Patent ID: 7382693

Claim:
An instantaneous mechanism for controlling the date indicator of a timepiece movement, comprising: a 24-hour wheel driven by the movement at the rate of one revolution per day and pierced with a first cutout, a date driving wheel mounted to rotate freely on the 24-hour wheel, coaxial therewith, said wheel having a pin which fits into said first cutout and a tooth which collaborates with said indicator to cause it to move on step by step each day at around midnight, and a spring balance collaborating with the pin, these components being shaped, sized and arranged in such a way as to perform the following cycle of operations: a few hours before midnight, the pin begins to act on the balance, then in its rest position, thereby arming its spring, at around midnight, the balance escapes from the pin and returns abruptly to its rest position, throwing forward the pin and the driving wheel whose tooth strikes the date indicator to cause it to move on by one step, and a few hours after midnight, the pin is once again caught by the first cutout in the 24-hour wheel and pushed until, a few hours before midnight, it comes back into contact with the balance, wherein said first cutout is the continuation, in the shape of an arc of a circle concentric with the 24-hour wheel, of a second cutout releasing a spring finger, the first cutout opening onto the end of the spring finger.