Abstract:
A bicycle shift control device comprises a base member for attachment to the bicycle, a operating member rotatably supported relative to the base member for rotating in first and second directions, a transmission control member rotatably mounted relative to the base member for controlling the pulling and releasing of a transmission control element, a bracket for supporting a transmission control element diverting surface, and an intermediate member coupled for rotation with the transmission control member. The intermediate member rotates around a first axis, and the intermediate member can move in the direction of the first axis between an engagement position, in which the intermediate member engages the bracket, and a disengagement position, in which the intermediate member is disengaged from the bracket. The intermediate member includes a first cam surface for causing movement of the intermediate member in the direction of the first axis toward the disengagement position during rotation of the intermediate member, and the intermediate member includes a positioning surface for preventing the intermediate member from rotating around the first axis when the intermediate member is in the engagement position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention is directed to control devices for bicycles and, more particularly, to a twist-grip shift control device for shifting a bicycle transmission.  
           [0002]    An example of a twist-grip shift control device is shown in U.S. Pat. No. 5,921,139. That shift control device comprises a fixed member that is nonrotatably fixed to the bicycle handlebar, a handgrip operating member rotatably supported relative to the fixed member for rotating in first and second directions, a takeup member rotatably mounted relative to the fixed member for controlling the pulling and releasing of a transmission control element, and an intermediate member coupled for rotation with the takeup member. Ratchet teeth are formed on the fixed member and the intermediate member for holding the intermediate member, and hence the takeup member, in a plurality of fixed positions. Additional ratchet teeth are formed on the intermediate member and the handgrip operating member for rotating the intermediate member and the takeup member for pulling and releasing the transmission control element. A pulley is mounted to a bracket that extends from the base member for changing the direction of the transmission control element after the transmission control element exits the takeup member so that the transmission control element can extend in the direction of the bicycle handlebar.  
           [0003]    It was learned that the tension on the transmission control element affects the operation of the shift control device. More specifically, the amount of the transmission control element pulled or released between the fixed positions of the takeup member would vary depending upon the tension applied to the transmission control element, thus causing the transmission attached to the transmission control element to be placed in a position that was not optimum for the selected gear. Such positioning errors could cause the transmission to generate undesirable noise or to malfunction.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention is directed to a twist-grip shift control device that operates reliably even when the transmission control element experiences high tension. In one embodiment of the present invention, a bicycle shift control device comprises a base member for attachment to the bicycle, a operating member rotatably supported relative to the base member for rotating in first and second directions, a transmission control member rotatably mounted relative to the base member for controlling the pulling and releasing of a transmission control element, a bracket for supporting a transmission control element diverting surface, and an intermediate member coupled for rotation with the transmission control member. The intermediate member rotates around a first axis, and the intermediate member can move in the direction of the first axis between an engagement position, in which the intermediate member engages the bracket, and a disengagement position, in which the intermediate member is disengaged from the bracket. More specifically, the intermediate member includes a first cam surface for causing movement of the intermediate member in the direction of the first axis toward the disengagement position during rotation of the intermediate member, and the intermediate member includes a positioning surface for preventing the intermediate member from rotating around the first axis when the intermediate member is in the engagement position. Having the intermediate member engage the bracket in the engagement position minimizes or eliminates variations in performance caused by tension exerted on the transmission control element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a side view of a bicycle which incorporates a particular embodiment of a twist-grip shift control device according to the present invention;  
         [0006]    [0006]FIG. 2 is an oblique view of a particular embodiment of a twist-grip shift control device according to the present invention;  
         [0007]    [0007]FIG. 3 is a partially exploded view of the twist-grip shift control device shown in FIG. 2;  
         [0008]    [0008]FIG. 4 is a partial cross sectional view of the twist-grip shift control device shown in FIG. 2;  
         [0009]    [0009]FIG. 5 is an exploded view of the twist-grip shift control device shown in FIG. 2;  
         [0010]    [0010]FIG. 6 is a rear view of the intermediate member shown in FIG. 5;  
         [0011]    [0011]FIGS. 7A and 7B are cross sectional views depicting the shapes of the gear portions of the intermediate member, the bracket, and the operating member;  
         [0012]    FIGS.  8 A- 8 D are schematic views showing the operation of the twist-grip shift control device when the operating member is rotated in a first direction;  
         [0013]    FIGS.  9 A- 9 B are schematic views showing the operation of the twist-grip shift control device when the operating member is rotated in a second direction; and  
         [0014]    [0014]FIG. 10 is an oblique view of an alternative embodiment of a twist-grip shift control device according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0015]    [0015]FIG. 1 shows a mountain bicycle  1  provided with the shift control device according to the present invention. This bicycle is equipped with a front wheel  2 , pedals  4 , a derailleur  6  for moving a chain  5  over a sprocket cassette  7  attached to a rear wheel  3 , a brake mechanism  9 , and the like. A twist-grip shift control device  10  that is attached to a handlebar  8  operates the derailleur  6  via a shifting cable  11 . As used herein, the terms “front direction,” “back direction,” “transverse direction,” and the like refer to the directions with respect to the bicycle. For example, “right” means to the right of the rider sitting on the saddle.  
