US3246079A

US3246079A - Method and means for the preparation of printing forms, especially of intaglio printing surfaces

Info

Publication number: US3246079A
Application number: US142407A
Authority: US
Inventors: Teucher Rudolf
Original assignee: European Rotogravure Association ERA eV
Current assignee: European Rotogravure Association ERA eV
Priority date: 1959-04-17
Filing date: 1961-10-02
Publication date: 1966-04-12
Anticipated expiration: 1983-04-12
Also published as: FI40970B; BE607402A; NL268860A; DE1123561B; FR1301509A

Description

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SR GRQSMS REFERENGE SEARCH Roon m2 3,246,079

April 12, 1966 R TEUCHER 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OF INTAGLIO PRINTING SUR'FACES Flled Oct. 2, 1961 5 Sheets-Sheet l MIRO@ N .mt

April 12, 1956 R. TEUcHl-:R 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OF INTAGLIO PRINTING SURFACES Filed Oct. 2, 1961 5 Sheets-Sheet 2 IHIIIIIIIIH PULS GENE/9,4 T01? VOL 7465 SUP/ZY ANO CA/I'OL SYSTEM Mcm/M PUMPS Jn vena r: fw? MJ Maya.

April 12, 1966 R. TEUCHER 3,246,079

METHOD AND MEANS FOR THE PREPARATION 0F PRINTING FORMS, ESPECIALLY OF INTAGLIO PRINTING SURFACES Filed Oct. 2. 1961 5 Sheets-Sheet 5 Fig.. 3

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April l2, 1966 R. TEUcHx-:R 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OF INTAGLIO PRINTING SURFACES Filed Oct. 2. 1961 5 Sheets-Sheet 4 Fig. 4

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-j Wma April 12, 1966 R, TEUCHER 3,246,079

METHOD AND MEANS FOR THE PREPARATION OF PRINTING FORMS, ESPECIALLY OE INTAGLIO PRINTING sURFACEs Filed Oct. 2. 1961 5 Sheets-Sheet 5 Fig. 5

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United States Patent O 3,246,079 METHD AND MEANS FOR THE PREPARATEDN F PRNTING FRDIS, ESPECIALLY 0F IN- TAGLI() PRJNTING SURFASES Rudolf Teacher, Sprendlingen, Oifenbach, Germany, as-

signor to Era European Rotogravure Association, Basel, Switzerland lFiled Oct. 2, 1%1, Ser. No. 142,407 Claims priority, application Germany, Oct. 22, 1960, T 19,174 Claims. (Cl. Mii-6.6)

Printing forms are made mainly by the photo-chemical process. Owing to the large number of operations required, however, thisl process is time-consuming and requires considerable experience in the art and also great skill. The result always depends decisively upon the individual treatment of the separate operations.

It is also known to make printing forms by physical machining methods. These include a known process wherein the required material removal operation is carried ont by a stylus controlled by the original to be Ieproduced. Another proposal provides for removal of the material by spark discharge, an electrode being moved over the surface of the material of the printing form. All these processes entail a certain amount of ine-rtia as a result of the mass of the stylus or electrodes and are therefore relatively slow in operation.

In another known method, use is made of the materialremoving properties of an electron beam. An electron beam is sluiced through a pressure stage system into .the working chamber, which is under atmospheric pressure, and continuously removes material from the printing block, form or plate material therein, the amount of material being removed depending upon the intensity of the beam. The intensity is controlled by the light-dark scale of the original to be reproduced.

Another known process utilises the material-removing properties of an electron beam for the production of small spheres.

A method of treating materials by means of a beam of charged particles is also known, for example, to make holes in a plate.

ln another known method and apparatus for material machining by means of a charge-carrying beam, the pattern of a printed circuit is developed by means of a chargecarrying beam. The original is photographed by a television camera and the deflection signals serving to control the television pick-up tube scanning beam serve at the same time for the synchronous detiection of the chargecarrier beam over the object to be machined, and the video-signals furnished by the television camera serve to control the intensity of the charge-carrier beam` meeting the object.

Finally, a method is known wherein material is removed and thus printing forms, blocks or plates are produced by spark discharge between a pointed electrode and the surace of said form, block or plate. It is also pos-sible to use corpuscular radiation to give the surface of metals the character of a printing form, block or plate. The latter two methods have not hitherto been used in practice.

