US 2996981 A
Description (OCR text may contain errors)
Aug. 22, 1961 R. REINARTZ ETAL 2,996,981
WETTING DEVICE FOR OFFSET PRINTING MACHINES Filed Feb. 15, 1960 INVENTORS HRMANK FI'sc her;
United States Patent 2,996,981 WETTING DEVICE FOR OFFSET PRINTING MACHINES Robert Reinartz and Hermann Fischer, Augsburg, Germany, assignors to Maschinenfabrik Augsburg-Numberg, A.G., Augsburg, Germany Filed Feb. 15, 1960, Ser. No. 8,809 Claims priority, application Germany Mar. 5, 1959 7 Claims. (Cl. 101-148) This invention relates to a wetting device for offset printing machines. In particular, the invention is directed to a ductor roller which is immersed in a water tank, with moisture being taken from the ductor roller by intermittent contact with a swinging roller and passed to the distributing and inking rollers. The moisture applying surface of the ductor roller is composed of a number of independently movable and/or spaced rings.
In offset printing, the need for moisture varies factual- 1y with the difference in size of the inking surfaces. The control of the moisture is, on one hand, achieved by a smooth or stepless shifting forward of the ductor roller in a peripheral direction and, on the other hand, by a variation in the quantity of moisture along the longitudinal length of the ductor roller. In the latter case, squeezing rollers of different widths and in different numbers have been used to squeeze off the water at the places in whose area there are larger inking surfaces on the offset plate which require less water. This is an expensive and time-consuming method and does not permit an accurate regulation of the moisture so that excess water enters the inking apparatus, combines with the ink to form an emulsion, and thus results in a poor print. Also, narrow felt rings or leaf springs have been applied against the ductor roller or air blast nozzles located closely side by side were mounted along the ductor roller, with the individual nozzles being opened where necessary to blow off excess wetting water. Again, ductor rollers have been used which are composed of series of brushes which are divided along the longitudinal length of the roller into individual brush sections which can be arranged as desired. Furthermore, wetting devices exist in which nozzles are used to spray a wet mist, with the individual nozzles being opened and closed in the desired positions. Another conventional wetting device is a distributing roller having its liquid applying surface divided into ring-shaped zones extending perpendicularly to the longitudinal axis of the roller. All of these known devices do not give a practically satisfactory application of the moisture.
The object of this invention is to produce a ductor roller which will accurately apply the quantity of moisture desired on certain areas of the printing plate.
According to this invention, the disadvantages of the prior art are overcome by using a ductor roller immersed in a water tank with the roller having a moisture applying surface composed of a number of independent movable or exchangeable spaced rings whose circumferential surfaces lie in planes which are inclined with respect to the longitudinal axis of the shaft of the ductor roller. The adjacent rings are spaced from each other a distance, at most, such that a continuous film of liquid is drawn off the swinging transfer roller during one revolution of the ductor roller. By this means, a locally concentrated or small quantity of water can be applied by means of a simple lateral displacement of the rings on the ductor roller, with the small width of the rings permitting a precise gradation of the water transferred from the roller. The inclination of the ring surfaces achieves simultaneously a laterally displaced application of the strip of moisture so that the annular concentration of the liquid produced by ring surfaces perpendicular to the axis of the roller is avoided. The invention also makes it possible to obtain a more uniform distribution of the moisture over the whole length of the roller by spacing the inclined rings more closely toward the ends of the roller. As the area of the moisture applying surface of the roller can be varied, squeezing becomes unnecessary so that the considerable wear and tear on the ductor cylinder linings is reduced. This invention also has the advantage in that the position of the rings can be correctly adjusted as determined by the variation in the quantity of wetting liquid required in proportion to the size of the applying surface, whereas in air blast regulation, the moisture quantity depends, not only upon the number of the nozzles, but also upon the intensity of the air blast and the speed of the printing press.
