Sprocket carrier and sprocket carrier and gear shifting disc subassembly for a bicycle rear wheel

Abstract

A sprocket carrier and a subassembly of a sprocket carrier and a gearshift disc for a rear wheel of a bicycle are provided. The gearshift disc (20) has the first n sprockets (26a, 26b, 26c), where 6≥n≥3, which are fixedly connected to one another to form an integral kit (26), which is adapted to be directly positively engaged with a coupling profile (16) formed on the radially outer peripheral surface of a sprocket carrier (14) by means of a coupling profile (32) formed on the radially inner surface of at least the largest sprocket (26a) of the kit (26). The direct positive connection between the largest sprocket (26a) of the kit (26) and the sprocket carrier (14) and the fact that this direct connection is made between the radially outer peripheral surface of the sprocket carrier (14) and the radially inner surface of the largest sprocket (26a) of the kit (26) (or the largest sprocket) make it possible to have a very high robustness and coupling rigidity, thereby ensuring maximum actuation accuracy of a transmission using the subassembly.

Description

Technical Field

[0001] The present invention relates to a sprocket carrier and a subassembly for a bicycle rear wheel, the subassembly being formed by the sprocket carrier and a shifting disc, the shifting disc being coaxially mounted on the sprocket carrier by shape engagement of the shifting disc on a coupling contour formed on the radial outer peripheral surface of the sprocket carrier and extending in the axial direction. Background Art

[0002] . In the following, spatial indications (especially radial, axial and circumferential) will be given with reference to the axis of rotation of the rear wheel of the bicycle, which axis of rotation coincides with the axis of the gearshift plate, the axis of the sprocket carrier, the axis of the hub of the wheel and generally the axes of all elements rotating with the wheel. Furthermore, an axial direction will be indicated towards the outside if it is away from the longitudinal median plane of the bicycle or away from the hub of the wheel; conversely, an axial direction will be indicated towards the inside if it is towards such median plane or towards the hub. Furthermore, in radial directions, an orientation away from the axis of rotation will be indicated as peripheral; conversely, an orientation towards the axis of rotation will be indicated as internal.

[0003] In order to mount the gearshift disc on the hub of the rear wheel of a bicycle, a so-called sprocket carrier is usually used, which is made on one side to rotate as a unit with the sprocket by a form coupling and on the other side to rotate as a unit with the hub (however, in a unidirectional manner) by a set of ratchets or the like (usually called freewheels). In this way, the transmission chain engaged with the various sprockets is able to transmit torque to the hub in the forward direction of the bicycle.

[0004] The sprocket carrier consists essentially of a tubular body which, at its radially outer peripheral surface, is mechanically coupled to a central mounting opening made in the sprocket. The radially outer peripheral surface of the sprocket carrier is shaped with substantially axial ribs and grooves alternating in the circumferential direction, which are suitable for allowing coupling of the aforementioned shape. To this end, the central mounting opening of the sprocket is provided with a radially inner extension or projection (i.e. pointing towards the axis of rotation), which is coupled to a groove present on the sprocket carrier.

[0005] .Thus, the sprockets are axially mounted on the sprocket carrier in sequence starting with the sprocket with the largest diameter, so that when the sprocket carrier is mounted on the hub of a wheel of a bicycle, the sprocket with the largest diameter is positioned toward the inside, i.e., close to the rear wheel, while the sprocket with the smallest diameter is positioned toward the outside.

[0006] In most modern bicycle transmissions, especially for bicycles intended for racing, there is a well-known trend towards increasing the number of sprockets. When the gearbox reaches 11, 12 or even more sprockets, it is possible to have no front derailleur; this simplifies the bicycle and makes it lighter, which is undoubtedly advantageous for the cyclist, as long as this is not accompanied by a negative impact on the availability of gear ratios.

[0007] To achieve this result, it is necessary to have small sprockets in the shift plate with a very small number of teeth, such as 10 or 9. However, a reduction in the number of teeth is obviously accompanied by a reduction in diameter, which may eventually make the diameter too small to fit on a conventional sprocket carrier.

[0008] .Thus, a gearshift disc has been realized in which the smallest sprockets are made fixedly connected to one another to form a one-piece set (also called a duplex, triplex or quadruplex, precisely because it groups two, three or four sprockets together), and the central opening for mounting on the sprocket carrier extends axially only at the largest sprocket of the set; the smallest sprockets extend more toward the axis of rotation, but do not engage directly with the sprocket carrier, since their movement can be ensured by the fact that they are fixedly connected to the largest sprocket of the set. In this way, the smallest sprocket of the set can have 10 teeth or even fewer; on the other hand, the largest sprocket of the set must have at least 11 teeth in order to engage with the sprocket carrier.

