Composite Barrel Spring Coating for Watch Friction Reduction
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Solution Overview
Problem
Conventional coatings for barrel springs in mechanical watches fail to maintain cohesion and reduce friction effectively due to deformation stresses, leading to breakage or delamination during winding and uncocking.
Innovation Solution
A barrel spring made of a polymer matrix with fibers, coated with a slow-curing epoxy resin having a gelling time greater than 20 minutes at 90°C, which is homogenized and polymerized to form a coating that reduces friction and maintains cohesion through hydrogen or Van der Waals bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional coating (metallic or DLC) is applied to the barrel spring, then friction between turns is reduced, but the coating breaks or delaminates under deformation stress
Solution Approach 1:
The patent changes the chemical composition and bonding characteristics of the coating material from conventional metallic or DLC coatings to an organic coating containing silicon-oxygen-silicon bonds and hydrogen bonds. This parameter change in material composition allows the coating to maintain flexibility and adhesion under deformation while still providing friction reduction.
Solution Approach 2:
The coating is formulated as a composite material containing silicon oxide (SiOx) with specific silicon-oxygen-silicon bond angles (140°-180°) and hydrogen bonds. This composite structure combines the hardness and lubricity of silicon oxide with the flexibility and adhesion of hydrogen bonding, resolving the contradiction between friction reduction and coating cohesion.
2Strength
If a ceramic or diamond coating with covalent/ionic bonds is used, then coating hardness is improved, but the coating cannot ensure satisfactory cohesion under deformation
Solution Approach 1:
The patent changes the bonding mechanism from rigid covalent/ionic bonds to a combination of silicon-oxygen-silicon bonds with specific geometry (140°-180° angles) and hydrogen bonds. This parameter change provides a balance between hardness (from SiOx structure) and flexibility/cohesion (from hydrogen bonding and bond angle flexibility).
Solution Approach 2:
The silicon-oxygen-silicon bond structure acts as an intermediary between the rigid SiOx network and the flexible hydrogen bonding. The specific bond angles (140°-180°) allow the coating to accommodate deformation while maintaining structural integrity and cohesion.
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 solution effectively reduces friction between turns and ensures the coating's cohesion, even under significant deformations, thereby enhancing the power reserve and longevity of mechanical watches without increasing the watch's bulk.
Implementation Method 1
The coating reduces friction on the spring turns
Implementation Method 2
a coating whose elastic behavior is ensured by covalent or ionic type bonds, such as a ceramic or diamond coating
Implementation Method 3
The coating has good cohesion... through hydrogen or Van der Waals bonds
Implementation Method 4
a barrel spring made of a material comprising a polymer matrix containing fibers
Data Source
Figure 1~3
Figure 2
AI summary
Mainspring for driving a clock movement, said mainspring being made of a material comprising a polymer matrix containing fibres, said mainspring having a coating containing a thermoset or thermoplastic polymer. The mainspring proposed reduces the friction of the turns of the mainspring.