EP0788879A1 - Rotary printing press - Google Patents

Abstract

The rotary printing machine has the printing cylinders (16) at each printing station (1,2,3) directly driven by a vectorial asynchronous motor (26) controlled by an electronic circuit (101) regulating angular position. The set angular position is delivered over time from a central synchronisation controller. The assembly of cylinder, shaft and rotor is mobile in axial translation, to allow correction of lateral position of the printing plates or the cylinder. Reference marks printed by each station are monitored to determine the misalignment. Errors are corrected by an adjuster mechanism (35) driven by an electric motor (25). An angle encoder on each shaft provides rotational position information.

Description

The present invention relates to a rotary printing machine for strip or plate elements, and more particularly to a polychrome printing machine comprising several printing stations of fundamental colors, these prints overlapping to give the image final. Each station comprises, inter alia, an internal plate cylinder working jointly on the one hand with an ink cylinder and an underlying transfer cylinder and on the other hand with an upper support cylinder.

As such, the document EP 352 483 describes a printing machine in which all the support cylinders are driven by bevel gears engaged with a first mechanical shaft driven by a first electric motor, and all the cylinders carries -clichés are animated from a second mechanical shaft driven by a second electric motor. These two engines are controlled by a digital computing center adapting the angular speed of the plate cylinder cylinder shaft in case their diameter does not correspond to that of the support cylinders, which avoids having to change them.

However, this type of drive by means of one or two shafts supplemented with angle transmission mechanisms is rather expensive. The precision of this training is also limited, especially since a jerk in one of the stations affects the others. In addition, this drive can easily vibrate due to its low natural mechanical frequency.

Document FR 2,541,179 describes a machine for making folding boxes from cardboard sheets, in which a printing section with four printing units is interposed between an upstream introduction section and discharge sections, '' notching, cutting, folding and then receiving downstream. A DC motor M1 drives the lower and upper conveyors of each printing unit, the plate cylinders of which are driven individually by four M2-M5 DC motors. The setting of the longitudinal marking between the printing units is carried out by acting electrically on the angular position of each of the motors M2 to M5. The printing cylinder of each printing unit is arranged so that it can also be moved laterally to align the prints of different groups between them. To do this, it is mounted on bearings allowing lateral movement of the cylinder under the action of motors M105 to M108.

This machine comprises a motor drive device M1 to M5 consisting of a control group, comprising a setpoint generator circuit and a synchronization circuit per motor; a calculation group consisting of a microcomputer with input / output circuits; a signal conditioning group comprising a direction discrimination and pulse multiplication member from pulse generators G1 to G5 of the motors M1 to M5 as well as a conditioning circuit for interphase and shaping of the signals going from the first and second groups; and a control logic group composed of a logic circuit for selecting the drives and a logic circuit for selecting the manual commands.

This device produces between the motors M2 to M5 a virtual electric shaft for synchronizing the printing units, and this by setting them on the master motor M1 for general drive of the sheets from which it receives electrical pulses from an encoder. This device notably performs the verification of the agreement between the programmed values and the actual state in which the machine components are found; a prepositioning of the motors M1 to M5 during a change of work or after rupture of the electric shaft connecting them; the execution of the angular corrections of the motors M1 to M5, whether on order by push-button or by control units for locating the sheets, as well as the execution of the lateral corrections by acting on the motors M105 to M108; and monitoring the proper functioning of the various engines.

Already more precise, this machine is however handicapped by the drawbacks inherent in DC motors, namely: their size due to necessarily large enough diameters; the regular maintenance of the brushes allowing the rotor circuits to be looped in conventional machines, or their price in the case of so-called "brushless" motors, since it is necessary to sinter large magnets on the rotor to form the poles.

A recent development, described for example under the name SYNAX in the catalog of the electric motor manufacturer MANNESMANN REXROTH of September 1994, consists in using asynchronous electric motors with so-called "vectorial" control including electronic control and position control circuits angular of the motor are connected by a transmission loop to an electronic central computation station synchronization between them, this central unit addressing to each control circuit a position reference value "fleeing", ie evolving with the desired machine speed.

