HK1083611B - A wheel spoke and a method for the manufacture thereof - Google Patents

Description

Spoke and method for manufacturing same

Technical Field

The present invention relates to a spoke and a method for manufacturing the same, and particularly, the present invention is preferably applied to the production of spokes using a lightweight alloy. These materials are not suitable for producing spokes using conventional methods due to their mechanical strength properties.

Background

In general, spokes (including those made of light alloy) comprise a shaft having an end for connection to a hub (for example, formed with an enlarged head) and screws at axially opposite ends to which nipples for connecting the spokes to the rim are adjustably screwed. Spokes with these characteristics are easily produced from high strength materials such as steel, but when made from aluminum alloys, some mechanical strength problems arise. The greatest problem occurs in the threaded region of the nipple, which is prone to yielding and damage under stress. The spokes loosen or break.

Japanese patent JP60080901a2 to MITSUBISHI RAYON co.ltd. describes a composite material spoke comprising a reinforced resin shaft subjected to fiber reinforcement, fitted at its ends with metal tips, respectively. However, this solution is not suitable for producing lightweight alloy spokes, since it requires a considerable increase in the dimensions of the spoke ends in the region of the tip, with respect to the shaft. In the lightweight alloy spokes, the shaft itself already has a large thickness.

Substantially the same problem is encountered with spokes as described in us patent 6036279 to Campagnolo srl.

Disclosure of Invention

The main task of the present invention is to provide a high-strength, reliable spoke, preferably with a lightweight alloy shaft.

Within the scope of this task, an important object of the present invention is to provide a method for producing such a spoke, which is carried out in a reliable and safe manner, while having a suitably low production cost.

Another object of the invention is to limit the dimensions of the spokes, in particular in the threaded zone and/or in the head zone of the nipples.

It is a further object of the present invention to allow the use of conventional rims and nipples while using lightweight alloy spokes.

According to the invention, there is provided a spoke comprising a shaft having two opposite longitudinal ends on which a terminal element is fixed by means of fixing means, the terminal element having means for connecting the spoke to a respective wheel member, characterized in that the terminal element is provided at both longitudinal ends of the spoke and in that the fixing means comprise a stud-bolt type connection between the shaft and the terminal element, the shaft being made of a material having a mechanical strength which is less than that of the terminal element.

Brief description of the drawings

The characteristics and advantages of the present invention will become more apparent from the detailed description of a preferred embodiment thereof, which is described by way of non-limiting example with reference to the accompanying drawings, in which:

fig. 1 is a front elevational view, partly in section, of a detail of a bicycle wheel provided with a spoke according to the present invention.

Figure 2 is an enlarged scale front view of a detail of the spoke shown in figure 1.

Figure 3 is a front view, partly in section, of a detail of a bicycle wheel provided with a spoke according to a variant of the present invention.

Fig. 4 and 5 are front views on an enlarged scale of the detail indicated by arrows IV and V, respectively, of fig. 3.

Figures 6 and 7 are front and side views, partly in section, of a spoke according to a further variant of the invention.

Figure 8 is an enlarged scale section through a detail of the spoke shown in figures 6 and 7.

Figure 9 is a front view of a further spoke according to the invention.

Figure 10 sets forth a series of cross-sectional views of various profiles of the spoke shown in figure 9.

Figures 11 to 17 are front views of spokes with various shapes produced according to the invention.

The pairs of figures 18-19, 20-21 and 22-23 are respectively a front view and a side view of a corresponding number of spokes produced according to the invention.

Figure 24 is a side view of yet another spoke according to the invention.

Detailed Description

In the figures, a wheel provided with spokes is indicated by R, which comprises a rim C connected to a hub (not shown) by a plurality of spokes 10. Each spoke is connected at one of its ends to the hub by a connector having a head 11 (the shape and arrangement of the head 11 may vary as required), and at the other end to the rim C by a respective nipple N.

Each spoke 10 comprises a straight shaft 12, which in the embodiment shown in figures 1 and 2 is formed integrally with the head 11 from a light alloy, for example an aluminium alloy. Among the alloys most suitable for this purpose are the following: 100 type high-strength corrosion-resistant aluminum alloy (Antiriodal 100), 22 type Avermen aluminum alloy (Aronal 22), 14 type Avermen aluminum alloy (Aronal 14), 24 type Avermen aluminum alloy (Aronal 24), 55 type aluminum magnesium zinc alloy (Ergal 55).

A terminal element 15 for the nipple N with a thread 19 is fixed by means of a fixing device 14 at the longitudinal end 13 of the shaft 12 remote from the head 11.

According to the invention, the fixing means 14 comprise a stud-bolt type connection having an axial blind hole 16 in the end of the shaft 12 and a self-tapping screw 17 on the terminal element 15.

The terminal element is made of steel and therefore has a higher mechanical strength than the material of which the shaft is made. The hole 16 and the screw 17 are each formed in a tapered shape.

