Abstract:
The present invention discloses a bicycle hub speed-change assembly having a planetary gear set disposed therein, a speed-change gear wheel separately disposed on both left and right sides of the planetary gear set, and a first ratchet jacket and a second ratchet jacket respectively disposed on the external side of the speed-change gear wheels, such that control ratchets of the first ratchet jacket and second ratchet jacket are selectively hidden or driven by an external ring of the planetary gear set to couple the first ratchet jacket with a hub, so as to provide three different speeds and the invention features the advantages of stable speed, simplified components, and light weight.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a bicycle hub, and more particularly to a built-in three-speed hub having the features of a simple structure, an easy manufacture and a stable speed change. 
   BACKGROUND OF THE INVENTION 
   Referring to  FIGS. 1 and 2  for the exploded view and the cross-sectional view of a traditional built-in three-speed hub respectively, the traditional hub includes an axle shaft  1 , a hollow planetary gear set  2  passing through and connecting the middle of the axle shaft  1 , a clutch  3  having a plurality of teeth disposed at an end of the clutch  3  for engaging an interior of a driving member  4 , an external ring  5  disposed at the external periphery of the planetary gear set  2  and having two corresponding ratchets  5   b , a hub  7  having a plurality of internal teeth  8  disposed on a sidewall of the hub  7 , and a driving member  4  having its external periphery engaged with a bicycle sprocket  9 , such that if the sprocket  9  drives the driving member  4  to rotate, the clutch  3  situated at the driving member  4  will be driven by the clutch  3 , and a ring gear  3   a  in the clutch  3  will be latched with the internal teeth of the planetary gear set  2  for driving the planetary gear set  2  to rotate, and four planetary gear wheels  2   a  drive the external ring  5  to rotate, and two protruded teeth  5   a  of the external ring  5  are engaged with the internal teeth  8  disposed at a side of the hub  7  to rotate the hub  7 . If the clutch  3  is withdrawn and separated from the planetary gear set  2 , an end of each ratchet  5   b  of the external ring  5  will be pushed outward, so that another embedding end at the external side is hidden and will not drive the hub  7  to rotate, and a plurality of wheel teeth  4   a  of the driving member  4  are engaged with the protruded teeth  5   a  of the external ring  5  for driving the external ring  5  to rotate, and four planetary gear sets  2  in the external ring  5  can be rotated, and the embedding teeth  2   b  can be engaged with the internal teeth  8  at the other side of the hub  7 , so that the hub  7  can be rotated. The movement of the clutch  3  is controlled by the displacement of a gear lever  1   a  in the axle shaft  1 . When the slope of a skewed groove  1   b  of the axle shaft  1  guides the ring gear  3   a  at the internal side of the clutch  3  for a connection, the ring gear  3   a  is guided slantingly into the skewed groove  1   b  during a rotation, so that the driving member  4  can drive the external ring  5 . When the gear lever  1   a  is pushed inward again, the clutch  3  pushes the planetary gear set  2 , and the embedding teeth  2   b  are engaged with the internal teeth  8  of the hub  7  to drive the hub  7  to rotate. 
   Since the foregoing internal teeth  8  disposed on both sides of a traditional hub  7  are in the hub  7 , the process for manufacturing the teeth is not easy, and the skewed groove  1   b  of the axle shaft  1  is in a spiral shape which makes the manufacturing process more difficult. Further, the prior art speed-change hub consists many complicated components, and thus causing a heavy total weight and incurring a high manufacturing cost. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide a hub speed-change assembly having a structural design for achieving a stable speed change, an easy manufacture, and a simple structure of components to reduce the manufacturing cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of a traditional built-in three-speed hub; 
       FIG. 2  is a cross-sectional view of a traditional built-in three-speed hub assembly; 
       FIG. 3  is an exploded view of a preferred embodiment of the present invention; 
       FIG. 4  is a cross-sectional view of the preferred embodiment of the present invention; 
       FIG. 5  is a perspective view of the preferred embodiment of the present invention; 
       FIG. 6  is a schematic view of the two-speed movements of the preferred embodiment of the present invention; and 
       FIG. 7  is a schematic view of the three-speed movements of the preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 3 to 5  for a bicycle hub speed-change assembly of the present invention, the bicycle hub speed-change assembly comprises a hollow axle shaft  10 , a screw rod  11  disposed separately on both left and right sides of the hollow axle shaft  10 , a gear wheel  12  disposed at the middle portion of the hollow axle shaft  10 , a bushing  13  disposed separately on both left and right sides of the gear wheel  12 , a fixing pin  131  for radially connecting the surrounding walls of the bushing  13  and passing through a long groove  18  of the axle shaft  10 , a gear lever  14  of passing through a lateral side of the interior of the axle shaft  10 , a gear shift guiding rod  15  disposed between two fixing pins  131  and passing and connecting the interior of the axle shaft  10 , and an end of the axle shaft  10  is sheathed into a spring  16  and locked by a screw bolt  17 , and the gear lever  14  is passed and connected to another side of the axle shaft  10 . 
