Textiles: weaving – Fabrics – Drier felts
Patent
1994-09-06
1995-10-17
Bell, James J.
Textiles: weaving
Fabrics
Drier felts
428257, 162901, D03D 2300
Patent
active
054586933
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a woven fabric for use in papermaking, cellulose manufacturing or like machines, said fabric comprising at least two systems of warp threads and at least one system of weft threads.
In the making of paper in a papermaking machine, an aqueous slurry of fibres is flowed on to a horizontally moving forming fabric or into the nip between two running forming elements, of which at least one is a forming fabric. A major portion of the aqueous content of the fibre slurry is dewatered through the forming fabric, and a coherent paper web is formed thereon. The formed paper web is transferred on a press felt into a press section, where more water is squeezed from the web in one or more press nips. Finally, the paper web is transferred to the drying section of the papermaking machine, where, by engaging hot cylinders, it is dried by evaporation of the moisture. The web is brought into engagement with the drying cylinders by means of a dryer fabric.
In the forming of the paper web, the fibre slurry, commonly known as the stock, generally contains above 99% water, of which the major part should be removed by allowing the water to flow through the forming fabric. The throughflow of water takes place in the parts of the forming fabric where the thread material therein does not obstruct such passage. It is however vital that the throughflow areas are very limited, i.e. the fabric must be very fine-meshed, to avoid fibre losses and paper markings, but at the same time the permeability of the forming fabric must be sufficient to allow substantial amounts of water to pass through. Thus, the fabric surface next to the fibre web must be fine-meshed, with many, small throughflow areas, which means that the fabric material must consist of thin threads. At the same time, the fabric must be wear-resistant and dimensionally stable, which means that additional and generally coarser thread material must be included in the forming fabric. This combination of desired properties has been achieved by using several thread systems in one or both directions of the forming fabric.
When the paper web is formed on the surface of the forming fabric, this must be done without reflecting the design of the forming fabric in the paper sheet in the form of a so-called wiremark, which is caused by a non-uniform forming surface. In forming fabrics having several thread systems in one or both directions, these thread systems must be interlaced without interfering with the fine-mesh fabric part that might give rise to a wiremark.
In the drying of the paper web, use is today generally made of monofilament fabrics which, like the forming fabrics, are usually multi-layered with several thread systems in one or both directions. Also in the drying process, an uneven fabric surface may give rise to wiremarks on the paper web.
The above-mentioned interlacing of the thread systems in a forming or drying fabric with several thread systems can be achieved in different ways: binder weft threads. U.S. Pat. No. 3,885,603 discloses a forming fabric in which the thread systems have been interlaced by special binder warp threads. Swedish Patent Specification 7806764-2 discloses a forming fabric where the thread systems are interlaced by special binder weft threads. where the warp thread from one woven fabric interlaces with the weft thread from another woven fabric. Such interlacing is disclosed in EP 0 349 779. system, interconnecting these systems, in the other direction of the woven fabric. Such interlacing is disclosed in U.S. Pat. No. 4,071,050.
When using separate binder threads according to case (a) above, these must be very thin to produce minimum interference in the structure. Such a binder thread may, however, be subjected to heavy internal wear in the case of unfavourable operational conditions or choice of pattern.
To combine a fine surface with a wear-resistant and stable structure, the thread systems usually consist of at least one fine thread system next to the paper web and at least one coarser thread system as a lower pl
REFERENCES:
patent: 5152326 (1992-10-01), Vohringer
Albany Nordiskafilt AB
Bell James J.
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