel unit 200 and which functions as an axially stationary, internal coupling part 312, as will be described in more detail below. It is thus clear that in this way an axially stationary, internal coupling part 312 is arranged inside, that is to say in the axial hole, in the stationary sprocket wheel axle 304. Variant embodiments of the axially stationary, internal coupling part 312 are possible, provided that the axially stationary internal coupling part 312 is not displaced along the axial direction, that is to say along the direction of the rotation axis 20, during a coupling operation or decoupling operation of the modular bicycle hub 100, when the sprocket wheel unit is fitted on the first blade 14 of the fork 10. Furthermore, it is also clear that, according to this embodiment, the outer diameter of the axially stationary, internal coupling part 312 is smaller than the inner diameter of the axial hole of the stationary sprocket wheel axle 304. Furthermore, it is also clear that the inner diameter of the axial hole of the rotatable sprocket wheel hub 302 is in itself greater than the outer diameter of the stationary sprocket wheel axle 304, so that there is sufficient radial intermediate space to fit bearings 306. As can further be seen in Figure 1 , the rotatable sprocket wheel hub 302 contains an axially stationary, rotatable coupling part 330 arranged thereon. As is illustrated, the axially stationary, rotatable coupling part 330 is arranged coaxially on the sprocket wheel hub 302 on the side near the wheel unit 200. The axially stationary, rotatable coupling part 330 is arranged on the sprocket wheel hub 302, so that it can rotate about the rotation axis 20 together with the sprocket wheel hub 302. In this case, the axially stationary, rotatable coupling part 330 remains positioned in a fixed axial position with respect to the rotatable sprocket wheel hub 302. As is illustrated, the axially stationary, rotatable coupling part 330 is formed as a cylindrical ring which is arranged on the inner wall of the hole of the sprocket wheel hub 302, this cylindrical ring contains axial teeth or splines on its inner side. According to an alternative embodiment, these axial teeth or splines may be arranged directly in the inner surface of the body of the sprocket wheel hub, on the side which, in the mounted state, is situated near the wheel unit 200, similarly to the sprocket wheel unit known from US201 1/0133543. According to further alternative embodiments, the axially stationary, rotatable coupling part 330, instead of being fixedly connected to the rotatable sprocket wheel hub 302, may be connected to the rotatable sprocket wheel hub 302 for example, by means of a freewheeling coupling, similarly for example to the sprocket wheel unit known from EP1213217. In the latter case, the axially stationary, rotatable coupling part 330, according to one rotational movement direction relative with respect to the sprocket wheel hub 302, is coupled to the sprocket wheel hub 302 for transmitting a drive torque and is, according to the opposite rotational movement direction relative with respect to the rotatable sprocket wheel hub 302, separately rotatable about the sprocket wheel axle 304.

Figure 1 furthermore also shows that the separately removable wheel unit 200 contains a stationary wheel axle 204. In the illustrated mounted state, the stationary wheel axle 204 is removably fastened to the second blade 12. In this case, the stationary wheel axle 204 extends axially along the rotation axis 20 from the second blade 12 in the direction of the first blade 14 up to the stationary sprocket wheel axle 304 of the sprocket wheel unit 304. According to the illustrated embodiment, the stationary wheel axle 204 is also a hollow cylindrical axle essentially having a similar cross section to that of the stationary sprocket wheel axle 304. As is illustrated in the illustrated mounted state from Figure 1 , the stationary wheel axle 204 and the axially adjoining stationary sprocket wheel axle 304 form a continuous stationary hollow tubular axle which extends axially along the rotation axis 20 between the first blade 14 and the second blade of the fork 10 of the bicycle 1. The respective side where the stationary sprocket wheel axle 304 and the stationary wheel axle 204 make contact, respectively, is formed by a virtually radial contact surface in the illustrated exemplary embodiment. However, according to alternative exemplary embodiments, these respective contact surfaces may be provided with, for example, means to improve the coaxial alignment and/or coupling of the wheel axle 204 and the sprocket wheel axle 304, such as, for example, axially complementary conical, convex, hollow, etc. elements on the respective contact surfaces. The respective contact surfaces of the stationary wheel axle 204 and the stationary sprocket wheel axle 304 must be able to axially closely adjoin in the mounted state in order to guarantee a good bending stiffness, but in this case it has to be ensured that the stationary wheel axle 204 can be radially removed separately from the sprocket wheel axle 304, whereas the latter remains fastened to the first blade 14 of the fork 10, as will be explained below with reference to Figure 2.

