Round Wire Paper Machine Thread Wobble for Security Paper Flatness
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Solution Overview
Problem
Conventional methods for producing security paper with window security threads face challenges in achieving good flatness and clear window configurations when using non-rectangular thread windows, leading to restrictions in design motifs and processing issues.
Innovation Solution
A round wire paper machine is used to produce security paper with partially embedded window security threads, where the round wire circumference is equal to or twice the offset period, allowing for non-rectangular thread windows and synchronized thread and window wobbling to ensure precise placement of the security thread within the paper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If non-rectangular thread windows are used, then design motif versatility is improved, but flatness deteriorates and window configuration becomes unclear
Solution Approach 1:
The invention introduces a dynamic wobble mechanism where the security thread is deliberately moved in a controlled wobble pattern during paper production. This dynamic approach allows non-rectangular thread windows to maintain clear configurations by ensuring the thread consistently centers within the window area across multiple sheets, resolving the flatness and configuration clarity issues while preserving design versatility
Solution Approach 2:
The invention implements periodic wobble action with a specific period corresponding to the paper production cycle. By synchronizing the thread wobble period with the production rhythm, the system ensures that thread windows appear at consistent positions in the final paper stack, maintaining manufacturing precision while enabling non-rectangular designs
2Manufacturing precision
If rectangular raised embossings are used for thread windows, then flatness is maintained, but design motif selection is limited
Solution Approach 1:
The invention replaces static rectangular embossings with a dynamic wobble mechanism that can accommodate various non-rectangular window shapes. The controlled thread movement during production ensures that even with complex window geometries, the threads center properly and flatness is maintained through the wobble effect distributing pressure evenly
Solution Approach 2:
The invention changes the key parameter from fixed window geometry to controlled thread position during production. By adjusting the wobble parameters (amplitude, frequency, phase), the system can produce different window shapes and motifs while maintaining manufacturing precision, thus expanding motif selection without sacrificing flatness
3Adaptability or versatility
If thread wobble is increased to accommodate non-rectangular windows, then design flexibility is improved, but flatness deteriorates
Solution Approach 1:
The invention optimizes the wobble dynamics by controlling the amplitude and frequency to match the specific non-rectangular window geometry. The wobble is tuned so that threads from different sheets land in complementary positions, filling in gaps rather than creating uneven stacks, thus maintaining flatness while providing design flexibility
Solution Approach 2:
The invention incorporates feedback control where the wobble parameters are adjusted based on the specific window configuration and production conditions. This ensures that the thread distribution maintains flatness while accommodating various non-rectangular designs, resolving the contradiction between flexibility and precision
Data Source
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AI summary
The invention relates to a drum screen (12) of a drum-screen papermaking machine (10) for producing security paper (42A, 42B) with a partially embedded window security thread (22), the drum screen (12) drawing a paper mass in the form of a fibre-water suspension (14) from a vat (16) during the paper production process, and the drum screen (12) containing a production screen jacket (30) with a circumferential direction (U) and a transverse direction (Q) perpendicular thereto, which production screen jacket is provided in the circumferential direction (U) with a plurality of raised thread window elements (34), on which the window security thread (22) rests during the paper production process in order to locally prevent the accumulation of fibre-water suspension (14) for the generation of thread windows (40). According to the invention, the thread window elements (34) are arranged along the circumference with a periodic offset (36) in the transverse direction (Q), the drum screen circumference Ru being an integer multiple of the offset period P. The invention also relates to an associated method for producing a security paper.