EP0403434A1 - 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 understood to mean in general 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 a unit in the machine bearings, respectively disassembled completely 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.

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 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 an irregular pressure on the cylinder during printing or wiping which would tend , during these operations, has deform the mounted printing plates.
- For reasons of economy, it is advisable to reuse the ferrule in the printing machines with the reel by fixing there other printing plates, because its internal bore being slightly conical to marry perfectly the corresponding conical shape of l machine shaft 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 is known from GB 368 609. According to this patent, the ends of the plate are bent at right angles and rods are fixed by screws on these folded ends. However, by this means, one does not ensure a perfectly continuous surface of the plate, respectively of the plates on the cylinder, because of the flanges formed by the folded ends of the plates which therefore cannot be abutted perfectly. It is even admitted in this patent that in practice there remains a space between the ends of the plate of approximately 1 to 2 mm. In addition, the corner action is carried out between one of the rods and the wedge bar.

The object of the present invention is to propose a method of fixing intaglio printing plates to a plate cylinder or to a ferrule in a very easy manner while ensuring a perfectly continuous surface of the plate, respectively of the plates. , printing stretched on the cylinder.

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 connection 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.

Preferably, cuneiform bars are also provided to create a force in the radial direction.

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 where appropriate the other elements, in the corresponding grooves and to obtain the desired tightening by the , or the wedge bar functioning as a wedge.

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 5.

The invention also relates to an installation for fixing printing plates, an installation which is defined by claim 6. Preferred alternative embodiments of the installation are defined by claims 7 to 11.

• La figure 1 est une vue partielle en coupe de deux pla­ ques 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 partielle en coupe radiale de la virole selon figure 2, munie de deux plaques d'impression taille-douce, fixées selon cette première variante;
• La figure 4 est une vue latérale de la virole munie de secteurs annulaires pour tendre axialement les plaques.
• La figure 5 est une vue en coupe selon la ligne V-V de la figure 4.
• La figure 6 est une vue analogue à celle de la figure 4 d'une deuxième variante d'exécution dans le cas d'une virole.
• La figure 7 est une vue en coupe selon la ligne VII-VII de la figure 6.
• La figure 8 est une vue latérale d'un cylindre porte-­plaques muni de secteurs annulaires pour tendre axiale­ment des plaques.
• La figure 9 est une vue en coupe selon la ligne IX-IX de la figure 8.

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

• Figure 1 is a partial sectional view of two pla printing ques 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 partial view in radial section of the shell according to Figure 2, provided with two intaglio printing plates, fixed according to this first variant;
• Figure 4 is a side view of the shell provided with annular sectors for axially tensioning the plates.
• FIG. 5 is a sectional view along the line VV of FIG. 4.
• Figure 6 is a view similar to that of Figure 4 of a second alternative embodiment in the case of a ferrule.
• Figure 7 is a sectional view along line VII-VII of Figure 6.
• Figure 8 is a side view of a plate cylinder provided with annular sectors for axially tensioning plates.
• FIG. 9 is a sectional view along the line IX-IX in FIG. 8.

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 first present an absolutely flat bottom 2.1 and two walls 2.2 and 2.3 perpendicular to the bottom 2.1. The wall 2.2 is parallel to the axis of the ferrule, while the wall 2.3 is inclined relative to the axis of the ferrule thus forming a wedge-shaped groove.

Metal rods 5 and 6 are prepared which will be fixed to the ends parallel to the axis of the shell 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 which are identical, has two faces 5.1, 5.2, respectively 6.1, 6.2 parallel to each other and perpendicular to a third face 5.3, respectively 6.3, which will come into contact with the flat bottom 2.1 of the groove 2. The upper faces 5.4, respectively 6.4, of the rods 5 and 6, are curved and adapted to the curvature of the peripheral surface of the shell 1. A wedge-shaped bar 7 (Figure 3) is formed in such a way that in the mounted state thereof and the two rods 5.6 exactly fill the groove 2 so that the missing part, removed by milling, of the shell 1 is exactly completed.

