JPH0443321Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to an offset printing machine, and in particular improves the structure of the dampening water return port of a water boat in which the water source roller of the dampening water device is immersed. In particular, the present invention relates to a dampening water circulation device that uniformly forms a film of dampening water over the entire width of a water source roller.

(Background of the idea) Offset printing utilizes the property that ink and dampening water repel each other, so it goes without saying that the dampening water supplied to the printing plate has a very large effect on print quality. stomach.

In order to supply dampening water to the printing plate, a calling roller is intermittently brought into contact with and separates from a water base roller immersed in a water boat. ) and continuously rotating dampening devices (the Dahlgren type is a typical example) in which a water/ink application roller is constantly in contact with a water base roller have been used.

Taking the former type of dampening water device as an example, and referring to the schematic side view in FIG. 6 and the partially enlarged explanatory diagram in FIG. The water head roller 2 with hydrophilic chrome plating is immersed across its entire width (in the direction perpendicular to the drawing), and is powered by the printing press itself or by an independent motor (not shown). rotated by.

The dampening water that adheres to the surface of the water base roller 2 as a water film is transferred from the water base roller 2 to the lateral oscillating roller 4 by the calling roller 3 that makes an intermittent oscillating motion.
and is supplied to the plate surface of the plate cylinder 6 via the applicator roller 5.

On the other hand, the ink is transferred from the ink reservoir 7 to the ink forming roller 9 via a large number of roller groups by the doctor roller 8 and transferred to the plate surface.

Note that 10 indicates a blanket cylinder, but the impression cylinder is omitted.

The water boat 1 contains the dampening water sent out via the water base roller 2 and the dampening water that disappears by evaporation, as well as ink and paper powder that return from the printing plate etc. via the calling roller 3. Despite contaminants such as paper fibers, there is always a constant amount (in other words, a constant water level), constant ingredients (constant alcohol content), and constant conditions (constant humidity, and , the above-mentioned impurities must be removed and clean), dampening water must be secured.

In order to meet these demands, a circulation unit 11 is provided, and this circulation unit 11 and water boat 1
are connected by a dampening water feed pipe 12 and a dampening water return pipe 13, thereby forming a dampening water circulation device. Although the circulation unit 11 is shown simply as a black box in the drawing, as is already well known in the art, the circulation unit 11 includes a pump for circulation, a cooler for cooling, an alcohol adjustment supply device, and a contaminant. Contains filters, etc. to remove

The feed pipe 12 connected to the circulation unit 11 supplies dampening water from the feed port 14, and
The dampening water is returned from the return port 15 through the return pipe 13.

(Problem to be solved by the invention) It has been pointed out that printing quality is greatly affected by the state of supply of dampening water to the plate surface, and in order to obtain good printing quality, first,
Unless the dampening water is formed as a uniform water film over the entire width of the water base roller 2 immersed in the water bucket 1, dampening water cannot be supplied to the plate surface in a well-balanced manner. Furthermore, it goes without saying that the newly formed water film must not contain paper dust or paper fibers.

After many experiments, the inventor of this invention determined the uniformity of the water film formed on the surface of the water head roller 2 (the thickness of the water film must be constant over the entire width). The uniformity of the water film formed in the water tank 2 depends on the surface flow velocity of the dampening water in the water tank 1." In other words, the bottom layer current velocity in the water boat 1 (the water level of the water boat 1 is roughly divided into the surface layer and the bottom layer, and the flow velocity there is the problem).
No matter what, it is the surface flow velocity of the dampening water in the water boat 1 that determines the state of water film formation on the water head roller 2. , constant, preferably close to 0,
They discovered that a uniform water film was formed. Furthermore, the uniformity of the water film formed on the rotating water base roller 2 immersed to a certain depth in the water fountain 1 is extremely dependent on the flow velocity distribution of surface water very close to the surface of the dampening solution. That's what I'm doing.

If we consider the above knowledge by returning to the structure of the dampening water circulation system, we can see that the water boat 1 has a feed port 1 of the feed pipe 12.
4 and the return port 15 of the return pipe 13, dampening water flows between it and the circulation unit 11. Considering only from the viewpoint of print quality, it is necessary to avoid disturbing the surface layer flow velocity distribution. It's good to do that.

However, as mentioned above, it is unavoidable that foreign substances such as paper dust and paper fibers that have returned from the atmosphere and the surface of the printing plate float in the water boat 1. Therefore, it is necessary to circulate these foreign substances floating on the surface layer. It must be removed by the unit 11 and recycled as clean dampening water.

(Summary of the invention) The present invention was made in view of the above-mentioned problems and provides an advanced dampening water circulation device. The objective is to reliably remove floating objects in the water tank, thereby achieving good printing quality.

