Assembly of toothed wheels for a bicycle

An assembly of toothed wheels of a bicycle has at least two toothed wheels of different diameter and at least one support member of at least one toothed wheel of the at least two toothed wheels on a component of a bicycle, like for example a free body of a hub for a rear bicycle wheel. The at least one support member is at least partially housed in at least one cavity of at least one other toothed wheel of the at least two toothed wheels. In this way, the distance between the toothed wheels is lower than the thickness of the support member of the toothed wheels themselves. The support member can thus maintain a strong resistant section at the attachment area to the respective toothed wheel. At the same time, it is possible to mount a greater number of sprockets on a free body of standard size.

FIELD OF INVENTION

The present invention relates to an assembly of toothed wheels of a bicycle.

BACKGROUND

Sprockets are coupled with a rear wheel of a bicycle through a hub. This comprises a first body, rigidly fixed to the rim of the bicycle through spokes, and a second body, rigidly coupled with the sprockets and able to rotate freely with respect to the first body in a direction of rotation, and to make it rotate in the opposite direction, thus giving the rear driving wheel its forward motion. In the technical jargon, this second body is called “free body.”

Since a bicycle is a means of transport using muscular propulsion, there is a general requirement for the power transmission system from the cyclist to the driving wheel to allow the least tiring possible.

As known, the combination of a guide toothed wheel with a small diameter with a sprocket with a large diameter allows demanding climbs to be ably handled. However, this same combination, over flat land or going downhill, is disadvantageous since the cyclists energy is dissipated, due to the fact that the cyclist is obliged to pedal quickly while the bicycle moves forwards slowly.

In order to make the aforementioned combination more suitable for the route to be made, it is known to equip the bicycle with a plurality of guide toothed wheels and with a plurality of sprockets, which can be combined with each other based upon requirements, through appropriate gearshifting devices.

Over the past few years the number of transmission ratios available in gearshifting devices has progressively increased and on the market currently there are groups of wheels with ten sprockets and groups of wheels with three guide wheels.

Above all in the field of racing bicycles, the progressive increase in the number of toothed wheels requires an ever-increasing search to reduce the weight of the assembly of wheels.

For this reason, assemblies of sprockets have been made comprising a plurality of sprocket support members that carry respective toothed wheels, in the form of circular toothed crowns: since the support members are made from a lighter material than the material of the toothed wheel, the desired reduction in weight of the assembly is obtained.

Since bicycle components have reached a high degree of standardization, the characteristic size of components like the frame, the gearshifting device and the free body are now almost fixed. In the prior art, some limits have been established in the maximum number of guide toothed wheels and of sprockets that can be mounted on standard sized bicycles. These limits currently seem insurmountable without modifying the standardized size of the bicycle components, in particular without increasing the axial size of the aforementioned groups of guide toothed wheels and of sprockets.

Indeed, keeping fixed the aforementioned standardized axial size, an increase in the number of toothed wheels would result in the need to arrange such toothed wheels in positions ever closer one to the other and the space available for the support members of the toothed wheels would become increasingly small, which may thus no longer have the characteristics of rigidity and strength necessary to support the toothed wheels.

SUMMARY

An assembly of toothed wheels of a bicycle, comprises at least two toothed wheels of different diameter and at least one support member of at least one toothed wheel of the at least two toothed wheels on a component of a bicycle, wherein the at least one support member is at least partially housed in at least one cavity of at least one other toothed wheel of the at least two toothed wheels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Introduction

Throughout the present description and in the subsequent claims the expression “assembly of toothed wheels” is used to indicate a structural unit comprising at least two toothed wheels and at least one support member of at least one of these toothed wheels.

In the present patent application, by toothed wheels of a bicycle it is meant both the guide toothed wheels, made to rotate by direct coupling with the pair of crank arms of the bicycle, and the driven toothed wheels, mounted on a rear bicycle wheel and made to rotate by the guide toothed wheels through the chain of the bicycle. Such driven toothed wheels are also known in technical jargon as “sprockets.”

An assembly of toothed wheels of a bicycle of the type considered above is capable of allowing an increase in the maximum number of guide toothed wheels and/or of sprockets that can be mounted on a bicycle having standard sized components.

Therefore, an assembly of toothed wheels of a bicycle, comprises at least two toothed wheels of different diameter and at least one support member of at least one toothed wheel of the at least two toothed wheels on a component of a bicycle, wherein the at least one support member is at least partially housed in at least one cavity of at least one other toothed wheel of the at least two toothed wheels.

In the assembly, the distance between the toothed wheels of the aforementioned assembly is lower than the thickness of the support member of the toothed wheels themselves. In this way, unlike known assemblies, the distance between the toothed wheels of the assembly is not strictly linked to the thickness of the support member, which can thus maintain a strong, resistant section at the attachment area to the respective toothed wheel.

