Patent ID: 8157281

Claim:
A driving mechanism for a bicycle, the bicycle having a frame, a front wheel and a rear wheel, the front and the rear wheels being disposed on a front fork and a rear fork of the frame, the driving mechanism comprising: a transmission disc, disposed on the frame; a transmission belt, a part of the transmission belt surrounding the transmission disc, the transmission belt and the transmission disc being in an operative relationship, the transmission belt being adapted to drive the front wheel or the rear wheel; a pair of cranks, disposed on both sides of the frame respectively, each crank having a crank fixed end and a crank distal end, the crank fixed ends being connected by an axle, the axle inserting through a center of the transmission disc, the cranks and the transmission disc being in an operative relationship, each crank being rotatable about its crank fixed end; a pair of arms, disposed on both sides of the frame respectively, each arm having an arm fixed end and an arm distal end, the arm fixed ends being pivoted to distal end of the rear fork; a pair of connecting bodies, each connecting body having two pivoting ends, which are pivoted to the crank distal end of the crank at the same side and the arm distal end of the arm at the same side respectively, each connecting body further having a connecting portion between its two pivoting ends; and a pair of pedals, disposed on the connecting portions of the connecting bodies respectively, each pedal being movable in an orbit, the orbit having a topmost point, a bottommost point, a front most point and a rearmost point, a vertical distance between the topmost point and the bottommost point is H, a horizontal distance between the front most point and the rearmost point is W, which satisfies the following relationship: H/W ≧ 5/3.