Transmission assembly for a bicycle having forward/back gear

A bicycle transmission assembly comprising:

• a gear shifting device comprising a follower gear, a first idler gear, a second idler gear, and a transmission gear, the follower gear and the first idler gear being coaxially mounted with each other, the first idler gear and the second idler gear being meshed with each other and both mounted to a carrier member, the carrier member being rotatably supported such that the transmission gear is capable of meshing with one of the first idler gear and the second idler gear, the gear shifting device includes a gear shifting plate for fixing to the bicycle frame and a gear shifting lever, the gear shifting plate including a plurality of engaging holes, the gear shifting lever including an engaging protrusion with the end of the gear shifting lever pivotally connected with the gear shifting plate, the engaging protrusion of the gear shifting lever being selectively engaged with one of the engaging holes of the gear shifting plate and thus positioned at one of a neutral gear, a forward gear, and a back gear, the other end of the gear shifting lever being connected to the carrier member of the gear shifting device by a link and an arm, wherein pivotal movement of the gear shifting device controls selective engagement of the transmission gear of the gear shifting device with one of the first idler gear and the second idler gear;
• a reciprocating pedal device comprising a single direction gear mechanism, a first pedal rod, and a second pedal rod, the single direction gear mechanism including a single direction gear that is connected to the follower gear by a transmission element;
• and
• the gear shifting device and the reciprocating pedal device being adapted to be mounted to a bicycle frame, whereby reciprocating movements of the first pedal rod and the second pedal rod drive the single direction gear to turn, which, in turn, drives the first idler wheel and the second idler wheel via transmission of the transmission element, wherein the bicycle moves forward when the first idler gear meshes with the transmission gear, and wherein the bicycle moves rearward when the second idler gear meshes with the transmission gear.