Chambered doctor blade

A chambered doctor blade utilizes parallel, axially extending spaced working and sealing doctor blades, together with spaced end plates to define an ink chamber. Free axial ends of the working doctor blade extend beyond the ends of the end plates and remove built-up ink beads. This removed ink flows down the surface of the inwardly inclined end plates.

FIELD OF THE INVENTION 
The present invention is directed generally to a chambered doctor blade. 
More particularly, the present invention is directed to a chambered doctor 
blade for an inking system. Most specifically, the present invention is 
directed to a chambered doctor blade for an inking system of a rotary 
printing press. The chambered doctor blade is utilized with a screened 
surface ink roller to transfer ink to the surface of the screen roller and 
thence to one or more printing plates. The ink chamber is defined by a 
working doctor blade, a sealing doctor blade and two spaced end plates. 
The working doctor blade extends axially beyond the end plates and 
prevents beads of ink from forming on the screen roller. 
DESCRIPTION OF THE PRIOR ART 
Chambered doctor blade assemblies are generally known in the art and are 
typically used with an ink roller, such as a screen surface ink roller, to 
supply printing ink to a plate cylinder. The chambered doctor blade has an 
ink chamber which is formed by generally parallel, spaced working and 
sealing doctor blade that extend in the axial direction of the ink roller, 
and by axially spaced end plates or parting plates which are generally 
perpendicular to the two doctor blades. Ink supplied to the ink chamber of 
the chambered doctor blade is applied to the screened surface ink roller 
as it passes through the ink chamber. Excess ink is scraped off the ink 
roller by the doctor blade. 
In the prior art devices a bead of ink has been apt to form in front of the 
end or sealing doctor blade and this bead of ink has been carried forward, 
in the direction of rotation of the ink roller past the working doctor 
blade. Such a bead of ink can cause blots or other printing errors in the 
printed product since the beads of ink are transferred from the screen 
roller along to the printing plates. This is particularly significant 
problem when different ink colors are being used next to each other on the 
same screen roller. 
One prior attempt to correct this problem of the formation of beads of ink 
at the ends of the sealing doctor blade has been the forming of grooves or 
recesses on the periphery of the inking roller. The ink beads that 
accumulate are pushed into these grooves. However, the disadvantage of 
this prior solution is that the grooved ink roller cannot be used in 
various printing devices, such as panorama printing devices. 
In German patent No. DE PS 39 09 878 there is shown a chambered doctor 
blade in which the working doctor blade is longer than the end or sealing 
doctor blade. This structure has lessened the formation of beads of ink on 
the screen roller. A limitation of this prior device is that ink 
accumulates in a wedge formed by the drain plate and the side wall at both 
ends of the working doctor blade. Since the printing ink is apt to be 
thixotropic, it hardens and hinders the flow of ink behind it. In 
addition, it is difficult to clean this prior art device. 
It will thus be apparent that a need exists for a chambered doctor blade 
which overcomes the limitations of the prior art devices. The chambered 
doctor blade in accordance with the present invention provides such a 
device and is a significant improvement over the prior art devices. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a chambered doctor 
blade. 
Another object of the present invention is to provide a chambered doctor 
blade for an inking system. 
A further object of the present invention is to provide a chambered doctor 
blade for an inking system of a rotary printing press. 
Still another object of the present invention is to provide a chambered 
doctor blade which prevents the formation of ink beads. 
Yet a further object of the present invention is to provide a chambered 
doctor blade which prevents transfer of ink beads to the ink roller from 
the screen roller. 
Even still another object of the present invention is to provide a 
chambered doctor blade which prevents blots and imperfections in the 
printed image. 
As will be discussed in greater detail in the description o the preferred 
embodiment which is set forth subsequently, the chambered doctor blade in 
accordance with the present invention utilizes spaced working and end 
doctor blades in conjunction with spaced end plates. The working doctor 
blade has free ends that extend in the axial direction of the screen 
roller beyond the end or separating plates. The lower ends of the 
separating plates are also inclined inwardly into the ink chamber of the 
chambered doctor blade and have drain slits or slots. 
The chambered doctor blade of the present invention is particularly 
effective in removing or wiping the laterally spaced ink beads off the 
surface of the screen roller. This is due to the extension of the ends of 
the working doctor blade in an unsupported manner beyond the ends of the 
end doctor blade. The beads of ink which are prevented from forming by the 
working doctor blade run down the side of the angled end or separating 
plates and return to the ink reservoir without splashing. The ink does not 
accumulate in corners and does not harden in hard to reach areas so that 
cleaning is more readily accomplished. 
