Pressure roll

Details Pressure roll Pressure roll

1997-01-03

1998-08-11

Fisher, J. Reed

Printing

Intaglio

Rotary

492 7, B41F 900

Patent

active

057912459

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a pressure roll in accordance with the preamble of claim 1.
Pressure rolls of the named kind are often used in printing machines, in particular in rotogravure printing machines, as pressure rolls which cooperate with a printing cylinder in each case. A known pressure roll of this kind is executed with a highly elastic roller jacket in the form of a hollow cylinder of polyurethane or an elastomer which permits bending deflections transverse to its longitudinal axis and has a cross-section of substantially stable shape (K. A. Springstein "Die Spitzenqualitat im Tiefdruck hangt auch vom Presseursystem ab" (top quality in rotogravure printing also depends on the pressing system), reprint from the trade journal "Deutscher Drucker", No. 28 dated 15 Sep. 1988). The roll jacket of the known pressure roll is pressed against the printing cylinder via hydrostatic support elements, with the formation of a substantially linear pressing zone with a relatively slight extent in the peripheral direction of the roll jacket. In that arrangement the pressing zone can be widened in a deflection zone which arises through a compression of the roller jacket to such an extent that a printing zone with a width of approximately 10 to 18 mm is formed. The ink applied to the printing cylinder in a printing machine must in each case be transferred to the matter to be printed in the region of this printing strip.
In order to ensure a reliable ink transfer at a printing speed of, for example, 15-20 m/sec, it is known to provide the roll jacket with an indirect or direct electrostatic printing aid (ESA). These known printing aids are, however, relatively complicated and expensive and maintenance-intensive systems. To achieve a high print quality, it is furthermore essential that the width of the printed strip or band remains constant during the printing process. In previous pressure rolls of the named kind, and as a result of load changes in the roll zone in certain cases, e.g. when printing printed matter with longitudinal sections of differing thickness, correspondingly differing tangential forces can act on the individual longitudinal sections, with it being possible for the respective effective width of the printing strip to vary and thus for distortions of the printed matter to arise, through which the quality of the ink transfer can be impaired.


SUMMARY OF THE INVENTION

The object of the invention is to provide a further developed pressure roll suitable for various applications of the initially named kind which enables the formation of a pressure zone with a constant gap width that is adjustable independently of the respective loading and which permits an intentional influencing of the dwell time of a web of material passing through the pressing position, which can be used for a treatment, and which ensures a treatment of the web of material travelling through the pressure zone that is free from electrostatic auxiliary devices, or can at least be achieved with reduced electrostatic charging, even at a running speed of 20 m/sec or more.
Through the flexibility in the radial direction of the roll jacket of the press roll designed in accordance with the invention, a press gap can be achieved between it and the counter-roll whose width, in comparison with previous embodiments, can be freely chosen within a larger peripheral region of the counter-roll, and this width can amount to a multiple of the gap widths possible with previous embodiments. Accordingly, a low-distortion guidance of the material web--e.g. a paper or textile web--can be achieved which is independent of the respective stressing, and/or its dwell time in the press gap can be lengthened to such an extent that the use of electrostatic auxiliary devices is superfluous or that their use can at least be largely restricted. The pressure roll executed in accordance with the invention is particularly advantageous for printing machines since, on the one hand, e.g. in decorative printing, it ensures

REFERENCES:
patent: 4188874 (1980-02-01), Heuss
patent: 4503769 (1985-03-01), Andersen
patent: 4518460 (1985-05-01), Hauser
patent: 4570314 (1986-02-01), Holik et al.
Patent Abstracts of Japan, vol. 12, No. 45 (M-667), Feb. 10, 1988 & JP,A,62 196189 (Showa Denko), Aug. 29, 1987, cf. Abstract.
Patent Abstracts of Japan, vol. 95, No. 5, Jun. 30, 1995 & JP,A,07 042728 (Tokai Rubber), Feb. 10, 1995, cf. Abstract.

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