WO2024256551A1

WO2024256551A1 - Rear derailleur with double arm tensioner

Info

Publication number: WO2024256551A1
Application number: PCT/EP2024/066392
Authority: WO
Inventors: Mikel Zubieta Andueza; Jon Madariaga Landajo
Original assignee: Zuma Innovation S.L.
Priority date: 2023-06-14
Filing date: 2024-06-13
Publication date: 2024-12-19
Also published as: ES1304087U; ES1304087Y

Abstract

Rear derailleur (10) for bicycles comprising a moving member (1) movable with respect to a base member (2), a tensioner shaft (3) rotationally mounted on the moving member (1) and a tensioner (4) fixed to the tensioner shaft (3), wherein the tensioner shaft (3) completely crosses the moving member (1) and is fixed to the tensioner (4) on both sides of the moving member (1) which allows the anchoring points of the tensioner with respect to the moving member to be as far apart as possible, thus obtaining the stiffest and most resistant possible tensioner structure, and resulting in a more precise and reliable gear shift.

Description

DESCRIPTION

REAR DERAILLEUR WITH DOUBLE ARM TENSIONER

TECHNICAL SECTOR

The present invention falls within the sector of rear derailleurs for bicycles.

BACKGROUND

In the state-of-the-art of rear derailleurs, the tensioner part is usually linked to the moving member on one side only (the side closer to where the sprockets are located), so the tensioner is cantilevered with some limitations in terms of rigidity and resistance. Due to these limitations, and as described in FR1319997A, the parts that constitute the tensioner cannot be made of plastic to save costs. However, in order to reduce costs, different geometries have been developed that facilitate manufacturing from flat metal sheets, such as those shown in US6949040B2.

The only known exception to this geometric configuration is that of Acros (https://www.disraeligears.co.uk/site/acros_a-ge_1000460790_10-speed_derailleur.html), in which the tensioner is also attached to the moving member at its center, in addition to being attached to the sprocket-side. In this way, a more rigid and resistant arrangement is achieved, by reducing the amount of material in the tensioner and obtaining one of the lightest rear derailleurs in history. The problem with this arrangement is that it makes assembly difficult, especially when preloading the tensioner spring.

Normally the assembly of the tensioner with respect to the moving member is carried out without any spring preload, then the entire tensioner is rotated (usually somewhere between 0.5 and 1 .5 turns) with respect to the moving member to preload the spring, and finally a stop is fixed on the tensioner so that the tensioner cannot move back with respect to the moving member beyond a certain position that represents a minimum preload. These levels of rotation of the tensioner with respect to the moving member are only possible when the tensioner is completely on one side of the moving member. For this reason, in the Acros derailleur the spring has to be preloaded without the help of the tensioner (and for this it has been made accessible from the outside), which complicates the process.

In the state of the art, screw systems are known to adjust the preload of the tensioner spring, such as those shown in US6350212B1 and CN111846100B.

DESCRIPTION OF THE INVENTION

In order to provide a solution to the shortcomings of the state of the art, the present invention proposes a rear derailleur for bicycles that comprises: a moving member movable with respect to a base member, a tensioner shaft rotationally mounted on the moving member, and a tensioner fixed to the tensioner shaft, where the tensioner shaft completely passes through the moving member and is fixed to the tensioner on both sides of the moving member.

With this connection, the anchoring points of the tensioner with respect to the moving member are as far apart as possible (more than in any rear derailleur in the state of the art, including the Acros rear derailleur), thus obtaining the stiffest and most resistant possible tensioner structure, and resulting in a more precise and reliable gear shift.

In some embodiments the rear derailleur comprises a torsion spring concentrically mounted with respect to the tensioner shaft, the first end of the torsion spring being attached to the tensioner shaft and the second end of the torsion spring being attached to the moving member.

Being the spring held between the tensioner shaft and the moving member, both rotationally mounted with respect to each other and with unlimited rotation possibilities between them, the relative rotation between these two parts can be used to apply tension to the spring, in a manner equivalent to how it is made in conventional rear derailleurs with the tensioner and the moving member.

In some embodiments, the rear derailleur comprises a mechanism for fixing the tensioner shaft to the tensioner which, in an intermediate fixing position, and in order to adjust the preload level of the torsion spring, allows the rotation of the tensioner shaft with respect to the tensioner while the moving member remains in its final mounting position with respect to the tensioner. By defining an intermediate fixing position in which all the parts are in their final assembly position, but the tensioner is not yet fixed to the tensioner shaft, it is possible to adjust the spring preload because the tensioner shaft can rotate as required with respect to the moving member, and then fix the tensioner shaft to the tensioner using the fixing mechanism. In this situation the tensioner will rotate with respect to the moving member, due to the spring preload, until it stops against some part of the moving member, where it will maintain a residual preload.