The main object of the invention is to provide methods of producing printing forms, more particularly intaglio forms, by means of electron beams, these methods being intended to give a considerable improvement of the lightdark values and hence improved quality of the reproduction, in the production of printing forms from singleor multi-coloured originals, by the defined removal of material by an electron beam.

A further object of the invention is to provide methods and apparatus for the production of printing forms, blocks or plates `from singleor multi-coloured originals,

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wherein the printing forms can be made in a significantly shorter time than has been possible with the previous stylus processes or chemical etching processes.

A further object of the invention is to provide methods of the aforesaid kind wherein any required correction may be provided in simple manner in the transmission between the original and the printing form, block or plate, in order thus to obtain any required modilication of the form, block or .plate in comparison with the original.

A further object of the invention is to provide methods and apparatus whereby a very uniform and required shaping of the individual cells lcan be achieved, in other words the quality of the cell-s can be improved, through a removal of surace material by means of an electron beam.

A further object of .the invention is to provide methods and apparatus of the aforesaid kind whereby known processes are simpliiied.

A further object of the invention is to make printing Iforms, using electron beams, a speci-al control system being used to ensure `that the individual printing elements are depicted sharply .and in accordance with the original, with an adjustable control characteristic.

A further object of the invention is to prov-ide methods and apparatus of the aforesaid kind whereby any required storage of ythe pulses recorded from the original and reproduction at any required time and at any required location are possible for the production of printing forms, blocks or plates.

The principle on which the invention is based is that it is pos-sible to scan coloured or black and white originals with or without a screen and to use the electrical currents or voltages which are proportional to the grey or colour values of the original to control mechanical, electrical or electronic components which remove from the surfaces of the printing stock Imaterial volumes of material which, taking into account the printing ink, are in a denite relationship to the scanned grey or colour values of the original.

In the method according to the invention, for the production of print-ing forms, use is made of electron bea-In pulses which meet each individual surace elemental area of the form mate-rial one or lmore times, it being possible to control the intensity of the pulses, the number of pulses per element of surface area, their duration and their focussing sharpness, electrically or magnetically by means of the light-dark value which is scanned photoelectrically from the corresponding surace elemental area of the original. The resultant dilTe-rential removal of material from the different surface elements of area gives rise to a printable relief image of the original on a printing plate, a printing cylinder, or the like.

It is `accordingly within the scope of .the invention to inilnence the printing stock material as required by influencing the beam intensity, the focussing, pulse duration and the time between two pulses. It is also within the scope of the invention to vary the shape, depth and contour of the printing form elements by one of the said steps or by a combination of said steps. It is further within the scope of the invention to use appropriate masks, which are reproduced on a reduced scale on the printing form material by the electron beam, so as to obtain individual cells of a required shape, for example a square or diamond shape, while the depth off the cells and their surace form can be inuenced by the steps explained hereinbefore.

According to one embodiment, the method according to the invention may be performed in practice by optically scanning each individual element of an original which, for example, may comprise singleor multi-colour matter, by means of a scanning device, converting the scanned values in a photo-electric cell into yvoltage or current values corresponding to the brightness of the original, dividing up into individual fixed pulses the resultant signals which are in the form of voltage fluctuations, and feeding the resultant pulses, after further amplification if required, to a high-voltage electron gun, and using these pulses to control the electron beam in the form of pulses.

According to a practical embodiment of the invention, it is possible to feed the voltage `fluctuations which, for example, are produced by a photo-electric cell according to the brightness values, to a pulse generator which operates in lthe manner of a chopper and which furnishes the pulses which are to 'be converted, the .amplitude of these individual pulses being directly proportional to the light and dark values or fluctuations of these values in the original. The further conversion of the resultant pulses which correspond to the Abrightness values of the original can be performed in various ways according to the invention.

According to one embodiment of the method of the invention, this may be carried out electrically, the pulses produced in the pulse generator being superimposed on the carrier Wave for emission of 4the latter at the reception station, which is at high voltage.

According to `a further embodiment of the method of the invention, the pulses proportional to the brightness of the original may be `fed to a cathode-ray oscillograph, and the brightness of the picture element produced there is thus controlled. By means of an electrically separate receiver at high-voltage on the reception side these pulses can be reconverted to electrical pulses `and fed to the highvoltage electron gun.

