Abstract:
A bicycle shifter for pulling and releasing a control cable connected to a gear change mechanism mountable at or near an end of the handlebar that returns to a neutral position after each shift operation to decrease aerodynamic drag encountered by the rider. The shifter includes a takeup member, a control mechanism, a holding mechanism and a return assembly. The takeup member is rotatable about a shift axis for winding and unwinding the control cable thereon in a cable-pull direction and a cable-release direction. The control mechanism is movable in a first direction to rotate the takeup member in the cable-pull direction and in a second direction to rotate the takeup member in the cable-release direction. The holding mechanism retains the takeup member in a selected position and the return assembly returns the control mechanism to the neutral position after each shift operation.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to bicycle shifters and more particularly to a bicycle shifter mountable to an end of a handlebar and having a control mechanism that returns to a neutral position after each shift operation.  
         [0002]     Bicycle racing is becoming an increasingly popular and competitive sport. One type of bicycle racing is time trials where the cyclist races against the clock for a certain distance. During these time trials, the aerodynamics of both the bicycle and rider are very important. Typically, a time trial bicycle will have hook-type handlebars. This type of handlebar is generally u-shaped with the “u” pointing in the riding direction and the end of each side of the “u” is turned upwardly. A typical shifter is mounted to the end of each side of the “u.” One disadvantage of these shifters is that they increase the aerodynamic drag encountered by the rider because the lever does not return to a neutral position after each shift operation rather the neutral position of the lever changes depending on which gear is selected. Furthermore, this configuration is not ergonomic and has a complicated design. Accordingly, there is a need for a simple shifter that is mountable to an end of a handlebar that returns to an aerodynamic/ergonomic position.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention provides a bicycle shifter for pulling and releasing a control cable connected to a gear change mechanism. The bicycle shifter includes a housing, a takeup member, a control mechanism, a holding mechanism and a return assembly. An attachment assembly mounts the housing at or near an end of a bicycle handlebar. The takeup member is rotatable about a shift axis for winding and unwinding the control cable thereon in a cable-pull direction and a cable-release direction. Preferably, the shift axis is substantially perpendicular to an axis of the handlebar. The control mechanism is movable in a first direction to rotate the takeup member in the cable-pull direction and in a second direction opposite the first direction to rotate the takeup member in the cable-release direction. The holding mechanism retains the takeup member in a selected position. The return assembly returns the control mechanism to a neutral position after each shift operation to decrease the aerodynamic drag encountered by the rider.  
         [0004]     In one embodiment of the present invention, the control mechanism includes a control lever, a driver rotatably coupled to the control lever and a clutch mechanism operatively coupled to the driver for transferring the motion of the control lever to the takeup member. The control lever is rotatable about the shift axis in the first and second directions to pull and release the control cable and sweeps substantially perpendicular to the handlebar axis. The driver and clutch mechanism are configured to matingly engage. The clutch mechanism is biased toward the driver in the neutral position. In response to the actuation of the control lever, the driver axially and rotationally displaces the clutch mechanism toward the takeup member to transfer the motion of the control lever to the takeup member.  
         [0005]     In one embodiment, the driver is rotatable about the shift axis and includes at least two teeth engageable with at least two recesses of the clutch mechanism. The driver teeth include angled surfaces corresponding to angled surfaces of the recesses of the clutch mechanism. Alternatively, the clutch mechanism may include teeth that engage recesses of the driver. The clutch mechanism is rotatable about the shift axis and includes a plurality of clutch teeth engageable with a plurality of takeup teeth of the takeup member in response to actuation of the control lever. With this configuration, when the control lever is actuated, the driver rotates, forcing the angled recesses of the clutch mechanism to move along the angled surfaces of the driver teeth causing the clutch mechanism to displace axially away from the driver toward the takeup member until the clutch teeth engage the takeup teeth. Once the takeup member stops the clutch mechanism from displacing axially, the clutch mechanism starts to rotate. Since the clutch teeth are now engaged with the takeup teeth, the takeup member also rotates.  
