US2086798A

US2086798A - Photoelectrical device for producing half-tone cuts

Info

Publication number: US2086798A
Application number: US618796A
Authority: US
Inventors: Greenberg Otto William
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-06-22
Filing date: 1932-06-22
Publication date: 1937-07-13
Anticipated expiration: 1954-07-13

Description

July 13, 1937. o. w. GREENBERG 2,085,798

PIH'I'EJECTR:[CAL DEVICE FOR PRODUCING HALF TONE CUTS Filed June 22, 1932 4 Sheets-Sheet l @viii @041mg July 13,1937# o. w. GREENBERG 2,086,798

PHOTOELECTRICAL DEVICE FOR PRODUCING HALF TONE CUTS F'ilea June 22, 1952 4 sheets-sheet 2 www July 1.3, 1937. v o. w. GREENBERG PHOTOELECTRICAL DEVICE FOR PRODUCING HALF TONE CUTS Filed June 22, 1932 4 Sheets-Sheet 5 FEP?- TIEEQA.

/N VENTO/e July 13, 1937 o. w. GREENBERG 2,086,798

PHOTOELECTRICAL DEVICE FOR PRODUCING HALF TONE CUTS Filed June 22, 1932 4 Sheets-Sheet 4 TI EE. /N VENTO/e Patented July 13, 1937 PHOTOELECTRICAL DEVICE FOR PRODUC- ING HALF-TONE CUTS Otto William Greenberg, Ocean City, N. J.

Application June 22, 1932, Serial No. 618,796

11 Claims.. (Cl. 11S-6.6)

This invention has reference to machines wherein a photo-electric cell is employed in the production of half-tone cuts used for printing illustrations. The photo-electric cell scans the illustration to be reproduced and a tool controlled by the current passed by the cell forms the half-tone on the surface of a blank.

Hitherto the appearance ofvshading in halftones so produced was broughtY about by parallel lines of varyingV widths cut into the surface of a blank.

The object of my invention relates to the means to produce the appearance of shades by dots or minute areas of variable size formed in the surface of the blank. A further object of this invention relates to the means to obtain more certain and positive reactions to the illumination on the photo-electric cell, and other desirable effects.

' The eye has a natural tendency to follow lines and can observe and diierentiate one from another more readily than it can distinguish one f dot from another, so that the appearance of uniformity in a shaded area produced by dots is much greater than in that produced by parallel lines. This is particularly true where the lines vare farther apartvas they must of necessity be in half-tones printed on coarse paper, such as used for newspapers.

The photo-engravings produced'by the photographic and chemical processes are made up of dots to produce the elect of shading, and are therefore universally preferred although as is well known the process of producing them is long-drawn out, complex and relatively costly, requiring the careful and constant manipulation and attention of expert and skilled artizans.

Attempts have been made to produce halftones consisting of dots employing the photoelectric cell method by cutting conical depressions in the surface of a blank by means oi a tapered revolving drill but owing to the inherent characteristics of a drill tapered to an extremelypine point essential for this work, it has been found impractical and has been abandoned. The ne point of the drill has no cutting edge and cannot cut the very minute depressions required, 'besides it is too delicate to resist breakage. The blank, traversing the drill at right angles, applies a lateral pressure on the point.

The objects of this invention are accomplished primarily by providing the machine with a reciprocating tapered compression tool in the place of' a rotating cutting tool, and by impressing sufficient force upon the said tool to compress the material of the blank to form minute indented areas which appear as dots when a printed impression is made therefrom. The production of half-tones consisting of dots, the main objectof my invention, may also be accomplished in another way, in two operations. One by reproducing the image on the blank with a series of parallel lines cut into the surface of the blank, and the second by again reproducing the image by a series of parallel lines cut across the rst set and in angular relation thereto, thereby forming minute areas polygonal in form.

The compression tool employed to produce the half-tones is tapered and the size of the dot produced at the surface of the blank is proportional to the depth of the indentation. The depth of the indentations is controlled by novel electromagnetic devices. These devices operate by virtue of the ymagnetic hold on an armature in contact or substantially in contact with the core of an electro-magnet, as distinguished from operation at a distance through a gap.

This results in stability and exactitude of response and requires a minimum current for maximum elects. 25

There are several other novel features that take part in accomplishing the objects of this invention, which will be hereinafter described.

Referring to the drawings, Fig. l is a front elevation of an exemplification of the machine. 30

Fig. 2 is a plan View of Fig. 1 with the crosshead of the machine partly broken away.

Fig. 3 is a side elevation on a larger scale with the crosshead partly broken away.

Fig. l is a cross section on the line 4-4 of Fig. 3 of parts of the machine.

Fig. 5 is an enlarged section on the line 5-5 of Fig. l, ci parts of the machine.

Figs. 6 and '7 are front elevations and details of one of the electro-magnetic control devices shown mounted on the machine in Figs. 1 and 3.

Fig. 8 is a modified form of a compression tool.

Fig. 9 is a bottom view of Fig. 8.

Fig. l0 is a compression tool and holder for same in section. l

Fig. ll is a bottom View of Fig. 10.

Figs. i2 and 13 are front elevations of an alternative form of the electro-magnetic device to control the depth of the indentations.

Fig. 14 is a side elevation of Figs. 12 and 13.

Fig. l5 is still another and preferred form oi the electro-magnetic device to control the depth of the indentations.

Fig. 16 is a side elevation of Fig. l5.

Fig. i7 is a front elevation of a modified form of control mounted on a presser foot and provided with a plurality of electro-magnets each of which controls the descent of the tool to a different depth.

Fig. 18 is the same as Fig. 17 with the parts in a different operative position.

