Pneumatic Thread Conveying Channel with Return Flow Deflection
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Solution Overview
Problem
Existing devices for pneumatically conveying and guiding multifilament threads face challenges with backflow of compressed air, which impedes the entry of threads, especially at high overpressures, and previous solutions either reduce conveying capacity or allow ambient air to impede thread entry.
Innovation Solution
A return flow channel is introduced between the thread inlet and compressed air supply, forming a rounded transition surface and inclining to direct backflow into the environment, utilizing the Coanda effect to deflect air and create suction for thread entry, while additional supply air enhances flow deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the overpressure of compressed air is increased to generate high conveying force on the yarn, then the conveying effect is improved, but backflow occurs within the conveying channel which impedes the yarn's entry
Solution Approach 1:
The conveying channel is divided into multiple sections with different cross-sectional areas. The channel cross-section is expanded in the area below the compressed air supply, creating distinct zones that separate the high-pressure conveying region from the yarn entry region, thereby preventing backflow while maintaining conveying force
Solution Approach 2:
The cross-sectional area of the conveying channel is varied along its length, with expansion occurring specifically below the compressed air supply. This geometric parameter change allows the channel to accommodate high overpressure without causing backflow to the yarn inlet opening
2Object-affected harmful factors
If the conveying channel has a cascade-like cross-sectional expansion to reduce backflow, then backflow is reduced, but delivery capacity is reduced
Solution Approach 1:
The cross-sectional expansion is applied locally and selectively in specific areas of the conveying channel (below the compressed air supply) rather than uniformly throughout. This localized geometric modification reduces backflow at critical points while preserving the overall channel capacity for yarn delivery
3Object-affected harmful factors
If additional orifices and throttles are added to throttle backflowing air, then backflow is reduced, but ambient air builds up at the thread which promotes broken filament emergence
Solution Approach 1:
The harmful backflow is extracted and redirected into a separate return flow channel that connects to the ambient atmosphere. This isolation removes the backflow from the yarn guidance environment, preventing both the backflow problem and the harmful buildup of ambient air at the thread inlet
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 solution enables trouble-free thread entry and maintains high conveying capacity even at high air pressures, allowing broken filaments and loops to pass through, suitable for melt spinning and carpet yarn production.
Implementation Method 1
Fast air currents preferentially adhere to and flow along walls. Such physical properties are also known as Coanda effects. In this respect, the natural behavior of the flow within the conveying channel is used to divert the backflow into a return flow channel.
Data Source
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AI summary
A device for pneumatically conveying and guiding a multifilament thread has a closed conveying channel which has a thread inlet opening at one end and a thread outlet opening at the opposite end. An injector zone having at least one compressed air channel which opens into the conveying channel is formed between the thread inlet opening and the thread outlet opening, wherein the compressed air channel can be connected to a compressed air source. In order to avoid blowing air from flowing back from the injector zone at the thread inlet opening, a return flow channel is formed in a channel section of the conveying channel between the thread inlet opening and the opening of the compressed air channel, which return flow channel connects the conveying channel to ambient atmosphere.