Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to moistening apparatus for
lithographic printing presses and more particularly to an
improved spray dampening system for high quality offset
printing.
Basic spray dampening systems suitable for highly
satisfactory operation under varied conditions of press feed,
paper sur~ace and ink requlrement~ are known, for example, United
States Patent No. 3,651,756~1ssued Narch 28, 1972. However,
where very high quality printing on certain very smooth paper
ls required, such dampening systems tend to occasionally
produce slight printing irregularlties or streaks correspond-
ing to minor variations in the density of moisture disposi-
tion along the spray path. particularly troublesome in this
regard is the moisture disposition at the ends of the spray
receiving roll or rolls, since it requires the end spray
nozzles to be placed in positions which result in roll end
overspray which tends to wet adjacent shafts and machine
p~rts. This is especially undesirable in the meticulously
maintained presses utilized for very high quality printing.
Attempts to circumvent the problem by utilizing extra long and/
or reciprocating rollers to respectively receive and smooth
the uneven moisture film heretofore have been eit~er impracti-
cal or create new problems, such as excesæ water or ink form-
ing into rings at the edge of rolls and being slung off at
high rotational speeds.
The principal ob~ects of the present inventlon are:
to provide spray dampening apparatus for high quality offset
printing presses which creates a highly uniform moisture film
application; t~ provide such a system where~n the spray is
applied to dampening rolls without edge overspray; to provide
such a system wherein the spray member is reciprocated for
additional moisture film uniformity; to provide such a
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dampening arrangement wherein mo~sture transPer rolls have a length relation-
ship to each other which is practical and avoids the problem of moisture or
ink slinging off at the ends; to provide such a system which utilizes an
oscillating transfer roll between a dampening roll and form roll for smoothing
the moisture film; to provide such offset press dampening apparatus which
permits end spray nozzles to be placed in overspray positions without produc-
ing overspray; and to provide æuch an arrangement which is relatively in-
expensive to produce, reliable in use, easily maintained and generally well
adapted for its intended purpose,
According to the invention there is provided, in combination with a
printing press having a frame, an inking train and an offset plate cylinder
which engages a blanket cylinder for transferring an ink image thereto,
dampening apparatus comprising: an elongated spray member having a line of
several dampening liquid atomizing spray nozzles positioned on said press in
laterally spaced relation; dampening roller means having opposite ends, said
dampening roller means being positioned to receive spray from said nozzles
and having a length between said roller means ends less than the spray path
witth emitted from said nozzles whereby said spray path extends beyond said
roller means ends; a pair of spray shield means associated with said spray
member and respectively positioned to intersect and prevent overspray beyond
said roller means ends; said spray shield means having free dripping lower
portions positioned over said roller means whereby intersected spray is
dripped onto said roller means; and transfer means contacting said dampening
roller means and transferring moisture to said plate cylinder.
Other objects and advantages of this invention will become apparent
from the following description taken in connection with the accompanying
drawings wherein are set forth by way of illustration and exemplify certain
embodiments of this invention
Figure 1 is a schematic side elevation illustrating
~ ~ 2
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an offset printing press ink and moisture roller train
embodying this invention.
Fig. 2 is a fragmentary, schematic, front elevation
showing the relationship between the spray member and ~arious
rollers in the moisture train.
Fig. 3 is a fragmentary perspective view further
illustrating the relationship between the spray member and
dampening rollers.
Fig. 4 is a fragmentary schematic, front elevation
similar to Fig. 2 but on a larger scale and showing the
relationship between the spray bar and a moisture receiving
roller.
Fig. 5 is a fragmentary ~ide elevatlonal view show-
lng the relationship between the spray member end shield and
a pair of dampening rollers.
Fig. 6 is a view similar to Fig. 5 but showing a
modified form which utilizes a single dampening roller.
Fig. 7 is similar to Fig. 4 but showing a modified
form utillzing a stationary spray member.
Referring to the drawings in more detail:
Reference numeral 1 (Fig. 1) generally indicates a
printing press incorporating dampening apparatus embodying
thiæ invention. The press 1 has an inking train, generally
designated 2, which carries ink to an offset plate cylinder 3
engaging a blanket cylinder 4 for transferring an ink image
thereto. The image is deposited, in this example, upon a
paper web 5 which is backed by a suitable impression cylinder
6.
The ~nking train 2 is comprised of an inking foun-
tain 7 containing, in this example, suitable paste ink 8 which
is fed to a hard surface fountain roller 9 and carried by a
reciprocating, resilient surface ductor roller 10 to a hard
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surface distributor roller 11. Resilient surface distributor
rollers 12 and 13 and hard surface distributor rollers 14 and
15 operate to smooth the ink film and transfer it to hard
surface vibrator roller 16 and further distributor rollers 17
and 18, the vibrator roller 16 being in contact with resilient
surface form rollers 19 and 20 which deposit the ink film,
where appropriate, onto a printing plate 21 carried by the
plate cylinder 3. The distributor roller 18 runs in contact
with a vibrating oroscillating roller 22 which, in this
example, contacts a further form roller 23 in operative engage-
ment with the printing plate 21.
