CA1116461A

CA1116461A - Process for smooth cut printing and a machine for working out said process

Info

Publication number: CA1116461A
Application number: CA000295538A
Authority: CA
Inventors: Daniel Beaune
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-01-28
Filing date: 1978-01-24
Publication date: 1982-01-19
Also published as: JPS6221628B2; IT1092321B; DE2803492C2; GB1594315A; CH628289A5; JPS53102114A; DE2803492A1; IT7819617A0; ATA61078A; AT368077B; ES466983A1; BR7800514A

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides in a copper plate printing process the improvement wherein the non-printing surfaces of the printing plate carrying engraving cuts are coated with at least a layer of an anti-adherent for printing inks.

Description

6~
The present irlvention provic~es a process and a machine for copper p]ate printing as well as the products thus obtained.
The usual processes for printlng of documents consist in using a thin plate, a she]l, a collar or a cylinder, all of them called plate in the following Specification, preferably made of metal wherein -the pattern to be reproduced by the printing is engraved. Some areas of said plate are coated with ink so that the ink penetrates the hollows or cuts thereon. The inked surface is wiped out in order to leave ink only in the cuts and hollows and the surfaces thus inked and wiped out is applied against an appropriate support, such as a sheet or a strip of paper, by means of a pressing cylinder. Thus, a part of the ink is transferred from the hollows onto the support.
According to some processes, an indirect transfer of the ink contained in the hollows of the plate is performed by means of a cylinder carrying a flexible coating and positioned between the plate and the support.
In the known processes, the wiping operation causes a great loss of ink. As a matterof fact, the coating of the engraved plate with ink is performed a-t 100%, and the wiping thereof removes, depending on the case, about 75% of said ink.
This corresponds to the parts of the area which do not carry any cut and do not serve for printing. Said 75% of wiped ink is wasted. Where printing with several colors is involved using one and the same plate each zone of which receives inks of different colors, the problems raised by waste remain the same. Further-more in view of the wiping, therei-s arisk of forming runs of colors into one another and also to mix the colors which spoils the quality of the print.
A process and a machine for printing disclosed in French Patent 1,564,653, which process consists in coating the plate before inking it, with a colorless liquid, non-miscible wi-th ink, then applying the ink. Gen~ra]ly, the non-miscible liquid is filtered water. Such an improvement -to standard processes is aimed to minimise the losses of ink and to increase the sharpness of the printed pa-tterns, as well as to prevent or simplify the wiping operation. Unfortunately, practice has shown that this process which is based on a physical balance between the water and ink is suitable only for a given depth of the cut and not for all depths of smooth cuts with most of them having various depths. This greatly limits the scope of the process and practically prevents its use.
The present invention avoids these drawbacks and provides a process and a machine for copper plate printing which makes it possible to save a large quantity of printing ink, as well as the accessory cleaning products used for printing, and to avoid all the wiping operations which not only result in a loss of ink but furthermore gives rise to the risk of mixing inks of various colors or to leave runs.
According to the present invention there is provided a copper plate printing process wherein the non-printing surfaces of the plate carrying the smooth cuts of the engraving are coated with at least a layer anti-adherent for printing inks. Pre-ferably, said layer consists of a fluorocarbon resin deposited in particular electrolytically. By means of this process, the engraved plate is coate~ ~nlywith the quantitv of ink reauired to fill the engravings, without any excess of ink on the non-engraved surfaces which will thus perform no printing.
According to a further embodiment of the present invention, so as to deposit said anti-adherent layer, the cuts of the engraving of the plate are first obturated with an electrical non-conductor material, the solid anti-adherent layer is deposited electrolytically and the material bloc]cing the cuts of -the en-graving is dissolved.