Fig. 19 is a modication of the control device shown in Figs. 17 and 18.

Fig. 20 shows a portion of Fig. 19 with the parts in a different operative position.

Fig. 21 illustrates diagrammatically one of the ways in which a solenoid may replace the mechanical means: for operating the up-and-down movement of the tool and the source of current Supply.

Fig. 22 illustrates diagrammatically a photoelectric cell with amplifiers applicable to the various devices for controlling the tool.

Fig. 23 shows similar par'ts of two of the machines located at distant points electrically connected and provided with means for synchronization, whereby an illustration mounted on one machine can reproduce a. half-tone on a blank on the other machine as well as on a blank mounted on the same machine.

Figs. 24 and 25 are schematic diagrams showing novel circuits employing a plurality of gridglow tubes, the output current of which varies in value and is a function of the current passed by a photo-electric cell.

Fig. 26 is a schematic diagram of a photo-electric cell, amplifying circuit and means whereby the output current is utilized to reciprocate a compression tool as well as to control the depth of the indentations thereof, applicable for the reproduction of certain kinds of half-tones.

Figs. 27 and 28 illustrate a novel method for producing half-tone engravings made up of dots by means of lines cut in the surface of the blank across each other in two separate operations.

The mechanical parts of the machine and its operation will be described first.

Referring to Figs. 1 to 5, the machine consists of a base 30, on which is mounted a cross frame 3|, extending from one side of the base 30 to the other and supported on upright portions at each end. Dovetail grooves 32 cut in its upper surface extend from one side of the base 30 to the other.

Two sub-carriages 33 and 34, one on each side of the machine, are slidably mounted in the grooves 3 2 enabling them to be moved from right to left and vice versa. The upper surface of each sub-carriage 33 and 34 is provided with dovetail grooves 35 cut transversely to the dovetail grooves 32 in the base 30.

A carriage 36 for the illustration 31 that is to be reproduced is slidably mounted on the subcarriage 33 in the grooves 35. A similar carriage 38 for a` blank 39 to be made into a halftone is slidably mounted on the sub-carriage 34 in the grooves 35.

It is thus evident that the carriage 36 with the illustration 31 thereon and the carriage 38 carrying the blank 39 are movable forward and backward as well as in a direction perpendicular thereto from right to left.

The illustration 31 and the blank 39 are secured to plates or intermediate-holders 40 and 4|, respectively, by suitable clamps 42. The intermediate-holders serve to hold the illustration and the blank in place on their respective carriages. They are exact squares in outline and i'ltdepressions in the surface of each carriage, providing convenient means for removing the work for examination and for returning same to the accenna exact location on the carriage from which they were removed. These intermediate-holders will be again referred to in this specification.

A motor 43 mounted on the cross frame 3| drives the power shaft 44, supported in bearings on the frame.

A connecting shaft 45 mounted diagonally transmits power from the shaft 44 to a lower shaft 46 through operative connection by means of bevels 41 at its upper and lower ends.

'Ihe lower shaft 46 is mounted in a bearing 49 on the base 3|! of the machine, on a bearing on the sub-carriage 33 and one on the sub-carriage 34; the two latter bearings are free to slide axially on the shaft 44 with their respective carriages.

Two

bevels

49 and 56 facing each other and secured to an elongated sleeve 5| which is slidably keyed in a slot on the shaft 46, alternate under control in meshing with a bevel 52 on a threaded rod 53 to reverse its rotation as one or the other is engaged.

The threaded rod 53 operates to move the carriage 33 back and forth in the grooves 35 on the sub-carriage 34 as it is rotated in one direction or the other.

The reversing bevels 49 and 50 are alternately brought into mesh with the bevel 52 by a crank lever 59 which engages a sleeve 5I by means of pins carried in a yoke and held in an annular groove in the sleeve. The crank lever 59 is pivotally mounted on the sub-carriage 34 and is operated by a bar 54 slidably mounted in bearings 55 on the sub-carriage to which it is pivotally connected at the end of its long arm at 56.

The slide bar 54, Figs. 3 and 23, is shifted to one or the other of its positions at the end of each stroke of the carriage 38 by bumpers 58 provided with springs which alternately apply pressure on opposite sides of an upwardly ex. ,i

tending portion of the slide bar 54.

The bumpers 59 are carried on the lower end of brackets 69 adjustably secured by T-bolts in a T-slot 6l formed in the side of the carriage 38.

A pin 62 engages alternately two notches formed in the upwardly extending portion of the slide bar 54 at points which correspond to the two positions of said slide bar and holds it against the pressure applied by one or the other of the bumpers 58 as they are advanced by the travel of the carriage 38.

An arm 63 extending from each bracket 60 cooperates with each bumper 58 and serves to withdraw the pin 62 out of engagement with the slide bar 54. The end of the arm 63, advancing a suitable distance behind the bumper, engages the cam on the under surface of a cross piece 64 attached to the pin 62 and operates to raise it against the action of a spring 65 after sufficient pressure has been applied by the bumpers against the slide bar 54, so that when the pin 62 disengages the slide bar 54 it is suddenly shifted to its other position. The travel of the carriage 38 is reversed and the operation repeated in the opposite direction when it reaches the end of the return stroke.

The pin 62 is formed on the lower end of. a bar which serves as a plunger for a solenoid 13, which when energized by an electric current, will also Withdraw the pin 62 from engagement with the slide bar 54.

The solenoid 13 is employed only when the machine is used for reproducing a half-tone on a machine located at a .distance at a receiving station.

A bracket 14, Fig. 4, secured to the sub-carriage 34, serves to support the solenoid 13 and provides a guide 15 forvthe pin 62.

