EP0624466A1 - Stamp printing method on a printing machine, such as an offset press, and device therefor - Google Patents

Abstract

The invention relates to a method for the stamped printing of sheets of paper or card on a printing press (1), comprising a press cylinder (3) and a plate cylinder (4) of parallel axes. Prior to passing sheets between the cylinders (3, 4), a thin plate (13) covered with a photopolymer layer is fixed around the plate cylinder (4), on which layer is formed a pattern in relief and inside out, and the plate cylinder (4) is forcibly applied against the press cylinder (3) then, in order to print one face of the sheets (17b) as an impression, each sheet (17b) of paper or card is engaged between the cylinder (3, 4). The invention also relates to a device for the implementation of such a method. <IMAGE>

Description

The present invention relates to a stamped printing process for sheets of paper, cardboard or the like, on a printing machine, such as an offset press, and a device for carrying it out.

It is known to emboss sheets of paper or cardboard on typographic presses.

To this end, three embossing devices, described below, are commonly used to form raised and recessed patterns on sheets of paper or cardboard.

A first embossing device comprises a rotary press with two cylinders with parallel axes between which a strip of paper or cardboard is engaged, and two storage reels on which is wound the strip of paper or cardboard downstream and upstream of the rotary. One of the cylinders has a pattern engraved in relief on its surface and the other cylinder can have on its surface the same pattern engraved in hollow.

The cylinders are compressed against each other along their common generatrix in order to emboss the engaged strip. This device has many drawbacks, in particular a very high cost, because it is necessary to engrave a different cylinder for each new pattern, not to mention that the cost price of a single engraved cylinder is very high. Therefore, in practice, a uniform embossing of the entire strip is carried out in order to use the same engraved cylinder for different uses of the strip. Even if a partial embossing of the surface of the strip is carried out according to a particular pattern, that is to say that the strip has non-embossed locations commonly designated under the name of "windows" or "reserves", it is very difficult to cut the strip with precision because the marking on it can vary by a few centimeters. However, this cutting is necessary if we want to later apply colors or characters on the embossed sheet.

We therefore do not always obtain an exact superposition of the characters and colors with the previously embossed and reserved parts of the precut sheet.

A second embossing device comprises a press with two flat plates, a first plate being fixed and supporting on one face of the plates engraved in relief, and the second plate being articulated laterally in rotation on the first plate being able to compress the plates of the first deck.

The plates are fed sheet by sheet, each sheet being embossed by the plates engraved during the compression of the plates. The speed of production by this alternative embossing device is significantly slower (about 1,500 sheets per hour on average) than by the previous device, because in the latter, the press is fed by a scrolling strip. The cost price of each embossed sheet is therefore increased.

In addition, the second embossing device requires the use of engraved plates of great thickness, for example brass, copper or zinc, the unit cost of which is very high. It is also necessary to engrave a different plate for each new motif. Finally, because of the large contact surface of the plates, it takes a very high pressure to emboss a cardboard sheet in depth, and often several passages, of the order of six, are necessary to carry out the embossing, which results in a extra cost, and a waste of time. Devices with two plates generally do not have enough pressure to achieve a deep embossing of a cardboard sheet in a single pass.

A third embossing device comprises a rotary cylinder, the cylinder being able to compress a flat plate. This device is also fed sheet by sheet, each sheet winding on the upper part of the cylinder, and engaging between the lower part of the cylinder and the plate.

Embossed plates are mounted on the face of the plate which is compressed by the cylinder. The plate performs a horizontal translational movement perpendicular to the axis of the cylinder, in order to emboss the sheets.

The manufacturing speed by this alternative device is slightly faster than by the previous device (about 2,000 sheets per hour on average), but still significantly slower than by the first embossing device.

In addition, surprisingly, the pressure necessary to carry out a deep embossing of a cardboard sheet remains very high, and several passages are also necessary to carry out the embossing.

Also used in this device engraved plates of great thickness and therefore very expensive.

It is known to deposit on a printed or unprinted sheet, a film, such as a gilding or a color. This technique is generally known under the name of "gilding" and it is generally implemented using the last two embossing devices, described above, by rolling the film in front of the plates engraved in relief. The film is deposited on the sheet by hot pressing the two plates or the plate and the cylinder. During the laying of the gilding, the manufacturing speed is further reduced due to the fact that the presses have to be stopped to change the film reels when they are exhausted, and thus one falls at an average manufacturing speed of approximately 1,200 sheets per hour for the second device and approximately 1,500 sheets per hour for the third device.

