Abstract:
A wheel hub having a central tubular portion and at least one end cap which is formed integrally with the central portion and has thickness greater than the central tubular portion. The hub is a monolith fiber-reinforced plastic structure wherein the central portion and the side cap form a continuous surface.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a wheel hub for a bicycle, specifically a competition bicycle. 
     The main objective of competition bicycle manufacturers is to reduce the weight of the single components as much as possible. In the case of wheel hubs, conventional technology involves the use of metallic light alloys, such as aluminium alloys and similar. Various solutions have been proposed to reduce the weight of the wheel hub in which the central tubular part of the wheel hub is made of carbon fibre incorporated in a plastic material resin and in which a pair of side caps made of aluminium alloy are fastened to the ends of the carbon fibre central portion. The side caps are provided with housings for supporting rolling bearings and holes for anchoring the wheel spokes. 
     SUMMARY OF THE INVENTION 
     The objective of this invention is to provide a wheel hub which is lighter and presents better characteristics in terms of rigidity with respect to the known solutions mentioned above. 
     This objective is attained by a wheel hub comprising a central tubular portion and a pair of side caps, which diameter is larger than said central portion, characterised in that said hub comprises a monolith body made of fibre-reinforced plastic material including said central portion and said side caps. 
     As is explained in more detail in the following part of this description, the hub according to this invention is lighter and more rigid than the known solutions. The greater rigidity in correspondence to the rolling bearing housings formed inside the side caps reduces the radial play on the bearings and facilitates wheel assembly and centering operations, especially in the case in which the wheel rim as made of fibre-reinforced plastic material, specifically carbon fibre. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This invention will be better explained by the following detailed descriptions with reference to the accompanying figure as non-limiting example, whereas: 
     FIG. 1 is a perspective partial view of a bicycle wheel with a hub according to this invention, 
     FIG. 2 is a partially sectioned elevated front view of a front wheel hub according to this invention, and 
     FIG. 3 is a partially sectioned elevated front view of a rear wheel hub according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, numeral  10  indicates a bicycle wheel comprising a rim  12  and a hub  14  connected to the rim  12  by means of a plurality of spokes  16 . 
     The hub according to this invention comprises a monolith body  18  consisting of fibre-reinforced plastic material. Preferably, the plastic material is a thermosetting resin and the reinforcement fibres are carbon fibres. The body  18  comprises a tubular central portion  20  and a pair of side cap  22  formed integrally with the central portion  20  with a larger diameter than said central portion. 
     FIG. 2 shows a first form of the invention, destined to be used on a front wheel. In this embodiment, each end of the tubular central portion terminates in an end cap  22 . Each of the end caps  22  is provided with a ground housing  24 , in which the external race of a roller bearing  26  is arranged. Each end  22  also is provided with an area  28  where the thickness of the hub is increased over that of the central portion. The increase in thickness is gradual and the exterior of the end cap retains a continuous, generally curvilinear, surface. Each end cap  22  is provided with a set of holes  28 , which are position in the thickened area  23  and used to anchor the head portions of the spokes  16 . 
     In a conventional manner, the roller bearings  26  support the rotation of the body  18  around a pin  32 . 
     FIG. 3 illustrates a second form of embodiment of the hub according to those described above are indicated with the same numerals. The hub shown in FIG. 3 in destined to be fitted on a rear wheel. One of the side caps  22 , (the one on the left in the figure), is configured as previously described with reference to FIG. 2; one of the side caps  22 , (the one on the right in the figure), is configured to receive a chainring  84  of a freewheel device. The chainring  34  can be made of light metal alloy, for example aluminum alloy. The chainring  34  is provided with holes  36  for anchoring the spokes  16  and presents a ground housing  38  for the external race of a roller bearing  26 . The chainring  84  is fastened with interference in a housing  44  formed inside the respective cap  22 . The other cap  22  (the one on the left in FIG. 3) is made identically as described above in relation to the hub for the front wheel. 
     The cape  22  made of carbon fibre confer a considerable rigidity in the radial direction to the hub  18 . The radial deformations of the caps  22  induced by the tension of the spokes  16  are practically negligible with respect to those obtained by light alloy caps. This characteristic is particularly advantageous because in the hub according to this invention the tension of the spokes  16  does not produce an increase of play in the roller bearing housing  26 . 
     The use of the hub according to this invention is particularly advantageous when used in combination with a rim also made of carbon fibre-reinforced plastic material. In this case, both the hub and the rim are practically not deformable and the only elastically deformable elements are the spokes  16 . This facilitates wheel centring and prevents rim ovalisation and undesired increased play on the hub bearings. 
     Naturally, numerous changes can be implemented to the construction and forms of embodiment of the invention herein envisaged, all comprised within the context of the concept characterising this invention, as defined by the following claims.