US2510863A - Exposing apparatus for the making of photographs, photoprints, negatives, and the like - Google Patents

Description

June 6, 1950 w. M. BUSKES 2,510,853

EXPOSING APPAR FOR THE MAKING OF PHOTOGRAPHS,

PHOTOPR NEGATIVES, AND THE LIKE 1 ed Oct. 9, 1946 IQTTORNEKS Patented June 6, 1950 EXPOSING APPARATUS FOR THE MAKING OF PHOTOGRAPHS, PHOTOPRINTS, NEGA- TIVES, AND THE LIKE Willem Marie Buskes, Velden, Netherlands, as-

signor to Chemische Fabriek L. van dcr Grinten, Venlo, Netherlands, a company of Netherlands Application October 9, 1946, Serial No. 702,162 In the Netherlands October 11, 1945 8 Claims.

This invention relates to improvements in exposing-apparatus for the making of photographs, photo-prints, negatives and other photo-prints.

In the normal contact printing from transparent originals, including negatives, positives, drawings, letters, on sensitized sheets and also in the production of reflex-copies or screen reflexcopies by means of sheet like materials, exposingapparatus are commonly used, in which the material to be exposed (i. e. the original in contact with sensitized sheet), is moved in relation to the luminous source.

The most common form of apparatus are those having a curved unperforated or solid panel, over the outer wall of which is moved an endless conveyor cloth. The material to be exposed is placed between the conveyor cloth and the panel and is caused to slide over the surface of the panel, on the other side of which are one or more sources of light.

With this type of apparatus it sometimes happens that at any rate, part of the material to be exposed and which is moved over the panel (which, in normal contact printing is the original: in refiectography, the sensitized, possibly screened sheet or the separate sheet-like screen) adheres to the panel, while the sensitized paper or original in contact with the conveyor cloth is moved forward. This sticking (i. e. the exposed material is checked or impeded, it sticks fast, thus it lags or is retarded) will sometimes last for some time but even when it is of short duration (only a second) the two layers, due to the speed of the exposure-apparatus, will have shifted several centimeters relatively to each other, so that a true contact-copy is out of the question.

This sticking which tends to occur particularly with films that have a smooth or glossy surface can, in dry atmosphere, probably be attributed to frictional electricity; in moist atmosphere it occurs mostly at the beginning of work, or when the surface in contact with the panel is itself moist. This is the case when a diazotypeprint on film (e. g. superficially saponified cellulose-esterfilm) is developed by means of a thin film of a liquid developer and shortly thereafter serves as original for further copying by the normal contact-printing method.

To overcome this sticking, special exposure apparatus have been proposed comprising either a rotatable glass cylinder or an extra transparent belt in addition to and movable with the conveyor cloth. These apparatus are not only complicated, but have other objections. Thus with the combined transparent belt and con veyor cloth in which the transparent belt is not endless, the work only can be continued for a limited time. Thereafter the device has to be readjusted before it can be restarted. Likewise with co-rotating glass cylinders of larger dimensions, there is the objection, that they nearly always contain one or more bubbles, which upon each revolution are reproduced on the sensitized material.

In practice therefore, the earlier type of panel apparatus firstdescribed has been retained and although attempts have been made to overcome sticking and other difficulties by replacing the panel by a perforated plate, this has not been applied in practice.

This invention is concerned with exposureapparatus of the earlier type, having an unperforated or solid glass or other light permeable panel, and conveying-devices for conveying the material to be exposed, which is made up of at least two layers (an original and the sensitized sheet) that move over the panel in contact with one another. According to the invention, the operative surface of the panel over which the material moves, is uneven and possesses projections and depressions over its whole working area in such number and of such form, that the chance of sticking is reduced, if not eliminated when a smooth surfaced film of a size of the operative surface is moved over it. The projections may take the form of ridges, ribs or suchlike.

With certain uneven structures, however, another type of relative displacement between the layers of the material to be exposed is liable to occur and this displacement will henceforth be termed shifting. .Whereas sticking occurs oftener with a smooth than an uneven surfaced panel and mainly with smooth films only and when it does occur, mostly causes an appreciable displacement between the layers or at least displacement over a relatively great distance, which varies with every exposure, the displacement due to shifting only occurs for a certain type of uneven panel and shows up both with smooth and other films or materials. While this displacement is practically always the same it does not occur at all with a smooth wall. Sticking and shifting are therefore different phenomena. On a closer examination of the shifting the following appeared i. e.: a

The relative displacement due to shifting is which the material to be exposed is moved over These factors are not however' ofparamount-iniportance in practice.