A washing device for cleaning ductor rollers is known which has inclined groves in a roller in order to produce a squeezing effect on the ductor roller. However, these grooves are out so as to be chevron-shaped or arrowpointed. Grooves of this kind do not permit a proportioned distribution of moisture taken from the ductor roller.
The means by which the objects of the invention are obtained are disclosed more fully with reference to the accompanying drawings, in which:
FIGURE 1 is a front view of the ductor roller partly shown in section;
FIGURE 2. is a cross-sectional view on the line 22 of FIGURE 1; and
FIGURE 3 is a front view of a wetting ring partially broken away.
Ductor roller 1 is mounted in the press frames 2 and 3 and partially immersed in a water tank 4. Water picked up by the ductor roller is transferred by a swinging roll 5 in a conventional manner to the distributing roll 6 and so on to the printing plate. Roller 1 is formed as a hollow cylinder upon which are slide rings 8 whose surfaces are inclined with respect to the longitudinal axis of roller ll. These rings may be of different widths and are spaced from one another in such a manner that their surf-ace areas overlap longitudinally of the roller. Rings 8 are keyed against turning on roller 1 by means of spline '9. A spindle it is mounted in a groove in the surface of roller 1 on an eccentric axis and, in turn, contains a dove-tail slot holding a strip of resilient material 11, such as rubber, which projects slightly out of the dovetail slot. Spindle it) has a square bolt head end 12 projecting through the flange plates 13 which are secured to the ends of roller 1 by means of bolts .14. As spindle 10 is turned by bolt head 12, the resilient material 11 is brought into 'wedging engagement with the rings 8 to secure them against longitudinal movement along the roller 1.
End rings 8a have their outer end side perpendicular to the axis of roller 1. Rings of small width can be mounted close together adjacent the end rings 8a in order to obtain a better transfer of moisture in these end areas. When spindle 10 is loosened, the rings can be distributed along the length of the roller 1 in accordance with the moisture requirements of the press and then secured against longitudinal movement by the turning of spindle It In order to ensure a good transfer of liquid, each ring 8 has a roughened surface and is coated with a nettle-like cloth as shown at 81). Due to the inclined surfaces of the rings, the surface of the swinging transfer roll 5 is appropriately wetted during each revolution of roller 1 so that the required distribution of the moisture on the printing plate is assured.
Having now described the means by which the objects of the invention are obtained,
1. A ductor roll for transferring moisture in an offset printing press comprising a cylindrical roll, a plurality of rings concentrically mounted on said cylindrical roll and having their circumferential surfaces inclined with respect to the longitudinal axis of said cylindrical roll, said rings being spaced from each other a distance such that the surface of one ring laps the surface of an adjacent ring during one revolution of said cylindrical roll, and spindle means eccentrically mounted on said cylindrical roll for adjustably securing said rings to said cylindrical roll.
2. A ductor roll as in claim 1, further comprising spline means for keying said rings to said cylindrical roll.
3. A ductor roll as in claim 2, further comprising a strip of resilient material joined to said spindle means and extending outwardly of the surface of said spindle means for engagement with said rings.
4. A ductor roll as in claim 1, further comprising a longitudinal groove in the surface of said cylindrical roll, flanged plates secured to the ends of said cylindrical roll,
4 said spindle being mounted in said groove and iournalled in said flanged plates, and a square end on said spindle for turning said spindle.
5. A ductor roll as in claim 1, said rings each having a roughened outer circumferential surface.
6. A ductor roll as in claim 1, said rings each being covered with an adhesive nettle cloth.
7. A ductor roll as in claim 1, further comprising end rings on said cylindrical roll with each end ring having its outer side edge extending perpendicular to the longitudinal axis of said cylindrical roll.
References Cited in the file of this patent UNITED STATES PATENTS 958,440 Sackman May 17, 1910 FOREIGN PATENTS 601,883 Great Britain May 13, 1948 731,530 Great Britain June 8, 1955