Note: Descriptions are shown in the official language in which they were submitted.
PREPARATION OF -fhlE INKING UNI f OF A ~°~r'~~r'~~ ~~
PRINTING PRESS FUR A CHANGE OF PRIN-faNG UUEi
Specification
The invention relates to a rotary printing press,
particularly offset printing press, the printing unit of
which comprises a printing forme, a damping unit as well
as an inking unit, said inking unit being provided with
a set ink profile.
In printing presses of the initially mentioned kind, it
is necessary, for the running-on state, to build up in
the inking unit an ink profile appropriate to the
subject to be printed. If the ink profile suitable for
running on does not yet exist at the start of printing,
then, after proofing, a large amount of waste is first
of all produced before the necessary ink profile and
thus also a stable ink/damping-solution equilibrium are
obtained. In order to prevent or in order considerably
to reduce waste, therefore, it is necessary to provide
the appropriate ink profile already at the start of
printing. This applies in particular if a new printing
forme is being used with a subject that differs from the
previous printing job. Furthermore, in order to prevent
waste also after lengthy interruptions in printing (i.e.
when an already used printing forme is used again), the
necessary ink profile should-have been set in the inking
unit when proofing takes place.
Known from DE-OS 38 00 570 is a printing unit for rotary
printing presses that comprises at least two ink-
conducting cylinders, such as plate cylinder and rubber-
blanket cylinder. In order to set a state suitable for
running on, an engageable/disengageable ink-reducing
unit is assigned to at least one of the ink-conducting
cylinders. Said ink-reducing unit assumes the function
- of the stock, i.e. the film of ink and damping solution
~~)~;~~~~~.
supplied from the inking unit and from the damping unit
is transferred in a manner appropriate to the subject
onto the ink-conducting cylinder, from where it is
accepted by the ink-reducing unit. This makes it
possible to set the ink profile necessary for running on
without it being necessary to print the stock. GJaste
can thus largely be prevented.
Furthermore, it is known, when changing printing jobs,
i.e. when using a new printing plate involving a change
of subject as compared with the previous printing forme,
first of all to clean the inking unit, with the result
that the ink profi7.e existing in the inking unit for the
previous printing job is eliminated by removal of the
ink. The removal of the entire volume of ink from the
inking unit, which is accomplished in particular by
scraping-pff and subsequent washing, is very elaborate
and thus time-consuming. Furthermore, it is necessary,
for a new start of printing, to build up an entirely
new ink profile within the inking unit, i.e. it is
necessary first of all to re-introduce a corresponding
valume of ink.
The object of the invention, therefore, is to indicate a
rotary printing press of the initially mentioned kind in
which it is possible in simple manner and at short
notice to change the ink profile, with the result that
there is a shortening of the set-up times when there is
a change of printing job. Furthermore, the state
suitable for running on is to be achieved as quickly as
possible when proofing, so that waste is largely
prevented.
The object of the invention is achieved in that, in
order to eliminate the previous ink profile and to
prepare the buildup of a new ink profile, the printing
~~;,~~~3 ~~
forma is inked aver its entire surface area with the
inking unit. As a result, the previously existing ink
profile is destroyed ar equalized. The inking of the
printing forma aver its entire surface area means that
there is a corresponding ink distribution as far as into
the inking unit, i.e. there too, there is an equalized
ink distribution over the longitudinal extent of the
inking-unit rollers. This creates a good basis for
building up the new ink profile, necessary for the next
printing job, on the thus formed "base ink-film
thickness". This dispenses with the need to remove the
entire volume of ink from the inking unit, with the
result that there is a considerab7.e shortening of the
set-up times when there is a change of printing job.
Moreover, the new ink profile can be built up
considerably faster on the equalized base ink film than
in the case of an inking unit that has been washed and
that is ink-free. With the inking of the printing forma
over its entire surface area according to the invention,
the ink-profile presetting of the metering elements in
the region of the ink duct of the inking unit can either
maintain the old presetting or the printer can already
make the new presetting there. Preferably, however, it
is also alternatively possible for there to be a neutral
setting there. If the ink-profile presetting
appropriate to the new printing job is already performed .
when the printing plate is inked, this makes it possible
all the sooner to achieve the subject-dependent ink
profile suitable for running on, with the result that
v~aste is largely prevented.
Preferably, in order to ink the printing forma over its
entire surface area, the damping unit is controlled in
such a manner that no damping solution or only a reduced
quantity of damping solution is supplied to the printing
w forma. The absence of damping solution or the presence
of an insufficient amount thereof means that, also
during running on, ink-free regions of the printing
forma accept ink, as a result of which there is the
full-surface-area inking according to the invention.