         [0016]    [0016]FIG. 2 is an oblique view of a particular embodiment of a twist-grip shift control device  10  according to the present invention, FIG. 3 is a partially exploded view of shift control device  10 , and FIG. 4 is a partial cross-sectional view of shift control device  10 . In general, rotating an operating member  16  around a first axis X that runs along the handlebar  8  rotates a transmission control member in the form of a wire takeup member  18  which, in turn, pulls and releases an intermediate wire  11   a  that is connected to a deflection pulley  21  rotatably mounted to a bracket  15 . An inner wire  11   b  of control cable  11  is connected to deflection pulley  21  and to derailleur  6  so that rotation of operating member  16  ultimately pulls and releases inner wire  11   b  to operate derailleur  6 . Intermediate wire  11   a  and inner wire  11   b  together function as a transmission control element. In this embodiment, seven-step shifting can be accomplished with shift control device  10 , but the number of steps can be varied depending upon the application.  
         [0017]    In this embodiment, deflection pulley  21  is rotatably mounted to a pivot shaft  15   a  of bracket  15  by a screw  23  so that deflection pulley  21  can rotate around a second axis Y that is perpendicular to the first axis X. Deflection pulley  21  includes a transmission control element diverting surface  21   a  for receiving intermediate wire  11   a  and a transmission control element diverting surface  21   b  for receiving inner wire  11   b . Transmission control element diverting surfaces  21   a  and  21   b  serve to change the direction of the transmission control element from the radially outwardly extending direction of intermediate wire  11   a  to the axial direction of inner wire  11   b . Transmission control element diverting surfaces  21   a  and  21   b  also can be used to adjust the cable pull/release rate of the transmission control element. In other embodiments, a transmission control element in the form if a single wire could be directly attached to takeup element  18 , and deflection pulley  21  could include a single transmission control element diverting surface for changing the direction of the single wire as it leaves takeup element  18 . Alternatively, as shown in FIG. 10, a shift control device  10 ′ could eliminate deflection pulley  21  entirely, and a bracket  15 ′ could include a curved portion  15 x for changing the direction of an inner wire  11   x  of a transmission control cable  11 ′.  
         [0018]    The structure of shift control device  10  will now be described in detail. The inventor has discovered that the source of the problem of the variations in performance caused by tension exerted on the transmission control element arose from the placement of the positioning mechanism on the base member in the prior art. Shift control device  10  solves the problem by placing the positioning mechanism on bracket  15  as noted in more detail below. Although the description that follows refers to the shift control device  10  that is used to control the rear derailleur  6  and that is attached to the right side of the bicycle handlebar  8 , the same shift control device can be provided on the left side of the handlebar.  
         [0019]    As shown in FIGS. 4 and 5, shift control device  10  comprises a base member  14  attached to bracket  15  in such a way that it cannot rotate in relation to the handlebar, a handgrip actuating member  16   a  mounted on base member  14  for rotation around axis X and held in place by retaining tabs  14   a  on base member  14 , a flexible cover  12  surrounding handgrip actuating member  16   a  to facilitate gripping, an auxiliary actuating member  16   b  having coupling tabs  16   c  that engage coupling grooves  16   d  in handgrip actuating member  16   a  so that handgrip actuating member  16   a  and auxiliary actuating member  16   b  rotate as a unit, an intermediate member  17  that meshes with both bracket  15  and auxiliary actuating member  16   b  in a manner described below, the takeup member  18  having a coupling groove  18   a  that slidingly and nonrotably engages a coupling tab  17   a  on intermediate member  17  so that takeup member  18  and intermediate member  17  rotate as a unit, a fixing washer  19  having coupling tabs  19   a  that engage corresponding coupling grooves  15   b  in bracket  15 , and a spring washer  20  for biasing intermediate member  17  towards auxiliary actuating member  16   b  and bracket  15 . Handgrip actuating member  16   a  and auxiliary actuating member  16   b  together form operating member  16 . A wire winding surface  18   c  is formed on the outer peripheral surface of takeup element  18 , and this wire winding surface  18   c  takes up the intermediate wire  11   a . A coupler  18   d  connects the tip of the intermediate wire  11   a  with the takeup member  18 .  
