DE19812894A1 - Continuous precision sheet processing in offset printing - Google Patents

Abstract

The method includes the steps of taking a sheet or a section from a stack, transporting them on a conveyor belt, whereby the sheets are subjected to a precise, constant advancement for the precision work step, and the sieve circulation is adjustable with respect to the print advancement. The circulation speed of the sieve drum is adjusted to the identical run speed of sheets during the duration of the precision work, and a referencing is performed through acceleration and/or delay of the sieve circulation speed.

Description

The invention relates to a method and its application and an apparatus for continuous precision processing of sheets or sections.

Today there is an enormous variety of techniques for arches and sections coat. On the one hand, it's classic offset and gravure, both Qualities in the field of photo technology are achievable. On the other hand the pure painting, and in between a large number of coating processes, especially for effect and special prints, e.g. with thick colors, shag colors or Fluorescent colors. Depending on the user, a distinction can also be made between Packaging printer, wrapping paper manufacturer or offer folder manufacturer and ring binders. Is within the various coating and printing processes screen printing or screen color printing, which has been known since the earliest times, is still strong today spread. In the past, screen printing was only used as screen printing. Today, rotary screen printing is also used. For rotary screen printing that is Printing performance compared to flat screen printing significantly higher. The main disadvantage in rotary screen printing is that at the higher throughput speeds only continuous paper can be processed from roll to roll. In addition, the Processing width is limited in relation to paper and is usually 20 to 60 cm. In gravure printing, both continuous webs and sheets or sections can be used be printed. The same applies to painting. The enormous variety Different process technologies has the advantage that for each Coating task an optimal technology is offered. In contrast but there are big price jumps in the individual techniques, depending on whether one Small edition or a large edition is made. This can lead to the situation that the production of a large-scale advertising sheet is only a fraction of the total costs in relation to varying special prints with partial series from the Large edition. E.g. with a sales network of 30 sales outlets corresponding number of special address imprints often not economically realizable. Despite the very high level of technology in the entire field In many cases there is the paradoxical situation that mass-produced goods are surprisingly cheap  is producible, but each individually adapted small series is prohibitively expensive and often different processors have to be involved. From the inventors has been recognized that at least screen printing, painting and application of special materials such as glues / adhesives not just related techniques there is also a real need for a single processor to process these can use different techniques. Screen printing has the great advantage that relatively small forces between the circular screen and the arches are required.

EP-PS 235 166 shows a simple application z. B. for the painting of Material webs. The material web can run in the same direction and in the opposite direction be moved. The movement of the applicator roller is in relation to the movement of the Material web insensitive.

DE-PS 30 17 271 shows the coating of arches. It will be in this The document appears to be only the detachment of the sheets from the application roller described. The whole problem is indicated, however, which arises during processing of single sheets. In the case of single sheets, the ratio of transport speed match the application or painting speed.

The level of precision is even higher Transport of the sheet and the speed of circulation z. B. a circular sieve for the rotary screen printing. Here both have to move absolutely synchronously. The de- PS 693 00 644 shows a special embodiment of a screen printing machine. Here it is proposed to have a short inside a mechanical endless conveyor Arrange guide device with the highest precision, so that the individual arches be moved absolutely synchronously with the printing cylinder. DE-PS 693 00 644 provides as it were the other extreme of a commissioned work for endless webs, in which only one varnish is applied.

The invention was based on the object of coating sheets and to improve sections so that even in smaller series inexpensive and can be coated efficiently, and in particular that several and / or different working techniques can be carried out in one system.

The inventive method is characterized in that the arches or Sections taken from a stack, transported on belts and for the Precision work step to be subjected to a precise constant delivery and the Sieve circulation position can be adjusted or regulated relative to the forced conveyance.  

The device according to the invention is characterized in that it has a Has a feeder, a belt transport device and a precision work station, with the precision workstation as a precise constant conveyor throughout is formed and the rotary screens have a controllable or regulatable drive for the referencing of the circular screen in relation to the arches or sections.

For advantageous embodiments of the method, claims 2 to 8 Referred. According to a particularly advantageous embodiment of the method become in the transition from a belt transport to the mechanical Forced transport the sheets or sections are gripped mechanically and by means of the mechanical gripper in a uniform, horizontal working plane through the Precision section drawn. There is thus a double clocking of the Sheet transport speed takes place, a first cycle takes place from the feeder to the prefers scaled delivery and a second cycle in the transition area from the belt transport to the mechanical forced transport by means of grippers instead. The Sheets or sections can be automatically removed from a stack, on one Scaled suction belt table, fed to a handover with mechanical grippers and be accelerated precisely to the working speed. In case of a After coating, the material is then dried, hardened or stabilization. For further advantageous embodiments of the Device is referred to claims 10 to 14.

