EP0972639B1 - Device for positioning a flexible printing plate on a form cylinder - Google Patents

Abstract

The positioner, for a flexible plate on a carrier cylinder (3) with a lengthwise slit (1) in its shaft, is actuated by a lateral movement of the carrier cylinder beyond a set course by an exterior component fixed to the printing machine frame at one end of the cylinder and a crown cam (14) at the other. The inner edges (12, 13) of the crown cam act as guides for a roller (11) on a mobile base plate. Two other cams are located at the base of the roller shaft slit to control the movement of rollers (15) linked to the base plate.

Description

The subject of the present invention is a device for positioning of a flexible plate on a forme cylinder, device allowing in particular to skew this flexible shot on the cylinder slide holder of a rotary printing machine.

Frequently used in the packaging industry for printing of plate elements such as sheets of paper or carton, such machines are usually called machines flexo printing and include several constituent stations, namely according to a logical development upstream downstream referring to the meaning of moving elements in plate, an introductory station successively seizing one leaf after another from below a stack, a suite of one or more printing groups that can be chosen be intercalated by one or more dryers, and finally a station of receipt collecting the printed elements. The transport of the leaves of a station or group to group is by the top of these by means of a train of rollers and a suction system thus releasing totally the lower surfaces printed with leaves.

It is in the printing groups that the positioning of a cliche finds its use. Each of these groups printers, usually dedicated to printing a certain color, includes a cylinder cliché around which wraps and y is stretched the flexible snapshot. Coated ink thanks to a screen cylinder, this cliché prints on the sheet, depending on the number of print forms it includes, one or more patterns at each rotation of the cylinder on the scrolling sheet between the forme cylinder and a pressure roller all two arranged so that printing is done on the underside of the leaves.

The printing form, consisting of a rubber material or plastic, is usually bonded to a flexible support base in polyester such as Mylar to form a set that will be designated from then on by the term of cliche. After the manufacture of the form impression, the stage of his collage on the polyester base is a decisive operation. Made by the manufacturer, it conditions directly the quality of the identification of prints between different colors. The upstream and downstream ends of the flexible support base are equipped with a plastic strip of which one of the longitudinal edges is shaped-shaped U and allows the fixation of the cliche in a claw secured to the cylinder forme. This claw is itself arranged parallel to the axis of rotation of this cylinder. A thin metal plate, riveted to the strip plastic and with an oblong hole of upstream-downstream longitudinal axis, allows a quick and precise lateral positioning of the shot on its cylinder by nesting on a centering pin integral with the claw.

If, when gluing on its flexible support base in polyester, a defect of lateral or longitudinal positioning of the shape printing can be easily overtaken respectively by a lateral displacement or rotation of the forme cylinder around its axis, it is not the same when the defect found results from a biasing the print form. In the latter case, its sides are not more oriented in a direction parallel or perpendicular to the edges upstream and downstream of the polyester base, and it follows a positioning in Inaccurate bias of the print form relative to the given direction by the axis of rotation of the forme cylinder.

In the case where several forms of printing would be glued on the flexible polyester base and would all be affected by the same lack of bias, have considered, which is generally the case, that the upper edges of each of these print forms are all aligned and can thus be likened to a single great form of printing particularly affected by a positioning defect resulting from a collage slantwise.

To remedy this problem, various known devices rotate the front and rear claws relative to the axis of rotation of the forme cylinder so as to skew the cliche of a quantity equal but opposite to the defect found.

For this purpose, US Pat. No. 5,488,904 describes a device comprising two parallel bars grasping the ends of the plate. A mechanism, controlled by the manual rotation of a graduated eccentric, allows to print a lateral displacement (parallel to the axis of rotation of the cylinder) at the back bar fixing the snapshot and pivoting the bar before thanks to a set of bent parts articulated around several pivots arranged at its ends. Thanks to an articulation dynamic spring-driven at one end of the back bar, the latter is automatically rotated to a position parallel to that occupied by the front bar when the shot is held by both ends in this device. The whole mechanism is arranged in the body of the platen cylinder at the bottom of a wide and deep groove machined parallel to the axis of rotation of the cylinder. The eccentric controlling the mechanism is reported on one of the side faces of the forme cylinder.

