US2553421A - Contact printing device - Google Patents

Description

y 1951 s. L. MONSEN 2,553,421

CONTACT PRINTII IG DEVICE Filed Dec. 21, 1948 lllllll l atented May 15,

UNITED STATES PATENT OFFICE CONTACT PRINTING DEVICE Gordon L. Monsen, Chicago, Ill.

Application December 21, 1948, Serial No. 66,431

1 Claim. 1 This invention relates to a device for making contact prints from photographic negatives.

One of the primary objects of this invention is to provide means which will produce shar contact prints.

A further object of the invention is to provide means for contact printing photographs in which the contrast between the lights and darks is easily controlled.

Still a further object of the invention is to pro vide an apparatus which is extremely simple in operation, which is economical to construct, which requires no lenses and which is extremely simple to operate.

A further object of the invention is to provide a structure comprising means for varying the contrast of prints made with my new device and utilizing my new method.

Certain other objects of the invention lie in theprovision of specific constructional features for carrying out the novel means.

With the foregoing and other objects in view which will appear as the description proceeds, my invention comprises certain novel methods which presently I will elucidate and also includes apparatus the construction and arrangement of such parts of which I consider to be novel and will describe and illustrate in the accompanying drawings. While I have described my apparatus for use in the practice of contact printing, I do not wish to limit myself thereby but rather would include all variations which do not depart fromv the spirit of my invention in its application along any-analogous lines, as I will point out in the appended claims.

For the purpose of facilitating an understanding of my invention I have illustrated in the accompanying drawings certain diagrams explaining the operation thereof, as well as a preferred embodiment of my apparatus which, together with my discussion and the following description should result in an understanding of the manner of practice of my invention; the mode of construction, assembly and operation of the apparatus thereof and in an appreciation of the many advantages inherent herein.

Referring to the drawings in which the same characters of reference are employed to indicate corresponding or similar parts throughout the several figures of the drawings.

Fig. l is a perspective view of a cabinet having apparatus associated therewith for carrying out my invention.

Fig. 2 is a top plan view of the adjustable aperture mechanism of my invention.

Fig. 3 is a sectional view taken along the line 33 of Fig. 2 and in the direction indicated.

Fig. 4 is a sectional view taken through the detent mechanism shown in Fig. 2 along the line 44 and in the indicated direction.

Figs. 5 and 6 are diagrammatic sectional views taken through a negative and a piece of film and showing the operation of my invention.

My invention consists of utilizing a point source of light or as close thereto as feasible for the purpose of contact printing from photographic negatives. I have found that with such a point source not only is a sharp print obtainable, but as well contrast control is made available by means of various sizes of aperture capable of being used with my invention.

The apparatus of my invention is extremely simple, consisting merely of a cabinet the length of which is commensurate with the size of negative to be utilized, said cabinet having a negative holding device on one end thereof with means for retaining a piece of photographic film in contact with the negative thereat. At the other end of the cabinet there is provided a chamber completely enclosed with the exception of an opening in the center thereof. Below the opening there is disposed a high intensity electric lamp arranged so that its rays will come through said opening. Over the opening is provided a translucent member whose purpose is to prevent projection of the lamp filament. The opening is relatively small'compared to the size of the cabinet so that in effect it provides a point source of light. The effect of such a point source is that the rays of light which impinge against the sensitive film upon which images are being printed do not affect the film beneath the darkned portions of the photographic film or plate. In other words, substantially perfect shadows of the darkened portions are projected upon the sensitive film without the fringe caused by methods' heretofore used.

In order to take advantage of my discovery relative to control of contrast between the light anddark portions of the printed image I provide a mechanism having a plurality of orifices or apertures capable of being operated from externally of the cabinet and having a different size aperture into registry with the light opening whereby the respective apertures act as irises when disposed for printing an image.

It will be apparent as the description proceeds that the many equipments which are used with this type of apparatus such as for example, timers, switches, elaborate plate and film holding devices and the like have not been referred to or described inasmuch as they do not form a part of my invention.