The invention further relates to the application of the method and the use the device and is characterized in that for screen printing as Color printing or varnishing of sheets or sections or for the application of special application media such as glue, etc. with the appropriate design, the Screen cylinder as a quick change cylinder z. B. as screen printing cylinder, screen coating cylinder or is designed as a special screen application cylinder, one or more Screen cylinder in one precision work station, or in several precision work stations can be used.

The new invention solves the task in a particularly interesting way and allows a real multi-purpose system, as it were, and in a sense represents a combination between a roller printing, coating and rotary screen printing system. Medium or large batches of goods to be finished such as calendar sheets, advertising sheets, posters are used as sheets etc. understood. Sections are usually smaller formats, but book or booklet pages can be as small as labels. The forced guidance does not in any way prevent pure full-surface painting, but allows the use of screen printing cylinders if the sheets or sections are fed to the circular screen in register. On the other hand, in the same system, the accurate registration does not interfere if the entire surface of a sheet or a section or only partially, e.g. Varnish or paint must be applied. Especially if the screen cylinder is designed as a quick-change cylinder, it is possible to change from one specific job to another within a very short time. The new invention is also very interesting for the processing of UV-curable application materials. The new solution uses the advantages of the known painting technology as well as the screen printing technology and allows to work cheaper at least for some of the applications. In the known printing technology with circular screens, the problem of precision is solved in that the promotion of the printed sheets and likewise the construction and installation as well as the drive of the circular screens is aimed at with the highest precision. The new invention shifts the problem of high precision to three other areas.

• 1. It is the greatest possible constancy of the conveying speed of the sheet or Sections sought.
• 2. The screen circulation position in relation to the sheet or section is running exactly calculated or set.
• 3. And as a third area, the circulation speed of the screen cylinder exactly on the Conveying speed brought to the sheet or section.

The screen cylinder is preferably driven by a servo motor and by a High-performance computer or motor controller that controls the necessary corrections calculated within milliseconds and given to the servo motor as a control command. this has the very big advantage that only at one point, namely in the screen cylinder Cruise control must be made. The respective Conveying speed of the sheets or section is recorded and the computer signals. The length of the controlled system for referencing is exactly defined, so that by controlling the speed of rotation of the rotary screen an exact screen printing is also possible without the circular screen with respect to it Storage or its dimensions require the highest precision. The actually highest precision is concentrated on the exact circulation control of the rotary screen.

According to a further embodiment, the circular screen is arranged such that the common tangent of round screen and curved cylinder to the horizontal is inclined in such a way that the possibility is created that from the circular screen coating material coming from below can be collected in a tub.  

By a corresponding diagonal arrangement of the circular sieve can also in Circular sieve optimally existing coating material through the circular sieve be coated. Arches or sections are advantageously in the area of the lower quarter of the bow cylinder to the outer surface, and the Coating approximately in the middle of the upper quarter of the same side of the Shell surface of the bow cylinder performed. The side of the sheets to be coated or sections before coating, also on the outer surface of the Arch cylinder brushed so that the surface of the arches or sections one allows higher quality of the coating. Brushing on the cylindrical Curvature is very effective for the final quality of the coating. Furthermore, suggested that the screen cylinder both in the direction of movement of the arches or sections as well as at right angles to it. With that, too Deviations in register accuracy easily corrected and as required the circular screen can be lifted off the bow cylinder. This is very important in Test series especially for the first setting or optimization of the Investment parameters. For another coating process on the same The work station should be able to replace the screen cylinder with little effort. A The main point is the quick interchangeability of the Sieve cylinder without changing the register. This can make the productive Time can be improved compared to the unproductive time and also allows small series inexpensive to manufacture, as long as it takes the entire lead time for one relevant order. The sheets or sections become a stack removed, scaled on a suction belt table, fed to a handover and on the sheet cylinder by means of grippers forcibly on the sheet cylinder circulation speed accelerated and fed to the coating. With that, too favorable conditions created for simpler techniques, eg. B. for one full-surface painting. To do this, the screen cylinder can be used with a fine-pored screen be equipped. The sheets or sections are made after coating forcibly by means of a drying, hardening or stabilizing system of the coated material transferred.

