Device for removing ink applied to non-printing parts on waterless planographic printing plate and planographic printing machine and method using the same

Printing ink attached to non-printing parts on a waterless planographic printing plate can be removed by bringing a rotary roller having a circumferential adhesive surface coated with viscous ink having higher viscosity than that of the printing ink applied to the printing plate into contact with the printing plate in rotation. The viscous ink applied to the rotary roller is higher in viscosity than the printing ink applied to the printing plate for printing, so that the ink transferred from the printing plate to the rotary roller can be steadily captured thus the unnecessary printing ink attached to the non-printing parts on the printing plate is completely removed. Consequently, clear and sharp printed matter with print images excellently reproduced can be obtained at a low cost.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates to an ink removing device applicable to a printing 
machine using a waterless planographic printing plate, which has an 
excellent function of removing ink applied to non-printing parts on the 
waterless to planographic printing plate, so that clear and sharp printed 
matter with print images excellently reproduced can be obtained at a low 
cost. This invention further relates to a planographic printing machine 
provided with the aforesaid ink removing device and a planographic 
printing method by use of the planographic printing machine. 
Description of the Prior Art 
Of various sorts of printing methods which have been put to practical use, 
a waterless planographic printing method is easily practicable, and 
therefore, it is now widespread. The waterless planographic printing 
method will be described in rough outline, referring to FIG. 5 
schematically illustrating a planographic offset printing machine. Ink in 
an ink fountain 50 is fed to a row of distributing rollers 52 through a 
ductor roller 51. This roller set 52 is generally composed of more than 
twenty distributing rollers, so that the ink applied and transferred to 
the distributing rollers in succession is spread to be made thinner to 
about several .mu. thickness. The ink is further fed from a plate cylinder 
54 to a blanket cylinder 55, consequently to be transferred to a sheet of 
paper 57 interposed between the blanket cylinder 55 and an impression 
cylinder 56. 
Incidentally, non-printing parts defined on the planographic printing plate 
applied for the waterless planographic printing method are formed of 
ink-repellent silicone rubber, whereas the silicone rubber is weak in 
ink-repellency compared with a common planographic printing plate using 
damping water and apt to be soiled. Accordingly, the waterless 
planographic printing inevitably has need for use of viscous ink which is 
required to be uniformly kneaded to be made thin by being transferred 
among lots of distributing rollers. Consequently, the printing machine 
turns out to be complicated and cannot be produced and maintained at a low 
cost. 
Besides, the temperature of the distributing rollers and the printing plate 
in service happens to rise due to the heat which is increased when the ink 
is repetitiously kneaded among the distributing rollers and generated 
mechanically when rotating the printing cylinders. As a result, the 
viscosity of the ink disadvantageously becomes lower than the prescribed 
viscosity of the ink. When the viscosity of the ink is decreased, the ink 
tends to linger in spots on the non-printing parts of the printing plate, 
resulting in ink spot stains on the printed matter resultantly obtained. 
Furthermore, in the waterless planographic printing using no damping water, 
the increase of heat generated on the printing plate when rotating the 
plate cylinder cannot be suppressed because there is no cooling means such 
as damping water. To overcome such shortcoming of the waterless 
planographic printing, attempts are being made to flow cooling water 
through the rollers or blow the plate cylinder with cooling air. 
Consequently, the printing system calls for such an expensive and 
complicated cooling mechanism, resulting in increased production and 
maintenance costs of the printing system. 
OBJECT OF THE INVENTION 
To eliminate the drawbacks suffered by conventional planographic printing 
methods as described above, this invention has an object to provide an ink 
removing device applicable to a waterless planographic printing machine 
for removing printing ink attached to non-printing parts of a waterless 
planographic printing plate, which can make a printing system simple in 
construction and low in price and produce clear and sharp printed matter 
with print images excellently reproduced at a low cost by use of ink which 
is lower in viscosity than that used for a conventional waterless 
planographic printing plate. 
Another object of the present invention is to provide a waterless 
planographic printing machine using the aforementioned ink removing device 
for removing the ink attached to the non-printing parts of the waterless 
planographic printing plate. 
Still another object of this invention is to provide a waterless 
planographic printing method using the aforesaid waterless planographic 
printing machine. 
