Note: Descriptions are shown in the official language in which they were submitted.
CA 02249698 1998-09-16
DE LA RUE GIORI S.A. LAUSANNE / SWITZERLAND
Silk-screen printing machine.
FIELD OF THE INVENTION
The present invention relates to a screen printing
machine comprising, for printing at least one first
area in a defined color, an impression cylinder and a
screen cylinder, and at least one second screen
cylinder interacting with the same impression cylinder
and being provided with means for printing at least
one second area in a different color from that of the
first area.
PRIOR ART
The use of screen printing machines comprising an
impression cylinder and a screen cylinder for printing
an area of a defined color is known. When it is
desired to print juxtaposed or superimposed areas of
another color, the first printing is dried and then
the paper runs through a second machine comprising an
impression cylinder and a screen cylinder for
superimposed or juxtaposed printing of the second
image in a color different from the first. Therefore
in multicolor printing, there is one pass for each
color after the ink of the previous printing has
dried.
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CA 02249698 1998-09-16
US-A-3934502 discloses a screen printing machine
comprising an impression cylinder and at least two
screen cylinders interacting with the impression
cylinder for the printing of at least two areas, each
area being in a different color from that of the
other.
US-A-39 90 363 discloses a similar machine as the
previous excepted that the printed areas are not
superimposed and the second screen cylinder does not
come into contact with the impression cylinder on the
area printed by the screen cylinder.
With the concern to find means making security papers
difficult to copy or counterfeit, various types of
printing have been used on the same security paper
including, inter alia, screen printing. Nevertheless,
the printing of the various designs using different
processes, and the intermediate drying which must take
place, lengthen the time for printing the documents
and problems of registration between the various
printings make these printing operations tricky and
increase the costs by the addition of equipment.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a
machine for the screen printing of certain areas of a
paper with at least two non-superimposed designs of
different colors without having to run through an
intermediate drying unit and using a relatively simple
machine which is less voluminous than a multicolor
screen printing plant used hitherto.
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The screen printing machine according to the invention
is organized so that the said second area is outside
the first area, the second screen cylinder comprising
at least one raised part on which a screen is arranged
so the second screen cylinder does not come into
contact with the impression cylinder on the areas)
printed by the first screen cylinder.
The advantages of the machine according to the
invention are as follows:
- printing in a single pass of the paper on a
single impression cylinder of at least two non-
superimposed areas in at least two different colors,
which, on the one hand, makes intermediate drying
between the two printings unnecessary and, on the
other hand, results in a less voluminous machine,
since only a single impression cylinder is used, and
therefore a less expensive machine;
- additionally, it is easier to obtain good
registration between the screen printing images
printed in succession by means of the same impression
cylinder.
These results are, of course, obtained by virtue of
the fact that the second area is printed by a screen
cylinder provided with means for printing at least one
second area of the paper which is not yet printed and
does not touch the area already printed by the first
screen cylinder. The means with which the second
screen cylinder is provided comprise at least one
raised part on which a screen is arranged. Thus, it is
only the raised part or parts which come into contact
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with the impression cylinder on areas not printed by
the first screen cylinder. Devices pushing the ink
through the screen are provided inside the screen
cylinder, these devices being preferably, but not
exclusively, squeegees. The latter may be a
conventional screen cylinder or, for example, like the
one proposed in the applicant's European patent
application No. 0723864. By avoiding the second screen
cylinder touching the areas already printed during the
first pass, it is not necessary to carry out
intermediate drying. It is clear that, in such
printing, it is necessary tc maintain a sufficient
spacing between the two areas in order to avoid the
screen of the second screen cylinder coming into
contact with the previously printed area.
According to a preferred variant of the invention, the
screen of the first cylinder is designed to print
several spaced-apart areas in a defined color (the
design could be the same or different for each area)
and the second cylinder also has several raised areas
enabling the same design or several designs to be
printed in a second color in spaces left by the
previous printing.
According to another embodiment variant, the machine
may comprise several screen cylinders with raised
means in order to print, in succession and by means of
a single impression cylinder, non-superimposed areas
of different colors, the raised features of the
various cylinders being arranged so that they do not
come into contact during printing with the areas
printed previously.
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According to one embodiment, the raised areas of the
screen cylinder or of each of the screen cylinders
have an axial shape extending parallel to the axis of
the cylinder, along that surface of the latter on
which the screen is arranged. In this case, the
squeegee, or the equivalent device, is provided with a
mechanism enabling the squeegee to move radially in
order to be able to follow the configuration of the
internal side of the periphery of the cylinder, so as
to push the screen arranged on the raised part of the
cylinder and to be retracted when, by rotation of the
cylinder, the set-back part comes against the
squeegee, and so on.
According to one embodiment, the mechanism enabling
the squeegee to perform these movements in the radial
direction is a cam rotating in synchronism with the
screen cylinder and acting on the end of a lever whose
other end is fastened to the squeegee.