For this, the two rods 5 and 6 are arranged in the groove 2 by placing the rod 6 so that its face 6.1 comes into contact with the face 2.2, while that the faces 5.2 and 6.2 of the two rods 5, 6 are in close contact. The wedge bar 7 has an inclined side face adapted to the inclination of the wall 2.3 of the groove 2 and an upper face adapted to the curvature of the surface of the shell 1; the dimensions of the bar 7, which is used as a corner when placing the printing plates, allow the remaining space (fig. 3) to be filled with the groove 2 after the rods 5 and 6 have been put in place .

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.

When this work is finished, each plate is placed on the ferrule 1 so that the rods 5, 6 as well as the rods being at the ends not shown, take place in the groove 2, respectively in the groove being in the position diametrically opposite of ferrule 1, as already described. The fact that the two plates have been bent with a radius of curvature less than that of the ferrule allows the plates to remain in place by the tightening obtained because of this difference in radius of curvature. When the two adjacent ends of two plates 3 and 4 are in the desired position, the wedge bar 7 is introduced into the groove 2 and by pushing it as far as possible the two rods 5 and 6 are brought into close contact by their faces 5.2 and 6.2 respectively and therefore also the respective ends of the plates 3 and 4. The same operations are carried out in the groove being diametrically opposite, which makes 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. By tightening in the peripheral direction, it also naturally creates a radial force and a perfect and regular application of the plates on the surface of the shell.

The establishment and the thrust force on the wedge bar 7 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 3 being above the bar 7, 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. When the bar 7 is sufficiently introduced into the groove 2 and the desired tightening is obtained, the two rods 5, 6 and the bar 7 (fig. 3) are locked in the final position by means of three screws 8, 9, 10 arranged in passages 11, 12, 13 passing through the shell 1 and which are perpendicular to the bottom 2.1 of the groove 2. The seal between the interior of the shell 1 and the outer surface and in particular the groove 2 is provided by seals 14 arranged between the screw heads 8, 9, 10 and the corresponding shoulders of passages 11, 12, 13. Of course, it is possible to use several screws arranged axially. It is understood that the diametrically opposite rods and bars serving to fix the second end of the two plates are fixed and locked by similar means.

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

The forces created by the wedge is only in the peripheral direction of the plates, they do not take account of any shrinking in the width direction of the plates, that is to say in the axial direction. Likewise, during printing, the plate is subjected to great compression which can locally cause 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. 4 and 5.

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 is performed in the same manner as that described in connection with Figure 3, the lateral edges thereof 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 displaceable 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.

Arranged alternately 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 being at the height 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 stamped in the plate serving as a housing for the head of the screws which thus do not protrude from the plate (see the partial section of Figure 4). 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-shaped rods 7 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 when printing. The sectors 15a, 15b have notches corresponding to the rods 7 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 6 and 7 shows another installation for fixing printing plates 3 ′, 4 ′ on a ferrule 1 ′ with a modified corner blocking. Each groove 2 ′ is symmetrical with respect to a radial plane of the ferrule and perpendicular to the bottom 2.1 ′ of the groove 2 ′. The two lateral faces 2.2 ′ and 2.3 ′ of the grooves 2 ′ are inclined symmetrically with respect to said radial plane. There is inside each groove a T-shaped section 30 fixed by screws 31 introduced by radial housings inside the ferrule 1 ′, the sealing being ensured by O-ring seals 32, the lower face 30.1 of the profile 30 is inclined relative to the plane of the bottom of the groove 2.1 ′.

Rods 5 ′ and 6 ′ at the ends of two printing plates 4 ′ and 3 ′ are fixed in the same manner as above except that their dimensions and shape are different. Indeed the rods 5 ′, 6 ′ shown in FIG. 6 have a trapezoidal shape each having an inclined face 5.1 ′ respectively 6.1 ′ and their height is less than the depth of the groove 2 ′.

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 implementation is done as follows: we introduce into each groove 2 ′ the strips 33a and 33b, then we place the strips 5 ′, 6 ′ fixed to the ends of the plates 3 ′, 4 ′, we introduce the first pair of wedge bars 34a, 34b to ensure the positioning in the peripheral direction of the rods and consequently of the printing plates as in the case of FIG. 3 and thereafter; 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.

