Patent Publication Number: US-10759494-B2

Title: Bicycle rear derailleur with a damper assembly

Description:
This application is a continuation of U.S. patent application Ser. No. 14/460,492, filed Aug. 15, 2014, the contents of which are herein referenced in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to bicycle rear derailleurs and more particularly to a bicycle rear derailleur with a damper assembly. 
     As is known, a bicycle derailleur performs shifting operations by shifting the chain between a plurality of adjacent sprockets of a sprocket assembly of a bicycle. A further, also very important function of the derailleur is to ensure a sufficient chain tension. A bicycle derailleur is generally constructed in the following manner. A base member is mounted to the bicycle frame. Further, a movable member is movably connected to the base member and a chain guide assembly is movable connected to the movable member with respect to rotation about a rotational axis. The movable member is movable in the axial direction, to move the chain guide assembly between the sprockets of the sprocket assembly, so that the chain may be shifted from an initial sprocket to a target sprocket. The chain guide assembly is biased in a rotational direction by a torsion spring or the like, namely in the direction of tensioning of the bicycle chain which is guided by the chain guide assembly, to maintain the chain in a tensioned state or to restore a tensioned state after an antecedent state of insufficient chain tensioning. This rotational or pivoting direction is also referred to as “chain tensioning direction.” A rotation of the chain guide in this direction increases the tension of the chain and at the same time decreases the tension of the torsion spring acting on the chain guide assembly. Depending on the current sprocket of the sprocket assembly with which the chain is engaged at a given point, the chain guide assembly will take various rotational positions relative to the movable member with regard to the axis of rotation. 
     Impact on the chain and the chain guide assembly not only results from the shifting of the derailleur by shifting the chain between various sprockets of the sprocket assembly, but also from riding itself. For example, when riding on uneven surfaces, the derailleur and the chain are subjected to blows and vibrations which may act on the chain guide assembly in a rotational direction opposite to the “chain tensioning direction.” A rotation of the chain guide assembly in the direction opposite to this “chain tensioning direction” increases the tension of the tension spring acting on the chain guide assembly and directly results in a reduction of the chain tension or at least results in a greater risk of a subsequent reduction of the chain tensioning below a necessary level. Negative effects may be a drop in the chain tensioning with unwanted slackness or “dangling” of the chain. In a worst case, the chain may fall off the sprocket assembly. 
     To face these problems, conventional solutions are provided with a damper assembly that provides a resistance to rotational movement of the chain guide assembly in the rotational direction of the chain guide assembly opposite to “chain tensioning direction.” In this respect, the known solutions each have a one-way clutch and a friction unit, which act together in such a way that the resistance regarding the rotational movement of the chain guide assembly is affected in a rotational direction opposite to the “chain tensioning direction.” 
     The movable member and the chain guide assembly are rotatable relative to each other, but are frictionally coupled via the friction unit and the one-way clutch, which due to the characteristics of the one-way clutch is only effective in the rotational direction opposite to the “chain tensioning direction,” so that a dynamic friction is only present in this rotational direction to act against the rotation. In the other rotational direction corresponding to a backwards rotation of the chain guide in the sense of a tensioning of the chain, the chain guide assembly is decoupled from the movable member due to these one-way clutch characteristics, so that the tensioning of the chain by rotating the chain guide assembly encounters no resistance or at least only an irrelevant degree of resistance. 
     Such a rear derailleur is disclosed in US 2009/0054183 A1. The derailleur includes a damper assembly having a friction unit including a plurality of axially supported friction plates. A one-way roller clutch assembly is arranged radially outwardly of these friction plates in the same axial area, which results in the necessity of a relatively large dimension for the movable member in the radial direction. An advantage of this solution is an adjustment unit having an exposed adjustment nut for adjusting the friction engagement and thus the damping force acting as resistance. This configuration allows the rider to adjust the damping force. However, for such an adjustment a tool is required and the question arises if an average rider has the necessary knowledge to adjust the damping force correctly. Further, the exposed adjustment nut is not protected from undesired rotation which may result in undesired adjustment of the damping force. 