As can be seen in Figure 1 , an axially movable, internal coupling part 212 is arranged in the axial hole of the stationary wheel axle 204. In the illustrated mounted and coupled state, this axially movable, internal coupling part 212 extends axially along the rotation axis 20 from the quick-release system 210 through an opening or hole 13 in the second blade 12 of the fork 10, through the axial hole of the stationary wheel axle 204 and into the axial hole of the stationary sprocket wheel axle 304, where it is coupled to the axially stationary, internal coupling part 312 of the sprocket wheel unit 300. The axially movable, internal coupling part 212 contains an axle 21 1 which has, at its end near the axially stationary, internal coupling part 312, an internally threaded female part which can be screwed onto the end of the male part 31 1 of the bolt 310 which forms the axially stationary internal coupling part 312. The quick- release system 210 is arranged on the opposite end of this axle 21 1 of the axially movable, internal coupling part 212 in a known manner in order thus to make the screwing movement for screwing the axially movable, internal coupling part 212 onto the axially stationary, internal coupling part 312 during a coupling operation possible. In this case, the coupling of the axially movable, internal coupling part 212 which is screwed onto the axially stationary, internal coupling part 312 can be completed by axially tensioning the internal coupling parts 212, 312, which have been screwed together, by means of the clamping action of the lug of the quick-release system 210. In this way, in the mounted state illustrated in Figure 1 , the wheel axle 204 and the sprocket wheel axle 304 are subjected to an axial retaining force and tensioned between the two blades 12, 14 of the fork 10. The coupling of the axially movable, internal coupling part 212 is selective, as both internal coupling parts 212, 312 can be uncoupled again after the clamping element of the quick-release system 210 has been released and the axially movable, internal coupling part 212 of the axially stationary, internal coupling part 312 has been unscrewed by means of the quick-release system 210, as will be explained further with reference to Figure 2. Furthermore, it is clear that, as is illustrated, the axially movable, rotatable coupling part 230 contains an axial bore which forms the axial inner wall 231 of the axially movable, rotatable coupling part 230 and which is sufficiently large to be able to axially move around the wheel hub 204 and/or the sprocket wheel hub 304. As can also be seen in Figure 1 , the wheel unit 200 contains a wheel hub 202 mounted on the wheel axle 204. This rotatable wheel hub 202 is rotatably mounted in a known manner by means of ball bearings 206, or another suitable bearing system, and is formed as a hollow hub which runs coaxial to the wheel axle 204 for rotation about the rotation axis 20 in the mounted state. As can be seen, an axially movable, rotatable coupling part 230 is arranged on the wheel hub 202 on the side near the sprocket wheel unit 300. This axially movable rotatable coupling part 230 is shown in a coupled position in Figure 1 , in which case it is coupled to the axially stationary, rotatable coupling part 330. As is illustrated with reference to, for example, Figures 8 - 1 1 , on the opposite side of the axially stationary, rotatable coupling part 330 and vice versa, this axially movable, rotatable coupling part 230 contains corresponding axial teeth or splines 234; 334, configured to mate in this coupled position so that a drive torque can be transmitted. According to the illustrated embodiment, the axially movable, rotatable coupling part 230 is arranged on the wheel hub 202 via a freewheeling coupling 232. It is clear that, according to alternative embodiments, for example, when the axially stationary, rotatable coupling part 330 is fastened to the sprocket wheel hub 302 by means of a freewheeling coupling, the axially movable, rotatable coupling part 230 may also be fitted to the wheel hub 202 via other means, for example, via suitable axial teeth or splines which mate with corresponding axial teeth or splines, arranged on the inner wall of the axial hole of the wheel hub 202 near the side of the sprocket wheel unit 300, similar to what is known from, for example, EP1213158. As will be explained below with reference to Figure 2, the axially movable, rotatable coupling part 230 can be moved axially from the coupled position illustrated in Figure 1 to the uncoupled position illustrated in Figure 2, in order thus to be selectively coupled to the axially stationary, rotatable coupling part 330. By means of this relative axial movement on the opposite side, the axially movable, rotatable coupling part 230 and the rotatable coupling part 