Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
^`" :I.:ll6S~
~ BACKGROUND OF INVENTION
. _ _
To combat "ghosting", inkers for lithographic
newspaper printing plates generally comprise four form
rollers in rolling engagement with a printing plate, each
of -the form rollers receiving ink from one or more vibrator
rollers in a train of rollers of varying diameters. Ink
is usually delivered to the train of rollers ovar a ductor
roller which oscillates into and out of engagement with a
film of ink formed by a flexible doctor blade urged into
engagement with the hard surface of an ink fountain roller
by ink keys in an effort to vary ~he input of ink to
conform to the output.
The multiple roller inkers require complex drive
trains and are relatively expensive to operate because of
the power required for rotating the rollars. Difficulty
has been encountered in metering and applying ink uniformly
to printing plates.
In~ers o~ the type disclosed in U.S. Patent No.
4,~33,898 which issued November 18, 1980 to Harold P. Dahlgren
~0
entitled "REVERSI~LE NE~SPAP~R PRESS", offered significantly
improved ink metering and control because ink ~as continuously
suppli~d to a sinc~le form roller by a variable speed transfer
roller. The speed of the hard surfaced transfer roller could be
adjust.ed to increase or decrease the volume of ink supplied to a
165~76
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1 resilient surface on the form roller.
The present invention addresses the problem of reducing
the power required to drive rollers at different speeds in an
inker of the type disclosed in Dahlgren Canadian patent application
serial number 325,681 filed April 18, 1979 while retaining
the improved metering capability which results ~rom "slipping"
the rollers.
SUMMARY OF THE INVENTION
The improved inker construction comprises a metering
roller and a transfer roller one having a hard surface and
the other having a resilient surface urged into pressure
indented relationship. The metering roller is adapted to
meter an excess of low viscosity ink at a flooded metering nip
~etween the metering roller and the transfer roller such that a
uniform film of ink is metered onto the surface of the transfer
roller. The film of ink on the transfer roller is sheared and
metered at a transfer nip between the transfer roller and an
applicator roller. The speed differential between the
applicator roller and the transfer roller permits slippage
2~ for forming a thin, smooth layer o ink on the applicator
roller. The applicator roller applies ink to the form roller.
The applicator roller and the form roller are driven
at approximately the surface speed of the printing plate
which engages the form roller.
If the printing plate is hard, the form roller should
have a resilient surface. To reduce power required for
slipping rollers at the transfer nip, the applicator roller is
provided with a hard surface and is driven at a greater surface
speed than a resilient covered transfer rollex against which it
slips-
When two rollers are urged together in pressure
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indented relation and rotated at equal surface speeds,
the thickness of the ink films on the two rollers will
be approximately e~ual. Thus, a transfer roller engag-
ing a form roller will carry a thinner film than a
transfer roller which engages an applicator roller
which in turn engages a form roller, if the form roller
carries a film of the same thickness in each instance.
By slippin~ between the transfer roller and the
applicator roller, rather than between the transfer
roller and a form roller, lubrication is sufficient
to reduce power required to meter the ink.
The applicator roller and the transfer roller
are preferably smaller in diameter than the form roller
to minimiæe the shèar area of indentàtion at the
transfer nip. Since the hard surface on the applica-
tor roller is driven faster than the adjacent resilient
surface on the transfer roller, the resilient surface
moving into the transfer nip is maintained in tension
to prevent excessive deformation of the resilient cover.
Variation in deformation of the resilient surface
at the trarlsfer nip results in variation of the stripe
width and the shear area at the transfer nip.
When the portion of the resilient sur~ace
approaching the transfer nip is moving faster than
the adjacent hard surface, the resilient surface is
subjected to compressive loading and tends to wrap
around the hard surface. This would increase the
stripe width and increase the power requirea to slip
one roIler against the other because additional power
is required to deform the resilient cover material.
In the preferred embodiment of our invention,
the applicator roller is an idler roller in rolling
engagement with the form roller. The transfer roller
is driven by a variable speed motor at a slower sur-
face speed than the applicator roller. Thus, the
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applicator roller, in pressure indented relation withthe faster driven ~orm roller and the slower driven
transfer roller, is driven at an intermediate speed
such that most or all of the slippage occurs between
the applicator roller and transfer roller. The sur-
face speed of the applicator roller varies with changes
in pressure between the applicator and transfer rollers,
with change$ in differential speed of the form roller
and the transfer roller, and the thickness of the film
of ink on the applicator roller and the transfer roller.
