LIVE FROM BASEL - PATEK PHILIPPE'S REF. 5204 PERPETUAL CALENDAR SPLIT SECONDS CHRONOGRAPH

THE NEW PATEK PHILIPPE REF. 5204 PERPETUAL CALENDAR SPLIT SECONDS CHRONOGRAPH
By Suzanne Wong

The new Patek Philippe ref. 5204 perpetual calendar chronograph with split seconds function improves on the current iteration of the Patek Philippe 5004 with a fully in-house movement instead of the Lemania base that was previously used. The Lemania CH 27, an industry workhorse which has been used by numerous brands and is still used by Vacheron Constantin, was never meant to support a split seconds chronograph complication. In a previous interview, Patek’s Philippe Stern explained, “We had to create an isolator mechanism to enable the us to create a rattrapante, because with its slow vibrational speed, the CH27 would experience a drop in amplitude each time the split seconds function was activated.” As such, the current movement, the CHR 29-535 is a clearly superior beast, which comes through when the chronograph is activated. There are two new technical innovations which accompany the calibre CHR 29-535.

The split second hand lever is traditionally reset with a hammer that contacts the heart cam on the chronograph seconds wheel and brings the two rattrapante hands back into alignment. In practice, there is often a slight, undesirable, vibration of the split seconds hand when it is brought back to catch up with the chronograph seconds hand. The new rattrapante reset hammer implemented in the CHR 29-535 utilises a smaller ruby roller set between two shoulders that securely locks the position of the split seconds hand when the roller reaches the lowest point of the heart cam on the chronograph seconds wheel. As compared to the previous construction which incorporated a single, large ruby roller at the end of the rattrapante hammer, allowing some slight play of the hammer when it reaches the lowest point on the heart cam (caused jointly by the size of the roller and also the force of the return) the patented roller-and-shoulder construction offers more security and a more precise motion.

The second innovation has to do with the isolator mechanism in the movement that disengages the split seconds lever from the heart cam of the chronograph seconds wheel (hence allowing for the rattrapante function in the first place). Previously the isolator was activated by a multi-armed switcher that rotated unidirectionally to activate or deactivate the split seconds hand. The new CHR 29-535 incorporates a bi-directional switcher that is far more energy efficient as well as providing for a simpler and thinner construction that, ultimately, makes for a smoother (ie better) mechanism.

Thierry Stern reminds us that the brand’s in-house chronograph movement was created from the ground up to be able to sustain a split seconds function. Chief amongst the improvements is the 4Hz (28,800vph) vibrational speed which provides greater resistance to rattrapante drag.




The CHR 29-535 in action



The new isolator mechanism