US2160951A

US2160951A - Process and device for the reproduction of designs on printing plates by means of photoelectrically controlled gravers

Info

Publication number: US2160951A
Application number: US88240A
Authority: US
Inventors: Alice Francesco
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-07-05
Filing date: 1936-06-30
Publication date: 1939-06-06
Anticipated expiration: 1956-06-06
Also published as: DE748274C; FR808605A

Description

June 6, 1939.

PROCESS AND DEVICE FOR THE REPRODUCTION OF DESIGNS 0N PRINTING PLATES BY MEANS OF PHOTOELECTRICALLY CONTROLLED GRAVERS Filed June 30, 1936 4 Sheets-Sheet l f" 1 I 4 I 4 4 r \n n FA June 6, 1939. AL|E 2,160,951

PROCESS AND DEVICE FOR THE REPRODUCTION OF DESIGNS ON PRINTING PLATES BY MEANS OF PHOTOELECTRICALLY CONTROLLED GRAVERS Filed June 30, 1936 4 Sheets-Sheet 2 1" FALICE June 6, 1939. F. ALICE 2,160,951

PROCESS AND DEVICE FOR THE REPRODUCTION OF DESIGNS ON PRINTING PLATES BY MEANS OF PHOTOELECTRICALLY CONTROLLED GRAVERS Filed June 30, 1936 4 Sheets-Sheet 3 June 6, 1939. 2,160,951

PRO

F. ALICE CES N EVICE THE REPRODUCTION OF DESIGNS 0N PRINTING FLA S MEANS PHOTOELECTRICALLY CONTROLLED GRAVE Filed June 30. 1936 4 Sheetset 4 Patented June 6, 1939 PATENT OFFICE PROCESS AND DEVICE FOR, THE REPRO- DUCT'ION F DESIGNS ON PRINTING PLATES BY MEANS OF PHOTOELECTRI- CALLY CONTROLLED GBAVEBS Francesco Alice,

Oniegna, Italy Application June 30, 1936, Serial No. 88,240 In Italy July 5, 1935 8 Claims. (Cl. 178-13) It is known that for printing fabrics, wall paper and the like, metallic rollers, generally of copper, are used, whereon the design to be printed has been engraved by suitable means and which, placed on suitable machines and coated with colour, print the various designs on the fabric, paper or the like. Various systems exist for engraving said rollers according to the design to be reproduced and the effect to be obtained.

The new system forming the object of the invention, instead, has for its purpose to utilise the photo-electric cell and to transfer directly onto the plate to be engraved, having preferably a cylindrical shape and covered with a varnish, the design made on any suitable support, lor instance paper, and to a proper scale, with the only necessary corrections of the white portions. The reductions in width or in height and the hatching are made automatically. The necessary inclination is also given automatically to the design. By this method the time for preparing the drawing is enormously reduced as it is not necessary to engrave zinc sheets or to design directly on rollers. The design may be made conveniently on paper, whereon the lines which .will form the hatchingsaie printed by lithographic process. This sheet may be wrapped on an expansible roller which allows the application of drawings of different dimensions. The roller is introduced into the apparatus. A lantern, provided with an electric lamp combined with an optical system intensively illuminates the portion of design ,to be explored. An objective of small focal length may suitably magnify the image and project it on an adjustable diaphragm. Through the diaphragm will pass only the beam from a spot of the design, which excites the photo-electric cell. Said cell transforms the light impulses into variations or impulses of electric currents which may be amplified by a. suitable amplifier, for instance with thermionic valves. The lantern-cell system has a translating motion. 1

The roller to be engraved has a rotary motion synchronous with the roller which bears the design. A battery of electric gravers, having a translating motion along the roller to be engraved, synchronous with that of the lantern, receives the currents from the amplifier and reproduces the design on the coating of the roller, which is thus ready for etching.

The attached drawings represent as a not limitative example an apparatus for the embodiment of the invention in the case of engraving rollers; in said drawings.

Fig. 1 is the diagrammatic general plan of the apparatus.

