EP0403434B1 - Method for preparing as well as fixing and installation for fixing printing plates on a cylinder of a gravure printing machine - Google Patents

Abstract

To fix two plates (3, 4) on the cylinder formed by a shell (1) or by a plate cylinder of an intaglio printing machine, two axial grooves (2) are formed on this cylinder, in such a way that the plane of one of the lateral faces of each groove (2) is inclined relative to the axis of the cylinder. Welded to the concave face of the two ends of each plate (3, 4) is a batten (5, 6), of which the face adjacent to the end of the plate is perpendicular to said plate. The edge of each plate (3, 4) projecting beyond the corresponding batten (5, 6) is then cut off in such a way that the edge of the plate forms with the face of the batten a continuous surface and that the sum of the lengths of the plates is equal to the length of the periphery of the cylinder. Subsequently, the plates are arranged on the cylinder (1) by introducing the adjacent battens (5, 6) into a groove (2), and the free space of the groove is filled by a wedge-shaped bar (7) for tensioning the plates and for obtaining a butt joint. <IMAGE>

Description

The present invention relates to a method and an installation for fixing printing plates on a cylinder formed by a ferrule or a plate cylinder of an intaglio printing machine, according to the preamble of claim 1, respectively claim 6.

In the printing field, the term "plate cylinder" is generally understood to mean the assembly composed of the body of the cylinder which carries printing plates and of the shaft on which this body of the cylinder is integral, and under the term "ferrule" only the cylindrical tube or mantle without a shaft. Plate cylinders are generally used in sheet printing machines and must be installed as an assembly in the machine bearings, respectively completely disassembled from the machine by removing the bearing shaft, while the ferrules , generally used in coil printing machines, can be simply mounted on the shaft, respectively removed from their shaft, the printing plates being mounted on the ferrule before it is mounted on the shaft.

As the present invention relates to both plate cylinders and ferrules, it has been agreed to use the term "cylinder" to define both when spoken of generally in the description and in the claims.

• Les plaques d'impression, après leur fixation sur la périphérie du cylindre, doivent se trouver bord à bord sans aucune séparation entre elles et former ainsi une surface continue, pour éviter des chocs sur cette surface dûs aux très grandes pressions auxquelles est soumis le cylindre lors de l'essuyage et de l'impression, chocs qui risquent de provoquer des déformations des plaques d'impression, notamment sous l'influence des efforts tangentiels dus au roulement de deux cylindres en contact. En outre, cette surface périphérique continue est nécessaire dans le cas des machines d'impression à la bobine afin d'obtenir une impression en continu sans pertes de papier.
• Il faut aussi avoir une concentricité parfaite du cylindre afin, d'une part, assurer un essuyage parfait après encrage et, d'autre part, pour éviter une pression irrégulière sur le cylindre lors de l'impression ou de l'essuyage qui tendrait, pendant ces opérations, à déformer les plaques d'impression montées.
• Pour des raisons d'économie, il convient de réutiliser la virole dans les machines d'impression à la bobine en y fixant d'autres plaques d'impression, car son alésage intérieur étant légèrement conique pour épouser parfaitement la forme conique correspondante de l'arbre de la machine sur lequel elle est fixée lors de l'impression, la fabrication de cette virole demande un usinage extrêmement précis et le coût de fabrication est très élevé.

For intaglio printing, this cylinder must meet certain very strict requirements which guarantee, on the one hand, the sharpness of the print and, on the other hand, the perfect register between the different images. The main requirements are:

• The printing plates, after their fixing on the periphery of the cylinder, must be edge to edge without any separation between them and thus form a continuous surface, to avoid shocks on this surface due to the very great pressures to which the cylinder is subjected. during wiping and printing, shocks which may cause deformation of the printing plates, in particular under the influence of tangential forces due to the rolling of two cylinders in contact. In addition, this continuous peripheral surface is necessary in the case of web printing machines in order to obtain continuous printing without loss of paper.
• It is also necessary to have perfect concentricity of the cylinder in order, on the one hand, to ensure perfect wiping after inking and, on the other hand, to avoid irregular pressure on the cylinder during printing or wiping which would tend, during these operations, to deform the mounted printing plates.
• For reasons of economy, it is advisable to re-use the ferrule in the printing machines with the reel by fixing other printing plates there, because its internal bore being slightly conical to marry perfectly the corresponding conical shape of the shaft of the machine on which it is fixed during printing, the manufacture of this ferrule requires extremely precise machining and the manufacturing cost is very high.