The assembly can comprise more toothed wheels for the same standardized axial size of the component of the bicycle on which the assembly itself is mounted. For example, the assembly allows, in the case of the rear bicycle wheel, a sprocket assembly to be made comprising a eleven sprockets, like for example the one described in detail hereinafter.

Moreover, the support member can be made from lighter material than the material of the toothed wheel, for which reason the increase in the number of toothed wheels mounted on the bicycle does not imply an increase in weight of the sprocket assembly.

The assembly of toothed wheels may comprise a first support member of at least one first toothed wheel that comprises a first substantially annular central portion and at least one plurality of first arms extending radially outwards from the first substantially annular central portion, each of the first arms comprising at least one first through hole for housing a respective first attachment element to the at least one first toothed wheel, each of the first arms being at least partially housed in a respective cavity of at least one second toothed wheel. Therefore, the distance between the first toothed wheel and the second toothed wheel may be lower than the thickness of the support member of the first toothed wheel.

Each of the first arms may be axially displaced by a predetermined amount, with respect to the first substantially annular central portion, towards the at least one second toothed wheel.

The at least one first toothed wheel may comprise a plurality of first radial extensions facing inwardly, each of the first radial extensions comprising at least one second through hole aligned with the at least one first through hole for coupling with the first support member through the first attachment element.

The assembly of toothed wheels may comprise a further first toothed wheel having a diameter different to that of the at least one first toothed wheel and associated with the first support member on the same side as the at least one first toothed wheel and in a more axially inner position with respect to the at least one first toothed wheel, the further first toothed wheel being at a predetermined distance from the at least one first toothed wheel.

The further first toothed wheel may comprise at least one plurality of third through holes aligned with the first and second through holes for coupling with the first support member and with the at least one first toothed wheel through the first attachment elements. The further first toothed wheel is then associated with the first support member through the same attachment elements used to associate the first toothed wheel with the first support member. Thus, the number of attachment elements used in the assembly is thus contained, this implying the weight of such an assembly being consequently also contained.

Each of the first attachment elements may comprise a substantially tubular body at least partially housed in a respective first hole and an intermediate portion projecting radially outwards and acting in abutment against the at least one first toothed wheel on the opposite side to the first arm. Thus, the tubular shape of the attachment element ensures a contained weight while ensuring at the same time an adequate level of strength.

Moreover, the intermediate portion may be operatively arranged between the further first toothed wheel and the at least one first toothed wheel. Thus, the aforementioned intermediate portion acts as a spacer between the sprockets supported by the support member.

Further, the intermediate portion may be circumferentially grooved. Advantageously, the circumferential groove contributes to reducing the weight of the attachment element.

Each of the first arms comprises an abutment surface having generatrixes substantially parallel to a rotation axis of the assembly and acting in abutment on the intermediate portion and on the at least one first toothed wheel. Therefore, the aforementioned abutment surface provides a radial support to the intermediate portion of the attachment element and to the first toothed wheel. Therefore, just the further first toothed wheel is supported cantilevered by the first support member.

In an embodiment thereof, the assembly comprises a second support member of the at least one second toothed wheel that comprises a second substantially annular central portion in abutment against the first substantially annular central portion at a first abutment plane and at least one plurality of second arms extending radially outwards from the second substantially annular central portion, each of the second arms comprising at least one fourth through hole for housing a respective second attachment element to the at least one second toothed wheel, each of the second arms being at least partially housed in a respective cavity of the at least one first toothed wheel, the first arms being angularly staggered with respect to the second arms in a circumferential direction. Thus, the distance between the first toothed wheel and the second toothed wheel is also lower than the thickness of the support member of the second toothed wheel.

Each of the second arms may be axially displaced by a predetermined amount, with respect to the second substantially annular central portion, towards the at least one first toothed wheel, and the at least one second toothed wheel is arranged on the opposite side to the at least one first toothed wheel with respect to the first abutment plane.

The at least one second toothed wheel may comprise a plurality of second radial extensions facing inwardly, each of the second radial extensions comprising at least one fifth through hole aligned with the at least one fourth through hole for coupling with the second support member through the second attachment element.

The assembly may comprise a further second toothed wheel having a diameter different to that of the at least one second toothed wheel and associated with the second support member on the same side as the at least one second toothed wheel and in a more axially outer position with respect to the at least one second toothed wheel, the further second toothed wheel being at a predetermined distance from the at least one second toothed wheel.

The further second toothed wheel may comprise at least one plurality of sixth through holes aligned with the fourth and fifth through holes for coupling with the second support member and with the at least one second toothed wheel through the second attachment elements. Thus, the further second toothed wheel is then associated with the second support member through the same attachment elements used to associate the second toothed wheel with the second support member. The number of attachment elements used in the assembly is thus contained, this implying the weight of such an assembly being consequently also contained.

Each of the second attachment elements may comprise a substantially tubular body at least partially housed in a respective fourth hole and an intermediate portion projecting radially outwards and acting in abutment against the at least one second toothed wheel on the opposite side to the second arm.

