GB1389992A - Machine for making tissue paper - Google Patents

Abstract

1389992 Paper-making machines VALMET OY 19 April 1973 19133/73 Heading D2A [Also in Division F4] In a machine for making tissue paper comprising a headbox 1, a forming wire 2 onto which stock is deposited and a principal transport wire 6 onto which the formed web 5 is transferred at a return roll 7 and which conveys the web 5 to a drying section, the drying section includes at least one suction cylinder 21 having a permeable surface around which the web is passed before being directed by a pick-off roll 24 to winding apparatus 33, 34. The web is dried by hot air impinging on it and passing through it as it passes cylinder 21. As shown, the headbox I supplies stock onto a breast roll 3 containing vacuum chambers 4 for initially dewatering the web, further dewatering being effected by centrifugal forces at the return roll 7, perhaps boosted by an overpressure chamber 8, white water being collected by save-alls 9, 11. In a modification (Fig. 2-not shown) the breast roll 3 is replaced by a shoe (36) having a curved surface and a series of foils (37) connected to suction means. A blow pipe 13 separates the web 5 from the forming wire 2, the web then being carried by the transport wire 6 past suction boxes 14 and through press rolls 16, 17 and vacuum chamber 18 between the wire 6 and a second transport wire 15. After passing around a transfer roll 19 having a permeable surface and an overpressure chamber 20 to assist in drying the web 5, the web is passed over the permeable surface of cylinder 21. Pressurised air heated by radiator 45 is forced by blower 40 into the spaces 23a, 23b between the cylinder and an enclosing hood 42. Water evaporates from web 5 as hot air impinges upon it and as hot air passes through it under the action of a vacuum source 42 connected to the interior of the cylinder. The dried web is picked-off by rolls 24, 29 each of which has a permeable surface and over pressure chambers 27, 28, 30, 31. Chamber 31, together with cleaning means 46, serves to clean the wire 6. The finished web is passed from roll 29 to a winding cylinder 33 and reel 34.