Extruder Screw Segmentation for Plastic Melt Degassing
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Solution Overview
Problem
Existing devices for extruding thermoplastic synthetic products fail to prevent direct material and gas flow from the plasticizing section into the degassing section, leading to contamination and pressure fluctuations, due to the reliance on dynamic seals and viscosity-dependent tightness of oppositely directed feed screw sections.
Innovation Solution
An extruder screw with a feed screw flight operating in the same direction as the screw is placed between the oppositely operating feed screw flight and the flow channel outlet, incorporating a degassing opening to prevent gas and dirt flow, and a return channel with a check valve to ensure only filtered plastic returns to the plasticizing section, along with a threadless degassing space and additional oppositely operating feed screw section to enhance decoupling and prevent plastic flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If oppositely directed feed screw sections are used to prevent overflow, then plastic flow control is improved, but dynamic seal tightness deteriorates due to viscosity and speed dependence
Solution Approach 1:
A stationary sealing element is introduced as an intermediary between the two feed screw sections. This stationary element provides a reliable seal that is not dependent on the dynamic conditions (speed, viscosity) of the rotating screw sections, thereby resolving the contradiction between flow control and seal reliability.
Solution Approach 2:
The sealing function is segmented from the dynamic screw sections and assigned to a separate stationary sealing element. This segmentation allows the sealing mechanism to operate independently of the screw rotation dynamics, providing consistent tightness regardless of operating conditions.
2Ease of operation
If oppositely directed feed screw sections are used to prevent overflow, then material flow control is improved, but gas and moisture flow prevention deteriorates
Solution Approach 1:
The stationary sealing element acts as an intermediary barrier that effectively blocks gas and moisture flow between sections. Unlike the dynamic screw sections, this stationary seal provides consistent prevention of harmful factor migration regardless of operating conditions.
3Reliability
If oppositely directed feed screw sections are used, then plasticizing section sealing is improved, but pressure fluctuations worsen due to excessive degassing
Solution Approach 1:
The stationary sealing element provides reliable section isolation that prevents excessive pressure buildup, thereby stabilizing pressure during degassing operations without compromising seal integrity.
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 configuration ensures the production of uniformly cleaned and degassed plastic by preventing contamination and pressure fluctuations, while reducing wear on the feed screw and maintaining constant degassing and discharge pressures.
Implementation Method 1
a melt filter (4)
Implementation Method 2
at least one degassing opening (8) in the transitional zone between the two feed screw flights (3, 7)
Implementation Method 3
a return channel (12) with a check valve (13)
Data Source
AI summary
The invention relates to a device for the extrusion of thermoplastic synthetic material featuring an extruder screw (2) which is mounted on a housing (1) including a plasticizing section (P) at the inlet side, a degassing section which is mounted upstream on a discharge section (A) and a conveying outlet (3) operating in the opposite direction which is located between the plasticizing section (P) and the degassing section (E). A flow channel (5) that contains a melt filter (4) is bridged over by at least one of the conveying outlets (3) in the opposite direction. To create favorable production conditions, the extruder screw (2) forms a similar conveying outlet (7) operating in the same direction between the conveying outlet (3) in the opposite direction and the downstream port (6) of the flow channel (5). The housing (1) has at least one degassing vent (8) at the transition area of the conveying outlet (3) operating in the opposite direction and the conveying outlet (7) operating in the same direction.