Abstract:
Electronic shifting systems, mechanisms and methods of using and/or controlling the systems to operate a bicycle that allows front and rear gear changer mechanisms to be controlled with only two switches. The switches can be arranged so that each hand is only required to operate one switch to shift the bicycle.

Description:
[0001]    This application is a continuation application of U.S. Non-Provisional Application Ser. No. 14/516,021, filed Oct. 16, 2014, which claims the benefit of U.S. Non-Provisional Application Ser. No. 13/228, 588 filed Sep. 9, 2011, both of which are referenced herein in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This present invention relates to bicycles and electronic shifting systems and methods of operating such systems. 
         [0003]    Bicycles with prior art electronic shifting systems which use electric motors to shift front and rear gear changers are known in the industry, but suffer from some deficiencies. For example, typically four buttons are employed in prior art systems to operate front and rear gear changers. These systems have a front gear changer upshift button, a front gear changer downshift button, a rear gear changer upshift button, and a rear gear changer downshift button. This arrangement requires each hand to operate two buttons, typically with the right hand controlling the rear gear changer buttons and the left hand controlling the front gear changer buttons. A disadvantage of this kind of system is that it is easy for riders to accidentally press the wrong button when they are focusing on the road ahead. 
         [0004]    There is a demand, therefore, to provide a bicycle with a shifting system that is effective and reduces or avoids unintended and/or m is-shifts. The invention satisfies the demand. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention is directed to electronic shifting systems, mechanisms and methods of using the systems that allow both front and rear gear changer mechanisms to be controlled with only two switches. The switches can be arranged so that each hand is only required to operate one switch to shift the bicycle. This eliminates the risk of accidentally actuating the wrong switch and simplifies shifting. For purposes of the invention, and unless specified otherwise, the term “switch” or “switch mechanism” will be understood to mean a single device, for example a button with an associated set of contacts or a toggle with an associated set of contacts, the actuation of which (opening or closing) causes a continuous or a momentary change of state, preferably in an electric circuit, and not referring to a housing or the like containing a plurality of such devices. Actuation refers to the act of causing the change of state of the switch and thus the system such that a signal is generated. 
         [0006]    The invention generally includes a pair of handlebar mounted switches used to control a bicycle electronic shifting system. In one embodiment, a first switch may be configured to shift a rear gear changer in an upshift direction and a second switch may be configured to shift the rear gear changer in a downshift direction. No greater than two switches are required for the system to produce all of the necessary signals and actions for controlling a bicycle with front and rear gear changers. For purposes of this application, downshift will be understood to mean the act of changing to a sprocket and producing less gear inches or, in other words using a rear gear shift scenario, shifting from a first sprocket to a second sprocket, wherein the second sprocket has a larger diameter than the first sprocket. 
         [0007]    When both switches are operated at the same time or concurrently (overlapping in duration), a front gear changer is shifted from a current chainring to the other chainring of a two chainring system, for example. In other words, if the switches are normally in an open state, if both switches are caused to be in a closed or an actuated state concurrently, the front gear changer is caused to perform a shift operation. 
         [0008]    The switches can be mounted to opposite sides of the handlebar so that one switch can be operated with the left hand and the other operated with the right hand. The switches can be mounted to the bar ends of a time-trial bicycle, inboard of the hand grips on a flat bar bicycle, or in a brake support structure typically used on drop-bar road bikes, for example. Other suitable locations are contemplated by the invention including the possibility of mounting two switches on the same part or adjacent parts of the bicycle structure. 
         [0009]    Another advantage of the invention is that possibility of accidentally shifting the front gear changer, a large gear change that could cause a crash if it happens unexpectedly, is greatly reduced because two switches must be actuated concurrently. 
         [0010]    One aspect of the invention provides an electronic shifting system for a bicycle including a first switch mechanism and a second switch mechanism. A control unit is in communication with and responsive to signals from the first and second switch mechanisms. A front gear shift mechanism is in communication with and responsive to command signals from the control unit, wherein the control unit is configured to determine when both the first switch mechanism and the second switch mechanism are actuated concurrently and responsively sends a front shift command signal to the front gear shift mechanism to perform a front gear shift operation. 