330 can be selectively coupled and uncoupled, respectively, for transmitting a drive torque by means of the corresponding axial teeth 234, 334 which mesh with each other in the coupled position. In order to make this axial movement possible, the wheel unit 200 furthermore contains an axial coupling 240 which extends through the stationary wheel axle 204 and which is configured to selectively transmit the axial movement of the axially movable, internal coupling part 212 to the axially movable, rotatable coupling part 230. According to the illustrated embodiment, this axial coupling 240 is formed by a number of balls 242 which are arranged in corresponding axial slots 208 in the stationary wheel axle 204. In Figure 1 , two balls and a corresponding number of slots can be seen. Figures 6 and 7 show a variant embodiment of the stationary wheel axle 204 having three slots for a corresponding number of balls 242. As is illustrated, the slots 208 are preferably uniformly distributed over the radial circumference of the stationary wheel axle 204 in order to achieve a stable axial coupling 240. However, variant embodiments are possible in which at least one of such axial slots is arranged in the stationary wheel axle 204 and the axial coupling is formed by at least one corresponding ball 242 which is arranged in this slot 208. As can be seen, according to this exemplary embodiment, the balls 242 extend radially; through the respective axial slot 208, between the axial outer wall of the axially movable, internal coupling part 212 and the axial inner wall 231 of the axially movable, rotatable coupling part 230. As can be seen in Figure 1 and is illustrated in more detail in Figures 9 to 1 1 , the axially movable, rotatable coupling part 230 contains a track 236 around the axial inner surface 231 with a recess having a curvature which is suitable for mounting the ball 242, so that when the ball 242 performs an axial movement, this movement is transmitted to the axially movable rotatable coupling part 230 and vice versa. The balls 242 which form the axial coupling 240 make it possible to selectively axially couple the axially movable, rotatable coupling part 230 to the axially movable, internal coupling part 212 during a part of its axial movement trajectory between the coupled position illustrated in Figure 1 and the uncoupled position illustrated in Figure 2. This is possible because the axial coupling 240 is configured such that the axial movement trajectory of the axially movable, internal coupling part 212, from an uncoupled position illustrated in Figure 2 in the direction of the first blade 14 to a coupled position in which, as is illustrated in Figure 1 , the axially movable, internal coupling part 212 is completely coupled to the axially stationary, internal coupling part 312, and vice versa, is not completely transmitted to the axially movable, rotatable coupling part 230. As illustrated, the axial slots 208 in the stationary wheel axle extend axially from an end point 208B closest to the second blade 12 to an end point 208A near the stationary sprocket wheel axle 304 of the sprocket wheel unit 300. In addition, as illustrated, the wheel unit 200 furthermore contains an axial pretensioner 250, according to this embodiment in the form of a compression spring 250, which axially pretensions the axially movable, rotatable coupling part 230 and thus also the balls 242 to a stop which limits the movement of the axial coupling 240 in the direction of the first blade 14. According to this exemplary embodiment, this stop is formed by this end point 208A of the slots 208, which limits the movement of the balls 242 in the direction of the first blade 14. As is illustrated in Figure 1 , the axially movable, rotatable coupling part 230 is then in the coupled position with the axially stationary, rotatable coupling part 330. In this coupled position, the compression spring 250 exerts an axial coupling force on the axially movable rotatable coupling part 230, which force is not transmitted to the wheel hub 202 and the sprocket wheel hub 302 and thus does not axially load their bearings 206, 306, as a result of which the risk of increased resistance is avoided. This means that the rotatable coupling parts 230 and 330 do not exert an axial force on the wheel hub 202 and the sprocket wheel hub 302 which exceeds a certain coupling force threshold value. In the coupled position and the mounted state illustrated in Figure 1 , the axially movable internal coupling part 212 and the stationary, internal coupling part 312 exert a resulting axial retaining force on the stationary wheel axle 204 and the stationary sprocket wheel axle 304, which force exceeds a retaining force threshold value, so that a high bending stiffness of the modular bicycle hub 100 can be guaranteed. It is clear that