Abstract:
A control device for a derailleur of a bicycle is described, comprising a support body, a cable-winding bush supported for rotation with respect to the support body, an indexer mechanism housed in the support body and suitable for controlling the angular position of the cable-winding bush, and a single manual actuation lever, the indexer mechanism comprising a toothed wheel integral in rotation with the cable-winding bush and having a first and a second plurality of slanting teeth, a first pawl integral with a driven arm of the lever and brought into thrusting engagement upon the first teeth while the lever is manually moved in a first direction beyond a predetermined rotation threshold, and a second pawl driven out of retention engagement with the second teeth by the driven arm of the lever while the lever is manually moved in the first direction up to the predetermined rotation threshold.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
     The present application is the U.S. national stage entry of PCT application No. PCT/IT2006/000037 filed Jan. 23, 2006, which is incorporated by reference as if fully set forth. 
     FIELD OF INVENTION 
     The present invention relates to a control device used to drive a bicycle derailleur. 
     BACKGROUND 
     A bicycle is normally provided with a rear derailleur associated with the sprocket set, which consists of a set of coaxial toothed wheels (sprockets), with different diameters and numbers of teeth, integral with the hub of the rear wheel. 
     A bicycle is typically also provided with a front derailleur associated with the crankset, which consists of a set of toothed wheels (toothed crowns) with different diameters and numbers of teeth, associated with a bottom bracket axle driven into rotation by a pair of pedals. In less expensive bicycles, only one toothed wheel is associated with the bottom bracket axle and there is the rear derailleur only. 
     A transmission chain for transmitting the pedaling motion into the motion of the rear wheel extends in a closed loop between the sprocket set and the crankset. 
     The rear derailleur and the front derailleur—if present—engage the transmission chain, displacing it on toothed wheels with different diameters and numbers of teeth, so as to obtain different gear ratios. 
     By convention, one speaks of downward gearshifting when the chain shifts from a larger diameter toothed wheel to a smaller diameter toothed wheel, of upward gearshifting when the chain shifts from a smaller diameter toothed wheel to a larger diameter toothed wheel. In this regard it should be noted that in a front gearshift group, downward gearshifting corresponds to the passage to a lower gear ratio and upward gearshifting corresponds to the passage to a higher gear ratio; vice versa in a rear gearshift group, downward gearshifting corresponds to the passage to a higher gear ratio and upward gearshifting corresponds to the passage to a lower gear ratio. 
     The displacement in the two directions of a derailleur is obtained through a control device mounted so as to be easily handled by the cyclist, namely normally on the handlebars, near to the handgrips where there is also the brake lever to control the brake of the front and rear wheel, respectively. Control devices that allow driving both a derailleur in the two directions and a brake are commonly known as integrated controls. 
     By convention, the control device of the front derailleur and the brake lever of the front wheel are located near to the left handgrip of the handlebars, and vice versa the control device of the rear derailleur and the brake lever of the rear wheel are located near to the right handgrip. 
     More specifically, in a mechanical gearshift, each derailleur is moved between the toothed wheels, in a first direction by a traction action exerted by a normally sheathed inextensible cable (commonly known as Bowden cable), in a second opposed direction by releasing the traction of the cable and/or by the elastic return action of a spring provided in the derailleur itself. 
     Normally, but not necessarily, the direction in which the displacement is caused by the release of the traction of the cable and/or by the return spring is that of downward gearshifting; vice versa, the traction action of the traction cable normally occurs in the direction of upward gearshifting, in which the chain is displaced from a smaller diameter wheel to a larger diameter wheel. 
     The traction cable extends along the bicycle frame up to the control device. In the control device, the traction cable is traction- or release-actuated through winding and unwinding on a rotor element, commonly known as cable-winding bush, the rotation of which is controlled by the cyclist through suitable manual actuation means. 
     Typically, the manual actuation means comprise a pair of levers, a pair of buttons, a button and a lever, or a bidirectional lever. 
