Abstract:
A bicycle shift control device comprises a base member; an operating member structured to be mounted around a handlebar so as to rotate in first and second directions around the handlebar; a transmission control member coupled to the operating member and rotatably mounted relative to the base member for pulling and releasing a transmission control element; a first position setting member; a second position setting member structured to rotate with the operating member and to move axially, wherein the second position setting member moves between an engagement position in which the second position setting member engages the first position setting member and a disengagement position in which the second position setting member is disengaged from the first position setting member; a first coupling member that moves in response to rotation of the operating member; a second coupling member coupled to the second position setting member for engaging the first coupling member so that rotation of the operating member causes rotation of the second position setting member; and wherein the first coupling member and the second coupling member are structured so that rotation of the operating member rotates the transmission control member for a selected rotational distance without moving the second position setting member toward the disengagement position.

Description:
BACKGROUND OF THE INVENTION 
   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. 
   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 (position setting) 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. 
   Twist-grip shift control devices have long been used to control bicycle transmissions such as derailleurs and internal hub transmissions. In derailleur transmissions, it is sometimes desirable to provide an overshift function when shifting from one sprocket to an adjacent sprocket. When performing this function, the derailleur chain guide temporarily moves the chain beyond the destination sprocket to ensure that the chain has engaged the destination sprocket and then returns the chain into proper alignment with the destination sprocket. JP 1969-26571 and U.S. Pat. No. 5,102,372 both disclose twist grip shifting devices that perform this function. In JP 1969-26571 a spring-biased ball moves within a space to provide the overshift function, whereas in U.S. Pat. No. 5,102,372 a leaf spring moves within a space to provide the overshift function. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a twist-grip shift control device that provides the overshift function in a novel way. In one embodiment of the present invention, a bicycle shift control device comprises a base member; an operating member structured to be mounted around a handlebar so as to rotate in first and second directions around the handlebar; a transmission control member coupled to the operating member and rotatably mounted relative to the base member for pulling and releasing a transmission control element; a first position setting member; a second position setting member structured to rotate with the operating member and to move axially, wherein the second position setting member moves between an engagement position in which the second position setting member engages the first position setting member and a disengagement position in which the second position setting member is disengaged from the first position setting member; a first coupling member that moves in response to rotation of the operating member; and a second coupling member coupled to the second position setting member for engaging the first coupling member so that rotation of the operating member causes rotation of the second position setting member. The first coupling member and the second coupling member are structured so that rotation of the operating member rotates the transmission control member for a selected rotational distance without moving the second position setting member toward the disengagement position. 
   In another embodiment of the present invention, a bicycle shift control device comprises a first base member having a first coupling member; a second base member having a second coupling member; an operating member structured to be mounted around a handlebar so as to rotate in first and second directions around the handlebar; wherein the first base member and the second base member are structured to move relative to each other in response to rotation of the operating member; a transmission control member coupled to the operating member and rotatably mounted relative to the first base member for pulling and releasing a transmission control element; a first position setting member; second position setting member structured to rotate with the operating member and to move axially, wherein the second position setting member moves between an engagement position in which the second position setting member engages the first position setting member and a disengagement position in which the second position setting member is disengaged from the first position setting member; a third coupling member that moves in response to rotation of the operating member; and a fourth coupling member coupled to the second position setting member for engaging the operating member so that rotation of the operating member causes rotation of the second position setting member. The first coupling member and the second coupling member are structured so that rotation of the operating member rotates the transmission control member and moves the first base member and the second base member relative to each other for a selected distance without moving the second position setting member toward the disengagement position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       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; 
       FIG. 2  is an oblique view of a particular embodiment of a twist-grip shift control device according to the present invention; 
       FIG. 3  is an exploded view of the twist-grip shift control device shown in  FIG. 2 ; 
       FIG. 4  is a cross sectional view of the twist-grip shift control device taken along line IV—IV in  FIG. 2 : 
       FIG. 5  is a partial cross sectional view of the base member shown in  FIG. 3 ; 
       FIG. 6  is a view taken along line VI—VI in  FIG. 4 ; 
       FIGS. 7A and 7B  are cross sectional views depicting the shapes of the ratchet teeth of the position setting member, the base member, and the operating member; 
       FIGS. 8A–8G  are schematic views showing the operation of the twist-grip shift control device when the operating member is rotated in a wire pulling direction; 
       FIG. 9  illustrates an overshift operation according to the present invention; 
       FIG. 10  is a cross sectional view of an alternative embodiment of a twist grip shifting device according to the present invention; and 
       FIGS. 11A–11G  are schematic views showing the operation of the twist-grip shift control device when the operating member is rotated in a first direction. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1  shows a bicycle  1  provided with a twist-grip shift control device  10  according to the present invention. Bicycle  1  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. Twist-grip shift control device  10  is attached to a handlebar  8  and operates the derailleur  6  via a Bowden-type control 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. 