Another device for biasing a snapshot is given by the patent EP-232'730 where the inventor proposes a mechanism based on the pivoting of two tension bars in which are maintained tight the ends of the cliche. The tension bars are connected between they at their ends by two articulated triangular shaped plates and mounted on two fixed pivots integral with the forme cylinder. The pivots of the joints have a rectangular configuration so that that the snapshot tension bars rotate around a virtual P point in the median axis of the forme cylinder. The control organ is arranged on one of the lateral faces of the forme cylinder and comprises a complex mechanism consisting of articulated levers that can be operated by a cylinder when the cylinder is stationary in a position determined.

JP 62-56146 solves the problem of biasing a snapshot by a device comprising two bars each actuated by two hydraulic cylinders. When the position of the snapshot needs to be corrected diagonally, the oil pressure in these four cylinders is reduced by so that four springs, previously compressed by the four jacks, can relax and push back the snap fixing bars in an opening movement. The correction value is introduced numerically in a controller that converts it to an oil pressure corresponding and applied to two other additional cylinders arranged on the same side at one end of the fixing bars. Under the action of these two other cylinders, two inclined planes can be independently moved in a rectilinear motion so as to force, when closing the snap-fastening bars, one of the ends of each of these bars in a perpendicular displacement thanks to the triangular geometric shape of the inclined plane. The inclined planes can also, according to a preferred embodiment, be actuated by a motorized screw mechanism.

• la présence d'un mécanisme, dit embarqué, encombrant et nécessitant, dans le corps du cylindre porte-cliché, l'aménagement d'une saignée aux dimensions importantes par rapport au diamètre du cylindre,
• l'apport d'un balourd peu souhaitable, crée par l'importance de l'agencement d'un tel mécanisme, engendrant des contraintes naissant dans les paliers du cylindre lorsque ce dernier atteint une certaine vitesse de rotation,
• à disposition autour du cylindre, une surface de travail circonférentielle réduite par la taille importante de la largeur de la saignée que nécessite le dispositif de biaisage,
• la présence dans certains cas d'un réglage manuel nécessitant un arrêt complet de la machine ce qui implique un temps de réglage prolongé,
• l'impossibilité de recourir à une automatisation complète du réglage du cliché dans le cas où d'anciens travaux devraient être repris; travaux pour lesquels les valeurs de réglage auraient pu être sauvegardées et mémorisées numériquement,
• la nécessité de commander le mécanisme entraínant le biaisage du cliché, dans le cas d'un réglage non manuel, à l'aide d'un actuateur supplémentaire et indépendant de celui qui permet déjà le déplacement latéral ou circonférentiel du cylindre porte-cliché.

These devices draw up an inventory of several disadvantages which include:

• the presence of a mechanism, said embedded, bulky and requiring, in the body of the forme cylinder, the arrangement of a groove with large dimensions relative to the diameter of the cylinder,
• the contribution of an undesirable imbalance, created by the importance of the arrangement of such a mechanism, generating constraints arising in the bearings of the cylinder when the latter reaches a certain speed of rotation,
• provided around the cylinder, a circumferential working surface reduced by the large size of the width of the groove required by the biasing device,
• the presence in some cases of a manual adjustment requiring a complete stop of the machine which implies a prolonged adjustment time,
• the impossibility to resort to a complete automation of the adjustment of the cliché in the case where old works should be resumed; jobs for which the setting values could have been saved and stored digitally,
• the need to control the mechanism leading to the biasing of the plate, in the case of a non-manual adjustment, with the aid of an additional actuator and independent of the one that already allows the lateral or circumferential displacement of the forme cylinder.

The device for biasing a plate according to the invention aims to to overcome these disadvantages while providing a simple organ and automated, occupying only a minimal volume in the cylinder body cliché holder, and does not require stopping the machine for its use. The desire to want to occupy a minimal volume contributed in particular to to realize a device with the advantage of not having to be dependent on a snapshot mechanism actuated by an actuator housed in the body of the forme cylinder. Thus, the device described in this invention uses to drive his snapshot mechanism a snapshot electric motor attached to the frame of the machine, which is none other than the already allowing the displacement of the whole cylinder-cylinder during its lateral wedging. This solution offers on the one hand a more rational use of the actuator already existing for lateral registration of the cliché, and secondly allows to obtain, for a better cost, a little biasing mechanism bulky, robust and reliable, which is easily adaptable to cylinders cliché holders which do not have one. Finally thanks to this mechanism, the use of an external electronic controller, connected to several sensors positioned on the outside of the cylinder, makes it possible to measure and memorize the different setting positions suitable for work which can easily be resumed later without their registering operation is necessary. This last alternative offers an additional asset that lends itself particularly well to mechanism imagined in the present invention.

