The invention has to do with a mechanism for setting the density of ink dots on a print substrate according to the first portion of Claim 1.
Rotary printing machines possess at least one ink transfer roller which conveys towards a print substrate ink from an ink reservoir, which as a rule is an ink pan or a coater chamber supplied with ink from an ink tank. With flexoprinting machines of the more recent type of construction both the anilox roller, which conveys ink from the ink chamber coater to the press plate, as well as the press plate itself that takes up ink from the anilox roller and further conveys it to the print substrate, are ink transfer rollers as defined in the invention at hand. With rotogravure only the gravure cylinder is to be characterized as an ink transfer roller.
The formulation “towards” in the first portion of Claim 1 is to be understood in reference to the transfer direction of the ink by means of the respective rollers.
With the printing process on rotary printing machines it is often desired to alter the intensity of the hue to be applied to the print substrate. The intensity effect is caused by means of the density of the ink.
Various options exist to influence the intensity of a hue on the print substrate. The ink density on the print substrate on the one hand is influenced by the quantity of printing ink applied. The quantity of the ink applied is thereby often influenced in that the color separation is varied between the individual rollers involved in the printing process. For this purpose the viscosity of the printing ink is influenced. With the varying quantity of ink transferred by means of the rollers, however, the layer densities applied to the print substrate can be different.
As an alternative thereto the ink density on the print substrate can also be set by means of the ratio of color pigments to solution in the printing ink. With such a familiar type of method the ink density first is measured with an appropriate measuring device, somewhat like a densitomer, in order to set the ink density on the print substrate. In order now to be able to vary the ink density, the ratio of ink particles to solutions in the ink supply tank must be modified. The ratio of ink particles to solutions in the ink supply tank is modified by refilling concentrated printing ink and/or solution. This is very laborious because this process often becomes necessary several times, often leads to inconclusive results and all the old ink must be uniformly thoroughly mixed in with the ink components added later in order to obtain a stable print image. For this reason the printing process often even has to be interrupted.
For this reason the task for the invention at hand consists in proposing a method and a mechanism that provide the option of being able to influence the ink density on the print substrate without refilling printing ink and/or solution into the ink tank.
The problem is resolved by means of the distinguishing characteristics of Claim 1.
Preferably bellows are planned for supporting the evaporation of the solution. They blow a suitable gas, for example air, onto one of the ink transfer rollers so there is an exchange of ambient air enriched with solutions.
Particularly advantageous is the arrangement of suckers for supporting evaporation of the solution. With aid of such a sucker the volume stream of an appropriate gas, for example air, led by the ink transfer roller is increased so that even here there is an exchange of enriched ambient air with solutions.
Of course besides the bellows other functional units supporting evaporation can be assigned to the ink transfer roller as well. These can be infrared, microwave or other radiation emitting devices that irradiate the ink on the ink transfer roller. Moreover, mechanisms for separating laminar border layers adhering to moved parts can be utilized. It is known that these laminar border layers have a stark adverse effect on air exchange and thereby evaporation. The separating of a laminar border layer is necessitated by means of mechanical components, for example the turbulence generators depicted in DE 100 34 708 A1, but also by means of electrical and/or magnetic fields (cf. DE 195 25 453 A1 and DE 100 50 301 A1). Finally, mechanisms for heating up of the ink transfer rollers can also be designed.
It is particularly advantageous to arrange between the blower and the next ink transfer roller a second ink reservoir, which provides the option of applying additional ink to the ink transfer roller. Thus the volume loss arising by means of evaporation of solution can be offset so that even with various evaporation rates of the solution the same volumes of printing ink are still transferred to the next ink transfer rollers.
In order to have a most varied possible ability to influence the ink transfer roller, in an additional preferred embodiment at least one additional mechanism for supporting evaporation is planned that has an effect on another part of the scope of an ink transfer roller.
In a particularly preferred arrangement, in the direction of ink transfer in the printing machine a mechanism for supporting evaporation of solution on an ink transfer roller in each case follows each ink reservoir through which the ink is applicable to an ink transfer roller.
In order to be able purposefully to influence the quantity of color pigments that are finally applied to the printing substrate, the output of the mechanisms for supporting evaporation of the solutions is controllable and/or adjustable.
A rotary printing machine according to the invention:
With the invention-related method for setting the ink intensity on a print substrate, the mixing ratio of color pigments and solution in the printing ink is set by purposefully influencing the evaporation of solutions on one of the ink transfer rollers. In this way the density of the ink on the print substrate can be controlled without having to interrupt the printing process.
The individual figures show:
The printing roller 4 conveys printing ink onto the print substrate 5 in an inherently familiar way, whereby the print substrate 5 that is introduced by a guide roller 7 rests on a counter-pressure cylinder 6.
The
The delivery of ink to the printing roller 4 is made difficult by this condition, since a poorer contact occurs between printing ink and printing roller 4 if the ink fountain 8 in the coater roller 3 is not filled to its upper rim. The color separation is thus modified. For this reason, with the embodiment pursuant to
On the way between the second ink chamber coater 12 and the print substrate 5 fresh ink is now able to etch the film. Both parts of the printing ink can commix. The printing ink now contained in the ink fountain 8 has a slightly elevated color pigment portion in relation to the original printing ink. On the print substrate 5, an increased ink density can be subsequently observed that leads to a heightened intensity in the corresponding color.
With the mechanism shown in
Number | Date | Country | Kind |
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102-46-271.2 | Oct 2002 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP03/10264 | 9/15/2003 | WO | 3/21/2005 |