Improvements in Apparatus for Holding and Adjusting Flexible Forms for Printing.
Year: 1889

page_text: Date of Application, 29th Apr., 1889
Complete Specification Left, 29th Jan., 1890-Accepted, 15th Mar., 1890
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Holding and Adjusting Flexible
Forms for Printing.
A communication from abroad by WILLIAM HARRINGTON FORBES, of Boston, in the
State of Massachusetts, United States of America, Manufacturer.
I PHILIP MIDDLETON JUSTICE of 55 and 56 Chancery Lane, in the County of
Middlesex Fellow of the Institute of Patent Agents, do hereby declare the nature of
this invention to be as follows:-
This Invention is applicable to printing presses adapted for printing from sheets of
zine or equivalent material either lithographically, in which case the design is on
the flat surface of the metal, or typographically, when it is etched into relief. Its
object is to hold firmly the ends of such a form, so that the position given to it
may be maintained, and so that said position on the supporting surface may be
changed definitely and exactly by suitable appliances.
The arrangement of parts hereinafter set forth are applicable to presses of a great
many different kinds; in fact to any press in which flexible forms can be printed,
but they will be found most valuable when the form is bent to a cylindrical
curve upon a suitable underlying support, as is necessary in cylindrical and rotary
presses.
According to this Invention a bar constructed as hereinafter described passes from
end to end of the form cylinder parallel to its axis. This bar is placed and held
in a "gap" or depression of such a depth as to receive the same wholly and to
keep it under the general surface of the form cylinder, so that it shall not come
into contact with the form inking rollers, or with the paper used in printing. The
straining-bar so placed, is provided with a gripper or pinching vice along its length,
into which the end of the sheet of zinc is put and in which it is firmly held by
powerful screws. Such straining-bars are generally used in pairs, one being
attached to each end of the flexible form. This being accomplished, it will be
readily understood that as the bars are moved about, by suitable adjusting and
clamping screws on the bottom of their respective gaps, the flexible sheet of metal
between them may be tightly strained or moved with them in different directions.
The ends of this sheet of metal are bent over and caught in the clamp which is an
essential part of the straining-bars. The hold upon the zinc is maintained in this
case by the pressure exerted by screws upon the strip which bears against the metal
between it and the body of the bar.
On short cylinders each straining bar may be kept down by pieces over its ends,
and under which it can be moved sufficiently but when presses of great width are
furnished with this means of holding and adjusting the form it is necessary to apply
pinching screws with large heads passing freely through holes in the face of the bars
and into the of the cylinder.
To enable the zinc or other sheet to be held in such a way by the bar as to render
its escape impossible, the clamp may be of peculiar construction on the upper face of
the straining-bar and the end edges of the zinc may be prepared in a novel manner
for seizure by said clamp.
These arrangements are accomplished as follows:-In the straining-bar a
V shaped groove is formed which runs its entire length, and an independent
clamping strip is shaped like a wedge to correspond, substantially with said groove.
This wedge is forced into the groove by the clamping screws. The flexible sheet has

