Improvement in Means for Bending Printing Plates.
Year: 1892

page_text: Date of Application, 2nd Aug., 1892
Complete Specification Left, 29th Nov., 1892-Accepted, 4th Feb., 1893
PROVISIONAL SPECIFICATION.
Improvement in Means for Bending Printing Plates.
1, ALEXANDER GRAY of The Mansion, Frognal, N.W. Consulting Engineer
do hereby declare the nature of this invention to be as follows:-
This improvement consists in the use of hydraulic or pneumatic pressure for
bending plates used in printing machines with a curved surface.
The pressure is applied to the printing surface of the plate by means of a flexible
bag into which water or air or other fluids are forced and the plates are thereby
bent over a mould accurately to any desired curve without risk of injury to the
printing surface however great the pressure which is applied.
Dated this 1st day of August 1892.
ALEXR. GRAY.
COMPLETE SPECIFICATION.
Improvement in Means for Bending Printing Plates.
I, ALEXANDER GRAY of The Mansion, Frognal, London, N.W. Engineer
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:-
The object of this invention is to bend plates used in rotary printing machines
accurately to any desired curve, so that they conform to the curve of the cylinder
on which they are to be used.
The invention consists in the use of hydraulic or pneumatic pressure applied to
the plate through a flexible material which is pressed down over the plate by the
fluid used.
By the methods at present adopted the bending of the plates is often effected
imperfectly and the plates are to some extent damaged whilst being bent.
To remedy this, I bend the plates by placing them over a mould and pressing
them on to the mould by fluid pressure acting against a back of flexible material,
placed over the face of the plate. In this way the whole surface of the plate is
uniformly and simultaneously pressed down on to the mould, without any risk of
injury to the printing surface from the pressure, and the irregular curvature which
now often arises from want of uniform and simultaneous pressure over the whole
plate is avoided.
The apparatus I use is shown in the drawings. Figure I is a side elevation,
Figure II is a front elevation, Figure 11 is a plan.
A is the base, B the top plate; these are tied together by the bolts or pillars D.
C is a table which rises and falls guided by the pillars D, supported by the
toggles G, and it carries upon it a mould F. EE are a pair of brackets attached
to the table C, on which the mould F is run out for convenience in working.
His a lever for working the toggles G, and thereby raising or lowering the table C.
Springs not shown in the drawing may be added to assist in supporting the table,
so as to make the raising it more easy. The top B is a casting hollow below with
a flange all round to which a frame B2 is bolted with a sheet of water-proof
canvas B between the frame and flange, so as to close in the hollow space water-
tight. The mould is mounted on rollers so as to run in and out of the press on
the brackets E E. The rollers are mounted on shafts provided with springs which
raise the mould so that it can run on the rollers; when pressure is applied to the
mould these springs yield and allow the mould to rest on the top of the table C.

page_text: The mould F is turned to a radius rather smaller than that of the cylinder, to
which the plates are to be fitted. The exact radius must be determined by trial
in each case, since it varies not merely with the size of cylinder but also with the
nature of the backing metal or type-metal used, and with the thickness of the plate
and also with the amount of curvature.
At one side of the mould is a raised guide F2 by which to set the plate square on
the mould.
To operate the machine, the table C is lowered, the mould F run out on the
brackets, and there heated sufficiently to make water hiss. The plate to be bent,
having been previously heated in the usual way, is laid on the mould, covered with
a piece of felt, and the mould with the plate now run back into the press, the
table C is now raised by the lever H, till the shaft G¹ rests against the stop G³.
Water or air is now forced into the top B, and the canvas is thereby pressed down
on to the plate with a pressure of about 100 lbs. per square inch. The plate is
allowed to remain under pressure for about half a minute; the water is then
allowed to escape, the table lowered, the mould run out, and the plate taken off
and allowed to cool.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what
claim is―
1. Bending plates used in rotary printing machines to the required curvature by
pressing the plates on to a mould by fluid pressure, applied direct to the back of
flexible material placed over the face of the plate substantially as described.
2. The herein described press to be used for the above purpose consisting of a
hollow water-tight chamber having a concave flexible bottom, a table which can be
raised, and lowered below this chamber and a mould which can be run along the
table to bring it into position below the water-tight chamber or to one side of
the press.
Dated 2nd Novembox 180°
ALEXR. GRAY.