The intermediate portion is operatively arranged between the further second toothed wheel and the at least one second toothed wheel.

Moreover, the intermediate portion may be circumferentially grooved.

Each of the second arms comprises an abutment surface having generatrixes substantially parallel to a rotation axis of the assembly and acting in abutment on the intermediate portion and on the at least one second toothed wheel. Thus, the aforementioned abutment surface provides a radial support to the intermediate portion of the attachment element and to the second toothed wheel. Therefore, just the further second toothed wheel is supported cantilevered by the second support member.

The second attachment element may be substantially the same as the first attachment element.

In an alternative embodiment of the assembly, the at least one second toothed wheel is associated with the first support member.

The first support member may also comprise a plurality of second arms extending radially outwards from the first substantially annular central portion, each of the second arms comprising at least one fourth through hole for housing a respective second attachment element to the at least one second toothed wheel, each of the second arms being at least partially housed in a respective cavity of the at least one first toothed wheel.

Moreover, the at least one second toothed wheel may comprise a plurality of second radial extensions facing inwardly, each of the second radial extensions comprising at least one fifth through hole aligned with the at least one fourth through hole for coupling with the first support member through the second attachment element.

The assembly may comprise a further second toothed wheel having a diameter different to that of the at least one second toothed wheel and associated with the first support member on the same side as the at least one second toothed wheel and in a more axially outer position with respect to the at least one second toothed wheel, the further second toothed wheel being at a predetermined distance from the at least one second toothed wheel.

Moreover, the further second toothed wheel may comprise at least one plurality of sixth through holes aligned with the fourth and fifth through holes for coupling with the first support member and with the at least one second toothed wheel through the second attachment elements.

Each of the second attachment elements may comprise a substantially tubular body at least partially housed in a respective fourth hole and an intermediate portion projecting radially outwards and acting in abutment against the at least one second toothed wheel on the opposite side to the second arm.

Moreover, the intermediate portion may be operatively arranged between the further second toothed wheel and the at least one second toothed wheel.

Moreover, the intermediate portion may be circumferentially grooved.

Each of the second arms may comprise an abutment surface having generatrixes substantially parallel to a rotation axis of the assembly and acting in abutment on the intermediate portion and on the at least one second toothed wheel.

The second attachment element may be substantially the same as the first attachment element.

The at least one second toothed wheel may be associated with the first annular central portion of the first support member.

Moreover, the at least one second toothed wheel may be connected to the first annular central portion through riveting.

In another embodiment thereof, the assembly may also comprise a third support member of at least one third toothed wheel that comprises a third substantially annular central portion in abutment against the second substantially annular central portion on the opposite side to the first substantially annular central portion at a second abutment plane.

The third support member may comprise at least one plurality of third arms extending radially outwards from the third substantially annular central portion, each of the third arms comprising at least one seventh through hole for housing a respective third attachment element to the at least one third toothed wheel, each of the third arms being at least partially housed in a respective cavity of a toothed wheel supported by the second support member.

Moreover, the third arms may be angularly staggered with respect to the second arms in a circumferential direction. Thus, the distance between the toothed wheel supported by the third support member and a toothed wheel supported by the second support member is lower than the thickness of the support member of the third toothed wheel.

The at least one third toothed wheel may be arranged on the opposite side to the at least one second toothed wheel with respect to the second abutment plane.

The at least one third toothed wheel may comprise a plurality of third radial extensions facing inwardly, each of the third radial extensions comprising at least one eighth through hole aligned with the at least one seventh through hole for coupling the at least one third toothed wheel with the third support member.

The assembly may comprise a further third toothed wheel having a diameter different to that of the at least one third toothed wheel and associated with the third support member on the same side as the at least one third toothed wheel and in a more axially outer position with respect to the at least one third toothed wheel, the further third toothed wheel being at a predetermined distance from the at least one third toothed wheel.

The further third toothed wheel may comprise at least one plurality of ninth through holes aligned with the seventh and eighth through holes for coupling with the third support member and with the at least one third toothed wheel. Advantageously, the further third toothed wheel is then associated with the third support member through the same attachment elements used to associate the third toothed wheel with the third support member. The number of attachment elements used in the assembly is thus contained, this implying the weight of such an assembly being consequently also contained.

Each of the third attachment elements may comprise a substantially tubular body at least partially housed in a respective seventh hole and an intermediate portion projecting radially outwards and acting in abutment against the at least one third toothed wheel on the opposite side to the third arm.

The intermediate portion may be operatively arranged between the further third toothed wheel and the at least one third toothed wheel.

The intermediate portion may be circumferentially grooved.

Each of the third arms may comprise an abutment surface having generatrixes substantially parallel to a rotation axis of the assembly and acting in abutment on the intermediate portion and on the at least one third toothed wheel. Thus, the aforementioned abutment surface provides a radial support to the intermediate portion of the attachment element and to the third toothed wheel. Therefore, just the further third toothed wheel is supported cantilevered by the third support member.