page_text: left, or constructed on its end edge, a projection which practically is a part of the
plate itself. This strip fiis a depression, notch or recess on one side of the wedge
shaped clamping strip while the projecting part of the wedge butts solidly against
the up-turned shoulder or edge of the zinc in contact with it. When the sheet of
metal is bent downwards and inserted between the recessed side of the clamping strip
and the flat side of the V shaped groove and the former is then depressed by means of
the screws, the two opposed and parallel faces, acting like the jaws of a vice
approach each other and grasp the thin metal between them so that it is practically
inextricable except by releasing the screws. In clamping by this device, it will be
understood that the pressure exerted by the clamping screws is much increased upon
the sheet-metal, by reason of the wedge shape given to the strip. This way of
applying the necessary pressure is believed to be the best because of the advantages
stated and for the reason that while the stiffness and solidity of the straining-bar
is increased, all the movable parts used in grasping the ends of the flexible form,
can be easily kept clear of the form-rollers."
When the sheet of zinc or other metal constituting the form which is to be held
is moderately thick, it is preferred to make the shoulder on the same by protecting
with an etching ground the strip which is to become the projection, and then etching
down the metal inside said strip with an acid. Or, with the help of a simple
planing tool the metal may be cut away mechanically parallel to the edge, leaving
the projection in a way that will be readily understood. But, when the sheet of zinc
is so thin that the removal of its substance to the requisite depth, would weaken it
too much and endanger its tearing, the edge of the metal may be turned over and
flattened it down so as to give rise to a projection which is double or more than
double the thickness of the original plate. When in place and grasped by the
clamp the flexible form so prepared behaves exactly as if the projection were
solid.
Or the ends of the sheet may be tightly rolled for a short distance, or a stiff wire
may be folded in and covered by the zinc, or a strip of suitable size may be soldered
down upon the sheet-metal; in all of which cases the recessed portion of the
clamp must of course be made to correspond to the shape which is given to the end
of the form.
When it is desired to strain the sheet metal tightly upon the form supporting
surface it is only necessary to screw up the long bolts. These force the bars back
by butting against the side of the gap; and, by slacking the screws of one bar and
advancing those of the other, the whole form is made to travel in one direction over
the cylindrical surface. When the form has to be shifted to the right or left
across the press, other screws are used which butt against the end of the gap, and admit
of shifting the bar end wise, within certain limits which are sufficient for the purpose.
There is still a third movement which is sometimes essential, especially so when
flexible forms are used upon chromatic presses. In these one form has to be
brought into exact register with one or more forms printing different colours. To
accomplish this it is not sufficient to move the surface which is to print round the
cylinder in either direction, or endways upon it, but a kind of partial rotation or
twist is also requisite by which one corner of the plate is advanced, and the opposite
corner at the same end moved backward. It is obvious that the simultaneous use
of the two sets of screws will accomplish this kind of twist, the requisite screws
being slacked to let the flexible form go back, and those at or near the other
diagonal of the plate being tightened up until the slack ones bear again against the
sides of the gap.
When the right position has been found the bars may be fixed steadily by
set-screws, which butt against the bottom of the gap and throw the ends of the
straining-bar up against the holding pieces, or, flat-headed bolts entering the body
of the cylinder at the bottom of the gap and passing freely through the base of the
bar, as already described, may be tightened up.

page_text: From the foregoing it will be seen that each bar can be moved with precision in
the gap in every direction, and will take the flexible form with it, and secure it in
the end tightly strained and fixed.

page_text: To adjust by sliding the zinc in either direction across the cylinder the bolts 9 are
used, the long screws 8 being first turned back a little to diminish the friction.
These horizontal bolts 9 pass through lugs on the ends of the bars and butt against
the segments 5 throwing the bar, and with it the zinc, to the right and left as
required.
To adjust the diagonals of the design, leaving its centre unaffected the long bolts 8
at the ends of the straining bar are used, but alternately, one being tightened and the
other slackened in each bar.
In doing this it is desirable to free the ends of the bars in the rabbets to a very
slight extent which is accomplished by raising the screws 10 the ends of which rest
on the bottom of the gap, so that the ends of the straining bar drop from the
segments 5 and the bar is freed sufficiently to permit of the diagonal adjustment.
The screws 9 and 10 which aid in giving the lateral and diagonal adjustments with
precision may generally be dispensed with when a press of this kind is used (as it
often will be) to print one colour only, for then the position of the design upon the
web or sheet has no reference to any other design, as is the case when the press is
used chromatically, and slight inaccuracies in the position it should occupy are not
perceptible..
It will be seen that the position of the nipping bar 6 is such that the zinc slopes
upward from it to the rounded edge of the gap so that when the inking rollers come
from the ink table they do not strike an abrupt edge.
To enable a form cylinder for zinc printing to receive and hold zinc sheets of
different lengths suitable to the designs upon them, one or both of the gaps described
may be made larger than is required for the movements of the straining bar. Part
of the gap (or gaps) so enlarged is then filled in the manner shewn by the pieces 11
to accomodate the largest form which can be printed on the cylinder, the arrangement
shown in Figures 1 and 2 providing for five different lengths of zinc. These pieces
are flush with the general surface of the cylinder and are held in place by the bolts 12.
To suit a smaller form than that shown, one or more of the pieces 11 is removed,
the lip piece 13 is screwed into the last which remains and the straining bar is
pushed up to receive the turned over edge of the zinc as before, after the return of
the bolts 12. The lip piece 13 is necessary to provide a rounded edge over which
the zinc is drawn. As shown the pieces 11 are of equal size and are all in place
together when a form of maximum length is on the cylinder but the changes in length
of the supporting surface may also be effected by making the moveable pieces of
different sizes and using only one at a time.
When this method is adopted each piece is given a rounded edge where the zinc
passes over it and the lip piece 13 is used only upon the edge of the gap when the
smallest form goes upon the cylinder.
With short cylinders the straining bar may very well be kept down by the
segment pieces 5 over its ends as described but with long cylinders it is preferable
to employ pinching screws with large heads passing freely through holes in the face
of the bars and into the body of the cylinder as will be described in connection
with the modified form of straining bar illustrated in Figures 3 to 9 and now
referred to.
In this straining bar 4 a V shaped groove is formed which runs its entire length,
and in this is a clamping strip 6 shaped like a wedge to correspond substantially
with said groove. This is forced into the same by the clamping screws 7. The
flexible form 1 has left or constructed on its end edge the projection shown at 14
which is a part of the plate itself. This strip fits a depression, notch or recess 15
on one side of the wedge shaped clamping-strip, while the projecting part at 16
butts solidly against the upturned shoulder or edge of the zinc in contact with it.
When, as shown in the drawings, the sheet of metal is bent downward and inserted
between the recessed side of the clamping-strip 6 and the flat side of the V shaped
groove, and the former is then depressed by means of the screws 7, the two opposed
and parallel faces, acting like the jaws of a vise, approach each other and grasp
the thin metal between them, so that it is practically inextricable except by releasing

