Abstract:
The invention is a universal front and rear derailleur configured to work with a variable mechanical transmission of the chain and sprocket type. A hollow axle is mounted adjacent to the sprockets. At least one radial arm serving as a chain lifter is rotatably mounted on the hollow axle in the chain-free sector of the sprockets. An operator controlled mechanism forces the lifter to move axially against a spring towards the sprockets. Upon contact, the sprockets entrain the lifter under the chain. The chain is lifted from the active sprocket and deposited onto another sprocket. Completing a full circle, the lifter is pushed back by the spring in its stowing position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to bicycle derailleurs. More specifically, this invention relates to a derailleur design, which is universally suited for the front, driving chain ring assembly as well as for the rear, driven sprocket assembly. 
         [0003]    2. Description of Related Art 
         [0004]    Conventional bicycle front derailleurs typically use an axially movable cage to force the chain against the adjacent larger sprocket when an up shift is initiated. The combination of rotation and friction eventually forces the chain to climb the larger sprocket and engage the teeth. Conversely, axial pressure by the cage forces the chain to derail from the larger sprocket and drop on the smaller sprocket. Since these movements of the chain occur in the loaded section of the chain, the rider has to reduce the pedaling force in order to allow the chain to climb the side of the larger sprocket, as friction is not sufficient to overcome the downward pressure of the tensioned chain. Similarly, when the chain derails from a larger to a smaller sprocket, the rider has to reduce the pedaling force, or the chain will slam on the smaller sprocket. Although the problem is not so acute for the rear sprocket assembly as the shifting initiates in the unloaded section of the chain, it is nevertheless present and has not been resolved in a definitive way. 
         [0005]    Various approaches have been tried to resolve this issue. The prevailing approach has been to form pins or ramps on the sides of the chain rings and sprockets. One such example can be seen in U.S. Pat. No. 5,078,653, where a combination of pins and reduced teeth facilitate the derailing of the chain from a larger to a smaller sprocket. A similar solution is proposed in U.S. Pat. No. 5,738,603 and claims to facilitate both up shifts and downshifts. While the implementation of such chain shift facilitating means has been proved helpful, they usually are a compromise, where either the up shift or downshift is improved, but not both. It needs to be said that this approach is more successful when applied to a multiple sprocket rear assemblies, where a smaller difference in the diameter of the adjacent sprocket results in a smoother shifting. This, however, has resulted in unnecessarily large sprocket assemblies. 
         [0006]    U.S. Pat. No. 5,205,794 describes a shifting mechanism, which is a radical departure from traditional derailleurs. A sector of the sprocket cluster is hinged and allows the chain to change tracks like a train on a railway switch. While the idea behind this invention is promising, the resulting complexity and likely elevated production cost of the system makes it an unlikely winner in the marketplace. 
         [0007]    A much earlier invention shown in FIG. 1—U.K. patent No. 9192 of 1901 issued to Edmund Hodgkinson, describes a derailleur where the sprocket cluster is axially movable when a pair of chain lifters is engaged. The operator moves the chain lifters via a lever between the chain and active sprocket and then backpedals, fully lifting and disengaging the chain. After sliding the desired sprocket under the chain, he pedals forward retracting the chain lifters in the rest position. While revolutionary for the time, few cyclists would accept such mode of operation today. 
         [0008]    For the foregoing reasons, there is a need for a universal chain shifting device that: (i) can shift under full load without skipping, (ii) will not create friction, (iii) can support a reduced number of sprockets with a large span of diameters (iv) will not require adjustment, (v) will allow for a greater clearance from the ground, (vi) will be less prone to damage, (vii) is less complex than mainstream derailleurs and (viii) is better suited for mass production and hence is relatively inexpensive to produce. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is a universal front and rear derailleur, which has chain lifters mounted coaxially with the sprockets and which interpose between the sprockets and the chain rotating 360° in tandem with the sprocket assembly when engaged. The result of this motion is that the chain is lifted from one sprocket and deposited onto another sprocket without scraping and skipping. A special mechanism moves the chain lifters selectively and axially from a stow position in the chain-free sector and forces them to be entrained by the sprockets under the chain. Upon completion of a full circle the chain lifters are forced by springs to return axially in the initial stow position. 
