JPS6134129Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device for controlling the wetness of a printing plate surface mounted on a plate plate of a lithographic proofing machine.

FIG. 1 shows a schematic configuration of a known planographic proofing machine.

A pedestal 4 is placed on the upper surface of a frame 1 on which a plate plate 2 and a paper plate 3 are arranged side by side, and the pedestal 4 is reciprocated along the frame 1 as appropriate.

A blanket cylinder 5, a water roller device 6, and an inking roller device 7 are pivotally supported on the pedestal 4.

A water leveling plate 9 is disposed at one end of the frame 1 to make the amount of water contained in the damping device 8 and the water roller device 6 uniform, and an inking device 10 is disposed at the other end. .

The water roller device 6 and the inking roller device 7, while they pass through the area of the paper surface plate 3,
It is configured to be appropriately raised by a cam mechanism or the like and separated from the upper surface of the paper surface plate 3.

To perform proof printing with the apparatus shown in the first figure, first, a lithographic printing plate is placed on the plate platen 2 and a printing paper is placed on the paper platen 3, and the pedestal 4 is driven back and forth. Then, at both ends of the reciprocating stroke of the pedestal 4, the water roller device 6 is supplied with dampening water from the damping device 8, and the inking roller device 7 is supplied with printing ink from the inking device 10, and the plate platen is It is supplied and coated onto the printing plate mounted on No. 2.

The ink on the printing plate surface is further transferred to the surface of the bracket cylinder 5 and printed on the paper surface mounted on the paper surface plate 3.

Lithographic proofing machines with such a configuration are widely used, but during proof printing, the time interval between the reciprocation of the pedestal 4 is relatively long, and during that time, moisture on the plate surface is not sufficiently maintained due to evaporation. This may cause problems.

As a countermeasure against this, by cooling the plate plate 2, the printing plate mounted on it is cooled to a temperature near the dew point, condensing moisture in the air, providing moisture, and reducing the amount of moisture supplied to the plate surface. Measures are taken to prevent dampening water from evaporating.

However, it is not possible to properly control the cooling temperature using only such means, and if the cooling is too high, there will be too much dampening water, which will mix with the ink and cause the ink to become emulsified. There is a risk of causing a phenomenon. Furthermore, when the humidity or temperature in the room changes, it is difficult to keep the plate surface constant.

This emulsified ink causes the image on the printed matter to lose its luster, deteriorating the image quality, and also causes various problems such as poor ink transfer and scumming.

This invention relates to a humidity control device for a printing plate surface in a lithographic proofing machine, and in order to maintain an appropriate amount of dampening water on the printing plate, the temperature of the plate surface is related to the relative humidity in the room at that time. The relative humidity of the surface air is maintained at an optimum value near the dew point.

FIG. 2 shows the configuration of an embodiment of the present invention. Reference numeral 11 denotes a cooling water circulation system including a cooler, a heat exchanger, a circulation pump, etc. (not shown), and the cooling water is circulated through pipes 12, 12. The water is circulated inside the platen 2 to cool the platen 2.

In order to keep the condition of the dampening water on the printing plate constant, it is best to suppress the evaporation of the dampening water as much as possible. In other words,
It is preferable to maintain the relative humidity of the atmosphere of the printing plate or plate plate 2 close to saturation.

In other words, the temperature of the plate plate 2 should be kept at a temperature slightly higher than the current dew point, even if the weather conditions change.
For example, the temperature may be maintained at about 1 to 10°C higher than the dew point.

The present invention provides a small chamber communicating with the outside air that accommodates the detection part of the relative hygrometer in a part of the plate surface plate, and makes the temperature inside the small chamber substantially equal to the temperature of the surface of the plate surface; The surface temperature of the plate plate is controlled so that the absolute humidity in the small chamber is substantially equal to that of the atmosphere (outside air) in which the lithographic proofing machine is installed, and the relative humidity in the small chamber is maintained at a constant value. By doing so, the condition of the dampening water on the surface of the printing plate is maintained constant regardless of the temperature and humidity conditions of the outside air.

For this purpose, a relative hygrometer detector 14 is installed at an appropriate location on the plate surface plate 2.

In the embodiment shown in FIGS. 3 and 4, the detector 14 of the relative hygrometer is mounted on the side surface of the plate surface plate 2, and has a channel shape with one end closed and the other end serving as an air intake part 16. A guide 15 is attached to the side of the plate surface plate 2 so as to cover the detector 14 of the relative humidity meter, and air is sucked in by a fan 27 through a pipe 19 connected to a connecting pipe 22 in the guide 15, and the plate is heated. Air flows along the sides of the surface plate.