[0009] .Therefore, there are constraints that reflect the practical possibilities of manufacturing. For example, in the case of a duplex (one-piece set of two sprockets), it is necessary to have a first sprocket with 10 teeth (and not 9 or less) or to accept a tooth difference between the first and second sprocket equal to or greater than 2; however, this condition does not suit cyclists who are usually accustomed to a difference of a single tooth between the smallest adjacent sprockets.

[0010] In some cases, in an attempt to manage the constraints imposed by specific conditions, form couplings with projections or teeth extending in the axial direction between the largest sprocket of the one-piece set and the sprocket carrier, or couplings by threads that engage differently between the one-piece set and the sprocket carrier, are used. However, these couplings do not ensure the same robustness as form couplings with grooved profiles.

[0011] .Therefore, there is a need for greater flexibility in selecting the number of teeth of the smallest sprocket of the gear shifting plate. Summary of the invention

[0012] Thus, the present invention in its first aspect relates to a gear shifting disc for a bicycle rear wheel; in its second aspect, the present invention relates to a subassembly for a bicycle rear wheel. Preferred features of the gear shifting disc and the subassembly are also given in the description.

[0013] .More particularly, according to the first aspect of the present invention, the speed change plate includes a plurality of axially adjacent sprockets between a first sprocket having the smallest number of teeth and a last sprocket having the largest number of teeth, wherein the first n sprockets (wherein 6≥n≥3) are fixedly connected to each other to form an integrated kit, wherein the integrated kit is suitable for directly shape-engaging with a coupling profile formed on the radially outer peripheral surface of the sprocket carrier through a coupling profile formed on the radially inner surface of at least the largest sprocket of the integrated kit.

[0014] . Having at least three sprockets grouped as a one-piece set makes it possible to have a sprocket with 11 teeth suitable for direct engagement on the sprocket carrier and two or more smaller sprockets suspended; thus, the first sprocket can have as few as 9 teeth (or less), without having to accept a difference of more than 1 between the number of teeth of the adjacent smallest sprockets. Furthermore, the fact that a direct positive connection is provided between the largest sprocket of the one-piece set and the sprocket carrier, and the fact that this direct connection is made between the radially outer peripheral surface of the sprocket carrier and the radially inner surface of the largest sprocket of the one-piece set (or the largest sprocket), makes it possible to have a very high solidity and rigidity, thus ensuring maximum actuation precision of the transmission using the subassembly, which is comparable to the precision of a transmission in which the sprockets of the gearshift disc are all mounted separately and directly so as to rotate as a unit on the sprocket carrier.

[0015] Preferably, the first sprocket has 10, 9 or even 8 teeth. Very long gear ratios of the transmission can thus be achieved.

[0016] Preferably, the number n of sprockets of the one-piece kit is equal to 3, 4, 5 or even 6. The greater this number n, the greater the flexibility in choosing the number of teeth per sprocket and therefore the gear ratio.

[0017] In the case of a one-piece kit having five sprockets, the coupling contour between the one-piece kit and the sprocket carrier is preferably formed on the radially inner surfaces of the two largest sprockets of the one-piece kit.

[0018] In the case of a one-piece kit having six sprockets, the coupling contour between the one-piece kit and the sprocket carrier is preferably formed on the radially inner surfaces of the three largest sprockets of the one-piece kit.

[0019] These features make it possible to maintain the robustness and rigidity of the connection between the sprockets of the one-piece kit and the sprocket carrier even in the case of a relatively high number n of sprockets of the one-piece kit.

[0020] Preferably, the speed change plate comprises 12, 13 or even 14 sprockets. The invention is indeed particularly noteworthy when the number of sprockets is greater than 11.

[0021] .According to a second aspect of the invention, a subassembly includes a sprocket carrier and a shift plate coaxially mounted on the sprocket carrier, wherein the shift plate includes a plurality of axially adjacent sprockets between a first sprocket having a smallest number of teeth and a last sprocket having a largest number of teeth, wherein the first n sprockets (wherein 6≥n≥3) are fixedly connected to each other to form an integrated kit, and wherein the integrated kit is directly shape-engaged with a coupling profile formed on a radially outer peripheral surface of the sprocket carrier via a coupling profile formed on a radially inner surface of at least the largest sprocket of the integrated kit.