         [0010]    In one embodiment of the proposed invention the first, up shifting chain lifter is formed as a sector of a cone with chain guiding teeth leading from larger to smaller sprockets. The second, downshifting chain lifter is also formed as a sector of a cone with chain guiding teeth leading from smaller to larger sprockets. 
         [0011]    In another embodiment of the proposed invention, both chain lifters are L-shaped radial arms with spring biased collapsible parallelogram bridges at the ends. The upper surfaces of the parallelograms have slots engaging the chain and shifting it sideways. The up shifting occurs when the up-shift chain lifter is engaged and its parallelogram collapses under chain pressure from a larger towards a smaller sprocket. The downshifting occurs when the downshift chain lifter is engaged and its parallelogram collapses under chain pressure from a smaller towards a larger sprocket. 
         [0012]    The proposed invention is compatible with existing bicycle designs and can be fitted to frames and sprocket assemblies in current production as well as to be retrofitted to existing bicycles. The requirement to the shift control unit is simple: the cable has to be spring biased at the handlebar control in one position so it can be paid out by compressing this spring or retracted in the other direction against a weaker spring on the derailleur. In the first case an up-shift is initiated, in the second, a downshift. Both are completed in one full turn and continue until the shifter is released. Shifting can occur either in forward pedaling or pedaling backwards. The assembly is mounted on the rear wheel axle for a rear derailleur and on the bicycle bottom bracket shell for a front derailleur. Since the chain moving elements rotate with the sprockets/chain rings, no adjustments are required like in the traditional derailleurs that have chain moving elements attached to the bicycle frame. 
         [0013]    These and other features and advantages of the present 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 
         [0014]      FIG. 1  is a prior art drawing illustrating a derailleur with chain lifters. 
           [0015]      FIG. 2  is a perspective view of a first embodiment of a rear derailleur shown in the process of up shifting. 
           [0016]      FIG. 3  is a perspective view of the same embodiment shown in the process of downshifting. 
           [0017]      FIG. 4  is an exploded view of the constituent parts of this particular embodiment. 
           [0018]      FIG. 5  is a perspective view of an alternative embodiment of a rear derailleur shown in the process of up shifting. 
           [0019]      FIG. 6  is a perspective view of the alternative embodiment shown in the process of downshifting. 
           [0020]      FIG. 7  is an exploded view of the constituent parts of the alternative embodiment. 
           [0021]      FIG. 8  is a close-up perspective view of the stacked parallelogram bridges of the alternative embodiment. 
           [0022]      FIG. 9  is a close-up perspective view of the alternative embodiment in the process of downshifting. 
           [0023]      FIG. 10  is an exploded view of the actuator mechanism common to both embodiments. 
           [0024]      FIG. 11  is a perspective view of the fully assembled actuator mechanism. 
           [0025]      FIG. 12  is a general view of the first embodiment as a front derailleur. 
           [0026]      FIG. 13  is a general view of the alternative embodiment as a front derailleur. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0000]    
       
         
           
             The described invention includes 2 embodiments, which do not limit its scope. Both embodiments can be designed to be used as front or rear derailleurs. 
             In order to avoid unnecessary duplication of description, only the construction and function of a rear derailleur is presented. 
             The front derailleur version differs only in size and attachment location. The same design of the actuator mechanism is common for both embodiments. 
             A simple 3-sprocket set is shown for clarity. Both embodiments can incorporate any number of sprockets. 
             Whenever the term downshifting for a rear derailleur is used, it should be understood that the chain is being transferred from a smaller to a larger sprocket. Conversely, up shifting refers to the chain being transferred from a larger to a smaller sprocket. It should be understood, that this order is inverted for a front derailleur. 
             Two elements of the complete system are described marginally, as they are not claimed—the chain tensioner and the shift controller. 