         [0011]    Another aspect of the invention provides an electronic gear shifting system for a bicycle including a first switch mechanism and a second switch mechanism. A control unit is in communication with and responsive to signals from the first and second switch mechanisms. A rear gear shift mechanism is in communication with and responsive to command signals from the control unit. Actuating the first switch mechanism sends a first signal to the control unit which is configured, in response to the first signal, to send a first command signal to the rear gear shift mechanism to perform an upshift. Actuating the second switch mechanism sends a second signal to the control unit which is configured, in response to the second signal, to send a second command signal to the rear gear shift mechanism to perform a downshift. A front gear shift mechanism is in communication with and responsive to the command signals from the control unit, wherein the control unit is configured to determine when both the first switch mechanism and the second switch mechanism are actuated concurrently and responsively sends a front shift command signal to the front gear shift mechanism to perform a front gear shift operation. 
         [0012]    Yet another embodiment of the invention provides a method of shifting a bicycle with an electronic gear shifting system, wherein the electronic gear shifting system includes a first switch mechanism, a second switch mechanism, a control unit in communication with and responsive to signals from the first and second switch mechanisms, a front gear shift mechanism and a rear gear shift mechanism, the front and rear gear shift mechanisms in communication with and responsive to command signals from the control unit, including the steps of actuating the first switch mechanism to perform an upshift with the rear gear shift mechanism, actuating the second switch mechanism to perform a downshift with the rear gear shift mechanism, and actuating both the first and second switch mechanisms concurrently to cause the front gear shift mechanism to perform a front gear shift operation. 
         [0013]    Yet another aspect of the invention provides a method of shifting a bicycle with an electronic gear shifting system, wherein the electronic gear shifting system includes a first switch mechanism, a second switch mechanism, a control unit in communication with and responsive to signals from the first and second switch mechanisms, and a front gear shift mechanism in communication with and responsive to command signals from the control unit, comprising the steps of determining with the control unit that both of the first and second switch mechanisms are actuated concurrently, and performing a front gear shift operation with the front gear shift mechanism. 
         [0014]    It will be understood that the various signals from the switches and generated by the control unit(s) and so on, may take various forms. For example, signals from the switches may be individual or discreet or somehow modified in certain circumstances, such as when both switches are actuated concurrently (caused to be both in a changed state at the same time or overlapping in duration). The signals may be the change of state of a circuit, or some other indication that the switch or circuit or circuitry has changed state such that the control unit can detect the change of state and determine if and/or when some responsive action may be generated. 
         [0015]    These and other features and advantages of the invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In the drawings: 
           [0017]      FIG. 1  shows a bicycle with drop-style handlebars incorporating an embodiment of the invention; 
           [0018]      FIG. 2  shows a shift unit according to an embodiment of the invention; 
           [0019]      FIGS. 3 and 4  show the invention adapted to be used on a flat handlebar, like that usable on a mountain bike; 
           [0020]      FIG. 5  shows a diagram of front and rear gear changers and front and rear sprockets; 
           [0021]      FIG. 6 a    shows one embodiment of a gear change control unit according to an embodiment of the invention; 
           [0022]      FIG. 6 b    shows an alternate embodiment of a gear change control unit; 
           [0023]      FIG. 7  shows a rear gear change mechanism according to an aspect of the invention; 
           [0024]      FIG. 8  shows a front gear change mechanism according to an aspect of the invention; 
           [0025]      FIG. 9  shows a flow chart illustrating a process control method for the control unit according to an aspect of the invention; 
           [0026]      FIG. 10  shows a flow chart illustrating a process control method for the rear downshift method according to an aspect of the invention; 
           [0027]      FIG. 11  shows a flow chart illustrating a process control method for the rear upshift method according to an aspect of the invention; 
           [0028]      FIG. 12  shows a flow chart illustrating a process control method for the front shift method according to an aspect of the invention; 
           [0029]      FIG. 13  shows a flow chart illustrating another embodiment of a process control method for the control unit according to the invention employing a timer; 
           [0030]      FIG. 14  shows a flow chart illustrating a rear shifter status store routine; 
           [0031]      FIG. 15  shows another diagram of front and rear gear changers and front and rear sprockets, wherein the front sprockets comprise 3 chainrings; 
           [0032]      FIG. 16  shows a flow chart illustrating an embodiment of a front gear change method; and 
           [0033]      FIG. 17  shows yet another flow chart illustrating an embodiment of a front gear change method. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Preferred embodiments of the invention will herein be described with reference to the drawings. It will be understood that the drawings and descriptions set out herein are provided for illustration only and do not limit the invention as defined by the claims appended hereto and any and all their equivalents. 
