Patent Description:
A toothed pulley with a ring made of an elastically deformable material is disclosed in <CIT> in the form of a sprocket, wherein a circular cushioning rings serve as cushions between the teeth of the sprocket and the link plates of a roller chain trained engaged with the sprocket. As disclosed therein, the circular cushioning rings may have an annular or rectangular cross section. Document <CIT> shows the preamble of claim <NUM>.

Further toothed pulleys with respective circular cushioning rings made of an elastically deformable material are disclosed in <CIT> in the form of sprockets of a multi-gear cassette for a rear wheel of a bicycle, wherein the circular cushioning rings dampen the forces produced by the chain members running from the slack span of the chain onto a sprocket. These circular cushioning rings have rectangular cross sections.

The prior art pulleys have the problem that nevertheless they are relatively noisy and buckling in operation.

Bicycle chains of an unconventional type, so-called flattop chains (or AXS chains), are known in the art, wherein the respective tops of the link plates are straight-lines, which enables a narrower chain construction with increased strength and durability.

If such a chain is used in a bicycle having a derailleur, there may be the problem that such a chain has some difficulties to run low-noise and smoothly through the derailleur. In particular, there would be the problem that the operation is very noisy and buckling. Accordingly, it is an object of the present invention to provide a pulley for a bicycle rear derailleur with silencing characteristics which is very low-noise in operation and runs very smoothly also with flattop chains.

The above object and further objects which will become apparent hereinafter are achieved by a pulley having the features of claim <NUM>.

The present invention also provides for a rear derailleur of a bicycle according to claim <NUM> including the pulley of the invention.

Further advantageous features are set out in the dependent claims.

According to the invention, the pulley is for a bicycle rear derailleur. Such a derailleur usually comprises, as is known in the art, a guide pulley and a tension pulley both being rotatably mounted on a derailleur cage which is movable with respect to the bicycle and adapted to guide and tension a bicycle roller chain in an S-shape feeding to the cassette. The cage can be positioned under the desired sprocket of a multi-gear cassette attached to the hub of a rear wheel of a bicycle by an arm that can swing back and forth under the sprockets. Gear shifting is carried out by moving the arm which transfers the chain from one sprocket to another while pedaling.

According to one aspect of the invention, the pulley includes respective circumferential supports formed adjacent to or in each side face of the pulley, wherein a respective cushioning ring is formed on or in a respective circumferential support. In a side view of the pulley, as seen in the axial direction of the pulley, each cushioning ring has a polygonal outline at the external side thereof, i.e. the face thereof facing the roller chain, and is provided by molding thereof at the circumferential support, wherein the number of corners of the polygon is equal to the number of teeth of the pulley and wherein the corners of the polygon are angularly offset from the centers of the teeth of the pulley by the half angular distance between adjacent teeth of the pulley in the mounted state of the cushioning ring having the polygonal outline.

The circumferential support may be embodied as extending axially away from the side face of the pulley or as a circumferential recess in the side face of the pulley. It is also envisaged that the circumferential support is embodied as combination of sections extending axially away from the side of the pulley and circumferentially recessed sections in the side of the pulley. Any circumferential recess may be embodied, at least in part, as a through opening in the pulley.

In the specification, whenever the terms "radial direction" and "axial direction" are respectively used, they intend the radial and the axial directions of the pulley.

Furthermore, in the present specification, the cushioning ring having a polygonal outline at the face thereof facing the roller chain, will be designated as polygonal cushioning ring.

According to the invention, the polygonal cushioning ring having a polygonal outline provided by molding of the polygonal cushioning ring on the circumferential support should be understood as a polygonal cushioning ring developing said polygonal outline due to the molding step, so that the polygonal outline of the polygonal cushioning ring is present in a completed state of or after the molding step.

In the specification, whenever the polygonal cushioning ring is being referred to as being present in a mounted state, this reference should indicate that the polygonal cushioning ring is present on the circumferential support of the pulley after the molding step.