The third attachment element may be substantially the same as the first and second attachment element.

In another embodiment of the assembly, the number of the second arms and the first arms is the same. Moreover, the number of the third arms may be lower than that of the first and second arms. Indeed, due to the fact that the toothed wheels associated with the third support member have a diameter smaller than that of the wheels supported by the first and second support member, less strengthening is necessary and it is thus possible to limit the fixing points to the third support member.

The third arms may have a shorter radial extension than that of the first and second arms. In this way problems of interference between the third arms and the sprockets and/or the attachment elements mounted on the first and second arms are avoided.

In a further embodiment of the assembly, the at least one second toothed wheel is adapted to be coupled directly with the component of the bicycle.

In a further embodiment of the assembly, the at least one second wheel is not associated with the first support member.

In all of the embodiments thereof, the assembly of toothed wheels can comprise a lightening throat formed at the base of each arm.

Moreover, the at least one cavity entirely may cross the thickness of the respective toothed wheel.

There is a plurality of the cavities and they are substantially equally spaced apart circumferentially.

In another embodiment of the assembly of toothed wheels, the toothed wheels are sprockets of a rear bicycle wheel and the component is a free body of a hub of a rear bicycle wheel.

The at least one support member may comprise a radially inner surface having a profile adapted to transmit a torque to the free body.

Moreover, the surface may be a grooved surface.

Even further, the profile may comprise a plurality of teeth of the same shape and at least one tooth of a different shape. Thus, the presence of the differently shaped tooth ensures that the assembly is mounted on the free body of the hub in a single predetermined position.

The thickness of the at least one sprocket and the distance between the at least two sprockets are selected so that their sum is comprised between 3 mm and 4.5 mm, more preferably between 3.5 and 4 mm.

In an alternative embodiment of the assembly of toothed wheels, the toothed wheels are guide toothed wheels of a bicycle and the component is a shaft of a bottom bracket assembly of the bicycle.

In a second aspect thereof, a sprocket assembly comprises at least one assembly of toothed wheels of the type described above.

Such a sprocket assembly may have individually or in combination all of the structural and functional characteristics discussed above with reference to the assembly of toothed wheels and therefore has all of the aforementioned advantages.

In particular, the aforementioned sprocket assembly comprises, as well as the assembly of toothed wheels, at least one free toothed wheel adapted to be directly coupled with the component of the bicycle.

In a third aspect thereof, a bicycle comprises at least one assembly of toothed wheels of the type described above.

Such a bicycle has individually or in combination all of the structural and functional characteristics discussed above with reference to the assembly of toothed wheels.

In a fourth aspect thereof, an attachment element of two toothed wheels of a bicycle to a toothed wheels support member, comprises a tubular body and an intermediate portion projecting radially outwards from the tubular body, the intermediate portion having a circumferential groove on an outer edge thereof.

Thus, such an attachment element can be used in the assembly of toothed wheels described above.

Such an attachment element has individually or in combination all of the structural and functional characteristics discussed above with reference to the attachment element of the toothed wheels of the assembly and therefore it has the aforementioned advantages.

In particular, in an aforementioned attachment element the aforementioned intermediate portion is made in one piece with the tubular body, but in an alternative embodiment it can be a piece distinct from the tubular body.

DESCRIPTION

With particular reference toFIG. 1, a bicycle51is shown to which a sprocket assembly, wholly indicated with16, is applied, such a sprocket assembly comprising an assembly of toothed wheels in accordance with the present invention.

In particular, hereinafter the non-limiting example of an assembly of toothed wheels mounted on a rear driving wheel57of the bicycle51is described, such an assembly constituting a portion of the sprocket assembly16indicated inFIG. 1. As shall become clear from the following description, the assembly of toothed wheels of the invention can also be mounted on the shaft of a bottom bracket assembly of a bicycle.

The bicycle51ofFIG. 1comprises a frame53to which a front wheel55and the rear driving wheel57are connected.

What makes the front wheel55different from the rear driving wheel57is that the second one receives the motion from the motion transmission system59of the bicycle51. This system comprises a pair of crank arms50directly coupled with one or more guide toothed wheels12. The crank arms50are supported in rotation in the frame53through a bottom bracket assembly14comprising a shaft and bearings. The guide toothed wheels12engage a chain15to transmit the torque applied by the cyclist on the crank arms50to the sprocket assembly16coupled with the rear driving wheel57.

In particular, the rear driving wheel57comprises a rim58, some spokes18and the hub20. The hub20is per sè known and for this reason it is only schematically illustrated: it comprises a first body coupled with the rim58through the spokes18and a second body that rotates as a unit with the sprocket assembly16. The second body is indicated with reference numeral22inFIG. 2and it is the free body since it is free to rotate with respect to the first body in a direction of rotation, and makes it rotate with it in the opposite direction. The rotation axis is indicated with X inFIG. 2.