         [0035]    Referring to  FIG. 1 , the invention is shown adapted to a bicycle  20  with drop-style handlebars  22 , like that for a road or a cyclocross style bike or the like. It will be understood that any suitable mounting arrangement of the system components is contemplated by the invention, the controls for which are preferably on the handlebar or on a handlebar associated structure as depicted, or anywhere they can be accessed by a user. The shifting system  24 , according to an embodiment of the invention, may include a pair of shift units  26 , mounted to the handlebars  22 . A control unit  28  is also shown mounted to the handlebars  22 . A front gear changer or front gear shift mechanism  30  may be positioned on the seat tube  32  adjacent the front sprockets  34  so as to effect gear changes to the front sprockets or an associated structure. A rear gear changer or rear gear shift mechanism  36  is mounted to a frame member  38  of the bicycle, such as a mount or rear dropout or an associated structure as is known, in a position to effect gear changes to a rear sprocket  40 . A communication link  42  is provided between the control unit  28  and the shift units  26 , the front gear changer  30 , and the rear gear changer  36 . The system may also be applied, in some embodiments, to a bicycle where only a front or only a rear gear changer is used. 
         [0036]    The control unit  28  is shown mounted to the handlebar  22 , but could be located anywhere on the bicycle  20  or, in the alternate, distributed among the various components with routing of the communication link  42  to accommodate the necessary signal and power paths. It would also be possible to locate the control unit  28  other than on the bicycle, for example on the user&#39;s wrist or in a jersey pocket, for example. The communication link  42  could include wires or be wireless, or be a combination thereof. 
         [0037]    One of the shift units  26  is shown in more detail in  FIG. 2 . It will be understood that a bicycle will preferably be provided with a pair of shift units, or a number in an amount and positioned as desired. For example, a time trial bicycle may be provided with shift units on the brake lever housings and another pair of modified shift units may be adapted to the time trial bar extensions. The shift unit  26  may include a brake support  44  mounted to the handlebar  22  and a brake lever  46  pivotally mounted to the brake support. A switch mechanism  48  is mounted to the shift unit  26 , and preferably in or on the brake support  44  and may pivotally support a shift lever  50 . The lever  50  may be permitted to rotate inward in response to actuation of the brake lever  46  without operating the switch mechanism  48 . The switch mechanism  48  preferably includes a normally open contact switch (not shown) configured such that the switch closes or is actuated when the shift lever  50  is moved in an inward direction toward the center plane or center line (not shown) of the bicycle  20 . Alternatively, a shift button  52  could be employed on the brake support  44  or some other location on the shift unit  22  to actuate the switch mechanism  48 . 
         [0038]    The invention is not limited to the depicted placement or configuration of the switch mechanism  48 ; a signal can be generated by a button  52  located on the brake support  44 , brake lever  46 , or handlebar  22 , for example, or by a shift lever pivotally connected to the brake support  44 , brake lever  46 , or handlebar  22 , for example. Other actuating mechanisms may be employed to generate a signal to the control unit  28 . The switch mechanism  48  could also be configured to be operated by pressing the brake lever  46  inward toward the center plane of the bicycle  20 , for example. 
