Rolex Just Filed a Patent for a New Type of Mainspring

The mainspring is one of the oldest components in watchmaking. For centuries, it has been little more than a coiled ribbon of metal inside a short barrel, wound by crown or rotor, quietly storing and releasing energy. Rolex’s newly published international patent (WO2024/121368) proposes something very different.

Spotted by Coronet Magazine, the filing is officially dated 13 June 2024 by WIPO, though Coronet reported the story this September. Interestingly, the design originated with four Dutch inventors before Rolex acquired the rights — a reminder that the brand is willing to pursue innovation even in areas most would consider settled.

This isn’t the first such move. Earlier this year Rolex launched its Dynapulse escapement in the Land-Dweller, abandoning the centuries-old Swiss lever in favour of a geometry designed to improve efficiency and reliability. Now, the mainspring — the very reservoir of energy — is up for reinvention.

How the Design Works

Image Source: WIPO Patent WO2024121368

Rather than one continuous strip, the spring is built from repeating S-shaped elements linked together in a spiral. Each element flexes in a controlled way, with optional micro-slits to spread stress. A guiding system keeps adjacent coils aligned as the spring expands and contracts, preventing rub or jam.

In the patent, the central section does the bulk of the “energy work,” while the ends attach to arbor and barrel in the traditional way. The idea is simple: increase usable energy within the same footprint and deliver it more evenly through the wind.

Why It Matters

Image Source: WIPO Patent WO2024121368

A conventional mainspring delivers peak torque when fully wound and steadily loses force as it unwinds. The most stable timekeeping usually sits in the middle of the reserve. By turning the spring into a series of tuned flexing units, Rolex aims for higher energy density and a more consistent push to the gear train.

In practice, that could mean longer running time without enlarging the movement, or enough extra power to drive additional complications without thickening the case.

Materials and Manufacturing

Syloxi Hairspring From Rolex Caliber 7140 (Silicon & Silicon Oxide Composite). Image Source: Rolex

The filing leaves scope for modern micro-fabricated materials such as silicon or silicon-carbide. These lend themselves to the precise geometries and fine surfaces required for the S-shaped units. The text also mentions the possibility of stacking or layering multiple elements to further increase capacity.

The Bigger Picture

Rolex's Dynapulse Escapement in the Land-Dweller's new Caliber 7135. Image Source: Rolex

Rolex has spent the past decade squeezing more performance out of existing volumes: Chronergy escapement efficiency, 70-hour reserves across much of the catalogue, and the packaging innovations that allowed the Daytona’s calibre 4130 to stretch to around 72 hours.

The Dynapulse escapement was already a significant leap — Rolex’s first entirely new escapement architecture since the lever became standard. A redesigned mainspring is the logical next step: improve the reservoir itself.

Current Benchmarks

Rolex Caliber 3255. Image Source: Rolex

For context, calibre 3255 carries around 70 hours of reserve, while the Daytona’s 4130 sits at about 72. Both are already “long weekend” watches, able to be set aside Friday and restarted Monday. A denser mainspring with steadier torque could push beyond that, giving collectors fewer windings and better consistency without changing how the watch wears.

Other Approaches to the Same Problem

FP Journe's Remontoire D’égalité Constant Force Mechanism. Image Source: Revolution Watch

Different houses have pursued similar goals by other means. F.P. Journe’s remontoire d’égalité smooths torque with a secondary spring in the gear train. A. Lange & Söhne’s fusee-and-chain does it mechanically. Omega has looked to escapement tuning and barrel design, while Seiko has experimented with advanced alloys.

Rolex’s angle is more fundamental: refactor the mainspring itself rather than adding a constant-force device. The philosophy aligns with past innovations — change the foundation so the entire movement benefits.

The Paperwork

The WIPO record lists Rolex SA as applicant and owner, alongside the four inventors. The abstract describes a spiral spring made of “mutually connected repeating elements” separated by a guiding system — precisely the S-block architecture shown in the drawings.

While WIPO records the publication date as June 2024, Coronet Magazine framed the story as new in September 2025, which is when most collectors first heard about it.

Final Thoughts

A patent filing is not a product launch. Rolex works on its own timeline, and plenty of concepts never make it past the drawing board. But the fact remains: redesigning the mainspring is an audacious swing.

If the architecture scales to production, the most realistic win is greater power reserve with steadier torque, achieved without larger cases. That is classic Rolex — re-engineer a fundamental component, just as it did with the Dynapulse escapement, and let the benefits cascade across the movement.