Abstract:
A bicycle transmission has a plurality of cone gears with multiple gear surfaces and a corresponding plurality of ratio-change assemblies for selecting one of the gear surfaces of each cone gear. One cone gear provides reductions of the input rotary speed while the other cone gears provide increases in the input rotary speed. The ratio-change assemblies include means for moving its gear surface both vertically and horizontally.  
     The transmission includes a telescopic pedal arm assembly for input power and torque. The telescopic pedal arm is driven between an extended position and a retracted position during each revolution so that the available torque increases in conjunction with available leg power.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention generally relates to a transmission assembly for use in manually powering a device such as a bicycle. More particularly, the invention concerns a multispeed, gear-driven transmission bicycle transmission having a broad range of gear ratios making it suitable for operation in a wide variety of terrains. Moreover, the transmission includes an eccentric cranking mechanism which ergonomically takes advantage of the cranking power available from an individual.  
           [0002]    Bicycle driving mechanisms are, of course, known in the prior art. For example, U.S. Pat. No. 628,184 which issued to Plass concerns a bicycle driving mechanism having a multigear transmission casing mounted in a frame which is vertically movable in the casing between the crank shaft and a second shaft. An operating rod raises or lowers the frame to the require position. Transmission gear wheels are fixed to upper, central, and lower shafts that, in turn, are journaled between to bars of the first frame. Movement of the second frame engages the alternate driving gear wheels and imparts motion to the mechanism.  
           [0003]    It is also know to employ multiple gears of various diameters mounted o a frame in a bicycle transmission. A lever mounted on the frame carries a gear adapted to mesh with the gears of the pedal shaft. Multiple gears mounted on the frame transmit movement of the pedal shaft to the multiple gears mounted on an auxiliary frame. See U.S. Pat. No. 1,938,157.  
           [0004]    A bicycle transmission having a steering lever provided with a number of levers connected to and operated by each other through suitable gearing is also known. The levers communicate with rotary movement to a connect a central shaft from which the axle is driven. See, U.S. Pat. No. 397,144.  
           [0005]    A bicycle transmission with a shiftable gear drive arrangement combined with a chain to connect a rotary power input to the driven wheel is also known. A two-speed arrangement is illustrated. A lever slides a gear assembly between two different positions on a shaft to provide the two operating speeds. See, for example, British Patent No. 25,975.  
           [0006]    Of course, drive gear transmissions are also generally known for use in a tricycle. Such a transmission can include an element constructed from a pair of gear wheels on a common shaft.  
           [0007]    Other patents related generally to bicycle transmissions are also known, see, for example, U.S. Pat. Nos. 222,779; 283,697; 573,285; 668,784; 881,729; 1,332,709; 2,518,537; 2,687,897; 4,077,648; German 72,199; and French 541,261.  
           [0008]    Known of those known transmission assemblies however provide the broad range of gear ratios needed for current recreational and competitive cycling. Moreover, the known transmission assemblies do not take advantage of the enhanced driving power available from a cranking mechanism which is eccentrically positioned relative to the transmission input axis so as to ergonomically power the transmission.  
         OBJECTS AND SUMMARY OF THE INVENTION  
         [0009]    A general object of the present invention is to provide a bicycle transmission having multiple gear ratios and providing a direct driving connection between a power input and the driven wheel.  
           [0010]    A more particular object of the present invention is to provide a bicycle transmission having multiple gear ratio controls each providing multiple gear ratios so as to increase the range of gear ratio connections between the input shaft and the driven wheel of a bicycle.  
           [0011]    A further object of the invention is the use of an eccentrically powered crank assembly in connection with a multi-speed bicycle transmission. The eccentrically powered crank assembly is operative to make efficient use of the torque and power available from a person operating the bicycle.  
           [0012]    A bicycle transmission which satisfies these and many other advantages includes a gear train connected to an over-running clutch on a driven wheel of a bicycle. The gear train of the transmission includes multiple gear shifting devices, each of which is capable of changing the gear ratio of the transmission through several speed changes determined by the ratios of the gears on the associated sprocket.  
           [0013]    The gear shifting devices can include a shaft directly connected to a shaft carrying a spur gear in the transmission. By moving the shaft vertically upwardly, the associated spur gear moves between several different positions in driving relationship with portions of a corresponding sprocket, each of which corresponds to a different gear ratio. The shaft can also be manipulated to move the spur gear downwardly to reverse the gear ratio change by moving it laterally and pushing downwardly until the appropriate gear ratio is obtained.  