The molding may be performed as by overmolding of the polygonal cushioning ring on the circumferential support of the pulley (and in this case the pulley and circumferential ring are preformed outside the mold) or it may be performed by means of two consecutive molding steps, wherein in a first molding step the pulley including the circumferential support is molded and wherein in a second molding step the polygonal cushioning ring is also formed by molding on the circumferential support. Overmolding and two step molding are well known in the art and will not be described in detail hereinafter. The term "molding" as used herein intends any type of molding, including injection molding, suitable to form the pulley with the circumferential support and/or the polygonal cushioning ring made of the materials described hereinbelow.

Further, the term "outline" is intended to cover manufacturing tolerances or polygons with slightly rounded corners or polygons with otherwise slightly modified corners or polygons with small indentations or modifications in the straight portions.

The polygonal cushioning rings are provided by molding on the respective circumferential support in a rotationally secured manner. The circumferential supports may be advantageously made in one piece with the pulley, for instance in a molding step if the pulley is made of a plastic material or in a metal working step if the pulley is made of metal. Alternatively, particularly if the circumferential supports extend from the pulley, the circumferential supports may be fixedly joined with the pulley. In a further alternative, one of the circumferential supports may be formed in one piece with the pulley and another circumferential support may be fixedly joined to the pulley.

Advantageously, as the polygonal cushioning ring has a polygonal outline at the face facing the roller chain, the outline of the circumferential support may have any shape, as long as the outline of the circumferential support conforms the outline of the polygonal cushioning ring at the face thereof facing the circumferential support. In this way, a decoupling of the shape of the outline of the circumferential support from the shape of the outline of the polygonal cushioning ring at the face facing the roller chain is achieved, as seen in the axial direction.

In view of the decoupling of the respective shapes discussed above, the amount of the material of the polygonal cushioning ring may be increased or adjusted as need be. By increasing the amount of material of the polygonal cushioning ring a more silent operation of the pulley can be achieved as compared to solutions, wherein the cushioning ring is elastically retained on a support and conforms exactly to the outline of the support.

Further, in view of the above discussed decoupling of the respective shapes, the circumferential support may have a different outline, as seen in the axial direction, than the outline of the polygonal cushioning ring at its face facing the roller chain, as seen in the axial direction, as far as shape and/or angular orientation is concerned.

In one embodiment, the circumferential support may have a circular or an elliptical or any outline different from the outline of the polygonal cushioning ring at its face facing the roller chain, as seen in the axial direction. Preferred in terms of manufacturing is a circular or an elliptical outline.

The outline of the circumferential support may be continuous or interrupted and the circumferential support may extend from the pulley or be provided as a circumferential recess in the pulley. Also, combinations, wherein sections of the circumferential support extend from the pulley and sections of the circumferential support are provided as circumferential recesses in the pulley are envisaged. Any circumferential recess can be provided, at least in part, as a through opening in the pulley.

It is also imaginable that the outline of the circumferential support and the outline of the polygonal cushioning ring at the face facing the roller chain, as seen in the axial direction, describe the same geometrical form, i.e., a polygon, but have a different angular orientation. In other words, the shape of the outline of the polygonal cushioning ring at the face facing the roller chain, as seen in the axial direction, may be angularly offset with respect to the shape of the outline of the circumferential support, as seen in the axial direction.

As the outline of the circumferential support, as seen in the axial direction, is freely selectable, as compared to conventional solutions, the degree of rotational security of the polygonal cushioning ring can be adjusted according to the requirements by the free choice of the outline of the circumferential support.

Inasmuch as, the corners of the polygon are angularly offset from the center of the teeth of the pulley, the polygonal cushioning rings have respective straight portions, each straight portion extending under one respective tooth of the pulley and being angularly aligned with the respective tooth of the pulley.

The angular offset of the polygon corners from the teeth is particularly suitable in cases, wherein the derailleur is intended for chains of an unconventional type, wherein tops of the link plates are straight-line which enables a narrower chain construction with increased strength and durability. Such chains are known in the art as AXS or "flattop" chains and are manufactured by the SRAM corporation.