So as to bet-ter improve the ink output of this process, the solid anti-adherent layer for example of a fluorocarbon resin can be covered with a very thin layer of a greasy product, preferably based on organosilic or by-products, so as to complete the anti-adherent characteristics of the non-printing surface of the plate.
The saving of ink by the process of the present invention is considerable and depending on the cuts involved provides a saving ranging from 300 to 400%. Thus, while 100%
of ink is used, according to standard processes 25% only really serves for printing and 75% constitutes waste. In the process of the present invention the ink is fully used. This means that in said process, a quarter or a third portion of the ink is sufficient relative to the quantity of the ink required in the conventional copper plate printing. Furthermore, this process makes it possible to save the cleaning products of the wiper cylinder. Now as these products, as well as inks used, are expensive, this results in a most important saving.
According to another embodiment of the present invention the plate is coated with printing ink and said ink is compacted in the cuts of the engraving. The compacting is effected by a compacting cylinder the purpose of which is only to remove any slight surplus of ink in the engravings and to push it down to the bottom of said engravings by opposing the surface tension forces so that the meniscus formed by the ink contained in engravings is slightly concave, which is a necessary condition for obtaining a sharp engraving.
Also, the present invention provides a machine for copper plate engraving comprising a rotary cylinder carrying at leastone portionhaving smooth cut engravings, at least one assembly of devices for applying ink, a printing cylinder providing sheets of paper, a cylinder for applying a liquid anti-adherent product, sai.d cylinder bei.nc3 positi.oned upstredm o-f the assemblies applying in~ and a compactor cylinder positioned downstream of -the assemblies applying ink.
Said machine not only has the advantage of being simpler than the conventional machine since it has no wiping cylinders nor accessory devices hut, it also makes it possible to work under better conditions of cleanliness and hygiene. Thus as there is essentially no surplus of ink, clogging of the machine is reduced to a minimum. The removal of the cleaning devices avoids the use of solvents which give off harmful vapours.
According to a further embodiment of the present invention, each assembly of ink appliers comprises an ink applier cylinder, cut in correspondence of the areas of the plates to be inked and at tangent to the rotary cylinder, an ink feeding cylinder for the ink applier cylinder at a tangent to said ink applier cylinder and rotatable in the reverse direction as well as of a cleaning means at a tangent to the ink applier cylinder positioned upstream of the rotary cylinder and adapted to remove from the ink applier cylinder a mixture ink and anti-adherent. The presence of said cleaning means is indispensable for obtaining good printing. The liquid anti-adherent applied by its applier cylinder tends to mix up with the ink. If said mixture was not removed by said cleaning means, it would cover the ink applier cylinder about its point tangent to its feeding cylinder, and the mixture would thus spoil the fresh ink which would badly fill in the cuts of the engraving in the following run.
Where a monochromic printing is involved, a printing wherein the ink appl.ier cylinder is not cut, any scraping system can be used for preven-ting the contamination of the fresh ink. ~owever, and according to another embodiment of the in~

