One of the successful outcomes of the Patek Philippe Advanced Research project involved a significant reduction of the negative impact of the center – of – mass imbalance on the isochronism of the balance spring itself. A glance at the Spiromax ® balance spring made of Silinvar ® shows that the outer boss is now paired with an inner boss. The outer boss, also referred to as the Patek Philippe terminal curve, improves the isochronism of the balance in all positions by assuring the adequately concentric expansion and contraction of the balance spring. It compensates the disruption of isochronism caused by the escapement and the rotation of the balance regardless of the amplitude. Conversely, the inner boss offsets positional changes of the center of gravity to assure the highest possible rate accuracy in vertical orientations. For the owner, this means that the watch will not run slower or faster regardless of its orientation. The production of hairsprings with the DRIE process guarantees a perfect reproduced geometry, including the positional changes of its center of gravity. Because silicon cannot be deformed, its properties are not affected even when the watch is worn daily. The precisely defined geometry of the inner boss causes a controllable position change of the center of gravity while the spring contracts and expands. This significantly reduces or even eliminates the center – of – mass imbalance of the hairspring during each semi – oscillation. The result is a degree of rate accuracy that exceeds nearly all standards for mechanical watches regardless of their orientation.

Rate precision from Patek Philippe’s perspective

The Patek Philippe Seal imposes very stringent requirements on all of the manufacture’s mechanical watches. The mean rate of movements with a diameter of more than 20 mm must range within – 3 to +2 seconds per day. For Patek Philippe tourbillon timepieces, the tolerance is a strict 3 seconds per 24 hours. Hundreds of repetitive measurements performed by Patek Philippe’s certification laboratories have shown that a mechanical Patek Philippe movement with a Spiromax ® balance spring that has both an outer and an inner boss can be adjusted to a mean rate of – 1 to +2 seconds per 24 hours, which matches the rate accuracy of a Patek Philippe movement with a tourbillon.

Trailblazing technologies for a promising future

The new Spiromax ® balance spring with an inner and outer boss reconfirms the extraordinary benefits of Silinvar ® , the silicon derivative that Patek Philippe launched in 2005 as a world debut. Machining it with the DRIE process allows the geometry of the hairspring to be al tered at any location to systematically influence its oscillation behavior and thus its isochronism. This is an ambitious goal because a precise and dependable rate is an important prerequisite for assuring the successful future of the proud tradition of mechanical timekeeping. For this reason, Patek Philippe’s objective is to gradually integrate the balance spring with this geometry in its current production schedule. But Patek Philippe Advanced Research also extends to other fields as illustrated by the n ext innovation within the framework of this presentation.