Body for bicycle rear wheel hub and cassette adapted to be mounted on the hub by means of such a body

Abstract

A mounting body and a cassette suitable for mounting on a bicycle rear wheel hub in combination with the body. The body has an inner radial portion for coupling with rear wheel hub and an outer radial portion for mounting the cassette and a portion with a plurality of attachment areas for attachment to a cassette. The cassette has an axial centering opening for centering on the mounting body and a plurality of cassette attachment areas that align with the mounting body attachment areas to unite the mounting body and cassette for transmission of pedaling torque.

Claims

1. A body for mounting a cassette on a bicycle rear wheel hub, comprising: a radially inner first portion, of tubular shape, with an axial cavity arranged along an axis (X) of the body and configured for coupling with the hub through a free-wheel system, and a radially outer surface for mounting the cassette free of torque transmission, wherein the first portion has axial extension between a first face and a second face of the body, and a radially outer second portion for coupling with the cassette, wherein the second portion: has a shorter axial extension than the axial extension of the first portion; extends radially outwards from the first portion; and has a plurality of attachment areas for attachment to the cassette.

2. The body according to claim 1, wherein the attachment areas each comprise a support surface for the cassette and at least one hole at the support surface passes entirely through the axial thickness of the attachment portion of the body.

3. The body according to claim 2, wherein the support surfaces of the attachment areas are coplanar to one another and perpendicular to the axis (X) of the body.

4. The body according to claim 2, wherein the support surfaces of the attachment areas extend radially outwards as much as the radially outer second portion.

5. The body according to claim 2, wherein the holes of the attachment areas are divided into two series, a first series of holes at a first radial distance from the axis (X) of the body and a second series of holes at a second radial distance from the axis (X) of the body, greater than the first radial distance.

6. The body according to claim 5, wherein each attachment area comprises a hole of the first series and a hole of the second series, at a same support surface.

7. The body according to claim 1, wherein the radially outer second portion of the body is star-shaped, comprising a plurality of legs, wherein every leg comprises one of the attachment areas at its own radially outer end.

8. The body according to claim 1, wherein the attachment areas are equally spaced apart in the circumferential direction, around the axis (X) of the body.

9. A body for mounting a cassette on a bicycle rear wheel hub, comprising: a radially inner first portion, of tubular shape, with an axial cavity arranged along an axis (X) of the body and intended for coupling with the hub through a free-wheel system, and a radially outer surface for mounting the cassette, wherein the first portion has axial extension between a first face and a second face of the body, and a radially outer second portion for coupling with the cassette, wherein the second portion: has a shorter axial extension that is less than 25% of the axial extension of the first portion; extends radially outwards from the first portion; and has a plurality of attachment areas for attachment to the cassette, and wherein the radially outer surface of the first portion of the body is free of any structure for torque transmission to the cassette.

10. A body for mounting a cassette on a bicycle rear wheel hub, the body comprising: a tubular radially inner first portion with an axial extension between a first face and a second face of the body, an axial cavity arranged along an axis (X) of the body for coupling with the hub through a free-wheel system, and a radially outer surface for mounting the cassette; and, a radially outer second portion for coupling with the cassette that has a shorter axial extension than the axial extension of the first portion, extends radially outwards from the first portion, and a plurality of attachment areas for attachment to the cassette; wherein, the radially outer surface for mounting the cassette is substantially cylindrical and free of any structure for transmission of torque.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

(1) Further features and advantages of the invention will become clearer from the following detailed description of a cassette and of a body of a bicycle transmission, made with reference to the attached drawings. In the drawings:

(2) FIG. 1 is a rear perspective view of a cassette and a body of a bicycle transmission, mounted together;

(3) FIG. 2 is a front perspective view of the cassette and of the body of FIG. 1, mounted together;

(4) FIG. 3 is a section view of the cassette of FIG. 1;

(5) FIG. 4 is a rear view of part of the cassette of FIG. 1;

