Rolex Patented a Dual-Arm Hairspring Attachment
There are two key springs inside any mechanical watch: the mainspring, which gets wound up to store energy and power the movement, and the hairspring, which works with the balance wheel to control how that energy is released in precise, regular intervals–making timekeeping possible. Hairsprings are extremely thin (often <0.03 mm thick) and designed to operate within a precise horizontal plane. Vertical forces during servicing (e.g., adjusting screws, handling with tweezers) can deform the spring. In 2024, Rolex was granted a patent for a two-arm attachment that connects the spring blade (outer portion of the hairspring) to the movement, designed to help absorb vertical pressure and protect the hairspring, particularly during servicing. Here’s a quick overview of this dual-arm hairspring attachment patent.
Pierre Villaret has been involved in at least 9 distinct Rolex patents, and this is one of them. While this probably won’t shock the world like the Dynapulse escapement from Rolex’s 2025 releases, this dual-arm hairspring attachment patent is worth a look.
How Does a Hairspring Normally Connect?
The hairspring is usually attached at its inner end to the balance wheel and at its outer end to a stationary part of the movement, like the balance cock or bridge. These attachment points are typically fixed, so when you adjust other parts of the watch (e.g. screws), it can accidentally bend or deform the hairspring.
What’s Different About the Rolex Dual-Arm Hairspring Attachment Patent?
Patent US 20240248432 A1 (the American equivalent of EP4407382A1, originally filed in 2023) is for a two-arm hairspring attachment. Instead of just one “arm” connecting the spring blade to the bridge (or another fixed part of the movement), there are two. The first arm is flexible and absorbs all the stress while the second arm stays fixed and protects the delicate spring from bending.
A 2013 patent from inventor Ho Ching addresses a similar engineering concern, but instead of adding a second arm, Mr. Ho’s design stiffens a section of the spring blade near its connection point. Ho works for Master Dynamics of Hong Kong, the first company in Asia to develop a silicon hairspring from scratch. Aside from Master Dynamics, I’m not aware of any other companies attempting to address the issue that Rolex’s two-arm hairspring attachment patent addresses.
Will This Make Rolex Watches More Shock-Resistant?
Rolex’s two-arm hairspring connector patent seems specifically designed for absorbing axial (meaning “vertical”) stress during service. Don’t expect this Rolex patent to improve the watch’s ability to, say, absorb the impact from a drop. Still, this patent is a good example of the tiny random things Rolex is always looking to improve.
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