IMPROVEMENTS IN FORMING METAL PLATES WITH DEVICES IN RELIEF FOR ORNAMENTAL PRINTING AND OTHER PURPOSES
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Robert Brown at the Office of
the Commissioners of Patents, with his Petition, on the 8th April
1875.
"
I, ROBERT BROWN, of Paisley, in the County of Renfrew, North
Britain, Pattern Drawer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN FORMING METAL PLATES WITH DEVICES IN
RELIEF FOR ORNAMENTAL PRINTING AND OTHER PURPOSES," to be as follows, that
is to say :-
This Invention has principally for its object the formation in a superior
but economical manner of plates, such as are commonly made of type
metal or analogous metallic alloy or compound for printing ornamental
designs on paper or on woven fabrics; the improvements may however
be also advantageously used in forming plates for printing names or other
imprints, or in forming name plates or other plates to be affixed on
machines or other articles,

page_text: In carrying out the Invention according to one modification a slab is
formed of plaster of Paris or other composition of a similar nature, and
the design or device is cut into the surface of this slab by means of a
rapidly revolving cutter, which is guided or held so as to penetrate to a
uniform depth in the plaster slab. The cutter differs from an ordinary
drill, having a very acute angle instead of the usual obtuse angle
between its two cutting edges, and it is fixed vertically in a holder
carried by a jointed arm, being driven by a cord which acts on a small
pulley on its holder, and which is led round guide pulleys at the joints
of the arm, so that the horizontal movement of the end of the arm over
the plaster slab does not affect the driving action. The driving cord
may be actuated by means of a treadle motion or otherwise.
The design to be cut may be traced on the surface of the plaster slab,
and the cutter may be traversed over it by means of a handle jointed to
the arm; it is however preferred to combine a set of jointed pieces for
the arm on the well-known principle of pantograph with a tracer
attached at a point thereof, so that an enlarged copy of the device may
be traced, whereby increased accuracy will be obtained in the com-
paratively reduced device actually cut into the plaster. Whilst the
plaster is being operated upon it is by preferenco just covered with:
water, which is found to facilitate the process, and to keep the cutters
longer without requiring to be sharpened.
When the cutting of the devices is completed and the cuttings are
washed out the plaster is dried, and the type or other metal is cast upon
the slab so as to fill the cut-out parts, and in addition form a plate on
the surface. The casting when separated from the plaster presents the
devices in relief, and the edges of these devices being filed or otherwise
rendered truc form the actual printing surfaces.
If preferred the plaster may be cast on an iron or other suitable
surface, and of a thickness no greater than the intended depth of cut, so
that the cutter will penetrate down to such surface, which will thus
correspond to the actual printing surface of the metal plates afterwards
cast.

page_text: neously by using many cutters on one pantographic frame; or a metal
cast of the device having been taken from the plaster slab may be used
to indent wood or other suitable material by pressure to form a mould or
moulds from which a number of metal casts can be taken.