EP1066160B1 - Offset printing method and an offset printing machine - Google Patents

Description

The invention relates to an offset printing method and a Offset printing machine according to the preamble of the claims 1 and 9.

Find in offset printing and especially in sheetfed offset printing Usually use inks, their binders based on water-repellent linseed oil, mineral oil or Resin varnishes are built up and their drying in Difference to drying of many other printing inks does not appear evaporation of a solvent, but on the one hand on a physical drying process by knocking it away, i.e. penetration of binder components in the Substrate, as well as on a chemical drying process by oxidation, i.e. a network of Binder components through absorption of atmospheric oxygen.

To prevent the ink from smearing on the substrate prevent and the fastest possible further processing of the To enable printed substrate, it is in offset printing The drying processes mentioned have long been known through additional measures, in particular through UV drying, IR drying and hot air or gas flame drying too accelerate.

For UV drying, mainly in sheetfed offset printing is used, the printing ink with UV lamps irradiated with ultraviolet light, the Photo initiators contained in the ink break down into radicals. These very reactive molecules accelerate the polymerization of the binder so that the printing ink increases in a very short time hardens a nail-hard scratch-resistant color film. adversely UV drying, however, includes the high cost of required special UV inks, the relatively high Energy consumption, the limited operating time of the UV lamps and the need for special, in part harmful detergents.

For IR drying, which is also predominantly in the Sheetfed offset printing is used, the substrate is after printing with IR emitters in the short-wave and irradiated medium wave range, causing the temperature of the Substrate and the printing ink increased and therefore without that Requires special inks to both knock off and chemical drying also accelerates. Disadvantages of IR drying are the strong heat generation that the UV drying even higher energy consumption and proportionate high investment costs. It can also be caused by heating of the substrate to dimensional changes and possible Registration differences come.

The hot air and / or gas flame drying is particularly in web offset printing in connection with so-called heat set printing inks used, the drying by evaporation of the Solvent takes place. The substrate is replaced by a Led in the dryer, in which he heated air with high pressure and is fed at high speed from nozzles so that Evaporation of solvents and other volatile components to accelerate and the polymerization of the ink promote. In addition to a very high energy consumption this drying especially the undesirable drying out of the Printing material disadvantageous, leading to dimensional changes through shrinkage. This is used in sheetfed offset printing Type of drying rarely used because it becomes one leads to excessive increase in the length of the sheet displays and air blown into the inside of the sheet delivery Swirling of powder caused with that in the sheet delivery the pressurized sheets are dusted in order to Sheet stack stack to prevent the sheet from being deposited.

A printing press is already known from WO 97/04962 known type, in which the arcuate Printing material is dried with the help of infrared radiators, between the printing units of the printing press and behind the last printing unit or in the sheet delivery, with additional coolness near each infrared heater dry air is supplied to the drying of the ink to accelerate and also the operating temperature reduce neighboring facilities. Behind the last one Printing unit are the infrared emitters together with gas lines and blow nozzles to supply air either in the immediate vicinity Arranged near the last impression cylinder, or if there there is no space within the sheet delivery between the dreams of the sheet conveyor. In the first mentioned The air will fall into one between the printing press and the Blown delivery area blown in for Changes in flow conditions is sensitive to that et al can lead to a disruption of sheet travel. In the last mentioned case the air on the from the funding strand of the Blown delivery blown sheet, creating a Drying without IR radiation is insufficient to get a the sheets are placed on a stack without sticking sure.

EP 0 723 128 A1 describes a method for hardening of paint or aqueous or solvent-based paints Objects and especially for drying Printing inks on substrates already known per se, air to blow onto the surface of the object that was previously through run a dryer and remove moisture has been dried so that it is low absolute Moisture values and therefore a quick even Drying process allows. The dried air is there however, via a system of blown air rods with holes blown onto the surface of the substrate and by means of Extracted suction devices.

In Swiss Patent No. 113365 is also already disclosed a printing machine for sheet printing, in the printed sheets in a sheet delivery through openings a bridge roller with air on its unprinted underside be acted upon to increase their drying effect previously over calcium chloride or other moisture absorbent substance has been conducted. By feeding the pre-dried air to the unprinted side of the substrate instead of a quick drying of the ink rather an undesirable drying of the substrate reached.

It is also known from German patent specification 436 933 Air-dried print products that are first used to dry Reducing their absolute humidity chilled and then again is warmed up because then the printed matter quickly dries as it removes the moisture contained in them eager to take up.

Proceeding from this, the invention is based on the object in a method and a device of the beginning mentioned type the drying of the sheets without the use of To improve infrared radiators so that a trouble-free Transport and a sticky deposit of the sheets on the Sheet stack is possible without being in the delicate Area between the last printing unit of the printing press and the sheet delivery requires internals or the Air flow conditions are changed.

