As the operations of printing are now so common in every civilized country, it would be a waste of time to de scribe them here. We shall, therefore, proceed to de scribe the various improvements which have been succes sively made upon the printing press.
The ?lpollo Press.
In consequence of the impression being taken by two successive pulls with the ordinary press, a part of the middle of each sheet received two separate pressures; and the effect of this was, to diminish the uniformity of the impression on the paper. Besides this defect, a great deal of time was lost in two separate pulls, so that it be came highly desirable to have a press, the platen of which was sufficiently large to print a whole sheet at one pull. The first press of this kind, with which we are acquainted, was the Apollo press, which was brought from France many years ago. In this press, the platen was made of iron instead of wood, and was large enough to print the whole sheet. The lower surface of the platen, which was formed of brass, was ground truly flat, and it was made sufficiently strong not to bend, or yield at the points most distant from the centre of pressure. The spindle was joined by connecting rods, with a long lever placed at the side of the press, which was wrought by the pressman with both hands in a vertical plane, like the handle of a pump. These presses were used in printing newspapers, but, from the great fatigue of working them, they soon fell into disuse.
Prossen's Printing Press.
• This printing press, for which ,a patent was taken, is described in the eighth volume of the Repertory of .arts, p. 368. The improvement on which the patent princi pally rested, consisted in placing a spring between the cap and head, to resist the upward pressure, and another below the winter, to resist the downward pressure.
Roworth's Printing Press.
The first real improvement on the printing press was made by Mr. Roworth, a printer, in London. The spindle, in place of being furnished with a screw, is entirely plain, and has its upper extremity turned into a smooth cylinder, which works through a socket fitted into the head of the press. On the upper end of the spindle, immediately beneath the head, a short cross 'arm of hardened steel is fixed, the polished surface of which acts against a circular inclined plane of hardened steel, which, being actually a part of a screw, causes the spindle to descend. The
inclined plane, however, has different inclinations at dif ferent parts. At first, the inclination is great ; so that,•at the beginning of the pull, the descent of the platen is rapid, but when the platen has approached near to the tympan, and, consequently, when the force is really re quired, the inclination of the plane is very slight, so as to produce a great mechanical effect.
'The Stanhope Press.
One of the greatest improvements upon the printing press was made by the late Earl of Stanhope, a nobleman distinguished by his ingenuity and his mechanical know ledge. This press, which is described minutely in Stower's Printers' Grammar, is represented in perspective in Fig. 2, and in section in Fig. 3, where AA is the body of the press, or a massive cast iron frame, formed in one piece, which rests upon a wooden cross BBC, to which it is firmly screwed down. Two horizontal rails Dll, are screwed at bb to two projecting pieces, cast all in one with the body of the press, in order to sustain the carriage when the pull is made. The ribs of the carriage slide in grooves formed along the upper surfaces of these rails, and it is moved by the handle m, with a spit and leather belts, very similar to those of the common press.
In the upper part d of the body of the press a brass nut, or female screw, is fixed, in which the upper end of the spindle works. The chief improvement in Lord Stan hope's press, consists in his method of giving the descend ing motion to the screw. The handle 11 by which the press is worked, is firmly fixed into the lower end of the vertical bar M, the lower part of which moves in a bole in the main frame, while the upper end of it passes through a collar in the projecting piece c. After passing through this collar, the end of the bar M joins a short lever N, which is again connected by the link 0 with another short lever P, fixed upon the upper end of the screw.