For this purpose, the dampening water circulation device according to the present invention divides the return port of the return pipe by a weir, and essentially connects the surface water intake of the dampening water to the weir from the water source roller. The intake port is located far away and has a relatively small intake volume so as not to disturb the surface flow velocity distribution as much as possible, and the bottom water intake port is provided with a relatively large intake volume. ,
It is designed to ensure circulation of a certain amount of dampening water.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of the dampening water circulation device according to the present invention, FIG. 2 is a sectional view taken in the direction of the arrow in FIG. 1, and FIG. 3 is the main part of FIG. 1. The enlarged plan view, FIG. 4, is a sectional view taken along the - line in FIG. 3, and FIG. 5 is also a sectional view taken along the - line. The same reference numerals are given.

The water cannon 16 is a tray for dampening water containing isopropyl alcohol, and it goes without saying that it has a width sufficient to immerse the fountain roller 2 over its entire width.

The water base roller 2, which is coated with hydrophilic chrome plating, is supported at both ends by side walls (not shown), and is driven and rotated by the power of the printing press itself or an independent motor. The water base roller 2 is contacted by a calling roller 3 in the case of a calling type dampening device, and a water/ink forming roller 9 in the case of a continuous rotary dampening device. Supply dampening water from inside the boat to the plate.

A feed pipe 1 is connected to the water boat 16 from the circulation unit 11.
2 are connected to each other, and dampening water is circulated through a return pipe 13.

Both ends of the feed pipe 12 are connected to a water feed sill 17 fixed to the water boat 16, and one end of this water feed sill 17 is extended downward to form a feed port 18, which is opened below the water surface of the dampening water. are doing. In this way, feed port 1
8 is opened below the water surface (in other words, the reference water level for dampening water is set at a higher position than the feed port 18), so that the surface flow velocity is not disturbed even if it is on the water feed side.

A water boat 16 having a generally rectangular planar shape is located at a location opposite to the feed port 18 in the width direction of the water boat 16.
A return port 19 of the return pipe 13 is provided at a location where the return pipe 13 is particularly extended. The dampening water in the water cannon 16 passes through the return pipe 13 from this return port 19 to the circulation unit 11.
I will return to . Therefore, as best shown in FIG. 5, the height of the top surface of this return port 19 basically determines the water level of the dampening water in the water cannon 16.
Therefore, the return port 19 greatly influences the surface layer flow velocity distribution of dampening water. Further, as described above, foreign substances such as paper powder and paper fibers that may float in the water boat 16 must also be collected and removed through the return port 19.

In the present device, the return port 19, which is separated from the water head roller 2 in plan view, is divided into sections in the water boat 16 by weirs 20. In this weir 20, there is a surface water intake port 21 that takes in only the surface water near the water surface out of dampening water, and a bottom water intake port that takes in only the bottom water near the bottom of the water boat 16. 22 is cut out.

Among these, the surface water intake port 21 is
The cutout is located as far away from the water head roller 2 as possible and has a narrow width so that the intake amount is relatively small enough to mainly take in floating foreign matter.

On the other hand, the bottom layer water intake ports 22 are cut out at two locations and have a wide width so that the intake amount is relatively large, regardless of the presence of the water head roller 2.

Therefore, in the present device, the small-capacity surface water intake port 21 can remove suspended matter without disturbing the surface layer flow velocity distribution, and the large-capacity bottom layer water intake port 22 allows Adequate circulation is ensured for dampening water cooling and conditioning. A uniform water film is always formed on the water source roller 2, optimizing the supply of dampening water to the plate surface, and ensuring good printing quality.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of a dampening water circulating apparatus according to the present invention, FIG. 2 is a sectional view taken from the direction of the arrow in FIG. 1, FIG. 3 is an enlarged plan view of the main part of FIG. 1, FIG. 4 is a sectional view taken along line - in FIG. 3, FIG. 5 is a sectional view taken along line - in FIG. 6 is a schematic side view showing a conventional dampening water apparatus, and FIG.
FIG. 2 is a partially enlarged explanatory diagram of the water source roller; 6 is a plate cylinder; 11 is a circulation unit; 12 is a feed pipe; 13 is a return pipe;
16...water boat, 17...water supply shallow, 18...feed outlet, 19...return outlet, 20...weir, 21...surface water intake, 22...bottom water intake.

Claims (1)

[Scope of Claim for Utility Model Registration] A dampening water circulation device for an offset printing press in which dampening water is circulated by a circulation unit through a feed pipe and a return pipe through a water boat in which a water head roller is immersed. The return port of the return pipe is divided in the water boat by a weir, and the surface water intake of the dampening water is placed in the weir at a place essentially far from the water head roller, and the intake amount is is provided with a relatively small capacity, and on the other hand, the bottom layer water intake of the dampening water is provided with a relatively large intake volume.