JPH03120048A - Sheet to guide sheet paper as packing paper for sheet paper delivery cylinder and corresponding impression cylinder of sheet paper offset press for perfecting printing - Google Patents

Abstract

PURPOSE: To prevent adhesion of ink by providing hemispherical protrusions of same height on the surface of a foil formed of at least one supporting layer having a surface subjected to systematic surface machining and coated with a silicone layer. CONSTITUTION: Surface of a foil 2 for guiding a sheet is subjected to systematic surface machining by providing hemispherical protrusions 3 distributed statistically uniformly across the surface. Formation of moire pattern on a print product is avoided by such a systematic surface machining. All hemispherical protrusions 3 have same height and a uniform pressure resisting face 4 is formed on the top of the protrusion 3. The pressure resisting face provides a satisfactory supporting part for a sheet to be printed on the other side thus ensuring reliable ink rejecting characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The invention relates to a sheet guiding sheet of the type defined in the preambles of claims 1 and 2.

In conventional double-sided printing, the still-moist side of the sheet that has just been printed is pressed, after the sheet has been turned over, against the sheet-guiding surface of the impression cylinder of the subsequent printing mechanism. In order to obtain consistently good print quality, it is important that as little ink as possible adheres to the outer circumferential surface of the subsequent impression cylinder and sheet transfer cylinder.

Various efforts have therefore been made to create cylinder coatings with the lowest possible ink-receiving properties and the best possible ink-ejection properties. As a result DE-PS
The upholstery described in document No. 2,446,188 was obtained. In other words, the sheet-guiding outer circumferential surfaces of the corresponding impression and sheet transfer cylinders of the rotary printing press have a textured surface in the form of hemispherical projections.

The hemispherical projections have the same height and are distributed statistically over the surface of the torso. The structured surface treatment itself reduces the counterpressure surface and thus the contact surface during backprinting. The uniform height of the hemispherical projections provides a uniform counterpressure surface, whereas the statistically uniform distribution of the hemispherical projections prevents the risk of Moire formation in the printed product. Ru.

In order to maintain as little ink-receiving properties as possible from the beginning, nickel is used as the sheet material. Nickel has desirable physical and chemical properties. That is, nickel repels ink, is abrasion resistant, and is chemically well resistant to the chemicals used in printing presses.

An improvement to said upholstery is proposed in DE-O3 2916505. That is, the textured surface of the support layer is made from a durable, wear-resistant and non-recurring material (e.g. nickel) with excellent ink release properties. A thin chrome layer is applied which compensates for the micro-roughness. On the one hand, this extends the service life of the sheet by the service life of the chromium layer;
On the other hand, the smoothness of the sheet surface facilitates the cleaning of the sheet that is required at predetermined time intervals.

In practice, the ink release properties of chromium and nickel are particularly important when the sheathing is applied to plate cleaners (plate cleaners).
It became clear that this was noticeable after treatment with a cleaner.

In an attempt to achieve this, it was determined that the ink release properties of the metals occur only in conjunction with the addition of fountain solution, which is essential in offset printing.

Problem to be Solved by the Invention It is an object of the invention to provide a lining for an impression cylinder in which ink adhesion is prevented by the structured surface treatment and by the low surface tension of the coating material. .

Means for Solving the Problems According to the present invention, the problems have been solved by the structures set forth in claims 1 and 2.

Advantages of the Invention The low ink-accepting properties and good ink-ejection properties of the surface are related to the textured surface treatment as well as to the selection of the surface material. In the present invention, it has been chosen to give the upholstery a suitably structured surface treatment as hemispherical projections of the same height distributed statistically evenly over the surface. Such a structured surface treatment is particularly advantageous if the sheet is used as a lining for an impression cylinder. A further advantage of the invention is that the sheet-guiding surface is textured (for example by sandblasting). Both of the above-mentioned textured surface treatments serve to reduce the surface area and thus the contact area between the newly printed sheet side and the cylinder outer circumferential surface. In addition to the already mentioned advantages of providing a textured surface treatment to the upholstery, the material of the upholstery is also important with respect to the desired poor ink-receiving properties or good ink release properties. This desirable property becomes more pronounced as the surface tension of the coating material decreases. Therefore silicone was chosen. The surface tension of silicone is only about half that of chromium.

These properties of silicones are well known.

As is clear from the UGRA Report, 1984 Edition, Volume 1, silicone rubber plates are used in waterless offset printing. In water-free offset printing, the perfect printing result is due to the fact that after exposure, the surface tension of the non-imprint surface, which supports the actual covering layer of silicone rubber, is slight and that the non-imprint surface and the printing ink are diametrically opposed to each other. can be obtained only if the ratios of are approximately the same. This printing process is therefore only carried out using special inks.