           
         
       
     
         [0033]      FIG. 4  illustrates the detailed construction of the first preferred embodiment. Typically the rear bicycle wheel rotates on an axle  38  fixedly attached to the frame (not shown). The hub containing the bearings also carries the freewheel and the sprockets B. Locknuts hold the hub in place axially. Locknut  40  on the sprocket side serves as the stop for the hollow axle  41 , which is held tight in place by another nut  45  recessed in the axle pit. The following components are assembled in order on said hollow axle  41 : diaphragm spring  46 , up shifting lifter  47 , diaphragm spring  53 , downshifting lifter  54 , fixed depressor plate A 2 , rotating depressor plate A 1 . When inactive, lifters  47  and  54  are held away from the sprocket assembly B by spring  46 . 
         [0034]    When initiating an up shift, the actuator A pushes only lifter  47  towards sprocket  39 , compressing spring  46 , where a ridge  52  catches on a protrusion  39 . Since spring  53  holds lifter  54  in a distal, inactive position, only lifter  52  rotates with the sprocket assembly B. Going to  FIG. 2 , it can be seen how the chain  36  is guided by the row of teeth  31   b  from the medium sprocket  34  to the smallest sprocket  39  effecting an up shift. 
         [0035]    When initiating a downshift, the actuator A pushes both lifters  54  and  47  towards sprocket  39 , compressing spring  46 , where a ridge  52  catches on a protrusion  39 . Spring  53  remains compressed and both lifters, closely nestled rotate with the sprocket assembly B. In this position lifter  54  occludes lifter  47  allowing interaction only between the teeth of lifter  54  and the chain  36 . A protrusion  51  on lifter  47  remains inserted in an opening  56  on lifter  54  keeping both lifters aligned. Going to  FIG. 3 , it can be seen how the chain  36  is guided by the row of teeth  32   b  from the smallest sprocket  35  to the medium sprocket  34  effecting a downshift. 
         [0036]    There is a redundant row of teeth on each lifter. Teeth row  31   c  on lifter  47  serves the purpose of carrying the chain through the lifter  47  on sprocket  35  should the rider try to initiate a further (inexistent) up shift. Similarly, teeth row  32   c  on lifter  54  serves the purpose of carrying the chain through the lifter  54  on sprocket  33  should the rider try to initiate a further (inexistent) downshift. 
         [0037]      FIG. 9  illustrates the detailed construction of the second preferred embodiment. All the elements of this preferred embodiment are the same except for the chain lifters. In the first embodiment the side displacement of the chain occurs gradually, with the chain meshing with the appropriately beveled teeth. In the second embodiment, the side displacement of the chain is effected by bridge structures mounted on radial arms. 
         [0038]    The shape and function of these bridges is better illustrated on  FIG. 10  and  FIG. 12 . Looking at  FIG. 10 , the two bridges  72  and  73  can be seen in superimposed inactive position. As one possible execution of this embodiment the lifters are single pieces of flat spring steel stamped and bent to a shape resembling the letter L. The short portion of the L is furthermore bent to form parallelograms  72  and  73  with cutouts in the corners  76 - 81 . These cutouts weaken the corners allowing the parallelograms to collapse under pressure. The arms of the lifters and the bases of the parallelograms are stiffened by forming ridges or creases. Slots are cut in the upper surfaces of the parallelograms, designed to engage the chain laterally. One of the parallelograms is slanted and collapses towards a larger sprocket (downshifting), while the other is slanted and collapses towards a smaller sprocket (up shifting).  FIG. 12  illustrates a phase of downshifting, where only the lower lifter  71  is active. The chain  36  is caught in one of the slots and is displaced from sprocket  35  to the plane of sprocket  34  by the collapsed parallelogram prior to meshing. The process is better seen in its entirety in  FIG. 8 .  FIG. 7  illustrates an up shift, where both lifters move in tandem with the upper parallelogram  73  engaging the chain. Ridges  75  on lifter  71  keep lifter  72  aligned. A tooth  79  on lifter  71  meshes with the teeth of sprocket  35 , entraining lifter  71 . 
