Abstract:
A spoked wheel for tubeless tires, particularly for motorcycles, cars and similar vehicles includes a rim, a hub, and spokes suitable for fixing the rim to the hub. Each spoke is connected to the rim by a fastening device inserted in two opposite ears located in an inner surface of the rim.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a spoked wheel for tubeless tires, also called tubeless, particularly for motorcycles, cars and similar vehicles. Tubeless tires have been preferred for some time now in the motorcycle industry as well, especially for high-performance motorcycles. It is a known fact that tubeless tires have numerous advantages compared to tires with inner tubes. 
     Tubeless tires are safer and are not subject to bursting, and because they have no inner tube, this cannot be lacerated. In case of a flat tire, they deflate fairly slowly, making it possible to ride the motorcycle as far as a tire-repair shop. 
     Furthermore, they are not subject to any sliding or rotation of the tire with respect to the rim, which in the case of tires with inner tubes could cause the valve to tear away from the inner tube. For operation and assembly, tubeless tires require an airtight rim with a special seal profile for the tire bead. For this reason, in most cases, cast or pressed rims are used, almost always with rigid spokes. In fact, because, traditionally, a spoked wheel comprises a rim with through holes to fix the spokes using nipples, it is very difficult to seal the hole area where the fixing nipples are fitted. 
     Alternatively, e.g. in the patent EP-B-O 143 394, rims for spoked wheels have been presented with the spoke fitting seats arranged on the edges of the rim, so as to allow fitting tubeless tires. The rim of the patent EP-B-O 143 394 has considerably thick sides, because it also has to contain the spoke seats, and is therefore heavier than standard type rims. Furthermore, manufacturing the rim is also more difficult with increase in production costs. 
     Another problem regarding the rims currently in use for spoked wheels, and in particular for off-road, enduro or supermotard motorcycle competitive use, is that of the relevant lack of sturdiness of the rim. In fact, the traditional manufacture of spoked wheels for motorcycles envisages that the rim be made of aluminum alloy by extrusion with subsequent rolling until a round element is obtained that is then closed by welding. 
     The structure of the rims obtained in this way is not sturdy enough to withstand off-road stresses, and therefore often breaks. On the other hand, spoked wheels are preferred in the off-road sector for their greater elasticity and their ability to withstand the stresses of off-road, enduro, motocross riding, etc. 
     SUMMARY 
     One object of the invention is to upgrade spoked wheels for tubeless tires of the known type. 
     Another object of the invention is to present a spoked wheel for tubeless tires that is particularly strong and lightweight. 
     Another object of the invention is to present a spoked wheel for tubeless tires that can absorb high stresses and/or hard knocks, and therefore be advantageously used in the off-road motorcycle industry. 
     In conformity with one aspect of the invention, a spoked wheel for tubeless tires is presented according to the claims, which refer to preferred and advantageous embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood and implemented with reference to the attached drawings, which illustrate an exemplary and non-limitative form of embodiment, in which: 
       the  FIG. 1  is a partial side perspective view of the spoked wheel according to the invention; 
       the  FIG. 2  is a partial section of the spoked wheel in  FIG. 1 ; 
       the  FIG. 3  shows an enlarged detail of the spoked wheel in the previous figures; and 
       the  FIGS. 4, 5 and 6  show other enlarged details of the spoked wheel in the previous figures. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to the figures,  1  denotes in its entirety a spoked wheel comprising a rim  2  of the type suitable for accommodating a tubeless tire (not shown), a series of spokes  4  and a hub  13 , connected together according to methods explained in detail below. 
     The rim  2  has a channel  3  having a specific profile for fitting the beads of the tire so that a perfect air seal is obtained, including without inner tube. In this respect, it should be noticed that the channel  3  of the rim is totally devoid of holes, in fact, the spokes  4  are connected to the rim  2  by means of fastening means  5  not passing through the channel  3 . 
     The rim  2  has an inner surface  6  opposite the channel  3  on which are obtained a series of ears  7 ,  8  placed on two circumferences which are in a substantially symmetric position with respect to a centre line plane of the rim  2 . 
     Each of the fastening means  5  is connected to the rim  2  by means of two opposite ears  7 ,  8  which are in a corresponding and symmetric position on the two circumferences of the inner surface  6 . 
     According to  FIGS. 3 and 4 , the fastening means comprise a cylindrical part  5 , having a shoulder  9  resting on an inner side of one of the ears  7 ,  8  on the right, or on the left, when the spoke  4  connected to the cylindrical part  5  is tensioned. 
