Pocket Air Filter Bag with Variable-Width Webs for Uniform Airflow
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Solution Overview
Problem
Conventional filter bags for pocket air filters have a reduced effective filter surface due to their trapezoidal design, which is necessary for uniform airflow but limits the filter surface area and increases pressure drop, making it difficult to achieve optimal air purification.
Innovation Solution
The filter bag design includes weld section widths that increase from the opening side to the bottom edge, allowing for adjustable web section widths and shapes, such as V-shaped or linearly increasing weld seams, to optimize the distance between side parts and enhance the filter surface area without altering the side part angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filter bag is designed with a trapezoidal cross-section to achieve uniform airflow, then the airflow distribution is improved, but the effective filter surface area is reduced
Solution Approach 1:
The patent applies local quality by making the web section width variable along the flow direction. The web width decreases from the inlet to the outlet, creating different local geometries that compensate for the changing cross-sectional area. This allows the side parts to maintain a rectangular cross-section (maximizing filter surface) while the varying web width ensures uniform airflow velocity distribution throughout the filter bag.
2Reliability
If the web section width decreases from opening to bottom edge to reduce distance between side parts, then the filter bag spacing is optimized, but the filter surface area is reduced
Solution Approach 1:
The patent resolves this contradiction by shifting the geometric variation from the cross-sectional dimension to the longitudinal dimension. Instead of tapering the side parts (which would reduce filter surface area), the web width varies along the flow direction. This dimensional shift allows the side parts to maintain full rectangular cross-section while achieving the required spacing control through the varying web geometry in the longitudinal direction.
3Manufacturing precision
If the side parts are configured trapezoidally to enable decreasing distance between side parts, then the distance control is improved, but the available filter surface is reduced
Solution Approach 1:
The patent applies segmentation by dividing the filter bag into multiple sections along the flow direction, each with different web widths. This creates discrete zones with controlled spacing characteristics. The side parts themselves maintain a rectangular cross-section, and the spacing control is achieved through the segmented web structure rather than through the side part geometry, thereby preserving maximum filter surface area.
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 design increases the available filter surface area, reduces pressure drop, and allows for easier assembly while maintaining constant airflow speed, thereby improving air purification efficiency.
Implementation Method 1
The welding device has a number of sonotrodes with which the filter material webs and the flexible material web can be welded to one another by ultrasound
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a filter bag (1) for pocket air filters having two abutting side parts (2, 3) which are made of an air-permeable filter material that is weldable by ultrasonic welding. The side parts (2, 3) are continuously welded to one another in side edge portions (4) on three sides (5, 6, 7) of the side parts (2, 3), so that a pocket (8) having two opposite side edges (9, 10), a bottom edge (11) and an opening (12) opposite said bottom edge (11) is formed by the two side parts (2, 3) which are welded to one another. A plurality of webs (13) made of a flexible material web (14) are formed in the pocket (8). The webs (13) connect the side parts (2, 3) to each other and are oriented to run from an opening side (15) of the filter bag (1) in the direction of the bottom edge (11). The flexible material web (14) is at least in some regions alternately connected with in each case one of the side parts (2, 3) in the welding portions (16). The welding portions (16) are delimited transversely to the direction of flow (18) by at least one weld seam so that the flexible material web (14) is connected in a welding portion (16) to in each case only a side part (2, 3). The webs (13) are formed by web portions (19) of the flexible material web (14). The web portions (19) each run between two adjacent welding portions (16), by which the flexible material web (14) is connected to two mutually opposite side parts (2, 3). A web portion width (20) of the web portions (19), which is defined by a length of one web portion (19) between the side parts (2, 3), decreases in each case from the opening side (15) to the bottom edge (11). A welding portion width (21) of at least one welding portion (16) decreases at least in sections from the opening side (15) in the direction of the bottom edge (11).