GB903161A - Method and apparatus for making formed fibrous webs - Google Patents

Abstract

903,161. Paper-making machines. PULP & PAPER RESEARCH INSTITUTE OF CANADA. Feb. 17, 1961 [April 22, 1960], No. 5989/61. Class 96. In an apparatus for making fibrous webs, pulp, e.g. paper pulp, is introduced through a slice 37 into a nip between a tensioned foraminous belt 22, e.g. a wire screen, and a rotating foraminous cylinder 10, and, in a first zone 1, which is supplied through a line 42 with air pressure, the pulp is compressed and water expelled both outwardly through the belt 22 to a trough 39, and inwardly as far as into the apertures 13 of the metal plate surface 12 of the cylinder 10, the fibrous web then passing to zone 2, which is pressurized by an air supply line 46 so that water is again expelled outwardly through the belt, without however, dislodging the web and belt away from the cylinder surface. The web then passes to an optional zone 3 connected to a vacuum line 50 whereby water is sucked from the web; this zone may be supplemented or replaced by an inwardly-acting pressure-chamber (not shown) located outside the cylinder and in sliding contact with the opposite side of the belt 22. Rolls 23, 25, 26, 27, 28 guide the belt 22 and one or more may drive or tension it; roll 26 preferably incorporates a suction chamber 35 to guide the formed web and both rolls 23 and 26 may be located close to the cylinder 10 to assist water expulsion by suction. The cylinder 10 has a wire mesh surface 14 and its end-plates 15, 16 have sleeves 17 (Fig. 2) which encircle a hollow stationary shaft 18 and which are journalled in bearings 19, 20 in a framework 21. Pressure-lines 42 and 46 and vacuum line 50 communicate with stationary coaxial supply pipes 43, 47 and 18, respectively. The apparatus preferably includes a pressure-box 52 to ensure transfer of the web to the belt 22, a doctor 54 to clean off web adhering to the cylinder 10, a cleaning shower 56 for the belt 22, doctors 58 to assist in water removal from the first and second zones, and an arcuate backing-plate (not shown) to control the inward flow of water in the first zone. If desired, webs from more than one unit may be superimposed on one another on the same belt to form a laminated web. The air pressure differential increases from the first zone to the third zone, e.g. from as low as <SP>1</SP>/ 10 of an atmosphere to up to as high as 5 atmospheres.