Variable transmission

A power transmission system used in connection with a vehicle power wheel of a bicycle or other vehicle which has a fixed axle and which utilizes a rotating chain sprocket engaging an endless chain for receiving an input torque and transmitting an output torque. The system includes a transmission ratio varying apparatus that is operably connected to the wheel by the endless chain. The transition ratio apparatus incorporates a drive collar fixedly secured to a sprocket and having one or more input and output drive rings. A drive body is displaceable with respect to the input and output drive rings and includes input and output pawls pivotally connected to the drive body and engageable with the input and output drive rings. A shifter housing is moveable with respect to the fixed axle cam to rotatably shift the drive body with respect to the drive ring and change the relationship between the input and output pawls and thereby vary the torque transmission ratio. An operator lever and a cable connecting the operator lever with the shifter collar functions to move the shifter housing with respect to the fixed axle cam.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a power transmission system and, more 
particularly, to a system wherein input and output pawls are utilized to 
be driven by an input drive ring and drive an output drive ring through a 
plurality of different torque transmission ratios. 
2. Description of the Prior Art 
A variety of variable transmission systems having pulleys with varying 
diameters are known such as those shown in U.S. Pat. No. 1,626,701 
(Sleeper) and U.S. Pat. No. 1,279,271 (Sock1). These devices contain 
variable pulleys associated with belt drive power transmission systems. 
Another type of system is shown in U.S. Pat. No. 3,956,944 which discloses 
a variable ratio chain sprocket where a plurality of chain engaging 
segments are slidably affixed first between a pair of discs and are 
constrained to move in a radial direction with respect thereto. There are, 
however, variables in this type of construction that make it difficult to 
precisely adjust the transmission and to avoid excessive wear. More 
recently, a system shown in U.S. Pat. No. 5,354,240 covers a variable 
transmission system utilizing in one embodiment a shifter device with a 
stationary shifter ring, a moveable shifter plate, and an appropriate 
control mechanism for selectively displacing the shifter plate with 
respect to the shifter ring and sprocket. While this patented device 
reflects a relatively new approach to variable speed transmission systems, 
there is a limitation with respect to the range within which the torque 
transmission ratio can vary. 
Thus, there is a need to provide an even more efficient and greater 
variation in the torque transmission ratio range of such transmission 
system. It is to this need that the present application is directed. 
SUMMARY AND OBJECTIVES OF THE INVENTION 
The present invention is a new and improved power transmission system for 
bicycles and other vehicles utilizing a standard fixed axle and rotating 
chain sprocket engaging an endless chain that receives an input torque and 
transmits an output torque. The system includes a transmission ratio 
varying apparatus having a drive collar secured to the sprocket and at 
least one input drive ring and one output drive ring. A drive body is 
displaceable with respect to the input and output drive rings, and input 
and output pawls are pivotally connected to the drive body and engageable 
with the input and output drive ring. A shifter housing is moveable with 
respect to the fixed axle to rotatably shift the drive body with respect 
to the drive ring and change the relationship between the input and output 
pawls. Movement of the shifter housing to change the relationship between 
the input and output pawls changes the torque transmission ratio. The 
system is highly flexible and expandable to encompass a broad range of 
torque transmission ratios. 
From the summary set forth above, it can be seen that a primary objective 
of the present invention is to provide a new and improved power 
transmission system for bicycles and other vehicles which has all of the 
advantages of prior art assemblies and none of the disadvantages. 
It is another objective of the present invention to provide a new and 
improved power transmission system of the type described which utilizes 
input and output pawls that experience a changing relationship with each 
other to be driven by the input drive ring and drive the output drive ring 
and thereby vary the torque transmission ratio accordingly. 
Yet still another objective of the present invention is to provide a new 
and improved power transmission system of the type described which is 
capable of being retrofitted to existing rear axles of the majority of 
standard size bicycles. 
Thus, there has been outlined the more important features of the invention 
in order that the detailed description that follows may be better 
understood and in order that the present contribution to the art may be 
better appreciated. There are, of course, additional features of the 
invention that will be described hereinafter and which will form the 
subject matter of the claims appended hereto. In this respect, it is to be 
understood that the invention is not limited in its application to the 
details of construction and to the arrangement of the components set forth 
in the following description or illustrated in the drawings. The invention 
is capable of other embodiments and of being practiced and carried out in 
various ways. 
