Patent Description:
In this description, the gearshift to which particular reference is made is the rear one. Such a gearshift moves the chain among the different sprockets of the sprocket assembly associated with the rear wheel of the bicycle.

In addition to the function of correctly moving the chain, the rear gearshift performs the function of keeping the chain correctly tensioned when it is engaged by any of the different sprockets and during the gearshifting, so as to prevent the chain from dropping.

The rear gearshift typically comprises a first body associated with the frame of the bicycle and a second body that supports a rocker arm. The latter comprises an inner plate, an outer plate and a pair of toothed wheels arranged between the inner and outer plates and configured to engage the chain.

Throughout this description, the terms "inner plate" and "outer plate" refer to the plate of the rocker arm that, when the rocker arm is mounted on the bicycle, faces the wheel of the bicycle and the plate of the rocker arm that, in the aforementioned mounting condition, is arranged in a more external position with respect to the wheel of the bicycle, respectively.

The second body is connected to the first body through a pair of articulated connection rods so as to form an articulated quadrilateral actuation linkage. Such a linkage is actuated mechanically by a sheathed cable or electrically by an electric motor.

Upon actuating the aforementioned linkage the second body is moved with respect to the first body so as to move the rocker arm at the sprocket selected by the cyclist and engage the chain on such a sprocket.

The rocker arm is rotatably connected to the second body at a predetermined rotation axis.

Throughout the present description and in the following claims, the terms "axial" or "axially" are used to indicate a direction coinciding with or parallel to the aforementioned rotation axis, the terms "circumferential" or "circumferentially" are used to indicate a direction that rotates about the aforementioned rotation axis, whereas the terms "radial" or "radially" are used to indicate a direction passing through and perpendicular to the aforementioned rotation axis.

An elastic element, typically a torsion spring, pushes the rocker arm into rotation about such a rotation axis in a direction of rotation that will be indicated hereinafter as "chain tensioning direction". When observing the outer plate of the rocker arm mounted on the bicycle from the front, the chain tensioning direction corresponds to a direction of rotation in the clockwise direction of the rocker arm about the aforementioned rotation axis.

During the gearshifting operations and/or during travel, especially in the case of an irregular road surface, the rocker arm is subject to oscillations about the aforementioned rotation axis. During such oscillations, the rocker arm moves in a direction of rotation opposite to the chain tensioning direction, causing a momentary detensioning of the chain and a consequent risk of chain dropping.

In order to damp the oscillations of the rocker arm it is known to provide a unidirectional damping device between the rocker arm and the second body. Such a damping device is configured so as to apply a friction force to the rocker arm when the rocker arm is moved about the rotation axis in the direction of rotation opposite to the chain tensioning direction and to allow the rocker arm to be free to rotate in the chain tensioning direction.

<CIT> describes, with reference to <FIG> thereof, an embodiment of a bicycle rear gearshift comprising a unidirectional rotation device consisting of a unidirectional roller bearing <NUM> and a damping device <NUM> comprising a friction element <NUM> having an annular shape and operatively arranged between a shaft <NUM> fixedly connected to the rocker arm and the unidirectional roller bearing <NUM>. The friction element <NUM> comprises a frusto-conical or wedge-shaped friction surface that interacts with a sleeve <NUM> fixedly connected to the inner ring of the unidirectional roller bearing <NUM>. An adjustment element <NUM> acts on the friction element <NUM>, said element <NUM> being screwed onto the shaft <NUM> and exerting an axial preload force on the friction element <NUM>.

The Applicant has observed that, due to the frusto-conical or wedge-shaped friction surface thereof, the friction element <NUM> exerts on the sleeve <NUM> a thrust having both a radial component and an axial component.

The Applicant has identified a series of drawbacks in the aforementioned bicycle gearshift.

Firstly, due to the aforementioned axial component, only part of the axial preload force exerted by the adjustment element <NUM> on the friction element <NUM> is converted into a radial thrust on the inner ring of the unidirectional roller bearing <NUM>. Moreover, since the aforementioned radial thrust is generated only by the axial preload force generated by the adjustment element <NUM>, it is necessary to act on such an adjustment element <NUM> in order to compensate a possible reduction in the amount of the radial thrust due to the wearing of the components or to the dimensional tolerances of the components. Furthermore, it is necessary to obstruct the axial movement of the sleeve <NUM> in order to have a sufficient radial thrust on the inner ring of the unidirectional roller bearing <NUM>. Finally, it is difficult to prevent a part of the friction force from also acting on the interface between the shaft <NUM> and the element <NUM>, and this makes the performance of the system inefficient and not constant.

According to the Applicant, the aforementioned drawbacks, if not properly considered, can cause the gearshift not to have an optimal operating efficiency and constancy of performance over time in response to stresses that would tend to move the rocker arm in the direction of rotation opposite to the chain tensioning direction.

<CIT> discloses a bicycle gearshift according to the preamble of claim <NUM>.

The problem at the basis of the present invention is that of making a bicycle gearshift that comprises a damping device that ensures a greater efficiency and constancy of performance over time with respect to that described with reference to the prior art.

The present invention therefore relates to a bicycle gearshift according to claim <NUM>.

