Abstract:
A chainless bicycle includes a drive system having a speed change arrangement is provided. In a first mode of speed change a forward pulling of a forward cable clockwise pivots a front pivotal member to move the forward sleeve rearward so that a first toothed portion of the forward sleeve clears a second gearwheel to move into a first gearwheel to mesh with a toothed portion of the first gearwheel whereby rotating a shaft will rotate a drive gear, the first gearwheel, the second gearwheel, the forward sleeve, a drive shaft, a rear sleeve, a fourth gearwheel, second inner engaging members, second outer engaging members, a third gearwheel, and a rear axle co-rotating with a rear wheel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The invention relates to chainless bicycles and more particularly to a chainless bicycle drive system having a speed change arrangement. 
         [0003]    2. Description of Related Art 
         [0004]    Chainless (i.e., shaft-driven) bicycles are well known in the art. Chainless bicycles have the advantages of presenting no danger of clothing or fingers being drawn into the chain and sprockets, less maintenance cost, etc. 
         [0005]    A conventional chainless bicycle is shown in  FIG. 1 . In driving a bicycle a shaft  1  is rotated by pedaling. And in turn, a first bevel gear  2  rotates. A second bevel gear  6  meshed with the first bevel gear  2  rotates same. A drive shaft  5  has one end mounted with the second bevel gear  6  and the other end mounted with a third bevel gear  7 . Hence, both the drive shaft  5  and the third bevel gear  7  rotate. A fourth bevel gear  4  meshed with the third bevel gear  7  rotates same. Finally, a rear axle  3  coaxially mounted with the third bevel gear  7  rotates. 
         [0006]    One drawback of the conventional chainless bicycle is that only single speed can be effected. That is, it is not a labor saving bicycle. Thus, the need for improvement still exists. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore one object of the invention to provide a chainless bicycle drive system having a speed change arrangement 
         [0008]    The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view of drive system of a conventional chainless bicycle; 
           [0010]      FIG. 2  is an exploded view of a first preferred embodiment of drive system of a chainless bicycle according to the invention; 
           [0011]      FIG. 3  is a perspective view of the assembled drive system of  FIG. 2 ; 
           [0012]      FIG. 4  is a cross-sectional view of the drive system of  FIG. 3 ; 
           [0013]      FIG. 5  shows details of the areas in circles A and B of  FIG. 4 ; 
           [0014]      FIG. 6  is a view similar to  FIG. 4  showing a pedaling operation of the bicycle; 
           [0015]      FIG. 7  is a side elevation of the drive system of  FIG. 3  showing a speed change operation of the bicycle by pulling the forward cable forward; 
           [0016]      FIG. 8  is a cross-sectional view of the drive system of  FIG. 7  also showing the speed change operation of the bicycle; 
           [0017]      FIG. 9  shows details of the areas in circles C and D of  FIG. 8 ; 
           [0018]      FIG. 10  is a side elevation of the drive system of  FIG. 3  showing a speed change operation of the bicycle by pulling the rear cable rearward; 
           [0019]      FIG. 11  is a cross-sectional view of the drive system of  FIG. 10  also showing the speed change operation of the bicycle; 
           [0020]      FIG. 12  shows details of the areas in circles E and F of  FIG. 11 ; 
           [0021]      FIG. 13  is an exploded view of a second preferred embodiment of drive system of a chainless bicycle according to the invention; 
           [0022]      FIG. 14  is a cross-sectional view of the drive system of  FIG. 13 ; and 
           [0023]      FIG. 15  shows details of the areas in circles G and H of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Referring to  FIGS. 2 to 12 , a drive system of a chainless bicycle in accordance with a first preferred embodiment of the invention is shown. The bicycle comprises a typical frame  10 . The drive system comprises the following components as discussed in detail below. 
         [0025]    A forward drive gear  20  comprises a plurality of outer projections  201  arranged as a circle formed on an inner surface and a plurality of inner projections  202  arranged as a circle formed on the inner surface. Both the outer and inner projections  201 ,  202  are concentric and proximate an annular edge of the drive gear  20 . The drive gear  20  further comprises a centrally located cutout (not numbered) fitted onto one end of a shaft  40  and threadedly secured to the shaft  40  housed in a bottom bracket (not numbered). 
         [0026]    A rear driven gear  21  is coaxially mounted with a rear hub  50  having a rear axle (not numbered) which is coaxially mounted with a rear wheel (not shown) and corotates therewith. The driven gear  21  comprises a plurality of outer projections  211  arranged as a circle formed on an inner surface and a plurality of inner projections  212  arranged as a circle formed on the inner surface. Both the outer and inner projections toothed sections  211 ,  212  are concentric and proximate an annular edge of the driven gear  21 . 
