The Swiss reinvent the watch

Home Technologist Online The Swiss reinvent the watch

For the first time in 200 years, the heart of the mechanical watch has been reinvented. Swiss researchers have developed a new type of oscillator that – turning continuously in one direction – could make the ticking of traditional watches a thing of the past.

Clock mechanism

A group of researchers from École Polytechnique Fédérale de Lausanne (EPFL) has crafted a unidirectional, continuous oscillator that could become the new timekeeper in mechanical watches. This would revolutionise the mechanical concept, which has remained unchanged for centuries.

IsoSpring, the name of the new oscillator, was recently revealed to the public at the Journée d’Etude de la Société Suisse de Chronométrie, the annual conference of the Swiss watch industry. Bypassing the most complicated mechanism of traditional watches, IsoSpring could make watches more precise and autonomous – and completely silent, according to its creators.

“Our prototype weighs four kilograms but we’re already trying to miniaturise it so as to fit it in a wristwatch; the watch industry has expressed great interest in the project,” says Simon Henein, EPFL researcher and director of Instant-Lab, in a press release.

IsoSpring differs from the pendulum, spiral-balance wheel and tuning fork – the three oscillators used in traditional clocks and watches.Animation of anchor escapement

From energy-waster to smooth operator

Mechanical watches depend on a system of gears to drive the alternating oscillations of the balance wheel – the timekeeping device – and the motion of the watch hands. The part that connects the gears and the balance wheel is called the escapement – allowing one tooth of the gear to ‘escape’ every time the balance wheel changes direction. Causing the entire gearing mechanism to continually start and stop, the escapement produces the familiar ticking sound.

“This stop and go motion wastes enormous energy; for this reason even the best escapements are limited to 40 per cent efficiency,” Henein explains.

Thanks to its continuous rotation, IsoSpring eliminates the need for an escapement, which is the most challenging part of a watch from an engineering perspective. Gone are the traditional intermittent mechanisms, now substituted by smooth motion based on so-called compliant mechanisms. Compliant mechanisms use the elastic properties of matter to produce the motion of mechanical components, eliminating friction and the need for lubrication.

“Our concept is in a mechanical tradition. We do not appeal to high technology and our methods are accessible to 18th century engineers,” Henein points out.

“A return to continuous time – as in the motion of the stars”

So how does IsoSpring work, exactly? Imagine an ancient sling where you use a leather strap to make a stone turn in a circle. If you replace the strap with an elastic band, the stone will now move in an ellipse and its speed will no longer be constant. On the other hand, its period will now be constant so it can be used to measure time precisely. This principle, discovered by Isaac Newton in the 17th Century, is the conceptual basis of the new oscillator. The rotation is maintained by the traditional barrel spring.

“Our watch is a departure from chopped-up ticking time and a return to continuous time as seen in nature by the motion of the stars,” Henein concludes.

Adapted from EPFL Mediacom

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