paper-machine

Century Dictionary and Cyclopedia

1. n. A machine for making paper.
2. n. Specifically, the machine used in the final process of paper-making and following the various machines used in the rag-mill and pulp-mill in cleaning, shredding, grinding, bleaching, refining, and mixing the rags, wood-pulp, or other material, in water to form the stock fed to the paper-machine. Paper-mills are known as one-machine, two-machine mills, etc., independently of their pulp-making capacity. Two types of paper-machines are in general use. In the cylinder machine the stock, composed of about 96 parts of water and 4 parts of pulp of some kind mechanically suspended in the water, is fed in a continuous stream to a series of narrow vats placed side by side and forming the first part of the machine, where the process of paper-making begins. In each vat is suspended a cylindrical frame covered with fine brass wire cloth. Each cylinder, supported horizontally in the vat by an arbor which passes through the ends of the vat, revolves while partially submerged in the liquid stock, none of the liquid being able to escape through the bearings of the shaft or to enter the ends of the cylinder. The water of the stock passes freely through the wire cloth and enters the interior of the cylinder and is led out of the machine. The pulp floating in the water cannot pass the wire cloth and is drawn against it, rapidly covering the cylinder with a film. On reaching the highest point in the revolution of the cylinder the film of pulp meets a continuous web of felt traveling horizontally in the same direction as the surface of the cylinder at this point. Immediately above the felt is a roll, called the couch-roll, which presses upon the felt, causing the film of pulp to leave the cylinder and cling firmly to the felt. Each cylinder in the series of vats contributes its film of pulp to the traveling felt, all being pressed together and moving on the felt as a continuous band of wet pulp until it passes out of this first part of the machine and is delivered to the next or second part. The second, third, and fourth parts are essentially the same as the corresponding parts of the Fourdrinier machine described below. In the Fourdrinier machine, the production of a continuous film of pulp on wire cloth is effected in a different way. The first, or Fourdrinier, part of the machine consists essentially of a traveling-apron of wire cloth, called the wire, supported by table-rolls in a horizontal position. On each side of the wire a thick endless rubber band, called a deckle, rests upon the moving wire and travels with it The wire and the two deckles form a shallow moving trough and into this trough is fed a thin stream of stock which fills it and moves onward with it The rubber deckles act as dams on each side to prevent the escape of the liquid and also serve to define the edges (deckle edges) of the rapidly forming film of pulp. The water in the stock sinks downward through the wire into the save-all boxes and is led out of the machine. The pulp, unable to pass through the wire, is caught on it and moves onward as a continually formed and continuous film. As more water escapes through the wire the film becomes more coherent and passes under a dandy roll which compacts it more firmly together. Finally, the water being almost completely extracted and the film changing from a sheet of pulp into a band of soft paper, the endless deckles, moving over suitable rolls, leave the wire, while the latter passes between large couch-rolls which cause the paper to leave it and to pass out to the second part of the machine. The second part of a paper-machine, called the press part, consists essentially of three pairs of rolls called press-rolls. The soft wet paper, from the first part of the cylinder or of the Fourdrinier machine, is transferred to a woolen felt and passes with it between each pair of press-rolls, each in turn serving to press more and more water out of the paper, compacting it together and making it comparatively strong and dry. The third part consists of a long series of hollow iron cylinders filled with steam and called the driers. This part is usually covered with a hood having suitable pipes for withdrawing the clouds of steam that rise from the drying paper. The web of paper passes in turn round all the steam-heated driers and is completely freed from its moisture, reaching the end of the third part as finished plain or uncalendered paper. In the fourth part the web of paper is passed over and around calender rolls, is given its final surfacing, and is wound on the reel. When full, the reel is unwound and the paper passed through the slitting-machine and cut to commercial sizes and rewound in rolls ready for shipment.