According to Ia further embodiment, the invention may also be performed by wireless transmission, directly to the high-voltage electron gun, of the current values which are scanned from the original by the scanning device and which fluctuate according yto the brightness, said current values continually controlling the intensity of the electron beam produced at the electron gun.

In performing the methods of the invention explained hereinbefore it is preferable to `mount the original on a cylinder and rotate this cylinder at a constant speed of revolution and to advance -it slowly per unit of time so that a fixed beam of light scans the original in a spiral having a very small pitch, the speed of revolution of this original natural lbeing in synchronism with the speed of revolution of the printing form at the reception station.

In a further embodiment of the invention, a plane original may be used, the said plane original ybeing moved beneath a fixed beam of light with linewise scanning of the original.

According `to a further embodiment of the invention, the original to be reproduced may oscillate Vat a required frequency so that the plane original can be scanned according to any required pattern. In this case, of course, the scanning station or the original at the reception end must be moved correspondingly.

According to a further embodiment of the method according to the invention, where a rotating cylinder is used for the original to `be reproduced, it is preferable to `rotate a pulse generator device in synchronism with the said cylinder, by means of which pulse generator the signals coming from the scanning device in the form of voltage fluctuations, as already explained, are split up into individual pulses which are fixed as to time and location by the printing cylinder and the value of which is proportional to the brightness of the original to be reproduced.

According to a further embodiment of the invention, it is possible positively to couple the drive for the cylinder of the original to the pulse generator mechanically at the reception station so that the pulses which are fed at the lreception station to an electron-optical system to be explained hereinafter are absolutely in synchronism with the pulses produced in the pulse generator, without any correcting device being necessary for the purpose. This embodiment is particularly simple because the position of the pulses with respect to their location on the printing cylinder is definitely fixed from the outset. The pulse repetition frequency of the pulse generator is thus determined lby the speed of `revolution of the printing cylinder at the original scanning station.

The tmethod of the present invention can be modified by 'controlling the electron beam by the production of square pulses by a pulse generator disc or equivalent element rotating synchronously with the printing cylinder, the said square pulses being applied in the same IWay to the high-voltage side of the electron-optical system as the pulses corresponding to the `brightness values of the original. Additionally according to a further embodiment of the invention, `for this purpose it is possible for the electron-optical system to incorporate a beam tube, to one control electrode of which the square pulses are applied to open or interrupt the beam, `and to feed the fluctuations corresponding to the original brightness values to a second control electrode, Iwhich fluctuations in the rhythm of the pulses produced lby the pulse generator interrupt the electron beam, the intensity of `which varies according to the brightness values of the original.

According to one feature of the invention, a variation of the pulse action can be obtained by variation of the focussing, and this is effected, for example, by means of control electrodes. Assuming that an electron beam contains a certain number of electrons and hence has a certain electron density, variation of the voltage at the control electrodes of the electron-optical system will give a variation in the current density of the electron beam and this may be effected firstly by varying the beam bunching and secondly by varying the current magnitude.

It is within the scope of the invention to obtain a variation in the depth of the cells by the above-explained steps as a consequence of the scanned pulses or the number of pulses. The cell diameter can be varied at the same time by this pulse control, so that the shape and/ or the diameter of the cell also varies as a result, whereby the volume of the cell can also be varied as required.

This embodiment has the particular advantage that as a result of the beam focussing all the metal is vaporised instantaneously and this avoids the disadvantage that, for example, Where use is made of a single relatively long pulse there might be insufficient intensity at the edges of the beam, due to poor focussing of the latter, to vaporise all the metal instantaneously, so that at the edges of the cell melting zones form which result in a crater edge projecting from the plane of the printing form, block or plate. Thus since according to the invention any required focussing can be used for the electron beam and the low-energy regions of the beam which are not adequate for melting are masked out by a suitable mask, the advantage of instantaneous vaporisation of all the material is obtained without any craters being formed; at the same time, as already indicated, cells of any desired shape may be made in accordance with the manner of focussing.

The top limit of the pulse duration may if desired be about microseconds, but operation is preferably carried out below that value. The energy density in the beam cross-section should then be in the region of at least 10,000 kw. per sq. cm. in order to obtain a sufficiently deep engraving.

From the electronic standpoint, there is no upper limit to the engraving speed which would be limited only by the mechanical movement of the printing support. When rotating printing supports are used, speeds of 30,000 printing elements per second can be obtained without difhculty.