A primary object of the invention is to pro-
vide an inker wherein the ink film thickness is con-
trolled by varying the surface speed of one form
roller relative to the surface speed of an adjacent
roller.
Another object of the invention is to provide
an inker equipped with rollers having relatively
small diameters to provide substantial indentation
and pressure at a transer nip ~hile minimizing the
stripe width and shear area between a transfer roller
and an applicator roller.
Another object is to minimize the power required
to slip one roller against another roller at an ink
transfer nip ~y maintaining an ink film thickness
~ 25 adjacent the trans~er nip to assure lubrication.
; A further object is to provide a hard sur-
faced roller and a resilient surfaced roller in pres-
sure indented relation to meter ink wherein the
resilient surface moves slower than the hard surface
to minimize deformation of the resilient surface at
the nip.
A still further object of the invention is to
provide a hard surfaced idler roller between a pair
of resilient rollers, the resilient rollers having
different surface speeds, to control the thickness
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of an ink film applied to one of the resilient rollers.
Other and further objects will become apparent
upon referring to the following detailed description
and the attached drawings.
BRIEF DESCRIPTI~ON OF THE DRAWINGS
Drawings of a preferred embodiment of the
invention are annexed hereto so that the invention may
be better and more fully understood, in which:
Figure 1 is a diagrammatic illustration of the
inking system for a lithographic printing press
illustrating the various films of ink and dampening
~luid;
Figure 2 is a front elevational view illustrat-
ing the metering, transfer, and applicator rollers
and support structure;
Figure 3 is a cross-sectional view taken along
line 3-3 of Figure 3;
Figure 4 is a diagrammatic view of a standard
printing unit;
Figure 5 is a diagrammatic view of a reversed
printing unit;
Figure 6 -is a diagrammatic view of the electrical
hookup of the motors of dampening and inking units.
Numeral references are employed to designate
like parts throughout the various figures of the
drawing.
DESCRIPTION OF A PREFERRED EMBODIMENT
In Figure 1 of the drawing, the numeral 1
generally designates an ink applicator apparatus for
applying ink and dampening fluid to a lithographic ,
; printing plate of a printing press. The water ap-
plicator 200 is a dampener of the type disclosed in
United States Patent No. 3,937,141, entitled "DAMPENER
FOR LITEIOGRAP~IC PRINTING PLATES" which issued
February lOr 1976 to Harold P. Dahlgren~ r---
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1 As best illustrated in Figure 2, ink applicator 1
comprises spaced side frames 2 and 4 joined by tie bars
(not shown) forming a strong rigid structure for supporting
form roller 90, ink applicator roller 10, ink transfer roller
12 and ink metering roller 14. Side frames 2 and 4 may be the
side frames of a press or may comprise inker side frames
connectable to side frames of a printing press.
Throw-off links 16 and 18 are pivotally secured by
stub shafts 20 and 22 to the respective side frames ? and 4.
0 Throw-off cylinders 24 and 26 are pivotally connected between
side frames 2 and 4 and throw-off links 16 and 18, respecti~ely,
for pivoting throw-off links 16 and 18 about stub shafts 20
and 22 for moving transfer roller 12 into position, as will
be hereinafter more fully explained, for deliverin~ ink over
an applicator roller 10 to a form roller 90 in a lithographic
printing system.
~ A skew arm 28 is mounted for pivotal movement of one
end of a metering roller 14 about the axis of ink transfer
roller 12. As diagrammatically illustrated in Figure 2,
skew arm 28 is rotatably secured to stub shaft 30 extending
between link 18 and skew arm 28 adjacent an end of ink
transfer roller 12.
Skew arm 28 and throw-off link 16 have grooves 28a
and 16a, respectively, formed in the inner surfaces thereof in
which blocks 36, carrying self~aligning bearings 38, are
slidably disposed. Blocks 35 axe rigidly secured in the upper
portion of grooves 28a and 16a by screws 37 to provide suitable
support for shafts 31 and 32 of the ink transfer roller 12.
