GB931976A - Improvements in or relating to paper-making machines - Google Patents

Abstract

931,976. Paper-making machines; paper. BLACK-CLAWSON CO. Oct. 13, 1959 [Oct. 13, 1958], No. 34676/59. Class 96. A paper-making machine comprises two perforate forming webs looped around two breast rolls and two couch rolls and so arranged that in the forming zone they travel vertically but slightly convergently and means for delivering liquid stock to the nip between the breast rolls. As shown, pulp is supplied from a flow-box 40 to the nip between two wire-cloths or felts or woven bands 25, 35 travelling about breast rolls and between pairs of suction rolls 21, 31 &c. which co-operate with seal rolls 130 to form suction enclosures so that the pulp is under suction from both sides throughout its vertical travel. White water passes into the suction rolls directly at the nips, and intermediately via deflector plates 155 which prevent pools of water from forming near the nips. Seals between the opposed edges of the adjacent portions of the forming webs to prevent lateral flow of stock from the space between them, or entry of air into the space comprise tubes of flexible material, e.g. polyethylene filled with a liquid at a pressure higher than that exerted on the tube by the stock. The height and lateral position of the flow-box 40 are adjustable by screws 173 coacting with sloping support-blocks 171. The wirecloths &c. are cleaned by showers 50 and the suction rolls by showers 53. Jets 54 trim the edges of the web, the strips 55 being removed as illustrated. The trimmed web is couched at 47 to a felt 46. The whole assembly is supported on four pedestals (two shown at 61 and 63), each section having provision for pivotal movement about a vertical axis on the pedestal, not shown, and having support blocks 74 which may be removed from the pedestal 61 or 63, pistons 75 raising the section for this removal and then being retracted, so that the section may be turned about its pivot for wire-changing &c. The interiors of the pedestals, not shown, are hollow and are connected with a source of vacuum, so that they act as conduits for the removal of white water. Rolls of the take-off section may be synchronized with the presssection, and the other forming-section synchronized by electric tachometers 106. The Specification includes also the subject-matter of Specifications 931,977 and 931,978. If the stock comprises fibres of different lengths and filler materials, then in the finished paper the longer fibres will be concentrated towards the centre of the thickness of the sheet, and the shorter fibres and filler materials towards both surfaces. Both surfaces then have practically matching physical characteristics, and require minimum amounts of surface coating before being printed upon.