         [0039]    In the alternate, while the invention contemplates operating the switches to generate signals by closing the switch, e.g., closing an electrical circuit, the invention also could be operated by actuating, operating or causing a switch to open, e.g., causing an open circuit or changing the state of the mechanism and thus, the associated circuit. Furthermore, the switches could be optical or other types of switches, for example. The function of the switches are generally to permit the user/operator to cause a change of state of the switch, and thus potentially of the system, and generate a signal which the control unit uses to detect and interpret an action of the user and generate an appropriate response or initiate an appropriate next step or number of steps. 
         [0040]    Returning to  FIG. 1 , the drive unit  70  comprises a chain  72 , front sprocket assembly  34 , which is coaxially mounted with a crank  74  having pedals  76 , and an electrically controlled front gear changer or gear change mechanism  30 , a rear sprocket assembly  40  coaxially mounted with the rear wheel  78 , and an electrically controlled rear gear changer or gear change mechanism  36 . 
         [0041]    The invention is shown on a mountain or comfort or urban style bicycle  54  with flat style bars  56  in  FIG. 3 . It will be understood that the system  24  will be similar to that of the above described system with adaptations to the particular style of bicycle and its components. A top view of the mountain bicycle handlebar  56  is shown in  FIG. 4 . A left shift unit  58  and right shift unit  60  are mounted to the handlebar  56 . Each shift unit  58 ,  60  contains a button  52  that operates a switch (not shown) mounted to or within a respective shift unit. 
         [0042]    The switch units  58 ,  60 , control unit  28 , front gear changer  62 , and the rear gear changer  64  are connected by a communication link  68 . The communication link  68  could be wired (as in the present example) or wireless, or a combination of each. The buttons  52  can be configured so that the right button  52   b  is actuated by the right hand, and the left button  52   a  is actuated by the left hand. The switches of each button  52   a ,  52   b  can be configured to be normally open or normally closed. The switches in this example are preferably configured to be normally open, and will close momentarily when acted upon. It will be understood that the examples given herein are for the purpose of disclosing an embodiment of the invention without the intention of introducing limitations that narrow the scope thereof. 
         [0043]    Turning to  FIG. 5  (and also referring to  FIG. 1 ) the front sprocket assembly  34  may include two coaxially mounted chain rings, gears or sprockets F 1 -F 2 , and rear sprocket assembly  40  may include ten gears, cogs or sprockets R 1 -R 10 . The number of teeth on front sprocket F 1  is preferably less than the number of teeth on sprocket F 2 . The numbers of teeth on rear sprockets R 1 -R 10  typically gradually decrease from rear sprocket R 1  to sprocket R 10 . Front gear changer  30  moves from a first operating position to a second operating position to move the chain  72  between sprockets F 1  and F 2 , and the rear gear changer  36  moves between ten operating positions to switch the chain to one of rear sprockets R 1 -R 10 . Preferably, a front gear position sensor  112  is used to sense the operating position of the front gear changer  30 , and a rear gear position sensor  114  is used to sense the operating position of the rear gear changer  36 . Gear position sensors  112 ,  114  may comprise rotary encoders, potentiometers, or other devices capable of sensing position in a gear changer mechanism. Preferably, a battery  84  ( FIG. 1 ), or more than one battery, or some other power source powers the front and rear gear changers  30 ,  36  as well as other electric components within the system. 
         [0044]    The control unit  28  comprises a microprocessor that is programmed to receive signals from the shifting system and responsively generate signals to effect gear changes. One example of such a control unit  28  is shown diagrammatically at  FIG. 6 a   , which will be described in the context of the example shown in  FIGS. 1 and 2 , and includes a controller, including a gear shift controller  100 , a switch interpreter  102 , and a memory  141  to store a program (computer executable code) and operational variables. The hardware that stores the program and performs computer operations based on the instructions in the memory and signals being generated by the various electronic components, such as the position sensors and the switches includes a microcontroller or programmable logic device (PLD) or a similar component capable of performing the functions described herein. 
