Abstract:
A one-way transmission module includes two rings and at least one catch. The first ring is used for connection to a hub. The second ring is used for connection to a flywheel-bearing drum. The catch is arranged between the first and second rings to allow the first ring to rotate the second ring in a first direction but prevent the first ring from rotating the second ring in a second direction opposite to the first direction. The first or second ring includes a non-circular profile while the second or first ring includes a non-circular opening.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to a bicycle and, more particularly, to a one-way transmission module arranged between a hub and a flywheel set. 
         [0003]    2. Related Prior Art 
         [0004]    A typical bicycle includes a frame, a fork rotationally connected to a front portion of the frame, a front wheel rotationally connected to the fork, a rear wheel rotationally connected to a rear portion of the frame, a sprocket rotationally connected to a middle portion of the frame, two cranks operatively connected to the sprocket, a flywheel set connected to the rear wheel, and a chain for operatively connecting the flywheel set to the sprocket. The rear wheel includes rim, a hub and spokes for connecting the rim to the hub. A one-way transmission mechanism is arranged between the hub and the flywheel set. Thus, the flywheel set rotates the hub, but the hub does not rotate the flywheel set. 
         [0005]    As disclosed in Taiwanese Patent M314697, a conventional hub assembly includes a one-way transmission mechanism arranged between a hub 20 and a drum 40. The drum 40 is used to support a flywheel set. The one-way transmission mechanism includes a ring 24 fit in an opening 23 made in the hub 20, a ring 41 formed on the drum 40, and catches or pawls 42 arranged between the ring 41 and the ring 24. Each catch 42 is formed with a sharp end and an obtuse end. The ring 41 includes recesses each for receiving the obtuse end of a corresponding catch 42 so that the catches 42 can pivot relative to the ring 41. A C-clip is used to keep the catches 42 on the ring 41. The ring 24 is formed with teeth for engagement with the sharp ends of the catches 42. The ring 41 is inserted in the ring 24. When the ring 41 rotates in a first direction, the sharp ends of the catches 42 engage with some of the teeth of the ring 42 so that the ring 41 rotates the ring 24 in the first direction. As the ring 24 stops or rotates in a second direction, the sharp ends of the catches 42 rattle and slide on the teeth of the ring 42 to allow the ring 24 to rotate in the first direction relative to the ring 41. Inevitably, the teeth of the ring 24 and the catches 42 wear away against each other. In such a case, the ring 24 and the catches 42 should be removed from the hub 20 and replaced with new ones. However, it is difficult to remove the ring 24 from the hub 20. In fact, it is almost impossible to remove the ring 24 from the hub 20 without causing damage to the hub 20. Therefore, in practice, the entire hub assembly is replaced with a new hub assembly when only the ring 24 and the catches 42 are worn out. 
         [0006]    The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art. 
       SUMMARY OF INVENTION 
       [0007]    It is the primary objective of the present invention to provide a one-way transmission module that can easily be arranged between a hub and a flywheel set and removed from the hub and the flywheel set. 
         [0008]    To achieve the foregoing objectives, the one-way transmission module includes two rings and at least one catch. The first ring is used for connection to a hub. The second ring is used for connection to a flywheel-bearing drum. The catch is arranged between the first and second rings to allow the first ring to rotate the second ring in a first direction but prevent the first ring from rotating the second ring in a second direction opposite to the first direction. The first or second ring includes a non-circular profile while the second or first ring includes a non-circular opening. 
         [0009]    Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]    The present invention will be described via detailed illustration of two embodiments referring to the drawings wherein: 
           [0011]      FIG. 1  is an exploded view of a one-way transmission module according to the first embodiment of the present invention; 
           [0012]      FIG. 2  is a cross-sectional view of the one-way transmission module shown in  FIG. 1 ; 
           [0013]      FIG. 3  is a front view of the one-way transmission module shown in  FIG. 1 , with a sealing ring removed; 
           [0014]      FIG. 4  is an exploded view of a hub assembly including the one-way transmission module shown in  FIG. 1 ; 
           [0015]      FIG. 5  is a cross-sectional view of a one-way transmission module according to the second embodiment of the present invention; and 
           [0016]      FIG. 6  is a front view of the one-way transmission module shown in  FIG. 5 , with a sealing ring removed. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0017]    Referring to  FIGS. 1 to 3 , a one-way transmission module  10  includes a first ring  20 , a second ring  30 , a catch or pawl set, an elastic ring  42  and a sealing ring  12  according to a first embodiment of the present invention. The first ring  20  includes teeth  21  on an internal face, a non-circular profile  22  on an external face, and two shallow cavities  28  each made in an end. The non-circular profile  22  is preferably a hexagonal profile including six planar facets  24  and six convex facets  26 . 
         [0018]    The second ring  30  includes an insert  31  and a flange  38  formed at an end of the insert  31 . The insert  31  includes three deep recesses  33  made in an external face, three shallow recesses  35  each in communication with a corresponding deep recess  33 , and an annular groove  37  in communication with all of the deep and shallow recesses  33  and  35 . In another embodiment, the insert  31  can include another number of deep recesses  33  and shallow recesses  35 . The deep recesses  33  are preferably semi-circular ones. The second ring  30  includes a non-circular space  32  on an internal face. The non-circular space  32  is preferably a hexagonal profile including six planar facets  34  and six convex facets  36 . 
