Abstract:
A brake disc of the type comprising a braking band, a connecting portion and connecting spokes made in a single piece. In said disc at least one spoke exhibits an active section reduction that is sufficient to prevent vibrations and whistling during the braking phase. The disc, according to the present invention, is not subject to vibrations and possesses a limited gyroscopic effect and mass.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a brake disc for vehicles; in particular, the present invention relates to brake discs that are suitable for being used on motorcycles. 
       BACKGROUND OF THE INVENTION 
       [0002]    As we know, in some motorcycles the front or back wheels often comprise an integrally formed brake disc, in other words comprising a portion for connecting to the hub, a braking band and a plurality of spokes made in a single piece. 
         [0003]    During braking, these brake discs may suffer vibrations that cause an irritating whistling. 
         [0004]    Solutions suitable for eliminating this inconvenience are not known in the art. 
       SUMMARY OF THE INVENTION 
       [0005]    The problem of the present invention is to make a brake disc for vehicles that resolves the inconveniences stated with reference to the prior art. 
         [0006]    These inconveniences are resolved by a brake disc for vehicles according to claim  1 . 
         [0007]    Other brake disc embodiments according to the invention are described in the subsequent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Further characteristics and advantages of the present invention will be appreciated from the following description of a preferred embodiment, which is given by way of example and not limiting, wherein: 
           [0009]      FIG. 1  represents a perspective view of a brake disc according to an embodiment of the present invention; 
           [0010]      FIG. 2  represents a front view of the disc in  FIG. 1 , from the side of the arrow II in  FIG. 1 ; 
           [0011]      FIG. 3  represents a front view of a brake disc according to a further embodiment of the present invention; 
           [0012]      FIG. 4  represents a perspective view with separate parts of a disc according to a further embodiment of the present invention; 
           [0013]      FIG. 5  represents a front view of the disc in  FIG. 4 , from the side of the arrow V in  FIG. 4 ; 
           [0014]      FIG. 6  represents a section view of the disc in  FIG. 5 , along the VI-VI section line in  FIG. 5 ; 
           [0015]      FIG. 7  represents a perspective view with separate parts of a brake disc according to a further embodiment of the present invention; 
           [0016]      FIG. 8  represents a perspective view of the disc in  FIG. 7  in an assembly configuration, from the side of the arrow VIII in  FIG. 7 ; 
           [0017]      FIG. 9  represents a perspective view of the disc in  FIG. 7  in an assembly configuration, from the side of the arrow IX in  FIG. 7 ; 
           [0018]      FIG. 10  represents a perspective view of a disc according to a further embodiment of the present invention; 
           [0019]      FIG. 11  represents a front view of the disc in  FIG. 10 , from the side of the arrow XI in  FIG. 10 ; 
           [0020]      FIG. 12  represents a section view of the disc in  FIG. 10 , along the XII-XII section line in  FIG. 11 ; 
           [0021]      FIG. 13  represents a perspective view of a disc according to a further embodiment of the present invention; 
           [0022]      FIG. 14  represents a front view of the disc in  FIG. 13 , from the side of the arrow XIV in  FIG. 13 ; 
           [0023]      FIG. 15  represents a section view of the disc in  FIG. 13 , along the XV-XV section line in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    The elements or parts of elements in common between the subsequently described embodiments will be indicated with the same numeral references. 
         [0025]    The term radial direction means a direction that is substantially perpendicular to an X rotation axis of the disc. 
         [0026]    The term axial direction means a direction that is substantially parallel to the X rotation axis of the disc. 
         [0027]    The term tangential direction means a direction that is substantially perpendicular to the axial direction and to the radial direction. 
         [0028]    With reference to the above drawings, a brake disc for vehicles with an X rotation axis is generally indicated with reference numeral  4 . 
         [0029]    The brake disc  4  comprises a connecting portion  8  to a wheel hub of a vehicle, a braking band  12  and at least one spoke  16  for the connection between the connecting portion  8  and the braking band  12 . 
         [0030]    The braking band  12  is preferably connected to the connecting portion  8  by means of a plurality of spokes  16  that are preferably arranged in step. 
         [0031]    The brake disc  4  is formed integrally, in particular, the braking band  12  is integral with the connecting portion  8  and with the spokes  16 . 
         [0032]    Advantageously, at least one spoke  16  comprises an active section reduction  18  to exhibit reduced rigidity in relation to the corresponding integral section. 
         [0033]    According to an embodiment of the present invention, said section reduction  18  is made with a lightening  19  that is suitable for reducing the axial thickness of a portion of the spoke. 
         [0034]    According to an embodiment ( FIGS. 11 ,  12 ), the lightening  19  exhibits a tangential course that is sufficient to influence the whole tangential width of the spoke  16 . The lightening  19  can be defined by one or more chamfers or flares  20 , which are arranged tangentially and parallel between each other. 
         [0035]    According to a further embodiment ( FIGS. 13-15 ), the lightening  19  exhibits a circular course defining a cylindrical pocket. 
         [0036]    Said lightening  19  with a circular course is preferably defined by a chamfer or flare  20  arranged on the side of one face of the disc. 
