Patent Application
20210001620
The invention relates to a dryer for treating a running printing web with gas in a rotary printing press, having a nozzle body.
Rotary printing presses are essentially printing presses in which printing webs or material webs located on rolls are unrolled and printed and then rolled up again. The printing presses are conceived for different materials, for example, paper or film. Furthermore, different inks are used, such as solvent inks, water-based inks, or indicator inks.
In rotary printing presses, drying nozzles are used to dry the printing ink of the images printed on the printing web. For this purpose, a drying gas is introduced into a nozzle body, the nozzle slot of which is oriented toward the printing web, so that the printing web is treated as uniformly as possible with the drying gas over its entire width and is thus dried.
Furthermore, using a sheet metal body which is divided into two chambers as a dryer is known. One chamber (supply air chamber) guides the heated gas to the material web to be dried, the other chamber (exhaust air chamber) guides the air enriched with solvent or water away from the interior web. A so-called nozzle lance is located in the supply air chamber, 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. In addition to the wedge-shaped shape, small baffles have been incorporated so that better air flow is achieved.
A drying nozzle with a hollow nozzle body is known from DE 20 2016 102 780, for example, wherein the nozzle body has a nozzle slot extending transversely to the running direction of the printing material web. In order that the drying nozzle may be adapted easily to different applications, the nozzle body has an inner tube and an outer tube surrounding the inner tube, which each have at least one outlet opening in its circumferential wall, and 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 in relation to the outer tube.
An arrangement of multiple nozzles extending in succession over the entire width of the printing web is known from EP 3 112 156 A1. This arrangement is very large and is therefore only suitable for use as a post-drying arrangement.
In the dryers known from the prior art, it has furthermore proven to be disadvantageous that the irregularity of the airflow results in an uneven drying result. This means the ink has a different “drying level” with respect to the width of the material web. In addition, the material web travels back and forth on the cylinder in the case of drying performance required by computer, whereby matching variations/register variations result in the printing process, which significantly reduce the printing quality. The result is that the required drying power cannot be set and the actual possible performance of the drying is thus not achieved.
The object of the invention is to provide a dryer which is capable of operating at lower gas speeds/pressures and thus lower performances.
This object is achieved according to the invention in that the nozzle body as at least two openings extending over only a part of a width of the printing web for the exit of heated gas and has at least one opening for recirculating the cooled gas.
Using a dryer according to the present invention, better dryer properties can now be achieved in a simple manner, which are essentially independent of the material to be printed.
In this way, a uniform airflow can advantageously be achieved over the entire printing web with relatively little space required, which leads to a uniform drying result. Significantly less turbulence, which does not influence the material web, occurs due to the homogeneous air guiding. The dryer increases the printing quality enormously due to this property. In comparison to conventional dryers, it is now additionally possible to install it and remove it for cleaning purposes without dismantling further components. Due to the modular structure, individual components may be removed and under certain circumstances this may even be done without tools.
It has proven to be particularly advantageous if the openings are arranged at least partially offset. It is thus possible that every region of the printing web is also dried.
Good results can be achieved if the at least one opening as a round or oval shape or shape approximating such a shape. The openings can all have the same shape or different shapes. Good results have been achieved, for example, with openings which have an outlet opening in the range of 1 to 10 mm, preferably 2 to 5 mm.
According to one preferred embodiment of the invention, the dryer is designed in such a way that the nozzle body has a cavity, through which the heated gas is supplied to the printing web. In this way, for example, a fitting can be provided for supplying the heated gas to the nozzle body, by which the heated gas is supplied into the cavity.
It has proven to be advantageous if the at least one opening for the exit of heated gas protrudes from a circumferential surface of the nozzle body. It can be ensured in this way that the heated gas is supplied directly to the printing web.
According to a further advantageous design of the invention, the one opening for recirculating the cooled gas is provided outside the cavity. It is thus possible, for example, to draw off the cooled gas along the nozzle body and laterally.
It can be advantageous here that a suction unit is provided for recirculating the cooled gas.
Good results have been achieved when ambient air is used as the gas.
To achieve particularly good drying results, it can be advantageous for the nozzle body to have essentially at least the width of the printing web.
According to a further aspect, the present invention relates to a method for drying a moving printing web in a rotary printing press, wherein the running printing web is dried by means of heated gas from a dryer having a nozzle body, the cooled gas is returned into the dryer at least partially along the surface of the nozzle body opposite to the printing web, and wherein there is a negative pressure at least essentially in the region between the exit of the heated gas and the printing web. This negative pressure ensures that contamination of the environment can be greatly reduced or even prevented.
Such a method can provide good drying results in particular if the negative pressure is present permanently and uniformly during operation.
Good results can be achieved in a cost-effective manner if ambient air is used as the gas.
According to one particularly preferred embodiment of the present invention, the cooled gas is recirculated by means of suction.
In addition, it can be provided that the cooled gas is supplied to filtration. In this way, it would be possible to reuse the gas or return it into the atmosphere.
The dryer according to the present invention can be used in particular as an intermediate drying nozzle in a rotary printing press.
According to still a further aspect, the invention relates to a rotary printing press comprising a printing cylinder for printing a moving printing web and a dryer for treating the printing web with gas, having a nozzle body, characterized in that the nozzle body has at least two openings extending over only a part of a width of the printing web for the exit of heated gas and has at least one opening for recirculating the cooled gas, wherein there is a negative pressure at least essentially in the region between the exit of the heated gas and the printing web.
In the following, exemplary embodiments of the invention are explained in greater detail on the basis of the drawings.
In the drawings:
The heated gas required for drying, for example, air, flows out of openings 2 which protrude from the nozzle main body 5 and are formed as nozzles, small “holes” here, is incident on the freshly printed material web or printing web, and is suctioned in again by other provided openings 3. It is thus possible to prevent air-solvent mixture from reaching the atmosphere. The openings can be seen well in
In the embodiment shown, a type of plate 4 is provided on the nozzle body, which is formed here as a grid plate, which is fastened by means of rivets, for example, on the base body 5, which is milled, for example. This base body 5 is in turn fastened in a main frame, for example, by means of screws.
According to the illustrated preferred embodiment, there is a uniform permanent negative pressure in the region between dryer and counter pressure cylinder, which prevents the solvent-laden air from flowing into the environment, on the one hand, and suctions in and discharges the solvent-laden air from the entire printing unit, on the other hand.
An exemplary structure of a nozzle body 1 is shown in a perspective view in
The air, which is either already heated or is still being heated, passes through a connecting piece 6 into the cavity 7 of the nozzle body or the excess pressure region. The air leaves this through the small outlet openings 2 (arrow 8), strikes against the material of the web to be printed, reverses (arrow 10), and reaches the lateral ends 11 through the openings in the milled base body (arrows 9 and 10). Arriving there, the medium flows “above” the excess pressure region or past the excess pressure region in the direction of the suction opening 12. Preferably so-called stud bolts 13, to which the air suction unit is attached, are located above this suction opening. Depending on the width of the nozzle, the air suction unit consists of different screwed-on connecting pieces. A flexible, solvent-resistant, and heat-resistant hose is attached to these connecting pieces, which transports the solvent-laden air to a manifold.
It can be seen that the entire drying unit is arranged here, for example, between a cross member 14 and a central cylinder 15 in a rotary printing press. Two dryers are visible for this purpose in
As can be seen clearly from
| Number | Date | Country | Kind |
|---|---|---|---|
| 18020082.6 | Feb 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/025053 | 2/26/2019 | WO | 00 |
