GB2143179A

GB2143179A - A method and device for simultaneous wetting and inking in offset printing

Info

Publication number: GB2143179A
Application number: GB08408710A
Authority: GB
Inventors: Luigi Ghislaberti
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-06-17
Filing date: 1984-04-04
Publication date: 1985-02-06
Also published as: IT8302922A0; GB8408710D0; JPS604060A; GB2143179B; DE3343562A1; IT1195383B

Abstract

The plate cylinder A and inking system B are provided with two further inking rollers (5, 6) in contact with the plate. An intermediate axially reciprocated roller (13) is provided to connect with unit 8. A further roller (12) is also provided, located between said two rollers (5, 6), on the surface of which the wetting solution is supplied from a container (14, 14A, 14B) divided into two sections for maintaining at a constant rate the amount of wetting solution and alcohol percent. In the container (14, 14A, 14B) is a metering or proportioning roller and a metering feeding roller (9, 8) supplying the metered solution to a transfer roller (7) contacting said intermediate roller (12). Upon start-up, only rollers 5 and 6 contact the plate, forme rollers 1-4 being brought into operation later. <IMAGE>

Description

SPECIFICATION A method and apparatus for simultaneous matrix wetting and inking in offset printing This invention is concerned with a method and device enabling simultaneous matrix wetting and inking in offset printing, achieving an optimum balance between ink and wetting solution.

As is well known, such a balance between ink and wetting solution is of a very high importance in a printing process in order to prevent ink from adhering to the not printing zones (countergraphism) of the plate, without any interference with respect to the printing zones (graphisms), which are instead intended to receive ink. It often occurs that this balance is made unstable by the development of at- tractive and repulsive forces at molecular level between ink and water or wetting solution, thus being prejudicial to the possibility of providing good printing results if the amounts of the two components have not been suitably adjusted or placed at poor contact with each other.

The systems at present known mostly contemplate to provide a uniform amount of water without worrying about ensuring the basic stability of the thermodynamic balance between ink and wetting solution. Such systems are mostly based on the concept of ink and water transfer on the matrix or on the first inking rollers. By practical printing tests it has been found that a series of subsequent disadvantages would occur, even if a uniform and constant film is initially distriuted or transferred.

It is the object of the present invention to provide a method and device having the purpose of improving the accuracy in adjusting the wetting solution, and also operating on the ink amount to provide a pre-emulsion in vibrating battery, since a satisfactory inking would depend on the arrangement of the inking rollers and hence on the ink distribution.

The invention will now be described in further detail with reference to an unrestrictive embodiment thereof to be considered in connection with the accompanying drawings, in which: Figure 1 is a view schematically showing a machine or device according to the invention; Figure 2 is a diagram showing graphs for the compound distribution percents; Figure 3 is a schematic general view, also enablin a comparison with the prior art state; and Figure 4, 5 and 6 are views showing several operative steps of the wetting and inking device.

Referring first to Fig. 1, to be considered together with the other Figures of the drawings, it will be seen that provision is made for a plate carrying roller designated at A and a unit of inking and vibrating rollers designated by general reference B.

According to the invention, there is provided two new inking rollers 5 and 6 in contact with the matrix A, by an intermediate vibrating roller 1 3 providing the contact with the vibrating unit B. Reference numerals 1, 2 and 3, as well as the various references indicated for the upper rollers of the vibrating unit B, merely indicate a conventional arrangement for the vibrating battery and will not be herein further indicated as included in the general reference designated by B in Fig.

1. From this last Figure, the provision will be seen for a further vibrating roller 1 2 in contact with the inking rollers 5 and 6, as well as in contact with a transfer roller 7, which can be moved to and away with respect to two further metering or proportioning and feeding rollers 8 and 9, the working steps being more clearly shown in Figs. 4, 5 and 6, where there is also shown the contact and separation of the rollers 5 and 6 with respect to the roller or cylinder A, as well as the contact and separation of the roller 7 with respect to the rollers 8 and 9. These two last mentioned rollers 8 and 9 draw in a reservoir or container generally designated at 14 and which is divided into two sections respectively designated by reference numerals 1 4A and 1 4B.This expedient has the purpose of maintaining at a constant value the amount of wetting solution and alcohol percentage. The section 1 4a collects a minimum amount of wetting solution to avoid the evaporation of the alcohol therein contained, while the section 14B collects the excess liquid for supply thereof to the mixer (not shown) providing for recycling.