     Other rear derailleurs with damper assemblies are disclosed in US 2012/0083371 A1 and US 2012/0083872 A1. These damper assemblies also include one-way roller clutch assemblies. The rotational axis of the chain guide assembly serves as an inner clutch member of the roller clutch. The friction unit includes a leaf spring encircling an outer clutch member of the roller clutch and having two end portions radially protruding between two rotational cams or alternatively between an adjustment screw and a rotational cam, which serve for adjusting a basic friction and for controlling a momentarily acting friction via a control lever or the like, so that the cyclist—according to his wishes, for example when riding on different terrain—may select the momentarily acting friction and thus the momentarily acting damping force by the control lever which is movable between two index positions. Providing the cyclist with such a choice calls for a relatively high mechanical effort. 
     US 2013/0203532 A1 discloses a rear derailleur that includes a sleeve-like friction element extending circumferentially around the roller clutch assembly and having a tapered or conical outer surface. The rotational axis rotatably supporting the chain guide assembly forms the inner clutch member of the roller clutch assembly. Also, U.S. Pat. No. 4,406,643 discloses several different embodiments of a rear derailleur with a damper assembly. Generally, the damper assembly includes a one-way ratchet clutch and a friction unit having axially arranged friction surfaces. One of the embodiments includes a nut threaded into an inner thread of a tubular holder or threaded onto an external thread of a support shaft and serving as counter-bearing of the friction unit including a friction plate and a dish-shaped spring. The assembly of these prior art embodiments necessarily involves an adjustment of the damping force, since the frictional engagement depends on the actual position of the nut in the respective internal thread or on the respective external thread. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a bicycle rear derailleur which is mechanically simple. 
     Another object of the present invention is to provide a bicycle rear derailleur which may be easily assembled during manufacturing and provides the correct damping force with high certainty. 
     Another object of the present invention is to provide a bicycle rear derailleur that has a compact movable member, in particular a radially compact movable member. 
     Another object of the present invention is to provide a bicycle rear derailleur which has favorable damping characteristics. 
     One embodiment of the present invention provides a bicycle rear derailleur including a base member mountable to a bicycle frame. A movable member is movably coupled to the base member. A chain guide assembly is rotatably connected to the movable member for rotation about a rotational axis. A biasing element is configured to bias the chain guide assembly for rotation in a first rotational direction with respect to the movable member. A damper assembly is operatively disposed between the chain guide assembly and the movable member to apply a damping force to the chain guide assembly when the chain guide assembly rotates in a second rotational direction opposite to the first rotational direction. The damper assembly may include a one-way roller clutch assembly and a friction unit. The one-way roller clutch assembly and the friction unit are disposed coaxially about the rotational axis. The friction unit may be biased against and in frictional engagement with the one-way roller clutch assembly. The one-way roller clutch assembly and the friction unit may be sized and shaped to deform the friction unit against the one-way roller clutch assembly. The friction unit may be disposed about or within the one-way roller clutch assembly to deform the friction unit. 
     The friction unit may include a damping spring having a spring engagement portion extending circumferentially over a circumferential angle coaxially about the rotational axis. The one-way roller clutch assembly includes inner and outer clutch members disposed coaxially about the rotational axis. 
     The spring engagement portion may include an inner circumferential engagement surface biased against and in frictional engagement with an outer circumferential counter engagement surface of the outer clutch member. The outer circumferential counter engagement surface has a first diameter which expands the spring engagement portion to a corresponding diameter of the inner circumferential engagement surface giving rise to a spring force of the spring engagement portion biasing the inner circumferential engagement surface against the outer circumferential counter engagement surface. When the damping spring is in a relaxed state the inner circumferential engagement surface of the spring engagement portion has a second diameter which is smaller than the first diameter. 
     The spring engagement portion may include an outer circumferential engagement surface biased against and in frictional engagement with an inner circumferential counter engagement surface of the inner clutch member. The inner circumferential counter engagement surface has a first diameter which compresses the spring engagement portion to a corresponding diameter of the inner circumferential engagement surface giving rise to a spring force of the spring engagement portion biasing the outer circumferential engagement surface against the inner circumferential counter engagement surface. When the damping spring is in a relaxed state the outer circumferential engagement surface of the spring engagement portion has a second diameter which is larger than the first diameter. 