     FIG. 2  is an oblique view of a particular embodiment of shift control device  10  according to the present invention,  FIG. 3  is an exploded view of shift control device  10 , and  FIG. 4  is a cross-sectional view of shift control device  10 . In general, rotating an operating member  16  around an 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 inner wire  11   a  of control cable  11  to operate derailleur  6 . 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. 
   More specifically, shift control device  10  includes a clamping band  22  that is fastened to handlebar  8  with a screw  26  in a conventional manner. Clamping band  22  includes a connecting arm  30  that is fixed to a portion  34  of a housing  38  by a screw (not shown). Housing  38  includes a side wall  42  that defines an opening  46  such that side wall  42  circumferentially fits within a fixing groove  50  formed in one end of a tubular base member  54  that also fits around handlebar  8 . 
   Wire takeup member  18  is rotatably supported on base member  54 , and it includes a wire winding groove  58  for winding and releasing inner wire  11   a  and another wire winding groove  62  for winding and releasing an auxiliary wire  66  that may be used for controlling some other bicycle device such as a remotely located gear indicator. Inner wire  11   a  is guided within a channel  70  formed in housing  38 , and auxiliary wire  66  is guided within a channel  74  formed in housing  38 . Wire takeup member  18  is formed as one piece with a planet gear carrier  78 . A shown in  FIGS. 3 ,  4  and  6 , planet gear carrier  78  includes a plurality of (e.g., five) pivot shafts  82  for rotatably supporting a corresponding plurality of planet gears  86 . Planet gear carrier  78  also includes a plurality of mounting bases  90 , wherein each mounting base  90  includes a mounting shaft  94 . A cover plate  98  is fitted to planet gear carrier  78  such that cover plate  98  rests against the plurality of mounting bases  90  and each pivot shaft  82  and mounting shaft  94  is press fit within a corresponding opening  102  formed in cover plate  98 . Each planet gear  86  meshes with the teeth  105  of a sun gear  106  formed as one piece with the outer peripheral surface of base member  54 . Each planet gear  86  also meshes with ring gear teeth  110  formed on the inner peripheral surface of a ring gear  114 . It should be readily recognized that sun gear  106 , planet gear carrier  78  (and cover plate  98 ), planet gears  86  and ring gear  114  form a planetary gear mechanism. 