A first advantage of asynchronous motors is that they are cheaper to buy and maintain than the fact that their rotors only have large turns short-circuited on themselves.

The major advantage of asynchronous motors is the remarkable precision of the output torque, and thereby of the speed and the angular position, obtained by a so-called "vector" control in which the stator is supplied by means of a voltage inverter by acting on the frequency and on the amplitude of the stator voltage. As an alternative, instead of controlling the stator frequency, the phase of the stator voltage with respect to the rotor flux is controlled, which makes it possible to obtain a faster response.

Usefully, the position setpoints are transmitted from the central computer to the control circuits digitally along a loop of optical fiber, this transfer being particularly insensitive to electromagnetic disturbances present in the workshops.

Furthermore, angular encoders are known which are intended to be mounted at the end of the rotary axis and which generate a sinusoidal output signal, the interpolation of which makes it possible to determine the angular position of the axis to 1/2000000 of a millimeter. Then, the regulation carried out by a control circuit whose feedback loop receives the signal from such an encoder makes it possible to ensure a synchronization precision of less than 0.005 angular degrees, which, for a plate cylinder of usual diameter of the order of 800 millimeters, corresponds to a peripheral error of 0.07 millimeter, that is to say far below the positioning error of 0.10 millimeter usually tolerated in printing.

It can then be proposed to directly connect the output axis of the vector asynchronous motor to the axis of the plate cylinder, which makes it possible to eliminate any usual reduction coupling always comprising an elastic clearance disturbing the transmission of the torque and the position. Better, it is proposed to produce an axis common to the motor rotor and to the plate cylinder, this axis being of larger and hollow diameter to optimize the ratio between the stiffness of torque transmission and the inertia of rotation.

Furthermore, and as mentioned in the description of the machine with DC motors, it is important to be able to correct the position of a plate cylinder during production as a function of that of the others when the corresponding impression is obtained. turns out to no longer be in the register. When the error is in the direction of travel of the element, we speak of a "longitudinal" error, and it is necessary to modify the peripheral position of the photograph, therefore the angular position of the corresponding cylinder. When the error is transverse, we speak of a "lateral" error, and the plate cylinder should be moved along its axis.

Document EP 401 656 describes, for example, a device for driving and adjusting a plate cylinder and its support cylinder, which device is located on one side of the machine. In this device, the drive torque of the cylinders is transmitted by three toothed wheels in series with helical teeth. The second toothed wheel is mounted to rotate freely on the axis of the plate cylinder via a bearing. A double toothed wheel has, next to the first toothed wheel with helical teeth, a toothed crown with straight teeth which meshes on a toothed wheel with also straight teeth mounted rigidly on the axis of the plate cylinder. The lateral identification is then carried out by advancing or retreating the axis of the plate cylinder, which has no consequence on the speed of rotation of the cylinders because of the straight teeth and the second floating wheel. The peripheral identification is carried out by moving the double toothed wheel parallel to the axis, therefore the first helical wheel relative to the second, which advances or decreases the peripheral position of the plate cylinder relative to the support cylinder.

The documents US Pat. with straight teeth, the corrections can be made separately, by hand or remotely using electric motors. Incidentally, the use of gears makes it possible to insert a reducer reducing the necessary power of the motor, and also dividing the necessary resolution of the calculations of subsequent corrections by the value of the reduction factor.

However, these known double correction devices involve the presence of gear reduction devices interposed between the drive motor and the axis of the plate cylinder, reducers whose operation is modified according to the correction desired by a set of connecting rods , cams or levers acting either on one or the other of the toothed wheels or on such or such other support bearing of the cylinder axis. These complex devices are firstly expensive to produce. These devices then involve significant inertia to be overcome either manually or using powerful engines which slow down the implementation of the correction. In addition, the inevitable wear of the parts over time induces mechanical play within the devices altering the precision of the corrections.

These effects then significantly reduce the advantage of using sophisticated electric motors, in particular asynchronous motors with high precision vector control. For machines using this type of engines, it then remains a control of the complex longitudinal location by means of wandering rollers for modifying the belt tension between two stations, and no lateral correction is expected.