An elongated spray member or bar 24, preferably of
the general type described in U. S. Patent No. 3,651,756, has
several aligned, liquid atomizing, spray nozzles 25 positioned
in laterally spaced relation, the group including end nozzles
26 and 27. The nozzles 25 are fed through suitable sou~ces
(not shown) connected by flexible liquid and compressed air
. llnes 28.
; In the example of Figs. 1, 2, 3 and 5, a pair of
contacting, resllient surface (e.g., 25-30 durometer) dampen-
ing rolls 29 and 30 are positioned to receive spray mist 31
from the respective nozzles 25 and each has a length generally
equal to the effective spray path width emitted from the com-
bined nozzles, as explained further below. A pair of spray
shields 32 and 33 are mounted on the spray bar 24 and respec-
- tively positioned near opposite ends of the line of spray
nozzles 25. The shields 32 and 33 project into close relation
to the dampening rollers 29 and 30 and respectively have
inside surface~ 34 and 35 positioned to intersect a portion
of the spray emitted from the end nozzles 26 and 27.
In the example of Figs. 1-4, the spray bar 24 is
suitably mounted upon a rod 36 for lateral reciprocal motion
` 1OaU~EU6S
along the dampening rollers 29 and 30. A motor 37 is illus-
trated as driving a crank arrangement 38 to produce the recip-
rocation through an appropriate connecting link 39, however,
it is to be understood that any suitable means of reciprocal
mounting and driving may be utilized for the purpose, includ-
ing a mechanical take-off from the printing press drive (not
shown).
The length o~ the dampening rolls 29 and 30, that
is, the distance between the ends 40 and 41 thereof, is
slightly greater than the distance between the spray shield
inside surfaces 34 and 35 plus the distance of the spray bar
crank stroke 42, Fig. 4. Thus, the spray shields 32 and 33
project into close relation to the dampening rollers 29 and 30
and the inside surfaces 34 and 35 are positioned to prevent
overspray beyond the ends 40 and 41. Liquid dripping from the
shields 32 and 33 is milled into the uniformly thin moisture
film formed on the roller 30 by coaction with the roller 29
note the bight formed therebetween, Fig. 1.
The oscillating roller 22 contacts the roller 30,
in addition to the wet form roll 23 and distributing roll 18,
for further smoothing and transferring moisture to the plate
21. The oscillating roller 22 has a length or distance be-
tween ends 43 and 44 generally equal to the length of the form
roller 23 plus the stroke length of the oscillating roller 22,
in Fig. Z. To complete the proper relationship, the dampening
rollers 29 and 30 have a length slightly less, for example
around 1/8 inch, than the length of the oscillating roll 22
plus the oscillating roll stroke length 45.
Oper~ting parameters may vary considerably in the
practice of the invention, however, recommended stroke length
of the reciprocating spray bar for typical 17'l to 20" web
presses range from 3/4 of an inch to 4 inches and oscillating
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speed preferably varies with operating press speed, a suitable
relationship being 150 bar strokes per minute when the press
is rotating at a speed of l,000 web feet per minute. Also, it
is desirable to control the relative diameters of the dampen-
ing, oscillating and form rollers so that there is no contin-
uously repeating relationship whicb would tend to affect the
smooth application of the moisture film. This avoidance of
continuously repeating relationship should also be considered
in determining the reciprocating frequency of the spray bar
24 and oscillating roll 22.
Fig. 7 illustrates a form of the invention wherein
the spray bar 46 is stationary. In this embodiment, the spray
shield inside surfaces 47 and 48 do not move but are contin-
ually located ~ust inside the ends 49 and 50 of the dampening
roller 51 receivlng the spray, thereby preventing overspray
as described abo~e. Any excess moisture collecting on the
surfaces 47 and 48 drips from the dampening roller or rollers
and is milled into the uniformly thin moisture film carried
to the printing plate.
Rig. 6 illustrates a further modified form of this
invention which utilizes a single dampening roller 52 co-act-
ing with the spray bar 53 and spray shields 54, instead of
the pair of dampening rollers described above. In the embodi-
ment of Fig. 6 the dampening roll 52 receives the spray or
mist from the spray bar 53 and carries it directly to the
oscillating roll 55 for thin film formation and delivery
along the roller train.
In operation, a highly uniform and effective film
of moisture is,transferred to the printing plate for high
3o quality offset printing without dampening roller overspray
and without the formation of moisture or ink rings at the
end of transfer rollers, which would tend to sling off,
10368~;5
causing difficulties during production runs.