The inventive pulley with polygonal cushioning rings is particularly suited when embodied as a guide pulley of a rear derailleur in conjunction with AXS "flattop" chains devised as mentioned above. In a rear derailleur, the chain is running with the straight tops (flattops) over the guide pulley and the straight tops are perfectly matching the straight portions of the polygonal cushioning ring of the guide pulley. Accordingly, the impact of the chain on the guide pulley is smooth and silent.

While the polygonal cushioning ring according to the invention is particularly advantageous for the guide pulley of a bicycle rear derailleur if used with AXS "flattop" chains, also the tension pulley of a bicycle rear derailleur may advantageously have a polygonal cushioning ring if interacting with the flattop of a "flattop" type chain.

Preferably, the circumferential support, if embodied as extending from the side face of the pulley, may also include a radial extension which extends outwardly in a radial direction from the circumferential support and which forms preferably a flange extending upwardly from the circumferential support.

According to the invention antirotation means are provided for securing the polygonal cushioning ring against a rotation with respect to the circumferential support.

Said antirotation means may be designed as at least one recess extending in the radial direction (in the following radial recess) in the circumferential support with a corresponding protrusion extending in the radial direction (in the following radial protrusion) of material in the polygonal cushioning ring fitting into said recess and/or as at least one radial recess in the polygonal cushioning ring with a corresponding radial protrusion of material in the circumferential support fitting into said radial recess.

Alternatively, said antirotation means may be provided by means of a sinuous or cornered outline of the circumferential support, as seen in the axial direction, and a corresponding inner shape of the polygonal cushioning ring at the face facing the circumferential support.

Also, any complementary shapes, as long as such shapes provide for a rotational security, may be provided. Such complementary shapes may include polygonal shapes, like triangular, square, pentagonal, hexagonal, heptagonal, octagonal, but are not limited to the same.

If the circumferential support is designed in the shape of a polygon, as seen in the axial direction, the corners of the circumferential support can be rounded. The corners of the radial extension of the circumferential support may also be rounded.

The circumferential support and the radial extension may be made in one piece with the pulley, for instance by molding of by metal working. Alternatively, they may be manufactured separately and fixedly joined to the pulley. In a further alternative, the circumferential support and the radial extension at one side of the pulley may be made in one piece with the pulley and the circumferential support and the radial extension at another side of the pulley may be fixedly joined to the pulley.

Each polygonal cushioning ring may advantageously project radially from the radial extension of the circumferential support, preferably by at least <NUM>/<NUM> of the total radial height of the polygonal cushioning ring and more preferably by at least <NUM>/<NUM> of the total radial height of the polygonal cushioning ring.

The straight portions of the polygonal cushioning ring dampen the impact of the chain rollers on the depressions or valleys between consecutive teeth. As known in the art, the depressions or valleys are formed between consecutive teeth of a pulley as seen in the axial direction. Advantageously, the straight portions of the cushioning ring prevent, at least during the initial contact of the chain with the pulley, the contact of the chain rollers with the depressions or valleys between consecutive teeth, such that the polygonal cushioning ring is contacted only by the link plates of the chain. As straight portions of the polygonal cushioning ring are decoupled from the outline of the underlying circumferential support, the amount of cushioning material can be increased and accordingly the silencing or cushioning effect is improved.

The polygonal cushioning rings may have well known cross sections, for example square, rectangular or circular. In a preferred embodiment of the invention each polygonal cushioning ring comprises, at least on its side facing the roller chain, a groove extending along its entire perimeter length, which groove, as seen in a cross-sectional view through the polygonal cushioning ring, is a recess flanked by two protrusions, wherein the protrusions are adapted and orientated to come in contact with outer and inner link plates, respectively, of a roller chain running over the pulley. This further contributes to make the derailleur very silent and smooth running, because by the two protrusions which may be much narrower than the total width of the outer and inner link plates, relatively weak dampening forces can be provided.

In the above preferred embodiment, in a cross-sectional view through the polygonal cushioning ring the protrusions on each polygonal cushioning ring may be curved convexly and may be connected contiguously by the recess which is curved concavely, as seen from inside the polygonal cushioning ring.