The supply of damping solution can be suppressed in that
the damping-solution applicator roller or damping-
solution applicator rollers of the damping unit assume a
disengaged position with respect to the printing forma
during the inking of the latter. If damping unit and
inking unit are connectable to one another through the
intermediary of an intermediate roller, said
intermediate roller must be brought into a disengaged
position with respect to the damping unit and/or inking
unit, so that, also, no damping solution is able to pass
via the intermediate roller to the inking unit and from
there to the printing forma.
In order for the printing forma, inked over its entire
surface area, to be freed again from the ink, a rubber-
blanket washing apparatus, assigned to a rubber-blanket
cylinder, is provided, said rubber-blanket washing,
apparatus washing the printing forma in that the rubber-
blanket cylinder assumes an engaged position with
respect to the printing forma. Thus, not only does the
rubber-blanket washing apparatus wash the rubber
blanket, but, as a result of the engaged position of the
rubber-blanket cylinder with respect to the printing
forma, i.e. with respect to the printing plate clamped
onta a plate cylinder, the washing liquid is supplied
also to the printing plate. Should the design of the
printing press not allow an exclusive engaged position
between rubber-blanket cylinder and plate cylinder, but
should it have to be expected that a backpressure
cylinder conducting the stock (paper, for example) will
come at least as close to the rubber-blanket cylinder
5
~~~i~~ i~
that, there too, 'the 'transfer of washing liquid is to tae
feared, then the paper-thickness compensator, provided
in actual fact for paper-thickness compensation, can
preferably be adjusted in such a manner that there is a
sufficient distance between backpressure cylinder and
rubber-blanket cylinder in order to prevent the
transfer of washing liquid.
In order to ensure that the equalized ink profile built
up in the inking unit is not destroyed by the washing
liquid, a separation must be made during washing between
the printing forma and the inking unit. The inking unit
comprises preferably at least one inking roller, sand
inking roller cooperating with the printing forma. Said
inking roller must, therefore, during washing, be moved
into a disengaged position with respect to the printing
f orme .
The invention relates further to a process for the
building up of a new ink profile in an inking unit of a
rotary printing press comprising a printing forma,
particularly an offset printing press, preferably for
the carrying-out of a new printing job, in which, in
order to destroy/equalize the previous ink profile, the
printing forma is inked over its entire surface area
with the inking unit. After the previous ink profile
has been destroyed or equalized, the printing forma can
be washed. This washing operation can take place in the
printing press, with, in this case, however, it being
necessary for the inking unit to assume a disengaged
position pith respect to the printing forma, so that no
washing liquid is transferred. It is provided, in
particular, that the washing operation is performed with
a rubber-blanket washing apparatus. For this purpose,
the rubber blanket assumes an engaged position with
respect to the printing forma, which is preferably in
the form of a printing plate (aluminiurn plate) clamped
onto a plate cylinder.
The invention is illustrated with reference to a
specimen embodiment in the drawings, in which:
Fig. 1 shows a diagram of rollers of an inking unit
and damping unit in an offset printing press;
and
Fig. 2 shows the diagram of rollers from Fig. 1, with
a rubber-blanket washing apparatus disposed on
a rubber-blanket cylinder.
Fig. 1 shows a diagram of rollers in an offset printing
press (printing press not represented in any greater
detail). An inking unit 1 and a damping unit 2 are
provided. The inking unit 1 is provided with an ink
duct 3, which has metering elements (not shown) for
setting zonal inking gaps. An ink-duct roller 4
withdraws ink in metered manner from the ink duct 3
during operation. A vibrator 5 cooperates with the ink-
duct roller 4 as well as with a driven distributor,6.
xhe damping unit 2 comprises a damping-solution box 26
filled with damping solution 27, with a fountain roller
28 being partially immersed in the damping solution 27.
The fountain roller 28 cooperates with a metering roller
29. Further provided is a rubber-covered roller 30.
Inking unit l and damping unit 2 additionally comprise
further driven distributors 7, 8, 9 and l0. In
addition, there are six rider and transfer rollers 11 to
l6 and nine rubber-covered rollers 17 to 25. If
necessary, inking unit 1 and damping unit 2 can be
connected to one another through the intermediary of an
intermediate roller (not shown).
7
Both ink and damping solution 27 axe supplied to a
printing forma 32 via the described roller arrangement.
The printing forma 32 is a printing plate (not shown),
said printing plate being clamped onto a plate cylinder
33. The transfer of ink and damping solution 27 from
the inking unit 1 and damping unit 2, respectively, to
the printing plate is effected by the rubber-covered
rollers 18, 20, 25 and 30. Consequently, said rubber-
covered rollers are referred to also as inking rollers
34 and the rubber-covered roller 30 transferring the
damping solution is referred to as damping-solution
applicator roller 35.
