JPS5838161A - Offset printer - Google Patents

Abstract

PURPOSE:To prevent the staining of the ground of a printed material by properly controlling the supply of moistening water by providing a moistening water supplier to a branket cylinder by which the master image is transferred to a printing paper for printing. CONSTITUTION:An etching liquid from an etching unit 5 is coated on a master wound around a plate cylinder 1, an ink from an inking unit 6 and moistening water from a moistening water supplier are mixed together and coated on the master, and then the image of the master is transferred to a branket cylinder 2 and printed on a printing paper sent to the pressing portion between the branket cylinder 2 and a pressure cylinder 2. In such an offset printer, a water supplieer 8 to properly and controllable supply moistening water A stored in a supply tank 8a through a water supply roller 8b, a water transfer roller 8c, and a morton roller 8d is provided to the branket cylinder 2.

Description

[Detailed description of the invention] This invention relates to an offset printing machine.

In an offset printing press, as is well known, the master (plate material) set in the plate cylinder is etched (desensitized) in advance.

This etching is carried out in order to make the non-image area of the master desensitized, thereby preventing ink from adhering to the non-image area, thereby preventing so-called smearing of printed matter. When applying ink to each star, ink and dampening water are applied to the master in order to maintain the effectiveness of the etching layer of the master.

By the way, in conventional offset printing machines, the above-mentioned dampening water is mixed into ink and applied to the master. Therefore, the amount of dampening water supplied to the master is approximately constant during any printing process. The dampening water applied to this master is transferred to or absorbed by the printing paper during printing. Therefore, in general, when the amount of paper printed is large (around 100 sheets), more dampening water on the master is absorbed by the printing paper than the amount of ink consumed, and the ink on the master and dampening water are mixed. This has the disadvantage that the quantitative balance is disrupted and scumming occurs on printed matter. When such dirt occurs,
Conventionally, operators have been able to prevent this from occurring by adjusting the amount of ink supplied based on their experience.

However, the occurrence of background smudges due to insufficient supply of dampening water varies considerably depending on the quality of the printing paper.
Avoiding this by simply adjusting the supply amount of Lt I/K was not very effective.

In other words, when the printing paper is paper that absorbs a large amount of dampening water, such as straw paper or medium-quality paper, and when it is paper that absorbs a relatively small amount of dampening water, such as high-quality paper, The number of prints where background smear occurs and the degree of background smear vary significantly. Therefore, as a workaround by adjusting the amount of ink, what is the paper quality and number of prints? There is a risk of causing new defects such as the hassle of constant monitoring and the fading of ink images due to insufficient ink supply.

Furthermore, when several types of paper of different paper quality are printed alternately, such as when printing slips, the amount of dampening water absorbed by the paper changes for each paper, so the conventional It is almost impossible to prevent the occurrence of background smudges depending on the printing method.

The present invention has been made in view of the above-mentioned problems, and its object is to provide an offset printing machine which eliminates the shortage of supply of dampening water.

The present invention will be explained below with reference to an embodiment shown in the drawings.

The figure is a schematic diagram of an offset printing press according to the invention.

As is well known, in printing by this type of offset printing press, in FIG. 1, a master (not shown) is first wound around a plate cylinder 1. Then, before applying ink to this master. Then, the etching liquid is applied to the master plate using the Molton roller of the etching unit 5.

Next, the inking unit 6 and the dampening water supply device 7
The ink and dampening water are mixed together and deposited on the master. The ink deposited on the master is transferred to the blanket cylinder 2, which rotates in contact with the master.

The paper feed roller 4 transfers the image to the printing paper fed into the pressure contact portion of the blanket cylinder 2 and the pressure cylinder 3. After the printed paper is peeled off from the pressure cylinder 3 by a paper discharge claw, it is discharged onto a paper discharge table 12 via a paper discharge presser roller 11.

A feature of the offset printing press according to the present invention is that, as shown in the figure, a water replenishing device 8 is provided for supplying dampening water AY to the blanket cylinder 2.

This water supply replenishment device 8 includes a replenishment tank 8a refilled with dampening water A, and a water supply roller 8b whose peripheral surface is partially submerged in dampening water flowing out to the dampening water supply section of the replenishment tank 8a. The water transfer row 28C rotates in contact with the water supply row 28b.
, and a molton roller 8d that rotates in contact with the water transfer roller 8C and the blanket cylinder 2.

In this water supply replenishing device, before the ink transfer process to the blanket cylinder 2 (during the above-mentioned printing process), the Molton roller 8d is separated from the blanket cylinder and rotates for warming up. After the ink is transferred to the blanket cylinder 2,
The malt/roller 8d contacts the surface of the blanket roller 2 and rotates. This malt/roller 8d separates from the blanket cylinder 2 again when printing is completed and the master is discharged, and the operation of the apparatus σ is stopped.

The structure of this water supply replenishing device is substantially the same as that of the well-known dampening water supply device 17 and the etching unit 5, so a detailed description thereof will be omitted. In some cases, it may be in constant contact with the blanket cylinder, or it may be rotated into and out of contact with the blanket cylinder sequentially depending on the type of printing paper and the amount of dampening water supplied.

Further, the water supply means of this water supply replenishment device may be replaced with a Molton roller sprayer or the like.

In addition, the background smudge condition of the blanket cylinder (or printed material) can be detected in advance using a sensor or visually, and the operation time of the malt/roller etc. (water supply time to the blanket cylinder) can be determined accordingly. It may be automatically controlled.

By the way, printing? The finished blanket cylinder 2 is cleaned by a cleaning unit 9.

Ready for next print.

As described above, the offset printing machine according to the present invention is equipped with a water supply replenishment device for replenishing dampening water to the blanket cylinder at the appropriate time. Can prevent dirt on cylinders and prints.

Also, dampening water? Since we are refilling the blanket cylinder rather than the master, will the master become smudged (a fatal drawback in printing) when it is refilled? The amount of dampening water supplied to the master does not change depending on the quality of the printing paper.

In addition, as dampening water supplied from this device.

It consists of water, alcohol, etchant diluent, activator, etc.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the present invention. 1...Plate cylinder, 2...Blanket cylinder, 3...G L/, shear? Linda-1A... dampening water. 8... Water supply replenishment device. Agent Kabayama = Δ1 blade h = 23

Claims (1)

[Claims] 1. An offset printing machine having a plate cylinder, a blanket cylinder, and a pressure cylinder, characterized in that a blanket cylinder water supply device is provided to supply dampening water to the blanket cylinder in a timely manner.