Dryer unit in a printing machine

A dryer unit which is integrated as a module into a printed material guide system of a printing machine in order to facilitate two-sided drying of printed material is provided. The printed material guide system includes a guide surface which has a plurality of openings and an air system which is selectively operable in positive or negative pressure modes to assist the guiding of the printed material. The dryer module is arranged in an opening in the guide surface such that it heats at least one side of the printed material. At least one outlet opening is associated with the dryer module. The outlet opening is open into the plane of the guide surface and is coupled to a cooling system which is operable to provide cooling air to the dryer module.

FIELD OF THE INVENTION 
This invention generally relates to printing machines and, more 
particularly, to a dryer unit for an offset printing machine. 
BACKGROUND OF THE INVENTION 
Drying units are used in offset printing machines to dry and/or cure the 
ink or varnish which is applied to the sheet or web material. One such 
dryer unit is disclosed in EP 0 035 741 Bl. Specifically, this reference 
discloses a sliding table having a cooling surface which is arranged 
opposite a dryer device. The sliding table acts as a printed material 
guide system and is arranged with its cooling surface facing the unprinted 
side of the printed material. In order to dry the printed material, which 
is described as a thermoplastic sheet material, the dryer device blows air 
in the direction of the cooling surface. The printed material guide system 
further includes coolant ducts which are connected to a cooling system 
comprising a heat exchanger and circulating pump. 
A deliverer in a sheet-fed printing machine which has dryer devices 
arranged in a modular construction within the chain conveyor system is 
disclosed in PCT/WO 95-01930. Air assisted printed material guide systems 
are arranged opposite the dryer devices and underneath the sheet conveying 
path. 
Another dryer unit is disclosed in DE 92 14 459 Ul. This particular dryer 
unit is constructed with a cooling system which includes a heat exchanger, 
a flow monitor, a compensation container and a circulation pump. The 
cooling system further includes a coolant line interconnecting the 
circulation pump and a sheet guide plate which provides coolant to the 
sheet guide plate. In addition, the coolant outlet of the sheet guide 
plate can be coupled by means of a connecting line to a dryer unit 
positioned opposite the sheet guide plate in order to also provide coolant 
to the dryer unit. The cooling of the dryer unit and the sheet guide plate 
prevents heat from building up within the printing machine. In order to 
accelerate the oxidative drying of the printing inks, the printed material 
itself is heated by means of infrared radiation. 
DE 43 08 276 Al also discloses a sheet guide device having a cooling device 
which cools the sheet guide surface when a dryer unit is operating. The 
sheet guide surface has a plurality of openings through which air is 
blown. One of the openings is formed by an end face integrated in the 
sheet guide surface as an impact face and includes a flow duct which opens 
at an angle into the sheet guide surface. The cooling device is configured 
as a cooling trough having a trough bottom and a lid wherein the lid of 
the trough constitutes the sheet guide plate. 
One of the significant problems with these designs is that the dryer units 
are always arranged opposite the printed material guide system. Thus, the 
printed material is dried only from one side (the front side). This leads 
to problems in the drying process including, for example, smearing 
(setting-off) of the ink and/or varnish which resulting from inadequately 
dried printed materials reaching the deliverer stack. 
A drying device for printed products which is arranged to dry both the 
front and rear side of the printed material is disclosed in DE 38 28 753 
C2. The drying device includes an energy transmission device comprising a 
fiber optic cable and a rectilinearly fanned-out beam splitter device. The 
drying device is arranged on both sides of printed material in the sheet 
deliverer, however, and is not integrated with a sheet guide system. 
OBJECTS AND SUMMARY OF INVENTION 
Accordingly, in view of the foregoing, it is a general object of the 
present invention to provide a dryer system for a printing machine which 
substantially reduces the smearing of ink and varnish in the deliverer 
stack on printed material processed on either one or both sides. 
A further object of the present invention is to provide a dryer system for 
a printing machine which can be integrated into the printed material guide 
system such that the printing machine can be easily configured to provide 
two-sided drying. 
Another object of the present invention is to provide a drying system for a 
printing machine which reduces the drying time of the printed material and 
which also reduces the space required for the drying section in the 
printing machine. 