   A planetary gear set  20  comprises a hollow external ring  21 , a pair of notches  22  disposed at corresponding positions of two sidewalls of the external ring  21 , and a plurality of internal teeth  23  disposed on the internal wall of the external ring  21 , and four planetary gear wheels  24  are engaged with the internal teeth  23  to produce revolutions, and each planetary gear wheels  24  includes an insert rod  241  disposed on both left and right sides of each planetary gear wheel  24  for connecting an insert hole  251  on both left and right sides of a gear carrier  25 , such that each planetary gear wheels  24  is exposed from a window hole around the surrounding surface of the gear carrier  25  and engaged with the internal teeth  23  of the external ring  21 , and the gear carrier  25  includes two corresponding notches  252  disposed on the left and right sidewalls of the gear carrier  25 . 
   Two speed-change gear wheels  30   a ,  30   b  are hollow and disposed on the left and right sides of the planetary gear set  20 , and each speed-change gear wheel  30   a ,  30   b  includes an external ring gear  31   a ,  31   b , and each external ring gear  31   a ,  31   b  has two corresponding embedding portions  311   a ,  311   b  protruded from the radial surface of the planetary gear set  20  and a chamber  32   a ,  32   b  disposed therein for separately containing the two internal ring gears  33   a ,  33   b , and each internal ring gear  33   a ,  33   b  has two engaging portions  331   a ,  331   b  protruded from the corresponding positions at the external sides of the internal ring gear  33   a ,  33   b , and each chamber  32   a ,  32   b  includes a plurality of ring gears  34   a ,  34   b  disposed around the lateral sidewall of the chamber  32   a ,  32   b.    
   A first ratchet jacket  40  is a hollow member disposed at an external side of the speed-change gear wheel  30   a , a pair of resilient ratchets  41  pivotally coupled to a lateral sidewall, and a pair of control ratchets  42  disposed at a middle section. The control ratchets  42  are in the shape of a hook having an end as a control end  42   a  that can move freely on the walls of the ratchet jacket  34  and another end exposed to the outside as a driving end  42   b  for engaging an internal ring gear  33   a  of the speed-change gear wheel  30   a . The first ratchet jacket  40  comprises an indent tooth  43  disposed at each of the four corners of the external periphery, a screw thread  44  disposed on an external side of the first ratchet jacket  40 , and a first bearing  45  coupled to an opening at the external side of the first ratchet jacket  40  and a first cover  46  secured onto a screw rod  11  at the right side of the axle shaft  10 , such that the first bearing  45  is installed between the exterior of the first cover  46  and the internal wall of the first ratchet jacket  40 , and a first screw nut  47  locked with the axle shaft  10  and disposed on the external side of the first cover  46 . 
   A second ratchet jacket  50  is a hollow member comprising a resilient ratchet  51  disposed at the middle section of the second ratchet jacket  50  and can be pressed and withdrawn flexibly, a pair of control ratchets  52  disposed on a lateral sidewall of the resilient ratchet  51 , and the control ratchets  52  are substantially in the shape of a hook having an end as a control end  52   a  disposed in the hollow interior of the second ratchet jacket  50  and another end being disposed at an external side and serving as a driving end  52   b  and the second ratchet jacket  50  is coupled to a bicycle chain tooth a, a second bearing  53  coupled to an opening at the external side of the second ratchet jacket  50 , and a second cover  54  screwed to another side of the axle shaft  10 , and the second bearing  53  is installed between the second ratchet jacket  50  and the second cover  54  and locked with the axle shaft  10  by a second screw nut  55  to fix the second cover  54 . 
   A hub  60  is a hollow cylindrical body comprising an interior connected to the axle shaft  10 , a planetary gear set  20 , two speed-change gear wheels  30 , a first ratchet jacket  40 , a second ratchet jacket  50 , and a third bearing  61  installed between the internal walls of the first ratchet jacket  40  and the hub  60 . 
   During a first level speed change of the foregoing structure, the chain tooth a directly drives the second ratchet jacket  50  to rotate. The resilient ratchets  51  of the second ratchet jacket  50  and the driving ratchets  52  are engaged with the external ring gear  31   b  and the internal ring gear  33   b  respectively to drive the external ring gear  31   b  and the internal ring gear  33   b  to rotate, and the external ring gear  31   b  can be inserted into the notches  22  of the external ring  21  by its embedding portion  311   b  to drive the external ring  21  of the planetary gear set  20  to rotate. The internal ring gear  33   b  is connected to the notches  252  of the gear carrier  25  by its engaging portion  331  and planetary gear set  20  to drive the gear carrier  25  and the four planetary gear wheels  24  to rotate. Since the internal ring gear  33   b  drives the gear carrier  25  to rotate by means of rotating the four planetary gear wheels  24  to drive the external ring  21 , the rotation of the external ring  21  is accelerated, and the external ring  21  drives the external ring gear  31   b  to accelerate its rotation and forces the resilient ratchets  51  of the second ratchet jacket  50  to slide without being exerted by an external force. 