     SUMMARY 
     The invention concerns a control device for a bicycle derailleur, comprising a support body, a cable-winding bush supported for rotation with respect to the support body, an indexer mechanism housed in the support body and suitable for controlling the angular position of the cable-winding bush, and a single manual actuation lever, the indexer mechanism comprising a toothed wheel integral in rotation with the cable-winding bush and having a first plurality of slanting teeth and a second plurality of slanting teeth, a first pawl integral with a driven arm of the lever and brought into thrusting engagement on the first teeth while the lever is manually moved in a first direction beyond a predetermined rotation threshold, and a second pawl driven out of retention engagement with the second teeth by the driven arm of the lever while the lever is manually moved in the first direction up to the predetermined rotation threshold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       Further features and advantages of the present invention shall become clearer from the following detailed description of some preferred embodiments thereof, made with reference to the attached drawings, merely as a non-limiting example, wherein: 
         FIG. 1  shows a side view of a right integrated control device according to the invention, mounted on curved bicycle handlebars; 
         FIGS. 2 to 13  show the control mechanism of the device of  FIG. 1  in various steps during gearshiftings; 
         FIG. 14  shows a second embodiment of the indexer mechanism of the control device according to the invention; 
         FIGS. 15 to 18  show a third embodiment of the indexer mechanism, in various steps during gearshiftings; 
         FIGS. 19 to 22  show a fourth embodiment of the indexer mechanism, in various steps during gearshiftings; 
         FIGS. 23 and 24  show a perspective view and a cross-sectional view of a right control device according to the invention, mounted on straight bicycle handlebars; and 
         FIG. 25  shows a perspective view of a right integrated control device according to the invention, mounted on straight bicycle handlebars. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Introduction 
     A control device for a bicycle derailleur comprises a support body, a cable-winding bush supported for rotation with respect to the support body, an indexer mechanism housed in the support body and suitable for controlling the angular position of the cable-winding bush, and a single manual actuation lever, the indexer mechanism comprising a toothed wheel integral in rotation with the cable-winding bush and having a first plurality of slanting teeth and a second plurality of slanting teeth, a first pawl integral with a driven arm of the lever and brought into thrusting engagement on the first teeth while the lever is manually moved in a first direction beyond a predetermined rotation threshold, and a second pawl driven out of retention engagement with the second teeth by the driven arm of the lever while the lever is manually moved in the first direction up to the predetermined rotation threshold. 
     While the lever of the control device is manually moved up to the predetermined rotation threshold, the first pawl comes into not interfering engagement with the first teeth, in other words it is inserted between the teeth, but the direction of rotation of the toothed wheel and the slant of the first teeth are such that the rotation of the toothed wheel is not prevented by the first pawl, and at the predetermined rotation threshold, the first pawl comes into interfering engagement with the first teeth. 
     Moreover, while the lever is manually moved beyond the predetermined rotation threshold, the second pawl comes into not interfering engagement with the second teeth, in other words it is inserted between the teeth, but the direction of rotation of the toothed wheel and the slant of the second teeth are such that the rotation of the toothed wheel is not prevented by the second pawl. 
     Furthermore, while the lever rotates in a second direction opposite the first direction, i.e. when the lever is released by the cyclist, the first pawl is out of engagement with the first teeth and the second pawl is in retention engagement with the second teeth. Therefore, the second pawl retains the new position of the toothed wheel, and thus of the cable-winding bush. 
     Preferably, when the lever is manually moved within the predetermined rotation threshold, the toothed wheel and the cable-winding bush rotate in the unwinding direction of a traction cable of the derailleur, fastened to the cable-winding bush. In this way, the traction force of the cable and/or of a spring associated with the derailleur automatically causes the rotation of the cable-winding bush in the unwinding direction. 
     More preferably, when the lever is manually moved up to the predetermined rotation threshold and then, when it is released, it rotates in a second direction opposite the first direction, the toothed wheel and the cable-winding bush carry out a rotation in the unwinding direction by an amount equal to one pitch between the second teeth, and the second pawl moves from a first gap between the second teeth to an adjacent gap between the second teeth, in this way causing a single gearshifting from a first toothed wheel of the sprocket set or of the crankset to the immediately adjacent toothed wheel, even more preferably to a toothed wheel with a smaller diameter. 
     Preferably, moreover, when the lever is manually moved beyond the predetermined rotation threshold, the toothed wheel and the cable-winding bush rotate in the winding direction of the traction cable fastened to the cable-winding bush. In this way, the actuation force of the cyclist is intended to overcome the traction force of the traction cable and/or of the spring associated with the derailleur. 
     More preferably, when the lever is manually moved beyond the predetermined rotation threshold, the toothed wheel and the cable-winding bush carry out a rotation in the winding direction by an amount equal to at least one pitch between the second teeth, and the second pawl moves from a first gap between the second teeth to an adjacent or subsequent gap between the second teeth, in this way causing a single or multiple gearshifting from a first toothed wheel of the sprocket set or of the crankset to the immediately adjacent toothed wheel, even more preferably to a toothed wheel with a greater diameter. 
     Advantageously, the rotation of the lever within the predetermined threshold takes place about a pivot supported by a connecting member coaxial with the toothed wheel. In this way, the motion of the driven arm of the lever and therefore of the first pawl is a pure motion towards and away from the toothed wheel, optimal for the purposes of the operation of the first pawl. 
