Timepiece Balance Felloe with Nested Inertia Blocks

Solution Overview

Problem

Watch balance designs face challenges in achieving a larger diameter without increasing moment of inertia, which can lead to reduced mass and friction issues, affecting chronometric performance and isochronism.

Innovation Solution

Incorporating inwardly directed studs with threaded holes in the balance felloe, allowing inertia blocks to be screwed in from the inside, which can adjust the moment of inertia without extending beyond the external surface, and can be distributed between arms or in recesses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the diameter of the felloe is increased without changing the moment of inertia, then the balance will have less mass and reduced friction in the bearings, but the felloe becomes too weak to carry the adjusting inertia blocks

Engineering Contradiction:

Improvemass of the balanceVSAvoidstrength of the felloe

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The inertia blocks are nested within the felloe structure by screwing them into threaded holes that pass through the felloe. The studs protruding inward from the inner surface of the felloe provide support for the inertia blocks, allowing them to be contained within the overall diameter of the felloe. This nesting approach allows the balance to achieve larger diameter with reduced mass while maintaining the strength needed to carry the inertia blocks.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Instead of increasing the radial thickness of the felloe to maintain strength, the design uses the axial dimension by screwing the inertia blocks into the felloe through threaded holes. This allows the strength requirement to be met by utilizing the depth of the felloe rather than increasing its radial cross-section, thereby maintaining reduced mass while achieving the desired strength.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the cross section of the felloe is decreased to maintain the same moment of inertia with a larger diameter, then the mass is reduced and friction is reduced, but the felloe becomes too weak to carry the inertia blocks

Engineering Contradiction:

Improvediameter of the felloeVSAvoidstrength of the felloe

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The inertia blocks are nested within the felloe structure by screwing them into threaded holes that pass through the felloe. The studs protruding inward from the inner surface of the felloe provide support for the inertia blocks, allowing them to be contained within the overall diameter of the felloe. This nesting approach allows the balance to achieve larger diameter with reduced mass while maintaining the strength needed to carry the inertia blocks.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Instead of increasing the radial thickness of the felloe to maintain strength, the design uses the axial dimension by screwing the inertia blocks into the felloe through threaded holes. This allows the strength requirement to be met by utilizing the depth of the felloe rather than increasing its radial cross-section, thereby maintaining reduced mass while achieving the desired strength.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If inertia blocks are screwed into the felloe from the inside with threaded holes passing through the felloe and studs, then the moment of inertia can be adjusted without extending beyond the external surface, but the device complexity increases

Engineering Contradiction:

Improveadjustability of the moment of inertiaVSAvoidcomplexity of the balance structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The threaded holes passing through the felloe serve multiple functions: they provide the threading for securing the inertia blocks, they define the positioning of the inertia blocks, and they allow for adjustment of the moment of inertia. The studs protruding inward from the inner surface of the felloe provide additional support and positioning for the inertia blocks. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enables a balance with a larger diameter or higher frequency while maintaining reduced mass, enhancing chronometric performance by allowing precise adjustment of the moment of inertia without compromising structural integrity.

Implementation Method 1

a balance for a timepiece movement, comprising a felloe and arms connecting the felloe to an arbour, to be associated with a balance spring to form, in a conventional manner, the mechanical oscillator

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the pertinent parameter of the balance is the moment of inertia. Since the role of the arms is very limited in the moment of inertia, the latter depends foremost upon the dimensions (diameter and cross section) and density of the felloe and the elements connected thereto

Methodology Applied

Scientific EffectMoment of inertia: Moment of Inertia

Data Source

PatentUS7661875B2Balance for timepiece movement

Publication Date: 2010.02.16 NIVAROX FAR SA

AI summary

The balance comprising a felloe (3), arms (4) connecting the felloe (3) to the balance staff and inertia blocks (11) is characterized in that the felloe (3) includes studs (7) in its inner surface, a threaded hole (9) into which said inertia blocks (11) are screwed from the inside, without passing beyond the external surface of the felloe (3), passing through said felloe (3) and said studs (7).