vention which more precisely applies to cases wherein the machine is designed to produce a polychrome printing and carries several assemblies of ink appliers, the cleaning means consists of a cleaning cylinder rotatable in the same direction as that of the ink applier cylinder, which partly wipes it and collects a mixture ink and anti-adherent to pass it to a scraping device which takes it to a vessel.
Said mixture contained in the vessel can be recovered, then crushed and mixed up with fresh ink so as to be used again.
The present invention will be further described with reference to the accompanying drawings in which:
Figure 1 is a diagrammatic cross-sectional view, on an enlarged scale, of a plate used for copper plate printing, according to the Prior Art;
Figure 2 is a cross-sectional view, on an enlarged scale, of a cut of the engraving obturated with a varnish which is a non-conductor of electricity, Figure 3 is a cross-sectional view, on an enlarged scale of a cut of the engraving after the electrolytic deposition of the anti-adherent layer and the dissolution of the varnish, Figure 4 is a diagrammatic cross-sectional view of a cut of the engraving,-similar to Figure 3, after the application of a second anti-adherent layer, Figure 5 is a diagrammatic cross-sectional view, on an enlarged scale, of a cut of the engraving after inking of same, Figure 6 is a cross-sectional view, on an enlarged scale, of a cut of the engraving after compacting of the ink.
Figure 7 is a diagrammatic view of a printing machine for effecting the copper plate printing process of the present invention.
Referring to Figure 1 a standard metal printing plate 1 of whose thickness a, may be a thin plate, a shell, a collar or a cylinder. The cross-sectional view of theplate diagrammatically shows only one cut 2 of the engraving. 'rhe tot~l surface of said plate is generally coated with a layer 3 of chromium which protects the plate against corrosion due to the ink. According to the process of the present invention, a film of a liquid anti-adherent material, or a layer of a solid anti-adherent material with or without a second liquid anti-adherent layer is deposited onto the plate.
The following description refers to the case of a plate coated with a solid-anti-adherent layer and with a liquid anit-adherent layer. As shown in Figure 2, after having made a cut 2 in the plate 1, and after having deposited a layer 3 of chromium onto the surface of the plate 1 and inside the cut 2, said cut 2 is obturated by means of a mass 4, such as a varnish which is a non-conductor of electricity or with any other material which is a non-conductor of electricity. It is preferab~e to use a varnish capable of easily dissolving in the usual solvents such as, for example, methyl-ethyl ketone and trichlorethylene.
As shown in Figure 3, after solidification of the mass 4, the plate 1 is degreased and covered either or, generally, by coating with a thin layer 5 by electrolytic deposition of thickness ranging, for example, from 5 to 20 microns. The layer 5 is a layer to which printing inks do not adhere, such as a synthetic resin and, particularly, a fluorocarbon resin. The plate 1 is then dipped in a bath of solvent so as to dissolve the material 4 blocking the cut 2. The mass 4 contained in the cuts 2 of the engraving is dissolved. Thus, the surface of the plate 1 is coated with a layer of an anti-adherent material 5 while the sides and the bottom of the cut 2 carrv only the layer 3 of chromium or other protecting layer.
As shown in Figure 4, the surface of the plate 1 is covered, should it be necessary, with the exception of the cut 2, with a second anti-adherent layer 6 such as, for example, a thin layer of a greasy procluct, preferably based on organo-silicon by-products, so that the surface portions of the plate 1 which do not effect any printing be perfectly anti-adherent towards inks.
Said layer 6 may be deposited on the coating 5 before the plate is inked.
As shown in Figure 5, when inking is performed, a certain quantity of ink 7 goes into the cut 2 but not on the anti-adhesive layer of layers 5,6 which reject the ink.
In order to ensure a good printing, without any overflow, the ink 7 contained in the cut 2 should have a concave meniscus7'.
To achieve such a meniscus 7', the ink 7 is driven into the cut

2 as shown in Figure 6. To effect said driving in, a means of compression is used which removes said ink from the cut 2 by removing any cavity which could exist between the ink 7 formerly deposited and the walls of said cut 2. Thus compression may be suitably effected by the printinq roller which is suitably covered with a layer of rubber or anv hard plastic of from 70 to 90 share A which forces the fattv ink on the surface of the roller to penetrate in to the deposit of the cuts of the engraving.
As shown in Figure 7, the machine for effecting the copper plate printing process comprises a rotating cylinder 8 the whole surface of which carries at least a thin plate 1 carrying ink engraving 2, defining the pattern to be reproduced by printing.
The plate 1 is coated, according to the invention with a solid anti-adherent layer 5. Said plate 1 is permanently fed by as many ink applier groups 20a, 20b as there are various colored inks to be applied. The ink applier groups 20a, 20b, as well as the manner in which they work, willbe described with more detail hereinafter. Nevertheless, it is to be stressed that while Figure 7 shows two ink applier groups the number could be varied.
A printing cylinder 15 adapted to apply the sheets of paper to be printed 17 against the plates 1 is associated with a means providing blank sheets of paper 17. As soon as they are printed, said sheets 17' are moved away by a clearing me~ns 18. The feeding means 16 and clearing means 18 for the sheets of paper 17 and 17' are very diagrammatically shown and may be any suitable conventional devices. Furthermore, and as shown in Figure 7, the machine carries upstream of the ink applier groups 20 in the rotating direction of the cylinder 8 according to arrow A, and applier cylinder 9 for the liquid anti-adherent layer 6. The applier cylinder 9 is combined with a mechanism for dosing and levelling the ink 10. The machine carries downstream of the ink appliers 20 a contacting cylinder 13 which rotates in perfect synchronization with the surface of the plate 1 and which is combined with a system for recovering the ink 14.
~eans (not shown), make it possible to strongly apply the cylinders which apply the anti-adherent products 9, the ink applier groups 20 and the printing cylinders 15 against the cylinder 8 which supports the plates 1. In addition, said machine carries a means (not shown) for drivingly rotating the cylinders.
As shown in Figure 7, each ink applier group 20a comprises an applier cylinder lla cut in dependence of the areas of the plate 1 to be inked, of a feeding cylinder or again of the ink applier cylinder 12a at a tangent to the ink applier cylinder lla which turns in the opposite direction, and associated with an ink storage tank 21a, as well as of a cleaning means adapted to remove from the ink applier cylinder lla any trace of anti-adhesive product. Said cleaning means comprises a cleaning cylinder 22a rotating in the same direction as the ink applier cylinder lla which partly wipes it and recovers the mi~ture ink-anti-adhesive product so as to move it towards the scraping device 23a which deposits it into a vessel 24a.
In operation of the ink applier group 20a works fresh ink coming from the ink storage tank 21a is deposited in a thin layer onto the feeding cylinder 12a and transmitted to the ink applier cylinder lla at point I. The areas in relief of the roller lla thus inked will at point II deposit some ink inside the cuts 2 of -the en~raving carried by the plate 1. Between the cuts 2 of the plates 1, on the surface of said plates 1, the liquid anti-adherent product 6 applied by the cylinder 9 tends to mix with the ink. If said mixture would not be stopped by the cleaning cylinder 22a, it would go up to the point I on the feeding cylinder 12a and would thus spoil the fresh ;nk.
Such a spoiled ink would deposit inside the cuts 2 of the en-graving during the following run. The cylinder 22a which rotates in the same direction as the roller lla partly wipes the surface thereof and drives the mixture an-ti-adherent product and ink towards the point III where the scraping device 22a recovers it to move it into the vessel 24a. Thus, the ink which has been mixed up with little anti-adherent product 5 does not run the risk of mixing with the fresh ink spread over the feeding cylinder 12a and thus of spoiling the printing.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a copper plate printing process the improvement wherein the non-printing surfaces of the printing plate carrying engraving cuts are coated with at least a layer of an anti-adherent for printing inks.