(6) FIG. 5 is a rear perspective view of the body of FIG. 1;

(7) FIG. 6 is a section view of the body of FIG. 1;

(8) FIG. 7 is a front perspective view of the body of FIG. 1;

(9) FIG. 8 is a rear perspective view of the cassette of FIG. 1;

(10) FIG. 9 is an axial section view of the cassette and of the body of FIG. 1, mounted together;

(11) FIG. 10 is a front perspective view of an alternative embodiment of the body of FIG. 7;

(12) FIG. 11 is a rear perspective view of an alternative embodiment of the cassette of FIG. 8;

(13) FIG. 12 is an axial section view of the cassette of FIG. 11 and of the body of FIG. 10, mounted together;

(14) FIG. 13 is a front perspective view of another alternative embodiment of the body of FIG. 7;

(15) FIG. 14 is a rear perspective view of another alternative embodiment of the cassette of FIG. 8;

(16) FIG. 15 is an axial section view of the cassette of FIG. 14 and of the body of FIG. 13, mounted together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(17) With particular reference to FIGS. 1 and 2, a cassette 10 and a body 50, intended for a bicycle transmission (not shown as a whole), are shown. In particular, the body 50 is intended for mounting on a hub of a bicycle rear wheel (not shown) by means of a free-wheel mechanism RL, per se known, only some recesses of which formed in the body 50 are visible in FIG. 1. In FIGS. 1 and 2, the cassette 10 is shown mounted on the body 50, by means of screws V; clearly, in normal use the mounting of the cassette 10 on the body 50 takes place only after the latter has been mounted on the hub.

(18) The cassette 10 comprises a plurality of sprockets 11, fixedly connected to one another and adjacent along an axis; the axis of the cassette 10 coincides with an axis of the body 50, when they are mounted together; furthermore, the axis of the body 50 coincides with an axis of the hub, when the body 50 is mounted on the hub. Given the coinciding of these axes when the cassette 10, the body 50 and the hub are mounted together, hereinafter and in the figures they will all be indicated with reference symbol X.

(19) The cassette 10 illustrated in FIGS. 1 and 2 as well as in the other figures comprises twelve sprockets 11, each provided with teeth 12 separated by recesses 13; clearly, however, the number of sprockets 11 can be different according to requirements, as well as the number of teeth 12 (and of recesses 13) of each sprocket 11 is selected according to the requirements.

(20) As can be seen in FIG. 3, the cassette 10 is made monolithic, from a single piece of material (preferably steel of the suitable type) suitably machined; preferably, this machining is carried out by means of a numerically-controlled machine tool, from a forged semi-machined product. The sprockets 11 are equally spaced apart in the direction of the axis X, by means of joining portions or connections 14, which are formed between pairs of adjacent sprockets 11 so as to be at the recesses 13 of the smallest sprocket 11 of the pair.

(21) At the axis X, the cassette 10 comprises an axial centering opening 15 (visible in FIG. 2 or rather in FIGS. 8 and 9), intended for mounting centered on the body 50, without possibility of transmission of torque between cassette 10 and body 50. For this purpose, the centering opening 15 does not comprise any inner grooved profile or other elements suitable for a shape coupling with the body 20.

(22) As can be seen in FIG. 8, the cassette 10 also comprises a plurality of attachment areas 20, intended to allow the attachment of the cassette to the body 50. The attachment areas 20 are arranged in the cassette 10 at a distance in the radial direction from the axis X greater, and indeed much greater, than the radius of the centering opening 15; preferably, the distance in the radial direction of the attachment areas 20 from the axis X is equal to at least three times, even more preferably from three to six times, the radius of the centering opening 15. As can be seen in FIG. 8, this implies that the attachment areas 20 are, for example, at the fourth largest sprocket 11 of the cassette 10, or even further out.

