US1788229A - Process and apparatus for engraving printing cylinders - Google Patents

Description

Jan. 6, 1931. P. BONNAUD ET AL 1,738,229

I PROCESS AND APPARATUS FOR ENGRAVING PRINTING CYLINDERS- Filed July so, 1928 's Sheets-Sheet 1 Jan. 6, 1931. P. BONNAUD ET AL 1,738,229

PROCESS AND APPARATUS FOR ENGRAVING PRINTING CYLINDERS Filed July so, 1928 s Sheets-Sheet 2 [5 [I Z0 I V /ZV/ a \\\\\\\\\\\\\x \x Jan. 6, 1931. P. BONNAUD ET AL 8,

PROCESS AND APPARATUS FOR ENGRAVING PRINTING CYLINDERS Filed Jul so, 1928 3 Sheets-Sheet 3 Patented Jan. 6, 1931 UNITED STATES PATENT OFFICE PIERRE BONNAUD AND LOUIS MAX AIME J'OURDAN, 0F LYON, FRANCE, ASSIGNORS, BY

MESNE ASSIGNMENTS, TO NASHUA MANUFACTURING COMPANY, OF BOSTON, MASSA- CHUSETTS, A CORPORATION OF NEW HAMPSHIRE PROCESS AND APPARATUS FOR.ENGRAVING PRINTING CYLINDERS Application filed July 30, 1928, Serial No. 296,145, and in France June 19, 1928.

It is known that printing on cloths or other material is carried out by means' of either hand printed blocks or hand engraved rollers depending onwhether the impression is to be made on a small surface or on cloths of indefinite length.

The present invention is more especially applicable to cylinders in order to obtain a very clear impression. It can likewise be utilized for direct monochrome or polychrome photographic reproductions, preserving the details and half-tones obtainable in Finally, the photo photography and which hand printing cannot reproduce exactly.

Attempts have certainly been made to print cloths by means of rollers, the surfaces of which are engraved chemically after a photo-- graphic reproduction has been obtained on them, but only the processes known hitherto hotoc-hromoengraving, simili-engraving and the like) could be applied to this form of printing. But it is impossible with such processes to produce with delicate half-tones,

etchings sufiiciently deep to obtain on all kinds of cloths, reproductions which are equivalent to those obtained on paper suited to this type of printing. The reason is that the parts rendered insoluble by the present processes do not offer suflicient resistance to the action of the acid concentrated to the requisite degree in order to bite sulficiently the exposed metal of the cylinder. The consequence is that in order to obtain both hollows of maximum depth and the greatest number of half-tones possible, the duration of the action of the mordant must be strictly limited. Notwithstanding the care exercised, the hollows are not sufliciently accentuated. and most of the half-tones are completely or in great part underbitten. I

aphic reproductions obtained on cloths wit the means in use at present are generally defective and often really bad.

On the contrary, the present invention ab lows perfect photographic reproductions of all subjects, even the most delicate of them, to be obtained on any kind of cloth, on velvets or other hair cloths, on skins and in general on all materials which do not at present lend themselves to reproductions. It has moreover the advantage of being very rapidly carried into efiect and of enabling polychrome reproductions, comprising a great number of colours (15 to 20 for example) and only requiring three rollers at the maximum, to be obtained just as easily as monochrome reproductions, whereas the usual textile printing processes call for almost as many rollers as there are colours to be reproduced.

The invention is characterized by the following particulars:

1. The photograph to be reproduced is obtained by interposing a screen, which is transferred to the surface of the printing roller in two successive operations contrary to the usual method. The first operation consists in transferring the screen exclusively on to the roller by means of a special process which makes said screen Very resistant to the action of the mordant. The second operation consists in transferring the photographic image on to said screen. I

2. The surface of the printing roller of cylinder is an electrolytic metal adapted to receive the special composition of the transfer of the screen.

3. The methods and special compositions of the screen transfers and of the photographic image proper; the chemical engravmg and contingently strengthening of the latter in particular cases.