     The damper assembly may be disposed within a cavity of the movable member coaxially about a rotational shaft supporting the chain guide assembly for rotation about the rotational axis. The rotational shaft may form the inner clutch member of the one-way roller clutch assembly. Alternatively, the rotational shaft may be connected to the inner clutch member for common rotation. 
     The damping spring may be coupled with the movable member for supporting the spring engagement portion against rotation with respect to the movable member. The wedge member may eliminate the rotational play between the damping spring and the moveable member. The damping spring may include a spring retaining portion extending radially outwardly with respect to the spring engagement portion for coupling the spring engagement portion with the movable member. The spring engagement portion may have a free end. At least one wedge member may be operatively disposed between the spring retaining portion and the movable member. The wedge member may bias the spring retaining portion against a first abutment surface of the movable member. Further, the wedge member may be located between the spring retaining portion and a second abutment surface opposite to the first abutment surface. 
     At least two wedge members may be operatively disposed between the spring retaining portion and the movable member urging the spring retaining portion in opposite directions between a first abutment surface and a second abutment surface opposite to the first abutment surface. At least one first wedge member may be located between the spring retaining portion and the first abutment surface and at least one second wedge member is located between the spring retaining portion and the second abutment surface. 
     The damping spring may be configured such that a frictional force which is caused by the frictional engagement between the inner circumferential engagement surface and the outer circumferential counter engagement surface or is caused by the frictional engagement between the outer circumferential engagement surface and the inner circumferential counter engagement surface and which acts against a rotation of the chain guide assembly in said second rotational direction is one of increased and decreased when the chain guide assembly rotates in the second rotational direction. 
     The spring engagement portion of the damping spring may wrap around the outer circumferential counter engagement surface. The spring engagement portion may wrap more tightly about the outer circumferential counter engagement surface when the chain guide assembly rotates in the second rotational direction to increase the frictional force. The spring engagement portion may wrap more loosely about the outer circumferential counter engagement surface when the chain guide assembly rotates in the second rotational direction to decrease the frictional force. 
     Another aspect of the present invention is a subassembly unit for a bicycle rear derailleur. The subassembly unit includes a movable member movably couplable to a base member. A rotational shaft is supported for rotational about a rotational axis in a cavity of the movable member. The cavity forms a passage extending between opposite first and second axial sides of the movable member. The rotational shaft is connectable to a chain guide assembly at a first axial end of the rotational shaft. The rotational shaft is supported by a support surface of the movable member in a first axial direction corresponding to a direction from a second axial end of the rotational shaft to the first axial end of the rotational shaft. A damper assembly is disposed in the cavity of the movable member and operatively disposed between the rotational shaft and the movable member. The damper assembly includes a one-way roller clutch assembly disposed coaxially about the rotational axis and a friction unit including a damping spring having a spring engagement portion extending circumferentially over a circumferential angle coaxially about the rotational axis. The spring engagement portion has an inner circumferential engagement surface biased against and in frictional engagement with an outer circumferential counter engagement surface of the one-way roller clutch assembly. The damping spring has a spring retaining portion extending radially outwardly with respect to the spring engagement portion between opposite abutment surfaces of the movable member for coupling the spring engagement portion with the movable member. 
     The first axial end of the rotational shaft may be accessible from the first axial side of the movable member for connection with the chain guide assembly and the rotational shaft and the damper assembly is inserted into the cavity from the second axial side of the movable member. A retaining flange of the rotational shaft may be axially located between the support surface of the movable member and the damping spring. The retaining flange may be axially located between the first axial end and the damping spring. 
