DRYER

Description

[0001] The invention relates to a dryer for gassing a running printing web in a rotary printing machine, with a nozzle body.

[0002] Rotary printing presses are essentially printing machines that unwind and print on webs of material from spools, then rewind them. These presses are designed for different materials, such as paper or film. Furthermore, different inks are used, such as solvent-based, water-based, or indicator inks.

[0003] In rotary printing presses, drying nozzles are used to dry the ink of the images printed on the web. To do this, a drying gas is introduced into a nozzle body whose nozzle slot is directed toward the web, ensuring that the entire width of the web is exposed to the drying gas as evenly as possible, thus drying it.

[0004] It is also known to use a sheet metal body divided into two chambers as a dryer. One chamber (supply air chamber) directs the heated gas to the drying material web, while the other chamber (exhaust air chamber) carries the solvent- or water-enriched air away from the material web. The supply air chamber contains a so-called nozzle lance, which can be removed from the chamber for cleaning. This lance consists of a 5 mm wide slot from which the gas flows to the material web. To achieve better air flow, small baffles are incorporated in addition to the wedge-shaped design.

[0005] For example, DE 20 2016 102 780 discloses a drying nozzle with a hollow nozzle body, wherein the nozzle body has a nozzle slot extending transversely to the direction of travel of the printing substrate web. To ensure that the drying nozzle can be easily adapted to different applications, the nozzle body has an inner tube and an outer tube surrounding the inner tube, each of which has at least one outlet opening in its peripheral wall. The nozzle slot is formed by an overlap zone of the outlet openings of the inner tube and the outer tube and is adjustable by changing the angular position of the inner tube relative to the outer tube.

[0006] EP 3 112 156 A1 discloses an arrangement of several nozzles arranged one behind the other, extending across the entire width of the printing web. This arrangement is very large and therefore only suitable for use as a post-drying arrangement.

[0007] Another disadvantage of state-of-the-art dryers has proven to be that the uneven airflow leads to uneven drying results. This means that, depending on the width of the web, the ink exhibits a different "drying state." In addition, the web moves back and forth on the cylinder at the calculated required drying power, causing register fluctuations during the printing process, which significantly reduces print quality. The result is that the required drying power cannot be set, and therefore the actual possible drying performance cannot be achieved.

[0008] EP 0 103 876 A2 discloses a ventilation device for a printing press, in particular for a rotary gravure printing press. The ventilation device comprises a ventilation hood in which several ventilation sections are provided. Extraction holes are provided between the ventilation sections.

[0009] The object of the invention is to provide a dryer that is capable of operating at lower gas velocities / pressures and thus lower performances.

[0010] This object is achieved according to the invention by a dryer according to claim 1, namely a dryer for gassing a moving printing web in a rotary printing press, with a nozzle body which has a plurality of openings for the outlet of heated gas which extend only over a part of a width of the printing web and protrude from a nozzle base body of the nozzle body and are designed as nozzles, and the dryer has a plurality of openings for sucking in the cooled gas, which are arranged at least partially between the openings for the outlet of heated gas, wherein the nozzle body has a cavity through which the heated gas is supplied to the printing web and the openings for sucking in the cooled gas are provided outside the cavity, wherein a grid plate is arranged on the nozzle base body, in which the openings for sucking in the cooled gas are provided.

[0011] With a dryer according to the present invention, it is now possible to achieve better drying properties in a simple manner, which are essentially independent of the material to be printed.

[0012] This advantageously allows for a uniform airflow across the entire printing web with relatively little space required, resulting in consistent drying results. The homogeneous airflow significantly reduces turbulence, which does not affect the material web. This property significantly improves print quality. Compared to conventional dryers, it is now also possible to install and remove the dryer for cleaning purposes without disassembling other components. The modular design allows individual components to be removed, sometimes even without tools.

[0013] Advantageous developments of the present invention are the subject of the dependent claims.

[0014] It has proven particularly advantageous if the openings for the heated gas outlet are at least partially offset. This makes it possible for every section of the printing web to be dried.

[0015] Good results have been achieved when at least one opening has a round, oval, or approximately such a shape. The openings can all have the same or different shapes. For example, good results have been achieved with openings with an exit opening in the range of 1 to 10 mm, preferably 2 to 5 mm.

[0016] According to a preferred embodiment of the invention, the dryer is designed such that the nozzle body has a cavity through which the heated gas is supplied to the printing web. For example, a connection for supplying the heated gas can be provided on the nozzle body, through which the heated gas is supplied into the cavity.

[0017] It has proven advantageous if at least one opening for the discharge of heated gas protrudes from a peripheral surface of the nozzle body. This ensures that the heated gas is fed directly to the printing web.

[0018] According to a further advantageous embodiment of the invention, one opening for returning the cooled gas is provided outside the cavity. This makes it possible, for example, to draw the cooled gas along the nozzle body and laterally.

[0019] It may be advantageous to provide an extraction system to return the cooled gas.

[0020] Good results have been achieved using ambient air as the gas. To achieve particularly good drying results, it may be advantageous for the nozzle body to be at least the width of the print path.

[0021] According to a further aspect, the invention relates to a rotary printing press comprising a printing cylinder for printing a moving printing web and the above-described dryer for gassing the printing web, so that a negative pressure is present at least substantially in the region between the outlet of the heated gas and the printing web.

[0022] In the following, embodiments of the invention are explained in more detail with reference to the drawing.

