Perforated Metal Fiber Sensor Tubes Without Drilling Damage

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Solution Overview

Problem

Existing methods for producing optical fiber sensors with metal casings face challenges such as damage to fibers during hole drilling, limitations in tube diameter and wall thickness, and deformation of holes during diameter reduction, leading to mechanical stress and weight issues.

Innovation Solution

A continuous process involving laser welding and controlled drilling methods to form and perforate metal hollow profiles with fiber conductors, allowing for precise control of energy input and hole formation without deformation, enabling smaller diameters and reduced weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If holes are made in the metal jacket before fiber insertion, then fiber damage during drilling is avoided, but the production process requires additional steps and time

Engineering Contradiction:
Improvefiber integrityVSAvoidproduction efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by making holes in the metal strip before forming it into a tube and inserting the fiber. This ensures that the holes are already positioned and sized correctly before the fiber is vulnerable to drilling damage, thereby protecting fiber integrity while maintaining production efficiency through a streamlined process sequence.

Inventive Principle:
Principle #10Preliminary action

2Ease of manufacture

If arc welding process is used, then welding can be performed, but wall thicknesses smaller than 0.15 mm cannot be welded reliably and weld beads protrude into the pipe interior

Engineering Contradiction:
Improvewelding capabilityVSAvoidweld quality and pipe interior smoothness
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical arc welding process with laser welding technology. This substitution enables reliable welding of thin-walled tubes (smaller than 0.15 mm) with precise control over the welding parameters, producing smooth welds that do not protrude into the pipe interior, thereby resolving both the welding capability and weld quality issues.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Length of moving object

If pipe diameter is reduced using drawing dies or rollers, then smaller diameters can be achieved, but the previously made perforation closes due to compressive stress

Engineering Contradiction:
Improvepipe diameterVSAvoidhole geometry
Core Design Contradiction:
Length of moving objectVSManufacturing precision

Solution Approach 1:

The patent performs the hole-making operation after the pipe diameter reduction process. By reversing the sequence of operations—first reducing the pipe to its final small diameter, then creating the holes—the compressive stress that causes hole deformation is eliminated. This allows precise hole geometry to be achieved in the final, reduced-diameter pipe.

Inventive Principle:
Principle #10Preliminary action

4Strength

If larger diameter metal tubes are used, then fiber protection is adequate, but minimum bending radius increases and weight increases

Engineering Contradiction:
Improvefiber protectionVSAvoidtube weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent changes the material parameter by using laser welding technology, which enables the fabrication of thin-walled, small-diameter tubes that maintain sufficient structural strength. This parameter change allows the use of smaller diameter tubes (reducing weight and bending radius) while still providing adequate fiber protection through optimized wall thickness and laser-welded joints.

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

Enables the production of high-quality, perforated metal hollow profiles with diameters down to 1 mm, reducing material usage, weight, and allowing for longer lengths, while minimizing fiber damage and mechanical stress.

Implementation Method 1

The edges which abut flush against one another are welded together using a laser or another welding device

Methodology Applied
Scientific EffectLaser welding: Laser Beam Welding

Implementation Method 2

a wall of the metal hollow profile is perforated by a drilling device, in particular by a laser

Methodology Applied
Scientific EffectLaser drilling: Laser Ablation

Data Source

PatentEP3832365B1Method for the continuous production of optical fibre conductor sensors mounted in a perforated metal hollow profile
Publication Date: 2023.08.30 NEXANS SA
  • EP3832365B1 patent drawingFigure 1~5b
  • EP3832365B1 patent drawingFigure 2
  • EP3832365B1 patent drawingFigure 3

AI summary

A method (100) for the continuous production of a thin-walled, perforated metal hollow profile with one or more fiber conductors embedded therein comprises feeding (102) a flat metal strip at a first feeding speed to a forming device that continuously forms the metal strip into a metal hollow profile with a longitudinally extending slot. Two opposing edges of the metal strip formed into the metal hollow profile, which lie flush against each other in a contact area extending longitudinally along the metal hollow profile, are continuously welded together (110), withdrawn from the welded area, and perforated.The method according to the invention further comprises positioning a protective tube extending into the welded hollow metal profile on the pull-out side up to behind the perforation point and feeding (111) one or more fiber conductors from one or more fiber unwinders via the protective tube, so that the fiber conductor(s) are inserted from the guide or protective tube into the perforated hollow metal profile behind the perforation point in the pull-out direction. The perforated hollow metal profile with the fiber conductor(s) stored therein is received in a receiving device (124).