Thin Disc Barrel Structure for Watch Power Reserve

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Solution Overview

Problem

Mechanical watches with limited dimensions face challenges in maximizing power reserve due to the constraints of barrel size, where the diameter of the barrel is smaller than the movement's radius, limiting the storage of energy within a small volume.

Innovation Solution

The solution involves reducing the thickness of the barrel's discs to maximize the useful height available for the mainspring, allowing for a greater power reserve without increasing the barrel's size, using materials like ceramic, ruby, or high-performance metal alloys for thin disc production and optimizing the annular projection for mechanical strength and tribological performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If the thickness of the barrel walls is reduced to increase the spring housing height, then the power reserve is improved, but the mechanical strength and reliability deteriorate

Engineering Contradiction:
Improvepower reserveVSAvoidmechanical strength of barrel walls
Core Design Contradiction:
Duration of action of moving objectVSStrength

Solution Approach 1:

The patent applies parameter changes by reducing the thickness of the barrel walls from conventional values (typically 0.2 mm) to much thinner values (less than 0.05 mm, preferably less than 0.02 mm). This parameter change enables the barrel walls to be sufficiently thin to maximize the spring housing height and power reserve, while the use of advanced materials compensates for the reduced thickness to maintain mechanical strength.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials, specifically advanced ceramics (such as silicon nitride, silicon oxide, or zirconium oxide), to replace conventional metal materials for the barrel walls. These ceramic materials provide high mechanical strength and rigidity despite their thin cross-section, enabling the barrel to maintain structural integrity while having reduced wall thickness to maximize the spring housing volume and power reserve.

Inventive Principle:
Principle #40Composite materials

2Duration of action of moving object

If the barrel size is increased to store more energy, then the power reserve is improved, but the device dimensions increase

Engineering Contradiction:
Improvepower reserveVSAvoidbarrel volume
Core Design Contradiction:
Duration of action of moving objectVSVolume of moving object

Solution Approach 1:

The patent applies parameter changes by dramatically reducing the wall thickness parameter (to less than 0.05 mm, preferably less than 0.02 mm), which increases the internal volume available for the mainspring without increasing the external dimensions of the barrel. This allows the spring housing height to be maximized within the constrained barrel volume, thereby increasing power reserve while maintaining compact size.

Inventive Principle:
Principle #35Parameter changes

3Duration of action of moving object

If the disc thickness is reduced to maximize spring height, then the power reserve is improved, but the manufacturing precision and reliability deteriorate

Engineering Contradiction:
Improvepower reserveVSAvoiddisc thickness precision
Core Design Contradiction:
Duration of action of moving objectVSManufacturing precision

Solution Approach 1:

The patent uses advanced ceramic materials (silicon nitride, silicon oxide, zirconium oxide) for the barrel discs and walls, which can be manufactured with high precision and consistency at very thin thicknesses (less than 0.05 mm, preferably less than 0.02 mm) using specialized ceramic processing techniques. These materials and processes enable reliable production of ultra-thin components with controlled thickness, overcoming the manufacturing precision challenges that would arise with conventional materials.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent applies parameter changes by reducing the disc thickness to extreme values (less than 0.05 mm, preferably less than 0.02 mm) while using advanced ceramic materials and manufacturing processes that can achieve and control such thin dimensions with high precision. This parameter change, combined with appropriate material selection and processing, enables the discs to be sufficiently thin to maximize spring height and power reserve while maintaining manufacturing feasibility and reliability.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2437125B1Timepiece
Publication Date: 2019.09.04 ROLEX SA
  • EP2437125B1 patent drawingFigure 1
  • EP2437125B1 patent drawingFigure 2a
  • EP2437125B1 patent drawingFigure 2b~3

AI summary

The movement has a barrel (1) for a housing of a mainspring whose diameter is less than radius of movement. The barrel has a cylindrical sidewall (2) surrounded by teeth (3). The sidewall has edges closed by disks (4, 4'), where each disk has an axial opening for passage of arbor (7). Height of the housing ranges between 85 percentage and 97 percentage of total height at periphery of the barrel. One of the disks has thickness ranging between 0.04 and 0.12 mm. The opening is encircled by annular projection (6) connected to a surface of the disk that is formed from silicon, quartz and diamond.