JPH0327790Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] This invention relates to a dampening device in, for example, an offset printing press.

[Background of the idea]

In general, in offset printing presses, it is necessary for the dampening liquid to spread flat and form a thin film to uniformly supply moisture to the plate cylinder. Conventionally, devices of this type have attempted to spread a dampening liquid film evenly, uniformly, and evenly over the surface of the plate cylinder.

There are dampening devices for offset printing presses as shown in FIGS. 3 to 7. Fig. 3 is a block diagram of the offset rotary press, Fig. 4 is a block diagram of the rollers of the printing unit, Fig. 5 is a vertical sectional view of the dampening water supply group, and Fig. 6 is a sectional view of the dampening water supply group in the conventional technology. , FIG. 7 is a characteristic diagram showing the amount of dampening water in FIG. 6.

In the figure, paper 2 is fed out of a web 1 by a paper feeder 3. This paper 2 is fed to a printing unit 4 and printed on the paper 2. This printing unit 4 consists of two rubber cylinders 5,
5', a pair of plate cylinders 6, 6' arranged parallel to and in contact with each other in the axial direction of the rubbers 5, 5', and an ink supply group 10 and a dampening water supply group 11 connected to the plate cylinder 6 in the axial direction. They are arranged so as to be in parallel pressure contact.

The paper 2 printed by the printing unit 4 is dried by being blown with hot air by a drying device 7. Thereafter, the paper is cooled by a cooling roller 8 to fix the ink on the paper, folded by a folding machine 9, and discharged.

A water cannon 12 for storing fresh water or a liquid 13 mixed with additives is fixed to the lower part of the dampening water supply group 11 by a holder (not shown). Inside this water boat 12 is a former roller 14 that pumps up the liquid 13.
is pivoted for fine adjustment. This original roller 1
4 is connected to a DC motor (not shown).
A transfer roller 15 is pivotally supported above the original roller 14 so as to have a predetermined slip ratio and can be finely adjusted. The side of this transfer roller 15 is attached to the applicator roller 1.
6 is pivotally supported with a predetermined sliding ratio so as to be finely adjustable. The application roller 16 is an elastic roller whose surface is wrapped with synthetic rubber or resin. The forming roller 16 and the plate cylinder 6 do not slip relative to each other and have the same circumferential speed.

With the above configuration, when the original roller 14 is driven to rotate, the liquid 13 is drawn up onto the outer peripheral surface of the original roller 14 and held there. Thereafter, the liquid 13 is supplied to the transfer roller 15 and the applicator roller 16 in this order and adheres to the plate cylinder 6. At this time, the thickness of the liquid 13 is
Original roller 14, transfer roller 15 and application roller 1
6, the thickness gradually becomes thinner as shown in a, b, and c of FIG. A thin liquid film is then deposited on the non-image area of the plate cylinder 6, and then the ink kneaded in the ink supply group 10 is applied to the image area to which the liquid 13 is not attached. After that, apply the ink on the printing area to the rubber cylinder 5.
The printing pressure is applied between the blanket cylinders 5 and 5' which are vertically opposed to each other, and the paper 2 is passed through for printing. At this time, between the original roller 14 and the transfer roller 15 and between the transfer roller 1
5. As shown in FIG. 7, the liquid film between the forming rollers 16 is thicker toward both ends than in the center, so the amount of dampening water is oversupplied by δ, and printing It becomes difficult to adjust the balance between the ink and the liquid inside, and small droplets of liquid fly onto the paper 2, causing white spots to appear locally. In addition, excessive emulsification of the ink reduces the viscosity of the ink. This has led to problems such as a decrease in the brightness of the printed matter, an increase in wrinkles due to drying, an increase in scumming, and other deterioration in print quality.

[Purpose of invention]

The object of this invention is to provide a dampening device which eliminates the above-mentioned problems and makes it possible to supply a uniform film of dampening solution over the entire width of the roller.

[Summary of the idea]

In order to achieve the above object, this invention is characterized in that the outer diameter of the transfer roller is larger at both ends than at the center.

[Example of idea]

An embodiment of this invention will be described below with reference to FIGS. 1 and 2. Note that parts that are the same as those in the conventional device are designated by the same reference numerals. FIG. 1 is a front view of the dampening device in this device, and FIG. 2 is a characteristic diagram showing the amount of dampening water between the rollers in FIG. In the figure, the outer diameter of the central portion of the transfer roller 15 is gradually increased toward both ends. Therefore, between the transfer roller 15 and the original roller 14, the transfer roller 15
The contact pressure between the applicator rollers 16 is higher at both ends than at the center, so that the amount of dampening water supplied can be kept constant as shown in FIG. As an example,
In the case of a roller surface length of 550 mm and a roller diameter of 100 φ, the outer diameter of both ends should be 0.02 to 0.1 mm larger than the center, and 0.05 mm is particularly appropriate.

According to the above embodiment, it is possible to form a uniform thin liquid film over the entire width of the roller, and therefore (1) there is no need for fine adjustment during operation. (2) Paper waste is reduced. (3)
The emulsification of the ink is reduced and the brightness of the printed matter is increased.
(4) Reduce ink consumption by approximately 15%. In addition, since the amount of dampening water is kept to a minimum, drying humidity can be lowered, thereby reducing wrinkles in printed matter.

[Effect of idea]

As described above, this invention has the effect of being able to form a uniform thin film over the entire width of the roller.

[Brief explanation of drawings]

Figure 1 is a front view of the dampening device in this invented device, Figure 2 is a characteristic diagram showing the amount of dampening water between the rollers in Figure 1, Figure 3 is a configuration diagram of the offset rotary press, and Figure 4 is a diagram showing the amount of dampening water between the rollers in Figure 1. The figure shows the configuration of the rollers in the printing unit.
FIG. 5 is a longitudinal sectional view of the water supply group, FIG. 6 is a sectional view of the water supply group in the prior art, and FIG. 7 is a characteristic diagram showing the amount of dampening water in FIG. 6. 6... Plate cylinder, 11... Water supply group, 12... Water boat, 13... Water, 14... Original roller, 15... Transfer roller, 16... Forming roller, a... Water of original roller Adhesion, b...Water adhesion to the transfer roller, c...
...Adhesion of water on the forming roller, δ...Difference in the amount of dampening water, x...Difference in the outer diameter of the transfer roller.

Claims (1)

[Scope of utility model registration request] A water boat forming a tank for dampening liquid; a source roller disposed within the water boat for pumping up the dampening liquid; and a roller that is in pressure contact with the plate cylinder and attaching the dampening liquid to the plate cylinder. In a dampening device for an offset printing press comprising a roller and a transfer roller that is in pressure contact between the form roller and the original roller and transfers the dampening liquid, the dampening device is provided in a dampening device that extends from the center of the transfer roller to both ends thereof. Therefore, the dampening device is characterized in that the outer diameter is gradually increased, and the diameter at both ends is 0.02 to 0.1 mm larger than the diameter at the center.