WO2007082762A2

WO2007082762A2 - Spoke wheel for tubeless tires, particularly for motorcycles, and method and machine for its manufacture

Info

Publication number: WO2007082762A2
Application number: PCT/EP2007/000467
Authority: WO
Inventors: Savario Rompani
Original assignee: Rompani Srl
Current assignee: Rompani Srl
Priority date: 2006-01-20
Filing date: 2007-01-19
Publication date: 2007-07-26
Anticipated expiration: 2008-07-20
Also published as: ITMI20060097A1; WO2007082762A3

Abstract

A spoke wheel (1) for tubeless tires, particularly for motorcycles, comprising a rim (2), a hub (3) and a plurality of spokes (4) which are anchored between the rim (2) and the hub (3); in order to anchor the spokes (4) the wheel (1) comprises nipples (7) exclusively at the hub (3), the nipples (7) being fixed to one end of a respective spoke (4); the rim further comprises a plurality of lugs (13a, 13b) arranged in a substantially symmetrical position with respect to the central plane of the wheel in order to engage the head of each spoke (4) on the rim (2), the rim is formed by means of a radial ring rolling mill.

Description

SPOKE WHEEL FOR TUBELESS TIRES, PARTICULARLY FOR MOTORCYCLES, AND METHOD AND MACHINE FOR ITS MANUFACTURE Technical Field The present invention relates to a spoke wheel for tubeless tires, particularly for motorcycles, and to the method and machine for its manufacture. Background Art

Currently, in motorcycle wheels there is an increasing tendency to use tubeless tires, which are used preferably on high-performance (high-speed) motorcycles.

In known spoke wheels which use this type of tire, the main drawback is due to the excessive weight of the wheels, particularly in the rim region, which has a negative effect on on-road driving of the motor vehicle due to the gyroscopic effect.

Moreover, known methods for manufacturing the rim of spoke wheels for motorcycles always entail welding and drilling the channel, and such operations worsen rigidity and safety. Disclosure of the Invention The aim of the present invention is to obviate the drawbacks of the background art, by providing a spoke wheel for motorcycles which is suitable for fitting tubeless tires, has a low gyroscopic effect, and is safer and more rigid.

Within this aim, an object of the invention is to provide a wheel which is lightweight without losing rigidity and mechanical strength.

Another object of the invention is to provide a spoke wheel which is at least equal in terms of weight performance, but stronger than, monolithic wheels (cast or forged) of the known type, thus making it usable also on high-performance road motorcycles. Another object of the invention is to provide a spoke wheel which is highly reliable, relatively easy to provide and at competitive costs.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by a spoke wheel for tubeless tires, particularly for motorcycles, comprising a rim, a hub and a plurality of spokes which are anchored between the rim and the hub, characterized in that in order to anchor the spokes the wheel comprises nipples exclusively at the hub, said nipples being fixed to one end of a respective spoke.

Preferably, the rim comprises a plurality of lugs which protrude from its bottom surface and substantially toward the inside of the rim, for engagement of the head of a respective spoke. Such rim is advantageously without welds, since it is provided by means of a flow forming process or more preferably a rolling process.

In particular, according to one aspect of the invention, a machine for manufacturing the rim of said spoke wheel is provided comprising a radial ring rolling mill which has at least one main roller and one secondary roller which face each other, the main roller being movable radially toward the secondary roller, the main roller and the secondary roller being shaped substantially complementarily with respect to the contour of the rim to be manufactured. Moreover, the invention also provides for a method for manufacturing the rim described above, characterized by the steps of:

(a) providing said machine;

(b) providing a rough ring, which corresponds to a slice of pipe or a centrally pre-perforated circular blank, preferably made of aluminum and/or magnesium alloy. c) mounting the rough ring on the machine, so that the main roller is external to the rough ring and the secondary roller is internal to said rough ring; d) forming the rim by turning the main roller and the secondary roller about the respective axis of rotation and moving with a progressive radial approach the main roller toward the secondary roller. Brief Description of the Drawings

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the wheel according to the invention, to the machine and to the method for manufacturing it, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of a wheel according to the invention; Figure 2 is a schematic plan view of the wheel of Figure 1 ;

Figure 3 is a schematic sectional view of the wheel of Figure 1, which shows only two spokes for the sake of simplicity;

Figure 4 is a diagram of the arrangement of the rollers in the machine according to the invention; Figures 5 and 6 are axial sectional views of the contoured rollers preferably used in the machine according to the invention. Ways of carrying out the Invention

With reference to the figures, the wheel according to the invention is generally designated by the reference numeral 1 and comprises a rim 2, a hub 3 and a plurality of spokes 4 which connect the hub to the rim.

The spokes 4 comprise a stem 5, which has, at one end, an enlarged head 6 and, at the opposite end, a thread for screwing an anchoring nipple 7.