Suitable means such as resilient springs 40 between
blocks 35 and 36 urge blocks 36 longitudinally of skew
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arm 28 and throw-off link 16 in a direction away from
the longitudinal axis of transfer roller 12. A pres-
sure adjustment screw 42 urges block 36 longitudinally
of skew arm 28 and throw-off link 16 against the bias
of springs 40. Stub shafts 44 and 46, extending out-
wardly from opposite ends or metering roller 14, are
received in self-aligning bearings 38 to rotatably
secure metering roller 14 in pressure indented relation
with transfer roller 12. Stub shafts 31 and 32,
extending outwardly from opposite ends of transfer
roller 12, are received in bearings 39 in blocks 35.
It should be readily apparent that rotation of
pressure adjustment screws 42 will move opposite ends
of metering roller 14 relative to the axis of transfer
roller 12 for controlling pressure between transfer
roller 12 and metering roller 14.
As illustrated in Figure 3, suitable means is
provided for establishing and maintaining a desired
angular relationship between throw-off link 18 and
skew arm 28. In the form of the invention illustrated
in Figure 3, an adjusting screw 50 is rotatably secured
to skew arm 28 and extends through threaded apertures
in pivotal blocks 52a and 52b. Blocks 52a and 52b are
pivotally secured to lug 54 on arm 28 and lug 56 on
link 18. By adjusting screw 50, the spacing between
lugs 54 and 56 is adjusted to move skew arm 28 relative
to link 18 about shaft 30.
Side frames 2 and 4 have suitable adjustable
stop means such as stop blocks 5 having set screws 5a
extending therethrough for engaging throw-off links 16
and 18 when rods of throw-off cylinders 24 and 26 are
extended for establishing a desired pressure relation-
ship between the transfer cylinder 12 and an ink coated
applicator roller 10 arranged to transfer ink over a
form roller 90 in a lithographic or relief printing
6S 1 16
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plate 112 on plate cylinder P, as will be hereinafter
more fully explained. Stop means such as stop blocks
6, having set screws 5a secured thereto, provide an
"of~-impression" limit when piston rods of throw-off
cylinders 24 and 26 are retracted to move the transfer
roller 12 away from the surface of applicator roller
10 .
Stub-shaft 31, extending outwardly from the end
of transfer roller 12, has a gear 60, rigidly secured
thereto by a key 61, which is in-meshing relation
with a gear 62 secured on shaft 44.
Gear 62 is secured in meshing relation with
gear 71 on shaft 58 which is rotatably secùred through
an opening in side frame 2. Shaft 58 is secured to
the shaft of a reversible variable speed drive means
such as a reversible variable speed electric gear-
motor 69. It should be appreciated that gear-motor 69
may be replaced by other drive means such as gears,
sprockets, or pulleys arranged to be driven from the
printing press drive, preferably through a gear box or
similar variable speed control apparatus~
Power supply line 80 is connected through a
variable rheostat 84 to the terrninals of motor 69 so
that motor may be run at variable speeds to control the
speed of rotation, and, consequently, the surface
speeds of transfer roller 12 and metering roller 14
independently of the press drive. If it is deemed
expedient to do so motor 69 could be replaced by a
speed~variable coupling which connects shaft 58 to
the press drive means, as hereinbefore described.
Suitable means is provided for delivering an
abundant supply of ink to the ink metering nip N bet-
ween adjacent surfaces of transfer roller 12 and meter-
ing roller 14. In the particular embodiment of the
invention illustrated in Figure 1, a portion of the
l~l6~1 76
surface of metering roller 14 is submerged in ink 14a
in ink pan 14b.
Ink 14a pxeferably comprises a low viscosity
ink such as the type employed for inking raised image
5 areas in letter press p.rinting or the type used in
direct or offset lithographic printing or newsprint
or similar materials.
Trans.fer roller 12 preferably comprises a hol-
low tubular sleeve having stub shafts 31 and 32 formed
thereon. ~ resilient cover 12c is secured about the
outer surface of the sleeve. The material of transfer
roller 12 is selected so as to be oleophillic and the
surface may be smooth or textured.
