Eta Sa Fabriques D'ebauches

Florian Serex

Denis Burdet

Fr&eacute;d&eacute;ric Leuba

The timepiece includes a time base ( ), a generator ( ) formed in particular of a rotor ( ) with permanent magnets and at least one coil ( ), a barrel ( ) with a mainspring coupled to said generator in order to drive it, analogue time indicating means ( ) also driven by said barrel. These time indicating means operate substantially synchronously relative to said time base as long as the torque C provided by said barrel is greater than or equal to a minimum synchronisation torque C . The timepiece also includes means ( ) for braking said generator, magnetised means ( ) having with the rotor, when the generator is stopped, a static positioning torque C allowing said rotor to be kept in a substantially stationary position. The generator braking means are activated as soon as the time indicating means are no longer operating in a substantially synchronised manner with the time base, and the magnetised means are arranged such that the static positioning torque C is greater than or substantially equal to a reference torque C for which the torque C exerted by the barrel on the rotor is equal to said minimum synchronisation torque C .

Timepiece including a generator

In order to adjust the oscillation frequency of a sprung balance intended for or fitted to a mechanical timepiece, in a first step a balance spring is manufactured with a greater elastic torque than a reference torque corresponding to the oscillation frequency provided for the sprung balance. Once the sprung balance is assembled, the balance spring is machined by means of a laser beam to reduce its elastic torque until it substantially reaches the reference elastic torque. In particular, the laser machining consists in removing matter in order either to reduce the height of the balance spring in certain regions, or to reduce the thickness of the strip forming said balance spring. This invention allows conventional regulating means, in particular pins associated with an index, to be omitted. This enables working errors of the timepiece as a function of its position, to be avoided.

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Prêles, Switzerland

Florian Serex