THE CYLINDER MACHINE FOR MAKING PAPER
There is another type of paper-making machine which is used for coarse papers, pasteboard, etc. This is known as a cylinder machine. The wire gauze is formed into a cylinder which revolves in the liquid pulp. A slight suction is maintained in the cylinder which causes the water to flow in through the gauze; leaving the fiber drained on the surface. The cylinder revolves, carrying the drained pulp on its surface until it encounters a felt roll that picks off the web and carries it to the pressing and drying rolls. One disadvantage of this type of machine is that the cylinder in dragging the drained pulp through the water causes the fibers to be combed in a direction parallel to the run of the paper web, so that the paper, while strong in the direction of its length, is comparatively weak in the transverse direction. This is corrected to a certain degree by the use of “riffles” or devices that produce eddies which disturb the even flow of the pulp.
In the making of pasteboard, a number of cylinders contribute their webs to form a single sheet of several plies.