Patent ID: 7520196

Claim:
A variable length crank mechanism for use on a bicycle, comprising: an axle mounted in sealed bearings with said axle being made hollow with external splines mounted to opposing ends, a gear driven transmission unit mounted to each of said axle's ends; said axle being threaded with right-handed threads on the right side and left-handed threads on the left side; said axle having threaded nuts spacers and bearing inner races mounted against a shoulder of the axle; the axle and said bearings are mounted in pinion gears which are threaded for assembly to a frame member, said pinion gear threads being left-handed for the right side, and right-handed for the left side so that they remain tight with use and do not rotate; with said pinion gears each having a groove around the circumference for the containment of an o ring seal, with the seals outside diameters making contact with and being compressed for the retention of oil and exclusion of outside contaminants; each said transmission unit having an outer arm with internal splines and bolts used to fasten said outer arm to external splines of a proximal gear of a primary crank arm assembly; said proximal gear being positioned by and rotating on sealed, flanged bearings; with said outer crank arms being threaded for the mounting of pedals; each said primary crank arm containing a train of gears in a primary housing assembly, said train of gears are even in number and located between said pinion gear and said proximal gear; said pinion gears each having a number of teeth being equal in number to the number of teeth on each of the proximal gears, producing a ratio of 1:1, one of the primary housing assemblies having a chain, and at least one sprocket mounted with bolts to said primary housing assembly; said gear train being enclosed within said primary housings assembly, each gear of the gear train mounted between the pinion gear and the proximal gear; said gears of the gear train being mounted on bearings and pins which are sealed on each end with o rings that fit into grooves on the face of each shoulder, with each shoulder to keep the pin centered in said primary housing assembly; said pins being hollow, said bearings inner races mating the major outside diameter of said pin, said bearings inner races being retained in the bore of the gears of said gear train by snap rings and a metal to metal fit; spacers located on each side of said bearings inner race centered in said primary housing assembly preventing friction and increasing efficiency; said primary housing assembly having an inner and outer crank housings which are bolted together with bolts and alignment sleeves, said alignment sleeves also serving as a strengthening member, preventing unwanted movement between the inner and outer crank housings; the inner and outer crank housings having mating surfaces sealed with a suitable sealant for the retention of oil and for the exclusion of contaminates.