Actuation device for a control cable for a bicycle gearshift

The described actuation device comprises a casing, intended for the attachment to the handlebar of the bicycle, a cable-winding bobbin, angularly mobile in the casing about a main axis of the device, a first driving mechanism, acting on the bobbin to rotate it in a first angular direction, a second driving mechanism, acting on the bobbin to rotate it in a second angular direction opposite the first, as well as indexer assembly for removably holding the bobbin in predetermined angular positions. In accordance with the invention, the indexer assembly comprise first countering means, to counter the rotation of the bobbin in the first direction, and second countering means, distinct from the first countering means, to counter the rotation of the bobbin in the second direction. Asymmetric operation is thus obtained which allows active actuation to be set both for upward gearshifting and for downward gearshifting.

FIELD OF THE INVENTION

The present invention concerns an actuation device for a control cable for a bicycle gearshift. The following description is made with reference to devices specially designed for bicycles with straight handlebars (typical of mountain bikes), but the invention clearly does not depend upon the shape of the handlebars and upon the consequent design of the actuation device; therefore, the invention can also be used in devices for racing cycles, with curved handlebars.

BACKGROUND

A bicycle is normally provided with two gearshifts, a front one associated with the crankset and a rear one associated with the sprocket set. In both cases, the gearshift comprises a derailleur which engages the drive chain moving it on toothed wheels with different diameters and numbers of teeth, so as to obtain different transmission ratios; the derailleur, be it that of the rear gearshift or that of the front gearshift, is moved in a direction by a traction action applied by an inextensible cable that is normally sheathed (commonly known as Bowden cable), in the opposite direction by the elastic return action of a spring provided in the gearshift itself. Normally, the direction in which the displacement is determined by the return spring is that in which the chain passes from a toothed wheel of greater diameter to a toothed wheel of smaller diameter, i.e. that of so-called downward gearshifting; vice-versa, the traction action of the control cable takes place in the direction of so-called upward gearshifting, in which the chain moves from a toothed wheel of smaller diameter to a toothed wheel of greater diameter. It should be noted that in a front gearshift downward gearshifting corresponds to the passage to a lower transmission ratio, whereas in a rear gearshift it corresponds to a greater transmission ratio.

The displacement in the two directions of the control cable of a gearshift is obtained through an actuation device mounted so as to be easy to operate by the cyclist, i.e. normally on the handlebars, near to its grips. By convention, near to the left grip there is the actuation device of the control cable of the front gearshift and vice-versa near to the right grip there is the actuation device of the control cable of the rear gearshift.

In the actuation device, the control cable is actuated into traction or into release through winding and unwinding on a rotor element, commonly known as cable-winding bobbin, the rotation of which is controlled by the cyclist with different means according to the type of gearshift. In a typical configuration, the actuation device provides two distinct ratchet gear levers, to control the rotation in the two directions of the bobbin.

In any case, the actuation device must provide that the bobbin be held still in rotation in a number of predetermined angular positions, corresponding to the different positions of the derailleur required by the different ratios, i.e. on the different toothed wheels of the gearshift. Thus, the actuation device of a front gearshift has a relatively low number of predetermined angular positions (typically three), corresponding to the positions of the front derailleur on the different crowns of the crankset; a rear gearshift, on the other hand, has a relatively high number of predetermined angular positions (typically from seven to ten), corresponding to the positions of the rear derailleur on the different sprockets.

The holding in the predetermined positions is obtained by so-called indexer assembly, which must ensure that the cable-winding bobbin is held sufficiently strongly to keep the set position with precision even in the presence of knocks and bangs during ride, but at the same time also sufficiently yielding to allow the passage from one position to the other when the cyclist actuates the levers to change ratio.

Fundamentally, two types of actuation devices are known, those known as release and active devices.

In release actuation devices, the rotation of the cable-winding bobbin in the winding direction of the cable takes place thanks to the physical force applied by the cyclist on the appropriate lever, whereas the rotation in the opposite direction is obtained substantially by freeing the cable-winding bobbin and letting the return spring on the gearshift act in the direction to unwind the cable from the bobbin, clearly in a controlled manner. In these devices, therefore, during upward gearshifting, the cyclist must first overcome the holding action of the indexer assembly, then the return action of the spring of the derailleur, until the gearshifting is completed; during downward gearshifting, on the other hand, the cyclist must only overcome initially the holding action of the indexer assembly, whereas the return action of the spring of the derailleur is of help during the entire gearshifting. The return action of the spring of the derailleur, however, comes from an elastic-type force, and is therefore different according to the position; in particular, it is greater towards the high gear positions and smaller towards the low gear positions (by high and low gears meaning not long or short ratios, but rather ratios at which one arrives with upward gearshifts or with downward gearshifts). This determines an operative asymmetry that may be unwelcome for the cyclist, especially in demanding conditions of use like during a race.

To remedy the drawbacks of release devices, active devices have been developed, in which the cyclist is required to apply an active force during the entire gearshifting, be it downwards or upwards. In such a device, an elastic member is provided that counters the return action of the spring of the derailleur. The action of such elastic means is balanced with that of the spring of the derailleur, so that—if as a hypothesis the indexer assembly were missing and the only actions on the bobbin were those of the elastic means and of the return spring—the cable-winding bobbin would be arranged in an intermediate position, thus corresponding to an intermediate ratio of the gearshift.