SUMMARY OF THE INVENTION 
To attain the objects described above according to the present invention, 
there is provided a device for removing printing ink applied to 
non-printing parts of a waterless planographic printing plate, which 
comprises a rotary roller having a circumferential adhesive surface, which 
comes into contact with the waterless planographic printing plate so as to 
capture printing ink attached to the non-printing parts of the waterless 
planographic printing plate. 
Onto the circumferential adhesive surface of the rotary roller, there may 
be applied viscous ink having higher viscosity than that of the printing 
ink attached to the non-printing parts of the waterless planographic 
printing plate. 
The rotary roller may be made of synthetic rubber containing lipophilic 
ingredients. 
A waterless planographic printing machine according to the invention 
incorporates the aforementioned ink removing device, so that the rotary 
roller comes into contact with the waterless planographic printing plate 
so as to capture the printing ink attached to non-printing parts of the 
waterless planographic printing plate while transferring the printing ink 
applied to the printing plate on a plate cylinder to a blanket cylinder. 
In a method according to this invention, the printing ink attached to the 
non-printing parts of the printing plate is removed while transferring the 
printing ink applied to the printing plate on a plate cylinder to a 
blanket cylinder. 
Other and further objects of this invention will become obvious upon an 
understanding of the illustrative embodiments about to be described or 
will be indicated in the appended claims, and various advantages not 
referred to herein will occur to one skilled in the art upon employment of 
the invention in practice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 through FIG. 4, one embodiment of an ink removing 
device according to this invention, which is adapted for removing printing 
ink attached to non-printing parts of a waterless planographic printing 
plate will be described hereinafter along with examples of a planographic 
printing machine provided with the ink removing device and a planographic 
printing method using the ink removing device according to this invention. 
The ink removing device 1 comprises a roller 2 as shown in FIG. 2. The 
roller 2 is supported by a rotary shaft 5 which is rotatable about a 
normal direction when viewed from one end face 4. The roller 2 is made of 
synthetic rubber such as nitrile rubber, polychloroprene rubber and 
urethane rubber, which are used for rollers in a common planographic 
printing machine. The roller 2 has a circumferential adhesive surface 3 so 
as to capture printing ink attached to non-printing parts of a waterless 
planographic printing plate when coming into contact with the non-printing 
parts. 
The adhesive surface 3 of the roller 2 may be formed of viscous ink having 
a higher viscosity than that of the printing ink which is applied to the 
printing plate for printing and should be removed only from the 
non-printing parts of the printing plate. The degree of viscosity of the 
viscous ink is determined in accordance with the printing ink applied to 
the waterless planographic printing plate for printing, but preferably to 
more than 12 in tack value (inkometer value at 30.degree. C. at 400 rpm). 
The viscous ink may be colored or colorless, but it may be preferably of a 
non-drying type to stably maintain its adhesive property for a long time. 
The roller 2 having such characteristics may be produced by applying 
viscous ink to a nip portion between a rocking roller 12 and a kneading 
roller 13, and rotating the rollers 12 and 13 to make the viscous ink 
thinner on the order of 5 .mu.m to 10 .mu.m, thus transferring a thin 
film-like ink layer to the circumferential surface 3 of the roller 2, as 
shown in FIG. 2 by way of example. 
As another example of the roller 2 with the circumferential adhesive 
surface 3, the roller may be formed by adding lipophilic ingredients to 
synthetic rubber such as nitrile rubber, polychloroprene rubber and 
urethane rubber. As the lipophilic ingredients, there are vegetable oil 
such as flaxseed oil, china wood oil, soybean oil and castor oil which are 
used as carrying liquid contained in printing ink, processed oil obtained 
from the vegetable oil, machine oil, spindle oil, mineral oil such as 
light oil, and rosin, by way of example. The lipophilic content is 
preferably determined to be 50 to 80% by weight relative to the synthetic 
rubber. It is desirable to form the roller 2, containing the lipophilic 
ingredients, with a hardness of 30 or less, preferably 20 or less 
(Penetration provided under JIS K2207). 
The roller 2 having such characteristics can be produced by mixing 
lipophilic ingredients with synthetic rubber by a common molding method. 
The ink removing device according to this invention is applicable to not 
only waterless planographic printing, but also any conventional 
planographic printing using damping water. 
