Thermoplastic Cable Jointing Extrusion Moulding
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Solution Overview
Problem
The existing methods for jointing high voltage cables using tapes are cumbersome and time-consuming, and thermoplastic injection-moulding results in material shrinkage leading to microvoids and detachments.
Innovation Solution
The process involves extrusion-moulding of thermoplastic material into a mould during cooling to compensate for shrinkage, with controlled temperature and pressure monitoring to ensure a continuous, homogeneous insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermoplastic material is injection-moulded into a mould, then the insulating layer is formed quickly, but the material shrinks during cooling causing microvoids and detachments
Solution Approach 1:
The mould is preheated to a temperature above the melting point of the thermoplastic material before injection, ensuring the material remains in molten state longer during cooling. This preliminary thermal preparation prevents premature solidification and shrinkage-induced defects, resolving the contradiction between fast formation and integrity.
Solution Approach 2:
The patent controls the cooling rate and maintains specific temperature parameters during the moulding process. By carefully managing the temperature gradient and cooling profile, the material solidifies uniformly without excessive shrinkage, preventing microvoids while maintaining production efficiency.
2Reliability
If tapes are used to rebuild the insulation system, then the joint has reliable insulation properties, but the process is cumbersome and time-consuming
Solution Approach 1:
The patent replaces the mechanical tape-winding system with a thermoplastic injection-moulding system. The thermoplastic material is injected in molten state and then cooled under controlled conditions to form the insulation layer, eliminating the multi-step manual taping process while maintaining insulation reliability through proper material selection and process control.
Solution Approach 2:
The patent utilizes the phase transition of thermoplastic material from solid to molten state during injection, and back to solid during controlled cooling in the mould. This phase change enables the material to flow and conform to the mould cavity, forming a seamless insulation layer that replaces the layered tape structure, significantly reducing jointing time while maintaining reliability.
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 method provides a quicker and more reliable jointing process for high voltage cables by preventing microvoids and ensuring the integrity of the insulation system, facilitating faster and more accurate joint formation.
Implementation Method 1
heating the mould to a temperature above the melting point of the thermoplastic material
Implementation Method 2
temperature above the melting point of the thermoplastic material
Implementation Method 3
injecting under pressure a quantity of molten thermoplastic material into the mould
Implementation Method 4
cooling the mould to a temperature below the melting point of the thermoplastic material
Data Source
AI summary
In one example, an apparatus for jointing power cables includes a mold extending along a longitudinal axis, and having a feeding inlet and being made of two halves forming a longitudinal pass-through seat for receiving the cables. An extruder is connected to the feeding inlet. A heating system and a cooling system is associated with the mold. A measuring system for detecting temperature or pressure includes a plurality of probes for detecting temperature or pressure.