Bicycle lever assembly

An improved bicycle lever transmission assembly, which may be in kit form, is provided for installation on a conventional bicycle having a pedal crankshaft with a journalled portion rotatably mounted in a bicycle frame having a pair of pedal cranks extending oppositely from the journalled portion. The lever transmission assembly or kit includes a pedal crank with a pivot boss extending therefrom in spaced parallel relation with the journalled crankshaft portion, a drive sprocket to mesh with a drive chain to drive a bicycle wheel, the drive sprocket being rotatably mounted on the crankshaft journalled portion adjacent a pedal crank, a fixed lever link affixed to the drive sprocket with an end portion thereof extending beyond the pitch diameter of the fixed lever link, and leverage transmission components including at least one lever link pivotally connected with the pivot boss and with the extending end portion of the fixed lever. The lever transmission components may include a second lever link having first and second end portions respectively pivotally connected to the drive sprocket and to the first lever link, and a third lever link having first and second end portions adapted respectively for connection to the extending end portion of the fixed lever link and to an intermediate portion of the second lever link.

BACKGROUND OF THE INVENTION 
The present invention relates generally to bicycle drive transmission 
assemblies, and more particularly to improved bicycle lever transmission 
assemblies wherein lever links transmit rotary driving force and motion of 
the pedal crankshaft to the drive sprocket to reduce required pedal force. 
In conventional bicycles, as well as related three and four-wheeled 
vehicles or pedal-driven boats, and the like, driving force appplied by 
the feet of the user to pedals oppositely disposed on a crankshaft, is 
transmitted to a driven wheel, or equivalent output component, via a chain 
drive and a drive sprocket on the pedal crankshaft. 
It has been necessary, in order to provide sufficient driving force to the 
driven wheel in such vehicles, in some applications or to accommodate some 
individuals, to provide additional mechanisms to provide alternate gear 
ratios to adapt the drive mechanisms to various operating conditions and 
for use by persons of reduced capacity for providing pedal effort. 
It is therefore an object of the present invention to provide an improved 
bicycle lever transmission assembly intermediate the pedals and drive 
sprocket of a bicycle. 
It is an object of the invention to provide such a lever transmission 
assembly of simplified and economical construction. 
It is an object of the invention to provide such a lever transmssion 
assembly which comprises lever links intermediate the pedals and drive 
sprocket. 
An object of the invention is to provide an improved bicycle lever 
transmission assembly for reducing the forces required for application to 
the pedals. 
SUMMARY OF THE INVENTION 
The foregoing objects, as well as other objects and advantages which will 
become apparent from the detailed description of the preferred embodiment, 
are attained in an improved bicycle lever transmission assembly installed 
or installable intermediate the pedals and the drive sprocket of a bicycle 
wherein a pedal crankshaft has a journalled portion rotatably mounted in a 
bicycle frame and wherein a pair of pedal cranks extend oppositely from 
the journalled portion. 
The lever transmission assembly, or the kit components for providing the 
assembly, include a pedal crank having a pivot boss to extend in spaced 
parallel relation to the journal crankshaft portion, a drive sprocket 
rotatably mounted on the crankshaft journal portion adjacent a pedal crank 
and adapted to mesh with a drive chain for driving a bicycle driven wheel, 
a fixed lever link fixed to the drive sprocket and having an end portion 
extending beyond its pitch diameter, and leverage transmission means 
including at least one lever link pivotally connected with the pivot boss 
and pivotally connected with the fixed lever extending end portion. 
The lever transmission assembly may include second and third lever links. 
In such an arrangement, the first lever link is adapted for pivotal 
connection to the pivot boss, a second lever link pivotally connected to 
the drive sprocket and pivotally connected to the first lever link, and a 
third lever link having respective end portions pivotally connected to the 
extending end portion of the fixed lever link and to an intermediate 
portion of the second lever link, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 illustrate portions of a conventional bicycle apparatus with 
which a lever transmission assembly of the invention is installed. The 
bicycle assembly includes a bearing housing 20 of a bicycle frame having a 
pedal crankshaft 10 which has pedal cranks 12, 14 extending in opposite 
directions from a central crankshaft portion journalled in a bearing 
supported in bearing housing 20. A pedal 16 is rotatably mounted at the 
outer end portion of each of the crank arms 12, 14. A drive chain 32 
interconnects a drive sprocket 30 with a driven sprocket (not shown) at 
the rear wheel of the bicycle. 
The drive sprocket 30 is mounted on the central portion of crankshaft 10 
and is retained by a collar 38 integral therewith. Whereas the sprocket is 
conventionally mounted for rotation with the crankshaft, in the assembly 
of the invention, the sprocket is rotatable relative to the central or 
journal portion of the crankshaft. 
The transmission assembly of the invention includes a transmission plate 50 
rigidly bolted to one side of the sprocket 30, a pivot boss on pedal crank 
12 spaced from and parallel to the central journal portion of the pedal 
crankshaft, and lever link members hereinafter described. 
FIGS. 1, 2 and 4 illustrate a preferred embodiment of bicycle lever 
transmission assembly according to the invention. The lever transmission 
60 includes a fixed lever link 68 rigidly secured to transmission plate 50 
and to sprocket 30, and having an extension portion 168 extending beyond 
the pitch diameter of the drive sprocket. A first lever link 64 has a 
first end portion in pivotal engagement at 42 with the pivot boss 40 on 
the pedal crank. A third lever link 66 has a first end portion pivotally 
connected at pivot 24 to extension portion 168 of the fixed lever, and has 
its second end portion pivotally connected to said intermediate portion of 
the second or sickle lever link 62. 
A second or sickle link 62 has a first end portion pivotally connected at 
22 to the transmission plate 50, an arcuate portion extending about the 
crankshaft journal, an intermediate portion 82 and a second end portion 
pivotally connected to a second end portion of the first lever link 64. 
In this train of lever links, the lever links are arranged with their 
driven ends at successively smaller radii from the center of rotation of 
the assembly, which is axis of rotation of the pedal crankshaft journal 
portion. Through the interaction of the several components of the lever 
transmission 60, the effort or force required of the person using the 
bicycle, in terms of load applied to the pedals, is appreciably reduced 
from that required by a conventional pedal crank assembly, wherein 
sprocket 30 is directly secured to the pedal crankshaft 10. 
Sprocket 30 and transmission plate 50 have a plurality of registering 
openings, typically openings 36 and 56, through which fasteners, such as 
bolts, are extended rigidly to secure the components together or to serve 
as pivots for the components, in respective embodiments of the invention. 
FIG. 5 shows a modified and simplified form of lever transmission assembly 
according to the invention, wherein the sickle link 62 is rigidly secured 
to the transmission plate 50 by appropriate fasteners or bolts 77, 92, 
against relative rotation to any material extent. The transmission of 
driving force from the pedals is thereby altered, and the arrangement 
serves as a means of adjustment to adapt the lever transmission assembly 
of the invention to the requirements of the user. 
A simplified embodiment of the invention is in FIG. 6, wherein a single 
lever link 166 is pivotally connected to the extension portion of the 
fixed link 68, and has its other end portion pivotal on the pivot boss 40.