CN110712424A

CN110712424A - Sheet printing machine with dampening unit

Info

Publication number: CN110712424A
Application number: CN201910630205.0A
Authority: CN
Inventors: C·鲁帕纳; C·哈斯; M·莱瓦; U·昂斯特; U·费伦贝格
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 2018-07-12
Filing date: 2019-07-12
Publication date: 2020-01-21
Also published as: DE102019208576A1

Abstract

The invention relates to a sheet printing press comprising a printing station, a guide device (12) for printing a sheet (11), and a dryer. A dampening device (8) having a first roller (31) for dampening the printed sheet (11) is arranged downstream of the dryer in the sheet transport direction (T), wherein the first roller (31) protrudes from the guide device (12).

Description

Sheet printing machine with dampening unit

Technical Field

The invention relates to a sheet printing press comprising a printing station, a guide device for printing a sheet, and a dryer.

Background

DE 102016125960 a1 describes a sheet-fed printing press with printing units in which inkjet printing heads are used. Between these printing units, in each case one sheet transport cylinder is arranged which interacts with a sheet guide. A drying unit comprising an infrared or hot air dryer is arranged after the last printing unit. After the drying mechanism, an upper varnish module is arranged, by means of which the printed sheets are finally coated.

A disadvantage here is that the printed sheets lose moisture due to infrared or hot air dryers, which leads to sheet deformations. However, moisture can no longer be supplied to the printing sheet by the varnish application in the varnish application module, since this varnish application takes place on the previously printed image on the printing unit, which has a protective effect on the printing sheet.

Disclosure of Invention

The object of the invention is to provide a sheet printing press in which sheet deformation caused by the dryer is avoided.

The object is achieved by a sheet printing press comprising a printing station, a guide device for printed sheets, and a dryer, wherein a dampening device is arranged downstream of the dryer in the sheet transport direction, said dampening device having a first roller for dampening (R ü ckbefeuchten) the printed sheets, wherein the first roller protrudes from the guide device.

The advantage of the sheet-fed printing press according to the invention is that the rewetting of the printed sheet by the dampening unit can be carried out on an unprinted sheet of the printed sheet, which sheet can absorb this rewetting liquid well.

There are many possible improvements:

the moistening device may have a spraying device, which may be directed towards the first roller.

The spraying device may have a centrifugal disc.

A transport device having gripper bars can be provided, which can transport the printed sheet over the first roller.

The first roller may be a component of a sheet finisher (sheet finisher).

The sheet finisher may have a first convex surface and a second convex surface that may face each other, wherein the first convex surface may be constituted by the first roller.

The second convex surface may be constituted by the second roller.

The sheet flattener can have a vacuum wedge (Vakuumzwickel) that can be positioned between the first convex surface and the second convex surface.

The dryer may be a thermal dryer.

The printing station may have at least one inkjet print head.

A blowing device can be provided, which can pneumatically press the printed sheet onto the first roller.

The blowing device can be arranged within the running track of the gripper of the circulation (endlosen).

Drawings

Further refinements result from the following description of the exemplary embodiments and the corresponding figures, which show:

FIG. 1: a full view of a sheet printing press having a dampening device;

FIG. 2: a detailed view of a first embodiment of the wetting apparatus; and

FIG. 3: a detailed view of a second embodiment of the wetting apparatus.

Detailed Description

Fig. 1 shows a sheet printing press 1, which sheet printing press 1 has: a sheet feeder 2, a printing station 3 equipped with an inkjet print head 4 for multicolor printing, a dryer 5 and a sheet receiver 6. The printing press 1 further comprises a transport device 7, which transport device 7 transports the printed sheet past a dampening unit 8. The conveying device 7 is a chain conveyor and is arranged in the sheet feeder 6.

The dryer 5 is a thermal dryer and radiates hot air and/or infrared rays onto the printed sheet to dry the inkjet ink thereon. The dampening device 8 is a dampening device and is used to dampen the printed sheet. The substrate of the printed sheet (for example paper or cardboard) loses moisture as a result of the irradiation of the dryer 5, which is an unavoidable side effect and leads to disturbing sheet deformations if no countermeasures are taken. By means of measures in the form of rewetting, the loss of moisture of the substrate caused by drying is at least partially compensated.

A moistening device 8 is arranged in the sheet feeder 6 and moistens the printed sheets after they have been processed by the dryer 5 and before they have been dusted by the dusting device 27. Finally, the sheets are placed in the sheet receiver 6 on the sheet stack 9 formed therefrom.

