Monolithic Spiral Spring Ferrule Assembly for High Torque, Low Stress
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Solution Overview
Problem
Existing ferrule geometries for balance springs in high-precision watch movements are not satisfactory, as they fail to provide the highest possible tightening torque on the balance staff while minimizing stress in the material, leading to potential breakage and imbalance, which degrades chronometric performance.
Innovation Solution
A monolithic assembly of a single or double balance spring and an unslotted ferrule with a non-circular central opening, featuring at least two opposite balance staff receiving parts connected by flexible sections that deform elastically during insertion, ensuring precise positioning and optimal torque control without increasing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the ferrule is made monolithic from brittle material (silicon, diamond, quartz), then manufacturing precision and integration are improved, but the ferrule breaks quickly when stresses exceed the maximum allowable stress and elastic limit
Solution Approach 1:
The ferrule is divided into multiple parts: rigid receiving parts for precise positioning and flexible connecting parts for elastic deformation. This segmentation allows the rigid portions to maintain manufacturing precision while the flexible portions absorb stresses to prevent breakage, resolving the contradiction between monolithic manufacturing precision and reliability.
Solution Approach 2:
The rigidity parameter is varied spatially within the ferrule structure. The receiving parts have high rigidity for precise positioning, while the connecting parts have low rigidity for elastic deformation. This parameter change allows the ferrule to maintain precision while adapting to stress conditions, preventing catastrophic failure.
2Force
If the ferrule geometry is optimized for high tightening torque, then torque resistance is improved, but stress in the material increases leading to potential breakage
Solution Approach 1:
The ferrule is segmented into rigid receiving parts that provide high tightening torque and flexible connecting parts that deform elastically under stress. This segmentation allows the structure to achieve high torque resistance while the flexible portions reduce peak stresses, preventing material failure.
Solution Approach 2:
The connecting parts are designed as flexible elements with reduced rigidity, allowing elastic deformation to accommodate stress. These flexible portions act as stress-absorbing elements that enable high torque transmission without exceeding material stress limits, resolving the contradiction between torque resistance and stress reduction.
3Adaptability or versatility
If the ferrule is designed with flexible sections for elastic deformation, then adaptability to balance staff diameter variations is improved, but positioning precision of the balance spring attachment point may shift
Solution Approach 1:
The ferrule is divided into rigid receiving parts that maintain precise positioning and flexible connecting parts that provide adaptability. The rigid receiving parts ensure the balance spring attachment point remains precisely positioned, while the flexible connecting parts accommodate variations in balance staff diameter through elastic deformation, resolving the contradiction between adaptability and positioning precision.
4Ease of manufacture
If classic ferrule designs are used with pressing and/or gluing, then ease of manufacture is improved, but the ferrule cannot provide optimal torque control and may break under stress
Solution Approach 1:
The ferrule design merges rigid receiving parts for precise positioning with flexible connecting parts for stress absorption into a single integrated structure. This combination maintains ease of manufacture through monolithic fabrication while providing optimal torque control and preventing breakage under stress, resolving the contradiction between manufacturing ease and reliability.
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 provides enhanced torque resistance and reduced stress, preventing significant shifts in the balance spring's attachment point, thereby maintaining precise positioning and improving chronometric performance.
Implementation Method 1
two connecting parts which have a rigidity lower than that of the receiving parts, so as to be able to deform elastically during the insertion of a balance staff
Data Source
Figure 1~3
Figure 4~7
Figure 8(a)~8(j)
AI summary
The invention relates to a monolithic spiral spring - ferrule assembly (1) comprising: - a first receiving part not deforming or not substantially deforming during operation or during mounting of the monolithic assembly on the balance staff and intended to bear against a balance staff, - a second receiving part not deforming or not substantially deforming during operation or during mounting of the monolithic assembly on the balance staff and intended to bear against the balance staff, - a first connecting part deforming elastically during operation or during mounting of the monolithic assembly on the balance staff and intended to connect the first and second receiving parts, - a second connecting part deforming elastically during operation or during mounting of the monolithic assembly on the balance staff and intended to connect the first and second receiving parts,and - an element capable of continuously surrounding the balance shaft and comprising receiving and connecting parts.