A planographic printing machine 20 according to this invention includes the 
aforementioned ink removing device 1 as shown in FIG. 1. In the ink 
removing device 1 incorporated in the printing machine, the roller 2 comes 
into contact with the printing plate mounted on a plate cylinder 25 so as 
to capture ink attached to non-printing parts of the printing plate while 
continuously transferring the printing ink applied from the printing plate 
on the plate cylinder 25 to a blanket cylinder 26. The ink removing device 
1 may be driven by the rotation of the plate cylinder 25, or spontaneously 
operate in conjunction with the plate cylinder 25. 
The size of the ink removing device 1 incorporated in the planographic 
printing machine 20 depends on the dimension of an entire printing system 
and other peripheral components, but may in general be determined so that 
the diameter of the ink removing device 1 becomes 0.1 to 0.4 times as 
large as that of the plate cylinder 25. 
Next, the planographic printing method adopting the planographic printing 
machine 20 noted above will be described. The planographic printing method 
is applicable to not only waterless planographic printing, but also common 
planographic printing using damping water. An example in which the 
printing method of this invention is applied to the waterless planographic 
printing will be described herein. 
Planographic printing ink 30 in an ink fountain 21 is transferred to 
distributing rollers 23 through lifter rollers 22. The waterless 
planographic printing ink 30 is lower in viscosity than that applied for 
conventional planographic printing. As one example, it is desirable to use 
printing ink of 4.0 to 6.0 in tack value. 
The waterless planographic printing ink is transferred among rollers 
including the distributing rollers 23, thereby turning out to be thinner 
in thickness. The ink is easily made thin because of its low viscosity, so 
that the number of distributing rollers 23 can be decreased in comparison 
with a conventional printing machine, as shown in FIG. 1. Since FIG. 1 
shows conceptually the printing machine, the number of rollers illustrated 
is not always equal to that in an actual machine put to practical use, but 
the number of rollers in the printing machine according to this invention 
can be reduced to half or less of that in the conventional planographic 
printing machine. 
The printing ink 30 thus thinned uniformly is continuously transferred to 
the circumferential surface of the plate cylinder 25 which rotates in the 
direction shown by the arrow in FIG. 1, through form-inking rollers 24. At 
this time, the printing plate 35 has ink spots (ink stains) formed on the 
non-printing parts 36 because of the low viscosity of the printing ink 30, 
as shown in FIG. 3. Then, the circumferential surface 3 of the roller 2 in 
the ink removing device 1 comes into contact with the plate cylinder 25 in 
rotation on the route from the hindmost form-inking roller 24 to the 
blanket cylinder 26. At this time, the spots of ink 30 on the non-printing 
parts 36 are transferred to the circumferential surface 3 and captured by 
the roller 2. As a result, unnecessary ink attached to the non-printing 
parts 36 is wiped up and removed from the printing plate 35 mounted on the 
plate cylinder 25 while passing through the roller 2, but the necessary 
printing ink attached to the printing parts 37 is left. 
The printing part 37 is receptive to ink and depressed like a dent formed 
in the printing plate, so that the undesired ink spot attached to the 
non-printing part 36 rising on the printing plate becomes higher than that 
attached to the depressed printing part 37. Thus, when bringing the 
circumferential surface 3 of the roller 2 into contact with the printing 
plate 35, only the undesired ink attached to the non-printing parts 36 is 
removed, even though the roller 2 comes in uniform contact with the whole 
surface of the printing plate without distinction of the printing part 37 
and non-printing part 36. 
As a result, the printing ink 30 left on the printing plate 35 is 
transferred to the blanket cylinder 26 and further to a web of paper 40 
put between the blanket cylinder 26 and an impression cylinder 27. Since 
no ink is left on the non-printing parts 36, images are clearly reproduced 
on the web of paper, and resultantly, high quality printed matter can be 
obtained. 
Next, the present invention will be made more clear upon referring to the 
following description about experimental examples obtained as the result 
of experiments performed on the method according to the invention, whereas 
the present invention is by no means limited only to the conditions under 
the experiments were conducted. 
EXPERIMENTAL EXAMPLE 1 
An ink removing device as shown in FIG. 1 was constructed by using a roller 
(6 cm diameter and 50 cm length) having its circumferential surface coated 
with viscous ink (Trade name "TA-MEDIUM" made by Taniguchi Ink Mfg. Co. 