Referring now to the figures, reference character IE2 designates generally a cabinet with which my invention is adapted to be associated. Said cabinet has a negative and sensitive film holding mechanism indicated generally at H installed at one end of said cabinet [0, said mechanism including a pair of frame members l2 and 13, a glass M, a latch mechanism l5, and counterweights I6 and is arranged to receive therein the photographic negatives and the sensitized member upon which images of the negative are adapted to be printed.

The cabinet includes side walls l1 and a step 18 in the front thereof upon which the operator may stand. The bottom of the cabinet has a chamber 19 which is separated from the main cabinet space 20 by means of a diaphragm 24. The diaphragm 2! is provided with a bracket 22 upon which is mounted a high intensity electric lamp 23 so arranged that its rays will shine through an opening 24- provided in said diaphragm whereby said rays indicated at 25 will enter said chamber 20 and be directed against the photographic negative and sensitized film. The upper surface of the diaphragm 2! is provided with a member of translucent material 26, same being formed of opal glass. The effect of the translucent member 25 is to diffuse the light rays 25 so that thereis a singlesource of light within the chamber 20 defined by the orifice or aperture.

The aperture is approximately two inches in diameter. In comparison to dimensions on the cabinet l this source of light is equivalent to a theoretical point such that the light rays projected into the chamber 25 are substantially parallel. I have found that such an effect produces a sharply defined image the reason for which will be explained hereinafter.

Referring to Figs. and 6. Fig. 5 is a diagrammatic View taken through the film and the photosensitive member designated respectively 21 and 28. The emulsion of the film is indicated at 29 formed on the surface of said film or a photographic plate whichis equivalent thereof. Rays of light are indicated at 25. The arrangement described provides for such substantially directed light rays so that the shadow cast by the darkened portions 29 of the film 2'! will be substantially perfectly defined irrespective of the rounded corners 30 of the dark portions 29 of emulsion. The sensitized film 28 will therefore have a grain formed thereon as shown, uniformly and sharply defined by said shadows as indicated at 3|.

In Fig. 6 I have shown a plate or film 21 having identical darkened portions formed as emulsion thereof as shown in Fig. 5 and engaged against the surface of a sensitive film 28. In this diagram, however, the light which impinges upon the surface of the film 28 is the usual random rays indicated at 32 found in printing devices heretofore used. The effect of such random rays is that not only are the shadows caused. by the darkened portions 29 provided with overlapping edges due to the rays bypassing the corners 30, thereby building up the grain portions 33 under the corners of the dark spots 29, but as well as center of exposed spaces receives the greatest amount of light whereby the deposit formed on the film 28 is not uniform but instead consists of deposits which are heavy in the center thereof as indicated at 34.

My printing apparatus therefore embodies the exposing of photo-sensitive members to the direct rays of a substantially point light source whereby to provide a uniform, sharply defined image of a photographic film or plate engaged in contact with said photo-sensitive member.

In addition to the above I have discovered that the contrast capable of being obtained can be varied by varying the size of the aperture 24. This is done in my construction by means of an orifice or aperture wheel which is secured to a shaft by means of pin 3? and the hub 38. The shaft is adapted to rotate upon a bearing 39 which is mounted upon the diaphragm 2i ofiset from said orifice 24. Around its periphery the wheel 35 is provided with orifices 40, 4|, .2, 4 3, 44 and 55, said apertures being respectively of decreasing size. Said centers of apertures are radially equi-distant from the center of the wheel 35 and are adapted to align with the aperture 24 so that as the wheel is rotated bringing any of the apertures 45 to 5 over the aperture 24, the size of the light source will be determined by the size of the respective aperture of the wheel 35. Said wheel 35 therefore provides varying dimensions of apertures for the light source. The wheel 35 is adapted to protrude from the side wall it of the cabinet so that same may be manually moved. Detent notches 46 are provided about the circumference of the wheel corresponding to the various sizes of aperture. Indicia indicated at 41 are marked upon the wheel to indicate the size of the aperture which is over the aperture 2 4. These indicia ll cooperate with a pointer 38 secured to the side wall I7 and the detent notches 25 cooperate with a detent mechanism attached to the wall H by means of the bracket 55. A detailed view of said detent mechanism is shown in Fig. 4-.

