US1995199A - Blue print machine - Google Patents

Description

March 19, 1935. H. J. BRUNK BLUE PRINT MACHINE 2 sheets sneet 1 Filed May 28, 1952 min W paw/g March 19, 1935. H. J. BRUNK BLUE PRINT MACHINE Filed May 28, 1932 2 Sheets-Sheet 2 liwen/or' 9 a4 wla AIl3/ju/L/ i 7 Patented Mar. 19, 1935 PATENT OFFICE 1,99s.199 BLUE PRINT MACHINE Harold J. Brunk, Chicago, Ill., assignor to The C. F. Peace Company, a corporation of Delaware Application May' 28, 1932, Serial No. 614,152

5 Claims.

This invention relates to improvements in blue print machines and in the method of developing the blue prints and so-called white prints, 1. e., prints having blue lines on a white background.

Ordinarily blue print paper is coated with a solution containing mixtures of potassium ferricyanide and organic salts of iron such as ferric ammonium oxalate. During the period of exposure to this light the potassium ferricyanide is partly reduced to potassium ferrocyanide while the ferric ammonium oxalate is reduced to ferrous ammonium oxalate.

After exposure, the paper is washed with clear water which removes all the unexposed chemicals from the areas which were behind the opaque portion of the tracing or other negative and also removes the loose exposed or reduced chemicals 1. e., that portion which does not adhere to the fibres of the paper. This washing,

,in a certain sense, also starts the process of oxidation of the reduced chemical which action is necessary in the formation of the blue lines or areas. In other words, if left long enough in the water the so-called potash treatment herein- 25 after referred to, is unnecessary. It is the prac tice, however, to complete the oxidation by applying potassium bichromate or some other strong oxidizing agent to the surface of the paper immediately after the application of the first 30 water wash. The excess bichromate or so called potash must be washed off the surface by applying a second water wash, after which the paper is ready for drying.

Prints made in this manner are far from'satisfactory or dependable when first class blue prints with clear white lines or blue line prints on a. clear white background are desired. The cumculties may be analyzed as follows:

When making blue line prints or blue lines on a white background from negatives of tracings, the fully exposed chemical in the area outside of or between negatives runs down into the white background and stains it blue immediately when waters is applied to the surface of the paper.

The blue lines themselves at certain exposures run down into the white ground giving them a ragged appearance.

In the case of blue prints, or white lines on a blue ground (which are obtained when a tracing or positive original is used) the blue in the ground runs over the line giving it a bluish cast and at the same time closing up on the line making it narrower than the line the original tracing and at full exposures of e blue ground the line may be lost completely.

Various methods of washing have been tried with the idea of preventing this running or (bleeding mentioned above but none has proven successful heretofore. No method of changing the application of water is successful because 5 the bleeding is caused by the formation of insoluble Prussian blue when the unexposed chemi cal on the print mixes with or combines with the exposed orreduced portions. The Prussian blue formed, runs into the white and cannot be 10 washed out, once it stains the print. From this it is evident that moisture applied to the paper in a quantity sufiicient to remove the surplus chemical, regardless of how applied, is bound to cause the exposed chemical to mix with the 15 unexposed portion, as nothing separates the two, and even if the blue formed is not in sufficient quantities to run very far, the line itself will be unsatisfactory.

The object of the present invention is to pro- 20 vide a. machine for developing prints of this character without the objectionable running or bleeding of the color, regardless of the speed of operation of the blue print machine or of the length of exposure, and which also results in the production of clear white full lines on blue prints, a perfectly white background on blue line prints, a deep Prussian blue following full exposures and one which does not fade readily,

a wide range of exposure without the need of many different printing speeds and the successful printing from tracings or from negatives without changing the speed.

A contributory object is to provide an improved printing and developing machine in which the foregoing advantages are attained by developing the paper immediately after printing and before any water has been applied to the surface, after which the prints are washed and may then be treated with an oxidizing agent in the usual way and then dried.

An additional object is to provide equipment for developing blue prints in this manner, comprising an attachment for continuous blue print machines, such as are now on the market.