The most important consideration in addition to the distance through which the material "is moved is the average space between thehigh spots of the surface of the panelywhich -in carrying out the invention is by preference made small,

and by choice such that the mutual shifting of the layers of the material tobe'expo'sed, that occurs during movement over'thepanel', amounts,

in the course of a single stretch "of exposureto less than 0.03 mm. (for ordinary photo-prints still just admissible). Where the elevationgconsist of parallel crests and troughs,-then'-=it-appears that their direction in relation tothe direction of movement has an effect on the shifting so .that this factor should be taken intoaccount.' 1 The-uneven surface on the wall of the panel may. be obtained by small"parlticles bfflaisiibstance that hardens ,or by ,attaching' strips or other pieces of suitable material to it; 'ithowever is',preferred tohave the elevationsincorporated in. the material of the panel. These so-called uneven surfaces especially in conditions of'corisiderable moisture show a considerable .diminutionof. .sticking in comparison with the'norm'al (smooth) surface. Practically no shifting"iwill occur where a glasspanel is' brought into "a condition of dullness b rubbing it with anemery powder or" by means o'f's'and blasting and then polishing on the tops of the. "elevations" so formed in the surface; such as with colcoth'aror by melting or grinding. It goeswithout-saying, that. the latter process must not be carried out to such-ah extent that a smooth 'or nearly smooth r surface is again obtained. Tests have shown thata reasonable rounding off of the elevations has adesirable effect.

.A glass surface. .over which the elevations are regularly distributed may for instance be obtainedby covering the spots that must remain as elevations and by deep etching the remainder of .the surface. This method is not only suitable for coarse, but for fine structures, "e...g...as"fine" as that of the screens. used in the. technique .of printing. and in screen reflectography;

Good" results can be secured with panes of fine cathedral glass, finely figured glass, finely ribbed glass, crystal glass, engraved glass, ornamental glass and similar'kinds of glass with an uneven surface, many kinds'or'which are"available"in commerce. M

The structure should by preference be such that the quantity oflight'passingto'the material to be exposed "(estimated for 'the full length or stretch of ex osure) does not vary appreciably in directions transverse'to the direction fmoves ment. When using ribbed'tglass; the direction of the ribs should "thereforenot be selected'to coincide'with the direction'of movementi 1 .From tests withregularly spaced" elevations soihe'furth'er rou'glr'lins of conduct couldbe obtained. "Thediminution in the chances of sticking, especially .when considering .conditionso'f' extreme' moisture, which this invention'has' rendered possible, for those film-'materialsthat are most liable .to stagnate in practice under such conditions, and which-must rncve along'the'wall pervious to light,'is little dependent o the'deconveyor cloth i5, guided and 'tensioned' gree of coarseness or fineness of the structure, although for other reasons finer structures are to be preferred. It is obvious that the fining down --of the-structure can-not be continued ad infinitum', 'sincea smootnsurface would once again result. An experimental surface with distances of 25 mu between the crests or elevated portions of the structure has yielded excellent :-results. Tests further 'show that in general it is desirable for the ratio between the mean heights of .the crests or elevations and the intervals sepa- 'rati'ngadjacentcrests to be greater than 0.1.

Moreover .it isadvantageous to so dimension the relative areas occupied respectively by the crests and hollows that the former do not cover =more than' h alt' the total surface of the panel. "In-many cases this also results in the surface being easier to make. coupled with technical requirements (e. g. a rea- Technical feasibility tion and-hence the chance of the material when traversing the apparatus during exposure being creased, is 1essene.d.' This maystill further'b'e diminished by using a ribbed surface with ribs transverse to the line .of movement'so that it has a stretching influence on the material to be copied. V The invention is illustrated in the accompanying drawings in which Figs. 1=tof5 are diagrammaticplanviews of various types of glass surfaces prepared-aocording to the invention ---Fig. -6 is a sectional view showing anexposure apparatus with material to be+ex posed imposition. Figs. 7, 8-and-9 are part .plan views of alternative types :of surfaces. a #Fig. 10 is a vertical section of the main part ofan exposure machine, illustrated somewhat diagrammatically. I

-The light source (a mercury vapour tube) is indicatedin Fig-l0 by H.- It is located before the reflector I 2 -The light pervious panel l 3 especiallyis made accordingtothe invention, having numerous depressions and smooth top projections on its surface in .thewhole :area' with which the material to-be exposed-*will come in contact. The light emitting surface of the panel '3' is indicated by H."- Along thi surface 1-4 the material to be exposed is'-m-oved-by-"m'eans of the by three rollers'lflbneof which-is driven.