   An annular position setting member  118  (an example of a second position setting member) is rotatably supported on base member  54 , and it includes a plurality of circumferentially disposed position setting (ratchet) teeth  122  (examples of second position setting teeth) for selectively engaging three position setting teeth  126  (examples of first position setting teeth) evenly spaced circumferentially on a flange  130  (an example of a first position setting member) that extends radially outwardly from and one piece with base member  54 , a plurality of circumferentially disposed coupling (ratchet) teeth  134  (examples of second coupling members or teeth) for selectively engaging a corresponding plurality of coupling (ratchet) teeth  138  (examples of first coupling members or teeth) circumferentially disposed on an operating member body  142  of operating member  16 , and an axially extending coupling tab  140  forming an abutment  150 . Abutment  150  contacts an abutment  154  formed on a coupling tab  158  that extends axially from ring gear  114  so that position setting member  118  and ring gear  114  can rotate as a unit. A fixing washer  162  is mounted to base member  54  by coupling tabs  166  that are fitted in L-shaped coupling grooves  170  formed in base member  54  (only one such coupling groove is shown in  FIG. 3 ). A spring washer  174  is disposed between fixing washer  162  and position setting member  118  for biasing position setting member  118  toward flange  130  so that the plurality of position setting teeth  122  firmly engage the position setting teeth  126  formed on flange  130 , and the plurality of coupling teeth  134  firmly engage the plurality of coupling teeth  138  formed on operating member body  142 . 
   Operating member  16  includes operating member body  142  and a gripping cover  174 . Gripping cover  174  is formed from an elastic material, and it includes gripping projections  178  circumferentially formed over its outer peripheral surface to facilitate gripping. Gripping cover  174  includes a plurality coupling grooves  182  formed on its inner peripheral surface for engaging a corresponding plurality of coupling projections  186  formed on the outer peripheral surface of operating member body  142  to securely mount gripping cover  174  to operating member body  142 . Operating member body  142  is rotatably mounted on base member  54  and axially held in place against flange  130  by fixing tabs  190  on base member  54 , each of which includes a radially extending locking projection  194 . A circumferential recess (not shown) formed on the inner peripheral surface of operating member body  142  cooperates with a stop projection  196  ( FIG. 5 ) formed on the side of flange  130  opposite position setting teeth  126  to set the range of motion of operating member body  142  and hence operating member  16 . 
   As noted above, operating member body  142  includes a plurality of circumferentially disposed coupling teeth  138  that engage a corresponding plurality of coupling teeth  134  formed on position setting member  118 . Operating body  142  further includes an axially extending first drive tab  200  forming an abutment  204  and an axially extending second drive tab  208  forming an abutment  212 . Abutment  204  contacts an abutment  216  formed on an axially extending coupling tab  220  on ring gear  114  for rotating ring gear  114  in the direction A shown in  FIG. 3 . A return spring  224  has a first spring leg  228  contacting abutment  212  on second drive tab  208  and a second spring leg  230  contacting a second abutment  234  formed on coupling tab  220  for biasing ring gear  114  in the direction B shown in  FIG. 3 . 
   As shown in  FIG. 7(A) , the plurality of coupling teeth  138  on operating member body  142  are provided in a reference plane  142   s  facing the position setting member  118 . The plurality of coupling teeth  138  extend along the axis X away from the reference plane  142   s , and the height of each coupling tooth  138  in relation to the reference plane  142   s  is indicated as  138   h .In this embodiment, each coupling tooth  138  is formed as a ratchet tooth having a first ratchet tooth surface  138   a  and a second ratchet tooth surface  138   b  that functions as a cam surface in a manner described below. Similarly, the plurality of coupling teeth  134  on position setting member  118  are provided in a reference plane  118   s  facing the operating member body  142 . The plurality of coupling teeth  134  extend along the axis X away from the reference plane  118   s ,and the height of each coupling tooth  134  in relation to the reference plane  118   s  is indicated as  134   h .In this embodiment, each coupling tooth  134  is formed as a ratchet tooth having a first ratchet tooth surface  134   a  facing a corresponding first ratchet tooth surface  138   a  on operating member body  142  and a second ratchet tooth surface  134   b  that functions as a cam surface in a manner described below. When position setting member  118  is in the position shown in  FIG. 4 , a space S is formed between first ratchet tooth surface  134   a  of each coupling tooth  134  and first ratchet tooth surface  138   a  of each coupling tooth  138 . This space S provides the overshift function described below. In this embodiment, space S has a distance of between approximately 1.0 millimeter and 2.0 millimeters. However, since the winding radius of wire takeup member  18  and the gear reduction of the planetary gear mechanism determine the amount of pull of the inner wire  11   a , this space will differ for different applications. The width W represents the distance position setting member  118  moves when inner wire  11   a  is pulled to move derailleur  6  the distance between adjacent sprockets on sprocket cassette  7 . Thus, the distance between each coupling tooth  134  corresponds to one speed step. 