According to a further embodiment of the invention, the intensity of the electron beam may also be varied by varying the pulse height. It is assumed that a square wave voltage maintained over a certain period is applied to one control grid. By varying the current it is possible to obtain variation in the energy and hence a variation in the intensity of the pulse. In other words, the amplitude of the square Wave voltage can be varied and thus a variation of the energy content of an individual pulse from the original is obtained as a function of the control voltage applied. With the present embodiment of the invention this can be eifected by varying the voltage in the Wehnelt cylinder of the electron-optical system. In addition, the energy content of an individual pulse can be varied by a second control electrode by the fact that even when fully opened by this pulse the magnitude of the electrode beam current is limited by the potential applied to the second control electrode.

According to a further embodiment of the invention, a variation of the pulse intensity can be obtained by varying the duration of the square wave pulse.

According to the invention it is also possible to obtain a variation by varying the time between two control pulses. This variation has no direct iniiuence on the shape and size of an individual puise but it does vary the number of cells in the printing form, for example reduces such number, when the time between two pulses is increased.

Finally, according to the invention it is possible to obviate any errors in the original or vary the entire character of the original matter by suitable choice of transmission of the brightness values scanned from the original to the electron beam pulses used for engraving. By character of the original matter in this context, for example, is meant that contours are intensied, contrasts increased, and so on. According to the invention, this can be achieved by varying the amplification, more particularly by the use of non-linear amplifier elements, and can be carried out at any required stage of the transmission of the scanned brightness values or of the brightness values converted into electrical pulses.

According to a further embodiment of the method according to the invention, colour separations may also be made from coloured originals, and to this end, according to one embodiment of the method of the invention, a coloured original is split up into three images each containing their colour separations. With the photomechanical etching process conventional today in the production of printing blocks it is necessary first to make three colour separations from the coloured original, these separations containing the engraving values according to the individual colour components. These colour separations are then used to make the individual blocks required for the individual coloured print. The invention avoids this detour using at least three colour separations, since it enables the coloured original to be scanned by a beam of light and thisv beam of light to be converted directly into the corresponding density values by means of colour separation filters. The corresponding number of colour cylinders can then be effected direct from the original simultaneously by control of a corresponding number of engraving devices, the remarks made hereinbefore with respect to the yblack and white original again applying as regards apparatus. It is therefore only necessary to provide on the reception side a corresponding number of electronically operating en- `graving devices and then the printing forms can be used directly in the printing process.

As an example, the above-explained method of the invention may be performed in practice as follows:

It will be assumed that a coloured transparency has to be reproduced by printing processes. The original is clamped for example, on a cylinder and its colour values are scanned by means of a scanning device which, for example, may consist of a light source and one or more photoelectric cells. The beam of light originating from the light source is projected in the form of a dot on the surface of the original, passes through it and on the light reception side is split up into three identical image components, for example, by way of a multiple prism. In the photoelcctric cell circuits, therefore, three voltages having different uctuations according to the colour values are obtained and can in turn serve to control three engraving devices.

The three component beams are each scanned by a photoelectric cell through the medium of a colour separation filter, and from each point of the coloured original three output voltages are obtained which are identical to the photographic grey rvalues of the corresponding points of the colour separations. The three voltages are then fed, for example, to three computers and colourcorrected electronically by methods known per se. Component vo-ltages of the three pulses are also fed to another computer which `in turn calculates ythe black separation value of the point of the original in question.

'The four pulse sequences obtained in this way now serve to control four electron beams which in turn engrave the four printing forms, blocks or plates.

It also comes within the scope of the invention to allow a plurality of electron-optical systems to operate in parallel from a single original, in a similar manner to that used in splitting up the colour of a coloured original, the pulses derived from the original being fed to a plurality of electronically operating engraving heads, so that it `is possible to obtain printing `forms from a single original at a plurality of places which, if required, are situated very far apart.

By the interposition of suitable means between the scanning unit and the engraving unit a storage method may be adopted to enable the scanned matter to be recorded, for example, in the form of a magnetic tape. The magnetic tape can then be used to control an electron-optical system either subsequently or after a relatively long period of storage.

By varying the speed of ythe magnetic tape during the recording or engraving and by appropriate control of the mechanical lateral movement, an image on an enlarged or reduced scale in relation to the original may be produced on the printing material.