'Fig. 2 is an elevation 01? the same.

Figs. 34 are mechanical details of the gravers.

Fig. 5 is the detail of the optical exploring system.

Fig. 6 is a plan view of an electrodynamic graver.

Fig.7 is a diagrammatic view of a reflection type of analyzer.

Fig. 8 is a similar vie": of a transparent type of analyzer.

Figs. 9 and 10 are diagrams of the various types of drawings to be reproduced.

Fig. 11 is a schematic view of a circuit for the synchronization of the thermionic oscillators for effecting a direct reproduction.

Fig. 12 is a similar view of a circuit for the synchronization of the thermionic oscillators for effecting inverted reproduction.

Fig. 13 is a diagrammatic view of a mechanical oscillator.

In its essential structure, the apparatus for the embodiment of said system comprises a roller,

- preferably an expansible roller I, on which is wrapped the sheet of paper with the design to be reproduced. The diameter of this roller may be varied within certain limits so that it is possible to join exactly the upper end to the lower end of the design so as to obtain a cylindrical surface completely covered by the design without solution of continuity.

The roller, which is removable, is placed on the opposite supports 3|, Fig. 1. The lantern 21, adjustable by means of the screw 28, rests upon the roller. The lantern comprises an illuminating system consisting of an electric lamp 33 and an optical system converging the light on a small surface of the design. An objective 35 projects the image of said small portion of design on a total reflection prism 36 which reflects it on an adjustable screen 31.

The screen 31 leaves a passage only to the beams which are to be utilised for the impression of the photo-electric cell. It is thus possible to project on the photo-electric cell only beams coming from a very small portion of the design, which can be considered as a point. The roller I is rotated, through suitable gearing including the worm drive 24 by the motor 22. The lantern 21 has a translation motion trans- 'mitted thereto by the worm 30,'said lantern sliding on the guides 39 The lantern is locked to the thread of the screw 30 by means of the lever 29,.Fig. 5, so

that by actuating this lever the lantern can be disengaged from the screw-thread and displaced by hand and brought to the initial position for the reproduction of the design.

The screw 26 serves for the small micrometric displacements of the lantern, which are necessary to adjust the beam of light exactly with the beginning of the design. A Vernier 43 sliding on the graduated rod 40 facilitates this operation. The screw 30 is driven by the same shaft which rotates the roller I. permits varying of the ratio of displacement of the lantern, according to the necessities of the design. It is thus possible to explore the design on the roller i completely along a helix, the convolution of which will be more or less removed from each other according to the velocity of displacements given to the lantern by means of the gear 23. This exploration causes variations of intensity of light which the objective 35 projects on the photoelectric cell 38, Fig. 5, which transforms these variations of intensity of light into equivalent variations of electric current. An electric current modulated by the exploration of the design is thereby obtained and sent to a suitable thermionic valve amplifier 32. The roller 2 which is to be engraved is covered by an acid-proof coating and mounted on a suitable mandrel 44 provided with apposite bearings.

The roller 2 thus prepared is placed on the supports 3 of the apparatus. On the rulers I are mounted electromagnetic gravers 4 in a number equal to the number of repetitions or reproductions of the design to be contained axially on the roller. These electromagnetic gravers are actuated by the currents modulated and amplified issuing from the amplifier.

The rulers l6 which bear the gravers can slide axially of the 42 and are fixed by means of pivots ii to the carriage 46 which, by means of the screw I4, is given a motion of transmission synchronous with the translation of the lantern. The change speed gear l8 permits varying the ratio of displacement between the rulers l6 and the lantern according to the requirements of the design. The roller to be engraved receives a rotary motion by means of the worm gear i0 connected to the mandrel carrying the roller and an endless screw connected to the shaft 23 driven by means of the change speed gear 2| by the same motor 22 which drives the roller i carrying the design. Theroller to. be engraved rotates thereby with a velocity synchronous to that of the roller l but with different speed ratios given by the gear 2i, according to the number of repetitions of the design which must be comprised on the circumference of the roller to be engraved.

