The Patek Philippe Caliber 240 is fast approaching its half-century anniversary, as its first beat is dated 1977, within the reference 6006.
No one understood it well, in fact, but at that distant Basel Salon, a movement destined to make history was unveiled. The movement rotated the fine gold hour and minute hands of the Ellipse d'Oro men's wristwatch, an elegant model distinguished by its unusual shape and particularly slim architecture. Despite its reduced thickness, the watch did not require manual winding, as was usual for ultra-flat watches of the time, but possessed automatic winding.
At the height of the watchmaking crisis, when the advent of quartz was shaking the foundations of Swiss industry, the Geneva-based manufacturer had dared to invest in a new mechanical movement, thus defending a tradition of more than five hundred years.
In 1976, when Philippe Stern was about to take over as director of Patek Philippe, the world-renowned Swiss watch industry was going through a difficult period. The Stern family had taken over the company from the founders' descendants in 1932, in the difficult period following the Great Depression of 1929; it fell, therefore, to Philippe Stern and his father, President Henri Stern, to ferry the manufacture through a crisis that threatened to bring the entire branch to its knees. Some companies were converting to the production of quartz watches and were beginning to dispose of part of their fleet of machines. The Stern family, however, had always been a voice outside the mainstream. In the late 1960s, Patek Philippe had helped develop the legendary Beta 21 quartz movement, so the company was familiar with this technology, but its heart still beat for noble mechanics.
Elegance a guarantee for the future
In 1976, the manufacture's president Henri Stern and future director Philippe Stern conceived a bold plan: to develop a highly elegant self-winding movement that could surpass quartz movements, not so much at the level of running precision or even in the affordable segment, but with respect to the unquestionable criteria of beauty, reliability, durability and intrinsic value. Both were convinced of the imperishable character of the values inherited by Antoine Norbert de Patek and his partner Jean Adrien Philippe, destined to outlive entire generations of men and technologies. Thus, in the midst of the watchmaking crisis, with great courage and entrepreneurial spirit, they invested in the creation of a new self-winding mechanical movement. This caliber had to be extremely thin to enable the creation of flat watches of undeniable elegance. A result impossible to achieve with a central rotor. Yet in just six months, the first prototype was already on Philippe Stern's desk. Its main feature was the off-center mini-rotor entirely embedded at the level of the bridges. Thanks to this architecture, its thickness did not exceed that of a flat hand-wound movement.
The small planetary rotor, of course, could not offer the same performance as a large, heavy central rotor in terms of charge. But the team's engineers, led by Gérard Berret, found the solution. The 22-carat gold gave the mini-rotor superior mass, the unidirectional winding reduced losses due to friction by eliminating the reverser, and the brand-new gear train with optimized tooth-level geometry and polished teeth made it possible to further improve the transmission of energy from the winding to the barrel, and from there to the escapement. The use of a balance frequency of 3 Hertz (21,600 vibrations per hour) served to decrease the movement's energy consumption by an additional 20 percent, compared to movements at 4 Hertz. The future would prove the soundness of this choice: all movements based on Caliber 240 beat at 3 Hertz and with a rate accuracy that meets the criteria of a chronometer.
The basis of a large family of movements
Caliber 240 began its career in 1977 inside the ultra-flat Golden Ellipse Ref. 3738 with hour and minute hands. In this form, it has been beating since 2001 in the classic Calatrava Ref. 5120 watches with Clous de Paris bezel and since 2014 in the Calatrava for ladies Ref. 7200 with Officier case. Moreover, in its forty years of existence, it has proven to be the ideal "engine" for numerous additional functions.
In 1985, it was distinguished by the name Caliber 240 Q (Calanderio Perpetuo), only 3.75 mm thick, in the legendary ultra-flat perpetual calendar Ref. 3940, the progenitor of a long series of elegant timepieces.
It was used in 1991 inside Ref. 5000, where Caliber 240 PS was distinguished by the unusual position of the small seconds between 4 and 5 o'clock. In 1994, Ref. 5015, equipped with the same small seconds but also with moon phases and power reserve indication, marked the history of the manufacture as the first model in the "useful complications" range. Caliber 240 PS IRM C LU has, in addition, animated from 1997 to 2004 the legendary Ref. 5055 with its large polished smooth bezel.
The Universal Hour Ref. 5110 (caliber 240 HU) of 2000, the Celestial Ref. 5102 (caliber 240 LU CL C) of 2002, the First Complicated Nautilus Ref. 3712 (caliber 240 PS IRM C LU) of 2005, and the Ladies First Perpetual Calendar Ref. 7140 of 2012 represented as many chapters in the history of this mechanism and were received with great success by the public and professionals, demonstrating the versatility and reliability of the base caliber 240.
This movement has found its place, since 2008, in the spectacular Calatrava "Squelette" Ref. 5180/1 with Caliber 240 SQU entirely openworked and hand-engraved to offer the eye maximum transparency.
The 240 caliber to support innovation
Throughout its history, Caliber 240 has undergone several optimizations, while retaining its main basic features at the level of its architecture. It still beats at a frequency of 21,600 vibrations per hour, but is equipped with the Spiromax balance spring in Silinvar, patented and manufactured by Patek Philippe, which further improves its precision. The tooth profiles of the gears have also been optimized to reduce wear and improve the running of the timepiece, benefiting winding autonomy and long-term reliability. Within the Ref. 5550 "Patek Philippe Advanced Research" perpetual calendar, Caliber 240 welcomed a decisive innovation in 2011: the Oscillomax regulating organ. This ensemble, consisting of the Spiromax balance spring, Pulsomax escapement (anchor and anchor wheel in Silinvar) and GyromaxSi balance in Silinvar and 22-carat gold, enabled unprecedented values in precision to be achieved, and the winding autonomy increased from 48 hours in the standard Caliber 240 to over 70 hours.
