Integrated Silicon Hairspring with Angular Blade Offset
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Solution Overview
Problem
Existing balance-spring resonator designs with two superimposed hairsprings require complex adjustments and increased parts, leading to difficulties in achieving isochronism due to the axial offset and torque issues.
Innovation Solution
A hairspring design featuring multiple blades angularly offset and attached by their ends, with varying pitch and thickness, and potentially incorporating a layer of amorphous silicon oxide for thermal compensation, which replaces traditional components like eyebolts and allows for pre-tension adjustments to improve isochronism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two superimposed hairsprings are used with axial offset to compensate center of gravity variations, then isochronism is improved, but device complexity increases due to multiple parts and perfect synchronism adjustment requirements
Solution Approach 1:
The patent merges two separate hairsprings into a single integrated component where two blades are fixed to the same ferrule and operate in phase opposition. This combination maintains the center of gravity compensation effect while eliminating the need for separate pivots, carriers, and synchronization adjustments, thus reducing device complexity while preserving isochronism improvement
Solution Approach 2:
The single hairspring is segmented into two blades that are angularly offset by 180 degrees and fixed to the same ferrule. These segmented blades work in phase opposition to compensate center of gravity variations, achieving the same effect as two separate hairsprings but with a unified structure that reduces the number of parts
2Reliability
If two superimposed hairsprings are used with axial offset, then center of gravity compensation is achieved, but the height of the balance-spring resonator increases
Solution Approach 1:
Instead of positioning two hairsprings along the axial dimension (which increases height), the patent positions two blades of a single hairspring in the angular dimension, offset by 180 degrees around the balance wheel axis. This dimensional change from axial stacking to angular arrangement maintains center of gravity compensation while avoiding height increase
3Reliability
If the diameter of the hairspring is increased to reduce blade contact risk, then reliability is improved, but the volume of the balance-spring resonator increases
Solution Approach 1:
The patent introduces asymmetry in the blade configuration by angularly offsetting the two blades by 180 degrees and giving them different pitch and thickness characteristics. This asymmetric design creates sufficient clearance between blades during oscillation, preventing contact without requiring an overall increase in hairspring diameter, thus avoiding volume increase
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
Significantly improves isochronism and reduces the risk of blade contact during expansion and contraction, allowing for a more compact and efficient balance-spring resonator with reduced complexity and parts.
Implementation Method 1
a layer of amorphous silicon oxide for thermal compensation
Data Source
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AI summary
The hairspring has two plates (1a, 1b) that are integrated with respect to each other by their respective ends and coplanar, where the hairspring is made of single-crystal silicon or quartz. The plates are wound into spirals with an angular offset neutralizing lateral forces exerted on a central axle when one of the ends of each plate is angularly displaced around the central axle with respect to the other end of each plate. Thickness and height of the plates are variable, and the single-crystal silicon is covered with an amorphous silicon dioxide layer.