The object of the present invention is a printing machine based on asynchronous vector motors for direct drive of the plate cylinders, and if desired also of the support cylinders, this machine further comprising manual double correction means or automatic longitudinal and lateral plate registers excluding any reduction mechanism inserted between a motor and its plate cylinder.

These correction means must be as precise as possible, that is to say react effectively from very fine errors, and this in a dynamic manner, that is to say in a very short response time. For this, these means must first include organs whose structures are both rigid so as not to induce bending errors, and simple to reduce the production costs accordingly. These bodies must also be able to be assembled without play, or with simple compensation, in order to be able to transmit adequately correcting powers.

These goals are achieved by a rotary printing machine, the plate cylinder of each printing station is directly driven by an asynchronous vector electric motor controlled by an electronic circuit for controlling and controlling the angular position at a setpoint evolving over time and received from an electronic central station synchronization station, each plate cylinder axis being fixed in the extension of, or being common to the axis of the rotor of its motor , due to the fact that the cylinder / axis / rotor assembly of at least one station is movable in axial translation relative to the chassis of the machine and to the stator of the engine, and this for correction of the lateral location of the cylinder (s).

A priori for an electrical engineer, the displacement of a rotor relative to its stator induces substantial modifications of the fluxes internal electromagnetic changes which hardly predictably the mechanical torque output. However, in this case, rather longilinear vector asynchronous motors are known, for example of the order of 500 millimeters, while the range of displacement necessary for performing lateral corrections is only 10 millimeters. Workshop tests have shown that the small variations in flux could then be fully caught up by the control and servo circuit of the asynchronous motor.

Advantageously, the plate cylinders of all the stations are movable in translation with their associated rotor, and the machine comprises a device reading mark marks printed by each station, and establishing the possible lateral and longitudinal register error for each station. . Then, each lateral error is applied to the electronic control circuit of an electric motor of the corresponding station controlling, through a mechanism, the axial position of the rotor / axis / cylinder assembly, and each longitudinal register error is directly added to the cylinder position setpoint of the corresponding station.

As soon as it is possible to dispense with mechanisms with interposed gears to axially move the plate cylinder so as to preserve a rigid direct connection between this cylinder and its rotor, only then is a fine and dynamic longitudinal correction justified. by direct action of the asynchronous motor in combination with lateral correction. This proves to be particularly advantageous for machines for printing elements in bands, in which, in addition to the heavy correction mechanisms, it is also possible to make the wandering control cylinders disappear from the register by modifying the tension of this band.

According to a preferred embodiment, an angular encoder is mounted at one end of each rotor / cylinder axis to generate a signal representative of the angular position of the axis which is applied in the feedback loop of the control circuit and enslavement of corresponding asynchronous motor, the angular encoder housing being connected to the machine chassis by an angularly rigid attachment but allowing it to follow the axial displacements of the axis.

In particular, the attachment of the angular encoder may comprise a plurality of lamellae in the form of coaxial parallel crowns connected to each other by diametric pairs of fasteners arranged in quadrature from one lamella to the other.

Control of the angular position of the cylinder is thus particularly improved when the control and servo circuit has feedback information on the instantaneous angular position of the axis given by an angular encoder mounted directly on the axis, but as long as this information is reliable. To do this, it first proved preferable to keep the encoder in relation to the axis, and not fixed to the chassis. In particular, the fastener according to the invention ensures an axial movement without effort of the encoder housing to follow this axis, but also a very high torsional rigidity, an important condition for a correct reading of angular position. Above all, the attachment device of the angular encoder according to the invention avoids having to move the whole of the asynchronous motor with the cylinder, which would then have constituted a mass too large to allow the achievement of fine and dynamic lateral corrections.

Advantageously, the common axis of the rotor and of the cylinder is mounted on needle bearings, and it comprises a projecting flange taken by a fork displaced axially by a worm screw parallel to the axis and driven by the electric lateral correction motor. . Preferably then, the flange or the fork comprises a first ball or cylinder bearing for reducing friction force and taking up play. In addition, the fork is also guided through a second bearing along a support axis. The worm is, for example, connected to its motor by a reduction mechanism comprising a pinion and a toothed wheel, or a pinion connected to a pulley by a toothed belt.

