Sprocket support member for a bicycle sprocket assembly
A bicycle sprocket assembly having at least one subassembly including a sprocket support member and two sprockets is presented. The support member has at least one engagement portion for coupling it to a bicycle freewheel and at least one fastening portion arranged in a radially external position with respect to the engagement portion. Both sprockets are fixed on the sprocket support member on the same side of the fastening portion.
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This application is a Continuation of U.S. patent application Ser. No. 10/616,830, filed Jul. 10, 2003, which is incorporated by reference as if fully set forth.
FIELD OF INVENTIONThe present invention relates to a sprocket support member for a sprocket assembly of a bicycle rear wheel.
BACKGROUND OF THE INVENTIONOver recent years, the number of transmission ratios available on bicycle gear change devices has progressively increased and sprocket assemblies for the rear wheel of a bicycle having nine or ten sprockets are increasingly common on the market. The progressive increase in the number of sprockets requires ever increasing research for reducing the weight of the sprocket assembly. In U.S. Pat. No. 5,935,034, assigned to the same assignee as the present invention, a sprocket assembly is described that includes a support member having a radially internal portion shaped such that it couples with a freewheel device and a radially external fastener portion. Two sprockets are mounted on the opposite surfaces of the fastener portion. A third sprocket can be mounted on the support member in addition to the first two sprockets through a plurality of spacer bushings. U.S. Pat. No. 6,102,821 describes a sprocket assembly in which two sprockets are fixed on opposite sides of a sprocket support member by pins that engage with aligned holes of the sprockets and of the support member.
With the progressive increase in the number of sprockets, in addition to the need for reducing the weight of the assembly, there is also the need for arranging the sprockets in positions that are closer one to the other. As a consequence, the space available for the sprocket support member becomes more limited. On the other hand, this support member performs an important structural function and it is necessary to ensure that it has high rigidity and resistance characteristics.
SUMMARY OF THE INVENTIONThe present invention addresses the prior art's shortcomings by using a sprocket support member for a bicycle sprocket assembly comprising at least one engagement portion provided with means for coupling with a bicycle freewheel and at least one fastening portion arranged in a radially external position with respect to said engagement portion. The fastening portion has at least one hole for the mounting of at least one sprocket to the sprocket support member, wherein said fastening portion is axially displaced with respect to said engagement portion.
BRIEF DESCRIPTION OF THE DRAWING(S)The sprocket support member according to the present invention will become evident through the detailed description that follows, provided purely as a non-limiting example. In the detailed description, the following Figures are discussed.
With reference to
In the embodiment illustrated in
The individual sprockets 15, 16, 17, 18, 19, 20 are fixed together in pairs, 15 and 16, 17 and 18, 19 and 20 in the manner that will be described below. The sprocket pairs form three subgroups, indicated in
To perform this spacing function, the fastening portions 37 have a thickness, in the axial direction, equal to the desired distance between two adjacent sprockets. As shown in
With reference to
The sprocket support member 33 includes a plurality of fastening portions 37, arranged in radially in external positions with respect to and opposite the engagement portions 34. In the embodiment illustrated in the figures, the four fastening portions 37 are angularly spaced out at 90° from each other. Preferably the fastening portions 37 are on centerlines with the associated teeth 35. Each of these structural units is provided with an additional weight-saving cavity 39 located between the engagement portion 34 and the fastening portion 37. From the structural point of view, the sprocket support member 33 results to be formed by a series of equidistant structural units, each of which includes an engagement portion 34 and a fastening portion 37, the individual structural units being connected to each other by zones 38 of smaller radial dimensions.
The fastening portions 37 are axially displaced with respect to the engagement portions 34. More precisely, the fastening portions 37 are contained in a first plane 37′ orthogonal to the rotational axis of the sprocket support member 33, and the engagement portions 34 are contained in a second plane 34′ parallel to the first, see
Each fastening portion 37 includes a contact surface 40 and an outer surface 41. The surfaces 40 and 41 are preferably oriented in a radial direction and are mutually parallel. Each fastening portion 37 defines a mounting through hole 42. Preferably, each mounting hole 42 includes an enlarged portion 43 where it opens onto the outer surface 41.
Each fastening portion 37 includes an axial projection 44 located at the base of the contact surface 40. The axial, generally circular projection 44 creates a step between fastening portions 37 and the generally circular engagement portions 34. In practice, the axial projection 44 is formed by an axial displacement of the fastening portions 37 with respect to the engagement portions 34. Centering and support seats 45 are formed on the axial projections 44; each seat has the shape of a cylindrical sector coaxial with the respective fastening hole 42. The seat and fastening hole 42 are aligned to receiver a fastener.
With reference to FIGS. 5 to 7, the two sprockets 19, 20 are fixed on the same side of the fastening portion 37. The sprockets 19 and 20 are provided with respective holes 46 and 47, which are mutually coaxial and coaxial with the fastening holes 42 of the fastening portions 37. The fastening of the sprockets 19, 20 on the sprocket support member 33 is made by a plurality of fastening elements 48.
