阅读说明：本技术 具有润湿装置的页张印刷机 (Sheet printing machine with dampening unit ) 是由 C·鲁帕纳 C·哈斯 U·昂斯特 M·莱瓦 U·费伦贝格 C·希布 于 2019-06-14 设计创作，主要内容包括：本发明涉及一种页张印刷机,包括干燥器(5)。在页张输送方向(T)上在所述干燥器(5)后布置有用于在未被印刷的页面上进行承印页张(11)的重新润湿的润湿装置(8)。所述润湿装置(8)由控制装置(29)根据至少一个第一湿度传感器(23)的信号控制。所述第一湿度传感器(23)从下方朝向经过的承印页张(11)。(The invention relates to a sheet printing press comprising a dryer (5). A dampening unit (8) for dampening the printed sheet (11) on the unprinted sheet is arranged downstream of the dryer (5) in the sheet transport direction (T). The moistening device (8) is controlled by a control device (29) as a function of signals of at least one first humidity sensor (23). The first moisture sensor (23) faces the passing printed sheet (11) from below.)

1. A sheet printing machine comprises a dryer (5),

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

a dampening device (8) for dampening the printed sheet (11) on an unprinted sheet is arranged downstream of the dryer (5) in the sheet transport direction (T),

the moistening device (8) is controlled by a control device (29) according to the signal of at least one first humidity sensor (23), and

the first moisture sensor (23) is directed from below toward the passing printing sheet (11).

2. The sheet printing press according to claim 1,

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

the first moisture sensor (23) is arranged in a guide device (12) for the printed sheets (11).

3. The sheet printing press according to claim 2,

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

the guide means (12) has a guide surface (25) which contains a nozzle (28) therein.

4. The sheet printing press according to claim 3,

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

the nozzle (28) is a suction nozzle.

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 control device (29) is programmed to: the first moisture sensor (23) is configured to obtain a measured value only in a middle third and/or a rear third of the reference sheet conveying direction (T) of the respective printed sheet (11).

6. The sheet printing press according to claim 5,

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

the control device (29) is programmed to: the control device uses the measured values obtained in the middle third and/or rear third of the respective printed sheet (11) as a basis for calculating the control of the moistening device (8) during the rewetting of the first third of the reference sheet transport direction (T) of the printed sheet or of the following printed sheet.

7. Sheet printing machine according to one of claims 1 to 6,

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

the first humidity sensor (23) and the second humidity sensor (24) are connected to the control device (29),

wherein the first moisture sensor (23) is arranged upstream of the moistening device (8) and the second moisture sensor (24) is arranged downstream of the moistening device (8) as seen in the sheet transport direction (T).

8. Sheet printing machine according to one of claims 1 to 7,

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

the first humidity sensor (23) is a microwave sensor.

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 moistening device (8) is a spraying device.

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 dryer (5) is a thermal dryer.

Technical Field

The invention relates to a sheet printing press comprising a dryer.

Background

DE 102016125960 a1 describes a sheet-fed printing press with a printing unit 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, a varnish module is arranged, by which the printed sheets are finally coated.

The disadvantage is that the infrared or hot air dryer causes the printed sheet to lose moisture and thus to deform the sheet. However, by applying varnish in the varnish module, no more moisture can be supplied to the printed sheet, since varnish is applied to the printed image previously printed in these printing units, which has a sealing effect (versiegeld) on the printed sheet.

Disclosure of Invention

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

The object is achieved by a sheet printing press comprising a dryer, characterized in that a dampening unit is arranged downstream of the dryer in the sheet transport direction for dampening printed sheets (R ü ckbefeuchten) on unprinted sheets, said dampening unit being controlled by a control unit as a function of signals of at least one first dampening sensor, and the first dampening sensor being directed from below toward the passing printed sheets.

The sheet-fed printing press according to the invention has the advantage that the rewetting of the printed sheet by the dampening unit is effected on an unprinted sheet of the printed sheet, which sheet is well able to absorb such rewetting liquid.

Different modifications are possible:

the first moisture sensor can be arranged in a guide device for the printed sheets.

The guide means may have a guide surface with a nozzle contained therein.

These nozzles may be suction nozzles.

The control device can be programmed in such a way that the first moisture sensor only receives measured values in the middle third and/or the rear third of the reference sheet transport direction of the respective printed sheet.

The control device can be programmed in such a way that it uses the measured values obtained in the middle third and/or the rear third of the respective printed sheet as a basis for calculating for controlling the dampening unit when the first third of the reference sheet transport direction of the one or the next printed sheet is dampened again.