However, such a device does not totally solve the problem. Indeed, with it gearshifting (upward or downward) moving away from the intermediate ratio are countered, whereas gearshifting (upward or downward) moving towards the intermediate ratio are facilitated.

There is therefore the problem of making the force required of the cyclist more homogeneous for different gearshifting.

SUMMARY

The present invention relates to an actuation device for a control cable for a bicycle gearshift, comprising a casing, intended for the attachment to the handlebar of a bicycle, a cable-winding bobbin, angularly mobile in the casing about a main axis of the device, a first driving mechanism, acting on the bobbin to rotate it in a first angular direction, a second driving mechanism, acting on the bobbin to rotate it in a second angular direction opposite the first, indexer assembly to removably hold the bobbin in predetermined angular positions, wherein said indexer assembly comprise first countering means, to counter the rotation of the bobbin in the first direction, second countering means, distinct from the first countering means, to counter the rotation of the bobbin in the second direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Introduction to the Embodiments

In particular, the present invention concerns an actuation device for a control cable for a bicycle gearshift, comprising:a casing, intended for attachment to the handlebars of the bicycle,a cable-winding bobbin, angularly mobile in the casing about a main axis (B) of the device,a first driving mechanism, active on the bobbin to rotate it in a first angular direction,a second driving mechanism, active on the bobbin to rotate it in a second angular direction opposite the first,indexer assembly for removably holding the bobbin in predetermined angular positions, characterized in that said indexer assembly comprise:first countering means, to counter the rotation of the bobbin in the first direction,second countering means, distinct from the first countering means, to counter the rotation of the bobbin in the second direction.

Providing indexer assembly equipped with countering means that are different according to the direction of rotation of the bobbin allows the holding action of the indexer assembly to be calibrated independently with regard to the two directions of rotation of the cable-winding bobbin, and thus allows the return action of the spring of the derailleur of the gearshift to be balanced better.

Preferably, the first countering means counter the rotation of the bobbin in a different way to the second countering means. Thus, the clearly asymmetric influence of the return spring of the derailleur on the actuation device is easier to balance, with a corresponding asymmetric action in the opposite direction of the indexer assembly.

Preferably, the first or the second countering means—and even more preferably both—counter the rotation of the bobbin independently of the angular position of the bobbin itself. By this it is meant that the countering means counter the rotation of the bobbin with the same force for different gearshifting, both between low gear positions and between high gear positions; for example, therefore, to pass from the first to the second position one must overcome the same countering force that must be overcome to pass from the third position to the fourth position.

Preferably:the indexer assembly comprise at least one ball engaged both with a stationary member integral with the casing and with a rotating member integral in rotation with the bobbin;the first countering means comprise a first countering spring that acts upon the ball to keep it in a stop position in which the stationary member and the rotating member are made integral in rotation;the second countering means comprise a second countering spring that acts upon the ball to keep it in the stop position.

The use of an elastically biased ball—per se known in the art—makes the action of the indexer assembly particularly reliable and certain; the use of two distinct springs to bias the spring against the rotation of the bobbin in the two directions allows the differentiation of the countering means that forms the basis of the invention to be achieved in a simple manner.

Preferably, therefore, a rotation of the bobbin in the first angular direction biases the ball away from the stop position, in contrast to the first countering spring.

Preferably, in an analogous manner, a rotation of the bobbin in the second angular direction biases the ball away from the stop position, in contrast to the second countering spring.

Preferably:the indexer assembly comprise a ball-carrying disc, mounted in the casing and provided with at least one radial groove, said ball being mounted in said radial groove so that the ball is thrusted radially outwards from the first countering spring, the groove being open on at least one side of the ball-carrying disc and having a depth such that the ball projects in the axial direction from the ball-carrying disc;the indexer assembly comprise a first indexing disc, mounted in the casing in a position facing and adjacent to the ball-carrying disc, towards the side thereof from which the ball projects, and provided with a recess arranged according to a path that comprises stop zones and sliding zones alternating with each other;one from the ball-carrying disc and the first indexing disc is located in the stationary member, being mounted integral in rotation with the bobbin, whereas the other of them is located in the rotating member, being mounted locked in rotation with the casing;the second countering spring is mounted in the casing so as to axially bias the first indexing disc and the ball-carrying disc one against the other;the ball, projecting axially from the groove on the ball-carrying disc, is engaged in the recess on the first indexing disc.

It should be noted that the axial, radial and circumferential indications always refer, in the present patent text, to the axis of rotation of the cable-winding bobbin.

The engagement between the indexing disc and the ball-carrying disc is what defines the predetermined positions that the cable-winding bobbin must take up. Such engagement is obtained in a simple and extremely effective and precise manner through the ball and its engagement in the groove on the ball-carrying disc on the one hand and in the recess on the indexing disc on the other hand.

Preferably, to obtain the asymmetric behavior forming the basis of the invention, an intermediate stop zone is defined by a stop wall orientated according to a sliding direction (S), the stop direction (T) and sliding direction (S) of the same stop zone defining an acute angle (β) that does not enclose the main axis (B) of the device.

In such a way, the stop wall is undercut with respect to the radial direction, i.e. the direction of such a wall makes an acute angle (small in size, slightly more than zero is sufficient) with respect to the radial direction, and such an acute angle faces backwards with respect to the relative movement of the ball that thrusts in the circumferential direction on such a wall. Such an orientation prevents the ball thrusted circumferentially on the wall by a rotation action of the bobbin being able to move.