This object is achieved by the in the Claims 1 and 9 for the offset printing process and for resolved the features specified offset.

In investigations by the applicant on sheetfed offset presses has surprisingly found that by Loading the freshly printed tops of the sheets in one immediately behind the last cylinder of the Press area with air that previously passed through Dehumidification had been dried, both one significant improvement in the abrasion resistance of the Substrate as well as a significant reduction in up waiting time required for further processing has been reached because even difficult substrates like matt coated papers, dry tack-free within a short time were.

One of the main reasons for this is seen by the applicant that superficially by the supply of dried air unprinted areas of the substrate and on the printing ink adhesive, from the dampening units of the offset printing press moisture is removed even before it enters the Knock away printing material or be absorbed by powder particles can be applied to the substrate to a discard, i.e. a sticking together of several layers of the Prevent substrate.

The air previously dried with the removal of moisture has a very low absolute moisture content of less than 5 g / m ³ , so that when it comes into contact with the surface-adhering water it causes an abrupt evaporation without the moisture content inside the printing material being changed significantly , In this way, changes in dimension and / or blistering in the case of heavily coated papers can be reliably avoided.

The measures according to the invention make it possible for a Application in a delivery of a sheetfed offset press, the Ink in the relatively short period between the exit of the sheets from the last printing unit and their Place it on the stack of sheets to dry so far that a immediate handling is possible and a significantly shortened Waiting time until further processing can be achieved.

A preferred embodiment of the invention provides that the air for drying is passed through a refrigeration dryer to bring its absolute moisture to a value of less than 5 g / m ³ , corresponding to a dew point of approximately 0 ° C. and preferably less than 1 g / m ³ , corresponding to a dew point of approximately -19 ° C. Alternatively or additionally, a sorption dryer can also be used for drying, in which the air flows through a drying agent such as CaCl ₂ , BaO, Mg (ClO ₄ ) ₂ or the like. In such a dryer, the residual water content of the air can be reduced to values below 0.01 g / m ³ or even to values below 0.001 g / m ³ .

The air is released before it is brought near the substrate expediently warmed up a little, especially following one Cold drying, its temperature when in contact with the Printing material is preferably between 30 and 40 degrees, so that no thermal insulation of the sheet delivery against the Environment is required.

A further advantageous embodiment of the invention provides before that the supplied dry air after contact with the substrate and thus after absorbing moisture suctioned off at least partially by means of a suction device , which is preferably horizontal in sheetfed offset printing Section of the sheet delivery above the conveyor run of the Chain boom is arranged.

The dried air is preferably fed into the Proximity of the substrate immediately after the exit the substrate from the last printing unit of the printing press, the dried air after both for intermediate drying one-sided printing as well as for final drying of the printing material printed on both sides can serve. Further can already be between two printing units of the printing press dried air is directed near the substrate to create a. after each ink and dampening solution application superficial drying of the applied ink and the To achieve substrate.

In sheetfed offset printing looks a particularly preferred one Embodiment of the invention, at least part of the in the sheet delivery of the sheetfed offset printing machine Compressed air sheet guiding devices with previously dried To apply air. Such sheet guiding devices include, for example, pressurized air Sheet baffles that make up the air from below against the sheet flows, guide bar blowers, blowing air nozzles in front of the bow brakes or blown air rake above the sheet exit opening.

Alternatively or additionally, the dried air or a Part of the same through additionally provided nozzles Housing of the sheet delivery are blown, preferably at least partially in the space between an upper one Empty strand and a lower conveyor strand within the Housing arranged conveyor, which the printed Sheets are transported to a stack of sheets.

According to a particularly preferred embodiment of the invention the dried and preferably also filtered and with it from moisture as well as from powder or others Dust-like pollutants release air from outside in a targeted manner fed the case to the sheet delivery and into the area transported just behind the press, while at the same time an inflow of ambient air and / or with Moisture and powder contaminated air from inside the Display in this area is prevented. The air will preferably at a distance from the printing press into the housing guided and pulled by an empty dream of the Sheet conveyor transported to the printing press, causing a change in flow conditions immediately can be avoided behind the press. During the Inflow of ambient air through a closed housing wall can be prevented behind the press, the Influx of polluted air from inside the Sheet delivery can be prevented if a along the Empty run of the conveyor towards the printing press Air flow in the direction of movement of the empty run before the point where the dried air is interrupted is fed into the housing.

By charging one immediately behind the Display drum lying area with dried air achieved that on the substrate and the printing ink existing surface water and more volatile Components of the ink have evaporated before entering the area of the powder apparatus substantial amounts of powder on the substrate can reach and absorb this liquid. This will prevents liquid absorbed by the powder Decrease in the rub resistance of the ink causes because powder particles deposited on the damp printing ink when scrubbing while exposing those below incompletely dried surface areas from the Peel off the ink.

