EP3072690B1 - Sheet fed printer with accelerating station - Google Patents

Description

The invention relates to a sheet-fed press with acceleration station with the features of claim 1 and a method for operating such a sheet-fed press according to claim 5.

State of the art

For printing sheets of paper, cardboard and cardboard in short runs or with individual print motifs, the use of digital printing machines is known. When using inkjet heads for printing on the sheets, a respective sheet is moved by a transport system at a minimum distance below the inkjet heads.

As transport systems are circulating conveyor belts, for example, designed as suction belts, and rotating cylinders, so-called Jettingzylinder, or rotating tablets known.

In machine concepts using conveyor belts, a plurality of inkjet printheads are arranged above a conveyor belt, which print printed sheets at a small distance from the printheads. On the conveyor belt several sheets can be sucked in and transported simultaneously. To ensure high print quality and to avoid damage to the printheads, it is important that each sheet fits well on the tape. Such a conveyor belt is a so-called section-independent transport system.

An increase in performance of the digital printing press by increasing the transport speed are limited by the printing speed of inkjet heads. Also, the print quality decreases as the speed of the sheets to be printed increases.

It is also known to paint printed sheets after the printing process. This painting systems are used, which are designed as Flexolackierwerke with painting cylinder. Unlike the variable inkjet print heads, this works Paint shop with fixed shapes. A respective printed sheet must therefore be supplied to the coating unit in register, so that the paint register accurate, that is applied in the right place. Such a working with cylinders processing plant has a so-called. Sectional transport.

If sectional processing stations and section-independent processing stations are operated inline, ie in a machine with continuous material flow, then the processing speed of the sectioned processing stations predefines the processing speed of the section-independent processing stations. As a result, the performance of the machine can be low. From the prior art devices are known for the processing of cartons, but not for coating, which serve to position a carton to a processing tool. So shows eg the EP 2 386 509 A2 a device for feeding and processing on a processing machine with positioning rollers. The EP 2 058 115 B1 describes how folding cartons can be positioned relative to a rotary embossing tool. document EP-A-181 0826 discloses an apparatus according to the preamble of claim 1. [0010] It is an object of the present invention to provide a sheet-fed press with a digital printing station and a coating station which reduces the disadvantages of the prior art and allows economical operation of the machine. Another object is to describe a method for operating such a sheet-fed printing press.

The sheet-fed printing press according to the invention is used for printing sheets in particular of paper, cardboard and plastic and has a sheet feeder, a subsequent digital printing station, a subsequent coating station and a subsequent sheet delivery. The painting station has a coating unit with at least one paint cylinder, which is designed in particular as a Flexolackierwerk. With this coating unit, the sheet already printed in the digital printing station can be painted become. According to the invention, an acceleration station is arranged between the digital printing station and the coating station for accelerating sheets from a first lower transport speed in the digital printing station to a second, higher transport speed in the coating station. Advantageously, therefore, the distance between the sheets in the area of the digital printing station does not have to correspond to the spacing of the sheets in the area of the coating station, so that a higher productivity of the sheet-fed printing press can be achieved.

According to the invention, the acceleration station has a pair of rollers, a respective sheet being transported between the two rollers, thereby being clamped and accelerated.

In a particularly advantageous and therefore preferred development of the sheet-fed printing machine according to the invention, a section-independent transport area, e.g. using a conveyor belt, and in the area of the painting station a sectioned transport area, e.g. using a cylinder with grippers, before. In the section-independent transport area, a sheet can be transported in any position. In the sectioned transport area, a sheet can only be transported in certain, discrete sections and there are certain, discrete layers of the sheet during its transport.

In a further development of the sheet-fed printing machine according to the invention, the latter has a machine control for controlling at least the digital printing station, the acceleration station and the coating station, the operating speed of the coating station being determined as a function of the transport speed of the sheets and the distance and the length of the sheets.

In an embodiment variant of the sheet-fed printing machine according to the invention, the digital printing station is designed as a duplex digital printing station for double-sided printing of a respective sheet.

The invention also relates to a method for operating a sheet-fed printing machine as described above, whereby sheets are accelerated by the acceleration station so that existing gaps between two sheets are reduced, ie gaps in the sheet stream are reduced or completely closed. Such gaps between two sheets can arise especially when the sheetfed press is used in duplex mode and only every second sheet is continued to Lackierstation, every other sheet undergoes a return after a sheet transfer and printed a second time, now from the back, by the digital printing station is, especially when editing long bow. Alternatively, the accelerator station accelerates arcs so that existing gaps between two arcs are increased, ie gaps in the arc current are widened. Such too small gaps between two sheets can arise especially when short sheets are processed. By adjusting the arc gap, the coating unit, which is located in the sectioned transport area, can be operated in register and efficiently.

The invention also relates to an alternative method of operating a sheet-fed printing machine as described above, wherein sheets are accelerated by the accelerating station so that two short sheets are processed in the painting station during one revolution of the paint cylinder, d. H. can be painted. This makes it possible to operate the painting station at a high speed.

The invention described and the described advantageous developments of the invention are also in combination with each other - as far as is technically feasible - advantageous developments of the invention.

With regard to further advantages and constructive and functional advantageous embodiments of the invention, reference is made to the dependent claims and the description of exemplary embodiments with reference to the accompanying figures.

embodiment

The invention will be explained in more detail with reference to attached figures. Corresponding elements and components are provided in the figures with the same reference numerals. In favor of a better clarity of the figures was waived a true to scale representation.

