GB2096543A

GB2096543A - Adjustments in printing presses

Info

Publication number: GB2096543A
Application number: GB8210969A
Authority: GB
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1981-04-15
Filing date: 1982-04-15
Publication date: 1982-10-20
Also published as: CH656834A5; DE3115141C2; DE3115141A1; FR2504058A1; GB2096543B; FR2504058B1; BR8201851A; SE8202314L; SE447643B; JPS57178753A

Abstract

Diagonal adjustment of a plate cylinder on a sheet-fed rotary offset press is made possible by the fact that the bearing journal (20) of the plate cylinder (2) is mounted in a cylinder bearing (19), which has parallel external guide surfaces and is guided in a guide bearing (13) mounted in an eccentric bearing (11) for impression throw-on and is aligned and secured against rotation so that the guide surfaces run approximately at right angles to the plane connecting the axes of the plate cylinder and blanket cylinder. The cylinder bearing (19) in the guide bearing (13) can be adjusted by suitable adjusting devices. (22, 27). <IMAGE>

Description

SPECIFICATION Printing presses This invention relates to printing presses, particularly sheet-fed rotary offset presses, and to diagonal adjustment means for cylinders therein.

In offset printing a printing forme is placed as a flat plate around a plate cylinder and secured by suitable clamping devices. To ensure that all printing plates on one press can quickly be aligned in register, i.e.

all inks are in register one above the other after printing a sheet, particularly on multi-colour presses, it is known to provide on the fixing means for the printing plates a so-called register in the form of stops or the like, which are contacted by suitable matching pieces on the printing plate. The corresponding film originals for printing plate production are also based on this register. Despite all due care it may happen, however, that the film is displaced only by fractions of a millimetre in relation to the register during printing plate production, the results being displacement of one ink in relation to another during printing. To compensate for this defect, timeconsuming adjustments to the printing plate by loosening and moving the latter on the plate cylinder are then necessary.This is particularly timeconsuming and difficult, ifthefilm mounting for printing plate production was not copied in parallel, because the clamping devices for the printing plate must then be inclined in relation to the plate cylinder axis.

To simplify these time-consuming and difficult adjustments and shorten the resulting stoppages, arrangements permitting diagonal adjustment of the plate cylinder have been developed. An arrangement of this type is described, for example, in German Offenlegungsschrift 2817 075.

This publication discloses an arrangement for diagonal adjustment of the plate cylinders on a printing press, in which one of the plate cylinder bearings has an eccentric bush, in the outer bearing surface of which in the centre of the machine wall a pull-and-push rod for adjustment of the eccentric bush engages, the pull-and-push rod being designed as a lockable rack in the area of the eccentric bush and part of the outer contacct area of the eccentric bush being formed as a toothed segment engaged therewith.

A disadvantage of arrangements of this type, however, is that the impression throw-on settings change during inclination of the cylinders, so that they still have to be corrected after adjustment of the plate cylinder. The impression throw-on settings may be larger or smaller according to the adjustment direction of the platecylinder.

According to the present invention, there is provided a printing press including at least one cylinder mounted in an eccentric bearing which can be turned to adjust the contact pressure between that cylinder and a further cylinder in contact therewith, wherein the cylinder has a bearing journal mounted in a cylinder bearing having parallel external guide surfaces, the cylinder bearing is located in and surrounded by a quide bearing having parallel internal guide surfaces, the guide bearing is in turn guided in the eccentric bearing and rotationally fixed relative thereto, the planes of the internal and external guide surfaces being substantially normal to the plane of the axes of the two cylinders, and adjusting devices are provided to adjust the cylinder bearing in the guide bearing.

Hence the task of the invention accordingly may provide an arrangement for diagonal adjustment of the plate cylinder of a sheet-fed rotary offset press, in which there is no increase in the printing pressure during diagonal adjustment of the plate cylinder.

The diagonal adjuster of the invention may be designed in such a way that when operated the printing pressure is only slightly below the set value and no visible fall in the ink density occurs over the width of the machine.

The advantage of the arrangement according to the invention compared with already known arrangements is that the disadvantages of the latter are eliminated by selection of the adjusting gear in such a way that no further adjustments are necessary after diagonal adjustment of the plate cylinder.

Investigations have shown that no adverse effect on the bearing of the cylinder journal on the plate cylinder bearing side opposite the diagonal adjuster need be anticipated, so that the well-proven cylinder bearings can be retained.

The invention is illustrated by way of example with reference to a preferred constructional embodiment described in more detail below with references to the accompanying drawings in which: Figure 1 shows the schematic construction of an offset printing press, Figure 2 is an end view of a bearing of a plate cylinder with a diagonal adjusting device, and Figure 3 is a sectional view on the lines l-l in Figure 2.

An offset printing press 1 shown in Figure 1 has a printing unit consisting of a plate cylinder 2, a blanket cylinder 3 and an impression cylinder 4.

Individual sheets are fed to this impression cylinder 4 from a feeder pile 5 by a suitable feed arrangement. The printed sheets are fed by a take-off system 7 to a delivery pile 8 or to a further printing unit on multi-colour presses.

