Winding mechanism of a timepiece comprising at least one first power accumulator provided in order to supply a first mechanism with power and a second power accumulator provided in order to supply a second mechanism with power, said winding mechanism comprising a winding stem, a winding pinion and a sliding pinion carried by said winding stem and having face gear toothings, facing one another, provided in order to allow driving of the winding pinion by the sliding pinion in the two directions of rotation of the winding stem, said winding stem and the sliding pinion occupying a same axial winding position, the winding mechanism comprising a coupling device which cooperates with the winding pinion and is provided in order to occupy a first coupling position for coupling the winding pinion and the first power accumulator when the winding stem is turned in one direction, the second power accumulator being uncoupled, without any contact with said coupling device, and a second coupling position for coupling the winding pinion and the second power accumulator when the winding stem is turned in the other direction, the first power accumulator being uncoupled, without any contact with said coupling device, wherein the coupling device comprises a crown wheel which cooperates with the winding pinion and on which a coupling lever is mounted, carrying a driving pinion provided in order to be able to connect kinematically the crown wheel to one or other of the first and second power accumulators (3, 5), said coupling lever being mounted freely on the crown wheel and the driving pinion being mounted frictionally on the coupling lever: - so as to pivot integrally with said crown wheel into the first coupling position in order to connect cinematically the driving pinion to the first power accumulator, the driving pinion being provided in order to be able to mesh with a first ratchet which cooperates with the first power accumulator, when the driving pinion is in contact with of the first ratchet of the first power accumulator, the coupling lever is prevented from continuing to pivot and the driving pinion separates from the coupling lever due to friction, allowing driving of the driving pinion by the winding pinion via the crown wheel in order to wind the first power accumulator when the winding stem is turned in a first direction, and - so as to pivot integrally with said crown wheel into the second coupling position in order to connect cinematically the driving pinion to the second power accumulator, the driving pinion being provided in order to be able to mesh with a second ratchet which cooperates with the second power accumulator, when the driving pinion is in contact with of the second ratchet of the second power accumulator, the coupling lever is prevented from continuing to pivot and the driving pinion separates from the coupling lever due to friction, allowing driving of the driving pinion by the winding pinion via crown wheel in order to wind the second power accumulator when the winding stem is turned in a second inverse direction. - so as to pivot integrally with said crown wheel into the first coupling position in order to connect cinematically the driving pinion to the first power accumulator, the driving pinion being provided in order to be able to mesh with a first ratchet which cooperates with the first power accumulator, when the driving pinion is in contact with of the first ratchet of the first power accumulator, the coupling lever is prevented from continuing to pivot and the driving pinion separates from the coupling lever due to friction, allowing driving of the driving pinion by the winding pinion via the crown wheel in order to wind the first power accumulator when the winding stem is turned in a first direction, and - so as to pivot integrally with said crown wheel into the second coupling position in order to connect cinematically the driving pinion to the second power accumulator, the driving pinion being provided in order to be able to mesh with a second ratchet which cooperates with the second power accumulator, when the driving pinion is in contact with of the second ratchet of the second power accumulator, the coupling lever is prevented from continuing to pivot and the driving pinion separates from the coupling lever due to friction, allowing driving of the driving pinion by the winding pinion via crown wheel in order to wind the second power accumulator when the winding stem is turned in a second inverse direction.