This movement mechanism of the rotor / axis / cylinder assembly proves to be relatively simple to perform while ensuring precision of the movement by means of the reduction gear connecting the motor to the worm, and by the firm mounting by means of bearings. to take up play of the fork on the one hand along a rigid axis and on the other hand in its engagement with the collar of the axis.

Usefully, the end of the axis on the side opposite the motor is held by a removable bearing. Then, the plate cylinder is fixed on the axis by clamping its two end hubs between a first fixed cone on the motor side, and a second removable removable cone capable of being pushed towards the first by mechanical means, for example, by a nut engaged on a thread formed at the end corresponding to the axis.

When the plate cylinder has to be changed to another with a different diameter to better adapt to the format of a following series, the axis remaining permanently, only the cylindrical casing completed with two hubs is changed. end. This operation is much easier than the previous change of the cylinder with its axis and its gears, because this new assembly is much lighter, and can be threaded on a permanent axis which guides this installation. Clamping in position of the cylinder is simple and quick. In addition, the encoder is then preferably placed at the end of the axis on the motor side to leave free space for this change of cylinder, and incidentally so as not to be distorted by possible residual parasitic twists of the axis.

• la figure 1 est un schéma de principe de la machine selon l'invention,
• la figure 2 est un schéma de principe du dispositif de correction de l'erreur latérale et longitudinale d'une station d'impression de la machine,
• la figure 3 est une vue en coupe longitudinale d'un moteur électrique relié à son cylindre porte-clichés au sein d'une station d'impression de la machine, et
• la figure 4 est une vue en perspective de l'attache d'un codeur angulaire au châssis de la machine.

The invention will be better understood from the study of an embodiment taken without any limitation being implied and illustrated in the appended figures in which:

• FIG. 1 is a block diagram of the machine according to the invention,
• FIG. 2 is a block diagram of the device for correcting the lateral and longitudinal error of a printing station of the machine,
• FIG. 3 is a view in longitudinal section of an electric motor connected to its plate cylinder within a printing station of the machine, and
• Figure 4 is a perspective view of the attachment of an angular encoder to the chassis of the machine.

In Figure 1 is schematically illustrated a strip element 4, such as a strip of paper or cardboard, passing successively through three printing stations 1, 2 and 3 each comprising a plate cylinder 16 facing each other. screw of a support cylinder 14 working like a rolling mill. In the example illustrated, these stations successively deposit a square, circular and then cross impression intended to overlap exactly.

In the illustrated machine, all the axes 24 of the support cylinders 14 are mechanically connected to the same drive shaft 54 moving the machine upstream downstream along its printing stations. The coupling of these axes 24 of support cylinders is carried out by means of bevel gears 34 with bevel gears. This shaft 54 is driven by an electric motor 110 controlled by a first electronic circuit for controlling and controlling the angular position 100. The angular position a0 of the shaft 54, reflecting the advance of the strip 4, is read by an encoder 64 whose electrical signal representative of this angular position is applied in the feedback loop of the circuit 100.

Furthermore, the plate cylinder 16 of each of stations 1, 2 and 3 is directly mounted on an output axis 65 of an electric motor, that is to say that the rotor 26 of this motor is built on the very end of this axis, while the stator 36 is integral with the chassis of the machine. In this case, the diameter of this axis 65 is relatively wide, of the order of 50 to 80mm, to transmit significant torques without elastic tension, but it is also hollow in the middle to reduce its moment of inertia. These motors are preferably asynchronous alternating current controlled by an electronic control circuit and control of the angular position respectively 101, 102 and 103 for each of the stations.

In this machine, all the control and servo circuits 100-103 are connected by a loop network to a central computing unit 10. This unit includes a keyboard for data and instruction input, a microprocessor, a plurality of memories containing programs and management data according to the characteristics of the machine, as well as a screen for viewing the parameters entered and / or the data applied to the output on the loop. Preferably, this transmission loop consists of a coaxial optical fiber cable, a first strand connecting the output of the central unit 10 to the control circuit 100 of the drive motor of all of the support cylinders, a second strand connecting the circuit 100 to the motor control circuit 101 of the first station, a third strand connecting the circuit 101 to the motor control circuit 102 of the second station, a fourth strand connecting the circuit 102 to the control circuit 103 of the engine of the third station and, finally, a fifth strand ensuring the loop back to the central computing unit 10.

