Aerodynamic spoke for spoked wheels, in particular for bicycles

Abstract

An aerodynamic spoke for spoked wheels, in particular for bicycles, comprises a stem elongated in a dominant direction and means on the surface of said stem for reducing the aerodynamic resistance of the spoke. Said means for reducing the resistance comprises a plurality of undulations on at least a portion of the surface of said stem, with ridges and valleys extended transversely to said dominant direction.

Description

[0001] Aerodynamic spoke for spoked wheels, in particular for bicycles DESCRIPTION

[0002] The present invention relates to an aerodynamic spoke for spoked wheels, in particular for bicycles, comprising a stem elongated in a dominant direction, and configured in such a way as to improve the aerodynamic characteristics. A spoke of this type is for example known from DE202004001185U1. The document proposes to realize spokes with aerodynamics improved by the presence of imprints on the stem that form a plurality of micro-recesses similar to those present on the surface of golf balls. In an alternative embodiment the imprints are elongated in the longitudinal direction of the stem, or arranged in a spiral. The document argues that the presence of such repeated geometric formations contributes to reducing the aerodynamic resistance of the spoke during the rotation of the spoked wheel.

[0003] Another spoke is known from CN202863011(U). This document proposes a spoke provided with widenings repeated pitchwise with which the reflective surface of the spoke is increased to improve the night visibility of the wheel. However, the document has no bearing, however, on aerodynamic effects and is indeed a counterproductive suggestion in that respect.

[0004] US 2009 / 236902 Al instead describes a spoke wheel in which hub, spokes and rim are integral. The wheel is not provided with spokes in the proper sense, that is, of the type separated from hub and rim and provided with end fastening to these components. This wheel has therefore limited applications, is unsuitable for lightweight applications, such as wheels for racing bicycles and entails severe limitations in particular on the production technology and on the materials that can be used. For example, it is unthinkable to make the spokes from carbon fibre-based composites. The present invention fits into this technological direction, aiming at further improving the aerodynamics of the spoke. The technical problem addressed and solved by the invention is therefore that of making available a spoke for spoked wheels, in particular for bicycles, structurally and functionally designed to obtain a further reduced aerodynamic resistance with respect to what is achievable through the teachings of the cited prior art.

[0005] Within the scope of this problem, it is an object of the invention to make available a spoke in which the improved aerodynamics does not compromise the mechanical resistance of the spoke. Another object is to provide a spoke whose realization is possible without substantially altering the production cycle thereof.

[0006] A further object of the invention is to propose a spoke endowed with the aforementioned prerogatives and that can be realised with a variety of materials and technologies, including composite materials, metallic materials and thin-section machining.

[0007] This problem is solved and these and other purposes are achieved through an aerodynamic spoke for spoked wheels, in particular for bicycles, made in accordance with at least some of the features of the claims.

[0008] According to a first aspect thereof, the invention is directed to an aerodynamic spoke comprising a stem elongated in a longitudinal dominant direction and means to reduce the aerodynamic resistance of the spoke on the surface of said stem.

[0009] Preferably the aforesaid means comprise a plurality of undulations on the surface of said stem with ridges and valleys extended transversely to said longitudinal dominant direction.

[0010] Considering at the same time each of the cross-sections of the stem that are orthogonal to the longitudinal dominant direction of the stem itself, it is possible to identify a theoretical nominal average cross-section that deviates less from each of the cross-sections considered. By analysing each of the cross-sections of the stem, it is therefore possible to define as a ridge any portion of the cross-section concerned that extends outside the area identified by said nominal average cross-section. Instead, any area of space devoid of material which is identified by the difference between a given cross-section of the stem and said nominal average cross-section can be defined as a valley. Explanatory, but not limiting, examples will be provided below for the definition of ridges and valleys in some of the possible embodiments of the aerodynamic spoke.

[0011] It is understood that, in the case of other particularly complex forms of spokes, a technician skilled in the art, thanks to the definition reported above and the examples that will be provided, would be able to identify the theoretical nominal average crosssection and, consequently, the ridges and valleys that may be present on the spoke in question.

[0012] Preferably, the aerodynamic spoke comprises at the longitudinally opposed ends respective fastening elements to a hub and a rim of a wheel.

