US2532585A - Apparatus for the production of dot-composed negatives - Google Patents

Description

Dec. 5, 1950 L. M. VAN DER ROHE ET AL APPARATUS FOR THE PRODUCTION OF DOT-COMPOSED NEGATIVES 5 Sheets-Sheet 1 Filed June 26, 1946 m WATf/Fffff/SWANS Z ATTORNEY Illlllllllfllll lllllilllflll I Dec. 5, 1950 L. M. VAN DER ROHE ET AL 2,532,535

APPARATUS FOR THE PRODUCTION OF DOT-COMPOSED NEGATIVES 5 Sheets-Sheet 2 Filed June 26, 1946 WIIIXIIIIA Dec. 5, 1950 L. M. VAN DER ROHE ET AL 5 5 APPARATUS FOR THE PRODUCTION OF DOT-COMPOSED NEGATIVES Filed June 26, 1946 3 Sheets-Sheet 5 Patented Dec. 5, 1950 APPARATUS FOR THE PRODUCTION OF DOT-COMPOSED NEGATIVES Ludwig Mies van der Rohe and Walter Peterhans,

Chicago, 111.

Application June 26, 1946, Serial No. 679,308

4 Claims. (01. 88-24) This is a continuation-in-part of patent application Ser. #430,974, filed February 14, 1942, now abandoned, the latter being a continuationin-part of patent application Ser. #252,654, filed January 24, 1939, which has matured into Patent #2282337 on May 12, 1942.

Our invention relates to photography, and more particularly to an apparatus for the production of dot-composed or screened negatives.

The conventional apparatus for the production of dot-composed negatives require the use of a half-tone screen of substantially the same size as the negative. Half-tone screens are comparatively expensive, and, if a half-tone screen exceeds a certain size, the costs of manufacture of such large half-tone screens becomes so high, that they are burdensome for the trade. Therefore, hitherto placards or other large sheets bearing reproductions of images have been usually manufactured in such a manner, that a plurality of small dot-composed negatives are produced by the use of small half-tone screens and an equal number of electrotypes are prepared from said negatives. Each of said electrotypes is used for the reproduction of images forming a portion of the entire image on small sheets, and several individual small sheets are then pasted on a board to form in combination a placard showing the entire image.

An object of our invention is to provide an apparatus, by means of which a small half-tone screen may be used for the production of a continuously coherent dot-composed reproduction of a positive on a negative of any larger size than that of the half-tone screen, so that the available half-tone screens of small size only may be used for the production of large sheets bearing reproductions, such as placards, wallpaper, etc.

With the above and other objects of the invention in view, the invention consists in the novel construction, arrangement and combination of various devices, elements and parts, as set forth in the claims hereof, certain embodiments of the same being described in the speciiication and being illustrated in the accompanying drawings forming part of this specification, wherein:

Fig. 1 is a diagrammatic top plan view, partly in section, of an apparatus according to the invention,

Fig. 2 is a view of a portion of a half-tone screen and a mask in an enlarged scale,

Fig. 3 is a diagrammatic view of a negative and a half-tone screen, the latter being shown in its starting position and in its end position,

Fig. 4 is a diagrammatic top plan view, partly in section, of another embodiment of an apparatus according to the invention, wherein the half-tone screen is moved step by step,

Fig. 5 is an elevational view of the half-tone screen and the mask of the apparatus shown in Fig. 4, in an enlarged scale,

Fig. 6 is a sectional view taken on line 66 of Fig. 5,

Fig. '7 is a fragmentary elevational view of a half-tone screen and a mask equipped with automatic means for causing a predetermined stepby-step movement of the half-tone screen,

Fig. 8 is an elevational view, partly in section, of a latch mechanism shown in Fig. '7, and

Fig. 9 is a diagrammatic perspective view of the shutter, the objective, the half-tone screen, the mask, and driving means of another embodiment of an apparatus according to the invention, wherein the half-tone screen is continuously moved.