   As shown in  FIG. 7(B) , the position setting teeth  126  on flange  130  are provided in a reference plane  130   s  facing the position setting member  118 . The position setting teeth  126  extend along the axis X away from the reference plane  130   s , and the height of the position setting teeth  126  in relation to the reference plane  130   s  is indicated as  126   h . In this embodiment, position setting teeth  126  each are formed as a ratchet tooth having a first ratchet tooth surface  126   a  and a second ratchet tooth surface  126   b  that functions as a cam surface in a manner described below. Similarly, the plurality of position setting teeth  122  on position setting member  118  are provided in a reference plane  118   t  facing the flange  130 . The plurality of position setting teeth  122  extend along the axis X away from the reference plane  118   t , and the height of each position setting tooth  122  in relation to the reference plane  118   t  is indicated as  122   h .In this embodiment, each position setting tooth  122  is formed as a ratchet tooth having a first ratchet tooth surface  122   a  and a second ratchet tooth surface  122   b  that functions as a cam surface in a manner described below. 
   The operation of shift control device  10  when actuating member  16  is rotated in the direction A will now be described with reference to  FIGS. 8(A)–8(G) . For the sake of simplicity, the shape of the coupling and position setting teeth will be shown in simplified form.  FIGS. 8(A)–8(G)  show the teeth disposed in the rear of shift control device  10  when viewed from the front. Thus, the teeth move upwardly when operating member  16  rotates in the direction A. 
     FIG. 8(A)  shows operating member body  142  and position setting member  118  in an idle state before rotation of operating member  16 . In this state, the plurality of coupling teeth  134  on position setting member  118  mesh with the plurality of coupling teeth  138  on operating member body  142  such that there is the space S between each first ratchet tooth surface  134   a  and each first ratchet tooth surface  138   a .Position setting teeth  126  similarly mesh with a pair of the plurality of position setting teeth  122  on position setting member  118 . 
     FIG. 8(B)  shows the state upon initial rotation of operating member  16 . In this state, operating member body  142  has rotated the distance of the space S so that each first ratchet tooth surface  134   a  contacts its associated first ratchet tooth surface  138   a  while position setting member  118  has remained stationary. During this time, abutment  204  of first drive tab  200  of operating member body  142  contacts abutment  216  of coupling tab  220  of ring gear  114  to rotate ring gear  114  by the same distance. The rotation of ring gear  114  is communicated to the plurality of planet gears  83 , which rotate around the stationary sun gear  106  to cause a corresponding rotation of planet gear carrier  78  and wire takeup member  18  to wind the inner wire  11   a.    
   As shown in  FIGS. 8(C) and 8(D) , upon further rotation of operating member body  142  the first ratchet tooth surfaces  138   a  continue to press against the corresponding plurality of second ratchet tooth surfaces  134   a , but now position setting member  118  rotates around the axis X. At the same time, a cam surface  122   b  on a position setting tooth  122  and cam surface  126   b  on a position setting tooth  126  displace position setting member  118  axially away from flange  130 . Further rotation of operating member body  142  in the direction A causes the position setting teeth  122  of position setting member  118  to jump over the position setting teeth of the flange  130  as shown in  FIG. 8(E) . At this time, the position setting member  118  is again fixed by the position setting teeth  126  of base member  54 . However, it should be recalled that because of the original space S between ratchet tooth surface  134   a  and ratchet tooth surface  138   a , operating member body  142  and hence wire takeup member  18  have rotated by more than the amount (W) corresponding to movement of the derailleur from one sprocket to another, so the chain is in the automatic overshift position shown in  FIG. 9 . If further overshifting is desired, operating member body  142  may be further rotated as shown in  FIG. 8(F)  to produce additional manual overshift as shown in  FIG. 9  without causing a double shift to the next sprocket. That is a benefit of the inclined cam surfaces  122   b  and  126   b  in this embodiment. 
