Anti-marking coverings for printing presses

Details Anti-marking coverings for printing presses Anti-marking coverings for printing presses

2002-07-18

2004-11-02

Morris, Terrel (Department: 1771)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having voids in a component

C428S311110, C428S311510, C428S308400, C428S308800, C428S909000, C428S543000, C428S131000, C442S221000, C101S401400, C101S415100

Reexamination Certificate

active

06811863

ABSTRACT:

FIELD OF THE INVENTION
The present invention pertains to an improved anti-marking sheet and method for providing improved support along the entire width of a freshly printed sheet material in a printing press or similar machine and particularly to an improved anti-marking sheet/jacket for a print press transfer/perfector cylinder.
BACKGROUND OF THE INVENTION
Since the first printing press was placed into operation, operators have wrestled with the problem of freshly printed sheets becoming undesirably marked as they travel from one printing station to the next. To solve this problem, press manufacturers and innovators have tried various methods ranging from tracking/skeleton wheels, pneumatic devices, to cylindrical coverings of sandpaper, glass beaded paper, dimpled metal and loose mesh fabric. While most of these devices are effective to some degree, none of them fully satisfy the needs of a printer. A brief history illustrating the development of such anti-marking systems is outlined below.
In U.S. Pat. No. 2,085,845, Binkley applies “a coating granular material such as silicon carbide, emery, etc.” onto the face of the fabric which has a barrier coating adhered onto rear side and is adhered to the make-ready and then clamped to the tympan roll. Here, Binkley asserts that using a sandpaper-like material will provide the advantage of decreasing the marking of freshly printed sheets. In U.S. Pat. No. 2,555,319, Cross also studies the application of granular materials to rolls within a printing machine and tests granular materials ranging from glass culets, silicon carbide and aluminum oxide and compares them to spherical glass beads. He asserts that the spherical glass beads offer a smooth and round uniform surface that is superior to that of granular grit. Cross further asserts that spherical beads allow the freshly printed/inked sheet to be uniformly supported by the tops of millions of uniform glass beads resulting in a decrease of marking printed sheets. Cross also teaches of both the benefits of back coating a porous substrate and over-coating the beaded side to improve adhesion of the glass beads to the substrate as well as to aid in repelling printing inks/solvents.
In U.S. Pat. No. 4,694,750, Greene attempts to improve on known rolls having granular surfaces by using “an elastic member that is attachable to each flange and is stretchably positionable around the circumferential granular surface.” Greene's use of elastic bands to make an easily installable anti-marking product falls short in two areas: first the elastic bands impede use of the full width of the cylinder (thus limit sheet size). Second, since the elastic bands run circumferentially around the cylinder, they do not provide adequate uniform tension across the entire sheet resulting in movement of the granular sheet and ultimately marking results.
In U.S. Pat. No. 4,688,784, Wirz employs perforations in various textured surfaced anti-marking sheets that come into alignment with a hole or bore of the air ducts in the cylinder. The purpose of using compressed air is to aide in the transport of the freshly printed sheet as it travels mark-free from one printing station to the next.
In U.S. Pat. No. 3,791,641, DeMoore uses an ink repellent PTFE sheet that is affixed to skeleton wheel. Later, in U.S. Pat. No. 4,402,267, DeMoore improves upon this design by adding “a loosely retained ink repellent fabric covering” known in the industry as SUPER BLUE™ over the cylinder sheet. In U.S. Pat. No. 5,842,412, Greenway et al. also uses a light weight fabric with preferred axial air permeability not less than about 0.138 cfm and a surface structure with closely spaced features of a spacing not more than about 0.125 inch.” This fabric is known in the industry as QUACK™.
In U.S. Pat. No. 6,203,914 B1, Sudo et al. follows Cross's process for manufacturing an ink repellent anti-marking sheet as disclosed in U.S. Pat. No. 2,555,319. Sudo uses a urethane crosslinked silicone top coat well known in the industry and disclosed in U.S. Pat. No. 5,415,935 as an ink-repellent coating over the glass beaded surface.
In U.S. Pat. No. 6,244,178 B1, DeMoore recognizes the importance of easy installibility and further improves his SUPER BLUE™ fabric to include asserted improvements such as pre-stretched, pressed flat and pre-cut to the cylinder dimensions complete with anti static/conductive filaments and ink-repellent coating.
Despite the efforts made in these many patents or products in the market today, marking of printed sheets in printing presses remains problematic.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to overcome the problems of printing press anti-marking systems in the prior art, and particularly to solve the problem of wet ink marking/smearing on the sheet/web due to the contact of freshly printed sheets with the transfer cylinder or the anti-marking surface covering it. The present invention recognizes that for an anti-marking system to be optimal, it preferably meets four conditions:
1. Technically, the surface of the anti-marking system should perform its function of uniformly supporting and conveying the freshly printed sheet from one printing station to the next without marking the freshly printed sheet.
2. Installability, the anti-marking sheet/jacket should be uniformly applied to the surface of the desired cylinder. If the operator cannot easily apply the anti-marking cover uniformly over the cylinder, then ridges, bubbles and creases develop which by themselves create undesirable marks.
3. Durability, the anti-marking product should withstand contact with hundreds of thousands of printed sheets to include various thickness' and the inadvertent creased/folded sheet which typically can damage an anti-marking system.
4. Cleanability, the anti-marking surface needs to be easily cleaned upon completion of the printing job to include ink and oil residue from the printing machine.
The present invention provides an improved method and apparatus for supporting and conveying sheet or web material that has been freshly printed on at least one side wherein the printed material is supported by a cylindrical roll or skeleton or tracking wheels which has mounted on the outer surface thereof an anti-marking material having at least two layers. The anti-marking material comprises at least an outer textured surface layer and an inner microcellular layer. The outer textured surface layer is the surface that actually comes in contact with the wet printed sheet.
The contact between the outer textured surface and the wet printed ink is important to anti-marking performance. Too much surface or uneven contact will cause the wet ink to smear or mark. Too little surface or uneven contact will cause the sheet to be inadequately supported (resulting again in marking) as it is transferred from one printing station to the next. The pattern of the textured surface is therefore preferably uniform across the entire surface and strikes a delicate balance between adequate support for and good release of the wet printed sheet without marking.
A textured surface that contains uniform raised contact points spaced apart by lower areas is preferred. For embossed patterns, the percent area of the raised ridges should preferably not exceed about 60% or the contact area with the wet printed sheet will not release cleanly without marking. The percent area of the raised contact can be minimized by careful tooling of the embossing roll. Care should be taken to uniformly space the raised contact points while minimizing their surface area. The minimum area in this scenario approaches zero and is constrained only by current manufacturing processes to single digit percentages.
In accordance with another aspect of the present invention there is provided a method and apparatus for supporting and conveying sheet or web material that has been freshly printed on at least one side wherein the printed material is supported by a cylindrical roll or skeleton/tracking wheels which has mounted on the outer surface thereof an

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