In addition to the advantage-s as explained, the invention has the basic advantage that apart from the production of cells without any crater formation it is possible to produce perfect printing forms from originals in a much shorter time than was possible hitherto. Taking a normal etching process as basis, it may be stated that the period from the original up to the completed printing cylinder is about 8 to l0 hours using such a method, while when the method according to the invention is used only a fraction of this time is required from the original to the completed printing cylinder. A very considerable saving of Itime until the printing cylinder is ready is therefore obtained with the method according to the invention.

By Way of example, taking as a basis the production of 30,000 printing elements per second with a 70`screen, a printing cylinder, block or plate of the size of 1 sq. metre can be made in a period of about 30l minutes.

Particularly in printing technology the invention will permit of other basic indirect advantages inasmuch as the considerable saving in time will enable printing toy be carried out up to the very minute, i.e. it is possible to make printing cylinders from originals which were received at the editorial office just a relatively short time before the beginning of printing.

As already explained, according to the invention it is preferable to use a fixed scanning beam and a moving original and/or a moving printing form, block or plate. It comes within the scope of the invention to keep` the original and the printing form stationary and to move .the scanning beam and electron beam in relation thereto in a manner known from the television art, in which case, of course, the two beams must be controlled in synchronism.

The scanning movement of the scanning beam and of the electron beam which, in particular, will be a linewise movement, need not be explained in detail here since the means are known to those versed in the art. The conventional line scanning method or alternatively the interlaced scanning method may be used. Where use is made of originals in the form of a cylinder and a corresponding form, the scanning beam and the electron beam may oscillate in one plane and the original and the printing form be advanced linewise with respect thereto.

Embodiments of the invention are illustrated as examples in the drawings:

FIG. l is a block circuit diagram of the complete installation which schematically shows the construction of an apparatus for performing the method according to the invention.

FIG. 2 is a similar view to FIG. 1, wherein the type of drive for the original and the printing cylinder on the reception side are shown schematically.

FIG. 3 is a circuit diagram showing, the nature of the circuit at the reception station and the control pulse supply.

FIG. 4 shows schematically the electron-optical systern with the most important components.

FIG. 5 is a greatly enlarged view of a cell made by the method according to the invention.

FIG. 6 shows a cell with a ridge due to melting, this cell being of the kind made by a known method.

FIGS. 7 and 8 are plan views of two axial contour shapes of cells.

In order to explain the invention, FIG. 1 shows in principle the construction of a plant for performing the method according to the invention. The plant contains four essential main parts, the current supply part, the control part, the actual engraving device, and a vacuum pump station.

The electrical power supply part contains a highvoltage transformer A which produces the high-voltage of about 100,000 volts `required to produce the electron beam. This transformer A contains an isolating transformer B which enables other high-potential electronic apparatus to be operated, and a heating transformer C for vthe heater voltage for the electron-optical system. To keep the individual values constant, this high-tension transformer A is advantageously connected in series with a stabilizer D connected to the mains. Operation is carried out from a separate control desk E.

The high-tension transformer A.C. leads to a device F, which Iis insulated from earth and which will hereinafter be referred to as a potential tank, and which contains the electronic means required to control the beam. By means of control knobs G the corresponding values can be set to Ithe required magnitudes from earth potcntial, `for example the pulse duration and the pulse magnitude, and the receiver be set to the pulses coming from the scanning device L. Cables lead from the potential tank F to the actual engraving device which consists of the beam generator system H, H1 and a device to accommodate a printing cylinder J. This arrangement is in a vacuum-tight tank which is evacuated to a pressure below 10-3 mm. mercury column by means of a vacuum pump station K.

FIG. 2 is a construction similar to FIG. 1, in which like references have been used. In addition to the various parts shown diagrammatically in FG. 1, it shows a scanning device L for an original M which is coupled to a drive N which is in turn coupled to the printing cylinder J and wherein there is at the same time a driving connection O through gearwheels which slide the carrier of the printing cylinder I by way of a worm and wormwheel P. The drive N is also coupled through R to a pulse generator S.

FIG. 3 shows a circuit diagram of the installation.