The provision of a friction surface extending axially along a direction substantially parallel to the rotation axis of the rocker arm causes a friction force having only a circumferential component to be generated between the damping device and the unidirectional rotation device and the damping device to exert on the unidirectional rotation device a thrust having only a radial component, that is without undesired axial components.

The operating efficiency of the gearshift is thus improved since, once a certain radial preload has been applied to the unidirectional rotation device through the damping device, the entire preload force is converted into a radial thrust on the unidirectional rotation device.

During the useful life of the gearshift, possible dimensional divergences with respect to the design dimensions due to the wearing of the components of the gearshift or to the dimensional tolerances thereof can be compensated automatically by the damping device, which adjusts itself by suitably changing the radial thrust exerted on the unidirectional rotation device. There is thus an advantageous constancy of performance of the gearshift over time. Consequently, it is easier to provide and precisely control the behavior of the gearshift in response to the stresses that would tend to move the rocker arm in the direction of rotation opposite to the chain tensioning direction.

Hereinafter, preferred and/or optional features of the bicycle gearshift according to the present invention are described. Such features can be provided individually or in combination with one another, unless explicitly stated otherwise.

According to the invention, the damping device comprises at least two friction surfaces. For example, there can be two, three or four friction surfaces.

In the case of two friction surfaces, they are preferably arranged on opposite sides with respect to the rotation axis, i.e. about <NUM>° from one another.

In the case of three surfaces, they are preferably arranged about <NUM>° from one another.

In the case of four friction surfaces, they are preferably arranged about <NUM>° from one another.

In all of the above cases, the damping device acts on the unidirectional rotation device in a balanced manner about the rotation axis.

Preferably, the aforementioned friction surfaces are defined on respective jaws.

Preferably, each of said at least two friction surfaces extends circumferentially about said rotation axis for an arc of circumference having a center on said rotation axis and a center angle lower than <NUM>°.

Preferably, said center angle is comprised between <NUM>° and <NUM>°, more preferably between <NUM>° and <NUM>°, even more preferably it is equal to about <NUM>°.

Preferably, the damping device comprises at least two thrusting members, each of them being configured to thrust a respective friction surface of said at least two friction surfaces against said unidirectional rotation device with a predetermined load.

Each of such a thrusting member determines a preload force that, in turn, determines the value of the radial thrust exerted by the damping device on the unidirectional rotation device, and thus the extent of the damping action.

Moreover, each of the thrusting members makes it possible to recover possible dimensional divergences from the design dimensions caused by wearing or dimensional tolerances, contributing to actuate the abovementioned automatic compensation.

The provision of the aforementioned thrusting members allows to define the desired thrusting force in the assembly step of the gearshift, making it superfluous and/or needless any post-sale maintenance intervention aimed at adjusting the thrusting force exerted by the damping device on the unidirectional rotation device. Such an intervention would indeed by onerous since it would require the complete dismounting of the rocker arm, of the first elastic element and of the damping device.

In a first embodiment of the invention, and in the case in which such a gearshift comprises two friction surfaces arranged on opposite sides with respect to the rotation axis, said at least two thrusting members comprise a second elastic element housed in a through hole formed in said shaft along a direction perpendicular to said rotation axis.

Preferably, said second elastic element is arranged in a radially inner position with respect to the two friction surfaces.

The second elastic element crosses the shaft and pushes, at the two end portions thereof, the two opposite friction surfaces against the unidirectional rotation device with the same force. Therefore, the radial thrust that is exerted on a friction surface is counteracted by the opposite friction surface through the second elastic element.

Preferably, the second elastic element is a helical spring.

In this case, therefore, the radial thrust is solely a function of the elastic constant of the helical spring. In the assembly step of the gearshift, it will be possible to select, among various possibly available springs, the one having an elastic constant suitable for applying the desired radial thrust on the unidirectional rotation device.

Preferably, the two friction surfaces are formed on respective jaws provided with respective seats configured to house a respective end portion of the second elastic element.

Such seats contribute to prevent undesired axial movements of the second elastic element, ensuring that the entire preload force applied by the thrusting member is converted into a radial thrust.

In a second embodiment of the invention, and independently from the number of friction surfaces provided, each of said at least two thrusting members comprises at least one cup spring or at least one helical spring arranged between said shaft and the respective friction surface.

Also in this case the radial thrust is only a function of the elastic constant of the springs. In this case, however, the radial thrust that is exerted on a friction surface is counteracted by the shaft.

In the assembly step of the gearshift, also in this case it will be possible to select, among various possibly available springs, the one(s) having an elastic constant suitable for applying the desired radial thrust on the unidirectional rotation device.

In some embodiments of the gearshift of the present invention, the damping device comprises an adjustment device configured to adjust said predetermined load.

In a first embodiment thereof, said adjustment device comprises at least one first spacer element having a predetermined thickness.

Such at least one spacer element can be arranged between each of said at least two thrusting members and the respective friction surface or between each of said at least two thrusting members and said shaft or both between each of said at least two thrusting members and the respective friction surface and between each of said at least two thrusting members and said shaft.