     Similarly, but vice versa, the rotation of the lever beyond the predetermined threshold preferably takes place about an axis of the toothed wheel, integrally with the connecting member. In this way, the motion of the driven arm of the lever and therefore of the first pawl is purely circular, optimal for thrusting the toothed wheel into rotation. 
     Advantageously, the second pawl is formed on a driven arm of a swinging member pivoted onto the support body, and the driven arm of the lever, during its manual displacement up to the predetermined rotation threshold, controls a driving arm of the swinging member. 
     In an embodiment, the driven arm of the lever has a stepped profile for controlling the driving arm of the swinging member during the manual displacement of the lever up to the predetermined rotation threshold. With such a stepped profile, the displacement of the swinging member and thus of the second pawl is not continuous, and in particular the engagement of the second pawl between the second teeth is delayed. 
     In another embodiment, the driven arm of the lever has a peg or preferably a roller for controlling the driving arm of the swinging member, so as to reduce friction. 
     In another embodiment, the indexer mechanism further comprises a second swinging member having a first arm hinge-like coupled with the driving arm of said swinging member, and the driven arm of the lever, during its manual displacement up to the predetermined rotation threshold, controls a second arm of the second swinging member. By arranging such a second swinging member as a motion transmitting means between the lever and the swinging member on which the second pawl is formed, the second pawl can be taken further away from the driven arm of the lever without having to form it on a too long swinging member. Moreover, the degrees of freedom in the design of the arms and of the strokes of the swinging members are increased, to adapt the stroke of the second pawl to the geometry of the second teeth of the toothed wheel. 
     Preferably, the control device further comprises return means for biasing the lever into rotation in a second direction opposite the first direction. 
     Preferably the control device further comprises elastic means for biasing the second pawl into retention engagement with the second teeth. 
     The control device can further comprise a brake lever for controlling a brake of the bicycle, i.e. it can be an integrated device. 
     In case it is an integrated device, and in particular in case the integrated control device is for attachment onto curved handlebars, typical of racing bicycles, an actuation arm of the lever is preferably provided with an articulation pivot essentially parallel to a pivot of the brake lever, so as to be able to follow the braking movement. 
     The control device can, however, also be for attachment onto straight handlebars, typical of mountain bikes. 
     DESCRIPTION 
     The description of the control device according to the invention is made hereafter with reference to a right control device, i.e. associated with the right handgrip of the handlebars, but it is manifest that the left control device associated with the left handgrip of the handlebars will be totally analogous. 
     The control device  1  according to a first embodiment of the invention comprises a support body  2  to be fastened, at a rear side thereof  3 , frontally of a curved handgrip portion of handlebars M through known connection means, for example through a clip, and frontally projecting from the handlebars M. 
     In the present description and in the attached claims, spatial terms, in particular the terms front, rear, upper, lower and vertical, are used with reference to the mounted condition of the control device, and with reference to the handlebars in a neutral position, the term inner indicating towards the center of the handlebars. 
     In the front region  4  of the support body  2 , a brake lever  5  pivots about a pivot  6  essentially perpendicular to the advancing direction X of the bicycle. The head of a traction cable (not shown) is connected to the brake lever  5  in a known manner, for actuation of the brake when the cyclist pulls the brake lever  5  towards the handlebars M, typically with several fingers of the right hand other than the thumb. 
     A gearshift lever  9  projects downwards from the lower surface  8  of the support body  2 , and comprises a widened actuation portion  9   a  suitable for receiving a finger of the right hand other than the thumb rested on it, preferably the middle finger or the ring finger. The gearshift lever  9  extends behind and along the brake lever  5  and has an articulation about a pivot  10  to follow the movement of the brake lever  5 . 
     The support body  2  is typically covered by a protective sheath (not shown) and is shaped in such a way as to be able to be gripped by the cyclist, with the palm of the hand resting on its upper wall  11 . In a different guide position, on the other hand, the cyclist grips the handlebars M below the support body  2 . In both guide positions, the cyclist easily reaches both the brake lever  5  and the gearshift lever  9  with his/her fingers. 
     In the support body  2  an inner cavity is defined where an indexer mechanism  12  is placed. The indexer mechanism  12 , described hereafter, takes up a series of predetermined angular positions about an axis Y essentially parallel to the bicycle advancing direction X. The indexer mechanism  12  rotates in a first direction as a consequence of a rotation of the gearshift lever  9  by a comparatively small angle in a first direction (out of the page with reference to  FIG. 1 ), and rotates in the opposite direction as a consequence of a rotation of the gearshift lever  9  by a comparatively large angle in the same direction (towards the reader with reference to  FIG. 1 ). 
