Mechanical principles › Complications › Strikes

LES SONNERIES D’HORLOGE

The strike, along with the display of time, constitutes one of the two fundamental functions of the mechanical Clock. From the appearance of the first foliot movements in the Middle Ages, horologists sought to sound the hour by means of a chime or a bell, thus complementing the visual reading of the Dial with an audible signal. This function meets an obvious practical need before the widespread use of artificial lighting: it makes it possible to know the time at night, at a distance, or without consulting the dial.

Technically, striking the hour requires solving a specific mechanical problem: how to transform an angular position, that of the Hand hours, in a defined number of hammer strikes on a chime or Bell? Several solutions have succeeded one another over the centuries, each corresponding to a different compromise between simplicity of manufacture, cost, reliability, and precision.

The oldest movements, equipped with a Escapement with a verge wheel, relied on a delay-free mechanism actuated by a trigger, a simple but improvable solution. In the 17th century, the count wheel strike, or rack strike, became widespread in France, introducing a preparation Time, the delay, before the counting of the strikes. In 1676, the English Horologist (watchmaker) Edward Barlow invented the rack strike, where the number of strikes is directly read on a Snail (cam) attached to the Hour wheel, a principle that would become the standard for quality clocks and repeater watches.

This section presents these three families of striking mechanisms: the striking mechanism with a locking plate delay, the striking mechanism with a rack delay, and the striking mechanism without delay using a trip lever. For each, the operating principle, characteristic components, and historical context of their spread are detailed.

STRIKE WITHOUT DELAY WITH TRIP MECHANISM

The strike mechanism without delay with trip action is the oldest and simplest of the three: it was already fitted to movements with verge Escapement, before the widespread adoption of systems with locking piece and rack. Unlike these, it has no preparation phase (delay).