         [0019]    The catch set includes three catches  40  corresponding to the deep recesses  33  and the shallow recesses  35 . Each catch  40  includes a sharp portion  45  at an end, an obtuse portion  44  at an opposite end, and a groove  46  made in the sharp portion  45 . The obtuse portion  44  of each catch  40  is a semi-circular portion in compliance with the corresponding deep recess  33 . The sharp portion  45  of each catch  40  is shaped in compliance with the corresponding shallow recesses  35 . 
         [0020]    The obtuse portion  44  of each catch  40  is rotationally inserted in the corresponding deep recess  33 . The elastic ring  42  is used to keep the catches  40  on the insert  31 . The elastic ring  42  is inserted in the grooves  46  of the sharp portions  45  of the catches  40  and the annular groove  37  of the insert  31 . The catches  40  and the insert  31  are inserted in the ring  20 . The flange  38  is inserted in one of the shallow cavities  28 . The sealing ring  12  is inserted in the other shallow cavity  28 . 
         [0021]    When the second ring  30  is rotated in a first direction, the sharp portions  45  of the catches  40  engage with some of the teeth  21  of the first ring  20  as shown in  FIG. 3 . Thus, the second ring  30  rotates the first ring  20  in the first direction. 
         [0022]    When the second ring  30  is stopped or rotated in a second direction opposite to the first direction, the elastic ring  42  withdraw the sharp portions  45  of the catches  40  into the shallow recesses  35 . Thus, the sharp portions  45  of the catches  40  rattle and slide on the teeth  21  of the first ring  20 . Hence, the second ring  30  is prevented from stopping or rotating the first ring  20  in the second direction. That is, the first ring  20  is allowed to rotate in the first direction relative to the second ring  30 . 
         [0023]    Referring to  FIG. 4 , a hub assembly includes a hollow axle  50 , a hub  52  and a drum  54  in addition to the one-way transmission module shown in  FIGS. 1 to 3 . The hub  52  includes a non-circular opening  56  made in an end. The drum  54  includes a non-circular end  58 . The one-way transmission module  10  is inserted in the non-circular opening  56 . The hub  52  is not rotatable relative to the first ring  20  because the non-circular opening  56  is shaped in compliance with the non-circular profile  22 . The non-circular end  58  is inserted in the non-circular space  32 . The drum  54  is not rotatable relative to the second ring  30  because the non-circular end  58  is shaped in compliance with the non-circular space  32 . The hollow axle  50  is inserted in the drum  54 . The drum  54  is used to support a flywheel set (not shown) in operation. 
         [0024]    The one-way transmission module  10  is easily inserted in the non-circular opening  56  and located on the non-circular end  58 . If the one-way transmission module  10  is broken, it can easily be removed from the non-circular opening  56  and the non-circular end  58  without causing any damage to the hub  52  and the drum  54 . Then, only the one-way transmission module  10  is replaced with a new one without having to replace the hub  52  or the drum  54  with a new one. Thus, the cost of use and maintenance of the hub assembly of the present invention is low. 
         [0025]    Alternatively, the non-circular opening  56  can be made in the drum  54 , and the non-circular end  58  formed on the hub  52 . However, in such a case, the axis of the one-way transmission module  10  should be rotated for 180° before the one-way transmission module  10  is inserted in the non-circular opening  56 . 
         [0026]    Referring to  FIGS. 5 and 6 , there is a one-way transmission module according to a second embodiment of the present invention. The second embodiment is identical to the first embodiment except for several features. Firstly, the first ring  20  is formed with a smooth internal face  62  instead of the teeth  21 . Secondly, the second ring  30  includes slant recesses  66  instead of the deep and shallow recesses  33  and  35 . The depth of each slant recess  66  extends in a slant manner relative to any radius of the second ring  30 . Thirdly, each catch  40  includes a rod  60  and a spring  68  instead of a single element. Each catch  40  is inserted in a corresponding slant recess  66  by inserting the rod  60  in the slant recess  66  after then spring  68 . 
         [0027]    When the second ring  30  rotates in a first direction, the rods  60  are tightly sandwiched between the external face of the second ring  30  and the smooth internal face  62  of the first ring  20 . Accordingly, the second ring  30  pushes the rods  60 , and the rods  60  push the first ring  20 . Hence, the second ring  30  rotates the first ring  20  in the first direction. 
         [0028]    When the first ring  20  stops or rotates in a second direction opposite to the first direction, each rod  60  is allowed to retreat into the corresponding slant recess  66 . Thus, each rod  60  is allowed to slide or roll on the smooth internal face  60  of the first ring  20 . The second ring  30  pushes the rods  60 , but the rods  60  do not push the first ring  20 . Hence, the first ring  20  is allowed to rotate in the first direction relative to the second ring  30 . 
         [0029]    The present invention has been described via the detailed illustration of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.