[0022] Preferably, the one-piece sleeve comprises an axial abutment surface which is brought into abutting engagement with a corresponding outer axial abutment surface of the sprocket carrier. This allows for an accurate and stable axial positioning of the one-piece sleeve relative to the sprocket carrier.

[0023] .Preferably, the sprocket carrier includes a radially inner threaded portion.

[0024] Preferably, the subassembly further comprises a ring nut having a threaded portion which is screwed into the radially inner threaded portion of the sprocket carrier.

[0025] The attachment via the ring nut ensures a stable and precise positioning of the entire shift plate on the sprocket carrier in the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the accompanying drawings. In such drawings:

[0027] . Figure 1 is a perspective view of a hub of a bicycle rear wheel having a subassembly and a shifting plate according to the present invention;

[0028] . Figure 2 yes Figure 1 An axial cross-sectional view of a wheel hub;

[0029] . Figure 3 yes Figure 2 an enlarged cross-sectional view of a portion of a wheel hub;

[0030] . Figure 4 yes Figure 1 A perspective view of a subassembly of with parts removed to better illustrate the one-piece kit of the sprocket carrier and the smallest sprocket;

[0031] . Figure 5 yes Figure 4 A perspective view of the one-piece kit only is shown;

[0032] . Figure 6 and Figure 7 It is a stereogram of the variant of the one-piece kit from different angles;

[0033] . Figure 8 yes Figure 6 and Figure 7 A cross-sectional view of the integrated kit. DETAILED DESCRIPTION

[0034] . Figure 1 The hub 10 of the hub assembly 1 (not shown) of a bicycle rear wheel is shown, which is coaxially mounted on a pin 11 by means of a bearing 12; the hub 10 is thus free to rotate on the pin 11, while the pin 11 is intended to be fixedly mounted on the frame of the bicycle.

[0035] The wheel hub 10 is coupled to a sprocket carrier 14 via a freewheel mechanism (not highlighted), which ensures that the wheel hub 10 is set to rotate via the sprocket carrier 14 only in the direction determining the forward movement of the bicycle and not in the opposite direction. The sprocket carrier 14 has an approximately tubular shape and is freely mounted on the pin 11 by means of a bearing 15. The sprocket carrier 14 is provided on its radially outer peripheral surface with a coupling profile formed by grooves 16 arranged in the axial direction. Furthermore, the sprocket carrier 14 is provided near its axially inner end with an end stop 18 in the form of teeth protruding from the sprocket carrier 14 in the radial direction; alternatively, a flange extending along the entire circumference of the sprocket carrier 14 can be provided as the end stop 18 instead of the teeth.

[0036] The sprocket carrier 14 has a substantially annular axial abutment surface 17 at its outer axial end.

[0037] The speed change plate 20 is mounted on the sprocket carrier 14 to form a subassembly 2. The speed change plate 20 shown includes 12 sprockets arranged in order from the largest to the smallest as follows: the three largest sprockets 21a, 21b, 21c are made to be fixedly connected to each other to form an integral kit (or a triple piece) 21; the next three sprockets 22a, 22b, 22c are made to be fixedly connected to each other to form an integral kit (or a triple piece) 22; the next three sprockets 23, 24, 25 are independent of each other; and the three smallest sprockets 26a, 26b, 26c are made to be fixedly connected to each other to form an integral kit (or a triple piece) 26. These elements are peripherally mounted on the sprocket carrier 14, wherein the integral kit 21 is axially arranged at the end stop 18, the integral kit 22 is axially arranged at the integral kit 21, the sprocket 23 is axially arranged at the integral kit 22, the sprocket 24 is axially arranged at the sprocket 23, the sprocket 25 is axially arranged at the sprocket 24, and the integral kit 26 is axially arranged at the sprocket 25.

[0038] .The one-piece kits 21, 22 and the sprockets 23-25 ​​are slotted into the sprocket carrier 14 and are constrained in rotation relative to the sprocket carrier 14, but are essentially free in the axial direction; the rotational constraint is ensured in a conventional manner per se by grooves 16 engaging with corresponding protrusions (not visible in the drawings) on the radially inner surfaces of the one-piece kits 21, 22 and the sprockets 23-25.