: The metering roller 14 is preferably hard and
has an exterior surface which may be smooth or textured
and which is ink receptive or oleophillic. Ink meter-
ing roller 14 may, therefore, have an exterior surface
of materials such as copper, steel,or.p~astic. The
surface of metering roller 14 may be either hard or
resilient.
To reduce the tendency of ink to accumulate
adjacent the ends of transfer roller 12, metering rol-
ler 14 is longer than transfer roller 12 such that ends
: of the metering roller 14 extend beyond the ends of
transfer roller 12~ The transfer roller,12 is pre- ,.
ferably,longer than applicator roller 10 which is
in turn longer than form roller 90 to minimize
accumulation of excess ink adjacent ends of form
roller 90.
Form roller 90 is preferably cut to be the same
length as the printing plate to also eliminate accu-
; mulation of excess ink which will tend to build on the
form roll if longer than the printing plate.
Applicator roller 10 has a hard smooth surface
similar to that on metering roller 14.
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Referring to Figure 1 of the drawing, transfer
roller 12 i5 preferably positioned in pressure indented
relation with applicator roller 10~ Applicator roller
10 preferably has a metal tubular core to the ends of
which are secured stub shafts extending outwardly
therefrom and rotatably journaled in bearings (not
shown) carried by the side frames 2 and 4 which include
means to urge applicator roller 10 into pressure indented
relation with form roller 90.
Form roller 90 is preferably driven by a gear 90a
in meshing relation with a gear 90b driven with the
press and has a smooth resilient outer cover.
An ink storage roller 94a, preferably a vibrator
roller, is adapted to remove ink from areas 128" from
ink film 128 on the surface of form roll.er 90 and add
the ink to the depleted areas 128' thereby creating a
more uniform film of ink on the surface of roller 90
movin~ from the nip 120 toward nip A.
A second ink storage roller 94b, similar to
roller 94a, is positioned between plate cylinder P and
dampener 200 to smooth the ink film upon reversal of
form roller 90 as will be more :Eully explained herein-
after.
A material conditioning roller 86, preferably a
vibrator roller, is rotatably supported on shaft 86a
in blocks 36d and is adapted to condition and smooth
the surface of ink film 100 to make the film more re-
ceptive to accepting dampening fluid. Screws 86b and
86c are adapted to urge blocks 86d and roller 86 into
pressure indented relation with form roller 90. The
surface of material conditioning roller 86 is prefer-
ably of similar material to that of form roller 90 such
that the surface has the same affinity for ink as does
the surface of form roller 90.
As the ink film 100 emerges from the nip A be-
tween form roller 9Q and applicator roller 10, it is
slick, and calendared. A slick film of ink is not
76
particularly receptive to dampening fluid since the
surface tension of the molecules of ink ma~ reject the
thin layer dampening fluid to be applied ~y dampener
200. Material conditioning roller 86 will receive a
portion of the film 100 of ink thus splitting the film
100 of ink and producing a film 100' on roller 86 thus
leaving film lOOa with a matte finish having microscopic
indentations. The matte finish on film lOOa will more
readily accept the thin layer of dampening fluid due
to molecular attraction which is now greater than the
surface tension of the dampening fluid forming a film
216.
Material conditioning roller 86 and ink storage
rollers 94a and 94b are preferably constructed of
diameters such that as they rotate, ink will be proper-
ly applied or extracted and redistributed on the sur-
face of form roller 90.
Vibrator rollers 86, 94a and 94b are preferably
provided with drive means (not shown) to oscillate the
rollers in a longitudinal direction. Suitable oscil-
lator drive means is well known to persons skilled in
the printing art and further description is not deemed
necessary. Rotation is provided through friction con-
- tact with adjacent surfaces.
Dampener 200 is diagrammatically illustrated in
` Figure 1 and comprises a hydrophillic transfer roller
210 on shaft 210a and a resilient metering roller 212
on sha~t 212a, mounted in a similar manner to inker 1,
as described in Patent No. 3,937,141. Metering roller
212 meters dampening fluid 214a from pan 214 onto
transfer roller 210 through flooded nip Na. Water film
controlled by pressure between rollers 210 and 212
forms a thin layer of dampening fluid 204 which is
metered through`dampening fluid transfer nip 106a onto
the matte finish of ink film lOOa on the surface of form
roller 90.
