GB2040228A

GB2040228A - Supplying dampening fluid in a printing machine

Info

Publication number: GB2040228A
Application number: GB8001885A
Authority: GB
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1979-01-20
Filing date: 1980-01-21
Publication date: 1980-08-28
Also published as: GB2040228B; DD148606A1; DE2902229A1; IT8047639A0; IT1127565B

Abstract

A printing machine has a plate cylinder (2), an inking cylinder (1) by way of which the ink supply is effected, an ink-feed roller (12) for supplying ink to the inking cylinder (1), and a plurality of distributor rollers (3 to 8) abutting the inking cylinder (1). A dampening roller (14) arranged in one of the cusps between the inking cylinder (1) and the plate cylinder (2) can be selectively placed either against the plate cylinder (2) or against the inking cylinder (1). The choice of the position depends on whether a heavily covered subject or a thin subject is to be printed. In the former case, it is advantageous to apply the ink and the dampening fluid together via the inking cylinder (1), while in the second case ink and dampening fluid are applied separately on the plate cylinder (2). <IMAGE>

Description

SPECIFICATION Supplying dampening fluid in a printing machine This invention relates to the supplying of dampening fluid to the plate cylinder of a printing machine having an inking cylinder which delivers ink to the plate cylinder, an ink-feed roller supplying the inking cylinder with ink, and a plurality of distributor rollers abutting the inking cylinder and arranged in direction of rotation of the inking cylinder between the ink-feed roller and the plate cylinder.

An apparatus of this type, supplying the plate cylinder of a high pressure machine with ink, is known from German Patent Specification 1176674.

It is one object of the present invention, particularly although not exclusively, to improve apparatus for supplying fluid to the plate cylinder of a printing machine to the extent that it is usable while maintaining a space-saving type of construction for offset-printing presses, and at the same time is convertible without structural alterations as desired by the user to apply dampening fluid either directly onto the plate cylinder or onto the inking cylinder.

Convertibility of this kind is desirable because, when printing heavily covered subjects, the ink and the damping fluid can be applied advantageously by way of a common application roller, whilst when printing very thin subjects, a separate application of the ink and the damping fluid is preferable.

According to the present invention, there is provided a printing machine having a plate cylinder, an inking cylinder for delivering ink to the plate cylinder, an ink-feed rollerforsupplying inktothe inking cylinder, a plurality of distributor rollers abutting the inking cylinder and arranged in the direction of rotation of the inking cylinder between the ink-feed roller and the plate cylinder, and a moveable dampening roller disposed after the last distributor roller in a cusp between the inking cylinder and the plate cylinder, such that it may be selectively placed against either the plate cylinder or the inking cylinder.

One possible advantage of embodiments of the invention is that production may be simplified, because those customers who do not expressly want a convertible machine as such can nevertheless be supplied with a machine in accordance with the invention, since the convertibility does not require any greater expense worth mentioning.

To assist in understanding the invention and to show how it may be carried out, an embodiment thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawing, which shows a printing press in a schematic side elevation.

The illustrated embodiment comprises an inking cylinder 1 which is driven in the direction of arrow a and is in contact with a plate cylinder 2. The surface of the inking cylinder 1 consists of flexible, inkreceptive material. The diameter of the inking cylinder 1 is chosen to be somewhat smaller than the diameter of the plate cylinder 2. However, the diameters of the two cylinders can be the same.

Several distributor rollers 3 to 8 are provided on that side of the inking cylinder 1 which faces away from the plate cylinder 2. The distributor rollers 3 to 8 have metallic or plastic-coated, ink-receptive surfaces and are entrained bythe ink cylinder 1, by means of friction. Furthermore, the distributor rollers 3 to 8 are subject to an axially oscillating or vibrating movement when rotating, by means of which are knownperse and are not shown in greater detail. Preferably, the arrangement is such that the distributor rollers oscillate in pairs counter-currently.

Between each pair of counter-currently oscillating distributor rollers there is a respective rider roller 9 to 11. However, the rider rollers can be omitted.

