ELEMENT MOUILLEUR POUR PRESSE OFFSET

DAMPING UNIT FOR AN OFFSET PRINTING MACHINE

Abrégé anglais

In the case of a damping unit for an offset
printing machine having a pair of rolls consisting of an
applicator-roll and a metering roll, both trituration and
unimpeded return of excess damping agent from an associated
plate-cylinder into an upper nip between the said applicator-
and metering-rolls is made possible in that a friction-roll,
associated with the said pair of rolls, is in direct
frictional contact with the said metering roll.

Revendications

7424-88
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A damping unit for an offset printing machine
having a metering roll, a roll for applying a damping
agent to a plate-cylinder, a contact-zone formed by
mutual pressure between the metering roll and the
applicator-roll along the contacting, axially
parallel casings of these rolls; having drive means for
rotating the metering roll and the applicator-roll;
having substantially downwardly directed peripheral
velocities of these rolls in the vicinity of the
contact-zone; having a storage-area for the damping agent
located above the contact-zone formed by the casings of
the metering roll and the applicator-rol1 and by sealing
means at the ends of these rolls; and having a traversing
friction-roll co-operating with one roll-surface,
characterized in that the friction-roll is in direct
frictional contact with the said metering roll.
2. A damping unit according to claim 1, characterized
in that positive drive-means are provided for driving the
metering roll.

Description

7424-88 131 6~42
TITLE- DAMPING UNIT FOR AN OFFSET PRINTING MACHINE
SPECIFICATION
The invention relates to a damping unit for an
offset printing machine having a metering roll, a roll for
applyin~ a damping agent to a plate-cylinder9 a contact-zone
formed by mutual pressure between the metering roll and the
applicator-roll along the contacting, axially parallel
casings oF these rolls; having driving means For rotating the
metering and the applicator-roll; having substantially
downward1y directed peripheral velocities of these rolls in
the vicinity of the contact-zone; having a storage-area
; 15 located above the contact-zone formed by the casings o~ the
metering roll and the applicator-roll and by sealing means at
the ends of these rolls; and having a traversing
friction-roll co-operating with one roll-surFace.
A damping roll of this kind is known from German OS
2206 498. In this case, an oscillating friction-roll is
provided and is arranged at the applicator-roll between the
point of contact thereof with the plate-cylinder and the
storage-area for the damping agent in the nip between the~
applicator-roll ;and a metering roll adjusted thereto.
In earlier times, desirable trituration was
dispensed with in such damping-unit systems in order to
obtain unimpeded return of excess damping agent ~rom the
plate-cylinder to the storage-area (see U.S.Paten~ 4 455
938).
It is the purpose of the present invention to
propose a damping unit of this kind whereby it is possible to
obt~ain both~trituration and unimpeded return of excess
damping agent ~rom the plate-cylinder to the storage-area for
the said dampin~ agent.
This purpose is achieved with a damping unit
; ~ according to claim 1.

7424-88 -2- 13~6~42
The arrangement of the friction-roll according to
the invention counteracts both the so-called stencilling
effect and also linear overmoistening.
This arrangemen~ of the friction-roll must not pay
for the advantage of its evening-out effect by introducing
another disturbing influence which, in the case of known
damping units of ~his kind, comes into being as the result of
the casing of the applicator-roll being contacted, on its way
from the plate-cylinder to the storage-area for the damping
agent, by a friction-roll, whereby unimpeded return of the
said damping agentJ from the plate cylinder to the said
stora~e-area, may be disturbed.
A reliable drive for the friction-roll may be
ensured by positive drive-means for the metering roll.
In addition, the arrangement9 according to the
invention~ of the friction-roll also has the advantage of
allowing unimpeded transfer of the film of moisture formed in
the contact-zone to the plate-cylinder.
An example of embodiment of the invention is
illustrated diagrammatically in the drawing attached hereto~
Damping unit 1, adjusted to a plate-cylinder 2,
comprises a metering roll 3, an applicator-roll 4 for the
damping agent, and a friction-roll 5. Shaft 6 of metering
roll 3 is carried at both ends in stationary bearings in the
machine. On each side of metering roll 3 a bearing plate 7
is arranged to pivot about a journal at the end of shaft 6,
the said bearing plates being connected together by means of
cross-members 8. Each end of applicator-roll 4 is mounted
in a sliding shoe 9 which in turn slides in a linear guide-
sur~ace 10 incorporated into the said bearing plate.
Guide-plates 10 are substantially parallel with the direction
of a tangent to plate-cylinder 2 in a contact point with
applicator-roll~4. Each sliding shoe 9 is connected to a
shaft 11 provided with a thread at its free end which runs in
the direction of guide-surfaces 10 and is guided by relevant
.

