Abstract:
A front derailleur with controllable full rotational movement with two operator selectable radial arms—one for pole-vaulting the chain to larger sprockets, the other for sliding the chain to smaller sprockets.

Description:
CROSS REFERENCES TO RELATED APPLICATION 
     This is a continuation-in-part (CIP) of Ser. No. 12/533,634, filed Jun. 31, 2009, pending. The related application is hereby incorporated by reference, for all purposes, as if fully set forth herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to bicycle derailleurs. More specifically, this invention relates to a derailleur design, which is suited for the front, driving sprocket assembly. 
     2. Description of the Related Art 
     Conventional bicycle front derailleurs typically use a parallelogram mounted cage to force the chain against the adjacent larger sprocket when an upshift 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 operator 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. This happens usually when it is least affordable—while climbing a gradient. Similarly, when the chain derails from a larger to a smaller sprocket, the operator has to reduce the pedaling force, or the chain will slam on the smaller sprocket. Additionally, when the chain is not aligned between the front and rear sprockets, as in some gear combinations, the chain tends to rub against the sides of the cage producing noise and causing wear. Another problem with the typical front derailleur is the requirement of precise calibration of the travel of the cage in response to input from the control unit—the shifter. Deviation from very strict parameters causes the chain either to fail shifting or drop from the sprockets. To mitigate this problem, shifters have been continuously improved, resulting in complex and costly apparatuses, which can work only with the corresponding front derailleurs. Numerous attempts have been made to resolve these issues. Most make incremental improvements to the typical front derailleur as described in U.S. Pat. No. 4,734,083 to Nagano. An attempt to overcome the above mentioned shortcomings has been made by Sam Patterson in his U.S. Pat. No. 5,649,877 granted on Jul. 22, 1997. Yet another attempt can be seen in U.S. Pat. No. 8,337,343 granted to Chang Hui Lin on Dec. 25, 2012. Shifting precision has also been approached by introducing electronic control and actuation as seen in U.S. Pat. App. No. 20130061705. 
     The enumerated attempts fail to address the main cause of the shortcomings—the fact that the derailleur is stationary along the travel path of the chain: the cause of friction. 
     A different direction in which attempts have been made to overcome the shifting shortcoming is by modifying the sprockets in order to facilitate the derailing of the chain. An example of this approach can be seen in Schmidt, et al. U.S. Pat. No. 5,738,603 from Apr. 14, 1998. Besides putting an onus on manufacturing and the corresponding high cost, this kind of modification might weaken the sprockets. 
     A more radical attempt to solve the whole number of above stated problems has been made by Bruce Browning—U.S. Pat. No. 5,205,794 from Apr. 27, 1993. A brief look at the invention, however, reveals excessive complexity, weight and elevated manufacturing costs. Also, the invention has a very limited range of speeds and the sectored, articulated sprockets render them fragile and prone to failure. 
     SUMMARY OF THE INVENTION 
     It has long been admitted that a satisfactory solution to the problems of the front derailleur has not been found. It is the intention of this inventor to make a more imaginative attempt to solve the above described problems. For the purpose, an invention is proposed that offers the following benefits:
         the derailleur rotates with the sprockets and acts as an agent for transferring the chain between the sprockets thereby avoiding friction with the chain;   the derailleur is stowed away from the path of the chain when not in use and is impervious to scraping against an excessively angled chain;   insignificant input effort is required from the operator, as the shifting of the chain occurs under its own tension and not by operator induced derailleur pressure;   because of the above, the controller—shifter can be a very simple lever similar to, and smaller than a brake lever and not requiring calibration to the derailleur;   upshifting and downshifting can be done both during forward pedaling and back pedaling;   shifting when pedaling up a steep gradient does not require any reduction in pressure on the pedals;   the derailleur comprises only 3 parts which can be manufactured by ordinary stamping and bending;   most of the derailleur can be made from a number of light materials;   the assembly of the derailleur can be executed without any fasteners;   with a slight modification of the actuator the derailleur is very suitable for electronic control;   The ways and means of manufacturing such a derailleur are described henceforth.       