The first spacer element can, for example, be a washer having a calibrated thickness. In the assembly step of the gearshift, it will be possible to select, among possibly available spacer elements having different thicknesses, the one having a thickness suitable for applying the desired radial thrust on the unidirectional rotation device.

In another embodiment thereof, said adjustment device comprises a preload device comprising a thrusting pin moveable in a first hole extending in said shaft along a first direction perpendicular to the rotation axis and exerting a thrust on at least two thrust plates moveable in a second hole connected to said first hole and extending in said shaft along a second direction perpendicular to the rotation axis.

Preferably, the second hole is arranged in a radially inner position with respect to said at least two thrusting members.

The preload device makes it possible to adjust the preload force applied by the damping device on the unidirectional rotation device as desired.

Preferably, the first hole and the second hole are substantially perpendicular.

More preferably, said thrusting pin comprises a substantially wedge-shaped end portion.

Even more preferably, each of said at least two thrust plates comprises a substantially wedge-shaped end portion in abutment with the substantially wedge-shaped end portion of said thrusting pin.

Preferably, the aforementioned wedge-shaped surfaces are inclined by about <NUM>° with respect to the rotation axis, but they can also be inclined by different angles, comprised between <NUM>° and <NUM>°. In this way, the movement of the pin along the axis thereof is converted into a radial movement of the thrust plates, and the choice of the angle of inclination provides a greater or lower adjustment sensitivity.

Preferably, the axis of the pin is substantially perpendicular to the rotation axis.

In a further embodiment thereof, said adjustment device comprises a second spacer element having a predetermined thickness, the second spacer element being housed in a through hole formed in said shaft along a direction perpendicular to said rotation axis and arranged in a radially inner position with respect to said at least two friction surfaces.

Preferably, each of said at least two thrusting members comprises a plurality of cup springs housed inside a bushing which is housed in said through hole and which is arranged on opposite sides with respect to said second spacer element.

In this case, the radial thrust that is exerted on a friction surface is counteracted by the opposite friction surface through the second spacer element and the cup springs. The radial thrust exerted by the damping device on the unidirectional rotation device is therefore a function of both the elastic constant of the cup springs and the thickness of the second spacer element. In the assembly step of the gearshift it is thus necessary to suitably select, among various springs and various spacer elements, those having an elastic constant and a thickness, respectively, suitable for applying the desired radial thrust on the unidirectional rotation device.

In a preferred embodiment of the invention, said shaft comprises, in a radially inner position with respect to said damping device, an enlarged portion.

Preferably, said enlarged portion comprises at least two flat surfaces.

Preferably, said enlarged portion comprises a flat surface facing a respective friction surface.

Preferably, said adjustment device is arranged at said enlarged portion. The through hole configured to house the helical springs and/or the cup springs and/or the second spacer element discussed above is therefore formed on said enlarged portion and opens out onto two opposite flat surfaces of such an enlarged portion.

In the cases in which the enlarged portion of the shaft does not have the aforementioned through hole, each of the flat surfaces defines an abutment surface for the end portion of the thrusting member opposite the one which exerts the thrust on the friction surface.

In a preferred embodiment of the invention, the unidirectional rotation device comprises a radial bearing having an outer ring fixedly associated with said second body and an inner ring operatively associated with said at least two friction surfaces.

Preferably, the radial bearing is a roller bearing, so as to contain the radial dimensions of the bearing.

In a first preferred embodiment of the invention, the damping device is at least partially arranged in a radially inner position with respect to said inner ring. The gearshift, in this case, has a small axial dimension.

Preferably, the damping device is entirely arranged in a radially inner position with respect to said inner ring.

In a second preferred embodiment of the invention, the damping device is at least partially arranged in a radially inner position with respect to an annular element fixedly associated with, and axially adjacent to, said inner ring.

Preferably, in this case the gearshift comprises a self-lubricating bushing arranged between said shaft and said inner ring.

Such a bushing ensures the precise centering of the shaft with respect to the unidirectional rotation device, and thus with respect to the damping device, without generating undesired additional friction (i.e. further friction with respect to the friction force generated by the friction surfaces) between the damping device and the radial bearing.

Preferably, the annular element has a diameter greater than that of the inner ring of the radial bearing.

Preferably, the annular element is axially arranged between the inner ring of the radial bearing and the rocker arm.

In a preferred embodiment thereof, the gearshift of the invention comprises a pair of axial abutment surfaces arranged on opposite sides with respect to said damping device and configured to prevent an axial movement of said damping device, in particular of the friction surfaces.

Preferably, a first surface of said axial abutment surfaces is made in a single piece with the shaft.

Preferably, the first axial abutment surface is axially adjacent to the enlarged portion of the shaft, more preferably it is arranged between the enlarged portion of the shaft and the rocker arm.

In some embodiments, the first axial abutment surface is formed substantially at the middle of the shaft.

The other of the aforementioned axial abutment surfaces can be defined by the interface surface between the inner ring of the radial bearing and the aforementioned annular element, when provided, or by a flange associated with an end portion of the shaft opposite the one associated with the rocker arm, when the aforementioned annular element is not provided and the damping device is housed inside the inner ring of the radial bearing.

