EP1914004B1 - Method for controlling a powder applicator - Google Patents

Abstract

The method involves controlling a mantle-stream nozzle arrangement (13) using a control unit (25) based on operating parameters of a printing machine, where the parameters are different printed sheet-grammages. The parameters are adjusted in a face- and reverse printing mode and in a clear face-sided printing mode. Dispensing speed of mantle streams of the arrangement is changed based on the parameters. Dispensing speed of power air-core streams of the arrangement is maintained invariably during the change of the dispensing speed of the mantle streams.

Description

The present invention relates to a method for controlling a powder sprayer with a sheath flow nozzle arrangement in a printing press, according to the preamble of claim 1.

In the DE 100 01 590 A1 a powder sprayer is described with a sheath flow nozzle assembly. In this powder sprayer nozzle heads are arranged in a row. Each nozzle head has two nozzles, from each of which emerges a powder air jet. Above the nozzle heads a blowpipe is arranged, emerge from the compressed air jets. The delivery speed of these compressed air jets is about twice as high as that of the powder air jets. The compressed air jets together form a powder-free supporting air sheath flow, which surrounds the powder air jets on all sides. The supporting air sheath current shields the powder air jets against eddy currents caused by the movement of a gripper conveying the signature. This ensures that the powder air jets are unimpaired by the eddy currents pressurize the sheet. However, the print quality may be degraded when processing printed sheets of paper compared to the processing of printed sheets made of cardboard. Although the impulse exerted by the supporting air sheath flow on the printing sheet is suitable for the cardboard sheets, it is too large for the paper sheets. The impulse impairs the sheet travel of the paper sheets, which flutter as a result. Particularly in the case of freshly printed paper sheets on both sides, complications are to be expected. In many printing machines, the powder-based dust collector faces a sheet-guiding device, with the freshly printed sheet-top facing the powder-pulverizer and the likewise freshly printed sheet-underside of said sheet-guiding device. As a result of the fluttering, the paper sheets may strike the sheet guiding device, smearing the printed image on the underside of the sheet. As a result, the print quality is significantly reduced.

In the DE 199 37 090 A1 is a method for dusting printed sheets with powder described. In this method, a powder air stream is generated by means of a blower air generator whose performance is changed during operation. As a result, the performance of the air blower is adapted, among other things to the conveying speed of the sheet or the machine speed. The pressure of the powder air stream can be set to a value between 0.1 bar and 0.5 bar.

In the DE 42 37 111 B4 there is described a powder sprayer controlled by a programmed controller. The control device has a keypad via which basic parameters for the pending print job can be entered. These basic parameters include z. B. the format of the sheet and its conveying speed.

The invention has for its object to provide a method for controlling a powder sprayer with a sheath flow nozzle assembly, which ensures a consistently high print quality.

This object is achieved by a method having the features of claim 1. The method according to the invention for controlling a powder atomizer with a sheath flow nozzle arrangement in a printing press is characterized in that the sheath flow nozzle arrangement is controlled as a function of operating parameters of the printing press.

This makes it possible, for example, to change the air admission of the sheath flow nozzle arrangement of print job to print job, so that the air supply is optimally adapted to the requirements of the respective print job in printing operation and thus impaired sheet travel can be avoided by the powder. This ensures a consistently high print quality with every print job.

In the dependent claims advantageous developments of the method according to the invention are mentioned.

In a further development, the operating parameters are different sheet weights, d. h., different specific surface masses of the printed sheets. Sheet weights can differ from job to job, for example, when one works with lighter paper sheets and another with heavier cardboard sheets. In this case, the air admission of the sheath flow nozzle arrangement can be adapted to the different sheet weights.

In a further development, the operating parameters settings of the printing press on perfecting and on pure Perfecting mode. Here, the printing machine is a perfector with a turning device for turning the sheet. The turning device can optionally be set so that it uses the press sheets in fine and re-printing operation and transports the press sheets without the latter in pure straight printing mode. The bypass flow nozzle arrangement can be controlled in such a way that its application of air in perfecting operation is different than in pure straight printing operation. As a result, an undisturbed by powder dusting, stable sheet travel can be ensured even in perfecting operation.