A method as described in the preamble of claim 1 and an installation as described in the preamble of claim 5 are known from US Patent 1,461,068 (Fig. 10) for effecting, during the fixing of the plate, a tightening of that -this in the peripheral direction. For this, metal rods should be welded to the lower surface of the plate such that each edge of the plate and the outer lateral face of the corresponding rod is in the same plane. This condition is necessary in order to be able to bring the edges of the plate, respectively of the plates as well as of said lateral faces of the rods, until they lie flat.

The object of the present invention is to propose a process for preparing and fixing intaglio printing plates on a plate cylinder or on a ferrule in an easier manner while ensuring a perfectly continuous surface of the plate, respectively printing plates stretched on the cylinder in two directions, namely peripheral and radial.

To achieve this object, the method according to the invention is characterized by the characteristic clause of claim 1.

This process has the advantage that the bending of the plates facilitates their mounting and that, thanks to the rods, a perfect bond is ensured flat-joint of the adjacent edges of the stretched plates and therefore a continuous printing surface, without any separation, this which avoids any subsequent rectification.

The positioning of the plates is done quickly since it suffices to introduce the rods, which are provided with the two ends of each plate, and the other elements in the corresponding grooves and to obtain the desired tightening by the cuneiform bars functioning as corner.

The method according to the invention can be used both for fixing intaglio plates to a ferrule for printing on the spool and to a plate cylinder for printing to the sheet. In particular, for sheet printing this way of fixing the plates makes it possible to avoid the empty zones between two consecutive plates.

Although we have always spoken above of plural plates, the invention also refers to the case where the cylinder is intended to carry a single plate.

Preferred embodiments of the method result from dependent claims 2 to 4.

The invention also relates to an installation for carrying out the process, installation which is defined by claim 5. Preferred alternative embodiments of the installation are defined by claims 6 to 9.

• La figure 1 est une vue partielle en coupe de deux plaques d'impression munies de deux baguettes de fixation;
• La figure 2 est une vue partielle en coupe radiale d'une virole munie d'une rainure pour la mise en place des baguettes de fixation, selon une première variante;
• La figure 3 est une vue latérale partiellement en coupe radiale de la virole selon figure 2, munie de deux plaques d'impression taille-douce, fixées selon cette première variante; la virole e'tant munie de secteurs annulaires pour tendre axialement les plaques.
• La figure 4 est une vue en coupe selon la ligne IV-IV de la figure 3,
• La figure 5 est une vue analogue à celle de la figure 3 d'une deuxième variante d'exécution dans le cas d'un cylindre porte-plaques.
• La figure 6 est une vue en coupe selon la ligne VI-VI de la figure 5.

The invention will be described in more detail using the accompanying drawings.

• Figure 1 is a partial sectional view of two plates printing with two fixing strips;
• Figure 2 is a partial view in radial section of a ferrule provided with a groove for the establishment of the fixing rods, according to a first variant;
• Figure 3 is a side view partially in radial section of the ferrule according to Figure 2, provided with two intaglio printing plates, fixed according to this first variant; the ferrule being provided with annular sectors for axially tensioning the plates.
• FIG. 4 is a sectional view along line IV-IV of FIG. 3,
• Figure 5 is a view similar to that of Figure 3 of a second alternative embodiment in the case of a plate cylinder.
• Figure 6 is a sectional view along line VI-VI of Figure 5.