[0013] In accordance with a second aspect thereof, the invention is also directed to an aerodynamic spoke comprising a stem elongated in a longitudinal dominant direction. The aerodynamic spoke comprises respective fastening elements to a hub and a rim of a wheel, arranged at longitudinally opposed ends of the stem. The aerodynamic spoke comprises a plurality of undulations on at least a surface portion of said stem having ridges and valleys extended substantially transversely to the dominant direction.

[0014] The present invention, in one or more of the above aspects, may also have one or more of the following preferred features. In some embodiments the stem defines a major transversal dimension preferably orthogonal to the dominant direction. Preferably the consecutive ridges and / or valleys are spaced between each other with a pitch smaller than the major transversal dimension of the stem preferably orthogonal to the longitudinal dimension of the stem itself. This results in a high number of ridges and valleys that are densely arranged on the surface of the stem.

[0015] In some embodiments the undulations comprise ridges and valleys extended continuously between opposing longitudinal sides of the spoke.

[0016] In some embodiments ridges and valleys are contiguous between opposing longitudinal sides of the spoke.

[0017] In some embodiments the stem of the spoke has a flattened cross-section, preferably substantially elliptical.

[0018] In some embodiments the stem of the spoke has a flattened cross-section, preferably substantially rectangular.

[0019] In some embodiments said ridges and valleys are parallel to each other.

[0020] In some embodiments the major extension direction of each of said ridges and valleys forms, with the longitudinal direction of the stem, an angle comprised between 45° and 95°, and preferably equal to 90° + / - 5°.

[0021] In some embodiments, the aerodynamic spoke has at the longitudinally opposed ends respective fastening elements to a hub and a rim of a wheel. Preferably the undulations are terminated at a distance of 10-50mm from said respective fasteners. In some embodiments, the undulations present alternations of said ridges and valleys on opposing surfaces of the stem and, preferably, said alternations on opposing surfaces of the stem are symmetrical to each other.

[0022] In some embodiments, the maximum depth of the undulations is comprised between 0.1 and 1 mm, where depth means the difference in elevation from the axis of the stem between a ridge and a valley.

[0023] In some embodiments the undulations are provided on at least one of the opposing longitudinal sides of the spoke.

[0024] In some embodiments the undulations on at least one of said opposing longitudinal sides are connected to the corresponding undulations on the opposing surfaces.

[0025] In some embodiments the undulations on the opposing surfaces are reported on the stem of the spoke.

[0026] In accordance with a further aspect, the invention is also directed to a process for manufacturing an aerodynamic spoke preferably in accordance with one or more of the preceding aspects. Preferably the process comprises applying to a spoke stem elongated in a dominant direction, preferably longitudinally, a coating comprising a plurality of undulations on at least a surface portion of said stem, preferably with ridges and valleys extended transversely to the dominant direction.

[0027] In some embodiments, the coating is applied by co-moulding.

[0028] In some embodiments, the coating is applied by adhesivization.

[0029] In some embodiments, the ridges and valleys alternate on opposing surfaces of the spoke with a substantially matching arrangement of ridges with ridges and valleys with valleys.

[0030] In some embodiments, the coating is interrupted by longitudinally juxtaposed modules, preferably having a longitudinal extension smaller than the extension of the stem.

[0031] In some embodiments, the spoke comprises a core of composite material on which said coating is applied.

[0032] In some embodiments, opposing surfaces of the core are substantially free of undulations.

[0033] The characteristics and the advantages of the invention will become clearer from the detailed description of some preferred but not exclusive embodiments thereof illustrated by way of non-limiting example, with reference to the accompanying drawings in which:

[0034] Figure 1 represents an overall perspective view of a first embodiment of the invention;

[0035] Figure 2 represents a plan view of the first embodiment of the invention;

[0036] - Figure 3 represents a partial perspective view of a detail of the first embodiment of the invention;

[0037] Figure 4a represents a side orthogonal view of a portion of the first embodiment of the invention;

[0038] - Figure 4b represents a side orthogonal view of a portion of a second embodiment of the invention;

[0039] Figure 5 shows a partial sectional view of Fig. 4a carried out by means of plane V - V;

[0040] Figure 6 shows a sectional view of Fig. 4a carried out by means of plane VI - VI;

[0041] Figure 7 shows a sectional view of Fig. 4a carried out by means of plane VII - VII;

[0042] Figures 8 and 9 are partial perspective views of two further embodiments of the spoke of this invention;

[0043] Figure 10 is a partial perspective view of a further example of spoke falling within this invention;

[0044] Figure 11 is a front view of the spoke of Figure 10; Figure 12 is a side view of the spoke of Figure 10;

[0045] Figure 13 is a partial perspective view of a detail of a further embodiment of a spoke of this invention;

[0046] Figure 14 is a side view of the spoke of Figure 13;

[0047] Figure 15 is a front view of the spoke of Figure 13;

[0048] Figure 16 is a sectional view according to the line XVI - XVI of Figure 13;

[0049] Figure 17 is a sectional view according to the line XVII - XVII of Figure 13;

[0050] Figure 18 is a sectional view taken along line XVIII - XVIII of Fig. 13.