2. A process according to claim 1, wherein a liquid anti-adhesive layer is deposited on the plate.

3. A process according to claim 2, wherein a solid anti-adherent layer is deposited on the plate before depositing the liquid anti-adherent layer.

4. A process according to claim 1, wherein a solid anti-adhesive layer is deposited on the plate.

5. A process according to claim 4, wherein the solid anti-adhesive layer is formed by electrolytic deposition of a fluorocarbon resin.

6. A process according to claim 5, wherein before depositing the solid anti-adhesive layer the cuts of the engraving of the plate are blocked by means of an electrically non-conducting material the adherent layer being deposited electrolytically and the material obstructing the cuts of the engraving then being dissolved.

7. A process according to claim 1, 2 or 3, wherein the plate is coated with a printing ink and said ink is compacted into the cuts of the engraving.

8. A copper plate printing machine comprising a rotatable cylinder carrying a printing plate having smooth engraving cuts at least one ink applier assembly and a printing cylinder for providing sheets of paper to be printed and an applier a cylinder adapted to apply a liquid anti-adherent, said applier cylinder being located upstream of each ink applier assembly.

9. A machine comprising a rotatable cylinder carrying a printing plate having smooth engraving cuts at least one ink applier assembly and a printing cylinder for providing sheets of paper to be printed and an applier a cylinder adapted to apply a liquid anti-adherent, said applier cylinder being located upstream of each ink applier assembly a compacting cylinder loacted downstream of at least one ink applier assembly.

10. A machine according to claim 8 wherein each ink applier assembly comprises an applier cylinder cut in dependence of the areas of the plate to be inked and disposed at a tangent to the rotatable cylinder, tangent to the ink applier cylinder and rotatable in the opposite direction, and a cleaning means disposed at a tangent to the ink applier cylinder disposed downstream of the rotatable cylinder adapted to remove from the ink applier cylinder a mixture ink and anti-adherent product.

11. A machine according to claim 10, having a single ink applier assembly the cleaning means being a scraping device.

12. A machine according to claim 10, comprising at least two ink applier assemblies, the cleaning means comprising a cleaning cylinder rotatable in the same direction as the ink applier cylinder which is adapted to wipe so as to recover a mixture ink anti-adherent and pass the mixture to a scraping device which is adapted to pass the mixture into a vessel.