In addition, the pre-dried air supplied can do more Absorb moisture than from the area around the sheet delivery or printing machine sucked in undried air, whereby without additional measures of moisture content in the stack before and kept essentially unchanged after printing can be.

Another preferred embodiment of the invention provides that the pre-dried air at one or more between the point of interruption or the powder apparatus and the Display drum lying in the housing of the Sheet delivery and conveniently close to the path of movement an empty strand of the chain conveyor and fed by it Suction is transported towards the printing press. The along the empty run of the chain conveyor to the delivery drum flowing air is there together with the chain conveyor redirected towards the free end of the display, see above that are above and below that of the bow grabbers seized bow form air cushions that next to a Calming of the sheet run also for further drying of the Worry.

Because the supplied air has a very low absolute humidity possesses when on the delivery drum on the surfaces the freshly printed sheet hits, there is one sudden evaporation of the surface water and quickly Formation of a thin dried film on the surface the printing ink, which the one the further transport of the sheets Smudge the paint and stick to the powder Counteracts surface. On the unprinted areas of the Due to the immediate evaporation, Bogens beats few Moisture in the bow away, so that its moisture content hardly increases.

Especially for long ones, possibly with IR dryers or others additional drying facilities equipped sheet deliveries it may be preferable to interrupt the process Air flow and the subsequent supply of dried Air in one or more places along the empty span of the Repeat sheet feeder to ensure that the spread of pollutants towards the press is prevented and the supplied dried air up to Printing machine arrives. To do this, it can be useful the same facilities as in the upper horizontal section the sheet delivery, i.e. one with brushes if necessary equipped nozzle box arranged above the empty run, from the clean dried air down towards the Empty strand is blown, one below the nozzle box in the Space between the empty run and the funding run arranged, possibly equipped with brushes air suction and Deflection tank, which sucks some of the air in or Redirects the direction of the printing press, as well as one in Direction of the empty run behind the nozzle box and the Tub arranged air storage, from which generated by the Vacuum dried, powder-free air into the Housing of the sheet delivery is sucked. The air storage and the nozzle boxes are preferably with a cold and / or Sorption dryer connected by a compressor air compressed by the printing press with the withdrawal of Moisture is dried.

Depending on the length and construction of the sheet delivery, it may be sufficient instead of one of the above Facilities, i.e. Nozzle box, tub and air storage, only one air reservoir at a time on the top of the housing to be provided so that if necessary by the suction of the empty strand more dried air from the outside into the housing of the Sheet delivery can be sucked. The spread of Pollutants along the empty strand towards the Printing press can also pass through the break point one arranged between the empty strand and the conveyor strand, preferably from the point of interruption to Printing machine running partition can be prevented.

The air storage can be under a slight overpressure are kept so that the air is always inside the housing the sheet delivery is fed. The air is preferably in the Inside the air storage, however, under atmospheric pressure. This enables according to a further preferred embodiment or Alternative to the invention a simple control of the Air supply depending on the printing speed because higher printing speeds higher running speeds the Require sheet conveyor, which in turn a stronger suction is caused by the more air coming out the air reservoir is sucked in.

Depending on the moisture content of the ambient air it may be sufficient if only part of the air supplied is previously dried, while another part directly from the Environment is fed into the interior of the sheet delivery.

In order not to hinder access to the printing press and the Printing machine including sheet delivery as compact as possible design, sees a further preferred embodiment of the Invention before, the air drying device under the Arrange sheet delivery near the compressor, which the line length of the required air lines is also strong can be reduced.

Fig. 1: eine schematische teilweise geschnittene Seitenansicht einer erfindungsgemäßen Bogenoffsetdruckmaschine;

Fig. 2: eine vergrößerte teilweise geschnittene Seitenansicht der Bogenauslage der Druckmaschine aus Fig. 1;

Fig. 3: eine vergrößerte teilweise geschnittene Seitenansicht einer etwas abgewandelten Bogenauslage;

Fig. 4: eine vergrößerte teilweise geschnittene Seitenansicht einer verlängerten Bogenauslage;

Fig. 5: eine vergrößerte teilweise geschnittene Seitenansicht einer anderen verlängerten Bogenauslage;

Fig. 6: eine vergrößerte teilweise geschnittene Seitenansicht einer weiteren kurzen Bogenauslage;

Fig. 7: eine schematische teilweise geschnittene Seitenansicht einer zwischen einer Rollenoffsetdruckmaschine und einem nachgeschalteten Heißluft- oder Gasflammentrockner angeordneten Trocknungseinrichtung.