Referring now to Fig. 1, It! generall indicates a camera, which is mounted on a base I2 in any suitable manner. A mounting l4 rigidly secured to the base i2 by suitable means is arranged opposite the objective 23 of the camera It having a lens 25. A positive I8 may be attached to said mounting M in any suitable manner. A negative 23 in the shape of a film or a plate may be attached to a stationary holder 32 arranged inside the camera Hi. Thus, the positive 3 and the negative 28 are held in a fixed position with respect to each other and to the optical axis of the objective 23. An opaque endless belt or mask 40 surrounding the negative 23 is guided by rollers c2 rotatably mounted in a frame 4 Said mask 46 is provided with a window 54 receiving a half-tone screen 30 or" a size smaller than the size of the negative 23. The half-tone screen has a plurality of opaque dots 53 and transparent dots 59 as best shown in Fig. 2 in an exaggerated scale. According to Fig. 1, one of the rollers 42 is provided with a handle 56, so that the mask 48 and the half-tone screen 3c may be moved in close proximity to the negative 28 so as to place consecutive portions of the negative behind the half-tone screen. The portions of the negative not placed behind the half -tone screen are shielded by the mask 4%. A shutter generally indicated by 6%, which may be actuated by a suitable wire release or trigger (not shown), may be used for exposing such consecutive portions of the negative 28 to corresponding consecutive portions of the positive I8. According to Fig. 2, the trailing edge GI and the leading edge 62 of the window 5:3 of the mask as are parallel to each other. The distance cl between said edges BI and 62 is in such a predetermined relationship to the pattern of dots 53, 59 of the half-tone screen 3% arranged in the window 54, that the pattern of dots of the half-tone screen appearing in the window adjacent the trailing edge BI represents a continuation of the pattern of dots of the half-tone screen appearing in the window adjacent the leading edge t2.

When the apparatus shown in Fig. l is used for the production of dot composed: negatives by step-by-step movements of the half-tone screen 30 and the mask lit, at first the handle 56 is rotated so as to bring the half-tone screen 33 into a position in front of the portion a of the negative 28. When the half-tone screen 3% is at a standstill in said position in front of the portion a of the negative, a first exposure is made by an actuation of the shutter 68, so that the portion a of the positive I8 is reproduced through the half tone screen on said portion a of the negative 28. After said first exposure has been made, the handle 55 is turned so as to displace the halftone screen SE! is the direction A through a distance equal to its width 01' appearing in the window 5; of the mask to, whereby the half-tone screen is brought into a position in front of the consecutive portion 2) of the negative 23. Now, whenthe half-tone screen 39 is at a standstill in said. position in front of the portion b of the negative, a second exposure is made by means of the shutter 5%, so that the consecutive portion 1) of the positive I8 is reproduced through the half-tone screen on said portion 12 of the negative. As will be readily understood from Fig. 2, said displacement of the half-tone screen 33 in the direction A through a distance equal to its width (2 brings the trailing edge 6| into a position previously occupied by the leading edge 82. Therefore, the pattern of dots produced during said second exposure by means of the half-tone screen 39 on the portion 2) of the negative 28. is in continuity with the pattern of dots produced during the first exposure by means of the halftone screen on the portion a of the negative. After said second exposure, the half-tone screen 38 is again displaced in the directionA through a distance equal to its. width d, until it reaches a position in front of the consecutive portion of the negative 28. Thereupon, when the halftone screen is at a standstill, a third exposure is made for reproducing the consecutive portion 0 of the positive I8 through the half-tone screen on the portion 0 of the negative. Thus, a continuously coherent dot-composed reproduction of. the positive composed of a plurality of separate reproductions of consecutive portions a, b, c of the positive I8 is prepared. The dot composed negative thus obtained may be removed fromv the camera and may be used for the production of an electrotype according to any conventional process. Fig. 1 illustrates the three steps a, b and c for the production of a dot composed negative; it is understood, however, that a larger number of steps is used, when the width of the half-tone screen is smaller inproportion to the length of the negative.