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Dampener metering roller 212 is driven by a variable
speed reversible motor 269. As illustrated in Figure 6,
rheostats 84 and 284 are connected to a suitable
- electrical supply and are connected to a pair o~ ganged
double pole, double throw switches 81a and 81b to con-
trol the direction of motors 69 and 269.
The operation and function of the apparatus here-
inbefore described is as follows:
Pressure between the ends of transfer roller 12
and metering roller 14 is adjusted by rotating pressure
adjustment screws 42.
Since long rollers urged together in pressure
relation tend to deflect or bend, pressure adjacent
centers of such rollers i5 less than pressu~re adjacent
15 ends thereof. Pressure longitudinally of rollers 12
and 14 is adjusted by rotating screw 50 and rotating
skew arm 28 about the axis of transfer roller 12 to a
position wherein a desired pressure distribution longi-
tudinally o~ rollers 12 and 14 is obtained.
Adjustment screw 5a is positioned to engage throw-
off links 16 and 18 for establishing a desired pressure
between transfer roller 12 and applicator roller 10.
The surface speeds of rollers 12 and 14 are regu-
la~able by manipulating rheostat ~4 as has been here-
25 inbefore explained.
- Dampener 20 is adjusted in a similar manner as
inker 1.
For the purpose of graphically illustrating the
novel function and results of the process of the mech-
30 anism hereinbefore illustrated and described, a dia-
grammic view of the metering roller 14, the transfer
roller 12, applicator roller 10 and the form roller 90
is shown in Figure 1. Ink and water ~ilms shown are
exaggerated for clarity.
As shown in Figure 1, metering roller 14, when
employed to deliver ink to a printing plate 112, is
preferably a hard surfaced roller having a smooth
i5~ 6
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surface 14c thereon and has the lower side thereof
. immersed in ink 14a in pan 14. The metering roller 14
is preferably rotatably mounted in pressure indented
relation with transfer roller 12, and the pressure be-
tween adjacent roller surfaces is adjusted by screw 42,
as hereinbefore described, so that the surface.of trans-
- fer roller 12 is actually impressed by the surface of
roller 14 at ink metering nip N.
As the surface of roller 14 rotates toward the
ink metering nip N between rollers 12 and 14, a rela-
tively heavy layer 101 of ink is picked up and lifted
on the surface of roller 14. At the point of tangency,
or cusp area at the ink metering nip N, between the
rollers 12 and 14, a bead 102 of ink is pil~ed up form-
ing an excess of ink. The greatness of the excess ofink forming bead 102 is regulated by virtue of the fact
that excess ink will fall back into the pan. The bead
102 of ink becomes a reservoir from which ink is drawn
by transfer roller 12. As rollers 12 and 14 rotate in
pressure indented relation, a ~a~er of ink is sheared
and/or metered between adjacent surfaces of the two
rollers separated by a thin lubricating layer of ink
103. Since transfer roller 12 has a smooth oleophillic
surface thereon, a portion of the film 103 adheres to
the surface of roller 12 to form a film 104, the re-
maining portion 105 on surface 14c being rotated back
or fed back to the pan 14. The film of ink 104 is-dis-
tributed on the surface of roller 12 by reason of the
rotating,. squeezing action between rollers 12 and 14 at
their tangent point at ink metering nip N.
At applicàtion nip T, it will be observed that
applicator roller 10 is impressed into the resilient
surface of the transfer roller 12 and that the film of
ink 104 on transfer roller 12 contacts ink film 107 on
applicator roller 10. The outer surface of film 104
i~ 7~
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and the outer surface of the film of ink 107 on appli-
cator roller 10 are urged together to create a hydraulic
connection between roller 10 and roller 12 as they
rotate in close relationship, but there is no physical
contact between the roller surfaces.
It is an important act to note that the relative
thick film of ink 104 permits rollers 10 and 12 to be
rotated at different surface speeds as will be herein-
after explained.
Preferably, the applicator roller 10 is driven by
form roller 90 which is rotated by gear 90a at the same
surface speed as the printing plate 112, and is rotated
at a greater surface speed than the speed of roller 12.
