Deformable Intermediate Piece for Hairspring Assembly Stress Distribution
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Solution Overview
Problem
The existing driving-in processes for assembling parts in watchmaking often result in high stresses that can damage or break fragile materials like silicon-based hairsprings due to concentrated force, leading to reduced clamping quality and potential breakage.
Innovation Solution
A deformable annular intermediate piece is introduced between the stud and the hairspring, deforming to distribute stresses and prevent concentration, made from softer materials like gold or copper, allowing it to absorb excess force and reduce damage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first part is driven directly into the second part made of fragile material, then the assembly is achieved, but the second part may be damaged or broken due to concentrated high stresses
Solution Approach 1:
A deformable intermediate piece is introduced between the first part (stud/peak) and the second part (hairspring/fragile component). This intermediate piece acts as a stress-distributing mediator that deforms plastically during the driving-in process, preventing stress concentration on the fragile second part while still enabling secure assembly. The intermediate piece absorbs the mechanical shock and distributes forces over a larger area and longer time period.
Solution Approach 2:
The material properties of the intermediate piece are specifically selected to have lower elastic limit and higher ductility compared to the fragile second part. This parameter change in material characteristics allows the intermediate piece to undergo plastic deformation at lower stress levels, thereby protecting the second part from reaching its failure stress threshold during assembly.
2Strength
If high driving forces are applied to assemble the parts, then the assembly is secured, but the fragile second part may suffer damage or breakage
Solution Approach 1:
The deformable intermediate piece serves as a pre-positioned cushioning element between the driving force and the fragile second part. Its softer material properties and deformable nature allow it to absorb and dissipate the harmful driving forces before they reach the fragile component, while still transmitting sufficient force to achieve secure clamping of the first part to the second part.
3Stress or pressure
If the intermediate piece is made of softer material, then stress distribution is improved, but the intermediate piece may deform excessively
Solution Approach 1:
The intermediate piece is designed with specific geometric features including a reduced thickness zone positioned between the first and second parts. This local geometric modification creates a controlled deformation zone that concentrates plastic deformation in a specific area, allowing the rest of the intermediate piece to maintain its structural integrity and prevent excessive overall deformation while still achieving stress distribution benefits.
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 and breakage by distributing stress evenly, ensuring secure clamping and prolonged part lifespan.
Implementation Method 1
the intermediate piece 6 comprises an upper rim or collar 8 which bears against the upper face of the outer end 3 of the hairspring 1 to position the intermediate piece 6 axially in the hole 5. The peak 4 is then driven into the hole central crossing, designated by 7, of the intermediate piece 6, which deforms the latter and clamps it between the eyebolt 4 and the wall of the hole 5
Implementation Method 2
The material of the intermediate piece 6 is also preferably softer than that of the hairspring 1, that is to say has an elastic limit lower than that of the material of the hairspring 1. The intermediate piece 6 can thus occupy the space available in the hole 5 or even overflow a little from the hole 5 when the constraints received are too high.
Data Source
Figure 1~2
Figure 3~7
AI summary
The method involves introducing a deformable annular intermediate part (6) comprising a hole (7), in a hole (5) of a hairspring. A balance spring stud (4) is driven in the hole (7) so as to lock the intermediate part against a wall of the hole (5) by deformation of the intermediate part. The intermediate part is made of a material e.g. brass, having an elastic limit lower than that of a material e.g. silicon based material, forming the hairspring. Independent claims are also included for the following: (1) an assembly of two parts (2) a clock movement including an assembly of two parts.