Rolex Just Patented a New Kind of Mainspring

The mainspring used in most wristwatches has barely changed in centuries. It’s a coiled metal ribbon, tucked inside a short barrel, wound by your watch’s crown or rotor. The mainspring is the reservoir that powers everything. Rolex’s newly published international patent (WO2024/121368) sketches a very different spring architecture. This came to our attention through Coronet Magazine, which reported that Rolex acquired the rights from four Dutch inventors. Coronet also described the patent as published this week (early September 2025), though the WIPO record shows the filing’s publication date as June 13, 2024.

That acquisition detail is telling: Rolex is willing to pursue innovation even in areas where most brands would never bother. The mainspring, like the escapement, is a part of the watch movement few expect to change. Yet earlier this year Rolex introduced the Dynapulse escapement in the Land-Dweller — a completely reimagined system that replaces the long-established Swiss lever design with a new geometry intended to improve efficiency and reliability. Now, with this mainspring patent, Rolex is again signaling its willingness to rethink the very foundations of a movement if it means measurable performance gains.

So What Is It?

Image Source: WIPO Patent WO2024121368

Instead of one continuous strip of material, the spring is built from repeating S-shaped “building blocks” that link together in a spiral. Each block is shaped to flex in a controlled way, and the design can include fine slits to spread stress. A guiding system sits between adjacent coils so they don’t rub or jam as the spring breathes. In the patent drawings and text, most of the real “energy work” happens in the middle section of the spring, while the ends attach to the arbor and barrel like normal. The point is simple: pack more usable energy into the same space and release it more evenly across the wind.

Why It Matters

Image Source: WIPO Patent WO2024121368

Traditional mainsprings deliver more torque when fully wound and less as they unwind. Rate stability is best in the middle of the reserve. By turning the spring into a series of tuned elements, Rolex is aiming for higher energy density and a smoother push to the gear train. In practice, that could mean longer running time without a larger movement, or room to power more demanding displays without thickening the case.

Materials and Manufacturing

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

The filing leaves the door open to micro-fabricated solutions, including silicon or silicon-carbide, which are well suited to precise, thin, springy structures like the S-shaped elements described. That’s important, because geometry like this benefits from high dimensional control and surface quality. (The patent also contemplates stacking or layering elements to increase capacity if needed.)

How This Fits Rolex’s Trajectory

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

Rolex has spent the last decade squeezing more from the same volume: Chronergy escapement efficiency, broader 70-hour reserves in modern calibres, and smart packaging in the Daytona’s 4130 that helped it reach ~72 hours. Most recently, the brand introduced the Dynapulse escapement in the Land-Dweller — its first new escapement architecture since the Swiss lever became standard. The Dynapulse is designed to optimize how energy transfers from the escape wheel to the balance, reducing sliding friction and improving long-term stability. That move alone showed Rolex’s willingness to rethink parts of the movement that had been untouched for centuries. This new mainspring concept reads like the next logical lever: improve the reservoir itself. If it ever makes production, it could push beyond today’s benchmarks without forcing case growth.

Benchmarks and Upside

Rolex Caliber 3255. Image Source: Rolex

As reference points, Calibre 3255 is rated at roughly 70 hours, and the 4130 in the Daytona at about 72 hours. Those numbers already cover a long weekend off-wrist. A higher-density mainspring that maintains steadier torque could extend that window while aiding rate stability, especially toward the ends of the reserve. For collectors, the practical appeal is clear: fewer windings, more consistency, no compromise to wearability.

How It Compares to Other Ideas

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

Watchmaking has taken different routes to similar goals. F.P. Journe’s remontoire d’égalité smooths delivery with a secondary spring in the train. A. Lange & Söhne’s fusee-and-chain evens torque mechanically. Omega has chased efficiency and reserve through barrel design and escapement tuning, and Seiko has leaned on advanced alloys. Rolex’s proposal is more fundamental, aimed at the mainspring itself rather than adding a constant-force device on top. The philosophy tracks with what the brand has done before: refactor a core part so the whole system benefits.

The Paper Trail

The international publication identifies Rolex SA as applicant/owner and lists four inventors, with the core abstract describing a spiral spring made of “mutually connected repeating elements” separated by a guiding system—exactly the architecture outlined above. Publication timing on the WIPO record is June 13, 2024, though as mentioned, Coronet Magazine framed the news as breaking in early September 2025.

Final Thoughts

Patents aren’t product announcements, and Rolex moves on its own clock. Still, redesigning the mainspring is a big swing. If the geometry scales in production, the most realistic win is power reserve, potentially without increasing case size, and steadier delivery. That’s Rolex through and through: re-engineer a foundational part — just as it did with the Dynapulse escapement — and let the benefits cascade through the movement.