         [0045]    The switch interpreter  102  monitors the switches in right and left shift units  27   a ,  27   b  and sends an appropriate command to the gear shift controller  100  responsive to the request or input signal from the switch mechanism  48  of each of the units  27   a ,  27   b . The front and rear gear changer  30 ,  36  each comprises a motor  104 ,  106  that may include gear reduction (not shown), a motor driver  108 ,  110  for driving the motor, and a position sensor  112 ,  114  that senses the operating position of the respective gear changers. The gear shift controller  100  then generates a command signal to move the appropriate gear changer  30 ,  36  to the requested operating position or gear in response to signals received from the shift interpreter  102  and the position sensor  112 ,  114 . 
         [0046]    In one illustrative example, the operation of the invention is as follows. When the right switch  27   a  is pressed, the rear gear changer  36  performs an upshift, when the left switch  27   b  is pressed the rear gear changer  36  performs a downshift. When both right and left switches  27   a ,  27   b  are pressed concurrently, the front gear changer  30  is shifted or toggled between the two front sprockets  34 , i.e. from one of to the other of the front sprockets. 
         [0047]    Alternatively, the gear shift controller  100  in  FIG. 6 a    could be replaced with a front shift controller  140  that includes a microprocessor located in or associated with the front gear changer  130  and a rear shift controller  142  that includes a microprocessor located in or associated with the rear gear changer  136  as shown in  FIG. 6 b   . In this embodiment the switch interpreter unit  102  would send gear shift signals to both the front shift controller  140  and rear shift controller  142  when requested. The control system shown in  FIG. 6 b    could otherwise have the same elements as that shown in  FIG. 6   a.    
         [0048]    As shown in  FIG. 7 , the rear gear changer  36  preferably includes a base member  144  mounted to the bicycle frame  38  that houses a gear shift motor and gear mechanism  106 , a link mechanism  146  pivotably connected to the base member, and a movable member  148  pivotably mounted to the link mechanism so that the movable member moves laterally relative to the base member in accordance with the operation of the motor housed within the base member. Movable member  148  pivotably supports a chain guide  150  so that lateral movement of the movable member switches the chain  72  among rear sprockets  40  (R 1 -R 10 ). 
         [0049]    As shown in  FIG. 8 , the front gear changer  30  preferably includes a base member  152  mounted to the seat tube frame member  32  of a bicycle that houses a front gear shift motor  104 , an output gear  154  coupled to the gear shift motor, a link mechanism  156  pivotably connected to the base member and coupled to the output gear, and a movable chain guide member  158  pivotably mounted to the link mechanism. Thereby, the movable chain guide member  158  moves laterally relative to the base member  152  in accordance with the operation of the motor  104  associated with the base member so that lateral movement of movable chain guide member  158  switches the chain  72  among front sprockets  34  (F 1 -F 2 ). 
         [0050]      FIG. 9  is a flow chart of a first embodiment of the process control  200  for control unit  28  or  128  of  FIG. 6 a    or  6   b , for example. It will be understood that where right and left switches are mentioned in the following, the reference to right and left are for illustrative purposes. Right and left could also be considered as first and second switches, for example, and thus it will be understood that the positional reference is being used for purposes of clarity. In the alternate, the functions and/or positions of the left and right (first and second) switches could be reversed either physically or electronically. 
         [0051]    In step S 1 , the control unit checks to see if the right switch  27   a  is closed. If it is determined that the switch  27   a  is closed, at step S 3  the control unit  28  or  128  checks if the left switch  27   b  is closed. If YES, processing is moved to step S 5  and the front gear changer  30  is shifted. If, at step S 3 , the left switch  27   b  is open, processing moves to step S 4  to check if the right switch  27   a  is still closed. If the right switch  27   a  is open, processing moves to step S 6  and the rear gear changer  36  is up-shifted. Once a right switch closed condition is detected at step S 1 , the control unit  28  or  128  loops through steps S 3 -S 4  until either the right switch  27   a  is released or the left switch  27   b  is pressed. Therefore, a rear gear changer upshift only occurs after pressing and releasing the right switch  27   a.    