Preferably, a sliding wall extends along the direction of sliding from the stop zone for the entire adjacent sliding zone.

In such a way, the direction of such a wall makes an acute angle with respect to the radial direction, and such an acute angle faces forwards with respect to the relative movement of the ball that thrusts in the circumferential direction on such a wall. Such an orientation allows the ball thrusted circumferentially on the wall by a rotation action of the bobbin to follow the wall itself, moving in the groove towards the inside of the ball-carrying disc.

Preferably, the stop walls are fitted to the sliding walls in a succession that forms an outer peripheral margin of the recess on the indexing disc. Such a recess may or may not be defined towards the inside by an inner peripheral margin corresponding to the outer peripheral margin; such an inner margin, however, is not operative.

Preferably, two opposite indexing discs can be provided, which together cooperate with the ball-carrying disc at opposite sides thereof. For such a purpose, therefore:the groove in the ball-carrying disc is open on both sides of such a disc and has a depth such that the ball projects in the axial direction from the ball-carrying disc, from both sides thereof; in whichthe indexer assembly also comprise a second indexing disc integral in rotation with the first indexing disc, mounted in the casing in a position facing and adjacent to the ball-carrying disc at the opposite side with respect to the first indexing disc and provided with a recess specularly corresponding to that of the first indexing disc; and in whichthe ball, projecting axially from the groove on the ball-carrying disc, is engaged both in the recess on the first indexing disc, and in the recess on the second indexing disc.

The presence of two indexing discs ensures more balance and more effectiveness for the device.

Equally, more balance and more effectiveness are preferably obtained by using not a single ball but two balls, operating substantially in parallel and preferably in 180° opposite positions. The use of a greater number of balls is also theoretically possible and advantageous, of course provided that there is sufficient angular space to house the necessary recesses on the indexing discs; this means that the complete stroke of the control cable between the extreme positions of the derailleur must be obtainable with a rotation of the cable-winding bobbin of less than 120° (to be able to provide three balls) or even less than 90° (for four balls), or else that a transmission with a ratio different from 1:1 between the rotation of the bobbin and the relative angular displacement between ball-carrying disc and indexing disc (or discs) is provided, or else that staggered action planes be provided for different balls.

Preferably, the first countering spring can be simply a helical spring compressed between the ball and an abutment on the ball-carrying disc, or else a flat spring (or leaf spring) suitably anchored on such a disc; in the case in which two opposite balls are used, it is preferred to use a single suitably shaped flat spring arranged between the two balls. These solutions are effective and constructively simple.

Preferably, the second countering spring is a Belleville washer, which thanks to its modest bulk in the axial direction allows the size of the actuation device to be kept sufficiently low, whilst still providing an elastic action even of a very high intensity.

DESCRIPTION

FIGS. 1 to 9show, as a first embodiment of the invention, an actuation device100of the control cable K of a front gearshift. With particular reference toFIGS. 1 and 2, the device100is mounted near to the left grip MS of a bicycle handlebar M; the handlebar M shown is a straight handlebar, normally used for mountain bikes. As stated, of course, the embodiment of the invention of the device100is not limited to application to such a handlebar, nor to the arrangement on the left thereof.

With particular reference toFIGS. 3 and 4, the device100comprises a casing102, that is fixed to the handlebar M in a conventional manner, for example through a support101with a band105.

In the casing102a central shaft103is provided, fixed with respect to the casing102and extending along an axis B. The axis B is—as shall become clear hereafter—the main reference axis for the elements that form part of the device100; with respect to it, all of the indications of direction and the like, such as “axial”, “radial”, “circumferential”, “diametric”, shall be referred; equally, the indications “outwards” and “inwards” referring to radial directions must be understood as away from axis B or towards axis B. About the axis B, two opposite angular directions are also defined, indicated with130and131, the first in a clockwise direction, the second in an counter-clockwise direction, observing the device100from above; nevertheless, it should be noted that in the plan views (FIGS. 2,6a,6b) as well as in most of the perspective views (FIGS. 4,5,7) the device100is seen from below.

On the shaft103a cable-winding bobbin104is mounted for free rotation, to which the cable K to be actuated is attached and around which it is wound. The bobbin104is provided with a shank106, realized in one piece or in any case integrally, which has a non-symmetrical shape, for example cylindrical with two leveled walls106a, so as to be able to fit elements thereto that must be integral in rotation with the bobbin104.

On the shank106, indeed, a first indexing disc107is fitted integral in rotation, provided for this purpose with a central hole107awith a shape matching the section of the shank106, i.e. cylindrical-shaped with two flat walls107b. Between the first indexing disc107and the bobbin104at least one Belleville washer127is arranged (in the illustrated example there are two facing Belleville washers127), compressed in the axial direction.

Again on the shank106, a ball-carrying disc108is also mounted; this disc108, however, is not fitted integral in rotation on the shank106and thus with the bobbin104, but is, on the other hand, provided with a central hole108athat does not interfere with the shank106. Vice-versa, the ball-carrying disc108is mounted locked in rotation in the casing102, thanks to two opposite radially projecting ears108b, which engage in corresponding seats102bin the casing102, on pins102cfixed to the casing102.