By means of a control apparatus (not shown) it is
possible for the inking rollers 34 and the damping-
solution application roller 35 to be moved into an
engaged or disengaged position with respect to the
printing forma 32. In the representation shown in
Fig. 1, the inking rollers 34 are in their engaged
positions and the damping-solution applicator roller 35
in its disengaged position.
Let it be assumed that a printing job - carried out with
the printing plate, clamped onto the plate cylinder 33 -
has been finished, i.e. a desired number of copies have
been printed. There is now to be a change of printing
job; a new printing run is to be performed with a
printing plate carrying a different subject.
So that an ink profile appropriate to the running-on
state of the new printing process can be set as quickly
as possible in the inking unit, the printing forma 32,
i.e. the previously used printing plate clamped on the
plate cylinder 33, is, according to the invention, first
of all inked over its entire surface area. This is
- achieved preferably in that, as a result of the
s ~~a.~~.'~
disengaged position of the damping-solution applicator
roller 35 with respect to the plate cylinder 33 and in
the absence of a connection between damping unit 2 and
inking unit 1 (if an intermediate roller is used, it
would have to be moved to a separation position), no
damping solution 27 reaches the printing forma 32.
Thus, regions of the printing forma 32 that are in
actual fact ink-free in the running-on state accept ink
(scumming). The inking of the printing forma 32 over
its entire surface area has repercussions on the ink
profile in the inking unit 1, where the previous ink
profile, originating from the printing job performed, is
destroyed, being, in particular, equalized. This leads
to a "base ink-film thickness", which forms the basis
for the building-up of a new ink profile for the next
printing job.
Before the new printing plate is clamped onto the plate
cylinder 33, the old printing plate, inked over its
entire surface area, is first of all to be cleaned. For
this purpose; as shown in Fig. 2, the inking rollers 34
are moved into disengaged positions with respect to the
printing forma 32. The damping-solution applicator
roller 35 remains in its disengaged position with
respect to the plate cylinder 33. A rubber-blanket
cylinder 36, which always exists in an offset printing
press, is brought into an engaged position with respect
to the plate cylinder 33. A rubber-blanket washing
apparatus 37 is assigned to the rubber-blanket cylinder
36. Said washing apparatus comprises two washing
rollers 38, running on the outer cylindrical surface of
the rubber-blanket cylinder 36, as well as a common
ro112r 39, connecting the washing rollers 38. Further
provided is a transfer roller 40, which is in contact
with the upper washing. roller 38 and to which washing
liquid can be supplied by means of a spray apparatus
~.~,a~a~~a~,~~~~
41. Assigned to the roller 39 is a doctor-blade
apparatus 42, under which is disposed a collection
trough. 43 .
In the washing position (Fig. 2), the washing liquid
supplied from the spray apparatus is transferred to the
rubber blanket of the rubber-blanket cylinder 36 by
means of the transfer roller 40 and the washing rollers
38. The rubber-blanket cylinder 36, in turn, transfers
a certain proportion of the washing liquid to the plate
cylinder 33, i.e. onto the printing forma 32, with the
result that the coating of ink forming the full-surface-
area inking is loosened and carried away. Residues of
ink and similar are passed in this manner as far as the
roller 39, where they are skimmed off by the doctor-
blade apparatus 42.
When the previously used printing plate has been
cleaned, it is removed from the offset printing press.
The printing plate to be used for the new printing job
can then be clamped onto the plate cylinder 33.
In order to equalize the previous ink profile in the
inking unit as well as in order to build up the new ink
profile required for the new printing job, it is
possible, at the metering elements of the ink duct 3,
already to set the tonal inking gaps to the new setting
while the printing forma 32 is being inked over its
entire surface area, said new setting being appropriate
to the subject of the new printing plate to be used for
the next printing job.
Further, as a variation on the previous versions) it is
also possible for the old printing plate first of all to
be removed and then for the new printing plate to be
clamped onto the plate cylinder 33. The new printing
10
plate is then inked over its entire surface area with
suitable setting of the ink profile, Subsequently, as
shown, the printing plate is then washed. Finally, the
actual printing process can be commenced. It is,
however, also possible for the ne~a printing plate,
inked over its entire surface area, to "run clean"
through the supply of damping solution, i.e. the full-
surface-area inking is removed by the supply of damping
solution to the ink-free regions. It is not then
necessary for there to be any washing operation (as
mentioned above). As an alternative to the cleaning of
the printing forma by means of the rubber-blanket
washing apparatus, it is also possible to use a plate-
cylinder washing apparatus.
