Paper Machine Screen Drawing-In Pattern for Tension Control

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Solution Overview

Problem

Papermaking fabrics often produce papers with unwanted markings due to uniform tension patterns and high symmetries, which lead to undesired tensions in the fabric.

Innovation Solution

Introducing irregularity in the assignment of warp threads to shafts through a drawing-in pattern with a repeating sub-repeat, allowing for non-uniform tension profiles and reduced shedding, thereby counteracting the build-up of tensions within the fabric.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform drawing-in pattern with high symmetry is used, then the fabric structure is regular and easy to manufacture, but tension patterns build up causing markings in the paper

Engineering Contradiction:

Improveease of manufactureVSAvoidmarkings in paper

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent applies asymmetry by introducing a deliberate non-uniform drawing-in pattern where warp threads are assigned to shafts in an asymmetric sequence rather than a uniform repeating pattern. This asymmetric arrangement disrupts the formation of regular tension patterns during weaving, thereby preventing the buildup of stresses that cause markings in the paper product while still maintaining manufacturability through a defined (though non-uniform) drawing-in repeat.

Inventive Principle:

Principle #4Asymmetry

2Productivity

If a repeating drawing-in pattern is used, then the weaving process is simplified and consistent, but tension patterns build up causing shedding and markings

Engineering Contradiction:

ImproveproductivityVSAvoidmarkings in paper

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a drawing-in pattern with varying local characteristics within the repeat sequence. Different segments of the drawing-in repeat have different shaft assignment patterns, creating local variations in tension distribution. This allows the fabric to be woven with consistent repeatability (maintaining productivity) while the local variations prevent uniform tension buildup that causes markings.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If warp threads are assigned to shafts in a uniform pattern, then the fabric has high symmetry and structural consistency, but this promotes tension buildup and shedding

Engineering Contradiction:

Improvefabric structure consistencyVSAvoidshedding

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent resolves this contradiction by introducing asymmetry in the shaft assignment pattern within the drawing-in repeat. The asymmetric arrangement disrupts the formation of uniform tension patterns that lead to shedding, while the defined repeat structure maintains sufficient fabric consistency for functional performance. The key is that the asymmetry prevents resonant tension buildup without completely randomizing the structure.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentEP1746202B1Method for manufacturing a paper machine screen

Publication Date: 2009.06.17 VOITH PATENT GMBH

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AI summary

The sieve belt includes wefts (116, 118) on both the web- and running sides respectively. At least two warp thread systems (120, 124, 128) are woven with these wefts. Each warp system is allocated a group of heddles, which move them for shed formation. The new method produces a repeating induction scheme for the warp systems, in which for at least one of the warp systems (120, 124, 128) a repeating under-pattern is provided. An independent claim is included for the corresponding sieve belt.