     The proposed invention comprises 3 elements:
         a base immovably fixed to the bicycle frame in a coplanar axial position inboard of the front sprockets   a ring with 2 superposed arms, rotatably mounted on the outboard face of the base
           the outboard arm, called the downshift arm, when positioned between a sprocket and the chain, rotates with the sprocket and causes the chain to slide down its smooth surface and land on a smaller sprocket;   the inboard arm, called the upshift arm, covers the downshift arm when activated and by means of at least one tooth catches the chain. Since the arm is flexibly cantilevered and inclined towards the sprockets, the downward pressure of the chain deflects the arm further until it rests in the plane and over a larger sprocket, thereby depositing the chain on the larger sprocket. The motion is similar to that of a pole vaulting athlete.   
           an actuator, designed to extend a cam surface at the pull of a Bowden cable. The actuator is a trapezoid frame where the two parallel shoulders slide along slide guides formed in the base, another side is formed as an arched cam and the 4th side is articulated at the corners. The 4th side is further split in 2 levers pivoted on fulcrums formed in the base, which are articulated at the point of confluence. An attachment point for a Bowden cable is formed at the point of confluence of the shoulders. At the pull of the cable, the distal portions of the shoulders move forward extracting the cam, which in turn pushes a follower formed at the flexible shank of the 2 arms out of a recess groove. The arms tilt towards the sprockets, with the downshift arm meshing a tooth with the teeth of the sprocket. The sprocket entrains the whole assembly in a circular path. 2 scenarios follow:       

     in case the operator pulls the lever shortly, the rotation of the assembly starts, the follower sliding along the edge of the base, but the cam retracts and the upshift arm is not positioned to engage the chain. The chain lands on the downshift arm, sliding to a smaller sprocket. 
     in case the operator keeps the lever pulled for a longer period of time, the cam is extended and through the follower positions the arm with at least one tooth under the chain. The chain lands on the tooth and its pressure moves the arm towards a larger sprocket, where it is deposited. 
     In another preferred embodiment, the actuator is operated by a push from a solenoid controlled by a button or an electronic controller on the handlebar. Thereafter, the sequence is identical to the manual embodiment. 
     These and other features and advantages of the present invention will become apparent from the following description of one or more embodiments of the invention, taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the proposed derailleur installed on the body of a square-taper cartridge bottom bracket within the bottom bracket shell of the bicycle frame. 
         FIG. 2  is an exploded view of the front drive assembly. 
         FIG. 3  is an outboard perspective view of the proposed derailleur. 
         FIG. 4  is an inboard perspective view of the proposed derailleur. 
         FIG. 5  is an exploded view of the proposed derailleur. 
         FIG. 6  is a inboard perspective view focusing on certain parts to be represented in enlarged views. 
         FIG. 7  is an enlarged view of the junction of the derailleur ring and the derailing arms. 
         FIG. 8  is an enlarged view of the ring lamellae with one of the ring races before and after mounting. 
         FIG. 9  is an outboard view of the derailleur base and the actuator in retracted position. 
         FIG. 10  is an outboard view of the derailleur base and the actuator in extended position. 
         FIG. 11  is an outboard view of another preferred embodiment of the derailleur base and the actuator in retracted position. 
         FIG. 12  is an outboard view of another preferred embodiment of the derailleur base and the actuator in extended position. 
         FIG. 13  is an outboard view of the derailleur in stowed position. 
         FIG. 14  is an enlarged view of the cam follower of the derailing arms in its stowed position. 
         FIG. 15  is an outboard view of the derailleur at rotation initiation. 
         FIG. 16  is an enlarged view of the cam follower sliding over the extended cam. 
         FIG. 17  is an enlarged view of the entraining tooth meshed with the teeth of the largest sprocket. 
         FIG. 18  is an outboard view of the derailleur upshifting from the smallest sprocket to the medium one. 
