Printing – Processes – With heating or cooling
Reexamination Certificate
2003-03-20
2004-01-20
Nolan, Jr., Charles H. (Department: 2854)
Printing
Processes
With heating or cooling
C101S148000, C101S142000, C101S350300
Reexamination Certificate
active
06679173
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method of tempering or controlling the temperature of a printing press by a circulating temperature control medium, the temperature of which is regulated.
It is necessary to temper or control the temperature of a printing press in order to maintain the temperature-dependent viscosity of the printing ink processed in the printing press approximately constant. Otherwise, excessively large fluctuations in the viscosity of the printing ink would manifest themselves in the form of excessively large fluctuations in the optical color density measurable in the printed image.
For a very long time heretofore, efforts have been made for improving the temperature control of printing presses, as documented by the following, briefly described publications of the prior art.
British Patent 1 242 095 describes a method wherein a temperature measuring sensor is assigned to a feedline and forerunning flow line, respectively, for a temperature control medium.
German Utility Model DE-U 73 43 273 describes an inking unit wherein the temperature of a tempering or temperature control medium emerging from rollers is measured by measuring sensors which are assigned to respective discharge and return lines.
German Patent DE 42 11 379 C2, corresponding to U.S. Pat. No. 5,355,796, makes reference to temperature registration or determination by inserting thermocouples into a cooling system, and measuring the temperatures of the coolant respectively supplied and discharged.
German Published, Non-Prosecuted Patent Application DE 198 37 174 A1, corresponding to U.S. Pat. No. 6,164,207, describes the state of the art to which reference is made in the first paragraph of the introduction hereto. In that publication, a method of temperature control is described wherein a mixing container is provided to which machine oil flowing back from an ink duct roller and serving as a tempering or temperature control medium is supplied and into which machine oil having a temperature controlled by a cooling assembly is also introduced. A temperature measuring sensor and a temperature regulating device are also used in order to implement the method.
All of the prior art cited hereinbefore is unable to satisfactorily solve a problem in the tempering or temperature control of printing presses, which has existed for a relatively long time. The problem is that, on the one hand, a very long preheating and warm-up phase is required until the temperature of the press has been tempered or controlled to the required operating temperature thereof, if only the flow temperature of the tempering or temperature control medium supplied to one printing unit of the printing press serves as the measurement and control parameter in the tempering or temperature control. On the other hand, temperature fluctuations of up to 7 Kelvin of the tempering or temperature control medium are to be expected, which in turn cause intolerably large optical color density fluctuations in the printed image if, during the tempering or control of the temperature, only the return temperature of the tempering or temperature control medium discharged from the printing unit is used as a measurement and control parameter.
A similar problem exists in printing presses which are set up at locations with ambient temperatures above the operating temperature of the printing press and, therefore, require a respective precooling and cooling operating phase preceding production printing, the respective phase serving for adjusting the operating temperature. The precooling and cooling operating phase, during which the temperature control medium (in that case a cooling liquid) is circulated through the printing press while printing cannot yet be performed because the printing press temperature has not yet fallen sufficiently, lasts too long in the heretoforeknown methods.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method of tempering or controlling the temperature of a printing press, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and in which, during production printing, only tolerably small temperature fluctuations occur and the temperature control phase (cooling or warm-up operating phase) preceding production printing is not unnecessarily long.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of tempering a printing press by a circulating tempering medium, which comprises regulating a temperature of the tempering medium. The temperature at a first measurement location is measured for purposes of control during production printing by the printing press. The temperature at a second measurement location is measured during a tempering phase of the printing press preceding production printing.
In accordance with another mode, the method invention further includes providing a control device for regulating the temperature. The control device is changed over automatically from measuring at the second measurement location to measuring at the first measurement location the instant that the temperature deviates from a temperature limiting value prescribed for the control device.
In accordance with a further mode, the method invention further includes providing the first measurement location between a heater and an inlet for the tempering medium. The tempering medium is heated with the heater.
In accordance with an added mode, the method invention further includes providing the second measurement location between an outlet for the tempering medium and a heater. The tempering medium is heated with the heater.
In accordance with an additional mode, the method invention further includes providing the first measurement location between a cooler and an inlet for the tempering medium. The tempering medium is cooled by the cooler.
In accordance with yet another mode, the method invention further includes providing the second measurement location between an outlet for the tempering medium and the cooler. The tempering medium is cooled by the cooler.
In accordance with a concomitant mode, the method invention further includes providing a mixing tank for the tempering medium between the first measurement location and an inlet for the tempering medium. Temperature fluctuations of the tempering medium in the mixing tank for the tempering medium are damped.
The method according to the present invention is of the general type referred to in the introduction hereto but advantageously calls for measuring the temperature at a first measurement location for control during production printing. The temperature at a second measurement location is measured during a temperature control phase (cooling or warm-up phase) of the printing press, which precedes the production printing.
In the method according to the invention, the respective disadvantages of the flow measurement and flow temperature control heretofore known from the prior art, and of the return measurement or return temperature control likewise known heretofore from the prior art, are eliminated.
Through the use of the respective control and regulation strategy upon which the method invention is based, on the one hand, unnecessary prolongation of the tempering or temperature control phase of the printing press is avoided and, on the other hand, assurance is provided that the temperature of the tempering or temperature control medium only fluctuates extremely slightly during production printing.
It is inherent in the method according to the invention that the temperature of the tempering or temperature control medium can never be controlled or regulated from measured values measured simultaneously at the two measurement locations. Although it is possible for the temperatures to be measured simultaneously at both measurement locations, at the instant of the simultaneous measurement of the temperatures, it is always only one of the measured values obtained at the two measurement locations which is used for the control o
Henn Andreas
Heuschkel Jörg
Hieb Christian
Mayer Martin
Greenberg Laurence A.
Hamdan Wasseem H.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Nolan, Jr. Charles H.
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