         [0006]     The return assembly includes a rotational biasing member for rotationally biasing the clutch mechanism to a rotational neutral position and an axial biasing member for axially biasing the clutch mechanism to an axial neutral position away from the takeup member and toward the driver. In one embodiment, the rotational biasing member may be a torsion spring and the axial biasing member is a compression spring disposed between the clutch mechanism and the takeup member. After each shift operation, the torsion spring rotates the clutch mechanism back to its rotational neutral position and the compression spring axially displaces the clutch mechanism away from the takeup member and toward the driver to its axial neutral position The holding mechanism includes a ratchet wheel and at least one detent spring. The ratchet wheel is rotatably coupled to the takeup member and includes a plurality of teeth that correspond to gear positions of the gear change mechanism The detent spring engages the plurality of teeth to retain the ratchet wheel and the takeup member in the selected position.  
         [0007]     These and other features and advantages of the present invention will be more fully understood from the following description of one embodiment of the invention, taken together with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     In the drawings:  
         [0009]      FIG. 1  is a side view of a bicycle shifter in accordance with one embodiment of the present invention;  
         [0010]      FIG. 2  is a cross-sectional side view of an attachment assembly for attaching the bicycle shifter of  FIG. 1  to a handlebar;  
         [0011]      FIG. 3  is a cross-sectional view taken along line A-A of the bicycle shifter of  FIG. 1 ;  
         [0012]      FIG. 3   a  is a cross-sectional view taken along line A-A of the bicycle shifter of  FIG. 1  in accordance with another embodiment of the present invention;  
         [0013]      FIG. 4  is an exploded view of a driver, a clutch mechanism and a takeup member of the shifter of  FIG. 1 ;  
         [0014]      FIG. 5  is a side view of a control lever of the control mechanism of the shifter of  FIG. 1 ;  
         [0015]      FIG. 6  is a cross-sectional view of a holding mechanism of the shifter of  FIG. 1 ;  
         [0016]      FIG. 7   a  is a partial cross-sectional view taken along line B-B of the bicycle shifter of  FIG. 3  showing the positions of the driver, clutch mechanism and the takeup member when the shifter is in a neutral position;  
         [0017]      FIG. 7   b  is a partial cross-sectional view taken along line B-B of the bicycle shifter of  FIG. 3  showing the positions of the driver, clutch mechanism and the takeup member during a shifting operation;  
         [0018]      FIG. 8   a  is cross-sectional view of the clutch mechanism and a rotational biasing member of the shifter of  FIG. 1  when the shifter is in a rotational neutral position;  
         [0019]      FIG. 8   b  is a cross-sectional view of the clutch mechanism and the rotational biasing member of the shifter of  FIG. 1  during a cable-pull operation; and  
         [0020]      FIG. 8   c  is a cross-sectional view of the clutch mechanism and the rotational biasing member of the shifter of  FIG. 1  during a cable-release operation.  
     
    
     DETAILED DESCRIPTION  
       [0021]      FIGS. 1-8  illustrate a bicycle shifter  10  in accordance with one embodiment of the present invention. The bicycle shifter  10  pulls or releases a control cable  12  connected to a gear change mechanism (not shown) to shift between gear positions of the bicycle. The gear change mechanism may be a rear derailleur, a front derailleur or other similar type of mechanism. The bicycle shifter  10  is shown as a time trial shifter for a road bike, however, the shifter  10  may be used on other types of bicycles such as a mountain bike. In this embodiment, the shifter  10  generally includes a housing  14 , a control mechanism  16 , a takeup member  18 , a holding mechanism  20  and a return assembly  22 . Looking to  FIG. 2 , the shifter  10  is mounted at or near an end  24  of a handlebar  26  by an attachment assembly  28  inserted into the end  24  of the handlebar  26 . The attachment assembly  28  includes a bolt  30  threadably connected to the shifter housing  14 , three wedges  32  disposed about the bolt  30  and a wedge spring  34  disposed about the three wedges  32 . The wedge spring  34  biases the wedges  32  radially inward towards the bolt. The bolt  30  includes a socket  36  for receiving a tool such as a hex wrench. To secure the shifter  10  at or near the end  24  of the handlebar  26 , the tool is inserted into the socket  36  and rotated, moving the bolt  30  towards the housing  14 . As the bolt  30  moves toward the housing  14 , tapered surfaces  38 ,  40  of the bolt  30  and housing  14 , respectively, deflect the wedges  32  radially outward against the inner surface  42  of the handlebar  26  securing the shifter  10  to end  24  of the handlebar  26 . Of course, other assemblies for attaching the shifter  10  to the handlebar  26  may be used.  
