GB2274812A

GB2274812A - Plate cylinder

Info

Publication number: GB2274812A
Application number: GB9402187A
Authority: GB
Inventors: Josef Hajek; Anton Neumeir
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1993-02-05
Filing date: 1994-02-04
Publication date: 1994-08-10
Anticipated expiration: 2014-02-04
Also published as: GB2274812B; GB9402187D0; DE4303381A1; FR2701233B1; FR2701233A1

Abstract

To assist in lifting a cylinder-mounted printing plate 13, 14 when it is due to be exchanged, bores 5, 16 are provided in the cylinder 1, to which compressed air can be admitted. The bores emerge from the surface of the plate cylinder 1 beneath the end of the printing plate 13, 14 in the vicinity of a non-printing zone. When the compressed air is supplied through compressed air supply lines an area of the plate 13, 14 is released from the surface of the cylinder and it can then be removed. <IMAGE>

Description

PLATE CYLINDER The invention relates to a printing unit cylinder to which plates are to be applied and from which they are to be removed.

By a printing unit cylinder of this kind is preferably to be understood a plate cylinder provided with an axially extending clamping groove such as is used in rotary offset presses. It is well known that in such rotary offset presses a plate change is necessary before the beginning or at the end of any print job, i.e. one or more of the printing plates located on the cylinder must be removed and replaced by a new plate or plates, and when the printing run is finished all the plates must be removed. As a result of the adhesion between the printing plate and the surface of the cylinder, of pressure from the impression cylinder or forme rollers or of contamination, for example by hardened printing ink, it is difficult to remove the printing plate, in particular to lift the ends of the plate laterally of the cylinder gap (groove).

In order to lift the plate somewhat from the cylinder surface the printers have hitherto resorted to applying a tool, for example a screwdriver, to its end.

Apart from the inconvenience of dealing with the problem in this way there is also the risk of damaging the printing plates, which often have to be reused for a later printing job. In addition damage to the cylinder itself is a possibility.

It is therefore an object of the present invention to provide means by which a plate, particularly a printing plate, can be lifted gently from the surface of a printing unit cylinder and which in case of need can also be employed to automate the plate changing process.

The invention is concerned with a plate cylinder provided with means for lifting a printing plate so as to free the plate from the surface of the cylinder.

The lifting means is located internally of the cylinder and preferably comprises channels in the cylinder emerging under an edge of the plate; compressed air can be applied through these channels to lift the plate edge.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a partial section through a forme cylinder; Figs. 2 and 3 show two longitudinal sections (also partial) through a forme cylinder for two different embodiments, and Fig. 4 shows a plan view from above of a printing unit tower with two superimposed printing units.

In Fig. 1 a printing unit cylinder, for example a plate or forme cylinder 1, is shown which can be fitted with a plate, for example at least one offset printing plate 3, of which the ends, not shown in detail, are introduced into a groove or channel 2 extending axially of the forme cylinder 1 in order to hold the printing plate 3 in position.

According to the invention a means is provided inside the cylinder, preferably beneath the so-called non-printing zone 4, as shown in Fig. 1, which usually has to be left on both sides of the groove 2, by which the printing plate 3 can be lifted, preferably at one axial end, not indicated as such, of the forme cylinder 1.

If the forme cylinder 1 can be fitted with several printing plates 13, 14 (Figs. 2 and 3), it is advantageous to provide a separate lifting means for each of the printing plates 13, 14 so that, as is preferred, the separate printing plates 13, 14 can be lifted individually. Hence for each of the printing plates 13, 14 respective axial bores 5, 6 are provided that proceed from the end face 10 of the forme cylinder 1 and preferably, at least at first, run axially and are connected to substantially radial outlet openings 16, 17, also in the form of bores. As can be seen, the openings 16, 17 emerge in the neighbourhood of a side wall (not shown in detail) of the groove 2. It is advantageous if several such outlet openings 16 or 17 are provided in succession in the axial direction for each of the plates 13, 14; in the drawing only two openings are shown.

In accordance with the invention a liquid or gaseous medium, preferably compressed air, is admitted to the openings or bores 5, 6 and passes through to the openings 16, 17 to lift the ends of the printing plates 13, 14 so that the printing plates 13, 14 can be lifted at at least one position, preferably in the region of one end of the plate, for the plate changing operation.

For this purpose the version shown in Fig. 2 offers stationary compressed air supply lines 7 and 8 spaced from the end 10 of the forme cylinder 1. The compressed air supply line 7 is located in the region of the axial bore 5 for the printing plate 13 and the compressed air supply line 8 is located in the region of the axial bore 6 for the plate 14. In this version with a spaced arrangement the compressed air supply lines 7, 8 do not have to be moved for the plate changing operation. Hence for supplying the compressed air they can be arranged permanently on a side wall 9, as is also indicated at 11 and 12 in Fig. 2.

Another possibility, shown in Fig. 3, is to bring compressed air supply lines 7 and 8 up to the respective bores 5 and 6 when the forme cylinder 1 is at a standstill. It is then advantageous to control the compressed air supply lines 7, 8 individually, for example by means of pneumatic or electromagnetic valves, as indicated but not shown in detail in Fig. 3.

In an equivalent manner - and thus making use of the idea underlying the invention - it is possible to use mechanical members, e.g. rams, controlled electromagnetically to move out of the outlet openings, to lift the printing plate 3.