Again on the shank106a second indexing disc109is thus fitted, which—like the disc107—is provided with a central hole109awith a shape matching the section of the shank106, or else cylindrical-shaped with two flat walls109b.

The discs107,108and109, together with the surrounding elements that cooperate with them, like for example the springs127, the seats102b, the walls106b, form indexer assembly for the device100.

A driving mechanism112for downward gearshifting is also provided, with an actuation lever112aprovided with a ring-shaped inner portion112brotatably fitted on the shank106and is held here in the axial direction by an elastic retention ring114(of the type commonly known as Seger ring), inserted in a corresponding annular seat114aformed on the shank106. The mechanism112is a per se conventional ratchet gear mechanism and comprises a first ratchet111, which is supported by a pin113mounted on the lever112aand engages in operation with a toothed sector126of the disc109; a closing spring135cooperates with the ratchet111, thrusting it towards an approach position to the toothed sector126, a position in which the ratchet111does not engage the toothed sector126when the lever112ais in a rest position, whereas it engages it as soon as the lever112ais actuated to carry out downward gearshifting. Finally, a return spring136is provided for the lever112a.

Furthermore, a driving mechanism118is provided for upward gearshifting, with an actuation lever118a. The mechanism118is also a per se conventional ratchet gear mechanism and comprises a plate115mounted on the shank106, provided with a central hole115asufficiently wide as not to interfere with the shank106and locked in rotation in the casing102, thanks to a radially projecting ear115b, which engages in one of the seats102bformed inside the casing102. The plate115carries a pin121on which both the lever118a, and a second ratchet117are hinged; in operation the ratchet117engages with a toothed bobbin116, fitted integral in rotation on the shank106of the bobbin104thanks to a central hole122with a shape matching the section of the shank106, i.e. cylindrical-shaped with two flat walls122a; an opening spring137cooperates with the ratchet117, thrusting it towards an approach position to the toothed bobbin116, a position in which the ratchet117does not engage the toothed bobbin116when the lever118ais in a rest position, whereas it engages it as soon as the lever118ais actuated to carry out upward gearshifting. Finally, a return spring132for the lever118ais provided.

Finally, again on the shank106, a cover119is mounted, held by a screw120screwed into a corresponding hole120a, formed axially in the shank106.

The indexer assembly of the device100are described hereafter, with particular reference toFIGS. 5 to 9.

In the ball-carrying disc108two radial grooves108′ are formed, closed towards the outside, the same as each other and diametrically opposite, in each of which a respective ball110is housed mobile; the two balls110are elastically biased outwards in the grooves108′ by a single flat spring125, mounted on the disc108. The grooves108′ are open on both sides of the disc108, which has a smaller thickness than the diameter of the balls110which thus project from it in the axial direction, as can clearly be seen inFIGS. 8 and 9.

In the indexing disc107two recesses123are formed that are the same as each other and point for point diametrically opposite; two specularly identical recesses (again indicated with reference numeral123) are formed in the indexing disc109.

Each recess123has a width and depth such as to receive the balls110, or rather the portion of such balls110that projects from the groove108′ of the disc108, and is arranged according to a path that comprises three stop zones124I,124II,124IIIalternating with two sliding zones134Iand134II.

In such a way, the balls110are engaged by a first part with a stationary member in the casing102, formed by the ball-carrying disc108with its grooves108′, by a second part with a rotating member integral in rotation with the cable-winding bobbin104, formed by the indexing discs107and108with their recesses123.

The intermediate stop zone124IIis defined by a stop wall124IIaand by a sliding wall134IIa, extending the first along a stop direction (indicated with T inFIG. 6b), the second along a sliding direction (indicated with S). The stop direction T and sliding direction S define an acute angle β between them that does not enclose the radial direction R passing by the stop zone124II, i.e. the main axis B of the device100. The stop wall124IIais thus undercut with respect to the radial direction R. The sliding wall134IIaextends along the sliding direction S from the stop zone124IIfor the entire sliding zone134IIadjacent to it.

The recesses123are closed at the ends, as well as towards the inside; they are thus defined by a continuous outer peripheral margin, regularly indented due to the presence of the succession of stop zones and sliding zones, and by an analogous inner margin.

The first stop zone124Iis defined by the initial end123aof the recess123and by a sliding wall134Ia, extending along a sliding direction for the entire adjacent sliding zone134I.

The last stop zone124IIIis defined by a stop wall124IIIaand by the end point123bof the recess123. The stop wall124IIIais thus undercut with respect to the radial direction R.

The fact that there are three stop zones means (as shall be seen more clearly hereafter, when the operation will be described) that the illustrated device100is intended for a gearshift with three ratios. Should it be necessary to operate on a gearshift with a different number of ratios (front gearshift with two, four or more crowns, or else rear gearshift with two, four or more sprockets), an equal number of stop zones must be provided. Clearly, there would in any case remain a first and a last stop zone, with a suitable number of intermediate stop zones in between.

The operation of the device100, with particular reference to its indexer assembly, is the following.

In static conditions of the device, when the cyclist does not act upon it, the ratio of the gearshift previously set must be maintained (for example the intermediate one), i.e. the cable K must neither be wound upon nor unwound from the bobbin104. In other words, the bobbin104must not rotate, even if subjected to the traction applied on the cable K by the return spring present in the gearshift, which would tend to make the bobbin104rotate in direction131, as well as knocks and bangs caused by the ride of the bicycle, which can clearly act in any direction.