           [0014]    The gear shifting device can also include corresponding cable pull arrangements attached to a corresponding spur gear in the transmission. By pulling up on the cable, the associated spur gear moves between several positions in driving relationship with a portion of the corresponding sprocket. By biasing the spur gear toward its initial, lowermost position, releasing tension on the corresponding cable allows the corresponding spur gear to move to the gear ratio associated with the lowermost sprocket position.  
           [0015]    Another important part of the invention concerns the cranking mechanism used to power the direct-drive transmission. More particularly, the cranking mechanism is arranged to be eccentrically driven. This eccentric driving relationship is obtained through use of driven, telescoping cranks on either side of the bicycle, one for each foot. The telescoping cranks are driven to extend the radial distance between the cranking axis and the pedal during a forward portion of the pedal orbit and are also driven to reduce the radial distance between the cranking axis and the pedal during a return portion of the pedal orbit. In this manner, the pedals traverse a pedal orbit which is eccentric to the axis of the input to the bicycle transmission. Moreover, the pedal position uses the power available from leg extension to drive the bicycle transmission while minimizing the power input as the leg bends backwardly at the knee. Thus, an ergonomically arranged pedal cranking mechanism is provided. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Many other objects and advantages of this invention will be apparent to those skilled in the art, when this specification is read in conjunction with the attached drawings, wherein like reference numerals are applied to like elements, and wherein:  
         [0017]    [0017]FIG. 1 is an overall view of a bicycle having the novel multi-speed, gear-driven transmission of the present invention;  
         [0018]    [0018]FIG. 2 is a detailed view, in cross section, of the multi-speed, gear driven transmission of the present invention;  
         [0019]    [0019]FIG. 3 is a cross-sectional view of the multi-speed, gear-driven transmission of the present invention taken along line  3 - 3  of FIG. 2;  
         [0020]    [0020]FIG. 4 is a cross-sectional view of a first embodiment of the ratio-change assembly taken along line  4 - 4  of FIG. 2;  
         [0021]    [0021]FIG. 5 is a cross-sectional view taken along line  5 - 5  of FIG. 4;  
         [0022]    [0022]FIG. 6 is an enlarged schematic view of a mechanism for laterally translating the shift gear;  
         [0023]    [0023]FIG. 7 is a cross-sectional view of a second embodiment of the ratio-change assembly;  
         [0024]    [0024]FIG. 8 is a plan view of the pedal offset mechanism;  
         [0025]    [0025]FIG. 9 is a cross-sectional view of the eccentrically offset pedal mechanism of the present invention taken along line  9 - 9  of FIG. 8;  
         [0026]    [0026]FIG. 10 is a detailed, cross-sectional view taken along line  10 - 10  of FIG. 8;  
         [0027]    [0027]FIG. 11 is an enlarged cross-sectional view taken along line  11 - 11  of FIG. 10;  
         [0028]    [0028]FIG. 12 is an enlarged cross-sectional view taken along line  12 - 12  of FIG. 10;  
         [0029]    [0029]FIG. 13 is an alternative embodiment of the mechanism for laterally shifting the change gear; and  
         [0030]    [0030]FIG. 14 is a cross-sectional view taken along the line  14 - 14  of FIG. 13. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    A most preferred embodiment of the present invention is depicted in FIG. 1. A bicycle  20  has a front wheel  22  and a rear, or driven, wheel  24  both of which are supported on a frame  26 . The frame  26  rotatably supports a fork assembly  28  through suitable conventional bearing at the front of the frame  26 . To steer the bicycle assembly  20 , suitable conventional handlebars  30  are provided which are directly connected to the fork assembly  28 .  
         [0032]    In a known manner, each wheel  22 ,  24  includes a plurality of spokes  21  which extend generally radially inwardly from the rim  23  which supports a balloon-type tire  25 . At the center of each wheel assembly  22 ,  24  is a hub  27  carrying suitable conventional thrust bearings to reduce rolling friction of the bicycle assembly  22 .  
         [0033]    To support the operator on the frame  26 , a suitable conventional seat  32  may be provided.  
         [0034]    While the wheels  22 ,  24  have been described as begin supported by spokes  21 , it will be apparent to those skilled in the art that there are other suitable support arrangements that have been used in bicycles in recent years. For example, the spokes  21  could be replaced by lightweight solid wheel disks extending from the hub to the rim.  
         [0035]    The lower part of the frame  26  rotatably supports a cranking mechanism  34  having a pair of pedals  35  (only one of which is shown in FIG. 1. In its simplest configuration, the cranking mechanism  34  can be a suitable conventional crank supported in the frame  26  by suitable conventional thrust bearings and arranged to drive the transmission  36 . However, as will be described more filly below, the preferred arrangement for the cranking mechanism is an eccentrically offset pedaling mechanism which is ergonomically designed to increase the torque available from the bicycle operator.  
