US2342000A - Method and means for processing motion picture film - Google Patents

Description

Feb. 15, 1944. M. s. LESHING ETAL METHOD AND MEANS FOR PROCESSING MOTION PICTURE FILMS Filed May 20, 1940 5. NF JV NT J? up K J i; u

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Ow J? K NF MP INVENTORS. Mz'chaei S. Lesiafng. By Ben ami/z CRoZzET son.

ATTORNEY.

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Patented Feb. 15, 1944 METHOD AND MEANS FOR MOTION PICTURE Michael S. Lesl'iing, Lo Christian Robertson, assignors to Twentieth poration, Los Angeles,

New York PROCESSING FILM s Angeles, and Benjamin North Hollywood, Calii'.,

Century-Fox Film Cor- Calii., a corporation of Application May 20, 1940, Serial No. 336,210

4 Claims.

This invention relates to the art of film processing and provides a, method and a means for overcoming certain well known deleterious effects in developing motion picture film.

In developing motion picture film where the film is run continuously through a tank of solution, it is a well known fact that, due to certain chemical reactions and physical conditions combined with the movement of the film, a directional effect on the film will occur in the developing process. Directional eiiect, as it is understood, is due to the fact that wherever development takes place certain reaction products are formed within the emulsion coating on the film which restrain further development. Under certain conditions these reactions may go so far as to form a spent solution and stop further development unless fresh solution is applied.v The products of the reaction, however, tend to diffuse out of the gelatin and unless the film or the solution is agitated they concentrate in a zone on or near the surface of the emulsion, thus preventing fresh solution from contacting the emulsion for further development. In the case of a film moving through developing solution, these reaction products will fiow backward along the film and will retard the normal developmentof succeeding exposed portions. The result is that instead of having a uniform development of densities on a uniformly exposed film the head end of the film will have a greater density than the tail end. This effect is known as a directional effect in film processing and many attempts have been made to eliminate it. Agitation has been used with beneficial results, but up to the present time the eflect still persists in motion picture film and in soundtrack film. The present invention embraces a method and a means which not only involves increased agitation but introduces a turbulent effect in the solutionitself. It is to be understood that the method and means to be described and claimed hereinafter are applicable to that type 01 film processing wherein the film travels in a plurality of vertical loops, each loop consistin: of anupwardly and a downwardly traveling section or film strand, through a tank of developing solution. Under our invention the developing solution is kept at a low level in the tank, from where it is continuously returned to the top of the vertical film strands and is allowed to flow downwardly by gravity over the film, thus continually supplying fresh solution to the film and at the same time producing increased agitation and turbulation of the solution. In practice it has been found that the directional effect of developing has been materially reduced under this method and that most noticeably the objectionable sprocket hole efiect on sound tracks has beenreduced. To those versed in the art of sound tracks, it is a well known fact that the area surrounding sprocket holes is developed to a higher density than other areas of the film, due presumably to the fact that as the film is drawn through the solution the sprocket holes set up an added agitation that produces a higher develop ment around each hole. In some cases the zone is so pronounced and of such an extent that it extends into the sound track and in reproduction sets up what is known as a 96 cycle tone or a sprocket hole hum. Since there is no way of eliminating the agitation effect of the sprocket holes when a film strip is drawn through developing solution, we conceived the idea of reducing the solution in the tank to a minimum level, thus removing all but the lower end of the vertical strips of film from the solution to avoid sprocket hole agitation and applying the solution in a sheet at the top of the film strands to permit the solution to run down the film and cause a uniform turbulation and agitation over the entire surface of the film, including the sprocket hole area. In use, we have found that the directional effect and the sprocket hole eiiect decrease as the level of the solution in the tank is lowered on the vertical film strands, which bears out one of the premises of this invention that the least possible amount of film should be run through solution standing in the bottom of the tank. Ac cordingly, it becomes an object of this invention to provide a method of developing motion picture film wherein the film is moved continuously in vertical loops, each loop consisting of an upwardly and a downwardly traveling section or film strand, through a tank having a minimum of developing solution therein, and the developing solution is applied at the top of the vertical strands and allowed to run down the film. Another obiect of this invention is to provide means for supplying developing solution to continuously moving vertical film loops at the top or the strands.