in this case the coupling force threshold value is lower than the retaining force threshold value and preferably lower by a factor of 10 to 100. According to the illustrated exemplary embodiment, this is achieved by the fact that, in this coupled position, the axial coupling 240 the axially movable internal coupling part 212 is completely axially uncoupled from the axially movable rotatable coupling part 230. As can be seen, in this state, the balls 242 are on a running surface 214 between two radial end surfaces 214A and 214B of an axial range of the axle 21 1 of the axially movable, internal coupling part 212, in which case it is clear that this axially movable internal coupling part 212 thus does not exert any axial forces on the axially movable, rotatable coupling part 230 by means of the axial coupling 240. In this state, the axially movable internal coupling part 212 is thus axially uncoupled from the axially movable, rotatable coupling part 230 by the axial coupling 240. In this way, the axial coupling 240 makes it possible to unscrew the axially movable, internal coupling part 212 from the axially stationary internal coupling part 312 from the coupled position in Figure 1 , after removal of the clamping connection of the quick-release coupling 210, and to travel a first part of its axial movement trajectory towards the completely uncoupled position illustrated in Figure 2, separate from the axially movable, rotatable coupling part 230. The radial surface 214A which delimits the part the axially movable, internal coupling part 212, forms a radial stop 214A which, in the coupled state, is situated axially between the end point 208A and the first blade 14. As soon as this radial stop 214A axially moves beyond this end point 208A when the coupling part 212 travels along the axial movement trajectory from the coupled position to the uncoupled position in the direction of the second blade 12, the balls 242 will be carried along by this radial stop 214A in the direction of the second blade 12, so that the axial coupling 240 thus axially couples both axially movable coupling parts 212 and 230 during this part of the movement trajectory, while the axial coupling 240 does not axially couple both axially movable coupling parts 212 and 230 during the preceding part of the movement trajectory and thus forms a selective axial coupling. As soon as this axial movement trajectory of the axially movable, internal coupling part 212 from the coupled position illustrated in Figure 1 to the completely uncoupled position illustrated in Figure 2, that is to say according to direction B, all axially movable coupling parts 212, 230 of the wheel unit 200 will be axially removed from the sprocket wheel unit 300 and the wheel unit 200 can be removed separately, as illustrated in Figure 3, via the opening 13 in the blade 12 according to the radial direction D at right angles to the rotation axis 200, while the sprocket wheel unit 300 can remain fastened to the first blade 14 of the fork 10. It is clear that alternative embodiments of the axial coupling are possible which are effective in only partly transmitting the axial movement trajectory of the axially movable, internal coupling part 212, from the coupled position in the direction of the second blade 12 to an uncoupled position, to the axially movable, rotatable coupling part 230, so that, during this part of the movement trajectory, the axially movable, rotatable coupling part 230 is also moved towards an uncoupled position in which the axially movable, rotatable coupling part 230 is uncoupled from the axially stationary, rotatable coupling part 330. Figures 12 and 13 show a detail near the axial coupling 240 of an alternative embodiment of the modular bicycle hub 100, similar to the embodiment illustrated in Figures 1 to 3. Similar elements are denoted by identical reference numerals and function in a similar way to that described above. The most important difference from the embodiment from Figure 1 relates to the radial stop 214A, which in this case is formed by a radial surface which protrudes from the inner wall of the rotatable wheel hub inwards into its axial hole and thus limits the first part of the axial movement trajectory of the axially movable, internal coupling part 212 from the uncoupled position illustrated in Figure 12 to the coupled position illustrated in Figure 13. The reason for this is that the radial stop 214A ensures that, as soon as the axially movable rotatable coupling part 230 reaches its coupled position, the axial coupling with the radially movable, internal coupling part 212 is released by the axial coupling 240 and, during the subsequent part of the movement trajectory, the radially movable internal coupling part 212 can move further separately towards its coupled position illustrated in Figure 13.