         [0036]    Extending between the cranking mechanism  34  and the hub of the rear wheel  24  is a multi-speed, gear-driven transmission assembly  36 . This transmission assembly  36  permits the bicycle operator to select from as many as  81  different gear ratios for the power connection between the cranking mechanism  34  and the rear wheel  24 .  
         [0037]    As shown in the cross-sectional view of FIG. 2, the transmission assembly  36  includes a housing  38  to hold and protect the gears of the transmission. The housing  38  is designed so that it can be opened to expose the gears therein. The housing  38  can be arranged to open along a plane generally parallel to a plane defined by the frame  26  of the bicycle. Alternatively, the housing can be arranged so that access to the gears occurs along a plane transverse to the bicycle frame  26 . Of course, any other desired arrangement can also be used for access to the gears for maintenance, assembly, and the like.  
         [0038]    The transmission  36  also includes an input gear  40  at the front end of the housing  38  which is constructed and arranged to be operated by the cranking mechanism  34 . In addition, the transmission assembly  36  includes an output gear  42  at back end of the housing  38  for driving connection with hub of the rear wheel. Between the input gear  40  and the output gear  42  are a plurality of different gears which are arranged to transmit power and torque therebetween while allowing for variable gear ratios. So that the cranking mechanism  34  and the rear wheel  24  turn in the same direction, it is necessary that there be an odd number of gears between the input gear  40  and the output gear  42 . It will be appreciated by those skilled in the art that all gears in the transmission which mesh with one another have gear teeth with the same shape and configuration so that meshing can be accomplished. In addition, it will also be apparent to those skilled in the art that the diameter of any given gear surface is determined by the number of teeth in that gear surface. Suitable gears for use in this invention are stock steel gears made by Browning having 14.5° pressure angle, {fraction (3/16)}″ face, and 32 pitch.  
         [0039]    The input gear  40  may, for example, have  40  teeth and is connected to a first cone gear  44  by a first idler gear  46 . The first idler gear  46  may also have  40  teeth so that the speed ratio across the input gear  40  and the first idler gear  46  is 1:1. The first cone gear  44  preferably includes three to five different gear surfaces so that three to five different gear ratios can be obtained. These different gear ratios can be obtained in several different ways. For example, the multiple gear ratios can be accomplished by casting a single gear with the desired different gear surfaces. Alternatively, the multiple gear surfaces can be obtained by building up the first cone gear  44  from a plurality of spur gears each of which has the desired diameter or number of gear teeth. Preferably, the first cone gear  44  has gear surfaces with 16 teeth, 20 teeth, 28 teeth, 32 teeth, and 40 teeth. It is also possible to use a simpler and less expensive arrangement of three gear surfaces with 16, 28, and 40 teeth. An objective in the gear teeth arrangement is to have at least one gear surface with 40 teeth so that the gear ratio leaving the first cone gear  44  is 1:1 with the input gear  40 .  
         [0040]    The transmission  36  also includes a second idler gear  48  which is rotatably mounted in the housing  38  and which is engaged by a first ratio-change assembly  50 . The second idler gear  48  preferably has  56  teeth while the first ratio-change assembly  50  preferably has 32 teeth. Moreover, the second idler gear  48  has a thickness corresponding to the distance between the side walls of the transmission housing  38  (see FIG. 3). In this way, the first ratio-change assembly can be constantly engaged with the second idler gear  48  regardless of the lateral position of the first ratio-change assembly  50 . The first ratio-change assembly  50  meshes with the second idler gear  48  and can be moved to mesh with each one of the different gear surfaces of the first cone gear  44 .  
         [0041]    The second idler gear  48  also meshes with a second ratio-change assembly  52 . (See FIG. 2). The second ratio-change assembly  52  preferably has 56 teeth so that the speed ratio into the first ratio-change assembly  50  and out of the second ratio-change assembly  52  is 1:1. The second ratio-change assembly  52  is constructed and arranged in a similar fashion to the first ratio-change assembly  50 .  