         [0022]     Looking to  FIGS. 1, 3  and  4 , the housing  14  includes a cover  44  screwed to the housing with three screws  46 . The housing cover  44  includes a bore  48  for receiving a bushing  50 . A shaft  52  extends through the housing  14  and is axially fixed relative to the housing  14  by a screw  54  threadably connected to an end  60  of the shaft  52  and a flange  58  also disposed at the end  60  of the shaft  52 . The shaft  52  has a shift axis that is substantially perpendicular to an axis of the handlebar. In one embodiment of the present invention, the control mechanism  16  includes a control lever  62 , a driver  64  and a clutch mechanism  66 . Looking to  FIG. 5 , the control lever  62  is rotatable about the shaft  52  and includes first and second legs  72 ,  74  clamped to the driver  64  by a screw  76  extending through the first and second legs  72 ,  74 . To secure the control lever  62  on the driver  64 , the screw  76  is tightened causing the first leg  72  to move towards the second leg  74  resulting in a clamping force against the surface of the driver  64 . The angular position of the control lever  62  relative to the housing  14  may be adjusted by selecting the position of the lever  62  relative to the driver  64 . This configuration allows the rider to adjust a neutral position of the control lever  62 .  
         [0023]     Looking to  FIGS. 3 and 4 , the driver  64  extends though the bushing  50  and is rotatably mounted to the shaft  52 . A thrust bushing  68  is disposed about the driver  64  between the control lever  62  and the housing cover  44 . The driver  64  and clutch mechanism  66  are configured to matingly engage. The driver  64  axially and rotationally displaces the clutch mechanism  66  in response to actuation of the control lever  62 . In this embodiment, the driver  64  includes two driver teeth  70  that engage the clutch mechanism  66 . The clutch mechanism  66  is rotatably mounted to the shaft  52 . The clutch mechanism  66  includes two recesses  78  for receiving the two driver teeth  70  and a plurality of clutch teeth  80  for engaging the takeup member  18 . The driver teeth  70  have angled surfaces  77  that are matingly engaged with corresponding angled surfaces  79  of the recesses  78  when the control lever is in the neutral position, see  FIG. 7   b.  Alternatively, the clutch mechanism may include teeth that are engageable with recesses of the driver. The clutch mechanism  66  further includes a cavity  82  for receiving the return assembly  22 .  
         [0024]     The return assembly  22  includes a rotational biasing member  84  for rotationally biasing the clutch mechanism  16  to a rotational neutral position and an axial biasing member  86  for axially biasing the clutch mechanism  16  away from the takeup member  18  to an axial neutral position. In this embodiment, the rotational biasing member  84  is a torsion spring and the axially biasing member  86  is a compression spring. Looking to  FIG. 8   a,  the torsion spring  84  includes two legs  88 ,  90  that are engageable with an extension  92 , in this embodiment a post extending from the clutch mechanism  66 , and a projection  94  extending from the housing  14  to bias the clutch mechanism  66  toward its rotational neutral position. A spring retainer  96  is attached to the clutch mechanism  66  by two screws  98  to prevent the torsion spring  84  from axially moving relative to the clutch mechanism  66 . The compression spring  86  is disposed between the clutch mechanism  66  and the takeup member  18 . Looking to  FIG. 7   a,  the compression spring biases the clutch mechanism  66  toward the driver  64  and away from the takeup member  18 .  
         [0025]     Looking to  FIGS. 3 and 4 , the takeup member  18 , in this embodiment a spool, is rotatably mounted to the shaft  52 . The compression spring  86  biases the takeup member  18  away from the clutching mechanism. The takeup member  18  includes a plurality of takeup teeth  100  located around the periphery of the takeup member  18  for engaging the clutch teeth  80  of the clutch mechanism  66 . The takeup member  18  further includes a groove  102  for receiving the control cable  12 . The groove  102  extends along the periphery of the takeup member  18 . The takeup member  18  is held in a selected position by the holding mechanism  20 . The holding mechanism  20  includes a ratchet wheel  104  and two detent springs  106 . The ratchet wheel  104  includes two projections  108  that are received in recesses  110  of the takeup member  18  to rotatably connect the ratchet wheel  104  to the takeup member  18 . The projections  108  are configured such that the ratchet wheel  104  has a small amount, in this embodiment approximately four degrees, of rotational play relative to the takeup member  18 . Alternatively, the takeup member  18  and ratchet wheel  104  may form one-piece, see  FIG. 3   a.  Looking to  FIG. 6 , the ratchet wheel  104  is rotatably mounted to the shaft  52  and includes two sets of teeth  112  disposed about the periphery of the ratchet wheel  102 . The teeth  112  on the ratchet wheel  102  correspond to gear positions of the gear change mechanism. The detent springs  106  include a first leg  114  supported by the housing and a second leg  116  engageable with the teeth  112  of the ratchet wheel  104  to retain the takeup member in the selected position.  
