Balance Spring Stud Attachment Using Off-Centre Coil Re-Centering

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Solution Overview

Problem

Existing balance springs in mechanical timepieces face challenges in maintaining isochronous oscillation due to factors like oxidation, magnetism, and assembly methods that introduce mechanical stresses or adhesion issues, affecting precision and reliability.

Innovation Solution

A balance spring design with off-centre coils that rearrange to a centred configuration upon attachment to a stud, using a hook-shaped stop means for secure engagement without adhesives or pins, ensuring resilient tension for reliable attachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesive or pin attachment methods are used to secure the balance spring to the stud, then the attachment strength is improved, but the device complexity and manufacturing precision are worsened due to additional components and assembly steps

Engineering Contradiction:

Improveattachment strengthVSAvoidassembly complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent removes adhesive and pin components from the attachment system, extracting the fastening function entirely from separate elements and integrating it into the balance spring's own structure through the resilient stop means that engages directly with the stud

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The balance spring's stop means possesses inherent resilient properties that enable it to attach to the stud without external fasteners or adhesives, using its own elastic deformation capacity to create the attachment mechanism

Inventive Principle:

Principle #25Self-service

2Reliability

If traditional assembly methods with pins or adhesives are used, then the attachment reliability is improved, but the manufacturing precision is worsened due to alignment and bonding variability

Engineering Contradiction:

Improveattachment reliabilityVSAvoidassembly precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces mechanical fastening systems (pins, adhesives) with an elastic-mechanical system where the stop means uses resilient deformation to achieve attachment, eliminating alignment and bonding variability issues

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If the balance spring coils are arranged off-centre in the free state, then the ease of manufacture is improved, but the shape stability is worsened until mounted

Engineering Contradiction:

Improveassembly easeVSAvoidcoil configuration stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The balance spring is pre-formed with off-centre coils in the free state to facilitate manufacturing and assembly, then undergoes a configuration change upon mounting where the resilient stop means engagement causes the coils to rearrange into a centred, stable configuration

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent accepts dynamic reconfiguration of the coil arrangement from off-centre in the free state to centred in the mounted state, using the resilient properties of the stop means to drive this transformation and achieve stable operation

Inventive Principle:

Principle #15Dynamics

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

This design enhances precision and reproducibility by simplifying assembly, reducing mechanical stresses, and ensuring consistent timing performance while avoiding detachment issues.

Implementation Method 1

the coils being arranged off-centre when the balance spring is in the free state and rearranging themselves in a concentric manner when the balance spring is in the mounted state

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the attachment of the balance spring to the stud inducing, in the coils of the balance spring, a resilient stress as a result whereof the stop means is attached in a captive manner to the stud

Methodology Applied

Scientific EffectResilient stress: Elasticity

Data Source

PatentUS12535770B2Balance spring of a sprung balance assembly of a mechanical horological movement

Publication Date: 2026.01.27 ETA SA MFG HORLOGERE SUISSE

AI summary

A balance spring (1) of a sprung balance assembly of a mechanical horological movement, formed by a succession of coils (S1, . . . , Sn) which extend between a first free end, referred to as inner first coil (2), and a second free end, referred to as outer last coil (6). The are arranged off-centre when the balance spring is in the free state, the outer last coil (6) terminating in a stop means for the attachment thereof to a stud (14). The balance spring (1) is centred and its spires concentric when the spring (1) is in the mounted state inside the sprung balance assembly, the coils being rearranged concentrically when the spring is in the mounted state. The attachment of the spring to the stud inducing, in the coils, a resilient stress as a result whereof the stop is attached in a captive manner to the stud (14).