Figure 14 shows an alternative embodiment of the rotatable coupling parts 230 and 330. In contrast to the embodiments described above, the corresponding teeth 234, 334 are not completely aligned with the axial direction according to the rotation axis 20, but they do contain an axial component which is sufficient to make it possible for the corresponding teeth 234 to slide into and out of each other when the rotatable coupling parts 230 and 330 perform a relative axial movement. As is illustrated, the corresponding teeth 234, 334 are arranged at a certain angle with respect to the axial direction for this purpose, for example, in the range from 3° to 30°. In this case, it is ensured that, when a drive torque is transmitted from the sprocket wheel unit 300 to the wheel unit 200 in the coupled position of the rotatable coupling parts 230, 330, an axial force component is created which forces the axially movable, rotatable coupling part 230 in the direction of the axially stationary, rotatable coupling part 330 in order to guarantee a strong drive coupling between the sprocket wheel unit 300 and the wheel unit 200. In addition, it is also possible to provide corresponding conical circumferential surfaces 233, 333, as illustrated, so that the axial alignment and the strength of the drive coupling by means of the rotatable coupling parts 230, 330 are improved further. In addition, these conical surfaces may furthermore contribute in creating a sufficiently large contact surface which couples the conical circumferential surfaces 233, 333 to each other on the basis of friction, so that they assist in transmitting the drive torque. This coupling of the conical circumferential surfaces 233, 333 on the basis of mutual friction may be increased still further by means of friction-increasing elements which are arranged on the conical circumferential surfaces 233, 333, such as for example, an increased surface roughness, a coating or covering with a slip-resistant layer, etc. Finally, it is also possible to provide corresponding ratchet wheel teeth 235, 335 on the radial contact surfaces of the rotatable coupling parts 230, 330, as illustrated, so that this may assist when detaching the conical surfaces by means of a relative rotation according to a direction of rotation opposite to the direction of rotation used to transmit the drive torque.

Figure 15 shows an embodiment of a fork 10 of a bicycle on which the modular bicycle hub 100 can be mounted, in a similar way to the above-described embodiments, between a first blade 14 and second blade 12. As illustrated, this fork 10 uses removable or replaceable dropouts 1 12, 1 14 to fasten the modular bicycle hub 100 to the fork 10. As can be seen, the dropout 112 of the second blade 12 uses a conventional dropout slot 1 13, which makes it possible to remove the wheel unit 200 from the bicycle hub 100 separately in a similar way to that illustrated in Figures 2 and 3. As is also illustrated in Figures 2 and 3, the sprocket wheel unit 300 can remain fastened to the first blade 14 of the fork. According to the illustrated embodiment in Figure 15, this may be achieved by means of a dropout 1 14 which, instead of a dropout slot, has a suitable bore 1 15 which is provided, as is illustrated, for example, with internal screw thread for screwing in, for example, a corresponding male screw element which is fastened to the stationary sprocket wheel axle. Such a combination of removable dropouts 1 12, 1 14 makes it possible to install the modular bicycle hub 100 on existing bicycle frames in a simple manner. Figure 16B shows a view similar to that of Figure 8 of a variant embodiment of the axially movable, rotatable coupling part 230 and similar parts are denoted by identical reference numerals. As is illustrated, the axially movable, rotatable coupling part 230 according to this embodiment contains a freewheeling unit 230A which contains the freewheeling coupling 232 and a toothing unit 230C which contains axial teeth 234. As is illustrated, the toothing unit 230C may be arranged axially on the freewheeling unit 230A in such a manner that, when assembled, an assembly is produced similar to that illustrated in Figures 8 to 1 1. To this end, both units may be provided with suitable complementary connecting means on the opposite side, such as, for example, complementary screw thread 238A, 238C, for a suitable screw connection. In such a case, the connecting means are preferably arranged in such a manner that they force both units 230A and 230C axially towards each other when transmitting a drive torque. Furthermore, it is clear that, as illustrated, both units 230A, 230C contain, in the assembled state, a continuous axial hole 231A, 231 C which makes it possible to introduce the wheel hub 204, as is illustrated in Figures 1 to 3. Furthermore, the strip 236 around the axial inner surface 231A for mounting the balls 242 is also visible. Figure 16A furthermore shows a left-hand side view of the freewheeling unit 230A and Figure 16C furthermore shows a left-hand side view of the toothing unit 230C. The separate units 230A and 230C can be produced in a simpler manner than the assembled assembly.