The invention is explained in more detail below with reference to some exemplary embodiments shown in the drawing.
Show it:

1: a schematic, partially sectioned side view of a sheet-fed offset printing machine according to the invention;

FIG. 2 shows an enlarged, partially sectioned side view of the sheet delivery of the printing press from FIG. 1;

3: an enlarged, partially sectioned side view of a somewhat modified sheet delivery;

4: an enlarged, partially sectioned side view of an extended sheet delivery;

5 is an enlarged, partially sectioned side view of another extended sheet delivery;

6: an enlarged, partially sectioned side view of a further short sheet delivery;

7: a schematic, partially sectioned side view of a drying device arranged between a web offset printing press and a downstream hot air or gas flame dryer.

In the drawing in Fig. 1 only partially and schematically illustrated eight-color sheetfed offset printing machine 2 Sheet of paper 1 in succession by means of an automated Sheet feed 4 from one in a sheet feeder 6 Printing machine 2 arranged paper stack 8 to a Transfer drum 10 of a first printing unit 12 and then through the first printing unit 12 and possibly further of the total eight printing units (only two shown) transported to them to print on one or both sides in one or more colors.

From an impression cylinder 16 of the last printing unit 14 take over delivery gripper systems 18 of a chain conveyor 20 a sheet delivery of the printing machine 2, the printed sheets 1 and transport them through a housing 24 of their Sheet delivery 22 to a sheet stack 26 on which the sheets 1 are placed one above the other. The chain conveyor 20 consists essentially of two in opposite lateral guide rails guided parallel chains (not shown), which at regular intervals by the also referred to as a gripper gripper systems 18 are. The chain conveyor 20 has a lower one, the bow transporting conveyor strand (leading system) 30 on the out of two sprockets of a delivery drum 32 at an angle is moved up and then redirected to the horizontal, before there are two drive sprockets 34 at the free end of the Sheet delivery 22 reached. His upper empty strand (retreating System) 36 moves horizontally from the sprockets 34 towards the printing press 2 before it slants down is deflected and returned to the delivery drum 32.

After delivery to the sheet gripper 18, each sheet is 1 in Direction of movement of the conveyor run 30 through sheet baffles 38 non-contact on laterally adjustable guide arm blowers 40 over and via a sheet brake 42 arranged behind it guided and then reaches an arch exit opening 44 on the underside of the horizontal section of the housing 24 of the sheet delivery 22 to the sheet brake 42 transferred and braked sheet With the help of several arranged above the outlet opening 44 Delivery fan 46 down onto the sheet stack 26 blown. This rests on a lifting mechanism 48 that the Stack 26 in sync with the speed of the sheet feed lowers.

Near the top of the sloping section of the Chain conveyor 20 shortly before the deflection of the conveyor run 30 horizontally there is a powder apparatus 50 in the intermediate space 52 arranged between the conveyor strand 30 and the empty strand 36. The Powder apparatus 52 pollinates the tops of those of the Arch grippers 18 of the conveyor run 30 kept pressurized Bow with a fine powdered starch powder to make a Glue the sheets together when they are attached To prevent stacking.

To prevent powder, moisture and solvents laden air from the area above the sheet stack 26 carried away by the suction of the chain conveyor 20 and an air flow generated above and below its empty run 36 within the housing 24 in the direction of the printing press 2 is transported, this airflow is in the upper horizontal section of the sheet delivery 22 interrupted.

For this purpose, approximately above a drive shaft 60 Lifting mechanism 48, i.e. in the direction of movement of the conveyor run 30 behind the powder apparatus 50 over the empty run 36 Nozzle box 58 arranged on its underside with a Variety of air outlet nozzles is provided, through which of Air that was not contaminated with powder above and previously dried is blown into the housing 24. Below the nozzle box 58 is a combined air suction and deflection tray 56 in Gap 52 between the conveyor run 30 and the empty run 36 arranged, which serves a part of the blown air together with the powder cleaned from the empty strand 36 aspirate and the rest of the air towards the press redirect.

The air suction and deflection pan 56 consists essentially from a thin-walled flat housing that on its top and bottom Bottom with slit-shaped air intake openings is provided and below the lateral guides of the Empty run 36 over the entire clear width of the sheet delivery extends. The housing forms a continuous closed Partition between a flow path along the production run 30 and a flow path along the empty run 36. This Partition 56 prevents the over its entire extent Air passes from top to bottom and vice versa.

The inside of the housing is controlled by control valves the extracted air volume and the negative pressure applied connected to a suction fan, which a dust separator with a Centrifuge and a fine filter upstream (not ) Shown.

Between the bottom of the nozzle box 58 and the top the air suction and deflection tray 56 are two rows arranged by brushes 66, 68, which extend over the entire clear width of the sheet delivery from above or from below into the Extend the path of movement of the empty strand 36.