Otherwise expressed, the present invention is directed to sensitizing paper with ferric compounds, exposing the sensitized paper to a source of light with portions of the surface shielded from the source of light whereby the compounds of the exposed portion of the sensitized paper are reduced to a ferrous state, thereafter treating the paper with a developer containing ferric compounds adapted to render insoluble the reduced ferrous compounds and then washing the paper so treated with water. Preferably the ferric compounds of the developer are of the same chemical characteristics as the ferric compounds used to sensitize the paper and in fact some of the identical coating compounds, washed from the paper, may be used as the developer, thus economizing in the use of the developing solution;

A further object of the invention therefore is to provide means for collecting the unexposed developer, washed from the paper and applying it to said paper as a developing solution or as supplementing said developing solution, whereby the initial supply of developer may be used almost indefinitely.

In the accompanying drawings I have illustrated two different embodiments of the inven tion.

Fig. 1 is a side elevation .of a complete print-- ing, developing and drying machine.

Fig. 2 is an elevation of the opposite end of the developing attachment. v

Fig. 3 is a section, somewhat diagrammatic, of a modified form of developer applying mechanism, by means of which the developer may be used repeatedly.

The frame of the machine 10 is similar to that of a well-known type of printing, washing and drying machine now on the market and since much of the mechanism used is the same as in said commercial machine, except for the means forapplying the developing solution between the printing stage and the water washing stage, said machine will be described very briefly.

The sensitized paper is supported on a suitable roller 11, at one end of the machine, said paper 12 being drawn past a sheet of curved glass 13, where it is exposed to a suitable source of ligl (preferably a row of arc lights) in a well-known manner, the paper leaving the printing section of the machine where it passes over a roller 14' and thereafter under a roller 15, rotatable on a shaft, the ends of which arecarried in blocks 15 secured to vertical, parallel chains 15. Thus said roller is free to move up and down, its weight being supported by the loop of paper as shown, thereby maintaining the proper tension on the paper and providing for expansion and contraction of the same.

The paper then passes the means for applying the developer which may have the form of a roll 16 dipping in a pan 1'7 containing the developing solution, supplied by a suitable reservoir 18. This roll, pan and associated parts may be in the form of an attachment, readily applicable to existing machines.

From the developer the paper travels past the first water wash consisting of a tube 19 with suitable nozzles which direct sprays of water against the inclined surface of the paper in a manner which has been used heretofore, the paper thereafter travelling over suitable rollers to the potash roller 20 which dips in a pan 21, supplied with bichromate of potash or other suitable oxidizing agent, contained in a reservoir 22. paper then travels upwardly past the final water wash, the water being supplied from the pipe 23, and thereafter passes through the dryer 24 where it is dried in the usual manner, and thereafter wound on a removable roller 25.

The paper used is sensitized with a ferricyanide and, after exposure, a reducing agent is used to convert the ferricyanide to ferrocyanide. The reducing agent at the same time is capable of forming with the reduced. ferrocyanide a blue precipitate (Prussian blue) having high tinc- The.

torial value. Any diffusion of the reduced ferrocyanide into the unexposed portions, such as would result in the formation of the same precipitate in the unexposed portions, is prevented by fixing, i. e,, precipitating said reduced ferrocyanide prior to washing with water.

A practical sensitizing formula is as follows: Potassium ferricyanide, 5 pounds in 5 gallons of water. Ferric ammonium oxalate, 34 pounds in 12 gallons of water. Ammonium oxalate, 1 pounds in 4 gallons of water. Mix the above to.- gether making a. total batch of 21% gallons of solution.

An appropriate developer for the above would be: 1 pound potassium ferricyanide in 1 gallon of water. 51/ pounds ferric ammonium oxalate in 2 gallons of water. Mixing together gives 3 gallons of developer.

The photochemical reaction consists in the reduction of ferricyanide to ferrocyanide by the conjoint action of sunlight and a photo sensitive reducing agent, as for example, an organic ferric salt broadly and, more specifically, ferric ammonium oxalate. There is no useful reaction between a ferric salt and a ferricyanide but cyanide was reduced to ferrocyanide and the ferric salt to ferrous salt in the exposed portions, and upon treatment with'wash water a migration or bleeding took place, resulting in an impairment or destruction of the highly desirable sharp definition between the exposed and unexposed portions.

The procedure described prevents the combination on paper of (l) the ferrous ammonium oxalate and potassium ferricyanide that was not exposed to the light, in the course of printing, and (2) the potassium ferrocyanide with any ferric ammonium oxalate that was not exposed to light in the course of printing. After developing as above, the prints are washed in a clear water wash and then completely oxidized with potassium bichromate or other agent, as previously stated, and the surplus can then be washed off and the prints ready for drying.