     More in detail, the cylindrical part  5  comprises two cylindrical portions with different diameters D 1 , D 2 , which define the above shoulder  9 , which rests on an inner side of the ear, being of smaller diameter. Because the spokes  4  are alternately angled in opposite directions to provide the camber needed to provide the wheel with a certain stiffness, the ears  7 ,  8  also have holes  10 ,  11  of different dimensions L 1 , L 2  respectively. 
     The holes  10 ,  11  have a slot shape and the dimensions L 1 , L 2  measured in a radial direction are respectively slightly greater than the diameters D 1 , D 2  of the cylindrical part  5 . From the  FIGS. 3 and 4  it is clear that the cylindrical parts  5  are resting on the lower part of the holes  10 ,  11 , thereby providing the centering of the rim  2  with respect to the hub  13 . The purpose of the radial play allowed by the slot shape of the holes  10 ,  11  is to offset the knocks and the deformations that could affect the wheel, permitting a greater capacity to absorb stresses compared to the constructions of known type. The spoke  4  is fixed to the cylindrical part  5  by means of a threaded hole  12 , which is angled to the same extent as the spoke  4 , and is substantially perpendicular to the axis of the cylindrical part  5 . 
     It must be noticed that the threaded hole  12  is arranged in the space between two opposite ears  7 ,  8 , and consequently the fixing of the spoke  4  is very reliable and sturdy. 
     The relative positions and angles of the cylindrical parts  5  with the shoulders  9 , the positions of the ears  7 ,  8  and of the spokes  4  are determined during wheel planning, so as to favor the quick positioning of the rim  2  with respect to the hub  13 , without the need for long centering operations. 
     The  FIG. 5  shows the hub  13  with seats  14  for housing the spokes  4  with relevant heads  15 . In this case as well, the seats  14  are shown with the same angle the spokes  4  must have to achieve wheel camber. 
     The spokes  4  have a straight head  15 , with a special housing for a tool for tensioning the spokes themselves. The tensioning operation of the spokes  4  is done by rotating these so they can be screwed or unscrewed with respect to the cylindrical part  5 . 
     The cylindrical part  5  can in turn rotate with respect to an axis substantially parallel with that of the wheel  1 , allowing a certain settlement of the whole assembly. As a whole, the spokes  4  are perfectly straight and thus provide greater strength as compared to rounded-head spokes. The spokes  4  can be made of any one of the following materials: stainless steel, titanium alloy, aluminum alloy or magnesium alloy with loaded matrix, or in pressable composite materials such as carbon fibers or the like. The construction of the spokes  4  in composite material is made possible precisely because of their straight shape and if necessary, for the threaded part, an inserted metal bushing can be provided. The cylindrical parts  5  can be made of stainless steel or titanium alloy. 
     Thanks to the fact that the seats  14  in the hub and the threaded holes  12  in the cylindrical parts  5  are already angled to obtain correct wheel camber, and that the cylindrical parts  5  are already arranged for their right position with respect to the rim by means of the shoulder  9 , the assembly of the hub  13  with the rim  2  and the spokes  4  is much simpler and quicker compared to the constructions of known type. 
     According to an advantageous version of the invention, the rim  2  and/or the hub  13  are made of aluminum or magnesium alloy, using the forging or hot pressing forming method. 
     According to a further version of the invention, the rim  2  and/or the hub  13  can be made of aluminum or magnesium alloy with loaded matrix, or else of pressable composite materials, e.g., carbon fibers and the like. Afterwards, the rim  2  and/or the hub  13  are finished by machining for the removal of shavings, e.g., using numerical control machines. It is thus possible to create the particular geometry that distinguishes the two above component parts. The forming technology by forging is currently the best with regards to the construction of monolithic light alloy wheels, but on spoked wheels it has thus far only been adopted in rare cases and for building the hub only. 
     Thanks to the construction by forging of the invention, the rim  2  is particularly resistant to the stresses and knocks that occur especially with regards to off-road vehicles, and is therefore the ideal solution for such use, thanks also to the use of the straight spokes  4 . 
     The spokes  4 , being straight, are intrinsically stronger and can be made using sturdier and more resistant materials, such as aluminum alloy or magnesium alloy with loaded matrix, or of pressable composite materials, e.g., carbon fibers and the like. 
     The composite materials for the hub, the spokes and the rim also allow obtaining wheels of very reduced weight. 
     The invention thus conceived is susceptible to numerous modifications and variations, all of which falling within the scope of the inventive concept. Furthermore all the details can be replaced with others that are technically equivalent. In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements without moving outside the protection scope of the following claims.