     A method of manufacturing a bicycle rear derailleur includes the following steps of assembling a subassembly unit. The subassembly unit includes a movable member movably connectable to a base member. A rotational shaft is supported for rotational about a rotational axis in a cavity of the movable member. The cavity forms a passage extending between opposite first and second axial sides of the movable member. The rotational shaft is connectable to a chain guide assembly at a first axial end of the rotational shaft. The rotational shaft is supported by a support surface of the movable member in a first axial direction corresponding to a direction from a second axial end of the rotational shaft to the first axial end of the rotational shaft. A damper assembly is disposed in the cavity of the movable member and operatively disposed between the rotational shaft and the movable member. The damper assembly includes a one-way roller clutch assembly disposed coaxially with respect to the rotational axis and a friction unit including a damping spring having a spring engagement portion extending circumferentially over a circumferential angle about and coaxial with respect to the rotational axis. The spring engagement portion has an inner circumferential engagement surface biased against and in frictional engagement with an outer circumferential counter engagement surface of the one-way roller clutch assembly. The damping spring has a spring retaining portion extending radially outwardly with respect to the spring engagement portion between opposite abutment surfaces of the movable member for coupling the spring engagement portion with the movable member. The rotational shaft and the damper assembly are inserted into the cavity from the second axial side of the movable member so that the first axis end of the rotational shaft is accessible from the first axial side of the movable member. The rotational shaft at the first axial end is connected with a chain guide assembly. The movable member is coupled to the base member. 
     These and other features and advantages of the present invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a side view of a rear derailleur including a damper assembly according to one embodiment of the present invention; 
         FIG. 2  is a side view of the rear derailleur of  FIG. 1 ; 
         FIG. 3  is a side view of the rear derailleur of  FIG. 1 , except a cap and a retaining ring are removed to expose an axial view of the damper assembly 
         FIG. 4  is an enlarged side view of the damper assembly of the rear derailleur of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the damper assembly taken along V-V of  FIGS. 2, 3 and 4 ; 
         FIG. 6  is an exploded view of the damper assembly with the base member, swing linkage and the movable member of the rear derailleur of  FIG. 1 ; and 
         FIG. 7  is an enlarged side view of a damper assembly for a rear derailleur according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments of the invention will herein by described with reference to the drawings. It will be understood that the drawings and description set out herein are provided for illustration only and do not limit the invention as defined by the claims appended hereto and any and all equivalence. For example, terms such as “first” and “second,” “upper” and “lower,” or “forward” and “rearward” are used for the sake of orientation and not as terms of limitation. Moreover, the terms preferably refer to the bicycle derailleur conventionally mounted to a bicycle and with the bicycle orientated for normal use unless otherwise indicated. For example, the front of an element would be that part of the element oriented/closest to the front of the bicycle. 
     Looking to  FIGS. 1-6 , a bicycle derailleur  10  is shown according to one embodiment of the present invention. The bicycle derailleur  10  generally includes a base member  12 , a movable member  16 , a swing linkage  18 , a chain guide assembly  26  and a damper assembly  38 . The base member  12 , also known as a “b-knuckle,” may be mounted to a bicycle frame  11  by a fastening element  14  such as a screw or the like. The swing linkage  18 , in this embodiment a parallelogram, includes outer and inner links  20 ,  22  pivotally connected to the base member  12  by a pair of pivot pins  24  or bolts. The movable member  16 , also known as a “p-knuckle,” is pivotally connected to the links  20 ,  22  at ends of the links  20 ,  22  opposite to the base member  12 . The movable member  16  is pivotally connected by a pair of further pivot pins  24  to the swing linkage  18  in a similar manner as the base member  12 . In principle, various means for coupling the movable member  16  with the base member  12  are imaginable within the scope of the invention. 
     The movable member  16  is movable by the swing linkage  18  in a well-known manner in a sideward direction relative to the bicycle frame  11  to shift a chain  35  (shown schematically in  FIG. 1 ) by the chain guide assembly  26  between the sprockets of a sprocket assembly  13  mounted to the rear wheel of the bicycle. The swing linkage  18  includes a biasing element  21 , in this embodiment a spring, to tension the derailleur  10  in the direction of an initial travel position as is common knowledge in this field of expertise. The chain guide assembly  26  is rotatably mounted to the movable member  16  and is biased in a chain tensioning direction T by a biasing element, in this embodiment torsion spring  44  (see  FIG. 5 ). Looking to  FIG. 1 , a forward direction F corresponds to the forward direction of a bicycle. A rotational direction of the chain guide assembly  26 , in which the guided chain is tensioned, is denoted with T. The rotational direction in the forward direction F opposite to the chain tensioning direction T is denoted by chain slackening direction L. Rotation of the chain guide assembly  26  in the chain slackening direction L may result in an undesired reduction of chain tensioning which may result in the chain disengaging with one of the sprockets. The chain guide assembly  26  includes an outer plate  28  and an inner plate  30 , spaced apart. An upper guide wheel  32  and a lower guide wheel  34  are rotatably arranged between the outer and inner plates  28  and  30  for receiving the chain  35 . 
