Balance Spring Geometry for Stable Timepiece Oscillation
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Solution Overview
Problem
Existing watch balance springs are sensitive to variations and defects in other movement components, as well as changes in power reserve or mainspring winding, leading to performance deviations that are difficult to correct without replacement.
Innovation Solution
A method for manufacturing watch balance springs that involves defining a numerical model with adjustment variables, identifying optimal values to minimize performance sensitivity to variability, and producing springs with specific geometries to reduce operational deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional balance springs are used, then mass production is enabled and magnetic field sensitivity is avoided, but performance deviations occur due to variations in oscillator operation and mainspring power reserve
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the balance spring, specifically implementing variable thickness along the spiral coils. The thickness transitions from a first value at the inner portion to a second value at the outer portion, creating optimized stiffness characteristics that compensate for variations in oscillator operation and mainspring power reserve, thereby maintaining consistent timekeeping performance across different production batches and operating conditions.
Solution Approach 2:
The patent implements local quality by creating non-uniform thickness distribution along the balance spring coils. Different sections of the spring have different thicknesses, with the inner portion having a first thickness value and the outer portion having a second thickness value. This localized variation in geometric properties allows different parts of the spring to perform different functions, compensating for performance deviations while maintaining mass production capabilities.
2Reliability
If balance springs with variable thickness are manufactured, then performance sensitivity to oscillator variability is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes through systematic variation of the thickness parameter along the length of the balance spring. By defining specific thickness values for different portions (inner portion with first thickness, outer portion with second thickness), the design achieves reduced sensitivity to oscillator variability while maintaining a relatively straightforward manufacturing process suitable for mass production.
Data Source
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AI summary
The invention relates to a method for manufacturing watch balance springs (10) for an oscillator of a movement of a timepiece, the oscillator being characterized by oscillations exhibiting variability under the effect of an escapement and/or a gear train and/or a mainspring of the movement of the timepiece, the manufacturing method comprising the following steps: - (100) defining a numerical model representative of a balance spring (10) that one wishes to obtain, said model comprising a plurality of adjustment variables, - (200) defining at least one performance indicator, representative of a desired behavior for the balance spring (10), - (300) identifying at least one optimal value for at least one adjustment variable, the optimal value providing a minimum sensitivity of the performance indicator to the variability of said oscillations of the oscillator,- (400) manufacture at least one spiral (10) with a geometry defined according to said at least one optimal value. The invention also relates to a spiral (10) whose particular geometry provides a minimum sensitivity of the performance indicator to the variability of said oscillations of the oscillator.