According to the embodiment of an apparatus shown in Figs. 4-6, again the camera I I0 is mounted on a base H2, and the positive H8 attached to the stationary mounting He and the negative 523 carried by the holder I32 are held in a, fixed position relative to each other and to the optical axis of the objective I2 5. The halftone screen I36 is mounted in a carriage I53 having rollers I6 for engagementwith stationary tracks I85, I56 arranged in the camera H8. The

ends of a flexible opaque mask I 58 laid around rollers M2 journalled in stationary parts of the camera iii are secured to the carriage I63 by screws Iii'i in such a manner, that the trailing edge It! and the leading edge I52 are in the same relationship to the pattern of dots of the half-tone screen I38 as described above in connection with the trailing edge iii and leading edge $2 of the window 54 of the mask 40 shown in Fig. 2. The half-tone screen ISiB arranged in the carriage its. connected with the mask I i!) may be moved along the tracks :55, 258 by rotating a handle I53 arranged on one of the rollers I52. A series of equally spaced indicating marks M1, M2, M3 are arranged on the track I65. Said indicating marks M1, M2, M's are at a distance e from each other equal to the width at of the halftone screen I30 appearing in the window I54 of the mask MS. Furthermore an indicating arrow or indicating means M is arranged on the carriage I63 for cooperation with said indicating marks M1, M2, M3. The indicating arrow M and the indicating marks M1, M2, M3 are visible through a window (not shown) of the camera.

When the apparatus shown in Figs. 4-6 is used, at first the half-tone screen I39 is displaced along the tracks 965, I55, until the indicating arrow M is in register with the first indicating mark M1 of the series of indicating marks M1, M2, M3, so that the half-tone screen I3!) is in front of the portion a of the negative I23 as shown in Figs. 4 and 5. Now, when the half-tone screen I35! is at a standstill, a first exposure is made by an actuation of the shutter I58 for the reproduction of a portion of the positive on said portion a of the negative I28. After said first exposure, the half-tone screen I33 is moved by a rotation of the handle I55, until the indicating arrow M is in register with the second indicating mark M2, so that the half-tone screen is displaced one step through a distance equal to its width d into a new position in front of the consecutive portion b of the negative. When the half-tone screen is at a standstill in said new position, a second exposure is made. Thereafter, the half-tone screen is moved another step, until the indicating arrow M appears opposite the third indicating mark Me, so that the half-tone screen is in front of the consecutive portion 0 of the negative. Now, the half tone screen being at a standstill, a third exposure may be made. Thus, the indicating marks M1, M2, M3 in cooperation with the indicating arrow M represent spacing means serving as controlling means for the determination of the proper stepby-step movement of the half-tone screen, so that the exposures may be carried out at the proper moments when the half-tone screen is. moved into a position wherein an exposure produces a pattern of dots on the negative in continuity with the pattern of dots produced by a preceding exposure.

Fig. 7 illustrates a mask and half-tone screen arrangement with mechanical controlling means for the step-by-step movement of the half-tone screen, which may be substituted for the mask and half-tone screen arrangement of the apparatus shown in Figs. 4-6. According to Fig. "I, t -e carriage I63 holding the half-tone screen E3!) is slidably engaged with the stationary tracks 55, I .arranged inthe camera Hi); The ends of the flexible mask I40 are secured to the carriage I63 in the same manner as described above in connection with Fig. 5, so that the edges I'6I and I62 are in the proper relationship to the pattern of dots of the half-tone screen I30. A series of latch-mechanisms generally indicated by L1, L2 to be described hereinafter is attached to the track I65. The various latch-mechanisms are spaced from each other at equal distances, so that the distance between the effective edge of the stopping means I68 of adjacent latchmechanisms equals the width at of the half-tone screen I30 appearing in the window I54 of the mask I40. An abutting member I04 is attached to the carriage I63 for cooperation with the effective edge of the various stopping means I68. As best shown in Fig. 8, each stopping means I68 comprises a member I 69 swingably mounted on a pin I10 arranged on the stationary track I65. An adjusting screw I1I having the effective edge I12 for cooperation with the abutting member I84 is screwed into threaded bores of the swingable member I69. A locking element I13 screwed on the threaded shaft of the adjusting screw Iii may be used to hold same in a predetermined adjusted position. A latch I14 swingably mounted at I15 on a plate I16 secured to the track I65 is arranged for cooperation with the edge I11 of the swingable member I59. A spring I18 ar ranged between a flange I19 0f the plate I16 and the latch I14 tends to urge normally the latch against a stop I00, so that the latch is in engagement with the swingable member I69 and holds the effective edge I12 of the adjusting screw I1I in the path of the abutting member I84. Each latch-mechanism L1, L2, is provided with an electromagnet I8I arranged opposite the latch 214. Each electrofnagnet I8I may be individually energized for lifting the latch I14 into the position I14 shown in dash and dot lines in Fig. 8. The carriage IE3 is under the action of a. load I82 connected with the carriage by a cord I83 laid around a roller I85 as shown in Fig. 7. Said load I82 urges the abutting member I34 of the carriage I'63 against the effective edge I12 of one of the stopping means I68 normally held in the path of the abutting member by the spring loaded latch I14.