[0039] As described above, in the subassembly 2 formed by the sprocket carrier 14 and the shifting disc 20, 12 sprockets are installed individually or in groups as a one-piece set. In particular, there is a very small sprocket (i.e., sprocket 26c) whose number of teeth is too small to be installed on the sprocket carrier 14 without being grouped into a one-piece set 26. In fact, if this small sprocket is individual, it will be too small to be slotted into the sprocket carrier 14; on the other hand, the one-piece set 26 can have an inner axial portion at the sprocket 26a (with 12 teeth) that is sized to be able to engage on the sprocket carrier 14.

[0040] .Integrated kit 26 (especially in Figures 4 to 814 (see Figure 14 ) comprises, at the largest sprocket 26a, a series of radially inwardly facing projections 32 which as a whole constitute an internally shaped coupling profile formed on the radially inner surface of the sprocket 26a. This coupling profile formed by the projections 32 has a shape corresponding to the shape of the coupling profile formed by the grooves 16 on the radially outer peripheral surface of the sprocket carrier 14. Thus, during installation, the one-piece set 26 is partially slotted onto the sprocket carrier 14, wherein the projections 32 engage in the grooves 16, while the smallest sprockets 26b and 26c of the one-piece set 26 remain axially suspended. This arrangement on the radially outer peripheral surface of the sprocket carrier 14 ensures that the entire one-piece set 26 (and therefore all its sprockets 26a, 26b and 26c) is made to rotate as a unit with the sprocket carrier 14 in a stable and secure manner; thus, any uncertainty in the coupling (i.e. any possibility of angular micro-displacements of the one-piece set 26 relative to the sprocket carrier 14) which would make the operation of the transmission using the subassembly 2 imprecise.

[0041] The one-piece sleeve 26 has a substantially annular axial abutment surface 27 at the inner shape coupling profile formed by the projection 32. The abutment surface 27 abuts against the corresponding axial abutment surface 17 of the sprocket carrier and thus serves as a reference for the axial positioning of the one-piece sleeve 26 to prevent axial sliding thereof.

[0042] Towards the inside in the axial direction (i.e. towards the hub 10), the entire shift disc 20 (i.e. the one-piece sleeves 21, 22 and 26 and the sprockets 23-25) is held by the end stop 18; towards the outside in the axial direction, the shift disc 20 is held by the ring nut 28, plugged onto the pin 11 and screwed to the sprocket carrier 14 by means of the outer threaded portion 29 of the ring nut 28 and the radial inner threaded portion 30 of the sprocket carrier 14. The ring nut 28 has a flange 31 which abuts axially against the outer side surface of the one-piece sleeve 26. The clamping of the ring nut 28 ensures that the entire shift disc 20 is locked on the sprocket carrier 14 by means of the axial pressure exerted on the shift disc 20 by the flange 31 and the end stop 18.

[0043] In use, due to the engagement of the projection 32 in the groove 16, the coupling of the one-piece sleeve 26 to the sprocket carrier 14 is particularly strong and thus ensures a high-precision actuation.

[0044] As mentioned above, Figures 1 to 5 The one-piece set 26 shown comprises the three smallest sprockets 26a, 26b and 26c of the gear shift plate 20. However, according to the invention, the number of sprockets of the one-piece set can also be higher, up to 6. For example, Figures 6 to 8An integrated kit 126 (quadruple) is shown which groups together four smallest sprockets 126a, 126b, 126c and 126d having 12, 11, 10 and 9 teeth respectively.

[0045] In the one-piece set 126, radially inner projections 132 are formed at the two largest sprockets 126a and 126b. Generally, when the number of smallest sprockets grouped as an one-piece set increases, it is possible to ensure that radially inner projections are formed at more than one sprocket in order to increase the robustness of the connection. If the number of smallest sprockets grouped as an one-piece set becomes particularly high (for example 5 or 6), it is undoubtedly preferred to form radially inner projections at more than one sprocket (for example 2 or 3) in order to reduce the axial extension of the suspension part of the one-piece set and thus increase the torsional rigidity of the one-piece set itself; this arrangement also facilitates the actuation accuracy of the transmission using this subassembly.