     A cable-winding bush  13  is coupled, integral in rotation, with the indexer mechanism  12 . A traction cable K, typically a sheathed cable commonly known as Bowden cable, is wound around the cable-winding bush  13  for a length dependent upon the angular position of the cable-winding bush  13 . In other words, it is wound and unwound as a consequence of the actuation of the gearshift lever  9 . The traction cable K extends along the bicycle frame and its opposite end is coupled with the rear derailleur—or with the front derailleur, respectively. The winding and unwinding of the traction cable K on the cable-winding bush  13  therefore cause the displacement of the derailleur and therefore the engagement of the motion transmission chain at one of the toothed wheels associated with the hub of the rear wheel—or with the bottom bracket of the bicycle respectively—corresponding to the desired gear ratio. 
     The indexer mechanism  12  is now described with reference to  FIGS. 2 to 13 , which show cross-sectional views carried out along the section plane II-II of  FIG. 1 , in different steps during gearshifting in a first direction ( FIGS. 2 to 7 ) and during gearshifting in a second direction ( FIGS. 2 ,  3  and  8  to  13 ). 
     A central pivot  14 , having axis Y as its axis, is fixed to the support  2  in a per sé known way. 
     The cable-winding bush  13  has a hollow shaft, again indicated with reference numeral  13 , pivotable about the central pivot  14 . Alternatively, the rotation-free coupling of the shaft of the cable-winding bush  13  with respect to the support body  2  can take place through one or more ball bearings or bushings circumferentially outside the shaft of the cable-winding bush  13 . 
     More specifically, the cable-winding bush  13  is integral in rotation with a toothed wheel  15 . The coupling integral in rotation of the cable-winding bush  13  and of the toothed wheel  15  is carried out for example through matched non-circular sections of the shaft of the cable-winding bush  13  and of a central hole of the toothed wheel  15 , as shown, but it is of course possible to provide for different couplings. 
     The cable-winding bush  13  and the toothed wheel  15  are biased into rotation, in the unwinding direction U of the traction cable K of the derailleur, by the traction of the cable itself and/or by the return force of a spring provided at the derailleur. 
     A connecting member  16  is pivoted about the central pivot  14 , for example inserted onto the shaft of the cable-winding bush  13  or onto a collar of the toothed wheel  15 . The connecting member  16  is forced in the unwinding direction U against the support  2  by return means, for example by the illustrated compression spring  17 , extending between the support  2  and an appendix  16   a  of the connecting member  16 . The helical compression spring  17  could be replaced by a coil spring having one end connected at a point of the connecting member  16  and the other end connected to the support body  2  or to the pivot  14 , in which case the connecting member  16  would lack appendix  16   a.    
     The gearshift lever  9 , only partially visible in  FIGS. 2 to 13 , is pivoted to the connecting member  16  through a pivot  18 . Return means, for example in the form of a coil spring  19  schematically illustrated in  FIGS. 2 to 13 , bias the gearshift lever  9  into a predetermined angular position with respect to the connecting member  16  and essentially vertical, shown in  FIG. 2 , counteracting the vibrations brought about by the travel of the bicycle. 
     A first pawl  20  is formed at the end of the driven arm  9   b  of the lever  9  to cooperate with a plurality of first slanting teeth  21  of the toothed wheel  15 . More specifically, the teeth  21 , seen in direction U, have an edge  91  of comparatively low slant with respect to the tangent to the toothed wheel  15 , and an edge  92  of comparatively high slant with respect to the tangent to the toothed wheel  15 . The first pawl  20  has a shape matching the shape of a gap  22  between two adjacent teeth  21 , and therefore has an edge  20   a  suitable for resting and thrust on the edge  92  of comparatively high slant of the first teeth  21 , therefore called “active edge” of the teeth. The first pawl  20  also has an edge  20   b  suitable for sliding on the edge  91  of comparatively low slant of the first teeth  21 , therefore called “inactive edge” of the teeth. In the rest state of the indexer mechanism  12  shown in  FIG. 2 , the first pawl  20  is in a position out of engagement with the first teeth  21 . 
     A second pawl  23  is formed at the end of a driven arm  24   a  of a swinging member  24  that is pivoted on the support body  2  through a pivot  25 . The second pawl  23  cooperates with a second plurality of slanting teeth  26  of the toothed wheel  15 . The second teeth  26 , seen in direction U, also have an edge  96  of comparatively low slant with respect to the tangent to the toothed wheel  15 , and an edge  97  of comparatively high slant with respect to the tangent to the toothed wheel  15 . The second pawl  23  has a shape matching the shape of a gap  27  between two adjacent teeth  26 , and therefore has an edge  23   a  suitable for acting as an abutment against the edge  97  of comparatively high slant of the second teeth  26 , therefore called “active edge” of the teeth. The second pawl  23  also has an edge  23   b  suitable for sliding on the edge  96  of comparatively low slant of the second teeth  26 , therefore called “inactive edge” of the teeth. 