For this purpose, the subject of the present invention is a device for positioning of a flexible snapshot in accordance with the claim 1.

In order to define some terms introduced in the this description and describing the position of certain elements within of the printing machine, we will name the appellations "driver side" (C.C.) and "opposite driver side" (C.O.C.) undoubtedly used for refer to a designated side with respect to the longitudinal median axis of the machine. This choice makes it possible to avoid any confusion occurring with conventional denominations left and right dependent on the point of view of the observer. In a similar perspective, we will describe the orientation certain axes or objects by the usual terms "longitudinal" and "lateral" always referring to the center axis of the machine whose orientation is determined by the direction of scrolling elements on plate. Finally it will be recalled that the terms "upstream" and "downstream" refer to in the sense of scrolling plate elements within the machine printing.

• les figures 1a et 1b illustrent, dans une vue en plan respectivement les tiers C.O.C. et C.C. du dispositif de biaisage monté sur le cylindre porte-cliché,
• la figure 2 représente une vue en coupe partielle de l'extrémité C.C. du dispositif de positionnement d'un cliché flexible sur le cylindre porte-cliché,
• les figures 3 et 4 sont des vues en coupe du dispositif de biaisage monté sur le cylindre porte-cliché, respectivement selon les lignes A-A et B-B des figures 1a et 1b,
• les figures 5a et 5b représentent, dans une vue on plan, respectivement les moitiés C.O.C et C.C. de la plaque de base et du support de griffe qui y est installé par dessus,
• la figure 6 représente, dans une direction parallèle à l'axe de rotation du cylindre porte-cliché, une vue on coupe partielle de ce cylindre au voisinage de la came C.C.,
• la figure 7 représente une vue en plan de la came C.C. et de l'étrier correspondant,
• la figure 8a représente une vue très schématique en plan du dispositif de biaisage du cliché; plus particulièrement lorsque ce mécanisme se trouve dans une position intermédiaire qui ne biaise tout d'abord pas le cliché,
• la figure 8b diffère de la figure 8a en ce que le mécanisme de biaisage du cliché se trouve en action dans une première position extrême faisant suite à une rotation dans le sens des aiguilles d'une montre,
• la figure 8c diffère de la figure 8b en ce que le mécanisme de biaisage du cliché se trouve en action dans une seconde position extrême opposée faisant suite à une rotation dans le sens inverse des aiguilles d'une montre.

The invention will be better understood from the study of an embodiment taken in no way limiting and illustrated by the appended figures in which:

• FIGS. 1a and 1b show, in a plan view respectively the thirds COC and CC of the biasing device mounted on the forme cylinder,
• FIG. 2 represents a partial sectional view of the end CC of the positioning device of a flexible plate on the forme cylinder,
• Figures 3 and 4 are sectional views of the biasing device mounted on the forme cylinder, respectively along lines AA and BB of Figures 1a and 1b,
• FIGS. 5a and 5b show, in a plane view, respectively the halves COC and CC of the base plate and the claw support which is installed thereon,
• FIG. 6 represents, in a direction parallel to the axis of rotation of the forme cylinder, a partial sectional view of this cylinder in the vicinity of the cam CC,
• FIG. 7 represents a plan view of the cam CC and the corresponding stirrup,
• FIG. 8a represents a very schematic plan view of the cliché biasing device; especially when this mechanism is in an intermediate position which does not bias the cliché first,
• FIG. 8b differs from FIG. 8a in that the mechanism for biasing the plate is in action in a first extreme position following a rotation in the direction of clockwise,
• FIG. 8c differs from FIG. 8b in that the clipping mechanism is in action in a second opposite extreme position following a rotation in the opposite direction of clockwise.