         [0027]    A drive shaft unit  30  is rotatably interconnected the drive gear  20  and the driven gear  21  as detailed below. The drive shaft unit  30  comprises a drive shaft  31  including an intermediate portion (not numbered), a first toothed member  311  at one end, an annular first flange  384  formed at a joining point of the intermediate portion and the first toothed member  311 , a second toothed member  312  at the other end, and an annular second flange  394  formed at a joining point of the intermediate portion and the second toothed member  312 . 
         [0028]    One end of the drive shaft  31  is rotatably supported by a first bearing seat  301  mounted on the bottom bracket of the frame  10  and the other end thereof is rotatably supported by a second bearing seat  302  mounted on a rear component (not numbered) of the frame  10  with the rear axle rotatably secured to. 
         [0029]    A cylindrical component (not numbered) of the frame  10  is interconnected the bottom bracket of the frame  10  and the rear component of the frame  10  and is parallel with the drive shaft  31 . 
         [0030]    A front pivotal member  38  has its central portion pivotably secured to the cylindrical component of the frame  10  and comprises, in addition to the first flange  384 , a lower bearing  381 , a forward cable  382  having one end secured to a top and the other end secured to a front shift lever (not shown) mounted on handlebars (not shown), and a forward coil spring  383  compressed between the first flange  384  and the lower bearing  381 . 
         [0031]    A rear pivotal member  39  has its central portion pivotably secured to the cylindrical component of the frame  10  and comprises, in addition to the second flange  394 , a lower bearing  391 , a rear cable  392  having one end secured to a top and the other end secured to a rear shift lever (not shown) mounted on handlebars (not shown), and a rear coil spring  393  compressed between the second flange  394  and the lower bearing  391 . 
         [0032]    A forward housing member  303  between the front pivotal member  38  and the first bearing seat  301  is mounted on the cylindrical component of the frame  10 . A rear housing member  304  between the rear pivotal member  39  and the second bearing seat  302  is mounted on the cylindrical component of the frame  10 . 
         [0033]    A first gearwheel  34  having a toothed portion  341  on an inner surface and a second gearwheel  35  having a toothed portion  351  on an inner surface are partially housed in the forward housing member  303  in a parallel configuration. A forward sleeve  32  has a first toothed portion  321  on an intermediate portion of an outer surface and a second toothed portion  322  on an inner surface. The second toothed portion  322  is meshed with the first toothed member  311  when the forward sleeve  32  is put on the first toothed member  311 . The first and second gearwheels  34 ,  35  are put on the forward sleeve  32  with the toothed portion  351  being meshed with the first toothed portion  321 . A rear end of the forward sleeve  32  is fixedly disposed in the lower bearing  381  of the front pivotal member  38  and a forward end thereof is spaced from the first bearing seat  301 . 
         [0034]    A third gearwheel  36  having a toothed portion  361  on an inner surface and a fourth gearwheel  37  having a toothed portion  371  on an inner surface are partially housed in the rear housing member  304  in a parallel configuration. A rear sleeve  33  has a first toothed portion  331  on an intermediate portion of an outer surface and a second toothed portion  332  on an inner surface. The second toothed portion  332  is meshed with the second toothed member  312  when the rear sleeve  33  is put on the second toothed member  312 . The third and fourth gearwheels  36 ,  37  are put on the rear sleeve  33  with the toothed portion  371  being meshed with the first toothed portion  331 . A forward end of the rear sleeve  33  is fixedly disposed in the lower bearing  391  of the rear pivotal member  39  and a rear end thereof is spaced from the second bearing seat  302 . 
         [0035]    The outer projections  201  and the inner projections  202  are meshed with the first gearwheel  34  and the second gearwheel  35  respectively. The outer projections  211  and the inner projections  212  are meshed with the third gearwheel  36  and the fourth gearwheel  37  respectively. 
