Patent ID: 7524402

Claim:
A gap type two fabric forming section for a paper making machine having a conveying forming fabric and a backing forming fabric, such that: (i) each of the forming fabrics has a paper side and a machine side; (ii) the forming fabrics move together in a machine direction through a forming zone with a layer of stock sandwiched in between; (iii) the forming fabrics are supported by a series of fabric support elements, chosen from the group consisting of rolls, static fabric contacting fabric support elements and both rolls and static fabric contacting fabric support elements, over which the machine sides of each of the forming fabrics pass in sliding contact, the fabric support elements being supported on a sequence of dewatering boxes, the dewatering boxes having a curved fabric support element supporting surface; and (iv) the dewatering boxes provide separate drainage zones and at least some of the dewatering boxes are connected to a source of vacuum to provide separate vacuum zones, wherein: (a) the forming zone comprises that portion of the forming section between the locus at which the forming fabrics come together to sandwich the stock between them and the locus at which the two forming fabrics separate with the stock continuing on one of them; (b) the dewatering boxes provide at least four separate and distinct vacuum zones within the forming zone; (c) radii of curvature of the curved surfaces supporting the fabric support elements decrease progressively in the machine direction; (d) a pitch of the fabric support elements decreases progressively in the machine direction; and (e) the dewatering boxes supporting the fabric support elements are selectively located on the machine sides of the first forming fabric and the second forming fabric in an opposed and at least partially offset sequence in the machine direction.