Per′fect-ing-press.
（
Printing.) One in which the paper is printed on both sides during one passage through the machine.
In Hoe's rotary-cylinder perfecting-press, two impression-cylinders and two form-cylinders are placed side by side in a horizontal frame, the impression-cylinders occupying the center, with the form-cylinders at each end. The two forms are attached to their cylinders, and inked as in the usual type-revolving press, the fountains and distributing cylinders being placed at the ends of the press.
The sheets are supplied by feeders in the usual manner; they are delivered by a feedingcylinder to the first impression-cylinder, whence they go to the second impression-cylinder, and are thence conducted right and left alternately to a sheet-flier at each end. See also
printing-press; web-press.
In the flat-bed perfecting-press the bed has a reciprocating motion, the paper being transferred automatically from the first impression-cylinder to the second, and then conducted by tapes to the self-acting sheet-flier.
The second cylinder is provided with reels holding a large roll of facing blanket, which, as it becomes soiled by the set-off from the first side of the sheet, is rolled up and a fresh portion brought into use.
The machine may be arranged to have an additional feedboard, from which a set-off sheet may be fed to the second impression-cylinder, the two sheets being thrown out together on the fly-board and separated by hand; or, a sheet-flier may be added for the set-off sheet, which is then separated automatically from the printed sheet and flown on a separate board.
In the press shown in
Fig. 3640, the sheets, as they come from the printing mechanism, are directed alternately on opposite sides, so as to be delivered in two piles, either by two separate fly-frames or a double-acting fly-frame.
The plates are clamped directly to the surface of the type-cylinder, so as to dispense with the use of blocks and iron frames commonly used.
A late style of perfecting-press uses a double form which engages with a cylinder both in its forward and backward movement, the cylinder performing only a partial revolution and returning with the form.
An inking-apparatus on each side of the cylinder inks the form as it passes, and a reversing apparatus on one side takes the sheet after the first printing, reverses it, and returns it to the grippers.
The back stroke of the press completes the printing, and the sheet is then cut in two.
The
Walter's English press, which prints the
London and the New York Times, is shown in
Fig. 3641. A roll of paper
a, three miles long, reels off over the pulley
b, which serves to keep it taut, and is damped in passing the cylinders
c c. The web then passes over the cylinder
d to the first type-cylinder
e, between which and the blanket-cylinder
f it receives its first impression.
Following the direction of the type-cylinder it passes between two blotting-cylinders, and is then delivered to the second printing-cylinder
g, receiving the impression at
h. It is then cut by a knife on the cylinder
i. The sheets are finally piled on the paper-boards
k k. The speed of the Walter press is said to be 11,000 printed sheets, or 22,000 impressions, per hour.
The
Bullock press, so named from the inventor, the late
William Bullock of
Philadelphia, carries the forms upon two
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cylinders, requires no attendants to feed it, and delivers the sheets printed on both sides.
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Bullock's self-feeding and perfecting press. |
The paper in the form of an endless roll is moistened by passing through a shower of fine spray.
A single roll will contain enough for several thousand sheets, and the printing operation, including the cutting of the paper into proper lengths, proceeds uninterruptedly until the roll is exhausted.
The roll of paper having been mounted in its place, the machinery is started, unwinds the paper, cuts off the required size, prints it on both sides at one operation, counts the number of sheets, and deposits them on the delivery-board at the rate of eight thousand to fourteen thousand per hour; or, counting both sides, at the rate of sixteen thousand to twenty-eight thousand impressions.
The labor is only that of placing the rolls on the press and removing the printed paper.
The press is shown in perspective in
Fig. 3342. The roll of paper
a on top is cut into sheets by a knife on roller
b acting against the cylinder
c. The sheets are seized by grippers, carried between the impression-cylinder
g and the
form e, receiving the first impression.
The printed sheet then follows the large cylinder
g to the second
form, receiving its second impression from this
from acting against the large drum
g. From the large cylinder the sheets are automatically delivered to the receivingboard.
i is a counting device or arithmometer.
The inkingrollers are shown above the making-cylinders, beneath which are the ink-troughs.
The starting-lever is shown on the right.
Fig. 3643 shows parts of the
Bullock press detached, for a better understanding of their operation.
A is a section midwise of the principal working parts.
a is the roll of paper which is cut off in sheets by the knife on cylinder
b, which strikes through the web of paper into slots in the cylinder
c. As soon as the sheet is cut off it is grasped by grippers on
c, passed to impression-cylinder
d, and around that, between it and typecylinder
e, where the first side is printed.
It is then seized by grippers on the large cylinder
g, and carried between that and the second type-cylinder
f to print the other side.
The sheets are taken from the large cylinder by endless belts which pass over pulleys, and are piled by the action of the flier
h.
The large cylinder
g is covered with a blotting-pad to prevent offset when the face of the freshly printed sheet is carried on to it from cylinder
d. The inking-rollers, not shown in this view, are kept constantly in contact with the type or plates on cylinders
e f. The grippers are so arranged that the delivery of a sheet from one set to another is certain and uniform.
B shows the cutting and receiving cylinders, with the grippers on the latter in their positions before and after the sheet is cut from the web.
C shows the knife
x and carrier
n, and the slotted block
m, into which the cut is made The carrier
n is a segment of cylinder
b, and
m is a similar portion of
c.
D is an end view of the printing-cylinders
e f. The plates from which the printing is done are of extraordinary thickness, and are cast to fit the cylinders in circular molds.
The molds are made in plastic material spread on a steel plate which is pressed flat, but which assumes a circular shape when released,
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curving the mold with it. Kellberg's arrangement of the
Bullock press cuts the sheets after printing.
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Bullock press (principle of action). |
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Perforator. |
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Periosteum-elevator. |
The Victory press, shown under
printing-press, is also a
web-press, and damps, prints, cuts, folds, and pastes at the back a 24-page paper like the Christian Union of New York, at the rate of 7,000 per hour.
