Electret Filter Production Using Charged Droplets for Uniform Fiber Charging
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Solution Overview
Problem
Existing methods for creating electret filter elements with high filter efficiency face challenges in achieving a homogeneous charge distribution without damaging the nonwoven structure, requiring high water pressure and subsequent costly drying processes that can reduce electrical charge.
Innovation Solution
The method involves polarizing fluid droplets using an electric field between a counter-electrode and the droplet as it breaks off, ensuring uniform charging of fibers with a preferred polarity, allowing for a controlled and efficient charge distribution without structural damage to the fibers, using a small amount of fluid and minimizing drying requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water droplets are sprayed onto the already finished nonwoven at high pressure to distribute charges homogeneously, then charge distribution homogeneity is improved, but the nonwoven structure is damaged
Solution Approach 1:
The patent applies preliminary action by charging the fluid droplets with a specific polarity BEFORE spraying them onto the nonwoven. The spray device is connected to a voltage source that charges the droplets as they form, so that when they are sprayed onto the nonwoven, they already carry the desired electrical charge. This eliminates the need for high water pressure and subsequent drying processes, thereby preserving the nonwoven structure while achieving homogeneous charge distribution.
2Manufacturing precision
If high water pressure is applied to distribute charges homogeneously within the nonwoven fabric, then charge distribution homogeneity is improved, but the nonwoven structure is negatively changed or destroyed
Solution Approach 1:
The patent replaces the mechanical system of high-pressure water spraying with an electrical system. Instead of using mechanical pressure to force water through the nonwoven, the invention uses an electric field to charge the fluid droplets and attracts them to the nonwoven surface. This substitution of mechanical force with electrical force allows for gentle, homogeneous charge distribution without damaging the nonwoven structure.
3Quantity of substance
If large amounts of water are sprayed onto the nonwoven to achieve sufficient electrical charge, then electrical charge amount is improved, but drying costs and equipment outlay increase
Solution Approach 1:
The patent applies parameter changes by modifying the electrical charge parameter of the fluid droplets before they contact the nonwoven. By adjusting the voltage applied to the spray device, the invention can control the amount of electrical charge on each droplet. This allows achieving sufficient total charge with much smaller amounts of fluid, thereby eliminating or minimizing the need for expensive vacuum drying equipment and processes.
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 approach results in a cost-effective production of electret filter elements with a homogeneous charge distribution and high filter efficiency, maintaining the fiber structure and extending the service life of the filter by 'freezing' charges within the polymers.
Implementation Method 1
The fluid droplets are polarized by an electrical field which forms between a counter-electrode and the fluid droplet itself which breaks away
Implementation Method 2
The fluid droplets are polarized by an electrical field which forms between a counter-electrode and the fluid droplet itself which breaks away. This electric field causes an excess charge on the fluid droplet, which remains after it breaks off
Data Source
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AI summary
A method for producing an electret filter element according to one of the preceding claims, comprising the steps: providing fibers (6), providing a spraying device (1) for a fluid, producing a spray cloud (3) of electrically charged fluid droplets (4), guiding the fibers (6) through the spray cloud (3), wetting the fibers (6) with the fluid droplets (4) and depositing the fibers (6) to form a fiber layer (8), is characterized, with regard to the problem of creating a filter element which has a homogeneous charge distribution and a high filter efficiency while being cost-effective to produce, in that the fluid droplets (4) are electrically charged by an electrical field between breakaway fluid droplets (4a) and a counter electrode (5). An electret filter element is produced according to the method.