Abstract:
A double chainring drivetrain system for bicycles that allows riders to apply force directly to a pair of chainrings, one on either side of the bottom bracket. The double chainring drivetrain system has two crank arms, each connected to a peripheral rim portion of the chainrings, and two drive chains. A hub on the rear wheel has two sprockets such that the two drive chains extend between the chainrings and the rear sprockets for transfer of applied rotational forces from the pedals on either side of the bicycle through the two chainrings to the rear sprockets on hub of the rear wheel.

Description:
RELATED APPLICATIONS 
     None. 
     FIELD OF THE INVENTION 
     The present invention relates to an improvement on a conventional pedal-driven, human-powered, single-track bicycle, and more particularly to a double chainring drivetrain system that distributes more power to the rear wheel of the bicycle and requires less human effort to power than possible with the conventional bicycle drive train. 
     BACKGROUND OF THE INVENTION 
     Conventional human-powered bicycles are usually driven by a drivetrain system which was developed to transmit power from riders to drive wheels by a variety of methods. Most bicycle drivetrain systems incorporate a freewheel to allow coasting. 
     The simpler bicycle drivetrain system consists essentially of a single chainring on the right side of the bicycle; a chain; a pair of pedals on either sides and a sprocket on the rear wheel. The system basically converts the reciprocating motion of the rider&#39;s legs into rotational motion of the chainring, which subsequently drives the chain which in turn drives the rear wheel. More complicated systems may consist of more than one chainrings attached to the crank set to which the pedals are attached. The chainring is connected to the bicycle frame at the bottom bracket, and to the rear sprocket, cassette or freewheel via the chain. More sophisticated bicycles also include a cogset, a derailleur gears, hub gears, gear case and other parts to enhance efficiency of the bicycle. 
     Conventional drivetrain systems, while driven by pedals on both sides of the bicycle, primarily only utilize a chainring on one side; usually the right side of the bicycle. Both pedals are connected at the center of the chainring(s) by their respective crank arms coupled to the axle or bottom bracket spindle. There are a variety of methods used to attach the crank arms to the bottom bracket spindle including wedge-shaped pins or cotters, square tapered spindles, hexagonal tapered spindles, and splined bottom bracket spindles. 
     The present invention is a double chainring drivetrain system which has two identical chainring drivetrains on both sides of a bicycle; working simultaneously and in-sync. It is believed that the present invention can increase the efficiency of bicycles by having two identical chainring drive train. 
     ADVANTAGES AND SUMMARY OF INVENTION 
     One object and advantage of the present invention is to provide a more efficient bicycle drivetrain system. 
     Another object and advantage of the present invention is to provide a more ergonomically comfortable pedal and crank arm system for riders. 
     Another object and advantage of the present invention is to couple the drivetrain to the chainrings directly instead of through the bottom bracket or axle. 
     Yet another object and advantage of the present invention is its ability to drive the chainrings on both sides of the bicycle. 
     Further details, objects and advantages of the present invention will become apparent through the following descriptions, and will be included and incorporated herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a representative isometric view of a double chainring drivetrain system  100  of the present invention. 
         FIG. 1B  is a representative isometric view showing pedals  102  and  202  with their respective chainrings  108  and  208 . 
         FIGS. 2A and 2B  are representative side views of a double chainring drivetrain system  100  of the present invention. 
         FIG. 3  is a representative top view of a double chainring drivetrain system  100  installed on a bicycle  300 . 
         FIG. 4  is a representative side view showing pedal  102  with its corresponding chainring  108 . 
         FIGS. 5A ,  5 B,  5 C,  5 D,  5 E and  5 F are representative side views of alternative embodiments  500 ,  510  and  520  of a double chainring drivetrain system of the present invention. 
     
    
    
     For a better understanding of the invention reference is made to the following detailed description of the preferred embodiments thereof which should be taken in conjunction with the prior described drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The description that follows is presented to enable one skilled in the art to make and use the present invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principals discussed below may be applied to other embodiments and applications without departing from the scope and spirit of the invention. Therefore, the invention is not intended to be limited to the embodiments disclosed, but the invention is to be given the largest possible scope which is consistent with the principals and features described herein. 
