WO2001045945A1

WO2001045945A1 - A method and device at a spray dampening apparatus

Info

Publication number: WO2001045945A1
Application number: PCT/SE2000/002568
Authority: WO
Inventors: Birger Hansson
Original assignee: Baldwin Jimek Ab
Priority date: 1999-12-21
Filing date: 2000-12-18
Publication date: 2001-06-28
Also published as: SE9904684D0; SE521304C2; SE9904684L; DE10085338T1; AU2418901A

Abstract

The amount of fountain solution sprayed on a printing press roller (2) from a spray dampening apparatus (1) arranged at the roller may have to be controlled. For this purpose at screening plate (6) provided with openings is arranged between spray nozzles (5) in the spray dampening apparatus and the roller for preventing portions of the fountain solution from reaching the roller.

Description

A METHOD AND DEVICE AT A SPRAY DAMPENING APPARATUS

Technical Field The present invention relates to a method and a device for controlling the amount of fountain solution sprayed in a pulsed manner on a printing press roller from a spray dampening apparatus arranged at the roller. Background of the Invention In the printing art it is well known that fountain solution is sprayed on a roller by means of spray nozzles. For obtaining the desired effect of this fountain solution on the roller and in the printing press it is of great importance that the appropriate amount of solution is evenly sprayed on the roller.

With presently used nozzles spray pulses or on-pulses can only be supplied to the nozzles at comparatively long intervals resulting in a spray time of say 10% of the total operating time, if the amount requirement shall be fulfilled. On the other hand, this means that the solution distribution on the roller will not be optimal. The solution distribution on the roller would be better if the frequency of the on-pulses could be increased, so that a spray time of say 30% could be achieved. With other factors unchanged, this would however lead to an excess amount of fountain solution being sprayed.

Possible remedies to the problem with excess fountain solution amount could be to decrease the size of each nozzle, the number of nozzles, and/or the on-time for each pulse. However, each of these remedies has its problems and drawbacks and does not practically provide the appropriate amount of fountain solution on the roller, if the on-time frequency of the nozzles is increased.

The main object of the invention is to find a way to solve the problem of spraying an appropriate amount of fountain solution at an increased on-time frequency. The Invention

This is according to the invention attained in that a portion of the sprayed fountain solution is mechanically prevented from reaching the roller. Practically, a screening plate or a screening cloth provided with openings may be arranged between the spray nozzles in the spray dampening apparatus and the roller. The Drawing

The invention will be described in further detail below reference being made to the accompanying drawing, in which

Figs 1A and IB illustrate two different pulse patterns at the spraying of fountain solution in a printing press, Fig 2 is a very schematic side-view of a spray dampening apparatus at a printing press roller,

Fig 3 is a top view of the arrangement shown in Fig 2 , and

Fig 4 is a view of a screening plate for use in the arrangement according to Figs 2 and 3. Description of Embodiments

As is well known in the printing art, fountain solution is sprayed on a roller in a printing press. It is of great importance that the fountain solution is sprayed as evenly as possible, but also with an appropriate volume per time unit. For this latter reason, it is not possible to allow fountain solution to be continouosly sprayed through spray nozzles in a spray beam arranged at the roller. Instead, the spray nozzles are operated pulsewise, as is shown in Fig 1.

In Fig 1A a presently used pulse pattern for the spray nozzles is illustrated. Short on-pulses are provided at regular intervals, resulting - in the shown case - in a spray time of 10% of the total time. A far better result with regard to the evenness of the spraying would be obtained with a pulse pattern as illustrated in Fig IB, where the on-time is 33%. With other factors unchanged, this would however result in that too much fountain solution would be sprayed on the printing press roller. A spray dampening apparatus 1 of a generally conventional design is shown in Figs 2 and 3. In this design, however, the above drawback is obviated.

The shown spray dampening apparatus 1 is mounted in the vicinity of a printing press roller 2. It comprises a spray beam 3 in a spray casing 4. Spray nozzles 5 are arranged in the spray beam 3 and are preferably evenly distributed for obtaining an even spray pattern on the roller 2, as is illustrated in Fig 3. In the shown case the number of nozzles 5 is five, but this number is of course dependant on for example the length of the roller 2 and the spray pattern from the nozzles 5.

A screening plate 6 is arranged in the spray casing 3. As is illustrated in a non-limiting example in Fig 4, the plate 6 has openings, so that a certain portion of the sprayed fountain solution passes through the openings and reaches the roller 2, whereas the remaining fountain solution hits the plate 6 and flows down in the spray casing 4 and may ultimately be returned to a supply therefore. The shape, size, and numbers of openings in the plate 6 as well as the position thereof in the spray casing may vary according to the actual circumstances.

The screening plate 6 may be provided with a number of circular holes, substantially as shown in Fig 4. Preferably, the openings are evenly distributed over the plate 6, but it may also be possible to choose another distribution for a specific purpose.

As an alternative to the screening plate it is also possible to make use of a screening cloth, preferably of a synthetic material.

Claims

1. A method for controlling the amount of fountain solution sprayed in a pulsed manner on a printing press roller (2) from a spray dampening apparatus (1) arranged at the roller, c h a r a c t e r i z e d in that a portion of the sprayed fountain solution is mechanically prevented from reaching the roller (2) .

2. A device for controlling the amount of fountain solution sprayed in a pulsed manner on a printing press roller (2) from a spray dampening apparatus (1) arranged at the roller, c h a r a c t e r i z e d in that a screening means (6) provided with openings is arranged between spray nozzles (5) in the spray dampening apparatus (1) and the roller (2) for preventing portions of the sprayed fountain solution from reaching the roller.

3. A device according to claim 2, in which the spray dampening apparatus (1) comprises a spray beam (3) with the spray nozzles (5) and a spray casing (4) extending towards the roller (2) , c h a r a c t e r i z e d in that the screening means (6) is fastened in the spray casing (4) .

4. A device according to claim 3, c h a r a c t e ri z e d in that the screening means is a screening plate

(6) .

5. A device according to claim 4, c h a r a c t e r- i z e d in that the screening plate (6) has an evenly distributed pattern of openings.

6. A device according to claim 3, c h a r a c t e ri z e d in that the screening means is a screening cloth, preferably of a synthetic material 7. A device according to claim 2, c h a r a c t e ri z e d in that means are provided for returning fountain solution, hitting the screening means (6) and not passing through the openings therein, to the supply for fountain solution.