According to another embodiment, the raised parts are
annular areas on which the screen is applied and in
this case the squeegee has the shape of a comb whoae
teeth always lie within the annular areas in order to
push the ink through the screen in which these annular
areas are equipped.
According to another embodiment variant, the second
screen cylinder is provided with an elastically
deformable screen so that contact with the impression
cylinder in line with the impression slot takes place
only under the thrust of the means such as a squeegee
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having in this case the shape of a comb, whose teeth
correspond to the areas to be printed, pushing the
screen so as to come into contact with the impression
cylinder, the space between the teeth corresponding to
printed or non-printed areas and with which the screen
does not come into contact. Further, the screen is
provided with spaced-apart rings with corresponding
spaces between two successive areas to be printed,
preventing the screen from deforming and from coming
into contact with the impression cylinder.
According to another embodiment variant, the machine
is a sheet-fed printing machine comprising an
impression cylinder with at least one notch housing
the device for seizing the sheet, and the ink-pushing
means of each screen cylinder comprise a mechanism
enabling them to move away from the screen when a
notch passes into the impression slot.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail by
means of four examples of a sheet-fed printing machine
and with the aid of the appended drawing.
Figure 1 is a lateral diagrammatic representation of a
plant comprising a machine forming the subject of the
present invention.
Figure 2 is a diagrammatic side view of a first
embodiment of a screen cylinder presenting raised
parts having the shape of rings concentric with the
cylinder.
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Figure 3 is a side view of the squeegee used in the
screen cylinder of the first embodiment according to
Figure 2.
Figure 4 is a diagrammatic side view of a second
embodiment of the screen cylinder presenting raised
parts having the shape of axial areas.
Figure 5 is a side view of the squeegee used in the
screen cylinder of the second embodiment according to
Figure 4.
Figure 6 shows the combination of the impression
cylinder and the two screen cylinders, according to a
first embodiment.
Figure 7 is a representation similar to that in
Figure 6, according to a second embodiment.
Figure 8 is a diagrammatic overall view enabling the
operation of the first embodiment according to
Figures 2, 3 and 6 to be explained.
Figure 9 is a representation similar to that in
Figure 8, in order to explain the operation of the
second embodiment according to Figures 4, 5 and 7.
Figure 10 is a diagrammatic side view of a third
embodiment of the screen cylinder.
Figure 11 is a side view of the squeegee used with the
screen cylinder in Figure 10.
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Figure I2 is an axial sectional view of a screen
cylinder of a fourth embodiment of the screen -
cylinder.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows a complete plant comprising a machine
for screen printing in two different colors, according
to the invention. The plant has a magazine 1
containing the sheets to be printed, a feeder device 2
for transferring the sheets along the path 3 to a feed
roller 4, a transfer roller 5 for conveying the sheets
of paper to a single impression cylinder 6, two screen
cylinders 7 and 8 interacting with the impression
cylinder 6 and a chain-type gripper system 9 which
transports the sheets to the sheet output magazines 10
comprising, in the present case, three stacks.
On the impression cylinder 6, which rotates clockwise,
the sheets first pass the first screen cylinder 7,
where they are partially printed in a first color, and
then they pass the second screen cylinder 8, where
they are printed in a different color in at least one
non-superimposed area, therefore an area outside the
areas printed by the first screen cylinder 7, without
prior drying of the areas printed by the cylinder 7
being necessary.
With regard to the operation of the screen cylinders,
the printing takes place by conventional means, that
is to say that the ink is introduced into each of the
screen cylinders and, during rotation of the cylinder,
it flows inside and is pushed by a corresponding
squeegee, or an equivalent device, in order to pass
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through the screen representing the design to be
printed.
The abovementioned offset of the areas of different
color is obtained by the fact that the screen cylinder
8 presents at least one raised part on which a screen
is arranged enabling the second area to be printed,
the combination being positioned and sized so that the
raised parts) of the screen cylinder 8 do not come
into contact with the areas printed by the cylinder 7,
this being of a construction like the one already
proposed by the applicant.
The second screen cylinder 8 according to the present
invention may be made according to four different
constructions, as represented in the following
figures: this second screen cylinder carries,
according to the first embodiment, the reference 18,
according to the second embodiment, the reference 28,
according to the third embodiment, the reference 48
and according to the fourth embodiment, the reference
4 8' .
Figure 2 shows, according to the first embodiment, a
screen cylinder 18 provided with raised parts 19 which
have the shape of rings concentric with the cylinder
18, these being arranged so as to spaced apart
axially, as shown more clearly in Figure 8. Inside
this screen cylinder 18 is fitted a squeegee 12, as
illustrated in Figure 3, the front edge of which is
adapted to the shape of the internal periphery of the
screen cylinder 18, and therefore has the shape of a
comb whose teeth 12a correspond, in terms of both size
and arrangement, to the annular raised parts 19 in
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order to push the ink, during printing, through the
screen covering the raised parts 19.
