Eccentric Actuation for Balance Spring Stiffness Adjustment

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Solution Overview

Problem

Existing mechanical watch regulating members face challenges in precisely regulating the balance spring rate due to sensitivity to play and the risk of chronometric errors from clamping the balance spring, as well as incompatibility with integrated regulating devices.

Innovation Solution

An actuation system comprising an eccentric that prestresses the adjustment means of the balance spring, allowing the rate of the regulating member to be adjusted by changing the position of the eccentric, thereby modifying the stiffness of the balance spring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the balance spring is clamped to the index key to eliminate play, then the chronometric stability is improved, but the balance spring is stressed and off-centred windings are created causing chronometric errors

Engineering Contradiction:

Improvechronometric stabilityVSAvoidchronometric errors from off-centring

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A new component called the 'regulating element' is introduced as an intermediary between the index key and the balance spring. This regulating element receives the clamping force from the index key and transmits it to the balance spring in a controlled manner, preventing direct stress concentration and off-centring of the balance spring windings while still eliminating play

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The connection between the index key and balance spring is segmented into multiple components: the index key, the regulating element, and the balance spring itself. This segmentation allows the clamping action to be distributed and controlled, preventing the harmful direct transmission of forces that cause off-centring

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If the index key is moved to regulate the rate after clamping, then the rate fine-tuning is improved, but the play removal changes the rate and prevents further adjustment

Engineering Contradiction:

Improverate fine-tuning precisionVSAvoidrate adjustment flexibility

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The regulating element is designed to be dynamically adjustable. It can be positioned at different locations along the balance spring, allowing the rate to be regulated continuously. The system transitions from a static clamped state to a dynamically adjustable state, enabling fine-tuning without requiring re-clamping

Inventive Principle:

Principle #15Dynamics

3Device complexity

If conventional index systems are used with integrated regulating devices, then the device simplicity is improved, but the chronometric properties become sensitive to play at the index key

Engineering Contradiction:

Improveindex system simplicityVSAvoidchronometric properties stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The regulating element serves as a mediator that decouples the play at the index key from the balance spring. It absorbs and isolates the play, ensuring that chronological properties remain stable even when play exists in the index key connection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The regulating element预先 (in advance) cushions against the harmful effects of play. By positioning this element between the index key and balance spring, the system prepares for and compensates for potential play before it can affect chronometric properties

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 enables precise adjustment of the regulating member's rate with high precision, reducing the risk of chronometric errors and ensuring compatibility with integrated regulating devices, thus enhancing the accuracy and reliability of mechanical watches.

Implementation Method 1

the actuation system comprises an eccentric actuating the prestressing means of the adjustment means

Methodology Applied

Scientific EffectEccentric mechanism: Eccentric

Implementation Method 2

prestressing means for applying a variable force or torque to the flexible element

Methodology Applied

Scientific EffectPrestressing: Mechanical Force

Data Source

PatentUS20250164932A1Timepiece regulating member comprising an actuation system provided with an eccentric

Publication Date: 2025.05.22 ETA SA MFG HORLOGERE SUISSE

AI summary

A regulating member (1) for a horological movement including an inertial mass, for example a balance (23), a balance spring (25), a balance cock (22), and an actuation system (20) for adjusting the rate of the balance spring (25), the balance spring (25) including a coiled ribbon (2) and device (30) for adjusting the stiffness of the balance spring, which device is provided with a resilient element (5) arranged in series with the coiled ribbon (2), the adjustment device (30) including a pre-stress device (6) for applying a variable force or torque to the flexible element (5), the actuation system (20) including an eccentric actuating the pre-stress device (6) of the adjustment device (30).