4:. The methods and devices utilized for obtaining a semi-automatic engraving on the surface of the cylinder of the combined effect of the two successive transfers.

In the accompanying drawings:

Fig. 1 illustrates, in end elevation, the apparatus for wrapping a negative about the surface of a cylinder to be engraved.-

wrapped round it.

Fig.5 shows a dryin stove used in one stage of the production the paper on which a negative of the photographic picture is to be taken.

Fig. 6 illustrates diagrammatically theapparatus for etching'the cylinder after the screen negative and photographic negative have been transferred to it.

invention can be carried into effect by the sequence of operations described below: The printing cylinder is faced with a layer of electrolytic metal of l or 2 cms. thickness formed by a copper deposit obtained b pass ing 150 amps. at 4 volts through a bat at 22 degrees Baum. The copper will preferably be of the same composition as that utilized in marine boilers.

For monochrome reproduction two negaof the screen are not reduced by the developer and remain soluble.

The sensitive surface of the paper is applied-against the electrolytic metal of the cylinder, the surface of which has been previously very carefully planished. The negative is applied on the cylinder through the instrumentality of the transferring machine illustrated in Figs. 1 to 4 of the accompany: ing drawing, in order to achieve a very accurate transfer which ensures that the retic ulations of the screen will join up exactly and avoids any appearance of discontinuity which would be fatal for the uniformity of the impression.

A fixed support 1 carries on each of the longitudinal sides thereof two vertical uprights 2 which act as guides for a slide-block bearin 3 which supports the trunnions 4a of the cylinder 4 to be. engraved. Each bearing 3 forms the head of a rack 3a passing down through the support 1 and meshing with a pinion 3b. The two pinions 3b are mounted on the sameshaft 5 which is rotated by a handle 5a'mounted on'one end thereof. The shaft tives are takenphotographically, one solely ,'5 rotates in iournals 6 carried by the support reproducing thescreen and the otherthe desired image (a subject taken from nature or taken. from a picture, drawing or the like).

The screen negative is obtained directly 'on elatino-bromide of'silver paper with a solu 1e under layer,-by photographing the paperbehind a screen similar to that used in heliograph (trans arent reticulation and opaque chequer). he paper is developed by means of a developer composed vby the combination of the two formulae given below:

Distilled water .1,000 cu. ems.

ydrous sodium sulbonate '40 grammes The'developer is obtained by dissolving the two compositions in equal quantities in an amount. of water approximately three times as great as the quantity of either composition. or example:

Water 300 cu. cms.

Formula No.1 to be dissolved a beforehand 100.cu. cms.

Formula No. 2 100 cu. cms.

The negativedeveloped in the aforesaid manner is distinguished in the following respects: 1

The portions acted on by the light and corresponding to the reticulations, are reduced by the developer and rendered highly in soluble whereas the-portions shielded from the light and corresponding to the chequers 1 (Fig. 1). This arrangement enables cylinders of different diameters to be placed in the bearings 2 and the height of their axes to be adjusted above the surface of atable 7 so that the periphery of the particular cy11nder selected can be made tojust clear the table.- The negative to be wrapped aboutthe cylinder 4 is placed on the table 7 in a mannor to be described presently. In the support 1 is formed a longitudinally extending channel 8 over the bottomv of which are laid two rails 9 on'. which runs a truck the platform 7 of which constitutes the aforesaid .table whose object it is to support the sensitized sheets which are to be wrapped about the surface of the cylinder 4. The top of the table is formed by a slab 10 made of hard rubber, at one end of which is placed a graduated rule 11 (Figs. 2 and 4).- One of the long sides of said slab is graduated in the manner illustrated in Fig. 2. The rule 11 has two slides 12 guided bythe screw-threaded studs 13 on which are threaded wing nuts "14 adapted to clamp the rule in the. position determined by the'operatoraccording to the diameter of the cylinder 4 to be engraved. A pressure roller 15 is carried by two arms 16 plvoted as at 16a to the support 1, said arms 16' being continuously drawn towards the cylinder 4 by tension springs 17.