'The material to be exposed consists of a layer Illand 'a'-- layer In normal contacfprinting the layer [9 "is transparent original and the layer 2E9 the light sensitive manner; In "normal reflex copying processes 'the' layer l'll isth-light 7 sensitive materialand the-layer 20 the oiiginal.

The materialto be'exposed is'laid down ont'he table 'IBIand movedon to thesurface by means ofithe guidi'ng'm'ember n. Referring'n'owto Figs. 1 to '5, the ribs consti- 5. tuting the crests of the uneven surface are shown by the full lines.

In the arrangement of Fig. 1 the ribs extend diagonally from the central zone of the panel in a direction to the sides thereof so that the angles formed in the central zone are directed like wedges against the direction of movement of the conveyor cloth (Fig. 1). Thus the central zone, where it has a perviousness to light differing noticeably from the rest, will, by preference, be more or less diagonal to the line of transport (Figs. 25). It will be understood that in place of continuous ribbing, as shown in Figs. 1-5, also interrupted ribs, i. e. crests and troughs giving a serrated effect, may be employed.

Fine structure surface with a uniform perviousness to light enable the invention to be applied to automatic apparatus, in which the conveyor cloth carries the material to be copied to a zone where the whole of it is exposed, where it is held stationary till the exposure is complete and then removes it from the exposure-zone (of. The British Journal of Photography dated 18th August 1939, page XII. This adaptation of the invention has particular advantages, because with intermittenlty operating apparatus, the chance of sticking is considerable, in consequence of the speed of operation and repeated acceleration of the material.

The light pervious panel and the ribbing or other uneven surface thereon may, of course, be made of any suitable material, e. g. glass or high molecular glass like substances. It is desirable for the surface unevennesses to be of tough and/or hard materials so as to eliminate wear and tear. Glass, and for special purposes, quartz, are particularly suitable.

To obtain the most satisfactory effects a regards light saving it is, of course, desirable for all parts of the surface to be pervious to light and that the elevated portions thereof set up as little dispersion of light as possible either by refraction or reflection.

Referring now to Fig. 6, l indicates part of the panel underneath which is a source of light not shown having a ribbed surface and over which the material to be exposed comprising a transparency 3, a sheet of sensitized paper 2, a felt backing 5 and a weight 6, is moved. The material moves across the panel at a rate of 2 cm. per sec. over a distance of 62 /2 cm., in the direction of arrow 4. The necessary pressure is obtained by the felt 5 and weight 6 of grams per cm? (normal pressure in making photo prints). The crests and troughs are 0.5 mm. wide (these measurements also apply to the c0rresponding parts in Figs. 7-9). When the transparency 3 consists of a film, then because of the ribbed surface less sticking will occur in damp weather than with a smooth panel. Where the transparency 3 is on ordinary transparent paper of 80 gr. per M practically no sticking will ever occur, but always a shifting of about 0.2 mm., which shifting, if the drawing is not too detailed, is not troublesome. When the same test is applied to Fig. 7 there is the same amount of sticking but less shifting. A panel according to Fig. 8 very rarely causes sticking, but the same amount of shifting occurs as in Fig. 6. A panel according to Fig. 9 gives more sticking but less shifting. In Figs. 7-9, the shaded portions represent the crests or elevations. In practice, structures are by preference selected, in which the distances separating the high spots of the elevations are smaller than 0.5 mm., so that shifting becomes smaller, which is desirable for finer photo-prints.

By selecting a ribbed panel with troughs less than 0.5 mm., in width (the crests also are then made narrower which has appeared to be favourable to avoid sticking), the shifting decreases and for the given distance of 62 cm. (lengths of this order are normal ones in present exposingapparatus) it becomes imperceptible even for the finest photo-prints, when the troughs are 0.05 mm. and less wide.

In the construction of Fig. 6 the angle between the direction of movement and that of the ribs is In Fig. 7 it is 45. With a distance between the ribs of 0.5 mm. and a movement of 62 cm. and where the angle is e. g. 10, the shifting is almost imperceptible.