Preferably, said first elastic element comprises a helical return spring.

The damping device can be arranged at least partially in a radially inner position with respect to said return spring. Such a provision makes it possible to keep the axial dimensions of the gearshift low.

Preferably, the damping device is entirely arranged in a radially inner position with respect to said return spring.

The damping device can also be arranged at least partially in an axially adjacent position with respect to said return spring. This is the case for example when the damping device is arranged at least partially in a radially inner position with respect to the inner ring of the radial bearing, which is arranged at least partially in an axially adjacent position to the return spring.

Further features and advantages of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings and given only for indicating and not limiting purposes. In such drawings:.

In <FIG>, reference numeral <NUM> indicates a bicycle gearshift according to a first preferred embodiment of the present invention.

In particular, it is a rear gearshift, i.e. a gearshift configured to be mounted on a bicycle frame (not shown) to move the chain (not shown) among the different sprockets (not shown) of the sprocket assembly associated with the rear wheel of the bicycle.

The movement of the chain is actuated through the movement of a rocker arm <NUM>. Such a movement is a consequence of the movement of an actuation linkage <NUM>.

The gearshift <NUM> can be mechanically actuated (through a sheathed cable) or motorized (through an electric motor). The attached figures show, as a non-limiting example, a motorized gearshift, wherein the movement of the rocker arm <NUM> takes place by means of a motor member <NUM> that is suitably driven, typically electrically. Once the motor member <NUM> is driven, the actuation linkage <NUM> deforms and the rocker arm <NUM> moves.

The actuation linkage <NUM> is an articulated quadrilateral linkage, preferably an articulated parallelogram linkage. It comprises a first body <NUM> configured to be associated with the frame of the bicycle, a second body <NUM> configured to support the rocker arm <NUM> and a pair of articulated connection rods <NUM> that connect the first body <NUM> and the second body <NUM>. The connection rods <NUM> are also respectively called "inner connection rod" and "outer connection rod", with reference to their relative position with respect to the frame of the bicycle.

The rocker arm <NUM> is associated with the second body <NUM>.

In the example illustrated herein, the motor member <NUM> is housed in the first body <NUM> and drives the deformation of the actuation linkage <NUM>, lengthening or shortening a diagonal of the articulated quadrilateral. In particular, a lengthening of such a diagonal is used to carry out an upward gearshifting (towards a sprocket having a greater diameter), whereas a shortening of the diagonal is used for a downward gearshifting (towards a sprocket having a smaller diameter).

Upon deformation of the actuation linkage <NUM>, the second body <NUM> is moved with respect to the first body <NUM>, the rocker arm <NUM> moves to the sprocket selected by the cyclist and the chain is engaged by such a sprocket.

The rocker arm <NUM> comprises a pair of opposite plates <NUM>, an inner one and an outer one, and a pair of toothed wheels 24a, 24b arranged between the inner and outer plates <NUM> and configured to engage the chain. The outer plate <NUM> is adjacent to the second body <NUM>.

The rocker arm <NUM> is rotatably connected to the second body <NUM> at a predetermined rotation axis X substantially perpendicular with respect to the planar extension of the outer plate <NUM>.

A shaft <NUM> is fixedly associated with the outer plate <NUM> of the rocker arm <NUM>. Such a shaft <NUM> extends coaxially to the rotation axis X through the second body <NUM> and is configured to rotate as a unit with the rocker arm <NUM> with respect to the second body <NUM> about the rotation axis X.

As shown in <FIG> and <FIG>, a fixing element <NUM> is coupled with the outer plate <NUM> of the rocker arm <NUM>. The fixing element <NUM> can be co-molded, glued, embedded with interference or joined in other per se conventional ways to the outer plate <NUM>.

The fixing element <NUM> has a hole <NUM> extending coaxially to the rotation axis X.

An end portion 23a of the shaft <NUM> passes through a through hole 22a formed in the outer plate <NUM> and is housed in the hole <NUM> of the fixing element <NUM>, for example through an interference or threaded coupling.

An opposite end portion 23b of the shaft <NUM> passes through a through hole 36a formed in the second body <NUM> and couples with a ring nut 37a. In the non-limiting example shown in <FIG>, the through hole 36a is formed in an insert 36c co-molded with the second body <NUM>.

A support bearing <NUM> is arranged between the end portion 23b and a corresponding end portion of the second body <NUM>. Such a support bearing <NUM> is housed in a seat 36b of the second body <NUM> coaxial to the rotation axis X. In the non-limiting example shown in <FIG>, the seat 36b is formed in an end portion of the insert 36c.

The ring nut 37a prevents the support bearing <NUM> from coming out of the seat 36b and axially locks the shaft <NUM>. The ring nut could be replaced by a Seeger ring.

The gearshift <NUM> also comprises a cover <NUM> removably associated with the second body <NUM> through a snap coupling, or a threaded coupling, or an interference coupling, or through screws, gluing or other per se conventional ways. The cover <NUM> is arranged above the end portion 23b of the shaft <NUM>, thereby also covering the support bearing <NUM>.