Information on the position setpoints of each of the engines passes through this transmission loop for a given instant t: respectively p0 (t) representative of the desired angular position of the engine 110, therefore of the shaft 54 and hence of all the cylinders support 14 defining values pL1 (t), pL2 (t) and pL3 (t) representative of the desired angular position of the station motors 1, 2 and 3 respectively, and therefore of the corresponding plate cylinders. Each set value is established by the calculation unit 10 so as to take into account the length of the machine, in particular the intervals between the stations, the format of each photograph possibly arranged on cylinders of different diameters, and this so as to ensure a rigorous synchronization of the stations between them so that the prints are superimposed correctly to give a final quality image. These quality guidelines. These position setpoints are "fleeting", that is to say that they change over time depending on the desired production speed of the machine.

In this way, instead of a traditional mechanical shaft parallel to the shaft 54, a virtual electrical synchronization shaft is produced in which all the motors of the machine are individually slaves of the computing center 10.

In addition, in each station, an angular encoder 56 delivers a signal a 1, a 2 and a 3 representative of the instantaneous angular position of the corresponding rotor 26, therefore of the plate cylinder as soon as it is accepted that the axis 65 is sufficiently rigid in its dimensions. In each station, the signal generated by this encoder 56 is applied in the feedback loop of the corresponding electronic control and servo circuit 101, 102 and 103.

These identical control and servo-control circuits 101-103 directly supply the stators of their corresponding motors with three-phase alternating electrical energy characterized respectively by the values of the stator intensity Is1-Is3, of peak-to-peak voltage amplitude Us1 -Us3, and of frequency f1-f3.

In the lower part of FIG. 2 is illustrated the block diagram of the control and servo-control circuit 101. This circuit firstly comprises a first torque servo subset G including a circuit Ki generating electrical energy stator Is1, Us1 and f1, as well as a feedback feedback loop either of the intensity by phases or of the flux for establishment of a possible correction error.

Such torque control circuits Ki for asynchronous motors are known. For example, document US Pat. No. 3,824,437 describes a circuit in which the magnetic field in its air gap and the stator current are measured, the measured stator current is transformed into two stator current components in quadratures oriented with respect to the measured magnetic field, and regulates one of the quadrature stator current components proportional to the set flow amplitude total rotor headcount at a constant level fixed by a reference quantity at the constant input corresponding to the setpoint amplitude of the total effective rotor flow and the other stator current component is varied in quadrature with a second quantity of reference or control applied to the input and proportional to the setpoint torque of the asynchronous motor. Another method of controlling an asynchronous motor described in the document SU-193 604 consists in regulating phase by phase the instantaneous stator phase currents of an asynchronous motor by comparing the setpoints and the measurements of instantaneous phase current of the stator , to vary the stator current with the quadrature sum of two stator current components, one of which is constant and corresponds to the constant magnetic flux to be reached, the other being variable as a function of a control quantity corresponding to the torque of the asynchronous motor. Simultaneously, the frequency of the stator current is varied with the sum of two frequencies, one of which is that of rotation of the rotor, the other being subject to the variation of the setpoint torque.

The control and servo circuit 101 further comprises a speed servo loop based on the signal PL1 (a) from the angular encoder 56, this signal being derived over time in the feedback loop to obtain a effective speed information which is compared to the set value for establishment of the possible error, then speed control in the circuit kV put in series with the torque control circuit Ki.

In fact, in the machine according to the invention, we especially want to ensure a position setpoint. For this, the information pL1 (a) from the encoder 56 is also compared with the reference signal pL1 (t) received from the fiber optic transmission loop for establishment of a possible position error, then servo-control in position in the cicuit Kp connected in series with the speed control circuit Kv. Thus, the angular position of the axis 65 of the motor output almost reflects the set value applied at the input.

