GB2265112A

GB2265112A - Inking device for forme roller.

Info

Publication number: GB2265112A
Application number: GB9305111A
Authority: GB
Inventors: Anton Hamm; Dieter Maurer
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1992-03-16
Filing date: 1993-03-12
Publication date: 1993-09-22
Also published as: ITRM930125A1; JPH0640014A; DE4208295A1; GB9305111D0; IT1261201B; ITRM930125A0

Description

2265112 Inking Device for a Forme Roller The invention relates to an

inking device for a forme roller, specifically for a forme roller for photogravure and other intaglio processes. Such a device generally has a doctor blade and an ink bath arranged below the forme roller, as well as an ink pump, and is preferably used in web-fed rotary printing machines.

Chamber doctor blades are known for inking forme rollers - see for instance DE 37 04 433 C2. The chamber doctor blade shown here contains a doctor blade holder with two doctor blades and two side portions for lateral sealing. Set on the forme roller the aforementioned parts together with the roller form a chamber which is filled and rinsed with ink conveyed by an ink pump.

The disadvantage with this inking device is that the doctor blades are secured in the doctor blade holder with only limited prestressing and cannot be subsequently stressed when the blades start to wear since the holder assumes a stationary position as a part of the inking chamber. With increasing wear of the doctor blades their force of abutment decreases and the blades require immediate replacement. The replacement itself is expensive as the doctor blades have to be fitted in from the side. Too much lateral play of the working doctor blades with respect to the side portions would lead to ink rings on the forme roller and consequently to deterioration in the printed image. Furthermore the side portions adjacent to the forme roller for the purpose of sealing are subject to wear. The resulting ablation tends to clog inkconveying deDressions or cells of the forme roller which can spoil the ink transfer, especially when printing panorama pages. Finally, with chamber doctor blades there are areas which are but poorly rinsed and consequently where the ink may emulsify and so-called emulsion pockets can form.

In another chamber doctor blade device (DE 38 43 017 Cl) the side portions are arranged on the forme roller with a spacing, and below the chamber doctor blade a bath is arranged for catching any escaping ink. In addition the working doctor blade is tightly fitted to the side portions.

It is true that this inking device avoids friction of the side portions on the forme roller such as can lead to wear clogging the depressions, but mixtures of this ink from adjacent sides are produced at the side portions, which leads to deterioration in the printed image, particularly when printing large widths of type areas. It is also true that the working doctor blade does not need to be fitted in. However in the pivoting region of the working doctor blades the device has a gap towards the side portions, the blade being subjected in the region of the gap to greater load with consequent greater wear.

Spraying printing ink onto a cylinder to be inked is known per se, for instance from DE-PS 456 308. However, this does not deal with forme roller inking, i.e. filling ink cells with typical consequent wiping of the lands, but simply with a voluminous ink-zonedosed application of an ink layer by means of spacedapart individual nozzles. The application of ink is effected in a stripwise manner which is not suitable for anilox inking units. In any case the row of nozzles is not suitable for inking the forme roller with simultaneous rinsing of the forme depressions.

An aim of the invention is to produce an inking device of the abovementioned type which is not hampered by the above-mentioned disadvantages of short service life of the doctor blade, sealing defects and 1 -1 unsatisfactory rinsing.

The invention provides an inking device for a forme roller, including a doctor blade to be applied to the forme roller, and a slotted nozzle for applying the ink to the forme roller, the doctor blade being arranged in the downstream direction from the nozzle.

The spray nozzle reliably applies the ink to the forme roller as a thin film. Because of this it is not necessary to include side portions preventing lateral dispersion or mixing of ink. A specific small excess of ink is used according to the distance of the nozzle from the forme roller, and is wiped off by the doctor blade. During the ink spraying the depressions in the forme roller are completely rinsed out by high impact pressure of the ink and freed from impurities such as e.g. paper dust. Excess ink is substantially completely wiped off by the doctor blade and runs back unhindered into the ink container, as a result of which ink emulsions are avoided. By eliminating the side parts which are usual in chamber doctor blades extremely wide type areas can be produced, and the thin application allows a good separation of different inks printed adjacently.

The separate attachment of the doctor blades, i.e. the fact that they are mounted independently on the machine frame, allows them be installed with a higher initial deflection, which results in a greater zone of automatic subsequent adjustment. Subsequent adjustment by moving the blade is also possible, and the doctor blade wear is uniform. All in all this means longer replacement cycles. In addition length-trimming and grinding are not necessary for replacement. Further features and advantages can be seen in the sub-claims in conjunction with the description. 35 For a better understanding of the invention an embodiment will be described below in more detail with -4 reference to the attached drawings, in which:

Fig. 1 is a side view of an inking device; Fig. 2 shows the detail Z from Fig. 1; Fig. 3 is a plan view of a slotted nozzle; and Fig. 4 is the circuit diagram of the control unit of the motor of the ink pump.