page_text: said screws.
In clamping by this device it will be seen that the pressure exerted
by the clamping-screws is much increased upon the metal sheet by reason of the
wedge shape given to the strip 6. This way of applying the necessary pressure is
believed to be the best, because of the advantages stated and for the reason that,
while the stiffness and solidity of the straining-bar is increased, all the movable
parts used in grasping the ends of the flexible form can be easily kept clear of the
form-rollers; but it is evident that in place of the wedge-shaped strip, plates or blocks
suitably notched or recessed to receive and embrace the sheet metal and the
projecting strip upon the same can be readily contrived, whereby approaching surfaces
controlled by screws may be made to embrace the ends of the flexible form which
overhang the supporting form-surface and to fit the projections upon the same,
substantially as above described.
When the sheet of zinc or other metal constituting the form which is to be held
is moderately thick, it is preferred to make the shoulder 14 on the same by
protecting with an etching ground the strip which is to become the projection, and
then etching down the metal inside said strip with an acid; or, with the help of a
simple planing tool, the metal is cut away mechanically parallel to the edge, leaving
the projection, in a way that will be readily understood; but when the sheet of zinc
is so thin that the removal of its substance to the requisite depth would weaken it
too much and endanger its tearing, the edge of the metal is turned over and
flattened down in the manner shown in Figure 9, so as to give rise to a projection 14*
which is double the thickness of the original plate, or a narrow parallel strip of
thin zinc may be soldered down upon the end of the form in the position which the
turned-over strip would take, or the sheet may be rolled or a wire be folded in and
the projection flattened. When in place and grasped by the clamp, the flexible
form so prepared behaves exactly as if the projection were solid, as shown in
Figures 3 and 8.
The straining bar shown is adjusted, controlled and fixed in position by the
screws 8 and 9 and the pinching screws 17. The long screws 8 butt against the
side of the gap and force the bar backward, thereby drawing the sheet of metal
held by its clamp tightly over the supporting form-surface, and the screw 9 and a
corresponding one at the other end of the bar, butt against the ends of the gap and
serve to move the bar to and fro in the direction of its length. When in position
the screws 17 hold it firmly, and with it the flexible form attached thereto.
Having now particularly described and ascertained the nature of my said Invention
as communicated to me by my foreign correspondent and in what manner the same is
to be performed 1 declare that what I claim is :-
1. A form cylinder of a printing press having gaps or depressions carrying an
adjustablo straining bar or bars provided with gripping devices for the form,
substantially as described.
2. A form cylinder of a printing press having gaps or depressions in the face
thereof, provided with form straining bars adjustable therein by screws which control
and secure the same in all positions substantially as described.
3. The combination with the form cylinder of a printing press having gaps or
depressions, of straining bars 4 provided with gripping devices, segments 5 for
holding same, and straining screws 8 substantially as described.
4. The combination with a form cylinder of a printing press having gaps or
depressions, of straining bars provided with gripping devices, retaining segments 5,
straining screws 8, adjusting screws 9, and releasing screws 10, substantially as
described.
5. The combination with a form cylinder of a printing press having gaps or
depressions, of a flexible form provided with a flat projecting strip left or added
at its end and a straining bar having a clamp constructed to embrace and grasp
said projection, substantially as described.
6. The combination with a form cylinder of a printing press having gaps or
depressions, of a flexible form provided with a flat projection or projections at its

page_text: end or ends, a straining bar for holding and adjusting said forms and a clamp
connecting the bar and form consisting of a bar provided with a V shaped groove
and a wedge shaped recessed strip fitted thereto and secured therein substantially as
described.
Dated this 90th dess of Tonunu 1000
PHILIP M. JUSTICE.