The transmission device disclosed is inserted between a rotating oscillating weight and an electric micro-generator in order to drive the generator rotor from the oscillating weight by multiplying the rotational speed. Its intermediate wheel and pinion includes a barrel (27) whose central shaft (24) is coupled to the drum (41) of the barrel by a spiral spring (30). The inner end of the spring has a bent portion (34) which engages via resilience in any one of a number of hollows (51) in the shaft and can be released by sliding over a slanting side (52) when the shaft exerts too great a torque in the given rotational direction. This arrangement prevents damage resulting from shocks, in particular in the case of a watch, without using a friction system.