JPH0539886Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cooling device installed immediately after a drying device for heating and drying a strip of printed material in a printing press, and particularly to a dew condensation prevention device for the cooling cylinder.

[Prior art and its problems]

Generally, printing machines such as gravure rotary presses and offset rotary presses are equipped with a drying device that evaporates the solvent in the ink mainly by blowing hot air in order to dry the ink film printed on the strip. In order to cool the printed material strip after leaving the drying device, a cooling device is provided that removes heat from the printed material strip by passing cooling water into a cylinder that rotates in contact with the printed material strip.

The main purpose of cooling the printed strip in this way is to solidify the resin in the ink film and fix the ink, and the other purpose is to return the elastic modulus of the printed strip to room temperature and stabilize the tension. As a result, the quality of printing is ensured. Note that the temperature of the printed strip after cooling is preferably equal to the room temperature, and at most 30° C. or lower.

Therefore, the surface temperature of the cooling cylinder needs to be considerably lower than the temperature at which the printed strip is to be cooled, and the temperature of the cooling water flowing through the cooling cylinder is required to be even lower than that. be done.

By the way, the average relative humidity of the atmosphere in Japan is about 60%, but this relative humidity varies depending on the winter and summer seasons and depending on the weather conditions, whether it is sunny or rainy. In order to avoid problems caused by static electricity when humidity is low, a humidifier is generally used in the printing room to increase the humidity, so the amount of moisture contained in the air inside the printing room is considerable. .

If you use cooling water with a temperature of 10℃ or lower, if there is no exchange of heat with the printed material, that is, if you are not printing, the temperature of the surface of the cooling cylinder will decrease. The temperature in the printing room is close to that of water, with a temperature of 20°C and relative humidity.
If it is 60%, the temperature on the surface of the cooling cylinder will be lower than the dew point and condensation will occur. Therefore, if operation is started in this state, if the material of the printed material is paper, it will cause paper breakage.

On the other hand, if printing is in progress, the surface temperature of the cooling cylinder will rise due to the transfer of heat from the printed material strip, making it difficult for dew condensation to form.Also, if the amount of dew condensation is small, the printed material material strip will carry away the dew water. , it is not a big problem if the amount is small. However, if the moisture content is high, even if the printed material is made of plastic film that does not cause paper breakage, the moisture carried by the printed material will be added to the ink in the next printing unit, reducing the ink density. This can cause problems that reduce print quality.

In addition, the printed material strip is not wrapped around the entire length of the cooling cylinder in the axial direction, but the width of the printed material strip is usually shorter than the axial length of the cooling cylinder, and both ends of the cooling cylinder are wrapped around the printed material strip. This area is defined as an area that does not come in contact with other people. Therefore, since this region of the cooling cylinder is not provided with heat by the printed material strip, its surface temperature is lower than that of the region that comes into contact with the printed material strip, and there is a very high possibility that dew condensation will occur.
As a result, moisture adheres to both ends of the strip-shaped printed material, causing problems when running the strip-shaped printed material due to the difference in elastic modulus between both ends of the strip-shaped printed material and the inside, and moisture condensed on the edge of the strip-shaped printed material is transferred to the next printing unit. Problems such as transportation are occurring.

On the other hand, in order to avoid the aforementioned dew condensation, the cooling capacity of the cooling cylinder is often lowered, but reducing the cooling capacity of the cooling cylinder in this way makes it difficult to maintain the temperature of the strip printed material at an appropriate temperature during high-speed printing. Since the tension does not reach a constant value and the tension is not stable, the printing quality is impaired, and as a result, the printing speed has to be lowered and productivity cannot be improved.

As one method for overcoming these problems, a device described in Japanese Utility Model Application Laid-open No. 61-74438 is known. As shown in FIG. 4, this known device is provided with a drum 1 and a shaft 2 that rotates the drum 1, a roller surface 5 around which a printing paper 4 is wound around the drum 1, and a roller surface 5 that wraps a printing paper 4 around the drum 1. A cooling water circulation space 6 for flowing cooling water is provided inside, and the cooling water circulation space 6 is communicated via a passage 7 with cooling means such as a refrigerator. In this known device, the length of the cooling water circulation space 6 in the axial direction is approximately equal to the minimum width W of the printing paper 4 wound around the roller surface 5, and both ends 1a of the drum 1, 1b is not cooled by cooling water. Therefore, dew condensation can be prevented at both ends 1a and 1b of the drum 1, where the printing paper 4 is less likely to be wrapped around.

