Patent ID: 7426944
Filing Date: 2008-09-23
Classification: D21F,Y10S

Abstract:
1. A double layer forming fabric for a papermaking machine woven to an overall repeating weave pattern requiring at least 8 sheds in the loom and comprising in combination a paper side layer having a first drainage area and a paper side surface, a machine side layer having a second drainage area, and a centre plane within the fabric, defined as a notional plane substantially parallel to and located between the paper side layer and the machine side layer and having a third drainage area, and wherein the fabric has at least (i) paper side layer yarns and machine side layer yarns each oriented in a first direction; and (ii) a set of yarns comprising only pairs of binder yarns interwoven with the paper side layer yarns and machine side layer yarns in a direction transverse to the first direction, wherein: (a) in the paper side surface, each pair of binder yarns occupies a single combined path; (b) the pairs of binder yarns are woven in the overall repeating weave pattern such that for each pair: (A) in a first segment of the single combined path, a first member of the pair interweaves with selected paper side layer yarns at an interweaving location, and a second member of the pair interlaces with at least one machine side layer yarn at an interlacing location; (B) in a second segment of the single combined path, the second member of the pair interweaves with selected paper side layer yarns at an interweaving location, and the first member of the pair interlaces with at least one machine side layer yarn; (C) the length of the first and second segments may be equal or unequal; (D) between each adjacent segment the members exchange positions at an exchange point, and the members are laterally displaced in relation to each other along the single combined path at and between each consecutive exchange point; and (E) for each member of each pair of binder yarns, between each interweaving location and an immediately subsequent interlacing location, and between each interlacing location and an immediately subsequent interweaving location, the member floats between the paper side layer yarns and the machine side layer yarns under at least four paper side layer yarns; (c) the machine side layer is woven to a repeating machine side layer weave pattern in which, for each pair of binder yarns, in each repeat the first member and the second member alternately interlace with selected machine side layer yarns but do not form a complete repeat of the machine side layer weave pattern; and (d) the fabric has a total warp fill after heatsetting of at least 100% (e) the first drainage area is between 25% and 50%; (f) the second drainage area is between 25% and 50%; and (g) the third drainage area is between 8% and 20%.