Curved Clock Movement Spring for Low-Stress Energy Storage

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Solution Overview

Problem

Watch mechanism springs face challenges in minimizing mechanical stresses within a given size while adjusting forces effectively, with existing designs either having high mechanical constraints or being difficult to manufacture industrially.

Innovation Solution

A spring design with a body extending between two ends, featuring a deformable zone along a curved section that is highly deformable, allowing for optimal preload and energy storage with low angular rigidity, and adjustable pivot distances for varying forces and functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If a spring with elongated blade shape is used to minimize mechanical stresses, then the spring can provide adequate force, but the available volume is exceeded and the spring cannot be easily adjusted

Engineering Contradiction:
Improvemechanical stressesVSAvoidavailable volume
Core Design Contradiction:
Stress or pressureVSVolume of stationary object

Solution Approach 1:

The spring is divided into distinct functional zones: a first end for attachment, a deformable zone with specific curvature for stress management, and a second end for actuation. This segmentation allows each zone to be optimized independently - the deformable zone handles stress while the overall geometry fits within volume constraints.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The spring features a deformable zone with specific curvature characteristics that differ from the rest of the spring body. This local variation in geometry allows the spring to have different mechanical properties in different regions - higher deformability in the curved zone for stress management while maintaining structural integrity elsewhere.

Inventive Principle:
Principle #3Local quality

2Force

If a V-shaped spring lever with blocked spring part is used, then the spring can provide restoring force, but the angular rigidity is insufficient and forces on the stem are not optimized

Engineering Contradiction:
Improverestoring forceVSAvoidangular rigidity
Core Design Contradiction:
ForceVSStability of the object's composition

Solution Approach 1:

The spring incorporates a deformable zone with specific curvature (concave or convex) rather than straight segments. This curvature allows the spring to achieve both flexibility for restoring force and angular rigidity for stable positioning, resolving the contradiction between soft restoring action and rigid positioning.

Inventive Principle:
Principle #14Spheroidality (Curvature)

3Volume of stationary object

If wire springs are used to reduce size of energy storage device, then the size is reduced, but bending tolerances are very difficult to guarantee

Engineering Contradiction:
Improveenergy storage device sizeVSAvoidbending tolerances
Core Design Contradiction:
Volume of stationary objectVSManufacturing precision

Solution Approach 1:

The spring design specifies particular geometric parameters including the curvature of the deformable zone, the dimensions of connection elements, and the relative positions of attachment points. These controlled parameters allow the spring to achieve compact size while maintaining manufacturability and consistent performance through defined geometric constraints.

Inventive Principle:
Principle #35Parameter changes

4Use of energy by moving object

If a spring with single pivot point in center of blade is used, then the spring can accumulate energy, but the energy storage capacity is low at given maximum internal stress

Engineering Contradiction:
Improveenergy storageVSAvoidmaximum internal stress
Core Design Contradiction:
Use of energy by moving objectVSStress or pressure

Solution Approach 1:

The spring transitions from a single-pivot configuration to a two-pivot configuration with a deformable zone between them. This dimensional change in the support structure allows the spring to store more energy by distributing stresses more effectively across the deformable zone, increasing energy storage capacity at the same maximum internal stress level.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 minimizes mechanical stresses and forces, maximizes energy storage, and facilitates industrial production, enabling optimal performance in a compact volume with adjustable force ranges for different watch mechanisms.

Implementation Method 1

The body comprises at least one deformable zone (14) extending along a curve (18). The curve comprises a first concave part (18a) seen from the first end (12). The zone (14) has a substantially rectangular section which is highly deformable under an action of a given intensity.

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP2798414B1Spring for clock movement
Publication Date: 2024.03.20 ROLEX SA
  • EP2798414B1 patent drawingFigure 1~2
  • EP2798414B1 patent drawingFigure 3~4

AI summary

Spring (10) for clock mechanism, the spring comprising a body (11) extending between a first end (12) of the spring and a second end (13) of the spring, the spring being intended to be connected mechanically to a housing at each of the first and second ends, the spring comprising, between the first and the second end, at least one member (17) intended to act by contact on an element (42) of the clock mechanism, characterized in that the body comprises a deformable zone (14) extending in a curve (18) and in that the curve comprises a first part (18a) that is concave when viewed from the first end.