         [0037]    The lightening  19  preferably limits the active section of the spoke  16  to maintain the continuity, level with said spoke  16 , between the connecting portion  8  and the braking band  12 . In other words, the lightening  19  reduces the active section of the spoke  16  but does not completely interrupt the continuity of the same spoke, or rather the mechanical connection that the spoke forms between the braking band  12  and the connecting portion  8 . 
         [0038]    The lightening  19  preferably reduces the active section of the spoke  16  to no more than 40% of the active section of the integral spoke  16 . In other words, the lightening  19  reduces the active section of the spoke  16  by at least 60% compared with the corresponding section of the integral spoke  16 . 
         [0039]    According to an advantageous embodiment ( FIGS. 1-5 ), said section reduction  18  creates an interruption  22  of the spoke  16  so as to divide the spoke  16  into two parts and interrupt the continuity between the connecting portion  8  and the braking band  12 . 
         [0040]    According to an embodiment, said interruption  22  is arranged level with a portion of the spoke  16  next to the braking band  12 . 
         [0041]    According to an embodiment, the interruption  22  comprises a direct channel  24  that is substantially tangential to the braking band  12  so as to affect the whole tangential thickness of the spoke  16  dividing it into two separate parts. 
         [0042]    Said interruption  22  preferably comprises at least one indentation  28  in relation to a radial direction, which is suitable for defining a slot  32  with said channel  24 . 
         [0043]    According to an embodiment, the interruption  22  comprises a pair of indentations  28  that are radially facing and arranged on each of the ends of the opposite portions of the spoke  16  facing each other, said indentations  28  defining a slot  32  with said channel  24 . 
         [0044]    The slot  32  is preferably symmetrical in relation to a radial direction passing the X rotation axis of the disc  4 . 
         [0045]    Said slot  32  is also preferably symmetrical in relation to a tangential direction, perpendicular to a radius of the disc. 
         [0046]    According to an advantageous embodiment, the disc  4  comprises at least one bush  40  contained in said slot  32  and said channel  24  so it is constrained by said indentations  28  in relation to a tangential direction. 
         [0047]    According to an embodiment, the bush  40  comprises a bush body  44  and constraining means  48 . According to an embodiment the bush  40  is formed integrally and level with an axial end, said constraining means comprise a first head  50 , and at the opposite end they comprise a second head  51 , which is achieved, for example, by riveting. These heads  50 ,  51  exhibit a greater diameter than the diameter of the slot  32  so as to axially constrain the bush  40  in relation to the slot  32 . 
         [0048]    An elastic element  52  is preferably inserted between said bush body  44  and one of said heads  50 , 51 , suitable for pre-charging the bush body  44  and the constraining means  50 , 51  in relation to an axial direction. 
         [0049]    According to an embodiment, said elastic element  52  is a washer spring. 
         [0050]    The mass of said bush  40  is preferably substantially equal to the mass of material removed from the spoke  16  to form said interruption. 
         [0051]    According to a further embodiment, said disc comprises at least one small plate  60  suitable for being connected to said slot  32  or said channel  24  so as to cover the interruption  22  at least partially. 
         [0052]    The small plate  60  preferably has a plate body  64 , for example that is flat and equipped with a pair of fastening flaps  68  that are suitable for being constrained by clicking or mortising to special fastening holes  72 , which are arranged, for example, on the spoke on the side of the connecting portion  8  and the braking band  12 . 
         [0053]    According to an embodiment, the plate body  64  comprises two flaps  76  suitable for being hooked by clicking onto side edges  78  of the spoke, which are separated by the interruption  22 . 
         [0054]    The plate body  64  preferably has a tangential extension so as to completely cover the interruption  22 . 
         [0055]    The mass of said plate  60  is preferably substantially equal to the mass of material removed from the spoke  16  to form the interruption  22 . 
         [0056]    Advantageously, in an assembly configuration of the disc  4  on the relative wheel hub, the disc is oriented angularly to bring the interruption  22  and the connectable bush  40  or plate  60  into a diametrically opposite position in relation to the inflation valve of the relative tyre to be connected to the rim. 
         [0057]    According to a further embodiment, at least two spokes  16  of the disc  4  comprise an active section reduction  18  to exhibit reduced rigidity in relation to the corresponding integral section. 
         [0058]    Said active section reduction  18  can be made with a lightening  19  or an interruption  20 . In an embodiment comprising two spokes  16 , with an active section reduction  18 , said spokes  16  are preferably arranged in diametrically opposite positions in relation to said X rotation axis of the disc  4 . 
         [0059]    In an embodiment comprising at least two spokes  16  or a plurality of spokes  16 , comprising an active section reduction  18 , said spokes  16 , comprising an active section reduction  18  are preferably arranged in step in relation to the X rotation axis. 
         [0060]    As we can appreciate from the description, the brake disc of the present invention enables the inconveniences exhibited by the brake disc of the prior art to be overcome. 
         [0061]    In particular, the disc according to the invention does not vibrate and whistle during braking. 
         [0062]    The disc in the present invention maintains a gyroscopic effect, as well as a reduced, non suspended mass. 
         [0063]    In order to satisfy specific and contingent needs, a person skilled in the art can make numerous modifications and variations to the above described brake discs, all of which are included in the scope of the invention, as defined by the following claims.