This is obtained thanks to the indexer assembly. The rotation of the bobbin104is prevented by the fact that the balls110on one side are blocked in the grooves108′, and thus prevented from any displacement that is not in the radial direction, and on the other side engaged in stop zones of the recess123.

The traction transmitted by the cable K ensures that each stop wall124IIathrusts in direction131against the ball110, but the undercut orientation of such a wall ensures that such a thrust cannot displace the ball110, blocked in the stop zone124II. This condition determines an axial thrust on the indexing discs107and109in the direction of their separation, prevented, however, by the springs127; therefore, the springs127must be sized in such a way that the axial thrust applied by them is sufficient to avoid the moving apart of the two indexing discs107and109. This closed condition of the indexing discs107and109is illustrated inFIG. 8; the position of the balls110in the stop zones can thus be defined a stop position, since in such a position the balls make the discs107,108and109integral in rotation.

Stresses in the opposite direction due to knocks or the like could, on the other hand, have the sliding walls134IIathrust upon the balls110in direction130. Such a thrust tends to thrust the balls110towards the inside of the grooves108′, but the movement is prevented by the elastic thrust of the spring125, which must be suitably sized.

The springs125and127thus constitute countering means, first and second respectively, to counter the rotation of the cable-winding bobbin104.

It is now assumed that the cyclist carries out upward gearshifting.

For upward gearshifting, the cyclist acts upon the appropriate lever118a, pressing it with the thumb of the left hand in the angular direction130. By doing so, the second ratchet117goes into engagement with the toothed bobbin116, thrusting it into rotation in the angular direction130together with the cable-winding bobbin104, with its shank106and with all of the elements fitted integral in rotation with it; in particular, the two indexing discs107and109are rotated in direction130.

First of all it should be noted that the first ratchet111does not prevent the rotation of the disc109, since—with the lever112anot actuated—the ratchet111is disengaged from the toothed sector126of the disc109.

To obtain the rotation of the bobbin104and of the indexing discs107and109in the angular direction130, the cyclist must apply a force large enough so that the balls110are thrusted by the sliding walls134IIatowards the inside of the grooves108′, overcoming the radial thrust towards the outside of the spring125. Whilst the action of the cyclist on the lever118acontinues, as the rotation of the bobbin104proceeds, the balls110then cross the sliding zone134II, finally reaching the height of the stop zone124III, where they are positioned, thrusted also by the spring125. In such a position the balls110stay, as just described, maintaining the new ratio even after the cyclist has interrupted his action. The released lever118agoes back into position thanks to the return spring132.

It may be noted that, substantially during all of the upward gearshifting, the cyclist must overcome both the traction force on the cable K applied by the return spring of the gearshift, and the counter force applied by the spring125on the balls110.

Preferably, to make upward gearshifting smooth, the counter force applied by the spring125on the two balls110is relatively low, with values for example of 1/20 of the axial thrust force applied by the springs127.

In the previous example, in which the starting condition was the intermediate ratio of a device with three ratios, clearly upward gearshifting can only be from such a ratio to a different ratio (that in the exemplified case of a front gearshift is a longer ratio) immediately next to it. On the other hand, in the case in which the starting condition permits it (for example, in the device100with three ratios considered, when one starts from the shortest ratio), the action of the cyclist can be applied until double or multiple gearshifting is obtained. In this case, the reaching of the first adjacent ratio shall be perceived by the cyclist as a momentary reduction in the force required by gearshifting, due to the fact that at the moment of the displacement of the balls110from the sliding zone134Ito the stop zone124IIthe spring125operates not against but helping the cyclist, thrusting the balls110radially outwards; at such a moment, the cyclist can decide to keep such a ratio and thus interrupt his/her action by releasing the lever118a, or else can proceed with his/her action until the subsequent ratio is obtained.

InFIG. 6b, the relative paths of one of the balls110in the recess123are indicated with B1and B2, during upward gearshifting from the lower ratio to the intermediate ratio (B1) and from the intermediate ratio to the higher ratio (B2).

For downward gearshifting, for example starting from the intermediate ratio, the cyclist acts, conversely, on the lever112a, pulling it with the index finger in the angular direction131. By doing so the first ratchet111goes into engagement with the toothed sector126of the indexing disc109, thrusting the bobbin104into rotation in the angular direction131together with its shank106and with all of the elements fitted integral in rotation with it; in particular, the indexing disc107and the toothed bobbin116are rotated in direction131.

It should first of all be noted that the second ratchet117does not prevent the rotation of the toothed bobbin116, since—with the lever118anot actuated—the ratchet117is disengaged from the toothed bobbin116.

During this action of the cyclist, the balls110cannot cross the path B1in the recess123backwards, due to the undercut stop walls124IIaof the stop zones124II. In these conditions, on the other hand, the action of the cyclist ensures that the balls110thrust upon the stop walls124IIacausing an axial thrust upon the indexing discs107and109in the direction of their separation, against the springs127. If the cyclist applies sufficient traction to overcome the counter action of the axial springs127, the indexing discs107and109go from the closed condition ofFIG. 8to the open condition ofFIG. 9. In such a condition, the balls110thus go out from the recess123and, due to the engagement in the grooves108′ which prevents a further radial displacement outwards, follow the arc of circumference path A2up to the stop zone124I, where they position themselves under the axial thrust of the springs127. In such a position the balls110stay, as just described, maintaining the new ratio even after the cyclist has interrupted his action. The released lever112agoes back into position thanks to the return spring136.