The rim 2 preferably has a contour constituted by two external flanges

8 and 9 for retaining the side wall of the tire, two bases 10 and 11 for supporting the internal part of the tire, and a channel bottom 12.

A plurality of lugs 13a and 13b are provided on the wall of the bottom

12 which is directed toward the hub 3 of the wheel and are arranged along two respective circumferences in a substantially symmetrical position with respect to the centerline plane of the rim and are directed substantially toward the inside of the wheel (Figure 3). The lugs 13a and 13b have a very low thickness, preferably on the order of 4-6 mm, are formed monolithically with the rim and protrude from the bottom 12 in a direction which is inclined with respect to the centerline plane of the wheel, away from the center of the wheel. Each lug 13a and 13b comprises an internal through hole 14, which is crossed by the respective spoke and is adapted to provide an abutment surface for the enlarged head 6 on the end of the spoke. The internal hole 14 is preferably flared.

In order to anchor the spokes 4 to the hub 3, respective nipples 7 are provided which are mounted exclusively on the hub and in which the threaded ends of the spokes 4 are screwed. The arrangement of the nipples on the hub allows to concentrate the heavy elements of the wheel at its center, thus reducing the gyroscopic effect.

Moreover, the gyroscopic effect is further reduced by providing in the peripheral regions of the wheel lightweight anchoring elements, constituted by the lugs 13a and 13b, which do not increase the weight of the peripheral region of the wheel, since they are provided monolithically with the rim and are made of the same material as the rim (aluminum or an alloy of aluminum and/or magnesium) and have a low thickness. Such anchoring elements are provided for the exclusive anchoring of the head of the spoke, i.e., of its lightweight end, while the heavy end, which is threaded and screwed into the nipple, is fixed to the hub.

Moreover, a further improvement in terms of gyroscopic effect is due to the particular arrangement of the lugs 13a and 13b on the rim. As shown, the lugs are arranged preferably at the bottom 12 of the channel, i.e., on the internal region of the rim which has a smaller diameter.

Going back to the preferred embodiment shown in Figure 1 , the hub 3 comprises a plurality of tabs 15 which protrude radially toward the outside of the hub and are arranged around the hub in a mutual position which is substantially symmetrical with respect to the centerline plane of the wheel 1. Each tab 15 comprises two through openings, inside which a respective nipple 7 is fixed. The axes of the openings provided in the tabs are preferably not parallel to each other and are directed substantially tangentially with respect to the cylindrical lateral surface of the hub. Even more preferably, the axes of each tab 15 are directed substantially toward respective lugs 13a or 13b which are arranged in the half-space that lies opposite the one in which the tab 15 is located, with respect to the central plane A of the wheel 1. In this manner, the spokes of the wheel, once assembled, cross each other. Of course, the person skilled in the art understands without difficulty that the particular type of fitting of the nipples described above is only an example and that the nipples can be fitted to the hub even in a different manner. For example, the nipples can be fixed to the hub so that they are not tangent to its cylindrical lateral surface, for example in a radial direction, or in a mixed radial/tangential direction.

A peculiarity of the invention consists in the method for manufacturing the rim 2 of the wheel, which avoids the need to provide the typical welds required to close the rim following the extrusion and calendering steps. In particular, the rim 2 according to the invention can be provided by means of a method called flow forming, usually used to provide car wheel rims. The method consists in a cold or hot plastic deformation of a previously forged aluminum casting or of a sheet of metal plate.

Plastic deformation is produced by means of machines which are similar to (but more powerful than) spinning lathes, in which the tool is constituted by at least one roller which shapes the forged casting or the metal plate, making it adhere to a negative die of the shape to be obtained.

It has been found that by using plates made of light alloy such as aluminum of the 6082-T6 type it is possible to obtain rim plate thicknesses of approximately 3 mm or even less, which are lower than the thicknesses obtained with known casting methods and are equally strong. Moreover, the step of welding the rim is avoided, thus achieving higher rigidity and safety accompanied by a particularly low weight of the rim and of the wheel as a whole. However, it has been observed that the same results are achieved by a providing the rim 2 by means of a rolling process, by using the machine for radial rolling according to the invention which has the components shown in Figures 4, 5 and 6.

The machine is a radial ring rolling mill, which comprises a structure 100 for forming the rim 2 of the wheel by means of rollers which are parallel to the axis of the rim 2. The rotation axes of said rollers are preferably oriented in a vertical direction, so that the rim is formed on a plane which is substantially horizontal and parallel to the ground.

Specifically, the structure of the rolling mill 100 comprises a main roller 101 and a secondary roller 102, at least one of which can move radially with respect to the ring 103 to be rolled.

