Patent ID: 6322669
Filing Date: 2001-11-27
Classification: D21F

Abstract:
A method for preventing rewetting of a web in a web former of a paper machine in which the web is formed by forming members while being supported by a wire and water is removed from the web by dewatering members, the wire being guided in a loop by alignment, guide and/or suction rolls, the improvement comprising the steps of:arranging at least a first and second vacuum box/chamber in a loop of the wire after a last one of the alignment, guide and/or suction rolls in a running direction of the web prior to separation of the web from the wire such that the web passes over the last roll and then over said first vacuum box/chamber and at least a portion of said second vacuum box/chamber prior to said web separating from said wire,generating a first vacuum of about 45 kPa to about 75 kPa in said first vacuum box/chamber in order to remove moisture from the wire and the web supported thereby,generating a second vacuum of about 15 kPa to about 45 kPa in said second vacuum box/chamber to prevent transport of moisture from the wire back into the web, andregulating the first and second vacuums such that the first vacuum is higher than the second vacuum, whereby rewetting of the web is prevented such that the water adhering to the threads and the bottom face of the wire is prevented from traveling to the upper face of the wire and coming into contact with the web.