A machine of a very dif ferent construction from the ordinary form is shown in Fig. 1059. The pulp, after passing through the strainer A, enters the vat B, in the centre of which, revolves a large drum or cylinder C. This cylinder is covered with fine wire-cloth, and on it the paper is made. As it re volves, the fibres attach themselves to the wire, and the water passes through the meshes, the latter being assisted by means of a pump. The sheet of paper thus formed is taken on to the endless felt on the conch-roll D, and travels along with it to the large drying cylinder E, heated by steam. It leaves the felt at F, and is then taken on to the cylinder, after travelling round which, it is suffi ciently dried, and is then wound off as at G. The felt, on its return journey, passes through the washer H. where it is cleaned, and freed from adhering particles, by the scraper I. It is squeezed free from excess of water by the rolls K. Paper made on such a machine is weaker than that made in the ordinary way, because it has not been found possible to give a shaking motion to the cylinder. and thus the fibres are not woven or intertwined.
A modification of this machine is used for making mill-boards, the difference being that it has no drying-cylinder. The felt carrying the paper passes between a pair of press-rolls, which squeeze out the water. The sheet of paper is then allowed to wind round the top press-roll until of the required thickness. When this happens, it is cut off the roll by a knife. The thick sheets so produced are dried, either in the open air, or in a room heated for the purpose.
Glazing.—For many purposes, the paper as finished on the machine, does not possess a sufficiently high surface. This may be increased in several ways. One method, called " web glazing," is to pass the paper between a number of rolls, alternately of polished iron and very highly-com pressed paper. The construction of such a calender will be understood by reference to Figs. 1060 (end elevation) and 1061 (front elevation). The reel of paper, as taken from the machine, is shown at A (Fig. 1060), its course over the rolls being indicated by arrows. After passing over the bottom roll, it is wound off on a wooden or hollow-iron cylinder B (Fig. 1060), driven by the toothed-wheel shown by the dotted line C, on the same shaft as the wheel D, which is driven by E, keyed upon the bottom roll. The whole machinery is driven by the large toothed-wheel F (Figs. 1060-1), which is itself driven by the small wheel G (Fig. 1060) on the main shaft H. The paper rolls are marked P, and the iron rolls I. It will be seen that there are two paper rolls in the middle, for the purpose of, as it were, reversing the paper, and so making both sides alike. Pressure is applied to the rolls by means of the screws, and by the weight L (Fig. 1060) acting on the compound lever M. The brake, which consists of a strap of leather pressing, by means of the weight and lever N, on the oircumference of the wheel 0, connected by toothed-wheels with the cylinder on which the paper is wound, is used for the purpose of preventing the paper from leaving the wheel too rapidly. But for this appliance, the
paper would be apt to crease. The paper rolls have an inner core of iron, the paper only extending to a depth of about 5 in. The iron rolls are hollow, and are connected with steam-pipes, by which they can be heated.
Another method, known as " friction-glazing," employed for giving a very high finish to paper, is to pass it between a large paper roll and a smaller iron one, the latter re volving at a much greater speed than the former. By this means, a very bright surface can be obtained. It is some times assisted by rubbing a small quantity of bees'-wax on the small iron roll. Plate-glazing, a method that is adopted for hand-made and the better qualities of paper, consists in applying heavy pressure to sheets placed between polished plates of copper or zinc. The metallic plates and the sheets of paper are made into bundles, and the whole is passed between two strong rollers, heavy pressure being communi cated to them by means of screws or levers and weights applied to the ends of the top roller.
By passing paper between rolls on which devices have been cut or turned, the " repped " and other similar papers are produced.
Cutting.—Except for special purposes, paper is usually sent from the mill in the form of sheets. The form of cutter generally used is shown in Fig. 1062. The paper from the webs A is drawn forward by the rolls B; it is then ripped into widths of a convenient size by means of two circular knives, the upper one of which is shown at C. It again passes between a pair of rollers, after leaving which, it meets a knife D fastened to-the revolving drum E, and pressing against a fixed knife not shown. The cut sheets then fall upon the endless travelling felt F. The action of the knives will be understood by reference to Fig.1063. The edges of the two knives are shown at A and B. The knife B has a slot, in which the bolt 0 slides, and it is kept in position by means of a spring. This spring causes the knife to slide back slightly as it comes against the fixed knife A. The position of the paper is shown by the dotted line C. The knife B is set on the drum not quite horizontally, so that one end meets the stationary knife a little before the other, thus acting in every respect like a pair of scissors. Fig. 1064 shows a pair of ripping-knives. The upper one A is kept in position against the lower one B by means of the spring C. The cutting surfaces are slightly hollowed out, so as to have a sharper edge. The paper is shown by the dotted line D. By altering the relative speeds of the drum E and the rolls B, by means of the expanding-pulley G, sheets of any de sired size can he cut. The cutting - knives are sometimes placed inclined to the draw ing-in rolls B, so that the sheet, instead of being cut into a rect angle, is cut into a rhomboid. Such paper is need chiefly for the manufacture of en velopes, this shape occasioning a smaller loss when the enve lopes are cut out.