GB2233603A - Printing machine operating method - Google Patents

Abstract

In a process for the operation of a printing machine, several work stages necessary for the conversion of the printing machine are carried out in at least partially overlapping manner. In the case of an offset printing machine in particular, after the ejection of a print forme, the rubber blanket is washed and dried, during which the insertion and the pre-moistening and inking of a new print forme take place. After the drying of the rubber blanket and the premoistening and inking of the new print forme, the rubber blanket is inked. As a result, the set-up times are reduced, thereby increasing the quantity output of the printing machine especially in the case of small print runs.

Description

DESCRIPTION PRINTING MACHINE OPERATING METHOD The invention relates to the operation of printing machines.

In order to convert an offset printing machine from printing one master to another, the following work stages are basically necessary: ejection of the sheet or of another suitable print forme, washing and drying of the rubber blanket, insertion of the new sheet, etching of the new sheet if applicable, premoistening of the new sheet, inking of the sheet and then inking of the rubber blanket. In the case of a small print run quantity in particular, the set-up time required for these work stages is markedly disadvantageous.

It is the task of the following invention to reduce the set-up time of an offset printing machine between the printing of different masters.

The process according to the invention, with the characterising features in the main claim, has the advantage that, with small expenditure, the overall performance of an offset printing machine can be improved by reduction of the set-up times.

Advantageous further developments and improvements of the invention given in the main claim are possible by means of the measures described in the sub-claims.

Constructional versions of the invention are represented in the drawing using several figures, with more detailed explanation in the description below. In the drawing: Fig. 1 shows a schematic representation of an offset printing machine with three cylinders; Fig. 2 and Fig. 3 show comparisons of the work stages according to the known process and that featured by the invention, with various operational parameters ; and Fig. 4 shows a computer program for the implementation of the process according to the invention.

In the offset printing machine 1 shown in Figure 1, a plate cylinder 2, a rubber blanket cylinder 3 and an impression cylinder 4 are provided respectively. For the application of the ink, the water and the etching medium, application rollers 5, 6 and 7 are positioned in the area of the plate cylinder. With the help of a sheet feed device 8 (only intimated in the drawing), the sheets are fed respectively to the plate cylinder 2, and are automatically removed from the printing machine 1 after the printing procedure at 9. The rubber blanket cylinder 3 is assigned a washing cylinder 10 and a blower 11 for drying *The cylinders 2, 3 and 4 are designated as PZ, GZ and DZ, respectively, since their respective German names are "Plattenzylinder", "Gum.m.ituchzylinder" and 1,Druckzylinder".

purposes. In a manner not shown in more detail, the devices 5 to 11 can be controlled by a control unit 12, which contains inter alia a microcomputer 13, and which controls other normal control procedures, such as the regulation of the number of revolutions of the printing machine and the start and end of the printing procedure.

After the completion of the printing of a master, the following work stages are required, in order to convert the printing machine for the printing of the next master: A Ejection of sheet B Washing of the rubber blanket C Drying of the rubber blanket D Insertion of the sheet E Etching of the sheet F Moistening of the sheet G Inking of the sheet and H Inking of the rubber blanket.

The duration of work stages B, E, F, G and H can be varied by means of pre-selector switches. Also, the duration of the respective work stages can be adjusted as the number of cylinder revolutions. The duration of work stages A, C and D is constant.

While work stages A to E are executed at a constant machine speed of, for example, 5000 revolutions per hour, the machine speed during work stages F, G and H corresponds to the mostly variable production run speed. In the diagrams shown in Figures 2 and 3, a production run speed of 9000 revolutions per hour, is assumed, which is normal in practice. Since work stage E "Etching of sheet" is not required for all printed sheets, work stage E can be switched on or off by the machine operator.

Figures 2 and 3 show the sequence of the individual work stages according to the known procedure, and according to the process featured by the invention for a conversion without etching (a and b) and with etching (c and d) of the sheet respectively. As a scale for the duration of the work stages, the respective number of revolutions has been chosen, and a corresponding scale has been represented in line e.

The representations in Figure 2 are based on the respective minimum setting for the duration of the work stages B, E, F, G and H, whilst in Figure 3, these work stages are represented by their longest duration.

Work procedures A and D require two revolutions respectively. The drying of the rubber blanket takes place within five revolutions. In the example represented in Figure 2, two revolutions are required for the washing of the rubber blanket and one revolution respectively for the pre-moistening and inking of the sheet and for the inking of the rubber blanket (work stages F, G and H). Etching (Figures 2c and 2d) also takes place within one revolution.

In the known process according to Figure 2a, a set-up time of 9.12 s is obtained under these preconditions, if all work stages are executed one after the other, and if one revolution lasts 0.72 s for work stages A to D, and 0.4 s for work stages F, G and H.

In the process according to the invention represented in Figure 2b, the new sheet is already inserted, as work stage D, during the drying of the rubber blanket (work stage C). As a result of a corresponding control, this occurs sufficiently early that the premoistening and inking of the sheet (F, G) and the drying of the rubber blanket (C) are concluded simultaneously, so that in work stage H, the rubber blanket, which has just been dried. can be inked. As a result, the set-up time is reduced to 6.8 s.

In the example represented in Figures 2c and 2d, the sheet is etched before the inking. In the case of the known process according to Figure 2c, this requires a further revolution of 0.72 s. Since, in the case of the process according to the invention, the etching is already executed during the drying of the rubber blanket, for which purpose the new sheet is inserted one revolution earlier, the overall set-up time is not changed as a result of the etching.