However, with the conventional cooling cylinder (roller) described above, since the width of the strip-shaped printed matter used in one printing machine varies, the cooling of both ends of wide-width strip-shaped printed matter is insufficient, and Particularly when a narrow width one is used, it still has drawbacks such as dew condensation.

Further, Japanese Utility Model Publication No. 58-36136 discloses a dew condensation prevention device for a cooling cylinder configured to blow air with low absolute humidity onto the surface of the cooling cylinder to prevent dew condensation.

This condensation prevention device is equipped with multiple nozzles that inject low-humidity air toward the cooling cylinder in areas where the strip material is not wrapped. It's starting to cool down.

However, in the dew condensation prevention device described in this publication, the surface of the cooling cylinder on the side around which the strip-shaped material is wrapped is in contact with high-humidity indoor air, and the strip-shaped material is not wrapped around the cooling cylinder before operation. If not, more than half of the surface of the cooling cylinder will be in contact with the humid indoor air. Therefore, especially when the operation is stopped for a long time, it is impossible to prevent dew condensation on the surface of the cooling cylinder.

[Purpose of invention]

An object of the present invention is to provide a cooling cylinder dew condensation prevention device that can prevent dew condensation on the surface of the cooling cylinder regardless of the width of the strip-shaped printed matter.

[Summary of the idea]

Condensation on the surface of the cooling cylinder occurs when the absolute humidity of the atmosphere surrounding the cooling cylinder is high and the surface temperature of the cooling cylinder is below the dew point temperature of the atmosphere. Therefore, if the cooling cylinder is confined in an atmosphere with low absolute humidity and the dew point of the atmosphere is much lower than the surface temperature of the cooling cylinder, no condensation will occur.

That is, in a device that blows air with low absolute humidity onto the surface of a cooling cylinder to prevent condensation, the entire cooling cylinder is surrounded by a housing having slits for introducing and discharging the printed matter in the form of a strip. By doing so, air with low absolute humidity is forced into the housing, and the inside of the housing is maintained at a more positive pressure than the outside of the housing, even though the relative humidity is the same.
The problem of condensation can be solved by utilizing the fact that low-temperature air has lower absolute humidity than high-temperature air.

[Example of idea]

The present invention will be explained below with reference to embodiments shown in FIGS. 1 to 3. This embodiment shows a case where the present invention is applied to a printing machine.

In the drawing, reference numeral 11 is a cylindrical cooling cylinder, and this cooling cylinder 11 is rotatably disposed on frames 13, 13' on both sides of the printing press via bearings 12, 12'. The cooling cylinder 11
A passage 14A along the center of the shaft neck 14, 14' of
is bored, and cooling water is circulated into the cooling cylinder 11 through this passage 14A, so that the cooling cylinder 11 is cooled. This cooling cylinder 11 is surrounded by a housing 16, and the housing 16 has frames 13, 1
3' with bolts 17. On the side of the housing 16 facing a drying chamber 18, which will be described later, there are provided an entrance slit 19 and an exit strip 20 through which the printed material strip 15 is introduced and discharged. Moreover, doors 21 and 22 that can be opened and closed are provided on the upper and lower sides of the housing 16 that face each other.
1 and 22 can be opened for easier work. Furthermore, a connection port 23 is formed on the side surface of the housing 16, and this connection port 23 is connected to a conduit 24 for feeding cooling air into the housing 16. In addition, pipe line 2
4 is provided with a damper 24a for adjusting the air volume.

As shown in FIG. 3, the pipe line 24 is communicated with a cooling air supply device 26 via a blower 25. As shown in FIG.
This cooling air supply device 26 includes an inlet 27 for introducing air as shown by arrow A, a filter 28 for removing dust and the like from the introduced air, and a filter through which refrigerant is circulated through a pipe 29. A heat exchanger 30 is provided to cool the air passing through 28 and discharge condensed moisture through a drain 30a, and an outlet 31 to send out the cooled air. Air sent out from this outlet 31 is sent to the blower 25 through a pipe line 32. Note that the pipe line 29 through which the refrigerant is circulated is connected to a refrigerator 33, so that the refrigerant is cooled by the refrigerator 33. Further, the refrigerator 33 is connected to a cooling tower 35 through a pipe line 34, and is configured to release heat absorbed from the refrigerant to the atmosphere via the cooling tower 35.

Furthermore, the printing press to which the present invention is applied has the above-mentioned drying chamber equipped with a supply duct 36 for drying the printed material strip 15 by blowing dry air and an exhaust duct 37 for discharging air containing solvent vapor. 18 are provided.

