Under the Loupe/Anti-Shock Systems
By their simplest definition, anti-shock systems are self-centering, reactive bearings.
The anti-shock or "shock-proof" system in a watch is generally used only on the upper and lower pivots of the balance wheel arbor. However, anti-shock systems may also sometimes be found protecting the pivots of the escape wheel as well.
The purpose of an anti-shock system is first and foremost to prevent breakage of the balance staff due to sudden and extreme shocks. Secondly, most anti-shock systems aim to reduce friction to the maximum at the contact points between the balance staff and anti-shock jewels.
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- 1. Spring
- The form of the anti-shock system's spring is engineered to absorb shocks, while maintaining enough resilience to return the cap jewel and balance staff jewel back into the fixed setting.
- 2. Cap Jewel
- The cap jewel is made from synthetic ruby; rounded on on top and polished flat on the bottom. This flat, polished surface is sometimes treated to facilitate a greater adherence of the oil which is applied there to lubricate the pivots of the balance staff.
- 3. Free Setting & Balance Staff Jewel
- Like the cap jewel, the balance staff jewel is made of synthetic ruby. It is crimped in a free setting, typically made of steel. This free setting helps to protect the jewel from chipping or shattering and also facilitates the self-centering of the balance staff jewel.
- 4. Anti-Shock Setting
- The anti-shock setting is fixed in the mainplate or balance cock. It serves as the base of the anti-shock system and holds the spring in place over the cap and balance staff jewels when the spring is in the locked position. It is hollow throughout and the lower portion of the setting is specially formed to guide the free setting, which holds the balance staff jewel and cap jewel, back to their exact position of rest following a shock.
How it Works
The free setting (or chaton in French), comprised of the balance staff jewel and cap jewel, is held in the anti-shock setting by the anti-shock spring. During normal use, this spring keeps the free setting in its optimal position, the goal of which is to minimize friction at the points of contact between the balance staff pivot and the jewels in and on which it turns. When a shock occurs, the free setting (complete with the cap jewel) is displaced. This displacement allows the shoulder of the balance staff to come into contact with the anti-shock setting and these together absorb the bulk of the force applied, as opposed to the balance staff pivot, which is very thin and prone to breakage. Once the shock has been absorbed, the anti-shock spring quickly and precisely returns the free setting back to its optimal position.
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