More particularly according to the invention, and as best seen in FIG. 3, the axis 65 is mounted to rotate freely in roller bearings or needles 40, 40 'and 40' 'also allowing axial displacement when desired, this displacement axial taking on the one hand the rotor 26 and on the other hand the plate cylinder 16. More precisely, these bearings are in contact with the axis 65 through friction rings 42. The first bearing 40 is installed in a base 32 located at the rear of the stator 36 of the motor and fixed to the chassis 37 of the machine by the casing 33 of the electric motor. The second bearing 40 'is located between the electric motor and the plate cylinder 16, more precisely installed in a ring 38 secured to the chassis 37. The third bearing 40' 'is, in turn, installed at the other end of the axis 65 and of the cylinder 16 within a block 80 of the chassis capable of being moved backwards for release.

As illustrated in FIGS. 1 and 3, the axial position of the rotor / axis / cylinder 26/65/16 assembly is imposed by a fork 55 engaged with a flange 45 projecting from the axis, this fork being able to be moved in parallel to the axis by a mechanism 35 driven by a synchronous stepping motor 25, itself controlled by an electronic control circuit 15.

More specifically, the flange 45 is composed of two bearings crimped on the axis 65 and pushed against a shoulder 44 of this axis by a nut 43 engaged with an external thread of the axis, this thrust taking place through a spacer 41 leaving free access to the fork 55.

For stiffness considerations, the fork 55 is itself mounted through a ball bearing 53 along a support axis 58 mounted in the chassis 37 parallel to the axis 65. This fork is brought in axial translation by a carriage 52 in two parts and engaged with a double worm screw 30. The adjustment of the tightening of these two parts of carriage 52 makes it possible to eliminate any residual play. The end of the worm 30 carries a pulley 29 driven by a toothed belt 28 in engagement with the output pinion 27 of a stepping motor 25 mounted rigidly on an upper flange 39 of the chassis 37.

As can be seen, this assembly can be carried out very rigidly. The precision of the displacement of the fork 55, therefore of the axis 65, is obtained on the one hand by the pitch of the micrometric screw 30 and on the other hand by the diameter ratio of the pulley 29 and the pinion 27.

Furthermore, the angular encoder 56 is mounted at the rear of the motor at the end of the axis 65. More particularly, the attachment 46 of the encoder housing with fixed base 32 is such that it allows axial movement of this housing to always remain in exact correspondence with its internal rotary mechanism 57 which, for its part, is integral with the axis 65, but is such that it rigidly maintains this housing in a fixed and precise angular position relative to this base 32 .

To do this, and as best seen in Figures 3 and 4, this fastener 46 is composed of a plurality of lamellae in the form of concentric crowns 47 attached to each other by diametrical pairs of fasteners 48, a pair between two lamellae being offset at right angles to the next pair. These slats being thin, they are flexible in the axial direction. On the other hand, the crown shape of these strips prevents any rotation relative to the central axis. This encoder 56 is protected by a cover 31 fixed to the base 32.

The printing machine according to the invention further comprises a device for locating marks printed at the edge of the strip by each of the stations, this locating making it possible to establish possible longitudinal and lateral register errors of one or the other impressions. As illustrated in FIGS. 1 and 2, the marks 5 pass under an optical read head 21 focusing a beam of light sent by a first part of a bundle of optical fibers 23. The reflected light is read by the read head 21 and conducted by the second part of the optical fiber 23 to photosensitive elements 20 whose generated electrical signals are applied to a register control unit 22.

This control unit 22 includes a processing circuit 220 for conditioning and selecting the signals which it directs either towards a circuit for calculating the longitudinal error 222, that is to a circuit for calculating the lateral error 224. The circuit 222 comprises three output lines making it possible to apply a signal representative of the longitudinal error dL1 to the control circuit and d servo 101 of the first station and, similarly, to apply the signals representative of a register error dL2 and dL3 to the control and servo circuits 102 and 103 of the corresponding stations. At the same time, the lateral error calculation circuit 224 comprises inter alia three outputs making it possible to apply a signal representative of the lateral register error dl1 to the preamplification and control circuit 15 of the motor 25 of the first station and, at the same time , signals dl2 and dl3 representative of lateral errors to the control circuits of the lateral correction motors 25 of stations 2 and 3 respectively.