The moistening device 8 is shown in detail in fig. 2. The transport device 7 comprises gripper bars 10, which gripper bars 10 serve to hold the sheet 11 in place at its front edge by means of a clamping action. Each gripper bar 10 draws the printed sheet 11 along a guide 12, wherein the guide 12 guides the printed sheet pneumatically by means of suction air. For this purpose, the guide surface 25 of the guide device 12 is configured as a nozzle surface with a nozzle 28 therein, which sucks in suction air. The guide surface 25 is flat. The guide device 12 may be referred to specifically as a sheet guide (bogeleitblech).

A passage opening 13 is provided in the guide device 12, through which passage opening 13 the dampening unit 8 damps the printing sheet 11. The dampening unit 8 is located partially below the guide 12 and damps the side of the printed sheet 11 which is located above and guided by the guide 12 and faces the guide 12. In other words, the dampening unit 8 damps the printed sheet 11 from below on its underside or back or the unprinted side. The application of moisture to this sheet is advantageous with regard to better moisture absorption by the sheet.

The through-opening 13 can be a window or, alternatively (if the guide 12 is multi-part and consists of plates arranged one behind the other in the sheet transport direction T), the through-opening 13 can be a gap between two plates. The moistening device 8 comprises a spraying device 18 with a housing 14, in which housing 14 an arrangement of centrifugal discs 16 is arranged. This disk arrangement extends in a horizontal manner and perpendicularly to the sheet transport direction T, and only one centrifugal disk 16 of the arrangement can be seen in the drawing. Each centrifugal disc 16 produces a fan-shaped or cone-shaped spray jet 17 of fluid. This fluid is water, but may have additives if desired. When wetting takes place, the spray jet 17 exits the housing 14 through the spray opening 15 of the housing 14.

The centrifugal discs 16 perform a rotation C, which may be driven by a common motor or by one motor per centrifugal disc 16.

The housing 14 is connected to the fluid circuit together with a pump 21. The pump 21 pumps fluid into the housing 14 and onto the centrifugal disks 16 via a supply line 22, wherein the supply line 22 can branch off into a plurality of branches and each branch can be directed with its outlet opening 37 toward another centrifugal disk 16. These centrifugal discs 16 generate the spray jet 17 by means of centrifugation. Excess fluid flowing away in the housing 14 is conducted from the housing 14 into the pump 21 via a drain line 20 connecting the housing 14 to the pump 21. These

conduits

20,22 may be pipes or hoses.

The first roller 31 is located in the through-opening 13, the spray jets 17 impinging on the first roller 31, the first roller 31 transfers the fluid to the underside of the printing sheet 11, which printing sheet 11 rests with its underside on the first roller 31, the first roller 31 can have a rubber-elastic circumferential surface, which is advantageous with respect to the pressing behavior (Andr ü ckverhalten), such a circumferential surface can additionally or alternatively be porous, which is advantageous with respect to the water-retaining properties.

Between the circumferential surface of the first roller 31 and the side of the running sheet 11 resting thereon, a defined slip (Schlupf) can occur, by means of which the fluid transfer is influenced in a positive manner. This slippage can be produced by driving the first roller 31 at a speed greater or less than the transport speed of the sheet 11. The first roller 31 can also run together with the printing sheet 11 without its own drive, wherein the first roller 31 can be braked for producing a slip by means of a bearing of the first roller 31 being restrained.

Indicated by means of double arrows in the first roller 31: by adjusting the height of the first roller 31, it is possible to vary the excess a by which the first roller 31 exceeds the guide surface 25 in relation to the operating parameters. The excess amount a can be set, for example, as a function of the paper stiffness of the individual printing sheet 11. The excess a is smaller in each setting than the spacing between the underside of the gripper bar 10 and the guide surface 25. The first roller 31 is resiliently supported.

In order to ensure reliable contact between the printed sheet 11 and the first roller 31 during moistening, a blowing device 23 is provided, which blowing device 23 presses the printed sheet 11 against the first roller 31. The blowing device 23 ensures sufficient moistening of the printed sheet 11, in particular in a section of the printed sheet 11 that is located downstream with respect to the sheet transport direction T. For this purpose, one or more blowing air jets of the blowing device 23 which impinge on the upper side of the printed sheet 11 are directed toward the first roller 31. The blowing device 23 can be a blowing tube and is arranged within the gripper running rails 24, along which gripper bars 10 move. Gripper running rails 24 are predefined by the endless chains of the chain conveyors, on which the gripper bars 10 are fastened.