     The teeth  21  and  26  for engagement with the two pawls  20 ,  23  can be different to each other, but preferably they are equal in number and geometry, so that the toothed wheel can be indiscriminately mounted in two positions angularly spaced apart by 180°. 
     Even if the teeth  21  and  26  are shown formed along two non-adjacent sectors of the toothed wheel  15 , a completely toothed wheel could alternatively be provided. 
     Return means, represented by a compression spring  28  extending between the support body  2  and the free end of the driven arm  24   a  of the swinging member  24 , force the swinging member  24  into the rest position of the indexer mechanism  12  shown in  FIG. 2 , wherein the second pawl  23  is engaged in one of the gaps  27  and the free end of the driving arm  24   b  of the swinging member  24  is in contact with the driven arm  9   b  of the lever  9 . 
     In the rest state shown in  FIG. 2 , therefore, the cable-winding bush  13  is retained in a predetermined angular position by the engagement of the second pawl  23  in the gap indicated with  27   a , an engagement that counteracts the traction force in the unwinding direction U, due to the cable K or to the spring provided at the derailleur. The gearshift lever  9  is also in rest position, essentially vertical as illustrated. 
     When the gearshift lever  9  is lightly pushed by the cyclist in the direction indicated with S in  FIG. 3 , it rotates with respect to the connecting member  16  about pivot  18 . In this regard, it should be emphasized that the elastic force of the spring  19  is comparatively weak and therefore yields and compresses, when the gearshift lever  9  is pushed. 
     The first pawl  20  formed on the driven arm  9   b  of the lever  9  and therefore in rotation about pivot  18 , faces one of the gaps, indicated with  22   a , between the first teeth  21 ; the pawl  20 &#39;s edge does not contact the active edge  92  of the tooth indicated with  21   a.    
     At the same time, the driving arm  24   b  of the swinging member  24  is biased to slide on the driven arm  9   b  of the lever  9 , and therefore the swinging member  24  swings in the direction indicated by the arrow  29 , against the force of the compression spring  28 , i.e. compressing it. The second pawl  23  therefore disengages from the gap  27   a  in which it was engaged. 
     The toothed wheel  15  and the cable-winding bush  13  are therefore free to carry out a small integral rotation in the unwinding direction U of the traction cable. The state shown in  FIG. 3  is therefore a non-static state, and the indexer mechanism  12  goes essentially immediately into the state shown in  FIG. 4 , in which the active edge  92  of the tooth  21   a  came to rest upon the first pawl  20 . 
     As a consequence of the small rotation of the toothed wheel  15  in the unwinding direction U, the second pawl  23  has passed over the ridge of the tooth  26   a  and now faces the subsequent gap  27   b.    
     If the gearshift lever  9  is released in this operative state, it is returned by the coil spring  19  in the direction S′ indicated in  FIG. 5 , opposite the direction S, and it causes the first pawl  20  to slide out from the gap  22   a , as shown in  FIG. 5 . At the same time, the thrusting action by the driven arm  9   b  of the gearshift lever  9  on the driving arm  24   b  of the swinging member  24  also ceases. The swinging member  24  is therefore biased, by the action of the spring  28 , in the direction  30  of rotation about its pivot  25  opposite the aforementioned direction  29 . The second pawl  23  therefore comes into a resting relationship on the inactive edge  96  of the tooth  26   a , on the side of the gap  27   b . It should be noted that during this non-static step illustrated in  FIG. 5 , the driving arm  24   b  of the swinging member  24  can lose the resting relationship on the driven arm  9   b  of the lever or not, depending on the speed of release of the gearshift lever  9  by the cyclist. 
     When the gearshift lever  9  goes back into the rest position, the first pawl  20  disengages from the first teeth  21 , and allows the rotation of the toothed wheel  15  and of the cable-winding bush  13  integral with it to freely rotate in the unwinding direction U, as illustrated in  FIG. 6 , which also shows a non-static state. During such a rotation, the second pawl  23  slides along the inactive edge  96  of the tooth  26   a , engaging in the gap  27   b.    
     The rotation in the unwinding direction U ends when the second pawl  23  comes into a resting relationship upon the active edge  97  of the subsequent tooth  26   b , as illustrated in  FIG. 7 . In such a state, the toothed wheel  15  and the cable-winding bush  13  are retained stationary by the engagement of the second pawl  23  in the gap  27   b.    