The separating or end plates of the chambered doctor blade of the present 
invention are provided with slots in their lower portions. These slots 
assure that excess ink pressure in the ink chamber is kept within the 
specified rang and thus the ink does not become overly pressurized in 
areas where this is not desired. 
The chambered doctor blade in accordance with the present invention 
overcomes the limitations of the prior art devices and provides an 
assembly that is a substantial advance in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1 and 2, there may be seen a preferred embodiment of 
a chambered doctor blade in accordance with the present invention. The 
chambered doctor blade has a base body 1, which can be of one piece, or 
for the purpose of facilitating cleaning, can be of two piece 
construction. A two piece base body 1, not specifically shown, would be 
divided in the axial direction of a screen roller 3 with which the 
chambered doctor blade cooperates. 
As may be seen in FIG. 2, a connector 2 is attached to the base body 1 and 
is used to supply ink to the chambered doctor blade from a suitable ink 
fountain, not shown. Ink flows through ink supply connector 2 in the 
direction indicated by arrow B in FIG. 2. 
The base body 1 extends in the axial direction of, and parallel to the 
screen roller 3 which is rotatable in the direction indicated by arrow C 
in FIG. 2. Upper surfaces 4 and 6 of the base body 1 are inclined and 
carry retaining strips 8 and 9. These retaining strips 8 and 9 are secured 
to the inclined faces 4 and 5 by suitable screws 7. A working doctor blade 
11 is secured between inclined surface 6 and retaining strip 8 while a 
sealing or end doctor blade 12 is secured between inclined surface 4 and 
retaining strip 9. An ink receiving chamber 13 is formed in the base body 
1 of the chambered doctor blade by the cooperation of the working doctor 
blade 11, the sealing or end doctor blade 12 and spaced separating or end 
plates 14 and 16. 
Referring now primarily to FIG. 1, it may be seen that the separating or 
end plate 14 has a lower portion which is angled inwardly into the base 
body 1 at an angle "d" with respect to the perpendicular, as indicated at 
17. The inclination of the lower ends of the end plates 17 and 16 are 
axially inwardly toward the center of the ink chamber 13. Each of the 
separating or end plates 14 and 16 is provided with a drain slit 15 in its 
angled portion. These drain slits 15 are sized so that the ink pressure in 
the ink chamber 13 will not increase above a certain level. Any ink 
passing out through the ink slits 15 will drain back into the ink fountain 
which cooperates with the chambered doctor blade. Suitable screws 18 are 
used to secure the end or separating plates 14 and 16 to the base body 1 
of the chambered doctor blade. 
Referring again to FIG. 1, it may be seen that the working doctor blade 11 
extends axially beyond the ends of the base body 1. The extent of this 
extension is indicated at "e". Thus the working doctor blade 11 has a free 
length which is greater than that of the end doctor blade by an amount of 
two times "e". The retaining strip 8 has a length corresponding to the 
length of the working doctor blade 11. 
Returning to FIG. 2, ink flows through the ink supply connector 2 into the 
ink chamber 13 in the base body 1. The ink chamber 13 can be partially 
divided by a divider strip 19 which has a free end that extends upwardly 
in the ink chamber 13 toward the screen roller 3. This divider strip 19 
assists in reducing or preventing the formation of vortices in the ink in 
the ink chamber 13 as the surface of the screen roller 3 passes through 
the upper part of the ink chamber 13. 
As the screen roller 3 rotates in the direction indicated by arrow C, ink 
is carried out of the ink chamber 13 by the screened surface of the roller 
3 and is scraped off by the working doctor blade 11. Ink beads that form 
exteriorly of the separating or end plates 14 and 16 are captured by the 
outer ends of the working doctor blade 11 which extend axially beyond the 
end plates 1 and 16 by the distance 2e. The ink collected from these ink 
beads runs down the inwardly tapering end plates 14 and 16 and falls into 
the ink funnel (not shown) which cooperates with the chambered doctor 
blade. The removal of these ink beads prevents them from causing a 
reduction in the quality of the printed product since the ink splashes or 
blots that have occurred, particularly during printing operations using 
multiple colors on one screen roller, are eliminated. 
While a preferred embodiment of a chambered doctor blade in accordance with 
the present invention has been set forth fully and completely hereinabove, 
it will be apparent to one of skill in the art that a number of changes 
in, for example, the size of the screen roller, the length of the 
chambered doctor blade, the type of ink used and the like may be made 
without departing from the true spirit and scope of the subject invention 
which is accordingly to be limited only by the following claims.