     The movable member  16  may include a chain guide locking mechanism  36  that fixes the chain guide assembly  26  in a certain rotational position with respect to the movable member  16  so that maintenance work may be easily performed (see  FIG. 1 ). Looking to  FIG. 5 , the outer plate  28  is connected in a rotatably fixed manner with a rotational shaft  50  which is supported for rotation in a cavity  90  of the movable member  16 . The cavity  90  may form a passage extending between opposite first and second axial sides  91 ,  93  of the movable member  16 . An intermediate washer  52  is located between the outer plate  28  and the movable member  16 . The intermediate washer  52  is connected to the outer plate  28  in a rotatably fixed manner by protrusions (not shown) engaging in openings of the plate. The outer plate  28 , including the intermediate washer  52 , is connected to a first axial end  55  of the rotational shaft  50  by a screw  54  being screwed into an internal thread of the rotational shaft  50 . The rotational shaft  50  includes a tool engagement feature  53  in a second axial end  57  opposite to the inner thread into which the screw  54  is engaged, which facilitates to tighten the screw  54 . The shaft  50  is axially supported by a retaining flange  51  abutting against an annular support surface  59  of the movable member  16  defining the cavity  90  in a stepped manner. The torsion spring  44  engages on the one hand with a coupling portion in a positive-locking manner in the movable member  16  and on the other hand with a coupling portion in a positive-locking manner in the intermediate washer  52  and the outer plate  28 , so that the spring  44  biases the chain guide assembly  26  in the chain tensioning direction T to maintain or restore the necessary tensioning of the chain which is engaged in the usual manner with the guide wheels  32 ,  34 . 
     Looking to  FIGS. 5 and 6 , the cavity  90  may be closed on the axial side opposite to the outer plate  28  by a cap  100 . The cap  100  may have an elastic seal  102  made of rubber disposed in a recess in the outer circumference of the cap  100  and in sealing engagement with the inner circumference of the cavity  90  of the movable member  16 . The cap  100  and seal  102  may be disposed entirely inside the cavity and may have a recess for receiving an end of the rotational shaft  50 , so that the rotational shaft may rotate relative to the cap  100 . For holding the cap  100  in its place, a retaining ring  104  may be provided, which engages in a groove  106  formed in the inner circumferential surface of the cavity  90  of the movable member  16 . 
     The movable member  16  includes the damper assembly  38  for damping the rotational movement of the chain guide assembly  26  relative to the movable member  16  in the chain slackening direction L opposite to the chain tensioning direction T. The damper assembly  38  generally includes a one-way roller clutch assembly  60  and a friction unit  61 . The damper assembly  38  applies a damping force to the chain guide assembly  26  which opposes a rotation in the chain slackening direction L opposite to the chain tensioning direction T relatively to the movable member  16 . 
     In this embodiment, the one-way roller clutch assembly  60  includes inner clutch member or the rotational shaft  50  and outer clutch member  63  and roller elements acting between the inner and outer clutch members. In this embodiment, the rotational shaft  50  forms the inner clutch member. Alternatively, the inner clutch member may be a sleeve or the like, connected in a rotatably fixed manner to the rotational shaft  50 . The outer clutch member  63  includes a first sleeve  79  and a second sleeve  80 . The first sleeve  79  is press fitted into the second sleeve  80  such that the first and second sleeves  79 ,  80  are connected in a rotatably fixed manner and do not move in the axial direction with respect to each other. The sleeve  80  may be made of hardened steel and may have circumferential groves along its outer surface to retain lubricating grease for safeguarding appropriate frictional characteristics of the friction unit  61 . The roller clutch assembly  60  is configured such that the rotational direction of the rotational shaft  50  corresponding to the chain tensioning direction T is the one-way rotational direction of the roller clutch assembly, in which the inner clutch member or shaft  50  may rotate freely with respect to the outer clutch member  63 . The chain slackening direction L being opposite to the chain tensioning direction T corresponds to the locking direction of the roller clutch assembly  60 , in which a rotation of the inner clutch member or shaft  50  with respect to the outer clutch member  63  of the roller clutch  60  is locked so that the rotational shaft  50  and thus the chain guide assembly  26  may only rotate in this direction by entraining the outer clutch member  63  for common rotation. 