In a further development, the delivery rate of supporting air-jacket flows of the bypass flow nozzle arrangement is changed depending on the operating parameters. In the case where the operating parameters are the various sheet grammages, depending on the sheet grammages, the delivery rate of the support air sheath streams of the sheath jet nozzle assembly is varied, with conversion of the press from processing of lighter sheet grammage to processing a heavier sheet grammage, the delivery rate of the supporting air sheath streams is increased. In the other case, that the operating parameters are the settings of the printing press on perfecting operation and on pure straight printing operation, the delivery speed of the supporting air-jacket flows of the bypass flow nozzle assembly is changed depending on said settings, wherein at a conversion of the printing press from the perfecting mode to the pure Perfecting mode, the delivery rate of the supporting air jacket currents is increased.

According to a further development, the rate of delivery of powder air core flows of the bypass flow nozzle arrangement is maintained unchanged when changing the delivery speed of the supporting air-jacket flows. In this case, the supporting air jacket currents can be generated by means of a first blower air generator and the powder air core streams by means of a second blower air generator.

The two last-mentioned developments assume that the sheath flow nozzle arrangement comprises a plurality of sheath flow nozzles, each comprising a core flow nozzle channel and a sheath flow nozzle channel surrounding the core flow nozzle channel. The respective sheath flow nozzle ejects from the core flow nozzle channel the powder air core stream, which is a blown air jet enriched with powder for dusting the printed sheet. From the sheath flow nozzle channel of the respective sheath flow nozzle of the supporting air sheath flow is ejected, which is not enriched with the powder blast air. Seen in the flow direction of the supporting air-jacket current, this has a substantially annular profile in the interior of which the powder-air core stream is located. The sheath flow nozzle channels of the sheath flow nozzles are connected to the first blower air generator, which supplies the sheath flow nozzle ducts with the blowing air of the support air sheath flows having a comparatively high pressure. The core flow nozzle channels are connected to the second blower air generator and are supplied by this with a comparatively low pressure having blown air of the powder air core streams, wherein the blown air discharged from the second blower air z. B. by means of an injector of the powder is added to form the powder air core streams.

The invention also includes a printing press, which is designed for carrying out the method according to the invention or one of its further developments. This printing machine comprises a powder sprayer with a sheath flow nozzle arrangement and is characterized in that the sheath flow nozzle arrangement by a Control device is driven in response to operating parameters of the printing press.

Other constructive and functional advantageous developments of the invention will become apparent from the following description of an embodiment and the accompanying drawings.

Figur 1

die Gesamtdarstellung einer Druckmaschine mit einem Bogenausleger und einem darin angeordneten Puderbestäuber,

Figur 2

eine Detaildarstellung des Puderbestäubers und

Figur 3

einen der Linie III-III in Figur 2 entsprechenden Schnitt durch einen Düsenbalken und einen daran angeordneten Düsenkopf des Puderbestäubers.

In this shows:

FIG. 1

the overall view of a printing machine with a sheet delivery and a powdered powder disposed therein,

FIG. 2

a detailed presentation of the powder sprayer and

FIG. 3

one of the line III-III in FIG. 2 corresponding section through a nozzle bar and arranged thereon a nozzle head of the powder sprayer.

FIG. 1 shows a printing press 1 with printing units 2 to 5 and a sheet delivery 6. The sheet delivery includes a chain conveyor 7, which deposits the sheet on a delivery stack 8. Furthermore, the printing machine 1 comprises a turning device 9, which can be switched from a pure Perfecting mode to a perfecting mode. In the pure straight printing mode without the use of a sheet, the printing sheets are printed both in the printing units 2 and 3 upstream of the turning device 9 and in the printing units 4 and 5 arranged downstream of the turning device 9 on the sheet front side. In the perfecting mode, the printed sheets are printed in the upstream printing units 2 and 3 on the sheet front side and in the downstream printing units 4 and 5 on the back of the sheet. In the sheet delivery arm 6, a powder sprayer 10 is arranged, which pollinates the printed sheet conveyed by the chain conveyor 7 with powder.

FIG. 2 shows that the powder atomizer comprises a nozzle beam 11 with arranged thereon sheath flow nozzles 12. The arranged in a row over the width of the printing sheet sheath flow nozzles 12 together form a sheath flow nozzle assembly 13. The nozzle beam 11 is connected to a first blower air generator 21 and a metering device 23 to a second blower 22. The metering device 23 comprises an injector 24, which introduces the powder into the blown air generated by the second blower 22 to form a powder-air mixture. Belonging to the powder sprayer 10 blower 21, 22, which may be located outside of the printing press 1, are controlled by an electronic control device 25.

FIG. 3 shows that the bypass flow nozzles 12 are each formed in the form of a nozzle head 14 which is attached to the nozzle bar 11. The respective sheath flow nozzle 12 comprises an outer sheath flow nozzle channel 15, which has a substantially annular cross section, and an inner core flow nozzle channel 16, which is enclosed by the sheath flow nozzle channel 15.