Figures 1a and 1b show, in an overview of plan, the device for positioning a snapshot arranged in a bleeding 1 machined parallel to the axis of rotation 2 of a forme cylinder 3. As best seen on the corresponding cuts illustrated by the Figures 3 and 4, the biasing device is supported by a base plate 4 on which is attached a claw before 5 immutable seizing, in a notch 7, the front edge of a plate 19 disposed around the cylinder 3. In front of the front claw 5, a movable rear claw 6, grasping the trailing edge of the plate 19 in a notch 8, has at its end C.O.C. a slide 9 engaged on a roller 10 screwed onto a stud 100 made integral with the forme cylinder 3 by two fixing screws. AT the opposite end of the positioning device (Figure 2), the base 4 is attached to a roller 11 placed between the flanks 12 and 13 of a circular cam-crown 14 mounted on the not shown frame of the machine. In Figures 1a and 1b there are two other rollers 15, 16 which are secured to the base plate 4, and which slide respectively in two cams 17 and 18 fixed rigidly to the bottom of the bleeding 1 of the forme cylinder 3. A member 101, consisting in particular of an electric motor, is above all mechanically connected to the cylinder plate holder 3 and allows to move it laterally along its axis of rotation 2.

As shown in FIGS. 1a, 1b and 3, the base plate 4 comprises several supports 20 in the form of rectangular pads, held by their base by screws 21, and above which are fixed, first and with the help of the screws 23, a protective plate 22 bent in its length, then the front claw 5 held by screws 24 which also seize the protective plate 22. In front of the front claw 5, the rear claw 6 is fixed by fastening members 103 (FIG 4) on a claw support 25 consisting of a metal plate pierced with a plurality of oblong holes 26 (Fig. 5a, 5b) through which are trunnions 27 for holding the rear claw 6 on its claw support 25 with fixing screws 28. The orientation of these holes oblong 26 allows on the one hand to respect a lateral movement required of the claw holder 25 relative to the rear claw 6, and other part of driving the latter in a longitudinal movement perpendicular to the axis of rotation 2 of the forme cylinder. This last movement concretizes the closing and opening of the rear claw 6 which allows respectively to extend or release the plate 19 of the cylinder 3. The claw support 25 is rigidly fixed by means of screws 29 on two studs 30, in the shape of a rectangular parallelepiped, sliding on two axes. 31. These axes are maintained at each of their ends by a support 32 fixed to the base plate 4 by screws 33. Au above each of these supports is a clamping screw 34 which allows to block the axis 31 in its support 32. Thus, it is possible to move longitudinally along the axes 31 the claw support 25 carrying with it the rear claw 6 thanks to the perpendicular orientation oblong holes 26.

The longitudinal opening movement of the rear claw 6 is Arbitrated by seven pneumatic cylinders 40 (Fig. 5a, 5b) working simultaneously fed by conduits 41 held on the plate of base 4 by attachment flanges 42, and interconnected by connectors 43. These jacks 40 are mounted, thanks to the screws 45, on 44 shaped supports of L that can also serve as attachment points for fixing the protective plate 22 and the front claw 7. These supports 44 are regularly spaced and positioned each on the baseplate 4 by two fixing screws. Plate 46, bent at right angles in their ends, are positioned in front of the jacks 40 and welded, standing on one of their two main stops, at the support of claw 25. At the pressurizing the pneumatic circuit which feeds the cylinders 40, the axes 47 of these (Fig. 1a, 1b) push the claw support 25 in front of them by resting on the plates 46. The rear claw 6 associated with the claw support 25 is then opened.

Closing of the rear claw 6 is performed once the pressure in the cylinders released, thanks to a plurality of springs 48 of compression (Fig. 4, 1a, 1b) which push back the claw support 25 into a longitudinal movement of closure. Each of these springs 48 is guided by the rod of a screw 49 which passes through the bent plate 46 on which is supported one of the ends of these springs. The second end of the springs 48 is supported on a plug 50 screwed into a retaining stud 51 itself maintained on the base plate 4 by two screws 52. The retaining studs 51 also serve as a mounting bracket for a second protective plate bent 53 which partially overlaps the top of the claw support 25. This protection plate 53 is fixed at its base by a plurality of screws 54 (Fig. 1a, 1b) housed in the retaining studs 51, and has circular openings leaving free access to the plugs 50.

The lateral positioning of the cliché 19 on the front claw 5 is provided by a centering pin 55 (Fig. 4) driven into the part upper of the front claw 5 and arranged precisely on the axis longitudinal of the printing machine.

