Triple layer industrial fabric for through-air drying process

#The present invention relates to industrial fabrics, more particularly to fabrics for use as through-air dryer fabrics to mold a web of cellulosic fibers into a three dimensional paper structure in a papermaking machine.

#In the manufacture of paper, an aqueous slurry of about 99% by weight of water and 1% by weight of cellulosic fibers and other papermaking constituents is deposited from a headbox onto a moving forming fabric, or in between two moving forming fabrics on a two-fabric papermaking machine. The web is initially formed and partially drained in the forming section, and is transported downstream where it is consolidated and dried by known means, such as conventional press dewatering in the press section, and evaporative drying in the dryer section. However, if the finished sheet is intended to have liquid absorbency properties, for end uses such as for tissue or towel, improved results can be obtained through the use of a through-air drying (TAD) instead of the conventional press and drying methods.

#Water removal in a TAD process occurs as air is passed through the web and through the TAD fabric being used to support and convey the web through the TAD dryer section. This air movement molds the web to the surface topography of the TAD fabric, while removing most of the remaining moisture. The molding creates a more three dimensional web, thus increasing the thickness (known as bulk) of the finished web, which improves the efficacy of the finished product for applications such as tissue or towel. One means of imparting a desired topography to a TAD fabric is to apply a polymeric resin with precision in a desired pattern to the paper contacting, or paper side (PS), surface of the fabric.

#The invention will now be described by way of reference to the Figures, in which

#FIG. 1 is a photographic isometric view of a first embodiment of the invention;

#FIGS. 2A to 2D show the paths in the CD of four successive weft yarn pairs of the embodiment of FIG. 1;

#Referring to FIG. 1, it can be seen that the fabric of this embodiment is woven to a plain weave design in each of the PS layer 70 and the MS layer 80, to which each member of each pair of weft yarns, identified by the generic reference numeral 100, contributes. In each embodiment, the paths of each member of each pair of weft yarns 100 in each repeat comprise two portions, so that each member alternates between the PS layer 70 and the MS layer 80, and so that between the first and second portions of the repeat, the first and second members of the pair of weft yarns 100 exchange positions at an exchange point 90. In the first portion, the first member is exposed over a preselected number N1 of PS warp yarns identified by the generic reference numeral 110, while the second member is exposed over a preselected number N2 of MS warp yarns identified by the generic reference numeral 120. In the second portion, after the exchange of the two members of the pair of weft yarns 100, the first member is exposed over a preselected number M1 of MS warp yarns 120 while the second member is exposed over a preselected number M2 of PS warp yarns 110.

#Referring to FIGS. 2A to 2D, the paths in the CD of four successive pairs of weft yarns 100 are shown. For each pair, a first member is shown by a solid line and ascribed an even number 30, 32, 34, and 36, and the second member is shown by a broken line and ascribed an odd number 31, 33, 35 and 37. These numbers correspond with the weft yarn numbering indicated at the left side of the weave diagram of FIG. 4.

#In the PS layer, a first set of warp yarns 110, shown as the odd numbered yarns forming the upper layer in FIGS. 1A to 1D, is vertically aligned with a second set of warp yarns 120, shown as the even numbered yarns forming the lower layer in FIGS. 1A to 1D, to form vertically stacked pairs. These numbers correspond with the warp yarn numbering indicated across the top of the weave diagram of FIG. 4.