Spring-Biased Shutoff Valve for Hot Runner Backflow Prevention
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Solution Overview
Problem
Existing shut-off valves in plastic injection molding systems are not universally applicable and fail to effectively prevent backflow of molten plastic material and ambient air ingress when the machine nozzle is retracted, leading to inconsistencies and substandard molded parts.
Innovation Solution
A spring-biased shutoff valve mechanism with a movable valve member that automatically closes when the machine nozzle is retracted, using Belleville spring washers to maintain the internal pressure and prevent ambient air entry, ensuring consistent molding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shut-off valve mechanism is provided to prevent backflow of molten plastic material, then backflow prevention is improved, but many existing valves are not universally applicable and cannot be easily modified for different applications
Solution Approach 1:
The shut-off valve mechanism is designed with a standardized body structure that can be universally applied across different injection molding machine nozzle sizes. The valve body incorporates standardized threading and mounting features that allow it to adapt to various applications without requiring custom design modifications, while maintaining effective backflow prevention through its spring-biased movable valve member.
2Productivity
If the machine nozzle is retracted between processing cycles, then productivity is improved, but backflow of plastic material and ambient air ingress occur affecting subsequent cycles
Solution Approach 1:
The spring-biased movable valve member is pre-positioned in a closed state that automatically seals the inlet to the hot runner manifold when the machine nozzle is retracted. This preliminary closing action occurs before the next injection cycle begins, preventing both backflow of molten plastic and ingress of ambient air, thereby maintaining process consistency and internal pressure readiness for the subsequent cycle.
3Stress or pressure
If ambient air enters the hot runner system when the nozzle is retracted, then air ingress occurs causing inconsistencies, but maintaining pressure requires a sealed system
Solution Approach 1:
The movable valve member is extracted or separated from the stationary valve body, creating a distinct sealing interface. When the movable valve member closes against the stationary valve body's sealing surface, it forms an effective barrier that prevents ambient air from entering the hot runner system while maintaining internal pressure, eliminating the harmful effect of air ingress without compromising pressure maintenance.
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 solution effectively prevents backflow of molten plastic and ambient air ingress, maintaining internal pressure and ensuring consistent part quality across various molding applications, including stack and rotary molds.
Implementation Method 1
The movable pin member is spring loaded by one or more spring members, such as stacked Belleville spring washers which bias the movable valve member to its open valve position.
Implementation Method 2
The movable pin member is spring loaded by one or more spring members, such as stacked Belleville spring washers
Data Source
AI summary
A shutoff valve mechanism for a plastic injection molding system and process. The shutoff valve mechanism is positioned between the nozzle of the injection molding machine and the hot runner manifold. Force applied by the machine nozzle moves an inner body member in the shutoff valve mechanism and opens a valve allowing molten plastic material to flow through the valve and into the hot runner, sprue bushings, and mold cavities. A biasing mechanism, such as a plurality of spring washer members, returns the inner body member to its rest position, thereby closing the valve mechanism when the machine nozzle is retracted.