When an apparatus equipped with the mechanism shown in Figs. '1 and 8 is used, at first the movable half-tone screen is brought into the position shown in Fig. '1, wherein the abutting member I84 abuts against the effective edge of the stopping means I68 of the first latch mechanism L1, so that the half-tone screen I is at a standstill in front of the first portion of the negative. Thereupon, the first exposure is made. After said first exposure, the electromagnet I8I of the first latch-mechanism is energized, whereby the latch I14 thereof is lifted into the position I14 shown in dash and dot lines in Fig. 8, so that the abutting member I84 being under the action of the load I82 may swing the stopping means I68 about the pivot I10 out of its path into the position IE8 shown in dash and dot lines in Fig. 8, whereby the half-tone screen I30 is automatically displaced one step through a distance f equal to its width d, until the abutting member I84 hits against the effective edge of the next stopping means I68 held in its path by the spring loaded latch of the next latch mechanism L2. After the passing of the abutting member I84 under the stopping means I68 of the first latch mechanism L1, the stopping means of the latter returns by its own weight into its normal position shown in full lines in Fig. 8, whereupon the electromagnet I8I of the first latch-mechanism may be deenergized for causing a locking of the stopping means by the spring loaded latch I14. Now, when the half-tone screen is held by the stopping means I68 of the latch mechanism L2 at a standstill in front of a second portion of the negative being consecutive to the first portion of the negative, a second exposure may be made. After said second exposure, the electromagnet I8I of the second latch-mechanism is energized, whereby a further step-movement of the half-tone screen is obtained in the same manner as described above. The step by step movements of the half-tone screen and the exposures between the steps when the half-tone screen is held in its position by a stopping means of a latch-mechanism may be repeated as often as necessary in dependence on the number of latch-mechanisms arranged in the apparatus.

According to Fig. 7, the various latch mechanisms L1, L2, the number of which corresponds to the number of step-displacements to be carried out by the half-tone screen, are arranged only on the upper track I65. If desired, however, an equal number of latch mechanisms may also be arranged on the lower track I66 for cooperation with a second abutting member secured to the carriage I63 holding the half-tone screen I30.

For the sake of simplifying the explanation of the apparatus with a controlled step-by-step movement of the half-tone screen, the assumption has been made above, that the distance c between the indicating marks M1, M2, M or the distance between the efiective edges I12 of the various stopping means I68 of the various latchmechanisms L1, L2 is equal to the width d of the half-tone screen appearing in the window I54 of the mask I49. This assumption is correct, if the half-tone screen is in contact with the surface of the negative. In practice, however, there may be a slight space I99 (see Fig. 6) of a thickness of a few millimeters between the half-tone screen I30 and the negative I28. If this is the case, the distance between adjacent indicating marks or the distance between the effective edges of adjacent stopping means should be slightly larger (about to 2 millimeters) than the width at of the halftone screen. The exact length of the distance may be readily found by calculations or a few experiments. The adjustable screws I1I of the embodiment shown in Figs. 7 and 8 permit an easy adjustment of the exact distance between the effective edges I12 of adjacent stopping means I68.

During above described methods for the reproduction of dot composed negatives the half-tone screen is moved step by step. However, the method for the reproduction of dot composed negatives with the positive and negative held in a fixed position relative to each other and to the optical axis of the objective may also be carried out with a continuous movement of the halftone screen.