The threaded rod 53 is rotetablymounted at each end in supports'onthe carriage 34, and is threaded in an enlarged rectangular screw nut 66, held against rotation in a pocket provided for it in the carriage 38,- Fig. 5. The screw nut 66 has axial play in the pocket, the amount of which can be regulated by lock bolts 61. This, as will be readily understood, gives the carriage 38 a limited lost motion at the beginning of each stroke, the object of which will be hereinafter explained.

The slide bar 54 is provided with a slot in its enlarged portion through which the end of a feed screw 68, Fig. 4, protrudes. The feed screw is rotatably mounted in the sub-carriage 34 and threaded in a post 69 on the base 30 of the machine.

An upperpawl 10 and a lower pawl 1| on the enlarged portion of the slide bar 54 engage a ratchet wheel 12 secured to the end of the feed screw 68. When the slidebar 54 is thrown to the right, Fig. 3 and Fig. 23, the lower pawl 1| actuates the ratchet 12 and turns the feed screw 68 a step counter-clockwise, and when the slide bar 54 is thrown to the left, the upper pawl 10 actuates the ratchet and turns the feed screw 68 a step in the same counter-clockwise direction.

-The reciprocation and the transverse feeding of the carriage 38 is communicated to the carriage 36 on which the illustration is mounted by means of levers in such a way that reverse cuts `to print facsimiles will be produced by the machine. These levers are provided with means whereby enlargements or reductions may be reproduced by varying the relative lengths of their arms.

A communicating lever 16 provided with a downwardly extending stud, Fig. 5, which can be secured in any part of a slot 11 in the lever by a nut pressing against a shoulder on the stud 18, is pivotally mounted on a boss 19 projecting upward from the base 30 which provides bearing for it.A A block 80 and a similar block 8| pivotally secured to each end of the lever 16 are slidably mounted in transverse T-grooves 82 and 83 in the under surfaces of the carriages38 and 36 so that movement of the former will be communicated to the latter but in the opposite direction.

Transverse feeding of the carriage 36 inl the same direction as that of carriage 38 is accomplished by a lever 84 pivotally mounted at one end on a stud in the base, indicated at 85. This lever 84 is provided with two slots 86 that engage pins on the end of

arms

81 and 88, the former adjustably secured and projecting from a bracket 89 on the sub-carriage 33, and the latter adjustably secured and projecting from a bracket 90 on the sub-carriage 34.

In the drawings the arms of levers 16 and 84 are shown adjusted to produce a half-tone of the same size as the illustration.

For reductions, the lever 16 is secured to the stud 18 in the slot 11 at a point to the right of its center, and for enlargements, at a point to the left, the relative lengths of the arms of the lever 16 determining the distance that the carriage 33 will travel in relation to that of the carriage 38. v

The distance that the carriage 36 will travel transversely in feeding in relation to that of the carriage 38 is determined by the relative positions of the

arms

81 and 88 to each other, in the slots in the lever 84. When the arm 88 is secured in the position indicated by broken lines, the carriage 36 will travel a greater distance than the carriage 38, corresponding to a position of the stud 18 in the slot of the lever 16 to the right for reductions. For enlarging the reproduction, the arm 81 is secured on its bracket 89 at a. point to engage the lever 84 closer to its fulcrum or stud 85 than the arm 88 engages it.

Similar markings on each lever, not shown in the drawings, facilitate in adjusting the machine for reductions and enlargements.

A photo-electric cell 9| enclosed in a housing 92, the cover of. which is shown removed, is mounted on a head 93, secured to the cross frame 3| at a point above the carriage 36 and in relation to the illustration 31 to be reproduced. The cell 9| is provided with a lens to focus the image reflected from the illustration 31 on to a4 shutter 94 which limits the light entering the photo-electric cell 9| to the unit area being scanned.

Two light sources 95, each enclosed in a housing, the cover of one of which is shown removed, concentrate light on the surface of the illustration 31 under the lens.

Above the carriage 38, and in relation to the blank 39, a head 96 is mounted and suitably secured to the cross frame 3|. A short shaft 91 passes through the head 96, on the front end of which it has a disk wheel 98, and on the rear end a bevel 99 which meshes with a bevel on the power supply shaft 44.-

The pin |04 also serves as a mounting and center of oscillation for an L-shaped armature |05 which, when held by the magnetic lines of force to the core |02 of the electro-magnet |03 oscillates therewith.

The lower arm of. the L-shaped armature |05 is provided with one or more holders |06 for a tapered tool |01, the leverage desired, determining the holder employed.

The tapered end of the tool |01 is positioned in close proximity to the surface of the blank 39 and on its descent with the oscillationl of the armature |05, Fig. '7, it comes in contact with and indents, by compression, the material of the surface of the blank 39. Thus an evenly increasing pressure is applied on the blank at the point of contact. The area depressed will not take ink, and in printing will register a light dot.

The number of oscillations bears a xed rela* tion to the linear distance traveled by the blank 39 in a given time, and the depressions which iollow one another in line until the end of the stroke of the carriage will be evenly spaced. When the end of the stroke is reached, the carriage is fed a step laterally and the direction of travel is reversed for the production of a succeeding line of depressions until the illustration has been completely scanned, and the half-tone completed.

To prevent the depressions in one line being formed opposite those in the preceding line, the carriage 38, as hereinbefore mentioned, is given a lost motion equal to half the distance between the depressions, so that the depressions formed in 'the succeeding line will lie opposite. the spaces between those of the preceding line, in staggered relationship to them thereby giving the appearance of diagonally located dots.

rllhe contour of the dots formed by the depressions will be circular if the tool employed is tapered like an inverted cone. However, my method of making depressions, enables me to obtain elementary areas that are square in contour, Figs. 8 to 11.