With reference toFIGS. 2 and 3, a first embodiment of the sprocket assembly16of the bicycle51is shown.

The sprocket assembly16comprises a plurality of driven toothed wheels, known as sprockets, having different outer diameters to each other: in the example illustrated inFIGS. 2 and 3, there are eleven sprockets and they are indicated with reference numerals1to11, from the sprocket1having the greater outer diameter up to the sprocket11having the smaller outer diameter.

A gearshifting device24, illustrated inFIG. 1, allows the chain15to be moved from an engagement condition with a sprocket to an engagement condition with another sprocket. A similar device can also be provided in the area of the crank arms50in the case in which there is more than one guide toothed wheel12. In this way, the sprockets and the toothed wheels can be associated with each other through the chain15in a plurality of combinations.

With particular reference toFIG. 2, the sprockets from1to11are divided in the sprocket assembly16into two groups, a first group26comprises the sprockets from7to11, hereafter the free sprockets because they are directly engaged with the free body22, and a second group30comprises the sprockets from1to6, known as fixedly connected sprockets because they are engaged with the free body22through support members, respectively indicated with60,62and64.

The group of sprockets30is in turn divided into structural units42,44and46each comprising two sprockets rigidly connected to one of the support members: in particular, the sprockets1and2are fixedly connected to the support member60, the sprockets3and4are fixedly connected to the support member62and the sprockets5and6are fixedly connected to the support member64. Each of the aforementioned structural units, in the most simple and general embodiment thereof, constitutes an assembly.

With reference toFIG. 2, the free body22, on the outer surface thereof, has a grooved profile32adapted to engage with a matching grooved profile made on the free sprockets7-11for a direct transmission of torque, and with an engagement profile67made on the support members60,62and64, for a indirect transmission of torque. A lockring38(also visible inFIG. 3) screwed at the head of the free body22keeps the sprocket assembly16in abutment against a shoulder40of the free body22.

Throughout the present description, with reference to the position and orientation of the components with respect to the rear wheel57on which the sprocket assembly16is mounted, by “outer side” of the sprocket assembly it is meant that going away from a middle plane M of the wheel57along the rotation axis X, the outer side being indicated inFIG. 2with the arrow O. By “inner side” of the sprocket set it is meant the side opposite the outer side and indicated with the arrow I inFIG. 2.

FIGS. 4-6illustrate in detail the support member60of the sprocket assembly16. In particular, the support member60comprises a substantially annular central portion66, extending around the rotation axis X, on the radially inner edge of which a profile67for engagement with the grooved profile32of the free body22is defined. The engagement profile67comprises a plurality of teeth68of the same shape and at least one tooth68aof a different shape to provide a reference for mounting on the free body22with a predetermined orientation.

A plurality of arms69(in the illustrated example, six arms) project from the substantially annular central portion66in a radially outer direction to support the sprockets1and2(FIGS. 2, 7 and 8). At the base of each arm69a lightening throat70is formed. The arms69are axially displaced by a predetermined amount with respect to the first substantially annular central portion66, i.e. they have an “engagement” in the direction of the axis X with respect to the substantially annular central portion66. In particular, as shall be made clear hereinafter, the arms69project axially outwards (i.e. in the direction O) with respect to the substantially annular central portion66.

The substantially annular central portion66has an inner abutment face72, which when mounted on the free body22is orientated in the direction of the axis X towards the inside of the wheel57so as to abut on the shoulder40, and an outer abutment face74, which is orientated in the opposite direction so as to abut on the support member62. The faces72and74are flat so that they extend along respective radial planes P1and P2, substantially perpendicular to the axis X (as can be seen inFIG. 9).

Each arm69has a first coupling face76, oriented like the inner abutment face72but not aligned with it, and adapted to couple with the sprocket2. The coupling face76is arranged between the planes P1and P2. Alternatively, the coupling face76can be arranged in a position aligned with the plane P2or even more axially outwardly, i.e. even farther away, in the axially outer direction to the wheel57, from the plane P1.

A second face78of the arms69, opposite the coupling face76, is arranged axially farther out with respect to the plane P2. In this way, the attachment of the arms69to the substantially annular central portion66is strengthened through a joining portion79between the second face78and the inner face74.

Each arm69also has a through hole80that extends from the coupling face76to the opposite face78. The holes80of the plurality of the arms69are preferably all arranged at the same radial distance. In use, the holes80are intended to house attachment elements90like for example rivets. In particular, the attachment elements project cantilevered from the coupling surfaces76and are intended to lock the sprockets1and2on the support member60, as shall be described in detail hereinafter.

In addition, each arm69, on the side of the coupling surface76, has an abutment surface82having generatrixes extending substantially parallel to the axis X, to provide an additional support in the radial direction to the canti-levered attachment elements90. Preferably, such an additional support surface is a concave surface, even more preferably it is a cylindrical surface portion, however flat or convex surfaces are not excluded.