Ref. 1A denotes the high-voltage transformer followed by a rectifier chain 2 and smoothing resistance 3, the negative end of which is connected to the cathode 4 of an electron-beam tube while the positive end is connected to earth through a measuring resistance 5. A heater transformer 6 serves to supply the hot-cathode 4. A pulse generator 7 and a rectifier 8 are provided in the potential tank F to produce a iixed bias for a control grid 9 of the electron-beam tube, this bias being externally adjustable by way of a variable resistance 10. The pulse generator 7 serves to produce the said square wave pulses which open and close the electron beam in the rhythm of the printing cylinder movement. Said pulse generator 7 is at high-voltage potential and can be triggered externally by means of a device (not shown). Another device 11 for the production of a D.C. voltage Serves to produce a fixed negative bias for the Wehnelt cylinder 12 of the electronbeam tube, and this bias can also be adjusted by means of a variable resistance 13. An A C. voltage can be applied to the Wehnelt cylinder by way of a working resistance 14 and a circuit not shown in detail here, and this voltage is indicated at Mrz and serves to control the electron-beam intensity according to the brightness values of the original to be reproduced. This alternating voltage 14a accordingly fluctuates in the rhythm of the lightdark values of the original.

Au isolating transformer (not shown) is connected to the terminals 15B and serves to feed the pulse generator 7 and the two auxiliary

voltage generating sources

8 and 11 and enables the conventional supply voltage of 220 v. A.C. to be coupled to the high-tension potential. The anode 16 of the electron gun is at earth potential and hence at plus kv. with respect to the cathode 4.

FIG. 4 shows the electron-optical system for producing the beam. The actual engraving device consists of a vacuum-tight housing 20, the top end of which is sealed by a high-voltage insulator 21, with high-voltage leads 22. Inside the housing 20 is the hot-cathode 4 surrounded by the Wehnelt cylinder 12. The control grid 9 serves for the light-dark modulation of the electron beam. The electrons emerging from the cathode 4 are accelerated by the anode 16. The electron beam 24 can be directed by means of an adjusting device 23 on to a mask 25 which masks out the inoperative part of the electron beam. An electron-beam image of the aperture 25 is produced on a printing cylinder 27 by means of a magnetic lens 26 and thus an engraving is produced which is denoted generally by reference 2d.

The electrons emerging from the cathode 4 are combined by the control grid 9 and the Wehnelt cylinder 12 to form a beam which is accelerated towards the printing cylinder 27 by means of the anode 16. An energy distribution governed by the system prevails in the electron beam and its inoperative edges are cut off by the mask Z5. The remaining part of the beam contains only the energyridge electrons which by means of the magnetic lens 26 are projected on to the printing cylinder Z7 to give a 'reduced image of the aperture 25. The electrons impinging upon the cylinder result in very intensive heating of the material at the point of impact, and this material thus vaporises spontaneously. A depression of predetermined size and depth is thus left on the printing cylinder according to the duration and energy of the electron beam.

The electron beam is opened only for short periods at a time by means of the control grid 9 and the pulse generator 7 while the voltage at the Wehnelt cylinder 12, which voltage is controlled by the brightness of the original by means of the resistance 14, determines the intensity of the electron beam during the opening period. Cells of the required depth and size are thus produced in the printing form, block or plate in dependence on the intensity of the electron beam or the electron beam pulses.

By means of a mechanical drive (not shown) the printing cylinder rotates about its lonigtudinal axis and is displaced along this longitudinal axis. The depressions produced by the electron beam are thus situated along a spiral line of predetermined pitch on the cylinder,

FIG. 5 shows how a cell according to the invention appears in the completed state. It will be seen that it has somewhat beveled anks and that there is no crater formation.

FIG. 6 shows the appearance of a cell with known processes. The crater formation is avoided in the invention by the fact that the inoperative edges of the electron beam are cut olf by the mask.

FIGS. 7 and 8 show how any required shaping of the cells can be obtained by suitable shape of the mask.

FIG. 7 is a plan view of a substantially square cell while FIG. 8 shows a diamond-shaped cell.

In addition to the above-explained advantages, the in- Vention has the advantage that the centre axes of the individual cells are substantially perpendicular to the surface of the original both in the case of plane and in the case of, for example, cylindrically shaped originals or forms, blocks or plates. This is due to the fact that with the method according to the invention a stationary electron beam and a moving origin-al are used. This in turn has the advantage that apart from a synchronism of the movement between the original and the form, block or plate no synchronising devices whatever are required between the scanning device and the elect-ron-optic-al system.