In the case of a curved outer surface of the curved cylinder, the curved cylinder can be designed on one side as an active processing side, from bottom to bottom a transfer cylinder, a brush system and the Sieve cylinder, and between the brush system and sieve cylinder a drip pan is arranged. A material control of the Coating medium assigned, both the amount of material in the Screen cylinder as well as the position of the squeegee in the screen cylinder controllable or adjustable  can be. It is also very important that the arch cylinder and screen cylinder are synchronized driven, so that the coating can be done really register. The circumference of the curved cylinder is preferably twice as large or as a multiple selected in relation to the circumference of the screen cylinder, the circumference of the Sieve cylinder is at least as long as the greatest length of the processed Bow.

In the following, the invention will now be described with the aid of a few exemplary embodiments explained further details. Show it:

Fig. 1 shows schematically the manufacture of the Siebzylinderdruckform for rotary screen printing according to the prior art;

Figure 2 shows the cooperation of a screen cylinder with a bow cylinder according to the new invention.

Fig. 3 shows a cross section of an apparatus for coating;

FIG. 4 shows a production plant with investors and offshoot of sheets;

FIG. 5 the system according to FIG. 4 supplemented with an upstream calender;

Figure 6 is a precision workstation with a screen cylinder for processing in a plane with respect to the belt conveyor.

FIG. 7 shows an entire plant for the treatment of sheets or sections corresponding to FIG. 6;

FIG. 8 shows an enlarged detail of FIG. 7;

Figure 9 is a precision workstation with inlet and outlet table as well as a calender.

Figures 10 and 11 are a plan view of the precision work station of Figure 9;

Figures 12 and 13 view and plan of a plant from feeder to the precision workstation.

Fig. 14 and 15, the control / regulation schematically show the screen drum with a control ramp.

Fig. 1 shows schematically the workflow from a printing template "A" to a ready-to-use screen printing cylinder 10 ("E"). The process is shown with five figures "A" to "E". The printing template 1 is exposed after a previous film production. At "B" the desired screen openings are washed out, so that a flat printing form 2 is obtained. The flat printing form 2 is then assembled into a cylinder and placed as a cylindrical printing form 3 on a prepared mold carrier 4 . The mold carrier 4 not only gives the cylindrical shape but also has a central axis 5 , so that the position of the axis of rotation is exactly determined. A stencil ring 6 is placed from above into the cylindrical printing form 3 and onto the axis 5 (“C”). The printing form is then glued to the carrier elements ("D") and the sieve cylinder which has now been produced is equipped with the necessary overdrive elements 7 , 8 ("E") and can be used in the machine. The whole process takes about half an hour. Since the screen cylinder has a large opening 9 on one side, the material feed 11 for the coating medium and a doctor blade 12 can be inserted through the opening 9 into the screen cylinder. This structure allows a very quick change of a screen cylinder 10 , from a first printing form to a second screen cylinder with a second printing form, etc. The production of a rotary screen printing cylinder is state of the art for the printing of continuous webs. The same screen cylinder can be used in two different ways, as can be seen from the following figures.

FIG. 2 shows a first possible solution with a rotary printing cylinder 10 in cooperation with a sheet cylinder 20 , which has gripper marks 21 , 21 'at least at two points along the circumference for the positive guidance of the sheets 22 , 22 '. Two single sheets are indicated in FIG. 2. The horizontal center line is labeled H. A straight line that passes through the two axes of rotation of the curved cylinder and the screen cylinder is designated R / r, and the tangent that is at the point of contact of both cylinders at a right angle to the straight line is designated by T. The center line H now makes an angle α with the straight line R / r which is in the range from approximately 30 ° to 70 °. With the arrow 23 is a discharge system z. B. a mechanical chain discharge and arrow 24 denotes a sheet roller or transfer cylinder.