An elastic element, which in the embodiment shown in <FIG> is a helical return spring <NUM>, is associated with the second body <NUM> and with the rocker arm <NUM> so as to push the rocker arm <NUM> in rotation about the rotation axis X in a chain tensioning direction. In <FIG>, which corresponds to a substantially frontal view of the outer plate <NUM> of the rocker arm <NUM> mounted on the bicycle, the chain tensioning direction corresponds to a direction of rotation of the rocker arm <NUM> in the clockwise direction.

As shown in <FIG>, a helical return spring <NUM> is housed in a seat <NUM> formed in the second body <NUM>.

An unidirectional rotation device <NUM> is operatively arranged between the shaft <NUM> and the second body <NUM>. Such a unidirectional rotation device <NUM> is configured to allow the rotation of the shaft <NUM> with respect to the second body <NUM> only in the chain tensioning direction.

In particular, the unidirectional rotation device <NUM> comprises a radial bearing having an outer ring <NUM> fixedly associated with the second body <NUM> and an inner ring <NUM>. In the non-limiting example shown in <FIG>, the outer ring <NUM> is fixedly associated with the insert 36c.

The radial bearing is preferably a roller bearing.

A damping device <NUM> is operatively arranged between the shaft <NUM> and the unidirectional rotation device <NUM>. Such a damping device <NUM> is configured to apply a friction force to the rocker arm <NUM> when the rocker arm <NUM> is moved about the rotation axis X in a direction of rotation opposite to the chain tensioning direction, i.e. - with reference to <FIG> - in the counter-clockwise direction of rotation.

As shown in <FIG>, the damping device <NUM> comprises two friction surfaces <NUM> that extend axially along a direction substantially parallel to the rotation axis X.

The two friction surfaces <NUM> are arranged on opposite sides with respect to the rotation axis X, i.e. about <NUM>° from one another.

Each friction surface <NUM> is defined on a jaw <NUM>.

In the example illustrated herein the jaw <NUM> has the shape of a cylindrical cap, with a cylindrical surface that defines the friction surface <NUM> and a flat base surface <NUM>. In particular, the jaw <NUM>, in any cross section thereof (i.e. in sections taken according to a plane perpendicular to the rotation axis X), is shaped like a circular segment defined by an arc of circumference and by the cord of this circumference. The friction surface <NUM> is defined at the aforementioned arc of circumference, whereas the flat surface <NUM> is defined at the aforementioned cord of circumference.

The friction surface <NUM> extends circumferentially about the rotation axis X for an arc of circumference having a center on the rotation axis X and a center angle lower than <NUM>°, preferably comprised between <NUM>° and <NUM>°, more preferably between <NUM>° and <NUM>°, even more preferably equal to about <NUM>°.

The friction surface <NUM> acts directly or indirectly on the inner ring <NUM> of the radial bearing to obstruct the rotation of the latter.

The friction surface <NUM> is preferably provided with knurlings and/or ribs, to convey the possible lubricant used for the internal members and prevent such lubricant from going on the outermost part of the surface <NUM>, which on the other hand must generate friction.

In the example shown in <FIG>, the inner ring <NUM> of the radial bearing is operatively associated with the friction surface <NUM> through an annular element <NUM> fixedly associated with the inner ring <NUM>. The annular element <NUM> therefore forms part of the unidirectional rotation device <NUM>.

The annular element <NUM> is axially adjacent to the inner ring <NUM>. In particular, it is axially arranged between the inner ring <NUM> of the radial bearing and the rocker arm <NUM>.

The annular element <NUM> has a diameter greater than that of the inner ring <NUM>. The latter is thus connected to the annular element <NUM> through a flat annular interface surface <NUM> that extends perpendicular to the rotation axis X. As described hereinafter, such an annular interface surface <NUM> defines an axial abutment surface for the jaws <NUM>.

A washer <NUM> is arranged between the annular interface surface <NUM> and the outer ring <NUM> of the radial bearing, and acts as a spacer.

In this embodiment of the gearshift <NUM> of the invention, the damping device <NUM> is arranged in a radially inner position with respect to the annular element <NUM>.

The shaft <NUM> comprises a cylindrical portion 23c adjacent to the end portion 23b and arranged in a radially inner position with respect to the inner ring <NUM>, and an enlarged portion 23d adjacent to the end portion 23a and arranged in a radially inner position with respect to the annular element <NUM>.

A self-lubricating bushing <NUM> is preferably arranged between the cylindrical portion 23c of the shaft <NUM> and the inner ring <NUM>. Such a self-lubricating bushing <NUM> supports the shaft <NUM>, ensuring a predetermined radial clearance with respect to the inner ring <NUM>. Such a radial clearance is suitable for avoiding the seizure of the shaft <NUM>, which is subjected to a torsional-flexional load by the rocker arm <NUM>.

Indeed, the self-lubricating bushing <NUM> performs the same function performed by the support bearing <NUM>. Therefore, there are embodiments in which only the self-lubricating bushing <NUM> is provided and not also the support bearing <NUM>, embodiments in which only the support bearing <NUM> is provided and not also the self-lubricating bushing <NUM>, and embodiments (like the one shown in <FIG>) in which both the self-lubricating bushing <NUM> and the support bearing <NUM> are provided.

