EP0706456A1

EP0706456A1 - Device for the adjustment of a flexographic printing machine unit

Info

Publication number: EP0706456A1
Application number: EP94909157A
Authority: EP
Inventors: Bernard Depond
Original assignee: SEROMA
Current assignee: SEROMA
Priority date: 1993-03-09
Filing date: 1994-03-07
Publication date: 1996-04-17
Also published as: FR2705612A1; WO1994020299A1; AU6210494A; CA2164640A1

Abstract

Device for the adjustment of a unit in a flexographic printing machine which includes at least two. Each unit includes a continuous tensioned paper web (13) moving successively through each of the units, ink means (16) with an ink fountain (22), an inking roller (20), printing means (26) with at least one co-operating plate holder roller (28) movable in vertical translation and designed to be in contact with the inking roller (20), means (30) for guiding the paper web to be printed. The device is characterized in that the first (44) and fourth tangent points are stationary, the second (46) and third (48) points are always simultaneously disposed within or without the two straight lines (41, 43) perpendicular to the straight line (45) joining the first (44) and fourth (50) points and passing by the first (44) and fourth (50) points so as to maintain constant the web length between the tensioning rollers (36, 38) and an almost identical setting of the plate in relation to the paper web (13).

Description

DEVICE FOR ADJUSTING A GROUP OF A FLEXOGRAPHJQDE PRINTING MACHINE

The subject of the present invention is a device for adjusting the contact pressure between an inked plate roller and a movable strip of paper in line with a pressure roller in a flexographic printing machine.

Flexographic printing machines generally comprise a plurality of successive printing groups, identical in their arrangement and in their operation, the printing plate and the ink color being only modified from one group to another.

A strip of paper passes through each of the groups successively. Each group is made up of:

- Inking means comprising an inkwell containing the liquid ink, a first bubbling roller which agitates the ink and a second ink roller known as "anilox".

- Printing means proper which comprise a plate-carrying roller on which is placed the plate which reproduces the pattern to be printed. This cliché roller is movable in vertical translation to come into contact with the anilox along a generator, which causes the cliché to be inked. This adjustment is very delicate because the two rollers placed too close cause too much ink deposition, the two rollers arranged too far apart lead to ink defects.

- means for guiding the paper strip comprising at least one input roller, one pressure roller, one tension roller and one output roller so that the four rollers are arranged at the vertices of a substantially rectangular quadrilateral, so preferential. The pressure roller is designed to receive the plate roller in support in order to deposit the ink following the pattern of the plate on the paper strip and the middle tension roller has a complementary guiding role.

- means for drying the ink thus deposited on the paper strip before entering a new group.

The adjustment of the application pressure of the plate roller on the ink roller and on the paper strip passing over the pressure roller is an important problem because only the plate roller is vertically movable and this unique degree of freedom must allow the adjustment of two application pressures simultaneously. These application pressures are also called "keys" in the printing field.

In addition, once these application pressures have been set, it is known that during operation, certain parameters will vary, such as the humidity of the paper or the rise in ink, which requires very precise adjustments of these application pressures.

One solution would be to also make adjustable the pressure roller but another constraint occurs, due to the timing of the paper strip. Indeed, the strip of paper scrolls through the printing units and it is imperative to synchronize them with respect to each other so that the different colors and the different patterns are deposited successively and perfectly aligned with respect to the primary pattern that was printed.

To ensure this synchronization, action is taken on the speed variator of the drive motor of the ink roller which drives, in known manner, the plate-carrying water by a set of gears. Several solutions have been proposed, in particular an article "Papier und Kunststoff-Verarbeiter Interna¬ tional" Number 2, December 1987, page 28-33, which proposes an adjustment in vertical translation of the plate roller and an adjustment in horizontal translation. ¬ zale of the ink roller.

This solution makes it possible to adjust one of the parameters, that is to say the ink intake by the plate holder, but it does not solve the problem of adjusting the ink transfer on the paper strip.

However, we know that the operator first sets the ink take-up key on the plate holder and then the transfer key on the paper strip. English patent GB-A-817,472 describes a printing unit in which there is a strip of paper plated on a tension roller mounted at the end of an arm movable in rotation about an axis disposed at the other end of this arm. The plate roller is also carried by the end of a movable arm rotating at its other end.