The metering or proportioning roller 9, which is out of phase in rotation with respect to the metering feeding roller 8, supplies the excess solution to said section 1 4B of the container 14.

Of course, suitable technical expedients would be resorted to as to the use of the material. For example, the roller 9 is provided with a surface of relatively hard material, such as steel, coated with resilient material, while the metering feeding roller 8 has a surface of coarse-grained not resilient material (preferably chromium because of being hydrophile).

The operation of the device as well as the method according to the invention would clearly appear from the foregoing. Thus, the method and device according to the present invention provide that the solution is supplied on the inking battery throughout the preinking operation, while only the two inking rollers 5 and 6 transfer the ink-water-alcohol compound on the matrix. Thus, the wetting solution can emulsify with the ink, giving rise to the most suitable conditions for starting the printing step without waste or discards.

In Fig. 5 the device is shown at printing step (second step). All of the inking rollers are in contact on the cylinder or roller A and supply thereto the ink-water-alcohol compound which is now stable owing to the previous vibration. This allows to eliminate a first wetting group and a second inking step, since both the ink and wetting solution are simultaneously transferred on the printing zones and on the not printing zones of the matrix.

Fig. 6 shows the rest step (third step). All of the inking rollers 1, 2, 3, 4, 5 and 6 separate or move away from the matrix A and the transfer roller 7 separates or moves away from the metering feeding roller 8. At this operative step, the roller 8 and the roller 9 continue to rotate maintaining constant the solution film.

The rollers of the wetting system are rotata bly driven by a variable speed motor, suitably controlled and here not shown. Particularly, the drive is given to roller 8, so that roller 9, which is acted upon for adjustment, will not directly receive the transmission vibrations which would adversely affect such an adjustment.

Finally, it should be pointed out that this wetting system contemplates the possibility of automatically accelerating the speed at start to compensate for, with a larger amount of water and alcohol, the ink being accumulated on the inking battery.

Referring to the graph of Fig. 2, in connection with Figs. 5 and 6, it will be seen that the inking rollers provided according to the invention provide or distribute ink in an amount of about 12% and reduce the contribution of ink by the original first inking roller 4 from 42 to 30%. Thereby, it results that the supply of the inking solution can be now effected more uniformly, and particularly without any significant alteration in the amount of ink arriving at the plate.

Of course, the invention is not limited to the practical details here shown and/or described, but also comprises all of the changes and equivalent forms provided on the ground of the present inventive idea.

Claims

1. A method of matrix wetting and inking in offset printing for simultaneous matrix wetting and inking, in which it is provided to supply the solution on the inking battery throughout the prewetting operation with the use of only two inking rollers, transferring the ink-water-alcohol compound on the matrix in the presence of an intermediate vibrating roller brought to contact with said two inking rollers, the surface of the intermediate roller having the wetting solution supplied thereon from a container, the latter having thereon a metering and feeding roller as well as an adjustment metering roller of offset speed relative to the metering and feeding roller on said container, and acting by a control system, in which said metering and feeding roller is driven, so that said second metering roller on the container is free of vibrations.

2. A method as claimed in Claim 1, in which a variable speed is imparted to said metering and feeding roller.

3. A device for carrying out the method according to the preceding claims, having in well known manner a plate carrying cylinder of roller and a unit of inking and vibrating rollers, in which the device comprises two further movable inking rollers contacting the matrix, an intermediate vibrating roller contacting the vibrating unit, a further vibrating roller located between said two further inking rollers, on the surface of which the wetting solution is supplied from a container divided into two sections for maintaining at a constant value the amount of wetting solution and the alcohol percentage, on said container there being provided a metering roller and a metering and feeding roller supplying the metered solution to a transfer roller contacting said intermediate roller.

4. A device as claimed in Claim 3, including comprising a drive unit for the rollers on the container, wherein the drive is provided on the metering and feeding roller, while the metering roller is offset with respect to the metering and feeding roller.

5. A method of matrix wetting and inking in offset printing for simultaneous wetting and inking substantially as described herein with reference to and as illustrated in the accompanying drawings.

6. A device for carrying out a method of matrix wetting and inking in offset printing substantialy as described herein with reference to and as illustrated in the accompanying drawings.