7424-88 ~3~
~3~42
bearing pla~e 7. A compression~-spring 12, supported by
bearing plate 7 acts upon each sliding shoe in the direction
of "breaking contact with the metering roll". Shaft 11
passes through an opening 13 in relevant bearing plate 7 in
which an actuator for relevant sliding shoe 9 is providedO
The actuator consists of a toothed-rack 17 arranged to slide
upon shaft 11 and adjusted to a sleeve 18 screwed to the
thread of shaft 11, and of a gearwheel (not shown) which
meshes with toothed-rack 17 and is coaxial with a worm~gear
16. The gearwheels (not shown), for displacing toothed-rack
17, are secured jointly to a shaft 19. Secured to shaft 19
is a worm-gear 16 which is in engagement with a worm 15.
Shaft 19 may therefore be rotated by means of an actuating
part 14 fitted to worm 15.
Located in the upper nip between metering roll 3
and applicator-roll 4 is the damping agent which is enclosed
herein by suitable sealing means (not shown) at the ends of
these rolls. A quantity of damping agent, adjustable by the
mutual pressure between these rolls by means of actuating
part 14~ is delivered through contact-zone 20 between these
rolls by the casing o~ applicator-roll 4 located below the
~ said contact-zone, to plate-cylinder 2. To this end the
-~ 25 damping unit comprises drive-means 21322 for rotating the
metering roll 3 and applicator-roll 4, the peripheral
velocities of the said rolls being directed downwardly in the
vicinity o~ contact-zone 20~ These drive-means drive
metering roll 3 at the peripheral speed of plate-cylinder Z
by means of driving gear~21 of the gear-train in the printing
machine meshing with a gearwheel 22 which is arranged
coaxially with metering roll 3 and is connected thereto by
means of a~freewheel not shown.
Applicator-roll 4 is driven from metering roll 3 by
friction in contact-zone 20.
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7424-88 -4- ~ 2
A traversing friction-roll 5 is adjusted to
metering roll 3 on a level with contact-zone 20, the said
fric~ion-roll being caused to rotate and traverse by friction
against the said metering rollO To this end, ~he ends of
axis 23 of friction-roll 5 are accommodated, but do not
: rotate, in elongated holes 24 in respective bearing plates 7.
Each elongated hole extends substantially towards the
metering hole and is adapted in width to the d~ameter of axis
23. Axis 23 is secured in the elongated holes by means of
adjusting screws 25 screwed into bearing plates 7, the said
screws pressing the axis against compression-springs 26
arranged in bearing plate 7.
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7424-88 ~5~
~311 ~2
LIST OF REFERENCE NUMERALS
1. damping unit
2. plate-cylinder
3. metering roll
4. applicator-roll
. friction-roll
6. shaft
7. bearing plate
8. cross-member
9. sliding shoe
10. guide-surfaces
11. shaft
12. compression-spring
13. opening
14. ac~uating part
15. worm
16. worm-gear
17. toothed-rack
18. adjusting sleeve
19. adjusting shaft
20. contact-zone
21. ~ driving gear :
22. ;gearwheel
23. ~ axis
24.: ~ elongated hole
25. . adjusting screw
26. compression-spring
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Dessin représentatif