As best shown in FIG. 2, the nozzle box 58 is connected by an air line 100 via an interposed controllable throttle valve 102 to a refrigeration dryer 106 arranged under the inclined section of the sheet delivery 22. The cold dryer 106 is acted upon by a compressor 108 with atmospheric air, which is drawn in from the surroundings of the printing press 2 and compressed by the compressor 108 to a pressure between 1.5 and 3.5 bar. A particle filter 110 is interposed between the compressor 108 and the cold dryer 106 in order to make the air fed into the nozzle box 58 dust-free. The compressed air supplied is dried in the cold dryer 106, some of its moisture being removed from it and its dew point reduced to approximately -19 ° C. This means that the air emerging from the refrigeration dryer 106 has a residual water content (absolute humidity) of approximately 1 g / m ³ .

The cold dryer 106 is controllable via another Throttle valve 116 connected to the sheet guide plates 38, wherein the line is not shown. That is, the Sheet air baffles 38 are exposed to dried air, which consists of a variety of air outlet nozzles on the Leaves the top of the sheets 38. The guide bar blowers 40 can with a controllable throttle valve 118 Cold dryer 106 may be connected, so that also for alignment the sheet uses dried air and thus the Moisture content of the air within the housing 24 is kept as low as possible.

The amount of air supplied in the nozzle box 58 is between 30 and 50 m ³ / h and is dimensioned such that only a part is sucked in through the upper air intake openings of the air suction and deflection pan 56, while the rest of the dried air is at the top of the air -Absaug- and deflection tray 56 is deflected in the direction of the printing press 2.

During the operation of the printing press 2 and the sheet delivery 22 the air is at a relatively low pressure of 1.5 to 2 bar supplied, while the air pressure at a downstream cleaning of the sheet delivery 22 to 3 to 3.5 bar is increased. The controllable throttle valve 102 in the Air line allows a clocked air supply in the Nozzle box 58.

The air blown down from the nozzle box 58 flows in the sheet grippers 18 and on the chains of the chain conveyor 20 passing, this being showered through the air and adhering Powder particles are carried down so that they from Empty strand 36 no further in the direction of the printing press 2 can be transported. By showering with air the chains and guide rails of the Chain conveyor 20 clean and saturated with fat so that a powder-related wear can be prevented. simultaneously the downward flow of air forms with the two brushes 66, 68 in this area of the sheet delivery 22 between a closed housing cover on the top and the tub 56 on the bottom a lock that prevents air laden with powder and moisture along the empty run 36 in the direction of the printing press 2 flows.

From the top of the tub 56 in the direction of movement Empty run 36 of deflected air is sucked in by Air at the rear edge and on the underside of the tub 56 Part deflected downwards, this air partly through air intake openings attached there is suctioned off and partly on the side facing away from the printing press 2 Front of the powder apparatus 50 flows down. On other part of the redirected air is caused by the suction of the empty strand 36 above the powder apparatus 50 past in the direction of Printing machine 2 out.

By interrupting the along the empty run 36 running air flow between the nozzle box 58 and the Trough 56 a negative pressure is generated there, the strength of the amount of air supplied through the nozzle box 58 depends. If relatively little through the nozzle box 58 Air is supplied, and the negative pressure is consequently greater, this vacuum can be used to dry more To suck air into the housing 24.

As shown in Fig. 3, this is at the top of the sloping section of the housing 24 above the empty strand 36 a ventilation grille 95 is arranged through which air from outside into the Interior of the housing 24 can enter. Most of this Air is drawn along by the suction of the empty run 36 the same carried in the direction of the printing press 2, while a smaller part behind one that acts as an air switch Air suction pipe 75 of the tub 56 flows down and along the back of the in the direction of the printing press 2 Powder apparatus 50 to the top of the sheets transported past to be led. These above and on both sides of the Powder Apparatus 50 Air Flows Help to convey the powder down to the bow and one Whirling up and spreading of whirled up powder prevent.

An air reservoir 97 is arranged above the ventilation grille 95, that from the cold dryer 106 via a pressure control valve 109 pre-dried air is supplied, which then in place of Ambient air is sucked through the ventilation grille 95. The Air in the air reservoir 97 is kept under atmospheric pressure, so that depending on the amount of 36 of the empty strand Chain conveyor 20 generated negative pressure more or less dried air is supplied to the interior of the housing 24. There the amount of negative pressure with the running speed of the Chain conveyor 20 increases, can be simple in this way Control of the air supply depending on the printing speed can be achieved.