The main roller 101 is the roller which can move radially, and for this purpose it is supported by an appropriate slider, which is not shown in the figures. The secondary roller 102 is instead supported preferably by supporting rollers 104 which optionally can also move parallel to the axis of the secondary roller 102.

The two rollers, the main one 101 and the secondary one 102, face each other along a diametrical direction of the ring 103 and define between them a rolling region for the ring 103. The mutual radial approach movement of the two rotating rollers causes an extension in a tangential direction of the material that constitutes the ring 103 and a consequent diametrical increase thereof, as shown by the sequence of Figures 5 and 6.

There are also centering rollers 105, which are arranged on opposite sides of the ring 103 and are adapted to maintain the circular shape of the ring during the work performed by the main and secondary rollers and to determine the final diameter of the ring. For this purpose, the centering rollers can move toward or away from each other.

Finally, the machine can comprise a measurement roller 106, which is arranged in a position which is diametrically opposite with respect to the position of the main roller 101 and is adapted to monitor the diameter of the ring 103 being worked.

The main roller 101 and the secondary roller 102 can have a smooth surface, as in Figure 4, or preferably can be shaped complementarily with respect to the shape of the outer and inner profiles of the rim 2 respectively, as shown in Figures 5 and 6.

In the first case, the machine according to the invention is programmed to form a ring whose diameter is substantially equal to the diameter of the rim 2, optionally with an offset of 3-5 mm with respect to the final thickness of the rim, and said ring is subsequently machined by turning or with chip-forming machining methods in order to obtain the final shape of the rim 2 shown in Figure 1. Machining occurs circumferentially, so as to not break the fibers which, indeed due to the fact that the ring is formed starting from an annular rough component (a slice of pipe or a pre- drilled circular blank), are arranged in a natural manner and substantially concentrically along the circumference of the ring 103.

In the second case, shown in Figures 5 and 6, the main roller 101 has, on its surface, an annular protrusion 1 1 1 which is coaxial to the roller 101 and is adapted to form, with the rotation of the roller 101 , the bottom wall 12 and the two bases 10 and 1 1 of the outer contour of the rim 2. Likewise, the secondary roller 102 has an annular recess 1 12 which is directed toward the annular protrusion 1 1 1 of the roller 101. The recess 1 12 can comprise an additional small protrusion 1 14 in a central position, which is adapted to form the two circular projecting regions 1 15 on the internal wall of the rim from which the lugs 13a and 13b are obtained by turning and subsequent milling. Advantageously, the recess 112 is arranged between two walls 1 13a and 1 13b which protrude radially from the surface of the secondary roller 102, so as to determine the axial dimension of the rim 2 and prevent an axial slippage of the ring during rolling. The wall 1 13a is integrated in the secondary roller 102, while the wall

113b can slide axially along the secondary roller 102, so that it can be removed in order to be able to install the rough ring to be formed, and can be locked in abutment (for example by means of an annular element, thread or other known means) against the peripheral region of the recess 112, in particular on the part which is symmetrically opposite to the wall 113a with respect to the recess 1 12.

The internal surface of the walls 1 13a and 1 13b can optionally be contoured so as to adapt to the contour of the recess 1 12 and thus complete the negative profile of the rim 2. In the radial rolling method according to the preferred embodiment of the invention, one begins with a slice of pipe or a centrally pre-drilled circular blank 103, made of aluminum or a light alloy of aluminum and/or magnesium (for example aluminum of the 6082-T6 type) and having a diameter which is smaller than the final diameter of the rim (typically an initial diameter of approximately 320 mm, with an internal hole of approximately 95 mm). The slice of pipe or the pre-drilled circular blank are machined internally and externally by means of the rollers 101 and 102 of the machine according to the invention (as shown schematically in Figures 5 and 6), which are moved toward each other so as to deform plastically the slice of pipe or the pre-perforated circular blank, increasing its diameter and shaping its profile, thus achieving the final configuration shown in Figure 6. The lugs 13a and 13b, the height of which can be already defined by the circular projections 1 15 by means of the protrusion 114 of the secondary roller 102, are finally outlined permanently by turning and subsequent milling. The method ends with the engagement of the head 6 of the spokes 4 with the lugs 13a and 13b and with the insertion of the threaded part of the spokes in the nipples 7 applied to the hub 3.

By using the machine and the method according to the invention and starting from a rough ring made of aluminum or light alloy, the resulting rim is much stronger than known rims of spoke wheels for tubeless tires, since with the processes described above the concentric fibers that cross the material along the circumference of the ring 103 are not broken.

It is further evident that with the process by means of the radial ring rolling mill with contoured rollers, the channel welding is no longer necessary, since the machining of the rim begins from a slice of a pipe or from a pre-perforated circular blank.

In practice it has been found that the wheel, the method and the machine according to the invention fully achieve the intended aim, since they allow to reduce the gyroscopic effect of wheels for motorcycles, which is particularly harmful during steering.

