Screw Tip Closure Body for Injection Molding Back-Flow Prevention
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Solution Overview
Problem
Existing injection units in injection-molding machines for processing polymer materials face complex structures and high cleaning efforts due to multiple parts and sensitive fits, leading to frequent clogging and increased scrap rates from unmaintained units.
Innovation Solution
A plastification and injection unit with a screw that is axially displaceable using a separate drive, where the screw tip acts as a closure body with a sealing surface, eliminating the need for separate back-flow barriers and reducing the number of parts, allowing for easier cleaning and precise metering of injection volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a freely movable part (ball, cone) is used as a back-flow barrier in a separate chamber, then return flow of injection mass is prevented, but the structure becomes complicated with many individual parts having sensitive fits and sealing surfaces
Solution Approach 1:
The closure body is integrated directly into the screw tip, merging the back-flow barrier function with the plastification screw. This eliminates the separate chamber and multiple individual parts, reducing structural complexity while maintaining the back-flow prevention function through a single integrated sealing surface on the closure body
Solution Approach 2:
The screw is given dual functionality: it performs both the plastification function (rotating to convey and melt material) and the back-flow barrier function (through the closure body at its tip). This multi-functionality eliminates the need for a separate back-flow barrier mechanism, simplifying the overall structure
2Reliability
If a separate chamber with movable part is used for back-flow barrier, then injection mass return flow is blocked, but the injection channel and chamber become prone to clogging requiring frequent disassembly for cleaning
Solution Approach 1:
By integrating the closure body into the screw tip, the invention creates a streamlined structure with fewer crevices and dead zones where material can accumulate. The simplified geometry allows for easier access and cleaning compared to the complex separate chamber design, reducing maintenance requirements
Solution Approach 2:
The invention extracts the back-flow barrier function from a separate vulnerable chamber and integrates it into the screw itself. This eliminates the separate chamber that is prone to clogging, while the closure body on the screw tip maintains effective back-flow prevention
3Reliability
If multiple individual parts with sensitive fits are used in the injection piston, then back-flow barrier function is achieved, but assembly errors and improper cleaning lead to frequent failure
Solution Approach 1:
The closure body is formed as an integral part of the screw tip, eliminating multiple individual parts with sensitive fits and sealing surfaces. This single integrated component is much easier to assemble and clean, reducing the risk of assembly errors and improper maintenance while maintaining the back-flow barrier function
Solution Approach 2:
The integrated closure body design creates a simpler, more robust component that is easier to replace if needed. The simplified structure reduces the cost and complexity of maintenance compared to the delicate multi-part system, making the system more resilient to operational wear
4Duration of action of stationary object
If thorough cleaning of multiple individual parts is performed regularly, then acceptable useful lifetime is achieved, but the cleaning process becomes very time-consuming and risky
Solution Approach 1:
The integrated closure body design reduces the number of parts that need cleaning from multiple individual components to a single unified structure. This dramatically reduces cleaning time and eliminates the risk of damage to sensitive fits and sealing surfaces during disassembly and reassembly
Solution Approach 2:
The simplified integrated structure is designed to be easier to clean, potentially allowing for quicker maintenance intervals or even in-situ cleaning without full disassembly. The reduced complexity means fewer critical surfaces that require special handling during cleaning operations
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
The simplified structure reduces cleaning effort, minimizes leakage, and enhances precision in injection volume, leading to lower scrap rates and enabling fully automated systems with reduced variations in injection volume.
Implementation Method 1
the closure body has a sealing surface for contact with the face surface of the screw cylinder
Data Source
AI summary
A plastification and injection unit in injection-molding machines for processing of polymer materials, for example rubber, has a plastification screw that is disposed so as to rotate in a screw cylinder, which simultaneously represents the injection piston. The screw cylinder is disposed in an injection cylinder, in an axially displaceable manner. The injection cylinder can be connected with the sprue channel of an injection-molding die by way of a nozzle, and the injection piston has a back-flow barrier. The screw is axially displaceable in the screw cylinder by means of a separate drive. The screw tip projects out of the screw cylinder and has a closure body having a sealing surface for contact with the face surface of the screw cylinder.