By regulating the differential surface speed between
transfer roller 12 and applicator roller 10, the amount
of ink transferred to the applicator roller 10 and
applied to form roller 90 may be regulated.
With.in limits, as will.be hereinafter more fully
explained, if the surface speed of transfer roller 12
is increased, the ink film 104 is presented at the ink
transfer nip T at a faster rate then more ink is trans-
ferred to the surface of applicator roller 10, form
roller 90 and to lithographic plate 112, and the oppo-
site is true, if the.surface speed of roller 10 is de-
creased.
The film of ink ~etween adjacent surfaces ofrollers 10 and 12 permits rollers 10 and 12 to be
rotated at different surface speeds in sliding relation-
ship, because the film of ink 104 actually provides
lubrication which permits slippage between adjacent
surfaces of rollers 10 and 12 without frictional
deterioration. ~y reason of the slippage between
rollers 10 and 12, the ink film 106a is metered and
distributed by shearing the ink between adjacent sur-
faces of roller 10 and roller 12 to create ink film 106a.The thickness of ink film 106a is controlled by the
pressure between metering roller 14 and transfer roller
12 and the speed of -transfer roller 12.
-15~
If it is assumed that a film of ink one unit
thick is applied to image areas on the printing plate,
the film 216 on form roller 90 will probably be about
two units thick, half being transferred to the plate
112 and half being retained as film 128' on the form
roller 90. If film 100 is equal to film 216, film 106a
would be three units thick because film 100 and film
107 are of approximately equal thickness since film
128' is combined with film 106a at nip A. Film 104,
assuming no slippage, would be four units thick and
film 106b would be three units thick. Therefore, it
should be apparent that 33% of the ink is removed from
appl~cator roller 10 at nip A while only 25% is re-
moved from txansfer roller 12 at nip T and more ink is
available at nip T to provide lubrication than at nip A.
Less power is required to slip between roller surfaces
at nip T than is required at nip A.
Transfer roller 12 preferably is driven at a sur-
face speed which is within a range of for example,
several hundred feet per minute slower than the surface
speed of applicator roller 10 and form roller 90. For
example, if a printing press has paper traveling there-
through at a surface speed of 1200 feet per minute, the
surfaces of printing plate 112, form roller 90, and
applicator roller 10 will ordinarily have surface
speeds of 1200 feet per minute. The transfer roller 10
would preferably rotate at a surface speed less than
240 feet per minute.
Ink films 106a and 130 will be combined at ink
application nip ~ and will split when sheared as rollers
10 and 90 rotate away from ink application nip A. The
fresh film 100 of ink adheres to the surface of form
roller 90. Ink rejected by form roller 90 forms a feed-
back film 107 of ink which may be slightly irregular
which adheres to the surface of applicator roller 10 and
is conveyed back to the nip T to be re-metered.
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Material conditioning roller 86 splits film 100,
taking on a film 100' to produce a matte finish on ink
film lOOa. Any irregularities or streaks in film 100
will be spread and equalized to form film lOOa of very
uniform thicknes's.
The interface tension between the outer surface of
the less viscous dampening fluid film 204 r by reason
of molecular attraction bet~een the surface of the more
viscous ink film lOOa, causes a portion 216 of the
smooth and regulated film 204 of dampening fluid to be
added to the surface of ink film lOQa, which in turn is
transferred to the plate at the tangent point between
the plate'll2 and form roller 90 at inking nip 120.
The lithographic printing plate 112 has hydro-
phillic, or water likingr non-image areas 121 and
oleophillic, or ink receptive, image areas i22 formed
on the surface thereof~ If printing plate 112 is pro-
vided with raised image areas, the dampener 200 would
not be required to prevent transfer of ink to non-image
areas.
At the nip 120 between form roller 90 and printing
plate 112, the ink film 100 or 216 is split, forming
thin films 12S of ink and'water over oleophillic sur-
faces 122'on the printing plate. The layer 216 of
dampening fluid, if dampening fluid is employed, is
carried on and in the film lOO of ink and is also dis-
tributed to form a thin film 216 o~ dampening fluid
over hydrophillic areas 121 of the printing plate. '
No appreciable amount of dampening fluid remains on
the surface of form roller 90 which is moving away from
the nip 120, but such dampening fluid as does remain
thereon is transferred with the ink film 128 to the ink
film 130a on the ink storage roller 94a where the damp-
ening fluid can be dissipated and/or evaporated to such
an extent as to be of no consequence in the inking
system.