Also in downward gearshifting, in the same way as what has been seen for upward gearshifting, multiple gearshifting is possible.

It may be noted that, substantially during all of the downward gearshifting, the cyclist has the help of the traction force on the cable K applied by the return spring of the gearshift, but must overcome both the counter force applied by the springs127on the discs107and109(in the initial step of gearshifting), and (during the entire gearshifting) the friction between the balls110and the two discs107and109. It should be noted that this friction, although in the presence of balls, is substantially sliding and not rolling friction, since the coupling of each ball on the disc107is opposite that on the disc109, so that the rotation of the balls110is actually prevented. The value of this friction can be suitably chosen by means of the sizing of the springs127which determine the force with which the discs107and109are pressed axially one towards the other; in such a way, it is possible in particular to ensure that such a friction force balances and overcomes the return force applied by the spring of the gearshift through the cable K, so as to have an active gearshift control.

FIGS. 10 to 17show, as a second embodiment of the invention, an actuation device200of the control cable K of a rear gearshift (not shown). With particular reference toFIGS. 10,11and12, the device200is mounted near to the right grip MD of a bicycle handlebar M; the handlebar M shown is also in this case a straight handlebar, normally used for mountain bikes. As stated for the device100, of course, the embodiment of the invention of the device200is also not limited to application to such a handlebar, nor to arrangement on the right thereof.

With particular reference toFIG. 13, the device200comprises a casing202, which is fixed to the handlebar M in a conventional manner, for example through a support201(which in the illustrated example also carries a brake lever F, outside of the invention and thus not described) with a band205.

In the casing202a central shaft203is provided, fixed with respect to the casing202and extending along an axis B. The axis B is—like in the case of the embodiment of the device100—the main reference axis for the elements that form part of the device200; with respect to it, all of the indications of direction and the like, such as “axial”, “radial”, “circumferential”, “diametric”, shall be referred; equally, the indications “outwards” and “inwards” referring to radial directions must be understood as away from axis B or towards axis B. About the axis B, two opposite angular directions are also defined, indicated with230and231, the first in an counter-clockwise direction, the second in a clockwise direction, observing the device200from above; nevertheless, it should be noted that in the plan views (FIGS. 11 and 15to17) as well as in most of the perspective views (FIGS. 13,14) the device200is seen from below.

On the shaft203a cable-winding bobbin204is mounted for free rotation, to which the cable K to be actuated is fixed and on which it is wound. The bobbin204is provided with a shank206, realized in one piece or in any case integrally, which has a non-symmetrical shape, for example cylindrical with two leveled walls206a, so as to be able to fit elements thereto that must be integral in rotation with the bobbin204.

An indexing disc270is mounted on the shank206; this disc270is not fitted integral in rotation on the shank206and thus with the bobbin204, but is, on the other hand, provided with a wide central hole208awhich does not interfere with the shank206. Vice-versa, the indexing disc270is mounted locked in rotation in the casing202, thanks to a radially projecting ear208b, which engages in a corresponding seat202ain the casing202, on a pin202cfixed to the casing202. Between the indexing disc270and the bobbin204at least one Belleville washer227is arranged (in the illustrated example there are three facing springs227), compressed in the axial direction.

Again on the shank206a ball-carrying disc280is also fitted integral in rotation, provided for the purpose with a central hole280awith a shape matching the section of the shank206, i.e. cylindrical-shaped with two flat walls280b.

The discs270and280, together with the surrounding elements that cooperate with them, like for example the springs227, the seat202b, the walls280b, form indexer assembly for the device200.

A driving mechanism212for downward gearshifting is also provided, with an actuation lever212aprovided with a ring-shaped inner portion212brotatably fitted on the shank206and is held here in the axial direction by an elastic retention ring214(of the type commonly known as Seger ring), inserted in a corresponding annular seat214aformed on the shank206. The mechanism212is a per se conventional ratchet gear mechanism and comprises a first ratchet211, which is supported by a pin213mounted on the lever212aand engages in operation with a toothed sector276of the ball-carrying disc280; a closing spring235cooperates with the ratchet211, thrusting it towards an approach position to the toothed sector276, a position in which the ratchet211does not engage the toothed sector276when the lever212ais in a rest position, whereas it engages it as soon as the lever212ais actuated to carry out downward gearshifting. Finally, a return spring236is provided for the lever212a.

Furthermore, a driving mechanism218is provided for upward gearshifting, with an actuation lever218a. The mechanism218is also a per se conventional ratchet gear mechanism and comprises a plate215mounted on the shank206, provided with a central hole215asufficiently wide as not to interfere with the shank206and locked in rotation in the casing202, thanks to a radially projecting ear215b, which engages in the seat202bformed inside the casing202. The plate215carries a pin221on which both the lever218a, and a second ratchet217are hinged; in operation the ratchet217engages with a toothed bobbin216, fitted integral in rotation on the shank206of the bobbin204thanks to a central hole222with a shape matching the section of the shank206, i.e. cylindrical-shaped with two flat walls; an opening spring (not highlighted in the figures) cooperates with the ratchet217, thrusting it towards an approach position to the toothed bobbin216, a position in which the ratchet217does not engage the toothed bobbin216when the lever218ais in a rest position, whereas it engages it as soon as the lever218ais actuated to carry out upward gearshifting. Finally, a return spring232for the lever218ais provided.

