Printing – Inkers – Roller
Reexamination Certificate
2000-01-14
2001-10-30
Funk, Stephen R. (Department: 2854)
Printing
Inkers
Roller
C101S153000, C101S478000, C492S030000
Reexamination Certificate
active
06308623
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a meterable screen or halftone roller, especially for an anilox inking unit in a rotary printing machine, with a multiplicity of printing ink-accepting depressions disposed on the peripheral surface of the screen or halftone roller.
In the arts of gravure printing and offset printing, inking units are provided wherein printing ink is introduced via a doctor chamber into dimples or groove-like depressions formed in a screen or halftone roller, for example, an anilox roller, which subsequently transfers the printing ink, generally via one or more intermediate rollers, to the surface of a printing-form cylinder.
Screen rollers having depressions formed in the surface thereof by engraving, etching or with the aid of lasers have become known heretofore, the rollers being made, for example, of steel, chromium, copper and/or ceramic. A factor that is common to all the screen rollers is that they have dimples or groove-like depressions, the volume of which is defined during the production of the roller and, except for wear caused by the doctoring operation, can generally no longer be altered thereafter.
Because the quantity of ink transferred to the printing form or plate is determined by the volume of the dimples or the groove-like depressions formed in the screen or halftone rollers, and the quantity of ink required overall depends upon the size of the area of the printing form or plate that is to be inked, it is desirable to be able to alter the quantity of ink from the viewpoint of an optimum adaptation or matching of the quantity of ink supplied to the respective print job.
In this connection, in the case of rollers made of ceramic partly filled with copper, it has become known heretofore to remove copper from the filler by etching the roller, in order thereby to increase the volume of the dimples or grooves. In the case of these rollers, however, a reduction in volume can be produced only by grinding over the latter, however, this entails a comparatively great mechanical effort and, in addition, results in a reduction in the circumference of the roller, that has a detrimental effect upon the printing process.
It has furthermore become known from German Patent 44 08 615 to introduce into the dimples or depressions of a screen or halftone roller a piezoelectric material that expands or contracts when an electrical voltage is applied and, consequently, produces an alteration in the volume of the dimples or depressions. A disadvantage with respect to the aforedescribed screen or halftone roller is that, in order to effect an alteration in the volume of the dimples or depressions that is visible in the printed image, the piezoelectric material in each of the dimples or depressions has to have a very high voltage applied thereto, which results not only in the occurrence of technical problems during the production of the screen or halftone roller, but also, because of the risk of voltage flashovers, constitutes a considerable safety risk during the operation of the roller.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a meterable screen or halftone roller, especially for an anilox inking unit of a rotary printing machine, which has a simple construction, is cost-effective to produce and with which an effective and specific alteration of the quantity of ink transferred by the roller is possible.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a meterable screen roller having a peripheral surface whereon a multiplicity of printing ink-accepting depressions are disposed, comprising a respective base for the depressions formed by a resilient material, and respective chambers located underneath and assigned to the depressions, the chambers being actable upon by a pressure medium for respectively enlarging and reducing the volume of the depressions.
In accordance with another feature of the invention, the screen roller includes a structured tube having an outer circumferential surface whereon the depressions are permanently formed, and having an inner circumferential surface formed with webs disposed between the depressions, the chambers being defined by the webs.
In accordance with a further feature of the invention, the screen roller includes a rotatably mounted roller core onto which the structured tube is slidable.
In accordance with an added feature of the invention, the screen roller includes a roller base member having a circumferential surface formed with recesses which are configured so as to accord with the shape of the depressions, said recesses being covered by a flexible covering so as to form said chambers, and feed ducts for applying pressure medium to the recesses.
In accordance with an additional feature of the invention, the recesses are formed as a spirally revolving groove.
In accordance with yet another feature of the invention, the recesses are formed by grooves extending in axial direction over the circumferential surface of the roller base member.
In accordance with yet a further feature of the invention, the roller base member, in the region of the outer circumferential surface thereof, is made of porous material connected to the pressure-medium feed ducts and formed with the recesses.
In accordance with yet an added feature of the invention, the roller base member includes a rotatably mounted core and a jacket member made of the porous material disposed thereon, the recesses being formed directly in the jacket member.
In accordance with yet an additional feature of the invention, the flexible covering is formed by a sleeve slidable axially onto the roller base member.
In accordance with still another feature of the invention, the depressions are formed in the sleeve as a permanently predefined structure.
In accordance still a further feature of the invention, the pressure medium is a liquid.
In accordance with an alternative feature of the invention, the pressure medium is a gas actable from the outside upon the circumferential surface of the screen roller, a respective increase and decrease in the gas pressure serving for the enlargement and reduction of the volume of the depressions.
In accordance with a concomitant feature of the invention, the screen roller is for an anilox inking unit in a rotary printing machine.
Thus, the meterable screen or halftone roller according to the invention is distinguished by the fact that the base of the depressions, i.e., the dimples or grooves, is formed by a resilient material, underneath which chambers are formed which are assigned to the depressions and to which a pressure medium, for example, compressed air or a liquid, can be applied for the purpose of enlarging or reducing the volume of the depressions. This provides the advantage that, by increasing or decreasing the pressure of the pressure medium, when all the chambers are acted upon cumulatively, the total quantity of ink conveyed by the screen roller can be altered in a relatively simple manner without incurring the risk, for example, of voltage flashovers or other secondary effects which disrupt the printing process. Provision can be made in a similar manner, however, for the chambers underneath the depressions to be connected in groups via appropriate feed ducts, to which a different pressure can be applied, independently of one another, via respectively associated valves. Thereby, if desired, an ability to alter the quantity of supplied ink in a relatively simple and reliable zonal manner is provided, such as is otherwise known only from blade inking units which are equipped with separately adjustable inking zone screws.
The provision of a structured tube having an outer circumferential surface wherein the depressions are formed, for example by etching or laser machining or in any other conventional manner, and an inner circumferential surface, arranged between the depressions, whereon webs are formed which laterally bound or define the chambers to which the pressure medium can be applied, results in the
Schonberger Wolfgang
Spilger Rolf
Funk Stephen R.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Lerner Herbert L.
Stemer Werner H.
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