Screwless Stud Holder for Silicon Balance Springs

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Solution Overview

Problem

Existing solutions for holding clockwork spiral springs in high-end timepieces often result in screw breakage due to torsion forces, and are not compatible with silicon balance springs that cannot withstand torsional or compressive stresses, as they pin the hairspring and require screw-based fixing mechanisms.

Innovation Solution

A two-part stud holder assembly with a rigid structure and a leaf spring that uses elastic return means to securely hold the stud without screws, allowing for easy introduction and extraction while maintaining the stud in a single indexed position, utilizing a chamber defined by the elastic lip and rigid structure to orient and lock the spiral spring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a screw-based fixing mechanism is used to hold the stud in the stud holder, then the stud can be securely fixed, but the screw head may be blocked and lead to regular breakage due to torsion forces

Engineering Contradiction:
Improvefixing reliabilityVSAvoidscrew breakage
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention extracts and eliminates the screw from the fixing mechanism. The stud holder is designed with a recess that directly receives and holds the stud without requiring a screw-based fixing mechanism, thereby removing the source of screw breakage while maintaining secure fixation

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using a screw to actively fasten the stud, the invention uses a passive recess structure where the stud is held by the geometry of the recess itself. The fixing mechanism is inverted from an active screw-fastening approach to a passive geometric constraint approach

Inventive Principle:
Principle #13The other way round (Inversion)

2Adaptability or versatility

If a traditional stud holder with screw threads is used, then the stud can be fixed, but it is not compatible with silicon balance springs that cannot withstand torsional or compressive stresses

Engineering Contradiction:
Improvecompatibility with silicon balance springsVSAvoidstress resistance
Core Design Contradiction:
Adaptability or versatilityVSStrength

Solution Approach 1:

The stud holder design provides a localized stress-free holding environment for the stud through a precisely shaped recess. This local geometric constraint allows the balance spring (especially silicon material) to be held without subjecting it to harmful torsional or compressive stresses, while maintaining secure positioning

Inventive Principle:
Principle #3Local quality

3Ease of manufacture

If a stamped flat part is used as the eyebolt carrier, then production is simplified, but the fixing mechanism still requires screws that can break

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidfixing reliability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The invention merges the holding function and the fixing function into a single integrated recess structure in the stud holder. This eliminates the need for separate screw components while maintaining secure fixation, thereby preserving manufacturing simplicity while improving reliability

Inventive Principle:
Principle #5Merging (Combining)

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 solution eliminates screw-based fixing issues, allows for the use of silicon balance springs, and simplifies machining and production by eliminating the need for screw threads or housings, while maintaining precise orientation and locking of the spiral spring, thus enhancing the reliability and compatibility of high-end timepiece movements.

Implementation Method 1

a leaf spring pressed against said rigid structure, said leaf spring comprising at least one elastic lip defining with said structure a chamber for receiving said stud

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP2876504B1Screwless clock stud holder
Publication Date: 2017.07.26 ETA SA MFG HORLOGERE SUISSE
  • EP2876504B1 patent drawingFigure 1~2
  • EP2876504B1 patent drawingFigure 3~5

AI summary

A watchmaking balance spring (21) retaining assembly (20) comprising a stud (1) and a stud holder (2), which includes means (6) for attaching said stud holder (2) to an escapement mechanism (30), said stud (1) having a lateral bearing surface (7) defining a direction for retaining or supporting said balance spring (21). Said stud holder (2) is in two parts, and comprises a rigid structure (5) supporting said attachment means (6), and a leaf spring (8) pressed against said rigid structure (5) and comprising at least one elastic lip (9) defining with said structure (5) a chamber (10) for receiving said stud (1) and cooperating with said lateral bearing surface (7) of said stud (1) for retaining said stud (1) in the indexed and locked position.