The screen cylinder 28 according to the second
embodiment, as represented in Figures 4 and 9, is
provided with raised parts in the form of axial areas
29 which are spaced apart and extend over the entire
length of the cylinder and on which a screen is
arranged. The squeegee 13 mounted inside this cylinder
28 is a conventional squeegee, as shown in Figure 5,
the front edge of which is straight. Because of the
axial raised areas of the cylinder 28, this squeegee
13 is provided with a device enabling it to be
retracted as the cylinder 28 rotates in order to pass
the set-back parts between the raised areas 29.
In order to understand the first embodiment more
clearly, reference is made to Figures 6 and 8 in which
have been diagrammatically represented the two screen
cylinders 7 and 18 as well as a printed sheet of paper
40 which, in Figure 8, is shown opened out. In the
present case, the diameter of the screen cylinder 7
and 18 is equal to one third of the diameter of the
impression cylinder 6, the surface area of which
corresponds to three sheets. A sheet 40 is shown in
Figure 8 and includes 5 x 9 - 45 impressions of bank
bills, arranged in transverse and longitudinal rows,
to which must be added two areas of different color,
namely, in the case in question, the first area
consisting of the character "a" and the second area
consisting of the character "B".
For this purpose, the machine according to Figure 6
comprises the impression cylinder 6 provided with
CA 02249698 2005-O1-24
three rows of grippers 31 housed in notches 3 0, said grippers 31 being
inteaded to
hold the leading end of a sheet 40 which comes from the transfer roller 5
(Figure 1) in
order to rurl it past the two seteen cylinders 7 and 18. The screen cylinder 7
is of the
type proposed in Canadian Patent Application 2,167,765 published on July 25,
1996
and enables the character "a" to be conventionally painted in a defined color
on each
bank bill impression. This cylinder 7 is provided on its axis with a cam 17
rotating
with it and acting on a lever in the shape of an angle bracket 15, one of the
ends of
which is paovided with a roller 16 corresponding with the cam 17, this angle
bracket
being under the action of a spring, not shown, which pushes it radially
outward toward
the screen. The vertex of the angle of the angle bracket I S is articulated to
a fixed
point 14, while the other end of the lever is fastened to the squeegee 11. The
purpose
of this cam 17 (as described in said Canadian Patent Application 2,167,765) is
'to
move the squeegee 11 away from the inside of the screen, against the action of
said
spring, when the projecting part 17a of the cam 17 comes into contact with the
roller
16 of the angle bracket 15. This takes place while one of the notches 30 in
the
impression cylinder 6 passes the impression slot between the cylinders 6 and
7,
therefore comes opposite the position of the squeegee 11, If the squeegee 11
were not
moved away, this would have the effect of damaging the screen, since, at this
point, the
impression cylinder 6 would x~ot present a surface against which the screen of
tlxe
cylznder 7 would bear under the pressure of the squeegee 11.
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It is clear that the squeegee could be driven by other
means, especially a hydraulic or pneumatic actuator
controlled by an electronic device, an
electromechanical device, etc.
Thereafter, the paper 40 runs past the second screen
cylinder 18 for printing the second area consisting of
the character "B". This cylinder 18 is provided with
annular raised parts 19 over each of which is
stretched a screen with the design to be printed, in
this case the letter "B". It will be noted that the
raised parts 19 of the cylinder 18 are offset
laterally with respect to the areas of printing by the
cylinder 7, comprising the letter "a". Thus, as the
sheet 40 passes between the cylinders 6 and 18, the
areas already printed by the cylinder 7 do not come
into contact with the cylinder 18 since these areas,
containing the "a"s, are opposite the set-back spaces
between two annular areas 19. Thus, the printing can
take place in a single pass by means of the same
impression cylinder and without waiting for the areas
printed by the cylinder 7 to be dried beforehand.
This arrangement of the annular areas allows printing
of the areas which are offset perpendicularly to the
direction of movement of the paper 40.
Inside the screen cylinder 18 is the squeegee 12, as
illustrated in Figure 3, in the shape of a comb with
teeth 12a; this squeegee 12 is mounted, as in the case
of the first screen cylinder 7, at one end of an angle
bracket 21 articulated at its vertex about a fixed pin
20 and carrying, at its other end, a roller 22 which
is in permanent contact with the surface of a cam 23
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provided with a projecting part 23a. This cam 23
therefore has the same configuration of the cam 17 of -
the cylinder 7 and acts for the same purpose, namely
to move the squeegee 12 back from the internal side of
the screen while one of the notches 30 in the
impression cylinder 6 is passing in front of the
impression slot.