Finally, a cover219is mounted on the shank206, held by a screw220screwed into a corresponding hole220a, formed axially in the shank206.

The indexer assembly of the device200are described hereafter, with particular reference toFIGS. 14 and 15.

In the ball-carrying disc280two radial grooves280′ are formed, closed towards the outside and towards the inside, the same as each other and diametrically opposite, in each of which a respective ball210is housed mobile; the two balls210are elastically biased outwards in the grooves280′ by respective helical springs275, mounted on the disc280in the same grooves280′ and compressed between the balls210and the inner radial abutments281. The grooves280′ are open on one side of the disc280facing towards the indexing disc270, and have a lower depth than the diameter of the balls210that thus project from them in the axial direction.

In the indexing disc270two recesses273are formed that are the same as each other and point for point diametrically opposite; the two recesses extend for a little less than 180°, and thus appear fitted together.

Each recess273has a depth such as to receive the balls210, or rather the portion of such balls210that projects from the groove280′ of the disc280, and is arranged according to a path that comprises ten stop zones (numbered from274Ito274x) alternated by nine sliding zones (numbered from234Ito234IX).

In such a way, the balls210are engaged at a first side with a stationary member in the casing202, formed by the indexing disc270with its recesses273, and at a second side with a rotating member integral in rotation with the cable-winding bobbin204, formed from the ball-carrying disc280with its grooves280′.

An intermediate stop zone, for example the zone274VII(but the same thing goes for all of the zones from274IIto274IX), is defined by a stop wall274VIIaand by a sliding wall234VIIa, extending the first along a stop direction (indicated with T), the second along a sliding direction (indicated with S). The stop direction T and sliding direction S define an acute angle β between them that does not enclose the radial direction R passing by the stop zone stop zone274VII, i.e. the main axis B of the device100. The stop wall274VIIais thus undercut with respect to the radial direction R. The sliding wall234VIIaextends along the sliding direction S from the stop zone274VIIfor the entire sliding zone234VIIadjacent to it.

The recesses223are not closed at the ends, nor towards the inside; they thus form a continuous outer peripheral margin, regularly indented due to the presence of the succession of stop zones and sliding zones, without an analogous inner margin.

The first stop zone274Iis defined like the others by a stop wall274Iaand by a sliding wall234Ia, extending along a sliding direction for the entire adjacent sliding zone234I.

In the same way, the last stop zone274Xis defined by a stop wall274Xaand by a sliding wall234Xa, extending in a sliding direction.

The fact that the stop zones are ten in number means that the illustrated device200is intended for a gearshift with ten ratios, clearly a rear gearshift. Should it be necessary to operate on a gearshift with a different number of ratios, an equal number of stop zones must be provided. Clearly, there would in any case remain a first and a last stop zone, with a suitable number of intermediate stop zones in between.

The operation of the device200, with particular reference to its indexer assembly, is the following.

In static conditions of the device, when the cyclist does not act upon it, the ratio of the gearshift set previously must be maintained (for example the seventh), i.e. the cable K must neither be wound upon nor unwound from the bobbin204. In other words, the bobbin204must not rotate, even if subjected to the traction applied on the cable K by the return spring present in the gearshift, which would tend to make the bobbin204rotate in direction231, as well as knocks and bangs caused by the ride of the bicycle, which can clearly act in any direction.

This is obtained thanks to the indexer assembly. The rotation of the bobbin204is prevented by the fact that the balls210are on one side blocked in the grooves280′, and on the other side engaged in stop zones274VIIof the recess223.

The traction transmitted by the cable K ensures that each ball210thrusts against the stop wall274VIIain the direction231, but the undercut orientation of such a wall274VIIaensures that such a thrust cannot displace the ball210, blocked in the stop zone274VIIa. This condition determines an axial thrust on the indexing discs270and ball-holders280in the direction of their separation, prevented, however, by the springs227; therefore, the springs227must be sized in such a way that the axial thrust applied by them is sufficient to avoid the moving apart of the two discs270and280. The position of the balls210in the stop zones can thus be defined a stop position, since in such a position the balls make the discs270and280integral in rotation.

Stresses in the opposite direction due to knocks or the like could, on the other hand, have the balls210thrust upon the sliding walls234VIIain direction230. Such a thrust tends to thrust the balls210towards the inside of the grooves208′, but the movement is prevented by the elastic thrust of the springs225, which must be suitably sized.

The springs227and275thus constitute countering means, first and second respectively, to counter the rotation of the cable-winding bobbin204.

It is now assumed that the cyclist carries out upward gearshifting (i.e. towards a lower ratio, concerning controlling a rear gearshift).

For upward gearshifting, the cyclist acts upon the appropriate lever218a, pressing it with the thumb of the right hand in the angular direction230. By doing so, the second ratchet217goes into engagement with the toothed bobbin216, thrusting it into rotation in the angular direction230together with the cable-winding bobbin204, with its shank206and with all of the elements fitted integral in rotation with it; in particular, the ball-carrying disc280is rotated in direction230.

