3D Knitted Flame-Resistant Undergarment With Hollow Air Pockets

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Solution Overview

Problem

Commercially available knitted functional underwear is unsuitable for use under racing suits or astronaut suits due to inadequate strength, abrasion resistance, and flame-retardant properties, and does not provide sufficient wearing comfort.

Innovation Solution

A seamless knitted functional underwear is developed using a special multifilament yarn with a 3D knitting structure featuring hollow shapes and air pockets, combined with a specific chemical composition of yarn filaments, including viscose, aramid, polyamide, elastane, and carbon fibers, to enhance strength, abrasion resistance, and flame protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If commercially available knitted functional underwear is used, then basic moisture management and comfort are provided, but flame-retardant properties and strength are insufficient for high-heat environments

Engineering Contradiction:
Improveflame-retardant propertiesVSAvoidwearing comfort
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent uses a multifilament yarn comprising four different fiber types: viscose filaments (55-65 wt%), aramid filaments (20-30 wt%), polyamide filaments (5-15 wt%), and elastane filaments (3-7 wt%). This composite material structure combines the flame resistance of aramid, the moisture management of viscose, the durability of polyamide, and the elasticity of elastane, thereby achieving both flame-retardant properties and wearing comfort simultaneously.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent implements different knitting structures in different body regions: a first knitting structure with higher stitch density in areas requiring flame protection (torso, arms, legs) and a second knitting structure with lower stitch density in areas requiring flexibility (underarms, groin). This localized differentiation optimizes both flame protection and wearing comfort in specific zones.

Inventive Principle:
Principle #3Local quality

2Reliability

If flame-retardant properties are enhanced through material selection, then protection in high-heat environments is improved, but strength and abrasion resistance may be compromised

Engineering Contradiction:
Improveflame protectionVSAvoidabrasion resistance
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The multifilament yarn combines aramid filaments (providing flame resistance) with polyamide filaments (providing strength and abrasion resistance). The specific weight ratio of 20-30% aramid and 5-15% polyamide ensures that flame protection and mechanical strength are both sufficiently provided without compromising either property.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent specifies precise parameter ranges for the yarn composition and knitting structure to optimize both flame protection and strength. The stitch density is controlled at 18-24 stitches per 5 cm, and the yarn composition is tightly defined to ensure minimum performance thresholds for both flame resistance and mechanical durability are met.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If stitch density is increased to improve flame protection, then heat resistance is enhanced, but flexibility and comfort may be reduced

Engineering Contradiction:
Improveheat resistanceVSAvoidflexibility
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent applies different knitting structures in different body regions: a first knitting structure with higher stitch density (18-24 stitches per 5 cm) in areas requiring flame protection and a second knitting structure with lower stitch density in areas requiring flexibility. This localized approach ensures heat resistance where needed while maintaining flexibility where required.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The inclusion of elastane filaments (3-7 wt%) in the multifilament yarn provides elasticity and flexibility that compensates for the higher stitch density in flame-protection areas, allowing the garment to maintain both heat resistance and comfort.

Inventive Principle:
Principle #40Composite materials

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 underwear provides improved flame resistance, enhanced wearing comfort, and maintains robustness, making it suitable for high-heat environments like racing suits and astronaut suits.

Implementation Method 1

a 3D knitting structure featuring hollow shapes and air pockets... to enhance strength, abrasion resistance, and flame protection

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

functional underwear is designed to effectively wick moisture away from the skin

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Data Source

PatentEP4556610B1Flame-resistant functional undergarment for racing drivers and astronauts and flame-resistant multifilament yarn
Publication Date: 2026.04.15 SWISS INTELLECTUAL PROPERTIES & LICENSING AG
  • EP4556610B1 patent drawingFigure 1~2
  • EP4556610B1 patent drawingFigure 3a~3b
  • EP4556610B1 patent drawingFigure 3c~3d

AI summary

The flame-retardant effect of knitted functional underwear made from a base yarn and a basic knitted structure along at least one area of ​​the functional underwear, with several additional areas having different functional knitted structures, is intended to be increased. This is achieved by the fact that the knitted, single-layer functional underwear predominantly has a 3D knitted structure knitted with the base yarn, which comprises a plurality of knitted, raised hollow shapes with air inclusions, i.e., tubular or circular.tubular and thus longer than wide hollow forms are knitted in during the knitting process and the base yarn of the 3D knitted structure is formed from a multifilament yarn of - between 80 and 120 individual yarn filaments, and wherein the total weight of the multifilament yarn is proportionally formed from: - 50wt% to 60wt% viscose filament, preferably > 55wt%, - 20wt% to 30wt% aramid filament, preferably 20wt% and 25wt%, - 10wt% to 20wt% polyamide filament, preferably between 15wt% and 20wt%, - 1wt% to 5wt% elastane filament, most preferably 3wt% and - 0.1wt% to 2wt% carbon fibers, preferably 1wt%.