In the extended sheet delivery 22 shown in FIG. 4 are in their lower horizontal section in two places one each with air lines (not shown) with the air dryer 97 connected to the cold dryer 106 via a mounted in the ventilation grille provided on the top of the housing, to ensure that the dried air despite the longer delivery 22 transported to the delivery drum 32 becomes. Alternatively or additionally, between the empty strand 36 and the conveyor strand 30 of the chain conveyor 20 one for Chain conveyor 20 parallel partition 99 may be arranged a reversal of the air flow before reaching the delivery drum 32 prevented. The partition 99 can extend to the rear Extend the outside edge of the tub 56 to above in this way of the powder apparatus 50 an entry of powder in the to prevent blown or sucked powder-free air.

Next to one in its lower horizontal section arranged and through air openings with the inside of the Air reservoir 97 connected to the housing has that in FIG. 5 shown extended sheet delivery 22 additionally in the direction of movement of the empty run 36 in front of the air reservoir 97 another nozzle box 59 and one below the Nozzle box 58 between the empty strand 36 and the conveyor strand 30 arranged air suction and deflection pan 57, their structure and function substantially that of the nozzle box 58 and corresponds to the air suction and deflection tray 56. The tub 57 is somewhat flatter than the tub 58 and is used by the Side walls of the housing 24 of the sheet delivery 22 worn. at even longer sheet displays 22 can also be two such Combinations of tub 57, nozzle box 59 and air storage 97 be provided.

At any point where such a combination of tub 57, Nozzle box 59 and air reservoir 97 is arranged, the Air flow along the empty strand 36 interrupted or after deflected below towards the conveyor run 30, as in FIG. 5 shown. Instead of the interrupted air flow enters part of the air blown through the nozzle box 59 as well as the air sucked in from the air reservoir 97, which from the Empty strand 36 are conveyed in the direction of the printing press.

The or blown in by means of the or the nozzle boxes 58, 59 or sucked in from the air reservoir (s) 97 and through the Suction effect of the empty run 36 of the chain conveyor 20 along the same to the end of the delivery 22 on the printing press side transported pre-dried air meets between the Sprockets of the delivery drum 32 on the freshly printed Surface of the bow by the bow grippers 18 of the Chain conveyor 20 from the impression cylinder 16 of the last Printing unit 14 are deducted so that the sheet immediately after leaving the last printing cylinder 16 with the dried air. Where the Delivery drum 32 not from two sprockets but from a continuous drum is formed, this is appropriately designed as an air cushion drum and from the inside with pre-dried air applied to the Pressure-damp surface of the sheet facing the drum circumference meets.

In view of their low absolute humidity, this causes dried air there a sudden evaporation of superficially on the printing ink and the substrate sticking water. This surface water is found all on the unprinted surfaces of the substrate as well as on those areas of the printing ink that already existed before Pass through the last printing unit were applied because these areas in the last printing unit with water Fountain dampened areas of the printing cylinder opposite, of which when peeling off the substrate Water is carried away. However, also stick to the last one Printing unit applied printing ink smaller quantities Surface water that previously emulsifies in the printing ink and migrated to the color surface when printing.

The water adhering to the printing ink and the substrate is caused by the exposure to the dried air evaporates before it is on the unprinted areas in the Knock away the printing material or on the printing ink applied powder can come into contact. Thus through the rapid evaporation of the surface water on the one hand the Water absorption in the substrate is reduced and secondly prevents water on the ink from powder particles is recorded.

The latter effect is particularly pronounced when by interrupting the air flow along the empty run 36 of the chain conveyor 20 and / or the partition 99 of the Inflow of carried powder in the area between the Delivery drum 32 and the powder apparatus 50 is prevented, so that only 50 powders on the below the powder apparatus Surface of the substrate and the printing ink can reach if this is already due to the supply of dried air is superficially dried. The same naturally applies to the case where the sheet is not inside the delivery at all is dusted with powder.

In the area of the delivery drum 32, the dry air deflected together with the chain conveyor 20, so that they after feeding them onto the freshly printed top of the sheets in the Direct current with these in the direction of movement of the conveyor run 30 is transported away, whereby their absolute moisture results evaporation of surface water increases. In which Embodiment in Fig. 5 causes the deflection of dry air in front of the tub 57 down that part of the pouring over the arch to the display and already with Moisture-laden air is replaced by dry air again becomes.

In the direction of movement, the sheet is behind the powder apparatus 50 part of the air laden with moisture and powder on the Aspirated bottom of the tub 56.

The measures described can cause moisture to build up the printing ink and the substrate without additional Drying facilities within a very short time, i.e. evaporated within 0.1 to 0.2 sec so that the Surface of the printing ink and substrate at The arc already passes under the powder apparatus 50 in this way are far dried that it is not or only in very little Extent to which powder adheres. This gives you a high gloss even with matt coated substrates Print product with very good image quality.

Furthermore, the measures described essentially only the superficial moisture supplied during printing eliminated without the moisture content inside of the substrate changed significantly. By the opposite the moisture content in the paper stack 8 essentially unchanged moisture content in the sheet deposit stack 26 can the time until further processing can be reduced.