The sheets of paper or cardboard are also subjected, during conventional embossing processes, to stresses which lead to the formation of "micro-cracks" in the folds of the sheet and to a deformation of its dimensions.

The initial mechanical qualities of the sheet are therefore altered and subsequent operations, in particular cutting, hot stamping and packaging, are carried out with difficulty because the location of the printed pattern loses its precision and the friction of the sheet on the different machines vary from sheet to sheet.

The object of the present invention is to propose a method and a stamped printing device which makes it possible to imprint hollow on one face, in the surface layer of a sheet, the most diverse patterns at low cost, with great simplicity and great speed, and which makes it possible to avoid the aforementioned drawbacks of conventional embossing processes.

Another object of the invention is to propose a method and a stamped printing device making it possible to imprint and to trace an ink simultaneously on the same printing machine.

The subject of the present invention is a stamped printing process for sheets of paper, cardboard or the like, on a printing machine comprising a pressure cylinder and a plate cylinder with parallel axes, characterized in that, beforehand when the sheets pass between the cylinders, a thin plate covered with a photopolymer layer is formed around the plate cylinder, on which a relief pattern is formed and upside down, and the cylinder is force applied plate against the pressure cylinder, then, to imprint one side of the sheets, each sheet of paper or cardboard is engaged between the cylinders.

This stamped printing process, unlike the already known embossing processes, allows to print in hollow only the front or back side of the sheet which is in line with the thin plate.

Thus, only the first layer or the surface layer of one face of the sheet is deformed during the stamped printing, which does not or very little alter the initial mechanical qualities of the sheet.

The risks of "micro-cracks" are also reduced because only the first layer of one face of the sheet is compressed.

Not undergoing dimensional deformation, the sheets can be perfectly identified for subsequent operations and the passage of the sheets on automatic machines is made reliable because the friction of the sheets on the machines remains constant.

The plate is generally made of steel, aluminum, plastic or a mixture of these.

• on dépose sur la plaque une couche uniforme d'une laque à base de résines polymères photosensibles,
• on dépose un masque en négatif sur la plaque pour former le motif en relief et on illumine la couche photopolymère en lumière ultraviolette au travers du masque.

To obtain a relief pattern on a plate, the following operations are carried out in sequence:

• a uniform layer of a lacquer based on photosensitive polymer resins is deposited on the plate,
• a negative mask is placed on the plate to form the relief pattern and the photopolymer layer is illuminated in ultraviolet light through the mask.

The unmasked areas of the photopolymer layer polymerize under exposure.
-then, to develop the plate, the unpolymerized resin is dissolved in a selective solvent in an "engraver" and the photopolymer layer is rinsed with water to evacuate the non-exposed areas of the photopolymer layer.

According to the present invention, an ink, such as a matt or glossy color or varnish, is advantageously deposited on the thin plate using ink rollers, for intaglio printing and simultaneously tracing a pattern on the sheets.

The present invention can in particular and advantageously be implemented on an offset press comprising ink rollers, a blanket cylinder constituting the plate cylinder, a second plate cylinder and a pressure cylinder.

Unlike a usual use of the offset press, in the present invention, a thin plate covered with a photopolymer layer is fixed around the blanket cylinder, instead of a blanket. To imprint the sheets, it is therefore not necessary to use the plate cylinder of the offset press or the ink rollers. In order to imprint a pattern on sheets, an offset press is usually used which is usually intended to transfer ink.

Advantageously, prior to the passage of the sheets, a printing plate is also fixed around the second plate cylinder on which a pattern is formed at the place, then an ink, such as a color or a varnish, on the printing plate using the ink rollers, and the ink is transferred onto the thin plate, to imprint the pattern on the sheets and simultaneously transfer a color or a varnish.

In a particular embodiment of the invention, each of the two opposite edges of the thin plate covered with a photopolymer layer or of the printing plate is fixed in the jaws of a wedging bar and mounts each timing bar on the blanket or plate cylinders.

An ink, such as a color, a varnish or characters, can be transferred onto the sheets, either before or after intaglio printing according to the stamped printing process of the present invention.

Likewise, a film, such as gilding or color, can be deposited by hot compression on the sheets, either before or after intaglio printing according to the stamped printing method of the present invention.

Advantageously, the intaglio printing is carried out in a single passage of each sheet between the rolls, unlike known embossing devices.

In a particular embodiment of the invention, there is formed in relief on the plate several identical reproductions of the pattern which must be imprinted on the sheet, because there is sufficient pressure to print all the reproduced patterns in a single pass.