[0051] In the figures, a spoke for a spoked wheel, for example a bicycle wheel or the like, is indicated as a whole with 1.

[0052] The spoke 1 comprises a stem 2, with a predominant longitudinal extension, that is, in which the longitudinal dimension is dominant and largely exceeds the thickness and the transverse extension of the stem. The stem 2 has an elongated portion 3 preferably with flattened, e.g. elliptical, cross-section, with opposing surfaces 4, 5 and opposing longitudinal sides 6, 7 defined along the sides of the spoke that connects the opposing surfaces 4, 5 to each other.

[0053] The elongated portion 3 is preferably terminated at both longitudinal ends with a cylindrical section 12 bearing fastening elements respectively to a wheel rim and a wheel hub by themselves conventional. Typically, such fastening elements may comprise an enlarged head 8 and a threaded section 9 for engaging a nipple, not shown.

[0054] The stem 2 may comprise two or more contiguous elongated portions 3 even if the provision of a single elongated portion 3 is preferable.

[0055] In the embodiments shown herein, the cylindrical sections 12 are connected to the elongated portion 3 by means of two substantially frustoconical connections 13; however, in other embodiments not illustrated, said connections 13 may not be present.

[0056] On at least one of the opposing surfaces 4, 5 of the elongated portion 3, and preferably on both, means are provided for reducing the aerodynamic resistance of the spoke, which comprise, in a preferred solution of the invention, a plurality of undulations on the surface of said stem with ridges 10 and valleys 11 extended transversely to said longitudinal dominant direction.

[0057] Preferably ridges and valleys 10, 11 are continuous, i.e. extended without interruptions between the opposing longitudinal sides 6, 7 of the spoke 1. Ridges and valleys are also preferably parallel to each other and approximately perpendicular to the longitudinal sides 6, 7 of the spoke.

[0058] The course of the undulations is intended to comprise an orientation of the major extension of each of said ridges and valleys 10,11 with respect to the longitudinal direction of an angle comprised between 45° and 95°, where said angle can be evaluated clockwise or counterclockwise. Preferably the orientation is at 90° ±5°, with respect to the longitudinal direction of the spoke.

[0059] Preferably the depth of the undulations, understood as the difference in elevation from the axis of the stem between a ridge and a valley, is of the order of 1 mm; a further preferable value is of the order of 0.1 mm. Furthermore, the undulations preferably terminate at a distance of 10-50mmm from the respective fastening elements 8, 9.

[0060] As can be noted from Figs. 4a and 4b, in the first two embodiments illustrated, the undulations present alternations of ridges and valleys 10, 11 on both opposing surfaces 4, 5, furthermore said alternations of ridges and valleys are symmetrical with each other. However, in other embodiments not shown, said alternations may not be symmetrical with each other, or still the undulations could have an alternation of ridges and valleys even on only one of the two opposing surfaces 4, 5.

[0061] Always with reference to Figs. 4a and 4b, it can be noted how said ridges and valleys 10, 11 can be obtained on said spoke 1 in different ways: in the first embodiment illustrated in Fig. 4a the elongated portion 3 has an initial diameter DI, contiguous connection 13, from which the ridges 10 are obtained through relief, while the valleys 11 are thus indirectly defined; in the second embodiment illustrated in Fig. 4b the elongated portion 3 has an initial diameter D2, contiguous connection 13, from which the valleys 11 are obtained through constriction, while the ridges are thus indirectly defined.

[0062] In both cases mentioned above the spoke has a reduced aerodynamic resistance as a result of the rotation of the spoked wheel on which it is mounted with respect to elliptical spokes in which the surfaces 4, 5 are free of undulations.

