This mechanical system aims to reduce the rotational speed of a shaft, like a gearbox. This kind of system is used in many different sectors, such as machine tools and automobiles, in order to have an adapted speed and torque on the output shaft. There are two major types of gearboxes. The first one is CVT (Continuously Variable Transmission) which can change seamlessly through a continuous range of effective gear ratios. But this type, based on friction transmission, is limited because of the wear on the belt.

Left: example of a CVT designed for cars. Right: principle of a variator (from wikipedia).

The second type of transmission involves cogwheels. There are many different ones including the chain drive and cogwheels (right or slanted). They are all transmitting the force through obstacles opposed to CVT. The speed reduction for the most famous system, the cogwheel, is the ratio of the two diameters of the sprocket-wheels. But the main limitation of the system is that it requires a clutch in order to decrease the torque to shift the gears.

Left: typical design of a gearbox. Right: illustration of cogwheels (from wikipedia).

The goal of the proposed system here is to avoid a clutch and avoid friction between materials. The following figures illustrate the system. The left image shows an elementary design where we can clearly see how it works. The right image is the 3D plot of the paths of each groove.

The system starts with the low gear, then shifts to the high gear.
Plot of the grooves: the input and output are shown in green and red, respectively, and rotate around the vertical axis. The blue circle shows the part with pins.

The design presented in the patent, and illustration at the top of the page, includes a system to shift gears. The shift is simply triggered and driven by the rotation of parts.

P.-L. Valdenaire, Mécanisme réducteur de vitesse angulaire, March 2017, FR3041731