It goes without saying that the number and arrangement of the various bores must be adapted to the particular application; instance, the lifting means can be used both for two-plate and for four-plate width machines.

Two-plate width machines can be serviced from one side, as can be seen from the Figures, while in the case of four-plate width machines two plates can be handled from each side, independently of one another, so that two printers can carry out the fitting or removal of the plates at the same time.

Such a four-plate width machine is illustrated in Fig. 4. It comprises two printing units 49, 50 superposed in a tower printing unit, the forme cylinder 1 being fitted with further printing plates 18, 19 in addition to the printing plates 13, 14. The forme cylinder 1 is journalled between two side walls 20, 21.

A forme cylinder 22 is similarly mounted above the forme cylinder 1 and is similarly fitted with four printing plates 23 to 26. The forme cylinders 1 and 22 are brought into contact with respective transfer cylinders 27 and 28 and print a web of printing substrate on the blanket-to-blanket principle. In the printing unit 50 arranged above the printing unit 49 a web of printing substrate is printed by forme cylinders 29, 30, fitted respectively with printing plates 31 to 34 and 35 to 38, by way of transfer cylinders 39, 40.

The two printing units 49, 50 are respectively accessible to an operator from a surface or platform 41, 42. Displays associated with the respective printing plates 13, 14, 18, 19; 23 to 26; 31 to 34; 35 to 38 are arranged in the side walls 20, 21, for example the displays 43, 44 showing the plate occupation for the printing plates 13, 14 on the forme cylinder 1. In a run changeover each of the printing plates 13, 14, 18, 19; 23 to 26; 31 to 34; 35 to 38 can be freed individually from its respective forme cylinder 1, 28, 29, 30 by an electropneumatically or electromagnetically controlled valve of a compressed air supply line 7, 8 (see Fig. 3) associated individually with it or by means of a mechanical element, operated for example electromagnetically.For this purpose each of the valves or mechanical elements is connected by way of a control line to a programming unit at the production planning position, which may for example be located at the print preparation station.

In this programming unit a plate clearance schedule can be programmed according to which the printing plates 13, 14, 18, 19; 23 to 26; 31 to 34; 35 to 38 are released after the end of a first press run. By means of optical indicators, for example LEDs such as the LEDs 45, 46 associated with the printing plates 13, 14, the printer is shown which of the printing plates 13, 14, 18, 19; 23 to 26; 31 to 34; 35 to 38 have to be exchanged. The printer then takes down the printing plate, which has already been freed pneumatically or mechanically from the surface of the respective forme cylinder 1, 22, 29, 30, and replaces it with a new printing plate. He confirms the plate exchange by pressing a release switch 47, 48 associated with the printing plate being exchanged, for example the printing plates 13, 14. This prevents the printing press from being started up again while the released printing plates are still lying on the forme cylinders 1, 22, 29, 30. By the confirmation by means of the release switch and the extinguishing of the associated LEDs the printer satisfies himself that the press is ready to run and that the plates are properly fitted.

It is thereby ensured that all the automatically released plates have also actually been removed and the new printing plates fitted ready for the run. This indication also saves the printer the need for further consideration during this operation. The displays can also be combined with the release switches (membrane keyboard).

Claims

Claims:

1. A plate cylinder provided with means for lifting a printing plate so as to free the plate from the surface of the cylinder.

2. A plate cylinder according to claim 1, in which the lifting means includes a generally axial bore proceeding from the end face of the plate cylinder communicating with one or more outlet openings leading to the printing plate.

3. A plate cylinder according to claim 2 and further including one or more compressed air supply lines arranged in use between the end face of the plate cylinder and a side wall of the printing unit, through which lines compressed air can be admitted to the bores and openings for lifting the printing plate from the plate cylinder.

4. A plate cylinder according to claim 3, in which the compressed air supply lines are stationary and are spaced from the end face of the plate cylinder.

5. A plate cylinder according to claim 3, in which the compressed air supply lines are movable up to the axial bores at the end face of the plate cylinder.

6. A plate cylinder according to claim 5, in which the compressed air lines are equipped with valves which can be individually controlled pneumatically or electromagnetically.

7. A plate cylinder according to any of claims 3 to 6 and having at least two outlet openings for the or each axial bore, the outlet openings being located beneath a non-printing zone and alongside one another in the direction of the cylinder axis.

8. A plate cylinder according to claim 7, in which the non-printing zone is located on either side of the plate cylinder groove.

9. A plate cylinder according to claim 1, in which the lifting means is a mechanical or electromagnetic device linked for actuation to one end of the plate cylinder.

10. A plate cylinder according to any preceding claim and having a plurality of printing plates each with a respective individually controllable lifting means, so that the printing plates can be lifted individually.

11. A plate cylinder substantially as described with reference to any of the accompanying Figures 1 to 3.

12. A printing press having one or more plate cylinders according to any preceding claim, in which the lifting means are connected to a programming unit by means of which a plate clearance schedule can be programmed according to which the printing plates on the plate cylinders are released for the run change by electropneumatic or electromagnetic control, and displays are provided to indicate the plate clearance schedule.

13. A plate cylinder according to claim 12, in which the displays are located in the side walls of the printing unit and that indicating means are provided for identifying the printing plates to be exchanged.

14. A plate cylinder according to claim 12 or 13, further including release switches associated with the printing plates to be exchanged and means for preventing continuance of the printing run after the printing plates have been exchanged until the associated release switches have been operated.