Hairspring-Collet Assembly with Asymmetric Abutments for Shock Protection
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Solution Overview
Problem
Existing hairspring-ferrule assemblies in clock movements suffer from permanent deformation or breakage due to radial shocks, especially when made from fragile materials like silicon, and previous solutions either interfere with normal operation or fail to provide adequate support during impacts.
Innovation Solution
A spiral-ferrule assembly with three elastic arms forming an equilateral triangular central opening, featuring abutments arranged in a regular angular distribution with varying radii to absorb shocks without hindering normal oscillations, made from materials like silicon or metals, using Deep Reactive Ion Etching or other processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three equidistant abutments are used to limit hairspring deformation during radial shock, then the hairspring is protected from excessive deformation, but the nearest abutment may be touched by the inner coil during normal operation with large oscillation amplitude, disturbing the movement operation
Solution Approach 1:
The patent applies asymmetry by positioning the three abutments at different radial distances from the balance shaft axis. Specifically, one abutment is positioned closer to the inner coil while the other two are positioned farther away. This asymmetric arrangement allows the inner coil to clear all abutments during normal operation with large oscillation amplitudes, eliminating interference while maintaining protection capability during radial shocks.
2Reliability
If the abutments are positioned closer to provide better support during impact, then the hairspring is better protected, but the furthest abutment may be too far away to act as support before the elastic limit is exceeded
Solution Approach 1:
The patent applies local quality by providing different abutment positions tailored to different shock scenarios. The closer abutment positions provide immediate support for severe shocks, while the farther abutment positions allow greater deformation range for less severe shocks. This differentiated arrangement ensures that at least one abutment is always within effective support distance regardless of shock magnitude.
3Strength
If the ferrule is made from fragile material such as silicon, then the hairspring can be made more resistant to deformation, but the ferrule itself may break under radial shock
Solution Approach 1:
The patent applies beforehand cushioning by incorporating three elastic arms that can deform elastically during radial shock to absorb impact energy before it reaches the fragile ferrule body. These elastic arms act as shock absorbers, protecting the silicon or other fragile material ferrule from breakage while still providing the necessary support to limit hairspring deformation.
Solution Approach 2:
The patent effectively creates a composite structure combining the fragile ferrule material (silicon, quartz, or glass) with elastic arm elements. This composite approach allows the ferrule body to maintain its dimensional stability and precision while the elastic arms provide shock absorption capability, combining the advantages of both fragile and elastic materials.
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
The solution effectively reduces the risk of damage by distributing stress homogeneously and providing a safety factor against excessive deformation, ensuring reliable operation during shocks without disturbing the balance wheel's oscillations, even at large amplitudes.
Implementation Method 1
The ferrule comprises three elastic arms arranged in a triangle... which elastically deforms the arms outwards
Data Source
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AI summary
A spiral/collet assembly for a horological movement comprises a collet (1) and a spiral (3) attached by its internal end to the collet (1). The collet (1) is suitable for being mounted on a spindle (2). The external contour of the collet (1) defines stops (10a, 10b, 10c) against which the internal turn of the spiral (3) can come to bear during a shock before the elastic limit of the internal turn is exceeded. The stops (10a, 10b, 10c) are situated at respective distances (Ra, Rb, Rc) from the centre (O) of the spindle (2) that increase in the direction (D) of the spiral (3) going from inside to outside from the point (8) where the spiral (3) joins the collet (1).