         [0036]    A pedaling operation of the bicycle will be described in detail below by referring to  FIGS. 3 to 6  specifically. First, a rotation of the shaft  40  by pedaling of the bicycle will rotate the drive gear  20 . Hence, the first and second gearwheels  34 ,  35  rotate in which a rotation of the first gearwheel  34  will not rotate the forward sleeve  32  and a rotation of the second gearwheel  35  will rotate the forward sleeve  32  due to the meshing engagement of the toothed portion  351  of the second gearwheel  35  and the first toothed portion  321 . And in turn, the drive shaft  31  rotates due to the meshing engagement of the second toothed portion  322  and the first toothed member  311 . And in turn, the rear sleeve  33  rotates due to the meshing engagement of the second toothed portion  332  and the second toothed member  312 . And in turn, the fourth gearwheel  37  rotates due to the meshing engagement of the toothed portion  371  of the fourth gearwheel  37  and the first toothed portion  331 . Thus both the outer projections  211  and the inner projections  212  rotate. But a rotation of the third gearwheel  36  is independent from that of the rear sleeve  33 . Finally, the rear axle rotates (i.e., the bicycle moves forward). 
         [0037]    A speed change operation of the bicycle will be described in detail below by referring to  FIGS. 7 to 9  specifically. First, pulling the cable  382  forward will clockwise pivot the front pivotal member  38 . And in turn, the forward sleeve  32  moves rearward with the forward coil spring compressed. The first toothed portion  321  then moves into the first gearwheel  34  to mesh with the toothed portion  341 . That is, the first toothed portion  321  and the second gearwheel  35  are disengaged. Next, a rotation of the shaft  40  by pedaling of the bicycle will rotate the drive gear  20 . Hence, the first and second gearwheels  34 ,  35  rotate in which a rotation of the second gearwheel  35  will not rotate the forward sleeve  32  and a rotation of the first gearwheel  34  will rotate the forward sleeve  32  due to the meshing engagement of the toothed portion  341  of the first gearwheel  34  and the first toothed portion  321 . And in turn, the drive shaft  31  rotates due to the meshing engagement of the second toothed portion  322  and the first toothed member  311 . And in turn, the rear sleeve  33  rotates due to the meshing engagement of the second toothed portion  332  and the second toothed member  312 . And in turn, the fourth gearwheel  37  rotates due to the meshing engagement of the toothed portion  371  of the fourth gearwheel  37  and the first toothed portion  331 . Thus both the outer projections  211  and the inner projections  212  rotate. But a rotation of the third gearwheel  36  is independent from that of the rear sleeve  33 . Finally, the rear axle rotates (i.e., the bicycle moves forward). But the moving speed of the bicycle is increased because the rotation of the rear axle is activated by the rotation of the inner projections  202  similar to derailing chains onto different sprockets in a chain-driven bicycle with speed change capability. 
         [0038]    An alternative speed change operation of the bicycle will be described in detail below by referring to  FIGS. 10 to 12  specifically. First, pulling the cable  392  rearward will counterclockwise pivot the rear pivotal member  39 . And in turn, the rear sleeve  33  moves forward with the rear coil spring compressed. The first toothed portion  331  then moves into the third gearwheel  36  to mesh with the toothed portion  361 . That is, the first toothed portion  331  and the fourth gearwheel  37  are disengaged. Next, a rotation of the shaft  40  by pedaling of the bicycle will rotate the drive gear  20 . Hence, the third gearwheel  36  rotates due to the meshing engagement of the toothed portion  361  of the third gearwheel  36  and the first toothed portion  331 . Thus both the outer projections  211  and the inner projections  212  rotate. But a rotation of the fourth gearwheel  37  is independent from that of the rear sleeve  33 . Finally, the rear axle rotates (i.e., the bicycle moves forward). But the moving speed of the bicycle is increased because the rotation of the rear axle is activated by the rotation of the inner projections  212  similar to derailing chains onto different sprockets in a chain-driven bicycle with speed change capability. 
         [0039]    Referring to  FIGS. 13 to 15 , a drive system of a chainless bicycle in accordance with a second preferred embodiment of the invention is shown. The second embodiment is identical to the first embodiment, except that a forward drive gear  60  comprises a plurality of outer through holes  601  arranged as a circle and a plurality of inner through holes  602  arranged as a circle. Both the outer and inner through holes  601 ,  602  are concentric and proximate an annular edge of the drive gear  60  A rear driven gear  61  comprises a plurality of outer through holes  611  arranged as a circle and a plurality of inner through holes  612  arranged as a circle. Both the outer and inner through holes  611 ,  612  are concentric and proximate an annular edge of the driven gear  61 . The outer through holes  601  and the inner through holes  602  are meshed with the first gearwheel  34  and the second gearwheel  35  respectively. The outer through holes  611  and the inner through holes  612  are meshed with the third gearwheel  36  and the fourth gearwheel  37  respectively. 
         [0040]    The pedaling and speed change operations of the second preferred embodiment of the invention are the same as that described in the first preferred embodiment of the invention. Thus, a detailed description thereof is therefore deemed unnecessary. 
         [0041]    While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.