The second embodiment according to Figures 7 and 9
allows printing of the areas, in the form of
characters "a" and "B", offset in the direction of
movement of the sheets of paper 41 which once again
include 5 x 9 impressions of bills. The screen
cylinder 7, with its squeegee, its angle bracket and
the cam 17, 17a, is identical to that in Figure 6 and
prints the first areas with the letter "a"; the
impression cylinder 6 also has the same construction
as that described in relation to Figure 6.
The second screen cylinder 28, which includes axial
raised areas 29 extending over its entire length, is
provided with a screen on each of the raised parts 29
for printing the letter "B" in another color than the
letter "a". This printing is, as may be seen in the
sheet 41 (Figure 9), printed offset in the direction
of movement of the paper. The squeegee 13 is
controlled by a cam 27 fixed to the spindle of the
cylinder 28 and rotating in synchronism with the
latter. This squeegee 13 is fixed to one end of an
angle bracket 25 articulated at its vertex to a fixed
pin 24 and provided at its other end with a roller 26
in permanent contact with a cam 27. The shape of this
cam 27 reproduces, on a smaller scale, the profile of
the screen cylinder 28, in negative, in order to
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enable the squeegee 13 to be guided inside said
cylinder 28 so that the squeegee 13 follows the
internal configuration of the periphery of the
cylinder 28. Provided on the periphery of this cam 27
is a projecting part 27a, corresponding to the non-
raised part 28a of the cylinder 28, adapted to a notch
30 in the impression cylinder 6, and pushing the
impression slot always simultaneously with one of
these notches 30, in order to withdraw the squeegee 13
during passage thereof. The remainder of the periphery
of this cam includes projecting parts 27b which
correspond to the parts 28b lying between the raised
parts 29 of the cylinder 28.
Figure 10 shows the third embodiment, a screen
cylinder 48 provided with a screen 49 which may be
elastically deformed. Arranged inside this cylinder 48
is a squeegee 51 fastened to an angle bracket 52, one
end of which is provided with a guide roller 53
interacting with a cam 50 driven in synchronous
rotation with the cylinder 48. The angle bracket 52 is
subjected to the action of a spring pushing the cam 51
radially against the screen 49. The vertex of the
angle bracket 52 is articulated to a fixed point 54.
The purpose of the cam 50 is to guide the squeegee 51,
as for the first screen cylinder 7, so that it is
moved away from the impression slot when a notch 30 in
the impression cylinder 6 lies in the impression slot.
For this third embodiment, the screen cylinder 48 does
not present a raised part, but the raised parts are
created in the impression slot by the interaction of
the front edge of the squeegee 51 which has the teeth
51a and the possibility of deforming the screen 49
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elastically. Thus, areas which are in contact with the
impression cylinder 6 are those areas of the screen 49
which are under the pressure of the teeth 51a of the
squeegee 51. The set-back parts 51b of the squeegee
correspond to the areas printed by the cylinder 7 or
the areas which it is desired not to print, the screen
49 in these areas not coming into contact with the
impression cylinder 6. It is clearly indispensable
that the screen 49 does not come into contact with the
areas already printed since the ink has not had the
time to dry and the dimensions of these areas 51b of
the squeegee are provided accordingly.
Finally, we have shown in Figure 12 a variant of the
third embodiment represented in Figure 10.
The screen cylinder 48' is provided between two
consecutive printing areas with two spaced-apart rings
55. It might be sufficient to have only a single ring
per space, depending on the width of the area which it
is desired not to bring into contact with the
compression cylinder. The role of these rings is to
ensure that the screen under the thrust of the
squeegee 51' will not come, over parts, into contact
with the impression cylinder. For this purpose, the
rings 55 have a diameter less than the diameter
enabling the screen 49' to be brought into contact
with the impression cylinder. The rings 55 are
preferably located at the ends of the areas which have
not to come into contact with the impression cylinder.
The rings 55 are preferably, but not exclusively,
arranged on the external surface of the screen.
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The invention is not limited to the embodiments which
have j ust been described, and other variants could be
envisaged, especially with regard to the configuration
of the raised parts of the second screen cylinder, as
well as the means for moving the squeegees radially
inside these cylinders. Furthermore, the invention
also relates to reel-fed printing machines.
It is also possible to provide more than two screen
cylinders, with parts in contact with the impression
cylinder which are offset with respect both to the
areas printed by the cylinder 7 and those printed by
the cylinder 8 or 28 or 48 or 48', and as long as the
dimensions and the placement of said cylinders so
allow, to have the possibility of printing more than
two non-superimposed areas in different colors with a
single impression cylinder.
Furthermore, the machine forming the subject of the
present invention may be adapted to any similar plant
or to the interior of a printing line comprising other
standard printing machines for security papers, such
as offset, intaglio, Orloff, etc.
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