Epicyclic Counting Chain for Compact 24-Hour Chronograph Displays

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Solution Overview

Problem

Existing chronograph mechanisms require numerous moving parts to achieve high gear ratios for 12 or 24-hour displays, leading to bulkiness and inefficiency, particularly in watch movements.

Innovation Solution

A clockwork mechanism incorporating an epicyclic gear train with one planetary gear fixed to the frame, allowing a compact design that can switch between 12 and 24-hour displays by replacing specific moving parts with an epicyclic gear train.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If numerous moving parts are arranged in the counting chain to achieve high gear ratios, then the required gear ratio for 12 or 24-hour display is achieved, but the bulk and complexity of the watch movement increases considerably

Engineering Contradiction:

Improvegear ratioVSAvoidnumber of moving parts

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent merges multiple gear functions into a single epicyclic gear train assembly. The compound planet gear combines sun gears, planet gears, and ring gears into one integrated mechanism that achieves the required 720:1 or 1440:1 gear ratio through the coordinated rotation of its components, eliminating the need for numerous separate gears stacked in series

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The epicyclic gear train employs a nested configuration where planet gears are positioned within the annular space between the sun gear and the ring gear. This nesting allows multiple gear stages to occupy a compact radial space, achieving high gear reduction without increasing the axial length or overall footprint of the movement

Inventive Principle:

Principle #7Nested doll (Nesting)

2Quantity of substance

If numerous moving parts are arranged in the counting chain to achieve high gear ratios, then the required gear ratio for 12 or 24-hour display is achieved, but the dimensions of the watch movement increase

Engineering Contradiction:

Improvegear ratioVSAvoidmovement dimensions

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent transitions from a linear arrangement of gears along the axis to a two-dimensional epicyclic configuration where gears are distributed radially around a central axis. This dimensional change allows the gear train to achieve high reduction ratios within a compact circular footprint, optimizing the use of available space in the watch movement

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Quantity of substance

If separate blanks are developed to rotate the display moving parts over 12 hours and 24 hours, then the required gear ratios are achieved, but the manufacturing complexity and part variety increases

Engineering Contradiction:

Improvegear ratioVSAvoidblank variety

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The epicyclic gear train is designed with dynamic characteristics that allow it to operate at different speed ratios depending on the engagement state. By selectively engaging different elements of the epicyclic train or adjusting the input speed, the same mechanism can provide the necessary gear reduction for both 12-hour and 24-hour displays, eliminating the need for separate dedicated mechanisms

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent designs a universal epicyclic gear train that can serve multiple functions - achieving the required gear ratios for both 12-hour and 24-hour chronograph displays. This multi-functional design allows a single mechanism to replace what would traditionally require separate dedicated gear trains, simplifying manufacturing and reducing part variety

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

Achieves high gear ratios with a compact design, enabling efficient 24-hour display without significantly increasing the movement's dimensions, using the same blanks for both 12 and 24-hour displays.

Implementation Method 1

an epicyclic gear train with one planetary gear fixed to the frame

Methodology Applied

Scientific EffectEpicyclic gearing: Epicyclic Gearing

Implementation Method 2

achieves high gear ratios with a compact design

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentEP3944026B1Timepiece mechanism with counting chain

Publication Date: 2025.12.31 ROLEX SA

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AI summary

Clock mechanism (110), in particular clock movement or chronograph module, comprising: - a frame (80, 81), and - a counting chain (100) comprising an epicyclic train (31, 32, 33, 34) including a first planetary gear (33) fixed to the frame. A method for assembling two separate mechanisms or two separate timepieces, comprising the following steps: - a step of supplying a frame (80, 81), - a step of mounting a drive wheel (20) onto the frame (80, 81), - a step of mounting an hour counter (40) onto the frame (80, 81), and - a step of assembling: • a wheel (30') meshing with the drive wheel and with the hour wheel, or • an epicyclic gear train (31, 32, 33, 34) meshing with the drive wheel and with the hour wheel. The method makes it possible to obtain two separate mechanisms but with identical frames, identical drive wheels, and an identical hour wheel.