[0023] They show: Fig. 1 is a perspective view of a nozzle body according to a preferred embodiment of the invention; Fig. 2 is a detailed view of the nozzle body according to a preferred embodiment of the invention; Fig. 3 is a perspective sectional view of the nozzle body according to a preferred embodiment of the invention; Fig. 4 is a cross-section of the nozzle body according to Fig. 3 ; Fig. 5 a detailed view of the nozzle body according to Fig. 1 ; and Fig. 6 shows a dryer according to another preferred embodiment in an installed state. Fig. 7 shows a fully assembled nozzle body in plan view.

[0024] In Fig. 1 A perspective view of a nozzle body 1 according to a preferred embodiment of the invention is shown below, with the structure of this nozzle being shown as an intermediate drying nozzle by way of example. According to the embodiment shown, the dryer consists of a so-called overpressure and a negative pressure zone.

[0025] The heated gas required for drying, for example air, flows out of openings 2, which protrude from the nozzle body 5 and are designed as nozzles, here small "holes," strikes the freshly printed material web or printing web, and is sucked back in through other openings 3 provided. This prevents the air-solvent mixture from escaping into the atmosphere. The openings are well-designed Fig. 2 , a detailed view. Fig. 1 shows the area from which the air flows out and is simultaneously sucked back in. From the zoom view of Fig. 2 the structure of the drying nozzle becomes visible.

[0026] In the illustrated embodiment, a type of sheet metal 4 is provided on the nozzle body, which here is designed as a grid plate, which is fastened, for example, by rivets to the milled base body 5. This base body 5 is in turn fastened to a main frame, for example by screws.

[0027] According to the preferred embodiment shown, there is a uniform, permanent negative pressure in the area between the dryer and the impression cylinder, which on the one hand prevents solvent-laden air from flowing into the environment, and on the other hand the solvent-laden air is sucked in and discharged from the entire printing unit.

[0028] Fig. 7 shows a nozzle body in a view of the outlet nozzles. The nozzles are the openings 2, which are essentially round and all of essentially the same design. The openings are arranged transversely in a line in the direction of travel of the printing web, while they are offset at an angle in the direction of travel of the printing web. The angle can range from 2 to 30°, preferably from 5 to 15°.

[0029] In Figur 3 An exemplary structure of a nozzle body 1 is shown in a perspective view. Fig. 4 shows a cross-section of this nozzle body.

[0030] The air, which is either already heated or still being heated, enters the cavity 7 of the nozzle body, or overpressure area, through a nozzle 6. The air exits this through the small outlet openings 2 (arrow 8), impacts the material of the ribbon to be printed, turns around (arrow 10), and passes through the recesses in the milled base body (arrows 9 and 10) to the lateral ends 11. Once there, the medium flows "above" the overpressure area or past the overpressure area toward the extraction opening 12. Above this extraction opening, there are preferably so-called stud bolts 13 to which the air extraction system is connected. Depending on the width of the nozzle, the air extraction system consists of differently screwed nozzles. A flexible, solvent-resistant, and heat-resistant hose is connected to this nozzle, which transports the solvent-laden air to a collecting pipe.

[0031] In Fig. 5 is a detailed view of the nozzle body 1 after Fig. 1 shown here is the inlet or nozzle for the heated or to be heated air or gas.

[0032] Fig. 6 shows a dryer according to a further preferred embodiment in an installed state.

[0033] It can be seen that the entire drying unit is arranged here, for example, between a cross-beam 14 and a central cylinder 15 in a rotary printing press. Fig. 6 Two dryers are shown, although more dryers can also be arranged. The nozzle body 1 is mounted in a printing unit by means of a holder 16. According to the embodiment shown, a collecting pipe 17, into which the exhaust air is discharged, is located on sheet metal holders 18 that are suspended in the crossbeam 14. By using flexible hoses to connect the nozzle body 1 to the collecting pipe 17, it is possible, for example, to move / pull the nozzle body slightly toward the crossbeam in order to remove material residue that has become caught on the sheet metal.

[0034] As from the Fig. 6As is clearly evident, with a dryer according to the present invention, the modular design makes it possible to install and remove it from the printing unit for cleaning purposes without disassembling other components. With appropriate connections, the modular design also allows individual components to be assembled without tools.

Claims

1. Dryer for supplying gas to a moving printing web in a rotary printing machine, having a nozzle body (1), wherein the nozzle body (1) has a plurality of openings (2) for the exit of heated gas, said openings extending only over part of a width of the printing web and projecting from a nozzle base body (5) of the nozzle body (1) and being formed as nozzles, and the dryer has a plurality of openings (3) for drawing in the cooled gas which are arranged at least partially between the openings (2) for the exit of heated gas, wherein the nozzle body has a cavity (7) through which the heated gas is supplied to the printing web and the openings (3) for drawing in the cooled gas are provided outside the cavity (7), characterised in that on the nozzle base body (5) a grid plate (4) is arranged in which the openings (3) for drawing in the cooled gas are provided.

2. Dryer according to claim 1, characterised in that the openings (2) for the exit of heated gas are arranged at least partially offset.

3. Dryer according to any one of the preceding claims, characterised in that at least one opening (2) has a round, oval shape or a shape approximating such a shape.

4. Dryer according to any one of the preceding claims, characterised in that a suction unit is provided for returning the cooled gas.

5. Rotary printing press comprising a printing cylinder for printing a moving printing web and a dryer for supplying gas to the printing web, according to any one of the preceding claims, such that a negative pressure is present at least substantially in the region between the exit of the heated gas and the printing web.