It is also to be understood that the phraseology and terminology employed 
herein are for the purpose of description and should not be regarded as 
limiting. Those skilled in the art will appreciate that the concept upon 
which this disclosure is based may be readily utilized as a basis for the 
designing of other structures, methods and systems for carrying out the 
several purposes of the present invention. It is important, therefore, 
that the claims be regarded as including equivalent constructions insofar 
as they do not depart from the spirit and scope of the present invention. 
Thus, the enumerated objectives and others identified hereinafter, along 
with the various features of novelty which characterize the invention, are 
pointed out with particularity in the claims annexed hereto and forming a 
part of this disclosure. For a better understanding of the invention, its 
operating advantages and the specific objectives attained by its use, 
reference is made to the accompanying drawings forming a part of the 
specification in which like characters of reference designate like parts 
throughout the several views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention utilizes a series of gear trains that are added 
together to obtain a desired ratio range for the transmission. While any 
number of gear trains may be used, an example incorporating four gear 
trains within the hub will be depicted herein and described in detail in 
this specification. It is to be understood that the invention can employ 
any number of gear trains added together to increase the ratio range as 
desired. 
Referring now to the drawings and particularly to FIG. 1, a cog 10 of a 
sprocket 12 is fixedly secured to a drive collar 14. Drive collar 14 
contains a first drive ring 16 including an array of teeth on the inside 
diameter which drives input pawl 18 (FIG. 3) as shown. Input pawl 18 
drives a drive body 42 which, in turn, drives an output pawl 22 which in 
turn drives an output drive ring 24. Input and output drive rings 16, 24, 
together with their associated pawls 18, 22 provides the first of a series 
of gear trains which continue until output drive ring 24 is rigidly 
secured in hub 26. 
To describe the apparatus more particularly, a gear train consists of an 
input drive ring 16, drive input pawl 18, which drives output pawl 22 
which drives output drive ring 24. Output drive ring 24 is fixedly secured 
to the next input drive ring 28 through a rigid connection 30 which drives 
the next train. The series of trains continues until the output drive ring 
is secured in hub 26. As the series of trains are added, the overall ratio 
of the transmission is building exponentially. For example, if one train 
is capable of generating 125% of range, then four trains can generate 125% 
to the fourth power (125.sup.4). 
Shifting the transmission system is done by positioning a lever 32 which 
moves a cable 34 that is secured to shifter collar 36. Shifter collar 36, 
when displaced by lever 32 and cable 34, rotates the shifter housing 38 
about axle cam 40. The series of drive bodies 20 are mounted with bearings 
44 on the outside diameter of shifter housing 38. When shifter housing 38 
is rotated, drive bodies 42 with pawls 18, 22 are offset as well. This 
change in radius that drive bodies 42 and pawls 18, 22 have relative to 
input and output drive rings 16, 24 causes the angular velocity of output 
drive rings 24 to be greater than that of input drive rings 16. The 
greater the offset of shifter housing 38, drive body 42 and pawls 18, 22, 
the greater the range of the transmission ratio. 
The power transmission system comprising the present invention is extremely 
efficient and, depending upon the number of trains, minimizes wear on the 
components of the system. The number of trains capable of being used is 
from a minimum of one to an infinite number. 
The power transmission system comprising the present invention has been 
illustrated and described in operable form. It is to be realized that 
optimum dimensional relationships for the parts of the invention to 
include variations in size, materials, shape, form, function and manner of 
operation, assembly and use are deemed readily apparent and obvious to one 
skilled in the art. All equivalent relationships to those illustrated in 
the drawings and described in the specification are intended to be 
encompassed herein. The foregoing is considered as illustrative only of 
the principles of the invention. Numerous modifications and changes will 
readily occur to those skilled in the art, and it is not desired to limit 
the invention to the exact construction and operation shown and described. 
All suitable modifications and equivalents that fall within the scope of 
the appended claims are deemed within the present inventive concept.