According to the above-described configuration, the strip-shaped printed material 15, which has passed through the drying chamber 18 and has been dried and whose temperature has increased, is introduced into the housing 16 through the entrance slit 19, and after contacting the cooling cylinder 11 for approximately half the circumference. It is discharged to the outside from the exit slit 20. At this time, the temperature of the printed material strip 15 is lowered below a certain level by contacting the cooling cylinder 11, while the heat absorbed by the cooling cylinder 11 is transferred to the outside by the cooling water flowing through the cooling cylinder 11. be discharged. Furthermore, the inside of the housing 16 is communicated with the outside through an inlet slit 19 and an outlet slit 20, and a blower 25 supplies cooling air with low absolute humidity produced by a cooling air supply device 26. By feeding through the connection port 23, the inside of the housing 16 can be maintained at a positive pressure and an atmospheric state with low absolute humidity can be maintained. As a result, dew condensation on the surface of the cooling cylinder 11 can be prevented regardless of whether or not the strip-shaped printed matter 15 is in contact with the cooling cylinder 11 .

To explain in more detail, the strip-shaped printed material 1 is heated to a high temperature after the solvent is evaporated by the printing drying device.
5 is cooled by the cooling cylinder 11, the surface temperature of the cooling cylinder 11 is lower than that of the printed material 1.
It is necessary that the temperature is about 17° C. at the contact portion with 5, and therefore it is necessary to circulate a considerable amount of cooling water at about 9 to 10° C. In this case, the temperature of the portion of the cooling cylinder 11 that does not contact the strip-shaped printed material 15 is 12 to 13°C.

By the way, the temperature inside the printing room is 20℃ and the relative humidity is 65%.
If so, the moisture contained in 1 kg of air is 0.00955 kg, that is, the absolute humidity is
It is 0.00955. Since the dew point of this air is 13.8° C., naturally condensation will occur on the portions of the cooling cylinder 11 that are not in contact with the strip-shaped printed matter 15. In summer or on rainy days, the absolute humidity often exceeds this level, and when the cooling cylinder is directly exposed to the atmosphere of the printing room, the problem of dew condensation inevitably occurs.

According to the dew condensation prevention device of the present invention, if cooled air of 12℃ or less is sent into the housing, no condensation will occur even if the relative humidity is as high as 80 to 90%. This eliminates printing problems such as moisture migration to adjacent printing units and tension fluctuations.

Conventionally, people were hesitant to cool the strip sufficiently for fear of these troubles, but the present invention makes it possible to cool the printed material strip 15 to the necessary and sufficient extent, and increase the printing speed to the full capacity of the mechanical printing machine. can. Please note that this condensation prevention device requires a refrigerator,
Although equipment such as an air cooler is required, the amount of air and amount of cooling heat required for each cooling cylinder 11 is small, and one set of refrigeration and cooling equipment can handle the cooling cylinders of many printing units. Since it is possible to deliver cooled air to the 11, the practical effect on the equipment cost is extremely large.

Note that by installing a pipe line returning from the housing 16 to the inlet 27 and reducing the amount of outside air taken in from the inlet 27, the load on the cooling air supply device 26 can be reduced.

[Effect of idea]

As explained above, according to the present invention, it is possible to achieve the practical effect of reliably preventing dew condensation on the surface of the cooling cylinder, regardless of the width of the strip-shaped printed matter.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional front view showing an embodiment of the dew condensation prevention device for a cooling cylinder according to the present invention, and FIG.
FIG. 3 is an explanatory view showing the related structure of the drying device and the present invention, and FIG. 4 is a vertical cross-sectional front view showing a conventional dew condensation prevention device for a cooling cylinder. 11... Cooling cylinder, 12, 12'... Bearing,
13, 13'...Frame, 15...Band-shaped printed matter,
16...Housing, 18...Drying room, 19,2
0...Slit, 21, 22...Door, 23...Pipe connection port, 24...Pipe line, 25...Blower, 26
...Cooling air supply device, 28...Filter, 30
...Heat exchanger, 33... Refrigerator, 35... Cooling tower.

Claims (1)

[Scope of utility model registration request] In a device for preventing dew condensation by blowing air with low absolute humidity onto the surface of a cooling cylinder, the entire cooling cylinder is surrounded by a housing having slits for introducing and discharging the printed material in the form of a strip. A dew condensation prevention device for a cooling cylinder, characterized in that the cooling cylinder is formed in a sealed shape, and air with low absolute humidity is forced into the housing to maintain the inside of the housing at a positive pressure from the outside of the housing.