         [0042]    The second ratio-change assembly  52  engages a second cone gear  54  having a plurality of gear surfaces. The second cone gear  54  can be constructed in the same manner as the first cone gear  44 , and the gear surfaces are preferably arranged to have the same number of teeth as the first cone gear. As seen from FIG. 3, the second cone gear  54  may be arranged so that the largest gear is on the side of the housing opposite from the largest gear of the first cone gear  44 . This arrangement permits more gear ratios to be obtained in the fixed space available between the cranking mechanism and the rear wheel. As with the first cone gear  44 , the largest gear surface of the second cone gear  54  also has 40 teeth. In this fashion, a speed ratio of 1:1 between the input gear  40  and the second cone gear  54  can be obtained, depending upon the selection of the first and second ratio-change assemblies  50 ,  52 .  
         [0043]    The second cone gear  54  meshes with a third idler gear  56  which, in turn, meshes with a third cone gear  58 . The third idler gear preferably has  64  teeth. This third cone gear  58  has its largest gear on the same side of the gear housing  38  as does the first cone gear  44 . As with the first and second cone gears  44 ,  54 , this third cone gear  58  includes a plurality of different gear surfaces so that different speeds can be obtained. Preferably, the gear surfaces have 40 teeth, 56 teeth, 64 teeth, 80 teeth, and 96 teeth. Importantly, the smallest gear surface should have 40 teeth so that a 1:1 gear ratio can be obtained between the input gear  40  and the exit of the third cone gear  58 . By using gear surfaces with more than 40 teeth in the third cone gear, the third cone gear also permits operation at speed ratios less than 1:1 and as low as 1:0.42 between the input gear  40  and the exit from the third cone gear  58 .  
         [0044]    The third cone gear  58  meshes with a third ratio-change assembly  60  which can be moved to engage any of the different gear surfaces provided on the third cone gear  58 . The third ratio-change assembly  60  meshes with a fourth idler gear  62  which, in turn, meshes with a fourth ratio-change assembly  64 . Like the second idler gear  48 , the fourth idler gear  62  extends between the sidewalls of the transmission housing  38  (see FIG. 3) so that the third ratio-change assembly  60  can be constantly meshed with the fourth idler gear  62  regardless of the lateral position of the third ratio-change assembly  60 . The third ratio-change assembly  60  preferably has a gear surface with 64 teeth. The fourth idler gear  62  preferably has 32 teeth. And, the fourth ratio-change assembly  64  preferably has 64 teeth. With this arrangement, the speed ratio entering the third ratio-change assembly  60  (see FIG. 2) and leaving the fourth ratio-change assembly  64  is 1:1.  
         [0045]    The fourth ratio-change assembly  64  meshes with a fourth cone gear  66 . The fourth cone gear  66 , like the other cone gears, has a plurality of different gear surfaces. Like the first and third cone gears  44 ,  58 , the largest gear surface of the fourth cone gear  66  is located against the same side of the transmission housing  38 . Moreover, the fourth cone gear  66  preferably has gear surfaces with the same numbers of teeth as the gear surfaces of the first and second cone gears  44 ,  54 . Since one of the gear surfaces of the fourth cone gear  66  also has 40 teeth, the transmission assembly is capable of providing a 1:1 gear ratio between the input gear  40  and the exit of the fourth cone gear  66 .  
         [0046]    The fourth cone gear  66  meshes with a fifth idler gear  68  preferably having 56 teeth which, in turn, meshes with the output gear  42  preferably having 40 teeth. Accordingly, depending upon the position of the four ratio-change assemblies  50 ,  52 ,  60 , and  64 , a 1:1 speed ratio is available between the input gear  40  and the output gear  42 .  
         [0047]    However, if the third ratio-change assembly  58  is positioned to engage the largest gear surface of the third cone gear  58 , while the first, second, and fourth ratio-change assemblies are positioned to give a 1:1 ratio, then the ratio of the input speed at input gear  40  to the output speed of the output gear  42  can be as low as 1:0.42, which is a very slow output speed. Conversely, if the third ratio-change assembly  58  is positioned to give a 1:1 ratio while the first ratio change assembly  44  is positioned to give its highest output speed, with the second and fourth ratio-change assemblies set at 1:1, then the ratio of the input speed of the input gear  40  to the output speed of the output gear  42  is 1:2.5. If the third ratio-change assembly  58  is positioned to give a 1:1 ratio while the first and second ratio-change assemblies are positioned to give their highest output speeds, while the fourth ratio-change assembly  66  remains at 1:1, then the ratio of input speed to output speed is 1:6.25. And finally, if the first, second, and fourth ratio-change assemblies  44 ,  52 ,  66  are positioned to give their highest output speeds, while the third ratio-change assembly is set at 1:1, then the ratio of input speed to output speed is 1:15.625.  