The present invention provides these and other advantages and overcomes the 
drawbacks of the prior art by providing a drying system which includes a 
dryer module integrated into the printed material guide system. By 
enabling at least one side of the printed material to be dried at the same 
time it is guided, the present invention facilitates configuring the 
printing machine to provide two-sided drying. As compared to applying heat 
to only one-side of the printed material, two-sided drying substantially 
reduces smearing of the ink or varnish, particularly in the deliverer 
stack. 
The printed material guide system includes a guide surface which has a 
plurality of openings and an air system which is selectively operable in 
positive or negative pressure modes to assist the guiding of the printed 
material. A dryer module is arranged in an opening in the guide surface 
and is adapted to dry at least one side of the printed material. 
Additionally, at least one outlet opening is associated with the dryer 
module. The outlet opening is open into the plane of the guide surface and 
is coupled to a cooling system which is operable to provide cooling air to 
the dryer module. 
These and other features and advantages of the invention will be more 
readily apparent upon reading the following description of a preferred 
exemplary embodiment of the invention and upon reference to the 
accompanying drawings wherein:

While the invention will be described and disclosed in connection with 
certain preferred embodiments and procedures, it is not intended to limit 
the invention to those specific embodiments. Rather it is intended to 
cover all such alternative embodiments and modifications as fall within 
the spirit and scope of the invention. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 schematically illustrates a portion of an offset printing machine 
which incorporates a drying system constructed in accordance with the 
teachings of the present invention. The drying system of the present 
invention includes a dryer module which can be integrated into a printed 
material guide system for the printing machine and as such enables the 
printing machine to be easily configured to provide two-sided drying of 
the printed material. For example, the dryer module (or unit) and guide 
system of the present invention is particularly suitable for arrangement 
underneath the plane within which the printed material is conveyed. This 
arrangement results in the rear or back side of the printed material being 
dried at the same time it is guided. A conventional drying unit may then 
be provided to dry the front side of the printed material. As will be 
appreciated, the conventional drying unit assigned to dry the front side 
of the printed material may be arranged either directly opposite, upstream 
or downstream from the drying module integrated into the guide system. 
Alternatively, the combination dryer module and guide system of the 
present invention may be arranged to dry and guide the front side of the 
printed material or at least two guide systems with integrated dryer 
modules could be arranged opposite one another such that both sides of the 
printed material are guided and dried. 
As compared to drying through heat applied to only one side of the printed 
material, two-sided drying significantly reduces the smearing of the 
printed material which is produced by the printing machine, particularly 
smearing which occurs in the deliverer stack. Two-sided drying also 
shortens drying times and improves the oxidative drying of the printed or 
varnished material as well as the absorption of the ink or varnish and the 
curing of the ultraviolet inks and varnishes. In addition, when sheets are 
utilized as the printed material, two-sided drying enables both sides of 
the printed sheets to be heated uniformly thereby preventing heat or cold 
bridges from forming between the individual sheets which otherwise could 
lead to smearing of the ink or varnish. Since with the present invention a 
dryer module is integrated into the printed material guide system of the 
printing machine, the overall length of the printed material conveying 
path which is dedicated to drying can also be reduced. 
As will be appreciated, the dryer module and guide system combination of 
the present invention can be incorporated into offset printing machines 
which are equipped with any combination of printing units and varnishing 
units. For example, FIG. 1 illustrates a portion of an offset printing 
machine which has printing units for multi-colored printing and includes a 
turning unit and two varnishing units arranged downstream from the turning 
unit. In the illustrated embodiment, the printed material 5 comprises a 
sheet, however, it will be appreciated that the present invention is 
equally applicable to web-like printed material. Moreover, a variety of 
sheet or web materials may be used including, for example, paper, 
cardboard, plastic or metal films, plastic or metal foils, or metal. 
In order to transport the printed material, a chain conveyor system 3 
driven by a chain wheel shaft 2 and equipped with gripper devices 4 is 
provided. The chain conveyor system 3 circulates in the deliverer such 
that the printed material 5 is conveyed in a conveying direction 12 from a 
printing cylinder 1, which in the illustrated embodiment comprises part of 
the second varnishing unit, to a deliver stack 8. The printed materials 5 
are deposited onto the deliverer stack 8 using a braking device 6 and a 
blower 7 which are arranged adjacent the deliverer stack. The deliverer is 
further equipped with a venting device 11 which is arranged generally on 
the top of the deliverer and acts to draw air away from the printing 
machine. 
