Ferrule Design Reducing Stress in Watchmaking Hairsprings
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Solution Overview
Problem
Ferrules in watchmaking are subjected to high stress variations and bending stresses due to contact with shafts, leading to potential material breakage and displacement issues.
Innovation Solution
A ferrule design with a triangular band featuring zones of constant width and a thickened zone between vertices, allowing for the redistribution of elastic deformation forces, reducing contact and bending stresses by 70% and 40% respectively, while maintaining a minimum tightening torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a ferrule with constant width band is used, then the structure is simple, but high contact stresses and bending stresses occur at contact points and vertices
Solution Approach 1:
The patent applies local quality by varying the band width along its length. The band has a first width in the region of contact points with the shaft and a second width in the region of vertices, with the first width being greater than the second width. This local variation in geometric property allows the ferrule to have higher stiffness at contact points (reducing contact stress) while maintaining flexibility at vertices (reducing bending stress), thus resolving the contradiction between structural simplicity and stress management.
2Stress or pressure
If the band width is increased at contact points, then contact stresses are reduced, but the overall device complexity increases
Solution Approach 1:
The patent segments the band into distinct regions with different width characteristics. The band is divided into a first region (near contact points) with a first width and a second region (near vertices) with a second width. This segmentation allows each region to be optimized independently for its specific functional requirements, reducing contact stress where needed while avoiding unnecessary complexity in other regions.
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 ferrule design effectively lowers internal stresses and improves stress balance, maintaining a secure attachment to the shaft with reduced material strain.
Implementation Method 1
the third zone, between the first and second zones, which comprises a width thickened with respect to those of the first and second zones and which is arranged to fit on a shaft making it possible to displace the elastic deformation forces
Data Source
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AI summary
Ferrule mounted elastically on a shaft whose geometry generates less internal stress, particularly at the points of contact and the vertices of its polygonal shape.