Variable-speed epicyclic gearbox for an aircraft propulsion system

An aircraft propulsion system, comprising:

• a thermal engine;
• a gearbox that includes an input shaft, an output shaft, a drive gear, a ring gear, a first layshaft assembly, and a ring gear rotational control device, the input shaft driven by the thermal engine, the drive gear and the ring gear coupled with the output shaft, the drive gear, the ring gear, and the output shaft rotatable about an output shaft rotational axis,
• the first layshaft assembly extending along a first layshaft rotational axis and including a first layshaft and a first layshaft input gear, the first layshaft input gear engaged with the drive gear and the input shaft, and
• the ring gear rotational control device including a first variable drive assembly coupled with the first layshaft, the first variable drive assembly including a first ring gear drive engaged with the ring gear, the first ring gear drive rotatable about the first layshaft rotational axis, the first variable drive assembly configured to drive rotation of the first ring gear drive with the first layshaft and drive rotation of the ring gear with the first ring gear drive;
• and
• a propulsion unit driven by the output shaft.

A method for driving a propulsion unit of an aircraft propulsion system, the method comprising:

• driving an input shaft with a thermal engine;
• driving an output shaft about an output shaft rotational axis with an epicyclic gear arrangement coupled with the input shaft by a first layshaft assembly, the epicyclic gear arrangement including a sun gear, a plurality of planet gears, a ring gear, and a carrier, the sun gear coupled with the first layshaft assembly, the plurality of planet gears engaged with the sun gear and the ring gear, the carrier mounted on the plurality of planet gears, the carrier connected to the output shaft;
• further driving the output shaft by driving the ring gear to rotate about the output shaft rotational axis with a ring gear rotational control device including a first variable drive assembly coupled between the first layshaft assembly and the ring gear, the first variable drive assembly including a first ring gear drive engaged with the ring gear and rotatable about the first layshaft assembly;
• and
• driving the propulsion unit with the output shaft.