PRINTING- MACHINE 



657 



roller B, which may be called the commencement of the one series of endless tapes. 

 The other series may be supposed to commence at the roller h ; it hns an equal 

 number of tapes, and corresponds with the former in being placed upon the cylinders 

 so that the sheets of paper may be held securely between them. This second snries 

 descends from the roller h, Jig. 1687, to the entering drum E, where it meets and 

 coincides with the first series in such a way that both sets of tapes proceed together 

 under the printing cylinder F, over H, under i, and round o, until they arrive at the 

 roller i,fig. 1685, where they separate, after having continued in contact, except at the 



places where the sheets of paper are held between them. The tapes descend from 

 the roller i, to a roller at Jc, and, after passing in contact with rollers at./, m, n, they 

 finally arrive at the roller h, where they were supposed to commence. Hence two 

 series of tapes act invariably in contact, without the least mutual interference. 



The various cylinders and drums revolve very truly by means of a system of 

 toothed wheels and pinions mounted at their ends. Two horizontal forms of types aro 

 laid at a certain distance apart upon the long carriage M, adjoining to each of which 

 there is a flat metallic plate, or inking-table, in the same plane. The common 

 carriage, bearing its two forms of type and two inking-tables, is moved backwards 

 and forwards, from one end of the printing machine to the other, upon rollers 

 attached to the frame-work, and in its traverse brings the types into contact with the 

 sheet of paper clasped by the tapes round the surfaces of the printing cylinders. This 

 alternate movement of the carriage is produced by a pinion working alternately into 

 the opposite sides of a rack under the table. The pinion is driven by the bevel 

 wheels K. 



The mechanism for supplying the ink, and distributing it over the forms, is one of 

 the most ingenious and valuable inventions belonging to this incomparable machine, 

 and is so nicely adjusted that a single grain of the pigment may suffice for printing 

 one side of a sheet. Two similar sets of inking apparatus are provided ; one at each 

 end of the machine, adapted to ink its own form of type. The metal roller L, called 

 the ductor roller, as it draws out the supply of ink, has a slow rotatory motion com- 

 municated to it by a catgut cord, which passes round a small pulley upon the end 

 of the shaft of the printing cylinder G. A horizontal plate of metal, with a straight- 

 ground edge, is adjusted by set screws, so as to stand nearly in contact with the 

 ductor roller. This plate has an upright ledge behind, converting it into a sort 

 of trough or magazine, ready to impart a coating of ink to the roller, as it 

 revolves over the table. Another roller, covered with elastic composition (see supra), 

 called the vibrating roller, is made to travel between the ductor roller and the 

 inking-table ; the vibrating roller, as it rises, touches the ductor roller for an instant, 

 abstracts a film of ink from it, and then descends to transfer it to the table. There 

 are three or four small rollers of distribution, placed somewhat diagonally across the 

 table at M (included only two inches from a parallel to the end of the frame), furnished 

 with long slender axles, resting in vertical slots, whereby they aro left at liberty to 

 revolve and to traverse at the same time ; by which compound movement they are 

 enabled to efface all inequality in the surface of the varnish, or to effect a perfect 



VOL. HI. U U 