Fig. 9 illustrates diagrammatically the mechanism for a continuous drive of the half-tone screen and for making automatically exposures in timed relationship to the movement of the half-tone screen. It is understood, that the tracks 265, 266, the slidable carriage 263 holding the screen 230, and the flexible mask 245 laid around the rollers 242 take the place of the corresponding elements of the apparatus shown in Figs. 4 and 5, when an apparatus according to the invention is designed for a continuous movement of the half-tone screen. According to Fig.

9:22; threaded spindle 236 is'rotata-bly but axially immovably arranged in, brackets 2E1 mounted on the stationary track 266. An element 238 attached to; the carriage 263 has athreaded bore in engagement with the threaded portion of the spindle 28-6. A sprocket wheel 289 is keyed to one end. of said spindle 286. 7

Another sprocket wheel 296 of exactly the same size and shape as the sprocket wheel 28% is keyed; to ashaft 25I journalled in suitable bearingslnot shown) of the apparatus. Furthermore, a disk-like shutter. 286 is keyed to said shaft 29 I, so that said shutter 26% may be rotated by a rotation of. the sprocket wheel 298. The shutter 260 arranged in front of the objective 223 has a series of equally spaced openings 292 each having a width 9. being a predetermined fraction of the distance 71, between adjacent openings.

A further sprocket wheel 293 is keyed tothe driving shaft 295 of an electromotorZtii. Furthermore, an idling wheel 29a; is loosely but axially immovably arranged on said shaft 294-. A chain 291 is trained around the sprocket wheels 2.89, 2.98, 293 and the idling wheel 28B. will be readily understood. a rotation of the driving. shaft 294 of the electromotor 295 causes a rotation of the threaded spindle 28% and the disklike shutter 266 at the same speed, as the sprocket wheels 289 and 29s are of ,the same size. Furthermore, as the half-tone screen 232' is moved along the negative I28 carried by the holder 32 by a rotation of. the threaded spindle 255 and as al ght flash is produced every time an opening 2-92 of the rotatable shutter Ziiil passes the objective 223, light flashes will be produced in a predetermined relationship to the movement of the half-tone screen 239.

As an example for the various relationships between the mechanismsv of the apparatus for the production of. a continuously coherent dotcomposed reproduction of a positive on negative the following dates may be given:

Assume that the negative 828 has a length i of 1- meter (see Fig. '3) and that 400i) dots 2&8 are to be produced at extremely small equal distances in a row on said negative I28 during a continuous movement of the half-tone screen 239 at a constant speed in the direction of the arrow B from the starting position shown in full lines into the end position 238 shown in dash and dot lines. Furthermore, suppose, the half-tone screen 2 38 has a width 02 of meter. Under these circumstances the half-tone screen 239 is to be moved into the position 230 through a distance z'+d=l /1o meters, and 440!) instantaneous exposures are to be made at regular intervals. As mentioned above, 400G dots are tops reproduced on the length i=1 meter of the negative HS; consequently, each dot has a width of /4 meter or A; millimeter, and likewisathewidth 5 (Fig. 2)- of a transparent dot of the halt-tone screen 239= A millimeter.

Furthermore, assume that the spindle 235 (Fig. 9) has 10 threads ercentimeter; that the shutter 260 has four open gs each having a width g= of the distance it between adjacent openings, and that the shutter make 1' revolution per second. Then the half-tone screen FEM-will: move 1 millimeter durin se ond or mi limeter during' ,4, of a seco furthermore, a light of 4 of a second will: pass through the halt-tone screen every 4 of, second.

As mentioned; above, each transparent dot. of the half-tone screen has a width of A; of a millimeter and the, half-tone screen ismoved /4 of a millimeter during ofa second. Therefore, the transparent dots of the half-tone screen are moved through a distance equal to their Width during 4 of a, second. Moreover, as mentioned above, a light flash of Of a second passes through the half-tone screen every A; of a second. In other words, the. time or" the instantaneous exposure is ,4, of second, the time required for relative movement between the negative 528 and half-tone screen for a distance of millimeter equal to thewidth of millimeter of a. transparent dot of the half-tone screen.

The data given above are to be taken only as an example. Satisfactory results are obtained if the instantaneous exposures made automatically by the shutter at moments, when the half-tone screen is moved into a position wherein its transparent dots pass over the loci of the prospective dots on the negative, take about 0 to /20 0f the time required for a movement of the half-tone screen through a distance equal to the width of a transparent dot of its pattern of dots. Furthermore, of course, a different type of a controlling mechanism could be used to obtain said features.

