Impact-Resistant Balance Hairspring for Stable Timekeeping

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Solution Overview

Problem

Existing timepieces with silicon-based hairsprings face issues of deformation or breakage at the inner curved portion due to impacts, affecting the accuracy of speed governing and timekeeping, while metal materials also suffer from deformation due to impacts.

Innovation Solution

A balance mechanism with a hairspring featuring a Grossmann curve and an Archimedes curve, supported by a collet and an impact-resistant member, which suppresses deformation of the Grossmann curve by maintaining the shape and center of gravity, even under impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the inner curved portion of the hairspring is made of silicon-based material with Grossmann type shape, then the accuracy of speed governing is improved, but the reliability under impact is worsened due to deformation or breakage

Engineering Contradiction:

Improveaccuracy of speed governingVSAvoidresistance to impact

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent combines silicon-based material for the hairspring with a metal material for the impact-resistant member, creating a composite structure that leverages the low density and corrosion resistance of silicon while utilizing the high strength and impact resistance of metal to protect the vulnerable inner curved portion

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The impact-resistant member is positioned beforehand to protect the inner curved portion of the hairspring from impact. This member absorbs or dissipates impact energy before it can reach the vulnerable Grossmann curve portion, preventing deformation or breakage that would occur without this protective element

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Strength

If the inner curved portion is made of metal material, then the strength is improved, but the accuracy of speed governing is worsened due to deformation under impact

Engineering Contradiction:

Improvestrength of inner curved portionVSAvoidaccuracy of speed governing

Core Design Contradiction:

StrengthVSMeasurement precision

Solution Approach 1:

The patent applies different material properties to different parts of the hairspring structure. The inner curved portion uses silicon-based material optimized for elastic properties and speed governing accuracy, while the impact-resistant member uses metal material optimized for strength and impact resistance, allowing each part to have the local quality needed for its specific function

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12468259B2Balance, timepiece, and method for manufacturing balance

Publication Date: 2025.11.11 SEIKO EPSON CORP

AI summary

A balance includes a balance staff rotatably supported by a main plate, a collet fixed to the balance staff, and a hairspring fixed to the collet, the hairspring including a Grossmann curve disposed at a side of the collet and an Archimedes curve coupled to the Grossmann curve, and an impact-resistant member configured to suppress displacement of a shape of the Grossmann curve at least at the side of the collet.