DE102012008552A1 - Device for printing object with printing ink in e.g. rotary printing machine for lithographic offset printing, has inkjet device delivering printing ink, and print tape receiving printing ink and transferring ink to object - Google Patents

Abstract

The device (1) has an inkjet device (3) that delivers printing ink (6). A print tape (4) receives the printing ink and transfers the ink to an object. A guide cylinder (5) is provided for the print tape. A pressure gap (9) is arranged between the guide cylinder and an impression cylinder (7). A gripper (8) in the guide cylinder dives into a channel (10). A sensor (11) detects an edge of a layer of the print tape. The inkjet device comprises two print heads (16) that are arranged in traveling direction of the print tape.

Description

The present invention relates to an apparatus for printing on an object with ink having the features of claim 1.

Industrial inkjet printing systems are primarily designed as web presses; H. The substrate is fed and printed as a quasi endless printing material through the machine. There are also industrial inkjet printing systems which print on individual substrates. Such systems use a ribbon for sheet transport and usually print only smaller formats, while in roll printing rather large formats are printed.

There may be a problem with the use of a substrate sheet transport belt that the pixel clock generation for triggering the pulses for ejecting ink droplets on the inkjet printing system is defective. Regardless of the mechanical design, there is always some slippage between the conveyor belt and an encoder roller to generate the pixel clock. Such slippage can be a source of error.

Furthermore, such an encoder roller should be positioned as close as possible to the inkjet printing system or its printhead. Since the print head usually occupies a large amount of space, the distance between the print head and conveyor belt can not be minimized arbitrarily. Even too great a minimum distance can be a source of error.

Furthermore, an encoder roll should not protrude over the substrate, i. H. the substrate, because it could damage it. For this reason, the encoder roller should only be mounted on the edge of a conveyor belt for the substrate or on its underside. These positions of the encoder roll can also be sources of error.

Furthermore, due to the unavoidable elongation of the conveyor belt, a deviation between the measured and the actual position of the substrate is produced, and this is the greater, the further the measuring location of the encoder roller and the printing location are remote from one another. Thus, this strain is also a possible source of error.

If the conveyor belt has an interface, the encoder signal caused and modified by this interface can be faulty or even unusable. Thus, even seams of the conveyor belt are possible sources of error.

Finally, an optical detection of the movement of the conveyor belt without encoder role is a possible source of error, since this has the disadvantage of a signal delay by the involved evaluation (image analysis) and thus can also adversely affect the print quality.

In addition to the above-mentioned possible sources of error for the pixel clock generation when printing sheets may continue to exist the problem that the substrate must be fixed by means of suction on the conveyor belt. The suction air can cause turbulence in the region of the print head, which adversely affect the trajectories of the individual droplets and thereby impair the print quality.

The integration of inkjet printing systems in sheet-processing machines, z. As for so-called inline spot finishes or for personalization, can also lead to the following problem: To achieve a necessary and desired resolution, inkjet printing systems usually use several, offset successively arranged print modules. Due to this arrangement of the printing modules, the inkjet printing head does not form a narrow nip to the substrate, but a printing surface. Therefore, it is usually not possible to use such a print head for printing on substrates, which are guided on the curved surfaces of transport cylinders.

Finally, there may be the problem that for the production of high-quality print results, the inkjet print head must be positioned very close to the substrate to be printed. However, substrate sheets are usually held with grippers during transport, and therefore the printhead must be raised by grippers each time it passes, or the grippers must be lowered to avoid collision between the grippers and the printhead.

The examples given above show that the use of inkjet printing systems can lead to a number of problems in the industrial printing of individual printing material sheets.

Against this background, it is an object of the present invention to provide a device for printing on an object with printing ink, which overcomes the above-mentioned problems.

This object is achieved by a device for printing an object with printing ink having the features of claim 1. Advantageous developments of this invention will become apparent from the appended subclaims as well as from the following description with the accompanying drawings.

An inventive device for printing an object, for. An arcuate substrate, with ink includes: an ink-jet device which discharges the ink; a printing tape which picks up the ink and transfers it to the object; and a guide cylinder for the printing tape.

By providing a printing tape according to the invention, the printing surface of the ink jet device can be reduced to a narrow printing gap and thereby advantageously also a pressure on a curved surface are made possible, for. B. on a printing material, which is transported on a cylinder surface. The printing gap can be formed between the printing tape and the substrate or the surface on which the substrate is guided. The term "pressure nip" means that all the ink that is dispensed by the inkjet device is transferred together at a defined location on the substrate.

By providing the printing tape, the distance between the inkjet device and the surface of the printing tape can be advantageously further minimized further than this z. B. between the ink jet device and the surface of the object would be possible or between the ink jet device and the surface of a device for transporting the object or its gripper. As a result, advantageously a higher print quality can be achieved.