We have described preferred embodiments of our invention, but it is cle 1' that numerous changes and omissions may be made Without departing from the spirit or our invention.

What we claim is:

1. In a photographic apparatus for the-production of dot-composed negatives from a positive, a stationary holder for a, negative in said apparatus, a negative disposed in said holder, a mask adjacent said negative and having a Window, and a dot-composed half-tone screen mounted in said window and adjacent said negative and being smaller than negative and including a pattern of alternating transparent and opaque dots, each two adjoining like dots bein spaced from each other for a certain distance in a predetermined direction, said screen being movable, with said mask, along said negative in a direction at a fixed angle to said predetermined direction, in combination with, means for moving said screen from one position to another along said negative comprising guiding means and a series of registry means intermediate said movable screen and said stationary holder, said registry means arranged to be spaced from each other for a distance constituting a multiple of said certain distance for preserving substantially exact dot-pattern continuity on said negative throughout the screen reproductions, and comprising a latch secured with relation to said screen and movable therewith, and a series of alt utrlent means spaced from each other for said last named distance and associated with relation to said stationary holder and operable to bemoved into the path of said latch engaging the same and to be moved out of said path for disengagement from said latch and for subsequent movement of said screen, and electrically controlled means for impelling said abutment means at leastv during one of said movements.

2. In aphotographic apparatus for the production of dot-composed negatives from a positive, a stationary holder for a negative in said apparatus, a mask adjacent said negative and being movable along the same and having an opening, and a dot-composed half-tone screen mounted to said mask at s -d openin and movable therewith and disposed adjacent said negative and being smaller than said negative and including a ipattern of alternating transparent and opaque dots, each two." adjoining like dots being spaced from each other for a certain distance in a predetermined direction, in combination with, means for moving said screen and mask, and registry means for holding said screen in selected positions opposite said negative and comprising, a latch carried at least with relation by said screen and movable therewith, a series of spaced abutment means movable in and out of the path of said latch and having a surface for engagement with said latch and disengagement therefrom to stop said screen at selected positions in its move under the impulse of said driving means and. to release it for subsequent resumed move, respectively, each said surface spaced from an adjoining surface for a dis tance, adjusting means associated with each abutment surface for varying said distance to a (predetermined multiple of said first named certain distance for preserving substantially exact dot pattern continuity on said negative, and electrically controlled means operable to move said abutment means out of said path for latch release.

3. In a photographic apparatus of the class described, in combination, a dot-composed screen movable in front of a stationary negative, said screen arranged to produce a dot-continuous image in step-by-step repeated exposures when moved for at least a single accurately predetermined distance, and means for moving said screen along said negative for a multiple of said distance comprising driving means for movement of said screen in one direction, registry means for said negative and screen including a latch associated with said screen, a series of latch engaging members spaced substantially for said last named distance and independently of the movement of said screen movable in and out of the path of said latch, and adjusting means for each of said engaging members to vary the posi- 10 tion of effective engagement between said latch and a member said adjusting means including a screw and a threaded holder surrounding said screw and said screw being rotatable for axial movement within said holder.

4. In a photographic apparatus of the class described, in combination, a dot-composed screen including adjoining light and opaque spots and movable in front of a stationary negative, said screen arranged to produce a dot-continuous image in step-by-step repeated exposures when moved for at least a single accurately predetermined distance, and means for moving said screen along said negative for a multiple of the combined width of a light and opaque spot comprising driving means for movement of said screen in one direction, registry means for said negative and screen including a latch associated with said screen, a series of latch engaging members spaced substantially for said last named distance and independently of the movement of said screen movable in and out of the path of said latch, adjusting means for each of said engaging members to vary the position of effective engagement between said latch and a member, and a solenoid interconnected to an electric circuit and operable to efiectuate at least one of the movements of each of said members.

LUDWIG MIES VAN DER ROI-IE. WALTER PETERHANS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,226,838 Wolber May 22, 1917 2,356,363 Thompson Aug. 22, 1944

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