According to FIGS. 1 to 3, as many axial grooves 2 (FIG. 2) are formed on the peripheral surface of a ferrule 1 as the number of printing plates intaglio that must be attached to it. In the example shown, two printing plates 3 and 4 have been chosen which must be fixed to the shell 1. In FIG. 1, only the ends of two plates 3 and 4 have been shown, the other two ends of the plates being symmetrical and prepared identically. The groove 2 (fig. 2) made by milling and precise machining is formed so as to present an absolutely flat bottom 2.1 and two lateral faces 2.2 and 2.3 which are perpendicular to the bottom 2.1 and inclined relative to the axis of the ferrule forming thus a wedge-shaped groove.

Metal rods 5 and 6 are prepared which will be fixed to the ends, parallel to the axis of the ferrule, of two plates 3 and 4, as well as similar rods for the other ends of two plates 3 and 4. Each of the rods 5, 6, the height of which is less than the depth of the groove 2, has a trapezoidal shape having lateral faces 5.1 and 5.2, respectively 6.1 and 6.2, the face 5.1, respectively 6.1 being inclined, a lower face 5.3, respectively 6.3 , as well as an upper face 5.4, respectively 6.4, which is curved and adapted to the curvature of the peripheral surface of the shell 1. The faces 5.2, respectively 6.2 of the two rods 5, 6 are intended, in the assembled state of the plates, and after machining, as described later, to be brought one against the other in close contact.

The printing plates 3 and 4 after having been prepared by known means and each having a length slightly greater than the half-periphery of the ferrule 1 are bent with a radius of curvature less than that of the radius of the ferrule. Then, the rods 5, 6, as well as the corresponding rods at the opposite ends, are fixed exactly on the ends of the two plates 3, 4, such that the length of the assembly of the plates, taken between said faces 5.2 and 6.2, is equal to the circumference of the ferrule. The strips are fixed preferably by laser welding, which prevents any deformation of the printing plates. After carrying out this fixing, the end of each of the plates is machined so as to form a continuous surface between the face 5.2 of the strip 5 and the end of the plate 3, as well as between the face 6.2 of the strip 6 and the end of the plate 4.

The fact that the two plates were bent with a radius of curvature less than that of the ferrule allows the plates, once ground, to remain in place by the tightening obtained because of this difference in radius of curvature.

In FIGS. 3 and 4 is shown the installation for fixing printing plates 3, 4 provided with rods 5, 6 according to FIG. 1, on a ferrule 1 provided with a groove 2 according to FIG. 2.

There is inside each groove a T-shaped section 30 fixed by screws 31 introduced by radial housings inside the ferrule 1, the seal being ensured by O-ring seals 32, the face lower 30.1 of the profile 30 is inclined relative to the plane of the bottom of the groove 2.1.

For the establishment of the plates 3, 4 there is available for each groove a pair of removable rods 33a, 33b and two pairs of wedge bars 34a, 34b and 35a, 35b. The rods 33a and 33b have, on the one hand, a notch of shape conjugated to that of the rods 5 and 6 and on their lower part a housing making it possible to partially surround the profile 30 leaving a free space between the inclined face 30.1 of the profile and the lower part of each of the rods 33a, 33b.

The positioning is done as follows: the rods 33a and 33b are introduced into each groove 2, then the rods 5, 6 fixed to the ends of the plates 3, 4 are placed there, the first pair of wedge bars 34a is introduced , 34b to ensure the positioning in the peripheral direction of the rods and therefore of the printing plates. In order to ensure the positioning of the assembly in the radial direction, the second pair of wedge bars 35a and 35b are introduced into said free space between the inclined face 30.1 of the profile 30 and the lower part of each of the rods 33a, 33b. thus ensuring the holding of the assembly in the radial direction.

