Girard-Perregaux reinvents the escapement

One word was on everyone’s lips, behind the scenes at the Girard-Perregaux stand at this year’s Salon International de la Haute Horlogerie: Constant, the name of one of the brand’s pioneers and that of the new escapement that is expected to make its contribution to mechanical watch precision. “As an entrepreneur,” explained Luigi Macaluso, Chairman of Sowind and owner of the brand, “I couldn’t help but be charmed by the approach to this new escapement, which our engineer Nicolas Déhon came up with while sitting in a train, playing with his ticket. Who hasn’t whiled away time bending their ticket between thumb and forefinger, then flicking the curve back and forth? Well this was the starting-point for our Constant escapement. Quite a stretch of the imagination, and I have to admit I took some convincing but the result is there: a completely different escapement from anything that currently exists, and which works. For the moment we have twenty working prototypes and expect to fit our first models with the Constant escapement as of 2010.

Five years' R&D

It will have taken a large dose of perseverance over these past five years, as the Constant escapement could only become reality, and fulfil its regulating function, thanks to the use of silicon, its base material, and to the development of brand-new technology that made it possible to machine parts to within a micrometer: the escapement’s blade spring is no thicker than a human hair. Silicon’s properties – lightweight, non-magnetic, high elasticity and excellent friction coefficient requiring no lubricant – were decisive in seeing through a project that relies on deep etching techniques. For the Manufacture, this represents a major breakthrough in chronometry as the Constant escapement must maintain constant amplitude and rate until all the energy has been supplied to the balance; a pre-requisite for extreme precision in a movement.

So much for the theory, how does this technological “trick” work? The Manufacture explains: “In their quest for precision, the greatest watchmakers have spent years searching for ways to improve the escapement. This mechanism, placed between the gears and the regulating organ, supplies the balance at regular intervals with energy stored in the mainspring. Its precision and its reliability are strategic for chronometry.”

New realms of possibility

In order to solve this equation, Girard-Perregaux set about inventing a mechanism with five constituent parts, the most strategic of which is the escapement spring with its famous silicon blade, machined in a single block with its butterfly-wing frame. Made to buckle (think back to that train ticket), this blade can be likened to a veritable micro-accumulator of energy as each time the oscillator vibrates, it stores then releases the energy needed to maintain the balance’s amplitude at a constant rate regardless of the power reserve (which is, by definition, variable). “Furthermore, like a lever escapement it has the advantage of providing two impulses per oscillation whereas previous attempts at constant-force mechanisms gave only one,” adds Girard-Perregaux.

“From the initial inspiration to the first ‘tick-tock’ of the prototype, the project went through countless ups and downs,” the Manufacture admits. “And this is just the beginning. The Constant escapement is a technological innovation which opens up a new realm of possibilities for producing mechanical watches with unprecedented chronometric potential.” Rendezvous in 2010.