FIG. 5b shows a fastener 60 attached to the end C.C. of the base plate 4 by screws 61. The roller 11 is positioned on the longitudinal axis of this fastener with a screw 62. Two holes 63, located around the first and the last third of the base 4, have a diameter substantially greater than that of two sockets 64 through them (Fig. 3). The excessive size of the holes 63 allows provide the necessary space for the movements of the base plate 4 while the now plated at the bottom of the groove 1 by holding organs 102; this in order to be able to fight against the effect of centrifugal force on the base plate 4 during the rotation of the forme cylinder. Organs 102 are constituted by sockets 64 around which two pads 65, of synthetic material with a low coefficient of friction, sandwich the base plate 4 and allow it to move easily. A compression spring 66, disposed between two other washers 67 and 68, and a screw 69 resting on the washer upper 68 and coming to screw into the bottom of the groove 1 after having through the bushing 64, maintain the clamping of the base plate 4 in a plane parallel to the section of the forme cylinder. The fastener 60 is also pierced with a hole 70 crossed by a screw 71 which both respectively the same functions as the holes 63 and screws 69 described just now.

As shown in Figures 5a and 5b, two openings rectangles 72, cut out of the base plate 4, make it possible to accommodate the cams C.C. 17 and C.O.C. 18 integral with the forme cylinder 3. These openings 72 are larger than the size of the bases 80 cams 17 and 18, so that the base plate 4 can to move freely around these cams without bumping against one of them. The openings 72 are lined in their width on each side by three aligned holes whose middle holes 73 position precisely a stirrup 74 with two cylindrical pins 75, and the end holes 76 are intended for fixing the stirrup 74 on the plate 4 by screws 77. As illustrated by FIGS. 6 and 7, the stirrups 74 constitute two bridges, integral with the base plate and arranged by above the cams 17 and 18, in the largest face of which are screwed from below the rollers 15 and 16 which slide in the respective cams 17 and 18. Screws 78 still make it possible to fix the protective plate 22 and the front claw 5 above the stirrup 74.

The cams 17 and 18 are symmetrical with respect to each other and consist of a staircase base 80, on the one hand pierced with a hole intended to receive a pin 81 of centering, and secondly breakthrough of two fixing holes 83 into which two screws 82 screwed into the forme cylinder 3. Above the base 80, two small projecting portions 84, of triangular shape and constituting the core of the cam, between which the roller 15 or 16 slides according to the considered cam C.C. or C.O.C.

In order to clearly perceive the operating principle of the mechanism constituting the present invention, FIGS. 8a, 8b and 8c very schematically illustrate three very different positions in which can be said device for positioning the plate. When no bias is applied to the snapshot, the configuration of the mechanism is in an intermediate position in accordance with the schematic illustration of Figure 8a.

When the snapshot needs to be biased in one direction or in another, only a simple lateral displacement of the forme cylinder in the direction of its axis of rotation 2 makes it possible to actuate the mechanism snapshot of the snapshot. The lateral movement of the forme cylinder 3 is controlled by the body 101 including an electric motor coupled to toothed wheels meshing with a worm. This mechanism Conventional makes it possible to convert the circular motion of the tree of the motor in a rectilinear motion necessary for the lateral displacement of the cliché cylinder. The displacement of the forme cylinder with the help of engine and this mechanism is further automated through sensors detecting the lateral position of the forme cylinder. These sensors are connected to an external electronic controller (not shown) controlling the motor of the organ 101. Thus for a given work, the bias of a snapshot can be easily controlled and stored by the electronic controller, via position sensors, simply by memorizing the displacement side of the platen cylinder.

As illustrated in Figure 8b, when the cylinder is moved from C.O.C. towards the C.C., the roller 11 will be supported, after a certain race, against the flank 12 of the cam-crown 14. It will follow a movement combined base plate 4, guided by rollers 15 and 16 which slide in the cams 17 and 18, consisting of both a pivoting of the base plate 4 around the roller 11 and a translation of this plate base marked by the sliding up of the same roller 11 the along the flank 12 of the crown cam 14. Sliding only longitudinally on the roller 10, the slide 9 of the rear claw 6 does not allows that to accept a translation and rotation movement around of the fixed pivot point formed by this roller 10 secured to the cylinder 3. Given the longitudinal orientation of this slide, no movement along the axis 2 can not be transmitted to the rear claw 6. Thus, thanks to the latter which can not move parallel to axis 2 cliché cylinder, and thanks to the combined movement that is also constrains the front claw 5, the front and rear edges of the snapshot can then be biased, as subtly as simply, in a shear movement while remaining parallel to themselves.

