Wheel hub for bicycle

The present invention relates to a wheel hub for a bicycle, in particular a racing bicycle.

The main target of manufacturers of components for racing bicycles is to reduce the weight of the individual components as much as possible. In the case of wheel hubs, the conventional technology envisages the use of light metal alloys, such aluminium alloys and the like. In order to reduce the weight of wheel hubs, solutions have already been proposed in which a tubular central part of the wheel hub is made of carbon fibres embedded in a resin of plastic material and in which a pair of side shells made of aluminium alloy are driven on the ends of the central portion made of carbon fibres. The side shells are provided with seats for supporting rolling bearings and for anchorage of the wheel spokes. Forming side shells made of carbon fibres in an integral way with the central portion would enable a further weight reduction but would entail serious problems as regards the way in which the spokes are anchored, above all in the case of spokes with L-shaped anchorage portions. If spokes of this sort were connected inside holes formed in a flange made of carbon fibres or the like, the stresses produced by tensioning of the spokes would give rise to contact pressures on the walls of the holes so high as to damage the hub in an irreparable way.

The purpose of the present invention is to provide a wheel hub that may overcome the aforesaid drawbacks.

According to the present invention, the above purpose is achieved by a wheel hub comprising a tubular body having at its ends a pair of flanges, each of which is provided with a plurality of holes for anchorage of respective spokes, in which at least one flange is made of fibre-reinforced plastic material and the aforesaid holes are associated to respective bushings made of metal material, each of which, in use, is set between an anchoring portion of a spoke and the inner wall of the respective hole.

Further characteristics and advantages of the present invention will emerge clearly from the ensuing detailed description, provided purely by way of non-limiting example, in which:

FIG. 1 is a partially sectioned front view of a hub according to the present invention;

FIG. 2 is a partially sectioned side view of the hub of FIG. 1;

FIG. 3 is a detail, at a larger scale, of the part marked with a circle in FIG. 2;

FIG. 4 is a variant of FIG. 3; and

FIG. 5 is a partially sectioned front view of a variant of a hub according to the invention.

In FIGS. 1 and 2, the reference number 10 designates a hub for a bicycle wheel. The hub 10 consists of a monolithic body made of fibre-reinforced plastic material. Preferably, the hub 10 is made of a carbon-fibre fabric embedded in a thermosetting resin.

The monolithic body forming the hub 10 comprises a tubular central portion 12 , a pair of side shells 14 provided with seats for bearings 16 , and a pair of end radial flanges 18 .

Each of the radial flanges 18 is provided with a plurality of holes 20 with axes substantially parallel to the longitudinal axis of the hub 10 , the said holes being designed to enable anchoring of spokes 22 having L-shaped attachment portions 24 .

As illustrated in greater detail in FIGS. 3 and 4, each hole 20 is associated to a bushing 26 made of metal material, preferably steel. Each bushing 26 has an outer cylindrical wall which is in contact with the inner wall of the respective hole 20 .

In the embodiment illustrated in FIG. 3, each bushing 26 has two edges 28 which rest against the opposite radial walls of the respective flange 18 . At least one of the edges 28 of each bushing 26 is obtained by plastic deformation (pressing) after insertion of the bushing into the respective hole 20 .

In the variant of FIG. 4, each bushing 26 has only one edge 30 , situated in a position corresponding to the head 32 of the respective spoke 22 .

If the bushings 26 were not present, the spokes would produce, on the edges designated by 34 and 36 , a very high pressure, higher than the breaking load of the material constituting the hub. The bushings 26 distribute the forces due to the tensioning of the spokes over more extensive contact surfaces, thus reducing the pressure on the walls of the holes. In particular, the bushings 26 avoid a pressure concentration on the edges 34 and 36 .

FIG. 5 illustrates a variant of a hub for a rear wheel. The hub 10 in this variant has a single flange 18 formed in an integral way with the tubular body 12 . At the opposite end, the shell 14 is fixed to a metal element 40 , made of aluminium or of an aluminium alloy, having a flange 42 provided with holes 44 which receive the ends 24 of the spokes 22 without interposition of the bushings 26 . The element 40 is provided with seats for the bearing 16 and for a free-wheel device 46 .