Printing – Planographic – Dampeners
Reexamination Certificate
2000-03-17
2002-03-12
Funk, Stephen R. (Department: 2854)
Printing
Planographic
Dampeners
C101S351200
Reexamination Certificate
active
06354202
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention lies in the printing technology field. More specifically, the invention relates to a dampening unit of a planographic printing machine, with a pan roller, a transfer roller, and a dampening unit roller. The transfer roller is held against the dampening unit roller with a regulating force, generated by a weight, gas-pressure, or a spring force (FF). The various rollers, in particular, are ink-friendly and therefore emulsion-carrying rollers.
U.S. Pat. No. 4,290,360 (German patent DE 29 02 228 C2) describes two different embodiments of a dampening unit. In the dampening unit of the first exemplary embodiment described therein (see FIG. 1 of the patent), which corresponds to the generic type mentioned above, a dampening unit roller bears against an applicator roller under the action of a spring, but the dampening unit roller is not pivotable about a pivot axis offset relative to the roller axis of a water pan roller. The water pan roller itself is not pivotable at all. Also, the pivot axis of the dampening unit roller which is coaxial with the water pan roller, does not lie essentially on a tangential line running through a circumferential contact point which is formed by the dampening unit roller together with the applicator roller. Instead, it is far removed from the tangential line. In the second exemplary embodiment described in the patent (see FIG. 5 of the patent) the dampening unit is different from the above-mentioned generic type. A dampening unit roller is mounted, together with a water pan roller, in a carrier and it is pivotable about a pivot axis that is offset relative to the roller axis of the water pan roller and is formed by a journal. Although a spring acting on the carrier ensures that the applicator roller remains in bearing contact against a plate cylinder, the dampening unit roller is not held against the applicator roller under the action of a spring force. Those two dampening units are not so-called emulsion film dampening units or alcohol-free direct film dampening units.
A further dampening unit is described in German published patent application DE 29 09 765. The transfer roller is pivotable about the roller axis of a water pan roller. It is not pivotable about a pivot axis that is offset relative to the roller axis.
A further dampening unit is described in German published patent application DE 28 22 350 A1. There, although a metering roller carried in arms is pivotable about a pivot axis offset relative to the roller axis of a pan roller, the metering roller is not held in bearing contact against a dampening unit roller under the action of a regulating force, such as, for example, a weight, gas-pressure or spring force. Moreover, the pan roller is not pivotable about the offset pivot axis. That prior art dampening unit, furthermore, is not a so-called emulsion film dampening unit, because not all the dampening unit rollers arranged in the transport path of the dampening medium are ink-friendly and, for example, rubberized. For the reasons mentioned above, the dampening unit described contradicts the principle of alcohol-free or reduced emulsion film dampening.
U.S. Pat. No. 4,949,637 describes a further dampening unit, in which each dampening unit roller guides both printing ink and dampening medium and, for this purpose, consists of rubber. The roller is driven at a circumferential speed that corresponds to the circumferential speed of the plate cylinder. Such dampening units are conventionally also designated as alcohol-free or reduced direct film dampening units or emulsion film dampening units. The dampening unit comprises a transfer roller which is mounted in a pivotable supporting element and which is pivotable about the longitudinal axis of a pan roller, certainly not about a pivot axis offset relative to this longitudinal axis. The applied pressure of the transfer roller against the pan roller and the thickness of the film layer conveyed through their roller nip can be set by the adjustment not of the pan roller, but of the transfer roller, along a slotted guide.
A further dampening unit is described in U.S. Pat. No. 5,540,145. That dampening unit is likewise an emulsion film dampening unit and is identical in many features to the just-described dampening unit.
A dampening unit described in Japanese published patent application JP SHO 51-92204 has an applicator roller which can be brought into frictional contact with the plate cylinder by a spring acting on a supporting lever. That dampening unit, however, lacks a pan roller and a transfer roller. The dampening unit comprises a metal roller which supplies the applicator roller with the dampening medium and which is in frictional contact with a body that absorbs dampening medium and the foot of which is dipped into a dampening medium container. The applicator is pivotable, together with the metal roller, about a supporting axis that is offset relative to the roller axis of the metal roller. The dampening medium quantity capable of being conveyed to the printing form by means of the absorbent body is comparatively small, so that that dampening unit is unsuitable for printing machines which print at high printing speeds.
German published patent application DE 29 49 594 A1 describes a dampening unit which has a pan roller, designated as a dampening duct roller, and a dampening applicator roller, but in which the dampening medium is transferred to the dampening applicator roller directly by the dampening duct roller, not via a transfer roller. Although the dampening applicator roller is pivotable about a pivot axis that is offset relative to the roller axis of the dampening duct roller, the dampening duct roller is not pivotable at all.
Furthermore, the prospectus “Printing Without Isopropanol (IPA)” [“Drucken ohne Isopropanol (IPA)”] from the prospectus series “GTO 52-Tips” issued by Heidelberger Druckmaschinen AG mentions a direct film dampening unit, for the operation and care of which instructions are given in the prospectus.
SUMMARY OF THE INVENTION
The object of the invention is to provide a further improved dampening unit for a planographic printing press which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind.
With the above and other objects in view there is provided, in accordance with the invention, a dampening unit of a planographic printing machine, such as a rotary offset printing machine, comprising:
a pan roller rotatably mounted about a pan roller axis;
a dampening unit roller;
a transfer roller disposed to be held in bearing contact against the dampening unit roller at a circumferential contact point with a regulating force;
the transfer roller and the pan roller being pivotably disposed about a pivot axis offset from the pan roller axis of the pan roller, the pivot axis lying substantially on a tangential line running through the circumferential contact point of the transfer roller and the dampening unit roller.
In accordance with an added feature of the invention, the regulating force is produced by a weight, a gas-pressure-generated force, and a spring force.
In accordance with an additional feature of the invention, the pan roller, the transfer roller, and the dampening unit roller are ink-friendly, emulsion-carrying rollers.
The dampening unit of a planographic printing machine, with a pan roller, a transfer roller and a dampening unit roller, the transfer roller being capable of being held in bearing contact against the dampening unit roller by means of a regulating force, in particular a weight, gas-pressure or spring force, is distinguished in that the transfer roller is pivotable, together with the pan roller, about a pivot axis offset relative to the roller axis of the pan roller and the pivot axis lies essentially on a tangential line running through a circumferential contact point which is formed by the transfer roller together with the dampening unit roller.
The fact that the common pivot axis of the transfer roller and of the dampening
Funk Stephen R.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Lerner Herbert L.
Stemer Werner H.
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