It should be observed that the arms69support at least two sprockets1and2, arranged on the same side as the arms69, with the sprocket1arranged in an axially more outer position than the sprocket2with respect to the arm69in the direction I.

FIGS. 10 and 11illustrate the second support member62of the sprocket assembly16ofFIG. 2. In such a support member, elements equal or corresponding to those of the support member60are indicated with the same reference numeral increased by 100.

The support member62differs from the support member60due to the orientation of the “indentation” of the arms169, as shall become clear hereinafter.

The support member62has a substantially annular central portion166with an inner abutment face172adapted to abut against the outer abutment face74of the first support member60, and an outer abutment face174adapted to abut against the third support member64. The abutment faces172and174extend along respective radial planes P3and P4, substantially perpendicular to the axis X (as can be seen inFIG. 9).

The arms169for supporting the sprockets3and4project radially from the substantially annular central portion166and have a coupling face176of the sprockets arranged between the planes P3and P4. Alternatively, the coupling face176can be arranged in a position aligned with the plane P3or even axially more inwardly, i.e. in a position even farther towards the inside from the plane P4. Opposite the coupling surface176there is a surface178axially more inwardly with respect to the plane P3.

In the illustrated example there are six support arms169and they are axially displaced by a predetermined amount towards the inside (i.e. in the direction I) with respect to the substantially annular central portion166.

A through hole180crosses the opposite surfaces176and178for the canti-levered insertion of attachment elements90, like for example rivets.

In particular, the attachment elements90project cantilevered from the coupling surfaces176and are intended to lock the sprockets3and4on the support member62, as shall be described in detail hereinafter.

In addition, each arm169has, on the side of the coupling surface176, an abutment surface182having generatrixes substantially parallel to the axis X to provide an additional support in the radial direction to the canti-levered attachment elements90. Preferably, such an additional support surface182is a concave surface, even more preferably it is a cylindrical surface portion, however flat or convex surfaces are not excluded.

It should be observed that the arms169support at least two sprockets3and4, arranged on the same side as the arms169, with the sprocket4arranged in an axially more outer position than the sprocket3in the direction O. As illustrated inFIGS. 7 and 8, the sprockets3and4are thus supported by the arms169on the opposite side to that in which the sprockets1and2are supported by the arms69, i.e. the engagement of the arms169is opposite that of the arms69, so that the arms69and169at least partially cross over in the axial direction (as can be clearly seen inFIGS. 12 and 13).

On the radially inner edge of the substantially annular central portion166the same engagement profile67of the first support member60is reproduced, with the identical teeth68and the at least one different tooth68a.

FIGS. 14 and 15show the third support member64of the sprocket inwardly16ofFIG. 2. In such a support member, elements equal or corresponding to those of the support member60are indicated with the same reference numeral increased by 200.

One of the main differences of this third member64compared to the other two is that it comprises just five support arms269for the coupling of the sprockets5and6. Indeed, since sprockets5and6have a smaller diameter than sprockets1-4, they need less strengthening and therefore a low number of fixing points to the support member64is sufficient.

Also the third support member64comprises a substantially annular central portion266with an inner abutment face272, adapted to abut against the outer abutment face174of the second support member62, and an outer abutment face274, adapted to abut against a spacer33for separating from the sprocket7. The abutment surfaces272and274extend along the radial planes P5and P6, substantially perpendicular to the axis X (as can be seen inFIG. 9).

The arms269project radially from the substantially annular central portion269but in this case they are completely arranged between the planes P5and P6. However, a variant of the third support member64described above, in which an “indentation” of the arms269is provided, for example similar to that of the arms169, is not excluded.

The arms269also have a front surface276for coupling with the sprockets5and6, crossed by a through hole280for the canti-levered insertion of attachment elements90, like for example rivets.

In particular, the attachment elements90project canti-levered from the coupling surfaces276and are intended to lock the sprockets5and6on the support member64, as shall be described in detail hereinafter.

In addition, each arm269has, on the side of the coupling surface276, an abutment surface282having generatrixes extending substantially parallel to the axis X to provide an additional support in the radial direction to the cantilevered attachment elements90. Preferably, such an additional support surface182is a concave surface, even more preferably it is a cylindrical surface portion, however flat or convex surfaces are not excluded.

The radially inner edge of the substantially annular central portion266comprises the same coupling profile67as the other two support members60and62, i.e. it has the same identical teeth68and the different tooth68a.

As illustrated inFIG. 16, by aligning the different teeth68aof the support members60,62and64, the axes of the arms69and169, and of the arms169and269respectively, are angularly staggered in the circumferential direction.

In particular, looking at the three support members60,62and64thus arranged along an axial direction, the arms69and169are angularly staggered apart in a regular manner, whereas the arms269are angularly staggered with respect to the arms169.