As a result of the variable focussing, the sharpness of the dot edges and the slope of the Hanks of the cells may be given an optimum value by means of the invention while the quality of the printed matter is improved since the depth of the cells on the forms, blocks or plates and the smoothness of their surfaces are controllable as required and as most suitable.

I claim:

1. Apparatus for producing an engraved printing form comprising in combination:

an electron beam generator for projecting on a given plane a sharply focused beam of electrons,

first mounting means for supporting and positioning an electron beam engravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means, means coupled thereto for producing a vacuum within said housing along the entire path of said beam,

means for causing said electron beam to traverse the surface of said engravable medium in accordance with a pattern which is identical and in absolute synchronism with a predetermined scanning pattern of an original,

means for coupling to said beam generator for controlling the intensity of the Ibeam a signal representative of the brightness values of said original along said scanning pattern,

and means directly synchronized with the traverse of the beam over the surface of the engravable medium for periodically suppressing the engraving action of said beam to provide the characteristic dot pattern of a printing form.

2. Apparatus for producing an engraved printing form comprising in combination:

an electron beam generator for projecting on a given plane a sharply focused bea-m of electrons,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing along the entire path of said beam, second mounting means for supporting an original,

an electro-optical device associated with said second mounting means for scanning the surface of said original in accordance with a predetermined scanning pattern, and for providing a voltage signal as a function of the brightness values thereof,

means for causing said electron beam to traverse the surface of said engravable medium in accordance with a pattern which is identical and in absolute synchronism with said predetermined scanning .pattern,

means coupling said signal output of said electro-optical device to said ibeam generator for controlling the intensity of the beam as a function of said voltage signal,

and means directly synchronized with the traverse of the beam over the surface of the engravable medium for periodically suppressing the engraving action of said beam to provide the' characteristic dot pattern of a .printing form.

3. Apparatus for producing an intaglio printing form comprising in combination:

an electron beam generator for projecting on a given plane a sharply focused stationary beam of electrons,

rst mounting means for supporting and positioning an electron beam engravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within said housing along the entire path of said beam,

second mounting means for supporting an original,

an electro-optical device associated with said second mounting means for scanning the surface of said original in accordance with a predetermined scanning pattern and for providing a voltage signal as a function of the brightness values thereof,

means coupled to said first mounting means to impart driven motion thereto for causing said stationary electron beam to traverse the surface of said engravable medium in accordance Iwith a pattern which is identical and in absolute synchronism with said predetermined scanning pattern,

means coupling said signal output of said electro-optical device to said beam generator for controlling the intensity of the beam as a function of said voltage signal,

and means directly synchronized with the traverse of the beam over the surface of the engravable medium for periodically suppressing the engraving action of said beam to provide the characteristic dot pattern of an intaglio form.

4. Apparatus for Iproducing an intaglio printing form comprising in combination:

a housing enclosing both said generator and said first mounting means,

second mounting means for supporting an original,

an electro-optical device associated with said second mounting means for scanning the surface of said original in accordance with the predetermined scanning pattern and for providing a voltage signal as a function of the brightness values thereof,

means coupled to said first mounting means to impart driven motion thereto for causing said stationary electron beam to traverse the surface of said engravable medium in accordance with a pattern which is identical and in absolute synchronism with said predetermined scanning pattern,

and an electro-mechanical signal generator having a driven element fixedly joined to said first mounting means for conjoint movement and having an output means coupled to said beam generator for periodically suppressing the engraving action of said beam in exact synchronism with the traverse of the beam over the surface of the engravable medium to provide the characteristic dot pattern of an intaglio form.

5. Apparatus according to claim 4, wherein the output means of said electro-mechanical signal generator comprises a photo-electric device having an output coupled to said beam generator, and wherein said driven element comprises means for pulse modulating the intensity of the illumination to which said photo-electric device is responsive.

6. Apparatus according to claim 5, wherein said rst ymounting means comprises a cylindrical support mounted for rotation on a shaft, and wherein said pulse modulating means includes a light modulating disc secured to said shaft for rotation therewith, rotation of said disc effecting the modulation of said illumination.