The reductions of the set-up times given as examples are, it is true, only of the order of a few seconds; however, in the case of small print runs, values of this sort can signify considerable economic advantages. Thus, for example, at a production run speed of 9000 prints per hour for 100 copies, a production run time of 40 s is required. With the adjustments according to Figures 2c and 2d, 49.84 s, inclusive of set-up time, are required in the case of the known process, and 46.88 s in the case of the process according to the invention. Accordingly.

with a print run of 100, in the case of the known process 577 sheets can be processed in an eight-hour day, and in the case of the process according to the invention the figure is 614 sheets. However, this saving becomes considerably larger if maximum preadjustment values are assumed for work stages D, E, F, G and H, which is shown in Figure 3. Also, a different scale has been chosen here than in Figure 2. With the adjustment according to Figure 3c, 375 sheets can be processed in one eight-hour day, whilst with the same adjustment using the process according to the invention (Figure 3d), an increase to 467 sheets is possible.

Figure 4 represents a flow chart of a constructional version of the process according to the invention essentially reproducing the program for the microcomputer 13 (Figure 1). The flow chart is divided into Figures 4a and 4b on pages 4/5 and 5/5.

Lines belonging together are identically labelled a to i. In addition, the abbreviation PZ has been chosen for the plate cylinder. and the rubber blanket cylinder is labelled GZ.

After a start at 21, the sheet is fed in at 22. At 23, an enquiry is made as to whether the sheet is placed ready for insertion. As long as this is not the case, the feed-in device is further actuated until the sheet is placed ready and is inserted at 24. In program part 25, the feed-in of the next sheet is initiated. Thereupon, in program part 26, the etching of the sheet is carried out until a set time or set number of revolutions has expired. An enquiry is made about this at 27, after which, if appropriate, the pre-moistening of the sheet is initiated in program part 28. If the pre-moistening of the sheet is completed, the inking of the sheet is carried out in program part 30. Here, likewise, a time is preset, at the expiry of which the program is guided from the branch 31 to program part 32, by which the inking of the rubber blanket is triggered.

If the inking of the rubber blanket is completed, then after the branch 33, the printing procedure takes place at 34, after the end of which the program is branched once again at 35, and at 36 an enquire is made as to whether an automatic production run should take place with another sheet. If this is not the case, the program is ended at 58. However, if the printing machine is set to automatic production run, then at 37, a section of the program is started serving optimised repeat operation according to the process featured in the invention. For this purpose, the process duration is optimised using the process values given, in a program part 38. Then, at 39, the working points for the conversion are determined, as represented for example in Figures 2 and 3.

Since, according to the procedure featured in the invention, different work stages take place in parallel, a parallel representation has also been chosen in the following program section, although there is no branch of the computer program here.

Here, the work stages relating to the plate cylinder are shown on the left and those on the rubber cylinder are shown on the right.

Specifically, work stage A (sheet ejection) is executed at 40, an enquiry is made at 41 as to whether a new sheet is placed ready for insertion, and at 43, the new sheet is inserted (work stage D).

If no sheet is placed ready for insertion at 41, the programm enters a waiting loop 42, 43, until the washing of the rubber blanket is completed.

Following this, the program is ended at 58, since if there is no sheet ready for insertion, there is no requirement or necessity for an optimised repeat operation. The program can then be restarted at 21 to process further printing orders.

After the sheet is inserted at 43, the next sheet is fed in at 45, and thus placed ready for the subsequent insertion. As already described in connection with program parts 26 to 29, the sheet is etched, pre-moistened and inked in program parts 46 to 51.

Parallel to the program parts 40 to 51, the rubber blanket is washed at 52, an enquiry is made at 53 as to whether the washing process is completed, and the drying of the rubber blanket is executed or completed in program parts 44 and 55. As a result of the program optimisation at 37 and 38, it is achieved that when the work stage "inking of sheet" is completed at 50, work stages 52 to 55 on the rubber cylinder are also completed, so that the program is continued at 32 with the inking of the rubber cylinder, as already described.

As a result of the program optimisation at 37 and 38, it is ensured that the inking of the rubber blanket cylinder GZ by contact of the rubber blanket cylinder with the plate cylinder only occurs if, on the one hand, the sheet is inked and, on the other hand, the rubber blanket cylinder GZ is dried.

It will be understood that the invention has been described above purely by way ofexample, and that various modifications of detail can be made within the ambit of the invention.

Claims (6)

1. A method of operating a printing machine, wherein, after the completion of the printing of one master, the conversion of the printing machine for the printing of another master is performed by a procedure in which a plurality of work stages necessary to convert the printing machine are carried out in a chronologically at least partially overlapping manner.

2. A method according to claim 1, wherein, after the ejection of a print forme, on an offset printing machine, the respective rubber blanket is washed and dried; the insertion, pre-moistening and inking of a new print forme being effected during the washing and/or drying of the rubber blanket; and the rubber blanket being inked after the drying of the rubber blanket and the pre-moistening and inking of the new print forme.

3. A method according to claim 2, wherein, in addition, the print forme is etched during the washing and/or drying of the rubber blanket.

4. A method according to claim 1, the printing machine being an offset printing machine having a plate cylinder and a rubber blanket cylinder, wherein two or more work stages on the plate cylinder are carried out in chronological overlap with work stages on the rubber blanket cylinder, and thereafter the rubber blanket is inked.

5. A method according to claim 4, wherein the timing of the work stages on the plate cylinder and rubber blanket cylinder is controlled in such a manner that the drying of the rubber blanket is completed at substantially the same time as the inking of the print forme.

6. A method according to claim 1, substantially as described with reference to Figures 2 and 3, or Figure 4, of the accompanying drawings.