Triangular Capillary Depth Gauge for High-Contrast Readings

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Solution Overview

Problem

Conventional capillary depth gauges face challenges in readability due to low contrast between air and water, leading to inaccurate depth measurements, especially when water drops form inside the tube, causing pressure differences and optical effects that hinder precise reading.

Innovation Solution

A capillary depth gauge with an isosceles triangular section and strategically positioned reflection faces, optimized with an angle of 50-55 degrees and a narrowest tube width less than 1.5 mm, ensures even pressure distribution and enhances optical effects for improved readability, featuring multiple capillary tubes for redundancy and enhanced visibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional round capillary tube is used, then the structure is simple, but the contrast between air and water is low making reading difficult

Engineering Contradiction:
ImprovereadabilityVSAvoidcapillary tube shape
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by changing the capillary tube cross-section from a conventional round shape to an isosceles triangular shape with specific angles (50-55 degrees). This asymmetric geometry creates favorable optical conditions for total internal reflection at the capillary walls when filled with air, significantly enhancing the contrast between the air-filled and water-filled states. The triangular profile with optimized angles ensures that light reflects off the capillary walls at angles that maximize visibility of the air-water interface, directly resolving the low contrast problem while maintaining manufacturing feasibility.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The patent applies parameter changes by optimizing specific geometric parameters of the triangular capillary tube - the base angles are set between 50-55 degrees and the width at the narrowest point is limited to less than 1.5 mm. These parameter optimizations create the ideal conditions for total internal reflection to occur at the capillary walls when air is present, while preventing excessive capillary pressure that would cause water droplet formation. By carefully controlling these parameters, the patent achieves high contrast readability without the harmful effects of water droplet accumulation.

Inventive Principle:
Principle #35Parameter changes

2Illumination intensity

If the capillary tube width is increased, then the optical effect is enhanced, but water drops form due to capillary pressure differences

Engineering Contradiction:
Improveoptical effectVSAvoidwater drop formation
Core Design Contradiction:
Illumination intensityVSReliability

Solution Approach 1:

The patent applies parameter changes by establishing an optimal range for the capillary tube dimensions - the base angles are specified as 50-55 degrees and the width at the narrowest point is constrained to less than 1.5 mm. These parameter choices create a balance: the triangular geometry with these specific parameters generates sufficient optical effect through total internal reflection while the limited width prevents excessive capillary pressure that would cause water droplet formation. The parameter optimization ensures both optical performance and reliability.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent converts the potentially harmful capillary pressure effect into a beneficial one. By using a triangular cross-section with specific angles and limited width, the capillary pressure that would normally cause water droplet formation is transformed into a uniform distributing force along the three sides of the triangle. This uniform distribution prevents localized pressure concentrations that lead to droplet formation, while the triangular geometry itself enhances the optical reflection effect. The design turns what could be a harmful pressure concentration into a beneficial uniform pressure distribution.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Stability of the object's composition

If an equilateral triangular section is used, then pressure is distributed evenly, but the optical effect may be reduced

Engineering Contradiction:
Improvepressure distributionVSAvoidoptical effect
Core Design Contradiction:
Stability of the object's compositionVSIllumination intensity

Solution Approach 1:

The patent applies parameter changes by deviating from the equilateral triangle (60-degree angles) and instead using isosceles triangles with base angles of 50-55 degrees. This parameter modification optimizes both pressure distribution and optical effect. The slightly smaller base angles compared to an equilateral triangle create more favorable conditions for total internal reflection at the capillary walls, enhancing the optical effect. Simultaneously, the triangular geometry maintains even pressure distribution along its three sides, preventing localized stress concentrations. The optimized parameters achieve a superior balance between structural stability and optical performance.

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

The triangular configuration and optimized dimensions enhance the optical contrast, providing clear and precise depth readings by distributing pressure evenly and maintaining visibility through total internal reflection, reducing the occurrence of water drops and improving the overall performance of the depth gauge.

Implementation Method 1

When the tube is full of air, under certain angle of incidence conditions, the difference in refractive index between the air and the material of the capillary produces total reflection of light.

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

water drops are formed in the capillary tube, since the pressure difference due to the capillary effect at the air-water interface is not uniform.

Methodology Applied
Scientific EffectCapillary effect: Capillary Action

Data Source

PatentEP2325603B1High-contrast capillary depth gauge and watch comprising such a depth gauge
Publication Date: 2018.05.23 THE SWATCH GRP RES & DEVELONMENT LTD
  • EP2325603B1 patent drawingFigure 1~2
  • EP2325603B1 patent drawingFigure 3a~3b
  • EP2325603B1 patent drawingFigure 4

AI summary

The gauge (1) has a capillary tube of triangular section that is arranged against a background opposite to an observation surface and visible by transparency from the observation surface. A tubular section is filled with water and a reflection surface is visible by reflection from the observation surface. The capillary tube forms an isosceles triangle whose equal angles having an angular value between 48-60[deg] . The reflection surface is arranged opposite on the sides of isosceles triangle. An independent claim is included for watch.