GB1588375A

GB1588375A - Rotary planographic printing unit

Info

Publication number: GB1588375A
Application number: GB777778A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1977-03-03
Filing date: 1978-02-27
Publication date: 1981-04-23
Also published as: DE2709151A1; FR2382334A1; CH626004A5; FR2382334B1

Abstract

In the printing unit which has been converted from letterpress printing to lithoprinting, the damping medium is applied to a plate cylinder (1) via damping units (15, 25). Each one of the damping units (15, 25) consists of a damping medium dispenser (19, 27) in the form of a damping medium spraying source, by means of which very small droplets of damping medium are projected without contact onto the outer surfaces of forme damping rollers (17, 23). The forme damping rollers (17, 23) consist of a solid steel core with a rubber or synthetic coating which accepts damping medium and repels ink and has a storage effect. The forme damping roller (23) is arranged in the lithoprinting operation at the point where the forme inking roller was located in the letterpress printing operation. <IMAGE>

Description

(54) ROTARY PLANOGRAPHIC PRINTING UNIT (71) We, MASCHINENFABRIK AUosBURo-NURNBERG AKTIENGESELLSCHAFT, a German com- pany, of 8900 Augsburg, Stadtbachstrasse 1, Germany (Fed. Rep), do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of converting a rotary relief printing machine into one for planographic printing.

Printing units having separate inking and dampening systems are widely used above all in the offset printing technique. In order to attain an even, thin dampening medium film on the non-printing parts of the plate cylinder, and to avoid the occurrence of dampening medium drops on the printing parts, a considerable number of further rollers are required in the dampening unit in addition to a dampening medium application or forme roller. Thus the mechanism known from the DT-AS 1 940 661 requires a transfer roller, an intermediate roller and a duct roller, and if need be squeezing roller and a blade mechanism, which work in conjunction with the duct roller.

Such a dampening unit is unsuitable if for example a relief printing machine for newspaper printing is to be re-adapted to direct planographic printing in which printing takes place directly from the plate cylinder onto the paper, because of the space limitations; that is, there is as little space in a relief printing machine for this multiplicity of dampening application rollers as there is space for an offset-impression cylinder.

According to the present invention, there is provided a method of converting a rotary relief printing machine having a plate cylinder adapted to carry removable relief printing plates or planographic printing plates and having an inking unit including two or more inking forme rollers, into a planographic printing machine, comprising shifting one of the inking forme rollers out of contact with the adjacent roller of the inking unit and providing it with a resilient coating the surface of which is receptive to dampening medium, and is ink repellent, whereby it is adapted to operate as a dampening forme roller, and providing a dampening medium dispenser which is adapted and arranged to produce a spray of dampening medium passing across an intermediate space onto the surface of the dampening forme roller with an even distribution thereon.

By this means it is possible to manage absolutely without additional space requirements in the case of reconstructing a relief printing machine.

Preferably, the dampening roller consists of a solid, steel core and the resilient coating is made of rubber or plastics material.

The invention thus includes a combination of two features, namely the use of a dampening medium dispenser and a dempening medium application roller having a particular construction, which combination produces the wholly unexpected effect that the dampening medium film sprayed onto such a dampening medium application roller already possesses an evenness and consistency such that it can be directly borne onto the plate cylinder. The invention has the advantage that it can be realised within a very small space and at favourable costs. It can be incorporated into many relief printing rotary machines - independent of the type of manufacture. With regard to the quality of print, a good newspaper quality can be attained with the invention. Therefore it can be also used in offset-printing machines for simple requirements.

The invention may be carried into practice in a number of ways but two specific embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a printing unit converted in accordance with the invention, with an alternative possibility of incorporating a dampening unit; and Figure 2 is a partial view of a relief printing machine temporarily converted to a printing unit in accordance with the invention.

A printing unit re-adapted from relief printing to direct planographic printing is shown in Figure 1. A plate cylindcr 1 is re-adapted from one for carrying stereotype plates to the use of thin planographic printing plates of 0.3 mm thickness by the incorporation of stretching gallows, i.e. tensioning means. This plate cylinder 1 operates in conjunction with an impression cylinder 3 and thus prints directly, and without the mediation of an offset blanket cylinder roller, onto a paper web 5 passing between the cylinders 1 and 3. An inking unit 7 acts on the plate cylinder 1 and comprises a plurality of inking vibrators 9, resiliently covered intermediate rollers 11 and inking application or forme rollers 13, and corresponds extensively to the original relief printing inking unit. A separate dampening unit 15 is located in front of the inking unit 7 relative to the direction of rotation of the plate cylinder 1, the dampening unit 15 being constructed of a dampening medium application or forme roller 17 and a spraying or squirting dampening medium dispenser 19.

