Flat Fire-Resistant Cable Design for Ash Contamination
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Solution Overview
Problem
Fire-resistant cables with round cross sections and insulating layers made of mica tapes face issues such as gaps leading to short circuits, contamination by ash, increased risk of short-circuiting due to twisted elements, and mechanical stress, which compromise their insulating protection and integrity during fires.
Innovation Solution
A flat fire-resistant cable design with an insulating layer made of polymeric materials capable of converting to a ceramic state at high temperatures, featuring adjacent and aligned conductors with a halogen-free outer jacket, reducing the risk of short-circuiting and mechanical stress, and minimizing ash-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a round cross-section cable design is used with twisted insulated elements, then the cable achieves flexibility and structural integrity, but the insulating layer becomes contaminated by ash from outer jacket combustion, causing cracks and increasing short-circuit risk
Solution Approach 1:
The patent transitions from a symmetric round cross-section to an asymmetric flat cable design with plane faces. This asymmetry prevents the superposition of insulated elements, eliminating the pathway for ash contamination that occurs in round cables where elements are twisted and layered. The flat configuration with elements arranged in a single plane fundamentally changes the spatial relationship between components, preventing the harmful interaction between outer jacket ash and inner insulating layers.
Solution Approach 2:
The patent reorganizes the spatial arrangement of insulated elements from a three-dimensional twisted configuration in round cables to a two-dimensional planar arrangement in flat cables. By constraining all conductor axes to lie in one and the same plane, the invention eliminates the vertical stacking and twisting that causes ash to fall onto and contaminate insulating layers during fire conditions.
2Temperature
If mica tapes are used as insulating layer, then fire resistance is achieved, but gaps in the mica tape wrapping expose conductors causing short circuits
Solution Approach 1:
The patent employs a composite insulating layer combining organic polymeric material with inorganic ceramic-forming filler. This composite structure provides both the flexibility and continuity needed to maintain electrical insulation and the thermal stability to resist fire. The polymeric matrix fills gaps and provides continuous coverage, while the ceramic-forming filler ensures fire resistance, eliminating the gap problem inherent in discrete mica tape applications.
Solution Approach 2:
The patent changes the material parameters of the insulating layer by selecting polymeric materials with specific properties: continuous formability to eliminate gaps, ceramic-forming capability for fire resistance, and appropriate dielectric strength for electrical insulation. This parameter optimization allows the insulating layer to simultaneously achieve continuous coverage and high-temperature resistance without the defects of mica tape applications.
3Temperature
If the outer jacket is converted to ash during fire, then fire resistance function is fulfilled, but the ash contaminates the insulating layer and increases volume and surface conductivity
Solution Approach 1:
The patent segments the cable structure into distinct functional layers with the flat configuration creating physical separation between the outer jacket and the insulating layer. By arranging all conductors in a single plane and providing adequate spacing, the design creates a barrier that prevents ash from the outer jacket from reaching and contaminating the insulating layer, thus isolating the harmful effect to the outermost layer only.
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 flat cable design enhances electrical strength, reduces short-circuit risks, and maintains physical and electrical integrity during fires by minimizing ash contamination and mechanical stress, while also reducing manufacturing costs and incandescence time.
Implementation Method 1
the insulating layer being formed from at least one polymeric material capable of being converted, at least on the surface, into the ceramic state at high temperatures in a fire
Data Source
AI summary
A fire-resistant safety cable may include at least two electrical conductors, an insulating layer around each of the at least two electrical conductors in order to obtain at least two insulated elements, and an outer jacket surrounding the at least two insulated elements. The cable may have, in cross-section, an external outline including at least two substantially plane faces that are substantially parallel to each other. The insulating layer may be formed from at least one polymeric material being adapted to be converted, at least on a surface of the at least one polymeric material, into a ceramic state at high temperatures in a fire. The at least two insulated elements may be mutually adjacent, side by side, with axes of the at least two insulated elements lying in a plane between the at least two substantially plane faces.