Another advantage arises from the fact that the ink jet device prints on the print tape and therefore disturbances caused by the object are not transferred to the ink jet devices. For example, a mechanical defect, such. As a wrinkling of a sheet of printing material, thus not lead to a collision with the ink jet head of the ink jet device.

The device according to the invention with its advantages described therefore allows the integration of an inkjet printing system in a printing material processing printing machine, for. B. an offset printing machine. In particular, the invention also allows integration into a printing machine with gripper-bound substrate transport.

A refinement of the device according to the invention which is advantageous and therefore preferred with respect to transport with grippers may be distinguished by the fact that the following is provided: an impression cylinder with at least one gripper for a flat object; a pressure gap between the guide cylinder and the counter-pressure cylinder; and a channel in the guide cylinder into which the gripper is immersed.

By providing the channel in the guide cylinder can be achieved in an advantageous manner that the guide cylinder does not need to be raised when a gripper passes through the pressure nip. Thus, disturbing movements of components of the device according to the invention can be avoided, which have a negative effect on the printed image to be generated.

An advantageous for the production of high quality prints and therefore preferred embodiment of the device according to the invention may be characterized in that a sensor is provided which detects the position of an edge of the printing tape. The signal generated by the sensor can be used to accurately guide the print ribbon and to perform edge control of the print ribbon. An edge control system may include the mentioned sensor, a servomotor and means for correcting the lateral position of the web, e.g. B. one or more adjustable or pivotable correction rollers include.

An advantageous and therefore preferred embodiment of the device according to the invention for a high accuracy of the control of the ink jet device or the pulse generation for the droplet ejection can be distinguished by a pixel clock rotary encoder. This rotary encoder can be mounted on the shaft of the guide cylinder and its encoder signals can be used to generate a clock with which individual ink jet printing modules of the ink jet device are driven such that the ejected ink droplets are in the right place at the right time be placed on the pressure belt. In this way, high-precision printed images can be produced on the printing belt and then transferred to the object or to a printing material sheet.

An advantageous for the production of high-quality prints and therefore preferred embodiment of the device according to the invention can be characterized by a printing tape whose length is an integer multiple of the distance between two directly following sheets of printing material, wherein the distance from the sheet leading edge of a sheet to the sheet leading edge of the other sheet along the transport path the bow is measured. Alternatively, the distance in single-speed cylinders can also be measured as the circumference of the counter-pressure cylinder conveying the sheet. In this way, one or more can be on the printing tape Print images are placed one behind the other and the ink jet device can color or fill the printed images after each contact with the object to be printed again. A cleaning of the printing tape is therefore not necessary in this embodiment of the invention. Alternatively, it can also be provided to provide a cleaning device in the vicinity of the printing tape, which cleans the printing tape of ink. The ink jet device will then apply a new print image to a cleaned print ribbon during the movement of the print ribbon. It is therefore not necessary to ensure that the job of new printing ink is done in accordance with a print image already on the printing tape.

An advantageous and therefore preferred development of the device according to the invention for the secure guiding of the printing tape and thus for the precise creation of printed images on the printing tape can be distinguished by a guide surface for the printing tape, which is arranged opposite the inkjet device with respect to the printing tape.

By the guide surface, the print tape in the area of the ink jet device or in the area of the ink application is guided on the print tape safely and thereby avoided positional deviations of the print tape, which could adversely affect the printed image. In particular, vibrations of the printing tape can be avoided.

A development of the device according to the invention which is advantageous and therefore preferred in terms of the production of multicolor prints can be distinguished by the fact that the inkjet device has at least two print heads which are arranged consecutively in the direction of movement of the print web and deliver different printing inks. In this function, the print ribbon effectively acts as a collection ribbon for different printhead colors. The individual inks are collected on the collecting belt and transferred as a common printed image in the nip on the surface of the object to be printed.

In the context of the invention is also a printing material processing machine, for. As a printing press, in particular a sheet-processing rotary printing press for lithographic offset printing, to see which is characterized by at least one as described above with reference to the invention for printing the printing substrate with at least one color. Such a substrate-processing machine may be distinguished in a development at least two devices for printing the substrate with a respective ink, which devices are arranged consecutively in the direction of movement of the substrate.

The invention as such as well as structurally and / or functionally advantageous developments of the invention are described below with reference to the drawings with reference to preferred embodiments.

The drawings show

1 to 6 a respective schematic representation of a preferred embodiment of a device according to the invention in different phases of the printing process; and

7 to 10 a respective schematic representation of a preferred embodiment of an alternative device according to the invention in different phases of the printing process.