By the introduction of the wedge bars, the two faces 5.2 and 6.2 of the two rods 5, respectively 6, were brought into close contact, and therefore also the respective ends of the plates 3, 4, which made it possible to tension the plates. and to ensure end-to-end contact between their ends, such that no subsequent intervention is necessary to ensure the continuity of the peripheral surface of the plates on the ferrule.

The establishment and the thrust force on the wedge bars can be carried out by any device, but in order not to exceed a force which could cause deformation or destruction of both the shell and the plate located at- above the bars, the introduction and especially the tightening is carried out by an adequate device such as a micrometric screw or a system using a jack whose force is controlled.

If the number of plates to be fixed on the ferrule 1 is more than two, the same method is used, providing as many grooves as there are plates.

The forces created by the bars do not take into account any shrinking in the width direction of the plates, that is to say in the axial direction. Similarly, during printing, the plate is subjected to great compression which can locally cause also instantaneous deformation of the plate. In order to prevent such a narrowing and such a deformation from occurring, means have been provided for exerting opposite axial forces on the lateral edges of the printing plates, which we will now describe with the aid of FIGS. 3 and 4.

The ferrule 1 is provided on either side with two annular sectors 15a, 15b, having the same diameter as it and lying in the extension of its lateral faces, one sector for each lateral edge of each plate 3, 4. When mounting the printing plates 3, 4 including tensioning in the direction peripheral and radial is carried out as described, the lateral edges of these are fixed to said sectors as described later. Each sector 15a, 15b is mounted axially to the ferrule by regularly distributed screws 16 which are screwed into axial recesses 17 blind and tapped from the end of the ferrule 1, while they freely cross sectors 15a, 15b of so that each sector 15a, 15b is axially movable relative to the shell 1. The holding in the radial direction and the guiding of the sectors are ensured by guides 18 regularly distributed. They are formed by pins driven axially in axial blind passages 18a of the lateral face of the ferrule, their dimension allowing them to slide in holes provided in each sector 15a, 15b.

Alternately arranged with the screws 16 and the guides 18 are screws 25 for positioning and lateral tension of the plates, these screws 25 being screwed only on the sectors 15a, 15b in threaded passages 27 thereof and penetrate into housings blind and opposite 20 and 21 extending axially, on the one hand, in the shell and on the other hand, in the sectors 15a, 15b facing the shell 1. The screws 25 abut against the bottom of the housings 20 and allow the axial positioning of the printing plates and the adjustment of the axial tension applied to them via said annular sectors. In these blind housings 20, 21 are housed coil springs 19 surrounding the screws 25 and pressing against the bottom of the housings 20 and 21. These pressure springs ensure a constant force in the axial direction thus pushing the sectors towards the outside, travel maximum that can be obtained by these springs is limited by the position of the screws 16. The screws 16 make it possible to compress the springs 19 during the mounting or dismounting of the plates and to axially position the sectors 15a, 15b by applying lateral tension to the plates.

Tapped holes 22 are drilled radially on the peripheral periphery of each sector into which screws 23 with countersunk heads can be screwed. When the printing plates 3 and 4 are put in place, the screws 16 are tightened to compress the springs 19. The lateral ends of these plates lying at the level of the sectors 15a, 15b have recesses 24 into which are screwed the screws 23 on the corresponding sectors. By the term recess is meant a shape pressed into the plate serving as a housing for the head of the screws which thus do not protrude from the plate (see FIG. 3). After fixing the plate by means of the screws 23, the screws 16 are slightly unscrewed so that the sectors 15a, 15b can yield under the action of the coil springs 19 which can thus act in traction on the plate. Thus when the plates are tightened by means of the wedge bars, an effort in the axial direction of the ferrule is also ensured by means of the springs 19 making it possible to counteract the axial narrowing to which the printing plates could be subjected and prevent instant local deformation during of printing. The sectors 15a, 15b have notches corresponding to the bars to allow the establishment or removal thereof without having to remove the sectors.

Likewise, to facilitate the dismantling of the plate when it is desired to change it, these screws 16 are again tightened to compress the springs 19.