An ink-feed roller 12 is provided between the point of contact of the inking cylinder 1 with the plate cylinder 2 and the first distributor roller 3 seen in direction of rotation a of the inking cylinder 1. The ink-feed roller is constructed in the illustrated embodiment as a lifting roller which cooperates with a slowly driven duct roller 13. Instead of an ink-feed roller which moves to and fro, an ink-feed roller in permanent contact with the duct roller 13 can be used, as is known from film inking devices.

A dampening roller 14, which has a flexible surface, is arranged behind the last distributor roller 8 in one of the wedge-shaped spaces, or cusps, between the inking cylinder 1 and the plate cylinder 2. The dampening roller 14 is in permanent contact with a dampening fluid roller 15, which in turn takes the dampening fluid from a water tank roller 16.

The dampening roller 14 is mounted on a support 17 which consists of two levers, each arranged at one of the two ends of the dampening roller 14. The levers which form the support 17 are pivotable around the axis of rotation of the dampening fluid roller 15. At least one spring 18 acts on the support 17, to urge the support 17 in the direction of arrow b, and thus the dampening roller 14 against the plate cylinder 2. Furthermore, at least one adjusting screw 19, which engages the thread of a fixed supporting structure 20, can cooperate with the support 17. As is shown in the drawing, the support 17 can be pivoted so far against the direction of arrow b, by means-of the adjusting screw 19 overcoming the bias of the spring 18, that the dampening roller 14 abuts the inking cylinder 1 while maintaining contact with the dampening fluid roller 15.The adjusting screw 19 serves thereby simultaneously to adjust the contact pressure of the dampening roller 14 on the inking cylinder 1. Other known means, for example an eccentric bearing, can be used instead of these means for readjusting the dampening roller 14.

If the inking cylinder 1 rotates during printing in the direction of arrow a, first of all ink is supplied to it via the ink feed roller 12. This ink is pressed out in the course of further rotation, by means of the distributor rollers 3 to 8, to a uniform thin layer of ink. Subsequently, dampening fluid is applied to the inking cylinder 1 by means of the dampening roller 14. Immediately after application of the dampening fluid, the corresponding section of the surface of the inking cylinder 1 comes into contact with the plate cylinder 2 and releases dampening fluid and ink onto this. An excessive emulsification of the ink with the dampening fluid cannot result on the path, which is only short, of a surface section of the inking cylinder 1 between the place where the ink and dampening fluid are released onto the plate cylinder. In addition the dampening fluid is located above the layer of ink, so that the sections of the plate on the plate cylinder 2 which do not take ink are dampened with a substantialiy pure dampening fluid.

If the plate cylinder 2 is to be dampened directly with dampening fluid, the adjusting screw 19 must be siackened back only so far until the spring 18 holds the dampening roller 14 in position on the plate cylinder 2. As a result of this simple convertibility of the dampening roller 14, the printer can operate with one position of the dampening roller at certain applications of pressure, while at other applications of pressure the other position is chosen.

Claims

1. A printing machine having a plate cylinder, an inking cylinder for delivering ink to the plate cylinder, an ink-feed rollerforsupplying inktothe inking cylinder, a plurality of distributor rollers abutting the inking cylinder and arranged in direction of rotation of the inking cylinder between the ink-feed roller and the plate cylinder, and a moveable dampening roller disposed after the last distributor roller in a cusp between the inking cylinder and the plate cylinder, such that it may be selectively placed against either the plate cylinder or the inking cylinder.

2. A printing machine according to claim 1, wherein the dampening roller is mounted on a support which is pivotable around the axis of rotation of a dampening fluid roller which supplies the dampening roller with dampening fluid.

3. A printing machine according to claim 1 or 2, comprising resilient bias means which urges the dampening roller towards the plate or inking cylinder and screw-adjustment means by which the dampening roller may be placed against the inking or plate cylinder, against said bias.

4. A printing machine substantially as hereinbefore described with reference to the accompanying drawing.