Co-injection Nozzle Integrated Back-flow Barrier
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Solution Overview
Problem
Existing co-injection nozzles for multilayer injection molding face challenges with back-flow of the second melt, leading to inaccurate barrier layers and complex, costly constructions due to additional movable parts and external back-flow control valves.
Innovation Solution
A co-injection nozzle design that integrates a back-flow barrier within the central bore, utilizing a recess in the valve needle to prevent back-flow of the second melt, simplifying the construction and reducing costs by leveraging the existing valve needle for both nozzle opening and back-flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external back-flow control valves and additional movable parts are added to prevent back-flow, then back-flow prevention reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the back-flow control function with the existing valve needle by forming a recess in the valve needle that acts as a back-flow barrier. This merging of functions eliminates the need for separate back-flow control valves and additional movable parts, thereby maintaining reliability while reducing device complexity
Solution Approach 2:
The valve needle is given dual functionality: it serves both as the nozzle opening/closing mechanism and as the back-flow control element through its integrated recess. This multi-functionality resolves the contradiction by eliminating dedicated back-flow control components while maintaining effective back-flow prevention
2Reliability
If external back-flow control valves and additional movable parts are added to prevent back-flow, then back-flow prevention reliability is improved, but manufacturing and maintenance costs increase
Solution Approach 1:
By integrating the back-flow control function into the existing valve needle structure through a recess formation, the patent eliminates the need for separate back-flow control valves and additional movable parts, thereby maintaining reliability while reducing device complexity
Solution Approach 2:
The valve needle is given dual functionality: it serves both as the nozzle opening/closing mechanism and as the back-flow control element through its integrated recess. This multi-functionality resolves the contradiction by eliminating dedicated back-flow control components while maintaining effective back-flow prevention
3Device complexity
If the valve needle is used to control both nozzle opening and back-flow prevention, then device complexity is reduced, but the ability to independently control melt streams is limited
Solution Approach 1:
The recess in the valve needle is positioned at a specific location to create a localized back-flow barrier that affects only the second melt stream. This localized intervention allows the valve needle to control both nozzle opening and back-flow prevention without interfering with the independent control of different melt streams
Data Source
AI summary
A co-injection nozzle for an injection moulding device for producing multi-layered injection-moulded products. The nozzle includes: a central bore; a valve needle for opening and closing a nozzle opening; an annular inner melt channel for the first melt; an annular central melt channel for a second melt; and an annular outer melt channel for the first melt. The inner, central and outer melt channels are fluidically combined in the region of the nozzle tip to form a concentrically-layered melt stream. The co-injection nozzle has a back-flow barrier, integrated into the central bore, for the second melt, this barrier formed by a cut-out in the valve needle and by a melt channel for the second melt, the channel penetrating the central bore. In the open position of the back-flow barrier, the cut-out is located such that the second melt can flow through the melt channel, whilst flowing in the central bore past the valve needle.