As required by printing machines, the design reproduced on the roller 2 must be made at a suitable angle of inclination to the axis of the roller. Normally with the other engraving process this result is obtained by tracing the design obliquely by hand, for instance a rhomb is designed for obtaining a square. The new apparatus permits the obtaining of this result automatically by means of the screws 9 which makes it possible to give an inclination to rulers l6 carrying the electromagnetic gravers either to the right or to the left with respect to the axis of the roller to be engraved.

Moreover, owing to other necessities of printing machines for fabrics, it is suitable to engrave electromagnetic roller on pivots A change speed gear 23.

stance, for printing a square or a circle it is necessary to engrave on the roller a rectangle or an ellipse. The change speed gear 20 enables the new apparatus to obtain this result automatically by varying the velocity of displacement of the rulers l6 withrespect to the velocity of displacement of the lantern 26.

The rollers to be engraved have diameters slightly different from each other; it must be possible, therefore, to move the rulers away from or towards the axis of the roller. The screws l2 fulfil this task by displacing the carriages 45 which sustain the rulers. The carriage 46 which impart the motion of translation to the rulers l6 carrying the electromagnetic gravers receives its motion from the screw i4 and slides on the guides i3 of triangular cross-section so that its motion may take place with the highest accuracy possible. The cranks 8 make it possible to rapidly adjust the inclinations of the rulers which by means of suitable graduated scales engraved on the relative supports enable the desired inclination to be rapidly obtained. The cranks Trapidly adjust the distance of the rulers from the axis of the roller.

Theoperation of the apparatus results clearly from the above description. On a sheet of paper whereon'can be lithographically printed a black and white hatching, the design is reproduced by black ink, or by photographic process, the black parts of the. design corresponding to the parts which are not to be engraved, whilst the white portions, which will result hatched correspond ness of the drawing and the fineness of the lines desired. The design thus prepared is ready to be put on the exploration roller l. The exploration is made by means of a beam of light which explores the design along a helix, and, by means of the photo-electric cell, the clear and dark zones of the design are transformed into impulses of current, suitably amplified and conveyed to electro-magnetic gravers 4 which engrave the coating on the roller to be engraved, according to the impulses of current corresponding to the clear and dark zones of the design. The reproduction is made along a helix, as the motions of rotation of the roller to be engraved and of translation of the electro-magnets are synchronous with those of the roller and lantern of exploration. If desired, a slight variation of the ratios of the velocity of displacement of the rulers which bear the electromagnetic gravers with respect to the displacement of the lantern makes it possible to vary the ratio between the width and height of the design of a determinate percentage and the inclination of the rulers makes it possible to obtain the desired inclination of the design.

The number of the rulers carrying the electromagnetic gravers may vary from one to six, depending upon the number of repetitions of the design contained on the circumference of the roller. For a small number it is preferable to have a ruler for every repetition. For higher reproduced by contemporary sections, the time of reproduction being reduced to the half or to the third part. A special amplifier or several separate amplifiers will send the currents to the various electro-mag'nets operating simultaneously actuated by the diflerent photo-electric cells.

With. a similar disposition, gravers operating I on separated rollers could also be actuated simultaneously and identically.

The lines which result on the white parts of the design will trace automatically the necessary hatching on the engraved portion of the roller.

When it is desired to reproduce the design on the paper formerly hatched, a sheet of hatched paper is placed on the exploration roller I and separate from the design. A lantern introduces the hatching automatically. Or else, an auxiliary hatched roller provided with a lantern is connected with the apparatus and by an operation synchronous with the exploration roller introduces the hatching automatically.

Instead of the sheet of paper for the reproduction of the design also photographic film may be used. In this case the exploration of the design is carried out by transparenceinstead of by reflection. According to the nature of the designs to be reproduced and to the methods to'be followed for the reproduction the various devices necessary will be suitably adapted, varied and completed so as to properly correspond to the various practical requirements.