     Therefore, as a consequence of the described push on the gearshift lever  9  with an angular travel of a comparatively small amount, the toothed wheel  15  and therefore the cable-winding bush  13  carry out an angular rotation in the unwinding direction U of the brake cable, of an angular amount corresponding to the pitch between the second teeth  26 . Such a rotation corresponds to the release of such a length of the traction cable K as to displace the derailleur and therefore the transmission chain to the adjacent toothed wheel of the sprocket set—or of the crankset, respectively. Advantageously, such a displacement in release is in the direction of a toothed wheel with a smaller diameter, or downward gearshifting. In other types of gearshifting, however, the displacement in release can cause gearshifting towards a toothed wheel with a greater diameter, or upward gearshifting. 
     To carry out gearshifting in the opposite direction, the gearshift lever  9  is pushed by the cyclist in the same direction S illustrated in  FIG. 3 , imposing however a greater rotation. The initial operation of the control mechanism  12  is the same as that described above with reference to  FIGS. 2 to 4 . In other words, in the initial rotation step of the gearshift lever  9 , the engagement of the first pawl  20  in the gap  22   a  between the first teeth  21 , in resting relationship upon the active edge  92  of the tooth  21   a , the disengagement of the second pawl  23  from the gap  27   a  between the second teeth  26 , and the small rotation of the toothed wheel  15  in the unwinding direction U, take place. 
     With reference to  FIG. 8 , however, as the push of gearshift lever  9  in the direction S continues beyond the limit position shown in  FIG. 3 , the first pawl  20  acts by thrusting on the active edge  92  of the tooth  21   a , causing the rotation of the toothed wheel  15  and therefore of the cable-winding bush in the winding direction W of the cable, opposite the unwinding direction U. More specifically, the gearshift lever  9  now rotates integrally with the connecting member  16  about the central pivot  14 , against the action of the compression spring  17 . In  FIG. 8 , indeed, it is possible to see a gap  31  between the left edge of the connecting member  16  and the support body  2 . 
     At the same time, the thrusting action of the driven arm  9   b  of the gearshift lever  9  on the driving arm  24   b  of the swinging member  24  also ceases. The swinging member  24  is therefore biased, by the action of the spring  28 , in the direction  30  of rotation about its pivot  25 . The second pawl  23 , which as a consequence of the rotation of the toothed wheel  15  in the winding direction W has once again passed over the ridge of tooth  26   a , once again engages in the gap  27   a  in which it was initially engaged (see  FIG. 2 ). 
     As the push in direction S on the gearshift lever  9  and the consequent rotation in the winding direction W of the toothed wheel  15  through the first pawl  20  continues, the second pawl  23  slides on the inactive edge  96  of the tooth indicated with  26   c , the subsequent one in the winding direction W, as illustrated in  FIG. 9 ; it passes over its ridge, as illustrated in  FIG. 10 ; and it engages in the gap indicated with  27   c , the subsequent one in the winding direction W, as illustrated in  FIG. 11 . 
     When the gearshift lever  9  is released, it is returned by the coil spring  19  in the direction S′ indicated in  FIG. 12 , opposite the direction S, and it causes the disengagement of the first pawl  20  from the gap  22   a , as shown in the non-static state of  FIG. 12 . The second pawl  23 , in a resting relationship upon the active edge  97  of the tooth  26   c , counteracts the tendency to rotate of the toothed wheel  15  and of the cable-winding bush  13  in the unwinding direction U, caused by the traction force of the traction cable and/or of the spring at the derailleur. The toothed wheel  15  and the cable-winding bush  13  are therefore retained stationary by the engagement of the second pawl  23  in gap  27   c.    
     It should be noted that in the release step of the lever  9  from the position of comparatively large rotation, its motion can be a composite motion of simultaneous rotation about the pivot  14  and with respect to the connecting member  16 , about the pivot  18 . 
     The connecting member  16  and the gearshift lever  9  finally go back in to the respective rest positions, as illustrated in  FIG. 13 , under the action of the springs  17  and  19 , respectively. 
     Therefore, as a consequence of the described push on the gearshift lever  9  with an angular travel of a comparatively large amount, the toothed wheel  15  and therefore the cable-winding bush  13  carry out an angular rotation in the winding direction W of the brake cable, of an angular amount corresponding to the pitch between the second teeth  26 . Such a rotation corresponds to the winding of a such length of the traction cable K as to move the derailleur and therefore the transmission chain to the adjacent toothed wheel of the sprocket set—or of the crankset, respectively. Advantageously such a winding movement is in the direction of a toothed wheel with a greater diameter, or upward gearshifting. In other types of gearshift, however, the winding movement can cause gearshifting towards a toothed wheel with a smaller diameter, or downward gearshifting. 