   Because the height  134   h  of the coupling teeth  134  of position setting member  118  is greater than the height  122   h  of the position setting teeth  122  of position setting member  118 , the coupling teeth  134  of position setting member  118  do not move over the coupling teeth  138  of operating member body  142  and remain captured by the same teeth even when the position setting teeth  122  of position setting member  118  has moved over the position setting teeth  126  of the flange  130 . In other words, the meshing relationship of the position setting member  118  relative to the operating member body  142  remains the same throughout the wire pulling operation. 
   When the rider ceases to rotate operating member  16  in the direction A, operating member body  142  rotates in the direction B as a result of wire tension from derailleur  6  to the position shown in  FIG. 8(G)  without moving position setting member  118 . This, in turn, causes a corresponding rotation of ring gear  114 , planet gears  86  and planet gear carrier  18 , and wire takeup member  78 , thus releasing inner wire  11   a  enough to remove the automatic and any manual overshift and return the derailleur  6  to a position such that chain  5  is located beneath the destination sprocket as shown in  FIG. 9 . 
   When operating member  16  is rotated in the direction B to release inner wire  11   a , the ratchet tooth surfaces  138   b  of operating member body  142  press against the ratchet tooth surfaces  134   b  of position setting member  118 . Since position setting member  118  cannot rotate because of the contact between the ratchet tooth surfaces  122   a  of position setting teeth  122  of position setting member  118  and the ratchet tooth surfaces  126   a  of position setting teeth  126  on flange  130 , position setting member  118  moves axially away from flange  130  until the position setting teeth  122  jump over position setting teeth  126  (since, as noted above, the height  134   h  of the coupling teeth  134  of position setting member  118  is greater than the height  122   h  of the position setting teeth  122  of position setting member  118 ), and position setting member  118  rotates by one speed step (W). The operation of operating member  16  and position setting member  118  in this direction is the same as disclosed in U.S. Pat. No. 5,921,139. At the same time, second drive tab  208  of operating member body  142  causes return spring  224  to press against abutment  234  on coupling tab  220  of ring gear  114  to rotate ring gear  114  in the direction B. Ring gear  114 , planet gears  82 , planet gear carrier  78  and wire takeup member  18  rotate accordingly to release inner wire  11   a  by one speed step. 
     FIG. 10  is a cross sectional view of a twist grip shifting device  10 ′ illustrating an alternative embodiment of the present invention. Many components are the same as in the first embodiment and are likewise numbered the same. Thus, only the differences will be described. 
   In this embodiment, the coupling teeth  138 ′ on operating member body  142 ′ are formed such that there is no space between the ratchet tooth surfaces  138   a ′ and the ratchet tooth surfaces  134   a  on the corresponding coupling teeth  134  on position setting member  118 . Instead, base member  54  in the first embodiment is converted into a first base member  54   a  and a second base member  54   b .First base member  54   a  has a tubular body  300  with radially outwardly extending locking projections  304  for engaging the side wall  42  of housing  38 , radially outwardly extending locking projections  308  for axially retaining second base member  54   b  and operating member body  142 ′ (similar to locking projections  194  in the first embodiment), and a radially outwardly extending coupling member in the form of a projection  310 . Second base member  54   b  is constructed substantially the same as base member  54  in the first embodiment, except that it is rotatably supported by first base member  54   a , and it includes coupling members in the form of abutments  314  and  318  ( FIG. 11(A) ) disposed on opposite sides of projection  310  to form a space S similar to space S between ratchet tooth surfaces  134   a  and  138   a  in the first embodiment. Second base member  54   b  is axially retained on first base member  54   a  by abutting against side wall  42  of housing  38  and by abutting against locking projections  308 . 