A movabletube- 18 perforated along its length maybe placed above the. cylinder 4 when the surface of thelatter has to be moistened. W A handle19'is fixed to one of the trunnions of thee linder 4 to be engraved in order to rotate the latter by hand.

. When the surfaceof the cylinder 4 of se-- 7 lectedf'diameter is to be covered with a sen sitized sheet, the cylinder is raised to prevent it from coming into contact with the rubber slab 10, then the position of the rule 11 is adjusted so that the distance at between its graduated edge and the geometrical axis of the cylinder 4 shall be equal to the circumference of the cylinder (Fig. 4) The sensiti'zed sheet 20 is now placed on the slab with its sensitive face uppermost and with one of its ends abutting the graduated edge of the rule 11. The cylinder 4 is then lowered until it cames into contact with the edge of the end of the sheet lying in the vertical plane X X (Fig. 4).

The operator then turns the handle 19 in the direction of the arrow, Fig. 4, with theresult that the table-truck 7 is set rolling by the frictionalforce exerted on the sheet 20 by the cylinder 4, but since the sheet 20 adheres firmly to the cylinder due to its composition of gelatine, said sheet wraps about the surface of the cylinder leaving the surface of the rubber slab 10. By the time the sheet completely surrounds the circumference of the cylinder, the two opposite edges have joined up exactly without any apparent sign of discontinuity.

The pressure roller 15 exerts pressure on the sheet 20 as soon as the latter has come into contact with it and such pressure persists as long as the cylinder 4 is kept rotating.

The ,graduations made along the rubber slab 10 facilitate the setting of the sensitized sheet 20 in'position. The graduations of the rule 11 enable the Width of the sheet 20 to be exactly accommodated to the length of the cylinder 4 and according to the drawings to be engraved.

The object of the hard rubber slab 10 is to,

prevent slipping of the sheet 20 on the table and to promote the adherence of said sheet to the cylinder 4 by allowing the latter to exert sufliciently strong pressure due to its weight. With this method of applying the screen negative to the surface of the cylinder to be engraved, the screen is fitted mathematically and no discontinuity can obtain. The length of the cylinder is covered by the negative.

After the screen negative has been wrapped about the cylinder, the latter is removed from its bearings 3, and then bathed first in tepid water and then in hot water to wash out the negative. Those parts of the negative which have been rendered insoluble (reticulation of the screen) adhere very firmly to the metal of the cylinder, whilstpthe other portions chequers) have been ellminated leaving the metal bare in the places they occupied. v

After drying, the cylinder with the screen is put back into its bearings 3 in order to receive the transfer of a negative of the photographic picture which is to be superposed onthe preliminary screen negative so as to form the entire photographic reproduction to be engraved on the cylinder intended for printing the cloth.

The negative is obtained on a charcoal paper sensitized and dried by the means described below:

Sensitivity is obtained by using the following solution:

Distilled water 1,000 cu. cms. Alcohol at 90 5 cu.cms. Ammonia 5 cu. cms.

Potassium dichromate grammes special stove Fig. 5 which is constituted as follows in order to dry completely the sensitized sheets ofpaper.

Two cases in the form of parallelopipeds 1 114 boxed one within the other and isolated' from each other by cork scrappings or other heat-insulating materials 115,-form the body of the stove which has one of its walls or a portion 115a removed in order to form an aperture through which .the glass plates may be introduced and withdrawn, said opening 115a being closed b a lidwhich is like? wise heat-insulated. ithin the central case are laid cross-pieces llfi and 117 acting as supports for the glass plates 118 and being provided to this end with retaining notches (twelve in number for example) Below the lower cross-pieces 117 is located a sieve 119 over which is spread a layer of calcium chloride. A basin 120 is placed on the bottom of the case in order to catch the water produced by the removal of the moisture from the glass plates and the gelatinized paper. A

Two rows of bafiies 121 and 122 are arranged respectively above and below the two rows of supporting cross pieces 116, 117 be tween their notches.

