Such an industrial and technological quantum leap is rare in watchmaking. Almost ten years after its first research into silicon, in association with the Institute of Microengineering in Neuchâtel (IMT-EPFL) and the Swiss Centre for Electronics and Microengineering (CSEM), Patek Philippe presents its latest innovation: the GyromaxSi®. Coming after the Spiromax® in 2006 and the Pulsomax® in 2008, this balance wheel in gold and Silinvar® – a derivative of silicon – is the final piece in a puzzle by the name of Oscillomax®. This ensemble composes the beating heart of a mechanical watch and is protected by 17 patents or patent applications. It brings together every Patek Philippe silicon component to date: pallet lever, escape wheel, balance spring and balance. So as to fittingly introduce these parts into its collections, the Geneva Manufacture has issued a special, limited-edition watch: the Patek Philippe Advanced Research Perpetual Calendar Ref. 5550P.
A "bow tie" shape
The GyromaxSi® has an unusual “bow tie” shape. Its Silinvar® structure has a discontinuous balance rim, with a 24k gold centrifugal mass at each end, integrated into the chassis using galvanic growth. This combination of very heavy gold and very light Silinvar® reduces mass at the arbor by two-thirds while maintaining a high level of inertia despite the small dimensions. The two sets of gold poising weights can be precision-adjusted. In addition to the absence of lubrication and reduced friction, another advantage of the GyromaxSi® is its improved aerodynamic for reduced air resistance. This is a non-negligible property, given that the balance wheel’s air resistance is responsible for some 60% of friction losses.
Any wrong positioning of the centrifugal masses inevitably results in the substantial imbalance of the balance wheel. This new concept thus requires the absolute manufacturing precision made possible by Deep Reactive Ion Etching (DRIE). Accurate to within one micron, the silicon parts are all rigorously identical in both shape and weight. Their surfaces are perfectly smooth and they require no poising, centring or polishing prior to use. Silicon is transformed into Silinvar® by means of oxidation in a vacuum.
A ten-year history
Research into Silinvar® began in 2001, when discussions between Ludwig Oechslin – now curator of the Musée International d’Horlogerie in La Chaux-de-Fonds – and the CSEM led to trials with silicon balance springs. Progress was slow in these early days, as silicon presented major problems of thermal compensation. The project was close to being shelved until three leading companies – Rolex, Patek Philippe and Swatch Group – stepped in. The result was Silinvar®, a proprietary name of the CSEM. This perfectly homogenous material (mass is evenly distributed) is very light, very hard, amagnetic, corrosion-resistant and insensitive to shocks. The ultimate material for watchmaking!
As Patek Philippe was quick to realise, Silinvar® had even greater potential. Deep Reactive Ion Etching can be use to produce unprecedented forms, which opened up new fields of investigation. Component geometry became a prime factor in improving performance. In 2005, the Geneva firm was first to present a Silinvar® escape wheel that required no lubricant. The following year, it launched the Spiromax® balance spring in the same material. Its integral collet and unusual terminal curve – the “Patek Philippe terminal curve” – contribute to its perfectly concentric development and, in doing so, improve isochronism and therefore rate accuracy. In 2009, Patek Philippe presented the Pulsomax®, the first escapement made entirely from Silinvar®. The pallets are no longer in ruby but Silinvar®, each with its own geometry. The escape wheel was also modified to have not 20 but 16 teeth.
In a perpetual calendar
Since 2005, Patek Philippe has put each of these three innovations to work in an annual calendar, powered by the automatic calibre 324 S IRM QA LU. These special “Patek Philippe Advanced Research” watches have been made as limited editions of 100 to 300, with all three selling out from the time of the launch. The Manufacture has gone further still for Oscillomax® and has integrated these Silinvar® components into its legendary automatic calibre 240 Q, a perpetual calendar. Named the Patek Philippe Advanced Research Ref. 5550P, it combines the very latest advances in technology with a most classic face: a 950 platinum Calatrava case, silvered dial with vertical satin finish, railway minute scale, luminous hour dots, and “leaf-shaped” hour and minute hands.
Of course, it’s on the inside that the Ref. 550P is dressed to impress. In addition to the Spiromax® and GyromaxSi®, calibre 240 Q Si incorporates a substantially improved Pulsomax®: the pallets now have “locking notches” which position the lever ideally just before the next impulse. Improvements have also been made to the escape wheel, which goes from having 16 to 15 teeth. Furthermore, the projections between two teeth softens accidental contact between the teeth and the pallets.
In a traditional mechanical watch, the oscillator-escapement duo absorbs more than 65% of the movement’s energy. The GyromaxSi® alone saves 21%. The revised Pulsomax® increases by 15% to 20% the amount of energy transmitted to the balance. Consequently, whereas the calibre 240 Q has a maximum power reserve of 48 hours, the calibre 240 Q Si increases this to 70 hours. Quite an advancement which, we can rest assured, is only a beginning for Patek Philippe.
Article published in BIPH