Balance Spring Wafer Correction for Consistent Stiffness
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Solution Overview
Problem
Existing methods for manufacturing horological balance springs result in geometric dispersion and contamination, leading to inconsistent stiffnesses within a batch, necessitating improved precision and accuracy.
Innovation Solution
A method involving forming balance springs with differing dimensions in a wafer, incorporating oscillating elements for stiffness indication, and applying dimensional corrections based on resonant frequency measurements to achieve a predetermined stiffness range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching techniques (laser, plasma, DRIE, wet etching) are used to manufacture balance springs in wafers, then manufacturing efficiency and consistency are improved, but geometric dispersion between balance springs occurs leading to inconsistent stiffness
Solution Approach 1:
The patent applies preliminary action by forming reference systems with known stiffness characteristics in the wafer before forming the balance springs. These reference systems serve as calibration standards that allow subsequent measurement and correction of balance spring stiffness, thereby compensating for geometric dispersion caused by etching techniques.
Solution Approach 2:
The patent implements feedback by measuring the resonant frequencies of reference systems, computing the actual stiffness values, comparing them with target values, and using this information to adjust manufacturing parameters or select balance springs that meet specified stiffness tolerances. This closed-loop approach corrects geometric dispersion effects.
2Measurement precision
If balance spring stiffness is determined by measuring frequency of balance spring coupled with balance, then stiffness accuracy is improved, but contamination of the wafer occurs during measurement
Solution Approach 1:
The patent extracts the measurement function from the balance spring itself by using separate reference systems that are formed in the wafer. These reference systems are specifically designed for stiffness characterization and can be measured without affecting the balance springs, thereby preventing contamination while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces reference systems as intermediary elements that mediate between the manufacturing process and the measurement process. These reference systems serve as proxies for characterizing wafer properties and etching uniformity, allowing indirect measurement that avoids direct handling and potential contamination of the balance springs.
3Manufacturing precision
If iterative measurement and correction steps are repeated to improve dimensional quality, then manufacturing precision is improved, but manufacturing time and complexity increase
Solution Approach 1:
The patent performs preliminary formation of reference systems with known characteristics before producing balance springs. This preliminary action establishes a calibration baseline that enables single-pass or minimal-iteration measurement and correction, reducing the need for repeated iterative cycles while maintaining high dimensional quality.
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
Ensures high precision and consistent stiffness within a batch of balance springs by correcting dimensional errors using systems for reference stiffness indication and material addition/removal processes.
Implementation Method 1
determining the stiffnesses of said systems formed; computing a dimensional correction to be applied to the balance springs formed, on the basis of the determined stiffnesses of said systems
Data Source
AI summary
There is provided a method for manufacturing a batch of horological balance springs (2a), the average of whose stiffnesses lies within a predetermined range, and the method includes forming in a wafer the horological balance springs (2b, 2c) with dimensions that differ from the dimensions required to obtain the batch of horological balance springs (2a), the average of whose stiffnesses lies within the predetermined range, determining the stiffnesses of the systems, computing a dimensional correction to be applied to the horological balance springs, and modifying the dimensions of the horological balance springs (2b, 2c) formed, on the basis of a dimensional correction computed to obtain the batch of horological balance springs (2a).