PRINTING PRESSES. 





V|K>ilo 



As tho operations of printing are now so common 

 in every civilized country, it v. mild h- a waste of time 

 to de-KTih- them here. \\> shall, therefore, pr 

 to ile-crilie the various improvements which have been 

 successively made upon the printing press.' 



The Apollo Preat. 



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 pres- 

 sures ; and the effect of this was, to diminish the uni- 

 formity of the impression on the paper. Besides this 

 defect, a great deal of time was lost in two separate 

 pulls, so that it became highly desirable to have a press, 

 the plattin of which was sufficiently large to print a 

 whole sheet at one pull. The first press of this kind 

 with wlrch we are acquainted was the Apollo press, 

 which was brought from France many years ago. In 

 this press the plattin was made of iron instead of wood, 

 and was large enough to print the whole sheet. The 

 lower surface of the plattin, 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 news- 

 papers, 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. SfiS. The improvement on which the patent prin- 

 cipally 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 pres- 

 sure. 



Rorvorlh's Printing Press. 



rth' The first real improvement upon the printing press 

 in g 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 fit- 

 ted 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 sur- 

 face 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 different parts. 

 At first the inclination is great ; so that, at the begin- 

 ning of the pull, the descent of the plattin is rapid, 

 but when the plattin has approached near to the tym- 

 pan, and, consequently, when the force is really requir- 

 ed, the inclination of the plane is very slight, so as to 

 produce a great mechanical effect. 



The Stanhope Press. 



be Stan- ^ ne ^ l ^ e greatest improvements upon the print- 

 >pe press, ing press was made by the late Earl of Stanhope, a 

 nobleman distinguished by his ingenuity and his me- 

 chanical knowledge. This press, which is described 

 minutely in Stow.er's Printer's Grammar, is represented 



ling 



in perspective in Fig. 2, and in section in Fig. S, where 

 A A is the body of the press, or a massive out iron 

 frame, formed in one piece, which rests upon a wooden 

 cross BBC, to which it is firmlj screwed down. Two 

 horizontal rails 1)1), are screwed at b b to two project- 

 ing pieces, cast all in one with the body of the press, 

 in order to sustain the carriage when the pull is mide. 

 The ribs of the carriage slide in grooves formed along 

 the upper surfaces of these rail*, 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 

 Stanhope's press, consists in his method of giving the 

 descending motion to the screw. The handle H 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 hole in the main frame, while the 

 upper end of it passes through a collar in the project- 

 ing piece c. After passing through this collar, the end 

 of the bar AI joins a short lever N, which is again con- 

 nected by the link O with another short lever P, fixed 

 upon the upper end of the screw. 



When the pressman pulls the handle H, he turns 

 round the spindle M, and by its connexion with the rod 

 O, &c. the great lever turns with it, and causes the plat- 

 tin to descend and produce the requisite pressure. The 

 power of the lever H is, however, transmitted to the 

 screw, so as to be proportioned to the effect which is 

 wanted at the different parts of the pull. At the be- 

 ginning of the pull, for example, when motion only is 

 wanted, the handle H lies in a direction parallel to the 

 frame across the press, and the short lever N, which is 

 nearly perpendicular to it, is also nearly perpendicular 

 to the connecting rod O ; but the lever P of the screw 

 makes a considerable angle with O, and then it acts by 

 a spindle radius to turn the screw. At the commence- 

 ment, therefore, of the pull at H, the lever N acts 

 with its full length upon a shorter length of lever on 

 P, so that the screw will be turned more rapidly than 

 if the link O were attached to it. On continuing the 

 pull, however, the situation of the levers changes, the 

 length of P continually increasing in its acting length 

 from its coming nearer to a perpendicular to O, and 

 the acting length of N diminishing, because, by the 

 obliquity of the lever, the link O approaches the cen- 

 tre. The handle H likewise comes into a mere favour, 

 able situation for the pull, as the pressman finally pulls 

 in a direction nearly at right angles to its length. In 

 this way the plattin is at first brought quickly down 

 upon the paper, where motion only is wanted ; but as 

 the levers are gradually coming into the most favour- 

 able position for exerting the greatest force, this maxi- 

 mum pressure is produced just at the moment when it 

 is wanted, namely, when the plattin touches the paper 

 to be printed. The range of the handle is limited by 

 a stop, which is moveable to a small extent, in order to 

 vary the pressure for different kinds of work. The 

 form of types, in place of resting upon a stone, lie on a 

 cast iron block, which has its upper surface ground 

 exactly Hat, and placed perfectly horizontal. 



In the Stanhope press the plattin is so large as to 

 print a whole sheet at one pull. 



In some of these presses, a variation of power is ob- 

 tained by a screw adjustment at the end of the link O, 

 by which it can be shortened. This is effected by fit- 

 ting the centre pin, which unites it to the lever P in a 

 bearing-piece, which slides in a groove formed on the 



Printing 

 I'mcct-. 



