Press release BASELWORLD 2006 Patek Philippe, Geneva
March 2006
Patek Philippe presents the SpiromaxR balance spring - a patented invention that improves the isochronism of mechanical watches.
A year after the launch of the first Swiss lever escapement with a silicon escape wheel (patent application No. EP05006186), Patek Philippe presents an additional fundamental innovation: the SpiromaxR balance spring made of SilinvarT. It is an epochal step forward in the constant quest for isochronism in portable mechanical watches. On the occasion of Baselworld 2006, the Geneva workshops will showcase the first watch with this innovation in a second limited "Patek Philippe Advanced Research" edition: the Ref. 5350 with a SpiromaxR spring and a silicon escape wheel. Isochronism is the key to every measurement of time based on any form of vibration. The greater the regularity of the vibration, the better the movement can be adjusted to achieve a high rate accuracy. If the source of the vibration is perfect, it is called isochronous. The key factors that disrupt isochronism are:

The asymmetry of the expansion and contraction of the balance spring changes of the elasticity of the spring in response to temperature changes
. magnetic fields
. the spring attachment points
. centrifugal forces and gravity
. inadequate balance-wheel poise
. the play between the curb pins
Ever since the spiral balance spring emerged, countless attempts have been made to eliminate its anisochronism. The history of the so-called hairspring is characterized by four milestones:
. 1675 - Invention of the balance spring by Christiaan Huygens:
theoretically isochronous
oscillator
. 1795 - Invention of the Breguet spring with Phillips curve: concentric
development of the
spring
. 1897 - Invention of Invar by Charles Edouard Guillaume: balance springs
made of an alloy
that offsets the influence of temperature changes
. 2005 - Invention of the SpiromaxR balance spring by Patek Philippe:
temperature
compensation and concentric development of a flat spring

A new milestone: the SpiromaxR spring by Patek Philippe
SpiromaxR is a totally new type of balance spring made of SilinvarT, a revolutionary material based on monocrystalline silicon. It was developed jointly with two partners in the Swiss watch industry and a leading research institute. But it is not the material that prevents the asymmetric development of the spring. To make it breathe concentrically, the fundamental research department at Patek Philippe developed a new terminal "curve" design. The patented "Patek Philippe terminal curve" exhibits a discernibly thicker region at the outer end, forcing a concentric development upon the SpiromaxR spring. This causes the expansion and contraction of the spring to be symmetric relative to its center over the entire plane of oscillation. And because the "Patek Philippe terminal curve" lies within this plane, the SpiromaxR spring can be crafted three times thinner than a spring with a Philips or Breguet overcoil, thus facilitating the construction of ultra-thin movements.

The SpiromaxR spring exhibits additional important design features. In the center, it has an integral self-centering balance staff collet with which it is attached to the balance staff. At the outer end, it has an integral stud attachment geometry which precisely defines the active length of the spring. With its revolutionary SpiromaxR spring, Patek Philippe has created an oscillating element that unites several decisive advantages. The active length of the SpiromaxR spring does not need to be painstakingly adjusted for each individual movement. The SpiromaxR spring vibrates with ideal concentricity even without an overcoil. It is designed to be isochronous regardless of the temperature, the orientation of the movement, or the presence of magnetic fields. The Patek Philippe terminal curve, the self-centering collet and the integral stud attachment are proprietary to Patek Philippe and patent registrations have been filed. SpiromaxR springs: consistently identical quality As is the case with the silicon escape wheel, the SpiromaxR spring is manufactured with the photolithographic Deep Reactive Ion Etching (DRIE) process. The material exhibits a contiguously homogeneous monocrystalline structure and can be machined to tolerances in the micrometer range. Accordingly, all SpiromaxR springs are of consistent, extremely high quality, a fact reflected by the remarkable rate accuracy of movements equipped with them.