[0063] Figs. 5, 6, and 7 show schematic and partial sections of the first illustrated embodiment of the aerodynamic spoke 1, adapted to exemplify the definition of any ridges and valleys 10, 11 starting from the identification of the theoretical nominal average cross-section M.

[0064] It is believed that the examples shown in Figs. 5 to 7 allow a skilled person to identify any ridges and valleys in a wide range of embodiments, even complex ones, for the aerodynamic spoke 1 subject matter of the present patent.

[0065] Two further embodiments of the spoke of this invention are illustrated in Figures 8 and 9, indicated respectively with references 22 and 23. Details similar to those of the previous figures are marked by the same numerical references.

[0066] In the two further examples the undulations affect at least one of the opposing longitudinal sides 6, 7 of the spoke 22, 23. In the example of spoke 22 the undulations are defined by ridges and valleys 10, 11 on one or preferably both opposing longitudinal sides 6, 7. In the example of the spoke 23 the undulations on the opposing longitudinal sides 6, 7 are continued on the opposing surfaces 4, 5 with a continuous substantially annular conformation for each ridge or valley 10, 11. The invention also contemplates any intermediate extension of the ridges and / or valleys 10, 11 that partially or totally affect the surfaces and / or sides of the spoke, for example undulations that start from one of the longitudinal sides 6, 7 of the spoke and that extend even partially along at least one of the opposing surfaces 4, 5.

[0067] A further embodiment of the spoke of this invention, indicated with the reference 24, is illustrated in Figures 10, 11 and 12. It should be observed that details similar to those of the previous figures are marked by the same numerical references.

[0068] Referring to Figure 11, it should be observed that the undulations on the opposing surfaces 4 and 5 are made by a series of identical consecutive imprints, repeated pitchwise, defined by depressions with cylindrical shell with an axis transverse to the longitudinal direction of the spoke 24.

[0069] In the example of Figures 13 to 18, a spoke 100, preferably of a flattened type in its elongated portion 3 of stem 2, is illustrated. The spoke 100 comprises a core 120 for example made of composite material with high-strength fibres, such as carbon fibres, kevlar or the like, in a resin matrix for example of epoxy type. Likewise, traditional steel or aluminium spokes can be used as a core. Such materials and their machining technique are known in the art. Preferably, with these materials and techniques, spokes are made whose stem has a smooth surface, that is, free of undulations. The core 120 has own opposing faces 104 and 105 essentially free of undulations. Ridges and valleys 10 and 11 are in this case reported on the core 120, or more generally on the stem 2, making a preferably adhesive coating 130 with a preferably soft and flexible material, for example with polymers in TPU or PA12 that effectively adhere to the surface of the carbon composites and can be co-moulded on the stem of the spoke by injection, applied with 3D printing, or (and preferably) applied with a coating in the form of a film, preferably adhesivised on a smooth face thereof and bearing on the opposing face the aforementioned ridges and valleys.

[0070] Preferably, as can be seen in Figure 14, ridges 10 and valleys 11 on the opposing surfaces 4 and 5 of the spoke 100 are symmetrically opposed to each other so that a ridge 10 on the surface 4 corresponds to a ridge 10 on the opposing surface 5. Similarly, also the valleys 11 are symmetrically opposed on the surfaces 4 and 5.

[0071] In some embodiments, not depicted, a different positioning is also provided. However, it has been experimentally found that the indicated positioning maximizes the aerodynamic result, allowing an improvement of the overall aerodynamic coefficient of the spoke by a value comprised between 10% and 20%.

[0072] Is should be noted that the adhesive coating 130 may cover the whole stem 2 entirely, or may cover only one or more portions of the stem 2.

[0073] In a preferred solution the coating is made as contiguous but separate sections, longitudinally juxtaposed, the length of which is a fraction of the overall length of the stem. In this way, the ridge and valley coating is prevented from breaking under load or detaching from the surface of the spoke in the presence of elastic elongations of the stem. In addition, it has been observed that applying an adhesivised or comoulded coating on the stem of the spoke prevents any delamination of the same as otherwise can occur under load with the carbon fibre spokes.

Claims

CLAIMS1. An aerodynamic spoke (l;22;23;24;100) for spoked wheels, in particular for bicycles, comprising a stem (2) elongated in a dominant direction and means to reduce the aerodynamic resistance of the spoke on the surface of said stem, characterized by the fact that said means comprise a plurality of undulations on at least a portion of the surface of said stem, with ridges (10) and valleys (11) extended transversely to said dominant direction, and by the fact that said aerodynamic spoke (1) has, at the longitudinally opposed ends, respective fastening elements (8, 9) for fastening to a hub and a rim of a wheel, respectively.

