Clockwork Clutch Lever With Elastic Friction Arms for Stable Torque

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Solution Overview

Problem

Existing unidirectional coupling devices in watch mechanisms face challenges with reliability, robustness, size, and assembly complexity, particularly in controlling the axial and radial movement of the corrector pinion, leading to variable pivoting torques and incomplete functionality.

Innovation Solution

A clutch device featuring a rocker with integrated friction elements and elastic arms, which applies radial forces to guide and pivot the corrector mobile, ensuring consistent friction torque and controlled rotation, using materials like Durnico steel or CuBe2 alloy for enhanced performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a sliding pinion is used in a unidirectional coupling device, then the device requires few components, but the axial and radial clearance of the pinion is difficult to control, leading to variable pivoting torque

Engineering Contradiction:
Improvenumber of componentsVSAvoidaxial and radial clearance control
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent changes the clearance parameters from fixed (conventional assembly) to variable and adjustable by introducing elastic arms that can deflect to accommodate different clearance conditions, allowing the system to adapt to manufacturing tolerances while maintaining functional performance

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic elements (elastic arms with defined stiffness) that allow the coupling device to adapt its geometry during operation, transforming a static clearance problem into a dynamic solution where the elastic deformation compensates for manufacturing variations

Inventive Principle:
Principle #15Dynamics

2Reliability

If a friction spring is added to the sliding pinion to ensure sufficient torque, then the pinion can move by torque effect, but the device becomes bulky and cannot be assembled independently

Engineering Contradiction:
Improvetorque generation capabilityVSAvoidassembly independence and size
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the friction spring function with the elastic arms structure, combining torque generation and positioning functions into a single integrated component rather than adding separate friction springs to an existing sliding pinion design

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The elastic arms automatically generate the necessary friction torque through their own elastic deformation when engaged with the driven wheel, eliminating the need for separate friction spring components and enabling self-contained assembly

Inventive Principle:
Principle #25Self-service

3Ease of manufacture

If conventional assembly means are used for a clutch lever, then the structure is simple, but the friction between the lever and correction wheels cannot be adequately controlled, making the coupling device unreliable

Engineering Contradiction:
Improveassembly simplicityVSAvoidfriction control consistency
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the friction control approach from relying on conventional assembly tolerances to using deliberately designed elastic arm stiffness parameters that actively control the contact force and friction between the lever and correction wheels

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The elastic arms provide inherent feedback control where the deflection of the arms automatically adjusts the contact force to maintain consistent friction engagement, compensating for variations in assembly conditions

Inventive Principle:
Principle #23Feedback

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

The solution provides a simple, reliable, and robust unidirectional coupling mechanism that optimizes torque control, ensuring proper functioning and easy assembly, with improved resistance to manufacturing and assembly tolerances.

Implementation Method 1

at least one friction element (62) intended to cooperate with an at least substantially cylindrical portion (10c) of the first mobile (1)

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

at least one elastic arm (6a, 6b) extending longitudinally to one end of the rocker (6)

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3499319B1Clutch lever and clutch device for a clockwork mechanism
Publication Date: 2025.01.15 ROLEX SA
  • EP3499319B1 patent drawingFigure 1~2
  • EP3499319B1 patent drawingFigure 3~4
  • EP3499319B1 patent drawingFigure 5~6

AI summary

Rocker (6) comprising at least one first element (61) for guiding in rotation of a first moving part (1), at least one friction element (62) intended to cooperate with at least a substantially cylindrical portion (10c) of the first moving part and at least one elastic element (63) intended to elastically return the at least one friction element in a state of cooperation with said portion of the first moving part, in particular in contact with said portion of the first moving part, the rocker being provided with an arm (600) of which a side (600a) is provided to be actuated by an additional control mechanism.