Barrier Extruder Screw Geometry for Higher Cable Extrusion Flow
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Solution Overview
Problem
Existing extrusion screws for electric cable manufacturing face challenges in achieving sufficient extrusion flow without increasing the extruder diameter, and they often reject dielectric fluids, affecting the quality of the extrusion composition.
Innovation Solution
The extrusion screw features a power area and a compression area with a single net each, where the net depth ranges between 0.11D and 0.16D, enhancing extrusion flow and preventing dielectric fluid rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the extruder diameter is increased to increase extrusion flow rate, then the extrusion flow rate is improved, but the device cost and complexity increase significantly
Solution Approach 1:
The patent changes the geometric parameters of the extrusion screw, specifically increasing the thread depth from conventional values to between 0.11D and 0.16D (where D is the screw outer diameter). This parameter modification increases the compression ratio and improves the extrusion flow rate without requiring an increase in the extruder diameter, thus resolving the contradiction between productivity and device complexity
Solution Approach 2:
Instead of increasing flow rate by increasing the extruder diameter (one-dimensional approach), the patent introduces a new dimensional approach by optimizing the thread depth as a proportion of the diameter (0.11D to 0.16D ratio). This creates a new design dimension that allows flow rate improvement while maintaining the same extruder size
2Productivity
If the thread depth is increased to improve extrusion flow, then the extrusion flow rate increases, but the mechanical strength of the screw may be compromised
Solution Approach 1:
The patent optimizes the thread depth parameter within a specific range (0.11D to 0.16D) that balances two competing requirements: increasing extrusion flow rate while maintaining sufficient mechanical strength. This controlled parameter change resolves the contradiction by finding the optimal value range that satisfies both productivity and strength requirements
Solution Approach 2:
The patent applies different thread depth values to different zones along the screw length (feed zone, compression zone, metering zone), creating a dynamic profile that optimizes both flow rate and structural integrity. The thread depth varies strategically along the screw to maintain strength where needed while maximizing extrusion efficiency in the compression zone
3Device complexity
If conventional extrusion screw profiles are used, then the screw structure is simple, but dielectric liquid is rejected towards the proximal end affecting composition quality
Solution Approach 1:
The patent modifies the thread depth parameter in the compression zone to a specific range (0.11D to 0.16D) that prevents dielectric liquid rejection. This parameter change alters the flow dynamics within the screw channel, ensuring uniform mixing and transport of the extrusion composition without segregating the dielectric liquid, thus improving manufacturing precision while maintaining reasonable structural simplicity
Data Source
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AI summary
The invention relates to an extrusion screw for an extruder for extruding at least one extruded thermoplastic layer surrounding an elongated electrically conductive element of an electrical cable, the extrusion screw having an outside diameter denoted D and comprising a screw body (24) extending along a longitudinal axis (A), the extrusion screw further comprising along this longitudinal axis (A): - a feeding zone (30) for at least one thermoplastic polymer in solid form, the feeding zone comprising a feeding thread (50) extending around the screw body, - a compression zone (32) for the extrusion composition comprising a compression thread (52) extending around the screw body, - a barrier zone (34) comprising a primary thread and a secondary thread for the gradual melting of the polymer into an extrusion composition, the distance separating the primary and secondary threads varying along the longitudinal axis (A),in which the feed (30) and compression (32) zones respectively comprise a single feed thread and a single compression thread, each of the feed and compression threads having a thread depth (Pa, Pc) taken perpendicular to the longitudinal axis (A) between a thread end and the screw body (24) between 0.11D and 0.16D.