Fibrous Web Transfer via Offset Dryer Axes
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Solution Overview
Problem
Existing machines for dewatering and drying fibrous webs, such as paper or cardboard, face challenges in transferring the web from a smooth transfer belt to a downstream dryer section, especially at high speeds, leading to rewetting and potential damage due to the complexity of the transfer process and high contamination levels.
Innovation Solution
A machine design featuring a serpentine path over heated dryer cylinders and vacuum-equipped guide rolls with offset axes, a pulper below the removal doctor, and a cleaning device with high-pressure fluid jets to ensure stable and contamination-free transfer of the fibrous web, along with extended press nips using cylindrical and shoe press rolls for effective dewatering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fibrous web is transferred from the transfer belt to the dryer section at high machine speeds, then productivity increases, but web travel stability deteriorates and rewetting occurs
Solution Approach 1:
The patent introduces a vertical offset between the axis of the first dryer cylinder and the axis of the following guide roll, creating a three-dimensional spatial arrangement. This vertical dimension provides additional space for the pulper to operate and stabilize the web during transfer, enabling stable web travel even at high machine speeds without causing rewetting
2Reliability
If the horizontal distance between dryer cylinder and guide roll is increased to accommodate pulper operation, then device complexity increases, but web transfer reliability improves
Solution Approach 1:
Instead of increasing horizontal distance which would complicate the machine structure, the patent utilizes the vertical dimension by offsetting the axes of the dryer cylinder and guide roll. This vertical arrangement provides the necessary space for pulper operation while maintaining a compact horizontal footprint, thus improving web transfer reliability without significantly increasing device complexity
3Productivity
If a removal doctor is used to transfer the fibrous web from the transfer belt, then transfer efficiency improves, but the risk of damage to the transfer belt increases due to contact pressure
Solution Approach 1:
The patent introduces a pulper as an intermediary device between the removal doctor and the fibrous web. The pulper receives the web from the removal doctor and provides additional support and stabilization, distributing the contact pressure and reducing the risk of damage to the transfer belt while maintaining efficient web transfer
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 stabilizes web travel at high speeds, reduces rewetting, and minimizes machine damage by providing sufficient space for pulper operation and effective cleaning, ensuring reliable and efficient transfer and drying of fibrous webs.
Implementation Method 1
vacuum equipped guide rolls
Implementation Method 2
heated dryer cylinders
Implementation Method 3
cleaning device which directs a cleaning fluid at a pressure of at least 50 bar onto the side carrying the fibrous web
Data Source
AI summary
A machine for dewatering and drying a paper, cardboard or other fibrous web, to which machine a fibrous stock suspension is fed which is formed at least partially from waste paper. The machine includes at least two press nips which are formed in each case by two press rolls, wherein a fibrous web runs through first press nip with a water absorbing dewatering belt on both sides. The fibrous web then runs through a second press nip with at least one other dewatering belt and a smooth impermeable transfer belt on both sides. A transfer belt transfers the fibrous web after second press nip to a belt in a downstream machine unit, e.g. dryer group. The dryer group allows the fibrous web to be guided in a serpentine manner alternatively over heated dryer cylinders and vacuum equipped guide rolls.