Two tubes 123 and 124 are passed through the median portion of 'one-of the vertical walls of the stove, which tubes are connected to the body 125 of an electrically driven fan which draws in air 'from outside to discharge it within thecentral case, the air, after having been. obliged to scrub the surface of the glass plates and of the papers adhering thereto, due to the disposition of the baflies 121 and 122 (as has been shown by the direction of the arrows), is then delivered to the outside atmosphere through a flue 126. On passing below the glass plates, the air passes over the calcium chloride which absorbs the moisture with which the air becomes laden during its passage. The moisture is vided with screens,

converted into water which falls into the basin 120.

Since the operations must be shielded from the light, the air inlet to the stove as well as the air outlet therefrom are prosuch for example as the hoods 127, 127a and 128, which block out the light rays. The air entering the case 113 is warmed by contact with an electrically heated resistance 123a arranged for example about the tube 123 or the tube 124 or eyenabout both of them. Owing to the continuous absorption of the moisture by the calcium carbide and to the heating of the air current, the atmosphere within the case 113 is very dry and enables the sensitized paper to be dried completely at the end of an hour approximately.

The glass plates with their paper facing are removed from-the stoveand by a quick,

7 regular movement eachsheet is taken off the glass.

Each sheet of charcoal paper sensitized and dried in accordance with the aforesaid formula and method, is then placed behind a positive glass plate printed from a negative of. the photographic picture to be reproduced subsequently on the cloth. The positives with the sensitive sheet are placed in a printingframe preferably neumatic and then exposed for the requisite length of time to quartz glass electric bulbs which very rich in violet rays- After having been acted on by the light, the sheet of charcoal paper is placed in the dry state on the surface of the cylinder 4- which, as has been previously stated, already bears the reticulations' of gelatine now-rendered insoluble In order to receive the sheet of charcoal paper, the cylinder 4 is placed in itsbearings inder '15 is retracted and the perforate tube 18 is applied against said cylinder which is rotated continuously and fairly slowly. A current of steam is sent through the tube 18 and the steam issues through the perforations in said tube onto the surface of the cylinder so as to moisten the insoluble gelatine reticulations.

The steam supply is then cut off and the charcoal paper negative is wrapped about the cylinder in the manner already described with reference to the transfer of the screen negative on to the said cylinder.

Inasmuch as the screen negative is simply moistened and that the wrapping operation is very rapid, the dry charcoal paper negative does not have sufficient time to undergo changes of dimension, from whence it follows that the transfer of the photographic picture on to the screen is absolutely accurate.

After drying for ten minutes approximately, the cylinder 4 is withdrawn and washed out first with te id and then with warm water, after whicli said cylinder is dried with degree of acidity emit a light 3; the pressure cyl-' the screen negative and photographic negative superposed on its surface and ready to undergo the acid treatment constituting the chemical engraving.

The engraving operation is carried out accurately and rapidly by the following method in'conjunction with the special ar- Iron perchloride at 48 Baum- 1,000 parts Nitric acid 6 parts Glycerine 10 parts i The bottom of the basin communicates by a tube 33 with a tube in which the solution can find it level and which contains a hydrometer 135 providing an instantaneous check of the the above solution.

Near the basin is located a vertical panel 138 fixed to a Wall for example and fitted with the instruments about to be described:

At the top is a water tank 139 fed through pipe 140 andprovided with an outlet pipe 139a connected to a distributor 142 enclosed in a fluid tight casing 141 and manipulated by means of an outer handle 143. The di'stributor is for example a hollow cylinder 142 of predetermined capacity (10 cu. ems.) through which 'is drilled a hole so situate with respect to the handle 143 that in the horizontal position of the latter (left side) as depicted in dotted lines ,said hole isat the top of the cylinder and is in communication with the tank 139 through the pipe 139a, so that the distributor is filled, whilst in the opposite position of the handle (depicted in full lines), the hole is at the bottom of the cylinder facing the outlet of the casing 141, so as to allow the water to drain from the distributor into a funnel 144 placed below it.