Other objects and advantages will become apparent as the description proceeds in conjunc tion with the drawing in which:

Figure l is a condensed longitudinal, vertical section of a conventional developing tank showing our invention arranged over the top of the vertical strands;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a top plan view of one of the vertical sections with our invention in place; and

Figure 4 is an enlarged sectional view of the top of one of the strands showing our invention in a working position.

Referring to the drawing, it will be seen that we have illustrated our invention as applicable to a process of developing motion picture film wherein the film F is run continuously through a tank If having a certain amount of developing solution. l2 contained therein. The conventional method of running the film through tanks of this nature consists in running the film through the solution in a plurality of vertical loops generally designated P. In Figure l we have shown the mechanism'of these vertical loops as comprising an upper roller 13 and a lower roller M. For the sake of simplicity, we have shown but two of the vertical loop or path arrangements which are identical, although it is to be under-- stood that a conventional developing machine has a plurality of such paths. It is also be understood that there are a plurality of rollers 13 and I4, as shown in Figure 2, and that when the machine is threaded with the film F the film runs between the rollers l3 and M in a series of vertical loop sections or film strands 8 (see Figure 2). No detail of construction or arrangement of the roller mechanism or driving mechanism therefor is shown, since this construction forms no part of the invention. In Figure 2 we have merely shown bars 85 and is connecting the plurality of the lower rollers 54 and upper rollers I3 with a sliding sleeve arrangement it, constructed to permit the entire roller assembly to be raised upwardly out of the solution in the tank. To those versed in the art of film processing, it is well understood how a film strip is threaded through and travels continuously through a developing machine of the above chanacter. Insofar as our invention is concerned, it is immaterial which direction the film travels.

In conjunction with the foregoing arrangement, which is standard construction, we add means for applying solution to the at the top of the film strands or, more specifically, at opposite points on the rollers 93. In practice we have found that the best results are obtained by applying the solution to the film on both sides of the rollers i3 so that the solution will contact the film at tangential points on the rollers and will flow downwardly over the film strands by force of gravity. It will also become evident under. our method of applying solution to opposite sides of the roller at the top of the strands that the solution is forced to fiow counter to the movement of the film on one side of the rollers and in accordance with the movement on the other side of the rollers, thus tending to cancel out the efiects of directional development. For this purpose we employ units designated A in their entirety and mount a unit over each one of the series of rollers i3. As best illustrated in Figure 3, the unit A comprises a pair of parallel pipes or casings l8 and 69, said casings having longitudinal slots 20 and 2| therein arranged to emit sheets of developing solution 22 and 23. The casings l8 and i9 are so arranged over the rollers l3 that the sheets of solution 22 and 23 will contact the film F at a tangential point on both sides of the roller and will cling to the film and fiow downwardly thereover in a turbulent and agitated form. The result is that not onl is fresh solution supplied to the film but the solution itself is agitated and, due to the flowing of the solution down the film, a turbulent eiiect is obtained which, in conjunction with the agitation, acts to remove all reaction products of development and continuously supply fresh solution to the film emulsion. As shown in Figure l, the solution fiows downwardly over the length of the film strands on both the upward and downward travel and is mingled with the solutio l2 m the bottom of the tank. It will be note in,

