Bistable Flexible Guide for Rotary Resonator

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Solution Overview

Problem

Existing rotary resonator mechanisms in mechanical watches suffer from low energy efficiency due to jerky movements, friction, and energy losses, which hinder the achievement of sufficient isochronism and independent operation in the gravity field.

Innovation Solution

A flexible guidance system for rotary resonator mechanisms is introduced, featuring a first support, a mobile element, and a pair of flexible blades connecting the support to the mobile element. The system includes prestressing means that apply a buckling force to the flexible blades, allowing the mobile element to move between two stable positions with zero residual moment, thereby achieving sinusoidal residual moment behavior.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If traditional pivots with ruby plain bearings are used to guide the balance wheel, then the resonator can rotate, but friction causes energy losses and rate disturbances

Engineering Contradiction:
Improveenergy lossesVSAvoidrate disturbances
Core Design Contradiction:
Loss of energyVSReliability

Solution Approach 1:

The patent replaces the traditional mechanical pivot-and-bearing system with a flexible guide mechanism composed of elastic blades. This substitution eliminates direct contact and friction between rotating parts, transforming the guidance system from a mechanical friction-based system to an elastic deformation-based system, thereby resolving the contradiction between energy loss and reliability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs flexible blades (thin elastic elements) to guide the resonator's movement. These blades deform elastically to accommodate the resonator's position changes without requiring physical contact or pivots, eliminating friction while maintaining guidance functionality, thus reducing energy losses and preventing rate disturbances

Inventive Principle:
Principle #30Flexible shells and thin films

2Ease of operation

If the Swiss lever escapement mechanism is used, then the resonator movements can be controlled, but the jerky movements and inclined plane friction reduce energy efficiency to around 30%

Engineering Contradiction:
Improveresonator movement controlVSAvoidenergy efficiency
Core Design Contradiction:
Ease of operationVSLoss of energy

Solution Approach 1:

The patent replaces the Swiss lever escapement mechanism with a flexible guide system that allows smooth, continuous resonator movement. The elastic blades provide gradual guidance forces instead of the jerky, discrete movements characteristic of lever escapements, eliminating inclined plane friction and significantly improving energy efficiency while maintaining movement control

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces dynamic flexibility through elastic blades that can deform continuously to guide the resonator. This dynamic system allows the resonator to move smoothly through its range of motion without the rigid, stepped control of traditional escapements, reducing energy losses from sudden movements and friction

Inventive Principle:
Principle #15Dynamics

3Reliability

If flexible reed guides are used to return the inertial element, then isochronism can be improved, but the restoring moment does not follow the ideal sinusoidal law required for perfect isochronism

Engineering Contradiction:
ImproveisochronismVSAvoidrestoring moment accuracy
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The patent modifies the physical parameters of the flexible guide system, specifically the blade geometry, material properties, and pre-stressing forces, to shape the restoring moment curve. By carefully adjusting these parameters, the system achieves a restoring moment that closely follows the ideal sinusoidal law, enabling perfect isochronism while maintaining manufacturing feasibility

Inventive Principle:
Principle #35Parameter changes

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 flexible guidance system enhances energy efficiency and achieves isochronism and independent operation in the gravity field by transforming the moment of linear recall into a bistable recall moment with a sinusoidal form, ensuring consistent rotation speed despite variations in drive force.

Implementation Method 1

a first pair of flexible blades (4, 5) connecting the first support (2) to the movable element (3), so that the movable element (3) can move relative to the first support (2) by bending the blades

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

pre-stressing means (7), the pre-stressing means being configured to apply a buckling force to the flexible blades (4, 5) by bringing the first support (2) closer to the movable element (3)

Methodology Applied
Scientific EffectBuckling:

Data Source

PatentEP3812843B1Flexible guide and set of stacked flexible guides for rotary resonator mechanism, in particular for a clock movement
Publication Date: 2025.04.23 ETA SA MFG HORLOGERE SUISSE
  • EP3812843B1 patent drawingFigure 1~4
  • EP3812843B1 patent drawingFigure 5~7
  • EP3812843B1 patent drawingFigure 8~10

AI summary

The invention relates to a flexible guide for a rotary resonator mechanism, particularly for a clockwork movement, the guide (1, 10, 30, 40, 50) comprising a first support (2, 11), a movable element (3, 13) relative to the first support (2, 11), a first pair of flexible blades (14, 15) connecting the first support (2, 11) to the movable element (3, 13), such that the movable element (3, 13) can move relative to the first support (2, 11) by bending the blades (14, 15) in a circular motion around a center of rotation (6, 18), the flexible guide (1, 10, 30, 40, 50) being arranged substantially in a plane, characterized in that it comprises prestressing means (7, 27, 37, 47), the prestressing means (7, 27, 37, 47) being configured to apply a buckling force to the flexible blades (14, 15) by bringing the first support (2, 11) closer to the moving element (3, 13), so that the flexible guide (1, 10, 30, 40,50) includes two stable positions (28, 29) of the moving element (3, 13) relative to the first support (2, 11) for which the restoring moment is zero, the two stable positions (28, 29) having a predetermined angle of rotation (2a) between them.