         [0048]    The output gear  42  can receive a suitable conventional splined connection to the hub of the rear wheel of the bicycle. It will be noted that the cone gears illustrated in FIGS. 2 and 3 are depicted with three gear components. That arrangement has been selected, however, for clarity of illustration and is not to be taken as a limitation. These cone gears can be provided with additional gears to provide even more gear ratios—for example, five component gears are considered to be desirable.  
         [0049]    Turning now to FIG. 4, a preferred embodiment of the gear ratio-change assembly  50  is illustrated. The other gear ratio-change assemblies  52 ,  60 ,  62  are similarly constructed and arranged so it will suffice to describe one of the gear ratio-change assemblies in detail. The gear ratio-change assembly  50  carries a gear  80  which is mounted on a corresponding shaft  82  by a suitable conventional bearing assembly such as, by way of example, a ball bearing. The outer race of the ball bearing is attached to the gear  80  while the inner race of the ball bearing is slidably mounted on the shaft  82  so that is can move from side to side within the transmission housing  38 . Each end of the shaft  82  is fixed to a yoke  84  that is slidably mounted in corresponding grooves  92 ,  94  on each side of the housing  38 . The grooves  92 ,  94  are arranged so that the center of the shaft  82  traverses the necessary path to properly position the gear  80  so that it meshes with the corresponding gear surfaces of the first cone gear while maintaining engagement with the second idler gear  48 . More particularly, the grooves  92 ,  94  are arcuate and are centered on the axis of the second idler gear  48 .  
         [0050]    The yoke  84  is operated by a rod  86  which projects through the top of the housing  38  so as to be operable by the rider of the bicycle. The upper end of the rod  86  may, preferably, include a knob  88  to make its operation easier. To prevent dust, dirt, moisture, and other foreign substances from entering the transmission, a suitable conventional boot  90  is provided about the rod  86  at the entrance to the housing  38 . The boot  90  is secured to the housing  38  and engages the rod  86  so that the rod  86  is slidable therein.  
         [0051]    To move the gear  80  laterally from one gear surface of the first cone gear to another gear surface thereof, the inner race of the bearing carries a pin  102  (see FIG. 6), which projects into a slot  104  of the shaft  82 . Within the shaft  82  is a worm gear  100  which carries one or ore worm threads  103 . The pin  102  of the bearing projects into the space between the worm threads  103  so that, as the worm gear  100  rotates, the pin  102  and the associated inner race of the ball bearing will move laterally along the shaft  82 . Thus, as the inner race of the bearing moves, so does the outer race and the gear  80  attached thereto.  
         [0052]    To rotate the worm  100 , the end of the worm is provided with a worm pinion  96 . The worm pinion meshes with a gear rack  98  positioned at one side of the groove  94  in the housing  38  (see FIG. 5). Accordingly, when the yoke  84  moves upwardly or downwardly in the associated grooves  92 ,  94  of the housing  38 , the gear rack  98  causes the worm pinion  96  to rotate. Thus, the worm gear  100  rotates moving the pin  102  and the gear  80  laterally between positions where it can engage various gear surfaces of the corresponding cone gear.  
         [0053]    While a worm gear cooperating with a pin carried by the inner bearing race have been described as a mechanism to move the gear  80  laterally, it will be apparent to those skilled in the art that there are a variety of other mechanisms which can provide similar control. For example, a cam surface on a shaft can replace the worm gear and offer more varied control over the lateral movement of the gear. More particularly, with a worm gear the lateral movement would be linear with rotation of the worm gear  100 ; whereas, with a cam and follower arrangement, the cam could prove nonlinear positional changes for the gear  80  as well as different linear rates of displacement which could prove useful during gear engagement and disengagement.  
         [0054]    Suitable conventional detent mechanisms can be provided to engage the yoke  84  and hold it in appropriate positions to engage the various gear surfaces of the cone gear. Such detent mechanisms may comprise, for example, spring-loaded balls carried by the yoke  84  which engage corresponding recesses of the housing grooves  92 ,  94 . Alternatively, the detent balls could be in the housing while the detent recesses are provided in the yoke  84 . Yet another arrangement may comprise a detent mechanism between the operating rod  86  and the housing  38 .  
         [0055]    It is also within the scope of this invention to provide a cable operated control for the gear ratio-change assembly  50 . See FIG. 7. For example, the free end of the rod  86  which moves the  1  yoke  84  may be attached to one end of a cable  110 . Suitable conventional cables  110  are the type often used in bicycles and may be braided stainless steel cables. The other end of the cable  110  is preferably positioned where the bicycle operator has easy access. Sometimes, for example, the second end of the cable  110  may be located on the cross-bar of the bicycle frame assembly where the operator can reach it quickly and efficiently.  