this respect that a minimum of solution I2 is kept in the tank for the purpose, as stated hereinbeiore, of removing as -much as possible of the vertical film strands from the solution to avoid sprocket hole agitation. 1n installations where the size of the tank would permit, it would be advisible to lower the solution completely below the bottom of the film strands to avoid all sprocket hole agitation. However, in most installations, a certain amount of solution is needed in the bottom of the tank to have sufiicient solution for developing purposes and to permit that it may be continuously returned from the bottom of the tank to the slotted casings l8 and 19, where it is again distributed over the film. The means for supplying the solution to'the casings l8 and 19 comprises a pump generally designated T arranged to communicate its inlet with the solution 52 in the bottom of the tank. The pump may be driven by a conventional drive pulley 24. The output of the pump flows into a. pipe 25, which in turn may be connected to a header pipe 26 that continues the full length of the tank ll and suppliessolution to each one of the units A. The

header pipe as is set up with a plurality of T's 271, corresponding to the number of units A to be served, into which a feeder pipe 28 is rotatably fitted and held in leak-proof engagement by any well known means for this purpose. A pair of short pipes 29 and 30 communicate with the ieeder pipe 28 and are so spaced on the pipe 28 as to include the series of rollers l3. Between the pipes 29 and 30 we run small pipes 31 and 82 for carrying solution to the casings l8 and I9. As shown, the casings i8 and I9 are annularly spaced around the pipes 3| and 32 and the pipes themselves are perforated on the top portion for emitting solution into the casings l8 and I9. In

addition. we may incorporate a valve V in the line 25 for controlling the output of the pump '1. The purpose of this construction is to permit control of the solution supply to the casings l8 and i9 so that the solution may run out of the slots 20 and 2! in a sheet under the force of gravity with no pressure, or only slight pressure, behind it. As before stated, the feeder pipe 28 is rotatably mounted in the T 21,

' which permits that the whole unit A may be rotated into the dotted position shown in Figure 1 to permit the film strands S, with their entire mechanism, to be raised from the tank. Since we are aware that other means may be designed and constructed for the same purpose, we do not intend to limit the invention to the particular means shown and described.

Our method may be practiced in any film processing laboratory where the film is run through the developing tank in a plurality of vertical strands and the means for practicing our method may be mounted upon any conventional film processing tank of the above character without involving any changes in the construction of the tank or the travel of the film.

Having shown and described our method and one form of means for practicing our invention, we claim: 1

1. In a system for developing motion picture film wherein the film travels through said system in a plurality of vertical loops, each loop having a downwardly and an upwardly traveling section, means for continuously supplying the developing solution to the plurality of film sections, said means including perforated pipes arranged along the top of each of said film sections, a casing annularly spaced around each of said pipes enclosing said perforations, said casing having a longitudinal slot in the lower wall thereof adapted to emit solution to the top of each of said sections.

2. A method for developing motion picture film wherein the film is moved alternately up and down in a series of vertical paths consisting in applying developing solution to the film at the top of said paths in suflicient quantity to cause the solution to flow freely downwardly by force of gravity in an agitated and turbulent form over the surface of the iilm in both paths.

3. In a system for developing motion picture film wherein the film travels through a developing tank in a plurality of vertical loops, each loop having an upwardly and a downwardly traveling section, a developing solution distributing member having a longitudinal slot therein arranged across the top of said sections to emit solution to the plurality of said sections at the top thereof so that the solution may flow freely downwardly in a turbulent sheet over each of said sections, and means for moving said solution distributing member into an out-of-theway position for raising said film loops out of said tank, said means including a feeder pipe screw threadedly connected to a supply line, and means for mounting said distributing member on said feeder pipe so that said distributing member may be swung into an out-of-theway position by rotating said feeder pipe in its screw threaded connection.

4. A method of developing motion picture film wherein the film is moved over a series of top and bottom rollers forming a plurality of vertical loops, each loop having an upwardly and a downwardly traveling section consisting of supplying developing solution to the iilm on both sides of said top rollers in sufficient quantity to cause 'the solution to flow freely downwardly by force of gravity in an agitated and turbulent form over the surface of the film in both sec- 25 tions.

MICHAEL S. LESHING. BBN'JAMIN CHRISTIAN ROBERTSON. I

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