Swiss Lever Escapement Pallet Width Optimization

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Solution Overview

Problem

Existing Swiss lever escapements have limitations in efficiency, with standard designs achieving around 43-49% efficiency, and there is a need to explore further improvements in parameters to enhance performance.

Innovation Solution

Optimizing the Swiss lever escapement by minimizing the relative width of the pallets (Lpl) and increasing the width of the escape wheel's tooth, while maintaining the same angular sector for energy transmission, and adjusting the ratio of impulse plane lengths to improve energy transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the impulse plane length of pallets is increased, then reliability is improved, but efficiency deteriorates

Engineering Contradiction:
ImprovereliabilityVSAvoidefficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies parameter changes by optimizing the impulse plane length of pallets to a specific range (0.15-0.30 times the escape wheel tooth height) and adjusting the ratio between pallet impulse plane length and tooth impulse plane length (0.5-2.0) to achieve optimal efficiency while maintaining reliability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating asymmetric impulse plane lengths where the entry pallet and exit pallet have different optimal lengths relative to the escape wheel teeth, with each pallet's impulse plane optimized for its specific functional requirements in the energy transmission process

Inventive Principle:
Principle #3Local quality

2Reliability

If the pallet width is increased, then reliability is improved, but efficiency deteriorates

Engineering Contradiction:
ImprovereliabilityVSAvoidefficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies parameter changes by optimizing the pallet width parameter to a specific range (0.10-0.25 times the escape wheel tooth height) to achieve the best balance between reliability and efficiency, transforming the conventional approach of wider pallets being always better

Inventive Principle:
Principle #35Parameter changes

3Loss of energy

If the escape wheel tooth width is decreased, then efficiency is improved, but manufacturing precision requirements worsen

Engineering Contradiction:
ImproveefficiencyVSAvoidmanufacturing precision
Core Design Contradiction:
Loss of energyVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by optimizing the escape wheel tooth width and the ratio between tooth impulse plane length and pallet impulse plane length to a specific range (0.5-2.0), achieving high efficiency while establishing achievable manufacturing precision requirements through defined parameter ranges

Inventive Principle:
Principle #35Parameter changes

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 approach results in a 10-11% increase in efficiency compared to standard configurations, with the optimized design achieving up to 51% efficiency for a 24-tooth escape wheel, as demonstrated by prototype testing and measurements.

Implementation Method 1

The teeth of the wheel as well as the pallets of the anchor with which they are alternately in contact are the connecting elements between the wheel and the anchor

Methodology Applied
Scientific EffectImpulse force: Impact Force

Implementation Method 2

the edge of the pallet wheel tooth is pushed by the torque provided by the barrel spring through the gear train against the plane of impulse of the input pallet, which generates a torque around the pivot axis of the anchor

Methodology Applied
Scientific EffectMechanical energy transmission: Mechanical Force

Implementation Method 3

an anchor provided on the one hand with an entry pallet and an outlet pallet, engaging alternately with the teeth of the escape wheel, on the other hand a fork engaging periodically with a pin of a plate secured to the shaft of a regulating balance

Methodology Applied
Scientific EffectOscillation: Harmonic Oscillator

Implementation Method 4

This torque puts the fork in contact with the pin of the balance plate and begins the transmission of energy to the balance

Methodology Applied
Scientific EffectEnergy storage: Mechanical Accumulator

Data Source

PatentEP2336832B1Swiss lever escapement
Publication Date: 2020.12.02 ROLEX SA
  • EP2336832B1 patent drawingFigure 1~2
  • EP2336832B1 patent drawingFigure 3~4
  • EP2336832B1 patent drawingFigure 5

AI summary

The escapement has an escapement wheel with teeth, and a lever provided with entry and exit pallets alternately engaged with the teeth. The lever comprises a fork regularly engaged with a dowel pin of a plate secured to a shaft of a crank regulator. The relative width of each of the pallets, expressed as a percentage of the cumulative arc length of one of the teeth and one of the pallets, measured on circumference of the wheel is a specific formula constituted of parameters of arc widths of the exit and entry pallets and arc width of the teeth and less than or equal to 45 percent.