Improvements relating to the Preparation of Plates for Printing.
Year: 1898

page_text: Date of Application, 27th June, 1898-Accepted, 10th Sept., 1898
COMPLETE SPECIFICATION.
Improvements relating to the Preparation of Plates for Printing.
I, JAMES HENRY SMITH, of No. 102, Westfield Street, Providence, Rhode Island,
United States of America, Lithographer, do hereby declare the nature of this
invention, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to processes of graining the plates employed for surface
printing, the object of the invention being to produce a plate having the required
even and uniform grain for receiving in the most perfect manner the design,
picture or the like to be drawn or transferred onto the grained surface of the
plate.
The graining of plates employed for surface printing has in some cases been performed
by reciprocating the plate under the action of a suitable quantity of sand and
abrading balis placed on the upper surface, whereby the plate is grained. The
object of thus graining the plate is to remove the case-hardened surface, that is
to say the surface which comes in immediate contact with the rolls of the rolling
machines and is thereby hardened, while the interior of the sheet still retains its
cellular or grain-like structure. Said method of graining is a decided advance over
moving a stone or other abrading object in contact with the hardened surface, as the
grained surface is left, and the grains or cells are not destroyed or flattened down
materially. Experience has proved that by reciprocating the plate as in the above
mentioned process, the abrading balls which are supported thereon are caused to
move in longitudinal parallel lines throughout the length of the plate, thus cutting
into or abrading only portions of the plate in a longitudinal direction and not
removing the hardened surface of the plate which is not subjected to the direct
action of the abrading balls. The objection was also encountered, that the sand
which is necessary for obtaining the proper abrading action tended to bank up
towards each end of the plate so that the hardened surface of the end-portions of the
plate were not as well treated as the intermediate portions.
The present invention is intended to effectually and thoroughly remove the entire
hardened surface of the sheet so that a perfect, even, and well-grained surface
throughout the plate is obtained.
An apparatus for producing this result is shown in the accompanying drawing, in
which
Figure 1 represents a central vertical section of the machine.
Figure 2 is a horizontal section on the line 2-2, Figure 1.
Figure 3 is a diagrammatic view showing the course of movement of the balls in
the old method.
Figure 4 is a diagram, showing how the balls move in the present invention.
Figure 5 shows a reproduction of the surface of a metallic sheet made in
accordance with the old method, and
Figure 6 shows a reproduction of the grained surface made by the present
process.
Similar letters of reference indicate corresponding parts.

page_text: Referring to Figures 1 and 2, A represents the frame work of the machine used in
my process, B the driving-shaft, a, a¹, intermeshing bevel-gears, of which there are
two paire, C indicates upright shafts journalled in suitable bearings in the frame and
which carry said bevel-gears, and D represents the crank-discs at the upper ends of
the shafts C, said discs being provided with crank-sockets d arranged at one side of
the axes of the shafts C. These crank-sockets d receive pins p extending downwardly
from plates E which are fixed to each end of the bottom of the tray or bed F, so that
upon turning the shaft B a circular shaking motion will be imparted to said bed,
upon which the zinc or other plate G to be grained is fastened. The bed F is
supported upon four anti-friction balls b which are held in depressions of the discs g, a
steel-plate g¹ being arranged at the bottom of the said depressions for the balls D to
roll upon. The zine plate G is secured to the bed in any suitable manner, and a
quantity of sand j is placed upon the same together with a large number of balls k
preferably made of glass, and termed abrading balls. The rotary motion of the bed
F is such that every point thereof describes during the rotation of the bed concentric
circles around an imaginary centre, and this motion causes the abrading balls k to
also revolve in circles or spiral and serpentine paths, see Figure 6, and to also turn
around their own axes with an action similar to the sun and planet gearing, so
that the said balls will describe intercrossing circles upon the surface of the zinc
plate. The motion of the balls in connection with the cutting action of the sand
and the assistance of the water will cause the hardened surface of the zinc or other
plate to be evenly and properly removed throughout, thus producing a printing-plate,
the drawing or transfer surface of which is perfect for the object for which it is
intended. By the peculiar movement, therefore, of the balls, and the action of the
sand and water on the surface of the plate, the same is perfectly grained.
The perfection of the grained surface of the zinc plate, prepared in accordance
with this process, as compared with the old process will be seen by comparing
Figure 5, showing the old, with Figure 6, showing the new plate.
The glass balls may be replaced by pieces of felt or similar porous material which
gradually becomes charged with sand and thus produces the same effect as that pro-
duced by the said glass balls. The pieces of felt have moreover the advantage of
producing a very fine grain and a perfectly even surface. The adoption of pieces of felt
permits of the production of excellent transfer plates and of dispensing with the use
of the nitric acid bath.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I
claim is :-
The process of graining the plates employed for surface printing, the same con-
sisting in placing a suitable quantity of sand and a number of abrading balls or
pieces of felt upon the surface of the printing-plate to be grained, rapidly moving said
plate in a circular path, whereby the balls are caused to travel around the surface of
the plate and to move in concentric intercrossing circles or curves, so that by the
assistance of the sand the entire surface of the printing-plate is removed and a per-
fectly grained and even surface is produced throughout, substantially as set
forth.
Dated this 27th day of June 1898
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.