At the same time, it forms in cocurrent with the conveyor run 30 of the chain conveyor 20 in the direction of the sheet stack 26 transported dried air after it was brought up to the Arch above and below an air cushion or Air cushions that help soothe the arc. On The underside of the arch can be filled with air by feeding of dried air from the sheet guide plates 38 and be reinforced, this air supply in particular sheets printed on both sides also on their printed sheets Underside still provides a certain drying effect.

Fig. 6 shows an embodiment without the features of the characterizing part of independent claims 1 and 9, with other configurations. In contrast to the previously described exemplary embodiments, the refrigeration dryer 106 is followed by a sorption dryer 120, in which further moisture is removed from the air pre-dried in the refrigeration dryer 106, so that its residual water content is less than 0.1 g / m ³ . The sorption dryer 120 contains a strongly hygroscopic medium, such as CaSO ₄ , BaO, KOH or another drying agent that is usually used for drying compressed air. The sorption dryer 120 has two chambers filled with the drying agent, one of which is flowed through by the compressed air, while the drying agent is regenerated in the other. If the air supplied to the compressor 108 is sucked in in the vicinity of the printing press 2 or the sheet delivery 22 and contains solvents, an adsorption filter (not shown) filled with activated carbon can be provided in addition to the sorption dryer 120 in order to also accelerate the solvent content of the air To reduce drying.

On the other hand, in this embodiment, not only the sheet guide plates 38 and the guide bracket blower 40 with dried air, but also additionally the delivery drum 32 designed as an air cushion drum the air brakes 42 and an arranged on the sheet brakes 42 Place the delivery fan 46 over the sheet exit opening 44 arranged air rake 124 with downward pointing Air outlet nozzles, from which blow air is controlled in cycles is blown on top of the respective spreading sheet in order to to calm them down and speed up the laying process. Next are in place of the nozzle box 58 in the rising part the sheet delivery 22 between the conveyor run 30 and the Empty strand 36 of the chain conveyor 20 three additional, in Distance from each other across the space 52 and blow air pipes 126, 128 provided with air outlet nozzles, 130 provided, through which the area above that on the Fördertrum 30 carried sheets with dried air is applied. To make the bow flutter on the To prevent delivery strand 30, the blow air nozzles 126, 128, 130 arranged above a close-meshed grid 132, the serves to smooth and calm the air flow.

The delivery drum 32, the blowing air nozzles 122, 126, 128, 130 and the blower air rake 124 are just like the sheet guide plates 38 and the guide bracket blowers 40 each with air lines connected to the sorption dryer 120, wherein in the Air lines arranged throttle valves 140 a clockwise and quantity or pressure controlled supply of the dried air allow.

Between the cold dryer 106 and the sorption dryer 120 a heat exchanger 134 is arranged, in which the Refrigeration dryer 106 cooled compressed air back to a Temperature between 30 and 40 ° C is heated to her Increase moisture absorption without losing the environment the sheet delivery 22 to heat up excessively. The heat exchanger 134 is fed with a warm heat transfer medium, the through the waste heat from drive motors of the printing press 2 can be heated or heated in other heat sources.

The blowing air nozzles 122, 126, 128, 130 are expediently a long standstill of the printing press 2 before Commissioning of the sheet delivery 22 with dried air acts to flush the housing 24 so that from the Ambient air with a higher moisture content can be removed from it.

By the measures described in connection with FIG. 6 are the sheets between their exit from the press 2 and their arrival on the sheet filing stack 26 so far dried that even without dusting with a powder no The arch is deposited. The one shown in Fig. 6 Sheet delivery therefore has no powder apparatus 50, whereby not just a powder load inside and around the sheet delivery 22 avoided, but also the time to Further processing can be shortened further because of the No evaporation from the printing ink or the substrate is hindered by powder applied.

In practice it was possible to use the in 3 described in connection with the invention Devices for accelerating drying and for Keep free the immediately behind the printing press 2 lying area of powder the waiting time before turning from about 3 hours to about 1 hour and the waiting time until Further processing reduced from about 10 hours to about 4 hours become. Neither the reprint nor the Further processing Print image violations are observed while in an otherwise the same, but not with the Devices provided devices according to the invention despite the longer waiting times for the reprint Damage to printed images and scratches during further processing on pages 3, 4, 8 and 9 and carbonation observed has been.