Figure 8c illustrates, in the opposite direction, the same combined movement resulting from the displacement of the forme cylinder 3 from C. to C.O.C. In this case, the roller 11 is supported and slides along the opposite flank 13 of the crown cam 14.

When the operator wants to correct the bias positioning of a snapshot 19, it will act on a command that will release slightly pressure in the cylinders 40, so as to relax and take off the cliché of the cylinder, and which will operate the engine of the organ 101 in order to move, in one direction or another, the cylinder plate 3. A time that the roller 11, come into contact with one of the flanks 12 or 13 of the cam-crown 14, has moved along the latter a distance corresponding to the desired bias, the forme cylinder 3 moves in the opposite direction so as to reposition it according to the lateral register that it is suitable for printing. This last move does not change anything the biasing of the plate 19 since, during this reverse movement, the roller 11 is immediately detached from the side of the cam-crown 14. Thanks to the adhesion cliché stretched on the platen cylinder, the skewed position of the snapshot remains preserved. Knowing the position of the lateral register of the cylinder cliché holder, it is then easily possible to automate the biasing of the snapshot of an angular value, to choice, by simple introduction of this value in the electronic controller.

a) Ouverture de la griffe arrière 6 à l'aide des vérins 40 qui compriment les ressorts 48.

b) Fixation du bord avant du cliché 19 dans l'encoche 7 de la griffe avant 5 et dans la goupille 55 de centrage latéral.

c) Mise en rotation lente du cylindre porte-cliché 3 autour de son axe 2 de manière à ce que le cliché 19 s'enroule autour du cylindre.

d) Fixation du bord arrière du cliché 19 dans l'encoche 8 de la griffe arrière 6.

e) Fermeture de la griffe arrière 6 par relâchement de la pression dans les vérins 40.

f) Mise en rotation rapide du cylindre porte-cliché 3 et actionnement des vérins 40 afin de décoller légèrement le cliché 19 du cylindre pour en permettre son biaisage.

g) Actionnement du biaisage du cliché 19 par déplacement latéral du cylindre porte-cliché 3 d'une certaine distance signée correspondant à l'inclinaison souhaitée.

h) Déplacement latéral opposé du cylindre porte-cliché 3 de manière à rétablir le registre latéral nécessaire pour l'impression.

i) Relâchement de la pression dans les vérins 40.

Thus, the operations for setting up and biasing a snapshot on a forme cylinder equipped with a device that is the subject of the present invention can be summed up in the following steps:

a) Opening of the rear claw 6 using the jacks 40 which compress the springs 48.

b) Attaching the front edge of the plate 19 in the notch 7 of the front claw 5 and in the pin 55 of lateral centering.

c) Slow rotation of the forme cylinder 3 around its axis 2 so that the plate 19 wraps around the cylinder.

d) Attaching the rear edge of the plate 19 in the notch 8 of the rear claw 6.

e) Closing the rear claw 6 by releasing the pressure in the jacks 40.

f) Rapid rotation of the forme cylinder 3 and actuation of the cylinders 40 to slightly peel off the plate 19 of the cylinder to allow its biasing.

g) Actuation of the biasing of the plate 19 by lateral displacement of the forme cylinder 3 by a certain signed distance corresponding to the desired inclination.

h) Opposite lateral displacement of the forme cylinder 3 so as to restore the lateral register necessary for printing.

i) Releasing the pressure in the cylinders 40.

In addition to fixing the cliché around its cylinder, all other operations described above can be easily automated thanks to the design and specific mechanism of the cliche bias imagined in this invention. When resuming an old job of printing, this device has the advantage of no longer requiring any adjustment manual snapshot if the calibration values, previously known from this last, we have been memorized. Finally, note that this device allows also to proceed to a bias of the cliché when the cylinder picture holder rotates at full speed. Position correction oblique cliche no longer requires the complete shutdown of the machine of printing, which makes it possible to reduce to a certain important start-up costs when preparing a new print job. Many improvements can be made to this device in the context of the claims.