During a usual ink transfer on sheets using an offset press, the blanket cylinder and the pressure cylinder hardly touch.

For example, for a pressure cylinder of length equal to approximately 1 meter, and having a crushing width of approximately 10mm, a pressure equal to 20 kg / cm 2 is exerted between the blanket cylinder and the pressure cylinder, c that is to say a pressing force equal to about 20 KPa.

To print intaglio sheets, this pressure is generally doubled.

The present invention also relates to a printing device stamped with sheets of paper or cardboard for the implementation of the method described above, characterized in that it comprises a pressure cylinder, a plate cylinder , a thin plate covered with a photopolymer layer in which a pattern is formed in relief and upside down, means for fixing the plate around the plate cylinder and adjustment means for applying the plate cylinder against the pressure cylinder.

Advantageously, the stamped printing device further comprises ink rollers.

To better understand the invention, we will describe below, by way of purely illustrative and nonlimiting example, an embodiment shown in the accompanying drawing in which the single figure is a schematic side view of the device stamped printing according to the present invention.

The figure shows an offset press 1 comprising a frame 2 in which are mounted, articulated in rotation about parallel axes, a pressure cylinder 3, a blanket cylinder constituting a first plate cylinder 4, a second cylinder plate 5 and two drive cylinders 6. In the vicinity of the upper part of the plate cylinder 5 is mounted an ink assembly 7. The ink assembly 7 comprises a plurality of ink rollers 7 a as well as a lever 7 b adapted bringing the ink rollers 7 a into contact with the upper part of the plate cylinder 5. The ink rollers 7 a contain ink, such as matt or glossy colors or varnishes.

A wetting assembly 8 is in the vicinity of a lateral part of the plate cylinder 5. The wetting assembly 8 comprises wetting rollers 8 a and a lever 8 b capable of bringing the wetting rollers 8 a into contact with the lateral part of plate cylinder 5. Generally, the wetting rollers 8 a contain water.

Two levers 9 and 10 allow the blanket cylinder 4 and the plate cylinder 5 to be displaced respectively in the vertical direction in order to adjust the contact pressure between these two cylinders and the pressure cylinder 3.

The blanket cylinder 4 and the plate cylinder 5 each have two timing bars 11 and 12, respectively. Each of the timing bars 11 and 12 has jaws.

A thin plate 13 covered with a photopolymer layer in which a pattern is formed in relief and upside down, is fixed around the blanket cylinder 4 in the jaws of the wedging bars 11.

During the usual use of the offset press 1, a blanket, not shown in the figure, is fixed around the blanket cylinder 4 in place of the thin plate 13, in order to produce a double transfer of the ink.

A thin plate 14 covered with a photopolymer layer in which a pattern is formed in relief and at the place, is fixed around the plate-carrying cylinder 5 in the jaws of the wedging bars 12. This thin photopolymer plate 14 can be replaced by a printing plate on which a flat pattern is formed and at the place comprising a printing part which is more sensitive and more receptive to ink which is a fatty liquid, and a non-printing part. more receptive to water which is a lean liquid. In this case, it is necessary to use the damper assembly 8.

A guide belt 15 is wound around the driving cylinder 6, and comprises three gripping members 16 equally spaced, such as clamps, in which the end is clamped downstream of a printed sheet 17a. The printed sheets 17 a are driven by the gripping members 16 by rotation of the drive cylinders 6 about their axis.

A gripping member 18, such as a clamp, is mounted on the surface of the pressure cylinder 3 and said gripping member 18 can clamp the downstream end of a sheet 17b not yet printed.

A sensor 19 is mounted slightly upstream of the pressure cylinder 3 in the vicinity of the place where the downstream end of the sheet 17 b not yet printed is clamped by the gripping member 18.

A margin table 20, slightly inclined relative to the horizontal, is located upstream of the pressure cylinder 3. The upstream end of the margin table 20 is at a level slightly higher than that of its downstream end, which facilitates the translational movement of the sheets 17b towards the pressure cylinder 3. For this purpose, the margin table 20 includes drive belts not shown in the figure.

A locating cleat 21 serves as a stop for the sheet 17 b and measures its placement so that the pattern of the plate 13 is perfectly superimposed on the pattern already printed on the sheet 17 b .