1 shows a device 1 for printing on an object 2 with printing ink 6 (the object 2 will be in the following 2 visible). The object 2 is preferably a printing material, z. B. of paper, cardboard or plastic or metal foil. The device 1 has for this purpose an ink jet device 3 with multiple printheads 16 on. Every single printhead 16 can be controlled separately and deliver a respective ink in the form of ink droplets. The delivery of the droplets takes place in accordance with the supplied image data such that a preferably multicolored print image is generated.

The device 1 also has a pressure band 4 on which the printing ink 6 picks up and on the object 2 transfers. Furthermore, the device 1 a guide cylinder 5 for the printing tape 4 on. The printing tape 4 becomes the guide cylinder 5 and two roles 17 guided around and is a quasi-endless printing belt, which preferably has no seam. Furthermore, the device 1 an impression cylinder 7 on, the pressure gap 9 with the guide cylinder 5 forms. The printing ink 6 is in the pressure nip 9 from the printing tape 4 on the surface of the object 2 transfer. The transfer of the printing ink 6 can be complete or incomplete.

The counter-pressure cylinder 7 indicates for the transport of the printing material 2 a gripper 8th (or more grippers or a gripper system) on. Each revolution of the impression cylinder 7 the gripper dives 8th into a corresponding channel 10 of the guide cylinder. The printing tape 4 is therefore in terms of its material properties such that a dipping of the gripper 8th in the channel 10 not to damage the tape 4 leads. Instead, the tape becomes 4 through the gripper 8th only in the channel 10 moved into it.

For the web edge control of the printing tape 4 is a sensor 11 provided, which is arranged such that movements of the printing tape 4 can be detected in a lateral direction and countermeasures can be taken. The countermeasures may consist in that a device, not shown, is provided, which generates a lateral counter-movement of the printing tape and thus in the context of a control loop, which also the sensor 11 includes, leads to a stable web guide of the printing tape.

Near the shaft of the guide cylinder 5 is a pixel clock encoder 12 arranged, which the rotation of the guide cylinder 5 followed and generated a clock, which the modules 16 the ink jet device 3 or whose control is supplied so that they eject according to the predetermined clock and in accordance with the image to be printed droplets. In this way it can be ensured that the individual pressure points caused by the droplets arrive at the right places on the printing material at the right time.

Furthermore, the device has a cleaning device 14 on which close to the surface of the printing tape 4 is arranged so that this device the pressure belt 4 in case of need of printing ink 6 can clean. It may be a conventional cleaning device with cleaning elements such. B. cleaning rollers or brushes act and the cleaning device can also use a liquid detergent.

Furthermore, a tensioning and regulating roller 18 provided, which from the inside to the pressure belt 4 acts and which via a servomotor 19 can be moved so that a voltage change in the printing belt 4 or a deflection of the printing tape 4 can be achieved. A balancing movement of the band 4 may be required, for example, when the gripper 8th in the channel 10 dips while keeping the pressure band 4 a little way into the canal 10 moved into it. In this case, the servomotor would 19 the roller 18 move such that a compensating movement of the printing tape is made possible and thereby the tension in the printing belt is kept constant.

2 shows the same device at a later stage of the printing process. The printing ink 6 that of the ink jet device on the print tape 4 has been transferred, along with the pressure band 4 moves on and moves in 2 and also in the following 3 on the pressure nip 9 to. Likewise, in the 2 and 3 recognizable that the substrate 2 which of the gripper 8th at its front edge 13 is recorded, on the pressure nip 9 moved. In 2 becomes the substrate sheet 2 from an upstream cylinder to the back pressure cylinder 7 to hand over. In 3 is the gripper 8th partly in the canal 10 dipped and at the same time is the order of ink on the printing tape 4 completed.

In the following 4 and 5 is recognizable as the printing ink 6 from the printing tape 4 on the substrate 2 in the printing gap 9 is transmitted by the so-called color splitting. In particular, in 5 recognizable that even after the nip 9 still a rest of ink 6 is on the printing tape and together with the printing tape 4 continue to the cleaning device 14 is transported. There is the remaining ink 6 ' from the cleaning device 14 from the printing tape 4 cleaned so that it cleaned of ink gets back to the position at which the ink jet device 3 on the pressure belt 4 prints.

6 shows the last step of a printing process in which a printed sheet 2 with printing ink 6 was printed. The trailing edge of the sheet leaves in 6 just the nip while the pressure belt 4 with remaining printing ink 6 in the cleaning area of the cleaning device 14 enters. At the same time, it can be seen that a further printed sheet the printing nip 9 is fed and that on the pressure belt 4 another print 6 was generated.

Because the printing tape 4 complete of printing ink 6 is cleaned, the other printed image, which is printed on the other sheet, may differ from the previously printed printed image. It is therefore possible to provide the successive sheets with different print images.