What I claim is:

1. An exposure apparatus for photographing, photoprinting and other reproduction work comprising in combination a solid stationary panel of a light-pervious substance adapted to transmit light from a light source to the material to be exposed and means for moving said material in contact with and against the surface of said panel, said surface having over its whole working area depressions and smooth top projections, of a maximum width of 0.5 mm., whereby during use any tendency of the material to stick when in contact therewith is substantially prevented.

2. An exposure apparatus for photographing, photoprinting and other reproduction work comprising in combination a solid stationary panel of a light-pervious substance adapted to transmit light from a light source to the material to be exposed and means for moving said material in contact with and against the surface of said panel, said surface having over its whole working area depressions and smooth top projections, in which the ratio between the height of the projections and the distance separating adjacent projections is greater than 0.1, the depressions and projections being of a maximum width of 0.5 mm., whereby during use any tendency of the material to stick when in contact with the said surface is substantially prevented.

3. An exposure apparatus for photographing, photoprinting and other reproduction work comprising in combination a solid stationary panel of a light-pervious substance adapted to transmit light from a light source to the material to be exposed and means for moving said material in contact with and against the surface of said panel, said surface having over its whole working area depressions and smooth top projections in which the area occupied by the tops of the pro- "jections is less than one-half the total surface of the panel, the depressions and projections being of a maximum width of 0.5 mm., whereby during use any tendency of the material to stick when in contact with the said surface is substantially prevented.

4. An exposure apparatus for photographing, photoprinting and other reproduction work comprising in combination a solid stationary panel of a light-pervious substance adapted to transmit light from a light source to the material to be exposed and means for moving said material in contact with and against the surface of said panel, said surface having over its whole working area depressions and smooth top projections in which the ratio between the height of the projections and the distance separating adjacent prozgsrmsea ency 'ofithe mateniallt'o stick when" ilrcOIltflChWitha fine sti ucture providing uniform pervi'ousnessto light over its entire 'efiectivearea, the tops'of theprojections and the distances therebetween being not mo'ret 015 mm. whereby during use any tendency of the material tor-stick when iii-contact; with saids'surfa'ce substantial-1yprevented and uniform: exposure is: obtained.

6. exposure apparatus for photographing, photoprinti'ng and-other reproduction workicomprising in combination, a. solid? stationary panel of al ight-pervious. substance. adapted. to; transmit light, from: a lightisource? tmthe: material: to: be ex'- posed. and; means fonmovinggsaid material; in contact with: and? against ther'sunfaceof said panel; saint surface having: over its whole working area depressions and smooth? top projections in the form: of ribsrunning; transverse to the direction,

of the movement of'thematerial to beexposed, theribs anditroughsltherebetween being not more than 025mm. wide; wherebyduring use'anytend.-

ency ofthe material to,' stick when in contact therewith is substantially prevented: and uni-- form exposure of the-material" uponcompletionofits movement eventhe panel is obtained.

7 An: exposure. appanatus; for. photograph ing,

8-. photoprintihg and other reproductionwork comprising in combination a solid stationary: panel of a light-pervious substance adtuzitecl to transmi't light from a lightsource to the material? 150* exposed and means for moving said material incontact with and against the-surface of said panel, said surf-ace having over its wholework;- ing area depressions and smooth top projections inthe form of ribs the depressions notbeing more than 0.5- mm. Wide and the-ribs-b'eing'nar rower than the depressions:

8. An exposure apparatus for photographing, photoprinting andother reproduction work-compr ising in combination" a solid stationary" panel of a light-pervi'ou'ssubstance adapted to transmit light from a light sourceto'the -material to beexposed; and means for moving said material-in contact with'and' against the surfaceof said panel, said surface having over its'whole' workingarea aseries of ribs which diverge inthedirec' tion' of the movementof the material from a zone substantially in the middlebf the panel asmeasured from the sides thereohthe' ratio be:- tween the height" of the ribs and the distance separating adj'acent ribs being" greater than 0:1. and both the ribs'='a-nd the-troughs" therebetween being not reater than 035mm; wide! E ens:

REFERENCES CLEED The following references are ,of record in the file of this patent? UNITED STATES- PATEN 'IS Number; Name'- Date 1,106,504 Fl'oeter Aug. I l-{1914a 12469 74 Marguis Nov. 20', 1917 1,500,372 Cossitt July s, 1924- 2g364351'4 Brunk Dec; 5; 1944 2302,5229 Sutherland June-2'5, 1-s4e 2,421,150 Jacobson- May 21;. 1 94-7

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