The enlarged portion 23d comprises two opposite flat surfaces 23e, each of them facing a respective jaw <NUM>.

The damping device <NUM> comprises a thrusting member <NUM> arranged between the shaft <NUM> and a respective jaw <NUM> and configured to push the jaw <NUM> against a radially inner cylindrical surface 86a of the annular element <NUM> with a predetermined load (preload).

The thrusting member <NUM> comprises cup springs or helical springs. In the non-limiting example shown in <FIG>, a plurality of cup springs <NUM> is provided at each jaw <NUM>.

In the non-limiting example shown in <FIG>, the damping device <NUM> also comprises an adjustment device <NUM> configured to adjust the aforementioned predetermined load. In a variant that is not shown, the adjustment device <NUM> can be omitted.

The adjustment device <NUM> comprises spacer elements <NUM> having a predetermined thickness, for example washers having a calibrated thickness. In particular, in the non-limiting example shown in <FIG>, two washers are provided at each thrusting member <NUM>.

Each of the two opposite flat surfaces 23e of the enlarged portion 23d defines an abutment surface for an end portion of the thrusting member <NUM> opposite the one which exerts the thrust on the jaw <NUM>.

In the non-limiting example shown in <FIG>, the two washers are arranged between the thrusting member <NUM> and the jaw <NUM>, in particular between the plurality of cup springs <NUM> and the flat surface <NUM> of the jaw <NUM>. Such washers can also or only be arranged between the flat surface 23e of the shaft <NUM> and the end portion of the thrusting member <NUM> adjacent thereto.

A substantially cylindrical seat 53a is formed on the flat surface <NUM> of each jaw <NUM>, said seat being configured to house the washers and, preferably, at least part of the cup springs <NUM>, so as to prevent undesired axial movements of the latter.

An axial abutment surface 51a is made in a single piece with the shaft <NUM> in a position axially adjacent to the enlarged portion 23d and arranged between the enlarged portion 23d and the rocker arm <NUM>. As shown in <FIG> and <FIG>, the axial abutment surface 51a is arranged between the enlarged portion 23d and the end portion 23a of the shaft <NUM> and cooperates with the annular interface surface <NUM> to hold the jaws <NUM> in a predetermined axial position.

The jaws <NUM> have two opposite axial abutment surfaces 54a configured to be axially contained by the axial abutment surfaces 51a, <NUM>, with a suitable clearance that prevents the sliding thereof.

In the non-limiting example shown in <FIG>, the damping device <NUM>, as well as the annular element <NUM>, is entirely arranged in a radially inner position with respect to the helical return spring <NUM>.

<FIG> and <FIG> show a second preferred embodiment of a bicycle gearshift <NUM> according to the present invention.

The components of the bicycle gearshift <NUM> of <FIG> and <FIG> analogous or functionally equivalent to those of the bicycle gearshift <NUM> of <FIG> are indicated with the same reference numeral and for their description reference should be made to what has been described above.

The bicycle gearshift <NUM> of <FIG> and <FIG> differs from the bicycle gearshift <NUM> of <FIG> substantially in that the adjustment device <NUM> comprises a preload device <NUM> comprising a thrusting pin <NUM> and a pair of opposite thrust plates <NUM>. The washers shown in <FIG> are not provided here, but embodiments analogous to that of <FIG> and <FIG> are foreseen in which washers analogous to those shown in <FIG> are provided.

The thrusting pin <NUM> is moveable inside a hole 23f extending in the shaft <NUM> at the enlarged portion 23d thereof.

The hole 23f extends along a direction perpendicular to the rotation axis X and opens out onto a surface <NUM> of the enlarged portion 23d that connects the two opposite flat surfaces 23e.

Each thrust plate <NUM> is moveable inside a respective hole <NUM> which extends in the shaft <NUM> at the enlarged portion 23d thereof.

Each hole <NUM> extends along a direction perpendicular to the rotation axis X and opens out onto one of the two opposite flat surfaces 23e.

Each hole <NUM> is connected to the hole 23f.

The two holes <NUM> are substantially aligned and can be connected together, to define a single through hole <NUM>.

The thrusting pin <NUM>, when pushed inside the hole 23f and brought into contact with the two thrusting plates <NUM>, causes the movement of the latter in the respective holes <NUM>.

The first hole 23f and each second hole <NUM> are substantially perpendicular to one another.

The thrusting pin <NUM> and each thrust plate <NUM> comprise respective substantially wedge-shaped end portions 159a, 160a configured to abut against one another. Preferably, the aforementioned substantially wedge-shaped surfaces 159a, 160a are inclined by about <NUM>° with respect to the rotation axis X, but they can also be inclined by different angles, comprised between <NUM>° and <NUM>°. The choice of the angle determines the adjustment sensitivity.

The thrusting pin <NUM> is actuated by a dowel <NUM> screwed into the first hole 23f. The dowel <NUM> is equipped with a shaped recess 161a configured to couple with a tool (not shown) to be used for the initial adjustment of the gearshift <NUM>. In the example of <FIG>, the shaped recess 161a is hexagonal star shaped and is configured to couple with a corresponding tool like for example an Allen key.