For the purpose of guiding the printed material as it is conveyed from the 
printing cylinder 1 to the deliverer stack 8, the illustrated sheet 
deliverer includes a printed material guide system 9. As shown in FIG. 1, 
the printed material guide system comprises a plurality of individual 
modules which are arranged approximately equidistant from each other and 
parallel to the conveying path defined by the portion of the chain 
conveyor system 3 between the printing cylinder 1 and the deliverer stack 
8. As shown in FIG. 2, each module of the printed material guide system 9 
essentially comprises what is generally referred to as a closed 
blower/suction box. The closed/blower suction box includes a box housing 
20 and a guide surface 19 which faces the rear side of the printed 
material 5 and defines one side or the "lid" of the box housing 20. 
Blower/suction boxes of this type are disclosed in DE 34 11 029 C2, and 
its U.S. counterpart U.S. Pat. No. 4,572,071, both which are assigned to 
the assignee of the present invention and incorporated herein by 
reference. 
In order to assist the guiding of the printed material, particularly at 
high conveying speeds, the printed material guide system 9 may be equipped 
with an air system 13. The air system 13 is selectively operable in either 
a positive pressure (blowing) mode or a negative pressure (suction) mode. 
In the positive pressure mode, the air system 13 provides a cushion of air 
which supports and guides the printed material 5. In the negative pressure 
mode, the air system 13 operates to draw the printed material 5 towards 
the guide surface 19 and thereby ensures positive contact between the 
guide surface 19 and the printed material 5. The negative pressure mode 
has particular application when the printed material guide system 9 is 
arranged opposite a transfer drum. In contrast, if the guide system 9 is 
arranged opposite a turning drum as opposed to a transfer drum, then the 
positive pressure mode of the air system 13 would be used to provide 
non-contact guiding of the printed side of the printed material 5. The air 
system 13, which may simply comprise a series of blowers, is arranged on 
the box housing 20, as shown in FIG. 2, and is operable through the 
plurality of openings 14 which are provided in the guide surface 19. 
In order to dry the printed material as it is conveyed from the printing 
cylinder 1 to the deliverer stack 8, the illustrated deliverer is equipped 
with a plurality of dryer units each of which is assigned to dry either 
the front or back side of the printed material. In particular, the 
deliverer includes a plurality of dryer units 10 which dry the front side 
of the printed material and a plurality of dryer modules or units 18 
integrated into individual modules of the printed material guiding system 
in accordance with the teachings of the present invention for drying the 
back side of the printed material. In the illustrated embodiment, each of 
the dryer units 10 is arranged adjacent a respective one of the modules of 
the printed material guide system 9 with one dryer unit 10 positioned 
adjacent the chain wheel shaft 2 just as the printed sheets begin the path 
from the printing cylinder 1 to the deliverer stack 8. A second dryer unit 
10 is arranged downstream from the first dryer unit in the portion of the 
sheet conveying path where it ascends towards the deliverer stack 8. 
To ease repair and replacement as well as to free up space within the 
printing machine, each of the dryer units 18 which heat the back side of 
the printed material are advantageously integrated in a modular 
construction into respective modules of the printed material guide system 
9. In the illustrated embodiment, each dryer unit 18 comprises a module 
which includes a pair of infrared radiators 17 arranged in an opening in 
the guide surface 19 such that when the dryer unit 18 is activated the 
back side of the printed material is heated as it is guided over the guide 
surface 19. The relatively large opening in the guide surface 19 which is 
provided for the dryer unit 18 may be covered with a metal grill or the 
like which is permeable to warm air and integrated into the guide surface 
19. Such a grill is particularly useful when the air system 13 is 
operating in negative pressure (suction) mode. Those skilled in the art 
will appreciate that other types of modular dryer units may be provided 
including a single infrared radiator or single or multiple ultraviolet 
radiators. The dryer unit 18 itself is preferably partitioned off from the 
other systems in the housing box 20, including the cooling system 15 
described below and the pneumatic system 13. For example, the dryer unit 
18 may be partitioned off from the other systems by a reflective metal 
sheet which would also help to concentrate the heat in the direction of 
the printed material. It will be appreciated that the dryer unit 18 may be 
arranged either centrally or eccentrically in the printed material guide 
system module. Additionally, more than one dryer unit 18 could also be 
provided in each module of the printed material guide system 9. 