Thus, if a lateral register error of one of the stations is detected by the control unit 22, the corresponding correction signal dl (i) triggers the rotation, in one direction or the other, of the motor 25 concerned which advances or moves back the fork 55 therefore the axis 65 with its plate cylinder, and thereby corrects the lateral position of the faulty plate.

The lateral error correction range is usually +/- 5mm. By retaining a rather elongated asynchronous motor, for example of active parts of length of the order of 500 mm, it can be seen that the offset of the rotor relative to the stator due to a lateral correction remains less than 1% of their total length, which only causes very slight disturbances in the flows which are moreover quickly caught up by the electronic control and servo-control circuit 10 (i). In addition, this displacement due to a correction of lateral register had no influence on the accuracy of the reading of the angular encoder 56 thanks to its special attachment 46, thus allowing the continuation of a correct operation of the control circuit and d servo of the vector asynchronous motor.

On the other hand, this rigorous respect for the proper functioning of the control of this asynchronous motor only then allows it to also be used to make corrections of longitudinal errors. With reference to FIG. 2, the longitudinal error signal dL1 is directly added in the addition of the setpoint signal pL1 (t) and the feedback signal pL1 (a) at the input of the control and servo circuit. 101. This error in locating dL1 is then simply and spontaneously treated as if it were only an error detected by the feedback. The asynchronous motor accelerates (or slows down) slightly during one revolution to readjust with respect to the advance of the strip 4 as imposed by the rotation of the counter-cylinders 14. A new marking mark is then read by the head of reading 21. If circuit 22 finds a residual error, it reapplies a lower adjustment correction dL1 'for the next round.

To facilitate and accelerate this check of the register, it is preferable to oversize the power of the asynchronous motor to a value between 4 and 5 kW. In addition, the installation of the engine in direct drive and very close to its plate cylinder makes it possible to reduce as much bending of intermediate parasitic torsions silencing that practically all of the correction is transmitted instantly.

For certain printing formats, it is useful to change the plate cylinder for another with a different diameter. Rather than using an axis 65 in several sections and connected by bolted flanges as currently used, it has been preferable to maintain the integrity of this axis across the entire width of the machine to install only one cylindrical casing removably attached. As such and with reference to FIG. 3, the cylinder 16 comprises a rigid and light cylindrical casing, for example made of aluminum, at the ends of which are fixed, by welding or other means, two hubs 74 having a central cavity outwardly oriented conical concave.

The axis 65 is then completed by a first cone 70 having a fixed position. For example, this first cone 70 is supported on the ring 42 emerging from the second roller bearing 40 '. The end of the axis opposite to the motor then comprises a first part of restricted diameter taken in the bearing 40 '', the following part then having an external thread on which can be engaged a nut 43 making it possible to push forward a second cone mobile 72.

A change of plate cylinder then takes place simply by releasing the bearing 40 '' from the axis by removing the movable block 80 and tilting. We can then unscrew the nut 43, which releases the second movable cone 72 and therefore the cylinder 16 which can be removed. It will then be noted that the presence of the pin 65 which has remained permanently makes it possible to guide the new cylinder on which it is threaded. The movable cone 72 is reinstalled and then pushed forward by rotation of the nut 44. The hubs 74 are thus clamped between the two cones 70 and 72, which achieves a rigid and playless attachment. The bearing 40 '' is finally reinstalled in advance of block 80. In particular, these cylinders being lighter than before, they are faster and more precise to handle. We can even consider automating such a change by means of a robot.

In addition, these simplified plate cylinders being less expensive to produce, one may wish to want to have a range of basic cylinders, for example coming in four standard diameters: 117.9mm 149.7mm, 181.5mm and 213.4mm. This is moreover facilitated by the virtual electric shaft managed by the central unit 10 of the machine. Indeed, it is then sufficient to carry out a new calculation of the setpoints of the leaking positions of the engine concerned, unlike the change of gears formerly necessary to ensure the agreement between the plate cylinder and the support cylinder.