         [0052]    If the result of step S 1  is NO, processing moves on to step S 2  and the control unit  28  or  128  checks if the left switch  27   b  is closed. The process is similar to the one described above except that when the left switch  27   b  is open (released) without pressing the right switch  27   a , processing moves to step S 7  and the rear gear changer  36  is downshifted. 
         [0053]      FIG. 10  is a flow chart of a rear downshift routine  300 . At step S 8  the processor of the control unit  28  or  128  checks to see if the rear gear changer  36  is in position  1  (i.e., aligned with the largest sprocket of the rear sprockets  40 , which may also be referred to a first position or first end position). If the result is YES, the routine is exited without executing a downshift, as no further downshifts are possible. If the result of S 8  is NO, the process moves to step S 9  and the rear gear changer  36  is caused to downshift. 
         [0054]      FIG. 11  is a flow chart of a rear upshift routine  400 . At step S 10  the processor checks to see if the rear gear changer  36  is in position  1  (i.e., aligned with the smallest of the rear sprockets  40  also referred to as a last position or second end position). If the result is YES, the routine is exited without executing an upshift, as no further upshifts are possible. If the result of S 10  is NO, the process moves to step S 11  and the rear gear changer  36  is caused to upshift. 
         [0055]      FIG. 12  is a flow chart of a front shift routine  500 . At step S 12  the control unit  28  or  128  processor checks to see if the front gear changer  30  is in the position  2  (i.e., aligned with the larger of the two chainrings). If the result is YES, processing moves to step S 14  and the front gear changer  30  downshifts. If the result of step S 12  is NO, the front gear changer is upshifted. Therefore, every time a front shift command is sent from step S 5  the front gear changer will toggle between position F 1  and F 2 , the direction depending on which position it is in initially. 
         [0056]      FIG. 13  is a flow chart of a second embodiment  600  of the process control for the control unit  28  or  128 . A difference in this embodiment compared with the embodiment shown in  FIG. 9  is that when a single switch is operated, a rear upshift or downshift will be executed after an elapsed time, without the need to release the switch. 
         [0057]    When a single shift switch (e.g., one of  27   a  or  27   b ) is closed and held, the operation is as follows: In step S 20 , the switches are read and the state of each (open or closed) is stored in memory  141 . In step S 21 , the system  28  or  128  checks if the state of any of the switches has changed since the previous read. In this case since a single switch was pressed (closed) the processor moves to step S 22  then on to step S 23  because a switch was closed. Since both switches were not closed, processing moves to step S 24  the variable RS is assigned a rear shift value (see  FIG. 14  below: “STORE RS”). The initial value of the RS variable upon program START is “null”. 
         [0058]      FIG. 14  is a flow chart  700  of the STORE RS routine. RS can be a value corresponding to one of “upshift,” “downshift,” or “null.” In step S 35  the processor of control unit  28  checks the memory  141  to see if the right switch  27   a  was closed during step S 20  of the flow chart  FIG. 13 . If the result is YES, processing moves to step S 36  and a value corresponding to “upshift” is assigned to variable RS. If the result of S 35  is NO, processing moves to step S 37  where a value corresponding to “downshift” is assigned to variable RS. Processing then moves to step S 25  of  FIG. 13  where a “pending timer” is started. The process moves back to step S 20  to read the input switches, then to step S 21  where the result will be NO since the inputs have not changed. 
         [0059]    Processing continues to loop through steps S 26 , S 20 , and S 21  until the pending timer expires. Processing then moves to step S 28  to check if a rear shift value has been assigned to variable RS. Processing moves to step S 29  where the value of RS determines if the rear gear changer will upshift or downshift. If RS=“downshift”, processing moves to step S 7  where a rear downshift is executed, otherwise processing moves to step S 6  and a rear upshift is executed. From either of step S 6  or step S 7  processing moves to step S 30  where the value RS is cleared and set to “null” and processing continues back to step S 20 . 