A taper on the end of the compression tool having a cross sectional area of a hexagon or other polygonv may be employed -if desired to obtain various effects in the half-tone print. One that is a square in cross section but formed diagonally to its shank, Figs. 8 and 9, will form squares diagonally positioned with respect to each other and will give a diagonal e'ect to the reproduction as a whole. This effect is very much desired in the art.

To obtain high lights in the print. all or nearly all the surface must be depressed. This can only be obtained with depressions of polygonal contour without the depressions overlapping each other. To obtain the high lights with circular depressions, one circle must overlap the other f and in attempts made hitherto to produce halftones with a rotating cutting tool, the cutting tool would creep where it overlapped a depression already formed,` resulting in unsatisfactory reproductions as well as in broken tool points.

Referring to Figs. and 11, a tool holder |08 is shown on an enlarged scale in which the tool |01 has lateral playand is held resiliently in vertical position A as by Isprings |09 secured to the holder |08 and'press'ing against the tool |01 in shallow depressions ||9 formed around its shank. 'I'his is to prevent interference with the travel of the blank during the time the tool |01 is in contact with it Where no provision has been made to halt the blank itself during the period of time it operated upon by the tool.

The mechanical power derived from the disk wheel 98 is capable of applying a force on the tool |01 suilcientto form a depression in the blank 39 to the maximum depth with each stroke, but

. the reaction to the work of compressionrbreaks the hold of the electro-magnet on the armature |05. When this occurs the force derived from the disk wheel 98v is no longer transmitted to the mum from the instant .that the point of the tooll makes contact with the blank until the maximum depth is attained. When the tool reaches a depth such that the reaction overcomes the magnetic hold on the armature, the armature is released and a spring |I| returns it to its position, indicated in broken lines, Fig. 7, against a'stop ||2, the tool |01 is withdrawn from the surface of the blank 39 and the compression is interrupted and ceases for that oscillation, the electro-magnet continuing its travel to its extreme position indicated in broken lines, Fig. 6.

On the next revolution of the disk wheel 98, the core |02 of the electro-magnet is once more brought into contact withthe armature |05 to reeestablish the hole, and the operation is repeated.

The strength of current flowing through the electro-magnet at any given time is a direct function of the amount of light reilected from the unit area of the illustration under the photo-electnc cell. This current determines at 'what depth of compression the armature is released, which in turn determines the area of the dot that will appear white in the print.

The amount of amplincation of current required for the electromagnetwill depend on the material of the blanks employed. for the greater the resistance to indenting, the stronger must be the hold on the amature for a given depth of depression. Thus zinc, copper, and the other materials in the plates employed for printing and stereotyping half-tones, oder different degrees of resistance to the indenting tool, all relatively high. To form a depression in these, a forcmust be applied capable of distorting the plate at its surface. forcing the material thereof from one place to another.

By employing plates made of vulcanized libre or of other material of a porous consistency, I am enabled, not only to utilize less current for the electromagnet, and less intense illumination on the copy, but also less power to operate the machine with less wear and tear on its parts.

The nature pf vulcanized fibre is such, that in making room for the point of the tool, it 03ers less resistance to compression than to the forcing of its substance from one place to another, and as a result, no burrs or ridges are formed onthe surface. Thus, when the plate is surfaced, as with an abrasive, and then subjected to the action of the tool to form the design thereon, it is not necessary to again surface the plate before-print ing or stereotyping therewith.

In Figs. 12, 13, and 14, there is shown an alternative form of the electro-magnet control device of my invention, in which the hold of an armature is utilized to provide a variable control by a different arrangement of parts. As shown in broken lines, Fig. 12, the force derived from the disk wheel 98 is applied alternately to straighten and to flex a toggle joint, through a connecting link H3. The upper link ||5 of the toggle is connected to one end of an armature ||6 of a fixed electro-magnet ill, the other end y of which is pivoted at I I1 to the head 96. The

lower link ||0 of the toggle is connected to a tool holder I9, slidably held in bearings |20 mounted on the head 96 and provided with a stop |2| which limits its motion upward. 'I'he entire force is applied on the tool to compress the material of the blank when the armature ||6 is held by the electro-magnet, but the reaction to the worktends to break that hold. When this occurs at a point as shown in broken lines, Fig. 13, a spring ||2 pulls up the armature and toggle and withdraws the tool from contact with the blank as shown in Fig. 13 until the next cycle. When the toggle joint is flexed, Fig. 12, the armature is again made to contact the electro-magnet and the cycle is repeated. 'Ihe pull of the spring |22 is adjusted to a tension just short of breaking the hold on the armature, when no light enters the photo-electric cell, so that the slightest resistance offered to the point of the tool |01 on making contact with the blank 39 will' cause its withdrawal. As in the device shown in Figs. 6 and 7, the depth of the depression is directly proportional to the strength of the current flowing in the electromagnet.

In Figs. and 16,l there is shown still another electro-magnetic control device which has a. number of features that make it the preferred form. A lever |23, rectangular in cross section, is caused to move up and down by the crank-pin |00 on the disk wheel 98. It is pivoted at |24 to the end of the armature IIE and is provided with 'ja slide piece |25. A yoke |26, formed on the upper end of the tool holder H9, is pivotally connected to the slide piece |25. 'Ihe tool holder ||9 is slidably mounted in the bearing |20, which is adjustably secured by T-bolts |21 engaging a slot |28 in the head 96.

` The spring |22 is adjusted inthe same manner and has the same purpose as that in Fig. 12.