An actuating key 18 having, for example, a hexagonal outer shape is provided at the intermediate portion of the terminal element for driving the terminal element 15 into the shaft 12. The terminal element 15 is preferably driven into the shaft 12 in an interference manner, so that local expansion deformations of the shaft 12, which are not noticeable in fig. 1, are caused.

To manufacture wheel disc 10, shaft 12 and terminal element 15 provided as an extension thereof are prepared separately. An axial bore 16 is then drilled into the shaft and the terminal element 15 is secured to the shaft by means of a stud-bolt type connection, so that the shaft and the terminal element are firmly secured together in an interference fit.

The spoke thus formed is tensile and light and strong in the tightening region of the nipple.

It is also limited in size, particularly with respect to the tightening region of the nipple, allowing the use of standard nipples.

The invention is also suitable for producing spokes with a head fixed to the rim and a nipple fixed to the hub.

Finally, the spoke may be provided at both its longitudinal ends with said terminal elements for fixing to the rim and to the hub by means of nipples or similar means. An example of such a spoke is shown in figures 3 to 5 and is indicated by reference numeral 30. The spoke 30 has a light alloy shaft drilled with blind holes 31 at both of its opposite ends. Respective terminal elements 32, 33 made of steel or other material with high mechanical strength are inserted into the two holes 31 with a stud-type connection. The first terminal element 32 is similar to the element 15 and is provided with a threaded portion for screwing the nipple N. The second terminal element is shaped as a standard connection piece with a head 11 and a bend 34. However, the second element may also be formed straight, or have a threaded portion, or be formed in another way. So set up, light alloy spoke can also be used in its overall structure (rim and/or wheel hub) all design be used for fixed steel spoke's wheel on to make rim and wheel hub all more compact and the size is littleer, in order to be favorable to making it have characteristics such as light and accord with aerodynamic requirement.

A third variant of the spoke according to the invention is indicated by 40 in figures 6 to 8. The shaft 41 of the spoke 40 is flattened at its middle portion by pressing or similar technique and has cylindrical end portions 42, 43 which are circular in cross section and in which axial blind holes 44, 45 are formed, respectively.

Each terminal element 46, 47 has a threaded portion 48, 49 that is screwed into the respective hole 44, 45, preferably in a press-fit manner. The terminal element 46 also has a second opposite threaded portion for screwing the nipple, and the element 47 has a head, which may be called a Z-shape, for engaging a corresponding hole in the hub.

The depth of the axial bores 44, 45 is such that when the respective threaded portions 48, 49 are fully screwed in, a free chamber 50 remains in the bore which is not less than one third of the total length of the bore. It has been found that this chamber 50 can be used to distribute, within a suitable and acceptable range of values, an excessive pressure which can be generated both by the deformation of the shaft of the spoke due to the compression of the respective terminal element and by an increase in the pressure of the liquid which remains in the chamber 50 during the tightening of the threaded portions 48, 49. In fact, since the screwing of the threaded portion is carried out without previously threading the blind hole, (in practice, the screws of the steel portions 48, 49 deform the aluminium alloy wall of the blind hole, thus forming a substantially liquid-tight self-tapping connection) as the volume of the chamber continues to decrease, the air is compressed together with any liquid and vapour trapped in the blind holes 44, 45, which causes an increase in the stress of the shaft of the spoke in the end region, which is already weakened by the presence of the blind holes 44, 45.

The present invention thus solves the problems set out and provides numerous advantages over the prior art. Firstly it allows the use of conventional rims and hubs without any special modifications. Moreover, the spoke is strong and reliable. This has the advantage not only of being lightweight and adaptable, but also of being able to be manufactured with a favourable aerodynamically favourable profile and/or a profile with a pronounced aesthetic effect, which in particular gives the assembled wheel a visual effect similar to a wheel with integrated spokes.

Some of the profiles described are described in italian patent application No. bo 2002a783, the content of which is contained in the present description and forms an integral part thereof. These profiles are shown by way of example as spoke cross-sections 114a-f described with reference to fig. 9 and 10. The processing method for producing spokes with these profiles consists in preparing a semifinished element in the form of a billet of a light alloy, for example the alloy mentioned above (trade names: Ergal, Avional, Peraluman, Anticorodal), cutting it into bars of suitable length and pressure forging in a press suitably equipped with dies and dies suitable for forging metal alloy spokes.

Figures 11 to 17 show an alternative embodiment of a spoke that can be produced with this method. Viewed from the front, they are substantially spear-shaped with a longitudinal bore 118 extending from the first end 102 towards the second end 104. In the first and second end regions, substantially triangular shaped side ribs 119 are provided in a reflection-symmetrical manner with respect to the longitudinal plane of symmetry of the spoke. The second end 104 is bent into an elbow (fig. 12) to facilitate engagement of the head 107 in a corresponding hole provided in the hub.

