GB2226986A

GB2226986A - Drier for a printed web

Info

Publication number: GB2226986A
Application number: GB8928091A
Authority: GB
Inventors: Guenter Hackenberger; Wolfgang Zoellner; Juergen Haeublein; Rudolph Gruenewald; Gerhard Hunkel
Original assignee: Kombinat Polygraph Werner Lamberz VEB; Polygraph Leipzig Kombinat Veb
Current assignee: Kombinat Polygraph Werner Lamberz VEB; Polygraph Leipzig Kombinat Veb
Priority date: 1988-12-12
Filing date: 1989-12-12
Publication date: 1990-07-18
Also published as: DE3927093A1; SE8904167L; FR2640198A1; DD277883A1; SE8904167D0; GB8928091D0

Description

DRIER FOR A PRINTED WEB The present invention relates to a drier for a printed web, especially for a rotary printing machine.

In known drying methods, printed webs are dried by evaporation and combustion of volatile components of the ink in order to avoid smearing of the printing. Equipment for drying of ink is described in CH patent specification 344 084, in which at least one burner unit is so arranged along a paper conveying path behind each of a plurality of printing cylinders that the printed paper surface is acted on over its entire width by a row of flames when running past the burner unit.

A device is also known, for example from CH-PS 474 366, in which a fresh air nozzle is arranged beside the gas burner, wherein the hot gas current and the fresh air current are so directed towards the material to be dried that both the currents intermix before they reach the material. Also known are devices, for example that according to CH-PS 569 942, in which hot gases are directed by means of nozzles towards the paper web and enhanced by suction exerted by drying air jets issuing from the nozzles.

In addition, DE-OS 3 635 833 describes a drier which acts on the web at one or both sides by air heated up by a gas burner so that solvents of high boiling point are discharged into the drier atmosphere and fed for thermal after-combustion. The heat energy produced in that case is used for heating of the drier atmosphere.

All these methods proceed from the principle of uniform action by drying energy according to the area component most difficult to dry and independently of the respective areal coverage, i.e. independently of the percentage of the paper surface printed on by ink for first form and perfecting form printing. This leads to consumption of more drying energy in the case of different areal coverage between first form and perfecting form printing than would be necessary, whereby a high proportion of the expended energy is effectively wasted. Moreover, in the case of substantial differences in the areal coverage between first form and perfecting form printing, there can be the consequence of a reduction of the printing image quality through overstressing of the web side bearing relatively little ink.

There is therefore a need to improve the drying of webs so that the efficiency of the drier is increased, whereby energy can be saved without the printing image quality being impaired through smearing in consequence of too low a drying performance. For preference, the drying process should be optimised in such a manner that loading of the web with hot air takes place in dependence on its degree of areal print coverage.

According to the present invention there is provided a drier for a printed web, comprising functionally separate upper drying means and lower drying means arranged for mutually independent and differentiated action on such web in dependence on print area proportions thereof and each comprising at least one respective burner chamber, a respective burner associated with the or each chamber, nozzle means for directing hot air produced by the burner or burners against the web, blower means for movement of such air, and duct means for conducting the air.

Preferably, the drier comprises an upper drier chamber and a lower drier chamber, which are functionally separate and each equipped with at least one respective burner chamber as well as with the same number of gas burners for mutually independent and differentiated action on the paper web by hot air in dependence on the printed area proportions of first and perfecting form printing by way of one or more fans, a nozzle group and an interior channel.Preferably, baffle plates are arranged between the nozzle group and the outer wall of the drier, and the upper drying chamber and the lower drying chamber are separated thereby as well as by the freely floating paper web, so that the temperature gradient achieved by the differentiated loading by hot air is maintained, in particular escape of hot air out from the drier and intermixing of upper and lower air within the drier are avoided as far as possible.

It is also advantageous to construct the drier so that the two drier chambers are each equipped with a respective regulating equipment which controls the air volume in dependence on the exhaust air composition, wherein the exhaust air is conducted towards or into the atmosphere open by way of an external duct and corresponding conveying means of after-combustion equipment.

Particular advantages of the drier are that if it is possible to charge the web with hot air which is settable in dependence on the area proportions provided with printing ink in first form and perfecting form printing, and independently of each other, by way of the two drying means functionally separated by the paper web and the baffle plates. Thus, the quality of the web and the printing ink is not negatively influenced by overstressing with heat, and a consistently high quality of the printing image as well as savings of energy and increase in operating reliability of the drier are achieved.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, which is a schematic illustration of a drier embodying the invention.

Referring now to the drawing, there is shown a drier 1 which comprises an upper drier unit 2 and a lower drier unit 3, which are each equipped with a burner chamber 4 with a respective gas burner 5.

Hot air produced in each burner chamber 4 is conducted by the fan 6 and thus drawn to a nozzle group 7 of the respective unit. The air is deflected off a freely floating, printed paper web 8 passing through the drier, and is conducted by the fan 6 through an interior channel 9 back to the burner chamber 4. The freely floating paper web 8, in conjunction with metal baffle plates 11 mounted in the drier 1 between the nozzle groups 7 and an outer wall 10-of the drier housing, prevents intermixing of the drying air of the lower unit 2 and the upper unit 3 so that a produced temperature gradient is maintained and a differentiated loading of the web 8 with hot air is achieved.

The exhaust air of the drier 1 is regulated in dependence on its composition by way of equipment which is arranged in each drier chamber and includes regulating devices (not illustrated in the drawing). In that case, the exhaust air of both units is conducted by the fan 6 through the interior channel 9, an external duct 13 and conveying equipment (not shown) either to an after-combustion device or into the atmosphere, wherein a feed of fresh air is provided in correspondence with this air volume.

The gas supply required for production of hot air by the burners is adjusted externally of the drier in dependence on the printed area proportions of first form and perfecting form printing on the web, adjusting equipment being provided for that purpose.

Claims

1. A drier for a printed web, comprising functionally separate upper drying means and lower drying means arranged for mutually independent and differentiated action on such web in dependence on print area proportions thereof and each comprising at least one respective burner chamber, a respective burner associated with the or each chamber, nozzle means for directing hot air produced by the burner or burners against the web, blower means for movement of such air, and duct means for conducting the air.

2. A drier as claimed in claim 1, wherein the burners are gas burners.

3. A drier as claimed in either claim 1 or claim 2, wherein the upper and lower drying means are separated from each other by baffle plates and, in use, by the web.

4. A drier as claimed in claim 3, wherein the plates are arranged between edges of the nozzle means and outer walls of the drier.

5. A drier as claimed in any one of the preceding claims, wherein each of the upper and lower drying means further comprises equipment for regulation of the composition of gas exhausted therefrom.

6. A drier substantially as hereinbefore described with reference to the accompanying drawing.

7. A rotary printing machine comprising a drier as claimed in any one of the preceding claims.