The inking device shown in Fig. 1 contains a nozzle 1 whose aperture has the shape of an elongate axial slot, arranged at a small distance below the photogravure forme roller 2. In addition a doctor blade 3 is set with a small spacing against the forme roller 2 downstream of the slotted nozzle 1, i.e. after it in the direction of rotation. Below the forme roller 2 an ink bath 4 is also arranged. The slotted nozzle 1 is located within this bath, and the doctor blade 3 roller above the bath.

The slotted nozzle 1 has a longitudinal slot 5 which is about 0.1 to 1.5 mm wide and extending substantially the whole width of the nozzle, as shown in Fig. 3. Parallel and close to this slot on the runin side it carries a second doctor blade 6 set negatively, i.e. acutely, on the forme roller. The slotted nozzle 1 is connected by means of a pipe line to an ink pump 7 (Fig. 4) in a manner not shown in detail but indicated on Fig. 1 by the arrow A.

The doctor blade 3 is clamped into a blade holder 8 which is pivotably mounted on a shaft 9. A working cylinder 10 articulatedly supported in the frame engages on the doctor blade holder 8 in order to adjust the setting of the blade as required, for instance to compensate for wear. The doctor 3, via the shaft 9, and the nozzle 1 are mounted on the frame of the printing machine, as is the roller 2. The nozzle 1 is fixed to a beam, not shown, likewise mounted in the frame. It will therefore be seen that the doctor 3 and the nozzle 1 are independently applied to the roller 2, 4 1 i.e. that they are not connected with each other as a unit. It would be possible in principle, however, to design such a unit which allowed adjustment of the doctor blade against the roller.

The inking device is advantageously designed to be as wide as a page and several inking devices are arranged adjacently on the forme roller 2 according to the number of printed pages adjacent to each other on the plate cylinder (Fig. 3). In Fig. 3 the reference a represents the page width and b the possible type area width.

Ink is fed from the pump 7 to the slotted nozzle 1. The doctored ink caught in the trough 4 is recirculated and is either fed directly to the pump 7 or is first filtered and otherwise processed and then passed into an ink container from which the pump sucks the ink. The nozzle 1 then sprays a thin film of ink onto the rotating forme roller 2. The amount of ink V to be conveyed to the slotted nozzle per unit time varies according to the machine speed or forme roller rotational speed. For this purpose the amount conveyed by the ink pump 7 is controlled by varying the rotational speed of the pump. The ink pump 7 is driven by a motor 11 whose control unit 12 is fed by sensors 13, 14 for the machine speed and the ink rheology. The machine speed is communicated to the control device 12 by the sensor or transmitter 13. Further values affecting the ink requirement, such as the ink temperature and basic rheological properties, are provided by the transmitter 14.

Excess ink is wiped from the roller 2 by the doctor blade 3 and collected by the ink bath 4. Thanks to the measured ink application a thin film of ink of only about 3/100 to 15/100 mm is adequate so that only a little ink needs to be wiped off. Furthermore because only small, controllable quantities are used the ink distribution is substantially restricted to the width of the longitudinal slot 5 which is so designed that exactly the necessary width of type area b is inked. Since furthermore the ink film is very thin and the ink volume on the roller is not under pressure side parts limiting the ink flow can be dispensed with. The housing surface 15 bordering the slotted nozzle 1 also contributes to this advantageous effect and can also be designed concentrically to the forme roller 2. On the whole a large width of type area b (see Fig. 3) can be used.

The second doctor blade 6 adjacent to the slot 5 eliminates aerodynamic influences at the run-in gap of the slotted nozzle 1 by disturbing the laminar air layers on the forme roller surface. Hence even with higher speeds of the forme roller 2 a reliable uniform inking thereof is guaranteed.

Claims

Claims:

1. Inking device for a forme roller of a printing machine, including a doctor blade to be applied to the forme roller, and a slotted nozzle for applying the ink to the forme roller, the doctor blade being arranged in the downstream direction from the nozzle.

2. Inking device according to claim 1, in which the doctor blade and nozzle are adapted to be mounted independently on the machine frame so that the doctor blade is adjustable.

3. Inking device according to claim 1 or 2 and having several slotted nozzles arranged directly adjacently to each other in the axial direction of the roller and designed to be as broad as a page.

4. Inking device according to any preceding claim and further including an ink bath to be arranged below the forme roller, and an ink pump connected to the nozzle.

5. Inking device according to claim 4, in which the slotted nozzle is arranged in the ink bath.

6. Inking device according to claim 4 or 5, and further including a control unit connected to sensors responsive to the machine speed and the properties of the ink, for controlling the ink pump.

7. Inking device according to any preceding claim, in which the slotted nozzle carries a second doctor blade arranged upstream of the slot in such a way as to be set negatively on to the forme roller.

8. Inking device according to any preceding claim, in which the slotted nozzle has a housing which surrounds the longitudinal slot.

9. An inking device substantially as described herein with reference to the accompanying drawings.

10. An inking unit comprising an intaglio forme roller and an inking device, as claimed in any preceding claim, applied to the roller.

11. A method of inking a forme roller by the use of an inking device as claimed in any of claims 1 to 9.