         [0039]    A crucial part of the proposed invention is the actuator mechanism. It allows the selective axial movement of the lifters of both embodiments; therefore it needs to be explained in further detail.  FIG. 14  is an enlarged exploded view of said actuator mechanism with the sandwiched cutout drawings of the bases of the chain lifters. The hollow axle has a base  41  and a collar  42 . The base has an opening  44  through which the wheel axle  38  is passed. The base  41  rests on locknut  40  and is fastened on the other side by locknut  45 . The collar  42  has bayonet cutouts  43   a  and  43   b  placed to accept locking sectors  58   a  and  58   b  on the fixed depressor A 2 . Spring  46 , and chain lifter  47  are rotatingly mounted on collar  42 . Chain lifter  47  has a collar  48  on which spring  53  and chain lifter  54  are rotatingly mounted. Fixed depressor A 2  is furthermore mounted on the protruding portion of collar  42  with sectors  58   a  and  58   b  locked in the bayonet cutouts  43   a  and  43   b . This way assembled, diaphragm spring  46  is partially relaxed, diaphragm spring  53  is fully compressed, cam  55   b  protrudes from slot  59   a , cam  55   a  protrudes from slot  59   c , cam  49   a  protrudes from slot  59   b , cam  49   b  protrudes from slot  59   a  and axle  38  protrudes from opening  61 . The rotating depressor A 1  is mounted on fixed depressor A 2  by means of locking tab  60   a  passing through slot  64   a  and locking tab  60   b  passing through slot  64   b . The tabs are bent, holding depressor A 1  loosely, so as to allow partial rotation. Finally the control cable  67   a  is passed through spring  68  and attached to tab  63  on the rotating depressor A 1 , with the cable housing  67  pushing tab  62  on depressor A 2 . A spring in the controller on the handlebar (not shown) holds spring  68  partially compressed.  FIG. 15  shows the assembled actuator A mounted on axle  38 . 
         [0040]    In operation, when the rider pays out cable against the controller spring (not shown), spring  68  pushes tabs  62  and  63  apart, rotating counterclockwise depressor A 1  relatively to depressor A 2 . Slanted tabs  65   a  and  65   b  depress cams  49   a  and  49   b  and move chain lifter  48  against diaphragm spring  46  proximally to sprocket  35  where tooth  52  catches on protrusion  39  entraining chain lifter  48  with the rotating sprocket cluster B. The cams remain depressed initially by depressor A 2 , and then by chain lifter  48  held by the chain  36 . If the rider releases the controller, the slanted tabs  65   a  and  65   c  clear slots  59   b  and  59   a  allowing cams  49   a  and  49   b  to emerge and stop the rotation of chain lifter  47  in its stowed position. During the rotation of chain lifter  47 , chain lifter  54  is held in its stowed position by diaphragm spring  53 . 
         [0041]    When the rider pulls the cable by means of the controller (not shown), tabs  63  and  62  are pulled closer, further compressing spring  68 . The resulting clockwise rotation of depressor A 1  forces slanted tabs  65   b  and  65   c  to sink cams  55   a  and  55   b  in slots  59   a  and  59   c , pushing in tandem chain lifter  54  and  48  axially towards sprocket  39 . Tooth  52  catches on protrusion  39  on sprocket  35  and the previously described cycle is repeated, this time with the superimposed chain lifter  54  engaging the chain  36 . 
         [0042]    The proposed invention is particularly suitable for implementation as a front derailleur. All components have the same design and function as the rear derailleur with the only differences being the size and the attachment point of the hollow axle.  FIG. 12  and  FIG. 13  illustrate the two different embodiments. A cutaway of the bottom bracket shell C of the frame carries the actuator and the hollow axle A. The right crank D is seen attached to the spindle E. 
         [0043]      FIG. 2-3  and  FIG. 5-6  also show marginally the chain tensioner. For the purpose of this invention, a simple chain tensioner with 2 rollers  37   a  and  37   b  has been chosen. The rollers allow the chain to move laterally following the chain positioning effected by the chain lifters. In retrofit applications of the invention, the parallelogram derailleur can be used as a chain tensioner only, after being disconnected from its control cable and return spring.