(Continued from page 133) POWER PRESSPerhaps no branch of ma-chinery has made more recent progress in improvement than that which is employed by the printer; the liberal patronage of the newspaper press of our country having greatly contributed to this advancement of the mighty promoter of modern civilization. When the printing press is mentioned, the mind of every American instantly reverts to that kind of press which has created so great a revolution in typographical machinery,we shall, therefore, first direct attention to what may be called " the model press lor rapid printing," viz.) Hoe's Power-Press. In every process which may be adopted for printing, we find that there are several distinct operations to be executed : it is necessary to apply the ink to the faces of the type, which must be done in such a manner that the ink shall be spread uniformly ; the sheet of paper must be so placed as to receive the impression of the type, and that, too, with a due regard to the appearance of the margin ; the paper must be forced down upon the form of type by a pressure sufficiently powerful to enable it to receive the printed characters, but not enough to cause the type to injure it, in the last place, the paper, when printed, must be withdrawn from the form and laid upon a table. The exigency that requires a machine of such wondrous capability as the modern newspaper press is therefore soon explained. The principal item in the expense of printing is the type-setting or composing, hence it is necessary to print the whole of an impression from one form, and consequently only one machine can be used, to print at least one side of a sheet ; perhaps this is no very great defect in book-work, but for ne wspapers which must, in many cases, be all struck off in the course of two or three hours at the utmost, a rapid printing press is of the utmost importance. There is, ho we ver, a certain limit to the capability of printing machines which merely increasing the velocity of the movements would not suffice to overcome. What we allude to is the fact that the sheets of paper must be delivered, one by one, to the machine by an attendant, but this manipulation, for a large newspaper, cannot be well done at a faster rate than twenty-five per minute, or fifteen hundred per hour. This apparently insurmountable obstacle is overcome in Hoe's revolving type cylinder press, by causing the type to have a circular motion instead of the usual horizontal reciprocating motion; the same principle has also been adopted by Ap-plegath, an English manufacturer and patentee, in constructing presses for some London iournals, but with this difference, that the latter places the axis of the type cylinder in a vertical position, whereas, in those of Hoe, it is horizontal, which is certainly a preferable construction, as all who have had experience in vertical shafts rotating at a great velocity will allow. Besides, Applegath's arrangement entails other defects, as will hereafter be shown ; indeed, if we may judge by a very recent patent of that maker, he is himself of this opinion. It is not, however, our intention to enter minutely into the respective merits of these two machines, in their general principles they are manifestly similar, the main difference being in the already-mentioned arrangement. We shall, therefore, resume our subject with a description of Hoe's printing press, to which the claim of superiority must be awarded by every unprejudiced person, over its English competitor. The following is the manner in which it is arranged : The columns of type are firmly secured in position upon strong beds, which are then fastened on the circumference of the type cylinder ; around this latter are placed the drums or cylinders intended to carry the sheets of paper, and which, in number, vary from four to eight. All the drums aie supported in bearings on a substantial frame, and those for the paper are driven, through the agency of geared wheels, by the type cylinder, so that their surfaces revolve at the same velocity as the periphery of the latter. It will now be easily understood that a sheet of paper, being supplied to one of these drums, the latter will seize it as in the ordinary power-presses, and carrying the paper around, encounter in its tturse the type-form on the large drum which s likewise revolving, and the two being thus n close contact, the paper is impressed. The iheet is then released from the paper cylinder ind carried away by a series of endless tapes, which conduct it to a self-acting flyer, this atter receives the paper, and, at the proper noment, by the impulse of the machinery, olds down and places it on a board, to be re-noved at the leisure of the attendant. The lontrivance of the flyer is another material point in which Hoe's press is superior to that )f Applegath, who employs a fly-boy for ach paper cylinder, to take charge of the jrinted sheet and lay it down smoothly with She othersa duty that, as we have just explained, is performed by Hoe's press itsell, without any attendant. We have described the action of one paper lylinder, but, as a matter of course, there are several of these, and it is evident that they all will have a similar action during the revolu-Sion of the type drum, so that from 4 to 8 copies,' according to the number of cylinders, will be printed on one side during a revolu-iion of the form. Such is a brief description Df this part of the machinery, but it is needless to mention that there is also a variety of details which are necessary to insure the correct working of the cylinders. For although the paper drums revolve constantly, and therefore make several revolutions during one revolution of the type, yet they must not be allowed to grasp the paper until the form approaches them, lor it must be observed that the beds on which the type are placed occupy only a portion of the cylinder's periphery. Again, in the reeding process, Applegath's press is inferior to Hoe's, the vertical arrangement involving the necessity of expensive feeding machinery for the attendant standing at a sloping desk in the usual manner, pushes tor-ward the paper, sheet by sheet, towards the fingers of the machine, which seize upon the paper ; and with horizontal cylinders this is done by delivering the paper to the drums, except when there are eight cylinders in which case the feeding apparatus is rather more complex, in order that the pressmen may not be in each other's way. Contrast this arrangement with the vertical mode ot construction, and you find that, in the latter, the paper must be first drawn down in a vertical direction between tapes, until its edges correspond with the position of the form of type on the printing cylinder, when arrived at this position, its vertical motion is stopped by a self-acting feeding apparatus, and it begins to move horizontally, and is thus earried towards the type. The difficulty of preventing the type from being displaced by the rapidity with which the iorm is whirled round must occur to every one, this apparent defect is surmounted in Hoe's improved power-press by an ingenious device. The ordinary chase is not at all used, but the type is placed on stoui iron beds, which are turned so as to iorm segments of the type cylinder with broad slots cut in them ; in these latter slide pieces ot brass, so that when the columns of type are placed on the bed they are firmly held by the column rules, which are of steel and so made as to act like wedges, the lower part also fitting in the slots between the brass pieces, so that when the whole is tightened up by set screws it is impossible for the form to shift. Not the least original pari of this machine is the arrangement for inking the ink fountain, and the usual inking apparatus are fixed at the lower part of the frame, and on that part of the type cylinder which is not occupied by the form are placed inking beds, which make a " distributing table," so that as the cylinder revolves, a roller transfers the ink on to this distributing bed, which, continuing its rotation, imparts the ink to rollers disposed around the framing. The inking rollers are forced against the type when it approaches their locality, so that the form receives a fresh supply of ink, previously to impressing each sheet. It is obvious that the distributing surface must be of less diameter than the type surface, and also that the roller which supplies the former with ink from the fountain, must be depressed when the type is about to pass it, so that they may not come in contact. (To be Continued.)
This article was originally published with the title "Machinery and Tools as they are.—Printing Presses"