In any case, it is desirable to reduce to the minimum the intensities of light necessary to generate the electric currents which actuate the gravers. This result, may be obtained by the use of very sensitive gravers, or by the use of a mechanical relay when there is a large number of gravers or by very eflicient optical devices.

The first of said results may beobtained by the use of electro-dynamic gravers constructed for instance according to the diagram of Fig. 6. In said type there is a magnetisable core 5| excited by means of an independent continuous current circulating in the coils 52. The point'of the graver 53 is connected to a small movable coil 54 wherein passes the current of photo-electric origin, preferably amplified. The coil is sustained and maintained perfectly centered by the elastic device 50. Said disposition makes it possible to obtain a great sensitivity and, "as said device is very light, a great rapidity of engraving is available. Said disposition also provides gravers which require a very small space in the axial direction, so that a great number thereof can be placed on the same machine, a considerable acceleration in the work being thus available.

On the other hand it is also possible to improve the efficiency of the optical systems so as to reduce correspondingly the intensity of the source of light necessary either by the reflection method, or by the transparency method,

In the first case the device represented by Fig. 7 may be adopted, wherein is employed a special photo-electric cell 55 the plate of which has a perforation 51 of suitable dimensions. Said cell is interposed betweeen the design and the optical system 58 with the sensitive part towards the design. The beams of light 'conccntered by the optical system pass through the cell without exciting it and goes on to hit a punctiform zone of the design. The white points of the latter will reflect anddiffuse said beams of light and, owing to the cell being very near, almost all the reflected or diffused beams will fall on its sensi- ,fore, to reproduce the ,paratus, or, more exactly,

tive surface. so as to exciteit with a very high luminous efliciency.

When a transparency method is to be followed, it will suflice to wrap the design, traced.on a transparent film, on a roller 59 also transparent, as shown by Fig. 8. In this case the lantern 60, external to the roller, concentrates the beams of light on a spot of the design and the beams emerging therefrom by transparency will fall directly on the photo-electric cell 6i placed inside the roller which cell has the motion of translation of the lantern.

Of course both the dispositions described may be susceptible of other modifications or integrations, so as to fulfil special working requirements. Another problem to solve derives from the fact that many designs are to be executed by hatching only, Fig. 9; whilst other must be delineated by neat outlines, Fig. 10, the discontinuous terminations of the hatching in the various zonesbeing not sufficient to delineate the design.

For a better comprehension of the nature and the difiiculties of the problem it must be observed that according to the process the designs are always reproduced only by points, so that each line transverse to the direction of translation will result decomposed into a plurality of points spaced by an interval equal to the distance between the exploring passages, which in the case of reproduction on rollers, corresponds to the pitch of the exploring helice. An analogous fact is verified in correspondence to all the lines oblique to the direction of translation such as for instance the lines for the formation of the hatching. The lines directed in the direction of translation do not permit the obtention of such punctiform reproduction,

By the system proposed it is possible, there- I I designs such as Fig. 9, whilst for reproducing the design of Fig. 10 the outline (at least the vertical lines) ought to be designed by a succession of points very near to each other, the interval being equal to the pitch of exploration.

This constitutes a considerable difliculty and a considerable loss of time in executing the designs. This drawback may be avoided so that the apparatus should reproduce by points also the vertical continuous lines of the design, and, therefore, also the outline of the design, Fig. 10.

This result can be attained by producing an automatic intermittence either in the light which illuminates the photo-electric cell, or in the electric current supplied by the cell, or in that of the amplifier. More simply it can be attained by acting on the current by means of thermionic or mechanical oscillators, the result of the operation of the same being that also the lines parallel to the direction of translation will result to decompose into a plurality of points spaced correspondingly to the frequency of the oscillating current employed. By this way fairly satisfactory results will be obtained. Practically, however, a higher accuracy is desirable or necessary. It is necessary, therefore, to adopt dispositions capable of synchronising the operation of the oscillator with that of the photo-electric apof rendering the first dependent upon the latter. Said devices will have a diiferent character and operation according to whether the reproduction of the design will be executed by direct or inverse method. Namely, when the light lines of the design are engraved, the synchronising devices actuated by the current supplied by the cell will not give oscillations when said cell is not illuminated, whilst the oscillations will beginwhen the cell begins to be illuminated and yields current. If,