The machine and process operate to prevent migration or diffusion by fixing the reduced ferrocyanide before washing the paper. By this fixing process the 'ferrocyanide is rendered insoluble and incapable of reacting with the ferric salt in the unreduced portions. In those cases Where a ferric organic salt is employed as the photosensitive lucing agent and is itself reduced to the ferrous condition, the fixing solution should also contain an agent, as for example a ferricyanide, to fix'the ferrous salt and prevent it from diffusing and combining with ferricyanide in the unexposed portions.

Tests have been. made with alarge number of possible developers including all of the common ferric compounds and most of the rare and other metallic salts, from which the following show possibilities as developersi Potassium ferricyanide; ferric ammonium oxalate; ferric ammonium citrate; ferric sodium oxalate; ferric chloride; ferric potassium oxalate"; and sodium perborate.

The potassium ferricyanide and the ferric ammonium oxalate in combination are by far the best and the potassium ferricyanide works well alone on the slower printing papers. The relative amount of potassium ferricyanide and ferric ammonium oxalate can be changed to give dif- .tainer 37 from which ferent shades of blue, the deeper shades of blue being obtained when the relative amounts of potassium ferricyanide in the sensitizing formula and in the developing solution balance. For example, a fast printing paper has less potassium ferricyanide in the formula than a slow printing paper; therefore, less should be used in the developing solution.

In addition to potassium bichromate other oxidizing agents may be used, such as other bichromates, hydrogen dioxide, sodium perborate, potassium persulphate, and potassium ferricyanide. It is understood that the use of any of these agents follows the washing of the paper.

In the form of developing apparatus shown in Fig. 3 as a modification of the developer applying portion of the machine first described (or as an attachment) the sensitized paper 25 is fed into the machine with the tracings or other negatives laid on it in the usual manner so that as the paper travels past the curved sheet of glass 26, it is exposed to the usual bank of arc lamps 27. The paper is carried along by an endless belt 28 passing over supporting rollers 29 and 30 from which said paper passes under roller 31 the weight of which is supported in part by the loop of paper as shown and as previously described in connection with the corresponding roller '15 in Fig. 1. The span of paper then travels upwardly over roller 32, under roller 33,

extends diagonally downwardly to the water wash described in connection with Fig. 1.

The developer is supplied to a suitable conit flows through a pipe 38 to a pump 39 of any suitable form'such as a centrifugal pump shown and which is operated by a shaft 40, the developer being pumped upwardly through the pipe 41 to the transverse discharge pipe 42 from which it is discharged through a series of orifices against the roll 33, forming a puddle 43 between the roll and the downwardly travelling span of sensitizedtpaper. This arrangement insures the necessary contact between the paper and the developing solution, the developer, or the major portion of it, thereafter flowing downwardly over the paper in the substantiallyvertical span between roll 34 and 35 and collecting in a further puddle 44 between the lower roller and the loop of paper, the excess developer running off near the ends thereof and being caught in a pan 45 with a discharge outlet 46 through which it is returned to the reservoir 37. Such film of developing solution as tends to adhere to the vertically moving span of paper between rolls 35 and 36 also flows downwardly forming a puddle tween the paper and the roller and is draine back into the reservoir 3'7.

The developing solution not only develops the exposed reduced portions of the sheet but also serves to wash offtor remove the unexposed portion of the coating compound, which, as previously stated, is very similar to or may be identical with the developing solution itself, so that the developer is used over and over and increases in concentration as the developing. operation continues. During long continued operation, the developer may be diluted by-adding small quantities of water from time to time to the reservoir 37, without exercising any great amount of care as to the precise amount added, as reasonable variations inthe water content do not appreciably aflfect the developing operation. The relatively long loop of paper depending from the rolls 34 and 36, is provided to give a sumcient length of wash not only to enable the developing solution to properly perform its developing function but more particularly to insure removal of the unexposed chemicals from the paper.