     It should also be noted that by pushing the gearshift lever  9  beyond the position illustrated in  FIG. 11 , it is advantageously possible to carry out multiple gearshifting in the winding direction W of the cable, again through the thrust of the first pawl  20  onto the active edge  92  of the tooth  21   a , since the second pawl  23  shall slide on the inactive edge  91  of the next tooth, engaging in the next subsequent gap again  27   d  in the winding direction W and so on. 
       FIG. 14  illustrates, in a position corresponding to that of  FIG. 4 , an embodiment of an indexer mechanism  12   a  that is modified with respect to the indexer mechanism  12  described above by the presence of a stepped profile  9   c  at the driven arm  9   b  of the gearshift lever  9 , which allows a different actuation of the driving arm  24   b  of the swinging member  24 . Indeed, while the driving arm  24   b  of the swinging member  24  slides on the step  9   c  during the pushing of the lever  9  by a comparatively large amount, the swinging member  24  does not swing about the pivot  25 , rather it remains essentially still. Therefore, the engagement of the second pawl  23  in the gap  27  between the second teeth  26  is delayed with respect to the previous embodiment. 
       FIGS. 15 to 18  only schematically illustrate an indexer mechanism  41  according to another embodiment of the invention, in the operative states respectively corresponding to those illustrated in  FIGS. 2 ,  3 ,  4  and  11 . In the figures, the various springs are left out for the sake of simplicity. 
     In the indexer mechanism  41 , the first pawl  42  is again integral with the gearshift lever  9  and the second pawl  43  is again formed on the driven arm  44   a  of a swinging member  44  pivoted to the support body  2  through a pivot  45 . A peg  46  or preferably a roller  46  essentially parallel to pivot  45  is formed on the driven arm  9   b  of the gearshift lever  9 . In the rest state illustrated in  FIG. 15 , the driving arm  44   b  of the swinging member  44  is in a resting relationship upon the peg or roller  46 . 
     When the gearshift lever  9  is rotated in direction S by a comparatively small amount, the peg or roller  46  thrusts the driving arm  44   b  of the swinging member  44 , and therefore the swinging member  44  rotates in the direction  29 , disengaging the second pawl  43  from the toothed wheel  15 , as illustrated in  FIG. 16 . The toothed wheel  15 , and therefore the cable-winding bush  13  integral with it, are free to rotate in the unwinding direction U until the engagement of the first pawl  42  with the toothed wheel  15 , as illustrated in  FIG. 17 . 
     When, as illustrated in  FIG. 18 , the gearshift lever  9  is rotated in direction S by a comparatively large amount and the first pawl  42  thrusts the toothed wheel  15 , and therefore the cable-winding bush  13  integral with it, into rotation in the winding direction W, the peg or roller  46 , on the other hand, is taken out of engagement with the driving arm  44   b  of the swinging member  44 . The lever  9  is mounted to support body  2  and rotates about both the first pivot  14  and the second pivot  18 . The first pivot  14  and second pivot  18  have parallel axes. 
     In particular when roller  46  is provided, the friction involved is less since the contact between the swinging member  44  and the roller  46  is a rolling contact instead of a sliding contact. 
     It should be noted that in the embodiment illustrated in  FIGS. 15-18 , the two pawls  42  and  43  are formed on different planes perpendicular to the axis of rotation of the toothed wheel  15 . In particular, the first pawl  42  is advantageously formed on an insert  47  articulated to the articulation pivot  10  of the lever  9  independently of the actuation portion  9   a  of the lever  9 . In this way, when the brake lever  5  ( FIG. 1 ) is pulled, the insert  47  does not accompany its movement and the first pawl  20  and the peg or roller  46  advantageously remain in the respective operative states. An opening of the lever  9  suitable for receiving the end of the connecting member  49  when the brake lever  5  is pulled is also illustrated with reference numeral  48 . 
       FIGS. 19 to 22  schematically illustrate an indexer mechanism  51  according to another embodiment of the invention, again in the operative states respectively corresponding to those illustrated in  FIGS. 2 ,  3 ,  4  and  11 . In the figures, the various springs are left out for the sake of simplicity. 
     In the indexer mechanism  51 , the first pawl  52  is again integral with the gearshift lever  9  and the second pawl  53  is again formed on the driven arm  54   a  of a swinging member  54  pivoted to the support body  2  through a pivot  55 . 