The downward force applied on the lever |23 by the disk wheel 98 operates to compress the blank 39 as indicated by the broken lines |23a and the reaction to this work tends to break the hold on the armature IIB. When this occurs the spring |22 raises the armature ||6 and the fulcrum end of the lever indicated by the broken lines |23b, thereby withdrawing the tool |01 from the blank 38 lto a. position limited by the stop I 2|. When the disk wheel 98 has raised the lever |23 to the position shown in full lines, the armature ||6 isagain brought into contact with the electro-magnet ||.4.

The slide piece |25, tool holder H9, and the mounting |20 for same may be secured at any point along the T-slot |28, as indicated by the position shown in dotted lines |29. At this position, not. only will the throw of the tool be increased, but much smaller variations in the current flowing in the electro-magnet will control the work to be performed owing to the change in leverage.

In Figs. 17 and 18, an electro-magnetic contro-l device is shown that differs from those hereinbefore described in that it consists of a numberv of units. Each unit controlling the compression tool i 01 operates to produce a depression of a certain xed depth for that unit. The units are adjusted to produce depressions ranging from a minimum to a maximum depth. In the drawings provision is made to obtain six different depths under control.

Within certain limits this control device is unaifected by variations in the line voltage when same is used as a source of electric supply for the photo-electric cell, amplifiers, or to illuminate the illustration.

The slide piece transmits pressure to the point of the tool |01 through the yoke |26 on the upper end of the tool holder.

A plurality of electro-magnets |35, each with an armature |36, normally held against a stop pin |31 by an adjustable spring |38, are connected either in series or parallel with the amplified current of the photo-electric cell 9|. The circuit of the electro-magnets |35 includes the circuit breaker |39 which breaks the circuit on each up stroke of the lever and which, by the action of its spring, re-establishes the circuit on the descent of the lever.

Each spring |38 is adjusted to a different tension increasing from the first spring on the left to the last Ione on the right. When the circuit is rc-establshed on each downward stroke of the too-l |01 one or more of the armatures |36, in succession from left to right, will be attracted to its related electro-magnet |35, the number so attracted increasing with the strength of the current in the circuit.

Each armature |36 hasan upwardly extending arm |40, the upper end of which, when the armature |36 is in its normal position against its stop pin |31, lies in the path of a related stop screw |4| projecting downwardly from the lever |30, and when engaged, stops the further descent of the lever.` But when the armature is drawn up the upper end oi the arm |40 is moved to one side of the path taken by its related stop screw which can then pass beyond it.

The stop screws |4| are adjusted and set in such manner that on the descent of the lever they may contact the upper end oi' the arms I4|| in succession from left to right, making contact with the first succeeding the one, thearmature of which is held by its electro-magnet. As shown in Fig. 18, wherein a current -of' intermediate strength has overcome the resistance of the ilrst three springs, the stop screw |4| of the fourth unit has` made contact and limits the descent o! the lever |30 at that point. I

In the device just described, the number oi' armatures drawn up by a given current strength, is determined by the tension of the springs |38; however, the same may be accomplished without departing from the spirit of the invention, by locating the stop pins |31 at different levels, or by introducing resistances or shunts of different values in each electro-magnetic unit, or by varying the number of turns of wire in each coil.

Certain shades in the illustration to be reproduced may be accentuated by adjustments of the stop screws 4| or by varying the tensions oi' the springs |38.

The device is shown mounted on an enlarged portion |42 of a presser foot |43, which, when in operation, is held against the surface of the blank |39 by an adjustable spring |44 on the head 96, but which can be raised and held in a position above the blank 39 by a cam lever |45 as indicated in broken lines. The presser foot is mounted on the head 96 by bearings formed in its enlarged portion |42 in which the shaft 91 rotates. By thus mounting the electric control device on the presser foot, its freedom to move up and down occasioned by variations in the thickness of the blank or warped condition thereof is not interfered with by reactions that secured to the lever |30 take the place of the' stop screws |4i in Figs. 17 and 18. These stops |46 move up and down with the lever |30 on one side of and in relation to each arm |40 extending upward from the armature |36 against which they present a cam surface |41 that operates to bring the armature |36 into contact with its electro-magnet i35, on each descent of the lever as in the position shown in Fig. 19.

When the current flowing through the coils of the electro-magnets 535 is not strong enough as against the tension of the spring |38 in a particular unit to maintain the hold on thearmature 36 of that unit, the upper end of the arm |40 will engage the stop |46 formed above the cam, |41, on the descent and stop the lever |30 at 'that point as indicated by the middle oi the three units shown in Fig. 20.

The adjustments are the same as in the con trol device shown in Figs. 17 and 18.

In this modification very much less control current is required and its reactions are more positive and dependable than that oi Figs. 17 and 18, 'by virtue of the fact that the hold on the armatures is utilized as a control. Further, the

CII

circuit breaker is dispensed with in this modiilcation.

The lever |30 is not necessarily operated up and down by mechanical means though same is preferred. It may be operated electrically, as shown in Fig. 21. Here the lever |30, the end only of which is shown, is connected to a plunger |49 of a solenoid |50, acting against the tension of an adjustable spring and actuated by` a source of alternating current as at |52.

The electric circuit that may be employed to transmit variations in a photo-electric cell current to the electro-magnet or magnets of the various control devices hereinbefore described is illustrated diagrammatically in Fig. 22, in which the photo-electric cell 9| and two stages of amplification |53 and |54 are directly coupled to each other. The output circuit |55 of the last stage includes the electro-magnet |03 representative of the electro-magnet or electro-magnets employed in the various modications.