In some embodiments, this residual preload value can be adjustable because the mechanism for fixing the tensioner shaft to the tensioner can fix the tensioner shaft in different angular positions with respect to the tensioner, and therefore apply different preload levels. The greater the preload of the tensioner, the greater the chain tension in the lower chain branch (chain line that goes from the bottom of the bicycle sprocket to the bottom of the chainring after passing through both tensioner pulleys), and therefore the greater the friction between the chain and the pulleys. But on the other hand, external forces on the chain that come from vibrations or inertia of the bike will mean less proportional variation in the chain tension, so the movement of the tensioner due to these forces will be smaller, and the oscillations in the chain will also be smaller, and therefore the risk of the chain coming off the chainring is also lower. In this way, with an adjustable tensioner preload, the derailleur can be adapted to different terrains (more or less bumpy) to have minimum friction in the transmission, while avoiding the risk of the chain coming off.

In some embodiments the mechanism for fixing the tensioner shaft to the tensioner is composed of a footprint for a hexagonal wrench on the tension shaft, a lobular groove that extends radially at one of the ends of the tensioner shaft, a complementary housing in the tensioner for the final fixing position and a screw that axially fixes the tensioner shaft with respect to the tensioner in the final fixing position.

Apart from this embodiment, in other embodiments other attachment methods can be used for a standard tool, a special tool, or for allowing hand gripping both the tensioner shaft and the moving member and thus facilitate the rotation of one relative to the other during the spring preload adjustment. Subsequently, in order to fix the tensioner to the tensioner shaft, it is necessary that the contact faces have some tangential interference in the final fixation position.

Preferably, the radial interference pattern between the faces will have some axial symmetry to allow assembly in different positions, and therefore with different levels of spring preload. In the event that the transition from the intermediate fixation position to the final fixation position is carried out by means of an axial movement of the tensioner shaft, it could be of interest that the interference pattern is progressive in such axial direction, for example with a certain conic shape, to make fixation easier and smoother.

In some embodiments the tensioner is formed by two arms that go from the part of the tensioner furthest from the tensioner shaft to both sides of the tensioner shaft. In this way, rigidity and resistance are maximized while giving very distinct aesthetics to the tensioner and the entire rear derailleur.

In some embodiments the tensioner is made of a non-metallic material and is manufactured by injection moulding. This allows obtaining a tensioner with a cost similar to or lower than those of the state of the art with mechanical properties of rigidity and resistance equal to or higher and with a clearly differentiated aesthetic character.

The concepts described can also be applied to other equivalent configurations and different sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description and in order to help better understanding the characteristics of the invention, in accordance with an example of its practical implementation, a set of figures is attached as an integral part of the description in which, with illustrative but not limiting purposes, the following has been represented:

Figure 1 shows a general view of the rear derailleur.

Figure 2 shows a partial view of the rear derailleur in exploded view.

Figure 3 shows a front view of the rear derailleur. Figure 4 shows a side view of the rear derailleur in the final fixing position.

Figure 5 shows a sectional view of the rear derailleur in the final fixing position according to line AA in Figure 4.

Figure 6 shows a side view of the rear derailleur in the intermediate fixing position.

Figure 7 shows a sectional view of the rear derailleur in the intermediate fixing position according to line BB in Figure 6.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

As it can be observed in Figure 1 , a first embodiment of the invention refers to a rear derailleur 10 for bicycles that comprises a base member 2 anchored to the bicycle frame and a moving member 1 movable with respect to a base member 2 according to a quadrilateral mechanism composed of an outer link 21 and an inner link of the same length as the outer link 21 and which remains parallel to it, so that the axis of the moving member 1 remains parallel to the base member 2 axis throughout the entire length of its movement path.

In other embodiments, the inner link may be of a different length than the outer link 21 so that the orientation of the moving member 1 varies with respect to the base member 2 along its movement path to, for example, orient this moving member 1 , or any element anchored to it, towards the bicycle chainring.

In these embodiments, both links are articulated at both ends, so that the 4 articulation axes are parallel and delimit the movement of the moving member 1 to a plane.

