GB1470173A - Twin-wire papermaking apparatus - Google Patents

Abstract

1470173 Web-forming apparatus INTERNATIONAL PAPER CO 17 March 1974 48345/73 Heading D2A In a method of forming a web of fibres, a dilute suspension of fibres is passed between a pair of endless foraminous forming carriers 30, 32 moving continuously into and through a forming section 46 over converging paths, the web being formed between the converging carriers 30, 32 by forcing water under pressure from the suspension without suction through each carrier 30, 32 into a respective plurality of successive seal boxes 48, 50 disposed adjacent that carrier 30. 32 on the side thereof opposite the flowing suspension. The water level in the respective seal boxes 48, 50 is maintained above the points of entry of the water from the carrier, the convergence of the carriers substantially blocking the flow of suspension out of the forming section 46 between the carriers 30, 32. As described, the suspension is passed through an inlet section 12 which stabilizes the velocity thereof by means of vanes 24 and a passageway 22 of substantially constant cross-section. The rate of flow of water through the seal boxes may be separately controlled so that the velocity of the remaining suspension through the forming section is substantially constant. The speed of the carriers 30, 32 is kept the same, the fibrous web leaving carrier 32 at transfer roll 82 before being transferred if required to a dryer fabric 86. The boundary layer of the suspension flowing through inlet section 10 may be removed through apertures adjacent seals 34, 36. The inlet of each seal box 48, 50 includes a foraminous support 52, 54 for the carriers 30, 32, each array of seal boxes 48, 50 being mounted on a common mounting which allows adjustment of the outlet 56 to accommodate different web thicknesses. Various modifications are described which allow manufacture of multilayer paper. In one modification, (Figure 8, not shown) a central vane 24 extends through a substantial length of the forming section, allowing two separated stabilized streams to be used, each coming into contact with a single support, the resultant webs joining adjacent the outlet 56. Wood and synthetic fibres may be employed. A three layered paper may be produced by a further modification (Figure 9, not shown), the outer layers resulting from the same stock, a second stock being separated from the first until being introduced, adjacent the forming section inlet 14, between the two parts of the first stream. Yet a further modification (Figure 10, not shown) allows the manufacture of a filled sheet. A suspension of filler enters at the inlet 14 being initially separated from a single stock until the web has been at least partly formed.