After the utility of cylindrical printing had been thus proved, it was thought highly desirable that the principle should he applied to printing fine book-work, where accurate register is indispensable. This was, to a certain extent. attained by using two large cylinders, the sheet of paper being conveyed from the bottom of the first cylinder (where it had received the first impression) by means of tapes, leading in a diagonal direction to the top of the second cylinder, round which the sheet was carried till the second side was printed. The first machine of this description was erected at Mi. Bens ley's office, where it continued at work for some years, till more modern machines superseded it.
In the course of 1818 Messrs. Applegath and Cowper took put a patent for improve ments in cylindrical priuting-machinery. The chief improvements were the application of two drums placed between the cylinders to insure accuracy in the register, over and under which the sheet was conveyed in its progress from one cylinder to the other. instead of being carried, as in Keinig's machine, in a straight line from the one cylinder to the other; and the mode of distributing the ink upon tables instead of rollers—two principles which have secured to machines of this construction a decided preference for fine work. Machines of this construction were made by Applegath and Cowper for the principal printing establishments in London, Paris, Edinburgh, and many other cities: and it is nearly upon the model of their machines that other manufacturers now construct their steam-presses for the execution of ordinary book-work. Printing-machines may he divided into two distinct classes—those for printing book-work, in which register is required, and those for printing newspapers, in which register is not sought for, and speed is of first consequence.
Applegath and Cowper's book-machine, as just mentioned, remains the best of its kind. The machine, moved by steam-power, from which the annexed engraving is taken, is. one of this description. It is about 15 ft. long by 5 broad, and consists of a very strong cast-iron frame-work, secured together by two ends and several cross-bars. To this frame all parts of the machine are fixed. In external figure, as seen in the cut, it is a huge apparatus of im posing appearance. On approaching it when at work, we perceive two cyl inders, as large as hogsheads, revolving on upright supports; two smaller cylin ders or drums revolving above them; and beneath, within the frame-work, a table, on which lie the types at both ends, going constantly backward and forward. A belt from a steam-engine, acting upon a shaft in the frame, gives motion to the whole apparatus. It will further be observed that a boy, marked a in the cut, is standing on the top of some steps feeding in sheets of paper, each of which, on being delivered, is swept round the first cylinder b (being held on by tapes), gets its impression below from the types, is carried over and betwixt the drums above, and then brought round on the second cylinder e; now it gets its second side printed, and issuing into the space between the cylinders, is seized by the boy d, who laya it on a table completely printed. The whole operation is
accompanied with a loud noise, from the revolving of the cylinders, the working of the notched wheels, and the driving of the table to and fro by a rack beneath, but without any strain on the mechanism, or risk of injury to the attendants. On minutely examining the parts, we observe that at each end there is an_apparatus of rollers taking ink from a doctor or reservoir of that material, and placing it upon a portion of the moving table beneath; here other rollers distribute it, while others take It off and roll it upon the pages of types, ready for each impression.
The two printing-cylinders are nearly nine feet in circumference each, and are placed about two feet apart. They are accurately turned, so that the surfaces of the type carriages and the cylinders may be perfectly parallel. The axis of each cylinder works in brass bearings in the upright frame-work, where, by means of screws, the degree of pressure with which the cylinders are allowed to rest upon the types may be regulated to any degree of nicety.
The cylinders have a continuous rotary motion toward each other, given by two large toothed wheels, whilst the type-carriages move backward and forward under them. The movements are so contrived that the type-carriages shall have gone and returned to the same point during the period that the cylinders have made one entire revolution ; conse quently, each successive impression is taken from the types by the same part of each cylinder. The two drums placed between the cylinders are for the purpose of causing the sheet of paper to pass smoothly and accurately from one printing cylinder to the other. To preserve the sheet in its proper place on the cylinders, and carry it forward through the different parts of its journey from the hand of the one boy to that of the other, there is an extensive apparatus of tapes, some of which are observable in the cut. These tapes are half an inch broad, and are formed into a series of endless hands, arranged at certain distances apart, so as to fall into the interstices and margins of the forms, and therefore escape being crushed between the types and the cylinders. The machine may be stopped at any instant by turning the handle of a lever. Such is 1113 form of the machine that has printed the present work.