Spunbond Diffuser Secondary Air Angles for Homogeneous Filament Deposition
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Solution Overview
Problem
Existing devices for producing spunbonded nonwovens from continuous filaments face challenges in achieving high filament speeds and low titers while maintaining the quality of the nonwoven web, particularly in terms of homogeneity and strength, especially at high production speeds.
Innovation Solution
A device with a diffuser system between the stretching and depositing units, featuring secondary air entry gaps with a specific inflow angle and a convergent-divergent diffuser configuration, along with a suction area design that ensures uniform air flow and minimizes turbulence, is employed to enhance filament deposition quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high filament speeds and low titers are used to increase productivity, then production speed increases, but the quality of the filament deposit deteriorates with reduced homogeneity and strength
Solution Approach 1:
The patent changes the aerodynamic parameters of the diffuser system by introducing secondary air entry gaps with specific inflow angles (less than 100°, preferably less than 90°) and optimizing the convergent-divergent section geometry. These parameter changes create optimal air flow conditions that maintain filament deposit homogeneity even at high production speeds and low titers, thus resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The diffuser acts as an intermediary device between the stretching device and the depositing device. It mediates the interaction between filaments and air by controlling air flow through secondary entry gaps and optimizing the convergent-divergent section, thereby ensuring homogeneous filament deposition at high speeds without direct contact between the stretching and depositing devices
2Quantity of substance
If high filament speeds are used to reduce titer, then filament fineness increases, but the strength of the nonwoven web decreases
Solution Approach 1:
The patent optimizes aerodynamic parameters including secondary air inflow angles and diffuser section lengths to create controlled air flow conditions that enhance filament alignment and inter-filament bonding during deposition. This resolves the contradiction by maintaining web strength through improved deposition quality even when using high speeds and low titers
3Device complexity
If conventional diffuser designs are used, then device simplicity is maintained, but filament deposit quality is insufficient at high production speeds
Solution Approach 1:
The diffuser is segmented into distinct functional sections: secondary air entry gaps, a convergent section, and a divergent section. This segmentation allows each part to perform its specific function optimally - the entry gaps introduce secondary air, the convergent section compresses the air-filament mixture, and the divergent section expands it for uniform deposition - thereby improving deposit quality while maintaining reasonable device complexity
Solution Approach 2:
The diffuser design incorporates dynamic air flow control through the convergent-divergent section geometry, which adapts the air flow characteristics to match the high-speed filament deposition process. This dynamic approach enables the diffuser to maintain optimal performance at high production speeds where static conventional designs fail
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 allows for high-quality, homogeneous filament deposition and nonwoven production at high speeds and low titers, achieving optimal fleece web laydown and maintaining quality even at high production speeds exceeding 400 m/min.
Implementation Method 1
a diffuser (10) is arranged between the stretching device (7) and the depositing device (21), so that filaments and primary air (P) from the stretching device (7) reach the diffuser (10), with in the area of the at least one diffuser at least two arranged on opposite sides of the diffuser secondary air entry gaps (11, 12) are provided through which secondary air (S) enters the diffuser (10)
Implementation Method 2
at least one suction device for sucking air or process air through the depositing device or through the depositing sieve belt is provided and wherein a suction area arranged below the diffuser outlet has a width b in the machine direction (MD), which width b is greater than the width B of the diffuser outlet
Data Source
Figure 1
Figure 2
AI summary
A device for producing spunbond nonwovens from continuous filaments, comprising at least one spinnerette, at least one cooling device, at least one drawing device, and at least one depositing device for depositing the filaments. At least one diffuser is arranged between the drawing device and the depositing device, allowing filaments and primary air from the drawing device to enter the diffuser. At least two secondary air inlet slots are provided on opposite sides of the diffuser. At least one secondary air inlet slot is configured such that the secondary air enters at an angle α to the filament flow direction, where the angle α is less than 100°. An extraction device is provided for drawing air through the depositing device.A suction area located below the diffuser outlet has a width b in the machine direction that is greater than the width B of the diffuser outlet.