7~
-17-
Ink of film 128 remaining on form roller 90 is
combined with film 130a on ink storage roller 94a and
split and collected on roller 94'a. Ink on roller 94a
is added to depleted areas 128l in film 128 thus re-
ducing the effect of ghosting and areas in film 128 byforming a more uniform film 130 be~ore re-entering
nip A.
The layer of dampening fluid 216 is applied in
substantially the same manner. An excess of dampening
fluid 201 is supplied to bead 202 to form a film 204 of
dampening fluid whi¢h is applied to ink film lOOa on
form roller 90 at nip 106'a. The film 217 of dampening
fluid is returned to bead 202 to be re-metered at nip ~a.
From the foregoing it should be readily apparent
that the improved apparatus for applying ink to printing
systems offers control of metering at ink metering nip N
to provide a film'104 of ink of precisely controlled
thickness by adjusting pressure between trans~er roller
12 and metering'roller 14 and further by controlling
surface speeds of the rollers relative to each othe'r.
The r~te at which the metered film 104 of ink is
,offered'to film 107` of ink on ap~ilicator roller 10 at
ink transfer nip T and also the hydraulic force for
obtaining the desired film thickness is controlle'd.
Figure 4 illustrates a pair of inkers 1 usea in the
standard configuratlon to print on both'sides of a web
W. A printing unit U generally has a pair of printing
couples C each of which comprise an inker unit 1 and
dampener unit 20'0. If it is necessary to print two
colors on one side of web ~, then the right hand couple
C as viewed in Figure 5 must be reversed such that the
web W may be routed for printing on a single side. In
reversing the direction of the form roller ~0, dampen-
ing flu~d will b,e applied over the thin ghosted film
of ink leaving the plate 112 after ink storage roller
~4b evens the ink film to some exten't. A fresh supply
of ink will be added to the dampening fluid and ink on
-18-
form roller 90 as the roller 90 moves th.rough nip A.
Thus, the couple C may be reversed ~y simply reversing
the drive to the couple and motors 69 and 269.
It should be readily apparent that -the films of
ink and dampening fluid illustrated in Figure 1 repre-
sent a standard printing couple moving in the normal or
standard direction and that their films would change in
location from those illustrated should the couple be
reversed to apply dampening fluid first and ink on the
dampening fluid.
Referring to Figure l, our.improved method of
metering ink generally comprises positioning a metering
roller 14 and transfer roller 12 in pressure indented
relation to form an ink metering nip N and rotating the
ink metering roller 14 and the ink:transfer roller 12
such that adjacent surfaces move in the same direction
to form a film 104 of ink on the transfer roller 14.
Ink applicator roller lO is positioned in pressure in-
dented relation with the resilient form roller 90 and
the i.nk transfer roller 14 and is rotated so that the
surface speed thereof is substantially equal to the
surface speed of form roller 90 and printing plate 112.
The ink transfer roller is rotated such that the surface
speed thereof is substantially less than the surface
speed of the ink applicator roller lO, for example less
than 20~ to ensure that ink is not accummulated to
flood the ink transfer nip T.
The resilient transfer roller 12 is rotated at a:
surface speed less than the su~face speed of the hard
applicator roller to maintain that portion of the
resilient surface on the transfer roller 12 which is
moving to the ink transfer nip T in tension~ The
radius of the portion of the resilient surface on the
transfe~ roller 12 entering the ink transfer nip T is
probably less than the radius of the portion exiting
said ink transfer nip T. Thus~ power is not consumed
to unnecessaril~ deform the resilient roller surface,
~6S~l7~
--19--
Transfer roller 12 and applicator roller 10 have a
smaller radius than the form roller such that the width
of the transfer nip T is less than the width of the
application nip A when the transfer roller surface is
indented equal distances into the form roller 90 at the
application nip A and into the transfer roller 12 at the
transfer nip T.
