Cooperative Patent Classification

CPC Definition - Subclass D21F

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Last Updated Version: 2016.11
PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
Definition statement

This place covers:

Methods and devices in the wet end, press section and drying section of a papermaking machine, embossing paper, forming discontinuous sheets of paper.

References
Limiting references

This place does not cover:

Calendering paper webs

Coating paper webs

Informative references

Attention is drawn to the following places, which may be of interest for search:

Making paper articles

Articles for writing or drawing upon

Handling webs in general

Making textile fabrics from fibers or filamentary material in general

Marking, inspecting, seaming or severing textile materials in general

Systems for controlling or regulating non-electric variables

Special rules of classification

Subgroups and main groups.

If a document concerns embodiments which are covered by several subgroups dependent on a higher hierarchy group, the following rules apply:

  • the specific technical information relevant for some of the subgroups is classified in all said subgroups, for example a fiber rearranging device located in the nozzle of a headbox is classified in D21F 1/0018 and D21F 1/028;
  • if relevant, the structural association (e.g. the combination) of the elements covered by the subgroups is classified in the head group;
  • analogously, if generic technical information common to all of the subgroups is disclosed and only schematic embodiments of the specific subgroup embodiments are represented, the documents is classified in the head group only.
Glossary of terms

In this place, the following terms or expressions are used with the meaning indicated:

Section

portion of a paper production machine effecting a certain process step, for example forming, pressing, drying, calendering, coating, etc.

Yankee

steam heated drying cylinder of large diameter, mainly used for the production of creped tissue paper

TAD

through air drying process, drying paper webs by passing streams of air therethrough

Wet end of machines for making continuous webs of paper
Definition statement

This place covers:

Wet end of papermaking machines, starting at the stable section, ending at the transfer/pick up to press section

{Regulating the freeness of the pulp}
Definition statement

This place covers:

Controlling and regulating drainage rate, fiber length or degree of refining of a paper pulp suspension.

{Devices for dispensing fibres in a fluid}
Definition statement

This place covers:

Devices or altering the distribution of the fibers in the suspension, like for example by pressure pulse or ultrasound, the suspension flowing through the headbox of a papermaking machine.

{Screen-cloths}
Definition statement

This place covers:

Screens or fabrics made from plastic materials and useable for forming paper webs in a paper machine by separating fibers from an aqueous suspension or also if usable for drying a paper web in the drying section of a paper machine.

{Triple layer fabrics}
Definition statement

This place covers:

Fabrics comprising two separate layers (paper side layer and machine side layer) and a system of binding yarns interconnecting said layers, the binding yarns can also contribute to the forming of the paper side layer (known as sheet support binding (SSB)).

References
Limiting references

This place does not cover:

Paper making felts

Informative references

Attention is drawn to the following places, which may be of interest for search:

Heat treatment of fabrics

{Fibre-rearranging devices}
Definition statement

This place covers:

Devices for altering the distribution of the fibers in the suspension, like for example by pressure pulse or ultrasound, the suspension being already spread on the forming screen.

Head boxes of Fourdrinier machines
Definition statement

This place covers:

Head boxes for all kind of paper machines (i.e. Fourdrinier, gapformer, twin- or hybrid-former) if not particularly suitable only for cylinder machines, in which case D21F 1/04 is appropriate.

References
Limiting references

This place does not cover:

Headboxes of paper machines suitable only for cylinder machines

Informative references

Attention is drawn to the following places, which may be of interest for search:

Valves in general

{Means for injecting material into flow within the headbox}
Definition statement

This place covers:

Devices for injecting additional dilution water, dilution suspension or chemicals into a pulp flow within the headbox.

Regulating pulp flow
Definition statement

This place covers:

Regulating the pulp flow into and out of the headbox.

Regulating consistency
Definition statement

This place covers:

Dilution devices before or in the headbox.

Wire-cloths (production of wire-cloths B21F)
Definition statement

This place covers:

Forming or drying wires only if made from metallic materials.

Shaking apparatus for wire-cloths and associated parts
Definition statement

This place covers:

Shaking apparatus for wire and screen cloths, including ultrasound principles.

in fourdrinier machines
Definition statement

This place covers:

Shaking apparatus in all type of Fourdrinier, gapformer, twinformer or hybridformer machines.

in cylinder machines
Definition statement

This place covers:

Shaking apparatus specially adapted for being used in a cylinder machine.

Tilting, raising, or lowering mechanisms for wire-cloths
Definition statement

This place covers:

Tilting, raising or lowering mechanisms for wire and screen cloths.

in Fourdrinier machines
Definition statement

This place covers:

Tilting, raising or lowering mechanisms in all type of Fourdrinier, gapformer, twinformer or hybridformer machines.

in cylinder machines
Definition statement

This place covers:

Tilting, raising or lowering mechanisms specially adapted for being used in a cylinder machine.