In other embodiments, the inner link can be articulated with respect to the base member 2 and the moving member 1 by means of ball joints, so it is not essential that the two axes of the outer link 21 are parallel, but preferably they will be parallel in order to maintain the movement of the moving member 1 in the plane.

Apart from these embodiments, other mechanisms can also be considered to obtain the relative movement of the moving member 1 with respect to the base member 2, such as linear guides, gear systems to coordinate link rotations, etc.

The preferred embodiment illustrated in the figures comprises a traction spring anchored at diagonally opposite points of the quadrilateral formed by the two links and which tends to bring the moving member 1 to its furthest position with respect to the bicycle sprockets.

On the other hand, Figures 1 and 3 show a cable 60 with a terminal 61 that pulls a third point of the quadrilateral in an approximately diagonal direction to move the moving member 1 towards its closest position to the bicycle sprockets.

In this way, pulling the cable 60 moves the moving member 1 in one direction, and when releasing the cable 60, it is the tension spring that moves the moving member 1 in the opposite direction, keeping the cable 60 in tension.

In other embodiments, the tension spring and the cable 60 can exchange the diagonals of the quadrilateral so that by pulling on the cable 60, the moving member 1 moves away from the sprockets and by releasing the cable 60, it moves closer to the sprockets. It is not essential that the terminal 61 of the cable 60 to coincide with an axis of rotation of a link, nor that the pull of the cable be on the diagonal of the quadrilateral, but any arrangement of the cable 60 is valid as long as it can exert a force component on the quadrilateral mechanism in the desired direction.

In the same way, it is not essential that the anchoring points of the traction spring correspond to the axes of the links, but any arrangement of the traction spring that exerts a force component on the quadrilateral mechanism in the desired direction is valid. As long as a force component is exerted on the quadrilateral mechanism in the desired direction, any other spring arrangement or elastic element can be used. For example, a concentric compression spring can be used with the cable 60, a torsion spring in one of the quadrilateral axes, or an elastomeric element between the links.

In the preferred embodiment, the pull of the cable 60, and therefore the position of the moving member 1 with respect to the base member 2, is controlled by an electric actuator 6. However, in other embodiments the pull of the cable 60 could come directly from mechanical controllers arranged on the bicycle handlebar. In other embodiments, other electrical actuators could be used that act on the quadrilateral mechanism exerting the desired force component. For example, a rotation actuator that controls the rotation of a link with respect to the base member 2 or moving member 1 or a linear actuator arranged between 2 opposite points of the quadrilateral.

In some embodiments, the electric actuator will be able to exert forces in both directions of movement, so the quadrilateral spring could be dispensed with or maintained as an aid or method to eliminate play in the actuator.

The rear derailleur 10 of the invention also comprises a tensioner shaft 3 rotationally mounted on the moving member 1 and a tensioner 4 fixed to the tensioner shaft 3 so that the tensioner 4, which comprises the upper pulley 45 and the lower pulley 46, rotates relative to the moving member 1 . In this preferred embodiment, the rear derailleur 10 also comprises a torsion spring 5 concentrically mounted with respect to the tensioner shaft 3, the first end of the torsion spring 5 being attached to the tensioner shaft 3, and therefore to the tensioner 4, and the second end of the torsion spring 5 being attached to the moving member 1. The torsion spring is mounted in such a way that it tends to move the lower pulley 46 away from the bicycle chainring, creating tension in the lower branch of the chain, to keep the chain engaged on the chainring, on the sprocket and on the pulleys 45 and 46.

As seen in Figure 2, in this first preferred configuration, the torsion spring 5 has a radial extension 59 at one of its ends that is inserted into the groove 19 of the moving member 1 to limit the relative rotation of the torsion spring 5 with respect to the moving member 1 , and also has a hook-shaped extension 58 that is inserted into the slot 38 of the tensioning shaft 3 to limit the relative rotation of the torsion spring 5 with respect to the tensioning shaft 3.

In other embodiments, the connection of the torsion spring 5 to the moving member 1 and tensioner shaft 3 can be carried out in alternative ways. For example, the tension spring may have axial extensions that are inserted into corresponding holes in the moving member 1 and the tensioner shaft 3.

In some embodiments, the torsion spring 5 can be complemented with a damping mechanism between the moving member 1 and the tensioner shaft 3 in order to stabilize the movements of the tensioner against vibrations and keep the length of the chain more stable. Damping can be obtained, for example, hydraulically or by friction. These damping systems can work in both directions or only in one (preferably limiting the direction that removes tension from the chain), including appropriate mechanisms for this purpose such as clutches or unidirectional bearings. Additionally, the torsion spring 5 and/or the damping mechanism can be complemented with an electronic actuator that controls the rotation of the tensioner 4 and it can even be considered to use an electronic actuator to control the rotation of the tensioner 4 without the torsion spring 5 and the damping mechanism.