(23) Therefore, there are five attachment areas 20 of the illustrated cassette 10, equally spaced in the circumferential direction around the axis X, i.e. angularly spaced apart by 72°.

(24) Each of the attachment areas 20 comprises a support surface 21 and a threaded hole 22, formed in the material of the cassette 10 at the support surface 21, so as to be surrounded by it. The holes 22 can be through holes or blind holes, provided that they are of sufficient depth to receive the screws V in mounting on the body 50, as will be illustrated hereinafter.

(25) The centering opening 15 of the cassette 10 must allow the correct and precise positioning of the cassette 10 on the body 50. For this purpose, as can be seen in FIG. 9, the centering opening 15 comprises an axial support area 31 and a radial support area 32: the first is formed from a conical surface, coaxial to the axis X, whereas the second is formed from a cylindrical surface, facing radially towards the axis X.

(26) The cassette 10, as stated, is intended to be mounted on the hub of a bicycle transmission by means of the body 50.

(27) As can be seen in FIGS. 1, 5, 6 and 9, the body 50 comprises two portions, a radially inner first portion 52 and a radially outer second portion 62; the two portions are fixedly connected to one another and are preferably obtained from a single piece, suitably shaped. The first portion 52 is intended to be mounted on the hub, whereas the second portion 62 is intended to receive the cassette 10.

(28) The first portion 52 has a tubular shape and extends axially from a first face 55 to a second face 56 of the body 50; it thus has axial extension equal to that of the body 50 itself.

(29) The second portion 62 has shorter axial extension than that of the first portion 52, preferably less than ¼ of it.

(30) The first portion 52 comprises an axial cavity 57, extending along the axis X and intended for coupling with the hub, through the free-wheel mechanism RL. The first portion 52 also comprises a radially outer surface 58, substantially cylindrical, extending in the axial direction between the second portion 62 of the body 50 and the first face 55, intended for coupling with the cassette 10.

(31) The second portion 62 extends radially outwards from the first portion 52 and comprises spider legs 63 (for example five spider legs 63, as shown in figures) that give the second portion 62 a star shape.

(32) The second portion 62 comprises a plurality of attachment areas 70 for the cassette 10, which are thus in radially outer position with respect to the first portion 52 of the body 50.

(33) There are five attachment areas 70 of the illustrated body 50, equally spaced in the circumferential direction around the axis X, i.e. angularly spaced apart by 72°.

(34) Each of the attachment areas 70 comprises a support surface 71 and at least one first hole 72, formed passing through the thickness of the second portion 62 of the body 50 at the support surface 71, so as to be surrounded by it. The support surfaces 71 are all coplanar to one another and perpendicular to the axis X.

(35) Preferably, as well as the first hole 72 a second hole 73 is also provided, also passing through the thickness of the second portion 62 of the body 50 and at the same support surface 71. Two series of through holes are thus formed, a first series of first holes 72 and a second series of second holes 73; the holes of each series are arranged the same radial distance from the axis X, with the first holes 72 arranged a shorter distance from the axis X than the second holes 73.

(36) According to the preferred embodiments shown in the figures, the attachment areas 70 are provided at each spider leg 63, in particular at the end 64 of every spider leg 63. The support surfaces 71 thus extend radially outwards, up to the ends 64, i.e. the outward radial extension of the support surfaces 71 corresponds to the outward radial extension of the second portion 62 of the body 50 and thus to the outward axial extension of the body 50 itself.

(37) The spider legs 63 of the body 50 are configured so that the mechanical stresses, determined by the drive torque transmitted from the cassette 10 to the hub through the body 50, are distributed as evenly as possible. Therefore, the profile of the spider legs 63 is broadly rounded, both close to the ends 64 and to the base, towards the first portion 52 of the body 50. Furthermore, the areas of the spider legs 63 not engaged by significant stresses are removed to lighten the body 50, with formation of an opening 65 at the base of every spider leg 63.