The first moisture sensor and the second moisture sensor can both be connected to the control device, wherein the first moisture sensor is arranged upstream of the moistening device and the second moisture sensor is arranged downstream of the moistening device, as viewed in the sheet transport direction.

The first humidity sensor may be a microwave sensor.

The wetting apparatus may be a spraying apparatus.

The dryer may be a thermal dryer.

Drawings

Further refinements result from the following description of the exemplary embodiments and from the drawings, in which:

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

FIG. 2: a detailed view of the wetting apparatus.

Detailed Description

Fig. 1 shows a sheet printing press 1, which sheet printing press 1 comprises: 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 also comprises a transport device 7 for transporting the printed sheet past a dampening device 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 unit 8 is a re-dampening unit and is used to dampen the printed sheet again. The substrate of the printed sheet (for example paper or cardboard) loses moisture due to the radiation of the dryer 5, which is an unavoidable side effect and leads to disturbing sheet deformations if no countermeasures are taken. By this counter-measure in the form of re-wetting, the moisture loss of the substrate caused by the drying process is at least partially compensated.

The 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 printed sheets are deposited 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 a gripper bar 10 for holding the sheet 11 stationary 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 11 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 nozzles 28 therein, which nozzles 28 suck in suction air. The guide surface 25 is flat, whereas if the conveying means 7 is a drum, the guide surface 25 may alternatively be bowl-shaped (or concave). The guide device 12 may be referred to as a sheet guide (bogeleitblech), among others.

A passage opening 13 is provided in the guide 12, through which opening 13 the dampening unit 8 damps the printed sheet 11 in a so-called tact phase (active phase). The dampening unit 8 is located below the guide 12 and damps the side of the sheet 11 facing the guide 12, wherein the sheet 11 is located above the guide 12 and is guided thereby. That is to say, the dampening unit 8 damps the underside or the rear side of the printed sheet 11 or the unprinted sheet from below. Moisture is applied to this sheet, which is advantageous in respect of a better moisture absorption of the sheet 11.

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), can be a gap between two plates. The moistening device 8 comprises a housing 14 in which an array of centrifugal discs 16 is arranged. This row extends horizontally and perpendicularly to the sheet conveying direction T, in the drawing only one centrifugal disc 16 in the row being visible. Each centrifugal disk 16 generates a fan-shaped or cone-shaped spray jet 17 of fluid, by means of which spray jet 17 the printed sheet 11 is to be moistened. After exiting the housing 14, the spray jets 17 converge into a single spray curtain which extends over the entire width of the printed sheet. The fluid is water, possibly with additives. When wetting is carried out in the clocked phase shown in fig. 2, the spray jets 17 emerge from the housing 14 through the spray openings 15 of the housing 14 and subsequently through the through-openings 13.

The tact mask 18, which may also be referred to as a dynamic shutter, is adjusted to the first position and the second position in a cyclically alternating manner at the transfer tact of the printed sheets 11. This adjustment is performed by means of a drive and is shown as a translation a with a double arrow. Such an actuator may comprise, for example, a pneumatic cylinder or alternatively an electric motor with a subsequent transmission, for example a cam transmission. In the first position, the beat stop 18 does not coincide with the spray opening 15 and does not close off this spray opening 15, so that the spray jet 17 is not blocked by the beat stop 18. In a first position corresponding to the tact phase, the printed sheet 11 coincides with the through-opening 13, so that the printed sheet 11 passing through the through-opening 13 is wetted from front to back.

In the so-called passage phase (deactivation phase/passive phase), in which no sheet 11 overlaps the passage opening 13, the gap 33 (so-called passage) between the trailing edge 34 of the preceding sheet 11 and the leading edge 35 of the following sheet 11 overlaps the passage opening 13. Corresponding to the passage phase is a second position of the beat stop 18, in which the beat stop 18 coincides with the spray opening 15 and closes off the spray opening 15, so that the spray jets 17 strike the beat stop 18 and are blocked by the beat stop 18 from exiting the housing 14. In this way, the dampening unit 8 is prevented from spraying into the sheet recesses 33, which would otherwise be accompanied by waste of fluid and machine contamination. The beat stop 18 is in the form of a strip which is slightly longer and wider than the slot-shaped spray opening 15 in order to completely cover this spray opening 15.