     The roller clutch assembly  60  may be formed as a drawn cup roller clutch, which is a sleeve-like element retaining on its inner circumference the roller elements and which is combined with the rotational shaft  50  which serves as inner clutch member. The drawn cup roller clutch includes a thin-walled, formed outer ring with locking rams on the inside diameter, a cage (typically plastic cage) and needle rollers positioned by springs. Torque is only transmitted in one direction and there is a low idling frictional torque in the other direction. A drawn cup roller clutch may be fitted by pressing into a housing. In order to support torque transmission, a drawn cup roller clutch may be supplied with a knurled outer ring. 
     The friction unit  61  includes a damping spring  82  which has a general shape shown in  FIGS. 4 and 5 . The damping spring  82  and the one-way roller clutch assembly  60  are disposed coaxially about the rotational shaft  50 . The damping spring  82  may be made from a metallic material such as spring-tempered steel or the like. The damping spring  82  includes a spring engagement portion  84  and a spring retaining portion  86  extending radially outwardly with respect to the spring engagement portion  84 . The damping spring  82  is supported against rotation with respect to the movable member  16  by the spring retaining portion  86  extending between opposite abutment surfaces of the movable member, as seen in  FIG. 4 . A wedge member  92 , in this embodiment a biasing clip, is inserted into the cavity  90  of the movable member  16  to bias the spring retaining portion  86  against an abutment surface of the movable member in the cavity  90  so that the spring retaining portion  86  is supported against rotation with respect to the movable member  16  in both rotational directions and does not move relative to the movable member  16 . The wedge element  92  may be made of spring-tempered sheet steel or the like. 
     The spring engagement portion  84  extends circumferentially over a circumferential angle coaxially about the rotational axis or shaft  50 . The spring engagement portion  84  has a free end  87 . The spring engagement portion  84  has an inner circumferential engagement surface that engages with an outer circumferential counter engagement surface of the second sleeve  80  of the outer clutch member  63 . The one-way roller clutch assembly  60  has an outer diameter that is larger than an inner diameter of the spring engagement portion  84 . For example, the one-way roller clutch assembly may have an outer diameter of 14 mm and the spring engagement portion  84  has an inner diameter of 13.5 mm in a relaxed state before being assembled with the one-way roller clutch assembly  60 . Thus, when the one-way roller clutch  60  is received in the inner diameter of the spring engagement portion  84 , the inner diameter of the spring engagement portion  84  expands to exert a radially inward directed force on the outer circumferential counter surface of the second sleeve  80  such that relative rotational movement is allowed between the second sleeve  80  and the damping spring  82  against frictional counter forces resulting from the frictional engagement between the inner circumferential engagement surface of the engagement portion  84  and the outer circumferential counter engagement surface of the second sleeve  80 . Alternatively, the second sleeve  80  may be eliminated and an outer circumferential engagement surface of the first sleeve  79  of outer clutch member  63  may be in direct frictional engagement with the inner circumferential engagement surface of the spring engagement portion  84 . From  FIGS. 5 and 6 , it is clear how and in which sequence the different components of the damper assembly  38  are to be inserted into the cavity  90 . 