Claims (18)

1. Offset printing method, in which a printing material in the form of individual sheets is printed in a sheet-fed offset printing machine (2) with one or more printing inks, whose drying is carried out by absorption and crosslinking as a result of oxidation, in which the sheets are then conveyed by a sheet conveying device (20) through a housing (24) of a sheet delivery (22) over a sheet deposit stack (26), and in which air previously dried by removal of water is fed into the housing (24) of the sheet delivery (22) in such a way that the immediately previously printed broadside areas of the sheets are acted on by the dry air fed in, characterized in that the dried air is fed into the housing (24) close to the movement path of a empty run (36) of the sheet conveying device (20), so that it is transported by the suction action of the empty run (36) into a region of the sheet delivery (22) which is located immediately downstream of a last cylinder (16) of the offset printing machine (2), and there strikes the immediately previously printed broadside areas of the sheets.
2. Printing method according to Claim 1, characterized in that the dried air is fed into the housing (24) of the sheet delivery (22) at a distance from the printing machine (2) and is transported in the direction of the printing machine (2) by the suction action of the empty run (36).
3. Printing method according to Claim 1 or 2, characterized in that the dried air is fed into the movement path of the empty run (36) of the sheet conveying device (20).
4. Printing method according to one of Claims 1 to 3, characterized in that, depending on the printing speed, more or less dried air is fed into the housing (24).
5. Printing method according to one of Claims 1 to 4, characterized in that at least some of the dried air, after being led up to the immediately previously printed broadside areas of the sheets, is deflected and transported away in cocurrent with the sheets.
6. Printing method according to one of Claims 1 to 5, characterized in that, during their transport to the sheet deposit stack, the immediately previously printed broadside areas of the sheets are subjected to the influence of the dried air for at least 0.2 s before they are dusted with a powder.
7. Printing method according to one of Claims 1 to 6, characterized in that, in a horizontal portion of the sheet delivery (22), air is extracted over the upper side of the sheets.
8. Printing method according to one of Claims 1 to 7, characterized in that an inward flow of air laden with moisture and/or with powder from the environment and/or from the interior of the sheet delivery into the region located immediately downstream of the last cylinder (16) of the printing machine (2) is blocked.
9. Offset printing machine for printing a printing material in the form of individual sheets with one or more printing inks, whose drying is carried out by absorption and crosslinking as a result of oxidation, comprising a sheet delivery (22) with a housing (24) and a sheet conveying device (20) that conveys the sheets over a sheet deposit stack (26), devices (108, 106, 58, 59, 95, 97, 120, 122, 126, 128, 130) for feeding air previously dried by removing water in a drier (106, 120) into the housing (24) of the sheet delivery, and devices (36, 58, 95, 97) to act on the immediately previously printed broadside areas of the sheets with the dried air, characterized in that the air feed devices (108, 106, 58, 59, 95, 97, 120, 122, 126, 128, 130) comprise at least one air inlet opening (58, 95), which opens into the housing (24) close to the movement path of an empty run (36) of the sheet conveying device (20), so that the dry air flowing in is transported by the suction action of the empty run (36) into a region of the sheet delivery (22) which is located immediately downstream of a last cylinder (16) of the offset printing machine (2), and there strikes the immediately previously printed broadside areas of the sheets.
10. Printing machine according to Claim 9, characterized in that the air inlet opening (58, 95) opens into the housing at a distance from the printing machine.
11. Printing machine according to Claim 9 or 10, characterized in that the air inlet opening (58, 95) opens into the housing (24) above the empty run (36).
12. Printing machine according to one of Claims 9 to 11, characterized in that the air feed devices (108, 106, 58, 59, 95, 97, 122, 126, 128, 130) comprise at least one air reservoir (97), which contains dried air at atmospheric pressure and communicates with one of the air inlet openings (95).
13. Printing machine according to one of Claims 9 to 12, characterized in that the air feed devices (108, 106, 58, 59, 95, 97, 122, 126, 128, 130, 134) comprise a refrigerating drier (106) and/or a sorption drier (120) for drying the air fed in.
14. Printing machine according to one of Claims 9 to 13, characterized in that the air feed devices (108, 106, 58, 59, 95, 97, 122, 126, 128, 130, 134) comprise a heating device (134) for heating the dried air.
15. Printing machine according to one of Claims 9 to 14, characterized in that sheet-guiding and sheet transfer devices (32, 38, 40, 124) belonging to the sheet delivery (22) can be acted on with the dried air.
16. Printing machine according to one of Claims 9 to 15, characterized by devices (58, 56, 59, 57, 66, 68) for blocking an inward flow of air laden with moisture and/or powder from the environment and/or from the interior of the sheet delivery (22) into the region located immediately downstream of the last cylinder (16) of the printing machine (2).
17. Printing machine according to one of Claims 9 to 16, characterized in that the amount of air fed into the housing (24) depends on the movement speed of the sheet conveying device (20).
18. Printing machine according to one of Claims 9 to 17, characterized by an air extraction device (56) arranged in a horizontal portion of the sheet delivery (22), above the upper side of the sheets.

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