JPS60225757A - Multicolor printer - Google Patents

Abstract

PURPOSE:To eliminate uneven print thickness by scraping off ink left on a plate cylinder with a doctor blade immediately before the plate cylinder is fed with ink in contact with an ink supply member. CONSTITUTION:When printing, a solenoid 16 turns a working press plate 13 synchronizing the rotation of an impression cylinder 1. With the compression of a spring 15, a plate cylinder 2 and a rotary plate 12 are pressed on the impression cylinder 1 to print ink on a sheet 6. The thickness (f) of ink which is left on the plate cylinder when it is separated from the sheet changes (g') as the ink is scraped off with a doctor blade 11. The ink thus left can be almost removed by adjusting the pressing force thereof 11. On the other hand, the thickness (c) of ink on an inking roller 3 is constant and that (e') thereof on the plate cylinder 2 is also invariably constant. This makes the thickness (e) of ink on the plate cylinder 2 constant regardless of the preceding printing pattern while the printing thickness (h) on the sheet 6 invariably constant thereby uneven thickness in printing is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-color printing press, and more particularly to a multi-color printing apparatus that prints a repeated pattern or a solid pattern over the entire surface sequentially.

Conventional configuration and its problems In the general method of multicolor printing, when the number of colors is, for example, four,
There are four separate printing presses in a row, each printing a different color.

These printing machines are very large, and in order for the printed materials to be printed by each printing machine without misalignment with each other, the operations of each printing machine must be synchronized. , the coordination of the equipment, and the control of its operation require significant effort. Furthermore, in the case of printing on a thin sheet that expands and contracts rapidly, alignment becomes even more difficult. Therefore, various improvements have been made to printing presses, especially when it comes to printing thin sheets.

An example of a conventional multicolor printing device will be described below.

FIG. 1 shows a side view of a conventional multicolor printing device, in which 1 is an impression cylinder, 2 is a plate cylinder, 3 is an ink deposition roller,
4 is a pressure roller, 5 is an ink reservoir, 6 is a sheet, 7 is a sheet supply reel, 8 is a sheet take-up reel, 9. is ink. The second printing cylinder is a letterpress (flexographic) printing cylinder. FIG. 2.3.4.5 shows an enlarged view of the solid color printing section of FIG. 1.

The operation of the conventional multicolor printing apparatus configured as described above will be described below.

The sheet 6 fed from the feeder V 7 is transferred to the impression cylinder 1
is wound onto a sheet winding reel/v8.

The sheet is conveyed at a constant speed by the pressure roller 4 and the impression cylinder 1. A plurality of plate cylinders 2 are pressed against a sheet 6 on an impression cylinder 1, and ink is supplied by a roller 3 for inking. The ink supplied onto the plate cylinder 2 is printed onto a sheet 6 on the impression cylinder 1. If the printing pattern for each color is a repeat of a single pattern such as a solid pattern,
In consideration of miniaturization of the device, a single pattern plate is formed on the plate cylinder 4, a means for moving the plate cylinder 4 (not shown) is provided, and a means for detecting rotation of the impression cylinder 1 (not shown) is provided. By providing a pressurizer (1) and bringing the plate cylinder 4 into contact with or separating it from the sheet 6 in synchronization with the rotation of the impression cylinder 1, a pattern with a free pitch can be printed in four colors regardless of the outer circumference of the plate cylinder 4. Is possible. In this case, there are four ink reservoirs 5, each containing ink 9 of a different color.

During continuous printing, only a small amount of ink 9 remains on the plate cylinder 2 after it has come into contact with the print cylinder 2, as shown in FIG. This is defined as the ink thickness a.

After the ink deposit is supplied by the roller 3, the ink thickness becomes b. The amount of ink supplied to the plate cylinder 2 by the roller 3 can be reduced by using the roller 3 as a gravure roller or a spiral roller and scraping off the excess ink with a doctor grade 10. It becomes stable by keeping it constant. Therefore, during continuous printing, the ink thickness on the plate cylinder 2 is constant, and the ink thickness d printed on the sheet 6 is also constant. In the area where ink is not printed on the sheet e, as shown in FIG. 3, the plate cylinder 2 is separated from the sheet 6, so the ink thicknesses b' and a' on the plate cylinder 2 are approximately constant. Also, compared to a in FIG. 2, a' in FIG. 3 is thicker because the sheet 6 is not printed. Since the ink thickness C on the roller 3 is constant, the ink thickness b' determined by C and a' is thicker than b in FIG. 2. Since the ink thicknesses a' and b' on the plate cylinder 2 are thus initial values, the thickness increases with each revolution of the plate cylinder 2. When printing with ink from this state, as shown in FIGS. 4 and 5, printing is performed on the plate cylinder 2 with an ink thickness b' and on the sheet 6 with an ink thickness d'. At this time, since b'>b, d')d.

However, after the plate cylinder 2 rotates once through the state shown in Figure 6, the ink thickness on the plate cylinder 2 becomes b, which is almost the same as in Figure 2. As shown in the figure, plate cylinder 2
After the printing thickness d' continues for the outer circumference length l, the printing thickness becomes d. Therefore, in this apparatus, if the length of the continuous printing pattern of one color is longer than the outer circumferential length l of the plate cylinder 2, the printing thickness changes from d' to d on the sheet, resulting in uneven printing. d
The value changes depending on the length of the part that is not printed on the 1-door J mark.

Furthermore, if the length of the non-printed portion is shorter than the outer circumferential length l of the plate cylinder 2, the length of the portion having the thickness d' on the sheet will also change.