These suction nozzles 28 also assist the abutment of the sheet 11 against the first roller 31. If these nozzles 28 are suction nozzles, the blowing device 23 can be omitted if necessary. If a blowing device 23 is provided, these suction nozzles 28 can be omitted if necessary, or can be replaced by blowing nozzles which allow a suspension guidance of the printed sheet 11.

Fig. 3 shows a modification of the moistening device 8, in which elements denoted by the same reference numerals as in fig. 1 and 2 are retained and are not described again.

This variant differs in that: the first roller 31 and the second roller 32 together form a sheet finisher 19, which sheet finisher 19 serves to flatten the printed sheet 11. By integrating the dampening device 8 into the sheet finisher 19, a versatile use of the first roller 31 is achieved. The second roller 32 is also arranged in the through opening 13, however, the second roller 32 does not protrude from the guide 12 as far as the first roller 31, or the second roller 32 does not protrude from the guide 12 at all.

The first and second rollers 31,32 sandwich a vacuum wedge 35 between them, said vacuum wedge 35 being attached to a suction air generator, as indicated by the arrow in the figure. The circumferential surfaces of the rollers 31,32 form a first convex surface 33 and a second convex surface 34, and the vacuum wedge 35 is located between the first convex surface 33 and the second convex surface 34. The vacuum loading of the vacuum wedge 35 causes the bend (schlink) of the printing sheet 11 to be sucked into the vacuum wedge 35 during the smoothing.

If the second convex surface 34 is formed by rounding down (Abrundung) the guide 12, the second roller 32 can be omitted.

List of reference numerals

1-sheet printing machine

2 sheet feeder

3 printing station

4 ink jet print head

5 dryer

6-sheet collector

7 conveying device

8 wetting device

9-sheet stack

10 gripping bridge

11 printing sheet

12 guide device

13 through opening

14 casing

15 spray opening

16 centrifugal disc

17 spray jet

18 spraying device

19 sheet finisher

20 leading away pipeline

21 pump

22 supply line

23 blowing device

24 gripper operation track

25 guide surface

27 dusting device

28 nozzle

31 first roll

32 second roll

33 first convex surface

34 second convex surface

35 vacuum wedge

Excess amount of A

C rotation

T sheet conveying direction

Claims

1. A sheet printing press comprising:

-a printing station (3),

-a guide device (12) for the printed sheets (11), and

-a dryer (5),

it is characterized in that the preparation method is characterized in that,

a dampening device (8) is arranged downstream of the dryer (5) in a sheet transport direction (T), said dampening device having a first roller (31) for dampening the printed sheet (11), wherein the first roller (31) protrudes from the guide device (12).

2. The sheet printing press according to claim 1,

it is characterized in that the preparation method is characterized in that,

the moistening device (8) has a spraying device (18) which is directed towards the first roller (31).

3. The sheet printing press according to claim 2,

it is characterized in that the preparation method is characterized in that,

the spraying device (18) has a centrifugal disk (16).

4. Sheet printing machine according to one of claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

a conveying device (7) having a gripper bar (10) is provided, which conveys the printing sheet (11) past the first roller (31).

5. Sheet printing machine according to one of claims 1 to 4,

it is characterized in that the preparation method is characterized in that,

the first roller (31) is a component of the sheet finisher (19).

6. The sheet printing press according to claim 5,

it is characterized in that the preparation method is characterized in that,

the sheet finisher (19) has a first convex surface (33) and a second convex surface (34) facing each other, wherein the first convex surface (33) is formed by the first roller (31).

7. The sheet printing press according to claim 6,

it is characterized in that the preparation method is characterized in that,

the second convex surface (34) is formed by a second roller (32).

8. Sheet printing machine according to claim 6 or 7,

it is characterized in that the preparation method is characterized in that,

the sheet flattener (19) has a vacuum wedge (35) located between the first convex surface (33) and the second convex surface (34).

9. Sheet printing machine according to one of claims 1 to 8,

it is characterized in that the preparation method is characterized in that,

the dryer (5) is a thermal dryer.

10. Sheet printing machine according to one of claims 1 to 9,

it is characterized in that the preparation method is characterized in that,

the printing station has an inkjet printing head (4).

11. Sheet printing machine according to one of claims 1 to 10,

it is characterized in that the preparation method is characterized in that,

a blowing device (23) is provided, which presses the printing sheet (11) onto the first roller (31).

12. The sheet printing press according to claim 11,

it is characterized in that the preparation method is characterized in that,

the blowing device (23) is arranged within an endless gripper running track (24).