As in the first embodiment according to Figures 4 and 5, the ferrule 1 ′ is provided on each side with two annular sectors 15′a, 15′b, mounted by means of the three elements, screws 16, guide 18 and screws 25, arranged alternately so that these sectors create axial tensions.

Figures 8 and 9 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 FIG. 7, cannot be screwed from the inside of the cylinder but from the outside.

This is the only difference compared to Figures 6 and 7, 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. 8 and 9 is formed in a manner equal to that of FIGS. 5, 6 and 7 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 period of operation 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 (11)

1. Method for fixing printing plates on a cylinder formed by a ferrule (1, 1 ′) or a plate cylinder (1a) of an intaglio printing machine according to which one forms on the peripheral surface of the cylinder (1, 1 ′; 1a) as many axial grooves (2, 2 ′) regularly distributed as the number of printing plates (3, 4; 3 ′, 4 ′) to be fixed, the two ends of each printing plate (3, 4; 3 ′ 4 ′) a strip (5, 6; 5 ′, 6 ′) whose face (5.2, 6.2) adjacent to the end of the plate is perpendicular thereto , the rods (5, 6; 5 ′, 6 ′) fixed on two adjacent ends of the, respectively of the printing plates, are placed in a groove (2, 2 ′) and the free space of the groove is completed. by means comprising at least one wedge-shaped bar (7; 34a, 34b; 35a, 35b), which is moved in the longitudinal direction to tension the plate or plates, characterized in that: at. one or more printing plates (3, 4; 3 ′, 4 ′) are prepared, the length of which, respectively the sum of the lengths of which is greater than the circumference of the cylinder (1, 1 ′; 1a); b. each printing plate is bent with a radius of curvature less than that of the peripheral surface of the cylinder; vs. said rods are fixed near the ends of each printing plate at positions such as the length of the plate, respectively of all of the plates (3, 4; 3 ′, 4 ′), taken between the planes of said faces (5.2, 6.2) of rods is equal to the circumference of the cylinder; and d. the ends of each plate (3, 4; 3 ′, 4 ′) are cut beyond the corresponding strip (5, 6; 5 ′, 6 ′) so that the edge of the plate with said face of the strip forms a surface keep on going; e. by pressing said wedge-shaped bar in the remaining space of the groove, said faces are brought closer to the rods and therefore the adjacent edges of the plate, respectively of the plates, until they lie flat. 2. Method according to claim 1, characterized in that the rods (5, 6; 5 ′, 6 ′) are made of metal and that their attachment to each printing plate (3, 4; 3 ′, 4 ′) is produced by laser welding. 3. Method according to claims 1 or 2, characterized in that at least one of the lateral faces of each groove (2, 2 ′) is formed as an 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 bar which is introduced into a space limited by this inclined face of the groove. 4. Method according to one of claims 1 to 3, characterized in that one fixes at the bottom (2.1 ′) of the groove a stop making it possible to radially retain at least part of said means completing the free space of the groove and having an inclined face directed radially towards the inside of the cylinder, and using at least one other wedge bar (354, 35b) cooperating with its inclined face with said inclined face of the stopper to ensure the positioning of said means (33a, 33b) and of the rods (5 ′, 6 ′) in the radial direction inside the groove (2 ′). 5. Method according to one of claims 1 to 4, characterized in that, after the placement of the rods (5, 6; 5 ′, 6 ′) inside the grooves (2, 2 ′), we applies axial tensile forces to the two lateral edges of each printing plate (3, 4; 3 ′, 4 ′) in the opposite direction in order to tension the printing plates axially. 6. Installation for fixing printing plates to a cylinder formed by a ferrule (1, 1 ′) or a plate cylinder (1a) of an intaglio printing machine, characterized in that the cylinder ( 1, 1 ′) is provided on its peripheral surface with as many axial grooves (2) regularly distributed as the number of printing plates (3, 4) to be fixed on said cylinder (1, 1 ′), and as for each groove is provided with several elements which exactly complete the missing part of the cylinder, said elements comprising two rods (5,6; 5 ′, 6 ′) and at least one wedge-shaped bar (7), said rods are fixed on the ends and lower side of the plates respectively, said wedge bar (7) being pushed into said groove and cooperating with its inclined face with a backing provided on one of the other elements or on a wall of said groove, such that it exerts a force in the peripheral direction so that said rods are joined flat with their side faces and that, or the plates whose edges are arranged end to end are stretched. 