         FIG. 19  is an enlarged view of the chain lifted by the lower tooth of the upshifting arm. 
         FIG. 20  is an outboard view of the derailleur with the chain transitioning from the smallest sprocket to the medium sprocket through the agency of the upshinfting arm. 
         FIG. 21  is a perspective view of the same process. 
         FIG. 22  is an outboard view of the derailleur with the chain transitioning from the largest sprocket to the medium sprocket through the agency of the downshifting arm. 
         FIG. 23  is a perspective view of the derailleur with the chain transitioning from the largest sprocket to the medium sprocket through the agency of the downshifting arm. 
         FIG. 24  is an enlarged view of the chain sliding down the downshifting arm during the process of downshifting. 
         FIG. 25  is a schematic diagram of the process of upshinfting from the smallest to the medium sprocket and from the medium to the largest sprocket. 
         FIG. 26  is a schematic diagram of the process of downshifting from the largest to the medium sprocket and from the medium to the smallest sprocket. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In broad terms, the proposed invention comprises 3 unitary elements: a base, a ring with 2 chain-shifting arms and an actuator. The ring and the actuator are mounted on the opposite faces of the base and then the assembly is fixed immovably to the bicycle frame. 
     With reference to the attached figures,  FIG. 1  represents the position of the proposed derailleur on a typical bicycle frame and  FIG. 2  is an exploded view of the same assembly. Typically modern bicycles have a bottom bracket  15  that screws into bottom bracket shell  11 . The crankset  20  is further attached to the bottom bracket spindle. Most bicycles also have a down tube  13 , a seat tube  12  and chain stays  14 . Some bicycles, however, dispense with the seat tube as is the case with full suspension bicycles and that creates a problem for traditional front derailleurs, which are usually attached to the seat tube  12 . In the proposed invention, the derailleur  16  is fastened by the bottom bracket  15  to the bottom bracket shell  11  rendering the seat tube  12  redundant for the purpose of support. 
     In  FIG. 3  the proposed derailleur is shown in inboard perspective, where the base  31  and the actuator  32  are illustrated.  FIG. 4  is an outboard i.e. towards the sprockets perspective view, showing the third component of the derailleur—the ring with the upshift and downshift arms. 
       FIG. 5  is a detailed exploded view of the 3 components of the derailleur where: the base  31  on its inboard (towards the frame) face has the following elements:  55   a , 55   b , 55   c  and  55   d  are sliders for actuator  32  shoulders  50   a  and  50   b .  56   a  and  56   b  are fulcrums to levers  51   a  and  51   b .  60  is a stop gate for the housing of a Bowden cable (not shown).  58  is a recess for follower  66  when the ring  41  is in a stationary (stowed) position.  57  is the edge of the base  31  on which the follower  66  slides after being ejected by the cam  53  of the actuator  32  from the groove  58 . The purpose of the bulge  59  is to deflect arms  62  and  63  in a flush position with the sprockets in order to prevent impinging on chain stay  14 . Tooth  64  on upshift arm  62  engages the chain from the smallest sprocket and carries it to the medium sprocket. Likewise, tooth  64  on arm  62  engages the chain from the medium sprocket and carries it to the largest sprocket. Downshift arm  63  performs two functions: 
     entrains the whole ring assembly  41  with the sprockets by meshing tooth  67  with the teeth of the largest sprocket and 
     lets the chain slide down from a larger to a smaller sprocket 
     Stopper flange  69  provides a restraint for the chain to further slide down and off the smallest sprocket, should the operator initiate a downshift while the chain is riding on the smallest sprocket. 