         [0026]     At rest the control lever  62  is located in a neutral position as shown in  FIG. 1 . When the control lever  62  is in the neutral position, the clutch mechanism  66  is biased away from the takeup member  18  by the compression spring  86  as shown in  FIG. 7   a  and is biased rotationally to the neutral position by the torsion spring  84  as shown in  FIG. 8   a.  To shift the gear change mechanism, the control lever  62  is rotated in a first direction A to pull the control cable and in a second direction B to release the control cable. When the control lever  62  is rotated in the cable-pull direction, the driver  64  rotates with the control lever  62  and as the driver teeth  70  of the driver  64  rotate, the recesses  78  of the clutch mechanism  66  move along angled surfaces  77  of the driver teeth  70 , axially displacing the clutch mechanism  66  toward the takeup member  18  until the clutch teeth  80  of clutch mechanism  66  engage the takeup teeth  100  of the takeup member  18  as shown in  FIG. 7   b.  Once the clutch mechanism  66  is prevented from displacing any further in the axial direction by the takeup member  18 , the extension  92  of the clutch mechanism  66  exerts a force against the leg  90  of the torsion spring  84  overcoming the biasing force of the torsion spring  84  and rotating the clutch mechanism  66  in the cable-pull direction, see  FIG. 8   b.  Since the clutch teeth  80  are now engaged with the takeup teeth  100 , the takeup member  18  and ratchet wheel  104  also rotate in the cable-pull direction resulting in the detent springs  106  to engage a next tooth on the ratchet wheel  104  corresponding to the next gear position of the gear change mechanism. If the rider wanted to shift more than one gear at a time in the cable-pull direction, the rider would continue to rotate the control lever until the desired gear position was reached. With this configuration, the rider may shift multiple gears in the cable-pull direction with a single stroke of the control lever  62 .  
         [0027]     After the control lever  62  is released, the driver  64  no longer exerts a force against the clutch mechanism  66  and the biasing force of the compression spring  86  causes the clutch mechanism  66  to displace away from the takeup member  18  back to its axial neutral position and the biasing force of the torsion spring  84  causes the clutch mechanism  66  to rotate back to its rotational neutral position as shown in  FIG. 8   a.  Since the clutch mechanism  66  is coupled with the driver  64  and the driver  64  is coupled with the control lever  62 , the driver  64  and the control lever  62  also return to their neutral positions. The takeup member  18  is retained in its current position by the detent springs  106  engaging the ratchet wheel teeth  112 .  
         [0028]     When the control lever  62  is rotated in the cable-release direction, similar to the cable-pull operation, the driver  64  rotates with the control lever  62  and as the driver teeth  70  rotate, the recesses  78  of the clutch mechanism  66  move along the angled surfaces  77  of the drive teeth  70  axially displacing the clutch mechanism  66  toward the takeup member  18  until the clutch teeth  80  of the clutch mechanism  66  engage the takeup teeth  100  of the takeup member  18 . Looking to  FIG. 8   c,  once the clutch mechanism  66  is prevented from displacing any further in the axial direction by the takeup member  18 , the extension  92  of the clutch mechanism  66  exerts a force against the leg  88  of the torsion spring  84  overcoming the biasing force of the torsion spring  84  and rotating in the cable-release direction. The takeup member  18  and ratchet wheel  104  rotate in the cable-release direction resulting in the detent springs  106  engaging a next tooth in the cable-release direction. If the rider wanted to shift more than one gear at a time in the cable-release direction, the rider would continue to rotate the control lever  62  until the desired gear position was reached. With this configuration, the rider may shift multiple gears in the cable-release direction with a single stroke of the control lever  62 . Similar to the cable-pull operation, after the release of the control lever  62 , the driver  64 , clutch mechanism  66  and the control lever  62  return to their neutral position and the takeup member  18  is retained in its current position.  
         [0029]     While this invention has been described in reference to a preferred embodiment, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the following claims.