         [0056]    With this alternative embodiment, a suitable conventional spring ball detent mechanism  112  may be provided which is operated by the cable  110 . The spring ball detent mechanism cooperates with and engages a collar  114  which is then securely mounted on the top of the housing  38  so as to surround the cable  110 . In addition, if desired, a boot may be used to keep dust, dirt, moisture, and other foreign matter out of the transmission.  
         [0057]    Turning now to FIG. 13, an alternative embodiment is provided for the shifting mechanism. An extension collar  200  is attached to the transmission housing  38 . The collar has an internal opening  202  which preferably is a generally circular bore. The internal opening  202  has a plurality of radially outwardly extending recesses  202 ,  204 ,  206  which are generally trapezoidal in cross section. The recesses  202 ,  204 ,  206  are axially spaced to correspond to the shift positions for the associated shift gear of the transmission. While three recesses are shown, it is understood that there would be one recess for each different position of the associated shift gear.  
         [0058]    Slidably mounted within the opening  202  for axial movement along the opening is a sleeve  210 . The lower end of the sleeve  210  may be closed, as illustrated, and is attached to the member  86  that, in turn, is connected to the associated shift gear. Positioned between the ends of the sleeve  210  are a pair of lateral ports  212 , 214 . These lateral ports are diametrically opposed to one another, preferably. Moreover, the lateral ports  212 , 214  are sized to permit free movement of corresponding detent balls  216 ,  218 . Slidably disposed within the sleeve  210  is a shaft  220  having the shift knob  88  attached at one end. The shaft  220  has a pair of circumferentially extending slots  222 ,  224  (see FIG. 14) which are diametrically opposed to one another. The circumferential extent of the slots  222 ,  224  is approximately 90°. Furthermore, one end  228 ,  230  of each slot  222 ,  224  is deeper than the other end each of each slot. The depth of these ends  228 ,  230  is sufficient to allow the associated detent ball  216 ,  218  to move radially inwardly toward the axis of the shaft  220  to a position where the detent balls  216 ,  218  are fully disengaged from any circumferential recess, e.g.  206 . The depth of the other end of these slots  222 ,  224  is selected so that the detent balls  216 ,  218  protrude radially outwardly from the axis of the shaft  220  so that the detent balls are received in a circumferential recess, e.g.  206 . As a result, as the knob  88  is rotated in one direction, e.g., clockwise, the detent balls  216 ,  218  are forced radially outwardly by the cam surfaces  226 ,  228  extending between the deep ends  228 ,  230  of the slots  222 ,  224  and the shallow ends of those slots, thereby axially fixing the position of the shaft  220  relative to the collar  200 . Correspondingly, as the knob  88  is rotated the opposite direction, e.g., counterclockwise, the detent balls  216 ,  218  can move radially inwardly thereby allowing the shaft  220  to move axially relative to the collar  200 .  
         [0059]    To bias the sleeve  210  so that it will move between shift positions corresponding to the position of the circumferential grooves  204 ,  206 ,  208 , a compression spring  240  may be used. One end of the spring  240  abuts a support element  242  carried by the collar  200 . The other end of the spring  240  bears upon the end of the sleeve  210 . Accordingly, when the know  88  is rotated to its first position to release the detent balls  216 ,  218 , the spring  240  pushes the sleeve  210 , the shaft  220 , and the know  88  upwardly pulling the associated shift gear at the same time. When the new gear position is reached, the knob  88  is rotated to its second position where the detent balls  216 ,  218  engage another circumferential recess of the opening  202 , thereby securing the assembly in the new shift position.  
         [0060]    With reference now to FIG. 8, the eccentric pedal crank mechanism  34  is illustrated. The eccentric crank mechanism  34  is rotatably supported on the frame of the bicycle by the generally cylindrical housing  120  located at the bottom of the frame. Suitable conventional thrust bearings are provided on both sides of the housing  120  to support the crank mechanism with low friction. The crank assembly  34  includes a pair of fixed arms  122 ,  124 , each of which receives a corresponding telescopic pedal arm  126 ,  128 . At the distal end of each telescopic pedal arm  126 ,  128  is a suitable conventional pedal  35  which is rotatably mounted on a pedal shaft  35 ′.  
         [0061]    Both telescopic pedal arms  126 ,  128  are identical so it will suffice to describe the details of one, it being understood that the details of the other are identical. The pedal arm  128  is slidably mounted within the fixed arm  124 . Preferably, a pair of suitable, conventional linear ball bearing assemblies  136 ,  138  are provided to support the telescopic pedal arm  128  within the fixed arm  124 . (See FIG. 9). One linear bearing assembly is provided on the top of the telescopic pedal arm  128 , while the other linear bearing assembly is provided on the bottom of the telescopic pedal arm  128 .  