The plate cylinder 2 of the offset press 1 has clamping devices of a known type not described here, with which a printing plate can be secured on the plate cylinder. As it repeatedly happens that a printing plate is inclined, i.e. the leading edge is not clamped parallel with the plate cylinder axis, despite all due care when clamping the plate, a bearing as shown in Figures 2 and 3 is provided on one side of plate cylinder 2, preferably on the side opposite the drive gearwheel. Forthis purpose a side column 9 of the offset press 1 has a hole 10, in which an eccentric bearing 11 fits. This eccentric bearing 11 is provided with an adjusting device 12 of known design to permit adjustment of the plate cylinder 2 in relation to the blanket cylinder 3.This adjustment is necessary in offset printing to optimise transfer of the image from a printing plate on the plate cylinder to a rubber blanket secured on the blanket cylinder 4.

Afurther guide bearing 13 with two parallel guide surfaces 14,15 is provided in the eccentric bearing 11. This guide bearing 13 is rotatable in relation to the eccentric bearing 11, but has a rotation limiter 16, which is made to engage in a slot 17 by means of a slotted block 18, to prevent rotation in relation to the side column 9. An actual plate cylinder bearing 19, which also has two guide surfaces 14.1, 15.1 receives the bearing journal 20 of the plate cylinder 2, and is located within the guide bearing 13.

The position of cylinder bearing 19 and thus the plate cylinder 2 relative to guide bearing 13 is fixed by a spring-loaded bolt 21 and an adjusting bolt 22.

These two bolts 21,22 act on pressure plates 23,24 opposite them on the periphery of the cylinder bearing 19. As the two bolts 21, 22 project into the side column 9, the eccentric bearing 11 has corresponding recesses 25, 26 in this area. These recesses 25,26 are so dimensioned that the eccentric bearing 11 can be operated by the adjusting device 12.

If it is necessary to adjust the plate cylinder 2 diagonally after clamping the printing plate and taking a proof impression, axial displacement of bolt 22 is effected via an adjusting cam 27. Depending on the adjustment of the adjusting cam 27 the cylinder bearing 19 then moves towards the adjusting cam 27 or the spring-loaded bolt 21. With the construction shown in Figure 2 and a maximum diagonal adjustment path of about 0.5 mm the pressure over the width of the plate cylinder 2 in relation to the blanket cylinder 3 is reduced by about 12,a. This small reduction in pressure is not visible in the finished printed product, so that there is no loss of quality despite diagonal adjustment of the plate cylinder 2.

Impression cannot be increased during diagonal adjustment, because the plane including the plate cylinder axis and the blanket cylinder axis runs approximately at right angles to the guide surfaces 14,15.

The adjusting cam 27 can be locked by a known clamping device to prevent accidental adjustment.

Claims

1. A printing press including at least one cylinder mounted in an eccentric bearing which can be turned to adjust the contact pressure between that cylinder and a further cylinder in contact therewith, wherein the cylinder has a bearing journal mounted in a cylinder bearing having parallel external guide surfaces, the cylinder bearing is located in and surrounded by a guide bearing having parallel internal guide surfaces, the guide bearing is in turn guided in the eccentric bearing and rotationally fixed relative thereto, the planes of the internal and external guide surfaces being substantially normal to the plane of the axes of the two cylinders, and adjusting devices are provided to adjust the cylinder bearing in the guide bearing.

2. A printing press according to claim 1,wherein the eccentric bearing has a guide bearing, which is provided with a straight guide with parallel internal guide surfaces, a cylinder bearing with external guide surfaces, corresponding to the internal guide surfaces is provided between the latter, the bearing journal of the cylinder being mounted in this bearing, and the cylinder bearing is provided with pressure plates opposite each other on its partial circumference, an adjusting mechanism consisting of an adjusting bolt and a spring-loaded bolt acting on the pressure plates, and the adjusting bolt can be operated by an adjusting cam in such a way that the cylinder bearing can be moved in the guide bearing against the force of the spring-loaded bolt on the guide surfaces, and the guide bearing is provided with a slot, into which a slotted block of a rotation limiter engages in such a way that the cylinder bearing cannot be rotated even when the eccentric bearing is adjusted.

3. A printing press according to claim 2 wherein the contacting surfaces of the pressure plates and bolts are hardened.

4. A printing press according to claim 2 or 3 and including a precision drive means for actuating the adjusting bolt.

5. A printing press according to any one of claims 1 to 4 wherein the cylinder is the plate cylinder of a sheet-fed rotary offset press, and in which the plate cylinder is mounted in an eccentric bearing, which can be turned to adjust the printing pressure between the plate cylinder and a blanket cylinder.

6. A printing press according to claim 5 wherein the bearing journal and guide bearing enable diagonal adjustment of the plate cylinder and are provided on the side of the plate cylinder opposite a drive gear wheel for driving the plate cylinder.

7. A printing press having means for diagonal adjustment of a cylinder substantially as hereinbefore described with reference to the accompanying drawings.