Moreover, the space85between two consecutive arms69is greater than or equal to the circumferential size of an arm169, and vice-versa the space86between two consecutive arms169is greater than or equal to the circumferential size of an arm69. In this way, the arms169, thanks to their indentation, at least partially penetrate into the space85between the arms69, and vice-versa, as can be seen more clearly inFIGS. 12 and 13, where the support members are illustrated in abutment in the same position that they take up in the mounted sprocket assembly16. In other words, the arms69and169cross over in the axial direction. InFIG. 13it is also clear that in the mounted condition the planes P2and P3coincide, as well as like the planes P4and P5.

FIG. 9shows the three support members60,62and64facing one another in the position that they take up before being brought into abutment to form the configuration illustrated inFIGS. 12 and 13.

The sprockets1-6, substantially shaped like a circular crown, comprise a plurality of radial extensions facing inwardly, each of such radial extensions comprising a through hole at positions that correspond to those of the through holes80(for sprockets1and2),180(for sprockets3and4) and280(for sprockets5and6): the through holes of sprockets1-6are aligned with the through holes80,180and280for coupling with the support members60,62and64through the attachment elements90.

InFIGS. 17 and 18, it is shown how, in the area between two consecutive radial extensions3aof the sprocket3, the arm69is partially housed in a cavity of the sprocket3itself: in particular, in the illustrated example, the aforementioned cavity is the cavity87defined on the inner profile of the sprocket3between two consecutive radial extensions3a, and it crosses the entire thickness of the arm69. Alternatively, the cavity can just occupy a portion of the entire thickness of the arm69.

In other words, the sprocket3is at least partially arranged over the arm69, i.e. in the aforementioned area between two radial extensions3athe sprocket3is arranged outwardly with respect to the arm69.

As shown inFIG. 7, the sprocket2is at least partially arranged over the arm169in a similar manner.

InFIG. 16it can be seen that the arms269of the support member64have a shorter radial extension than that of the arms69and169. Indeed, whilst the number of arms269is lower than that of arms169of the support member62and therefore the arms269cannot be regularly staggered with respect to the arms169, the arms269must not completely shield the arms169in the axial direction, so that problems of interference with the arms169and the sprockets and/or attachment elements90mounted on the arms169are avoided. As can be seen inFIG. 2in this way the sprocket4is at least partially arranged over the arms269.

FIGS. 7 and 18show the structural units42and44coupled together in the same configuration that they take up in the sprocket assembly16.

The structural unit42comprises the support member60and the sprockets1and2, fixedly connected thereto through the attachment element90. Both of the sprockets1and2are supported on one side of the support member60, in particular, they are arranged more inwardly with respect to the abutment plane P2with the second support member62, whereas the arms69are at least partially more outwardly with respect to such a plane.

The sprocket2is in abutment against the coupling surface76of the arms69and is kept in position by the attachment elements90. The attachment elements90cross the sprocket2and extend cantilevered for supporting also the sprocket1. Between the sprocket1and the sprocket2spacers91are arranged, which are an integral part of the attachment elements90and are sized so as to rest radially on the support surface82. In this way, the only sprocket supported cantilevered is the sprocket1, since the sprocket2is arranged between two areas of each attachment element resting at the support member60. The sprocket1, is also at least partially in a more inner position with respect to the abutment plane P1.

Similarly, the structural unit44comprises the second support member62and the sprockets3and4fixedly connected thereto. The abutment plane P3coincides with the plane P2and the sprockets3and4are supported in a more outer position with respect to such a plane whereas the arms169are arranged at least partially more inwardly with respect to such a plane. The sprocket3is directly in abutment on the coupling surface176held not cantilevered by the attachment elements90a, since between the sprocket3and the sprocket4there are spacers91, which are an integral part of the attachment elements90and are sized so as to rest radially on the support surface182: the attachment elements90thus also rest on the support surface182.

The sprocket4, on the other hand, is supported cantilevered by an extension of the attachment elements90and is partially in a more outer position with respect to the abutment plane P4.

Thanks to the fact that the support members60and62are at least partially arranged over one another, there is at the same time a resistant section of the arms69and169that is sufficiently strong and an arrangement wherein the sprockets1,2,3and4are spaced apart at particularly small distances Z. In particular, with reference toFIG. 8, the sprocket3is at least partially arranged over the arms69, so that they are at least partially arranged in the cavity87defined by the annular shape of the sprocket3. The same occurs for the arms169and the sprocket2. In this way the distance Z between the sprockets2and3can advantageously be lower than the thickness T of the arms69and169.

As an example, the same distance Z has been illustrated between all of the pairs of sprockets, and in particular the spacers91have the same thickness as the distance Z between the sprockets2and3. However, it is not excluded the possibility that this distance may vary from one pair of sprockets to the other. The values of the distances between consecutive sprockets, indeed, must take into account the thickness of the sprockets and of the chain intended to be used, to allow free engagement of the latter. Since the thickness of the sprockets can vary between sprockets having a greater diameter and sprockets having a smaller diameter, indicatively it is preferable to keep to consider combinations of thickness of sprockets and distances Z between sprockets such that their sum A is comprised in the range between 3-4.5 mm and even more preferably in the range between 3.5-4 mm.