     In this preferred embodiment, the whole ring with the arms assembly  62 , 63  is formed from a single cut or stamped flat form of spring steel material. After obtaining the flat form, downshift arm  63  is positioned under the upshift arm  62  by bending the connecting strip  68 . Internal edge  61  of ring  41  allows rotation about races  73   a , 73   b  and  73   c  formed on the outboard face of the base  31  as seen in  FIG. 6 .  FIG. 8  is an enlarged view of a portion of ring  41  where a cut forms 2 flexible lamellae  74   a  and  74   b  allowing the mounting of the ring  41  on races  73   a , 73   b  and  73   c  without implementation of fasteners or tools.  FIG. 8A  shows support  73   c  positioned under the lamellae  74   a  and  74   b .  FIG. 8B  shows the support  73   c  after passing through the gap of the flexed lamellae  74   a  and  74   b , restraining axial motion of ring  41 .
 
Returning to  FIG. 5 , it should be noted that the actuator  32  in this embodiment of the invention is also formed from a single cut or stamped flat form of spring steel material and consequently is resiliently flexible.
 
To mount the actuator  32  on the slide guides  55   a , 55   b , 55   c  and  55   d , shoulders  50   a  and  50   b  are pulled slightly apart, enough to pass over the restraining edges of the slide guides  55   a , 55   b , 55   c  and  55   d . This flexibility is allowed by cutouts  52   a ,  52   b ,  52   c  and  52   d , which also act as articulated spring joints when levers  51   a  and  51   b  pivot upon fulcrums  56   a  and  56   b.  
 
Flange  60  is for connecting the actuator  32  to the control lever-shifter (not shown or claimed) on the handlebar by means of a Bowden cable (not shown).
 
       FIG. 7  is at the heart of the invention. It is an enlarged view of the shank  42  connecting the ring  41  to the arms  62  and  63 . To be noted here, are cutouts  71  and  72 . They weaken the material, creating resilient, articulated joints. When the follower  66  in  FIG. 5  is pushed by the cam  53 , the joint formed by cutout  72  in  FIG. 7  flexes first. When the downshift arm  63 , better seen in  FIG. 6 , presses against the largest sprocket, the joint formed by cutout  71 , as seen in  FIG. 7 , also flexes, allowing further travel of the upshift arm  62 . 
       FIG. 9  and  FIG. 10  depict the operation of the actuator. In  FIG. 9  the actuator is in the inactive position, cam  53  is retracted and groove  58  is open. When the operator pulls the control lever (not shown) on the handlebar, the resulting tug of the Bowden cable  90  pulls the proximal ends of levers  51   a  and  51   b  causing by way of pivoting around fulcrums  56   a  and  56   b  an opposite direction movement of the distal ends. Shoulders  50   a  and  50   b  slide along slide guides  55   a , 55   b , 55   c  and  55   d  and extend cam 
       FIG. 13  shows an inboard view of the derailleur in its inactive (stowed) position with the sprockets  130  and the chain  131  in the background.  FIG. 14  is an enlarged view of the follower  66  recessed in the groove  58  and the cam  53  in retracted position. 
       FIG. 15  is an inboard view of the derailleur upon activation with the sprockets  130  and chain  131  in the background. At the pull of the lever by the operator, the actuator slides, extending the cam  53 . As better seen in  FIG. 16 , the cam  53  ejects the follower  66  from the groove. The follower  66  imparts a tilt of both arms  62  and  63 , until arm  63  comes to rest against the largest sprocket  130  and tooth  67 , as seen in  FIG. 17  and meshes with the sprocket teeth. The meshed tooth  67  entrains the whole ring assembly to rotate with the sprockets. 
     If the operator keeps the lever depressed, the extended cam, by way of the follower, positions arm  62  under the chain  131  as seen in  FIG. 18 , where the chain  131  is riding on the smallest sprocket  133 . In this position of the arm  62 , the lower tooth  65  is positioned directly under the chain  131  and upon further rotation engages and lifts the chain  131  as seen in  FIG. 19 . The downward pressure of the chain  131  forces the upshift arm  62  to pivot and lean against the downshift arm, moving the chain in the plane of medium sprocket  132 . 