The Patek Philippe SpiromaxR spring at a glance
Produced from monocrystalline silicon by deep reactive ion etching (DRIE)
. Concentric development thanks to patented geometry (Patek Philippe curve) for improved isochronism despite flat topology
. Antimagnetic
. Temperature compensation based on the material properties of SilinvarT
. Integral stud attachment end (Patek Philippe patent)
. Integral self-centering balance staff collet (Patek Philippe patent)
. No thermal or mechanical deformation at attachment points, contrary to
conventional springs
. More homogeneous material structure than Invar alloys
. Less internal friction and greater elasticity than Invar alloys
. Insensitive to minor shocks
. Reduced sensitivity to centrifugal and gravitational forces because the
SpiromaxR is three
times lighter than conventional springs
. No degradation of rate accuracy as a result of repetitive minor shocks in
daily use
. Complies with NIHS standards on randomized shocks
. Fulfills the criteria of the Geneva Seal


The first Patek Philippe watch with a SpiromaxR spring: the Ref. 5350 Annual Calendar in a limited "Patek Philippe Advanced Research" special edition A pioneering invention like the SpiromaxR spring deserves to be showcased. A second limited "Patek Philippe Advanced Research" edition of the self-winding Annual Calendar Ref. 5350 in 18K rose gold is therefore being launched on the occasion of Baselworld 2006. Its caliber 324 S IRM QA LU is the first movement fitted with a SpiromaxR spring made of SilinvarT. As a further exclusive feature, it is also equipped with a silicon escape wheel. To do justice to these technical innovations, the movement has a specially shaped balance cock that reveals a large portion of the SpiromaxR spring and the going-train bridge is milled so that the mysterious blue-violet sheen of the nearly black silicon escape wheel is more readily visible. Additionally, the sapphire-crystal back has an integrated loupe and bears the inscription "Patek Philippe Advanced Research." The solid 21K gold winding rotor features a zirconium ball bearing. Like the silicon escape wheel, the balls run dry and never need to be lubricated. The edition of this "Patek Philippe Advanced Research" model, the Ref. 5350R, is limited to three hundred watches.


Technical data
Patek Philippe Ref. 5350 in rose gold

Movement: Caliber 324 S IRM QA LU
Self-winding mechanical movement, Annual Calendar, moon
phase and power-reserve indicator

Diameter: 32.00 mm
Height: 5.30 mm
Number of parts: 355
Number of jewels: 36
Power reserve: Max. 45 hours
Winding rotor: 21K gold central rotor, unidirectional winding

Balance: Gyromax
Frequency: 28,800 semi-oscillations per hour (4 Hz)
Balance spring: SpiromaxR - (3 Patek Philippe patents)
Escape wheel: Silicon

Functions: Two-position crown:
- Pulled out: to set time
- Pushed in: to wind watch

Displays: Hours, minutes, and sweep seconds
Power-reserve indicator at 12 o'clock
Subsidiary dials: - Day of week at 9 o'clock and month at 3 o'clock

Apertures:
Date at 12 o'clock, moon phase display at 6 o'clock
Corrector buttons . At 10 o'clock: day-of-week correction
. At 2 o'clock: month correction
. At 4 o'clock: date and month correction
. At 8 o'clock: moon-phase correction
Included: correction stylus in ebony and 18K rose gold

Hallmark: Geneva Seal
Milled balance cock and going-train bridge
Features
Case: Case in 18K rose gold, water-resistant screw-down crown
Water-resistant to 25 meters
Special feature: Screwed sapphire-crystal case back, with an integrated
loupe and
engraved "Patek Philippe Advanced Research" inscription
Case dimensions: Diameter: 39 mm
Thickness: 11.70 mm
Width between lugs: 20 mm

Dial: Silvery gray
3 applied Breguet-style numerals in 18K rose gold, at 3, 9, and 12 o'clock
Eight applied baton hour markers in 18K rose gold
Leaf-shaped hour and minute hands in 18K rose gold with luminescent coating
Leaf-shaped day-of-week, month, and power-reserve hands in 18K rose gold
Counterbalanced seconds hand in 18K rose gold
Railway track minute scale transfer-printed on dial perimeter
12 luminous pearldrop hour markers
Strap: Alligator with large scales, matt dark brown, hand-stitched, with fold-over clasp in 18K rose gold.

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