Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-10-31
1998-06-30
Phasge, Arun S.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204242, 205742, B41F 732, B41N 308, C02F 1461
Patent
active
057728593
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The object of the present invention is a process and a device for treating the wetting liquid in printing presses, particularly for offset printing presses.
As we know, the efficiency of printing presses, especially offset printing presses, is related mainly to the speed at which the ink used for the printing dries.
The task of increasing the ink drying speed is thus a particularly acute problem in this area.
To carry out printing by the so-called "offset" method, the cylinder that holds the plate is inked by the inking cylinder and does the printing on a rubber cylinder which, in turn, transfers the printing to the sheet held by the printing cylinder.
The inking cylinder, in addition to being coated with ink, is "bathed" with a liquid that is usually composed simply of water, or a mixture of water and alcohol.
In the kind of printing that uses water as a wetting liquid, there-is the problem of low drying speed, which makes it impossible to reach high hourly production rates. In addition, the use of water causes smearing of the plate, resulting in poor-quality printing.
The kind of printing that uses water plus alcohol as a wetting liquid can achieve considerably better production rates in terms of both quality and quantity since alcohol, by reducing the surface tension of the water, makes it possible to distribute a finer layer of liquid and ink over the plate and thus ensures fewer smearing problems and a faster drying speed, facilitated by the volatility of the alcohol.
Along with these advantages, the use of water and alcohol as a wetting liquid poses some problems. As a matter of fact, the alcohol dilutes the ink, reducing the contrast effects in printing.
Moreover, an ink blurring effect that considerably degrades the quality of the printing is very commonly encountered.
Another problem is posed by the need for the machines with water-alcohol washing to have devices for cooling the alcohol in order to keep it from evaporating excessively.
An additional problem is the reduced tolerance of the personnel operating these machines for the alcohol vapors.
SUMMARY OF THE INVENTION
The primary task of the present invention is to solve the problems outlined above by devising a process and a device for treating printing-press wetting liquid that make it possible to eliminate the use of alcohol in the wetting liquid without impairing, and in fact directly increasing, the drying speed and thus the efficiency of these machines.
Within the framework of this task, one goal of the invention is to develop a process that makes it possible to achieve a printing quality that is better than that which can be obtained using water and alcohol as a wetting liquid.
Another goal of the invention is to propose a process that avoids the smearing problems which arise from using water alone as a wetting liquid.
A further goal of the invention is to propose a process that is simple to implement and that does not create problems of work environment contamination.
This task, as well as those and others that are presented in greater detail below, are accomplished by means of a process for treating the wetting liquid in printing presses, particularly offset printing presses, wherein said process consists of subjecting the wetting liquid, which is based on water and has preset levels of acidity and electrical conductivity, to electrolysis.
The process of the invention can be easily implemented using a device, wherein said device consists of a treatment tank, means of supplying this treatment tank with a wetting liquid that is based on water and has preset electric power supply that is connected to an anode and a cathode that are immersed in the wetting liquid contained in this treatment tank for electrolysis of the wetting liquid placed in this treatment tank.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the invention are presented in greater detail in the description in the form of a preferred, but not exclusive, embodiment of the process, as well as of the device of the
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patent: 5055170 (1991-10-01), Saito
patent: 5578193 (1996-11-01), Aoki et al.
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