The transfer key on the paper is thus adjustable.

As for the ink take-up key, it is adjusted by means of a set of two rollers, the first intermediate roller being fixed in translation and in contact with the printing plate roller and the second water roller being adjustable and immersed in the inkwell which thus ensures the transfer of an ink film of adjustable thickness on the first intermediate roller.

Such an arrangement is unsuitable for applications to current flexographic printing machines with several successive printing groups because the setting is not taken into account, only the adjustment of the different rolls relative to each other in the same group is envisaged.

The present invention provides an adjustment device which overcomes the drawbacks of the prior art, which allows very precise adjustments of the keys on each of the groups during operation while retaining the timing of the different groups with respect to the strip, which is simple which makes it reliable and leads to a low cost price and which is adaptable to certain existing machines.

To this end, the device for adjusting a group of a flexographic printing machine which comprises at least two, according to the invention, each group comprising a continuous strip of paper, ten¬ due, circulating successively in each of the grou¬ pes, inking means with an inkwell, an ink roller, printing means with at least one movable plate roller in vertical translation intended to cooperate by contact with the ink roller, means guiding the strip of paper to be printed with at least one upstream tension roller, a pressure roller, a middle tension roller and a downstream tension roller, defining an upstream strand and a downstream strand, a first point of tangency between the upstream strand and the upstream tension roller, a second point of tangency between this upstream strand and the pressure roller, a third point of tangency between the middle tension roller and the downstream strand, and a fourth point of tangency between the downstream strand and the roller downstream tensioner, the pressure roller being pre¬ seen to cooperate with the plate-carrying roller and mounted on a movable support equipped with means of displacement in translation along a straight line or a curve so as to adjust the distance between the strip of paper coated on the roller and the cliché of the cliché roll, is characterized in that the first and fourth points of tangency being fixed, the second and third points are always arranged simultaneously inside or simultaneously outside the two straight lines perpendicular to the right joining these first and fourth points and passing through these first and fourth points so as to keep constant the length of strip between the tension rollers and an almost identical setting of the plate with respect to the strip of paper. According to one embodiment of the invention, the sup¬ port of the pressure roller is an arm whose axis of rotation is located substantially in the middle of the segment joining the axes of rotation of the two ten¬ deur rollers.

According to another embodiment, the axis of rotation of the pressure roller is mounted movable in trans¬ lation along a straight line parallel to the right joining the axes of the two tensioning rollers.

According to a preferred embodiment, the single tensioning wheel is replaced by two rollers integral with a bar giving them a constant gap, this bar being movable in translation following a straight line parallel to the right joining the axes of the two tension rollers.

The present invention is described below according to a particular embodiment and with a varian¬ te, with reference to the accompanying drawings in which: - Figure 1 shows a schematic view in side elevation of a group A, in line full and part of a group B associated, in continuous line, of a flexography machine with the device for adjusting the contact pressure according to the invention, FIG. 2 represents a partial perspective view of an embodiment of the device for adjusting the contact pressure according to the invention mounted on a group such as group A in FIG. 1,

FIG. 3 represents a simplified view of the kinematics of the device for adjusting the contact pressure, and

- Figure 4 shows a simplified view of the kinematics of the contact pressure adjustment device for an alternative embodiment with a pressure roller, eliminating the middle tension roller.

In FIG. 1, two groups 10A and 10B are shown of a flexographic printing machine as well as means 12 for feeding the paper strip 13.

These supply means are known and are only shown very partially. Similarly, on leaving the machine, there are provided complex means for tensioning the paper strip as well as means for receiving the printed paper strip.

All these complementary members are not part of the present invention and are therefore not described.

We admit that a strip of paper is circulated with a given speed and subjected to a given tension, through groups A and B and others since the number of groups depends on the number of colors included in the pattern. to reproduce on the paper strip.