In addition, in order to eliminate printing unevenness, if the diameter of the plate cylinder 2 is increased and the outer circumference l is made longer than the length of the - color printing pattern, the entire device will become larger and it will be possible to print with various pitches. It becomes difficult to correspond to the printed pattern. In this case as well, since a' and b' in FIG. 3 do not have exactly the same thickness, the history due to the repetition of the printing pattern remains on the plate cylinder 2, causing various printing irregularities. Therefore, the letterpress flexographic printing apparatus having the above configuration has the problem of uneven printing thickness.

Purpose of the Invention The present invention solves the above-mentioned conventional problems.Among recent printed materials, in particular, print patterns of each color are solid or have a single pattern, such as dye-coated sheets for thermal transfer printers. The purpose of the present invention is to provide a multi-color printing device with less uneven printing thickness compared to conventional letterpress flexographic printing devices, which can be considered when repeating printing and in which a single-pattern plate cylinder is brought into contact with or isolated from a sheet. shall be.

Composition of the Invention The present invention provides a multi-color printing plate comprising an impression cylinder and a letterpress printing cylinder, means for moving the printing cylinder in synchronization with the rotation of the printing cylinder, and an ink supply member and a doctor blade in contact with the printing cylinder. is a printing device,
Immediately before the plate cylinder comes into contact with the ink supply member and is supplied with ink, the ink remaining on the plate cylinder is scraped off with a doctor grade, thereby making it possible to eliminate uneven printing thickness.

DESCRIPTION OF EMBODIMENTS FIGS. 6 and 7 are side views of a multicolor printing apparatus according to an embodiment of the present invention. In FIGS. 6 and 7, the same parts are given the same numbers in FIGS. 1 and 2. In FIGS. 6 and 7, 11 is the doctor blade of the plate cylinder, 12 is the plate cylinder rotating plate, 13 is the plate cylinder pressing plate, 14 is the plate cylinder rotating spring, 15 is the plate cylinder pressing spring, and 16 is the plate cylinder. The pressure solenoid is shown.

The operation of the multicolor printing apparatus of this embodiment configured as described above will be described below.

When printing is not performed, the plate cylinder 2 and press plate 13 are pulled by the spring 14 on the rotary plate as shown in FIG. 6, and the plate cylinder 2 does not come into contact with the sheet 6. The ink deposited from the roller 3 reaches a thickness of e on the plate cylinder 2, but is scraped off by the doctor blade 11.
After 1, the thickness becomes g. The thickness g can be almost eliminated by adjusting the pressing force of the doctor grade 11, etc. Further, the ink thickness C on the roller 3 is also constant due to the doctor blade 1o in contact with the roller 3. Since the ink thickness e on the plate cylinder 2 is determined by g and C, it is always constant.

When printing with plate cylinder 2, it will be as shown in Fig. 7.

A solenoid 16 operates in synchronization with the rotation of the impression cylinder 1 to rotate the press plate 13. By compressing the spring 15, the plate cylinder 2
The rotating plate 12 is pressed against the impression cylinder 1, and the ink on the plate cylinder 2 is printed on the sheet 6. The ink thickness f remaining on the plate cylinder when it is separated from the sheet is scraped off by doctor grade 11 and becomes g'.

The thickness g' can be almost eliminated by adjusting the pressing force of the doctor blade 11, etc. Furthermore, the ink thickness C on the roller 3 is also constant.

Since the ink thickness e' on the plate cylinder 2 is determined by g' and C, it is always constant and approximately equal to e in FIG. 5.

Therefore, regardless of the history of previous printing patterns, the plate cylinder 2
Since the ink thickness e on the sheet 6 is constant, the printing thickness on the sheet 6 is also always constant, and there is no uneven printing thickness. By scraping off the ink remaining on the plate cylinder with the doctor blade 11, it is possible to eliminate uneven printing thickness and improve printing characteristics when a single pattern is repeatedly printed.

In the above embodiment, a solenoid is used as a means for moving the plate cylinder 2, but an air cylinder or the like may also be used. Also, the rotation of the impression cylinder is detected and output in the form of an electric signal to control the solenoid, but a cam is attached to each of the impression cylinder and the plate cylinder, and the plate cylinder is moved in synchronization with the rotation of the impression cylinder. It's okay. As a multi-color printing device, four-color printing is possible if the printing units shown in Fig. 6 are installed at four locations as shown in Fig. 1, but if the impression cylinder is shared, one A compact printing device can be constructed by winding a sheet around an impression cylinder and providing four printing sections around it as shown in FIG. The ink supply member may be a reverse roller or the like in addition to a roller for gravure or spiral ink application.

Effects of the Invention As described above, the multicolor printing device of the present invention reduces uneven printing thickness in the case of repeated printing of a single pattern by providing a doctor blade in contact with the surface of the letterpress plate cylinder. It is possible to eliminate it, and its practical effects are great.

[Brief explanation of the drawing]

1, 2, 3, and 4 are side views of a conventional multicolor printing device, and FIGS. 5, 6, and 7 are side views of a multicolor printing device according to an embodiment of the present invention. FIG. 1...Impression cylinder, 2...Print cylinder, 6...
Sheet, 11...Doctor grade. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 8 Figure 2 Figure 5

Claims (1)

[Claims] 1111 A section for supplying ink to the printing cylinder, including an impression cylinder that transports the sheet by winding it around the circumference, and a printing cylinder that prints ink on the sheet; A multicolor printing device comprising: means for contacting or isolating the impression cylinder in synchronization with rotation of the impression cylinder; and a doctor blade is provided in contact with the printing cylinder at a position before the printing cylinder comes into contact with the ink supply member.