EP2159052B1 - Method for synchronising multiple impression cylinders - Google Patents

Abstract

The method involves engaging impression cylinders (14-1-14-3) to a central cylinder (10) under deformation of an elastomer surface layer (12) of the central cylinder in such a manner that effective radii (R1-R3) of the central cylinder at a point of each impression cylinder are proportional to actual radii (r1-r3) of the corresponding impression cylinder. Angle positions of the impression cylinders are measured during a printing process, and engaging positions of the impression cylinders to a counter impression cylinder are controlled based on the measured angle positions.

Description

The invention relates to a method for producing the synchronization of a plurality of printing cylinders, which are employed on a common central cylinder.

In rotary printing presses in central cylinder design, the substrate wraps around the central cylinder, and with the help of each of the plurality of printing cylinders, a color separation image is printed on the substrate. In order to maintain the repeat of the color separation images, all printing cylinders must have exactly the same angular velocity. If the printing material web is not stretchable and the printing cylinders to roll without slip on the printing material, which in turn rests without slipping on the peripheral surface of the central cylinder, so all cylinders must also have the same peripheral speed. However, these two conditions are compatible only if all cylinders have exactly the same diameter, which can be achieved in practice only with limited accuracy.

The object of the invention is to provide a method which makes it possible to compensate for such tolerances in the diameters of the impression cylinder.

This object is achieved in that a central cylinder is used, which has an elastic surface layer, and that each pressure cylinder is hired under elastic deformation of this surface layer so far against the central cylinder, that the effective radii of Zentralyzlinders at the locations of the respective pressure cylinder to the actual radii of these printing cylinders are proportional.

Advantageous embodiments are specified in the subclaims.

In EP 1 916 102 A1 describes a method in which the printing cylinder, before being installed in the printing press, are precisely measured in a mounting frame, so that their exact diameter is known exactly. These data are then transmitted to the printing press and serve there to automatically adjust the pitch positions for the axes of the various printing cylinders so that the printing cylinder with appropriate Pressure to be made against the central cylinder. In this case, the employment for the different sides of the printing machine, ie, for the opposite ends of each printing cylinder, take place independently of each other. With the proposed in this document mounting racks and appropriately equipped printing machines, the method proposed here can be particularly efficient perform.

In the following an embodiment will be explained in more detail with reference to the drawing.

Fig. 1

eine schematische Teilansicht eines Zentralzylinders mit mehreren daran angestellten Druckzylindern in einer unkorrigierten Anstellposition; und

Fig. 2

die Druckzylinder nach Fig. 1 in einer korrigierten Anstellposition.

Show it:

Fig. 1

a schematic partial view of a central cylinder with several employed pressure cylinders in an uncorrected setting position; and

Fig. 2

the impression cylinder after Fig. 1 in a corrected setting position.

In Fig. 1 one half of a central cylinder 10 is shown, which has an elastomeric surface layer 12, whose thickness is greatly exaggerated here.

A plurality of impression cylinders 14-1, 14-2 and 14-3, collectively designated by the reference numeral 14, are set against the circumference of the central cylinder 10 so far as to slightly depress the elastomeric surface layer 12, as exaggerated in the drawing is shown. Due to this deformation of the surface layer of the central cylinder 10 has at the location of the printing cylinder 14-1 the effective radius R _1, at the location of the printing cylinder 14-2 the effective radius R _2, and the point of the printing cylinder 14-3 the effective radius R ₃ ,

The radii of the printing cylinders are r ₁ , r ₂ and r ₃ .

As an example was in Fig. 1 Suppose that the radii r ₁ and r ₃ (at both ends of the respective cylinder) exactly match the nominal radius r of the impression cylinder. The radius r _{2 of} the impression cylinder 14-2 gives way on the other hand due to production-related inaccuracies by a factor (1 + k) of the nominal value r ab: r ₂ = (1 + k) r. In the example shown in the drawing, k has the unrealistically high value 0.1. In practice, the size deviations of the printing cylinders are typically of the order of a few μm, so that realistic values for k are approximately of the order of 10 ^-5 .

Due to the slightly too large radius r _{2 of} the impression cylinder 14-2, the elastomeric layer 12 is pressed in more strongly here, so that the effective radius R _{2 is} smaller than the effective radii R ₁ and R ₃ .

In this situation, the position of the axis of the impression cylinder 14-2 is corrected as shown in FIG Fig. 2 is shown. The pressure cylinder 14-2 has been further moved away from the central cylinder 10, and just so far that the effective radius R _{2 is} now by the factor (1 + k) greater than R ₁ and R ₃ . The ratio between the impression cylinder radius and the respective effective radius of the central cylinder 10 is therefore the same for all impression cylinders: R ₁ / r ₁ = R ₂ / r ₂ = R ₃ / r ₃ .