The dampening forme roller 17 is a customary resiliently covered roller comprising a rubber or plastics covering on a steel core, the surface of the covering consisting, however, of special coating, which has been vulcanised on or pulled on. This coating is receptive to the dampening medium and repels the ink, and possesses a considerable storing effect for the dampening medium, in that the surface finish does not appear smooth in connection with the dampening medium.

The dampening medium dispenser 19 sprays or squirts very small particles of the dampening medium with considerable energy through an opening 21 towards the dampening forme roller 17. The flow is evenly distributed and can be regulated over the whole width of the paper. The particles of the dampening medium cross the air space between the opening 21 and the dampening forme roller 17, freely and without contact with anything, and appear on the surface of the dampening forme roller 17 with almost upimpaired energy, where they merge, as it were, into a dampening medium film.

Although dampening unit 15 could be attached additionally to the inking unit if there is sufficient space there is the alternative possibility, in accordance with the invention, in the case of an inking unit 7 which originally has three inking forme rollers (13, 3 and 23 as shown in the embodiment of Figure 1) of constructing one of these inking forme rollers so that it can be used as the dampening forme roller 23 of an even simpler dampening unit 25. For this purpose, this roller 23 only needs to be lifted from the appertaining inking vibrator 9 and its surface to be provided with the coating mentioned. In the case of this dampening unit 25, only a dampening medium dispenser 27 is required in addition to the parts present for the relief printing.

Figure 2 shows a conventional newspaper relief-printing machine for printing a paper web 29 with three plate cylinders 31, 33 and 35, in which stretching gallows, i.e. tensioning clamping devices, are provided instead of relief printing plates, for thin planographic printing plates or offset plates. A respective inking unit 37, 39, 41 acts on each plate cylinder 31, 33, 35, each inking unit having a number of inking vibrators 43, intermediate rollers 45 and inking forme rollers 47, 49. Originally, each of the two lower inking units 37 and 39 had three inking forme rollers when acting as a reliefprinting inking unit. In order to convert the relief printing unit to direct planographic printing, the one application roller 49 in each case, which lies in front of the two other application rollers 47 relative to the direction of rotation of the plate cylinder 31, 33, is lifted from the respective inking vibrator 43, provided with the coating which is receptive to the dampening medium, repels ink and is capable of storing the dampening medium, and is equipped with a spraying or squirting dampening medium dispenser 51.

Therefore no additional roller at all is required for this adaptation and the dampening medium dispenser 51, which is the only additional apparatus necessary, is located on a part of the printing unit on which it does not in any way impede accessibility to the rollers and cylinders, in particular to the plate cylinders 31 and 33.

In the case of the upper printing unit 41 a printing unit moreover provided only as special optional equipment - that inking unit only possesses two forme rollers 47.

Therefore an additional roller constituting a dampening forme roller 53 is disposed here in contact with the plate cylinder 35, with a dampening medium dispenser 55. This is readily possible however because there is enough space for such an additional dampening forme roller 53. Also no disadvantage arises from the fact that the dampening forme roller 53 is disposed behind the inking forme rollers 47 relative to the direction of rotation of the plate cylinder 35, because the special coating of the dampening forme roller 53 guarantees a good conduction of the dampening medium even in this case.

WHAT WE CLAIM IS: 1. A method of converting a rotary relief printing machine having a plate cylinder adapted to carry removable relief printing plates or planographic printing plates and having an inking unit including two or more inking forme rollers, into a planographic printing machine, comprising shifting