Ltd.) having tack value of 10. 
The aforesaid ink removing device was assembled in a full automatic 
small-sized waterless planographic printing machine (Trade name "SF-A3 
MODEL" Printing Machine made by Shinohara Engineering Co. Ltd.), so that 
the roller is rotated with rotation of a plate cylinder in the state as 
shown in FIG. 1, thus forming a planographic printing machine. 
The planographic printing machine described above was further provided with 
a waterless printing plate (Trade name "WATERLESS PLATE" made by Toray 
Industries, Inc.) and a waterless paper printing plate (Trade name 
"PR-I-Type" made by Corporative Association "PRINTECHNO"). Printing was 
performed with waterless planographic printing ink (Trade name 
"TA-GERANIUM" made by Taniguchi Ink Mfg. Co. Ltd.) having tack value of 5 
at 3.degree. C. 
As a result, clear and sharp printed matter having no ink stain could be 
obtained, on which desired images are excellently reproduced, even after 
printing of 5000 sheets. 
EXPERIMENTAL EXAMPLE 2 
Printing of 5000 sheets was made by using the printing machine prepared in 
the foregoing Experimental Example 1 and planographic printing ink (Trade 
name "TECHNOCOLOUR WATERLESS GERANIUM" made by Taniguchi Ink Mfg. Co. 
Ltd.) having tack value of 5, which is commonly used with damping water. 
As a result, clear and sharp printed matter free from any ink stain could 
be obtained with excellent reproducibility, similarly to Experimental 
Example 1. 
EXPERIMENTAL EXAMPLE 3 
The ink removing device prepared in Experimental Example 1 was used for 
this experiment, except that the roller containing 60% mineral oil by 
weight was used. 
This ink removing device was assembled in the printing machine used in 
Example 1 so as to make printing of 5000 sheets under the same conditions 
as in Example 1. As a result, clear and sharp printed matter having no ink 
stain could be obtained with excellent reproducibility, similarly to 
Experimental Example 1. 
COMATIVE EXAMPLE 1 
Printing was performed with waterless planographic printing ink, which has 
been on the market (Trade name "TECHNOCOLOUR WATERLESS GERANIUM" made by 
Taniguchi Ink Mfg. Co. Ltd.) and diluted to 5 in tack value, by using a 
conventional printing machine (Trade name "HAMADASTAR" made by Hamada 
Press Manufacturing Co.) incorporating a waterless printing plate (Trade 
name "WATERLESS PLATE" made by Toray Industries, Inc.) and a waterless 
printing paper plate (Trade name "PR-I-Type" made by Corporative 
Association "PRINTECHNO") as shown in FIG. 5 under the same conditions as 
Experimental Example 1 described above. 
As a result, printed matter obtained even in the first printing embraced 
scumming stains. 
As is apparent from the foregoing description, by using the ink removing 
device according to the present invention, printing ink attached to the 
non-printing parts defined on the waterless planographic printing plate 
can be completely removed. That is, according to the invention, printing 
can be well performed no matter how much printing ink is attached to the 
non-printing parts on the printing plate. 
Accordingly, the planographic printing machine incorporating the aforesaid 
ink removing device makes it possible to use even printing ink of low 
viscosity (small tack value), which is apt to adhere to non-printing parts 
on a printing plate and has been so far of no practical utility for 
printing. Consequently, the number of distributing rollers can be 
decreased, and a cooling device becomes unnecessary for the printing 
machine. Thus, the printing machine can be made simple in spite of the 
fact that the ink removing device of the invention is added thereto, as a 
result of which the costs of production and maintenance of the printing 
machine can drastically be reduced. 
Furthermore, the planographic printing method according to the present 
invention enjoys an advantage in that clear and sharp printed matter being 
excellent in reproducibility can be obtained in either waterless 
planographic printing or planographic printing using damping water. 
As can be readily appreciated, it is possible to deviate from the above 
embodiments of the present invention and, as will be readily understood by 
those skilled in this art, the invention is capable of many modifications 
and improvements within the scope and spirit thereof. Accordingly, it will 
be understood that the invention is not to be limited by these specific 
embodiments, but only by the scope and spirit of the appended claims.