On the plate cylinder is usually threaded a sleeve of expanded material having a certain internal radial elasticity and on the hard peripheral envelope from which the plates are effectively fixed by gluing. To facilitate this sleeve installation, you can take advantage of the central hollow part of axis 65 to produce a compressed air circulation between the outside of the cylinder and the inside of the sleeve. More specifically, a flexible tube 67, protected by the cover 31, connects an external connection socket 68 of compressed air with the internal channel 66 of the axis. At the end of the axis, this channel 66 opens onto one or more radial openings 76 diffusing the compressed air inside the plate cylinder 18. The end hub can then comprise one or more internal channels 75 making it possible to diffuse the compressed air under the sleeve 19. Under the effect of this air cushion, this sleeve expands radially, thereby increasing its internal diameter, which eliminates any friction force. It is thus possible to use a range of sleeves having thicknesses between 2.5mm and 66.2mm used alone or in superposition.

The reference 17 designates a plate cylinder of particularly large diameter and on which plates are directly stuck, this configuration being useful in countries where the supply of flexible sleeves is deficient.

Many improvements can be made to the printing machine within the scope of the claims.

Claims (7)

Rotary printing machine in which the plate cylinder (16) of each printing station (1,2,3) is directly driven by an asynchronous vector electric motor (26/36) controlled by an electronic control and monitoring circuit. servo (101) of the angular position (a1) to a set value (pL1,2,3 (t)) evolving in time and received from a central electronic calculation unit (10) for synchronization of the stations between them , each axis (65) of plate cylinder being fixed in the extension of, or being common to, the axis of the rotor of its motor, characterized in that the cylinder / axis / rotor assembly (16/65/26 ) at least one station is movable in axial translation for correction of the lateral location of the cylinder (s). Printing machine according to Claim 1, in which all the plate-carrying cylinders (16) are movable in translation with their associated rotor (26), characterized in that it comprises a device (20-23) reading mark marks ( 5) printed by each station, and establishing the possible lateral (dl1,2,3) and longitudinal (dL1,2,3) register error for each station (1,2,3), in that each lateral error ( dl1,2,3) is applied to the electronic control circuit (15) of an electric motor (25) of the corresponding station controlling, through a mechanism (35), the axial position of the rotor / axis assembly / cylinder (16/65/26), and in that each longitudinal register error (dL1,2,3) is directly added to the cylinder position setpoint (pL1,2,3 (t)) of the corresponding station . Printing machine according to claim 1 or 2, characterized in that an angular encoder (56) is mounted at one end of each axis (65) of rotor / cylinder to generate a signal representative of the angular position ( a1,2,3) of the axis which is applied in the feedback loop of the control and servo circuit (101) of the corresponding asynchronous motor, the angular encoder housing being connected to the machine chassis by an angularly rigid clip (46) but allowing it to follow the axial displacements of the axis. Printing machine according to claim 3, characterized in that the attachment (46) of the angular encoder (56) comprises a plurality of lamellae (47) in the form of coaxial parallel crowns connected to one another by diametric pairs of fasteners (48 ) arranged in quadrature from one slat to another. Printing machine according to claim 1, characterized in that the common axis (65) of the rotor (26) and the cylinder (16) is mounted on needle bearings (40, 40 ', 40' '), and in that it comprises a projecting collar (45) taken by a fork (55) moved axially by an endless screw (30), parallel to the axis, driven by the electric motor (25) for lateral correction. Printing machine according to claim 5, characterized in that the collar (45) or the fork (55) comprises a first ball bearing or cylinder, in that the fork (55) is guided through a second bearing (53) along a support axis (58), and in that the worm (30) is connected to the motor (25) by a reduction mechanism comprising a pinion and a toothed wheel, or a pinion (27 ) connected to a pulley (29) by a toothed belt (28). Printing machine according to claim 1, characterized in that the end of the axis (65) on the side opposite the motor is held by a removable bearing (40 ''), and in that the plate cylinder ( 16,17,18) is fixed on the axis by tightening its two end hubs (74) between a first fixed cone (70) on the motor side, and a second removable removable cone (72) capable of being pushed in. direction of the first by mechanical means (43).

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