       FIG. 1A  is a representative isometric view of a double chainring drivetrain system  100  of the present invention. As best shown in  FIG. 1A , the present invention  100  consists essentially a twin sets of identical drivetrain systems  250  and  260 . Each drivetrain system  250  and  260  consists essentially of corresponding component parts. As best shown in  FIG. 1A , each system consists essentially of chainrings  108  and  208  which can be single chainring, multiple chainring system and other more sophisticated crankset system such as Shimano Deore crankset, Belt-drive crankset etc. The bicycle chain shown representatively as  110  and  210  can be a simple roller chain, block chain, skip-link chain or more sophisticated models and even cable. Pedal crank levers  106  and  206  and chainring crank lever couplings  104  and  204  couple pedals  102  and  202  to chainrings  108  and  208 , respectively. Finally, the assembly  100  comprises rear wheel sprockets  112  and  212 . 
     As best shown in  FIG. 3 , drivetrain systems  250  and  260  are installed on both sides of a bicycle  200 , with right drivetrain system  250  on the right hand side and left drivetrain system  260  on the left hand side of the bicycle  200 . In one embodiment, right and left drivetrain systems  250  and  260  are connected at two chainrings  108  and  208 , respectively, by double-end front axle  150 . At the centers of rear wheel sprockets  112  and  212  there is a double-end hub  160 . 
     In one embodiment, each chainring  108  and  208  is fastened to double-end axle  150 . Whereas in a conventional drivetrain system which includes a single crank arm connected at one end to a pedal and at another end to the single chainring, usually on the right side of the bicycle axle, by a bottom bracket that allows the crankset to rotate freely; it further contains a spindle to which the crankset is attached and the bearings that allow the spindle and crank arms to rotate. In one embodiment of the present invention, two chainrings  108  and  208  of the present invention  100  are connected by double-end axle  150 . Double-end axle  150  ensures that both chainrings  108  and  208  rotate in unison no matter which chainring receives force of rotation at any point of operation. As for the rear sprockets  112  and  212 , the mechanism is similar to conventional bicycles but instead of having one sprocket fastened to one side of the rear hub, rear wheel sprockets  112  and  212  are both fastened to double-end hub  160  on both ends thereof. 
     In alternative embodiments, rear wheel sprockets  112  and  212  and double-end hub  160  are in the form of thread-on freewheel and hub assembly, freehub and cassette assembly, Shimano cassette and freehub assembly and other more sophisticated embodiments including but not limited to Derailleur gears and other gear changing mechanism. The main function of a double-end hub  160  is to ensure rear wheel sprockets  112  and  212  always rotate simultaneously and in-sync no matter which sprocket is driving rotation at any time during its operation. 
       FIG. 1B  is a representative isometric view showing pedals  102  and  202  with their respective chainrings  108  and  208 . As shown in  FIG. 1B , on the left drivetrain system  250 , unlike conventional embodiments, pedal  102  is fastened to chainring  108  near its exterior rim section  109  instead of the center  111  by pedal crank lever  106 . Additionally, there is chainring crank lever coupling  104  that is fastened between an adjacent location near the rim  109  of chainring  108  and part way  105  along the length of pedal crank lever  106 . The embodiment on the right drivetrain system  260  is operatively the same and the two pedals  102  and  202  are mounted 180° out of phase. 
     The main advantages of having this particular pedal embodiment of the present invention  100  are that it provides torque and leverage between pedals  102  and  202  and their respective chainrings  108  and  208 . Moreover, riders apply force directly to chainrings  108  and  208 . The combination enhances overall efficiency of the bicycle  200 . As shown in  FIG. 1B , when rider [not shown] stands on or pulls up on pedal  102 , he/she will drive chainring  108  to rotate in direction A. In one embodiment, chainring  208  will be driven at the same rotational speed in direction B via double-end axle  150 . Thus, when riders are pedaling using both pedals  102  and  202 , both drivetrain systems  250  and  260  will drive the bicycle  200  together, and the combined rotational force generated will then power the bicycle  200 . 
