An innovative bicycle gearbox
The idea
I always thought that the current transmission system for bikes, both for walking and even more for racing bikes, had become obsolete and needed a new transmission system. Since it is a question of transferring the force from the pedals to the rear wheel, the chain or toothed belt is the one that absorbs the least energy at the time of transmission and therefore had to be kept.
The element to be innovated was the gear changing system made up of the traditional sprocket and derailleur set.
This system, presented for the first time at the Milan Fair in 1949, has undergone considerable improvements and effective gear changing systems but has never solved the problem of chain alignment between the front crown and rear sprockets. In fact, it happens that with a certain front gear the opposite rear sprocket is inadvisable, since the chain has to work in strong misalignment. Because of this, the chain undergoes strong and constant lateral stresses; this requires its replacement over time.
In systems dedicated to competition, it may be necessary to mount a new chain every time.
Furthermore, it is far from unusual for the chain to come out of the sprocket, creating quite a few inconveniences for the unfortunate cyclist.
So, how can the transmission system be innovated and overcome the limits of the traditional system based on the sprocket set and the relative derailleur?
In other words, is it possible to change gears while keeping the chain substantially aligned between the front chainring and the rear sprocket?
The challenge
Guided by the ultimate goal of creating a gear change that kept the chain aligned, it was an essential consequence that the movement should concern the individual sprockets and not the chain which had to slide in the centre.
Inspired by this vision, the project takes a precise direction but a series of questions immediately emerge.
How to make a guide that would force the chain to always slide aligned?
And above all with what mechanism to exchange the ratios to intercept the chain that runs and remains aligned in the center?
It was not possible to simply move the sprocket set because it would have taken up too much space next to the wheel (at least double the thickness of the current sprocket set).
While there are some designs that translate the sprocket set, these have never had practical application.
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The intuition
The individual sprockets are of different diameters and this allows you to create a cassette where the smallest sprocket "enters" the largest sprocket. (see figure alongside)
In order to keep the chain in the center, two opposing cassettes have been created with different diameters of the contained gears which force the chain to slide aligned.
To simplify the description here reference is made to a 4-speed gearbox located on the rear wheel. Such a 4-speed gearbox will contain gear #1 and #3 on the right cassette and #2 and #4 on the left cassette. Of course, gear no. 1 will have fewer teeth than gear no. 2 which will have fewer teeth than gear no. 3. Gear no. 4 is the one that will have the greatest number of teeth.
To force the chain to slide in the middle aretwo cages have been set up: one right and one left, inside which the gears are housed.
The project
All solved? Not at all!
The idea and intuition alone are not enough, you need to get to work and start designing.
So staying in the previous example we have two gear boxes while the chain runs in the center. Of the four cogs that make up our example shifter one will be positioned in the center and connect with the chain while the other three are inactive and find their place within their respective cassette.
The smallest ratio of each cassette works alone while the largest ratio drags with it the one with the least number of teeth, anchored to the rotation pin.
We have already described how only one cog will be positioned in the center between the two cassettes while the others find their idle position within the cassette.
A spacer ring will have the function of pushing the cog in the center to rest while the cog of the opposite cassette takes over.
But how to determine the thrust using only the rotational force of the gearbox?
In fact, the design has pursued the goal of not using external forces or subtracting force from the pedaling for the movement of the gears to make this system also suitable for racing bikes. In this context, the need is felt more not to disperse the pedaling force that is transmitted optimally only when the chain slides substantially aligned.
Here the challenge was really big, and the solution was found by applying three concentrically rising orthogonal lateral 'ridges' to each chainring. Three wheels, appropriately positioned by a cam mechanism, will complete the operation of pushing the chainring by exploiting the rotation of the rear derailleur itself.
The patent
The patent application was filed in Italy on February 2, 2022 and accepted with the number 102022000001736 entitled GEARBOX AND TRANSMISSION SYSTEM OF HUMAN OR MIXED PROPULSION VEHICLE AND BICYCLE.
Subsequently, an international patent application PCT n.PCT/IB2023/050876 was also filed, published under no. WO2023/148630A1
With no other invention is the useful so intimately connected with the pleasant
like with the bicycle. (Adam Opel)
Life is like riding a bicycle.
You have to move to keep your balance. (Albert Einstein)
Contact us
For information and requests for licensing or transfer of the Patent, contact the Law Firm
Lawyer Massimo Maccagnani
+39 051 306258
Bologna - ITALY
The lawyer Massimo Maccagnani deals with the protection of industrial and intellectual property, to which Giuseppe Malavolta, inventor and patent holder, has given the mandate.