Magnetically Pivoted Balance With Annular Magnets for Precise Centring

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Solution Overview

Problem

Existing magnetic pivot systems for horological components, such as balances, face challenges in centring due to low biasing force for small radial movements and millimetric inhomogeneities in magnets, affecting interaction with the escapement.

Innovation Solution

A mechanism using a pair of annular magnets, one carried by the rotary element and one by the mechanism structure, exerting a radial magnetic biasing force through magnetic attraction, with additional end magnets for enhanced centring, reducing friction and wear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional magnetic pivots with point contacts are used, then friction is reduced compared to mechanical bearings, but the magnetic biasing force is insufficient for small radial movements and centring is poor

Engineering Contradiction:

ImprovefrictionVSAvoidcentring precision

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The single point contact magnetic pivot is segmented into two annular magnets with distributed contact surfaces. The first annular magnet is carried by the rotary element and the second annular magnet is carried by the mechanism structure, creating a distributed magnetic field that provides both frictionless support and strong centring force through the annular geometry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from point contact (0D) to annular contact (1D surface) in the radial direction, and utilizes the axial dimension by positioning the two annular magnets at a defined axial distance. This multi-dimensional approach increases the magnetic interaction area while maintaining the frictionless benefit.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Force

If magnets with millimetric dimensions are used, then the magnetic pivot can support the rotary element, but inhomogeneities in the magnets affect centring accuracy

Engineering Contradiction:

Improvemagnetic support forceVSAvoidcentring accuracy

Core Design Contradiction:

ForceVSManufacturing precision

Solution Approach 1:

The magnetic pivot is segmented into two separate annular magnets positioned at an axial distance, which distributes the magnetic interaction across multiple zones. This segmentation reduces the impact of local inhomogeneities in each individual magnet on overall centring accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the geometric parameters from point contact to annular contact with specific inner and outer radii, and optimizes the axial distance between the two annular magnets. These parameter changes enhance the magnetic field distribution and reduce sensitivity to manufacturing inhomogeneities.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If the balance is not accurately centred, then the interaction with the escapement is affected, but increasing the magnetic biasing force may increase friction or wear

Engineering Contradiction:

Improvecentring accuracyVSAvoidfriction and wear

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The invention replaces the mechanical contact-based centring mechanism with a magnetic field-based centring mechanism using two annular magnets. This substitution provides accurate centring through magnetic attraction while maintaining frictionless operation, as the magnetic force acts at a distance without physical contact.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution provides effective radial centring and reduced friction, ensuring accurate alignment and reduced wear, enhancing the performance of horological movements.

Implementation Method 1

these first and second annular magnets being arranged in magnetic attraction so as to impart on one another a first axial magnetic force and, substantially as soon as the central axis of the rotary element deviates radially from the axis of rotation, a first radial magnetic force

Methodology Applied

Scientific EffectMagnetic attraction: Magnetism

Implementation Method 2

it is guided in rotation essentially by a magnetic device

Methodology Applied

Scientific EffectMagnetic levitation: Maglev

Data Source

PatentUS12517464B2Mechanical horological movement comprising a magnetically-pivoted balance

Publication Date: 2026.01.06 THE SWATCH GRP RES & DEVELONMENT LTD

AI summary

A mechanism including a rotary element and a magnetic device for guiding this rotary element in rotation arranged so as to exert a radial magnetic biasing force on the rotary element when a central axis of this rotary element undergoes a radial movement relative to a given axis of rotation. The magnetic device includes a pair of annular magnets the first annular magnet of which is carried by the rotary element and the second annular magnet is carried by a structure of the mechanism. The second annular magnet is parallel and axially superimposed with the first annular magnet when the central axis of the rotary element is coincident with the axis of rotation, the first and second annular magnets being arranged in magnetic attraction so as to impart on one another an axial magnetic force and a radial magnetic force.