- Figures 17A and 17B show a variant embodiment of a wheel unit 200 for use in a modular bicycle hub 100, similar to the embodiment illustrated in Figures 1 to 3 and similar elements are denoted by identical reference numerals. The axially movable, internal coupling part 212 here also contains axle 21 1 which can be operated by a quick-release system (not shown), similar to that described above. However, the end of the axle 21 1 of the axially movable, internal coupling part 212 which, in the mounted state, is situated near the axially stationary, internal coupling part 312 of the sprocket wheel unit is provided with a female part of a bayonet coupling 212 instead of with an internally threaded female part. As can be seen, this female part of the bayonet coupling 212 contains an L-shaped slot which can cooperate in a known manner with a corresponding male part 31 1 of a bayonet coupling which is provided on the axially stationary internal coupling part 312, and contains radial pins which can be introduced in a known manner in the L-shaped slot of the female part 212 of the bayonet coupling 212 in order to bring about a coupling between the internal coupling parts 212, 312. The quick-release system 210 will then be able to generate a retaining force in a similar way to the screw connection between the internal coupling parts 212, 312, as a result of which the internal coupling parts 212, 312 axially couple the wheel axle 204 and the sprocket wheel axle 304 at their opposite contact surface to each other. As is illustrated, the inner surface of the wheel axle 204 furthermore contains a radially inwardly projecting stop 207 which may, for example, be configured as an axial bore having a smaller diameter than the parts of the axial hole of the wheel axle 204 which are situated nearby. This stop 207 delimits the axial movement trajectory of the axially movable, internal coupling part 212 between the coupled position, as illustrated in Figure 17A, and the uncoupled position, as illustrated in Figure 17B. In addition, the wheel hub 200 contains a pretensioning element 213 in the form of a compression spring 213 which cooperates with the wheel axle 204 to pretension the axially movable, internal coupling part 212 in the direction of the uncoupled state, as is illustrated in Figure 17. As is illustrated, this is achieved by the fact that this compression spring 213 is fitted between the stop 207 and a radial surface of the axle 21 1 of the axially movable, internal coupling part on the side of the tensioning system, and thus on the side opposite the wheel unit 300. As a result thereof, during an uncoupling operation, after the retaining force of the quick-release system has been removed and the subsequent uncoupling of the bayonet coupling has taken place, the axially movable, internal coupling part 212 is automatically moved by means of the compression spring 213 from the coupled position in Figure 17A to the uncoupled position illustrated in Figure 17, until the radial surface of the axially movable, internal coupling part 212 bears against the stop 207 of the wheel axle 204 near the running surface 214 for the balls 242. During a coupling operation, a user can then, by means of the quick-release system (not shown), overcome the force of the compression spring 213 and move the axially movable, internal coupling part 212 back to the position illustrated in Figure 17, in which case the female part of the bayonet coupling of the axially movable internal coupling part 212 will bear against the male part of the bayonet coupling of the axially stationary internal coupling part 312. After the coupling of the internal coupling parts 212, 312 has been brought about by means of the bayonet coupling, it is then possible to apply the retaining force to the wheel axle 204 and the sprocket wheel axle 304 by means of the clamping system of the quick-release system. It is advantageous to pretension the axially movable, internal coupling part 212 to the uncoupled position, since this ensures, as is illustrated, that not only the axially movable internal axle 212 is automatically, quickly and reliably moved to the uncoupled position during an uncoupling operation, but also the axially movable, rotatable coupling part 230 by means of the axial coupling, via the balls 242. This makes separate removal of the wheel unit 200 in the mounted state in the fork 10 of a bicycle 1 in a quick and reliable manner possible.