   The operation of shift control device  10 ′ when actuating member  16 ′ is rotated in the direction A will now be described with reference to  FIGS. 11(A)–11(G) .  FIG. 11(A)  shows operating member body  142 ′, position setting member  118 , first base member  54   a  and second base member  54   b  in an idle state before rotation of operating member  16 ′. In this state the plurality of coupling teeth  134  on position setting member  118  mesh with the plurality of coupling teeth  138 ′ on operating member body  142 ′ so that first ratchet tooth surfaces  138   a ′ press against the corresponding plurality of first ratchet tooth surfaces  134   a , and position setting teeth  126  similarly mesh with corresponding pairs of the plurality of position setting teeth  122  on position setting member  118 . Projection  310  of first base member  54   a  contacts abutment  318  on second base member  54   b  so that space S is located between projection  310  and first abutment  314 . 
     FIG. 11(B)  shows the state upon initial rotation of operating member  16 ′. In this state, operating member body  142 ′ and second base member  54   b  have rotated the distance S to close the space between projection  310  and abutment  314  while position setting member  118  has remained stationary. During this time, abutment  204  of first drive tab  200  on operating member body  142 ′ contacts abutment  216  of coupling tab  220  on ring gear  114  to rotate ring gear  114  by the same distance in the same manner as in the first embodiment. The rotation of ring gear  114  is communicated to the plurality of planet gears  83 , which rotate around the stationary sun gear  106  to cause a corresponding rotation of planet gear carrier  78  and wire takeup member  18  to wind the inner wire  11   a.    
   As shown in  FIGS. 11(C) and 11(D) , upon further rotation of operating member body  142 ′, the first ratchet tooth surfaces  138   a ′ continue to press against first ratchet tooth surfaces  134   a ,but now position setting member  118  rotates around the axis X. At the same time, cam surfaces  122   b  on a position setting teeth  122  of position setting member  118  and cam surfaces  126   b  on position setting teeth  126  of flange  130  displace position setting member  118  axially away from flange  130 . Further rotation of the operating member body  142 ′ in the direction A causes the position setting tooth  122  of position setting member  118  to jump over the position setting tooth  126  of the flange  130  as shown in  FIG. 11(E) . At this time, position setting member  118  is again fixed by position setting teeth  126  on flange  130  of base member  54   b . However, it should be recalled that because of the original space S between projection  310  and abutment  314 , operating member body  142 ′, and hence wire takeup member  18 , has rotated by more than the amount (W) corresponding to movement of the derailleur from one sprocket to another, so the chain is in the automatic overshift position shown in  FIG. 9 . If further overshifting is desired, operating member body  142 ′ may be further rotated as shown in  FIG. 11(F)  to produce the additional manual overshift shown in  FIG. 9 . 
   When the rider ceases to rotate operating member  16 ′ in the direction A, operating member body  142 ′ and second base member  54   b  rotate in the direction B to the position shown in  FIG. 11(G)  so that projection  310  on first base member  54   a  abuts against abutment  318  without moving position setting member  118 . This, in turn, causes a corresponding rotation of ring gear  114 , planet gears  86 , planet gear carrier  18  and takeup member  78 , thus releasing inner wire  11   a  enough to remove the overshift and return the derailleur  6  to a position such that chain  5  is located beneath the destination sprocket as shown in  FIG. 9 . 
   Operation of shift control device  10 ′ when operating member  16  is rotated in the direction B is substantially the same as in the first embodiment. In this case projection  310  on first base member  54   a  contacts abutment  318  on second base member  54   b  for the duration of the shifting operation. 
   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.