'A flexible tube 145 connecting with the upper portion of the basin 129 is coupled to said funnel. ables the water to be run off into the basin at the opportune moment.

of the bath 132 formed by A cock 144a fitted on the funnel en- A fan 136 delivers air through a tube 137 into the basin 129 at the lower part of the acid bath 132 whereby the air by bubbling through the described solution and the water which is admitted into the bath to weaken its acidity mixes the two together.

A hygrometer and thermometer 146 as well as a watch or clock 147 are hung from the panel to allow the operator to control the operations.

The cylinder 4 to be engraved is slowly rotated preferably by a motor M at a speed determined by the operator according to the nature of the engraving. As is customary, the etching of the cylinder is started with the acid bath at the maximum strength selected, then the operator gradually decreases the degree of acidity in suitable stages by introducing into-the bath the quantity of water measured out by the distributor 142 and admitted by simply rotating the handle 143 through half a turn and also by opening the cock of the funnel.

Above the basin 129 is located ahod 148 supporting a fan 149 which draws off the. harmful acid vapours and conducts them away outside the building.

By varying the proportions of the acid solution and the water supply as well as the time intervals during which the electrolytic metal of the cylinder is acted on by the bath at the several degrees of acidity thereof, the operator willin a predetermined total time etch the engraving of a given subject to be reproduced to a greater or less depth according to the nature of the cloths, skins and other materials to be printed.

When the engraving obtained has to be backed up subsequently for use in connec tion with printing materials other than those foreseen, such backing up will be easily carried into efiect by depositing on the engraved surface of the cylinder a coat of varnish protecting the surface portions from the mordant action of a second acid bath in which the cylinder is placed in order to obtain a deeper etching. The varnish is obtained by dissolving J ews pitch in oil of turpentine in equal proportions; after filtering the ensuing paste it is mixed with oil of lavender the proportion of which is about 10% of the product obtained. The varnish is spread in a thin coating on a .zinc plate by means of a gelatine roller, the plate is then placed on the rubber slab 10 of Fig. 4, the engraved cylinder is put back in the bearings and slowly rotated whilst the plate with its coatingof varnish is displaced relative thereto, said'varnish being solely deposited on the portions in relief and not in the hollows.

The formulae, methods and devices for carrying theinvention into effect have been. described with a view to obtaining an engraved cylinder for producing monochrome prints of any kind of photographic reproduction. For polychrome prints, comprisingan indefinite number of colours, use is made o f three rollers engraved in accordance with the invention and whose photographic images which are to be superimposed on the screen negative, are obtained according to the well known three colour process by taking three panchromatic negatives taking due care to interpose in front of the plate three different filters in accordance with the selectivity method employed namely: the violet filter which retains yellow, the orange filter which retains blue and the green filter which retains red. From these three negatives three positives are then printed which serve for the engraving.

Each'of the three rollers or cylinders receives first the screen negative and then the photographic picture in two successive, separate stages, as has been previously stated. It should be noted that the superposition (giving the polychrome impression) of three screen images produces,'as is known, a moir antique result which is prejudicial to the reproduction efi'ect. This drawback is obviated according to the invention by substituting dots or granulations for the preliminary screening on two of the three cylinders and more particularly on those corresponding to the yellow and red tones, the screening being reserved for the cylinder corresponding to the blue tone. The dots orw granulations are.

produced on a gelatinoebromide plate with a soluble under layer and the same operations and formulae as those described in connection with the screen negative are used to transfer the granulations to the cylinder, it being of course understood that the dots replace the reticulation and the background the chequer.