     The operation of the damper assembly  38  is as follows. When the chain guide assembly  26  rotates in the chain slackening direction opposite to the chain tensioning direction T (counter-clockwise in  FIG. 1 ), the shaft  50 , which is supported for rotation with the cavity  90 , rotates with the chain guide assembly  26 . Since the shaft  50  is engaged with the rollers of the roller clutch assembly  60  and the roller clutch assembly  60  is configured to “lock” in this direction, the one-way clutch assembly  60  must also rotate in this direction with the shaft  50 . Because the spring engagement portion  84  of the damping spring  82  exerts a radially inwardly directed force on the sleeve  80 , frictional forces between the damping spring  82  and the sleeve  80  urge the damping spring  82  to rotate with the sleeve  80 . However, rotation of the damping spring  82  is prevented by the spring retaining portion  86  which abuts against a surface in the cavity  90  of the movable member  16  as shown in  FIG. 4 . Thus, the sleeve  80  rotates relative to the damping spring  82  and energy is dissipated to overcome the frictional forces between the sleeve  80  and the spring engagement portion  84  of the damping spring  82 . In this way, the rotational motion of the chain guide assembly  26  in the chain slackening direction L is dampened by a frictional counter force which acts against this rotation of the chain guide assembly  26  in the chain slackening direction L. 
     When the cage rotates in the chain tensioning direction T (clockwise in  FIG. 1 ), the shaft  50  rotates with it. The roller clutch assembly  60  is configured to allow relative rotation of the shaft  50  in this direction. In other words, the roller clutch assembly  60  allows the shaft  50  to rotate freely in this direction. Thus, the damper assembly  38  does not dampen motion of the chain guide assembly  26  in the chain tensioning direction T. 
     It should be noted that the damping spring  82 , according to the orientation of the spring engagement portion  84  with respect to the spring retaining portion  86  and the resulting wrapping sense of the spring engagement portion  84  with respect to the sleeve  80  is configured such that the engagement spring portion  84  has a tendency to “self-energize,” which means that it has a tendency to wrap even more tightly around the sleeve  80  when the sleeve rotates counter-clockwise in the chain slackening direction L, so that the friction between the damping spring  82  and the roller clutch  60  is increased. 
       FIG. 7  shows another embodiment of the present invention. A damping spring  182  wraps the opposite way around a sleeve  180  and therewith the assembly formed by the sleeve, the roller clutch  160  and the rotational shaft  150  which is supported for rotation in the cavity  190  of the movable member  116 . This alternative embodiment corresponds to the embodiment shown in  FIGS. 1-6  except for this alternative orientation and wrapping sense of the spring engagement portion  184 , so that further additional explanations are not necessary. For the second embodiment of  FIG. 7  the same reference signs are used as for the first embodiment of  FIGS. 1-6 , respectively increased by 100. 
     According to the alternative embodiment of  FIG. 7 , wherein the roller clutch assembly  160  rotates counter-clockwise in the chain slackening direction, the damping spring  182  has a tendency to “unwrap” itself from around the sleeve  180 , which has the result of reducing the friction between the engagement spring portion  184  and the sleeve  180 . This may have the benefit of “smoother” relative motion between the damping spring  182  and roller clutch assembly  160 . 
     According to the shown embodiments, the damping spring  82  with its spring engagement portion  84  is located radially outwardly with respect to the radial outer clutch member  63  of the roller clutch assembly  60 , and the spring engagement portion  84  is expanded by the roller clutch. It is feasible to arrange a damping spring with its engagement portion radially inwardly with respect to the radial inner clutch member of the roller clutch to be compressed by an effective inner circumference for achieving the frictional engagement providing the required damping forces. Such a damping spring could be coupled at a retaining portion of the rotational shaft and the outer clutch member of the roller clutch could be coupled with the movable member, so that the relative position of the roller clutch and the damping spring between the chain guide assembly on the one hand and the movable member on the other hand would be interchanged. 
     A major advantage of the embodiments according to the invention is that the damping assembly needs no adjustment, even no adjustment in the course of the assembly when the derailleur is manufactured. The frictional engagement between the damping spring and the one-way roller clutch assembly is defined by the dimensions of the involved components, i.e. the inner diameter of the engagement portion of the damping spring and the outer diameter of the outer clutch member of the roller clutch assembly in the present embodiments. These diameters are defined from the manufacturing of those components. Another advantage of the embodiments according to the invention is that the damper assembly may be relatively compact in axial direction as well as in radial direction, so that a compact movable member may be provided. 
     While this invention has been described by reference to several embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.