The bypass flow nozzle channel 15 is connected via a supporting air strand 17 to the first blower air generator 21 and the core flow nozzle duct 16 is connected via a powder air duct 18 to the second blower air generator 22. The support air strand 17 and the powder air duct 18 consist of formed in the nozzle bar 11 air channels and connected to the nozzle bar 11 hose or pipes. The sheath flow nozzle channel 15 ejects from its mouth a supporting air sheath stream 19 and the core flow nozzle channel 16 ejects from its mouth a powder air core stream 20 from.

In a modification not shown in the drawing, the sheath flow nozzle arrangement consists of a series of core flow nozzle channels, which is arranged between a series of sheath flow nozzle channels arranged in the sheet transport direction and a row of sheath flow nozzle channels arranged downstream in the sheet transport direction. Here, the core-stream nozzle channels eject powder-air core streams trapped between the two support air-jacket streams forming air blast curtains ejected through the two rows of sheath-flow nozzle channels.

• Der zweite Blaslufterzeuger 22 versorgt den Puderluftstrang 18 mit Blasluft, deren Druck mindestens 0,5 Bar und höchstens 1,0 Bar beträgt. Die Wirkung des zweiten Blaslufterzeugers 22 wird aber unvermeidlich durch den Injektor 24 vermindert. Infolgedessen beträgt die Summe der Kräfte, welche sich aus der Ableitung des Impulses der Puderluft-Kernströme 20 nach der Zeit ergeben, nur mindestens 0,1 Newton und höchstens 2,0 Newton; vorzugsweise mindestens 0,5 Newton und höchstens 1,0 Newton. Die Kräfte können an den Mündungen der Kernstrom-Düsenkanäle 16 gemessen werden und ihre Anzahl entspricht der Anzahl sämtlicher Düsenköpfe 14 des Düsenbalkens 11. Die Summe der Kräfte ist sozusagen die resultierende Kraft. Der erste Blaslufterzeuger 21 versorgt den Stützluftstrang 17 mit Blasluft, deren Druck ca. 0,2 Bar beträgt. Dieser Druck ist vergleichsweise gering, so dass eine zentrale Blasluftversorgung der Druckmaschine 1 als der erste Blaslufterzeuger 21 verwendet werden kann. Der zweite Blaslufterzeuger 22 kann ein von der zentralen Blasluftversorgung separater Verdichter sein. Die Summe der Kräfte, welche sich aus der Ableitung des Impulses der Stützluft-Mantelströme 19 nach der Zeit ergeben, beträgt mindestens 0,5 Newton und höchstens 18,0 Newton; vorzugsweise mindestens 2,0 Newton und höchstens 6,0 Newton. Diese Kräfte können an den Mündungen der Mantelstrom-Düsenkanäle 15 gemessen werden und die Anzahl dieser Kräfte entspricht der Anzahl sämtlicher Mantelstrom-Düsen 12 des Düsenbalkens 11, welche im gegebenen Beispiel 24 beträgt.

The powder sprayer 10 works as follows:

• The second blower 22 supplies the powder air duct 18 with blown air, the pressure of which is at least 0.5 bar and at most 1.0 bar. However, the action of the second blower 22 is inevitably reduced by the injector 24. As a result, the sum of the forces resulting from the derivative of the pulse of the powder air core streams 20 with time is only at least 0.1 Newton and at most 2.0 Newton; preferably at least 0.5 Newton and at most 1.0 Newton. The forces can be measured at the mouths of the core flow nozzle channels 16 and their number corresponds to the number of all nozzle heads 14 of the nozzle beam 11. The sum of the forces is, so to speak, the resulting force. The first blower air generator 21 supplies the supporting air duct 17 with blown air, the pressure of which is approximately 0.2 bar. This pressure is comparatively low, so that a central blast air supply of the printing machine 1 can be used as the first blower air generator 21. The second blast air generator 22 may be a compressor separate from the central blast air supply. The sum of the forces resulting from the derivative of the momentum of the supporting air sheath currents 19 with time is at least 0.5 Newton and at most 18.0 Newton; preferably at least 2.0 Newton and at most 6.0 Newton. These forces can be measured at the mouths of the sheath flow nozzle channels 15 and the number of these forces corresponds to the number of all sheath flow nozzles 12 of the nozzle beam 11, which is 24 in the example given.