The invention is suited for a special form of a bicycle rear derailleur wherein the pulleys are rotatably mounted to the cage by mounting means and an interposed radial bearing, wherein the mounting means are arranged so as to be spaced from the center of rotation of the pulleys and are positioned along a circular mounting opening provided in the cage spaced away from the center of rotation of the pulleys, so as to leave a free space in the center of the pulleys in its mounted state, as described in <CIT>.

The invention is also suited for common bicycle rear derailleurs, wherein, for instance, the pulleys are rotatably mounted between two lateral plates of the cage on central bearings which are fitted on central bolts which connect two lateral plates of the cage to each other.

The polygonal cushioning ring may be made from any elastically deformable material, like natural or synthetic rubber, polymer or elastomer or silicone or mixtures of the foregoing materials having a sufficient dimensional stability to maintain the polygonal outline in the mounted state thereof, i.e., after the molding step of the polygonal cushioning ring on the circumferential support, and in use. The pulley can be made of plastic, metal or a reinforced composite, in particular polyamide reinforced with carbon fiber.

The above and other features of the invention will become apparent from the following description of preferred embodiments, given by way of non-limiting example with reference to the accompanying drawings, wherein:.

Conventionally, pulleys of a rear derailleur may be rotatably mounted between two lateral plates of a cage on central bearings which are fitted on central bolts which connect two lateral plates of the cage to each other.

Pulleys as shown and described herein may also be mounted by mounting means (and not by central bolts) and an interposed radial bearing, wherein the mounting means are arranged so as to be spaced from the center of rotation of the pulley. The mounting means are positioned along a circular mounting opening provided in the cage spaced away from the center of rotation of the pulley. Such a bearing, which may be a ball bearing, a roller bearing or a slide bearing, may have a much larger radius than conventional bearings of the pulleys of a rear derailleur. The cage can be a single-plate or a two-plate cage. Such a bearing can be arranged so as to leave a free space in the center of the guide pulley in its mounted state, which provides for a free space which works against the accumulation of dirt because rotating pulley structural arms have been eliminated, and the chain guide is easy to clean. In addition, the free space, if provided at least in the center of the tension pulley, provides for a totally new and impressive look of the derailleur. With respect to this, reference is made to the pertinent teachings of a former patent application of the applicant of the present invention having the title "Improved chain guide for a rear derailleur of a bicycle" filed on <CIT>.

<FIG> is a schematic view of the rear part of a bicycle having a rear derailleur <NUM> which comprises a tension pulley <NUM> and a guide pulley <NUM> mounted at a cage <NUM>. The pulleys <NUM> and <NUM> may optionally each have a free space in their center. The rest of the derailleur <NUM> is shown only schematically. The cassette is shown also schematically at reference number <NUM>.

Pulleys as shown and described herein may be rotatably mounted between two lateral plates of a cage on central bearings which are fitted on central bolts which connect the two lateral plates of the cage to each other, or rotatably mounted on central bearings which are fitted on a single-plated cage.

Pulleys as shown and described herein may also be rotatably mounted between two lateral plates of a cage by mounting means (and not by central bolts) and an interposed radial bearing, wherein the mounting means are arranged so as to be spaced from the center of rotation of the pulley, as it is the case in <CIT>. Also, in this case the cage may be a single-plated cage, as described in <CIT>.

With reference to <FIG>, a first preferred embodiment of a pulley of a rear derailleur for a bicycle is described.

As shown therein, a pulley <NUM>, which is shown as a guide pulley but may also be embodied as a tension pulley, has a plurality of teeth <NUM> adapted to come in contact with link members of a roller chain <NUM> running over the pulley <NUM> (as partially shown in <FIG> and <FIG>). The roller chain <NUM> has, as well known in the art, outer link plates 23a, inner link plates 23b und chain rollers 23c held between the inner and outer link plates about respective pins.

