In the year 1815, Mr. Cowper turned his scientific and inventive mind to
the subject of printing machines, and has since, in co-operation with
his partner, Mr. Applegath, carried them to an unlooked-for degree of
perfection. In 1815 Mr. Cowper obtained a patent for curving stereotype
plates, for the purpose of fixing them on a cylinder Several machines
so mounted, capable of printing 1000 sheets per hour upon both sides,
are at work at the present day; twelve machines on this principle having
been made for the Directors of the Bank of England a short time previous
to their re-issuing gold. See _figs._ 918. and 919.
It deserves to be remarked here, that the same object seems to have
occupied the attention of Nicholson, Donkin, Bacon, and Cowper; viz.,
the revolution, of the form of types. Nicholson sought to effect this by
giving to the shank of a type a shape like the stone of an arch; Donkin
and Bacon by attaching types to the sides of a revolving prism; and
Cowper, more successfully, by curving a stereotype plate. (See _fig._
918.) In these machines Mr. Cowper places two paper cylinders side by
side, and against each of them a cylinder for holding the plates; each
of these four cylinders is about two feet in diameter. Upon the surface
of the stereotype-plate cylinder, four or five inking rollers of about
three inches in diameter are placed; they are kept in their position by
a frame at each end of the said cylinder, and the axles of the rollers
rest in vertical slots of the frame, whereby having perfect freedom of
motion, they act by their gravity alone, and require no adjustment.
The frame which supports the inking rollers, called the waving-frame, is
attached by hinges to the general framework of the machine; the edge of
the stereotype-plate cylinder is indented, and rubs against the
waving-frame, causing it to vibrate to and fro, and consequently to
carry the inking rollers with it, so as to give them an unceasing
traverse movement. These rollers distribute the ink over three-fourths
of the surface of the cylinder, the other quarter being occupied by the
curved stereotype plates. The ink is contained in a trough, which stands
parallel to the said cylinder, and is formed by a metal roller revolving
against the edge of a plate of iron; in its revolution it gets covered
with a thin film of ink, which is conveyed to the plate-cylinder by a
distributing roller vibrating between both. The ink is diffused upon the
plate cylinder as before described; the plates in passing under the
inking rollers become charged with the coloured varnish; and as the
cylinder continues to revolve, the plates come into contact with a sheet
of paper on the first paper cylinder, which is then carried by means of
tapes to the second paper cylinder, where it receives an impression upon
its opposite side from the plates upon the second cylinder.
Thus the printing of the sheet is completed. Though the above machine be
applicable only to stereotype plates, it has been of general importance,
because it formed the foundation of the future success of Messrs. Cowper
and Applegath’s printing machinery, by showing them the best method of
serving out, distributing, and applying the coloured varnish to the
types.
In order to adapt this method of inking to a flat type-form machine, it
was merely requisite to do the same thing upon an extended flat surface
or table, which had been performed upon an extended cylindrical surface.
Accordingly, Messrs. Cowper and Applegath constructed a machine for
printing both sides of the sheet from type, including the inking
apparatus, and the mode of conveying the sheet from the one paper
cylinder to the other, by means of drums and tapes. It is highly
creditable to the scientific judgment of these patentees, that in new
modelling the printing machine, they dispensed with forty wheels, which
existed in Mr. König’s apparatus, when Mr. Bensley requested them to
apply their improvements to it.
[Illustration: 920