         [0062]    Preferably, each telescopic pedal arm  128  includes a longitudinally extending channel  130  on the side opposite the pedal  35 . Ends of the channel  130  may be rounded as illustrated. One longitudinal edge  132  of the channel  130  is provided with a rack gear surface. The rack gear  132  may be integrally formed with the telescopic pedal arm  128  or it may be securely attached to the pedal arm  128  within the channel  130 . While it is preferred to include the rack gear surface in the channel  130 , it is within the scope of this invention to mount the rack on the side of the telescopic pedal arm  128 . Such an external mount, however, may expose the rack gear surface to damage during use, than does the protected arrangement of the channel  130 .  
         [0063]    A pedal pinion  134  engages and meshes with the rack gear surface  132  of the telescopic pedal arm  128 . It can be seen from FIG. 9 that there is a clearance between the circumference of the pedal pinion  134  and the channel  130  opposite to the gear rack surface  132 . That clearance is intentional and assures that there is no interference with free rotation of the pedal pinion  134 . The pedal pinion  134  is operable to rotate in two opposite directions. As the pedal pinion  134  rotates in a first direction, the telescopic pedal arm  128  is driven outwardly by the meshed gear rack surface  132  and the gear teeth on the pedal pinion  134  so that the pedal moves away from the fixed arm  124 . As the pedal pinion  134  rotates in a second direction, the telescopic arm  128  is driven inwardly so that the pedal moves toward the fixed arm  124 . With this arrangement, the pedals  35  move through an arc which is eccentrically positioned relative to the axis of the housing  120  (see FIG. 1). Thus, the pedals  35  move so that greater torque is applied to the pedal crank assembly  34  than would be available from a conventional assembly having fixed length pedal arms. Moreover, the telescopic pedal arms  126 ,  128  operate to provide greater ground clearance under the crank assembly than exists with fixed length pedal arms.  
         [0064]    The coordinated movement of the oppositely disposed telescopic pedal arms  126 ,  128  is explained more easily with reference to FIG. 10. The fixed arms  122 ,  124  are rigidly connected to a main shaft  150  which extends through the housing  120  and which engages and drives the input gear  40  of the transmission assembly  38 . Thus, as the pedals are actuated by the bicycle operator, rotary movement of the fixed arms  122 ,  124  and the connecting shaft  150  drive the transmission and, ultimately, the rear wheel of the bicycle.  
         [0065]    A pedal pinion  134 ,  134 ′ is provided for each pedal arm  126 ,  128 . The two pedal pinions  134 ,  134 ′ are connected by a shaft  152  which extends through the interior of the main drive shaft  150 . The shaft  152  is rotatably mounted in bearing blocks  154 ,  156  positioned so as to be in proximity to the ends of the housing  120  and coaxial within the main drive shaft  150 . The bearing blocks  154 ,  156  are attached to the interior surface of the drive shaft  150  and rotatably support the pedal pinion shaft  152 . In addition, a third bearing block  158  is positioned adjacent to the outside of the transmission housing  38 . This third bearing block  158  also rotatably supports the pinion shaft  152  relative to the main drive shaft  150  such that the bicycle transmission is disposed between the third bearing block  158  and one of the other bearing blocks  154 . Each of the bearing blocks  154 ,  156 ,  158  may have a suitable conventional antifriction bearing, such as a ball bearing or a roller bearing, to rotatably support the pinion shaft  152  with a low friction device.  
         [0066]    The drive shaft  150 , in turn, is supported relative to the transmission housing  38  and the bicycle frame by antifriction bearings  160 ,  162 ,  164 . These antifriction bearings may be ball bearings, roller bearings, or the like, and are positioned to be generally at the same axial position along the drive shaft  150  as are the bearing blocks  154 ,  156 ,  158 . In this manner, bending stresses on the drive shaft  150  can be reduced. As seen in FIG. 10, the drive shaft  150  is radially centered in the housing  120 , and the pinion shaft  152  is coaxial therewith.  
         [0067]    To move the telescopic pedal arms  126 ,  128  relatively to the fixed portions  122 ,  124 , the pinion shaft  152  is arranged to be driven in alternate rotational directions. To this end, the pinion shaft  152  is drivingly attached to a first reversing gear  172  (see FIG. 1l) which meshes with a second reversing gear  174  having the same diameter and number of teeth. The second reversing gear  174  is rotatably carried by the drive shaft  150  so as to be in constant meshed relationship with the first reversing gear  172 .  