Protecting wire-cloths from mechanical damage
Definition statement

This place covers:

Protecting wire and screen cloths from mechanical damage and contamination, coatings and impregnation agents.

Washing wire-cloths or felts
Definition statement

This place covers:

Washing wire or screen cloths or felts.

Guiding mechanisms (suction rolls D21F 3/10)
Definition statement

This place covers:

Wire or screen guiding mechanisms including air border layer seals, air cushion devices, guide rolls, stretching rolls, spreading rolls for the wire or screen.

References
Limiting references

This place does not cover:

Controlled deflection rolls

Informative references

Attention is drawn to the following places, which may be of interest for search:

Registering, tensioning, smoothing or guiding webs

Watermarking devices
Definition statement

This place covers:

Watermarking in general, watermarking devices acting on the fibrous suspension or layer while on the forming screen or wire; producing special forming wires or screens for making watermarks; separate watermark elements.

Suction apparatus (suction rolls D21F 3/10)
Definition statement

This place covers:

Suction apparatus in general, including regulation, steam application by suction, removing water, suction on both sides of the screen or wire, dewatering by change of direction or centrifugal effect.

Deckle frame arrangements
Definition statement

This place covers:

Sheet edge limiting devices; devices for setting the width of the web.

Pulp catching, de-watering, or recovering; Re-use of pulp-water
Definition statement

This place covers:

Treatment of white waters or broke, devices and processes in the short circulation of paper machines.

by flotation
Definition statement

This place covers:

Pulp catching, de-watering, recovering or re-use of pulp-water by flotation.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Flotation in general

Transferring webs from wet ends to press sections {(handling webs in general B65H)}
Definition statement

This place covers:

Transferring webs between paper machine sections in general, not only from the wet end to the press section.

References
Limiting references

This place does not cover:

Transfer belts, bands, felts or fabrics

{Belts or sleeves therefor}
Definition statement

This place covers:

Press shells, jackets, covers.

Arrangements thereof
Definition statement

This place covers:

Combinations of individual press elements forming a press section or part of such a section.

Pressure rolls
Definition statement

This place covers:

Web treatment rolls for press section.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Rolls, drums, discs or the like

Suction rolls, e.g. couch rolls
Definition statement

This place covers:

Suction rolls for forming, pressing and drying sections.

{Drying webs by contact with heated surfaces or materials}
Definition statement

This place covers:

Contact drying using anything except for rolls.

Drying on cylinders
Definition statement

This place covers:

Drying webs on heated cylinders.

References
Limiting references

This place does not cover:

Drying webs by hot air on a Yankee dryer

Drying webs by hot air through perforated cylinders

{Construction of the cylinders}
Definition statement

This place covers:

Construction details of cylinders for drying webs of paper, e.g. material of cylinder, production process like welding or casting, or isolation.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Details of heat-exchange rotary drums or rollers in general

{in combination with suction or blowing devices}
Definition statement

This place covers:

Drying sections including suction or blowing devices, for example including a single-tier drying group.

Festoon drying
Definition statement

This place covers:

Drying paper webs on loops formed by a series of rods, e.g. GB 820910

Drying webs by hot air
Definition statement

This place covers:

Drying paper webs by hot air.

References
Limiting references

This place does not cover:

Blow-on drying, impingement on cylinders

{Steam showers}
Definition statement

This place covers:

Steam blow boxes arranged in the paper machine.

References
Limiting references

This place does not cover:

Web conditioning devices in calenders

Damping devices

{Substantially impermeable for transferring fibrous webs}
Definition statement

This place covers:

Transfer belts, bands, felts or fabrics.

Complete machines for making continuous webs of paper
Definition statement

This place covers:

Complete machines (i.e. at least two sections combined) for making paper or for producing air-layed webs.

References
Limiting references

This place does not cover:

Complete machines (i.e. at least two sections combined) comprising a coating section combined with any other section

{paper or board consisting of two or more layers}
References
Limiting references

This place does not cover:

Machines and processes for making tissue papers

{Making patterned paper}
Definition statement

This place covers:

Methods for making patterned paper, e.g. non-planar surfaces or colour variations as obtained directly by the web-forming process.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Details of the base fabric of imprinting, embossing, texturing belts

Embossing

Crêping

Patterned paper

paper or board consisting on two or more layers
References
Limiting references

This place does not cover:

Machines and processes for making tissue papers

Making cellulose wadding, filter or blotting paper
Definition statement

This place covers:

Machines and processes specially adapted for forming tissue papers.

References
Informative references

Attention is drawn to the following places, which may be of interest for search:

Embossing

Crêping

Making hand-made paper
Definition statement

This place covers:

Making hand-made paper, restoration of paper.