Printing – Inkers – Roller
Patent
1989-08-21
1991-04-23
Fisher, J. Reed
Printing
Inkers
Roller
101169, B41F 3104, B41F 3134, B41F 3106, B41L 2736
Patent
active
050091590
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a printing unit comprising a rotary impression cylinder and a likewise rotary inking roller included in an inking device and adjustably spaced from said impression cylinder by means of a first lever device which is pivotal and eccentrically mounted in relation to the axis of rotation of said inking roller, the printing unit further having a doctor blade movable into wipe-off engagement with the inking roller.
A printing unit of this type is previously known from SE Patent Application 8304024-6 which is hereby included by reference. Although the object of the invention disclosed in this SE patent application is completely different from that of the present invention, the printing unit per se is of the same basic design. The printing unit includes a back pressure cylinder, an impression cylinder and an inking roller, all of which are rotatable, parallel to and adjustably spaced from each other. A fountain roller dips into an ink container and, during its rotation, deposits ink on the inking roller.
In recent years, new types of printing units have been developed in which the inking roller has been provided with a screen and the ink container is disposed directly underneath the inking roller which will thus at the same time serve as fountain roller. The excess ink drawn up from the ink container by the fountain roller must be scraped or wiped off by means of an elongate doctor blade engaging the fountain roller. The purpose is to ensure that the ink deposited on the inking roller forms a relatively thin layer. It has thus become even more vital that the excess ink be properly and accurately wiped off, for which reason the location and the design of the doctor blade have attracted increasingly greater attention.
In printing units of the above-mentioned type, use is often made of an elongate doctor blade which is mounted on the machine frame parallel to the inking roller and is movable into engagement therewith. However, this printing unit suffers from a number of drawbacks, especially in respect of the operation of the doctor blade.
During printing, it must be possible to adjust the spacings between the back pressure cylinder, the impression cylinder and the inking roller because of unevennesses in or wear of the printing block or varying thickness of the web to be printed. Since the doctor blade is mounted directly on the machine frame, there is no adaptation between the movements of the inking roller and the doctor blade. For each adjustment of the inking roller, the doctor blade must be reset by means of separate adjusting devices which are often insufficiently accurate. This procedure is complicated and also gives rise to such drawbacks as an uneven ink layer on the inking roller, uneven wear of both the doctor blade and the inking roller etc.
One object of the present invention therefore is to provide a printing unit in which the inking roller and the doctor blade are adjustable in a simple and accurate manner so as to overcome or at least substantially reduce the above-mentioned shortcomings.
Another object is to provide a printing unit in which the inking roller and the doctor blade constantly maintain their relative positions when adjusting the spacing between them or relative to other rollers and cylinders included in the printing unit.
A further object is to provide a printing unit which ensures even deposition of ink on the inking roller by means of the doctor blade.
These and other objects, which will appear from the following description, have now been achieved according to the invention by means of the printing unit stated in the introduction to this specification, which is characterized by a second pivotal lever device concentrically mounted in relation to the axis of rotation of the inking roller and eccentrically mounted in relation to the pivot axis of the first lever device, and that said doctor blade is supported by said second lever device, whereby the doctor blade and the inking roller will maintain their relative positions when adjusting the spacing betwe
REFERENCES:
patent: 4458590 (1984-07-01), Egnaczak
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