The pulley <NUM> carries on each of its axial side faces a polygonal cushioning ring <NUM> made of an elastically deformable material like natural or synthetic rubber, polymer or elastomer or silicone or mixtures thereof. The polygonal cushioning ring <NUM> made of such material has a polygonal shape which is present in the polygonal cushioning ring <NUM> in the mounted state thereof, i.e., after the molding step of the polygonal cushioning ring <NUM> onto the circumferential support <NUM>. The material is also such as to maintain the shape of the polygonal cushioning ring <NUM> in use. The pulley <NUM> can be made of plastic, metal or a reinforced composite, in particular polyamide reinforced with carbon fiber.

As is best seen in <FIG> as well as <NUM> and <NUM>, each polygonal cushioning ring <NUM> is supported by and accommodated on a circumferential support <NUM> formed adjacent to each side face to the pulley <NUM> and extending axially from the pulley <NUM>. In a side view of the pulley <NUM>, the polygonal cushioning ring <NUM> has a polygonal outline, wherein the number of corners of the polygon is equal to the number of teeth <NUM> of the pulley <NUM>. The corners of the polygon are, in the shown mounted state, angularly offset from the centers of the teeth <NUM> of the pulley <NUM> by the half angular distance between adjacent teeth <NUM> of the pulley <NUM>.

In the view of <FIG>, which is taken along the cross section at line <NUM>-<NUM> of <FIG>, the extension of the polygonal cushioning ring <NUM> in the radial direction is larger than the extension of the polygonal cushioning ring <NUM> in the radial direction shown in <FIG>, which is taken at the cross section at lines <NUM>-<NUM> of <FIG>. This is due to the preferred circular outline of the circumferential support <NUM> shown in <FIG>. Obviously, the extension of the polygonal cushioning ring <NUM> in the radial direction will vary according to the outline of the circumferential support <NUM>, in view of the polygonal outline of the polygonal cushioning ring <NUM> at the face facing the roller chain <NUM>.

<FIG> shows a view similar to <FIG>, which is taken along the cross section of line <NUM>-<NUM> of <FIG>. As distinct to <FIG>, the cross section also shows the engagement of the pulley with the roller chain <NUM>.

Although in the embodiments of <FIG> the circumferential support <NUM> is shown as an element extending axially, i.e. in an axial direction, away from the face of the pulley <NUM>, the circumferential support may also be embodied as a circumferential recess in the side face of the pulley <NUM>. It is also envisaged that the circumferential support is embodied as combination of sections extending axially away from the pulley and circumferentially recessed sections in the pulley. Any circumferential recess may be embodied, at least in part, as a through opening in the pulley.

The circumferential support <NUM> of <FIG> may be formed as a continuous shoulder. Preferably, a radial extension <NUM> is provided extending in a radial direction extending outwardly from the circumferential support <NUM>, such that a seating for the link plates of the roller chain <NUM> in the polygonal cushioning ring <NUM> is defined between the side face of pulley <NUM>, the radial extension <NUM> and the circumferential support <NUM>.

While in the embodiment shown in the <FIG> the radial extension <NUM> is shown as having a polygonal outline, as seen in the axial direction, the person skilled in the art will appreciate that other outlines, as seen in the axial direction, like a polygonal outline with rounded corners, a circular outline, a wave shape outline, a cornered outline or any other outline providing for the required degree of axial retention of the polygonal cushioning ring <NUM> may be provided. The radial extension <NUM> in any of the foregoing variations may be provided in portions only of the circumferential support <NUM>. The circumferential support <NUM> may be a continuous shoulder or interrupted.

Preferably, the circumferential support <NUM> has an essentially circular outline, as seen in the axial direction, as can be best seen on <FIG>. Nevertheless, the circumferential support <NUM> may have other outlines, as seen in the axial direction, as long as the outline or its angular orientation is different from the outline of the polygonal cushioning ring <NUM> at its face facing the roller chain <NUM>. A particularly advantageous outline, in addition to the circular outline, is the elliptical outline. A further advantageous outline is a polygonal outline with rounded corners, as seen in the axial direction.

Also, the circumferential support embodied as a circumferential recess may have any of the foregoing polygonal shapes and/or extensions.

