Imagine butterfly wings framing a rhythmically flexing blade. Imagine wheels and parts pivoting and moving behind the undulating movement of this violet-coloured insect. Together they form the Constant Escapement – named after Constant Girard, father of the brand – an innovation now integrated into a timepiece unveiled in March, in Zurich. The Manufacture had already lifted the veil on this revolutionary regulator, still at the prototype stage, back in 2008. Since then, the engineers and watchmakers at Girard-Perregaux have been working to ensure the system’s complete reliability and to normalise production. This new escapement delivers a unique and genuinely innovative concept, made possible by silicon technology.
Girard-Perregaux Constant Escapement
Ever since mechanical watches have existed, watchmakers have racked their brains to resolve the fundamental question of how to deliver power from the mainspring at a consistently precise rate. A number of solutions have come close, some very close even, but so far none had fully overcome the problem.
Now it seems that Girard-Perregaux has come up with the answer by applying a physical principle that had never been tried in watchmaking before: buckling. A part – an ultra-thin blade in the case of the Constant Escapement – is flexed to a point of instability. At this degree of tension, the lightest impulse is enough to cause the part to change shape. An impulse in the opposite direction returns it to its original shape, and so on.
The engineers at Girard-Perregaux have found a way to use and control this physical property and, in doing so, develop a new type of constant-force escapement. The shape of the blade is such that it releases a precise and constant amount of energy at each pulse, regardless of the tension in the mainspring. It automatically stops when there is no longer sufficient energy available to flex the blade, thereby eliminating the steady decrease in amplitude that occurs with most other regulators as the mainspring unwinds.
The heart of the Constant Escapement is a 14-microns thick blade that is part of the “butterfly wing” frame. Both frame and blade are made from silicon. Working hand-in-hand with the Centre Suisse d’Electronique et de Microtechnique in Neuchâtel, Girard-Perregaux developed the specific form of the blade which was then manufactured using UV-LIGA and DRIE techniques, the only means of achieving this distinctive wave-like shape which, as it moves from one position to the other, imparts its rhythm to the balance Wheel.
After the first prototype was revealed, extensive research focused on improving the system and ensuring its complete reliability. “While the concept hasn’t changed, numerous adjustments and improvements have been made,” Xavier Markl, marketing director at Girard-Perregaux, explains. “The structure of the silicon escapement spring [the frame] has been modified and patented, which required major investment. We also conducted additional research into the blade buckling system. New escape wheels have increased performance and reliability. The Constant Escapement is a completely revolutionary system. Nothing else in watchmaking even remotely resembles it, meaning developers had to progress through trial and error.”
Not just the form of the Constant Escapement set a challenge for the teams at Girard-Perregaux. They also had to find a means to measure its performance. Conventional testing instruments, such as by Witschi, calculate rate based on the beat noise of the escapement and could not be used here. Instead, controls were carried out by filming the escapement with a highly sophisticated camera.
Girard-Perregaux also used the five years since the first prototype to develop its first proprietary movement incorporating the new escapement. “We wanted an extended power reserve that would highlight the escapement’s performance, hence this first calibre has four drums containing a total three metres of spring!”
Although trials have been conducted at higher frequencies, the first watch in the new Constant Escapement Haute Horlogerie collection beats at 3 Hz to give a clear view of the regulator in motion. Some ten watches should be ready for delivery by the end of the year. ■