FIGS. 19 and 20show in detail the attachment element90, which comprises a tubular body94and an intermediate portion projecting radially outwards91preferably made in one piece with the tubular body94and with the function of a spacer between two sprockets engaged by the same attachment element90. The intermediate portion91has a circumferential lightening groove92on the outer edge thereof. Alternatively, the intermediate portion91can be made as a distinct piece from the tubular body94.

The opposite ends94aand94bof the tubular body94can be folded, in the radial direction, in annular cavities95aand95b(FIG. 7) formed respectively on the inner face of the sprocket1and on the face78of the arm69, about the through hole of the radial extension of the sprocket1and the through hole80. The ends94aand94bhave basically the same function as the ends of a rivet of the prior art.

As can be seen inFIG. 7, a similar attachment element90is used for the support member62, orientated so that it is inverted with respect to the element90used for the support member60, so that the opposite ends94band94aof the tubular body94can be folded, in the radial direction, on the face178of the arm169and in an annular cavity195aformed on the outer face of the sprocket4, about the through hole of the radial extension of the sprocket4.

As can be seen inFIG. 2, a similar attachment element90is also used for the support member64, orientated like the element90used for the support member60: the opposite ends94aand94bof the tubular body94can be folded, in the radial direction, on the inner face278of the arm269and in an annular cavity295aformed on the outer face of the sprocket6, around the through hole of the radial extension of the sprocket6.

FIG. 21shows a portion of a second embodiment of the assembly of toothed wheels according to the invention, which comprises a structural unit552that exactly corresponds to the assembly consisting of the two structural units42and44, arranged side-by-side. In the structural unit552, the support members60and62of the structural units42and44have been fused together in a support member560, made in a single piece.

This support member560has arms569ahaving a indentation towards the outside and corresponding to the arms69of the support member60, and arms569bhaving an indentation towards the inside and corresponding to the arms169of the support member62. The sprockets1and2are both fixedly connected to just the arms569aand both arranged on the inner side of such arms. Similarly, the sprockets3and4are both fixedly connected to just the arms569band both arranged on the outer side of such arms. In this way, the sprocket3is at least partially arranged over the arms569aand the sprocket2is at least partially arranged over the arms569b.

FIG. 22illustrates a portion of a third embodiment of the assembly of toothed wheels according to the invention. In such an assembly, elements equal or corresponding to those of the support member60are indicated with the same reference numeral increased by 300.

The assembly ofFIG. 22comprises a structural unit342comprising a support member360to which a single sprocket312is connected, through a plurality of first rivets390a. The support member360comprises a substantially annular central portion366and a plurality of arms369extending from it in the radial direction and having a shape and indentation similar to those of the arms69of the support member60.

In this case, the indentation of the arms369is exploited to at least partially penetrate into at least one cavity387of a free sprocket313, i.e. intended to be coupled directly with the hub of the bicycle, the free sprocket313being arranged at a side of the sprocket312.

FIG. 23illustrates a portion of a fourth embodiment of the assembly of toothed wheels according to the invention. In such an assembly, elements equal or corresponding to those of the support member60are indicated with the same reference numeral increased by 400.

The assembly ofFIG. 23comprises a structural unit442comprising a support member460to which a sprocket412is fixedly connected, through a plurality of first rivets490a. The support member460comprises a substantially annular central portion466and a plurality of arms469extending from it in the radial direction and having a shape and indentation similar to those of the arms69of the support member60.

In this case, the indentation of the arms469is exploited to at least partially penetrate into at least one cavity487of a sprocket413. The sprocket413is arranged at a side of the outer abutment face474of the substantially annular central portion466and is connected thereto through a plurality of second rivets490b.

In other words, the structural unit442thus comprises two sprockets412and413arranged on opposite sides of the support member460and fixedly connected thereto through rivets490aand490b, the arms469of the device at least partially penetrating into at least one cavity487of the sprocket413.

Just for illustrative purposes an arm469has been shown that has an indentation towards the outside to penetrate into a more outer sprocket413, however an opposite indentation to penetrate into a more inner sprocket412is not excluded.

Of course, a person of ordinary skill in the art can bring numerous modifications and variants to what has been described above purely as an example, in order to satisfy contingent and specific requirements, all of which are also covered by the scope of protection as defined by the following claims.

For example, all of the aforementioned detailed description has been made with reference to sprocket assemblies, but it is obvious that the toothed wheels of the assembly of the invention can also be the guide toothed wheels, mounted on the shaft of a bottom bracket assembly of a bicycle.

Moreover, it should be noted that, although all of the illustrated support members have five or six arms, this number of arms obviously is not restrictive and can vary from what has been illustrated.