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A printing unit re-adapted from relief printing to direct planographic printing is shown in Figure 1. A plate cylindcr 1 is re-adapted from one for carrying stereotype plates to the use of thin planographic printing plates of 0.3 mm thickness by the incorporation of stretching gallows, i.e. tensioning means. This plate cylinder 1 operates in conjunction with an impression cylinder 3 and thus prints directly, and without the mediation of an offset blanket cylinder roller, onto a paper web 5 passing between the cylinders 1 and 3. An inking unit 7 acts on the plate cylinder 1 and comprises a plurality of inking vibrators 9, resiliently covered intermediate rollers 11 and inking application or forme rollers 13, and corresponds extensively to the original relief printing inking unit. A separate dampening unit 15 is located in front of the inking unit 7 relative to the direction of rotation of the plate cylinder 1, the dampening unit 15 being constructed of a dampening medium application or forme roller 17 and a spraying or squirting dampening medium dispenser 19. The dampening forme roller 17 is a customary resiliently covered roller comprising a rubber or plastics covering on a steel core, the surface of the covering consisting, however, of special coating, which has been vulcanised on or pulled on. This coating is receptive to the dampening medium and repels the ink, and possesses a considerable storing effect for the dampening medium, in that the surface finish does not appear smooth in connection with the dampening medium. The dampening medium dispenser 19 sprays or squirts very small particles of the dampening medium with considerable energy through an opening 21 towards the dampening forme roller 17. The flow is evenly distributed and can be regulated over the whole width of the paper. The particles of the dampening medium cross the air space between the opening 21 and the dampening forme roller 17, freely and without contact with anything, and appear on the surface of the dampening forme roller 17 with almost upimpaired energy, where they merge, as it were, into a dampening medium film. Although dampening unit 15 could be attached additionally to the inking unit if there is sufficient space there is the alternative possibility, in accordance with the invention, in the case of an inking unit 7 which originally has three inking forme rollers (13, 3 and 23 as shown in the embodiment of Figure 1) of constructing one of these inking forme rollers so that it can be used as the dampening forme roller 23 of an even simpler dampening unit 25. For this purpose, this roller 23 only needs to be lifted from the appertaining inking vibrator 9 and its surface to be provided with the coating mentioned. In the case of this dampening unit 25, only a dampening medium dispenser 27 is required in addition to the parts present for the relief printing. Figure 2 shows a conventional newspaper relief-printing machine for printing a paper web 29 with three plate cylinders 31, 33 and 35, in which stretching gallows, i.e. tensioning clamping devices, are provided instead of relief printing plates, for thin planographic printing plates or offset plates. A respective inking unit 37, 39, 41 acts on each plate cylinder 31, 33, 35, each inking unit having a number of inking vibrators 43, intermediate rollers 45 and inking forme rollers 47, 49. Originally, each of the two lower inking units 37 and 39 had three inking forme rollers when acting as a reliefprinting inking unit. In order to convert the relief printing unit to direct planographic printing, the one application roller 49 in each case, which lies in front of the two other application rollers 47 relative to the direction of rotation of the plate cylinder 31, 33, is lifted from the respective inking vibrator 43, provided with the coating which is receptive to the dampening medium, repels ink and is capable of storing the dampening medium, and is equipped with a spraying or squirting dampening medium dispenser 51. Therefore no additional roller at all is required for this adaptation and the dampening medium dispenser 51, which is the only additional apparatus necessary, is located on a part of the printing unit on which it does not in any way impede accessibility to the rollers and cylinders, in particular to the plate cylinders 31 and 33. In the case of the upper printing unit 41 a printing unit moreover provided only as special optional equipment - that inking unit only possesses two forme rollers 47. Therefore an additional roller constituting a dampening forme roller 53 is disposed here in contact with the plate cylinder 35, with a dampening medium dispenser 55. This is readily possible however because there is enough space for such an additional dampening forme roller 53. Also no disadvantage arises from the fact that the dampening forme roller 53 is disposed behind the inking forme rollers 47 relative to the direction of rotation of the plate cylinder 35, because the special coating of the dampening forme roller 53 guarantees a good conduction of the dampening medium even in this case. WHAT WE CLAIM IS:

1. A method of converting a rotary relief printing machine having a plate cylinder adapted to carry removable relief printing plates or planographic printing plates and having an inking unit including two or more inking forme rollers, into a planographic printing machine, comprising shifting

one of the inking forme rollers out of contact with the adjacent roller of the inking unit and providing it with a resilient coating the surface of which is receptive to dampening medium, and is ink repellent, whereby it is adapted to operate as a dampening forme roller and providing a dampening medium dispenser which is adapted and arranged to produce a spray of dampening medium passing across an intermediate space onto the surface of the dampening forme roller with an even distribution thereon.

2. A method according to claim 1, in which the dampening roller consists of a solid, steel core and the resilient coating is made of rubber or plastics material.

3. A method according to claim 1 or 2, wherein the resilient coating has a surface finish which is capable of storing dampening medium.

4. A method of converting a rotary relief printing machine into one for planographic printing, the method being in accordance with claim 1 and substantially as specificially described herein with reference to Figure 1 or to Figure 2 of the accompanying drawings.