The circumferential support <NUM> comprises antirotation means <NUM> which in the embodiment of <FIG> are shown as radial recesses. Nevertheless, the person skilled in the art will appreciate that the antirotation means <NUM> can be embodied as radial protrusions. Furthermore, although <FIG> shows four antirotation means <NUM>, the person skilled in the art will appreciate that the number of antirotation means <NUM> can be variated to provide that the desired antirotation feature is sufficiently implemented. Same is true if the antirotation means <NUM> are implemented as radial protrusions. The matching antirotation means on the polygonal cushioning ring <NUM> is referenced by numeral <NUM> and is subject to the same variations as the antirotation means <NUM> of the circumferential support <NUM>.

Furthermore, the antirotation means can be provided by means of any complementary shapes in the circumferential support <NUM> and the polygonal cushioning ring <NUM>. For instance, the antirotation means can be provided in the shape of a wave or as cornered elements or in the shape of saw tooth or as crenelations. Also, combinations of different types or antirotation means may be provided.

Preferably each polygonal cushioning ring <NUM> projects radially from the radial extensions <NUM> by at least approximately <NUM>/<NUM> of a total radial height of the polygonal cushioning ring <NUM> or by at least <NUM>/<NUM> of a total radial height of the polygonal cushioning ring <NUM>. Advantageously, the compressibility and height of the polygonal cushioning ring <NUM> has to be chosen so that in operation the link plates of the roller chain <NUM> may contact the polygonal cushioning ring <NUM> but not the radial extensions <NUM>.

<FIG> are respective enlarged sectional views of a radial outer part of the pulley along the line <NUM>-<NUM> in <FIG>, i.e., through the gap between two consecutive teeth of the pulley and through the antirotation means, and along the line <NUM>-<NUM> in <FIG> through the center of a tooth where the antirotation means are missing. Due to the missing antirotation means in <FIG>, the circumferential support <NUM> is larger. Further, in a similar manner to <FIG>, the respective cross sections of the polygonal cushioning ring <NUM> have different extensions in the radial direction.

As seen best in <FIG>, preferably, the polygonal cushioning ring <NUM> comprises, at its side facing the roller chain <NUM>, one groove extending along its entire perimeter length. Advantageously, the groove, as seen in a cross-sectional view through the polygonal cushioning ring <NUM>, is provided by a recess <NUM> flanked by the two protrusions <NUM>, wherein the protrusions <NUM> are adapted and orientated to come in contact with outer and inner link plates, respectively, of the roller chain <NUM> running over the pulley <NUM>. Preferably, additional grooves can be provided at the lateral faces of the polygonal cushioning ring <NUM> facing the radial extension <NUM> and/or the pulley <NUM>, respectively.

Further preferably, the protrusions <NUM> are devised as convexly curved protrusions and the recess <NUM> is devised as a concavely curved recess, as seen from inside the polygonal cushioning ring <NUM>. The convexly curved protrusions <NUM> are connected contiguously by the concavely curved recess <NUM>. Accordingly, the polygonal cushioning ring <NUM> is molded onto the pulley <NUM> in a manner and orientation in which the two curved protrusions <NUM> and the one concavely curved recess <NUM> partially face the outer and inner link plates, respectively, of a roller chain <NUM> running over the pulley <NUM>. The inner protrusion <NUM> is able to contact and dampen the inner link plates of the roller chain <NUM>, and the outer protrusion <NUM> is able to contact and dampen the outer link plates of the roller chain <NUM>.

Generally speaking, the function of the groove at the face of the polygonal cushioning ring <NUM> facing the roller chain <NUM> is to dampen the forces produced by chain members running from the slack span of the roller chain <NUM> onto the pulley <NUM> in a smooth and well-defined manner and with fewer losses than cushioning rings having conventional annular or rectangular cross sections.

Otherwise, the cross section of the polygonal cushioning ring <NUM> shown in <FIG> may have three even sides.

As shown in the embodiment of <FIG>, the polygonal cushioning rings <NUM> comprise a number of straight portions being equal to the number of teeth <NUM> of the pulley <NUM> and the straight portions are angularly aligned with one respective tooth <NUM> in the mounted state of the polygonal cushioning rings <NUM>.