Figures 5 and 6 show a similar arrangement for fixing the printing plates 3, 4 on a plate cylinder 1a, therefore intended for a sheet printing machine. In this case, because of the cylinder body mounted on its shaft, the fixing screws 36 which each fix a T-shaped section 30, and with the same configuration as that described in relation to Figure 4, can not be screwed from the inside of the cylinder but from the outside. This is the only difference from Figures 3 and 4, the rods 5, 6, 33a, 33b and the wedge bars 34a, 34b, 35a, 35b being the same.

The device for fixing the plates in the axial direction shown in FIGS. 5 and 6 is formed in the same way as that of FIGS. 3 and 4 with two annular sectors 15 a and 15 b on each side, and the same means are represented by the same references.

If, after a more or less long period of operation of the printing machine, the printing plates have undergone, because of the deformations mentioned, an enlargement such as under the force of the coil springs exerting a permanent tension on the plates the screws 25 no longer abut at the bottom of the housings 20, after stopping the machine, all the screws 25 are tightened to make up for the play.

It is also possible to dispense with the coil springs 19 and, after a certain operating time of the machine, if necessary, the axial tension of the plates can be readjusted by tightening the screws 25.

If a cylinder is provided with a single plate, under these conditions a closed annular sector is used, therefore a ring, for each lateral edge of the plate.

The invention is not limited to the embodiments described, but also covers the many possible variants.

Claims (8)

1. Method for preparing and fixing printing plates onto a cylinder formed by a sleeve (1) or a plate cylinder (1a) of an intaglio printing machine, said cylinder (1) having on its peripheral surface the same number of regularly distributed axial grooves (2) as there are printing plates (3, 4) to be fixed, according to this method a strip (5, 6) whose face (5.2, 6.2) adjacent to the end of the plate is perpendicular to the latter is fixed close to the two ends of each printing plate (3, 4), the strips (5, 6) fixed on two adjacent ends of the printing plate or plates, respectively, are arranged into a groove (2) and the free space of the groove is completed by means comprising at least one wedge-shaped strip (34a, 34b; 35a, 35b) which is displaced in the longitudinal direction in the remaining space of the groove thus approaching said faces of the strips and therefore the adjacent edges of the plate or the plates, respectively, until they are in a close contact, characterized in that :

   a. one or more intaglio printing plates (3, 4) are prepared, the length of which, or the sum of the lengths of which, respectively, is greater than the circumference of the cylinder (1, 1a);

   b. each printing plate is bent with a radius of curvature less than that of the peripheral surface of the cylinder;

   c. said strips are fixed near to the ends of each printing plate in such the way that the length of the plate or of all the plates (3, 4), respectively, between the planes of said faces (5,2, 6.2) of the strips equals the circumference of the cylinder;

   d. the edges of each plate (3, 4) projecting beyond the corresponding strip (5, 6) are cut off such that the edge of the plate forms a continuous surface with said face of the strip, and