         [0060]    When the switch is opened (released) after the rear gear changer  36  has shifted due to a “pending timer expired” condition the operation will continue as follows: Step S 21  detects the switch open change and processing continues to step S 22 . Step S 22  (switch closed?) will be NO and processing continues to step S 27  (button released?) where a YES sends processing to step S 28  (RS=null?). Since the value of RS was set to “null” immediately after a rear downshift or upshift in step S 30 , the response will be YES and processing continues back to step S 20  and no additional rear shift will occur. 
         [0061]    However, if the switch was not opened (released) and a second switch was closed (pressed) after the rear gear changer  36  has shifted due to a “pending timer expired” condition the operation will continue as follows: When the processor executes step S 21  (switch changed since last read?) the result will be YES and processing moves to step S 22 . The result of S 22  (switch closed?) will be YES and processing continues to step S 23  (both switches closed?) where a YES result sends processing to step S 5  (shift front) and a front shift is executed. Therefore, if a first switch is closed and held past the “pending timer” duration then a second switch is closed, the system first shifts the rear gear changer  36 , and then shifts the front gear changer  30 . 
         [0062]    When a single shift switch is closed and opened before the pending timer expires, the operation is as follows: In step S 20  the input buttons are read and stored in memory  141 . In step S 21  the system checks if the switches have changed state since the previous read. In this case, since a switch was pressed, the processor will move to step S 22  then on to step S 23 . Since both switches were not closed processing moves to step S 24  where the variable RS is assigned a rear shift value. Processing moves to step S 25  where the pending timer is started. The process moves back to step S 20  then to step S 21  where the result will be NO. Processing continues to loop through steps S 26 , S 20 , and S 21  until the switch is opened or released. The change will be detected by step S 21  where the result will be YES and processing will continue to step S 22 . The result of step S 22  (switch closed?) will be NO, processing moves to step S 27 . The result of step S 27  (switch opened?) will be YES, and processing will move to step S 28  (RS=null?) to check if a rear shift value been assigned to variable RS. Processing moves to step S 29  where the value of RS determines if the rear gear changer will upshift or downshift. If RS=“downshift”, processing moves to step S 7  where a rear downshift is executed, otherwise processing moves to step S 6  and a rear upshift is executed. From either steps S 6  or S 7  processing moves to step S 30  where the value RS cleared and set to “null” and processing continues back to step S 20 . 
         [0063]    If a single switch is closed and a second switch is closed before the “pending timer” expires, the operation will be as follows: In step S 21  the system  28  checks if the switches  27   a ,  27   b  have changed since the previous read, in this case since a switch was pressed the processor will move to step S 22  then on to step S 23 . Since both switches were not closed just yet, processing moves to step S 24  where the variable RS is assigned a rear shift value, depending on which switch was closed. Processing then moves to step S 25  where the pending timer is started. The process moves back to step S 20  then to step S 21  where the result will be NO. Processing continues to loop through steps S 26 , S 20 , and S 21  until the second switch is closed. At this time the result of step S 21  will be YES and processing will move to step S 22  where the result will be YES and processing will continue to step S 23  (both switches closed?). The result of step S 23  will be YES and processing will move to step S 5  (shift front) and a front shift will be executed. Processing will continue to step S 30  where RS is set to “null” and processing continues back to step S 20 . When the switches are released processing will continue through steps S 21 , S 22 , S 27  and S 28 . In step S 28  (RS=null?) the result will be YES and processing will continue back to step S 20  and therefore no rear shifting will occur from the switch opening (release). 
         [0064]    The shift interpreter  102  may also be programmed to allow multiple rear shifts if a single switch is held for a long duration. The present invention could also be adapted to shift three chainrings as follows: When a FRONT SHIFT routine is executed if the front gear changer is in the large chainring position, then downshift. If the front gear changer is in the small chainring position, then upshift. If the current chainring is the middle chainring the shift interpreter  104  can use a measured parameter to determine whether an upshift or downshift is required, such as speed, acceleration, rear gear changer gear position, torque measured from a power meter, inclination of the road, among others. Another method to determine whether an upshift or downshift is requested when shifting from the middle chainring would be to use the RS variable that is set to the direction (upshift or downshift) of the switch that was pressed first. For example, when an upshift is desired from the middle chainring, the rider closes the right switch before the left switch, indicating the desire to upshift. 