Claims

1. A gear shifting disc for a rear wheel of a bicycle, the gear shifting disc being adapted to be coaxially mounted on a sprocket carrier (14), the gear shifting disc comprising a plurality of axially adjacent sprockets (21a, 21b, 21c, 22a, 22b, 22c, 23, 24, 25, 26a, 26b, 26c; 126a, 126b, 126c, 126d) between a first sprocket (26c; 126d) having the smallest number of teeth and a last sprocket (21a) having the largest number of teeth, in, The first n sprockets (26c, 26b, 26a; 126d, 126c, 126b, 126a) are fixedly connected to each other to form a one-piece kit (26; 126), wherein 6≥n≥3, and wherein the one-piece kit (26; 126) is suitable for directly engaging with a coupling profile (16) formed on the radial outer peripheral surface of the sprocket carrier (14) by means of an internal shape coupling profile (32; 132) formed on the radial inner side surface of at least the largest sprocket (26a; 126a, 126b) of the one-piece kit (26), wherein the internal shape coupling profile comprises a radially inwardly facing protrusion (32) at the largest sprocket (26a; 126a, 126b) of the one-piece kit (26; 126), wherein the shape of the internal shape coupling profile formed by the protrusion (32) corresponds to the shape of the coupling profile (16) formed by a groove on the radial outer peripheral surface of the sprocket carrier (14), and The smallest sprocket (26c) of the one-piece kit (26) is too small to be slotted into the sprocket carrier (14) and remains axially suspended outward relative to the entire sprocket carrier (14).

2. The speed change disc according to claim 1, wherein: The first sprocket (26c) has 10 teeth.

3. The speed change plate according to claim 1, wherein: The first sprocket (126d) has 9 teeth.

4. The speed change plate according to claim 1, wherein: The first sprocket has 8 teeth.

5. The speed change plate according to claim 1, wherein: n＝3。 6. The speed change plate according to claim 1, wherein: n＝4。 7. The speed change plate according to claim 1, wherein: n=5, and the coupling contour (132) between the one-piece sleeve (126) and the sprocket carrier (14) is formed on the radial inner surfaces of the two largest sprockets (126a, 126b) of the one-piece sleeve.

8. The speed change plate according to claim 1, wherein: n=6, and the coupling contour between the one-piece sleeve and the sprocket carrier is formed on the radial inner surfaces of the three largest sprockets of the one-piece sleeve.

9. The speed change plate according to claim 1, wherein: The speed change plate (20) includes 12 sprockets.

10. The speed change plate according to claim 1, wherein: The speed change plate (20) includes 13 sprockets.

11. The speed change plate according to claim 1, wherein: The speed change plate (20) includes 14 sprockets.

12. A subassembly for a rear wheel of a bicycle, comprising a sprocket carrier (14) and a shift plate (20) coaxially mounted on the sprocket carrier (14), in, The speed change plate (20) comprises a plurality of axially adjacent sprockets (21a, 21b, 21c, 22a, 22b, 22c, 23, 24, 25, 26a, 26b, 26c; 126a, 126b, 126c, 126d) between a first sprocket (26c; 126d) having the smallest number of teeth and a last sprocket (21a) having the largest number of teeth, wherein the first n sprockets (26c, 26b, 26a; 126d, 126c, 126b, 126a) are fixedly connected to each other to form an integrated kit (26; 126), wherein 6≥n≥3, and wherein the one-piece kit (26; 126) is directly shape-engaged on a coupling profile (16) formed on the radial outer peripheral surface of the sprocket carrier (14) by means of an internal shape coupling profile (32; 132) formed on the radial inner side surface of at least the largest sprocket (26a; 126a, 126b) of the one-piece kit (26; 126), wherein the internal shape coupling profile comprises a radially inwardly facing protrusion (32) at the largest sprocket (26a; 126a, 126b) of the one-piece kit (26; 126), wherein the shape of the internal shape coupling profile formed by the protrusion (32) corresponds to the shape of the coupling profile (16) formed by a groove on the radial outer peripheral surface of the sprocket carrier (14), and The smallest sprocket (26c) of the one-piece kit (26) is too small to be slotted into the sprocket carrier (14) and remains axially suspended outward relative to the entire sprocket carrier (14).

13. The subassembly according to claim 12, wherein: The one-piece sleeve (26; 126) includes an axial abutment surface (27) which is in abutting engagement with a corresponding outer axial abutment surface (17) of the sprocket carrier (14).

14. The subassembly of claim 13, wherein: The sprocket carrier (14) includes a radially inner threaded portion (30).

15. The subassembly of claim 12, further comprising a ring nut (28) having a threaded portion (29) which is screwed into a radially inner threaded portion (30) of the sprocket carrier (14).

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