(38) FIGS. 10 to 12 and FIGS. 13 to 15 illustrate a cassette 110, 210 and a body 150, 250 according to a second and a third embodiment of the invention, which differ from what has been described up to here and shown in FIGS. 1-9 only for the slightly different way of centering the cassette 110, 210 on the body 150, 250. Therefore, all details of the cassette 110, 210 and of the body 150, 250 that are identical to the corresponding details of the cassette 10 and of the body 50 are not described here; in FIGS. 10-12 and 13-15 as well as in the following description, these details are indicated by the same reference numerals as the corresponding details of the cassette 10 and of the body 50; only the analogous but different details are indicated by reference numerals increased by 100 and by 200, respectively.

(39) The centering opening 115 of the cassette 110 comprises an axial support area 131 and a radial support area 132: the first is formed from an annular flat surface, perpendicular to the axis X, whereas the second is formed from a cylindrical surface, facing radially towards the axis X. The body 150 has a greater extension in the axial direction.

(40) The centering opening 215 of the cassette 210 comprises an axial support area 231 and a radial support area 232: the first is formed from an annular flat surface, perpendicular to the axis X, whereas the second is formed from a cylindrical surface, facing radially outwards. The body 250 has an extension in the axial direction analogous to the body 150.

(41) The cassette 10, 110, 210 and the body 50, 150, 250 are used together, to transmit the drive torque to the hub, just as the cassettes and the bodies of the prior art are used together for the same purpose. Differently from known systems, however, with the cassette and the body according to the invention the torque is transmitted not by a shape coupling close to the axis X, but rather by the friction between the support surfaces 21 and the support surfaces 71, pressed against one another by the screws V, inserted in the through holes 72 or 73 and clamped in the threaded holes 22. The presence of the two series of through holes 72 and 73 makes it possible to mount equal cassettes 10, 110, 210 of two different sizes on bodies 50, 150, 250: small-sized cassettes, for which the first series of holes 72 is used, closer to the axis X, and larger-sized cassettes, for which the second series of holes 73 is used. This possibility increases the versatility of transmission.

(42) Thanks to the invention, the torque is thus transmitted through areas relatively far from the axis X, with a double advantage. On the one hand, the minimum dimension constraint for the smallest sprocket of the cassette, which does not need to be engaged with any shape coupling and can thus be as small as required by the transmission requirements is eliminated. On the other hand, the stress exchanged between the cassette and the body, for the same torque transmitted, becomes lower thanks to the greater application arm with respect to the axis X.

(43) Furthermore, the coupling between the cassette and the body is carried out in a very simple manner through the screws V, without therefore the need for tools or special equipment: a normal tool is sufficient to actuate the screws V, i.e.—depending on the shape of the head of the screws V—a screwdriver, a hexagonal key, a Torx key or other suitable key. The mounting and dismounting operations take little time, thus allowing quick replacements, for example during races.

(44) Finally, an assembly of cassette and body according to the invention is lighter than an analogous assembly of the prior art, due particularly to the smaller number of pieces and the more effective transmission of stresses due to the torque transmitted.

LIST OF ELEMENTS

(45) RL free wheel

(46) X axis

(47) V screws

(48) 10 cassette (110, 210)

(49) 11 sprockets

(50) 12 teeth

(51) 13 recesses

(52) 14 connections

(53) 15 centering opening (115, 215)

(54) 20 attachment areas

(55) 21 support surfaces

(56) 22 threaded holes

(57) 31 axial support area (131, 231)

(58) 32 radial support area (132, 232)

(59) 50 body (150, 250)

(60) 52 first portion

(61) 55 first face

(62) 56 second face

(63) 57 cavity

(64) 58 radially outer surface

(65) 62 second portion

(66) 63 spider legs

(67) 64 ends of the spider legs

(68) 65 opening in the spider legs

(69) 70 attachment areas

(70) 71 support surfaces

(71) 72 through holes (1st series)

(72) 73 through holes (2nd series)