Page:The American Cyclopædia (1879) Volume XIII.djvu/876

 852 PRINTING uel Rust. In this the frame was made in sec- tions, the principal parts of wrought iron, and was comparatively light; the power was ap- FIG. 3. Lord Stanhope's Press. plied, as in Stanhope's press, by a toggle-joint and lever. The essential parts of a press, as shown in fig. 4, are as follows: a, the iron framework, closed at top and bottom to resist the force of the levers ; &, the bed, on which the types are placed ; c, one of the two rails or grooved channels on which the bed slides as it is moved forward to receive the impression of the levers ; d, the rounce or crank, attached to a pulley which moves the bed to and fro ; e, the platen, or pressing surface, which covers the bed before impression is given ; /, the bar, which gives the impression by straightening the levers and depressing the platen; ^, the spiral spring, which gives a quick return move- ment to the platen after impression; A, the tympan (sheets of muslin and paper, stretched on a frame of wood), on which the sheet to be printed is placed; t, the frisket, a mask of perforated paper stretched on a frame of thin iron, to prevent soiling of the sheet by ink ; &, the inking roller and its frame. Pre- FIG. 4. Washington Press. paratory to taking an impression, the frisket is folded down on the tympan, the tym- pan is folded down on the bed, which opera- tion places the sheet of paper on the inked types, and the bed is then moved under the platen. The ink was formerly dabbed on by two soft leather-covered balls affixed to han- dles, which one pressman kept rubbing to- gether to distribute the ink evenly, while the other worked the press ; the pressmen usually alternated in this. Rollers, made of several thicknesses of cloth, wound around a wooden cylinder and covered with soft leather, were afterward introduced; these were superseded by rollers composed of glue and molasses melted together, and cast in a mould around a wooden cylinder. It still required one person, usually a boy, to apply the ink, and another to work the press. Later a self-inking apparatus was affixed to the press. With this the pressman, in giving the pull, raises a weight, which in its descent draws the roller over the form; one man, though with a considerable increase of exertion, is thus able to do the work of two. A good pressman will work off about 2,000 impressions a day ; but he cannot well run a press large enough to work a sheet of more than eight octavo pages. Repeated attempts were made to contrive a power press capable of doing work as well and more rapidly than the hand press. The first produced in America were by Daniel Treadwell of Boston, in 1822. His machines were used in New York by the American Bible society and the American tract society; in the former they were driven by steam power, and in the latter by mules. The Adams press, invented in 1830 by Samuel Adams of Boston, and since im- proved by Isaac Adams, has in this country su- perseded all other platen presses. Its principle is virtually the same as that of the Washington hand press, only that the impression is given by raising the bed upon which the form rests against a stationary platen, instead of bringing the platen down upon the bed. The sheets are placed one at a time upon the feed board, so that the edge is caught by a set of iron fingers which pull them down upon the frisket, which slides between the inked form and the platen, and the form then rises and gives the impression. The sheets, in passing back to- ward the inking apparatus, pass over a bellows the top of which is perforated with small holes, and are lifted or rather blown upon a set of endless tapes ; from these they are taken by a light frame, which, turning upon an axle at the proper moment, whirls them over, laying them in a regular pile at the end of the press opposite to that where they were received. The inking apparatus is quite complicated. A roller slowly revolves, its lower surface im- mersed in a trough of ink, so adjusted as to take up a quantity proportioned to the depth of its immersion, which is regulated by screws. Another roller, called " doctor " (Lat. ductor, leader), touches this at every impression, and transfers a portion of ink to the first of a set of distributing rollers, revolving in contact, one of which has also an oscillating motion, and still another, called the "crab," travels back and forth over the entire length of the