Patent ID: 8539987
Filing Date: 2013-09-24
Classification: D21F

Abstract:
1. A quadruple papermaking fabric, in particular a forming fabric for use in the forming section of a papermaking machine, having at least one fabric repeat unit and comprising: a set of warp machine direction (MD) top yarns; a set of weft cross machine direction (CMD) top yarns interwoven with the top MD yarns to form a top fabric layer; a set of central MD yarns; a set of central CMD yarns interwoven with the central MD yarns to form a central fabric layer; a set of bottom MD yarns; a set of bottom CMD yarns interwoven with the bottom MD yarns to form a bottom fabric layer; wherein in the fabric repeat unit the top layer is bound only to the central layer and the bottom layer is bound only to the central layer by respective independent binding patterns, formed by respective distinct sets of yarns arranged in the cross machine direction; the first binding pattern being formed by a set of pairs of binder yarns, each pair being positioned between two adjacent top CMD yarns and having at least one yarn that interweaves with both the top MD yarns and the central MD yarns; the binder yarns of each pair being twisted with respect to each other and vertically superimposed and positioned between two adjacent top CMD yarns; the second binding pattern being formed by at least some central CMD yarns that interweave with the central MD yarns and also with the bottom MD yarns ( and wherein the binder yarns comprise respective support portions, that interweave with the top MD yarns, and respective binding portions, that interweave with the central MD yarns beneath the top MD yarns; the binder yarns of each pair being twisted with each other and vertically superimposed, so as the support portions of a binder yarn of the pair are superimposed to the binding portions of the other binder yarn of the pair, and vice versa; the binder yarns of each pair passing, with the respective support portions, over the top MD yarns under which the top CMD yarns pass, and the support portions of the binder yarns pass instead under the top MD yarns over which the top CMD yarns pass, so that the binder yarns and the top CMD yarns form a plain weave pattern with the top MD yarns; and wherein the fabric is formed by three superimposed warp yarns defining a warp unit that recurs in the cross machine direction (CMD), and by five weft yarns defining a weft unit that recurs in the machine direction (MD); the ratio between weft yarns and warp yarns recurring in the machine direction and in the cross machine direction respectively being hence 5:3.