7. Installation according to claim 6, characterized in that each groove has a lateral face (2.2) parallel to the axis of the cylinder and a lateral face (2.3) inclined relative to the direction of the axis of the cylinder, that two rods (5, 6) and a wedge bar (7) per groove (2) are provided which completely fill said groove, the two rods (5, 6) fixed on said ends are identical and each have two parallel faces (5.1 , 5.2; 6.1, 6.2) between them and parallel to the axis of the cylinder (1), the wedge bar (7) is arranged between one of the rods (5) and the inclined face (2.3) of the groove to obtain the tension of each printing plate (3, 4), and that the cylinder includes means, in particular screws (8, 9, 10) for locking the rods (5, 6) and the wedge bar (7) . 8. Installation according to claim 6, characterized in that each groove (2 ′) has two lateral faces (2.2 ′, 2.3 ′) inclined relative to the axis of the cylinder, that a stop in the form of a T-profile ( 30) is fixed, for example by screws (31,36), on the midline of the bottom of the groove, the head of the profile being directed towards the top of the groove, the lower face (30.1) of said head being inclined relative to the axis of the cylinder, and that two pairs of rods and two pairs of wedge bars per groove (2 ′) are provided, the first pair of rods (5 ′, 6 ′) is fixed on said ends and has a trapezoidal section, the second pair of rods (33a, 33b) has on its upper part a female part complementary to that of the rods of the first pair (5 ′, 6 ′) and on its lower part a housing allowing to surround the profile (30) and leave a space between the inclined underside head of the profile and the lower parts of the rods (33a, 33b) of the second pair, intended to receive the first pair of wedge bars (35a, 35b) of shape complementary to said space ensuring the holding in the radial direction, the second pair of wedge bars (34a, 34b) is forced between the second pair of rods (33a, 33b) and the inclined faces (2.2 ′, 2.3 ′) lateral of each groove (2 ′) in order to exert a clamping in the peripheral direction. 9. Installation according to one of claims 6 to 8, characterized in that the cylinder (1, 1 ′) is provided at the two lateral sides with means for applying to the lateral edges of each printing plate (3, 4; 3 ′, 4 ′) opposite axial forces, said means comprising for each lateral edge of each printing plate an annular sector (15a, 15b; 15′a, 15′b), in the case of a single plate printing said sector being closed and forming a ring, these sectors have the same outside diameter as the cylinder and are provided with means, preferably screws (23), for attaching to the side edges of each printing plate and for being mounted to the lateral sides of the cylinder (1, 1 ′, 1a) in an axially displaceable manner in order to apply tension forces to the lateral edges of each printing plate in the axial direction. 10. Installation according to claim 9, characterized in that elastic means (19) are provided between said annular sectors (15a, 15b; 15′a, 15′b) and the lateral sides of the cylinder (1, 1 ′ , 1a), these elastic means applying thrust forces tending to move said annular sectors axially (15a, 15b; 15′a, 15′b) from the cylinder (1, 1 ′, 1a). 11. Installation according to claim 10, characterized in that said annular sectors (15a, 15b; 15′a, 15′b) are mounted alongside the cylinder (1, 1 ′, 1a) by screws (16) screwed axially on the cylinder and freely crossing the annular sectors to maintain them axially in the absence of printing plates and to compress the elastic means (19) during the mounting and dismounting of the printing plates, that said annular sectors are guided axially by axial pins (18) and that they comprise screws (25) screwed onto these annular sectors and abutting against the cylinder to allow the axial positioning of the printing plates and the adjustment of the axial tension applied to them by through said annular sectors, the elastic means being coil springs (19) surrounding said screws (25) screwed onto the annular sectors, and housed in housings (20) provided in the cylinder and into which these screws (25) penetrate.

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