Figure 18 shows a variant embodiment of the axially movable, rotatable coupling part having a number of features which are similar to those of the embodiment illustrated in Figure 14. Figure 18 shows an axial view, seen from the side of the sprocket wheel unit 300. In a similar way to Figure 14, the rotatable coupling part 230 also contains a conical circumferential surface 233. As can more clearly be seen in the radial view from Figure 19, this conical circumferential surface 233, according to this exemplary embodiment, contains an axial toothing 234. Likewise as illustrated, corresponding ratchet wheel teeth 235, 335 have been provided on the radial contact surfaces of the rotatable coupling parts 230, 330. As is illustrated, in this case, however, the ratchet wheel teeth 235, 335 produce the coupling between the rotatable coupling parts 230, 330, so that a drive torque can be transmitted from the sprocket wheel hub 302 to the wheel hub 204 according to one direction of rotation and a freewheeling coupling function can be realised in the other direction of rotation which allows a relative rotation of both rotatable coupling parts. The axial toothing 234 may assist during a coupling operation, as will be described in more detail with reference to Figures 21 to 23, in order to make is easy for the rotatable coupling parts 230, 330 and their respective ratchet wheel teeth to move past each other during the radial movement during a coupling operation. It is clear that Figure 19 shows a view in which the axially movable, rotatable coupling part 230 and the corresponding rotatable coupling part 330 are in a coupled position. Figure 20 shows a perspective view of a variant embodiment of the rotatable coupling parts 230, 330, as used in the embodiment of the bicycle hub 100 illustrated in Figures 21 to 23. Similar to that described in relation to Figure 19, the coupling between the rotatable coupling parts 230 and 330 is produced in this case by corresponding ratchet wheel teeth 235, 335 on the respective radial contact surfaces of the rotatable coupling parts 230, 330, in order to thus produce a freewheeling coupling which is suitable for transmitting a drive torque of the sprocket wheel hub 302 to the wheel hub 202. The axial teeth or splines 237, 337 on the outer circumference of these rotatable coupling parts 230, 330 only serve to mesh with corresponding axial teeth of the wheel hub 202 and the sprocket wheel hub 302, respectively, as will be described in more detail below with reference to Figures 21 to 23, in order to thus allow a limited axial movement of the rotatable coupling parts. The attachment of the rotatable coupling parts 230, 330 to the respective hubs 202, 302 may be similar to that known from, for example, EP1 121255. Preferably, the axial depth of the axial teeth 235, 335 is limited, for example to a maximum of 1 mm or 2mm.

Figures 21 to 23 show similar views to those from Figures 1 to 3 of a variant embodiment of a modular bicycle hub 100 which uses the embodiment of the rotatable coupling parts from Figure 20. Similar elements which have a similar function as described above with regard to Figures 1 to 3 are designated by the same reference numerals. Similarly to that which is described in Figures 1 to 3, the axially rotatable coupling part 230 is pretensioned by means of a pretensioning element 250, according to the illustrated embodiment in the form of a compression spring 250 which cooperates with a stop 252 on the wheel hub 202, in the direction of the corresponding rotatable coupling part 330 of the wheel unit 300. In contrast with the embodiment illustrated in Figures 1 to 3, there is no axial coupling 240 which extends through the stationary wheel axle 204 to selectively axially couple the axially movable, rotatable coupling part 230 to the axially movable, internal coupling part 212. This is possible because with the embodiment of the axially movable, rotatable coupling part 230 from Figure 20, the ratchet wheel teeth 235 automatically cause only a slight axial displacement during the radial movement of an uncoupling operation as illustrated in Figures 21 to 23 along direction D. During an uncoupling operation, it is thus sufficient to only sufficiently axially move the axially movable, internal coupling part 212 along direction B until it is removed from the sprocket wheel axle 304. Preferably, the corresponding rotatable coupling part 330 of the wheel hub 302 is also axially movably arranged and pretensioned by means of a suitable pretensioning element 350, such as, for example, a suitable compression spring 350 which bears against a similar stop 352 of the sprocket wheel hub 304 in order to pretension the axially movable, rotatable coupling part 330 in the direction of the corresponding axially movable, rotatable coupling part of the wheel hub 204. Preferably, both springs 250, 350 are similar, so that the relative axial movement of the rotatable coupling parts 230, 330 during