Textiles: weaving – Fabrics – Drier felts
Patent
1998-04-03
1999-12-14
Falik, Andy
Textiles: weaving
Fabrics
Drier felts
D21F 100
Patent
active
060004401
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is concerned with fabrics, which are particularly, but not exclusively, for use as papermachine clothing and ideally for use in the forming section of the papermachine.
2. Description of the Related Art
The original synthetic forming fabrics utilised one warp system and one weft systems. However these, so called, single-layer fabrics tended to narrow and stretch thus interfering with paper production and machine performance. So called mlti-layer fabrics were therefore developed to overcome the dimensional instability of the single-layer fabrics. Of these, the so called two-layer fabrics have become the most common type of forming fabric. Two-layer fabrics utilise one warp system which interlaces with two distinct weft systems. The warp system provides a greater amount of warp material, for stability, than the prior single-layer fabrics.
Two-layer weaves, in addition to improving fabric stability, also allow further benefits over single-layer fabrics. These benefits are due to the two separate weft systems.
The wearside weft system protects the load-bearing warp yarns by providing long "floats" which contact the dewatering elements on the papermachine. Furthermore as the wearside weft never appears on the paperside then relatively thick yarns can be used to provide a significant amount of material for wear. By this means improved fabric lives can be obtained without causing undesirable wiremark.
The paperside weft system interlaces with the warp to provide a surface for the formation, dewatering and release of the papersheet. Relatively thin weft yarns may be used to minimise wiremark, as these yarns do not appear on the wearside. Improved papermaking properties are thus obtained.
Single-layer fabrics were subsequently made using weave patterns which also offered inproved dimensional stability. For example U.S. Pat. No. 4,518,644 teaches that relatively stable single-layer fabrics can be obtained by causing "the longitudinal and/or transverse threads to change the direction of their course intermittently in the plane of the fabric". The resulting lateral crimp added a pronounced "diagonal" aspect to the usual three yarn orientations of: machine direction, cross-machine direction, and vertical crimp. The lateral crimp was of sufficient magnitude that adjacent yarns made intermittent contact such that a buttressing effect was achieved.
Improvements in single-layer stability were possible by this means. However as such structures still possess only single weft and warp systems it is not possible to obtain both the papermaking and wear resistance improvements which are provided with the two-layer structures.
Furthermore, U.S. Pat. No. 4,518,644 had the declared objective of obtaining a single-layer fabric with maximum thickness, maximum inner volume and a minimum open area (in vertical sight). It is now known that the foyer two properties can contribute to water carrying within the fabric body.
Fabric water carry is particularly undesirable on Gap Former machines. Such machines operate at relatively high speed and possess comparatively short dewatering sections with which to remove water from the sheet. Consequently such machines tend to produce sheets with an undesirably high moisture content. This problem is worsened by moisture carried within the voids of the fabric rewetting the sheet. Bearing this in mind an ideal structure for use on modern papermachines will possess relatively low thickness and void volume.
The single-layer structure described in U.S. Pat. No. 4,518,644 also maintained a high permeability indicating the relative openness of the structure and the limitation of the structure with regards to retention of fines and filler.
Latterly a need for paper with, for example, improved printing characteristics developed. It was realized that such paper could be produced by using two-layer fabrics with an increased paperside: wearside weft ratio of 2:1. Thus EP 0085363 allowed for the inclusion of an additional set of "floater" weft y
REFERENCES:
patent: 3858623 (1975-01-01), Lefkowitz
patent: 4518644 (1985-05-01), Vuorio
patent: 4739803 (1988-04-01), Borel
patent: 5025839 (1991-06-01), Wright
Falik Andy
Scapa Group PLC
LandOfFree
Multi-layer papermaking fabric does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer papermaking fabric, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer papermaking fabric will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-854887