         [0020]    Bracket  15  has an inner tubular portion  15   c  that contains coupling grooves  15   b  and that mounts to the outer peripheral surface of base member  14 , a radially outwardly extending side wall  15   d  (perpendicular to base member  14 ) containing diametrically opposed positioning teeth  151  formed in a plane  15   s  (FIG. 7B), and an outer tubular portion  15   e  disposed radially outwardly from the outer peripheral surface of auxiliary actuating member  16   b . The plane  15   s  that faces the intermediate element  17  and is perpendicular to the first axis X is referred to as “the reference plane  15   s  of the bracket.” The positioning teeth  151  extend along the first axis X away from the reference plane  15   s  of the bracket  15 , and the height of the positioning teeth  151  in relation to the reference plane  15   s  is indicated as  15   h . Auxiliary actuating member  16   b  includes a plurality of drive teeth  160  provided in a reference plane  16   s  (FIG. 7A) facing the intermediate element  17 . The plurality of drive teeth  160  extend along the first axis X away from the reference plane  16   s  of auxiliary actuating member  16   b , and the height of the drive teeth  160  in relation to the reference plane  16   s  is indicated as  160   h.    
         [0021]    As shown in FIGS. 5 and 6, the intermediate member  17  has an annular shape, and the inner peripheral surface  17   b  thereof is rotatably and slidably fitted on the outer peripheral surface  14   b  of base member  14 . Intermediate member  17  is spring-loaded in the direction of auxiliary actuating member  16   b  by spring  20  positioned between intermediate member  17  and fixing member  19  as shown in FIG. 4. The surface of intermediate member  17  that faces bracket  15  is equipped with a first gear portion comprising a plurality of gear teeth  170  that engage the positioning teeth  151  of bracket  15 , and a second gear portion comprising a plurality of gear teeth  171  that engage the plurality of drive teeth  160  of the auxiliary actuating member  16   b . The plurality of gear teeth  170  are located radially inwardly of the plurality of gear teeth  171 .  
         [0022]    The plurality of gear teeth  170  and  171  extend along the first axis X in the direction of auxiliary actuating member  16   b  and away from a reference plane  17   s  (FIGS.  7 A- 7 B) facing the auxiliary actuating member  16 . The height  171   h  of the plurality of gear teeth  171  of intermediate member  17  that engage the plurality of drive teeth  160  of auxiliary actuating member  16  is greater than the height  170   h  of the plurality of gear teeth  170  of intermediate member  17  that engage the positioning teeth  151  of bracket  15 .  
         [0023]    [0023]FIG. 7A schematically shows a cross section of the plurality of gear teeth  171  of intermediate member  17  that face the plurality of drive teeth  160  of auxiliary actuating member  16   b , and FIG. 7B schematically shows a cross section of the plurality of gear teeth  170  of intermediate member  17  that faces the positioning teeth  151  of bracket  15 . The plurality of gear teeth  171  of intermediate member  17  are provided with surfaces  171  a that extend in the direction of the first axis X, and with cam surfaces  171   b  that are inclined relative to the first axis X. The plurality of drive teeth  160  of the auxiliary actuating member  16  that face the plurality of gear teeth  171  of intermediate member  17  are provided with drive surfaces  160   a  extending in the direction of the first axis X for rotatably driving the intermediate member  17  and with cam surfaces  160   b  corresponding to the second cam surfaces  171   b  for axially driving the intermediate member  17 . The rotational widths W of the gear teeth of the intermediate member and the auxiliary actuating member  16   b  are set to a length equal to the displacement necessary for shifting the speed step by one step. The plurality of gear teeth  170  of intermediate member  17  are provided with positioning surfaces  170   a  that extend in the direction of the first axis X, and these surfaces come into contact with surfaces  151   a  of positioning teeth  151  of bracket  15 . The plurality of gear teeth  170  are also provided with first cam surfaces  170   b  that are inclined relative to the first axis X, and these surfaces come into contact with cam surfaces  151   b  of positioning teeth  151  in a manner described below.  