Claims (10)

1. Device for positioning a flexible printing plate (19) on a plate cylinder (3), the device being adapted to bias a printing plate in a rotary printing machine, the plate cylinder (3) having an axis of rotation (2) and formed with a groove (1) disposed parallel to the axis of rotation (2) and containing the said printing plate positioning device, characterized in that the device is actuated by lateral displacement, outside a certain travel distance, of the plate cylinder (3), which is moved by an external means (101) secured to the frame of the printing machine and by means of an annular cam (14), disposed outside the cylinder and facing the means (101), on the inner edges (12, 13) of which a roller (11) bears and is secured to a baseplate (4) which is movable and is held free from the plate cylinder (3) by holding means (102) and by two cams (17, 18) rigidly secured to the bottom of the groove (1) in the plate cylinder (3) and controlling the movement of two rollers (15, 16) connected to the baseplate (4), in an opposed sloping movement.
2. Device according to claim 1, characterized in that the external means (101) for moving the printing plate positioning device comprises a motor and a mechanism for conventional lateral movement of the plate cylinder (3) along its axis of rotation (2) and a digital controller for measuring and storing the value and the direction of the lateral movements of the plate cylinder by use of conventional sensors disposed in the printing machine frame.
3. Device according to claim 1, characterized in that each cam (17, 18) comprises a rectangular base (80) fixed and accurately positioned in the bottom of the groove (1) in the plate cylinder (3) by screws (82) and by at least one centering pin (81), and in that two triangular projecting parts (84) above the base are disposed so that the rollers (15, 16) can slide without clearance between the longest surfaces of the triangular projecting parts, which are oriented at 30° relative to the axis of rotation (2) of the plate cylinder (3).
4. Device according to claim 1, characterized in that the baseplate (4) has two rectangular openings (72) larger than the bases (80) and at the positions occupied by the cams (17, 18) so that the cams can extend through them, a number of holes (73, 76) adjoining each opening (72) for the purpose of rigidly and accurately securing two stirrups (74) holding the rollers (15, 16), other regularly spaced openings (63) being adapted to receive the means (102) for holding the baseplate (4) on the plate cylinder (3), the baseplate (4) also supporting a front claw (5) substantially equal in length to the groove (1) and rigidly secured thereto via blocks (20) and supports (44), a rear claw (6) is disposed facing the first claw and is held by fastening means (103) on a claw support (25) which cannot move independently of the rear claw (6) except parallel to the longer sides of the baseplate (4).
5. Device according to claim 1, characterized in that the holding means (102) each comprise a bush (64) substantially smaller in diameter than the opening (63) through which it extends, and round which the following are stacked in succession: a washer (67) resting on a bearing (65) disposed at the said place on the baseplate (4), a compression spring (66) and an upper washer (68) which bears the head of a screw (69) which extends through the bush (64) and is screwed into the bottom of the groove (1) in the plate cylinder (3).
6. Device according to claim 4, characterized in that the stirrups (74) form bridges, in the largest surfaces of which are screwed below the rollers (15, 16), the stirrups being disposed and fastened to the baseplate (4) above each respective cam (17, 18).
7. Device according to claim 4, characterized in that the claw support (25) comprises a metal plate, substantially equal in length to the front claw (5) and formed with a number of regularly spaced slots (26) oriented parallel to its longest sides and through which the fastening means (103) extend, each comprising a journal (27) into which a screw (28) is screwed and holds the rear claw (6) on the claw support (25), the support being mounted on at least two blocks (30) each sliding on an axis (31) disposed perpendicular to the length of the baseplate (4) and held at its ends by two supports (32) screwed into the baseplate (4) so that the rear claw (6) and the claw support (25) can slide along the axes (31) in a movement comprising closing and opening the rear claw (6).
8. Device according to claim 7, characterized in that the rear claw (6) is closed by a number of compression springs (48) each resting on a retaining block (51) secured to the baseplate (4) and pushing the rear claw (6) towards the front claw (5) via a number of metal plates (46) disposed upright and perpendicular to the front claw support (25) and secured to the lower surface thereof.
9. Device according to claims 7 and 8, characterized in that the rear claw (6) is opened by a number of pneumatic jacks fastened to the supports (44) and on a shaft (47) which pushes the plates (46) so as to compress the springs (48).
10. Device according to claim 8, characterized in that each retaining block (51) is formed with a threaded hole for inserting each compression spring (48) and in which a plug (50) is screwed and serves as a rest for the said springs (48).

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