on the contrary, the dark lines of the design are engraved the operation of the same devices will be inverted. In both cases a point will always and exactly correspond to each commencement of line and the design reproduced will result periectly neat and accurate. In the absence of synchronisation the point might not correspond to the exact commencement of each line parallel to the direction oi advancement and a succession of displacements would result, which would render the reproduction irregular. A device for the synchronisation of the thermionic oscillator applied to the non-inverted reproduction is diagrammatically represented by Fig. 11. Said device comprises a special thermionic valve comprising three grids, with indirect heating of the cathode. The first and second grid are connected to a regulable frequency oscillator (for instance from 50 to 1000 periods), and the current of the photo-electric cell is amplified by a suitable thermionic valve 64, provided in the plate circuit with a resistance 65, of a value adapted to the valves used. When the grid of the first valve is excited by the current of the photoelectric cell, a plate current will be determined,

which will produce through said resistance a difierence of potential at its terminals. This diflerence of potential is felt in the oscillating circuit of the second valve, which will enter into oscillation only when the cell will be illuminated, thus beginning its oscillation only at the beginning of the illumination.

When the reproduction must be inverted, the device diagrammatically shown in Fig. 12 will be adopted, wherein the first amplifying valve 66, which amplifies the current supplied by the photo-electric cell, is not varied. The resistance 01, however, will have a value lower than in the case of Fig. 11. The oscillator 68 will also be the same as the foregoing, but will be fed by an oscillating voltage capable of setting it to free oscillation independently of the currentof the photo-electric cell. The current of polarisation oi the oscillating valve will be derived from the resistance of the plate circuit of the first amplii'ying valve, so that when the first grid of said valve is sufiiciently polarised any oscillation is prevented. It appears that the oscillating valve will oscillate only when there will be no current in the photo-electric cell because this is not illuminated, and the oscillations will begin as soon as the illumination of the photo-electric cell will cease, in synchronism with the design, the reproduction of the black lines being made by points.

The same problem can be solved by the use of an oscillator 01' mechanical nature, such as represented by Fig. 13. This oscillator comprises a movable contact 6! connected to a small coil 10 placed in the magnetic field of the coil H fed by an independent direct current. The coil 10 is fed by the current supplied by the amplifier (which in this case will supply a direct current identical to that supplied by the photo-electric cell, but amplified). The contact 69 when displaced towards the left by the action of the first amplified current of the photo-electric cell, is detached from the spring 12 and opens the circuit, thus interrupting the amplified current passing through the small coil II. The movable point returns to the first position due to the action of a spring 13, thus re-establishing the circuit,

and the cycle will be repeated until the current of the photo-electric cell ceases. If the movable coils of the gravers are placed in series with the coil actuating the mechanical oscillator, their oscillations will follow and a reproduction by points will thus be obtained. If the movable point of the mechanical oscillator actuates a lation of the spring. Also in this case the vibratlons begin with the starting of the current supplied by the photo-electric cell and are, therefore, synchronised with the design. Obviously, a similar device may be adapted so that the system should act for inverted reproduction. When this type of vibrator is adopted, it is necessary that the amplifier should give at its issue an amplified direct current corresponding to the direct current of the photo-electric cell; this can be easily realised by various methods which are self-evident for the experts acquainted with the art. When the mechanical oscillator interrupts only the auxiliary current and is actuated'by one of the electric oscillators described above, its operation will be reduced to that of a simple mechanical relay controlling the gravers. This disposition may be employed advantageously in particular conditions of operation of the apparatus, for avoiding certain phenomena of optical-luminous character which may be verified. The systern may be suitable also when a great number of gravers is to be actuated and an amplifier of great power would not be advisable.

