Ultrathin Passivation Layer for Balance Wheel Inertia Control
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Solution Overview
Problem
The traditional method of setting metal balance wheels to achieve a desired beat frequency is time-consuming and requires reclassification due to the increase in inertia caused by conventional protective layers, which affects classification accuracy and tarnish resistance.
Innovation Solution
A passivation layer of less than 5nm thickness, formed by oxidation, nitriding, or carburizing, is applied to the balance wheel surface to protect against tarnishing without significantly increasing inertia, allowing consistent classification without reclassification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional protective layer (gold plating, electroplating, anodizing) is applied to the balance wheel, then tarnish resistance is improved, but the inertia increases and classification accuracy deteriorates
Solution Approach 1:
The patent changes the thickness parameter of the protective layer from conventional dimensions (micrometers to tens of micrometers for anodizing, microns for gold plating) to an ultrathin scale (less than 5nm). This parameter change allows the protective layer to provide tarnish resistance while adding negligible mass that does not affect inertia classification accuracy.
Solution Approach 2:
The patent employs an ultrathin passivation layer (less than 5nm) as a thin film protective coating. This thin film approach provides the necessary protection against tarnishing while being sufficiently thin that its mass contribution is negligible and does not degrade the balance wheel's inertia classification.
2Manufacturing precision
If material removal is performed to achieve sub-class accuracy, then classification precision is improved, but manufacturing time increases
Solution Approach 1:
The patent applies the passivation layer early in the manufacturing process, before final inertia classification and adjustment. This preliminary action ensures that the protective layer is already in place during classification, eliminating the need for reclassification after plating and streamlining the manufacturing workflow.
Solution Approach 2:
The patent enables continuous manufacturing flow by eliminating the reclassification step. The passivation layer is applied once and remains stable through subsequent handling and assembly, allowing the process to continue without interruption for remeasurement and readjustment.
3Reliability
If gold plating or electroplating is applied, then tarnish resistance is improved, but the balance wheel inertia increases significantly
Solution Approach 1:
The patent dramatically reduces the thickness parameter of the protective layer from conventional micrometer-scale plating to nanometer-scale passivation (less than 5nm). This parameter change reduces the mass of the protective layer by several orders of magnitude, making its contribution to total inertia negligible while maintaining protective functionality.
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 passivation layer maintains classification accuracy and prevents tarnishing while minimizing inertia variation, eliminating the need for reclassification and ensuring consistent performance across balance wheels.
Implementation Method 1
a passivation layer, which can be formed by oxidation, nitriding, or carburizing of the balance wheel's metal surface
Implementation Method 2
a passivation layer, which can be formed by oxidation, nitriding, or carburizing of the balance wheel's metal surface
Implementation Method 3
a passivation layer, which can be formed by oxidation, nitriding, or carburizing of the balance wheel's metal surface
Implementation Method 4
this passivation layer is applied by a dry process, such as by reacting the surface of the balance wheel metal with a gaseous chemical species like oxygen, nitrogen, or a hydrocarbon
Data Source
Figure 1
AI summary
Method for manufacturing a balance wheel (1) for a watch oscillator, comprising the steps of: - machining said balance wheel (1) in metal; - measuring the weight and/or inertia of said balance wheel (1); - optionally, classifying by material removal of said balance wheel (1); - applying a passivation layer (17) to at least a part of the surface of said balance wheel (1), said passivation layer (17) having a thickness of less than 5nm, preferably less than 3nm, even more preferably less than 2nm.