This invention has raised the quality of printing generally. In almost any old book will be perceived groups of words very dark, and other groups very light; these are technically called "monks and friars," which have been reformed altogether. The principal object in a newspaper machine is to obtain a great number of impressions from the same form, or one side of the sheet, and not from two forms, or both sides of the sheet, as in books.
In the Times machine, which was constructed on the joint invention of Messrs. Applegath and Cowper, the form passes under four printing cylinders, which are fed with sheets of paper by four lads, and, after the sheets are printed", they pass into the hands of four other lads; by this contrivance 4000 sheets per hour are printed on one side.
The annexed engraving affords a general or perspective view of one of Messrs. Cowper and Applegath's double machines, constructed on the principle of the diagram on page 346. A boy is represented as standing upon a platform, with a pile of paper A on a table on his left hand, from which he has taken a sheet of paper B, and is applying it to the machine. It first goes under the cylinder F, and is there printed on one side, it is then conducted over the intermediate cylinders H I, on to the cylinder G, passing round this, and underneath; the sheet of paper is thereby turned with its opposite side against the type, and receives the second or finishing impression, and is then conducted to the top of the pile of printed sheets, where a boy at Z is shown sitting on a stool, and receiving the sheets as they are presented, and laying them square on the pile before him. The separate forms of types designed to print both sides of the sheet, are placed at the requisite distance asunder, upon one long bed mounted on a carriage, which is moved backwards and forwards upon a railway, constructed to guide the carriage, with great accuracy, into contact with the cylinders F and G, to produce the impression.
The reciprocating motion of the carriage is effected by a pinion fixed upon the end of a vertical spindle, taking into the teeth of an endless rack, which is connected by a system of levers with the type carriage, in such a manner, that when the pinion is turned round, it engages, at alternate periods, in the teeth formed on the opposite sides of the rack, and consequently on the opposite circumference of the pinion; thereby a continuous motion of the pinion communicates a reciprocating motion to the rack and carriage. The vertical spindle is turned by a couple of bevelled wheels, from the pinion P, which receives its motion by an intermediate wheel Q from the toothed wheel upon the end of the main cylinder G. An inking apparatus is situated at each end of the machine. At N one of these is brought into view; it consists of a cylindrical metal roller, which has a slow rotatory motion, communicated to it by a eatgut band passing round a small pulley upon the end of the axis of the main.
cylinder G. The roller at N is adapted to carry down a thin film of ink upon its circumference, by turning in contact with a mass of ink disposed upon a horizontal plate of metal, the edge of which plate is ground straight, and the distance between the two surfaces is adjusted by screws. Upon an axis turning at P, is mounted a composition roller, connected by cranked levers with a small eccentric circle fixed upon the end of the axis of the cylinder g, causing it to move round the axis P, and remain for a short period in contact with the face of the ink-roller N, thereby receiving a portion of ink upon its surface: it then descends and rests with its whole weight upon the surface of the table, which is affixed to the end of the type carriage, the reciprocating motion of which causes the ink-table to receive ink upon its surface from the elastic roller before mentioned. In this situation, when the type-carriage returns, the surface of the table is made to pass under three elastic rollers; these rollers are mounted upon pivots in a frame, in such manner that they have liberty to move somewhat up and down, in order that the rollers themselves may bear severally upon the surface of the table; and to equalize the ink perfectly over the table, an end motion is given to the rollers by means of inclined planes, against which they come into contact; and by the further motion of the type-carriage, the ink-table is caused to pass under four other small elastic rollers, which in like manner bear with their weight upon the surface of the table, and thereby take up the ink upon their circumferences, which they impart to the types as the form travels backwards and forwards under them, thus touching every type eight times.
Whilst this operation of inking the types is going on at one end of the machine, the printing process is performed at the other end on one of the sides of the sheet from the types last inked, and vice vers â .
The improvements in printing machinery, patented by Mr. Wayte, a printer, of Mount Pleasant, London, in 1829, deserve notice on account of their originality and simplicity. In his specification is described a printing machine, or press, having two tables with a form on each, the one to press the first side of the sheet, and the other to perfect it, or print the second side. These two tables are placed on a vibrating frame, which is actuated by a crank, and brings them alternately under a pendent-platten, which is brought down upon them through the instrumentality of a crank, to give the impression. The frame which supports the form-tables consists of a parallelogram jointed at the angles, and therefore the horizontal position of the forms is preserved, both when they are elevated to the platten to receive the impression, and depressed to the rollers to receive a supply of ink. There is an inking apparatus for each form, placed at opposite ends of the machine: it consists of a long trough, and a ductor and supply-roller, of the usual description; with distributing-rollers, which traverse the forms, and are kept in their places by guides, with long vertical slits to receive their axes.