Forming Screen Thread Spacing to Reduce Hydraulic Marking

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Solution Overview

Problem

Existing fabric belts used in the production of fibrous webs cause undesirable hydraulic and topographical markings due to uneven drainage, primarily influenced by the weave pattern and constant spacing of lower longitudinal threads.

Innovation Solution

The fabric belt design features varying distances between lower longitudinal threads, with differences ranging from 20% to 175% of the upper thread diameter, and uneven spacing of upper longitudinal threads to reduce hydraulic diagonal markings, combined with a plain weave pattern to minimize topographical markings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the lower longitudinal threads are arranged at constant distance from each other, then the weave pattern provides structural stability, but hydraulic diagonal markings occur in the fiber web

Engineering Contradiction:

Improvehydraulic diagonal markingsVSAvoidconstant spacing structure

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent applies asymmetry by varying the spacing between lower longitudinal threads, creating an irregular pattern where some spaces are larger and some are smaller than the average spacing. This asymmetric arrangement disrupts the regular hydraulic flow paths that cause diagonal markings, while maintaining overall structural stability through the consistent average spacing of 0.5-2.0 mm.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent implements local quality by creating specific local variations in thread spacing rather than uniform changes throughout. Individual spaces between adjacent lower longitudinal threads are made larger or smaller than average, allowing localized disruption of hydraulic flow patterns that cause markings, while the overall fabric structure maintains its structural integrity through consistent average spacing.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the upper longitudinal threads are arranged at constant distance, then the surface for fiber web is smooth, but topographical markings are caused

Engineering Contradiction:

Improvetopographical markingsVSAvoiduniform thread arrangement

Core Design Contradiction:

Object-affected harmful factorsVSShape

Solution Approach 1:

The patent applies asymmetry to the upper longitudinal threads by varying their spacing, creating an irregular arrangement where individual threads are positioned at different distances from each other. This asymmetric spacing prevents the formation of regular topographical patterns on the fiber web surface, while the overall average spacing maintains the smooth surface quality needed for high-grade paper production.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent implements local quality by creating specific local variations in upper thread positioning. Individual upper longitudinal threads are placed at varying distances from their neighbors, creating localized irregularities that prevent systematic topographical markings, while the overall distribution maintains the smooth surface characteristics required for the fiber web.

Inventive Principle:

Principle #3Local quality

3Strength

If the lower longitudinal threads are made thicker, then the tensile strength and wear resistance are improved, but the hydraulic marks become more pronounced

Engineering Contradiction:

Improvetensile strength and wear resistanceVSAvoidhydraulic marks

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by varying the diameters of lower longitudinal threads, creating a mix of thicker and thinner threads within the same fabric layer. Thicker threads provide localized strength and wear resistance where needed, while thinner threads reduce the prominence of hydraulic marks in other areas. This local variation allows the fabric to simultaneously achieve high mechanical strength and reduced marking.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses asymmetry by creating an irregular distribution of thread diameters in the lower longitudinal threads. Instead of uniform thickness, the threads vary in diameter, which disrupts the regular hydraulic flow paths that cause diagonal markings. The asymmetric thickness distribution ensures that no single thread pattern dominates the hydraulic flow, reducing overall marking while maintaining structural strength through the presence of thicker threads.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentEP4306708B1Fabric tape

Publication Date: 2026.01.21 VOITH PATENT GMBH

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AI summary

The invention relates to a fabric belt, in particular a forming screen, for a machine for the production and/or processing of a fibrous web, comprising an upper fabric layer with upper longitudinal threads (O1-O3) and upper transverse threads interwoven with these, and a lower fabric layer with lower longitudinal threads (U1-U4) and lower transverse threads interwoven with these, wherein the two fabric layers are arranged one above the other such that, in the intended use of the fabric belt, the upper fabric layer faces the fibrous web to be produced and the lower fabric layer faces away from the fibrous web to be produced, wherein a first distance (A1) between two immediately adjacent lower longitudinal threads (U1-U4) is greater than a second distance (A2) between two immediately adjacent lower longitudinal threads (U1-U4), wherein the difference between the first distance (A1) and the second distance (A2) is between 20% and 175% of a diameter of an upper longitudinal thread (O1-O5).preferably between 25% and 175%.