Balance Wheel Rear-Facing Flyweight Adjustment

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Solution Overview

Problem

Existing balance-spring systems face difficulties in accessing and adjusting the inertia of flyweights, particularly when the balance wheel is mounted in a way that makes it hard to reach the weights, and there is a risk of flyweights striking the peak, impairing the balance's function.

Innovation Solution

A balance-spring system with a balance wheel that has a rear-facing flyweight mounted on an arm with a housing, allowing easy access and adjustment, where the flyweight's rod is flush with the recess, and the distance between the recess and the hairspring is within a specific interval, enabling compact design and easy manipulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the balance wheel is mounted with weights on the recessed side, then the clockwork movement can be more compact, but access to the weights for adjusting inertia becomes difficult or impossible without disassembly

Engineering Contradiction:

Improvesize of clockwork movementVSAvoidaccess to weights for adjustment

Core Design Contradiction:

Volume of moving objectVSEase of operation

Solution Approach 1:

The patent inverts the conventional mounting approach by placing the weights on the convex side (front face) of the balance wheel rather than the recessed side. This allows easy access to the weights for inertia adjustment while maintaining a compact movement design, directly resolving the contradiction between compactness and adjustability.

Inventive Principle:

Principle #13The other way round (Inversion)

2Volume of moving object

If the distance between the stud and the inner diameter of the rim is reduced to achieve compactness, then the clockwork movement becomes smaller, but the weights may strike the stud, impairing balance wheel operation

Engineering Contradiction:

Improvesize of clockwork movementVSAvoidproper operation of balance wheel

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent resolves the spatial conflict by changing the dimensional arrangement - placing weights on the front face (convex side) of the balance wheel rather than on the rim's inner diameter area. This dimensional repositioning allows the weights to be located close to the stud without risk of collision, enabling compact design while maintaining reliable operation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If the balance wheel design includes protruding elements in the recess to facilitate weight adjustment, then ease of operation improves, but the distance to the balance spring increases, preventing compact design

Engineering Contradiction:

Improveaccess to weight adjustment meansVSAvoidsize of clockwork movement

Core Design Contradiction:

Ease of operationVSVolume of moving object

Solution Approach 1:

Instead of adding protruding elements to the recess (which would increase the distance to the spring), the patent inverts the approach by placing the weights on the front face (convex side) of the balance wheel. This eliminates the need for protruding recess elements while maintaining easy access to weights and keeping the spring distance minimal for compact design.

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration allows for easy adjustment of inertia, reduces the size of the watch movement, and prevents flyweights from striking the peak, ensuring proper balance function while maintaining a compact and cost-effective design.

Implementation Method 1

a balance wheel (1) oscillating about a pivot axis (P) via a balance shaft (40) aligned on the axis P

Methodology Applied

Scientific EffectRotational inertia: Moment of Inertia

Implementation Method 2

at least one spring (2), an inner coil of which is fixed to said balance shaft (40) or to a ferrule (7) mounted integrally with said balance shaft

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP3227754B1Clockwork balance wheel-hairspring assembly

Publication Date: 2019.12.04 NIVAROX FAR SA

Figure 1a~1b
Figure 2

AI summary

The invention relates to a balance/hairspring assembly comprising a balance swinging about a balance arbour and a hairspring in which an inner coil is attached to the balance arbour or to a ferrule mounted secured to the arbour and in which an outer coil is attached to a stud secured to a bridge, the balance including a hub, a felloe, an arm connecting the hub to the felloe, a front surface having a countersink and a rear surface, the arm comprising an opening for receiving and holding a counterweight, and the hairspring being mounted opposite the front surface of the balance. According to the invention, the counterweight is mounted on the arm on the side of the rear surface of the balance, the distance between the bottom of the countersink of the front surface of the balance and the hairspring is within a predetermined interval of 0.05 mm to 1.50 mm.