Fig. 3 shows an entire device 25 cut for coating sheets or Ab, with a screen cylinder 10, a sheet cylinder 20 with transfer cylinder 24 as well as a Kettenaustrag 23rd The main working elements are one above the other and on the left side with respect to a vertical center plane S (through the arch cylinder). At the bottom is the transfer cylinder 24 , above it a brush system 26 and below the screen cylinder 10 a collecting trough in which the parts of the coating material falling off the screen cylinder 10 are collected. In front of the transfer cylinder is a suction belt table 28 on which a number of support rollers 29 are arranged, which hold the sheets or sections prepared on the suction belt table 28 . The suction belt table 28 can be raised and lowered in accordance with arrow 30 . The transfer of the single sheets is performed via a system 31/32 with the front lay and side alignment and a feeder. The sheets are shingled and transported to the transfer cylinder at a speed V1. After the transfer, the sheets 22 are already accelerated to a higher speed V2 on the sheet cylinder. Screen cylinder 10 and arch cylinder move with an identical peripheral speed V2. In an example shown, all essential work around the bow cylinder is carried out. This has the advantage of simple synchronization of all individual cylinders. The main drive can take place from the bow cylinder 20 . Arrow 33 indicates that even the hardening, for example. in the case of UV-curable application materials can also take place on the screen drum 20 .

However, since the system is not intended to be limited to UV-curable application materials, curing or drying, as shown in FIG. 4, can take place in a subsequent stabilization station 40 with drying lamps 41 . The entire system is preceded by a feeder 42 with a suction head 48 above a sheet stack 43 . After the sheets have been discharged from the coating device 25, there is an offshoot 44 with a stack 45 of finished sheets.

In Fig. 5, a sheet calender 46 and a shed alignment station 47 is also shown. The exemplary embodiments according to FIGS. 2 to 5 show a solution in which the arches or sections are placed on the cylindrically curved outer surface of an arc cylinder.

In Figs. 6 to 8, however, the sheet or portion is machined on a horizontal work plane, which forms as it were from the feeder to branch a working table plane 50. A precision work station 51 has a chain or toothed belt 52 which is tensioned over the entire precision work area PAL by means of deflection rollers 53 , 53 ', 53 '', 53 '''. The chain or toothed belt 52 is driven by a motor 54 , which can be controlled via a controller 55 . The sieve cylinder is indicated by 10 . Instead of the screen cylinder, however, an application unit 56 can also be swiveled in (indicated by dashed lines), so that, for example, at the same workstation. B. either screen printing or painting can be done. It is also possible, within the precision working length PAL further process steps such. B. to provide a calendering 58 or a brushing. A counter-pressure roller 59 , 59 ', 59 ''is arranged at each work station, as is customary in the prior art. The number 57 only indicates that one or more further identical or different stations can be arranged after one or in front of a precision work station 51 .

Mechanical positive guidance is important for the precision workstation across the entire PAL work area. In addition to the chain or toothed belt, this is ensured by a mechanical gripper station 60 at the beginning and a sheet release point 61 for the mechanical grippers.

Fig. 7 shows an entire system 70 for the treatment of sheets or portions 22. On the right in the picture is a feeder 42 followed by a belt transport 72 and the precision work station 51 . Following the latter is a station 73 for drying, hardening and stabilizing the processed sheets, followed by a deposit 44 . The gripper station is shown again on a larger scale in FIG. 8.

FIG. 9 shows a system in modular construction, a precision work station 80 comprising an entire controller 81 including a high-performance computer. The precision work station 80 is a screen printing station, on which an inlet table 82 and then an outlet table 83 are arranged beforehand. A known calender 58 is located in front of the infeed table.

FIGS. 10 and 11 show an example of a rapid-change screen cylinder 10 in a larger scale. The rotary screen is driven on both sides by a common servo motor 84 which can be controlled by a computer R. On the inlet 82 side , several sensors are e.g. B. arranged as light sensors or photocells 85 whose signals are used in the computer for referencing. The screen cylinder 10 can be lowered and raised in the vertical direction AA, this movement also being coordinated via the controller 81 . The screen cylinder can, as indicated by the letters P and DR, be adjusted for the diagonal repeat, and with the letter LR for the longitudinal repeat.

FIGS. 12 and 13 show elevation and plan view of a plant with a feeder 43, an aligning station 72 and the precision workstation 80, which may be designed as a belt conveyor with mechanical transport aids for a constant production or with a chain or toothed belt conveyor with mechanical grippers.