The machine comprises a solid chassis 14 preventing any deformation, on which the groups A, B and others are mounted. Each group includes:

inking means 16 with a bubbling roller 18, an ink roller 20 and an inkwell 22 containing ink 24, - printing means 26 comprising a plate roller 28,

guide means 30 with an upstream tensioning roller 32, a pressing roller 34, a middle tensioning roller 36 and a downstream tensioning roller 38, defining two portions of strip called upstream strand 40 and downstream strand 42, a first, a second, a third and a fourth point of tangency respectively 44, 46, 48 and 50, disposed respectively between the upstream tension roller and the upstream strand, between the upstream strand and the pressure roller, between the median tension roller and the downstream strand, between the downstream strand and the downstream tension roller, and

drying means 52 shown in the form of a column type dryer 54 through which the strip of paper 13 passes.

As is also shown in FIG. 2, the plate roller 28 is mounted movable in vertical translation by means of height adjustment 56 which comprise a screw-nut system 58, the translation taking place in the direction of the double arrow 60.

The support roller support shaft 62 is rotatably mounted and driven by a lateral pinion, not shown for clarity of the drawing, integral with this shaft 62 which meshes with a lateral pinion also not shown, integral with the shaft 64 of the ink roller 20.

The two ink rollers and plate holder are linked in rotation. A common electric motor, with variable speed drive, meshes by its pinion integral with its drive shaft with the lateral pinions of the two ink roller and plate holder so as to be able to adjust the positioning of the rollers and their vi¬ rotation tesse, as will be useful for the implementation of the machine, described later¬ ment. The height adjustment means 56 are integral with a beam 66 movable in translation along the double arrow 68 by means of displacement in translation 70 which also include a screw-nut system 72. This system essentially allows the beam to take two extreme positions front and rear.

Thus any movement of the beam causes the simultaneous de¬ placement of the plate roller 28. As shown in Figure 1, the tensioning rollers 32 and 38 are mounted in rotation relative to the frame and fixed in translation for a given arrangement of the pressure rollers 34 and middle tensioner 36.

The pressure rollers 34 and middle tensioner 36 are rotatably mounted and are integral with a carriage 74 movable in translation relative to the beam 66, along the double arrow 75 by means of displacement in translation 76 which comprise a screw system. nut 78. The implementation of group A is now described in order to show the advantages which the solution according to the present invention provides. The strip of paper 13 being in circulation, it passes under the upstream tension roller 32, on the presser water 34, on the middle tension roller 36, through the dryer 54 then under the downstream tension roller 38 before entering group B. The paper strip is adjusted in tension, the plate roller 28 carries the sleeve with its plate and it is arranged above the paper strip and above the ink roller 20, the beam being in the front position.

The contact pressure of the plate roller 18 on the ink roller 20 is adjusted using the translation means 56, more particularly using the screw-nut system 58.

Once the correct key has been set, the paper strip 13 is in the immediate vicinity of the key holder roller. It is then necessary to adjust the key of the paper strip on the printing plate roller, then the initial setting of the strip is adjusted.

We therefore act on the electric motor which rotates the plate roller to wedge a mark on the pattern of the plate roll with a mark carried by the strip of paper. as has been seen previously, it is often necessary to adjust the key during operation. The operator acts on the means of displacement in translation 76 and more particularly with the aid of the screw-nut system 78, it approaches or moves back the cha¬ riot relative to the beam 66 so as to adjust the touch. This is where the particular arrangement of the invention comes into play, which makes it possible to compensate by maintaining the initial setting while allowing this adjustment of the key, which is now explained with the aid of FIG. 3. The rollers in solid line correspond to the forward position of these rollers and in continuous line to the rearward position.

It can be seen that for a translational movement of the pressure and middle tension rollers, the displacement on the paper strip of the point of tangency is negligible.

In fact, the curve Ç is the circle which has for its center the point of tangency 44 which passes through 46A and this circle passes through the point 47A of tangency of the strip of paper with the printing roller, but also by the point 47B of tangency of the paper strip with the plate roller. This is due to the characteristic of the adjustment device according to which the two points 46 and 48 are arranged outside the perpendicular lines 41, 43 to the right 45 joining the centers of the two tension rollers and passing through the first and fourth points of tangency 44 and 50. Thus when the angle α, defined by the upstream strand 40 and the first perpendicular 41, decreases, the angle β, defined by the downstream strand 42 and the second perpen¬ dicular 43, increases.