It should first be noted that the first ratchet211does not prevent the rotation of the disc280, since—with the lever212anot actuated—the ratchet211is disengaged from the toothed sector276of the disc280.

To obtain the rotation of the bobbin204and of the ball-carrying disc280in the angular direction230, the cyclist must apply a force large enough so that the balls210are thrusted by the sliding walls234VIIatowards the inside of the grooves208′, overcoming the radial thrust towards the outside of the springs225. Whilst the action of the cyclist on the lever218acontinues, as the rotation of the bobbin204proceeds, the balls210then cross the sliding zone234VIIa, finally reaching the height of the stop zone274VIII, where they are positioned, thrusted also by the springs275. In such a position the balls210stay, as just described, maintaining the new ratio even after the cyclist has interrupted his action. The released lever218agoes back into position thanks to the return spring232.

It can be noted that, substantially during the entire upward gearshifting, the cyclist must overcome both the traction force on the cable K applied by the return spring of the gearshift, and the counter force applied by the springs275on the balls210.

Preferably, to make upward gearshifting smooth, the counter force applied by the springs275on the two balls210is relatively low, with values for example of less than 1/20 the axial thrust force applied by the springs227.

In the case in which the starting condition allows it, like in the case just considered in which the gearshift was in the seventh ratio, the action of the cyclist can be applied until double or multiple gearshifting is obtained. In this case, the reaching of the first adjacent ratio shall be perceived by the cyclist as a momentary reduction in the force required by gearshifting, due to the fact that at the moment of the displacement of the balls210from the sliding zone234VIIto the stop zone274VIIIthe springs275operate not against but helping the cyclist, thrusting the balls210radially outwards; at such a moment, the cyclist can decide to keep such a ratio and thus interrupt his/her action by releasing the lever218a, or else can proceed with his/her action until the subsequent ratio is obtained.

For downward gearshifting, for example starting from the seventh ratio, the cyclist acts, conversely, on the lever212a, pulling it with the index finger in the angular direction231. By doing so the first ratchet211goes into engagement with the toothed sector276of the ball-carrying disc280, thrusting the bobbin204into rotation in the angular direction231together with its shank206and with all of the elements fitted integral in rotation with it; in particular, the toothed bobbin216is rotated in direction231.

It should first be noted that the second ratchet217does not prevent the rotation of the toothed bobbin216, since—with the lever218anot actuated—the ratchet217is disengaged from the toothed bobbin216.

During this action of the cyclist, the balls210thrust upon the stop walls274VIIacausing an axial thrust upon the indexing disc270and ball-carrying disc280in the direction of their separation, against the springs227. If the cyclist applies sufficient traction to overcome the counter action of the axial springs227, the discs270and280go from the closed condition to the open condition. In such a condition, the balls210thus go out from the recess273and, due to the engagement in the grooves208′ which prevents a further radial displacement outwards, follow an arc of circumference path up to the stop zone274VI, where they position themselves under the axial thrust of the springs227. In such a position the balls210stay, as just described, maintaining the new ratio even after the cyclist has interrupted his action. The released lever212agoes back into position thanks to the return spring236.

Also in downward gearshifting, in the same way as what has been seen for upward gearshifting, multiple gearshifting is possible.

It may be noted that, substantially during all of the downward gearshifting, the cyclist has the help of the traction force on the cable K applied by the return spring of the gearshift, but must overcome both the counter force applied by the springs227on the discs270and280(in the initial step of gearshifting), and (during the entire gearshifting) the friction between the balls210and the two discs270and280. It should be noted that this friction, although in the presence of balls, is substantially sliding and nor rolling friction, since the coupling of each ball on the disc270is opposite that on the disc280, so that the rotation of the balls210is actually prevented. The value of this friction can be suitably chosen by means of the sizing of the springs227which determine the force with which the discs270and280are pressed axially one towards the other; in such a way, it is possible in particular to ensure that such a friction force balances and overcomes the return force applied by the spring of the gearshift through the cable K, so as to have an active gearshift control.

What has been outlined above are two example embodiments of the invention, but of course other embodiments are possible. Some indications, in any case not to be understood in the limiting sense, are given hereafter.

A device can have two indexing discs like the device100, but stationary like in the device200, with a rotating ball-carrying disc. Or else a device can have just one indexing disc like the device200, but rotating like in the device100, with a stationary ball-carrying disc.

Either device can without distinction be adopted to control a rear or front gearshift, the only restriction being that of the number of stop zones.

The toothed sector on which the ratchet of a driving mechanism acts can be formed on any element of the member rotating with the cable-winding bobbin, be it an element already present for other functions (like the ball-carrying disc280of the device200) or else an additional disc.

The first countering springs that thrust the balls radially outwards can be of various types (helical, flat or other) irrespective of the other characteristics of the device.

The second countering Belleville springs that thrust the discs axially one against the other can also be replaced by different elastic systems, such as groups of helical springs, elastomeric rings, etc.

The balls could also be replaced by members (sliding blocks or tappets) that do not rotate but slide, with a consequent increase in friction. In such a case, the sliding members could advantageously be integral or in one piece with the first countering springs. For this reason, in the previous description and in the subsequent claims the term “ball” must not be taken as limited to a spherical geometrical shape in the strict sense, but must also comprise any other functionally equivalent shape in the context and for the purposes of the present invention.