     A second swinging member  56  is pivoted to the support body  2  through a pivot  57  in an intermediate position between the first swinging member  54  and the driven arm  9   b  of the gearshift lever  9 . A first arm  56   a  of the second swinging member  56  has a concave surface that receives the driving arm  54   b  of the first swinging member forming a hinge-like coupling between the first swinging member  54  and the second swinging member  56 . 
     In the rest state illustrated in  FIG. 19 , a second arm  56   b  of the second swinging member  56  is in a resting relationship upon the driven arm  9   b  of the gearshift lever  9 , and more specifically upon an insert  58  thereof on which the first pawl  52  is formed, in accordance with the embodiment of the indexer mechanism  41  described above. Also in this embodiment, the lever  9  has an opening  59  suitable for receiving the end of the connecting member  60  when the brake lever  5  is pulled. 
     When the gearshift lever  9  is rotated in the direction S by a comparatively small amount, the second arm  56   b  of the second swinging member  56  slides on the driven arm  9   b  of the lever  9  and in particular on the insert  58 . The second swinging member  56  therefore rotates in direction  61  about the respective pivot  57 . The hinge-like coupling between the first arm  56   a  of the second swinging member  56  and the driving arm  54   b  of swinging member  54  causes the rotation of the swinging member  54  in direction  29 , disengaging the second pawl  53  from the toothed wheel  15 , as illustrated in  FIG. 20 . The toothed wheel  15 , and therefore the cable-winding bush  13  integral with it, are free to rotate in the unwinding direction U until engagement of the first pawl  52  with the toothed wheel  15 , as illustrated in  FIG. 21 . 
     When, as illustrated in  FIG. 22 , the gearshift lever  9  is rotated in direction S by a comparatively large amount and the first pawl  52  thrusts the toothed wheel  15 , and therefore the cable-winding bush  13  integral with it, into rotation in the winding direction W, the first arm  56   a  of the second swinging member  56 , on the other hand, is taken out of engagement with the driven arm  9   b  of the gearshift lever  9 . 
     The now described embodiment of the indexer mechanism  51  with double swinging member advantageously allows the second pawl  53  to be taken into the desired position along the toothed wheel  15 , still keeping the size of the swinging member  54  on which it is formed small. Moreover, the provision of the second swinging member  56  allows the degrees of freedom in the design of the arms  54   a ,  54   b ,  56   a ,  56   b  and of the strokes of the swinging members  54 ,  56  to be increased, to adapt the stroke of the second pawl  53  to the height of the teeth of the toothed wheel  15 . 
       FIGS. 23 and 24  illustrate a control device  71  according to a second embodiment of the invention, mounted on straight handlebars M. 
     The control device  71  comprises a support body  72  having a split ring portion  73  for attachment around a straight handgrip portion of the handlebars M. The body  72  of the control device  71  frontally projects from the handlebars M. 
     From the rear surface  74  of the support body  72  a gearshift lever  79  projects backwards, and it comprises a widened actuation portion  79   a  suitable for receiving the cyclist&#39;s thumb resting on it. The gearshift lever  79  extends under the handgrip of the handlebars M, in a position that can be easily reached by the cyclist. 
     In the support body  72  an inner cavity is defined where an indexer mechanism  12  is placed. The indexer mechanism  12 , shown in  FIG. 24 , is the same as the one described above in detail with reference to  FIGS. 2 to 13 . Alternatively, the indexer mechanism could be made in accordance with the other described embodiments. 
     In case the indexer mechanism is like the one of  FIGS. 15 to 18  or  19  to  22 , the insert  47 ,  58  and the opening  48 ,  59  on the lever shall of course be left out. 
       FIG. 25  illustrates a control device  81  according to a third embodiment of the invention, mounted on straight handlebars M. 
     The control device  81  comprises a support body  82  having a split ring portion  83  for attachment around a straight handgrip portion of the handlebars M. The body  82  of the control device  81  frontally projects from the handlebars M. 
     In the front region  84  of the support body  82  a brake lever  85  is pivoted, about a pivot  86  essentially perpendicular to the bicycle advancing direction X. The head of a traction cable for the actuation of the brake when the brake lever  85  is pulled by the cyclist towards the handlebars M, typically with the fingers of the right hand other than the thumb, is connected to the brake lever  85 , in a known way. 
     From the rear surface  87  of the support body  82  a gearshift lever  89  projects backwards, and it comprises a widened actuation portion  89   a  suitable for receiving the cyclist&#39;s thumb resting on it. The gearshift lever  89  extends below the handgrip of the handlebars M, in a position that can be easily reached by the cyclist, and it does not have articulations since it does not have to follow the movement of the brake lever  85 . 
     In the support body  82  an inner cavity is defined where an indexer mechanism like any of the described embodiments is placed.