7. Apparatus for producing an intaglio printing form comprising in combination:

an electron beam generator for projecting on a given plane a beam of electrons, said generator including a source of electrons, an apertured mask, means for accelerating a stream of said electrons along a converging path toward the aperture in said mask, and an electronic lens system positioned on the side of said mask which is remote from said source for focusing the electrons passing through said mask upon said plane in a sharply defined image of the aperture in the mask,

first mounting means for supporting and positioning an elcctron beam engravable medium in said plane in the path of said beam,

a housing enclosing both said generator and said first mounting means,

means for causing said electron beam to traverse the surface of said engravable medium in accordance with a pattern which is identical and in absolute `synchronism with said predetermined scanning pattern,

8. Apparatus for producing an intaglio printing form comprising in combination:

an electron beam generator for projecting on a given plane a beam of electrons, said generator including a source of electrons, an apertured mask, means for accelerating a stream of said electrons along a converging path toward the aperture in said mask, and an electronic lens system positioned on the side of Cil said mask which is remote from said source for focusing the electrons passing through said mask upon said plane in a sharply dened image of the aperture in the mask,

a housing enclosing both said generator and said first mounting means,

means coupled thereto for producing a vacuum within i said housing along the entire path of said beam,

second mounting means for supporting an original, an electro-optical device associated with said second mounting means for scanning the surface of said original in accordance with a predetermined scanning pattern and for providing a voltage signal as a function of the brightness Values thereof,

means coupled to said tirst mounting means to impart driven motion thereto for causing said stationary electron beam to traverse the surface of said engravable medium in accordance with a pattern which is identical and in absolute synchronism with said predetermined scanning pattern,

and an electro-mechanical signal generator having a driven element fixedly joined to said rst mounting means for conjoint movement and having an output means coupled to said beam generator for periodically suppressing the engraving action of said beam in exact synchronism with the traverse of the beam over the surface of the engravable medium to provide the characteristic dot pattern of an intaglio form.

9. Apparatus according to claim 8, wherein the output means of said electro-mechanical signal generator comprises a photo-electric device having an output coupled to said beam generator, and wherein said driven element comprises means for Ipulse modulating the intensity of the illumination to which said photo-electric device is responsive.

10. Apparatus according to claim 9, wherein said first mounting means comprises a cylindrical support mounted for rotation on a shaft, and wherein said pulse modulating means includes a light modulating disc secured to said shaft for rotation therewith, rotation of said disc effecting the modulation of said illumination.

References Cited by the Examiner UNITED STATES PATENTS 2,164,297 6/1939 Bedford. 2,195,489 4/1940 Iams 178-72 2,761,007 8/1956 ,Fisher et al. 178-5.2 2,909,598 10/1959 Litferth 178-6.6 2,923,590 2/1960 Lorenz 346-110 DAVID G. REDINBAUGH, Primary Examiner.

ROY LAKE, Examiner.

Claims

1. APPARATUS FOR PRODUCING AN ENGRAVED PRINTING FORM COMPRISING IN COMBINATION: AN ELECTRON BEAM GENERATOR FOR PROJECTING ON A GIVEN PLANE A SHARPLY FOCUSED BEAM OF ELECTRONS, FIRST MOUNTING MEANS FOR SUPPORTING AND POSITIONING AN ELECTRON BEAM ENGRAVABLE MEDIUM IN SAID PLANE IN THE PATH OF SAID BEAM, A HOUSING ENCLOSING BOTH SAID GENERATOR AND SAID FIRST MOUNTING MEANS, MEANS COUPLED THERETO FOR PRODUCING A VACUUM WITHIN SAID HOUSING ALONG THE ENTIRE PATH OF SAID BEAM MEANS FOR CAUSING SAID ELECTRON BEAM TO TRAVERSE THE SURFACE OF SAID ENGRAVABLE MEDIUM IN ACCORDANCE WITH A PATTERN WHICH IS IDENTICAL AND IN ABSOLUTE SYNCHRONISM WITH A PREDETERMINED SCANNING PATTERN OF AN ORIGINAL, MEANS FOR COUPLING TO SAID BEAM GENERATOR FOR CONTROLLING THE INTENSITY OF THE BEAM A SIGNAL REPRESENTATIVE OF THE BRIGHTNESS VALUES OF SAID ORIGINAL ALONG SAID SCANNING PATTERN, AND MEANS DIRECTLY SYNCHRONIZED WITH THE TRANSVERSE OF THE BEAM OVER THE SURFACE OF THE ENGRAVING MEDIUM FOR PERIODICALLY SUPPRESSING THE ENGRAVING ACTION OF SAID BEAM TO PROVIDE THE CHARACTERISTIC DOT PATTERN OF A PRINTING FORM.