THE SLIDING CLAMP

The sliding clamp is a safety device integrated into certain barrel springs. Its outer end, instead of being fixedly attached to the inner wall of the drum, is attached by a clamp that can slide against this wall once the spring is fully wound. This controlled slipping prevents the tension of the spring from exceeding a mechanical limit, thus preventing it from breaking due to overtension in the event of excessive winding. This system is essential in automatic watches, where the oscillating weight (rotor) can put strain on the spring continuously without the wearer’s intervention.

This device contrasts with the older solution of the winding stop, which physically blocks the crown once the spring is fully wound and exposes the winding mechanism to greater stress in case of forced winding. With a sliding clamp, only the very last degree of winding causes slipping: the rest of the power reserve remains fully usable, without any noticeable loss of autonomy for the wearer.