The dryer unit 18 and the guide system 9 are also equipped with a separate 
air cooling system in order to cool the dryer unit 18 when it is 
activated. Specifically, as shown in FIG. 2, each infrared radiator 17 
also has an associated outlet opening 16 in the box housing 20. These 
outlet openings 16 are coupled to a separate air cooling system 
(schematically shown and referenced as 21 in FIG. 2) such that an 
externally produced air flow cools the infrared radiators 17 when they are 
activated. Additionally, the outlet openings 16 open into the plane of the 
guide surface 19 such that the air flow used to cool the infrared 
radiators 17 also can be used for guiding the printed material 5. 
Those modules of the printed material guide system 9 which are arranged 
opposite a dryer unit 10 are also provided with a system for cooling the 
guide surface 19. In particular, a cooling system 15 is arranged inside 
the box housing just below the guide surface 19, as shown in FIG. 2, and 
is operable to draw away any heat build-up from the guide surface which 
may result from operation of the dryer units 10. In the illustrated 
embodiment, the ducts of the cooling system 15 are arranged in the areas 
between the openings 14 and actually form the lower or rear side of the 
guide surface 19. The cooling system generally comprises a heat exchanger, 
a flow monitor, a compensation container and a circulation pump which 
control the flow and temperature of a coolant, such as for example water, 
which flows through the cooling ducts. It will be appreciated that those 
modules of the printed material guide system 9 which are not arranged 
opposite or adjacent to a dryer unit do not need to be provided with a 
cooling system 15. For example, when the printed material guide system 9 
is arranged adjacent a transfer or turning drum to provide intermediate 
drying, the guide system 9 can simply comprise a blower/suction box having 
an integrated dryer unit 18, an air system 13 and a guide surface 19 with 
a plurality openings 14. 
Those skilled in the art will appreciate in operation sheet or web material 
is run through the printing machine and the finishing units and printed or 
varnished on one side or both sides. The printed material 5 is then fed to 
the deliverer stack 8 in the conveying direction 12 as shown in FIG. 1. If 
the printed material 5 is printed on only one side, then it is dried by at 
least one dryer unit 10 which is activated. The air system 13 and cooling 
system 15 of the printed material guide system 9 which is associated with 
the dryer unit 10 are also activated. Particularly, the air system 13 is 
operated in the negative pressure (suction) mode. Further, the dryer unit 
18 integrated into the associated guide system 9 is actuated, so that in 
addition to heat provided by the dryer unit 10 on the front side (recto 
printing side) of the printed material, the unprinted rear side of the 
printed material 5 is also heated by the dryer unit 18. The heating 
provided by the dryer unit 18 reduces or eliminates the temperature 
differential between the front side and rear side of the printed material 
5, and accordingly substantially reduces the smearing of the ink or 
varnish which results from heat/cold bridges in the deliverer stack 8. If 
a printed material 5 which is printed or varnished on only one side and 
has a relatively low basis weight, e.g. less than 150 g/m.sup.2, is being 
processed, it is not necessary to actuate the dryer unit 18. 
As with one sided-printing operations, if the printed material 5 is printed 
on both sides such as in a recto/verso printing operation, both the dryer 
unit 10 and the dryer unit 18 are actuated in order to dry the ink or 
varnish. Similarly, the cooling system 15 is activated, in order to cool 
the guide surface 19 of the printed material guide system 9. Unlike the 
situation where only one side of the printed material is printed, however, 
the air system 13 is operated in the positive pressure (blower) mode in 
order to provide a cushion of air to support and guide the printed 
material 5. 
While this invention has been described with an emphasis upon preferred 
embodiments, it will be obvious to those of ordinary skill in the art that 
variations of the preferred embodiments may be used and that it is 
intended that the invention may be practiced otherwise than as 
specifically described herein. Accordingly, this invention includes all 
modifications encompassed within the spirit and the scope of the invention 
as defined by the following claims.