With reference to
It will be understood that from the structural point of view that each fastening element 48 behaves like a beam resting on the hole 42 and the centering and support seat 45. The sprocket 20 is attached by four of the fastening elements 48 located as described. This allows a highly rigid connection to be achieved. Only the sprocket 19 is surface mounted on the fastening element 48. From the point of view of the connection rigidity, the solution according to the present invention is superior to those of the prior art in which the sprockets are fixed by opposite parts of the fastening portion of the sprocket support member, because in the solutions according to the prior art both of the sprockets are surface mounted.
Each sprocket subgroup 31, 32,33, is aligned on a wheel hub (not shown) using the engagement portions 34 and teeth 35 to align the sprocket subgroups on the wheel hub. Once aligned, the subgroups are tightened to the wheel hub using a standard fastener, generally known as a quick-release.
The sprocket support member 33 can be obtained through hot or cold plastic deformation or through material removal machining and can be made of steel, aluminum and its alloys, titanium or any other metallic material with good strength, hardness, and weight characteristics. The sprocket support member 33 can also be obtained through mould reticulation of a fabric made of structural fibers incorporated in a matrix of plastic material. The fibers are preferably either carbon fibers, glass fibers, aramid fibers, boron fibers, ceramic fibers or any combination thereof.
The shape of each sprocket support member 31, 32, 33 could differ from that illustrated. In a second embodiment of the sprocket support member 133 illustrated in
Each fastening element 48 could be constituted by a smooth cylindrical pin with ends to be deformed in situ to form the heads 50, 54 and the radial shoulder 52 could be substituted by a ring inserted on the pin between the two sprockets 19, 20. The contact surfaces 55, 56 of the radial shoulder 52 could be divergent or convergent with respect to the axis of the fastening element 48. In addition, each sprocket support member 31, 32, 33 could carry more than two sprockets.
Further, the present invention could also be used for the front gears of a bicycle transmission assembly.
Claims
1. A sprocket support member for a bicycle sprocket assembly, the sprocket support member comprising:
- at least one freewheel hub engagement portion having at least one tooth engagable with a splined surface of a bicycle freewheel hub; and
- at least one fastening portion having at least one hole for mounting the sprocket support member to at least one sprocket, the fastening portion lies in a first plane and the engagement portion lies in a second plane which is axially displaced from and parallel to the first plane.
2. The sprocket support member of claim 1, wherein the fastening portion has an axial thickness substantially equal to a desired axial distance between multiple sprockets of the sprocket assembly.
3. The sprocket support member of claim 1, including an axial projection located between the engagement portion and the fastening portion.
4. The sprocket support member of claim 3, wherein the axial projection forms a support against which a radially projecting portion of a fastening element can rest.
5. The sprocket support member of claim 4, wherein the axial projection has a centering and support seat having the shape of a cylindrical sector coaxial with a fastening hole of the fastening portion.
6. The sprocket support member of claim 4, wherein the axial projection is located at the base of a radial contact surface of the fastening portion.
7. The sprocket support member of claim 1, wherein one of the at least one fastening portion and one of the at least one engagement portion form at least one single structural unit, the one of the at least one engagement portion being aligned with the one of the at least one fastening portion in a radial direction.
8. The sprocket support member of claim 7, wherein the structural unit includes at least one weight-saving cavity located between the engagement portion and the fastening portion.
9. The sprocket support member of claim 7, including a plurality of single structural units angularly equidistant from each other and connected together by zones having reduced dimensions in the radial direction.
10. The sprocket support member of claim 1, wherein the support member is made of a material chosen among the group consisting of: steel, aluminum and its alloys, titanium, and fabric made of structural fibers incorporated in a matrix of plastic material, in which the fibers are chosen among carbon fibers, glass fibers, aramid fibers, boron fibers, ceramic fibers or any combination thereof.
11. A sprocket support member for a bicycle sprocket assembly comprising:
- an inner engagement portion having at least one tooth adapted for engagement with a spline of a bicycle freewheel hub, the inner engagement portion defining a first plane; and,
- an outer fastening portion having at least one position defined for the mounting the sprocket support member to a sprocket, the outer fastening portion defines a second plane that is immediately adjacent to and parallel with the first plane.
12. The sprocket support member of claim 11 wherein the inner engagement portion and the outer fastening portion have adjacent faces and free faces and wherein the free face of the inner engagement portion is spaced from the free face of the outer fastening portion by a predetermined distance adapted for a defined sprocket assembly.
13. A sprocket support member for a bicycle sprocket assembly comprising:
- an inner engagement portion having at least one tooth adapted for engagement with a spline of a bicycle freewheel hub, the inner engagement portion defining a first plane; and,
- an outer fastening portion having at least one position defined for the mounting the sprocket support member to a sprocket, the outer fastening portion defines a second plane that is immediately tangent to and parallel with the first plane.