2. An aerodynamic spoke (l;22;23;24;100) for spoked wheels, in particular for bicycles, comprising a stem (2) elongated in a dominated direction, wherein said aerodynamic spoke (1;22; 23; 24;100) has, at longitudinally opposed ends, respective fastening elements (8, 9) for fastening to a hub and a rim of a wheel, respectively, and comprises a plurality of undulations on at least a portion of the surface of said stem (2) having ridges (10) and valleys (11) extended substantially transversely to said dominant direction in such a way as to reduce the aerodynamic resistance of the aerodynamic spoke.

3. The aerodynamic spoke (l;22;23;24;100) according to claim 1 or 2, wherein said stem (2) defines a major transversal dimension orthogonal to said dominant direction, and wherein consecutive ridges and / or valleys (10, 11) are spaced between each other with a pitch smaller than said major transversal dimension.

4. The aerodynamic spoke (l;23;24;100) according to any one of the precedingclaims, wherein ridges (10) and valleys (11) are continuous between opposing longitudinal sides (6, 7) of the spoke.

5. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein the stem (2) of the spoke has a flattened crosssection.

6. The aerodynamic spoke (l;22;23;24;100) according to claim 5, wherein the stem (2) of the spoke has a substantially elliptical cross-section.

7. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein said ridges (10) and valleys (11) are parallel to each other.

8. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein the major extension direction of each of said ridges (10) and valleys (11) forms, with the longitudinal direction of the stem (2), an angle comprised between 45° and 95°.

9. The aerodynamic spoke (l;22;23;24;100) according to claim 8, wherein said angle is equal to 90° ± 5°.

10. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein the undulations terminate at a distance of 10-50mm from the respective fastening elements (8, 9).

11. The aerodynamic spoke (l;23;24;100) according to any one of the preceding claims, wherein the undulations present alternations of said ridges (10) and valleys (11) on opposing surfaces (4, 5) of the stem (2).

12. The aerodynamic spoke (l;23;24;100) according to claim 11, wherein the alternations of ridges (10) and valleys (11) on opposing surfaces (4, 5) of the stem (2) are symmetrical to each other.

13. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein the maximum depth of the undulations is comprised between 0.1 and 1 mm.

14. The aerodynamic spoke (22;23;24) according to any one of the preceding claims, wherein the undulations are provided on at least one of the opposing longitudinal sides (6, 7) of the spoke (1).

15. The aerodynamic spoke (23) according to claim 14, wherein the undulations on at least one of said opposing longitudinal sides (6, 7) are connected to corresponding undulations on said opposing surfaces (4, 5).

16. The aerodynamic spoke (l;22;23;24;100) according to any one of the preceding claims, wherein the undulations on said opposing surfaces (4, 5) are reported on the stem (2) of the spoke.

17. A process for manufacturing an aerodynamic spoke (100) wherein a coating (130) is applied to a spoke stem (2) elongated in a dominant direction, comprising a plurality of undulations on at least a portion of the surface of said stem (2) with ridges (10) and valleys (11) extended transversely to said dominant direction.

18. The process for manufacturing an aerodynamic spoke (100) according to claim 17, wherein the coating (130) is applied by co-moulding.

19. The process for manufacturing an aerodynamic spoke (100) according to claim 17, wherein the coating (130) is applied by adhesivization.

20. The process for manufacturing an aerodynamic spoke (100) according to claim 17, 18 or 19, wherein ridges (10) and valleys (11) are alternated on opposing surfaces (4, 5) of the spoke (100) with a substantially matching arrangement of ridges (10) with ridges (10) and valleys (11) with valleys (11).

21. The process for manufacturing an aerodynamic spoke (100) according to any one of claims 17 to 20, wherein the coating (130) is interrupted by longitudinally juxtaposed modules of longitudinal extension smaller than the extension of the stem (2).

22. The process for manufacturing an aerodynamic spoke (100) according to any one of claims 17 to 20, wherein the spoke (100) comprises a core (120) of composite material on which said coating (130) is applied.

23. The process for manufacturing an aerodynamic spoke (100) according to any one of claims 17 to 20, wherein opposing surfaces (104, 105) of the core (120) are essentially free of undulations.

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