This circuit may be connected to line Wires |56 by a switch |51 to transmit impulses to a distant point where, after amplication, as illustrated at |58, the current may be made to operate the control |03 for the compression tools on one or more machines similar to that of the transmitting end of the line. A means for synchronizing the machines will be hereinafter described. Thus a single illustration mounted on one machine may be reproduced not only on the same machine but also on one or more machines located at the same or at distant points.

Referring to Fig.` 23, there are shown parts of the carriage 38 and parts of the reversing mechanism of the machine at the transmitting end and that of the receiving end, the former on the left and the latter on the right, connected by li'ne wires |59 in the circuit |60. This circuit is used for synchronization.

In making half-tones at a distant point, the arms 63 and theA cross pieces 64 are not utilized to disengage the pins 62 from the cross bars 54. This function is performed by the solenoids 13 on the transmitting and on the receiving machines, and takes place at the end of each stroke but before the arms 63 have advanced far enough to operate and raise the cross pieces 64.

'I'he circuit 60 is provided with a suitable source of current supply 6| which serves to energize the solenoids at both ends to disengage the pin 62, and thereby reverse the stroke of the carriages 38 simultaneously.

One of the end Wires of the circuit |60 is connected in parallel 'to the brackets 60 on the transmitting machine as at |62.

The end of the arm 63 on either bracket serves as the terminal for the circuit |60. The other end wire of this circuit is connected to the electrically insulated cross piece 64, shown in section, which serves as the other terminal of the circuit. When the circuit |60 is not in use it is disconnected by means of the switch at |63.

Mounted on a sub-carriage 34 of each machine, in relation to the free end of the slide bar 54, is a switch |64 in the circuit of a suitable source of current supply |66, and the synchronous motor 43 which drives the shaft 44, Fig. 1. When the slide bar 54 is thrown to its position to the left, shown in broken lines, the switch |64 is closed and remains so closed.

The method of operation for the production of a half-tone at a distant point is as follows: The picture to be reproduced, having been mounted on the machine at the transmitting end, and the blank on the machine at the receiving end, the carriages 38 of both machines are set in the starting position shown in Fig. 23, wherein pressure is being applied by the bumper 66 against the slide bar 54 to throw same to the left, and the end of the arm 63 of the transmitting machine is in electrical contact with the cross piece 64. The switch |63 in the circuit |60, and a switch |64 in the power circuits at both ends are open. On closing the switch |63 the solenoids 1I at both ends are energized, the pins 62 are withdrawn and the slidebars 54 are released, thereby closing the switches |64 and starting the motors 43 in unison to operate the machines.

'I'he line |56 transmitting the photo-electric impulses is then switched in at |51, Fig. 22.

When the image has been reproduced each machine may be automatically stopped by opening the power circuit |65 as by a circuit breaker |61 on the base 30 of the machine, Fig. 2. The circuit breaker |61 is so positioned in relation to the sub-carriage 34 .that when the latter has reached a certain position to the left it will throw a lever |66 to separate the contacts on the circuit breaker |61.

Hitherto the grid glow tube has been limited in its application in electrical devices to its use as a relay. It has the advantage of being-very sensitive, instantaneous in response, and in supplying an output current relatively high in value, but iixed in intensity. The output current does not vary with variations in the input except to a very limited degreeunder special conditions, and the grid glow tube could not be employed to amplify variations in the photo-electric cell to produce half-tone cuts or to produce similar reactions or effects.

However, by a novel arrangement of circuits and combination of a plurality or grid glow tubes, I am enabled to obtain any desired number of graduated valuesin the output, each a function of the illumination on the photo-electric cell. It is adaptable to the operation of various electrical devices but is herein shown and described in connection with the production of half-tone cuts.

The schematic diagram in Fig. 24 shows six grid glow tubes and circuits as applied to the control device of Fig. 17. The grid glow tubes |69 are connected in parallel with the series part of the circuit which includes a source of direct current supply |1| and a circuit breaker |39 of Figs. 17 and 18.

A current limiting resistor |12 to prevent overloading, and the electro-magnets |35 of the control device, are connected in series with each tube |69 which, when it breaks into a glow and passes current, energizes that electro-magnet with which it is in circuit.

The grid resistor passes a little current and brings the potential of the grid near to that of the cathode, preventing the glow discharge and flow of current when the photo-electric cell is dark and passesv no current between the anode and grid. When the resistance of the photoelectric cell 9| is decreased by illumination and the value of the resistance |11 in the path to the grid of any given tube is not too great, the potential of the grid is brought nearer to that of the anode and the tube breaks into a glow and passes current.

The resistance 11 of each unit is so adjusted that one is .greater than the other so that, as shown in the drawings, the lowermost unit will operate with the minimum illumination on the cell. As the illumination is increased and the resistance of the photo-electric cell thereby reduced, more and more units will be thrown into a glow.

The circuit breaker |39 serves to interrupt the current supply of the tubes and stop the glow discharge thereof. The quantity of current passed by each tube being substantially the same, the tension of the springs |38, Figs. 17 and 18, is adjusted to offer the same resistance against the pull of the electro-magnets |35..

All the electro-magnets |35 may be connected in series in the main part of the circuit |10 so that the current passed by every tube will flow through all the electro-magnets. When so connected the current iiow will increase as more and more tubes break into glowl the tensions of the springs |38 determining the number of armatures drawn up.

v'Ihe schematic diagram shown in Fig. 25 is similar to that of Fig. 24. Here the circuit |10 is shown energized by an alternating current supplied as by an alternator |18. The circuit breaker |39 of Fig. 24 is not needed in this circuit as the discharge glow of the tubes is stopped in each cycle of the alternating currentwith the fall of potential. In addition to the grid resistors |15, grid condensers |19, are shown introduced in the coupling between' the grid |13 and the cathode |14 of 'each tube.