A feeder 22 is mounted on the frame 2 in the vicinity of the upstream end of the margin table 20. The feeder 22 comprises two suction cup members 22 a , capable of moving in horizontal translation between a first stop position, in which the two suction cup members 22 a respectively grip the downstream end and the center of a sheet 17 b on the top of a stack of sheets stored on a vertically sliding plate (24), and a second stop position, in which sheet 17 b is deposited on the upstream part of the margin table 20 The feeder 22 further comprises a lever 22 b capable of engaging the suction cup members 22 a with the stack 23.

A carriage 25 provided with a stop 25 a is plumb with the part of the belt 15 which is suspended between the two drive cylinders 6.

The printed sheets 17 a are deposited in the carriage after being released by the gripping members 16 when these arrive at the vertical of the stop 25 a .

A guide means 26 is mounted under the lower part of the mat 15 in order to support and guide the sheet 17 a as long as it has not yet been deposited in the carriage 25.

The operation of the device according to the invention is as follows:

The feeder 22 grabs a sheet 17 b from the stack 23 of sheets and deposits it on the margin table 20. The sheet 17 b is driven on the margin table 20 by drive belts to the locating cleat 21. Then, the sheet 17b is clamped by the gripping member 18 when the sensor 19 detects the presence of the downstream end of the sheet 17b in the vicinity of said gripping member 18. The pressure cylinder 3 then drives, in rotation around its axis, the sheet 17 b which engages between the pressure cylinder 3 and the blanket cylinder 4 on which the thin plate 13 covered with a photopolymer layer has been previously mounted. The sheet is printed intaglio, and possibly ink is transferred there during its passage between the rolls. Then the printed sheet 17 a is gripped by a gripping member 16 mounted on the mat 15 wound around the two drive cylinders 6. The drive rolls 6, by rotation about their axis, drive the printed sheet 17 a up to 'vertical to the carriage 25 where the printed sheet 17 a is released by the gripping member 16 when the latter is vertical to the stop 25 a .

In a variant not illustrated, an offset press can be used comprising several blanket cylinders 4, several plate cylinders 5 and / or several ink rollers 7 cooperating with the same pressure cylinder 3.

In another variant not illustrated, a printing machine can be used comprising only one pressure cylinder and several plate cylinders on which ink rollers may possibly be applied.

Still in another variant not illustrated, a printing machine can be used comprising a single pressure cylinder cooperating on the one hand, with a blanket cylinder and a plate cylinder for the ink transfer, and, on the other hand, with a plate cylinder for intaglio printing.

Although the invention has been described in connection with a particular embodiment, it is obvious that it is in no way limited thereto, and that it can be brought to many variations and modifications without departing from its scope or of his mind.

Claims (7)

Method for stamped printing of sheets of paper or cardboard on a printing machine (1) comprising a pressure cylinder (3) and a plate cylinder (4) with parallel axes, characterized in that, prior to passage of the sheets between the cylinders (3,4), a thin plate (13) is covered around the plate cylinder (4) covered with a photopolymer layer on which is formed a pattern in relief and upside down, and the plate cylinder (4) is applied by force against the pressure cylinder (3), then to imprint one side of the sheets (17 b ), each sheet (17 b ) of paper or cardboard between the cylinders (3,4). Stamped printing method according to claim 1, characterized in that an ink, such as a matt or glossy color or varnish, is deposited on the thin plate (13) using ink rollers (7 ), for intaglio printing and simultaneously tracing the pattern on the sheets. Stamped printing process according to either of Claims 1 and 2, characterized in that the printing machine is an offset press (1). Stamped printing method according to claim 3, in which the offset press (1) comprises a second plate cylinder (5) characterized in that, prior to the passage of the sheets, there is also fixed around said second cylinder plate (5) a printing plate (14) on which a pattern is formed at the place, then an ink, such as a color or a varnish, is deposited on the printing plate (14) at using the ink rollers (7) and the ink is transferred onto the thin plate (13), to imprint the pattern and transfer the ink simultaneously onto one side of the sheets. Stamping printing method according to any one of the preceding claims, characterized in that each of the two opposite edges of the plate (13,14) is fixed in the jaws of wedging bars (11,12) and the 'each timing bar (11,12) is mounted on the cylinders (4,5). Printing device embossed with sheets of paper or cardboard, for implementing the method according to any one of the preceding claims, characterized in that it comprises a pressure cylinder (3), a plate cylinder (4), a thin plate (13) covered with a photopolymer layer on which a pattern is formed in relief and upside down, means for fixing (11) the thin plate (13) around the plate cylinder (4) and adjustment means (9) for applying the plate cylinder (4) against the cylinder pressure (3). Stamped printing device according to claim 6, characterized in that it further comprises ink rollers (7).

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