Each hole <NUM>, and each thrust plate <NUM>, is arranged in a radially inner position with respect to a respective thrusting member <NUM>, which also in this case comprises a plurality of cup springs <NUM>.

Since the washers are not provided, each substantially cylindrical seat 53a of the jaws <NUM> is configured to house at least part of the cup springs <NUM>.

<FIG> show a portion of a third preferred embodiment of a bicycle gearshift <NUM> according to the present invention. What is not shown is identical to what is shown in <FIG>.

The components of the bicycle gearshift <NUM> of <FIG> analogous or functionally equivalent to those of the bicycle gearshift <NUM> of <FIG> are indicated with the same reference numeral and for their description reference should be made to what has been described above.

The bicycle gearshift <NUM> of <FIG> differs from the bicycle gearshift <NUM> of <FIG> substantially in that the thrusting member <NUM> comprises an elastic element <NUM> that is housed in a through hole 223i formed in the shaft <NUM> along a direction perpendicular to the rotation axis X. In particular, the through hole 223i is made at the enlarged portion 23d of the shaft <NUM> and opens out onto the two opposite flat surfaces 23e.

In the non-limiting example shown in <FIG>, the elastic element <NUM> is a helical spring.

A bushing <NUM> is arranged between the through hole 223i and the elastic element <NUM>. The bushing <NUM> contributes to prevent undesired axial movements of the helical spring.

The elastic element <NUM> is arranged in a radially inner position with respect to the two opposite jaws <NUM>.

The elastic element <NUM> thus passes through the shaft <NUM> and pushes, at the two end portions thereof, the two jaws <NUM>, thus pressing the two opposite friction surfaces <NUM> against the radially inner surface 86a of the annular element <NUM> with the same force.

Each jaw <NUM> is provided with a respective substantially cylindrical seat 53a that is configured to house a respective end portion of the elastic element <NUM>.

<FIG> show a portion of a fourth preferred embodiment of a bicycle gearshift <NUM> according to the present invention. What is not shown is identical to what is shown in <FIG>.

The bicycle gearshift <NUM> of <FIG> differs from the bicycle gearshift <NUM> of <FIG> substantially in that the adjustment device <NUM> comprises a spacer element <NUM> having a predetermined thickness and housed in a through hole 223i formed in the shaft <NUM> along a direction perpendicular to the rotation axis X. In particular, the through hole 223i is made at the enlarged portion 23d of the shaft <NUM> and opens out onto the two opposite flat surfaces 23e.

Moreover, in the non-limiting example shown in <FIG>, the thrusting member <NUM> comprises a plurality of cup springs <NUM> arranged on opposite sides with respect to the spacer element <NUM>. The cup springs <NUM> are at least partially housed in the through hole 223i.

A bushing <NUM> is arranged between the through hole 223i and the spacer element <NUM>. The cup springs <NUM> are, at least partially, housed inside the bushing <NUM>. The bushing <NUM> contributes to prevent undesired axial movements of the cup springs <NUM>.

The spacer element <NUM> and the cup springs <NUM> are arranged in a radially inner position with respect to the two opposite jaws <NUM>.

The set of cup springs <NUM> pushes the two opposite jaws <NUM>, so that the two opposite friction surfaces <NUM> press against the unidirectional rotation device <NUM> with the same force.

Each jaw <NUM> is provided with a respective substantially cylindrical seat 53a that is configured to house part of the cup springs <NUM>.

The substantially cylindrical seats 53a contribute to prevent undesired axial movements of the cup springs <NUM>.

<FIG> shows a fifth preferred embodiment of a bicycle gearshift <NUM> according to the present invention. <FIG> shows a portion of such an embodiment.

The bicycle gearshift <NUM> of <FIG> and <FIG> differs from the bicycle gearshift <NUM> of <FIG> substantially in that the damping device <NUM> is arranged in a radially inner position with respect to the inner ring <NUM> of the radial bearing of the unidirectional rotation device <NUM>. In this case, therefore, the annular element <NUM> is not provided.

The friction surface <NUM> of the jaws <NUM> therefore exerts a thrust directly on the inner ring <NUM> of the radial bearing.

Also in this case the radial bearing is preferably a roller bearing.

As shown in <FIG>, a fixing element <NUM>, provided with a threaded shank <NUM> and with a head <NUM>, is fixed to the outer plate <NUM> of the rocker arm <NUM>.

The shank <NUM> extends coaxially to the rotation axis X and passes through a through hole 22a of the outer plate <NUM>.

The head <NUM> is configured to be housed with axial abutment in a housing seat suitably provided in the outer plate <NUM>.

The fixing element <NUM> can be co-molded, glued, embedded with interference or joined in other per se conventional ways to the outer plate <NUM>.

An end portion 23a of the shaft <NUM> has a threaded blind hole 423a in which the threaded shank <NUM> of the fixing element <NUM> is screwed.

The shaft <NUM> can thus rotate as a unit with the rocker arm <NUM> about the rotation axis X with respect to the second body <NUM>.