For convenience here, as inthe diagram of Fig. 24, the values of the resistances |11 between the anodes and grids have been shown graduated to control the glow discharges. ject may be accomplished by graduating the capacities of the grid condensers |19 or the resistances |15 between the cathodes and grids or that of the current-limiting resistors |12, or by a combination of some or all of them. The photoelectric cell may be connected in series with the couplings between the cathode and grid instead of that between the anodes and grids, as shown. In such case, the tubes will breakinto glow when the photo-electric cell is dark and cease to glow when illuminated.

The grid glow tubes |89 are connected in parallel as to each other and in series with an electrical device which they are intended to operate and control. As a representative type a solenoid |80 is shown in Fig. 25 connected in the circuit |10. A plunger I8| in the solenoid carries the tool holder ||9 and the tool |01 on its lower end and is drawn down against the resistance of the adjustable spring \|82 by an electro-magnetic force depending upon the number of tubes passing current. The force applied is intermittent and always in the same direction, as the tubes pass current in one direction only. The solenoid |80 or an electro-magnet that may be employed in its place is applicable for the production of half-tones having a relatively large number 0i dots to the inch, where the depressions are smaller and of less depth, for it will be seen 'that the same current that controls the depth of the depressions must also provide sufficient energy to compress the material of the blank, whereas in the devices hereinbefore described a separate and more powerful source of energyis utilized to perform the latter function.

The rotor of the alternator |18 is geared to the shaft |46 of the machine so that the number of The same obalternations in the current generated will bear a fixed relation to the distance that the carriage 38 moves in a given period of time.

Referring to Fig. 26, the output from the last stage of a number of amplifiers |53 and |54 coupled to the photo-electric cell 9| may be utilized to operate the solenoid |80. The tool |01 is caused to move up and down by interrupting the illumination on the photo-electric cell 9| thereby interrupting the impulses in the output circuit |82. A revolving shutter |83 provided with two blades interrupts the illumination on the photoelectric cell 9| twice in each revolution of the shaft ||84 on which it lsmounted. 'I'he shaft |84 is geared to the shaft 48 of the machine so that the number of interruptions of the illumination on the photo-electric cell 9| and therefore the number of depressions produced by the tool |01 will bear a fixed relation to the distance that the carriage 38 travels in a given time.

As hereinbefore mentioned, the object of this invention may also be accomplished by cuttings made into the surface of the blank with a cutting tool in a novel manner.

Referring to Figs. 27 and 28, the tool |85 has a V-shaped cutting point, the ,depth of the cut determining the Width of the line produced. The tool is pivotally mounted on one end of an armature |86 of an electro-magnet |81 carried on the presser foot |43. at |88 and is provided with a at spring |89, the tension of which can be adjusted and set by a screw |90. `The spring |89 opposes the pull of the electro-magnet on the armature and normally holds it against a stop |31. the cutting point' of the tool |85 is just above the surface of the blank 39.

The electro-magnet |81 is connected in the output of one of thecircuits hereinbefore described. The current flowing through it is a function of the illumination on the photo-cell and determines the distance the armature-is drawn up and the depth of the cut resulting therefrom, which in turn determines the amount of printing surface removed from the blank.

The photo-electric cell 9| is caused to scan or traverse the illustration 31 and the tool |85 is caused to traverse the surface of the blank 39 to cut a. series of parallel lines thereinto.

As the width of each line under the influence of the photo-electric cell 9| varies along its length an image of the illustration is cut in the blank. When this image has been cut the illustration and the blank are again scanned or traversed to cut the blank and reproduce the image a .second time. This time with a series of lines that are cut across the rst image, preferably in perpendicular rela- 'Ihe armature |88 is pivoted In this position,

Cil

tion to the ilrst set, thereby producing a half-tone By mounting the illustration diagonally on its holder, both series of lines will lie diagonally across the image and the dots will give the wellknown diagonal effect thereto.

The two cutting operations, one in angular relation to the other, may be accomplished by pro- Viding the machine with means whereby the longitudinal and transverse feeding movements of the machine are interchangeable (not shown in the drawings). The tool would then be so mounted that it could be turned with its point as center to present its cutting edge in the proper direction for each cutting.

However, to avoid the complexity in the construction of the machine entailed in providing it with means whereby the longitudinal and feeding motions may be interchanged, I reset the illustration and the blank after the ilrst cutting and position 'them so that the second image will be reproduced with lines cut perpendicular to the iirst and will coincide with the'ilrst image.

I am enabled to do the resetting in a very simple manner, accurate and automatic, by means of the plates or intermediate-holders 4|! and 4|. It is not necessary to mark or otherwise mutilate the copy or the blank, and serves not only for producing half-tones of the same size, as the copy, yenlargements and reductions, but also serves to reproduce these copies in reverse direction. The illustration and the blank may be oi any size and shape and no special precautions are required in positioning themI on the holders.

The mode of operation is as follows: The ilrst image having been cut, the holder 49 with the copy thereon, is reset. It is removed from the `depression in which it rests, turned either to 'the right or the left through an angle of 90 degrees and replaced. Supposing it to have been turned to the left or counter-clockwise, the cor- Iner of the holderat |92 would then be located at |92' and a letter F representative of any portion of the copy would be positioned as shown in broken lines.

The holder 4| with the blank thereon is then reset. It is removed, also turned through an arc of 90 degrees, but -in the direction opposite to that in which the holder 40 is turned and then replaced. The corner |93 will then be located at |93', and the image |94 of the letter F on the blank will be positioned as shown in broken lines. The machine is then again started and the tool |85 will cut lines across those already there and reproduce a second image identical with the ilrst and coincident therewith.

