DE19945783A1 - Rotary offset printing machine; has several printing groups and at least one transfer cylinder arranged at step angle that is corrected for systematic errors in drive wheel rotation angle - Google Patents

Abstract

The machine has a row of several printing groups (1,2) with at least one transfer cylinder (6) arranged at a step angle, alpha , between the printer groups. The step angle is chosen according to the cylinder diameter, so that the same printing results occur at the same time in at least some of the printing groups. The cylinder arrangement has a corrected step angle, alpha k, which is determined from the theoretical step angle, alpha th, the diameter ratios and the number of synchronised printing groups, and is varied by an amount, which compensates for systematic rotation angle errors in the drive wheel that affect the synchronicity of the printing groups.

Description

The invention relates to an offset rotary sheet printing machine with several Printing units, in the same printing events in several or all printing units at the same time expire.

From DE 44 16 974 and DB 40 32 442 is the relationship between step angle α and phase angle ϕ between successive printing units of a printing press for usual diameter ratios of plate, rubber, printing and transmission cylinders known.

By choosing the step angle α (angle between the straight connecting line axis Printing cylinder - axis transfer cylinder and the horizontal) becomes dependent of the diameter ratios of the cylinders the phase angle ϕ and thus the number the printing units synchronized with each other (simultaneous execution of the same printing events) fixed.

The phase angle ϕ is the angle of rotation of a single-turn shaft between be neighboring printing units defined to offset the same printing events in each expire both printing units.

In a printing press with a step angle α = 22.5 ° and a diameter ratio Plate cylinder rubber cylinder: impression cylinder: transfer cylinder = 1: 1: 2: 2 for example the phase angle ϕ = 180 °, d. H. the printing cylinders in neighboring printing units ken are rotated by 180 ° to each other or run in every second printing unit at the same time same print events.

This relationship is based on the consideration of the pass angle γ (sum of the rotation angle of the individual cylinders when passing through an arc).

A disadvantage is the fact that the machine design is technically related Deviations from the theoretical angles of rotation, such as. B. by backlash, not considered be considered, so that especially with the automatic plate change difficulties with simultaneous positioning of the synchronously running plate cylinders occur. This the larger the number of printing units in a printing press, the greater.  

With a tooth clearance of 0.10 as a rule. . These add up to 0.15 mm long printing presses to deviations of the plate cylinder position from the target value in mil limeter area.

The invention is therefore based on the object, the positioning accuracy in particular Plate cylinders in printing presses with several synchronized printing units under Be taking into account the real conditions in the drive wheel train of a printing press with con improve structural measures.

The solution to this problem, according to the characterizing features of the first claim, is to arrange the axes of the transfer cylinders at a step angle α _k corrected in relation to the theoretical angle α _th in the printing press in such a way that misalignments of the cylinders caused by the drive wheel pull via a change in through running angle conditions are balanced.

This ensures in particular that when a plate cylinder is rotated into the plat all others with this synchronized plate cylinder in the same ben angular position.

The invention will be explained in more detail below using an exemplary embodiment. The drawing shows sections of the first two printing units 1; 2 an offset rotation sheet printing machine with several, for example 8 printing units and one over each transfer cylinder 6 between the printing units.

The plate cylinder 3 and blanket cylinder 4 are of a single size and the impression cylinder 5 and transfer cylinder 6 are of a double size. The phase angle ϕ between the individual NEN plate cylinders 3 should have an amount of 1800, so that the printing events in each of the second printing unit run synchronously. The theoretical step angle α _th required for this, as already mentioned above, is 22.5 °.

If the first plate cylinder 3 is now rotated into the plate changing position, they are there with synchronized plate cylinder 3 in the printing units 3, 5, 7 practically not in the same Position, since systematic rotation angle errors in the drive wheel train lead to deviations from the exact plate changing position.  

Essentially, the systematic errors are always present Backlash in the drive wheel train, which leads to an undesired rotation of the plate cylinder 3 leads to each other. The misalignments of the plate cylinder 3 are greater, the longer the Printing press is.

In the example of a printing press with 8 printing units and double sizes Printing cylinders 5 and transfer cylinders 6 guide a tooth that is normally present game of 0.10. . .0.15 mm per tooth engagement to an incorrect position of the last printing cylinder 5 compared to the first printing cylinder 5 of up to 2.25 mm.

Because the geometric relationships in the output from the pressure cylinder to the rubber cylinder 4 and plate cylinders 3 are the same in the individual printing units, there caused angular deviations in the same direction, so that only from the drive wheel the angle deviations caused must be compensated.

Assuming a gear wheel diameter of the double-sized pressure cylinder 5 and transfer cylinder 6 of 600 mm, 0.15 mm tooth play corresponds to an angular deviation of 0.030, ie the gear wheel of a pressure cylinder 5 would have compared to the upstream pressure cylinder gear wheel 5 due to the intermediate gear of the transfer cylinder 6 (two tooth engagement points) has an angular error of 0.060, by which the impression cylinder 5 rotates less than the impression cylinder 5 arranged in the direction of sheet travel. This misalignment is now compensated according to the invention by a reduction in the passage angle γ _{n, n + 1} on the transfer cylinder 6 during sheet travel from a printing unit to the subsequent printing unit by the step angle α _th being reduced accordingly. The reduction of the passage angle γ _{n, n + 1} on the transfer cylinder by 0.06 ° also results in a rotation angle of the pre-arranged impression cylinder reduced by 0.060 as a result of the gear coupling via the drive gear train and the assumed diameter ratio of 1: 1 (drawing).

Because of the relationship Y _{n, n + 1} = 4 α _th + 360 ° for the passage angle between two printing units, which is assumed for the cylinder diameter ratios assumed as an example, the step angle α has to be corrected by ¼ of the angular error - in the example therefore 0.0150.

The corrected step angle is thus α _k = 22.485 ° for the selected example.

If all printing units are now equipped with the corrected step angle α _k , it is ensured that when the first plate cylinder 3 positioned by means of an incremental encoder is rotated into the plate changing position, all other plate cylinders 3, which run in the same direction, are in exactly the correct angular position, for example automated plate changing is simplified.

List of reference symbols

1

first printing unit

2nd

second printing unit

3rd

Plate cylinder

4th

Rubber cylinder

5

Impression cylinder, impression cylinder gear

6

Transfer cylinder, transfer cylinder gear

7

Connection line between the axes of the impression cylinder and transfer cylinder

8th

Horizontal
α step angle
α _th

theoretical step angle
α _k

corrected step angle
γ pass angle
γ _{n, n + 1}

Pass angle during sheet travel from one printing unit to the next printing unit

Claims (1)

1. offset rotary sheet printing machine with several printing units in series with at least one transfer cylinder arranged at a step angle α between the printing units, the step angle α being selected as a function of the cylinder diameters such that the same printing events take place simultaneously in several or all printing units, characterized in that that the cylinder arrangement has a step angle α _k , which is ver compared to the theoretical step angle α _th , which is determined from the diameter ratios and the number of each other synchronized printing units in a known manner by an amount that the the simultaneity of the printing events in compensates for the systematic rotational angle errors in the drive wheel train that adversely affect the printing units.