In Figure 1 it can be seen that the upper pulley 45 is mounted on the tensioner 4 at a considerable distance from the tensioner shaft 3 so that its position depends highly on the angular position of the tensioner 4, that is, on the position of the lower pulley 46 in order to achieve the necessary tension in the lower branch of the chain. This arrangement is suitable for systems with a single chainring. In this arrangement it is possible to coordinate the position of the lower pulley 46 for sprockets of different sizes, with the position of the upper pulley 45 for tracking these sprockets, while the movement of the moving member 1 is maintained in a substantially horizontal plane, and therefore is less influenced by vibrations.

In other embodiments, the upper pulley 45 can be closer to the tensioner shaft 3 so that its position does not depend so much on the position of the lower pulley 46 and the size of the engaged chainring, and thus it can be used on bicycles with more than one chainring. In this case, the plane of movement of the moving member 1 should be inclined in order to track the sprockets.

In some embodiments, the upper pulley 45 can become concentric to the tensioner shaft 3, so that the tracking of the sprockets of the upper pulley 45 is completely independent of the engaged chainring. In this case it would be possible to anchor the upper pulley 45 to the tensioner shaft 3 instead of to the tensioner 4.

As seen in the figures, the characteristic that differentiates this invention from other derailleurs of the state of the art is that the tensioner shaft 3 completely passes through the moving member 1 and is fixed to the tensioner 4 on both sides of the moving member 1 . In this way, a firmer anchoring of the tensioner 4 is achieved with respect to the moving member 1 and a more robust tensioner 4 can also be dimensioned.

In this first preferred embodiment, as seen in Figure 3, the tensioner 4 is formed by two arms 41 , 42 that go from the part of the tensioner 4 furthest from the tensioner shaft 3 to both sides of the tensioner shaft 3. In this way, a much more rigid and resistant structure of the tensioner 4 is achieved than if the tensioner 4 was only anchored to one of the sides of the tensioner shaft 3. This structural advantage due to the geometry can be used to obtain a tensioner 4 that is lighter than those known in the state of the art if similar materials (steel, aluminum or carbon fiber) are used. This structural advantage can also be used to manufacture the tensioner 4 with alternative materials, such as plastic, that were not suitable for the single-side anchored tensioner configuration, thereby making its manufacturing cheaper.

Specifically, the preferred embodiment illustrated in the figures is sized so that the tensioner 4 and the rest of the complex structural parts (base member 2, outer link 21 , inner link, moving member 1 , upper pulley 45 and lower pulley 46) are of a plastic material with short fiber reinforcements, so that the main parts of the derailleur can be obtained very economically by injection moulding. In this regard, in Figure 1 it can be seen that the external link 21 has larger dimensions than what is usually used in the state of the art, so that it is possible to manufacture it in plastic (reinforced with short fibers), making its manufacturing cheaper, but without losing rigidity or resistance and without increasing weight. Thus, the only parts to be manufactured in metal would be the geometrically simplest ones (tensioner shaft 3, link axles, frame anchoring screw and other screws) which will also be economical to manufacture. Overall, this preferred embodiment would be cheaper to manufacture than more traditional arrangements, but without losing rigidity or strength compared to them, which represents a great competitive advantage. The aesthetics of this new structural configuration are easily distinguishable from the more traditional configurations and it can even be said that it is more proportionate and gives a feeling of robustness. This aesthetic advantage and own identity would be another commercial advantage of the invention with respect to the state of the art.

The structural advantage of being able to anchor the tensioner 4 to both sides of the moving member 1 frees up a large design space for the tensioner 4. It could be said that we would go from designing a flat tensioner 4 in 2 dimensions to a tensioner 4 with volume in 3D. This opens possibilities for an infinite number of designs, beyond the preferred embodiment illustrated in Figure 3, with very different structural and aesthetic properties.