Furthermore, silicones have the advantage that their chemical and physical properties can be modified within a wide range. In this case an important feature for the invention is obtained. This results in abrasion resistance, chemical resistance to the chemicals used in the printing process and non-compressibility (basic prerequisites for the use of silicone as coating material for impression cylinders).

In an advantageous embodiment, nickel, chromium or plastic is used as the support material. The advantage of providing a textured sheet with a silicone layer is that smooth surfaces can be cleaned more quickly and satisfactorily than with more or less rough support layers.

In an advantageous embodiment of the invention, a silicone layer is additionally applied to the multiple support layers of oleophobic material (for example chromium or nickel). In addition to providing excellent stability, this significantly extends the service life of the sheet. Good ink ejection properties are maintained even if areas of the silicone layer are ablated by abrasion. In another advantageous configuration, the hemispherical protrusions or roughened surfaces are a materially integral part of the silicone sheet. In this case, the sheets for guiding the sheets are either fixed directly to the impression cylinder or are stretched onto the impression cylinder via a clamping device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a plan view of the textured surface l of a sheet 2 for guiding sheets. This systematic surface treatment of the sheet 2 guiding the sheet is produced by hemispherical projections 3, which are distributed statistically evenly over the surface. A statistically uniform distribution means that on average the same number of hemispherical projections 3 are provided per unit area.

Since the distribution of hemispherical protuberances on the sheet guiding the sheet is uniform only from a statistical point of view, such a systematic surface treatment reduces moiré (moiré) in the printed product.
ir6) formation is avoided. Due to the precisely uniform distribution of the hemispherical projections per unit area, there is a risk that the points of contact with the evenly distributed halftone dots of the printed image will overlap in a pattern-forming manner on the printed product.

As is clear from FIG. 2, all of the hemispherical projections 3 are formed at the same height. The top of the hemispherical projection 3 forms a uniform counterpressure surface 4 .

The counter-pressure surface then forms a perfect support for the sheet to be printed on the other side. Furthermore, this arrangement of the hemispherical projections 3 prevents premature wear of the protruding support surface.

The sheet guiding the sheet is, as can be seen in FIG. 2, formed from two layers: a support layer 5 of nickel, chromium or plastic and a silicone layer 6. An advantage of this embodiment of the invention is that the surface is originally made of e.g.
The advantage is that the support layer 5 is significantly smoother than the support layer 5 which is molded from. Furthermore, the sheet that supports the paper sheets ensures reliable ink release characteristics from the time of use.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 shows a part of the surface of a sheet supporting sheets according to the invention, which has been subjected to a systematic surface treatment, and FIG. ■−■ in Figure 1
It is a sectional view along the line. l... Surface with systematic surface treatment, 2... Sheet, 3... Hemispherical protrusion, 4... Counter pressure surface, 5...
Support layer, 6... silicone layer

Claims (1)

[Scope of Claims] 1. Supporting the sheet in a sheet guiding the sheet as a cylinder tension for the sheet delivery cylinder and the corresponding impression cylinder of a sheet-fed offset printing machine for double-sided printing. Sheet (2)
is provided with statistically evenly distributed hemispherical protrusions (3) of the same height, and the sheet (2) is chemically durable, abrasion resistant and non-compressible. a silicone layer (6) on the textured surface (1) of the support layer (5);
1. A sheet guiding sheet as a lining for a sheet delivery cylinder and a corresponding impression cylinder of a sheet-fed offset printing machine for double-sided printing, characterized in that the sheet is coated with: 2. In a sheet that guides the sheet as a body tension for the sheet delivery cylinder and the corresponding impression cylinder of a sheet-fed offset printing machine for double-sided printing, the surface of the sheet that supports the sheet is rough. the sheet (2) is formed from at least one chemically durable, abrasion resistant and non-compressible support layer (5), the textured surface of the support layer (5) being processed; For a sheet-fed transfer cylinder and a corresponding impression cylinder of a sheet-fed offset printing press for double-sided printing, characterized in that a silicone layer (6) is applied on the treated surface (1). A sheet that guides the sheets of paper that serve as body coverings. 3. Sheet according to claim 1 or 2, wherein the support layer is made of an oleophobic material, such as chromium or nickel. 4. Sheet according to claim 1 or 2, wherein plastic is used as the support layer (5). 5. Sheet according to claim 1 or 2, wherein the sheet (2) guiding the sheet is made of silicone. 6. Two support layers consisting of nickel and chromium (5)
3. Sheet according to claim 1, further comprising a silicone layer (6) applied thereon. 7. Seat according to one of claims 1 to 6, wherein the seat (2) is fixed to the torso directly or via a tightening device.