The wheel, the method and the machine thus conceived are susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements. In practice, the materials used, as well as the dimensions, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. MI2006A000097 from which this application claims priority are incorporated herein by reference.

Claims

1. A spoke wheel for tubeless tires, particularly for motorcycles, comprising a rim, a hub and a plurality of spokes which are anchored between the rim and the hub, characterized in that in order to anchor the spokes the wheel comprises nipples exclusively at the hub, said nipples being fixed to one end of a respective spoke.

2. The spoke wheel according to claim 1, characterized in that said rim comprises a plurality of lugs which are arranged in a substantially symmetrical position with respect to the central plane of the wheel in order to engage the head of each spoke on the rim.

3. The spoke wheel according to claim 2, characterized in that the lugs are arranged approximate to the central plane of the rim and protrude substantially toward the center of the wheel.

4. The spoke wheel according to claims 2 or 3, characterized in that the lugs protrude from a bottom region of the rim.

5. The spoke wheel according to any one of the preceding claims, characterized in that the lugs protrude from the rim in a direction which is inclined with respect to the central plane of the wheel.

6. The spoke wheel according to any one of the preceding claims, characterized in that each of said lugs comprises an internal through hole which is crossed by the respective spoke and is adapted to provide an abutment surface for the enlarged head of the spoke.

7. The spoke wheel according to claim 1, characterized in that said rim has no welds, since it is provided by means of a flow forming method or a rolling method.

8. The spoke wheel according to any one of the preceding claims, characterized in that the hub comprises a plurality of tabs which protrude radially toward the outside of the hub and are arranged around the hub in a mutual position which is substantially symmetrical with respect to the central plane of the wheel.

9. The spoke wheel according to claim 8, characterized in that each tab comprises two through openings, inside which a respective nipple is fixed, the axes of the openings provided on the tabs being preferably not parallel to each other and being directed substantially tangentially to the cylindrical lateral surface of the hub.

10. The spoke wheel according to claim 9, characterized in that said axes are directed substantially toward respective lugs which are arranged in the half-space which lies opposite to the one in which the tab is provided, with respect to the central plane of the wheel.

11. A rim of a spoke wheel for tubeless tires for motorcycles, characterized in that it comprises a plurality of lugs which are formed monolithically with the rim and protrude from the bottom surface and toward the inside of the rim, for the engagement of the head of a respective spoke.

12. A machine for manufacturing a rim of a spoke wheel for tubeless tires for motorcycles, characterized in that it comprises a radial ring rolling mill provided with at least one main roller and one secondary roller which face each other, said main roller being movable radially toward the secondary roller, said main roller and said secondary roller being contoured substantially complementarily with respect to the contour of the rim to be manufactured.

13. The machine according to claim 12, characterized in that the main roller has, on its lateral surface, an annular protrusion which is coaxial to the main roller and is adapted to form the outer contour of said rim.

14. The machine according to claim 13, characterized in that the secondary roller has an annular recess which faces the annular protrusion of the main roller and is adapted to form the inner contour of said rim.

15. The machine according to claim 14, characterized in that the recess of the secondary roller comprises an additional protrusion in a central position, which is adapted to form two circular projecting regions on the internal wall of the ring being formed.

16. The machine according to claim 14 or 15, characterized in that said recess is arranged between two walls which are coaxial to the secondary roller and protrude radially from the lateral surface of the secondary roller, so as to determine the axial dimension of the rim and/or prevent an axial sliding of the ring during rolling.

17. The machine according to claim 16, characterized in that at least one of said walls which is coaxial to the secondary roller is fixed detachably to the secondary roller, so as to allow complete removal of said removable wall from the secondary roller.

18. A method for manufacturing a rim of a spoke wheel for tubeless tires for motorcycles, comprising the steps of:

(a) providing the machine according to one or more of claims 12 to

17; (b) providing a rough ring, which corresponds to a slice of pipe or to a centrally pre-perforated circular blank; (c) mounting said rough ring in said machine, so that said main roller is external to the rough ring and said secondary roller is internal to the rough ring; (d) forming said rim by rotating said main and secondary rollers about the respective rotation axis and moving with a progressive radial approach said main roller toward said secondary roller.

19. The method according to claim 18, characterized in that it comprises a step of turning and subsequent milling of said circular projecting regions on the internal wall of the formed ring, so as to obtain lugs, and a step for engaging on each lug a head of a respective spoke of the wheel.

20. The method according to claim 18, characterized in that said main and secondary rollers are cylindrical and lack contoured regions, and said step (d) for forming the rim is followed by an end step of turning or chip forming machining, in which the rim having a non-contoured profile obtained from step (d) is hollowed out along its circumference in order to obtain the intended contour.