   e. an abutment (30) is fixed to the base (2.1) of the groove enabling at least part of the said means completing the free space of the groove to be retained radially and having a face that is inclined radially toward the interior of the cylinder; at least one of the wedge-shaped strips (34a, 34b) is used in order to tension the plate or the plates, respectively, in the peripheral direction, and at least another wedge-shaped strip (35a, 35b) the inclined face of which co-operates with the inclined face of the abutment, is used in order to ensure the positioning of the said means (33a, 33b) and of the strips (5, 6) in the radial direction inside the groove (2).
2. Method according to Claim 1, characterized in that the strips (5, 6) are made from metal and in that their fixing on each printing plate (3, 4) is realized by laser welding.
3. Method according to one of Claims 1 or 2, characterized in that at least one of the lateral faces of each groove (2) is formed as inclined face (2.3) relative to the direction of the axis of the cylinder and adapted to the wedge-shaped face of said wedge-shaped strip that is introduced into the free space limited by this inclined face of the groove.
4. Method according to one of Claims 1 to 3, characterized in that, after the strips (5, 6) have been positioned inside the grooves (2), axial tensile forces are applied to the two lateral edges of each printing plate (3, 4) in the opposite direction so as to tension the printing plates axially.
5. Installation for fixing printing plates onto a cylinder formed by a sleeve (1) or a plate cylinder (1a) of an intaglio printing machine, said cylinder (1) being provided, on its peripheral surface, with the same number of regularly distributed axial grooves (2) as there are printing plates (3, 4) to he fixed on the said cylinder (1), and several elements are provided for each groove which complete exactly the missing part of the cylinder, characterized in that each groove (2) has two lateral faces (2.2, 2.3) inclined relative to the axis of the cylinder symmetrically relative to the radial plane of the cylinder and perpendicular to the base (2.1) of the groove (2), in that an abutment in the forme of a T-shaped profile (30) is fixed on the mid line of the base of the groove, the head of the profile being directed towards the top of the groove, the lower face (30.1) of the said head being inclined relative to the axis of the cylinder, and in that two pairs of strips and two pairs of wedge-shaped strips are provided per groove (2), the first pair of strips (5,6) being fixed on the ends and on the lower side of the plate or plates, respectively, the edges of which being arranged end to end and each forming a continuous surface with a lateral face of the respective strip, said strips of the first pair being intended to be jointed in a flat manner with their lateral faces and having a trapezoidal cross-section, the second pair (33a, 33b) of strips having, on its upper part, a female part which complements that of the strips (5, 6) of the first pair which are fixed to each printing plate (3, 4), and on its lower part, a housing enabling the profile (30) to be encased and a space to be left between the lower inclined face of the head of the profile and the lower parts of the strips (33a, 33b) of the second pair, which space is intended to accommodate the first pair of wedge-shaped strips (35a, 35b) with a shape which complements the said space ensuring the retention in the radial direction of the two abovementioned pairs of strips (5, 6; 33a, 33b) by pushing said first pair of wedge-shaped strips (35a, 35b), and in that the second pair of wedge-shaped strips (34a, 34b) is forced between the second pair of strips (33a, 33b) and the lateral inclined faces (2.2, 2.3) of each groove (2)) so as to exert a clamping force in the peripheral direction.
6. Installation according to Claim 5, characterized in that the cylinder (1) is provided at the two lateral ends with means for applying opposite axial forces to the lateral edges of each printing plate (3, 4), the said means comprising for each lateral edge of each printing plate, an annular sector (15a, 15b), in the case of a single printing plate the said sector being closed and forming a ring, these sectors have the same external diameter as the cylinder and are provided with means, preferably screws (23), in order to attach the lateral edges of each printing plate thereto and in order to be mounted on the lateral sides of the cylinder (1, 1a) so as to be displaceable axially in order to apply tensile forces to the lateral edges of each printing plate in the axial direction.
7. Installation according to Claim 6, characterized in that elastic means (19) are provided between the said annular sectors (15a, 15b) and the lateral sides of the cylinder (1, 1a), these elastic means applying compressive forces tending to move apart the said annular sectors (15a, 15b) of the cylinder (1, 1a) axially.
8. Installation according to Claim 7, characterized in that the said annular sectors (15a, 15b) are mounted on the sides of the cylinder (1, 1a) by screws (16) which are screwed axially onto the cylinder and pass freely through the annular sectors in order to secure them axially in the absence of printing plates and in order to compress the elastic means (19) when the printing plates are being mounted and disassembled, in that the said annular sectors are guided axially by axial pins (18) and in that they comprise screws (25) which are screwed onto these annular sectors and abut the cylinder in order to enable the printing plates to be positioned axially and the axial tension applied to them via the said annular sectors to be adjusted, said elastic means are helical springs (19) surrounding the said screws (25) screwed onto the annular sectors, and are housed in housings (20) provided in the cylinder and into which these screws (25) penetrate.

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