Multi-Layer Fibrous Web Forming and Pressing
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Solution Overview
Problem
Existing methods for producing multi-layer fibrous webs, such as packaging paper, often impair the whiteness of the top layer and require complex, costly press sections with multiple fabrics, leading to operational challenges like edge tears and high investment and operating costs.
Innovation Solution
A device with a wire section forming two layers, a press section using two last press nips with a smooth counter-element for smoothing, and a transfer belt for direct transportation from the forming unit to the press section, allowing the second layer to contact the smooth surface, thereby maintaining whiteness and simplifying the press section design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the second layer is dewatered through the first layer in the couching zone, then the multilayer fibrous web is formed, but the whiteness of the first layer is impaired
Solution Approach 1:
The dewatering process is segmented into two distinct stages: (1) initial dewatering in the couching zone where the second layer is deposited onto the first layer, and (2) final dewatering in the press section with two press nips. This segmentation allows the first layer to maintain its whiteness during the critical formation stage while still achieving sufficient water removal through the coordinated action of both dewatering zones.
Solution Approach 2:
The press section acts as an intermediary between the couching zone and the final product. By introducing a dedicated press section with two press nips, the system provides an intermediate dewatering stage that completes the water removal process without requiring the first layer to be used as a dewatering filter in the couching zone, thus preserving the first layer's whiteness.
2Productivity
If multiple fabrics are used in the press section for dewatering, then the dewatering capacity is sufficient, but the device complexity and operating costs increase
Solution Approach 1:
The press section merges multiple dewatering functions into a compact configuration with two press nips. Instead of using multiple separate press sections with different fabrics, the invention combines the dewatering operations in a unified press section that achieves sufficient water removal through the coordinated action of two press nips with a reduced number of fabrics.
Solution Approach 2:
The press section is designed with multi-functionality, where the two press nips work together to perform both dewatering and pressing operations. This universal design allows the press section to achieve sufficient dewatering capacity without requiring multiple specialized fabrics, thereby reducing device complexity and operating costs while maintaining productivity.
3Productivity
If multiple fabrics are used in the press section, then dewatering is effective, but the operating costs increase due to large number of coverings
Solution Approach 1:
The press section merges multiple dewatering functions into a compact configuration with two press nips. Instead of using multiple separate press sections with different fabrics, the invention combines the dewatering operations in a unified press section that achieves sufficient water removal through the coordinated action of two press nips, thereby reducing the number of fabrics required and associated operating costs.
4Manufacturing precision
If an inverted compact press is used, then the top layer can be smoothed, but the operational behavior becomes problematic
Solution Approach 1:
Instead of using an inverted compact press where the smooth surface contacts the top layer from above, the invention inverts the arrangement by placing the smooth surface on the counter element that contacts the web from below in the press section. This inverted configuration maintains the smoothing function while improving operational reliability and avoiding the problems associated with traditional inverted compact presses.
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 solution preserves the whiteness of the top layer, improves operational behavior by reducing edge issues, and allows for a compact, cost-effective press section with sufficient dewatering capacity, enabling efficient production of high-quality multi-layer fibrous webs like liner and white top kraft liner.
Implementation Method 1
a second press element with a common counter element with a smooth surface for smoothing one side of the multilayer fiber web
Implementation Method 2
The press section comprises at least two final press nips
Data Source
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AI summary
The invention relates to a device (1) for producing a multiple-layer fibrous web having a wire section (6), a pressing section (7) and a drying section (8), wherein the wire section (6) comprises a first forming unit (2) for forming a first layer (9) of the fibrous web (11) and a second forming unit (3) for forming a second layer (10) of the fibrous web (11), and the forming units (2, 3) are configured and arranged with respect to one another in such a way that the second layer is transferred onto the first layer in a couching zone (37) in order to configure the multiple-layer fibrous web, and wherein the pressing section (7) comprises at least two last press nips (12, 13), wherein the two last press nips (12, 13) are formed by way of a first pressing element (15) and a second pressing element (16) and a common counter-element (18) with a smooth surface for calendering one side of the multiple-layer fibrous web (11). The device (1) according to the invention is characterized in that a transfer belt (20) is provided for direct taking over of the multiple-layer fibrous web (11) from the first forming unit (2) and for further transporting of the multiple-layer fibrous web (11), in that a press belt (19) is arranged for direct taking over of the multiple-layer fibrous web (11) from the transfer belt (20), and in that the multiple-layer fibrous web (11) is guided together with the press belt (19) through the penultimate press nip (12) in such a way that the second layer (10) of the multiple-layer fibrous web (11) comes into contact with the smooth surface of the counter-element (18).