In the following claims the expression screen negative connotes a negative taken solely of the screen without the photographic picture. I

We claim: f

1.A process for engraving photographic pictures on printing cylinders, consisting in taking a screen negative on paper having a coating of gelatino-bromide of silver, in rendering insoluble the portions thereof acted on by the light, in wrapping said screen negative about the surface of a cylinder to be ennegative to adhere'firmly to said cylinder, in

wrapping about said-cylinder in superposed relation to said screen negative a negative of the photographic picture to be engraved, and in etching the surface of said cylinder with acid.. 2. A process for engraving photographic pictures on printing cylinders, consisting in taking a screen negative on paper having a coating of gelatino bromide of sllver, 1n developing said negative by means of a developer based on pyrogallic acid whereby the portions of said screen acted on by the light are rendered insoluble, in wrapping said screen negative about the surface of a cylinder to be engraved with the sensitive coating of said negative in contact with said cylinder, in causing the insoluble portions of said screen negative to adhere firmly to said cylinder, in wrapping about said cylinder in superposed relation to said screen negative a negative of the photographic picture to be engraved, and in etching the surface of said cylinder with acid.

1 3. A process for engraving photographic pictures on printing cylinders, consisting in taking a screen negative on paper having a gelatino-bromide of silver composition, in developing said screen negative with a developer based on pyrogallic acid, in wrapping said negative about the surface of a cylinder with the sensitive surface of the ne ative in contact with said cylinder, in was ing out said cylinder whereby the portions of said screen negative not previously acted on by the light are dissolved whilst the portions acted on by the light remain adhering to the cylinder, in taking a negative of the photoaphic picture to be engraved, in transerring said photographic negative to said cylinder by superposition on said screen nega-.

tive, and in etching the surface of said cylinder with acid.

4. A process for engraving photographic pictures on printing cylinders, consisting in taking a screen negative on paper having a gelatino-bromide of silver coating, in developin said screen negative with a developer based on pyrogallic acid, in wrapping said-negative about a cylinder with the sensitive surface of the negative in contact with the surface of said cylinder composed of an electrolytic metal, in bathing said cylinder in water so as to dissolve away the portions of said screen negative not acted on by the light, in sensitizing charcoal paper with an aqueous and alcoholic solution of a mixture of ammonia and potassium dichromate, in

takin a negative on said charcoal paper of the photographic picture to be engraved, in superposing said photographic negative on said screen negative, and in etching the surk face of said cylinder with acid.

5. A process for engraving photographic pictures on printing cylinders, consisting in taking a screen negative, in developing said negative whereby the portions thereof acted on-by the li ht are rendered insoluble, in wrapping said screen negative about the surface of a c linder to be engraved, in bathing said cylinder in water to dissolve away the portions of said screen negative not acted on w ith an aqueous solution of a mixture of ammonia and potassium dichromate, in spreading said charcoal paper on glass, in covering over. said charcoal paper. with elatinized paper, in drying the plate thus ormed, in

removing the dried sensitized paper from the glass, in mounting said sensitized paper behind a transparent positive of the photographic picture tobe engraved and sub'ecting said sensitized pa er to the action 0 light, in su erposing t e photographic negative transparent positive of the the light, in sensitizing charcoal paper 1 memes ing the plate thus ormed, in removing the,

dried sensitized paper from the glass, in mounting said sensitized plaper behind a p otographie picture to be engraved and sub ecting said sensitized paperto the action of light in moistening said screen negative, in superposing the photographic negative on said screen negative, in washing out said photographic negative, and in etching the surface of said cylinder with acid.

7. A process for engraving photographic pictures on cylinders, consisting in taking a screen negative on paper with gelatino-bro- 'mide of silver coating, in developing said LOUIS MAX AIME J OURDAN.

thus ormed' on said screen negative on said cylinder, and in etching the surface of said cylinder with acid.

6. A process for'engraving photographic pictures on printing cylinders, consisting in taking a screen-negative, in developing said

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