PRINTING PRESS, is a well-known machine for printing books, which, at an early period of the art, was brought to a considerable degree of perfection. Although the name of the inventor of the printing press has not been hand& d down to us, yet it is known to have received great improve ments from William Janson Blacw, who had been an as sistant and instrument-maker to Tycho Brache, who esta blished a priming-office at Amsterriam, where he printed several hooks of maps, from the observations of that celebrat ed astronomer. Till within the last fifty years, the common printing press remained in its original state; hut since that time the progress of improvement has been extremely ra pid, and many of the most material additions and changes have been made upon it. The introduction of printing machinery, too, has formed a new era in this art, and it is highly probable that, in very large establishments, the use of the ordinary printing press will be entirely superseded by that great invention. In giving an account of these im provements, we shall begin with the Common Printing Press.
A perspective representation of this press is given in Plate CCCCLXVIII. Fig. 1. The body of the press con sists of two cheeks or strong vertical posts A, A, bound to gether by four horizontal bars. The first of these bars B is called the cap, and merely keeps the parts at a proper distance. The second cross bar C, called the head is fitted by tenons at the ends into mortices between the checks; and the bar admits of a small motion or play, in conse quence of the mortices being filled up with pieces of paste board or soft wood. The head C is suspended from the cap B by two strong screw bolts, a a, and in the centre of it is fixed, by two short bolts, a brass nut, containing a fe male screw or worn), for receiving the upper end of the great vertical spindle or screw, by which the pressure is produced. The third bat, D, called the shelf, or till, is in tended to guide and keep steady a part called the hose, which contains the spindle and the screw. The next cross bar E, called the winter, is placed between the checks, in order to support the carriage; and it sustains the ellbrt of the press below, in the same manner as the head does above. The spindle, or screw,liF is a strong vertical bar of iron, terminated at the lower end with steel. Its upper end is formed into a small screw, which works in the small screw in the brass nut of the head; and in the eye of th( spindle. a little below its upper end, is fixed crooked bar or handle II, by which the press is wrongly.
Beneath the lower end of the spindle is placed the pla ten GG, or the body which gives the pressure to the paper. It is suspended from the point of the spindle by the hose, a square frame or block of wood, shown at K, which is guided by passing through the shelves. The lower end of the spindle passes through the hose, and rests by its point in the plug fixed in a brass pan, supplied with oil, which is again fixed to an iron plate let into the top of the platen. When the pressman, therefore, pulls the handle H, he turns the spindle, the round end of which moves in its screw box, and, by descending, brings down the platen, which thus presses upon the paper, lying above the types.
The platen is suspended from the spindle, and rises up again with it, by means of a garter, or fillet of iron, screwed to the hose, and entering into a groove round the upper end of the spindle, to prevent the hose falling down upon the spindle. The platen is hung truly level by four threads
passing from its four corners to the four corners of the low er part of the hose.
The next important part of the printing press is the carriage LL, the object of which is to bear the types, and carry them below the platen. The carriage is supported on a horizontal wooden frame, the fore part of which is sustained by the forestay in, while the back part rests on the winter. Beneath the plank of the carriage cramp irons, or short pieces or iron and steel are nailed, which slide upon two long iron bars or ribs, fixed upon the upper part of the horizontal wooden frame. In order to run the carriage in and out upon the wooden frame, there is placed beneath the carriage the spit, or a small spindle, having a double wheel on the middle of it, round which leather belts are fastened, the opposite' ends of the belt being nailed to each end of the plank of the carriage. On one of the ends of the spit is fixed the winch or handle n, by turning which the pressman can run the carriage in and out below the platen, at his pleasure. The carriage con sists of a strong wooden plank, on which is fixed a square wooden frame, forming the cell, in which a polished stone is placed to sustain the form or frame of types. Stay-belts of leather are fixed to this cell by one end, and by the other to the cheeks of the press, so as to prevent the carriage from running out too far, when drawn from under the pla ten. On the outer end of the plank is fixed the gallows 141 M, which sustains the tympans, when they are turned up to receive a new sheet of paper. These tympans, shown at N, N, are light square frames covered with parchment. They consist of three slips of thin wood, with a head-band or top-slip of thin iron. The two tympans are so const•uct ed that the one is small enough to lie within the other, and the exterior one is fitted by hinges of iron to the cell. Two or three folds of blankets are placed between the two tym pans, to equalize the pressure of the platen upon the sur face of the types. A square frame of very thin iron P, called the frisket, is fastened by hinges to the head-band of the exterior tympan. It is made to fall down on the tympan, to inclose the sheet of paper between them ; and the frisket is covered with a sheet of paper or parchment, which is cut out so that the sheet, when placed between the tym pan and frisket, and folded down together on the form of types, may receive the ink from the surface of the types, while the frisket-sheet preserves the margin from being soiled. When the tympan and frisket are thus folded down, they lay flat on the form of types. The carriage containing them is then run beneath the platen, so that when the handle H is pulled, the platen presses upon one-half of the form of types; the carriage is then run further in beneath the platen, so that a second pull of the handle causes the platen to press upon the other half of the form of types. In4his way the impression of the types is made upon the paper by two separate pulls. By turning the winch II, the carriage is withdrawn from beneath the platen, and the tympan, on being lifted up round its hinges, rests obliquely against the gallows. The frisket is then lifted up on its hinges, and supported by a slip of wood descending from the ceiling, till the printed sheet is taken out and a clean one put in.