Headbox Screen Angle and Protrusion for Paper Web Formation
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Solution Overview
Problem
Existing sheet forming systems for producing two- or multi-layer fibrous webs, such as paper or packaging paper, suffer from poor covering qualities and turbulence in the fibrous suspension jet, leading to hard and fine-grained formation structures, especially on the underside of the web.
Innovation Solution
The system incorporates a screen on the lower outer wall of the headbox nozzle with a screen angle of ≥15° and a screen protrusion of ≥1 mm, allowing for varying jet impingement angles while maintaining an unchanged headbox geometry, along with a twin-wire zone and strategically arranged slats on the forming table for improved dewatering and fiber orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional headbox nozzle design is used, then the structure is simple, but the covering quality is poor and turbulence occurs in the fibrous suspension jet
Solution Approach 1:
The headbox nozzle is divided into multiple segments including a screen component with adjustable screen angle and screen protrusion, allowing independent optimization of flow control and fiber distribution without redesigning the entire nozzle structure
Solution Approach 2:
The screen angle and screen protrusion are made adjustable rather than fixed, enabling dynamic adaptation of the jet flow characteristics to achieve optimal covering quality and reduce turbulence under different operating conditions
2Productivity
If high production speed is achieved, then productivity increases, but the formation structure becomes hard and fine-grained
Solution Approach 1:
The screen component prepares the fibrous suspension jet in advance by controlling the flow pattern and reducing turbulence before the web is formed, ensuring soft formation structure even at high production speeds
Solution Approach 2:
By adjusting screen angle and screen protrusion parameters, the flow characteristics of the fibrous suspension are optimized to maintain gentle fiber deposition and soft formation structure during high-speed operation
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 significantly smooths the fibrous suspension jet, enhancing covering quality and producing a soft formation structure on the fibrous web, enabling production at high speeds with improved basis weight and fiber orientation.
Implementation Method 1
a screen (27) on the lower outer wall (26.1) facing the fourdrinier wire (7.1), in that the screen (27) on the lower outer wall (26.1) facing the fourdrinier wire (7.1) has a screen angle (27.W) of ≥15°
Implementation Method 2
a wire section (6) with at least one endless wire (7) running around in a wire loop (7.L), which, in a pre-dewatering section (8) after or in the area of application of the at least one fibrous suspension (3) as a fibrous suspension free jet (3.S) by means of the two- or multi-layer headbox (4) over a stationary and preferably suction-controlled forming table (9)
Data Source
AI summary
The invention relates to a sheet forming system (1) for a machine (100) for producing a two-layer or multi-layer web (2) from at least one fibre suspension (3), comprising a two-layer or multi-layer headbox (4) with a headbox nozzle (5), which has at least two nozzle chambers (24.1, 24.2), separated from one another by at least one separating element (23), each of which guides a fibre suspension (3) as a fibre suspension flow (3.1, 3.2), each of which has downstream an exit slit (25.1, 25.2) extending over the width (B) of the headbox (4), wherein the two outer nozzle chambers (24.1, 24.2) each have on the outer side an outer wall (26.1, 26.2), and wherein a plate (27; 30) is arranged on the discharge side of at least one outer wall (26.1; 26.2), and a Fourdrinier wire at the bottom outer wall (26.1) facing the Fourdrinier wire (7, 7.1) has an plate angle (27. W) of > 15° and the plate (27) having an orifice projection (27. V) of > 1 mm.