As described above, if opening this 3D space for the design of the tensioner 4 with anchoring on both sides of the moving member 1 entails great advantages, it also presents a disadvantage: tension cannot be applied to the torsion spring 5 through the tensioner 4 as in the most common state-of-the-art systems. State-of-the-art rear derailleurs are typically mounted completely without the torsion spring being preloaded, which makes mounting easier, and then the torsion spring is preloaded by rotating the tensioner in the order of one turn and inserting a stop into the tensioner to prevent losing the preload. From here on, the rear derailleur has a working range in which the torsion spring increases preload during its movement but also ensures a minimum tension in the chain for any position of the tensioner. The three-dimensional volume of the tensioner 4 observed in the figures allows the rotation of the tensioner with respect to the moving member 1 in the working range but does not allow the additional rotation (about one turn) of the tensioner 4 to preload the torsion spring 5, so another mechanism should be considered to generate this preload in the torsion spring 5.

It must be remembered that in this invention the torsion spring 5 is anchored to the moving member 1 and the tensioner shaft 3, which is a separate part from the tensioner 4, so there is no need to rotate the tensioner 4 with respect to the moving member 1 in order to preload the torsion spring 5, but being simply necessary to rotate the tensioner shaft 3 with respect to the moving member 1 .

In this preferred embodiment, as seen in Figure 7, the rear derailleur 10 comprises a mechanism for fixing the tensioner shaft 3 to the tensioner 4 which, in an intermediate fixation position and to adjust the preload level of the torsion spring 5, allows the rotation of the tensioner shaft 3 with respect to the tensioner 4 while the moving member 1 remains in its final assembly position with respect to the tensioner 4. This fixing mechanism can fix the tensioner shaft 3 in different angular positions with respect to the tensioner 4.

More specifically, in the preferred embodiment, the mechanism for fixing the tensioner shaft 3 to the tensioner 4 is composed of a footprint 31 for a hexagonal wrench on the tensioner shaft 3, a lobular groove 30 that extends radially at one of the ends of the tensioner shaft 3, a complementary housing 40 in the tensioner 4 for the final fixing position, and a screw 32 that axially fixes the tensioner shaft 3 with respect to the tensioner 4 in the final fixing position as shown in Figure 5.

In this way, in the assembly process of the preferred embodiment, we would begin by assembling all the parts up to the intermediate fixing position illustrated in Figure 7 in which the torsion spring 5 is positioned but not preloaded. Then, using the corresponding hexagonal wrench, the tensioner shaft 3 is rotated, preloading the torsion spring 5 and in that angular position the tensioner shaft 3 is moved axially to fix it with respect to the tensioner 4 according to the lobular groove 30 and the complementary housing 40 (see figure 5). Finally, screw 32 is tightened to fix the tensioner shaft 3 in that axial position.

This preloading mechanism of the torsion spring 5 illustrated in the figures is simply one of the possibilities, but many other variants are possible according to the invention.

For example, it would be possible to preload the torsion spring 5 by rotating the tensioner shaft 3 with respect to the moving member 1 in the absence of the tensioner 4 and mount the tensioner 4 on the tensioner shaft 3 once the torsion spring 5 is preloaded. For this, it could be convenient for the fixation between the tensioner shaft 3 and the tensioner 4 to be radial instead of axial. For example, clamps could be used with two screws in a radial direction on each arm of the tensioner 4 that embrace the tensioner shaft 3 on each side of the moving member 1 . Or additional pieces can also be used to fix the tensioner shaft 3 with respect to the tensioner 4 when both are in the final fixation position.

An alternative fixing mechanism between the tensioner shaft 3 and the tensioner 4 can be a pin whose center coincides with the fitting diameter between the tensioner shaft 3 and the tensioner 4, so that the hole for the pin is partially in the tensioner shaft 3 and partially in the tensioner 4, resulting in a unique mounting position in which both partial holes have to coincide to mount the pin that transmits the torque between the parts and prevents their relative rotation. Instead of a circular pin, a rectangular section pin could be used to make torque transfer more efficient. Parts of any other shape/section can also be used for this torque transmission. If more than one (partial) hole is made in the tensioner shaft 3 and/or tensioner 4, both can be fixed in different relative positions, as many as the multiplication of holes in one and the other. If the same number of holes are available in the tensioner shaft 3 and in the tensioner 4 and these holes are equally spaced, it would be possible to connect both elements with as many pins as holes to have an improved torque transfer while allowing as many relative mounting positions as holes. If pins (one or more and of any section) are used for fixing the tensioner shaft 3 and the tensioner 4, it is not necessary to have an intermediate fixing position for preloading the torsion spring 5, since the torsion spring 5 can be preloaded when the tensioner shaft 3 and the tensioner 4 are in the final fixing position and they can be fixes afterwards by using the pins in such position.

