Coaxial Cable Insulator Void Ratio Design
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Solution Overview
Problem
Coaxial cables with void portions in the insulator face challenges in maintaining sufficient strength and stability under external pressure and bending, while also achieving low permittivity and prescribed electrical properties.
Innovation Solution
The coaxial cable design incorporates a high total void ratio of 43% or more, with void portions having a circular or elliptical cross-section and a void ratio per portion of 6.8% or less, ensuring mechanical strength and low permittivity, and is manufactured using an extruder with a specific die configuration to form continuous voids within the insulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cross-sectional area of each void portion is increased to lower permittivity, then the proportion of void portions to insulator increases, but the thickness of the insulator around the void portions becomes thin, making it difficult to ensure sufficient strength
Solution Approach 1:
The insulator is segmented into multiple discrete void portions rather than having one large void. This segmentation allows the total void ratio to reach 43% or more for low permittivity, while each individual void maintains sufficient surrounding insulator thickness for mechanical strength. The insulator is divided into regions with voids and regions without voids, creating a balanced structure.
Solution Approach 2:
Different regions of the insulator have different properties: regions with void portions provide low permittivity, while regions without void portions (or with smaller voids) provide mechanical strength. The void portions are strategically positioned and sized to optimize both electrical and mechanical properties locally throughout the insulator structure.
2Quantity of substance
If gas foaming or chemical foaming is used to lower permittivity, then the permittivity decreases, but it becomes difficult to stabilize the shape during insulator coating, resulting in fluctuation in outer diameter
Solution Approach 1:
The void portions are formed as hollow structures during the extrusion process itself, before the insulator is fully formed and cooled. The extrusion die is designed with specific features that create the hollow cross-sections, allowing precise control of the outer diameter and shape while incorporating the voids. This preliminary formation of voids avoids post-processing foaming that would compromise dimensional stability.
Solution Approach 2:
The patent changes the physical state and formation method of voids from post-extrusion foaming (gas or chemical) to in-extrusion hollow structure formation. By controlling the extrusion parameters and die geometry, the void portions are created with precise dimensions and stable shapes, eliminating the diameter fluctuation issues associated with conventional foaming methods.
3Quantity of substance
If the extent of foaming is increased to lower permittivity, then the permittivity decreases, but the foamed condition becomes deteriorated, degrading stability of longitudinal transmission characteristics
Solution Approach 1:
The hollow void portions are formed during the extrusion process itself, before the insulator material undergoes any foaming or curing. This preliminary formation ensures that the void structures are created under controlled conditions with stable dimensions, avoiding the degradation of transmission characteristics that occurs with excessive foaming.
Solution Approach 2:
The patent changes from using foaming extent as the parameter to control permittivity to using the geometry and distribution of pre-formed hollow voids. This parameter change allows precise control of permittivity through void size and arrangement without the harmful effects of excessive foaming on transmission characteristic stability.
4Quantity of substance
If conventional foaming methods are used to lower permittivity, then the permittivity decreases, but the adhesion strength of the foamed insulator to the conductor becomes low
Solution Approach 1:
The hollow void portions are formed during the extrusion process, before the insulator material is applied to the conductor. This preliminary formation of voids in the extruded insulator ensures that the insulator maintains its structural integrity and adhesion properties while achieving the desired low permittivity, avoiding the adhesion degradation caused by post-extrusion foaming.
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 design enhances the mechanical strength and stability of the cable, maintaining low permittivity and ensuring stable transmission characteristics, even under external pressure and bending, while meeting the requirements for impedance and capacitance.
Implementation Method 1
it is considered important that the insulator with which the outer circumference of the central conductor is covered have as low permittivity as possible
Implementation Method 2
the insulator to be used is foamed by gas foaming, chemical foaming or the like
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3
AI summary
A coaxial cable and a multicoaxial cable, in which permittivity is made low by ensuring a proportion of void portions to an insulator and in which sufficient strength is obtained, are provided. In a coaxial cable 11 in which a central conductor 12 is covered with an insulator 13 having void portions 14 continuing in a longitudinal direction, and an outer conductor 15 is arranged on an outer circumference of the insulator 13, each of the void portions 14 is formed to have a circular or elliptical cross section, the void portions 14 are evenly arranged in the insulator 13 in a set of six to nine. In a cross section perpendicular to the longitudinal direction of the coaxial cable, a void ratio of the entire void portions is 43 % or more, the void ratio being a proportion of the void portions to a sum of a total area of all the void portions 14 and an area of the insulator 13. Further, a multicoaxial cable may be provided by incorporating a plurality of the coaxial cables 11 described above.