Moisture-Barrier Coating for Thermally Compensated Balance Springs
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Solution Overview
Problem
Existing balance-spring resonators in watch movements are sensitive to climatic variations, leading to rate instability during severe condensation tests.
Innovation Solution
A non-metallic compensating balance spring with a core made of quartz or doped/undoped silicon, coated with a thin, moisture-resistant and impermeable layer of chromium, titanium, or tantalum to minimize sensitivity to climatic variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a balance spring is made from non-metallic materials like silicon or quartz with silicon dioxide coating, then thermal compensation is improved, but sensitivity to humidity and climatic variations worsens
Solution Approach 1:
The patent applies composite materials by combining non-metallic materials (silicon or quartz core with silicon dioxide coating) that provide thermal compensation properties with a moisture-resistant coating layer. This composite structure allows the balance spring to simultaneously achieve thermal stability and humidity resistance, resolving the contradiction between improved thermal compensation and worsened humidity sensitivity.
2Reliability
If a moisture-resistant coating is applied to the balance spring core, then reliability under condensation conditions is improved, but device complexity increases
Solution Approach 1:
The patent uses a thin film coating approach by applying a moisture-resistant coating layer with controlled thickness (less than 50 nm) onto the balance spring core. This thin film provides the necessary protection against humidity and condensation while minimizing the addition of structural complexity, as the coating is deposited as a uniform layer rather than requiring complex multi-component structures.
3Object-affected harmful factors
If the moisture-resistant layer thickness is increased, then protection against climatic variations is improved, but mechanical influence on the balance spring functioning worsens
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the moisture-resistant coating layer to be less than 50 nm. This parameter optimization ensures that the coating provides sufficient protection against humidity and climatic variations while remaining thin enough to avoid significant mechanical influence on the balance spring's elastic properties and oscillation characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compensating balance spring remains stable under severe condensation conditions, ensuring minimal operational disturbance and maintaining the resonator's performance.
Implementation Method 1
the core is entirely coated with a layer which is resistant and impermeable to humidity
Implementation Method 2
compensating balance spring for a thermally compensated balance-spring resonator
Data Source
Figure 1~7
AI summary
The invention relates to a compensating balance-spring (1) for a thermally compensated balance and spring resonator, comprising a core (9a, 9b, 9c, 9d, 9e, 9f) formed from at least one non-metal material (11a, 11b, 13b, 15b, 11c, 17c, 19c, 11d, 13d, 15d, 17d, 19d, 11e, 13e, 15e, 17e, 19e, 11f, 21f). According to the invention, the core (9a, 9b, 9c, 9d, 9e, 9f) is entirely coated by a layer (7) that is stable in relation to humidity in order to render the compensating balance spring (1) less sensitive to climate changes. The invention relates to the field of timepieces.