         [0068]    Positioned radially outwardly from the first and second reversing gears  172 ,  174 , are a pair of axially offset, arcuate, gear segments  180 ,  182  (see FIG. 10). These gear segments  180 ,  182  have a thickness which is less than half the axial length of the reversing gears  172 ,  174  so that the gear segments  180 ,  182  can be circumferentially positioned relative to one another so as to alternately engage the reversing gears  172 ,  174 . The engagement of the first reversing gear  172  with its corresponding arcuate gear segment  180  is illustrated in FIG. 11. The alternate engagement of the reversing gears  172 ,  174  with the corresponding gear segments  180 ,  182  causes the pinion shaft  152  to rotate in alternate directions depending upon which of the reversing gears  172 ,  174  is engaged with the corresponding gear segment  180 ,  182 . The alternate rotation of the pinion shaft  152  causes the pinions  134 ,  134 ′ to rotate in alternative directions thereby driving the telescopic arms  126 ,  128  in and out as the pedals rotate to drive the transmission.  
         [0069]    Operation of the second reversing gear  183  and the corresponding arcuate gear  182  is more easily understood from FIG. 12. The drive shaft  150  carries a second pinion  184  which is radially positioned to be engageable with the second arcuate gear  182 . The second pinion  184  also meshes with an idler gear  185  that, in turn, meshes with the second reversing gear  183 . The reversing gears  172 ,  183  are fixed to the pinion shaft  152  so as to rotate therewith. Suitable conventional keys, splines, interference fits, or the like may be used to prevent rotation of the reversing gears  172 ,  183  relative to the pinion shaft  152 .  
         [0070]    The pinions  174 ,  184 ,  186  are rotatably mounted on the main drive shaft. As see in FIG. 10, these gears may be mounted in an annular recess in the drive shaft  150 . Suitable openings are provided so that these gears can be in meshed relationship with the gears  172 ,  183  mounted to the pinion shaft  152 .  
         [0071]    It will be seen from FIG. 12, that the pinions  174 ,  184  are not necessarily of the same diameter. Such a diameter difference permits these pinions to engage the corresponding arcuate gears  180 ,  182  at different circumferential locations. However, the pitch and size of the gear teeth provide on the pinions  174 ,  184  and the corresponding arcuate gears  180 ,  182  must be appropriately coordinated so that the pinion shaft  152  rotates in one direction through the same angular displacement as it rotates in the opposite direction.  
         [0072]    Preferably, the arcuate gears  180 ,  182  subtend an arc of about 180°. The angular positions of these arcuate gears  180 ,  182  relative to one another is determined by the angular spacing between the pinions  174 ,  184  about the axis of the pinion shaft  152 . The leading edge  196  of the arcuate gear  180  is positioned to engage the pinion  174  just as the other pinion  184  leaves the trailing edge  198  of the second arcuate gear  182 . The leading edge of the second arcuate gear  182  is similarly positioned relative to the trailing edge of the first arcuate gear  180 . In this manner, one of the pinions  184 ,  184  is in driving engagement with its corresponding arcuate gear  180 ,  182  throughout the movement of the arrangement for telescopic motion of the arms.  
         [0073]    More particularly, the arcuate gears  180 ,  182  are spatially fixed relative to the bicycle frame and transmission housing. Accordingly, as the main drive shaft  150  turns, it carries the pinions  174 ,  184 , and idling gear  186 . The pinions  174 ,  184 , alternately engage the respective arcuate gears  180 ,  182  and are caused to rotate as their respective shafts orbit about the centerline of the drive shaft  150 . Since the pinions  174 ,  184  rotate during different parts of the rotation of the main drive shaft  150 , the pinions alternately drive the pinion shaft  152  in different rotational directions. Thus, the gears  134 ,  134 ′ at opposite ends of the pinion shaft  152  rotate in opposite directions to move the pedal arms in and out.  
         [0074]    Naturally, the various gear diameters, pitch and tooth shape can be adjusted by those skilled in the art to adjust the length of travel for the pedal arms to a predetermined, desired value.  
         [0075]    Many objects and advantages of the present invention will be apparent to those skilled in the art when this specification is read in conjunction with the appended claims. The embodiments of the invention described above are to be considered as exemplary and not limiting. Moreover, many modifications, variations, and equivalents for the various features and elements of the invention will be apparent to those skilled in the art. The appended claims are intended to cover the preferred embodiments discussed in the specification as well as all legal equivalents of the elements discussed herein.