By doing this, while the airflow from the outside air flows from the intake part 16 through the guide 15,
The temperature is controlled to be almost the same as that of the plate plate 2, and its absolute humidity is equal to that of the outside air.

Therefore, it is possible to measure the relative humidity of air that has approximately the same temperature as the platen 2 and the printing plate attached thereto, and has the same absolute humidity as the outside air.

A signal from the relative humidity detector 14 installed as described above reaches the control unit 18 through the signal line 17.

Based on the information from the relative humidity detector 14, the control unit 18 controls the cooler of the cooling water circulation device 11 through the signal line 21 so that the relative humidity remains at a preset constant value, thereby controlling the temperature of the printing plate. Make sure the amount of dampening water is kept at the optimum level.

FIGS. 5 and 6 are perspective views showing other examples of how the relative hygrometer is attached to the plate plate 2, respectively.

FIG. 5 shows a box-shaped cover 23 with a relative hygrometer 14 attached to the side of the plate plate 2 and with an opening on one side.
An example is shown in which the is installed.

FIG. 6 shows an example in which the relative hygrometer 14 is attached to the side surface of the plate plate 2, and a simple cover 24 with openings on both sides is attached.

In these two examples, airflow generating devices such as the pipe 19 and fan 20 are not used.

FIG. 7 shows a block diagram of the control section 18, in which 25 is a small signal amplifier, 26 is an arithmetic unit, 27 is a power amplifier, and 28 is an electromagnetic switch.

Its operation is to amplify the signal of the relative humidity detector 14 through the signal line 17 with the small signal amplifier 25,
The calculator 25 outputs a control signal for the cooler to cool the plate plate 2 to a temperature at which the printing plate retains appropriate moisture even if the relative humidity around the proofing machine changes.

This signal is amplified by a power amplifier 27 and controlled by an electromagnetic switch 28 by turning on and off the cooler power supply.

In addition, instead of the electromagnetic switch 28, SCR,
A semiconductor device such as a triax may also be used.

As described in detail above, according to the plate plate temperature control device of the present invention, it is possible to control the temperature of the plate plate 2 so that the amount of dampening water on the surface of the printing plate is optimized. Since there is no need to add or subtract water, the labor-saving effect is significant.

Although water is used in the embodiment as a medium for cooling the printing plate, other liquids or gases may be used. Further, an element having a Peltier effect as shown in Japanese Utility Model Publication No. 49-32161 may be used.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the schematic structure of a lithographic proofing machine, FIG. 2 is a perspective view showing an embodiment of a dampening water control device for a plate surface plate according to the present invention, and FIG. 2
FIG. 4 is a front view of the relative hygrometer mounting part in the illustrated embodiment; FIG. 4 is a plan view of the relative hygrometer mounting part; FIGS. 5 and 6 are perspective views and FIGS. FIG. 7 is an example of a block diagram of the control section. 1... Frame, 2... Print surface plate, 3... Paper surface plate, 4... Frame, 5... Blanket body, 6...
Water roller device, 7... Inking roller device, 8... Damping device, 9... Water leveling plate,
10... Inking device, 11... Cooling water circulation device, 12... Pipe, 13... Cooling water, 14...
Relative hygrometer, 15...guide, 16...intake part,
17...Signal line, 18...Control unit, 19...Pipe, 20...Fan, 21...Signal line, 22...
Connection pipe, 23...Cover, 24...Cover, 25
... small signal amplifier, 26 ... arithmetic unit, 27 ... power amplifier, 28 ... electromagnetic switch.

Claims (1)

[Scope of Claim for Utility Model Registration] A frame 4 on which a water roller device 6, an inking roller device 7, and a blanket cylinder 5 are pivotally supported runs on a frame 1 on which a plate platen 2 for mounting a printing plate is disposed, In a lithographic proofing machine that performs proof printing, a detection unit is installed in a cooling means attached to the plate surface plate and a part of the side surface of the plate surface whose temperature is substantially equal to the surface temperature of the plate surface plate. Based on the detected value of the relative hygrometer, the installed relative hygrometer measures the amount of dampening water that evaporates from the printing plate surface and the amount of water that condenses and adheres to the printing plate surface, so that the amount of dampening water that evaporates from the plate surface of the printing plate and the amount of water that condenses and adheres to the printing plate surface are almost equal. A device for controlling the humidity of a printing plate surface in a lithographic proofing machine, comprising a temperature control means for controlling the surface temperature of a plate plate to a temperature slightly higher than the dew point.