Segmented Twin-Screw Extruder for Independent Speed Control
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Solution Overview
Problem
Twin-screw extruders face challenges in achieving different rotational speeds at various processing stages due to the limitations of single rod-shaped screws, leading to potential material degradation from scorching and adherence in connecting pipes when using tandem-type extruders.
Innovation Solution
A twin-screw extruder design with independently rotatable upstream and downstream screws, where the downstream screw has a large diameter portion and a small diameter shaft portion that fits into the upstream screw's shaft hole, allowing for different rotational speeds and eliminating the need for a connecting pipe, thus reducing material degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a tandem-type extruder with connecting pipe is used to achieve different rotational speeds at different portions, then the rotational speed control is improved, but the raw material may be scorched and adhere to the inner wall of the connecting pipe causing degradation
Solution Approach 1:
The patent merges the upstream and downstream extruders into a single integrated extruder body, eliminating the connecting pipe between them. The upstream screw and downstream screw are both housed in the same barrel, allowing direct material transfer from the upstream to downstream portion without external connection, thus preventing scorching and adherence in connecting pipes
Solution Approach 2:
The patent divides the single screw into two independent segments: an upstream screw and a downstream screw, each capable of rotating at different speeds. These segmented screws are independently driven by separate motors, allowing different rotational speeds at different portions of the extruder while maintaining integration to prevent material degradation
2Device complexity
If a single rod-shaped screw is used, then the device complexity is reduced, but it is impossible to partially change the rotational speed in the longitudinal direction
Solution Approach 1:
The single screw is segmented into two independent screws (upstream screw and downstream screw) that can rotate at different speeds. Each screw is driven by its own motor, enabling independent speed control while maintaining a relatively simple overall structure compared to tandem extruders
Solution Approach 2:
The downstream screw is positioned coaxially within the barrel alongside the upstream screw, with both screws nested within the same extruder housing. This nested arrangement allows independent rotation of each screw at different speeds while maintaining a compact integrated structure
Data Source
AI summary
A twin-screw extruder is provided in which screws have different rotational speeds depending on the process of treating the raw material and in which degradation of the raw material is less likely to occur.Twin-screw extruder 1 has two screws 3, 5 that extend in parallel to each other. Each screw 3, 5 has cylindrical upstream screw 31 and downstream screw 35, wherein upstream screw 31 has shaft hole 315 that extends in longitudinal direction X and screw flight 316 on an outer circumferential surface thereof, and downstream screw 35 includes large diameter portion 353 having screw flight 357 on an outer circumferential surface thereof and small diameter shaft portion 351 that has a smaller diameter than large diameter portion 353, wherein small diameter shaft portion 351 of downstream screw 35 is inserted into shaft hole 315 of upstream screw 31. Upstream screw 31 and downstream screw 35 can be independently rotated. Twin-screw extruder 1 further includes upstream rotating mechanism 84 that rotates upstream screws 31 of two screws 3, 5, and downstream rotating mechanism 83 that rotates downstream screws 35 of two screws 3, 5.