It will be seen that the detent mechanism consists of a vertically arranged rod 5! which is adapted to engage within the notches 46 in order to prevent rotation of the wheel 35. The bracket 59 is grooved as shown at '52, within which groove the bottom portion 53 of the rod 5! is adapted to be disposed. Said portion 53 is pinned for swinging motion about the point 54. At the bottom of the bracket 50 there is provided a recess 54 formed for example, by drilling into said bracket between the walls of the groove 52. The rear face of. the portion 53 of the rod 5! is provided with a depression 55 aligned with the recess 54. anda coiled spring 56 is disposed within said recess and engaging within the depression 55 such as to push against the bottom end of the rod 5!. This tends to force the rod to swing in a counter-clockwise direction as viewed in Fig. 4, pushing the upper portion into engagement with the notch 46. If it is desired to move the wheel 35 the operator grasps the upper portion of the rod, 51 and pulls same away from the wall I1, whereby the notch 46 is clear, permitting rotation of the wheel 35.

From the above explanation it is believed obvious that my invention comprising a contact printing apparatus for practicing said invention has been completely set forth so that all of its ramifications shall be obvious to one skilled in the art. While I have set forth certain theo retical explanations of the manner of operation of my invention I do not wish to be lim-ited in such theories since the results obtained may or may not be explained thereby. Such exp1ana-,

tion has been included only with the end that the specification be more complete and clear. It is my desire to secure the invention as pointed out in the appended claim regardless of the theory by which same operates.

What is claimed and desired to be secured by Letters Patent of the United States is:

Apparatus for contact printing an image of a negative upon a photo-sensitive member comprising a cabinet, supporting means for a negative and photo-sensitive member mounted at the top of the cabinet, a diaphragm arranged horizontally in the cabinet and formed with'a central aperture, a light source disposed directly beneath the aperture, the aperture serving as a point light source for the rays of light that are projected upwardly toward the negative, a vertical shaft extending through the diaphragm at one side of the aperture, a horizontal disc mounted on the shaft for rotation therewith and disposed directly above the diaphragm, said disc having a plurality of different size orifices arranged around the peripheral portion thereof and adapted to selectively register with the aperture in the diaphragm, one edge portion of the disc extending through the side wall of the cabinet, the peripheral edge of the disc having notches therein corresponding to the various sizes of the orifices in the disc, a pivoted detent mounted on the outside of the cabinet, adjacent the protruding portion of the rotatable disc, one end portion of the detent engaging in the adjacent notch in the edge of the disc, and spring means coacting with the pivoted detent for holding the same in engagement with one of the notches to hold the rotatable disc in a selected position.

GORDON L. MONSEN.

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

UNITED STATES PATENTS Number Name Date 941,766 De Zeng Nov. 30, 1909 1,205,582 Tessier Nov. 21, 1916 1,205,632 Holst Nov. 21, 1916 2,588,425 John June 15, 1920 2,592,358 Hatt July 13, 1926 1,813,000 Thompson July 7, 1931 1,858,603 Sponable May 17, 1932 1,930,139 Altman et al Oct. 10, 1933 2,356,885 Reeves Aug. 29, 1944 2,357,541 Pfeil Sept. 5, 1944 FOREIGN PATENTS Number Country Date 782,001 France Nov. 29, 1934 OTHER REFERENCES Journal of the Society of Motion Picture Engineers, volume 47, No. 5, November 1946, Article by Buckingham et al. in Concentrated Arc Lamps on pages 376 to 399-pages 388 and 389 especially cited.

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