For any of these solutions proposed with pins (one or more and of any section), it could be possible that these pins were an integral part of the tensioner shaft 3 or the tensioner 4, which would require an intermediate fixing position to preload the torsion spring and then a final fixing position that would entail a relative axial displacement between the tensioner shaft 3 and the tensioner 4 for fixation. The specific case of 12 cylindrical pins integrated into the tensioner shaft 3 would be very similar to the lobular groove 30 solution described in the figures. By integrating another type of pins with a different section in the tensioner shaft 3 or tensioner 4, other shapes would be generated for the tangential interference between the tensioner shaft 3 and the tensioner 4, such as hexagonal or any other regular polygon, gear-shaped, Hirth-teeth shaped or with any other teeth shape, etc.

In cases where the fixing interference occurs directly between the geometry of the tensioner shaft 3 and the tensioner 4 and an intermediate fixation position is required, it could be useful for the interference geometry to be progressive in the axial direction so that this interference between the tensioner shaft 3 and the tensioner 4, progressively increasing between the intermediate fixing position and the final fixing position to facilitate assembly. For example, all of these interference geometries could be conical or correspond in some manner to conical pins.

In some embodiments, other attachment modes different from the hexagonal wrench footprint 31 can be used, both on the tensioner shaft 3 and on the moving member 1 , in order to facilitate the rotation of one with respect to the other during the preload adjustment of spring 5. For example, another standard tool can be used (torx wrench, Philips,...), a special tool, or a specific surface to be gripped with the hand.

In the preferred solution illustrated in Figure 5, a screw 32 is used to fix the axial position of the tensioner shaft 3 with respect to the tensioner 4. This arrangement is useful because by tightening the screw 32 from the intermediate fixing position in Figure 7, the screw 32 itself brings the tensioner shaft 3 to the final fixing position in Figure 5. In other configurations, the fixation of the tensioner shaft 3 with respect to the tensioner 4 in the final fixing position could be carried out with other methods, such as a circlip or with screws in radial direction.

In this text, the word “correspond” and its variants (such as “corresponding”, etc.) should not be interpreted in an exclusive way, that is, they do not exclude the possibility that what is described includes other elements, steps, etc.

On the other hand, the invention is not limited to the specific embodiments that have been described but also encompasses, for example, the variants that can be carried out by the average person skilled in the art (for example, regarding the choice of materials, dimensions, components, configuration, etc.), within what is deduced from the claims.

Claims

1.- Rear derailleur (10) for bicycles comprising a moving member (1) movable with respect to a base member (2), a tensioner shaft (3) rotationally mounted on the moving member (1) and a tensioner (4) fixed to the tensioner shaft (3), characterized in that the tensioner shaft (3) completely crosses the moving member (1) and is fixed to the tensioner (4) on both sides of the moving member (1).

2.- Rear derailleur (10) according to the first claim, comprising a torsion spring (5) concentrically mounted with respect to the tensioner shaft (3), the first end of the torsion spring (5) being attached to the tensioner shaft (3). and the second end of the torsion spring (5) being attached to the moving member (1).

3.- Rear derailleur (10) according to claim 2, which comprises a mechanism for fixing the tensioner shaft (3) to the tensioner (4) that, in an intermediate fixing position, and to adjust the preload level of the torsion spring (5), allows the rotation of the tensioner shaft (3) with respect to the tensioner (4) while the moving member (1) remains in its final assembly position with respect to the tensioner (4).

4.- Rear derailleur (10) according to claim 3, wherein the mechanism for fixing the tensioner shaft (3) to the tensioner (4) can fix the tensioner shaft (3) in different angular positions with respect to the tensioner (4).

5.- Rear derailleur (10) according to claim 4, wherein the mechanism for fixing the tensioner shaft (3) to the tensioner (4) consists of a footprint (31) for a hexagonal wrench on the tensioner shaft (3), a lobular groove (30) that extends radially at one of the ends of the tensioner shaft (3), a complementary housing (40) in the tensioner (4) for the final fixing position, and a screw (32) that fixes axially the tensioner shaft (3) with respect to the tensioner (4) in the final fixing position.

6.- Rear derailleur (10) according to any of the previous claims in which the tensioner (4) is formed by two arms (41 , 42) that go from the part of the tensioner (4) furthest from the tensioner axis (3) to both sides of the tensioner shaft (3).

7.- Rear derailleur (10) according to any of the previous claims in which the tensioner (4) is made of a non-metallic material and is manufactured by injection moulding.