FIGS. 14 and 15 schematically show the referencing of the cylinder mold, as well as bow. A single sheet can e.g. B. can be accelerated by means of a traveling stop 90 from a speed V1 to the precision transport speed V2, and is subsequently guided with a precise, constant conveying speed V2 on the constant conveyor 83 to the screen cylinder. With 85 a photocell arrangement is indicated with which the front end of the sheet is detected on the running conveyor. The photocells 85 are arranged at a regular distance RA in front of a theoretical screen printing line SD. The screen cylinder 10 rotates at a speed Vx at the point in time X at which the leading edge of the sheet triggers the arrival signal at the photocell 85 . The computer has additional sensor and storage means so that the exact position Px or Px 'of the corresponding reference point P on the screen cylinder 10 is recognized at the same time. The computer R immediately begins to calculate the circulating movement and then controls the circulating speed of the screen cylinder within milliseconds in such a way that the reference point P arrives at the theoretical screen printing line SD at the same time (or at time Z) with the leading edge Vk of the sheet, such that before the front edge Vk meets the reference point P, the circulating speed V3 has been reached and corresponds exactly to the precision transport speed V2.

Claims (15)

1. A method for the continuous precision processing of sheets or sections, in particular for the coating by means of rotary screens, characterized in that the sheets or sections are removed from a stack, transported on belts and subjected to precise constant conveyance for the precision work step and the screen circulation position relative to that Forced support is adjustable or controllable. 2. The method according to claim 1, characterized, that for the period of precision work, the rotational speed of the screen drum to the same throughput speed as the sheets, and the Referencing by acceleration and / or deceleration of the sieve circulation speed occurs. 3. The method according to claim 1 or 2, characterized, that the longitudinal repeat and / or the diagonal repeat is adjustable, in particular in particular the longitudinal repeat is electronically controllable. 4. The method according to any one of claims 1 to 3, characterized, that the screen cylinder is driven by an adjustable servo motor and via a Computer is controllable, the position of the sheet fed or Section relative to the screen cylinder movement in the distance before contact with the screen cylinder is monitored by at least one sensor. 5. The method according to claim 4, characterized, that the arch or section is by at least two or a plurality of Sensors, especially in relation to a diagonal position, are monitored and the distance (RA) as the standard distance, preferably by correcting the diagonal repeat is used.   6. The method according to any one of claims 1 to 5, characterized, that in the transition from the belt transport to the precise forced conveyance, the sheets or sections mechanically gripped and by means of the mechanical gripper in one uniform, horizontal working plane to and from the precision section be pulled away. 7. The method according to claim 6, characterized, that when the tape is handed over to the forced conveyance of the sheets or section is accelerated to the precise processing. 8. The method according to any one of claims 1 to 7, characterized, that the sheets or sections are taken from a stack on one Suction belt table scaled, a transfer, fed with mechanical grippers and on the working speed is accelerated precisely and in the case of a coating then drying, curing or stabilizing the coated Materials are fed. 9. Device for continuous precision processing of sheets or Ab cut, especially for the coating with circular screens, characterized, that they have a feeder, a belt conveyor and a precision work station tion, with the precision workstation throughout as a precise constant is designed conveyor and the rotary screens on a controllable or adjustable drive have, for referencing the circular sieve in relation to the arches or Sections. 10. The device according to claim 9, characterized, that the precision work station has a screen cylinder that is considered fast exchangeable screen printing cylinder is designed for rotary screen printing, which is preferably assigned a material control, the precise Forced conveyors and the screen cylinder have synchronizable drive means.   11. The device according to claim 9 or 10, characterized, that the screen cylinder both in the direction of the movement of the arches or sections and also adjustable at an angle to it, and for another coating process can be replaced quickly, preferably without changing the register. 12. The device according to one of claims 9 to 11, characterized, that the precision work station is an endless chain or toothed belt transport has, for the mechanical gripper means, the working level common level forms with the suction belts of the suction transport device. 13. The device according to one of claims 9 to 12, characterized, that the precision workstation also has suction belts for one pass without mechanical grippers. 14. Device according to one of claims 9 to 13, characterized, that it has several different workstations, e.g. B. for rotation screen printing and for a varnish for a coating for effect or special printing with specific colors. 15. Application of the method according to one of claims 1 to 8 or use the device according to one of claims 9 to 14, characterized, that for screen printing as color printing or varnishing sheets or sections or for the application of special application media such as glue etc. at correspond appropriate design of the screen cylinder as a quick-change cylinder, for example. as a sieve printing cylinder, screen painting cylinder or as a special screen application cylinder, wherein one or more screen cylinders in a precision work station, or in multiple precision workstations can be used.