The momentum of the supporting air sheath flows is varied not only depending on the machine speed, the format of the printing sheets, the setting values of the boom and a powder extraction, but also depending on the grammage of the printed sheets and depending on whether the printing press 1 is in pure fine printing operation or operated in perfecting mode.

For heavier grammages, a larger support air pulse is required than for lighter grammages. After the grammage of the printed sheet of the pending print job has been entered into the electronic control device 25, provides the control device 25 automatically adjusts the power of the first blower air generator 21 in such a way that it generates the air pressure in the support air line 17 necessary for the required support air pulse.

In pure Perfecting mode, a larger support air pulse is required than in perfecting mode. After the control device 25 provided for the upcoming print job operation of the printing machine 1, z. B. the pure Perfecting mode has been entered, the control device 25 accordingly sets the turning device 9 and the first blower air generator 21 a.

It is an advantage that the powder air and the supporting air are supplied from separate sources and that the pulse increase does not take place for both air strands, but only for the supporting air strand 17. Thus, to increase the pulse, the existing central air supply (first blower air generator 21) of the printing press 1 can be used. The powder air pulse generated by the second blower 22 can be maintained at a constant minimum value. The total air pulse, which is necessary to stabilize the powder-air jet, is generated primarily by the external support air and not by the internal powder air. As a result, costs and installation space can be saved. Of course, it is possible to follow the so-called powder curve, ie the amount of powder introduced into the printing machine 1, according to the respective efficiency of the powder application.

LIST OF REFERENCE NUMBERS

1

press

2

printing unit

3

printing unit

4

printing unit

5

printing unit

6

sheet delivery

7

chain conveyors

8th

delivery pile

9

turning device

10

powder spray

11

nozzle beam

12

Ducted nozzle

13

Ducted nozzle arrangement

14

nozzle head

15

Turbofan jet channel

16

Core flow nozzle channel

17

Support air train

18

Powder-air line

19

Support air ducted

20

Powder air-core current

21

first blower air generator

22

second blower air generator

23

dosing

24

injector

25

control device

Claims (8)

1. Method of controlling a powdering device (10) including a sheath current nozzle arrangement (13) in a printing press (1),
   characterized by
   the fact that the sheath current nozzle arrangement (13) is controlled as a function of operating parameters of the printing press (1),
   that the expulsion speed of support air sheath currents (19) of the sheath current nozzle arrangement (13) is modified as a function of the operating parameters, and
   that upon a modification of the expulsion speed of the support air sheath currents (19) the expulsion speed of powdered air core flows (20) of the sheath current nozzle arrangement (13) remains unchanged.
2. Method according to claim 1,
   characterized by
   the fact that the operating parameters are different printing sheet weights.
3. Method according to claim 1,
   characterized by
   the fact that the operating parameters are settings of the printing press (1) relating to perfecting and one-sided printing.
4. Method according to claim 1,
   characterized by
   the fact that the operating parameters are different printing sheet weights, and
   that the expulsion speed of the support air sheath currents (19) of the sheath current nozzle arrangement (13) are changed as a function of the printing sheet weights, the expulsion speed of the support air sheath currents (19) being increased when the printing press (1) is changed from processing more light-weight printing sheets to processing heavier printing sheets.
5. Method according to claim 1,
   characterized by
   the fact that the operating parameters are settings of the printing press (1) relating to perfecting and one-sided printing and that the expulsion speed of support air sheath currents (19) of the sheath current nozzle arrangement (13) is modified as a function of the settings, the expulsion speed of the support air sheath currents (19) being increased when the printing press (1) is changed from perfecting to one-sided printing.
6. Method according to claim 4 or 5,
   characterized by
   the fact that when the expulsion speed of the support air sheath currents (19) is increased, the expulsion speed of powdered air core flows (20) of the sheath current nozzle arrangement (13) remains unchanged.
7. Method according to claim 1 or 6,
   characterized by
   the fact that the support air sheath currents (19) are generated using a first blown air generator (21) and the powdered air core flows (20) are generated using a second blown air generator (22).
8. Printing press comprising a powdering device (10) with a sheath current nozzle arrangement (13),
   characterized by
   the fact that the sheath current nozzle arrangement (13) is actuated by a control device (25) as a function of operating parameters of the printing press (1) in such a way that the expulsion speed of support air sheath currents (19) of the sheath current nozzle arrangement (13) is modified as a function of the operating parameters, and that the expulsion speed of powdered air core flows (20) of the sheath current nozzle arrangement (13) remains unchanged when the expulsion speed of the support air sheath currents (19) is changed.

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