a coupling operation is approximately equally distributed over both coupling parts 230, 330. Since in this embodiment as well, the wheel unit 200 is configured in such a way that, during a coupling and/or uncoupling operation, the axial movement of the axially movable, internal coupling part 212 is greater than the axial movement of the axially movable, rotatable coupling part 230, it is possible to axially couple the wheel axle 202, and the sprocket wheel axle 302 by means of the internal coupling parts 212, 312 and the quick-release system with a retaining force which is not transmitted to the bearings 206, 306 of the wheel unit 200 and the sprocket wheel unit 300 in the coupled state, as is illustrated in Figure 21. It also makes it possible to remove the wheel unit 200 separately in a simple manner, even in the mounted state between a fork of a bicycle, as is illustrated in Figures 22 and 23. Finally, at the location of their near end, the wheel axle 204 and the sprocket wheel axle 304 each contain a respective stop 205, 305 which delimits the axial movement trajectory of the respective rotatable coupling parts 230, 330 in the uncoupled position, as is illustrated in Figure 23, so that afterwards, during a coupling operation, a radial movement along a direction opposite to direction D about the wheel unit 200 to the position illustrated in Figure 22 remains possible, in which case the rotatable coupling parts 230, 330 are automatically able to move past each other due to the action of their corresponding ratchet wheel teeth 235, 335. Figure 24 shows an exploded drawing of a number of parts of an embodiment of a modular bicycle hub similar to the embodiment from Figures 21 to 23, with internal coupling parts 212 with a bayonet coupling similar to that illustrated in the embodiment from Figures 17A and 17B. Similar elements are denoted by the same reference numerals and function in a similar manner to that described above. As can clearly be seen, the rotatable coupling parts 230, 330 are arranged at their respective nearby end of the wheel axle 204 and sprocket wheel axle 304 and subsequently the ends of the respective wheel axle 204 and sprocket wheel axle 304 are completed by means of a stop element 260, 360 which can be screwed on and contains the respective stops 205, 305. This makes efficient assembly of the respective units 200, 300 possible. As illustrated furthermore, the respective radial contact surfaces of the wheel axle 204 and the sprocket wheel axle 304, which are respectively formed by the radial contact surfaces of the respective stop elements 260, 360 which can be screwed on respectively contain a complementary conical element 262, 362 in order to enhance the axial alignment of the wheel axle 204 and the sprocket wheel axle 304 in the coupled state, as already mentioned above. It is also clear, from Figures 21 to 24, that the radial contact surface of the wheel axle 204 and the radial contact surface of the sprocket wheel axle 304 contact each other along their entire radial circumference in the coupled state. This means that these respective contact surfaces contact each other continuously along a radial range of 360° around the rotation axis 20. In this way the resulting axial force on the stationary wheel axle 204 and the stationary sprocket wheel axle 304, which preferably exceeds a predetermined retaining force threshold value, is distributed evenly along the entire radial contact surfaces, thereby reducing the risk in a bending moment acting on the wheel axle 204 and/or the sprocket wheel axle 304 as a result of the axial force in the coupled state. Such a bending moment could lead to deformation of the wheel axel 204 and/or the sprocket wheel axle 304 and a corresponding axial misalignment of the respective bearings 206 and/or 306 mounted thereon. Thereby an increase in resistance caused by such misalignment can be avoided. It is clear, also for the embodiments shown in Figures 1 to 20, also preferably, as shown, the radial contact surface of the wheel axle 204 and the radial contact surface of the sprocket wheel axle 304 contact each other along their entire radial circumference in the coupled state. Additionally according to ISO standard 4210, the retaining force threshold value should be chosen high enough such that in general there shall be no relative motion between the bicycle hub and the fork of the bicycle when a force of 2 300 N is applied symmetrically to either side of the bicycle hub for a period of 30 s in the direction of the removal of the bicycle hub and its corresponding wheel from the fork. A suitable retaining force threshold value is for example greater than 200N, for example greater than 350N, for example greater than 500N.

It goes without saying that numerous alternative embodiments and combinations are possible in addition to the exemplary embodiments described above as long as in general these are within the scope of protection as defined in the claims.