What I claim is:

1. An apparatus for engraving a multi-design on a fabric printing roll, comprising a fabric printing roll coated by a protective coating, a

roll containing a design to be reproduced, means for supporting said rolls for rotation, means for rotating said rolls in synchronism, a photoelecsaid printing roll, said means being operable independently of the scanner mounting whereby the engraved design is distorted relatively to the scanned design by a predetermined amount.

2. An apparatus for engraving a multi-design on a fabric printing roll, comprising a fabric printing roll coated by a protective coating, a roll, containing a design to be reproduced, means for supporting said rolls for rotation, means for rotating said rolls in synchronism, a photoelectric scanner, means for mounting said scanner for displacement axially of the roll containing the design to be reproduced, guide rails extending axially of said printing roll, a plurality of electromagnetic gravers mounted on said rails for movement axially of said printing roll, means for displacing said scanner and gravers in syn chronism along said rolls, means for inclining said graver guide rails relatively to the axis of said printing roll, said means being operable independently of the scanner mounting whereby ilgraverguiderailsreiativ ly a manner as to deform the graved design in one dimensional direction only.

3. An apparatus for engraving a multi-design on a fabric printing roll, comprising a fabric printing roll coated by a protective coating, a roll containing a design to be reproduced. means for supporting said rolls for rotation, means for rotating said rolls in syn a photoelectric scanner, means for mounting said scanner for displacement'axially of the roll containing the design to be reproduced, guide rails extending axially said printing roll, a plurality of electromagnetic gravers mounted on said rails for movement axiallyoi said printing roll, means (or said scanner and gravers in synchronism along said rolls, means for inclining said graver guide rails relatively to the axis or said printing roll, pendently oi the scanner engraved design is distorted relatively to the scanned design by a redetermined amount, means for speed of travel of the graversrelativetotliespeedotscanninginsuch amannerastodeiormthegraveddeaig'ninone dimensional direction only, and means for varying the relative speeds ofrotation'oi said rolls.

4. An apparatus for engraving a multi-design on a fabric printing roll, comprising a fabric printing roll coated by a protective coating, a roll containing a design to be reproduced, means for supporting said rolls for rotation, means for rotating said rolls in synchronism, a photoelectric scanner, means for mounting said scanner for displacement axially o! the roll containing the design to be reproduced, guide rails extendingaxially oi said printing roll, a plurality of eiec-. tromagnetic gravers mounted on said rails for/- movement axially oi said printing roll, means for displacingsaidscannerandgraversinsynchronism along said rolls, means for said to the axis or said printing roll, said means being operable independently of the scanner mounting whereby the engraved design is distorted relatively to the scanned design by a predetermined amount,

- and means for displacing said guide rails toward and away from said printing roll.

5. A process of transferring a design from a design roller and multiplying the same on a printing roll covered with a protective coating, comprising tracing the simple contour of the design to be reproduced on a support, applying said support on the design roller, separately producing hatching to be reproduced within the cono! the design on a separate support, applying said hatched support to said design roller, rotating said rollers in synchronism, separately photoelectrically scanning said supports to produce variation in an electric current, displacing a series of electromagnetic gravers over the printing roll in synchronism with the scanning of the design roller, actuating said gravers by the variations in said electric current. and applying a determined amount of distortion to the graved design relatively to the scanned designs.

8. AprocessaccordinItoclaim5,inwhich the original design is traced on a sheet provided with hatching previously printed on its whole surface, and the zones which result interposed between the single ngures traced on the sheet are covered with a coloring material proper to make the pre-existent hatching in said zones inert to the scanning operation.

"I. A process according to claim 5, in which scanning is effected by projecting a beam of light through a transparent design to be reproduced, and in which the current passing through the grav'ers is intermittently interrupted in correspondence with variations of said current.

8. A process according to claim 5, in which the scanning includes the additional steps of proiecting a beam of light on the design to be reprw duced,-optically enlarging t e reflected image, and utilizingma part of said image for the scanning o n.

FRANCESCO ALICE.