Fig. 1

eine erfindungsgemäße Bogendruckmaschine

Fig. 2

eine erfindungsgemäße Bogendruckmaschine mit Duplex-Funktion

It show in a schematic representation

Fig. 1

a sheet-fed printing machine according to the invention

Fig. 2

a sheet-fed press according to the invention with duplex function

FIG. 1 shows a sheet-fed printing machine 100 according to the invention, in which sheet 1000 can be printed in a printing station 2 and painted by a painting station 4. A respective sheet 1000 is transported by a feeder 1 in the transport direction T through the printing machine 100, thereby processed and laid out in a display 6.

In this case, a respective sheet 1000 passes through a section-independent transport area S1 and a section-related transport area S2. In the section-independent transport area S1 is a printing station 2, which has a plurality of inkjet heads 10, which are arranged at a small distance to the transport plane of the sheet 1000th In the section-independent transport area S1, the sheets 1000 are transported at a first transport speed v1, for example by a conveyor belt or a sucking conveyor belt. Due to the limited operating speed of the inkjet heads 10, it is advantageous if the sheets 1000 are moved through the inkjet heads 10 at a rather low speed and at a small distance from one another. Subsequently, the sheets 1000 are transported in a section-related transport area S2 on. In order to ensure that the sheets 1000 are inserted register-accurate in the coating unit 14, located between printing station 2 and painting station 4 is an acceleration station 3, which has a pair of acceleration rollers 16 in this section-related transport area S2 having. By the acceleration rollers 16, the sheets 1000 are accelerated to a second transport speed v2 and pass the Coating unit 14. Following the coating unit 14, a drying station 5 may be provided with a dryer 15.

In FIG. 2 an alternative embodiment of the above-described sheet-fed printing machine 100 is shown. This also has a curved switch 11, a turning pocket 12 and a sheet return 13, so that in the printing station 2, the sheet back can be printed. When the sheet-fed printing machine 100 is used in so-called duplexing, the sheets 1000 are not transferred directly to the subsequent acceleration station 3 after printing, but discharged by means of a curved switch 11 in the sheet return 13, where the sheet turned in a turning pocket 12 or a different type of turning device and be transported back to the entrance of the printing station 2. The sheets 1000 now pass through the printing station 2 for a second time, the inkjet heads 10 now printing the sheet back side. In order to enable continuous operation of the sheet-fed printing machine 100 in duplex mode, a completely unprinted sheet 1000 is fed alternately from the feeder 1 and an already printed on one side sheet 1000 from the sheet return 13 of the printing station 2. This also means that only every second sheet 1000 is transferred from the printing station 2 to the acceleration station 3. Using the acceleration rollers 16 of the acceleration station 3, these sheets of the coating station 4 can register and at the desired speed, d. h .bestimmt to the processing speed of the coating station 4, are supplied.

LIST OF REFERENCE NUMBERS

1

investor

2

printing station

3

accelerating station

4

painting station

5

drying station

6

display

10

inkjet heads

11

Bogenweiche

12

Wendetasche

13

Feedback sheet

14

Paint shop with paint cylinder

15

dryer

16

accelerating roll

100

press

1000

bow

T

transport direction

S

1 section-independent transport area

S2

sectioned transport area

v1

first transport speed

v2

second transport speed

Claims (6)

1. Sheet-fed printing machine (100) including a sheet feeder (1), a digital printing unit (2), a downstream varnishing unit (4), and a sheet delivery (6),
   wherein the varnishing unit (4) includes a varnishing device (14) with at least one varnishing cylinder, further including an acceleration unit (3) disposed between the digital printing unit (2) and the varnishing unit (4) for accelerating sheets (1000) from a first transport speed (v1) in the digital printing unit (2) to a second transport speed (v2) in the varnishing unit (4),
   wherein a transport region (S1) in the region of the digital printing unit (2) is phase-independent and a transport region (S2) in the region of the varnishing unit (4) is phase-dependent,
   characterized in
   that the acceleration unit (3) includes a roller pair (16),
   wherein a respective sheet (1000) is transported between the two rollers of the roller pair (16) and clamped and accelerated in the process.
2. Sheet-fed printing machine according to claim 1,
   characterized in
   that the sheet-fed printing machine (100) includes a machine control unit for actuating at least the digital printing unit (2), the acceleration unit (3), and the varnishing unit (4).
3. Sheet-fed printing machine according to any one of the preceding claims,
   characterized in
   that the digital printing unit (2) is embodied as a digital duplex printing unit.
4. Method for operating a sheet-fed printing unit according to any one of the preceding claims,
   wherein the acceleration unit (3) accelerates the sheets (1000) in a way to increase or decrease existing gaps between two sheets (1000).
5. Method for operating a sheet-fed printing machine according to any one of claims 1 to 3, wherein the acceleration unit (3) accelerates sheets (1000) in a way to be able to varnish two short sheets (1000) in the varnishing unit (4) upon one revolution of the varnishing cylinder.
6. Method for operating a sheet-fed printing machine according to claim 2,
   characterized in
   that the operating speed of the varnishing unit (4) is determined as a function of the transport speed of the sheets (1000) and as a function of the spacing and length of the sheets (1000).

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