   Since the engaging portion  331   a  of the internal ring gear  33   a  is inserted into the notch  252  on another side of the gear carrier  25 , therefore the internal ring gear  33   a  can be rotated as well. The two embedding portions  311   a  of the external ring gear  31   a  are embedded into the two notches  22  at another side of the external ring  21  and driven to rotate. The rotary speed of the external ring  21  is faster than the speed of the gear carrier  25 , such that the speed of the external ring gear  31   a  is faster than the speed of the internal ring gear  33   a , so as to drive the control ratchets  42  of the first ratchet jacket  40  to move. The gear carrier  25  drives the internal ring gear  33   a  to rotate slower, but the resilient ratchets  41  and the control ratchets  42  are rotated synchronously and situated at a sliding status of the resilient ratchets  41 , and the first ratchet jacket  40  is coupled to the hub  60 , so that the hub  60  rotates with the first ratchet jacket  40  to drive the bicycle forward. In this first level speed, the second ratchet jacket  50  rotates one round while the first ratchet jacket  40  is rotating 1.35 rounds. 
   Referring to  FIG. 6  for a second level of speed change, a gear lever  14  is pulled and a gear shift guiding rod  15  is driven by the tension of the spring  16  to move the fixing pin  131 , and the fixing pin  131  is pushed to the right side of the bushing  13  to prop the external wall of the bushing  13  against the control end  42   a  of the control ratchets  42  of the first ratchet jacket  40  outward, and the driving end  42   b  is withdrawn inward, such that when the chain tooth a drives the second ratchet jacket  50  to rotate and its resilient ratchets  51  can drive the external ring gear  31   b  to revolve and the control ratchets  52  drives the internal ring gear  33   b  to rotate. The external ring gear  31   b  and the internal ring gear  33  drive the external ring  21  and the gear carrier  25  to rotate. Since the internal ring gear  33   b  drives the gear carrier  25  to rotate and transmits the four planetary gear wheels  24 , the speed of the external ring  21  is accelerated, and the external ring  21  is driven in a reverse direction to drive and accelerate the external ring gear  31   b , so that the resilient ratchets  51  are slid without being exerted by an external force. In the meantime, the external ring  21  drives the external ring gear  31   a  to rotate at a speed faster than the speed of the internal ring gear  33   a  driven by the gear carrier  25 , such that the external ring gear  31   a  is moved first (exerted by a force). However, the driving end  42   b  of the control ratchets  42  is hidden inward, so that the external ring gear  31   a  is run idly, and the gear carrier  25  drives the internal ring gear  33   a  to revolve and drive the first ratchet jacket  40  to rotate, and the hub  60  will rotate according to the first ratchet jacket  40 . In this second level of speed, the second ratchet jacket  50  rotates one round while the first ratchet jacket  40  is rotating one round. 
   Referring to  FIG. 7  for the third level of speed change, the gear lever  14  is operated, such that the two fixing pins  131  drive the two bushings  13  to displace respectively, and each bushing  13  can push the control end  42   a  of the control ratchets  42  of the first ratchet jacket  40  outward, such that the driving end  42   b  is withdrawn inward, and push the control end  42   a  of the control ratchets  52  of the second ratchet jacket  50  outward, such that the driving end  52   b  is withdrawn inward. If the chain tooth a drives the second ratchet jacket  50  to revolve and the resilient ratchets  51  drive the external ring gear  31   b  to rotate, the external ring gear  31   b  will directly drive the external ring  21  to rotate and drive the external ring gear  31   a  to rotate, and the external ring  21  is driven by the four planetary gear wheels  24  to rotate the gear carrier  25 . Since the speed of the external ring  21  is faster than the speed of the gear carrier  25 , the external ring gear  31   a  can move first, but the driving end  42   b  of the control ratchets  42  is hidden, and thus the external ring gear  31   a  is rotated idly. Only the gear carrier  25  drives the internal ring gear  33   a  to rotate. Since the internal ring gear  33   a  is engaged with the resilient ratchets  41  of the first ratchet jacket  40  to rotate the first ratchet jacket  40 , the hub  60  rotates according to the revolving of the first ratchet jacket  40  to drive the bicycle forward. In the third level of speed, the second ratchet jacket  50  rotates one round while the first ratchet jacket  40  is rotating 0.75 round. 
   Compared with the prior art, the hub of the invention can achieve a light weight and a small volume, and the speed change for each level can be switched stably. Further, the invention also comes with an easy manufacturing process and simplified components, so as to lower the manufacturing cost.