With reference to <FIG>, a second preferred embodiment of a pulley of a rear derailleur for a bicycle is described, wherein the radial extension <NUM> is omitted. Otherwise, the second embodiment of <FIG> is the same as the first embodiment of <FIG> and the detailed description thereof is omitted.

In the side view of <FIG> the preferred antirotation means are shown in dashed lines in the circumferential support <NUM>. As the radial extension <NUM> is omitted, the preferred circular outline of the circumferential support <NUM> is visible. Further, in the enlarged view of <FIG>, the chain roller <NUM> is omitted.

Although in the embodiments of <FIG> the circumferential support <NUM> is shown as an element extending axially, i.e. in an axial direction, away from the face of the pulley <NUM>, the circumferential support may also be embodied as a circumferential recess in the side face of the pulley <NUM>. It is also envisaged that the circumferential support is embodied as combination of sections extending axially away from the pulley and circumferential recessed sections in the pulley. Any circumferential recess may be embodied, at least in part, as a through opening in the pulley.

The embodiments of <FIG> are particularly suited when embodied as a guide pulley of a rear derailleur. Such a rear derailleur would be suited for chains <NUM> of a special type wherein the tops of the link plates are straight-line (flattops) which are known as AXS chains, as mentioned above. In a rear derailleur, the chain <NUM> is running with the straight tops over the guide pulley <NUM>, as seen from <FIG> or <FIG>, and the straight tops are perfectly matching the straight portions of the polygonal cushioning ring <NUM> of the guide pulley <NUM>. Accordingly, the impact of the chain <NUM> on the pulley <NUM> is smooth and silent.

The tension pulley <NUM> of such rear derailleur may be of any known type or may be or a similar type as described herein. In operation, the conventional part of the link plates of the AXS chain <NUM> will interact first with the tension pulley <NUM> and subsequently in a reverse orientation over the guide pulley <NUM>, where the straight tops of the link plates of the chain <NUM> will cooperate with the straight portions of the guide pulley <NUM>. Thus, the impact of the chain <NUM> at both pulleys is silent and smooth.

In the embodiments of <FIG>, the pulley <NUM> is of a type having a free space <NUM> in its center, as described in <CIT>. In this case the pulley <NUM> will be mounted by mounting means (not shown) via an interposed roller bearing <NUM> to a single-plated cage of the rear derailleur. However, any conventional guide or tension pulley for a rear derailleur of a bicycle, wherein for instance the pulleys are rotatably mounted between two lateral plates of the cage on central bearings which are fitted on central bolts which connect two lateral plates of the cage to each other are envisaged as to be included in the scope of the present invention, as defined by the appended claims.

The disclosure of the present invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless indicated otherwise herein.

Where technical features mentioned in any claim are followed by reference signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, neither the reference signs nor their absence have any limiting effect on the technical features as described above or on the scope of any claim elements.

Claim 1:
A toothed pulley (<NUM>) for a bicycle rear derailleur (<NUM>), the pulley (<NUM>) carrying on each of its side faces a cushioning ring (<NUM>) made of an elastically deformable material and adapted to come in contact with link plates of a roller chain (<NUM>) running over the pulley (<NUM>), wherein
the pulley (<NUM>) includes respective circumferential supports (<NUM>) formed adjacent to or into each side face to the pulley (<NUM>), characterized in that
each cushioning ring (<NUM>) is supported in a rotationally secured manner at a respective circumferential support (<NUM>), and in that
in a side view of the pulley (<NUM>), as seen in the axial direction, each cushioning ring (<NUM>) is a polygonal cushion ring (<NUM>), having a polygonal outline at the face thereof facing the roller chain (<NUM>) and is provided by molding on the circumferential support (<NUM>), wherein the number of corners of the polygonal cushioning ring (<NUM>) is equal to the number of teeth (<NUM>) of the pulley (<NUM>), and wherein the corners of the polygonal cushioning ring (<NUM>) are angularly offset from the centers of the teeth (<NUM>) of the pulley (<NUM>) by the half angular distance between adjacent teeth (<NUM>) of the pulley (<NUM>).