       FIGS. 2A and 2B  are representative side views of a double chainring drivetrain system  100  of the present invention. As best shown in  FIG. 2A , when chainring  108  is driven to rotate in direction C, it will in turn drives chain  110  in direction D and eventually drives rear sprocket  112  in direction E. The mechanism is identical in right drivetrain system  260  as best shown in  FIG. 2B . When chainring  208  is driven to rotate in direction F, it will in turn drives chain  210  in direction G and eventually drives rear sprocket  212  in direction H. Since chainrings  108  and  208  are connected, both drivetrain systems  250  and  260  will drive each other at any point of operation and the combined rotational forces generated will then drive rear sprockets  112  and  212 . 
       FIG. 4  is a representative side view showing pedal  102  with its corresponding chainring  108 . In one embodiment, pedal  102 , and the two crank levers  104  and  106  are all fastened by mechanical coupling systems  402 ,  404  and  406 . In alternative embodiments, mechanical coupling systems  402 ,  404  and  406  can be a simple threaded nut and bolt mechanism or more sophisticated coupling systems such as rivets, welding, adhesive, or combinations thereof. In alternative embodiments, dimensions of pedal  102 , chainring crank lever  104  and pedal crank lever coupling  106  can be adjusted according to riders&#39; needs. Locations of mechanical mean coupling systems  402 ,  404  and  406  can also be adjusted to suit different riders. 
     In an embodiment of the present invention, the angle formed between crank arm  106  and bracimg member  104  is equivalent to about 45 degrees, or more or less. In such embodiment, the drive force applied to the pedal  102  is distributed to the chain ring  108  via crank arm  106  and bracing member  104  having a predetermined orientation in which the bracing member  104  lies at an angle of 45 degrees relative to the crank arm  106 . 
       FIGS. 5A ,  5 B,  5 C,  5 D,  5 E and  5 F are representative side views of alternative embodiments  500 ,  510  and  520  of a double chainring drivetrain system of the present invention. As best shown in  FIGS. 5B ,  5 C and  5 D, chainring crank lever  104  and pedal crank lever  106  combination shown in  FIG. 4  can be replaced by T-crank arms  502 ,  504  and  506 . In one embodiment, T-crank arms  502 ,  504  and  506  shaped like a letter “T” and all have a horizontal portion and a vertical portion. As best shown in  FIGS. 5A ,  5 E and  5 F, two ends of the horizontal portion of T-crank arms  502 ,  504  and  506  are fastened to the rim portion  109  of chainring  108 . The ends of the vertical portion of T-crank arms  502 ,  504  and  506  are attached to pedal  102 . In alternative embodiments, dimensions of T-crank arms  502 ,  504  and  506  can be adjusted to suit riders&#39; need. As best shown in  FIG. 5E , T-crank arm  506  can be mounted closer to the center of chainring  108  if desired. 
     It will be understood that, for example in the embodiment shown in FIG.  5 AB, the T-shaped crank arm  502  can also be triangular shaped or have secondary bracing support member shown) extending between the proximal  2  mechanical coupling points where the T-shaped crank arm  502  couples to the chain ring and the one mechanical coupling point adjacent the pedal  102 . Such secondary bracing members can be formed using flat stock, round stock or stock having any predetermined, cross-sectional shape desired. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Although any methods and materials similar or equivalent to those described can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications and patent documents referenced in the present invention are incorporated herein by reference. 
     While the principles of the invention have been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components used in the practice of the invention, and otherwise, which are particularly adapted to specific environments and operative requirements without departing from those principles. The appended claims are intended to cover and embrace any and all such modifications, with the limits only of the true purview, spirit and scope of the invention.