Balance Wheel Inertia Adjustment via Laser Ablation
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Solution Overview
Problem
Existing methods for adjusting the oscillation frequency of timepiece regulating assemblies, such as balance wheels and hairspring assemblies, are either expensive or yield mediocre accuracy due to the complexity of unbalance and inertia adjustments, particularly when assembling components that are within machining tolerances but require precise pairing.
Innovation Solution
A method that involves selecting a hairspring and balance wheel from toleranced production, measuring the restoring torque, calculating the theoretical inertia to achieve a predetermined oscillation frequency, and correcting the balance wheel's inertia by adding or removing material remotely from its surface, while keeping the hairspring attachment point unchanged, to ensure precise frequency adjustment without indexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional adjustment techniques (Omegametric or Spiromatic systems) are used, then frequency adjustment can be performed, but the process becomes extremely complex and accuracy is compromised
Solution Approach 1:
The patent extracts the adjustment operation to a single component (the balance wheel rim) rather than requiring complex coordination of multiple components. By isolating the inertia adjustment to material removal from the rim only, the complex pairing and coordination problems of conventional systems are eliminated, achieving high precision without complexity
Solution Approach 2:
The patent changes the physical state and distribution of material in the balance wheel rim through controlled removal. By varying the amount and distribution of material removed from the rim, the moment of inertia is precisely adjusted to achieve the target oscillation frequency, transforming a complex assembly problem into a simple parameter adjustment
2Productivity
If balance wheel and hairspring are assembled within machining tolerances, then production efficiency is maintained, but precise pairing becomes difficult without indexing
Solution Approach 1:
The balance wheel is designed with its own built-in adjustment capability through the rim structure. The rim can be directly modified to adjust the moment of inertia, allowing the component to self-adjust without requiring external indexing systems or complex pairing procedures with the hairspring, thus maintaining both productivity and precision
3Speed
If material is removed from the balance wheel rim, then the moment of inertia decreases to achieve higher oscillation frequency, but the structural integrity must be maintained
Solution Approach 1:
The patent applies material removal locally and selectively to the balance wheel rim rather than uniformly throughout the structure. By concentrating the adjustment operation in the rim area and controlling the depth and distribution of material removal, the moment of inertia is reduced to increase oscillation frequency while preserving the overall structural integrity of the balance wheel
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
This method allows for precise adjustment of the oscillation frequency with high chronometric performance, reducing the need for extensive component sorting and stock management, and enabling the assembly to meet both static and dynamic tolerances efficiently.
Implementation Method 1
a pulse is controlled by control means arranged to generate, sequence, interrupt any pulse, and to control the movements of a beam issuing from said transformation means... the inertia of this balance wheel is reduced by the removal of material from the rim or/and from at least one arm that comprises this balance wheel
Data Source
AI summary
Method of setting the oscillation frequency, to a predetermined oscillation frequency, of a clockwork adjusting assembly with no regulating unit with a hairspring assembly balance: - a particular hairspring assembly is randomly selected from a toleranced production; - the restoring torque of said hairspring assembly is measured; - a particular balance is selected randomly from a toleranced production; - a theoretical inertia (IT) of said particular balance is calculated for reaching said predetermined oscillation frequency, as a function of said measured restoring torque of said selected hairspring; the real inertia (IR) of said particular balance is measured; - by direct action on said particular balance, its inertia is corrected to said theoretical inertia value (IT) calculated for obtaining said predetermined oscillation frequency of said adjusting assembly constituted by said particular balance, and by said particular hairspring assembly.