In the 7 to 10 is the printing of static image content shown. Since thus during the rotation of the printing belt 4 repeatedly the same print image on the substrate 2 can come to a complete cleaning with each revolution of the pressure belt 4 be waived.

The printing tape 4 is in this embodiment as a toothed belt 21 executed or provided with teeth and also the guide cylinder 5 has matching teeth 20 on. Similarly, the two roles 17 and also the tensioning and regulating roller 18 teeth 22 respectively. 23 on that to the teeth of the toothed belt 21 fit. In this way is a slip-free coupling of guide cylinder 5 and printing tape 4 and also a slip-free leadership of the printing tape 4 along the inkjet device 3 possible.

The total length of the transfer belt 4 corresponds to an integer multiple of the circumference of the impression cylinder. The beginning of the print area can be on the print tape 4 be marked. By the execution of the belt as a toothed belt and the provision of a defined beginning of the printing area can be achieved that the pressure or the ink application to the printing tape 4 after each revolution of the printing tape 4 congruent to the previous print or paint.

In 8th it can be seen that a part of the applied printing ink is on the printing material sheet 2 while another portion of the untransferred ink is again on the print tape 4 to the inkjet device 3 to be led. This in turn carries ink in the area of the printed image on the printing tape 4 so that a complete printed image in the form of ink can be brought into contact with the following printing material sheet and a corresponding printed image can be printed. Cleaning the tape is not necessary and therefore not intended.

In 9 is recognizable as the inkjet device 3 Color droplets exactly to the position of the on the pressure belt 4 already located printing ink 6 applies and the printed image on the printing tape 4 therefore again completed with printing ink.

In 10 It can be seen that at the end of the printing process, ie without supply of printing material, the printing tape 4 by means of the cleaning device 14 of printing ink 6 can be cleaned. The printing tape can therefore be optimized for cleaning to be moved, in particular a slower movement of the printing tape and thus a better cleaning of the printing tape is possible.

LIST OF REFERENCE NUMBERS

1

contraption

2

bow

3

Inkjet device

4

print ribbon

5

guide cylinder

6

printing ink

6 '

printing ink

7

Back-pressure cylinder

8th

grab

9

nip

10

channel

11

sensor

12

Pixel clock encoders

13

Sheet leading edge

14

cleaning device

15

guide surface

16

printheads

17

roll

18

Tensioning and regulating roller

19

servomotor

20

teeth

21

toothed belt

22

teeth

23

teeth

Claims (10)

Device for printing on an object ( 2 ) with printing ink ( 6 ), comprising - an ink jet device ( 3 ), which the printing ink ( 6 ) gives up; - a printing tape ( 4 ), which the printing ink ( 6 ) and on the object ( 2 ) transmits; and - a guide cylinder ( 5 ) for the printing tape ( 4 ). Apparatus according to claim 1, characterized by - a counter-pressure cylinder ( 7 ) with at least one gripper ( 8th ) for a flat object ( 2 ); A pressure gap ( 9 ) between the guide cylinder ( 5 ) and the counter-pressure cylinder ( 7 ); and - a channel ( 10 ) in the guide cylinder ( 5 ), in which the gripper ( 8th immersed). Device according to one of the preceding claims, characterized by a sensor ( 11 ), which determines the position of an edge of the printing tape ( 4 ) detected. Device according to one of the preceding claims, characterized by a pixel clock rotary encoder ( 12 ). Device according to one of the preceding claims, characterized by a pressure belt ( 4 ) whose length is an integer multiple of the distance between two directly following printing material sheets ( 2 ), the distance from the leading edge of the sheet ( 13 ) of an arc ( 2 ) to the sheet leading edge ( 13 ) of the other bow ( 2 ) is measured along the transport path. Device according to one of the preceding claims, characterized by a cleaning device ( 15 ), which the pressure belt ( 4 ) of printing ink ( 6 ) cleans. Device according to one of the preceding claims, characterized by a guide surface ( 15 ) for the printing tape ( 4 ), which of the inkjet device ( 3 ) with respect to the printing tape ( 4 ) is arranged opposite one another. Device according to one of the preceding claims, characterized in that the ink jet device ( 3 ) at least two printheads ( 16 ), which in the direction of movement of the printing tape ( 4 ) are arranged successively and different inks ( 6 ) submit. Substrate processing machine - z. B. printing machine, in particular sheet-processing rotary lithographic lithographic printing press - characterized by a device ( 1 ) according to one of claims 1 to 8 for printing the printing substrate ( 2 ) with at least one printing ink ( 6 ). Substrate processing machine according to claim 9, characterized by at least two devices ( 1 ) according to one of claims 1 to 8 for printing the printing substrate ( 2 ) with a respective printing ink ( 6 ), which in the direction of movement of the printing substrate ( 2 ) are arranged consecutively.

Images