Balance-Spring Oscillator Assembly for High Torque Variation
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Solution Overview
Problem
Existing methods for assembling oscillators with spiral springs and balance wheels are either expensive or result in poor chronometric performance, especially when there is a large variation in torque among the balance springs.
Innovation Solution
A method involving measuring the average moment of inertia of a batch of balance wheels, providing spiral springs with an excess number of turns, making initial cuts to adjust torque, sorting by torque value, assembling to achieve intermediate frequency, and making final cuts to achieve precise oscillation frequency and attachment point angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the Omegametric system is used to classify and pair balance springs and balance wheels, then frequency precision is improved, but manufacturing cost and logistical complexity increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-cutting balance springs with an excess of 3 turns before assembly. This allows the springs to be prepared in advance with a standardized excess length, simplifying the classification process. The excess turns are then removed during assembly to achieve the precise final length, eliminating the need for complex post-assembly adjustments while maintaining frequency precision.
Solution Approach 2:
The patent segments the balance spring manufacturing process into two distinct stages: (1) initial production with excess turns for all springs, and (2) selective cutting of excess turns during assembly based on measured inertia values. This segmentation allows for simplified initial manufacturing while enabling precise final adjustment, reducing logistical complexity compared to the Omegametric system.
2Ease of manufacture
If the Spiromatic system is used to cut balance springs to adapt torque to balance wheel inertia, then manufacturing cost is reduced, but attachment point precision deteriorates with +/- 50° tolerance
Solution Approach 1:
The patent implements feedback by measuring the actual inertia of each balance wheel and using this measurement to determine the precise cutting point for the corresponding balance spring. This closed-loop approach ensures that the attachment point angle is accurately controlled based on actual component properties, achieving precision despite the simplified manufacturing process.
Solution Approach 2:
The patent changes the parameter of balance spring length dynamically based on measured inertia values. By providing an initial excess of 3 turns and then selectively removing turns based on measured parameters, the system achieves precise attachment point angles while maintaining economical manufacturing. The final spring length is adjusted according to the specific inertia measurement, optimizing both cost and precision.
3Adaptability or versatility
If balance springs with wide nominal torque distribution are used, then manufacturing flexibility is improved, but chronometric performance deteriorates due to difficulty in association and adjustment
Solution Approach 1:
The patent applies preliminary action by measuring the inertia of each balance wheel before assembly and using this information to select and cut the appropriate balance spring. This preliminary measurement and preparation enable the system to handle wide torque distributions effectively, as each spring is precisely adjusted to match its specific balance wheel, ensuring optimal chronometric performance despite manufacturing flexibility.
Data Source
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AI summary
The invention relates to a method for manufacturing an oscillator (1) for a timepiece made from a balance wheel (2) and a spiral spring (3), the method comprising the following steps: - measuring the average moment of inertia of a batch of balance wheels (2); - providing spiral springs (3) with collets, the spiral springs (3) having an excess number of turns forming up to three additional turns compared to the final number of turns; - making a first predetermined external cut of the spiral springs (3) over a length of one to two turns then measuring the torque of the spiral springs (3) and sorting them according to the measured torque value; - assembling the spiral springs (3) whose measured torque corresponds to the balance wheels (2) to form an oscillator of an intermediate frequency and determining the length to be cut to achieve a desired oscillation frequency;- performing a second external cut of the selected spiral springs (3) to achieve both the desired oscillation frequency, and to achieve a target value to obtain an angle (α) of the attachment point (6) at +/- 50° of the theoretical value.;