Fig. 13 is a front view of a spear-tipped spoke having a longitudinal slotted bore 118, the bore 118 being divided by a pair of bridge members 120 arranged generally in an X-shape. In the embodiment shown in fig. 14, two bridges 120 are arranged parallel to each other in a substantially diagonal manner, and fig. 15 shows a further embodiment provided with four substantially transverse bridges 120. In fig. 16, a further embodiment is shown in which four substantially diamond-shaped longitudinally aligned holes 118 are formed. Fig. 17 shows another embodiment of a spoke which can be produced according to the method of the invention, in which the first end 102 for fixing to the rim is substantially Y-shaped, with two stem portions 105, each stem portion 105 having a respective threaded portion 106 for engagement in a respective nipple. The spoke has a substantially Y-shaped central hole 118 corresponding to the shape of the spoke itself. The central portion of the spoke embodiment shown in fig. 11-17 has a composite cross-section and varies from one end of the same spoke to the other.

In fig. 18 to 23, the central portion 103 of the spoke has a simple or composite cross-section (in the illustrated embodiment, the central portion is substantially flattened), the first end portion 102 and the second end portion 104 each have a respective cylindrical stem portion 105, the stem portion 105 having a threaded end 106 for engagement in a corresponding nipple.

Fig. 22 and 23 show a front view and a side view, respectively, of the spoke shown in fig. 20 and 21, but in which the second end 104 forms a head 107 for engagement in the hub.

Fig. 24 shows an embodiment of a spoke that can be produced according to the method of the invention and in which the first and second ends 102, 104 are removable, i.e. interchangeable. In the spoke shown in fig. 24, each end portion 102, 104 is substantially in the form of a partially threaded shaft which is removably engaged in a corresponding internal thread formed in the central portion 103 of the spoke, by means of a locking nut 121. The ends 102, 104 form a cylindrical head 107 for fixing to the hub and the rim, respectively.

The spokes that can be produced according to the method of the invention are distinguished by high strength, toughness and elasticity and are very lightweight. It also enables the production of spokes with aesthetic and functional features with respect to the prior art, and moreover, considerable advantages in terms of further production can be achieved, and in that it is not necessary to provide a complete wheel die as in the production of single-piece die-cast wheels, but rather the geometry of the wheel can be significantly changed simply by replacing the dies and dies of which the spokes are forged.

Claims (18)

1. A spoke for wheels comprising a shaft having two opposite longitudinal ends on which terminal elements are fixed by means of fixing means, the terminal elements having means for connecting the spoke to a respective wheel member, characterized in that the terminal elements are provided at both longitudinal ends of the spoke and in that the fixing means comprise a stud-bolt type connection between the shaft and the terminal elements, the shaft being made of a material having a mechanical strength which is less than that of the terminal elements.

2. A spoke according to claim 1 in which the stud-bolt-type connection comprises an axial hole in the end of the shaft and a screw on the terminal element, the engagement between the hole and the screw being either threaded or self-tapping.

3. A spoke according to claim 1 in which the shaft is made of a lightweight alloy.

4. A spoke according to claim 1 in which the terminal element is made of steel.

5. A spoke according to claim 2 in which the screw has a tapered profile.

6. A spoke according to claim 1 or claim 2 in which an actuating key is provided in the intermediate portion of the terminal element to drive the terminal element into the shaft.

7. A spoke according to claim 1 or claim 2 in which the terminal element is driven into the shaft in an interference manner.

8. A spoke according to claim 1 or claim 2 in which the terminal element is provided at its end remote from the shaft with means for connection to a nipple.

9. A spoke according to claim 1 or claim 2 in which the terminal element is provided at its end remote from the shaft with means for attachment to a hub.

10. A spoke according to claim 8 in which the means for connection to a nipple comprises a threaded portion of the terminal element.

11. A spoke according to claim 9 in which the means for attachment to the hub comprise an attachment element.

12. A spoke according to claim 2 in which the bore in the shaft is blind and has a depth greater than the length of the threaded portion of the terminal element engaged in the bore to form a chamber in the bore.

13. A spoke according to claim 12 in which the axial depth of the chamber is greater than or equal to one third of the total axial length of the blind bore.

14. A method for manufacturing a wheel disc, comprising the steps of preparing a shaft from a material having a mechanical strength lower than that of the material from which the terminal element is made, and separately preparing at least one terminal element for being provided as an extension of the shaft, characterized in that the terminal element is fixed to the shaft by means of a stud-type connection, thereby firmly fixing the shaft and the terminal element together in the axial direction.

15. A method for manufacturing a spoke according to claim 14 in which the connection is extruded with interference.

16. A method for manufacturing a spoke according to claim 14 or 15 in which the stud-bolt type connection is effected by means of a self-tapping joint.

17. A spoke according to claim 1, made by press forging of a metal alloy and having a substantially Y-shaped configuration with two stems at the same end, said stems each having a threaded portion for engaging a respective nipple.

18. A spoke according to claim 17 having a central hole of a shape corresponding to the external shape of the spoke itself.