It will be understood that the preferred coating formula set out herein in conjunction with the preferred developing solution has been selected with particular reference to producing the desired shade of blue and to insure a very desirable contrast between the blue and the white portions of the finished print. These preferred formulae are particularly useful in making ordinaryblue prints wherein almost the entire surface coating is exposed and reduced, the only unexposed portions being the lines corresponding to the lines on the tracing, which lines in the aggregate constitute only a small fraction of the total area of the print. In such prints the blue background, of course, predominates and it is very desirable, therefore, that the proper shade of blue be obtained.

In making blue line prints, however, where most of the print ismasked by the negative and only a small area is exposed to the light and thus reduced, resulting in blue lines on a white back ground, it is less important to produce the same shade of blue as in the case of ordinary blue prints, and therefore in developing blue line prints the developing solution may be any one of a number of standard solutions used in coating blue print paper. In fact, it is to be understood that the formulae given herein do not differ gr:atly from standard coating solutions in their essential ingredients but have been developed as refinements for the purpose of giving the improved results heretofore pointed out.

In view of the foregoing, it will be apparent that where the machine is used exclusively or at least for considerable intervals of time in making 'blue line prints or so-called white prints, the

operation may be started by using nothing but clear water in the supply tank and after running possibly 25 yards or more of the blue print paper through the machine, sufllcient chemical solution will have collected in the supply tank to permit the operation to continue in the manner heretofore described, i. e. the print produced will be ing the developer as the machine may be oper ated in the ,usual way from the outset and the clear water pumped from the developer tank will act in the same way as the usual water wash and produce blue prints, or more particularly, blue line prints, of the same character now produced under prevailing methods. In other words, the prints initially produced will not have a uniformly sharp definition but as the operation progresses, they will improve in this respect until the machine is operating entirely in accordance with the improved process.

The prints resulting from the new process constitute a remarkable improvement over blue prints, white prints and the like made by the prevailing method, in that there is no at any speed or exposure, the blue prints show clear white full lines on a deep Prussian blue background, the blue line prints show a perfectly white background, the deep blue color fades slower than the present shades of blue when exposed to sunlight, and there is a wide range of exposure permissible which eliminates the need of providing sensitized papers with various different' printing speeds.

This application is a continuation in part of my application Serial No. 536,378, Blue prints and process of making the same, filed May 11, 1931, and issued May 31, 1932, as Patent No. 1,861,298. Said patent claims the method of producing nonbleeding photo-prints. The claims of the present application are directed to the apparatus.

. I claim:

1. A machine for making blue prints comprising, a developing section for a strip of blue print paper and means for conveying said blue print paper through the same, said developing section having a developer applying station and a roller at a lower elevation around which said paper passes from the higher station whereby the developer flows downwardly and collects between said roll and said span, a reservoir "beneath said roll, for collecting the developer flowing from the ends of said roll and means for recirculating said developer from said reservoir to said first station.

2. A machine of the class described for developing blue prints, comprising a developing section, means for moving a sheet of blue print paper past the same, said developing section comprising an upper and a lower roll around which said blue print paper passes, means for directing liquid developer against said upper roll to provide a puddle of developer between said roll and the approaching span of said sheet, said lower roll being positioned to cause a similar puddle of developer to form from the developing solution flowing down said sheet, a receptacle for receiving developer discharged from said lower roll and means for redelivering developer from said receptacle to said developer directing means.

3. A machine of the class described comprising past said sections, said zones being spaced sufficiently with respect to the rate of travel of said sheet through the same to aiford adequate time to develop the exposed portions of the chemical on said sheet and toremove the unexposed portions thereof prior to washing.

4. In a blue print machine, a reservoir for a developer, means for supporting a sheet of sensitized paper and causing it to travel in a loop, means adjacent said loop and connected to said reservoir for directing said developer against the inside surface of the upper part of said loop, whereby said developer will run down to the bottom of said'loop and collect therein, means for collecting the developer drained from said loop and delivering it to said reservoir, and means for subsequently applying water to said developed sheet, said means comprising the only water supply for said sheet to that point in its travel.

5. Developing apparatus for blueprint machines, comprising two rolls from which a loop of blue print paper may depend, a third roll at the bottom of said loop, a discharge pipe for developernear the top of said loop and on the side I of the paper corresponding to the inside of said loop, whereby said developer flows down the inner surface ofv one span of said loop to the bottom thereof, a pan to collect the developer drained from said loop, a reservoir, and a pump connected to said reservoir and to said discharge pipe.

HAROLD J. BRUNK.

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