Controlled porosity papermaking fabric

摘要

A multi-layered paper machine fabric having a preselected permeability value, comprising a single system of warp yarns and a multiple layers of weft yarns. The weft yarns include support surface weft yarns intermediate layer weft yarns and lower surface weft yarns all interwoven with the single system of warp yarns. The surface layer weft yarns are of a first thickness, the lower layer weft yarns are of a second thickness, and the intermediate layer of weft yarns are of a third thickness which differs from the first and second thicknesses. Certain ones of the support surface weft yarns are interwoven with the warp yarns to be vertically aligned with the lower surface weft yarns to form drainage channels therebetween. Certain of the intermediate weft yarns are interwoven with the warp yarns to be located intermediate of the surface weft yarns and the lower weft yarns and centrally of the drainage channels. The thickness of the intermediate weft yarn is selected between predetermined ranges to determine the preselected permeability.