Printing – Inkers – Fountains
Reexamination Certificate
2002-08-05
2004-10-05
Eickholt, Eugene H. (Department: 2854)
Printing
Inkers
Fountains
C101S350100
Reexamination Certificate
active
06799509
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink-furnishing apparatus, which furnishes ink stored in an ink fountain to an ink furnishing roller that is brought into contact with a plate cylinder, and an offset printing method using the same ink-furnishing apparatus.
FIG. 20
shows a general construction of a prior art ink-furnishing apparatus for an offset press. Ink stored in an ink reservoir is led to an ink transfer roller
904
side by rotations of an ink furnishing roller
903
. By causing the ink transfer roller
904
to alternately be brought into contact with the ink furnishing roller
903
and the top roller of a group of ink mixing rollers
905
, an ink membrane formed on the surface of the ink furnishing roller
903
is transferred onto respective rollers of the group of ink mixing rollers
905
one after another, and is fed onto the surface of a plate cylinder
901
via an ink application roller
902
. Further, an aqueous membrane is formed on the surface of a non-imaged portion of the plate cylinder
901
by a dampening device
506
, wherein no ink is transferred onto the non-imaged portions.
Since the above-described offset press ink is intermittently fed by swinging of the ink transfer roller, it is necessary that a uniform membrane of ink is formed while gradually transferring ink by a number of rollers of the group of ink mixing rollers, and the uniform membrane of ink is fed onto the surface of the plate cylinder. Therefore, the apparatus is complicated and large-sized, resulting in maintenance difficulty and an increase in production costs.
In order to solve the above-described problem incidental to intermittent furnishing of ink, offset presses disclosed by Japanese Unexamined Patent Application Publication Nos. 58-45955, 58-65663, and 58-84771 have been publicly known. In either of these offset presses, continuous furnishing of ink is employed, thereby removing a group of ink mixing rollers, wherein the apparatus is simplified and small-sized, maintenance thereof is facilitated, and production costs thereof are decreased.
However, since no group of ink mixing rollers is provided, an ink reservoir is located in the vicinity of a dampening device, wherein ink is remarkably emulsified to worsen the printing density, that is, so-called “emulsification” occurs. Also, a dampening water is likely to be mixed in the ink reservoir. In the worst case, roller stripping occurs, for which the ink is not permitted to be applied onto the ink furnishing roller better, and there occurs a possibility for ink not to be measured and fed. In order to avoid this roller stripping, accurate adjustment of the dampening water device is indispensable. However, the stabilized area thereof is very narrow, and there may be a case where the adjustment is disabled, depending upon specified combinations of ink to be used and the dampening water.
An offset press disclosed by Japanese Unexamined Patent Application Publication No. 55-7453 has been publicly known as such a type that can solve the above-described problems resulting from the dampening water. The offset press does not require the furnishing of the dampening water by employing emulsion ink (which is a colloid in which ink and an aqueous constituent are blended) as ink, wherein it is possible to prevent a roller stripping phenomenon from occurring, and no dampening water device is required. Further, it is possible to simplify and make the apparatus small, and to simplify maintenance and to decrease production costs.
In offset printing for which emulsion ink is used, it is necessary to break emulsion in order to divide the emulsion ink into ink constituents and aqueous constituents at the stage where the emulsion ink is transferred onto the ink application roller that is in contact with the plate cylinder.
Conventionally, some types have been publicly known as unit for breaking emulsion. One of the types (Japanese Unexamined Patent Application Publication No. 53-36308) is such that emulsion of emulsion ink is broken by actions of cooling unit and shearing force applying unit, which are provided at an ink application roller in an ink-furnishing apparatus, and another one thereof (Japanese Unexamined Patent Application No. 55-7453) is such that emulsion is broken by cooling and with an intensive shearing force brought about by an ink application roller in an ink-furnishing apparatus and an adjusting roller whose surface is hydrophilic.
Where an offset press is used, in which ink is continuously fed and emulsion ink is used, since the ink furnishing roller continuously rotates and the rotation speed thereof is comparatively fast, a rod-like ink clump (see
FIG. 21
, this is referred to as an “ink roll”) may be formed in parallel to the axial direction of the ink furnishing roller in an ink reservoir. If an ink roll is generated, fluidity and agitation of ink in the ink reservoir is hindered, ink existing in a comparatively surface layer of the ink roll is only consumed without being replaced by ink inside the ink roll. Therefore, in the case of a two-constituent blended liquid of ink and an aqueous constituent such as emulsion ink, balance between the ink and the aqueous constituent of emulsion ink, which is measured and fed to the ink application roller, is varied to adversely influence the printing performance (in particular, smirching resistance).
In order to break down the above-described emulsion, it is necessary that emulsion ink is cooled down and a shearing force is applied thereto. However, ink becomes remarkably hard due to a lowering in ink temperature (generally called “ink condensing”), wherein it becomes difficult to transfer ink, thereby causing such a problem of printing drawbacks such as shortage in density, whiteout, etc. Therefore, it is not desired that cooling is preferentially used as unit for breaking down emulsion,
Also, for application of a shearing force, ink has been subjected to slipping between rollers. However, since stability of emulsion is increased due to an increase in ink temperature resulting from friction by slipping between rollers, it becomes difficult for the emulsion to be broken down. Therefore, the relationship between a slipping amount and an effect to break down emulsion is not proportionate, wherein the effect of breaking down emulsion is limited even if the slipping amount is increased, and a sufficient effect of emulsion breakage cannot be obtained. Furthermore, the cohesion power of ink is lowered in line with an increase in ink temperature, wherein such a problem arises in that printing drawbacks such as ink fill-in and scumming, etc., occur.
Although an increase in ink temperature due to slipping between the above-described rollers can be suppressed by concurrently employing the above-described cooling unit, it becomes necessary to prepare cooling unit whose cooling output is large since the heat generation amount due to slipping is large.
In addition, the method for slipping between rollers results in remarkable wearing of the rollers. Further, such a problem arises in that, if an offset press is operated with no ink provided by mistake, the roller will be instantaneously damaged.
SUMMARY OF THE INVENTION
The present invention was developed in view of the above-described situations. It is therefore a first object of the present invention to provide an ink-furnishing apparatus that is able to suppress or prevent ink rolls from occurring in an ink reservoir, secure satisfactory fluidity and agitation of ink in the ink reservoir, and carry out smooth measuring of ink and furnishing thereof to an ink furnishing roller, and an offset printing method using the same.
The present invention was developed in view of the above-described and other problems, and it is therefore a second object of the present invention to provide an ink-furnishing apparatus and an offset printing method, which are able to apply an effective shearing force in order to break down emulsion, can be easily controlled during operations, where an increase in ink temperature and wearing of rollers are
Eickholt Eugene H.
Fuji Photo Film Co. , Ltd.
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