IMPROVEMENTS IN PRESSES FOR COLOUR PRINTING
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Edmund Johnson, Charles
Johnson, and George Frederick Pabst at the Office of the Com-
missioners of Patents, with their Petition, on the 1st September
1873.
WC, EDMUND JOHNSON and CHARLES JOHNSON, both of Castle Street,
in the City of London, and GEORGE FREDERICK PABST, of the City and
State of New York, United States of America, but now of Nicholas Lane,
in the City of London, all Printers, do horeby declare the nature of
the said Invention for "IMPROVEMENTS IN PRESSES FOR COLOUR PRINTING,"
to be as follows :-
-
Our improvements relate to printing machines or presses for printing
in colours from the peculiarly constructed blocks described in the
Specifications of Letters Patent dated June 1st A.D. 1871, (No. 1401),
and December 12th A.D. 1871, (No. 3365).
The said blocks are designed for obtaining a many coloured impression
by a single operation, and consists of sections or pieces of solid ink or
colour of the required shape fitted together and secured in a suitable
frame. As these blocks are formed of the inks or pigments which.

page_text: produce the colours of the impression it is obvious that the said blocks
diminish in thickness as they are used, therefore it has been found
necessary to provide the press with especial contrivances to compensate
for their diminution of thickness. Morcover great steadiness or freedom
from vibration has been found an essential requirement in the use of
these blocks, and we have therefore so constructed and combined the
various parts of the press as to meet these requirements in the most
advantageous manner.
We provide the said press with a substantial bed plate or table
carrying a slide which is moved to and fro by a crank or by hydraulic
rams, screws, or other convenient means, and it may have an equal
speed throughout its movements or a slow forward movement and quick
return. We prefer to use a vertical lever whose fulcrum is near the
bottom of the press and whose upper end is in a line with the said slide to
which it is connected by a suitable rod. About midway between its
fulcrum and upper end the said lever is connected with a crank, whose
shaft is rotated through a worm and worm wheel from a driving shaft.
Upon this slide we place the aforesaid blocks of prepared ink. The
paper to be printed upon is first damped or moistened with water or
other suitable medium.
To obtain the required pressure upon the paper in the process of
printing and to compensate for the wearing away of the said block or
form, a strong segment is suspended in bearings abovo the said slide and
is moved with it by cords or chains which give a smoother and more
regular motion than could be obtained by toothed racks or similar 2
mechanism, and we use in combination with the said segment hydraulic
rams or other apparatus for lowering the said segment uniformly during
the process of printing. The said hydraulic rams are provided with
safety valves to releive them from excessive strain. The said rams are
lowered by a pump worked at a suitable speed and raised by a balance a
weight or springs or both combined. By working the pump the
aforesaid segment is caused to descend and by opening an ordinary
relcase valve the said segment is caused to ascend.
In single acting machines we obtain the necessary clearance in the
return stroke of the segment by the following contrivance :-A simple 3
plunger without any valves is arranged in open conucction with the
aforesaid hydraulic rams, and is moved out at the commencement of the

page_text: return stroke and moved in at the commencement of the forward stroko
of the said segment by a suitably formed cam. The space vacated by
this plunger receives a certain portion of water or oil from the hydraulic
cylinders, whose rams are caused to rise with the segment by the
3 aforesaid balance weight or springs or both so as to give the necessary
clearance. Moreover as the plunger returns the water or oil is forced
back again into the said hydraulic cylinders, and the segment again
assuming its original position is ready for the printing of another sheet.
We sometimes modify the above described construction by arranging
the table or slide to move up and down, while the segment bearings or
supports are immovable.
At one end of the segment in single acting machines and at both ends
of the segment in double acting machines constructed according to our
Invention, grippers may be fixed to draw in the sheet of paper from a
table which is conveniently provided with the ordinary register or lay
apparatus, that is to say, it has receding points, whereby the sheets of
paper may be set and these points are adjusted by a cam; or the said
points may be fixed and the table made to rise and leave them behind
when a sheet of paper enters.
Another method of effecting the same object is to place these register
points along the aforesaid block on a spring frame or elastic substance,
which shall be depressed as the segment passes over it. In this case no
receiving table is required as the paper to be printed lies directly on the
surface of the ink, and can receive no impression until it is subjected to
a considerable pressure.
We further modify our said Invention by providing the machine with a
fixed platen instead of the rolling segment, and we may carry this
modification into practise in the following manner:-The said fixed
platen is held upwards against hydraulic pressure in tho aforesaid
cylinders by means of the counterweights. In place of the said small
pump we use a larger pump, or a number of pumps driven independently
to force water or oil into the hydraulic cylinders.
We retain the above described rocking lever and worm gearing, but
we combine therewith a slotted connecting rod so arranged that about
one-fourth of the crank's revolution at each end simply moves the lover
in the slot without sliding the table and ink block. By this contrivance

page_text: a period of rest is given to the table at each end of the stroke, and
sufficient time is allowed at one end of the stroke for the pressure,
and
at the other end for laying on and taking off the sheets of paper.
The safety valves are set according to the required pressure by sliding
their weights along the levers, the pump or pumps being constantly
working. But there is a loaded release valve through which all the
water passes, while the said valve is held up and the pumps only force
the rams down; then this release valve is lowered. Morcover this valve
being outside the pump delivery valves permits the return of the rams,
and also allows the platen to return to a stop (regulated by hand) 1
whenever it is raised. By means of a cam on the crank shaft this valve
is lowered during one-cighth of the crank's revolution or thereabouts,
and this period coincides with the termination of the stroke when the
block or form is under the platen. The pumps then act and give the
necessary pressure and the platen rises also before the slide returns, the 1
period of inaction at the end of the stroke thus gives time for tho
necessary pressure.