         [0024]    The operation of shift control device  10  will now be described with reference to FIGS.  8 A- 8 D and  9 A- 9 D. For the sake of simplicity, the shape of the gear teeth will be shown in simplified form.  
         [0025]    The manner in which the components move when operating member  16  is rotated in the takeup direction D 1  is shown sequentially from FIGS.  8 A- 8 D. First, the drive surfaces  160   a  of the plurality of drive teeth  160  of the auxiliary actuating member  16   b  press against the surfaces  171   a  of the plurality of gear teeth  171  of the intermediate member  17  and rotate intermediate member  17 , and hence takeup member  18 , around the first axis X. At the same time, the first cam surfaces  170   b  displace the intermediate member  17  in the direction of the first axis X as shown in FIGS. 8B and 8C. Further rotation of the operating member  16  in the takeup direction D 1  causes the gear teeth  170  of intermediate member  17  to jump over the positioning teeth  151  of the bracket  15  as shown in FIGS. 8D and 8E. Thereafter, the intermediate member  17  is again fixed by the bracket  15  in a position resulting from the shifting of the intermediate element  17  by a single speed step (W). Because the intermediate member  17  is in constant engagement with the takeup member  18 , the takeup member  18  moves a single speed step together with the intermediate element  17 . At the end of the operation, the positioning surfaces  170   a  of the intermediate element  17  are pressed against the corresponding surfaces  151   a  of the bracket  15 , and the intermediate element  17  is held in place with respect to the bracket  15 .  
         [0026]    Because the height  171   h  of the gear teeth  171  is greater than the height  170   h  of the gear teeth  170 , the gear teeth  171  do not move over the gear teeth  160  of the auxiliary actuating member  16   b  and remain captured by the same mating teeth even when the gear teeth  170  have moved over the positioning teeth  151  of the bracket  15 . In other words, the position of the intermediate element  17  relative to the auxiliary actuating member  16   b  remains the same as the position occupied before the operating member  16  has been manipulated.  
         [0027]    The movement of the intermediate member  17  and the takeup member  18  in relation to the bracket  15  when the operating member  16  is rotated the pay-out direction D 2  will now be described with reference to FIGS.  9 A- 9 D. Rotating the operating member  16  in the reverse direction D 2  causes the cam surfaces  171   b  of the gear teeth  171  of the intermediate member  17  to slide on the corresponding cam surfaces  160   b  of gear teeth  160  of auxiliary actuating member  16   b , thus moving the intermediate member  17  along the first axis X away from auxiliary actuating member  16   b  and bracket  15 . Because in this case the positioning surfaces  170   a  of the intermediate element  17  are captured by the corresponding positioning surfaces  151   a  of the bracket  15 , the positioning surfaces  170   a  merely slide on the corresponding positioning surfaces  151   a  of the bracket  15 , with the result that the intermediate member  17  does not rotate around the first axis at this time.  
         [0028]    Further rotating the operating member  16  in the direction D 2  causes the gear teeth  170  of the intermediate member  17  to move over the corresponding positioning teeth of the bracket  15  as shown in FIGS. 8C and 8D because the height  170   h  of the gear teeth  170  is less than the height  171   h  of the gear teeth  171 . Thus, the intermediate member  17  and takeup member  18  move one speed step (W) in the pay-out direction. In the process, the gear teeth  171  of the intermediate element  17  first move away from the gear teeth  160  of the auxiliary actuating member  16   b  but then engage the same teeth again once the gear teeth  170  of the intermediate member  17  move over the positioning teeth  151  of the bracket  15 .  
         [0029]    While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. For example, the size, shape, location or orientation of the various components may be changed as desired. Components that are shown directly connected or contacting each other may have intermediate structures disposed between them. The functions of one element may be performed by two, and vice versa. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the scope of the invention should not be limited by the specific structures disclosed or the apparent initial focus on a particular structure.