The holders 40 and 4| are shown square in outline for convenience. They may be shaped and formed diiierently and may be provided with other means for mounting them on the machine for the two operations than by means of depres- .sions in the surface of the two carriages.

There will be coincidence of the two images under all conditions when the machine is so assembled that in the position as shown in Fig. 28 the lateral distance between the centers about which the holders are turned for resetting is the same as the lateral distance |95 between the point of the tool and the center of the beam of reflected light.

Although two'operations are required to produce a half-tone consisting of dots made by a cutting tool as above described, it nevertheless has the advantage of speed over the method of producing half-tones of the same character by means of a reciprocating compression tool; however, the resistance offered to compression makes possible a better control in correct reproduction. Moreover, a compression tool has greater endurance than a cutting tool which has frequently to be reground with extreme precision.

I claim:

l. In a device for photo-electrically reproducing an illustration on a blank from a copy, a tool, driving means operatively connected to said tool to reciprocate the same into the blank, said operative connection including collapsible means for rendering said drive ineiective, magnetic means tric current under the control oi the radiant energy passing from the said copy.

2. A tool, driving means operatively connected to said tool for reciprocating the same into the work, said operative connection including collapsible means for rendering said drive ineil'ective, magnetic means for holding said means from collapsing, whereby the depth of penetration of said tool is determined by the strength of said magnet and means for varying the strength of said magnet.

3. In a device for reproducing an illustration on a blank by photo-electric means or in other similar devices wherein an electro-magnet controls the operation of a tool, a tool, driving means operatively connected to said tool for reciprocating the same into the work, said operative connection including collapsible means for rendering said drive ineffective, magnetic means for holding said means from collapsing, whereby the depth of penetration of said tool is determined by the strength of said magnet and electrical means for varying the strength-of said magnet.

4. In a device for reproducing an illustration on a blank by photo-electric means or in similar devices wherein an electro-magnet controls the operation of a tool, a tool operatively coupled to an armature of a magnet, driving means operatively coupled to the core of said magnet, means for contacting the said armature and co're, whereby operative connection between the said driving means and the said tool is established, and electric means for varying the strength of the said magnet, whereby the strength ot the operative connection is determined, and the amount o1' work of the tool controlled thereby.

5. In a device for reproducing an illustration on a blank by photo-electric means or other similar devices wherein an electro-magnet controls the operation of. a tool, a reciprocating tool to operate on the blank, an electro-magnet, a lever cou-` pled to the said tool and to the armature of the said electro-magnet, driving means to. oscillate the said lever, the said armature coupling or the said tool coupling serving as a fulcrum therefor, depending upon whether the `magnetic hold on the armature or the reaction developed by the Work of the tool on the blank oiers the greater resistance to displacement of the lever at the respective couplings, means whereby the Said driving means reestablishes contact between the armature and core after same is broken and means for varying the input current of the electro-magnet.

6. The method of photo-electrically reproducing an illustration on a plate for printing, wherein circumscribed elementary areas are formed at the surface of the plate proportional to the radiant energy passed from related areas of a copy, consisting in subjecting the surface of the plate to the action of a tool to form a series of linear grooves therein under the control of the said radiant energy passing from the copy and then again subjecting the same surface oi the said plate to the action of a tool to form a series of similar linear grooves therein in angular relation to the first series of grooves and under the control of the said radiant energy passing from the said copy.

7. A device for photo-electrically reproducing a half-tone illustration on a printing plate from a pictorial copy, including means whereby a photo-sensitive device scans the said copy and an indenting tool traverses the said plate vin a series of rectilinear and parallel paths, said indenting tool having a tapered end substantially square in cross section and diagonally positioned in relation to the said rectilinear paths, driving means to reciprocate the said tool into the plate and means whereby the radiant energy passing from the copy, controls the operation of the said tool.

8. A device for photo-electrically reproducing an'illustration on a blank from a copy, including a tapered tool, means for reciprocating same into said blank, means for traversing said blank with said tool and a holder for said tool provided with means to allow the end of said tool limited lateral play, whereby it may advance with said blank, when traversing and engaged therewith.

9. In a device for photo-electrically reproducing an illustration on a blank from a copy, a photo-sensitive device for scanning the copy, a tool for traversing the blank, a driving shaft, means operatively connected to the said driving shaft to reciprocate the said tool into the blank, means operatively connected to the said driving shaft to traverse the said tool over the blank, electro-magnetic means for controlling the reciprocations of the said tool, and means responsive to the photo-sensitive device through the electro-magneticv means, whereby the radiant energy received by the photo-sensitive device determines the depth of penetration of the said tool.

10. in a device for reproducing an illustration on a blank from a pictorial copy, a photo-sensitive device, means for scanning the copy with the photo-sensitive device, a reciprocating tool to form a series of parallel lines of depressions in the blank, means whereby the depressions in adjacent lines are formed in staggered relation to each other, means for traversing the blank with the tool, electro-magnetic means for controlling the operation or the tool. and means responsive to the photo-electric device for varying the strength of current through the electro-magnetic means, whereby the radiant energy received by the photo-sensitive device determines the depth of penetration of the tool.

11. The method of producing a plate for printing a halftone illustration, which consists in preparing a smooth surface suitable for receiving ink from an inking roller on a plate having a porous texture and then compacting in succession portions of the plate at the said surface with a tool at regular intervals to depress elementary areas thereof below the reach of the inking roller.

OTTO WILLIAM GREENBERG.