The length of the spray openings 15 (viewed orthogonally to the plane of the drawing) is at least as large as the width of the largest sheet format that can be handled by the sheet-fed printing press 1. In order that the dampening unit 8 does not spray laterally onto the printed sheets 11 when processing printed sheets 11 having a format smaller than the maximum sheet format, the dampening unit 8 then has a format control device which comprises two format shutters 19, which format shutters 19 can be moved closer to and further away from each other by a common drive or by a drive, respectively. One of the format shutters 19 is located at that end of the spray opening 15 which is located on the drive side of the printing press 1, so as to partially cover the spray opening 15, while the other format shutter is located at that end of the spray opening 15 which is located on the operating side of the printing press 1, so as to also partially close the spray opening 15. The spray jet 17 or parts of the spray jet 17 released by the centrifugal disks 16 outside the format width of the sheet to be processed impinge on the format masks 19 and are blocked by the format masks 19 from exiting the housing 14. Only one of the two format shutters 19, which are respectively wider than the spray opening 15, is shown in the drawing. During each print job, each gauge shutter 19 maintains its position set for the sheet gauge of that print job, and may be referred to as a static shutter. The drive can be an electric motor with a drive mechanism connected downstream, for example a screw drive. The calibration of each specification shutter 19 is performed in translation perpendicular to the sheet conveying direction T.

The centrifugal disks 16 perform a rotation C without interruption, both in the beat phase and in the channel phase, which can be driven by a common motor or by a respective motor for each centrifugal disk 16.

The housing 14 is connected together with a pump 21 to a circuit for the fluid. 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 centrifugal action. The excess fluid which is blocked by the shutters 18,19 and which flows away in the housing 14 passes from the housing 14 via a drain line 20 into a pump 21, by means of which drain line 20 the housing 14 is connected to the pump 21. These conduits 20,22 may be pipes or hoses.

A first moisture sensor 23 is arranged upstream of the passage opening 13 and a second moisture sensor 24 is arranged downstream of the passage opening 13 in the sheet transport direction T. The two moisture sensors 23,24 are inserted flush into the guide surface 25. These moisture sensors 23,24 measure the moisture content of each passing printed sheet 11 in a contactless manner. The moisture sensors 23,24 are microwave sensors, by means of which not only the measurement is carried out on the surface of the sheet 11, but rather a measurement is carried out through its entire thickness into the sheet 11. These moisture sensors 23,24 are connected to a control unit 29 via electrical lines 26 in order to signal the measured values or data to the control unit 29.

In the first third section of the printed sheet 11, with reference to the sheet travel direction T, the printed sheet 11 has a section 30 which rises obliquely from the guide surface 25 toward the gripper bar 10, in which section 30 the distance between the printed sheet 11 and the guide surface 25 and thus the measurement distance between the printed sheet 11 and the moisture sensor 23 (or 24) is not constant, and therefore no measurement is carried out here. In the middle and rear third sections of the printed sheet 11, the printed sheet 11 extends at a distance from the guide surface 25, wherein the measurement distance is at most 5 mm. If the sheet 11 is placed on the guide surface 25 in its middle third and rear third, the measurement interval can also be zero.

Since the measurement intervals are constant only in the middle and rear third sections of the sheet, the control device 29 only takes into account the values measured in the middle and rear third sections. In order to calculate the values for the first third section, the control device 29 uses extrapolation or averaging based on the values measured in the middle third section and the rear third section. For example, the second humidity sensor 24 generates a humidity characteristic curve (feuchterprofilel) in the control device 29. In the humidity characteristic curve, the average value is calculated by the control device 29. The control device 29 uses this average value as the moisture value for the first third of the sheet.

The control device 29 controls the wetting device 8 on the basis of the measured and calculated values, wherein the control device 29 varies the power or the rotational speed of the pump 21. In the case of the use of only the second moisture sensor 24 and not the first moisture sensor 23, or in the case of the use of the two moisture sensors 23,24 for measuring the sheet moisture before and after rewetting, the moistening device 8 can be regulated according to the principle of a closed regulating circuit (Prinzip des geschlossenen regelkreises). In the case of the use of only the first humidity sensor 23 and not the second humidity sensor 24, the moistening device 8 can be controlled only according to the principle of the open-acting process (Prinzip des of fen with the rkungsablafs).

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 beat screen

19 gauge shield

20 leading away pipeline

21 pump

22 supply line

23 first humidity sensor

24 second humidity sensor

25 guide surface

26 pipeline

27 dusting device

28 nozzle

29 control device

30 segment

33 page vacancy

34 rear edge

35 front edge

37 output port

A translation

C rotation

T sheet conveying direction