How it works

The transmission described in this section is only one example, and there are number of different ways to implement the principle. The explanations below show a belt, which is always a synchronous belt with teeth. It could of course also be a bicycle chain.

The basic principle consists in synchronizing a gear tooth just before it arrives in contact with the belt, by making it turn faster than the belt until the gear tooth may cooperate perfectly with one tooth of the belt. This faster turning speed is made possible because there is a free-wheel between the primary shaft and each gear tooth.

The V-belt pulleys

Each V-belt pulley is divided into three sectors, and each of these sectors transmits the rotation of the primary shaft to the corresponding gear tooth. More in detail, the primary shaft transmits its rotation movement to a freewheel, which in turn transmits it to the relevant V-belt pulley sector, and this V-belt pulley sector transmits it to the relevant gear tooth through a gear slide.

It is important to understand that the V-belt pulleys are used only for the purpose of maintaining the circularity of the belt or chain, and do not transmit any torque. The torque is transmitted only by the gear teeth.

Thus, two gear teeth can be engaged at the same time while having a rotating radius which varies.

When transmitting the torque to the belt, a gear tooth always has an angular speed which is that of the primary shaft. Thus, there is no friction between a tooth and the belt

The linear speed of the belt is therefore always equal to this angle multiplied by the rotating radius of the tooth.

As the radius can vary completely freely, continuously, without any problem, this means that the linear speed of the belt may also vary continuously.

The tooth synchronization

The question to be solved at this stage was therefore how to ensure that continuous variation is not a problem.

Except in the case where the radius is such that the circumference of the gear is a multiple of the pitch of the tooth of the belt, the next tooth (yellow) has no reason to arrive in front of a tooth of this belt.

An essential characteristic of the device, a gear tooth

If necessary, it is rotating faster just before it comes into contact with the belt. This is why there is a synchronization mechanism, which is represented here as a spring (purple) but which could quite possibly be a set of magnets or a small computer-controlled electric motor, depending on the effective radius to obtain the same result.

This mechanism moves the gear tooth faster than the belt until it may cooperate precisely with a tooth of the secondary shaft, without any friction or conflict.

As soon as it is inserted between two teeth of the belt, the gear tooth which cannot rotate slower than the primary shaft (this is the direction forbidden by the free-wheel) also starts to transmit its rotation movement to the belt at the angular speed of the primary shaft.

Unlike the toothed plate of a bicycle whose radius varies discontinuously but whose distance between two teeth is always fixed, the radius of this new gear changes continuously because the distance between two teeth may vary continuously.

The automatic adaptation of the gear ratio to the resistant torque

This is another major advantage of this invention.

It can be obtained when the gear slide is not a radius as shown in the previous diagrams, but a curve, for example a spiral as shown in the diagram below, where the angle of the spiral with the radius is constant at 40.

When the resistive torque is important, it leads the gear tooth to move either towards the primary shift or in the opposite direction, depending on the shape of the spiral.

An elastic return (not shown) opposes this displacement, and and this elastic force can be freely determined by the designer of the transmission as a function of the maximum torque of the motor for example. It can also be modified during operation according to any parameter.

It will be understood that, with this new organization, it is possible to determine, as desired, the modification of the radius as a function of the resistive torque.

In the above diagram, on may notice that one side of the slide has been crenelated. This makes it possible to favor certain locations, for example those for which the circumference of the secondary gear (the belt) is exactly a multiple of its pitch. The resisting torque will have the effect of automatically placing a gear tooth in one of these privileged positions. The advantage of favouring a radius where the the circumference of the secondary gear is exactly a multiple of its pitch is that there is absolutely no movement inside the gear during its rotation.

This diagram shows another synchronization method, where the synchronization teeth are arriving in contact with the belt before the relevant gear tooth and not after as the spring shown at the top of this page.

Next page: The first internal disclosure which happened in October 2016