14. A sprocket assembly for a bicycle comprising:
- at least one subgroup including a sprocket support member comprising at least one engagement portion provided with means for coupling with a bicycle freewheel and at least one fastening portion arranged in a radially external position with respect to the engagement portion, the fastening portion presenting at least one hole for the mounting of at least one sprocket to the sprocket support member, wherein the fastening portion is axially displaced with respect to the engagement portion; and
- at least two sprockets fixed to the fastening portion, wherein at least two of the sprockets are fixed on the same side of the fastening portion.
15. The sprocket assembly of claim 14, including a plurality of fastening elements for mounting at least a first and a second sprocket against a contact surface of the sprocket support member.
16. The sprocket assembly of claim 15, including at least one spacer means located between the first and second sprockets.
17. The sprocket assembly of claim 16, wherein the spacer means includes two mutually opposite contact surfaces against which respective contact portions of the first and second sprockets rest.
18. The sprocket assembly of claim 17, wherein the contact surfaces of the spacer means are parallel to the contact surface of the fastening portion.
19. The sprocket assembly of claim 15, wherein the fastening elements carry the spacer means.
20. The sprocket assembly of claim 19, wherein the spacer means is integrated with the fastening elements.
21. The sprocket assembly of claim 20, wherein each of the fastening elements includes an integral shoulder with two opposing contact surfaces.
22. The sprocket assembly of claim 14, wherein each of the fastening elements has a first cylindrical portion that engages two aligned coaxial holes of the fastening portion and the first sprocket.
23. The sprocket assembly of claim 22, wherein each of the fastening elements has a second cylindrical surface that engages a hole of the second sprocket.
24. The sprocket assembly of claim 23, wherein each of the fastening elements includes a radial shoulder between the first and the second cylindrical portion.
25. The sprocket assembly of claim 14, wherein each of the fastening elements has a first head with an outer surface substantially flush with an outer surface of the fastening portion.
26. The sprocket assembly of claim 25, wherein each of the fastening elements has a second head with an outer surface substantially flush with an outer surface of the second sprocket.
27. The sprocket assembly of claim 14, wherein each of the fastening elements has a radially projecting portion arranged to make contact with an axial projection located in a radially internal position with respect to the fastening portion.
28. The sprocket assembly of claim 14, wherein each of the fastening elements is a rivet.
29. A sprocket assembly for a bicycle, including a plurality of subgroups, each of which includes:
- a sprocket support member having at least one engagement portion shaped to engage a bicycle freewheel hub and at least one fastening portion arranged in a radially external position with respect to the engagement portion; and
- at least two sprockets attached to the fastening portion;
- wherein the subgroups can be axially mounted on the bicycle wheel hub in contact with each other.
30. The sprocket assembly of claim 29, wherein the fastening portion of at least one of the subgroups has an axial thickness substantially equal to the desired distance between two adjacent sprockets belonging to two different, mutually adjacent subgroups.
31. The sprocket assembly of claim 30, wherein the fastening portion of at least one of the subgroups has an outer radial surface that rests against an outer radial surface of a sprocket of an adjacent subgroup.
32. The sprocket assembly of claim 29, wherein the at least two sprockets are spaced apart from each other by a distance substantially equal to the axial thickness of the fastening portion.
33. A bicycle sprocket assembly comprising:
- a sprocket support member having: a planar frame defining a first plane; a plurality of fastening tabs fixed to and extending radially-outwardly from the frame and being co-planar with the frame, each tab having a through hole; an annular step fixed to and extending axially from the planar frame; a plurality of engagement teeth fixed to and extending radially-inwardly from the annular step and defining a second plane axially-spaced from the first plane; and,
- a pair of sprockets mounted on the support member and arranged so that both sprockets are positioned on the same side of the first plane and at least a portion of the first sprocket and a portion of the second sprocket are positioned on opposite sides of the second plane.
34. A bicycle sprocket assembly comprising:
- a sprocket support member having: a planar frame defining a first plane; a plurality of fastening surfaces on the frame, each surface having a through hole; an annular step fixed to and extending transverse to the planar frame; a plurality of engagement teeth fixed to and extending radially-inwardly from the annular step and defining a second plane axially-spaced from the first plane;
- a plurality of fasteners;
- a pair of sprockets having radially-inwardly projecting fastening tabs with a through hole, the sprockets being fixed on the same side of the support member by inserting one of the fasteners within aligned through holes in the sprocket fastening tabs and the support member fastening surfaces; and
- means for radially supporting each of the fasteners and the fastening tabs of at least one of the sprockets.
Type: Application
Filed: Nov 3, 2006
Publication Date: Mar 8, 2007
Applicant: Campagnolo S.r.l. (Vicenza)
Inventor: Maurizio Valle (Vicenza)
Application Number: 11/592,653
International Classification: F16H 55/30 (20060101); F16H 55/12 (20060101);