Sheet Manufacturing Apparatus Airflow Diffusion Section
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Solution Overview
Problem
In paper recycling apparatuses, insufficient diffusion of airflow within the forming drum leads to increased airflow speed variations, causing fibers to be caught by the small-hole screen, resulting in portions that cannot discharge fibers, which deteriorates the sheet texture.
Innovation Solution
A sheet manufacturing apparatus with a rotatable drum unit featuring a diffusion section that diffuses airflow further downstream, reducing the portion through which materials do not pass, and includes a suction unit to further disperse fibers and improve texture by suctioning outside air from the sliding contact part between the drum and housing units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If airflow is supplied to the forming drum without sufficient diffusion, then the structure is simple, but airflow speed variation increases and fibers are caught by the small-hole screen
Solution Approach 1:
The airflow diffusion section is divided into multiple segments with different cross-sectional areas along the airflow direction. The cross-sectional area progressively increases from upstream to downstream, creating staged diffusion zones that gradually expand and distribute the airflow, preventing sudden speed variations while maintaining structural organization
Solution Approach 2:
The diffusion section creates local variations in cross-sectional area at different positions along the airflow path. By making the cross-sectional area larger downstream and smaller upstream, the design achieves localized airflow expansion exactly where needed to prevent fiber accumulation at the screen interface
2Device complexity
If airflow is not sufficiently diffused, then the device complexity is low, but fiber aggregation increases and sheet texture deteriorates
Solution Approach 1:
The diffusion section performs preliminary airflow diffusion before the air reaches the small-hole screen. By pre-expanding and distributing the airflow in the diffusion section, the system prevents fiber aggregation at the screen interface, ensuring uniform fiber distribution and improved sheet texture quality
Solution Approach 2:
The diffusion section introduces a dimensional change in the airflow path by varying the cross-sectional area along the flow direction. This three-dimensional expansion transforms the airflow from a concentrated state to a distributed state, improving fiber dispersion without adding complex external structures
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 diffusion section efficiently disperses materials within the drum unit, reducing fiber lumps and aggregation, and improves sheet texture by enhancing airflow distribution and suctioning outside air to prevent fiber accumulation.
Implementation Method 1
a diffusion section in which airflow is diffused further on a downstream side than on an upstream side in a supply direction of the airflow
Implementation Method 2
a suction unit that suctiones air within the housing unit below the drum unit, in which outside air may be suctioned from a sliding contact part between the drum unit and the housing unit during suction by the suction unit
Data Source
AI summary
A sheet manufacturing apparatus includes a rotatable drum unit that includes an opening section having a plurality of openings on a surface thereof and a cylindrical section having no opening; a material supply unit that is provided to supply a material containing fibers to the drum unit by airflow; and a forming unit that forms a sheet by using the material passing through the openings, in which at least one of the drum unit and the material supply unit has a diffusion section in which airflow is diffused further on a downstream side than on an upstream side in a supply direction of the airflow.