In practice, the actual radii r _{i of} all printing cylinders (the index i identifies the individual printing cylinders) will deviate from the nominal value r, and the axes of all the printing cylinders will then be set so that R _i / r _i has the same value for all i. In principle, since the impression cylinders may also have a slightly conical shape so that their radius at the opposite ends may be different, the radii are measured at least at both ends of the impression cylinder and the adjustment is made for the opposite ends of the impression cylinders (the opposite sides the printing press) made independently.

In order to maintain the repeat of the color separations printed with the various printing cylinders during the printing process, all printing cylinders 14-1,... Are driven at the same angular velocity w. The peripheral speed v _{i of} the printing cylinder with the index i is accordingly v _i = w * r _i . So that each printing cylinder rolls without slippage on the surface of the central cylinder 10 (possibly slightly dented surface layer 12), also the central cylinder 10 at the point of contact must each Pressure cylinder have this peripheral speed v _i . If W is the angular velocity of the central cylinder, then: $${\mathrm{v}}_{\mathrm{i}}\mathrm{=}\mathrm{W}\mathrm{*}{\mathrm{R}}_{\mathrm{i}}\mathrm{=}\mathrm{w}\mathrm{*}{\mathrm{r}}_{\mathrm{i}}$$

gilt somit $$\mathrm{W}\mathrm{*}{\mathrm{R}}_{\mathrm{i}}\mathrm{=}\mathrm{w}\mathrm{*}\mathrm{r}\mathrm{*}\left(\mathrm{1}\mathrm{+}{\mathrm{k}}_{\mathrm{i}}\right)$$

und folglich $${\mathrm{R}}_{\mathrm{i}}\mathrm{=}\left(\mathrm{w}\mathrm{/}\mathrm{W}\right)\mathrm{*}\left(\mathrm{1}\mathrm{+}{\mathrm{k}}_{\mathrm{i}}\right)\mathrm{*}\mathrm{r}\mathrm{=}\left(\mathrm{w}\mathrm{/}\mathrm{W}\right){\mathrm{r}}_{\mathrm{i}}$$

If k _{i are} the dimensional tolerances in the radii of the printing cylinders, then: $${\mathrm{r}}_{\mathrm{i}}\mathrm{=}\left(\mathrm{1}\mathrm{+}{\mathrm{k}}_{\mathrm{i}}\right)\mathrm{*}\mathrm{r}.$$

is valid $$\mathrm{W}\mathrm{*}{\mathrm{R}}_{\mathrm{i}}\mathrm{=}\mathrm{w}\mathrm{*}\mathrm{r}\mathrm{*}\left(\mathrm{1}\mathrm{+}{\mathrm{k}}_{\mathrm{i}}\right)$$

and consequently $${\mathrm{R}}_{\mathrm{i}}\mathrm{=}\left(\mathrm{w}\mathrm{/}\mathrm{W}\right)\mathrm{*}\left(\mathrm{1}\mathrm{+}{\mathrm{k}}_{\mathrm{i}}\right)\mathrm{*}\mathrm{r}\mathrm{=}\left(\mathrm{w}\mathrm{/}\mathrm{W}\right){\mathrm{r}}_{\mathrm{i}}$$

That is, the effective radii R _{i of} the central cylinder 10 must be proportional to the actual radii r _{i of} the impression cylinders. With this setting, an exact synchronization of all printing cylinders, ie, a run with the same angular velocity and the same peripheral speed can be achieved, so that no pressure cylinder slip relative to the central cylinder or the printing material web thereon occurs and no tensile stresses are exerted on the printing material.

This method can e.g. in gravure printing and makes it possible to realize a gravure printing machine in central cylinder design.

In order to find the right setting for the printing cylinders, their diameters can be measured with high accuracy before installation in the printing press or inside the printing press. Alternatively, however, it is also possible to continuously measure the repeat of the color separations printed on the printing substrate and / or the angular positions of the printing cylinder during the printing process and to adjust the adjustment positions of the printing cylinders in such a way that all printing cylinders run without slip at the same angular velocity.

Claims (5)

1. Method for synchronising a plurality of printing cylinders (14) that are set against a common central impression cylinder (10), characterized in that a central impression cylinder (10) is used which has an elastic surface layer (12), and in that the printing cylinder (14) is set against the central impression cylinder with elastical deformation of said surface layer (12) to such an extent that the effective radii (R₁) of the central impression cylinder at the positions of the respective printing cylinders are proportional to the actual radii (r₁) of these printing cylinders.
2. Method according to claim 1, wherein the radii of the printing cylinders (14) are measured accurately and the set positions of the printing cylinders within the printing machine are determined in accordance with the measurements results.
3. Method according to claim 1, wherein the angular positions of each printing cylinder are measured continuously during the print operation and the set position of each printing cylinder against the central impression cylinder is feedback-controlled in accordance with the measured angular position.
4. Method according to any of the preceding claims, wherein the adjustment of the set position of the printing cylinders against the central impression cylinder is performed independently for the opposite ends of each printing cylinder.
5. Method according to any of the preceding claims, wherein the printing cylinders are gravure printing cylinders.

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