Motorcycle wheel, particularly for off-road use Technical field

The present invention relates to a motorcycle wheel of the type having the characteristics mentioned in the preamble of the principal claim. The present invention is primarily, but not exclusively, applicable to the field of off- road motorcycling. Technological background

In the field of the invention, there is a well-established need to use tyres with a low inflation pressure to optimize grip, with a consequent increase in the risk of puncture of the air chamber and/or detachment of the tyre from the rim.

To overcome these drawbacks, the known art provides for the replacement of the air chamber with elements made from resilient foam material. However, this solution entails a substantial increase in rotating mass to the detriment of the efficiency of the wheel.

The solution is also costly, since the foam easily deteriorates. An alternative to foam is that of "tubeless" tyres, which have no air chamber and are lighter, and have the advantage of relatively slow deflation in case of puncture. Tubeless tyres are suitable for the high speeds that may be reached in motorcycling, but are subject to the risk of detachment from the rim, in which the beads of the tyre become separated from the sides of the rim, thus causing sealing problems which may lead to the sudden deflation of the wheel. To overcome this drawback, small relief profiles, called "humps", are formed on the rim channel, at a predetermined distance from the sides, to retain the beads

of the tyre in the correct fitting position. However, there is a real risk of detachment from the rim when tubeless tyres are used with low inflation pressures.

The use of humps is less effective in the case of particularly low pressures and small tyre cross sections, owing to the reduction in the force required to ride over the hump in response to the high stresses typically encountered in off-road motorcycling.

Description of the invention

The principal object of the invention is to provide a motorcycle wheel which is structurally and functionally designed to accept the fitting of tubeless tyres with low inflation pressure, with the high reliability required for demanding motorcycling applications.

The aim of the invention is to provide a motorcycle wheel which can overcome all the technical drawbacks described with reference to the aforesaid known art.

This object and these aims are achieved by the invention by means of a wheel made in accordance with the following claims.

Brief description of the drawings

The characteristics and advantages of the invention will be made clearer by the detailed description of a preferred example of embodiment thereof, illustrated, for the purposes of guidance and without restrictive intent, with reference to the attached drawings, in which:

- Figure 1 is a partial cross-sectional view of a motorcycle wheel made according to the invention; - Figure 2 is a sectional view on an enlarged scale of the wheel of

Figure 1;

- Figure 3 is a perspective view of a detail of the wheel of the preceding figures;

- Figure 4 is a view in longitudinal section of the wheel of the preceding figures.

Preferred embodiment of the invention

In the figures, the number 1 indicates the whole of a motorcycle wheel including a rim 2 of the single channel type, a hub 3 and a plurality of spokes 4 which are shown only partially and schematically and which are fixed by their respective opposite ends to the rim 2 by means of nipples

5 and to the hub 3 by means of heads which are not shown. The rim 2 is provided with a channel 6 for fitting a tyre 7 of the tubeless type. The tyre is fitted in the channel 6 with its beads 8 bearing on corresponding shoulders 9 of the rim 2. Retaining means 10 are housed in the channel 6 to retain the beads 8 behind the shoulders 9.

The retaining means 10 comprise a belt 11, preferably made from aluminium, plastics material or similar relatively light and strong materials, mounted removably in the channel 6. The belt 11 can be tightened on to itself so that it is interposed in the form of a spacer between the beads 8, thus pressing them against the corresponding shoulders 9.

The belt 11 is extended longitudinally with two opposite ends. The first end, indicated by 12, is fixed to the rim as described below; the second end, indicated by 13, is free, before the wheel fitting is completed as

explained below. The second end 13 is fixed, by means of a clamp 16 for example, to a metal wire stay 14, extending outside the rim 2 through a fluid-tight fairlead 15.

The fairlead 15 comprises a tubular body 17 fixed radially in the channel 6 of the rim 2 by means of an adaptor 20, one end of which bears on the side of the rim 2 opposite the channel 6 while the other end bears on a radial flange 21 of the body 17.

A sleeve 18 is fixed to the tubular body 17 in the channel 6 by a threaded connection. O-ring sealing means 22 are provided between the channel 6 and the sleeve 18 to provide a tight seal between the fairlead and the rim.

At one end 23 of the tubular body 17 there is fixed a locking device 24 in the form of a clamp which can be tightened on the wire of the stay 14 by means of a nut 24a. A cap 25 is fitted in a sealed way on the flange 21 of the tubular body with the interposition of a second O-ring 27.

The first end 12 of the belt 11 is fixed to the sleeve 18 by means of a nut 19. The stay 14 is taken through the belt 11 using a bush 26 applied to the second end 13, and is cut off beyond the locking device 24. The wheel according to this invention is fitted in the following way. Firstly, one of the two beads of the tyre is fitted in the rim channel. The tubular body 17 is then attached to the rim 2 by bringing the adaptor 20 into contact with it, and the first end 12 of the belt 11 is fixed to the sleeve 18 by means of the nut 19. The belt 11 is housed in the channel 6 and remains slack so as not to interfere with the subsequent stages of fitting. The second bead is also placed in the rim channel, starting from

the area opposite the fairlead. Air is then introduced into the inflation chamber of the tyre to bring the beads into contact with the shoulders of the rim. When the fitting is completed, the second end 13 of the belt 11 is tightened on to the first end 12, by taking the stay 14 through the tubular body 17 of the fairlead 15 and pulling in such a way that the second end is also brought up to the fairlead 15. The stay 14 is then cut off beyond the locking device 24.

It should be noted that the transverse extension of the belt 11 is such that it locks the beads of the tyre 7 behind the corresponding shoulders, even in the presence of stresses and impacts applied transversely to the tyre, and even in case of severe deformations such as those generated in the case of partially inflated tyres.

Thus the invention achieves the proposed object and provides numerous advantages with respect to the known art. In particular, it makes it possible to produce light wheels having a lower rotating mass when tubeless tyres are used, without the risk of puncture and detachment from the rim in conditions of high stress, low inflation pressures and small tyre cross sections.