       FIG. 20  shows the arms/chain/sprockets assembly about ⅓ of full rotation. the front stretch of the chain  131  is still on the smallest sprocket  133 , while the stretch behind the upshift arm  62  has landed on the medium sprocket  132 .  FIG. 21  gives a perspective view for better visualization of the process. Not shown remains the complete travel of the ring after being released by the chain. The upshift arm continues to entrain the ring assembly with the rotating sprockets as long as the follower slides along the edge of the base. Only when the follower reaches the groove the resiliency of the bent shank nudges it inside. Tension of both arms is relieved and they assume their original position. This disengages the entraining tooth of the downshifting arm from the largest sprocket and the ring is locked in its inactive (stowed) position. 
       FIG. 22  shows in an inboard view of the derailleur, sprockets and chain in an advanced stage of downshifting. The selection of a downshifting sequence follows a short pull of the control lever—shifter by the operator. The entraining tooth of the downshift arm meshes with the largest sprocket and sets the ring in motion, but since the cam is retracted, the follower slides along the edge of the base keeping the upshifting arm out of the planes of the sprockets. This is better seen in  FIG. 23  and  FIG. 24 . The chain  131  slides down the smooth surface of the downshift arm  63  one sprocket at a time, since the lateral rigidity of the chain and the short stretch involved limit the chain side travel to one sprocket width. 
       FIG. 25  is a sectional schematic diagram showing all the phases of upshifting beginning from stowed position.  FIG. 25A  is of the ring in stowed position and the chain  131  rotates with sprocket  133 . Cam  53  is retracted, follower  66  is recessed in the groove of the base  31 , shank  61  is relaxed, arm  62  is upright and entraining tooth  67  is free. 
       FIG. 25B  shows the initiation of an upshift. The actuator  32  slides upwards and extracts the cam  53 , which in turn ejects the follower  66  from the groove, bending the shank  61 . Arms  62  and  63  tilt towards the sprockets  130 , 132  and  133 , arm  63  coming to a stop against sprocket  130  and entraining tooth meshing with the sprocket&#39;s teeth. Because the cam  53  remains extracted, arm  62  remains tilted and toot  63  is in the plane of sprocket  133  subsequently engaging and lifting the chain. 
       FIG. 25C  shows the side movement of the chain and its deposition on sprocket  132 . Under the downward pressure of the chain  131  on tooth  65 , the arm  62  pivots and rests on arm  63  bringing the chain in the plane of sprocket  132 . Upon further rotation, the chain lands on the teeth of sprocket  132 . Upon completing the cycle, the ring is brought back into the stowed position of  FIG. 25A  with the follower sinking into the groove and locking the ring in stationary position. 
       FIGS. 25D and 25E  show the same process of upshifting from sprocket  132  to sprocket  130 . It involves the upper tooth  64  of arm  62  which is positioned in the plane of socket  132  by the cam and follower. 
       FIG. 26  is another sectional schematic diagram showing all the phases of downshifting. 
       FIG. 26A  shows the ring in stowed position and the chain positioned on sprocket  130 . 
       FIG. 26B  shows the initiation of a downshift. The operator pulls the control lever-shifter shortly and ejects follower  66 . The arms tilt and entraining tooth  67  meshes with the teeth of sprocket  130  causing the ring to rotate with the sprockets. The cam  53  retracts. 
     As seen in  FIG. 26C , the ejected follower  66  slides along the edge of the base  31  preventing tooth  67  to disengage from the sprocket, at the same time since the cam  53  is retracted, arm  62  returns in a substantially upright position, away from the plane of the sprockets. This exposes the downshift arm  62  to the chain  131 , which lands on its smooth surface and starts sliding down under its downward pressure. Since the chain has a limited side flexibility and the stretch involved is short, it travels only one sprocket width, landing on the teeth of sprocket  132 . Upon completion of the cycle, the ring is brought back into the stowed position of  FIG. 26A  with the follower sinking into the groove and locking the ring in stationary position. 
       FIG. 26D  is the repetition of the same process from sprocket  132  to sprocket  133 . 
     Although the foregoing embodiment has been described in great detail of construction and material, variations and modifications in the spirit of the invention are possible. Accordingly, the disclosure, description and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.