         [0065]    Turning to  FIG. 15  (and also referring to  FIG. 1 ) the front sprocket assembly  234  may include three coaxially mounted sprockets F 1 -F 2 -F 3 , and rear sprocket assembly  40  may include ten sprockets R 1 -R 10 . The number of teeth on front sprocket F 1  is preferably less than the number of teeth on sprocket F 2 , and the number of teeth of F 3  is preferably greater than the number of teeth on sprocket F 2 . The numbers of teeth on rear sprockets R 1 -R 10  typically gradually decrease from rear sprocket R 1  to sprocket R 10 . Front gear changer  230  moves from a first operating position to a second operating position to move the chain  72  ( FIG. 1 ) between sprockets F 1  and F 2  and from the second operating position to a third operating position to change to sprocket F 3 . The rear gear changer  36  moves between ten operating positions, for example, to switch the chain to one of rear sprockets R 1 -R 10 . Preferably, a front gear position sensor  112  is used to sense the operating position of the front gear changer  230 , and a rear gear position sensor  114  is used to sense the operating position of the rear gear changer  36 . Gear position sensors  112 ,  114  may comprise rotary encoders, potentiometers, or other devices capable of sensing position in a gear changer mechanism. Preferably, a battery  84  ( FIG. 1 ), or more than one battery, or some other power source powers the front and rear gear changers  230 ,  36  as well as other electric components within the system. 
         [0066]      FIG. 16  shows a flow chart of another front shift routine  800 . At step S 40  the control unit  28  or  128  processor checks to see if the front gear changer  230  is in position  3  (i.e., aligned with the largest of the three chainrings). If the result is YES, processing moves to step S 14  and the front gear changer  230  downshifts to F 2 . If the result of step S 40  is NO, the control unit  28  or  128  checks to see of the front gear is in the position  2  (i.e., aligned with the middle of the three chainrings). If the result is NO, processing moves to S 13  and an upshift is performed. If the result at S 41  is YES, processing then checks to see if the rear gear changer is aligned with a rear sprocket greater than R 5 . If the result is NO, then a downshift is performed at S 14 . Conversely, if the result is YES, then an upshift is performed at S 13 . 
         [0067]    The front shift method illustrated in  FIG. 16  uses rear gear shift position criteria to determine how to shift the front gear change mechanism. This is an example of one criterion. Other criterion may include: crank speed (pedaling cadence), bicycle wheel speed; increasing bicycle speed (acceleration) or decreasing bicycle speed (deceleration); pedaling torque; and bicycle inclination (uphill vs. downhill) for example. Any of the above criteria may be determined and implemented in the invention with well known sensors and processing devices. 
         [0068]      FIG. 17  shows at  900  another front shift routine. At step S 43  the control unit  28  or  128  processor checks to see if the front gear changer  230  is in position  3  (i.e., aligned with the largest of the three chainrings). If the result is YES, processing moves to step S 14  and the front gear changer  230  performs a downshift to F 2 . If the result of step S 43  is NO, the control unit  28  or  128  checks to see of the front gear is in the position  2  (i.e., aligned with the middle of the three chainrings). If the result is NO, processing moves to S 13  and an upshift is performed. If the result at S 44  is YES, processing then checks at S 45  to see if RS equals “upshift,” (see  FIG. 14 ). If RS does not equal “upshift” then processing moves to step S 14  and the front gear changer  230  performs a downshift (to F 1 ). If RS equals “upshift” then processing moves to S 13  and an upshift is performed. 
         [0069]    While this invention has been described by reference to a particular 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. Also, where the claims do not expressly state or necessarily imply the sequence of all or some steps, it would cover the steps performed in any order or simultaneously.