Page:EB1911 - Volume 22.djvu/370

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
356
PRINTING

always rotates in the same direction, and twice for each copy given, once for the actual impression, and again to allow of the return of the forme-carriage in its reciprocating action. This also allows time for the feeding in of the next sheet to be printed. Among other advantages claimed for this press one is that the movement which governs the action of the type bed in reversing is so arranged that the strain which sometimes occurs in other reciprocating machines is considerably reduced; another is that the registering or correct backing of the pages on the second side in printing is uncommonly good; but this depends much upon the layer-on. In many of the old kinds of two-revolution machines, owing to the cylinder being geared separately from the type bed, it was apt to be occasionally thrown out, but in the Miehle, for instance, it is only out of gear in reversing, and in gear while printing. Great strength is imparted to the frame, and the type bed is particularly rigid. These points, together with a truly turned and polished cylinder, with carefully planned means of adjustment, much simplify the preparation of making-ready of any kind of type-forme or blocks for printing, which is carried out much in the same way as on the ordinary single cylinder, but in a more convenient manner. Many of these machines are made to print four double crowns, 60 × 40 in., or even larger.

EB1911 Printing - Payne & Sons' Two-colour Single Cylinder Machine.jpg

Fig. 8.—Payne & Sons' Two-colour Single Cylinder Machine.

The two-colour machine is generally a single cylinder (fig. 8) with one feed only, and the bed motion reciprocating. The two Two-Colour Machines. colours are printed each at one revolution from the two type-formes as they pass under the cylinder, which rotates twice in its travel. A double inking apparatus is of course necessary, and the inking arrangements are placed at the two extreme ends of the machine. In comparison with the ordinary single cylinder the two-colour machine is built with a longer frame, as is necessary to allow the two type-formes to pass under the cylinder, both in its travel forward and on its return. This cylinder on its return is stationary, in fact it might be called a double or rather an alternative stop-cylinder machine, with the inking facilities arranged somewhat on the same plan as on either a two-feeder or a perfecting machine. These two-colour presses are intended only for long runs, short runs may be worked to advantage separately on the ordinary single-colour machine. Generally, with the exception just mentioned, the machine is much the same as the ordinary stop or Wharfedale.

Before leaving the subject of printing with the reciprocating bed motion, it may be mentioned that although in all modern machines of that kind the printed sheet is self-delivered, the imprinted paper has generally been fed in by hand, and for some classes of work this is still done. But many automatic feeders have been invented from time to time, which for the many purposes for which they are suitable must be reckoned part of a modern printing establishment.

As distinct from flat bed printing with a reciprocating motion, printing on rotary principles is a most interesting study, and it is Rotary Machines. this department of printing mechanics which has developed so very much in recent years. It seems almost as though this branch had reached its limit, and as though any further developments can only be a question of duplication of the existing facilities so as to print from a greater number of cylinders than, say, an octuple machine. This would be merely a matter of building a higher machine so as to take a larger number of reels arranged in decks. As the name implies, these presses are so constructed that both printing surfaces and paper continuously rotate, the web of paper travelling in and out, in a serpentine manner, between various cylinders of two characters—one (the type cylinders) carrying the surface to be impressed, usually curved stereotype plates, and the other (the impression cylinders) giving the desired impression. Such a press, if driven by electric power, is set in motion by merely pushing a button or small switch, a bell first giving warning of the press being about to move. The number of duplicate sets of stereotype plates to be worked from by these presses is determined by the size and number of the pages to be printed, and this in turn is regulated by the capacity of the machine.

As already explained, the forerunners of the rotary presses of the present day were the type-revolving printing-machines, and, whilst they were still being used, experiments were being made to cast curved stereotype plates which would facilitate and simplify the work of producing newspapers. This was successfully accomplished by the use of flexible paper-matrices, from which metal plates could be cast in shaped moulds to any desired curve. These plates were then fixed on the beds of the Hoe type revolving machine, which were adapted to receive them instead of the movable type-formes previously used. This new method enabled the printers to duplicate the type pages and to run several machines at the same time, thus producing copies with far greater rapidity. In some large offices as many as five machines were in constant use. About this period the English stamp duty on printed matter was repealed, and this materially aided the development of the newspaper press.

Subsequently the proprietors of The Times made various experiments with a view to making a rotary perfecting press, and as a result started the first one about 1868. It was somewhat similar in design to the Bullock press, so far as the printing apparatus was concerned, except that the cylinders were all of one size and placed one above the other. The sheets were severed after printing, brought up by tapes, and carried down to a sheet flyer, which moved backwards and forwards, and the sheets were alternately “flown” into the hands of two boys seated opposite each other on either side of the flyers. Hippolyte Marinoni (1823-1904), of Paris, also devised a machine on a somewhat similar principle, making the impression and type cylinders of one size and placing them one over the other. About 1870 an English rotary machine called the “Victory” was invented by Messrs Duncan & Wilson. It printed from the web, and had a folder attached. An improved form of this machine is still in use. This machine had separate fly-boards for the delivery of the sheets. In 1871 Messrs Hoe & Co. again turned their attention to the construction of a rotary perfecting press to print from the reel or continuous web of paper, and from stereotype plates fastened to the cylinder.

The rotary presses in use at the present time are indeed wonderful specimens of mechanical ingenuity, all the various operations of damping (when necessary), feeding, printing (both sides), cutting, folding, pasting, wrapping (when required) and counting being purely automatic. These machines are of various kinds, and are specially made to order so as to cope with the particular class of work in view. They may be built on the “deck” principle of two, three, four, or even more reels of paper, and either in single width (two pages wide), or double width (four pages wide). Single and two-reel machines are generally constructed on the “straight line” principle, i.e. arranged with the paper at one end of the machine,