Similarly, the decrease in length of the strand 40 is offset by the increase in length of the strand 42.

This compensation is carried out identically if the two tangent points 46 and 48 are simul¬ taneously between the two perpendicular lines 41 and 43 over the adjustment range envisaged.

It is therefore understandable that the touch of the paper strip with the plate holder can be adjusted very precisely, which is of crucial importance since it directly affects the quality of the visible element of the flexographic printing job.

In addition, this adjustment can be made for one of the groups without adjusting the machine. Thus, a change of strip or a resumption of service with change of the plate-carrying roller is effected with durations considerably reduced compared to the devices of the prior art. Variations in paper quality from the same spool can be taken into account, in particular variations in tension between the lead and the core of the spool.

According to a variant of the invention, shown diagrammatically in FIG. 4, the carriage movable in translation and the two rollers is replaced by a single roller 80 mounted for rotation on an arm 82 pivoting around a point 84 disposed on the right joining the axes of the two tension rollers, in the middle. The compensation effects are identical.

Another advantage of the device of the invention flows from its arrangement and appears when one wishes to temporarily interrupt printing or when one is obliged to do so. Indeed, the operator, by maneuvering means for translational movement 70, moves the beam 66 back to the rear position.

In this configuration, the plate roller 28 always meshes with the pinion of the ink roller thanks to the length of the pinion teeth, because the displacement is very small but sufficient for the plate roller to no longer be in contact with the roller ink, which prevents fouling. In addition, the plate roller is in contact with the paper strip, which allows the removal of all the ink from the plate roller on this strip, which suffices to allow it to scroll for a few moments.

Upon resumption, simply approach the beam 66 which returns to its initial position, the plate roller is chocked without the need for additional adjustments.

All the elements described were for vertical mounting, but the same would be true for a horizontal arrangement.

The components such as screw-nut systems can be replaced by electric jacks with micrometric advance or by any other equivalent means such as hydraulic or pneumatic jacks.

Claims

CLAIMS 1. Device for adjusting a group 10 of a flexographic printing machine which comprises at least two, each group comprising a strip (13) of continuous, stretched paper, circulating successively in each of the groups, inking means (16) with an inkwell (22), an inking roller (20), printing means (26) with at least one film holder roller (28) movable in vertical translation provided for cooperate by contact with the ink roller, guiding means (30) of the strip of paper to be printed with at least one upstream tension roller (32), a pressure roller (34, 80) and a downstream tensioner roller (38 ), defining an upstream strand (40) and a downstream strand (42), a first tangent point (44) between the upstream tension roller (32) and the upstream strand (40), a second tangent point (46 ) between this upstream strand (40) and the pressure roller (34), a third point of tangency (48) between the tension roller (34, 80) and the downstream strand (42 ), and a fourth point of tangency (50) between the downstream strand (42) and the downstream tensioning roller (38), the pressure roller (34, 80) being provided to cooperate with the plate roller (28) and mounted on a mobile support (66, 82) equipped with means of displacement (66, 70) in translation along a straight line or a curve so as to adjust the distance between the strip of paper pressed on the roll and the plate of the support roll plate, characterized in that the first and fourth points of tangency (32, 50) being fixed, the second and third points (46, 48) are always arranged simultaneously inside or simultaneously outside the two straight lines (41, 43) perpendicular to the straight line joining these first and fourth points and passing through these first and fourth third points so as to keep constant the length of strip between the tensioning rollers (32, 38) and an almost identical setting of the plate relative to the strip of paper.

2. Adjusting device according to claim 1, characterized in that the support of the single pressing roller (80) is an arm (82) whose axis of rotation is located substantially in the middle of the segment joining the axes of rotation of the two tension rollers (32, 38).

3. Adjusting device according to claim 1, characterized in that the axis of rotation of the pressure roller (80) is mounted movable in translation along a straight line parallel to the right joining the axes of the two tensioning rollers .

4. Adjustment device according to any one of the preceding claims, characterized in that the single tension roller (80) is replaced by a pressure roller (34) and a middle tension roller (36) integral with a carriage ( 74) giving them a constant distance, this carriage being movable in translation along a straight line parallel to the right joining the axes of the tensioning rollers (32, 38).