The shaft <NUM> comprises an end portion 23a and an enlarged portion 23d. In this case, the cylindrical portion 23c shown in the previous figures is not provided.

The damping device <NUM> is arranged at the enlarged portion 23d and is arranged between the enlarged portion 23d itself and the inner ring <NUM> of the radial bearing.

Like in the gearshift <NUM> of <FIG>, the damping device <NUM> of the gearshift of <FIG> and <FIG> comprises two friction surfaces <NUM> that extend axially along a direction substantially parallel to the rotation axis X and circumferentially about the rotation axis X for an arc of circumference having a center on the rotation axis X and a center angle lower than <NUM>°, preferably comprised between <NUM>° and <NUM>°, more preferably between <NUM>° and <NUM>°, even more preferably equal to about <NUM>°.

Each friction surface <NUM> is defined on a respective jaw <NUM>, identical to the one described earlier.

The helical return spring <NUM> is axially adjacent to the inner ring <NUM>. In particular, the helical return spring <NUM> is axially arranged between the inner ring <NUM> of the radial bearing and the rocker arm <NUM>. The damping device <NUM> is therefore in an axially adjacent position with respect to the helical return spring <NUM>.

Like in the gearshift <NUM> of <FIG>, the enlarged portion 23d comprises two opposite flat surfaces 23e, each facing a respective jaw <NUM>.

The gearshift <NUM> of <FIG> and <FIG> comprises a pair of axial abutment surfaces 451a, 451b arranged on opposite sides with respect to the damping device <NUM> and configured to prevent an axial movement of the jaws <NUM>.

The axial abutment surface 451a is made in a single piece with the shaft <NUM>. In particular, it is arranged between the enlarged portion 23d and the end portion 23a. In the non-limiting example shown in <FIG> and <FIG>, the axial abutment surface 451a is formed substantially at the middle of the shaft <NUM>.

The axial abutment surface 451b, on the other hand, is defined by a flange <NUM> associated with a face of the enlarged portion 23d of the shaft <NUM> opposite the one facing towards the end portion 23a. In the non-limiting example shown in <FIG>, the flange <NUM> is fixed to the shaft <NUM> through a screw 451c.

The jaws <NUM> have two opposite axial abutment surfaces 54a which are axially contained between the axial abutment surfaces 451a, 451b with a suitable clearance that prevents the sliding thereof.

<FIG> shows a sixth preferred embodiment of a bicycle gearshift <NUM> according to the present invention. <FIG> shows a portion of such an embodiment.

The components of the bicycle gearshift <NUM> of <FIG> and <FIG> analogous or functionally equivalent to those of the bicycle gearshift <NUM> of <FIG> and <FIG> are indicated with the same reference numeral and for their description reference should be made to what has been described above.

The bicycle gearshift <NUM> of <FIG> and <FIG> differs from the bicycle gearshift <NUM> of <FIG> and <FIG> substantially in that the adjustment device <NUM> comprises a preload device <NUM> comprising a thrusting pin <NUM> and a pair of opposite thrusting plates <NUM>.

The preload device <NUM> is totally analogous to the one described above with reference to the second embodiment of the gearshift <NUM> shown in <FIG> and <FIG>.

Of course, in order to satisfy specific and contingent requirements, those skilled in the art can bring numerous modifications and variants to the various embodiments of the bicycle gearshift described above, all of which are in any case within the scope of protection of the present invention as defined by the following claims.

In particular, the damping device <NUM> shown in <FIG> and <FIG> could be replaced by the damping device <NUM> shown in <FIG> or by the damping device <NUM> shown in <FIG>. In general, those skilled in the art can combine the features of the different embodiments of the invention herein described and shown as desired.

Claim 1:
Bicycle gearshift (<NUM>), comprising:
- a first body (<NUM>) configured to be associated with a bicycle frame;
- a second body (<NUM>) connected to, and moveable with respect to, said first body (<NUM>);
- a rocker arm (<NUM>) rotatably connected to said second body (<NUM>) at a rotation axis (X);
- a shaft (<NUM>) extending coaxially to said rotation axis (X) and fixedly associated with said rocker arm (<NUM>);
- a unidirectional rotation device (<NUM>) operatively arranged between said shaft (<NUM>) and said second body (<NUM>) and configured to allow the rotation of said shaft (<NUM>) with respect to the second body (<NUM>) only in a first direction of rotation about said rotation axis (X);
- a first elastic element (<NUM>) associated with the second body (<NUM>) and with the rocker arm (<NUM>) and configured to push said rocker arm (<NUM>) into rotation about said rotation axis (X) in said first direction of rotation;
- a damping device (<NUM>) operatively arranged between said shaft (<NUM>) and said unidirectional rotation device (<NUM>) and configured to generate a friction force when said rocker arm (<NUM>) is moved about said rotation axis (X) in a second direction of rotation opposite to said first direction of rotation;
wherein said damping device (<NUM>) comprises at least one friction surface (<NUM>) extending axially along a direction substantially parallel to the rotation axis (X) and in contact with said unidirectional rotation device (<NUM>), characterized in that said damping device (<NUM>) comprises at least two friction surfaces (<NUM>).